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Revision 1.169 by root, Fri Jun 20 23:31:19 2008 UTC vs.
Revision 1.211 by root, Mon Nov 3 14:34:16 2008 UTC

…		…
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);
…		…
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);
…		…
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
…		…
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.
396		422
397	While nominally embeddable in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
398	all kernel versions tested so far.	424	all kernel versions tested so far.
		425
		426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		427	C<EVBACKEND_POLL>.
399		428
400	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
401		430
402	Kqueue deserves special mention, as at the time of this writing, it	431	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	432	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	433	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"	434	it's completely useless). Unlike epoll, however, whose brokenness
		435	is by design, these kqueue bugs can (and eventually will) be fixed
		436	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	437	"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)	438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
408	system like NetBSD.	439	system like NetBSD.
409		440
410	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	only for sockets (after having made sure that sockets work with kqueue on
…		…
413		444
414	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
419	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
420		452
421	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
422		454
423	While nominally embeddable in other event loops, this doesn't work	455	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	456	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	457	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	458	(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	459	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,
428	sockets.	460	using it only for sockets.
		461
		462	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
		463	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
		464	C<NOTE_EOF>.
429		465
430	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	466	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
431		467
432	This is not implemented yet (and might never be, unless you send me an	468	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	469	implementation). According to reports, C</dev/poll> only supports sockets
…		…
446	While this backend scales well, it requires one system call per active	482	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	483	file descriptor per loop iteration. For small and medium numbers of file
448	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	484	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
449	might perform better.	485	might perform better.
450		486
451	On the positive side, ignoring the spurious readiness notifications, this	487	On the positive side, with the exception of the spurious readiness
452	backend actually performed to specification in all tests and is fully	488	notifications, this backend actually performed fully to specification
453	embeddable, which is a rare feat among the OS-specific backends.	489	in all tests and is fully embeddable, which is a rare feat among the
		490	OS-specific backends (I vastly prefer correctness over speed hacks).
		491
		492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
		493	C<EVBACKEND_POLL>.
454		494
455	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
456		496
457	Try all backends (even potentially broken ones that wouldn't be tried	497	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	498	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
…		…
464		504
465	If one or more of these are or'ed into the flags value, then only these	505	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	506	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.	507	specified, all backends in C<ev_recommended_backends ()> will be tried.
468		508
469	The most typical usage is like this:	509	Example: This is the most typical usage.
470		510
471	if (!ev_default_loop (0))	511	if (!ev_default_loop (0))
472	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	512	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
473		513
474	Restrict libev to the select and poll backends, and do not allow	514	Example: Restrict libev to the select and poll backends, and do not allow
475	environment settings to be taken into account:	515	environment settings to be taken into account:
476		516
477	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	517	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
478		518
479	Use whatever libev has to offer, but make sure that kqueue is used if	519	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	520	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):	521	private event loop and only if you know the OS supports your types of
		522	fds):
482		523
483	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	524	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
484		525
485	=item struct ev_loop *ev_loop_new (unsigned int flags)	526	=item struct ev_loop *ev_loop_new (unsigned int flags)
486		527
…		…
507	responsibility to either stop all watchers cleanly yourself I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
508	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
510	for example).	551	for example).
511		552
512	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
513	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
514	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
515		556
516	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
519	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
544		585
545	=item ev_loop_fork (loop)	586	=item ev_loop_fork (loop)
546		587
547	Like C<ev_default_fork>, but acts on an event loop created by	588	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	589	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.	590	after fork that you want to re-use in the child, and how you do this is
		591	entirely your own problem.
550		592
551	=item int ev_is_default_loop (loop)	593	=item int ev_is_default_loop (loop)
552		594
553	Returns true when the given loop actually is the default loop, false otherwise.	595	Returns true when the given loop is, in fact, the default loop, and false
		596	otherwise.
554		597
555	=item unsigned int ev_loop_count (loop)	598	=item unsigned int ev_loop_count (loop)
556		599
557	Returns the count of loop iterations for the loop, which is identical to	600	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	601	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	616	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	617	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	618	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).	619	event occurring (or more correctly, libev finding out about it).
577		620
		621	=item ev_now_update (loop)
		622
		623	Establishes the current time by querying the kernel, updating the time
		624	returned by C<ev_now ()> in the progress. This is a costly operation and
		625	is usually done automatically within C<ev_loop ()>.
		626
		627	This function is rarely useful, but when some event callback runs for a
		628	very long time without entering the event loop, updating libev's idea of
		629	the current time is a good idea.
		630
		631	See also "The special problem of time updates" in the C<ev_timer> section.
		632
578	=item ev_loop (loop, int flags)	633	=item ev_loop (loop, int flags)
579		634
580	Finally, this is it, the event handler. This function usually is called	635	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	636	after you initialised all your watchers and you want to start handling
582	events.	637	events.
…		…
584	If the flags argument is specified as C<0>, it will not return until	639	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.	640	either no event watchers are active anymore or C<ev_unloop> was called.
586		641
587	Please note that an explicit C<ev_unloop> is usually better than	642	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	643	relying on all watchers to be stopped when deciding when a program has
589	finished (especially in interactive programs), but having a program that	644	finished (especially in interactive programs), but having a program
590	automatically loops as long as it has to and no longer by virtue of	645	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.	646	of relying on its watchers stopping correctly, that is truly a thing of
		647	beauty.
592		648
593	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	649	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	650	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.	651	process in case there are no events and will return after one iteration of
		652	the loop.
596		653
597	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	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	658	user-registered callback will be called), and will return after one
		659	iteration of the loop.
		660
		661	This is useful if you are waiting for some external event in conjunction
		662	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	663	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.	664	usually a better approach for this kind of thing.
604		665
605	Here are the gory details of what C<ev_loop> does:	666	Here are the gory details of what C<ev_loop> does:
606		667
607	- Before the first iteration, call any pending watchers.	668	- Before the first iteration, call any pending watchers.
608	* If EVFLAG_FORKCHECK was used, check for a fork.	669	* If EVFLAG_FORKCHECK was used, check for a fork.
609	- If a fork was detected, queue and call all fork watchers.	670	- If a fork was detected (by any means), queue and call all fork watchers.
610	- Queue and call all prepare watchers.	671	- Queue and call all prepare watchers.
611	- If we have been forked, recreate the kernel state.	672	- If we have been forked, detach and recreate the kernel state
		673	as to not disturb the other process.
612	- Update the kernel state with all outstanding changes.	674	- Update the kernel state with all outstanding changes.
613	- Update the "event loop time".	675	- Update the "event loop time" (ev_now ()).
614	- Calculate for how long to sleep or block, if at all	676	- Calculate for how long to sleep or block, if at all
615	(active idle watchers, EVLOOP_NONBLOCK or not having	677	(active idle watchers, EVLOOP_NONBLOCK or not having
616	any active watchers at all will result in not sleeping).	678	any active watchers at all will result in not sleeping).
617	- Sleep if the I/O and timer collect interval say so.	679	- Sleep if the I/O and timer collect interval say so.
618	- Block the process, waiting for any events.	680	- Block the process, waiting for any events.
619	- Queue all outstanding I/O (fd) events.	681	- Queue all outstanding I/O (fd) events.
620	- Update the "event loop time" and do time jump handling.	682	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
621	- Queue all outstanding timers.	683	- Queue all expired timers.
622	- Queue all outstanding periodics.	684	- Queue all expired periodics.
623	- If no events are pending now, queue all idle watchers.	685	- Unless any events are pending now, queue all idle watchers.
624	- Queue all check watchers.	686	- Queue all check watchers.
625	- Call all queued watchers in reverse order (i.e. check watchers first).	687	- 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	688	Signals and child watchers are implemented as I/O watchers, and will
627	be handled here by queueing them when their watcher gets executed.	689	be handled here by queueing them when their watcher gets executed.
628	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	690	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
…		…
633	anymore.	695	anymore.
634		696
635	... queue jobs here, make sure they register event watchers as long	697	... 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..)	698	... as they still have work to do (even an idle watcher will do..)
637	ev_loop (my_loop, 0);	699	ev_loop (my_loop, 0);
638	... jobs done. yeah!	700	... jobs done or somebody called unloop. yeah!
639		701
640	=item ev_unloop (loop, how)	702	=item ev_unloop (loop, how)
641		703
642	Can be used to make a call to C<ev_loop> return early (but only after it	704	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	705	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	706	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.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
646		708
647	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
648		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
649	=item ev_ref (loop)	713	=item ev_ref (loop)
650		714
651	=item ev_unref (loop)	715	=item ev_unref (loop)
652		716
653	Ref/unref can be used to add or remove a reference count on the event	717	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	718	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	719	count is nonzero, C<ev_loop> will not return on its own.
		720
656	a watcher you never unregister that should not keep C<ev_loop> from	721	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	722	from returning, call ev_unref() after starting, and ev_ref() before
		723	stopping it.
		724
658	example, libev itself uses this for its internal signal pipe: It is not	725	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	726	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	727	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	728	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>	729	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,	730	(but only if the watcher wasn't active before, or was active before,
664	respectively).	731	respectively).
665		732
666	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
667	running when nothing else is active.	734	running when nothing else is active.
668		735
669	struct ev_signal exitsig;	736	ev_signal exitsig;
670	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
671	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
672	evf_unref (loop);	739	evf_unref (loop);
673		740
674	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
…		…
679	=item ev_set_io_collect_interval (loop, ev_tstamp interval)	746	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
680		747
681	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)	748	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
682		749
683	These advanced functions influence the time that libev will spend waiting	750	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	751	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.	752	will try to invoke timer/periodic callbacks and I/O callbacks with minimum
		753	latency.
686		754
687	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	755	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	756	allows libev to delay invocation of I/O and timer/periodic callbacks
689	increase efficiency of loop iterations.	757	to increase efficiency of loop iterations (or to increase power-saving
		758	opportunities).
690		759
691	The background is that sometimes your program runs just fast enough to	760	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	761	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	762	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	763	events, especially with backends like C<select ()> which have a high
695	overhead for the actual polling but can deliver many events at once.	764	overhead for the actual polling but can deliver many events at once.
696		765
697	By setting a higher I<io collect interval> you allow libev to spend more	766	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,	767	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	769	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.	770	introduce an additional C<ev_sleep ()> call into most loop iterations.
702		771
703	Likewise, by setting a higher I<timeout collect interval> you allow libev	772	Likewise, by setting a higher I<timeout collect interval> you allow libev
704	to spend more time collecting timeouts, at the expense of increased	773	to spend more time collecting timeouts, at the expense of increased
705	latency (the watcher callback will be called later). C<ev_io> watchers	774	latency/jitter/inexactness (the watcher callback will be called
706	will not be affected. Setting this to a non-null value will not introduce	775	later). C<ev_io> watchers will not be affected. Setting this to a non-null
707	any overhead in libev.	776	value will not introduce any overhead in libev.
708		777
709	Many (busy) programs can usually benefit by setting the I/O collect	778	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	779	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	780	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>,	781	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.	782	as this approaches the timing granularity of most systems.
714		783
		784	Setting the I<timeout collect interval> can improve the opportunity for
		785	saving power, as the program will "bundle" timer callback invocations that
		786	are "near" in time together, by delaying some, thus reducing the number of
		787	times the process sleeps and wakes up again. Another useful technique to
		788	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
		789	they fire on, say, one-second boundaries only.
		790
715	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
716		792
717	This function only does something when C<EV_VERIFY> support has been	793	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	794	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	795	through all internal structures and checks them for validity. If anything
720	an error message to standard error and call C<abort ()>.	796	is found to be inconsistent, it will print an error message to standard
		797	error and call C<abort ()>.
721		798
722	This can be used to catch bugs inside libev itself: under normal	799	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	800	circumstances, this function will never abort as of course libev keeps its
724	data structures consistent.	801	data structures consistent.
725		802
726	=back	803	=back
727		804
728		805
729	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
730		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
731	A watcher is a structure that you create and register to record your	812	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	813	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:	814	become readable, you would create an C<ev_io> watcher for that:
734		815
735	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
736	{	817	{
737	ev_io_stop (w);	818	ev_io_stop (w);
738	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
739	}	820	}
740		821
741	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
742	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
743	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
744	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
745	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
746	ev_loop (loop, 0);	830	ev_loop (loop, 0);
747		831
748	As you can see, you are responsible for allocating the memory for your	832	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,	833	watcher structures (and it is I<usually> a bad idea to do this on the
750	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
751		838
752	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
753	(watcher *, callback)>, which expects a callback to be provided. This	840	(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	841	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	842	watchers, each time the event loop detects that the file descriptor given
756	is readable and/or writable).	843	is readable and/or writable).
757		844
758	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	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	846	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	847	is also a macro to combine initialisation and setting in one call: C<<
761	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
762		849
763	To make the watcher actually watch out for events, you have to start it	850	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	851	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	852	*) >>), and you can stop watching for events at any time by calling the
766	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
767		854
768	As long as your watcher is active (has been started but not stopped) you	855	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	856	must not touch the values stored in it. Most specifically you must never
770	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
771		858
772	Each and every callback receives the event loop pointer as first, the	859	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	860	registered watcher structure as second, and a bitset of received events as
774	third argument.	861	third argument.
775		862
…		…
838	=item C<EV_ERROR>	925	=item C<EV_ERROR>
839		926
840	An unspecified error has occurred, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
841	happen because the watcher could not be properly started because libev	928	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	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
843	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
844	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
845		936
846	Libev will usually signal a few "dummy" events together with an error,	937	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	938	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	939	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	940	the error from read() or write(). This will not work in multi-threaded
850	programs, though, so beware.	941	programs, though, as the fd could already be closed and reused for another
		942	thing, so beware.
851		943
852	=back	944	=back
853		945
854	=head2 GENERIC WATCHER FUNCTIONS	946	=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		947
859	=over 4	948	=over 4
860		949
861	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
862		951
…		…
868	which rolls both calls into one.	957	which rolls both calls into one.
869		958
870	You can reinitialise a watcher at any time as long as it has been stopped	959	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.	960	(or never started) and there are no pending events outstanding.
872		961
873	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
874	int revents)>.	963	int revents)>.
		964
		965	Example: Initialise an C<ev_io> watcher in two steps.
		966
		967	ev_io w;
		968	ev_init (&w, my_cb);
		969	ev_io_set (&w, STDIN_FILENO, EV_READ);
875		970
876	=item C<ev_TYPE_set> (ev_TYPE *, [args])	971	=item C<ev_TYPE_set> (ev_TYPE *, [args])
877		972
878	This macro initialises the type-specific parts of a watcher. You need to	973	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	974	call C<ev_init> at least once before you call this macro, but you can
…		…
882	difference to the C<ev_init> macro).	977	difference to the C<ev_init> macro).
883		978
884	Although some watcher types do not have type-specific arguments	979	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.	980	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
886		981
		982	See C<ev_init>, above, for an example.
		983
887	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	984	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
888		985
889	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	986	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	987	calls into a single call. This is the most convenient method to initialise
891	a watcher. The same limitations apply, of course.	988	a watcher. The same limitations apply, of course.
892		989
		990	Example: Initialise and set an C<ev_io> watcher in one step.
		991
		992	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		993
893	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	994	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
894		995
895	Starts (activates) the given watcher. Only active watchers will receive	996	Starts (activates) the given watcher. Only active watchers will receive
896	events. If the watcher is already active nothing will happen.	997	events. If the watcher is already active nothing will happen.
897		998
		999	Example: Start the C<ev_io> watcher that is being abused as example in this
		1000	whole section.
		1001
		1002	ev_io_start (EV_DEFAULT_UC, &w);
		1003
898	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
899		1005
900	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
901	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
902	non-repeating timers are being stopped when they become pending), but	1010	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	1011	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	1012	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.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
906		1014
907	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
908		1016
909	Returns a true value iff the watcher is active (i.e. it has been started	1017	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	1018	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	1060	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 :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
954		1062
955	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	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	1064	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.	1065	or might not have been clamped to the valid range.
958		1066
959	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
960		1068
961	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	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	1070	C<loop> nor C<revents> need to be valid as long as the watcher callback
963	can deal with that fact.	1071	can deal with that fact, as both are simply passed through to the
		1072	callback.
964		1073
965	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1074	=item int ev_clear_pending (loop, ev_TYPE *watcher)
966		1075
967	If the watcher is pending, this function returns clears its pending status	1076	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	1077	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>.	1078	watcher isn't pending it does nothing and returns C<0>.
970		1079
		1080	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1081	callback to be invoked, which can be accomplished with this function.
		1082
971	=back	1083	=back
972		1084
973		1085
974	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1086	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
975		1087
976	Each watcher has, by default, a member C<void *data> that you can change	1088	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	1089	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	1090	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	1091	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	1092	member, you can also "subclass" the watcher type and provide your own
981	data:	1093	data:
982		1094
983	struct my_io	1095	struct my_io
984	{	1096	{
985	struct ev_io io;	1097	ev_io io;
986	int otherfd;	1098	int otherfd;
987	void *somedata;	1099	void *somedata;
988	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
989	}	1101	};
		1102
		1103	...
		1104	struct my_io w;
		1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
990		1106
991	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
992	can cast it back to your own type:	1108	can cast it back to your own type:
993		1109
994	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
995	{	1111	{
996	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
997	...	1113	...
998	}	1114	}
999		1115
1000	More interesting and less C-conformant ways of casting your callback type	1116	More interesting and less C-conformant ways of casting your callback type
1001	instead have been omitted.	1117	instead have been omitted.
1002		1118
1003	Another common scenario is having some data structure with multiple	1119	Another common scenario is to use some data structure with multiple
1004	watchers:	1120	embedded watchers:
1005		1121
1006	struct my_biggy	1122	struct my_biggy
1007	{	1123	{
1008	int some_data;	1124	int some_data;
1009	ev_timer t1;	1125	ev_timer t1;
1010	ev_timer t2;	1126	ev_timer t2;
1011	}	1127	}
1012		1128
1013	In this case getting the pointer to C<my_biggy> is a bit more complicated,	1129	In this case getting the pointer to C<my_biggy> is a bit more
1014	you need to use C<offsetof>:	1130	complicated: Either you store the address of your C<my_biggy> struct
		1131	in the C<data> member of the watcher (for woozies), or you need to use
		1132	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1133	programmers):
1015		1134
1016	#include <stddef.h>	1135	#include <stddef.h>
1017		1136
1018	static void	1137	static void
1019	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1020	{	1139	{
1021	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1022	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1023	}	1142	}
1024		1143
1025	static void	1144	static void
1026	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1027	{	1146	{
1028	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1029	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1030	}	1149	}
1031		1150
…		…
1059	In general you can register as many read and/or write event watchers per	1178	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	1179	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	1180	descriptors to non-blocking mode is also usually a good idea (but not
1062	required if you know what you are doing).	1181	required if you know what you are doing).
1063		1182
1064	If you must do this, then force the use of a known-to-be-good backend	1183	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	1184	known-to-be-good backend (at the time of this writing, this includes only
1066	C<EVBACKEND_POLL>).	1185	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>).
1067		1186
1068	Another thing you have to watch out for is that it is quite easy to	1187	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	1188	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	1189	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	1190	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	1191	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	1192	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	1193	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.	1194	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1076		1195
1077	If you cannot run the fd in non-blocking mode (for example you should not	1196	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	1197	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	1198	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	1199	interface such as poll (fortunately in our Xlib example, Xlib already
1081	its own, so its quite safe to use).	1200	does this on its own, so its quite safe to use). Some people additionally
		1201	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1202	indefinitely.
		1203
		1204	But really, best use non-blocking mode.
1082		1205
1083	=head3 The special problem of disappearing file descriptors	1206	=head3 The special problem of disappearing file descriptors
1084		1207
1085	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1208	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,	1209	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	1210	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	1211	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	1212	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	1213	registered with libev, there is no efficient way to see that this is, in
1091	fact, a different file descriptor.	1214	fact, a different file descriptor.
1092		1215
…		…
1123	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1246	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1124	C<EVBACKEND_POLL>.	1247	C<EVBACKEND_POLL>.
1125		1248
1126	=head3 The special problem of SIGPIPE	1249	=head3 The special problem of SIGPIPE
1127		1250
1128	While not really specific to libev, it is easy to forget about SIGPIPE:	1251	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	1252	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	1253	sent a SIGPIPE, which, by default, aborts your program. For most programs
1131	programs this is sensible behaviour, for daemons, this is usually	1254	this is sensible behaviour, for daemons, this is usually undesirable.
1132	undesirable.
1133		1255
1134	So when you encounter spurious, unexplained daemon exits, make sure you	1256	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	1257	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).	1258	somewhere, as that would have given you a big clue).
1137		1259
…		…
1143	=item ev_io_init (ev_io *, callback, int fd, int events)	1265	=item ev_io_init (ev_io *, callback, int fd, int events)
1144		1266
1145	=item ev_io_set (ev_io *, int fd, int events)	1267	=item ev_io_set (ev_io *, int fd, int events)
1146		1268
1147	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1269	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	1270	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.	1271	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1150		1272
1151	=item int fd [read-only]	1273	=item int fd [read-only]
1152		1274
1153	The file descriptor being watched.	1275	The file descriptor being watched.
1154		1276
…		…
1163	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	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	1286	readable, but only once. Since it is likely line-buffered, you could
1165	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1166		1288
1167	static void	1289	static void
1168	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1169	{	1291	{
1170	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1171	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1172	}	1294	}
1173		1295
1174	...	1296	...
1175	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1176	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1177	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1178	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1179	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1180		1302
1181		1303
…		…
1184	Timer watchers are simple relative timers that generate an event after a	1306	Timer watchers are simple relative timers that generate an event after a
1185	given time, and optionally repeating in regular intervals after that.	1307	given time, and optionally repeating in regular intervals after that.
1186		1308
1187	The timers are based on real time, that is, if you register an event that	1309	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	1310	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	1311	year, it will still time out after (roughly) one hour. "Roughly" because
1190	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1312	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1191	monotonic clock option helps a lot here).	1313	monotonic clock option helps a lot here).
		1314
		1315	The callback is guaranteed to be invoked only I<after> its timeout has
		1316	passed, but if multiple timers become ready during the same loop iteration
		1317	then order of execution is undefined.
		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
		1494	=head3 The special problem of time updates
		1495
		1496	Establishing the current time is a costly operation (it usually takes at
		1497	least two system calls): EV therefore updates its idea of the current
		1498	time only before and after C<ev_loop> collects new events, which causes a
		1499	growing difference between C<ev_now ()> and C<ev_time ()> when handling
		1500	lots of events in one iteration.
1192		1501
1193	The relative timeouts are calculated relative to the C<ev_now ()>	1502	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	1503	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	1504	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	1505	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:	1506	timeout on the current time, use something like this to adjust for this:
1198		1507
1199	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1508	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1200		1509
1201	The callback is guaranteed to be invoked only after its timeout has passed,	1510	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	1511	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1203	order of execution is undefined.	1512	()>.
1204		1513
1205	=head3 Watcher-Specific Functions and Data Members	1514	=head3 Watcher-Specific Functions and Data Members
1206		1515
1207	=over 4	1516	=over 4
1208		1517
…		…
1232	If the timer is started but non-repeating, stop it (as if it timed out).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1233		1542
1234	If the timer is repeating, either start it if necessary (with the	1543	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.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1236		1545
1237	This sounds a bit complicated, but here is a useful and typical	1546	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	1547	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		1548
1262	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1263		1550
1264	The current C<repeat> value. Will be used each time the watcher times out	1551	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),	1552	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.	1553	which is also when any modifications are taken into account.
1267		1554
1268	=back	1555	=back
1269		1556
1270	=head3 Examples	1557	=head3 Examples
1271		1558
1272	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1273		1560
1274	static void	1561	static void
1275	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1276	{	1563	{
1277	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1278	}	1565	}
1279		1566
1280	struct ev_timer mytimer;	1567	ev_timer mytimer;
1281	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1282	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1283		1570
1284	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1285	inactivity.	1572	inactivity.
1286		1573
1287	static void	1574	static void
1288	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1289	{	1576	{
1290	.. ten seconds without any activity	1577	.. ten seconds without any activity
1291	}	1578	}
1292		1579
1293	struct ev_timer mytimer;	1580	ev_timer mytimer;
1294	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1295	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1296	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1297		1584
1298	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
…		…
1314	to trigger the event (unlike an C<ev_timer>, which would still trigger	1601	to trigger the event (unlike an C<ev_timer>, which would still trigger
1315	roughly 10 seconds later as it uses a relative timeout).	1602	roughly 10 seconds later as it uses a relative timeout).
1316		1603
1317	C<ev_periodic>s can also be used to implement vastly more complex timers,	1604	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	1605	such as triggering an event on each "midnight, local time", or other
1319	complicated, rules.	1606	complicated rules.
1320		1607
1321	As with timers, the callback is guaranteed to be invoked only when the	1608	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	1609	time (C<at>) has passed, but if multiple periodic timers become ready
1323	during the same loop iteration then order of execution is undefined.	1610	during the same loop iteration, then order of execution is undefined.
1324		1611
1325	=head3 Watcher-Specific Functions and Data Members	1612	=head3 Watcher-Specific Functions and Data Members
1326		1613
1327	=over 4	1614	=over 4
1328		1615
1329	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1616	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1330		1617
1331	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1618	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1332		1619
1333	Lots of arguments, lets sort it out... There are basically three modes of	1620	Lots of arguments, lets sort it out... There are basically three modes of
1334	operation, and we will explain them from simplest to complex:	1621	operation, and we will explain them from simplest to most complex:
1335		1622
1336	=over 4	1623	=over 4
1337		1624
1338	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1625	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1339		1626
1340	In this configuration the watcher triggers an event after the wall clock	1627	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	1628	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	1629	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.	1630	only run when the system clock reaches or surpasses this time.
1344		1631
1345	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1632	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1346		1633
1347	In this mode the watcher will always be scheduled to time out at the next	1634	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)	1635	C<at + N * interval> time (for some integer N, which can also be negative)
1349	and then repeat, regardless of any time jumps.	1636	and then repeat, regardless of any time jumps.
1350		1637
1351	This can be used to create timers that do not drift with respect to system	1638	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	1639	system clock, for example, here is a C<ev_periodic> that triggers each
1353	the hour:	1640	hour, on the hour:
1354		1641
1355	ev_periodic_set (&periodic, 0., 3600., 0);	1642	ev_periodic_set (&periodic, 0., 3600., 0);
1356		1643
1357	This doesn't mean there will always be 3600 seconds in between triggers,	1644	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	1645	but only that the callback will be called when the system time shows a
…		…
1384		1671
1385	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	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	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1387	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1388		1675
1389	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1390	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1391		1678
		1679	static ev_tstamp
1392	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1393	{	1681	{
1394	return now + 60.;	1682	return now + 60.;
1395	}	1683	}
1396		1684
1397	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1434		1722
1435	The current interval value. Can be modified any time, but changes only	1723	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	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1437	called.	1725	called.
1438		1726
1439	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1440		1728
1441	The current reschedule callback, or C<0>, if this functionality is	1729	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	1730	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.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1444		1732
1445	=back	1733	=back
1446		1734
1447	=head3 Examples	1735	=head3 Examples
1448		1736
1449	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1450	system clock is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1451	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1452		1740
1453	static void	1741	static void
1454	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1455	{	1743	{
1456	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1457	}	1745	}
1458		1746
1459	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1460	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1461	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1462		1750
1463	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1464		1752
1465	#include <math.h>	1753	#include <math.h>
1466		1754
1467	static ev_tstamp	1755	static ev_tstamp
1468	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1469	{	1757	{
1470	return fmod (now, 3600.) + 3600.;	1758	return now + (3600. - fmod (now, 3600.));
1471	}	1759	}
1472		1760
1473	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1474		1762
1475	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1476		1764
1477	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1478	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1479	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1480	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1481		1769
1482		1770
…		…
1485	Signal watchers will trigger an event when the process receives a specific	1773	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	1774	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	1775	will try it's best to deliver signals synchronously, i.e. as part of the
1488	normal event processing, like any other event.	1776	normal event processing, like any other event.
1489		1777
		1778	If you want signals asynchronously, just use C<sigaction> as you would
		1779	do without libev and forget about sharing the signal. You can even use
		1780	C<ev_async> from a signal handler to synchronously wake up an event loop.
		1781
1490	You can configure as many watchers as you like per signal. Only when the	1782	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	1783	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	1784	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	1785	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	1786	the last signal watcher for a signal is stopped, libev will reset the
1495	SIG_DFL (regardless of what it was set to before).	1787	signal handler to SIG_DFL (regardless of what it was set to before).
1496		1788
1497	If possible and supported, libev will install its handlers with	1789	If possible and supported, libev will install its handlers with
1498	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	1790	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	1791	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	1792	signals you can block all signals in an C<ev_check> watcher and unblock
…		…
1517		1809
1518	=back	1810	=back
1519		1811
1520	=head3 Examples	1812	=head3 Examples
1521		1813
1522	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1523		1815
1524	static void	1816	static void
1525	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1526	{	1818	{
1527	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1528	}	1820	}
1529		1821
1530	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1531	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1532	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1533		1825
1534		1826
1535	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1536		1828
1537	Child watchers trigger when your process receives a SIGCHLD in response to	1829	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	1830	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	1831	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	1832	has been forked (which implies it might have already exited), as long
1541	loop isn't entered (or is continued from a watcher).	1833	as the event loop isn't entered (or is continued from a watcher), i.e.,
		1834	forking and then immediately registering a watcher for the child is fine,
		1835	but forking and registering a watcher a few event loop iterations later is
		1836	not.
1542		1837
1543	Only the default event loop is capable of handling signals, and therefore	1838	Only the default event loop is capable of handling signals, and therefore
1544	you can only register child watchers in the default event loop.	1839	you can only register child watchers in the default event loop.
1545		1840
1546	=head3 Process Interaction	1841	=head3 Process Interaction
…		…
1559	handler, you can override it easily by installing your own handler for	1854	handler, you can override it easily by installing your own handler for
1560	C<SIGCHLD> after initialising the default loop, and making sure the	1855	C<SIGCHLD> after initialising the default loop, and making sure the
1561	default loop never gets destroyed. You are encouraged, however, to use an	1856	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	1857	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.	1858	that, so other libev users can use C<ev_child> watchers freely.
		1859
		1860	=head3 Stopping the Child Watcher
		1861
		1862	Currently, the child watcher never gets stopped, even when the
		1863	child terminates, so normally one needs to stop the watcher in the
		1864	callback. Future versions of libev might stop the watcher automatically
		1865	when a child exit is detected.
1564		1866
1565	=head3 Watcher-Specific Functions and Data Members	1867	=head3 Watcher-Specific Functions and Data Members
1566		1868
1567	=over 4	1869	=over 4
1568		1870
…		…
1600	its completion.	1902	its completion.
1601		1903
1602	ev_child cw;	1904	ev_child cw;
1603		1905
1604	static void	1906	static void
1605	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1606	{	1908	{
1607	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1608	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1609	}	1911	}
1610		1912
…		…
1625		1927
1626		1928
1627	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1628		1930
1629	This watches a file system path for attribute changes. That is, it calls	1931	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	1932	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.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1632		1935
1633	The path does not need to exist: changing from "path exists" to "path does	1936	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	1937	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	1938	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	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1637	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1638		1942
1639	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	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.	1945	your working directory changes, then the behaviour is undefined.
1641		1946
1642	Since there is no standard to do this, the portable implementation simply	1947	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	1948	portable implementation simply calls C<stat(2)> regularly on the path
1644	can specify a recommended polling interval for this case. If you specify	1949	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,	1950	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	1951	recommended!) then a I<suitable, unspecified default> value will be used
1647	five seconds, although this might change dynamically). Libev will also	1952	(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	1953	change dynamically). Libev will also impose a minimum interval which is
1649	usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1650		1955
1651	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1652	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1653	resource-intensive.	1958	resource-intensive.
1654		1959
1655	At the time of this writing, only the Linux inotify interface is	1960	At the time of this writing, the only OS-specific interface implemented
1656	implemented (implementing kqueue support is left as an exercise for the	1961	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	1962	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	1963	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		1964
1664	=head3 ABI Issues (Largefile Support)	1965	=head3 ABI Issues (Largefile Support)
1665		1966
1666	Libev by default (unless the user overrides this) uses the default	1967	Libev by default (unless the user overrides this) uses the default
1667	compilation environment, which means that on systems with large file	1968	compilation environment, which means that on systems with large file
1668	support disabled by default, you get the 32 bit version of the stat	1969	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	1970	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	1971	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	1972	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	1973	obviously the case with any flags that change the ABI, but the problem is
1673	most noticeably disabled with ev_stat and large file support.	1974	most noticeably displayed with ev_stat and large file support.
1674		1975
1675	The solution for this is to lobby your distribution maker to make large	1976	The solution for this is to lobby your distribution maker to make large
1676	file interfaces available by default (as e.g. FreeBSD does) and not	1977	file interfaces available by default (as e.g. FreeBSD does) and not
1677	optional. Libev cannot simply switch on large file support because it has	1978	optional. Libev cannot simply switch on large file support because it has
1678	to exchange stat structures with application programs compiled using the	1979	to exchange stat structures with application programs compiled using the
1679	default compilation environment.	1980	default compilation environment.
1680		1981
1681	=head3 Inotify	1982	=head3 Inotify and Kqueue
1682		1983
1683	When C<inotify (7)> support has been compiled into libev (generally only	1984	When C<inotify (7)> support has been compiled into libev and present at
1684	available on Linux) and present at runtime, it will be used to speed up	1985	runtime, it will be used to speed up change detection where possible. The
1685	change detection where possible. The inotify descriptor will be created lazily	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1686	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1687		1988
1688	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	Inotify presence does not change the semantics of C<ev_stat> watchers
1689	except that changes might be detected earlier, and in some cases, to avoid	1990	except that changes might be detected earlier, and in some cases, to avoid
1690	making regular C<stat> calls. Even in the presence of inotify support	1991	making regular C<stat> calls. Even in the presence of inotify support
1691	there are many cases where libev has to resort to regular C<stat> polling.	1992	there are many cases where libev has to resort to regular C<stat> polling,
		1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1692		1997
1693	(There is no support for kqueue, as apparently it cannot be used to	1998	There is no support for kqueue, as apparently it cannot be used to
1694	implement this functionality, due to the requirement of having a file	1999	implement this functionality, due to the requirement of having a file
1695	descriptor open on the object at all times).	2000	descriptor open on the object at all times, and detecting renames, unlinks
		2001	etc. is difficult.
1696		2002
1697	=head3 The special problem of stat time resolution	2003	=head3 The special problem of stat time resolution
1698		2004
1699	The C<stat ()> system call only supports full-second resolution portably, and	2005	The C<stat ()> system call only supports full-second resolution portably,
1700	even on systems where the resolution is higher, many file systems still	2006	and even on systems where the resolution is higher, most file systems
1701	only support whole seconds.	2007	still only support whole seconds.
1702		2008
1703	That means that, if the time is the only thing that changes, you can	2009	That means that, if the time is the only thing that changes, you can
1704	easily miss updates: on the first update, C<ev_stat> detects a change and	2010	easily miss updates: on the first update, C<ev_stat> detects a change and
1705	calls your callback, which does something. When there is another update	2011	calls your callback, which does something. When there is another update
1706	within the same second, C<ev_stat> will be unable to detect it as the stat	2012	within the same second, C<ev_stat> will be unable to detect unless the
1707	data does not change.	2013	stat data does change in other ways (e.g. file size).
1708		2014
1709	The solution to this is to delay acting on a change for slightly more	2015	The solution to this is to delay acting on a change for slightly more
1710	than a second (or till slightly after the next full second boundary), using	2016	than a second (or till slightly after the next full second boundary), using
1711	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2017	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1712	ev_timer_again (loop, w)>).	2018	ev_timer_again (loop, w)>).
…		…
1732	C<path>. The C<interval> is a hint on how quickly a change is expected to	2038	C<path>. The C<interval> is a hint on how quickly a change is expected to
1733	be detected and should normally be specified as C<0> to let libev choose	2039	be detected and should normally be specified as C<0> to let libev choose
1734	a suitable value. The memory pointed to by C<path> must point to the same	2040	a suitable value. The memory pointed to by C<path> must point to the same
1735	path for as long as the watcher is active.	2041	path for as long as the watcher is active.
1736		2042
1737	The callback will receive C<EV_STAT> when a change was detected, relative	2043	The callback will receive an C<EV_STAT> event when a change was detected,
1738	to the attributes at the time the watcher was started (or the last change	2044	relative to the attributes at the time the watcher was started (or the
1739	was detected).	2045	last change was detected).
1740		2046
1741	=item ev_stat_stat (loop, ev_stat *)	2047	=item ev_stat_stat (loop, ev_stat *)
1742		2048
1743	Updates the stat buffer immediately with new values. If you change the	2049	Updates the stat buffer immediately with new values. If you change the
1744	watched path in your callback, you could call this function to avoid	2050	watched path in your callback, you could call this function to avoid
…		…
1827		2133
1828		2134
1829	=head2 C<ev_idle> - when you've got nothing better to do...	2135	=head2 C<ev_idle> - when you've got nothing better to do...
1830		2136
1831	Idle watchers trigger events when no other events of the same or higher	2137	Idle watchers trigger events when no other events of the same or higher
1832	priority are pending (prepare, check and other idle watchers do not	2138	priority are pending (prepare, check and other idle watchers do not count
1833	count).	2139	as receiving "events").
1834		2140
1835	That is, as long as your process is busy handling sockets or timeouts	2141	That is, as long as your process is busy handling sockets or timeouts
1836	(or even signals, imagine) of the same or higher priority it will not be	2142	(or even signals, imagine) of the same or higher priority it will not be
1837	triggered. But when your process is idle (or only lower-priority watchers	2143	triggered. But when your process is idle (or only lower-priority watchers
1838	are pending), the idle watchers are being called once per event loop	2144	are pending), the idle watchers are being called once per event loop
…		…
1863		2169
1864	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2170	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1865	callback, free it. Also, use no error checking, as usual.	2171	callback, free it. Also, use no error checking, as usual.
1866		2172
1867	static void	2173	static void
1868	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2174	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1869	{	2175	{
1870	free (w);	2176	free (w);
1871	// now do something you wanted to do when the program has	2177	// now do something you wanted to do when the program has
1872	// no longer anything immediate to do.	2178	// no longer anything immediate to do.
1873	}	2179	}
1874		2180
1875	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1876	ev_idle_init (idle_watcher, idle_cb);	2182	ev_idle_init (idle_watcher, idle_cb);
1877	ev_idle_start (loop, idle_cb);	2183	ev_idle_start (loop, idle_cb);
1878		2184
1879		2185
1880	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1881		2187
1882	Prepare and check watchers are usually (but not always) used in tandem:	2188	Prepare and check watchers are usually (but not always) used in pairs:
1883	prepare watchers get invoked before the process blocks and check watchers	2189	prepare watchers get invoked before the process blocks and check watchers
1884	afterwards.	2190	afterwards.
1885		2191
1886	You I<must not> call C<ev_loop> or similar functions that enter	2192	You I<must not> call C<ev_loop> or similar functions that enter
1887	the current event loop from either C<ev_prepare> or C<ev_check>	2193	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1890	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2196	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1891	C<ev_check> so if you have one watcher of each kind they will always be	2197	C<ev_check> so if you have one watcher of each kind they will always be
1892	called in pairs bracketing the blocking call.	2198	called in pairs bracketing the blocking call.
1893		2199
1894	Their main purpose is to integrate other event mechanisms into libev and	2200	Their main purpose is to integrate other event mechanisms into libev and
1895	their use is somewhat advanced. This could be used, for example, to track	2201	their use is somewhat advanced. They could be used, for example, to track
1896	variable changes, implement your own watchers, integrate net-snmp or a	2202	variable changes, implement your own watchers, integrate net-snmp or a
1897	coroutine library and lots more. They are also occasionally useful if	2203	coroutine library and lots more. They are also occasionally useful if
1898	you cache some data and want to flush it before blocking (for example,	2204	you cache some data and want to flush it before blocking (for example,
1899	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2205	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1900	watcher).	2206	watcher).
1901		2207
1902	This is done by examining in each prepare call which file descriptors need	2208	This is done by examining in each prepare call which file descriptors
1903	to be watched by the other library, registering C<ev_io> watchers for	2209	need to be watched by the other library, registering C<ev_io> watchers
1904	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2210	for them and starting an C<ev_timer> watcher for any timeouts (many
1905	provide just this functionality). Then, in the check watcher you check for	2211	libraries provide exactly this functionality). Then, in the check watcher,
1906	any events that occurred (by checking the pending status of all watchers	2212	you check for any events that occurred (by checking the pending status
1907	and stopping them) and call back into the library. The I/O and timer	2213	of all watchers and stopping them) and call back into the library. The
1908	callbacks will never actually be called (but must be valid nevertheless,	2214	I/O and timer callbacks will never actually be called (but must be valid
1909	because you never know, you know?).	2215	nevertheless, because you never know, you know?).
1910		2216
1911	As another example, the Perl Coro module uses these hooks to integrate	2217	As another example, the Perl Coro module uses these hooks to integrate
1912	coroutines into libev programs, by yielding to other active coroutines	2218	coroutines into libev programs, by yielding to other active coroutines
1913	during each prepare and only letting the process block if no coroutines	2219	during each prepare and only letting the process block if no coroutines
1914	are ready to run (it's actually more complicated: it only runs coroutines	2220	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1917	loop from blocking if lower-priority coroutines are active, thus mapping	2223	loop from blocking if lower-priority coroutines are active, thus mapping
1918	low-priority coroutines to idle/background tasks).	2224	low-priority coroutines to idle/background tasks).
1919		2225
1920	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2226	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1921	priority, to ensure that they are being run before any other watchers	2227	priority, to ensure that they are being run before any other watchers
		2228	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2229
1922	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2230	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1923	too) should not activate ("feed") events into libev. While libev fully	2231	activate ("feed") events into libev. While libev fully supports this, they
1924	supports this, they might get executed before other C<ev_check> watchers	2232	might get executed before other C<ev_check> watchers did their job. As
1925	did their job. As C<ev_check> watchers are often used to embed other	2233	C<ev_check> watchers are often used to embed other (non-libev) event
1926	(non-libev) event loops those other event loops might be in an unusable	2234	loops those other event loops might be in an unusable state until their
1927	state until their C<ev_check> watcher ran (always remind yourself to	2235	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1928	coexist peacefully with others).	2236	others).
1929		2237
1930	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1931		2239
1932	=over 4	2240	=over 4
1933		2241
…		…
1935		2243
1936	=item ev_check_init (ev_check *, callback)	2244	=item ev_check_init (ev_check *, callback)
1937		2245
1938	Initialises and configures the prepare or check watcher - they have no	2246	Initialises and configures the prepare or check watcher - they have no
1939	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2247	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1940	macros, but using them is utterly, utterly and completely pointless.	2248	macros, but using them is utterly, utterly, utterly and completely
		2249	pointless.
1941		2250
1942	=back	2251	=back
1943		2252
1944	=head3 Examples	2253	=head3 Examples
1945		2254
…		…
1958		2267
1959	static ev_io iow [nfd];	2268	static ev_io iow [nfd];
1960	static ev_timer tw;	2269	static ev_timer tw;
1961		2270
1962	static void	2271	static void
1963	io_cb (ev_loop *loop, ev_io *w, int revents)	2272	io_cb (struct ev_loop *loop, ev_io *w, int revents)
1964	{	2273	{
1965	}	2274	}
1966		2275
1967	// create io watchers for each fd and a timer before blocking	2276	// create io watchers for each fd and a timer before blocking
1968	static void	2277	static void
1969	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2278	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
1970	{	2279	{
1971	int timeout = 3600000;	2280	int timeout = 3600000;
1972	struct pollfd fds [nfd];	2281	struct pollfd fds [nfd];
1973	// actual code will need to loop here and realloc etc.	2282	// actual code will need to loop here and realloc etc.
1974	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
1989	}	2298	}
1990	}	2299	}
1991		2300
1992	// stop all watchers after blocking	2301	// stop all watchers after blocking
1993	static void	2302	static void
1994	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2303	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
1995	{	2304	{
1996	ev_timer_stop (loop, &tw);	2305	ev_timer_stop (loop, &tw);
1997		2306
1998	for (int i = 0; i < nfd; ++i)	2307	for (int i = 0; i < nfd; ++i)
1999	{	2308	{
…		…
2038	}	2347	}
2039		2348
2040	// do not ever call adns_afterpoll	2349	// do not ever call adns_afterpoll
2041		2350
2042	Method 4: Do not use a prepare or check watcher because the module you	2351	Method 4: Do not use a prepare or check watcher because the module you
2043	want to embed is too inflexible to support it. Instead, you can override	2352	want to embed is not flexible enough to support it. Instead, you can
2044	their poll function. The drawback with this solution is that the main	2353	override their poll function. The drawback with this solution is that the
2045	loop is now no longer controllable by EV. The C<Glib::EV> module does	2354	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2046	this.	2355	this approach, effectively embedding EV as a client into the horrible
		2356	libglib event loop.
2047		2357
2048	static gint	2358	static gint
2049	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2359	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2050	{	2360	{
2051	int got_events = 0;	2361	int got_events = 0;
…		…
2082	prioritise I/O.	2392	prioritise I/O.
2083		2393
2084	As an example for a bug workaround, the kqueue backend might only support	2394	As an example for a bug workaround, the kqueue backend might only support
2085	sockets on some platform, so it is unusable as generic backend, but you	2395	sockets on some platform, so it is unusable as generic backend, but you
2086	still want to make use of it because you have many sockets and it scales	2396	still want to make use of it because you have many sockets and it scales
2087	so nicely. In this case, you would create a kqueue-based loop and embed it	2397	so nicely. In this case, you would create a kqueue-based loop and embed
2088	into your default loop (which might use e.g. poll). Overall operation will	2398	it into your default loop (which might use e.g. poll). Overall operation
2089	be a bit slower because first libev has to poll and then call kevent, but	2399	will be a bit slower because first libev has to call C<poll> and then
2090	at least you can use both at what they are best.	2400	C<kevent>, but at least you can use both mechanisms for what they are
		2401	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2091		2402
2092	As for prioritising I/O: rarely you have the case where some fds have	2403	As for prioritising I/O: under rare circumstances you have the case where
2093	to be watched and handled very quickly (with low latency), and even	2404	some fds have to be watched and handled very quickly (with low latency),
2094	priorities and idle watchers might have too much overhead. In this case	2405	and even priorities and idle watchers might have too much overhead. In
2095	you would put all the high priority stuff in one loop and all the rest in	2406	this case you would put all the high priority stuff in one loop and all
2096	a second one, and embed the second one in the first.	2407	the rest in a second one, and embed the second one in the first.
2097		2408
2098	As long as the watcher is active, the callback will be invoked every time	2409	As long as the watcher is active, the callback will be invoked every time
2099	there might be events pending in the embedded loop. The callback must then	2410	there might be events pending in the embedded loop. The callback must then
2100	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2411	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
2101	their callbacks (you could also start an idle watcher to give the embedded	2412	their callbacks (you could also start an idle watcher to give the embedded
…		…
2109	interested in that.	2420	interested in that.
2110		2421
2111	Also, there have not currently been made special provisions for forking:	2422	Also, there have not currently been made special provisions for forking:
2112	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2423	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2113	but you will also have to stop and restart any C<ev_embed> watchers	2424	but you will also have to stop and restart any C<ev_embed> watchers
2114	yourself.	2425	yourself - but you can use a fork watcher to handle this automatically,
		2426	and future versions of libev might do just that.
2115		2427
2116	Unfortunately, not all backends are embeddable, only the ones returned by	2428	Unfortunately, not all backends are embeddable: only the ones returned by
2117	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2118	portable one.	2430	portable one.
2119		2431
2120	So when you want to use this feature you will always have to be prepared	2432	So when you want to use this feature you will always have to be prepared
2121	that you cannot get an embeddable loop. The recommended way to get around	2433	that you cannot get an embeddable loop. The recommended way to get around
2122	this is to have a separate variables for your embeddable loop, try to	2434	this is to have a separate variables for your embeddable loop, try to
2123	create it, and if that fails, use the normal loop for everything.	2435	create it, and if that fails, use the normal loop for everything.
		2436
		2437	=head3 C<ev_embed> and fork
		2438
		2439	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2440	automatically be applied to the embedded loop as well, so no special
		2441	fork handling is required in that case. When the watcher is not running,
		2442	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2443	as applicable.
2124		2444
2125	=head3 Watcher-Specific Functions and Data Members	2445	=head3 Watcher-Specific Functions and Data Members
2126		2446
2127	=over 4	2447	=over 4
2128		2448
…		…
2156	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2476	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2157	used).	2477	used).
2158		2478
2159	struct ev_loop *loop_hi = ev_default_init (0);	2479	struct ev_loop *loop_hi = ev_default_init (0);
2160	struct ev_loop *loop_lo = 0;	2480	struct ev_loop *loop_lo = 0;
2161	struct ev_embed embed;	2481	ev_embed embed;
2162		2482
2163	// see if there is a chance of getting one that works	2483	// see if there is a chance of getting one that works
2164	// (remember that a flags value of 0 means autodetection)	2484	// (remember that a flags value of 0 means autodetection)
2165	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2166	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2180	kqueue implementation). Store the kqueue/socket-only event loop in	2500	kqueue implementation). Store the kqueue/socket-only event loop in
2181	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2182		2502
2183	struct ev_loop *loop = ev_default_init (0);	2503	struct ev_loop *loop = ev_default_init (0);
2184	struct ev_loop *loop_socket = 0;	2504	struct ev_loop *loop_socket = 0;
2185	struct ev_embed embed;	2505	ev_embed embed;
2186		2506
2187	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2188	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2189	{	2509	{
2190	ev_embed_init (&embed, 0, loop_socket);	2510	ev_embed_init (&embed, 0, loop_socket);
…		…
2246	is that the author does not know of a simple (or any) algorithm for a	2566	is that the author does not know of a simple (or any) algorithm for a
2247	multiple-writer-single-reader queue that works in all cases and doesn't	2567	multiple-writer-single-reader queue that works in all cases and doesn't
2248	need elaborate support such as pthreads.	2568	need elaborate support such as pthreads.
2249		2569
2250	That means that if you want to queue data, you have to provide your own	2570	That means that if you want to queue data, you have to provide your own
2251	queue. But at least I can tell you would implement locking around your	2571	queue. But at least I can tell you how to implement locking around your
2252	queue:	2572	queue:
2253		2573
2254	=over 4	2574	=over 4
2255		2575
2256	=item queueing from a signal handler context	2576	=item queueing from a signal handler context
2257		2577
2258	To implement race-free queueing, you simply add to the queue in the signal	2578	To implement race-free queueing, you simply add to the queue in the signal
2259	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2579	handler but you block the signal handler in the watcher callback. Here is
2260	some fictitious SIGUSR1 handler:	2580	an example that does that for some fictitious SIGUSR1 handler:
2261		2581
2262	static ev_async mysig;	2582	static ev_async mysig;
2263		2583
2264	static void	2584	static void
2265	sigusr1_handler (void)	2585	sigusr1_handler (void)
…		…
2331	=over 4	2651	=over 4
2332		2652
2333	=item ev_async_init (ev_async *, callback)	2653	=item ev_async_init (ev_async *, callback)
2334		2654
2335	Initialises and configures the async watcher - it has no parameters of any	2655	Initialises and configures the async watcher - it has no parameters of any
2336	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2656	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2337	believe me.	2657	trust me.
2338		2658
2339	=item ev_async_send (loop, ev_async *)	2659	=item ev_async_send (loop, ev_async *)
2340		2660
2341	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2661	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2342	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2662	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2343	C<ev_feed_event>, this call is safe to do in other threads, signal or	2663	C<ev_feed_event>, this call is safe to do from other threads, signal or
2344	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2664	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2345	section below on what exactly this means).	2665	section below on what exactly this means).
2346		2666
2347	This call incurs the overhead of a system call only once per loop iteration,	2667	This call incurs the overhead of a system call only once per loop iteration,
2348	so while the overhead might be noticeable, it doesn't apply to repeated	2668	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2372	=over 4	2692	=over 4
2373		2693
2374	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2694	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2375		2695
2376	This function combines a simple timer and an I/O watcher, calls your	2696	This function combines a simple timer and an I/O watcher, calls your
2377	callback on whichever event happens first and automatically stop both	2697	callback on whichever event happens first and automatically stops both
2378	watchers. This is useful if you want to wait for a single event on an fd	2698	watchers. This is useful if you want to wait for a single event on an fd
2379	or timeout without having to allocate/configure/start/stop/free one or	2699	or timeout without having to allocate/configure/start/stop/free one or
2380	more watchers yourself.	2700	more watchers yourself.
2381		2701
2382	If C<fd> is less than 0, then no I/O watcher will be started and events	2702	If C<fd> is less than 0, then no I/O watcher will be started and the
2383	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2703	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2384	C<events> set will be created and started.	2704	the given C<fd> and C<events> set will be created and started.
2385		2705
2386	If C<timeout> is less than 0, then no timeout watcher will be	2706	If C<timeout> is less than 0, then no timeout watcher will be
2387	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2707	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2388	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2708	repeat = 0) will be started. C<0> is a valid timeout.
2389	dubious value.
2390		2709
2391	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2710	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2392	passed an C<revents> set like normal event callbacks (a combination of	2711	passed an C<revents> set like normal event callbacks (a combination of
2393	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2712	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2394	value passed to C<ev_once>:	2713	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2714	a timeout and an io event at the same time - you probably should give io
		2715	events precedence.
		2716
		2717	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2395		2718
2396	static void stdin_ready (int revents, void *arg)	2719	static void stdin_ready (int revents, void *arg)
2397	{	2720	{
		2721	if (revents & EV_READ)
		2722	/* stdin might have data for us, joy! */;
2398	if (revents & EV_TIMEOUT)	2723	else if (revents & EV_TIMEOUT)
2399	/* doh, nothing entered */;	2724	/* doh, nothing entered */;
2400	else if (revents & EV_READ)
2401	/* stdin might have data for us, joy! */;
2402	}	2725	}
2403		2726
2404	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2405		2728
2406	=item ev_feed_event (ev_loop *, watcher *, int revents)	2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2407		2730
2408	Feeds the given event set into the event loop, as if the specified event	2731	Feeds the given event set into the event loop, as if the specified event
2409	had happened for the specified watcher (which must be a pointer to an	2732	had happened for the specified watcher (which must be a pointer to an
2410	initialised but not necessarily started event watcher).	2733	initialised but not necessarily started event watcher).
2411		2734
2412	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2413		2736
2414	Feed an event on the given fd, as if a file descriptor backend detected	2737	Feed an event on the given fd, as if a file descriptor backend detected
2415	the given events it.	2738	the given events it.
2416		2739
2417	=item ev_feed_signal_event (ev_loop *loop, int signum)	2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2418		2741
2419	Feed an event as if the given signal occurred (C<loop> must be the default	2742	Feed an event as if the given signal occurred (C<loop> must be the default
2420	loop!).	2743	loop!).
2421		2744
2422	=back	2745	=back
…		…
2554		2877
2555	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2878	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2556		2879
2557	See the method-C<set> above for more details.	2880	See the method-C<set> above for more details.
2558		2881
2559	Example:	2882	Example: Use a plain function as callback.
2560		2883
2561	static void io_cb (ev::io &w, int revents) { }	2884	static void io_cb (ev::io &w, int revents) { }
2562	iow.set <io_cb> ();	2885	iow.set <io_cb> ();
2563		2886
2564	=item w->set (struct ev_loop *)	2887	=item w->set (struct ev_loop *)
…		…
2602	Example: Define a class with an IO and idle watcher, start one of them in	2925	Example: Define a class with an IO and idle watcher, start one of them in
2603	the constructor.	2926	the constructor.
2604		2927
2605	class myclass	2928	class myclass
2606	{	2929	{
2607	ev::io io; void io_cb (ev::io &w, int revents);	2930	ev::io io ; void io_cb (ev::io &w, int revents);
2608	ev:idle idle void idle_cb (ev::idle &w, int revents);	2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2609		2932
2610	myclass (int fd)	2933	myclass (int fd)
2611	{	2934	{
2612	io .set <myclass, &myclass::io_cb > (this);	2935	io .set <myclass, &myclass::io_cb > (this);
2613	idle.set <myclass, &myclass::idle_cb> (this);	2936	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2629	=item Perl	2952	=item Perl
2630		2953
2631	The EV module implements the full libev API and is actually used to test	2954	The EV module implements the full libev API and is actually used to test
2632	libev. EV is developed together with libev. Apart from the EV core module,	2955	libev. EV is developed together with libev. Apart from the EV core module,
2633	there are additional modules that implement libev-compatible interfaces	2956	there are additional modules that implement libev-compatible interfaces
2634	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2957	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2635	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2958	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2959	and C<EV::Glib>).
2636		2960
2637	It can be found and installed via CPAN, its homepage is at	2961	It can be found and installed via CPAN, its homepage is at
2638	L<http://software.schmorp.de/pkg/EV>.	2962	L<http://software.schmorp.de/pkg/EV>.
2639		2963
2640	=item Python	2964	=item Python
…		…
2654	L<http://rev.rubyforge.org/>.	2978	L<http://rev.rubyforge.org/>.
2655		2979
2656	=item D	2980	=item D
2657		2981
2658	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2659	be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>.	2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		2984
		2985	=item Ocaml
		2986
		2987	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2660		2989
2661	=back	2990	=back
2662		2991
2663		2992
2664	=head1 MACRO MAGIC	2993	=head1 MACRO MAGIC
…		…
2765		3094
2766	#define EV_STANDALONE 1	3095	#define EV_STANDALONE 1
2767	#include "ev.h"	3096	#include "ev.h"
2768		3097
2769	Both header files and implementation files can be compiled with a C++	3098	Both header files and implementation files can be compiled with a C++
2770	compiler (at least, thats a stated goal, and breakage will be treated	3099	compiler (at least, that's a stated goal, and breakage will be treated
2771	as a bug).	3100	as a bug).
2772		3101
2773	You need the following files in your source tree, or in a directory	3102	You need the following files in your source tree, or in a directory
2774	in your include path (e.g. in libev/ when using -Ilibev):	3103	in your include path (e.g. in libev/ when using -Ilibev):
2775		3104
…		…
2819		3148
2820	=head2 PREPROCESSOR SYMBOLS/MACROS	3149	=head2 PREPROCESSOR SYMBOLS/MACROS
2821		3150
2822	Libev can be configured via a variety of preprocessor symbols you have to	3151	Libev can be configured via a variety of preprocessor symbols you have to
2823	define before including any of its files. The default in the absence of	3152	define before including any of its files. The default in the absence of
2824	autoconf is noted for every option.	3153	autoconf is documented for every option.
2825		3154
2826	=over 4	3155	=over 4
2827		3156
2828	=item EV_STANDALONE	3157	=item EV_STANDALONE
2829		3158
…		…
2999	When doing priority-based operations, libev usually has to linearly search	3328	When doing priority-based operations, libev usually has to linearly search
3000	all the priorities, so having many of them (hundreds) uses a lot of space	3329	all the priorities, so having many of them (hundreds) uses a lot of space
3001	and time, so using the defaults of five priorities (-2 .. +2) is usually	3330	and time, so using the defaults of five priorities (-2 .. +2) is usually
3002	fine.	3331	fine.
3003		3332
3004	If your embedding application does not need any priorities, defining these both to	3333	If your embedding application does not need any priorities, defining these
3005	C<0> will save some memory and CPU.	3334	both to C<0> will save some memory and CPU.
3006		3335
3007	=item EV_PERIODIC_ENABLE	3336	=item EV_PERIODIC_ENABLE
3008		3337
3009	If undefined or defined to be C<1>, then periodic timers are supported. If	3338	If undefined or defined to be C<1>, then periodic timers are supported. If
3010	defined to be C<0>, then they are not. Disabling them saves a few kB of	3339	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3017	code.	3346	code.
3018		3347
3019	=item EV_EMBED_ENABLE	3348	=item EV_EMBED_ENABLE
3020		3349
3021	If undefined or defined to be C<1>, then embed watchers are supported. If	3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3022	defined to be C<0>, then they are not.	3351	defined to be C<0>, then they are not. Embed watchers rely on most other
		3352	watcher types, which therefore must not be disabled.
3023		3353
3024	=item EV_STAT_ENABLE	3354	=item EV_STAT_ENABLE
3025		3355
3026	If undefined or defined to be C<1>, then stat watchers are supported. If	3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3027	defined to be C<0>, then they are not.	3357	defined to be C<0>, then they are not.
…		…
3059	two).	3389	two).
3060		3390
3061	=item EV_USE_4HEAP	3391	=item EV_USE_4HEAP
3062		3392
3063	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3064	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3065	to C<1>. The 4-heap uses more complicated (longer) code but has	3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3066	noticeably faster performance with many (thousands) of watchers.	3396	faster performance with many (thousands) of watchers.
3067		3397
3068	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3069	(disabled).	3399	(disabled).
3070		3400
3071	=item EV_HEAP_CACHE_AT	3401	=item EV_HEAP_CACHE_AT
3072		3402
3073	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3074	timer and periodics heap, libev can cache the timestamp (I<at>) within	3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3075	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3076	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3077	but avoids random read accesses on heap changes. This improves performance	3407	but avoids random read accesses on heap changes. This improves performance
3078	noticeably with with many (hundreds) of watchers.	3408	noticeably with many (hundreds) of watchers.
3079		3409
3080	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3081	(disabled).	3411	(disabled).
3082		3412
3083	=item EV_VERIFY	3413	=item EV_VERIFY
…		…
3089	called once per loop, which can slow down libev. If set to C<3>, then the	3419	called once per loop, which can slow down libev. If set to C<3>, then the
3090	verification code will be called very frequently, which will slow down	3420	verification code will be called very frequently, which will slow down
3091	libev considerably.	3421	libev considerably.
3092		3422
3093	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3094	C<0.>	3424	C<0>.
3095		3425
3096	=item EV_COMMON	3426	=item EV_COMMON
3097		3427
3098	By default, all watchers have a C<void *data> member. By redefining	3428	By default, all watchers have a C<void *data> member. By redefining
3099	this macro to a something else you can include more and other types of	3429	this macro to a something else you can include more and other types of
…		…
3116	and the way callbacks are invoked and set. Must expand to a struct member	3446	and the way callbacks are invoked and set. Must expand to a struct member
3117	definition and a statement, respectively. See the F<ev.h> header file for	3447	definition and a statement, respectively. See the F<ev.h> header file for
3118	their default definitions. One possible use for overriding these is to	3448	their default definitions. One possible use for overriding these is to
3119	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3449	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3120	method calls instead of plain function calls in C++.	3450	method calls instead of plain function calls in C++.
		3451
		3452	=back
3121		3453
3122	=head2 EXPORTED API SYMBOLS	3454	=head2 EXPORTED API SYMBOLS
3123		3455
3124	If you need to re-export the API (e.g. via a DLL) and you need a list of	3456	If you need to re-export the API (e.g. via a DLL) and you need a list of
3125	exported symbols, you can use the provided F<Symbol.*> files which list	3457	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3172	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3173		3505
3174	#include "ev_cpp.h"	3506	#include "ev_cpp.h"
3175	#include "ev.c"	3507	#include "ev.c"
3176		3508
		3509	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3177		3510
3178	=head1 THREADS AND COROUTINES	3511	=head2 THREADS AND COROUTINES
3179		3512
3180	=head2 THREADS	3513	=head3 THREADS
3181		3514
3182	Libev itself is completely thread-safe, but it uses no locking. This	3515	All libev functions are reentrant and thread-safe unless explicitly
		3516	documented otherwise, but libev implements no locking itself. This means
3183	means that you can use as many loops as you want in parallel, as long as	3517	that you can use as many loops as you want in parallel, as long as there
3184	only one thread ever calls into one libev function with the same loop	3518	are no concurrent calls into any libev function with the same loop
3185	parameter.	3519	parameter (C<ev_default_*> calls have an implicit default loop parameter,
		3520	of course): libev guarantees that different event loops share no data
		3521	structures that need any locking.
3186		3522
3187	Or put differently: calls with different loop parameters can be done in	3523	Or to put it differently: calls with different loop parameters can be done
3188	parallel from multiple threads, calls with the same loop parameter must be	3524	concurrently from multiple threads, calls with the same loop parameter
3189	done serially (but can be done from different threads, as long as only one	3525	must be done serially (but can be done from different threads, as long as
3190	thread ever is inside a call at any point in time, e.g. by using a mutex	3526	only one thread ever is inside a call at any point in time, e.g. by using
3191	per loop).	3527	a mutex per loop).
3192		3528
3193	If you want to know which design is best for your problem, then I cannot	3529	Specifically to support threads (and signal handlers), libev implements
		3530	so-called C<ev_async> watchers, which allow some limited form of
		3531	concurrency on the same event loop, namely waking it up "from the
		3532	outside".
		3533
		3534	If you want to know which design (one loop, locking, or multiple loops
		3535	without or something else still) is best for your problem, then I cannot
3194	help you but by giving some generic advice:	3536	help you, but here is some generic advice:
3195		3537
3196	=over 4	3538	=over 4
3197		3539
3198	=item * most applications have a main thread: use the default libev loop	3540	=item * most applications have a main thread: use the default libev loop
3199	in that thread, or create a separate thread running only the default loop.	3541	in that thread, or create a separate thread running only the default loop.
…		…
3211		3553
3212	Choosing a model is hard - look around, learn, know that usually you can do	3554	Choosing a model is hard - look around, learn, know that usually you can do
3213	better than you currently do :-)	3555	better than you currently do :-)
3214		3556
3215	=item * often you need to talk to some other thread which blocks in the	3557	=item * often you need to talk to some other thread which blocks in the
		3558	event loop.
		3559
3216	event loop - C<ev_async> watchers can be used to wake them up from other	3560	C<ev_async> watchers can be used to wake them up from other threads safely
3217	threads safely (or from signal contexts...).	3561	(or from signal contexts...).
		3562
		3563	An example use would be to communicate signals or other events that only
		3564	work in the default loop by registering the signal watcher with the
		3565	default loop and triggering an C<ev_async> watcher from the default loop
		3566	watcher callback into the event loop interested in the signal.
3218		3567
3219	=back	3568	=back
3220		3569
3221	=head2 COROUTINES	3570	=head3 COROUTINES
3222		3571
3223	Libev is much more accommodating to coroutines ("cooperative threads"):	3572	Libev is very accommodating to coroutines ("cooperative threads"):
3224	libev fully supports nesting calls to it's functions from different	3573	libev fully supports nesting calls to its functions from different
3225	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3226	different coroutines and switch freely between both coroutines running the	3575	different coroutines, and switch freely between both coroutines running the
3227	loop, as long as you don't confuse yourself). The only exception is that	3576	loop, as long as you don't confuse yourself). The only exception is that
3228	you must not do this from C<ev_periodic> reschedule callbacks.	3577	you must not do this from C<ev_periodic> reschedule callbacks.
3229		3578
3230	Care has been invested into making sure that libev does not keep local	3579	Care has been taken to ensure that libev does not keep local state inside
3231	state inside C<ev_loop>, and other calls do not usually allow coroutine	3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3232	switches.	3581	they do not call any callbacks.
3233		3582
		3583	=head2 COMPILER WARNINGS
3234		3584
3235	=head1 COMPLEXITIES	3585	Depending on your compiler and compiler settings, you might get no or a
		3586	lot of warnings when compiling libev code. Some people are apparently
		3587	scared by this.
3236		3588
3237	In this section the complexities of (many of) the algorithms used inside	3589	However, these are unavoidable for many reasons. For one, each compiler
3238	libev will be explained. For complexity discussions about backends see the	3590	has different warnings, and each user has different tastes regarding
3239	documentation for C<ev_default_init>.	3591	warning options. "Warn-free" code therefore cannot be a goal except when
		3592	targeting a specific compiler and compiler-version.
3240		3593
3241	All of the following are about amortised time: If an array needs to be	3594	Another reason is that some compiler warnings require elaborate
3242	extended, libev needs to realloc and move the whole array, but this	3595	workarounds, or other changes to the code that make it less clear and less
3243	happens asymptotically never with higher number of elements, so O(1) might	3596	maintainable.
3244	mean it might do a lengthy realloc operation in rare cases, but on average
3245	it is much faster and asymptotically approaches constant time.
3246		3597
3247	=over 4	3598	And of course, some compiler warnings are just plain stupid, or simply
		3599	wrong (because they don't actually warn about the condition their message
		3600	seems to warn about). For example, certain older gcc versions had some
		3601	warnings that resulted an extreme number of false positives. These have
		3602	been fixed, but some people still insist on making code warn-free with
		3603	such buggy versions.
3248		3604
3249	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3605	While libev is written to generate as few warnings as possible,
		3606	"warn-free" code is not a goal, and it is recommended not to build libev
		3607	with any compiler warnings enabled unless you are prepared to cope with
		3608	them (e.g. by ignoring them). Remember that warnings are just that:
		3609	warnings, not errors, or proof of bugs.
3250		3610
3251	This means that, when you have a watcher that triggers in one hour and
3252	there are 100 watchers that would trigger before that then inserting will
3253	have to skip roughly seven (C<ld 100>) of these watchers.
3254		3611
3255	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3612	=head2 VALGRIND
3256		3613
3257	That means that changing a timer costs less than removing/adding them	3614	Valgrind has a special section here because it is a popular tool that is
3258	as only the relative motion in the event queue has to be paid for.	3615	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3259		3616
3260	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3617	If you think you found a bug (memory leak, uninitialised data access etc.)
		3618	in libev, then check twice: If valgrind reports something like:
3261		3619
3262	These just add the watcher into an array or at the head of a list.	3620	==2274== definitely lost: 0 bytes in 0 blocks.
		3621	==2274== possibly lost: 0 bytes in 0 blocks.
		3622	==2274== still reachable: 256 bytes in 1 blocks.
3263		3623
3264	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3624	Then there is no memory leak, just as memory accounted to global variables
		3625	is not a memleak - the memory is still being referenced, and didn't leak.
3265		3626
3266	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3627	Similarly, under some circumstances, valgrind might report kernel bugs
		3628	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3629	although an acceptable workaround has been found here), or it might be
		3630	confused.
3267		3631
3268	These watchers are stored in lists then need to be walked to find the	3632	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3269	correct watcher to remove. The lists are usually short (you don't usually	3633	make it into some kind of religion.
3270	have many watchers waiting for the same fd or signal).
3271		3634
3272	=item Finding the next timer in each loop iteration: O(1)	3635	If you are unsure about something, feel free to contact the mailing list
		3636	with the full valgrind report and an explanation on why you think this
		3637	is a bug in libev (best check the archives, too :). However, don't be
		3638	annoyed when you get a brisk "this is no bug" answer and take the chance
		3639	of learning how to interpret valgrind properly.
3273		3640
3274	By virtue of using a binary or 4-heap, the next timer is always found at a	3641	If you need, for some reason, empty reports from valgrind for your project
3275	fixed position in the storage array.	3642	I suggest using suppression lists.
3276		3643
3277	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3278		3644
3279	A change means an I/O watcher gets started or stopped, which requires	3645	=head1 PORTABILITY NOTES
3280	libev to recalculate its status (and possibly tell the kernel, depending
3281	on backend and whether C<ev_io_set> was used).
3282		3646
3283	=item Activating one watcher (putting it into the pending state): O(1)
3284
3285	=item Priority handling: O(number_of_priorities)
3286
3287	Priorities are implemented by allocating some space for each
3288	priority. When doing priority-based operations, libev usually has to
3289	linearly search all the priorities, but starting/stopping and activating
3290	watchers becomes O(1) w.r.t. priority handling.
3291
3292	=item Sending an ev_async: O(1)
3293
3294	=item Processing ev_async_send: O(number_of_async_watchers)
3295
3296	=item Processing signals: O(max_signal_number)
3297
3298	Sending involves a system call I<iff> there were no other C<ev_async_send>
3299	calls in the current loop iteration. Checking for async and signal events
3300	involves iterating over all running async watchers or all signal numbers.
3301
3302	=back
3303
3304
3305	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3306		3648
3307	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3308	requires, and its I/O model is fundamentally incompatible with the POSIX	3650	requires, and its I/O model is fundamentally incompatible with the POSIX
3309	model. Libev still offers limited functionality on this platform in	3651	model. Libev still offers limited functionality on this platform in
3310	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3321		3663
3322	Not a libev limitation but worth mentioning: windows apparently doesn't	3664	Not a libev limitation but worth mentioning: windows apparently doesn't
3323	accept large writes: instead of resulting in a partial write, windows will	3665	accept large writes: instead of resulting in a partial write, windows will
3324	either accept everything or return C<ENOBUFS> if the buffer is too large,	3666	either accept everything or return C<ENOBUFS> if the buffer is too large,
3325	so make sure you only write small amounts into your sockets (less than a	3667	so make sure you only write small amounts into your sockets (less than a
3326	megabyte seems safe, but thsi apparently depends on the amount of memory	3668	megabyte seems safe, but this apparently depends on the amount of memory
3327	available).	3669	available).
3328		3670
3329	Due to the many, low, and arbitrary limits on the win32 platform and	3671	Due to the many, low, and arbitrary limits on the win32 platform and
3330	the abysmal performance of winsockets, using a large number of sockets	3672	the abysmal performance of winsockets, using a large number of sockets
3331	is not recommended (and not reasonable). If your program needs to use	3673	is not recommended (and not reasonable). If your program needs to use
…		…
3342	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3684	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3343		3685
3344	#include "ev.h"	3686	#include "ev.h"
3345		3687
3346	And compile the following F<evwrap.c> file into your project (make sure	3688	And compile the following F<evwrap.c> file into your project (make sure
3347	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3689	you do I<not> compile the F<ev.c> or any other embedded source files!):
3348		3690
3349	#include "evwrap.h"	3691	#include "evwrap.h"
3350	#include "ev.c"	3692	#include "ev.c"
3351		3693
3352	=over 4	3694	=over 4
…		…
3397	wrap all I/O functions and provide your own fd management, but the cost of	3739	wrap all I/O functions and provide your own fd management, but the cost of
3398	calling select (O(n²)) will likely make this unworkable.	3740	calling select (O(n²)) will likely make this unworkable.
3399		3741
3400	=back	3742	=back
3401		3743
3402
3403	=head1 PORTABILITY REQUIREMENTS	3744	=head2 PORTABILITY REQUIREMENTS
3404		3745
3405	In addition to a working ISO-C implementation, libev relies on a few	3746	In addition to a working ISO-C implementation and of course the
3406	additional extensions:	3747	backend-specific APIs, libev relies on a few additional extensions:
3407		3748
3408	=over 4	3749	=over 4
3409		3750
3410	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3751	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3411	calling conventions regardless of C<ev_watcher_type *>.	3752	calling conventions regardless of C<ev_watcher_type *>.
…		…
3417	calls them using an C<ev_watcher *> internally.	3758	calls them using an C<ev_watcher *> internally.
3418		3759
3419	=item C<sig_atomic_t volatile> must be thread-atomic as well	3760	=item C<sig_atomic_t volatile> must be thread-atomic as well
3420		3761
3421	The type C<sig_atomic_t volatile> (or whatever is defined as	3762	The type C<sig_atomic_t volatile> (or whatever is defined as
3422	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3423	threads. This is not part of the specification for C<sig_atomic_t>, but is	3764	threads. This is not part of the specification for C<sig_atomic_t>, but is
3424	believed to be sufficiently portable.	3765	believed to be sufficiently portable.
3425		3766
3426	=item C<sigprocmask> must work in a threaded environment	3767	=item C<sigprocmask> must work in a threaded environment
3427		3768
…		…
3436	except the initial one, and run the default loop in the initial thread as	3777	except the initial one, and run the default loop in the initial thread as
3437	well.	3778	well.
3438		3779
3439	=item C<long> must be large enough for common memory allocation sizes	3780	=item C<long> must be large enough for common memory allocation sizes
3440		3781
3441	To improve portability and simplify using libev, libev uses C<long>	3782	To improve portability and simplify its API, libev uses C<long> internally
3442	internally instead of C<size_t> when allocating its data structures. On	3783	instead of C<size_t> when allocating its data structures. On non-POSIX
3443	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3784	systems (Microsoft...) this might be unexpectedly low, but is still at
3444	is still at least 31 bits everywhere, which is enough for hundreds of	3785	least 31 bits everywhere, which is enough for hundreds of millions of
3445	millions of watchers.	3786	watchers.
3446		3787
3447	=item C<double> must hold a time value in seconds with enough accuracy	3788	=item C<double> must hold a time value in seconds with enough accuracy
3448		3789
3449	The type C<double> is used to represent timestamps. It is required to	3790	The type C<double> is used to represent timestamps. It is required to
3450	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3454	=back	3795	=back
3455		3796
3456	If you know of other additional requirements drop me a note.	3797	If you know of other additional requirements drop me a note.
3457		3798
3458		3799
3459	=head1 COMPILER WARNINGS	3800	=head1 ALGORITHMIC COMPLEXITIES
3460		3801
3461	Depending on your compiler and compiler settings, you might get no or a	3802	In this section the complexities of (many of) the algorithms used inside
3462	lot of warnings when compiling libev code. Some people are apparently	3803	libev will be documented. For complexity discussions about backends see
3463	scared by this.	3804	the documentation for C<ev_default_init>.
3464		3805
3465	However, these are unavoidable for many reasons. For one, each compiler	3806	All of the following are about amortised time: If an array needs to be
3466	has different warnings, and each user has different tastes regarding	3807	extended, libev needs to realloc and move the whole array, but this
3467	warning options. "Warn-free" code therefore cannot be a goal except when	3808	happens asymptotically rarer with higher number of elements, so O(1) might
3468	targeting a specific compiler and compiler-version.	3809	mean that libev does a lengthy realloc operation in rare cases, but on
		3810	average it is much faster and asymptotically approaches constant time.
3469		3811
3470	Another reason is that some compiler warnings require elaborate	3812	=over 4
3471	workarounds, or other changes to the code that make it less clear and less
3472	maintainable.
3473		3813
3474	And of course, some compiler warnings are just plain stupid, or simply	3814	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3475	wrong (because they don't actually warn about the condition their message
3476	seems to warn about).
3477		3815
3478	While libev is written to generate as few warnings as possible,	3816	This means that, when you have a watcher that triggers in one hour and
3479	"warn-free" code is not a goal, and it is recommended not to build libev	3817	there are 100 watchers that would trigger before that, then inserting will
3480	with any compiler warnings enabled unless you are prepared to cope with	3818	have to skip roughly seven (C<ld 100>) of these watchers.
3481	them (e.g. by ignoring them). Remember that warnings are just that:
3482	warnings, not errors, or proof of bugs.
3483		3819
		3820	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3484		3821
3485	=head1 VALGRIND	3822	That means that changing a timer costs less than removing/adding them,
		3823	as only the relative motion in the event queue has to be paid for.
3486		3824
3487	Valgrind has a special section here because it is a popular tool that is	3825	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3488	highly useful, but valgrind reports are very hard to interpret.
3489		3826
3490	If you think you found a bug (memory leak, uninitialised data access etc.)	3827	These just add the watcher into an array or at the head of a list.
3491	in libev, then check twice: If valgrind reports something like:
3492		3828
3493	==2274== definitely lost: 0 bytes in 0 blocks.	3829	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3494	==2274== possibly lost: 0 bytes in 0 blocks.
3495	==2274== still reachable: 256 bytes in 1 blocks.
3496		3830
3497	Then there is no memory leak. Similarly, under some circumstances,	3831	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3498	valgrind might report kernel bugs as if it were a bug in libev, or it
3499	might be confused (it is a very good tool, but only a tool).
3500		3832
3501	If you are unsure about something, feel free to contact the mailing list	3833	These watchers are stored in lists, so they need to be walked to find the
3502	with the full valgrind report and an explanation on why you think this is	3834	correct watcher to remove. The lists are usually short (you don't usually
3503	a bug in libev. However, don't be annoyed when you get a brisk "this is	3835	have many watchers waiting for the same fd or signal: one is typical, two
3504	no bug" answer and take the chance of learning how to interpret valgrind	3836	is rare).
3505	properly.
3506		3837
3507	If you need, for some reason, empty reports from valgrind for your project	3838	=item Finding the next timer in each loop iteration: O(1)
3508	I suggest using suppression lists.	3839
		3840	By virtue of using a binary or 4-heap, the next timer is always found at a
		3841	fixed position in the storage array.
		3842
		3843	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3844
		3845	A change means an I/O watcher gets started or stopped, which requires
		3846	libev to recalculate its status (and possibly tell the kernel, depending
		3847	on backend and whether C<ev_io_set> was used).
		3848
		3849	=item Activating one watcher (putting it into the pending state): O(1)
		3850
		3851	=item Priority handling: O(number_of_priorities)
		3852
		3853	Priorities are implemented by allocating some space for each
		3854	priority. When doing priority-based operations, libev usually has to
		3855	linearly search all the priorities, but starting/stopping and activating
		3856	watchers becomes O(1) with respect to priority handling.
		3857
		3858	=item Sending an ev_async: O(1)
		3859
		3860	=item Processing ev_async_send: O(number_of_async_watchers)
		3861
		3862	=item Processing signals: O(max_signal_number)
		3863
		3864	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3865	calls in the current loop iteration. Checking for async and signal events
		3866	involves iterating over all running async watchers or all signal numbers.
		3867
		3868	=back
3509		3869
3510		3870
3511	=head1 AUTHOR	3871	=head1 AUTHOR
3512		3872
3513	Marc Lehmann <libev@schmorp.de>.	3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3514		3874

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