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…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
60		62
61	// unloop was called, so exit	63	// unloop was called, so exit
62	return 0;	64	return 0;
63	}	65	}
64		66
65	=head1 DESCRIPTION	67	=head1 ABOUT THIS DOCUMENT
		68
		69	This document documents the libev software package.
66		70
67	The newest version of this document is also available as an html-formatted	71	The newest version of this document is also available as an html-formatted
68	web page you might find easier to navigate when reading it for the first	72	web page you might find easier to navigate when reading it for the first
69	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.	73	time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>.
		74
		75	While this document tries to be as complete as possible in documenting
		76	libev, its usage and the rationale behind its design, it is not a tutorial
		77	on event-based programming, nor will it introduce event-based programming
		78	with libev.
		79
		80	Familarity with event based programming techniques in general is assumed
		81	throughout this document.
		82
		83	=head1 ABOUT LIBEV
70		84
71	Libev is an event loop: you register interest in certain events (such as a	85	Libev is an event loop: you register interest in certain events (such as a
72	file descriptor being readable or a timeout occurring), and it will manage	86	file descriptor being readable or a timeout occurring), and it will manage
73	these event sources and provide your program with events.	87	these event sources and provide your program with events.
74		88
…		…
84	=head2 FEATURES	98	=head2 FEATURES
85		99
86	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
87	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
88	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
89	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
90	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
91	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
92	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
93	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
94	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
95	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
96		111
97	It also is quite fast (see this	112	It also is quite fast (see this
98	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
99	for example).	114	for example).
100		115
…		…
103	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	121	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	122	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	123	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	124	this argument.
110		125
111	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
112		127
113	Libev represents time as a single floating point number, representing the	128	Libev represents time as a single floating point number, representing
114	(fractional) number of seconds since the (POSIX) epoch (somewhere near	129	the (fractional) number of seconds since the (POSIX) epoch (somewhere
115	the beginning of 1970, details are complicated, don't ask). This type is	130	near the beginning of 1970, details are complicated, don't ask). This
116	called C<ev_tstamp>, which is what you should use too. It usually aliases	131	type is called C<ev_tstamp>, which is what you should use too. It usually
117	to the C<double> type in C, and when you need to do any calculations on	132	aliases to the C<double> type in C. When you need to do any calculations
118	it, you should treat it as some floating point value. Unlike the name	133	on it, you should treat it as some floating point value. Unlike the name
119	component C<stamp> might indicate, it is also used for time differences	134	component C<stamp> might indicate, it is also used for time differences
120	throughout libev.	135	throughout libev.
121		136
122	=head1 ERROR HANDLING	137	=head1 ERROR HANDLING
123		138
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	229	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	230	recommended ones.
216		231
217	See the description of C<ev_embed> watchers for more info.	232	See the description of C<ev_embed> watchers for more info.
218		233
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	234	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		235
221	Sets the allocation function to use (the prototype is similar - the	236	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	237	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	238	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	239	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	265	}
251		266
252	...	267	...
253	ev_set_allocator (persistent_realloc);	268	ev_set_allocator (persistent_realloc);
254		269
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	270	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		271
257	Set the callback function to call on a retryable system call error (such	272	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	273	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	274	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	275	callback is set, then libev will expect it to remedy the situation, no
…		…
276		291
277	=back	292	=back
278		293
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	294	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		295
281	An event loop is described by a C<struct ev_loop *>. The library knows two	296	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	297	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	298	I<function>).
		299
		300	The library knows two types of such loops, the I<default> loop, which
		301	supports signals and child events, and dynamically created loops which do
		302	not.
284		303
285	=over 4	304	=over 4
286		305
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	306	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		307
…		…
294	If you don't know what event loop to use, use the one returned from this	313	If you don't know what event loop to use, use the one returned from this
295	function.	314	function.
296		315
297	Note that this function is I<not> thread-safe, so if you want to use it	316	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,	317	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	318	as loops cannot be shared easily between threads anyway).
300		319
301	The default loop is the only loop that can handle C<ev_signal> and	320	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	321	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	322	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	323	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
344	flag.	363	flag.
345		364
346	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
347	environment variable.	366	environment variable.
348		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
		382
349	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
350		384
351	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
352	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
353	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
377	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and	411	This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and
378	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>.
379		413
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
		418
382	For few fds, this backend is a bit little slower than poll and select,	419	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	420	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	421	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	422	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	423
387	cases and requiring a system call per fd change, no fork support and bad	424	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	425	of the more advanced event mechanisms: mere annoyances include silently
		426	dropping file descriptors, requiring a system call per change per file
		427	descriptor (and unnecessary guessing of parameters), problems with dup and
		428	so on. The biggest issue is fork races, however - if a program forks then
		429	I<both> parent and child process have to recreate the epoll set, which can
		430	take considerable time (one syscall per file descriptor) and is of course
		431	hard to detect.
		432
		433	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		434	of course I<doesn't>, and epoll just loves to report events for totally
		435	I<different> file descriptors (even already closed ones, so one cannot
		436	even remove them from the set) than registered in the set (especially
		437	on SMP systems). Libev tries to counter these spurious notifications by
		438	employing an additional generation counter and comparing that against the
		439	events to filter out spurious ones, recreating the set when required.
389		440
390	While stopping, setting and starting an I/O watcher in the same iteration	441	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	442	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	443	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	444	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	445	file descriptors might not work very well if you register events for both
395		446	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		447
400	Best performance from this backend is achieved by not unregistering all	448	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible, i.e.	449	watchers for a file descriptor until it has been closed, if possible,
402	keep at least one watcher active per fd at all times.	450	i.e. keep at least one watcher active per fd at all times. Stopping and
		451	starting a watcher (without re-setting it) also usually doesn't cause
		452	extra overhead. A fork can both result in spurious notifications as well
		453	as in libev having to destroy and recreate the epoll object, which can
		454	take considerable time and thus should be avoided.
		455
		456	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		457	faster than epoll for maybe up to a hundred file descriptors, depending on
		458	the usage. So sad.
403		459
404	While nominally embeddable in other event loops, this feature is broken in	460	While nominally embeddable in other event loops, this feature is broken in
405	all kernel versions tested so far.	461	all kernel versions tested so far.
406		462
407	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	463	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
…		…
410	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	466	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
411		467
412	Kqueue deserves special mention, as at the time of this writing, it	468	Kqueue deserves special mention, as at the time of this writing, it
413	was broken on all BSDs except NetBSD (usually it doesn't work reliably	469	was broken on all BSDs except NetBSD (usually it doesn't work reliably
414	with anything but sockets and pipes, except on Darwin, where of course	470	with anything but sockets and pipes, except on Darwin, where of course
415	it's completely useless). For this reason it's not being "auto-detected"	471	it's completely useless). Unlike epoll, however, whose brokenness
		472	is by design, these kqueue bugs can (and eventually will) be fixed
		473	without API changes to existing programs. For this reason it's not being
416	unless you explicitly specify it explicitly in the flags (i.e. using	474	"auto-detected" unless you explicitly specify it in the flags (i.e. using
417	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)	475	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
418	system like NetBSD.	476	system like NetBSD.
419		477
420	You still can embed kqueue into a normal poll or select backend and use it	478	You still can embed kqueue into a normal poll or select backend and use it
421	only for sockets (after having made sure that sockets work with kqueue on	479	only for sockets (after having made sure that sockets work with kqueue on
…		…
423		481
424	It scales in the same way as the epoll backend, but the interface to the	482	It scales in the same way as the epoll backend, but the interface to the
425	kernel is more efficient (which says nothing about its actual speed, of	483	kernel is more efficient (which says nothing about its actual speed, of
426	course). While stopping, setting and starting an I/O watcher does never	484	course). While stopping, setting and starting an I/O watcher does never
427	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	485	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
428	two event changes per incident, support for C<fork ()> is very bad and it	486	two event changes per incident. Support for C<fork ()> is very bad (but
429	drops fds silently in similarly hard-to-detect cases.	487	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		488	cases
430		489
431	This backend usually performs well under most conditions.	490	This backend usually performs well under most conditions.
432		491
433	While nominally embeddable in other event loops, this doesn't work	492	While nominally embeddable in other event loops, this doesn't work
434	everywhere, so you might need to test for this. And since it is broken	493	everywhere, so you might need to test for this. And since it is broken
435	almost everywhere, you should only use it when you have a lot of sockets	494	almost everywhere, you should only use it when you have a lot of sockets
436	(for which it usually works), by embedding it into another event loop	495	(for which it usually works), by embedding it into another event loop
437	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for	496	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
438	sockets.	497	also broken on OS X)) and, did I mention it, using it only for sockets.
439		498
440	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	499	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
441	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	500	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
442	C<NOTE_EOF>.	501	C<NOTE_EOF>.
443		502
…		…
460	While this backend scales well, it requires one system call per active	519	While this backend scales well, it requires one system call per active
461	file descriptor per loop iteration. For small and medium numbers of file	520	file descriptor per loop iteration. For small and medium numbers of file
462	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend	521	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
463	might perform better.	522	might perform better.
464		523
465	On the positive side, ignoring the spurious readiness notifications, this	524	On the positive side, with the exception of the spurious readiness
466	backend actually performed to specification in all tests and is fully	525	notifications, this backend actually performed fully to specification
467	embeddable, which is a rare feat among the OS-specific backends.	526	in all tests and is fully embeddable, which is a rare feat among the
		527	OS-specific backends (I vastly prefer correctness over speed hacks).
468		528
469	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	529	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
470	C<EVBACKEND_POLL>.	530	C<EVBACKEND_POLL>.
471		531
472	=item C<EVBACKEND_ALL>	532	=item C<EVBACKEND_ALL>
…		…
477		537
478	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
479		539
480	=back	540	=back
481		541
482	If one or more of these are or'ed into the flags value, then only these	542	If one or more of the backend flags are or'ed into the flags value,
483	backends will be tried (in the reverse order as listed here). If none are	543	then only these backends will be tried (in the reverse order as listed
484	specified, all backends in C<ev_recommended_backends ()> will be tried.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
485		546
486	The most typical usage is like this:	547	Example: This is the most typical usage.
487		548
488	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
489	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
490		551
491	Restrict libev to the select and poll backends, and do not allow	552	Example: Restrict libev to the select and poll backends, and do not allow
492	environment settings to be taken into account:	553	environment settings to be taken into account:
493		554
494	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);	555	ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
495		556
496	Use whatever libev has to offer, but make sure that kqueue is used if	557	Example: Use whatever libev has to offer, but make sure that kqueue is
497	available (warning, breaks stuff, best use only with your own private	558	used if available (warning, breaks stuff, best use only with your own
498	event loop and only if you know the OS supports your types of fds):	559	private event loop and only if you know the OS supports your types of
		560	fds):
499		561
500	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);	562	ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
501		563
502	=item struct ev_loop *ev_loop_new (unsigned int flags)	564	=item struct ev_loop *ev_loop_new (unsigned int flags)
503		565
…		…
524	responsibility to either stop all watchers cleanly yourself I<before>	586	responsibility to either stop all watchers cleanly yourself I<before>
525	calling this function, or cope with the fact afterwards (which is usually	587	calling this function, or cope with the fact afterwards (which is usually
526	the easiest thing, you can just ignore the watchers and/or C<free ()> them	588	the easiest thing, you can just ignore the watchers and/or C<free ()> them
527	for example).	589	for example).
528		590
529	Note that certain global state, such as signal state, will not be freed by	591	Note that certain global state, such as signal state (and installed signal
530	this function, and related watchers (such as signal and child watchers)	592	handlers), will not be freed by this function, and related watchers (such
531	would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
532		594
533	In general it is not advisable to call this function except in the	595	In general it is not advisable to call this function except in the
534	rare occasion where you really need to free e.g. the signal handling	596	rare occasion where you really need to free e.g. the signal handling
535	pipe fds. If you need dynamically allocated loops it is better to use	597	pipe fds. If you need dynamically allocated loops it is better to use
536	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
537		599
538	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
539		601
540	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
541	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
561		623
562	=item ev_loop_fork (loop)	624	=item ev_loop_fork (loop)
563		625
564	Like C<ev_default_fork>, but acts on an event loop created by	626	Like C<ev_default_fork>, but acts on an event loop created by
565	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	627	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
566	after fork, and how you do this is entirely your own problem.	628	after fork that you want to re-use in the child, and how you do this is
		629	entirely your own problem.
567		630
568	=item int ev_is_default_loop (loop)	631	=item int ev_is_default_loop (loop)
569		632
570	Returns true when the given loop actually is the default loop, false otherwise.	633	Returns true when the given loop is, in fact, the default loop, and false
		634	otherwise.
571		635
572	=item unsigned int ev_loop_count (loop)	636	=item unsigned int ev_loop_count (loop)
573		637
574	Returns the count of loop iterations for the loop, which is identical to	638	Returns the count of loop iterations for the loop, which is identical to
575	the number of times libev did poll for new events. It starts at C<0> and	639	the number of times libev did poll for new events. It starts at C<0> and
576	happily wraps around with enough iterations.	640	happily wraps around with enough iterations.
577		641
578	This value can sometimes be useful as a generation counter of sorts (it	642	This value can sometimes be useful as a generation counter of sorts (it
579	"ticks" the number of loop iterations), as it roughly corresponds with	643	"ticks" the number of loop iterations), as it roughly corresponds with
580	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
581		657
582	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
583		659
584	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
585	use.	661	use.
…		…
600		676
601	This function is rarely useful, but when some event callback runs for a	677	This function is rarely useful, but when some event callback runs for a
602	very long time without entering the event loop, updating libev's idea of	678	very long time without entering the event loop, updating libev's idea of
603	the current time is a good idea.	679	the current time is a good idea.
604		680
605	See also "The special problem of time updates" in the C<ev_timer> section.	681	See also L<The special problem of time updates> in the C<ev_timer> section.
		682
		683	=item ev_suspend (loop)
		684
		685	=item ev_resume (loop)
		686
		687	These two functions suspend and resume a loop, for use when the loop is
		688	not used for a while and timeouts should not be processed.
		689
		690	A typical use case would be an interactive program such as a game: When
		691	the user presses C<^Z> to suspend the game and resumes it an hour later it
		692	would be best to handle timeouts as if no time had actually passed while
		693	the program was suspended. This can be achieved by calling C<ev_suspend>
		694	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		695	C<ev_resume> directly afterwards to resume timer processing.
		696
		697	Effectively, all C<ev_timer> watchers will be delayed by the time spend
		698	between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
		699	will be rescheduled (that is, they will lose any events that would have
		700	occured while suspended).
		701
		702	After calling C<ev_suspend> you B<must not> call I<any> function on the
		703	given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
		704	without a previous call to C<ev_suspend>.
		705
		706	Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the
		707	event loop time (see C<ev_now_update>).
606		708
607	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
608		710
609	Finally, this is it, the event handler. This function usually is called	711	Finally, this is it, the event handler. This function usually is called
610	after you initialised all your watchers and you want to start handling	712	after you have initialised all your watchers and you want to start
611	events.	713	handling events.
612		714
613	If the flags argument is specified as C<0>, it will not return until	715	If the flags argument is specified as C<0>, it will not return until
614	either no event watchers are active anymore or C<ev_unloop> was called.	716	either no event watchers are active anymore or C<ev_unloop> was called.
615		717
616	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
617	relying on all watchers to be stopped when deciding when a program has	719	relying on all watchers to be stopped when deciding when a program has
618	finished (especially in interactive programs), but having a program that	720	finished (especially in interactive programs), but having a program
619	automatically loops as long as it has to and no longer by virtue of	721	that automatically loops as long as it has to and no longer by virtue
620	relying on its watchers stopping correctly is a thing of beauty.	722	of relying on its watchers stopping correctly, that is truly a thing of
		723	beauty.
621		724
622	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle	725	A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
623	those events and any outstanding ones, but will not block your process in	726	those events and any already outstanding ones, but will not block your
624	case there are no events and will return after one iteration of the loop.	727	process in case there are no events and will return after one iteration of
		728	the loop.
625		729
626	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	730	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
627	necessary) and will handle those and any outstanding ones. It will block	731	necessary) and will handle those and any already outstanding ones. It
628	your process until at least one new event arrives, and will return after	732	will block your process until at least one new event arrives (which could
629	one iteration of the loop. This is useful if you are waiting for some	733	be an event internal to libev itself, so there is no guarantee that a
630	external event in conjunction with something not expressible using other	734	user-registered callback will be called), and will return after one
		735	iteration of the loop.
		736
		737	This is useful if you are waiting for some external event in conjunction
		738	with something not expressible using other libev watchers (i.e. "roll your
631	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	739	own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is
632	usually a better approach for this kind of thing.	740	usually a better approach for this kind of thing.
633		741
634	Here are the gory details of what C<ev_loop> does:	742	Here are the gory details of what C<ev_loop> does:
635		743
636	- Before the first iteration, call any pending watchers.	744	- Before the first iteration, call any pending watchers.
…		…
646	any active watchers at all will result in not sleeping).	754	any active watchers at all will result in not sleeping).
647	- Sleep if the I/O and timer collect interval say so.	755	- Sleep if the I/O and timer collect interval say so.
648	- Block the process, waiting for any events.	756	- Block the process, waiting for any events.
649	- Queue all outstanding I/O (fd) events.	757	- Queue all outstanding I/O (fd) events.
650	- Update the "event loop time" (ev_now ()), and do time jump adjustments.	758	- Update the "event loop time" (ev_now ()), and do time jump adjustments.
651	- Queue all outstanding timers.	759	- Queue all expired timers.
652	- Queue all outstanding periodics.	760	- Queue all expired periodics.
653	- Unless any events are pending now, queue all idle watchers.	761	- Unless any events are pending now, queue all idle watchers.
654	- Queue all check watchers.	762	- Queue all check watchers.
655	- Call all queued watchers in reverse order (i.e. check watchers first).	763	- Call all queued watchers in reverse order (i.e. check watchers first).
656	Signals and child watchers are implemented as I/O watchers, and will	764	Signals and child watchers are implemented as I/O watchers, and will
657	be handled here by queueing them when their watcher gets executed.	765	be handled here by queueing them when their watcher gets executed.
…		…
674	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	782	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
675	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	783	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
676		784
677	This "unloop state" will be cleared when entering C<ev_loop> again.	785	This "unloop state" will be cleared when entering C<ev_loop> again.
678		786
		787	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		788
679	=item ev_ref (loop)	789	=item ev_ref (loop)
680		790
681	=item ev_unref (loop)	791	=item ev_unref (loop)
682		792
683	Ref/unref can be used to add or remove a reference count on the event	793	Ref/unref can be used to add or remove a reference count on the event
684	loop: Every watcher keeps one reference, and as long as the reference	794	loop: Every watcher keeps one reference, and as long as the reference
685	count is nonzero, C<ev_loop> will not return on its own. If you have	795	count is nonzero, C<ev_loop> will not return on its own.
		796
686	a watcher you never unregister that should not keep C<ev_loop> from	797	If you have a watcher you never unregister that should not keep C<ev_loop>
687	returning, ev_unref() after starting, and ev_ref() before stopping it. For	798	from returning, call ev_unref() after starting, and ev_ref() before
		799	stopping it.
		800
688	example, libev itself uses this for its internal signal pipe: It is not	801	As an example, libev itself uses this for its internal signal pipe: It
689	visible to the libev user and should not keep C<ev_loop> from exiting if	802	is not visible to the libev user and should not keep C<ev_loop> from
690	no event watchers registered by it are active. It is also an excellent	803	exiting if no event watchers registered by it are active. It is also an
691	way to do this for generic recurring timers or from within third-party	804	excellent way to do this for generic recurring timers or from within
692	libraries. Just remember to I<unref after start> and I<ref before stop>	805	third-party libraries. Just remember to I<unref after start> and I<ref
693	(but only if the watcher wasn't active before, or was active before,	806	before stop> (but only if the watcher wasn't active before, or was active
694	respectively).	807	before, respectively. Note also that libev might stop watchers itself
		808	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		809	in the callback).
695		810
696	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	811	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
697	running when nothing else is active.	812	running when nothing else is active.
698		813
699	struct ev_signal exitsig;	814	ev_signal exitsig;
700	ev_signal_init (&exitsig, sig_cb, SIGINT);	815	ev_signal_init (&exitsig, sig_cb, SIGINT);
701	ev_signal_start (loop, &exitsig);	816	ev_signal_start (loop, &exitsig);
702	evf_unref (loop);	817	evf_unref (loop);
703		818
704	Example: For some weird reason, unregister the above signal handler again.	819	Example: For some weird reason, unregister the above signal handler again.
…		…
718	Setting these to a higher value (the C<interval> I<must> be >= C<0>)	833	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
719	allows libev to delay invocation of I/O and timer/periodic callbacks	834	allows libev to delay invocation of I/O and timer/periodic callbacks
720	to increase efficiency of loop iterations (or to increase power-saving	835	to increase efficiency of loop iterations (or to increase power-saving
721	opportunities).	836	opportunities).
722		837
723	The background is that sometimes your program runs just fast enough to	838	The idea is that sometimes your program runs just fast enough to handle
724	handle one (or very few) event(s) per loop iteration. While this makes	839	one (or very few) event(s) per loop iteration. While this makes the
725	the program responsive, it also wastes a lot of CPU time to poll for new	840	program responsive, it also wastes a lot of CPU time to poll for new
726	events, especially with backends like C<select ()> which have a high	841	events, especially with backends like C<select ()> which have a high
727	overhead for the actual polling but can deliver many events at once.	842	overhead for the actual polling but can deliver many events at once.
728		843
729	By setting a higher I<io collect interval> you allow libev to spend more	844	By setting a higher I<io collect interval> you allow libev to spend more
730	time collecting I/O events, so you can handle more events per iteration,	845	time collecting I/O events, so you can handle more events per iteration,
731	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
732	C<ev_timer>) will be not affected. Setting this to a non-null value will	847	C<ev_timer>) will be not affected. Setting this to a non-null value will
733	introduce an additional C<ev_sleep ()> call into most loop iterations.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
734		851
735	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
736	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
737	latency (the watcher callback will be called later). C<ev_io> watchers	854	latency/jitter/inexactness (the watcher callback will be called
738	will not be affected. Setting this to a non-null value will not introduce	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
739	any overhead in libev.	856	value will not introduce any overhead in libev.
740		857
741	Many (busy) programs can usually benefit by setting the I/O collect	858	Many (busy) programs can usually benefit by setting the I/O collect
742	interval to a value near C<0.1> or so, which is often enough for	859	interval to a value near C<0.1> or so, which is often enough for
743	interactive servers (of course not for games), likewise for timeouts. It	860	interactive servers (of course not for games), likewise for timeouts. It
744	usually doesn't make much sense to set it to a lower value than C<0.01>,	861	usually doesn't make much sense to set it to a lower value than C<0.01>,
745	as this approaches the timing granularity of most systems.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
746		867
747	Setting the I<timeout collect interval> can improve the opportunity for	868	Setting the I<timeout collect interval> can improve the opportunity for
748	saving power, as the program will "bundle" timer callback invocations that	869	saving power, as the program will "bundle" timer callback invocations that
749	are "near" in time together, by delaying some, thus reducing the number of	870	are "near" in time together, by delaying some, thus reducing the number of
750	times the process sleeps and wakes up again. Another useful technique to	871	times the process sleeps and wakes up again. Another useful technique to
751	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
752	they fire on, say, one-second boundaries only.	873	they fire on, say, one-second boundaries only.
753		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
		945
754	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
755		947
756	This function only does something when C<EV_VERIFY> support has been	948	This function only does something when C<EV_VERIFY> support has been
757	compiled in. It tries to go through all internal structures and checks	949	compiled in, which is the default for non-minimal builds. It tries to go
758	them for validity. If anything is found to be inconsistent, it will print	950	through all internal structures and checks them for validity. If anything
759	an error message to standard error and call C<abort ()>.	951	is found to be inconsistent, it will print an error message to standard
		952	error and call C<abort ()>.
760		953
761	This can be used to catch bugs inside libev itself: under normal	954	This can be used to catch bugs inside libev itself: under normal
762	circumstances, this function will never abort as of course libev keeps its	955	circumstances, this function will never abort as of course libev keeps its
763	data structures consistent.	956	data structures consistent.
764		957
765	=back	958	=back
766		959
767		960
768	=head1 ANATOMY OF A WATCHER	961	=head1 ANATOMY OF A WATCHER
769		962
		963	In the following description, uppercase C<TYPE> in names stands for the
		964	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		965	watchers and C<ev_io_start> for I/O watchers.
		966
770	A watcher is a structure that you create and register to record your	967	A watcher is a structure that you create and register to record your
771	interest in some event. For instance, if you want to wait for STDIN to	968	interest in some event. For instance, if you want to wait for STDIN to
772	become readable, you would create an C<ev_io> watcher for that:	969	become readable, you would create an C<ev_io> watcher for that:
773		970
774	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	971	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
775	{	972	{
776	ev_io_stop (w);	973	ev_io_stop (w);
777	ev_unloop (loop, EVUNLOOP_ALL);	974	ev_unloop (loop, EVUNLOOP_ALL);
778	}	975	}
779		976
780	struct ev_loop *loop = ev_default_loop (0);	977	struct ev_loop *loop = ev_default_loop (0);
		978
781	struct ev_io stdin_watcher;	979	ev_io stdin_watcher;
		980
782	ev_init (&stdin_watcher, my_cb);	981	ev_init (&stdin_watcher, my_cb);
783	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	982	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
784	ev_io_start (loop, &stdin_watcher);	983	ev_io_start (loop, &stdin_watcher);
		984
785	ev_loop (loop, 0);	985	ev_loop (loop, 0);
786		986
787	As you can see, you are responsible for allocating the memory for your	987	As you can see, you are responsible for allocating the memory for your
788	watcher structures (and it is usually a bad idea to do this on the stack,	988	watcher structures (and it is I<usually> a bad idea to do this on the
789	although this can sometimes be quite valid).	989	stack).
		990
		991	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		992	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
790		993
791	Each watcher structure must be initialised by a call to C<ev_init	994	Each watcher structure must be initialised by a call to C<ev_init
792	(watcher *, callback)>, which expects a callback to be provided. This	995	(watcher *, callback)>, which expects a callback to be provided. This
793	callback gets invoked each time the event occurs (or, in the case of I/O	996	callback gets invoked each time the event occurs (or, in the case of I/O
794	watchers, each time the event loop detects that the file descriptor given	997	watchers, each time the event loop detects that the file descriptor given
795	is readable and/or writable).	998	is readable and/or writable).
796		999
797	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	1000	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
798	with arguments specific to this watcher type. There is also a macro	1001	macro to configure it, with arguments specific to the watcher type. There
799	to combine initialisation and setting in one call: C<< ev_<type>_init	1002	is also a macro to combine initialisation and setting in one call: C<<
800	(watcher *, callback, ...) >>.	1003	ev_TYPE_init (watcher *, callback, ...) >>.
801		1004
802	To make the watcher actually watch out for events, you have to start it	1005	To make the watcher actually watch out for events, you have to start it
803	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	1006	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
804	*) >>), and you can stop watching for events at any time by calling the	1007	*) >>), and you can stop watching for events at any time by calling the
805	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	1008	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
806		1009
807	As long as your watcher is active (has been started but not stopped) you	1010	As long as your watcher is active (has been started but not stopped) you
808	must not touch the values stored in it. Most specifically you must never	1011	must not touch the values stored in it. Most specifically you must never
809	reinitialise it or call its C<set> macro.	1012	reinitialise it or call its C<ev_TYPE_set> macro.
810		1013
811	Each and every callback receives the event loop pointer as first, the	1014	Each and every callback receives the event loop pointer as first, the
812	registered watcher structure as second, and a bitset of received events as	1015	registered watcher structure as second, and a bitset of received events as
813	third argument.	1016	third argument.
814		1017
…		…
872		1075
873	=item C<EV_ASYNC>	1076	=item C<EV_ASYNC>
874		1077
875	The given async watcher has been asynchronously notified (see C<ev_async>).	1078	The given async watcher has been asynchronously notified (see C<ev_async>).
876		1079
		1080	=item C<EV_CUSTOM>
		1081
		1082	Not ever sent (or otherwise used) by libev itself, but can be freely used
		1083	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		1084
877	=item C<EV_ERROR>	1085	=item C<EV_ERROR>
878		1086
879	An unspecified error has occurred, the watcher has been stopped. This might	1087	An unspecified error has occurred, the watcher has been stopped. This might
880	happen because the watcher could not be properly started because libev	1088	happen because the watcher could not be properly started because libev
881	ran out of memory, a file descriptor was found to be closed or any other	1089	ran out of memory, a file descriptor was found to be closed or any other
		1090	problem. Libev considers these application bugs.
		1091
882	problem. You best act on it by reporting the problem and somehow coping	1092	You best act on it by reporting the problem and somehow coping with the
883	with the watcher being stopped.	1093	watcher being stopped. Note that well-written programs should not receive
		1094	an error ever, so when your watcher receives it, this usually indicates a
		1095	bug in your program.
884		1096
885	Libev will usually signal a few "dummy" events together with an error,	1097	Libev will usually signal a few "dummy" events together with an error, for
886	for example it might indicate that a fd is readable or writable, and if	1098	example it might indicate that a fd is readable or writable, and if your
887	your callbacks is well-written it can just attempt the operation and cope	1099	callbacks is well-written it can just attempt the operation and cope with
888	with the error from read() or write(). This will not work in multi-threaded	1100	the error from read() or write(). This will not work in multi-threaded
889	programs, though, so beware.	1101	programs, though, as the fd could already be closed and reused for another
		1102	thing, so beware.
890		1103
891	=back	1104	=back
892		1105
893	=head2 GENERIC WATCHER FUNCTIONS	1106	=head2 GENERIC WATCHER FUNCTIONS
894
895	In the following description, C<TYPE> stands for the watcher type,
896	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
897		1107
898	=over 4	1108	=over 4
899		1109
900	=item C<ev_init> (ev_TYPE *watcher, callback)	1110	=item C<ev_init> (ev_TYPE *watcher, callback)
901		1111
…		…
907	which rolls both calls into one.	1117	which rolls both calls into one.
908		1118
909	You can reinitialise a watcher at any time as long as it has been stopped	1119	You can reinitialise a watcher at any time as long as it has been stopped
910	(or never started) and there are no pending events outstanding.	1120	(or never started) and there are no pending events outstanding.
911		1121
912	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	1122	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
913	int revents)>.	1123	int revents)>.
		1124
		1125	Example: Initialise an C<ev_io> watcher in two steps.
		1126
		1127	ev_io w;
		1128	ev_init (&w, my_cb);
		1129	ev_io_set (&w, STDIN_FILENO, EV_READ);
914		1130
915	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1131	=item C<ev_TYPE_set> (ev_TYPE *, [args])
916		1132
917	This macro initialises the type-specific parts of a watcher. You need to	1133	This macro initialises the type-specific parts of a watcher. You need to
918	call C<ev_init> at least once before you call this macro, but you can	1134	call C<ev_init> at least once before you call this macro, but you can
…		…
921	difference to the C<ev_init> macro).	1137	difference to the C<ev_init> macro).
922		1138
923	Although some watcher types do not have type-specific arguments	1139	Although some watcher types do not have type-specific arguments
924	(e.g. C<ev_prepare>) you still need to call its C<set> macro.	1140	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
925		1141
		1142	See C<ev_init>, above, for an example.
		1143
926	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])	1144	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
927		1145
928	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro	1146	This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
929	calls into a single call. This is the most convenient method to initialise	1147	calls into a single call. This is the most convenient method to initialise
930	a watcher. The same limitations apply, of course.	1148	a watcher. The same limitations apply, of course.
931		1149
		1150	Example: Initialise and set an C<ev_io> watcher in one step.
		1151
		1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
		1153
932	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)	1154	=item C<ev_TYPE_start> (loop *, ev_TYPE *watcher)
933		1155
934	Starts (activates) the given watcher. Only active watchers will receive	1156	Starts (activates) the given watcher. Only active watchers will receive
935	events. If the watcher is already active nothing will happen.	1157	events. If the watcher is already active nothing will happen.
936		1158
		1159	Example: Start the C<ev_io> watcher that is being abused as example in this
		1160	whole section.
		1161
		1162	ev_io_start (EV_DEFAULT_UC, &w);
		1163
937	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1164	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
938		1165
939	Stops the given watcher again (if active) and clears the pending	1166	Stops the given watcher if active, and clears the pending status (whether
		1167	the watcher was active or not).
		1168
940	status. It is possible that stopped watchers are pending (for example,	1169	It is possible that stopped watchers are pending - for example,
941	non-repeating timers are being stopped when they become pending), but	1170	non-repeating timers are being stopped when they become pending - but
942	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1171	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
943	you want to free or reuse the memory used by the watcher it is therefore a	1172	pending. If you want to free or reuse the memory used by the watcher it is
944	good idea to always call its C<ev_TYPE_stop> function.	1173	therefore a good idea to always call its C<ev_TYPE_stop> function.
945		1174
946	=item bool ev_is_active (ev_TYPE *watcher)	1175	=item bool ev_is_active (ev_TYPE *watcher)
947		1176
948	Returns a true value iff the watcher is active (i.e. it has been started	1177	Returns a true value iff the watcher is active (i.e. it has been started
949	and not yet been stopped). As long as a watcher is active you must not modify	1178	and not yet been stopped). As long as a watcher is active you must not modify
…		…
975	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
976	(default: C<-2>). Pending watchers with higher priority will be invoked	1205	(default: C<-2>). Pending watchers with higher priority will be invoked
977	before watchers with lower priority, but priority will not keep watchers	1206	before watchers with lower priority, but priority will not keep watchers
978	from being executed (except for C<ev_idle> watchers).	1207	from being executed (except for C<ev_idle> watchers).
979		1208
980	This means that priorities are I<only> used for ordering callback
981	invocation after new events have been received. This is useful, for
982	example, to reduce latency after idling, or more often, to bind two
983	watchers on the same event and make sure one is called first.
984
985	If you need to suppress invocation when higher priority events are pending	1209	If you need to suppress invocation when higher priority events are pending
986	you need to look at C<ev_idle> watchers, which provide this functionality.	1210	you need to look at C<ev_idle> watchers, which provide this functionality.
987		1211
988	You I<must not> change the priority of a watcher as long as it is active or	1212	You I<must not> change the priority of a watcher as long as it is active or
989	pending.	1213	pending.
990		1214
		1215	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		1216	fine, as long as you do not mind that the priority value you query might
		1217	or might not have been clamped to the valid range.
		1218
991	The default priority used by watchers when no priority has been set is	1219	The default priority used by watchers when no priority has been set is
992	always C<0>, which is supposed to not be too high and not be too low :).	1220	always C<0>, which is supposed to not be too high and not be too low :).
993		1221
994	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1222	See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of
995	fine, as long as you do not mind that the priority value you query might	1223	priorities.
996	or might not have been adjusted to be within valid range.
997		1224
998	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1225	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
999		1226
1000	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1227	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1001	C<loop> nor C<revents> need to be valid as long as the watcher callback	1228	C<loop> nor C<revents> need to be valid as long as the watcher callback
1002	can deal with that fact.	1229	can deal with that fact, as both are simply passed through to the
		1230	callback.
1003		1231
1004	=item int ev_clear_pending (loop, ev_TYPE *watcher)	1232	=item int ev_clear_pending (loop, ev_TYPE *watcher)
1005		1233
1006	If the watcher is pending, this function returns clears its pending status	1234	If the watcher is pending, this function clears its pending status and
1007	and returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
1008	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1009		1237
		1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
		1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
		1254
1010	=back	1255	=back
1011		1256
1012		1257
1013	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
1014		1259
1015	Each watcher has, by default, a member C<void *data> that you can change	1260	Each watcher has, by default, a member C<void *data> that you can change
1016	and read at any time, libev will completely ignore it. This can be used	1261	and read at any time: libev will completely ignore it. This can be used
1017	to associate arbitrary data with your watcher. If you need more data and	1262	to associate arbitrary data with your watcher. If you need more data and
1018	don't want to allocate memory and store a pointer to it in that data	1263	don't want to allocate memory and store a pointer to it in that data
1019	member, you can also "subclass" the watcher type and provide your own	1264	member, you can also "subclass" the watcher type and provide your own
1020	data:	1265	data:
1021		1266
1022	struct my_io	1267	struct my_io
1023	{	1268	{
1024	struct ev_io io;	1269	ev_io io;
1025	int otherfd;	1270	int otherfd;
1026	void *somedata;	1271	void *somedata;
1027	struct whatever *mostinteresting;	1272	struct whatever *mostinteresting;
1028	};	1273	};
1029		1274
…		…
1032	ev_io_init (&w.io, my_cb, fd, EV_READ);	1277	ev_io_init (&w.io, my_cb, fd, EV_READ);
1033		1278
1034	And since your callback will be called with a pointer to the watcher, you	1279	And since your callback will be called with a pointer to the watcher, you
1035	can cast it back to your own type:	1280	can cast it back to your own type:
1036		1281
1037	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1282	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1038	{	1283	{
1039	struct my_io *w = (struct my_io *)w_;	1284	struct my_io *w = (struct my_io *)w_;
1040	...	1285	...
1041	}	1286	}
1042		1287
…		…
1053	ev_timer t2;	1298	ev_timer t2;
1054	}	1299	}
1055		1300
1056	In this case getting the pointer to C<my_biggy> is a bit more	1301	In this case getting the pointer to C<my_biggy> is a bit more
1057	complicated: Either you store the address of your C<my_biggy> struct	1302	complicated: Either you store the address of your C<my_biggy> struct
1058	in the C<data> member of the watcher, or you need to use some pointer	1303	in the C<data> member of the watcher (for woozies), or you need to use
1059	arithmetic using C<offsetof> inside your watchers:	1304	some pointer arithmetic using C<offsetof> inside your watchers (for real
		1305	programmers):
1060		1306
1061	#include <stddef.h>	1307	#include <stddef.h>
1062		1308
1063	static void	1309	static void
1064	t1_cb (EV_P_ struct ev_timer *w, int revents)	1310	t1_cb (EV_P_ ev_timer *w, int revents)
1065	{	1311	{
1066	struct my_biggy big = (struct my_biggy *	1312	struct my_biggy big = (struct my_biggy *)
1067	(((char *)w) - offsetof (struct my_biggy, t1));	1313	(((char *)w) - offsetof (struct my_biggy, t1));
1068	}	1314	}
1069		1315
1070	static void	1316	static void
1071	t2_cb (EV_P_ struct ev_timer *w, int revents)	1317	t2_cb (EV_P_ ev_timer *w, int revents)
1072	{	1318	{
1073	struct my_biggy big = (struct my_biggy *	1319	struct my_biggy big = (struct my_biggy *)
1074	(((char *)w) - offsetof (struct my_biggy, t2));	1320	(((char *)w) - offsetof (struct my_biggy, t2));
1075	}	1321	}
		1322
		1323	=head2 WATCHER PRIORITY MODELS
		1324
		1325	Many event loops support I<watcher priorities>, which are usually small
		1326	integers that influence the ordering of event callback invocation
		1327	between watchers in some way, all else being equal.
		1328
		1329	In libev, Watcher priorities can be set using C<ev_set_priority>. See its
		1330	description for the more technical details such as the actual priority
		1331	range.
		1332
		1333	There are two common ways how these these priorities are being interpreted
		1334	by event loops:
		1335
		1336	In the more common lock-out model, higher priorities "lock out" invocation
		1337	of lower priority watchers, which means as long as higher priority
		1338	watchers receive events, lower priority watchers are not being invoked.
		1339
		1340	The less common only-for-ordering model uses priorities solely to order
		1341	callback invocation within a single event loop iteration: Higher priority
		1342	watchers are invoked before lower priority ones, but they all get invoked
		1343	before polling for new events.
		1344
		1345	Libev uses the second (only-for-ordering) model for all its watchers
		1346	except for idle watchers (which use the lock-out model).
		1347
		1348	The rationale behind this is that implementing the lock-out model for
		1349	watchers is not well supported by most kernel interfaces, and most event
		1350	libraries will just poll for the same events again and again as long as
		1351	their callbacks have not been executed, which is very inefficient in the
		1352	common case of one high-priority watcher locking out a mass of lower
		1353	priority ones.
		1354
		1355	Static (ordering) priorities are most useful when you have two or more
		1356	watchers handling the same resource: a typical usage example is having an
		1357	C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle
		1358	timeouts. Under load, data might be received while the program handles
		1359	other jobs, but since timers normally get invoked first, the timeout
		1360	handler will be executed before checking for data. In that case, giving
		1361	the timer a lower priority than the I/O watcher ensures that I/O will be
		1362	handled first even under adverse conditions (which is usually, but not
		1363	always, what you want).
		1364
		1365	Since idle watchers use the "lock-out" model, meaning that idle watchers
		1366	will only be executed when no same or higher priority watchers have
		1367	received events, they can be used to implement the "lock-out" model when
		1368	required.
		1369
		1370	For example, to emulate how many other event libraries handle priorities,
		1371	you can associate an C<ev_idle> watcher to each such watcher, and in
		1372	the normal watcher callback, you just start the idle watcher. The real
		1373	processing is done in the idle watcher callback. This causes libev to
		1374	continously poll and process kernel event data for the watcher, but when
		1375	the lock-out case is known to be rare (which in turn is rare :), this is
		1376	workable.
		1377
		1378	Usually, however, the lock-out model implemented that way will perform
		1379	miserably under the type of load it was designed to handle. In that case,
		1380	it might be preferable to stop the real watcher before starting the
		1381	idle watcher, so the kernel will not have to process the event in case
		1382	the actual processing will be delayed for considerable time.
		1383
		1384	Here is an example of an I/O watcher that should run at a strictly lower
		1385	priority than the default, and which should only process data when no
		1386	other events are pending:
		1387
		1388	ev_idle idle; // actual processing watcher
		1389	ev_io io; // actual event watcher
		1390
		1391	static void
		1392	io_cb (EV_P_ ev_io *w, int revents)
		1393	{
		1394	// stop the I/O watcher, we received the event, but
		1395	// are not yet ready to handle it.
		1396	ev_io_stop (EV_A_ w);
		1397
		1398	// start the idle watcher to ahndle the actual event.
		1399	// it will not be executed as long as other watchers
		1400	// with the default priority are receiving events.
		1401	ev_idle_start (EV_A_ &idle);
		1402	}
		1403
		1404	static void
		1405	idle_cb (EV_P_ ev_idle *w, int revents)
		1406	{
		1407	// actual processing
		1408	read (STDIN_FILENO, ...);
		1409
		1410	// have to start the I/O watcher again, as
		1411	// we have handled the event
		1412	ev_io_start (EV_P_ &io);
		1413	}
		1414
		1415	// initialisation
		1416	ev_idle_init (&idle, idle_cb);
		1417	ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ);
		1418	ev_io_start (EV_DEFAULT_ &io);
		1419
		1420	In the "real" world, it might also be beneficial to start a timer, so that
		1421	low-priority connections can not be locked out forever under load. This
		1422	enables your program to keep a lower latency for important connections
		1423	during short periods of high load, while not completely locking out less
		1424	important ones.
1076		1425
1077		1426
1078	=head1 WATCHER TYPES	1427	=head1 WATCHER TYPES
1079		1428
1080	This section describes each watcher in detail, but will not repeat	1429	This section describes each watcher in detail, but will not repeat
…		…
1104	In general you can register as many read and/or write event watchers per	1453	In general you can register as many read and/or write event watchers per
1105	fd as you want (as long as you don't confuse yourself). Setting all file	1454	fd as you want (as long as you don't confuse yourself). Setting all file
1106	descriptors to non-blocking mode is also usually a good idea (but not	1455	descriptors to non-blocking mode is also usually a good idea (but not
1107	required if you know what you are doing).	1456	required if you know what you are doing).
1108		1457
1109	If you must do this, then force the use of a known-to-be-good backend	1458	If you cannot use non-blocking mode, then force the use of a
1110	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1459	known-to-be-good backend (at the time of this writing, this includes only
1111	C<EVBACKEND_POLL>).	1460	C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
		1461	descriptors for which non-blocking operation makes no sense (such as
		1462	files) - libev doesn't guarentee any specific behaviour in that case.
1112		1463
1113	Another thing you have to watch out for is that it is quite easy to	1464	Another thing you have to watch out for is that it is quite easy to
1114	receive "spurious" readiness notifications, that is your callback might	1465	receive "spurious" readiness notifications, that is your callback might
1115	be called with C<EV_READ> but a subsequent C<read>(2) will actually block	1466	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1116	because there is no data. Not only are some backends known to create a	1467	because there is no data. Not only are some backends known to create a
1117	lot of those (for example Solaris ports), it is very easy to get into	1468	lot of those (for example Solaris ports), it is very easy to get into
1118	this situation even with a relatively standard program structure. Thus	1469	this situation even with a relatively standard program structure. Thus
1119	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1470	it is best to always use non-blocking I/O: An extra C<read>(2) returning
1120	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1471	C<EAGAIN> is far preferable to a program hanging until some data arrives.
1121		1472
1122	If you cannot run the fd in non-blocking mode (for example you should not	1473	If you cannot run the fd in non-blocking mode (for example you should
1123	play around with an Xlib connection), then you have to separately re-test	1474	not play around with an Xlib connection), then you have to separately
1124	whether a file descriptor is really ready with a known-to-be good interface	1475	re-test whether a file descriptor is really ready with a known-to-be good
1125	such as poll (fortunately in our Xlib example, Xlib already does this on	1476	interface such as poll (fortunately in our Xlib example, Xlib already
1126	its own, so its quite safe to use).	1477	does this on its own, so its quite safe to use). Some people additionally
		1478	use C<SIGALRM> and an interval timer, just to be sure you won't block
		1479	indefinitely.
		1480
		1481	But really, best use non-blocking mode.
1127		1482
1128	=head3 The special problem of disappearing file descriptors	1483	=head3 The special problem of disappearing file descriptors
1129		1484
1130	Some backends (e.g. kqueue, epoll) need to be told about closing a file	1485	Some backends (e.g. kqueue, epoll) need to be told about closing a file
1131	descriptor (either by calling C<close> explicitly or by any other means,	1486	descriptor (either due to calling C<close> explicitly or any other means,
1132	such as C<dup>). The reason is that you register interest in some file	1487	such as C<dup2>). The reason is that you register interest in some file
1133	descriptor, but when it goes away, the operating system will silently drop	1488	descriptor, but when it goes away, the operating system will silently drop
1134	this interest. If another file descriptor with the same number then is	1489	this interest. If another file descriptor with the same number then is
1135	registered with libev, there is no efficient way to see that this is, in	1490	registered with libev, there is no efficient way to see that this is, in
1136	fact, a different file descriptor.	1491	fact, a different file descriptor.
1137		1492
…		…
1168	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or	1523	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1169	C<EVBACKEND_POLL>.	1524	C<EVBACKEND_POLL>.
1170		1525
1171	=head3 The special problem of SIGPIPE	1526	=head3 The special problem of SIGPIPE
1172		1527
1173	While not really specific to libev, it is easy to forget about SIGPIPE:	1528	While not really specific to libev, it is easy to forget about C<SIGPIPE>:
1174	when writing to a pipe whose other end has been closed, your program gets	1529	when writing to a pipe whose other end has been closed, your program gets
1175	send a SIGPIPE, which, by default, aborts your program. For most programs	1530	sent a SIGPIPE, which, by default, aborts your program. For most programs
1176	this is sensible behaviour, for daemons, this is usually undesirable.	1531	this is sensible behaviour, for daemons, this is usually undesirable.
1177		1532
1178	So when you encounter spurious, unexplained daemon exits, make sure you	1533	So when you encounter spurious, unexplained daemon exits, make sure you
1179	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon	1534	ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1180	somewhere, as that would have given you a big clue).	1535	somewhere, as that would have given you a big clue).
…		…
1187	=item ev_io_init (ev_io *, callback, int fd, int events)	1542	=item ev_io_init (ev_io *, callback, int fd, int events)
1188		1543
1189	=item ev_io_set (ev_io *, int fd, int events)	1544	=item ev_io_set (ev_io *, int fd, int events)
1190		1545
1191	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	1546	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
1192	receive events for and events is either C<EV_READ>, C<EV_WRITE> or	1547	receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or
1193	C<EV_READ | EV_WRITE> to receive the given events.	1548	C<EV_READ | EV_WRITE>, to express the desire to receive the given events.
1194		1549
1195	=item int fd [read-only]	1550	=item int fd [read-only]
1196		1551
1197	The file descriptor being watched.	1552	The file descriptor being watched.
1198		1553
…		…
1207	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1562	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1208	readable, but only once. Since it is likely line-buffered, you could	1563	readable, but only once. Since it is likely line-buffered, you could
1209	attempt to read a whole line in the callback.	1564	attempt to read a whole line in the callback.
1210		1565
1211	static void	1566	static void
1212	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1567	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1213	{	1568	{
1214	ev_io_stop (loop, w);	1569	ev_io_stop (loop, w);
1215	.. read from stdin here (or from w->fd) and haqndle any I/O errors	1570	.. read from stdin here (or from w->fd) and handle any I/O errors
1216	}	1571	}
1217		1572
1218	...	1573	...
1219	struct ev_loop *loop = ev_default_init (0);	1574	struct ev_loop *loop = ev_default_init (0);
1220	struct ev_io stdin_readable;	1575	ev_io stdin_readable;
1221	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1576	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1222	ev_io_start (loop, &stdin_readable);	1577	ev_io_start (loop, &stdin_readable);
1223	ev_loop (loop, 0);	1578	ev_loop (loop, 0);
1224		1579
1225		1580
…		…
1228	Timer watchers are simple relative timers that generate an event after a	1583	Timer watchers are simple relative timers that generate an event after a
1229	given time, and optionally repeating in regular intervals after that.	1584	given time, and optionally repeating in regular intervals after that.
1230		1585
1231	The timers are based on real time, that is, if you register an event that	1586	The timers are based on real time, that is, if you register an event that
1232	times out after an hour and you reset your system clock to January last	1587	times out after an hour and you reset your system clock to January last
1233	year, it will still time out after (roughly) and hour. "Roughly" because	1588	year, it will still time out after (roughly) one hour. "Roughly" because
1234	detecting time jumps is hard, and some inaccuracies are unavoidable (the	1589	detecting time jumps is hard, and some inaccuracies are unavoidable (the
1235	monotonic clock option helps a lot here).	1590	monotonic clock option helps a lot here).
1236		1591
1237	The callback is guaranteed to be invoked only after its timeout has passed,	1592	The callback is guaranteed to be invoked only I<after> its timeout has
1238	but if multiple timers become ready during the same loop iteration then	1593	passed (not I<at>, so on systems with very low-resolution clocks this
1239	order of execution is undefined.	1594	might introduce a small delay). If multiple timers become ready during the
		1595	same loop iteration then the ones with earlier time-out values are invoked
		1596	before ones of the same priority with later time-out values (but this is
		1597	no longer true when a callback calls C<ev_loop> recursively).
		1598
		1599	=head3 Be smart about timeouts
		1600
		1601	Many real-world problems involve some kind of timeout, usually for error
		1602	recovery. A typical example is an HTTP request - if the other side hangs,
		1603	you want to raise some error after a while.
		1604
		1605	What follows are some ways to handle this problem, from obvious and
		1606	inefficient to smart and efficient.
		1607
		1608	In the following, a 60 second activity timeout is assumed - a timeout that
		1609	gets reset to 60 seconds each time there is activity (e.g. each time some
		1610	data or other life sign was received).
		1611
		1612	=over 4
		1613
		1614	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1615
		1616	This is the most obvious, but not the most simple way: In the beginning,
		1617	start the watcher:
		1618
		1619	ev_timer_init (timer, callback, 60., 0.);
		1620	ev_timer_start (loop, timer);
		1621
		1622	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1623	and start it again:
		1624
		1625	ev_timer_stop (loop, timer);
		1626	ev_timer_set (timer, 60., 0.);
		1627	ev_timer_start (loop, timer);
		1628
		1629	This is relatively simple to implement, but means that each time there is
		1630	some activity, libev will first have to remove the timer from its internal
		1631	data structure and then add it again. Libev tries to be fast, but it's
		1632	still not a constant-time operation.
		1633
		1634	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1635
		1636	This is the easiest way, and involves using C<ev_timer_again> instead of
		1637	C<ev_timer_start>.
		1638
		1639	To implement this, configure an C<ev_timer> with a C<repeat> value
		1640	of C<60> and then call C<ev_timer_again> at start and each time you
		1641	successfully read or write some data. If you go into an idle state where
		1642	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1643	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1644
		1645	That means you can ignore both the C<ev_timer_start> function and the
		1646	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1647	member and C<ev_timer_again>.
		1648
		1649	At start:
		1650
		1651	ev_init (timer, callback);
		1652	timer->repeat = 60.;
		1653	ev_timer_again (loop, timer);
		1654
		1655	Each time there is some activity:
		1656
		1657	ev_timer_again (loop, timer);
		1658
		1659	It is even possible to change the time-out on the fly, regardless of
		1660	whether the watcher is active or not:
		1661
		1662	timer->repeat = 30.;
		1663	ev_timer_again (loop, timer);
		1664
		1665	This is slightly more efficient then stopping/starting the timer each time
		1666	you want to modify its timeout value, as libev does not have to completely
		1667	remove and re-insert the timer from/into its internal data structure.
		1668
		1669	It is, however, even simpler than the "obvious" way to do it.
		1670
		1671	=item 3. Let the timer time out, but then re-arm it as required.
		1672
		1673	This method is more tricky, but usually most efficient: Most timeouts are
		1674	relatively long compared to the intervals between other activity - in
		1675	our example, within 60 seconds, there are usually many I/O events with
		1676	associated activity resets.
		1677
		1678	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1679	but remember the time of last activity, and check for a real timeout only
		1680	within the callback:
		1681
		1682	ev_tstamp last_activity; // time of last activity
		1683
		1684	static void
		1685	callback (EV_P_ ev_timer *w, int revents)
		1686	{
		1687	ev_tstamp now = ev_now (EV_A);
		1688	ev_tstamp timeout = last_activity + 60.;
		1689
		1690	// if last_activity + 60. is older than now, we did time out
		1691	if (timeout < now)
		1692	{
		1693	// timeout occured, take action
		1694	}
		1695	else
		1696	{
		1697	// callback was invoked, but there was some activity, re-arm
		1698	// the watcher to fire in last_activity + 60, which is
		1699	// guaranteed to be in the future, so "again" is positive:
		1700	w->repeat = timeout - now;
		1701	ev_timer_again (EV_A_ w);
		1702	}
		1703	}
		1704
		1705	To summarise the callback: first calculate the real timeout (defined
		1706	as "60 seconds after the last activity"), then check if that time has
		1707	been reached, which means something I<did>, in fact, time out. Otherwise
		1708	the callback was invoked too early (C<timeout> is in the future), so
		1709	re-schedule the timer to fire at that future time, to see if maybe we have
		1710	a timeout then.
		1711
		1712	Note how C<ev_timer_again> is used, taking advantage of the
		1713	C<ev_timer_again> optimisation when the timer is already running.
		1714
		1715	This scheme causes more callback invocations (about one every 60 seconds
		1716	minus half the average time between activity), but virtually no calls to
		1717	libev to change the timeout.
		1718
		1719	To start the timer, simply initialise the watcher and set C<last_activity>
		1720	to the current time (meaning we just have some activity :), then call the
		1721	callback, which will "do the right thing" and start the timer:
		1722
		1723	ev_init (timer, callback);
		1724	last_activity = ev_now (loop);
		1725	callback (loop, timer, EV_TIMEOUT);
		1726
		1727	And when there is some activity, simply store the current time in
		1728	C<last_activity>, no libev calls at all:
		1729
		1730	last_actiivty = ev_now (loop);
		1731
		1732	This technique is slightly more complex, but in most cases where the
		1733	time-out is unlikely to be triggered, much more efficient.
		1734
		1735	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1736	callback :) - just change the timeout and invoke the callback, which will
		1737	fix things for you.
		1738
		1739	=item 4. Wee, just use a double-linked list for your timeouts.
		1740
		1741	If there is not one request, but many thousands (millions...), all
		1742	employing some kind of timeout with the same timeout value, then one can
		1743	do even better:
		1744
		1745	When starting the timeout, calculate the timeout value and put the timeout
		1746	at the I<end> of the list.
		1747
		1748	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1749	the list is expected to fire (for example, using the technique #3).
		1750
		1751	When there is some activity, remove the timer from the list, recalculate
		1752	the timeout, append it to the end of the list again, and make sure to
		1753	update the C<ev_timer> if it was taken from the beginning of the list.
		1754
		1755	This way, one can manage an unlimited number of timeouts in O(1) time for
		1756	starting, stopping and updating the timers, at the expense of a major
		1757	complication, and having to use a constant timeout. The constant timeout
		1758	ensures that the list stays sorted.
		1759
		1760	=back
		1761
		1762	So which method the best?
		1763
		1764	Method #2 is a simple no-brain-required solution that is adequate in most
		1765	situations. Method #3 requires a bit more thinking, but handles many cases
		1766	better, and isn't very complicated either. In most case, choosing either
		1767	one is fine, with #3 being better in typical situations.
		1768
		1769	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1770	rather complicated, but extremely efficient, something that really pays
		1771	off after the first million or so of active timers, i.e. it's usually
		1772	overkill :)
1240		1773
1241	=head3 The special problem of time updates	1774	=head3 The special problem of time updates
1242		1775
1243	Establishing the current time is a costly operation (it usually takes at	1776	Establishing the current time is a costly operation (it usually takes at
1244	least two system calls): EV therefore updates its idea of the current	1777	least two system calls): EV therefore updates its idea of the current
1245	time only before and after C<ev_loop> polls for new events, which causes	1778	time only before and after C<ev_loop> collects new events, which causes a
1246	a growing difference between C<ev_now ()> and C<ev_time ()> when handling	1779	growing difference between C<ev_now ()> and C<ev_time ()> when handling
1247	lots of events.	1780	lots of events in one iteration.
1248		1781
1249	The relative timeouts are calculated relative to the C<ev_now ()>	1782	The relative timeouts are calculated relative to the C<ev_now ()>
1250	time. This is usually the right thing as this timestamp refers to the time	1783	time. This is usually the right thing as this timestamp refers to the time
1251	of the event triggering whatever timeout you are modifying/starting. If	1784	of the event triggering whatever timeout you are modifying/starting. If
1252	you suspect event processing to be delayed and you I<need> to base the	1785	you suspect event processing to be delayed and you I<need> to base the
…		…
1256		1789
1257	If the event loop is suspended for a long time, you can also force an	1790	If the event loop is suspended for a long time, you can also force an
1258	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1259	()>.	1792	()>.
1260		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
		1823
1261	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1262		1825
1263	=over 4	1826	=over 4
1264		1827
1265	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1828	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1288	If the timer is started but non-repeating, stop it (as if it timed out).	1851	If the timer is started but non-repeating, stop it (as if it timed out).
1289		1852
1290	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1291	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1292		1855
1293	This sounds a bit complicated, but here is a useful and typical	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1294	example: Imagine you have a TCP connection and you want a so-called idle	1857	usage example.
1295	timeout, that is, you want to be called when there have been, say, 60
1296	seconds of inactivity on the socket. The easiest way to do this is to
1297	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1298	C<ev_timer_again> each time you successfully read or write some data. If
1299	you go into an idle state where you do not expect data to travel on the
1300	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1301	automatically restart it if need be.
1302		1858
1303	That means you can ignore the C<after> value and C<ev_timer_start>	1859	=item ev_timer_remaining (loop, ev_timer *)
1304	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1305		1860
1306	ev_timer_init (timer, callback, 0., 5.);	1861	Returns the remaining time until a timer fires. If the timer is active,
1307	ev_timer_again (loop, timer);	1862	then this time is relative to the current event loop time, otherwise it's
1308	...	1863	the timeout value currently configured.
1309	timer->again = 17.;
1310	ev_timer_again (loop, timer);
1311	...
1312	timer->again = 10.;
1313	ev_timer_again (loop, timer);
1314		1864
1315	This is more slightly efficient then stopping/starting the timer each time	1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1316	you want to modify its timeout value.	1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1867	will return C<4>. When the timer expires and is restarted, it will return
		1868	roughly C<7> (likely slightly less as callback invocation takes some time,
		1869	too), and so on.
1317		1870
1318	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1319		1872
1320	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1321	or C<ev_timer_again> is called and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
1322	which is also when any modifications are taken into account.	1875	which is also when any modifications are taken into account.
1323		1876
1324	=back	1877	=back
1325		1878
1326	=head3 Examples	1879	=head3 Examples
1327		1880
1328	Example: Create a timer that fires after 60 seconds.	1881	Example: Create a timer that fires after 60 seconds.
1329		1882
1330	static void	1883	static void
1331	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1884	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1332	{	1885	{
1333	.. one minute over, w is actually stopped right here	1886	.. one minute over, w is actually stopped right here
1334	}	1887	}
1335		1888
1336	struct ev_timer mytimer;	1889	ev_timer mytimer;
1337	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1890	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1338	ev_timer_start (loop, &mytimer);	1891	ev_timer_start (loop, &mytimer);
1339		1892
1340	Example: Create a timeout timer that times out after 10 seconds of	1893	Example: Create a timeout timer that times out after 10 seconds of
1341	inactivity.	1894	inactivity.
1342		1895
1343	static void	1896	static void
1344	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1897	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1345	{	1898	{
1346	.. ten seconds without any activity	1899	.. ten seconds without any activity
1347	}	1900	}
1348		1901
1349	struct ev_timer mytimer;	1902	ev_timer mytimer;
1350	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1903	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1351	ev_timer_again (&mytimer); /* start timer */	1904	ev_timer_again (&mytimer); /* start timer */
1352	ev_loop (loop, 0);	1905	ev_loop (loop, 0);
1353		1906
1354	// and in some piece of code that gets executed on any "activity":	1907	// and in some piece of code that gets executed on any "activity":
…		…
1359	=head2 C<ev_periodic> - to cron or not to cron?	1912	=head2 C<ev_periodic> - to cron or not to cron?
1360		1913
1361	Periodic watchers are also timers of a kind, but they are very versatile	1914	Periodic watchers are also timers of a kind, but they are very versatile
1362	(and unfortunately a bit complex).	1915	(and unfortunately a bit complex).
1363		1916
1364	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1917	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1365	but on wall clock time (absolute time). You can tell a periodic watcher	1918	relative time, the physical time that passes) but on wall clock time
1366	to trigger after some specific point in time. For example, if you tell a	1919	(absolute time, the thing you can read on your calender or clock). The
1367	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1920	difference is that wall clock time can run faster or slower than real
1368	+ 10.>, that is, an absolute time not a delay) and then reset your system	1921	time, and time jumps are not uncommon (e.g. when you adjust your
1369	clock to January of the previous year, then it will take more than year	1922	wrist-watch).
1370	to trigger the event (unlike an C<ev_timer>, which would still trigger
1371	roughly 10 seconds later as it uses a relative timeout).
1372		1923
		1924	You can tell a periodic watcher to trigger after some specific point
		1925	in time: for example, if you tell a periodic watcher to trigger "in 10
		1926	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1927	not a delay) and then reset your system clock to January of the previous
		1928	year, then it will take a year or more to trigger the event (unlike an
		1929	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1930	it, as it uses a relative timeout).
		1931
1373	C<ev_periodic>s can also be used to implement vastly more complex timers,	1932	C<ev_periodic> watchers can also be used to implement vastly more complex
1374	such as triggering an event on each "midnight, local time", or other	1933	timers, such as triggering an event on each "midnight, local time", or
1375	complicated, rules.	1934	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1935	those cannot react to time jumps.
1376		1936
1377	As with timers, the callback is guaranteed to be invoked only when the	1937	As with timers, the callback is guaranteed to be invoked only when the
1378	time (C<at>) has passed, but if multiple periodic timers become ready	1938	point in time where it is supposed to trigger has passed. If multiple
1379	during the same loop iteration then order of execution is undefined.	1939	timers become ready during the same loop iteration then the ones with
		1940	earlier time-out values are invoked before ones with later time-out values
		1941	(but this is no longer true when a callback calls C<ev_loop> recursively).
1380		1942
1381	=head3 Watcher-Specific Functions and Data Members	1943	=head3 Watcher-Specific Functions and Data Members
1382		1944
1383	=over 4	1945	=over 4
1384		1946
1385	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1947	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1386		1948
1387	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1949	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1388		1950
1389	Lots of arguments, lets sort it out... There are basically three modes of	1951	Lots of arguments, let's sort it out... There are basically three modes of
1390	operation, and we will explain them from simplest to complex:	1952	operation, and we will explain them from simplest to most complex:
1391		1953
1392	=over 4	1954	=over 4
1393		1955
1394	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1956	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1395		1957
1396	In this configuration the watcher triggers an event after the wall clock	1958	In this configuration the watcher triggers an event after the wall clock
1397	time C<at> has passed and doesn't repeat. It will not adjust when a time	1959	time C<offset> has passed. It will not repeat and will not adjust when a
1398	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1960	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1399	run when the system time reaches or surpasses this time.	1961	will be stopped and invoked when the system clock reaches or surpasses
		1962	this point in time.
1400		1963
1401	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1964	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1402		1965
1403	In this mode the watcher will always be scheduled to time out at the next	1966	In this mode the watcher will always be scheduled to time out at the next
1404	C<at + N * interval> time (for some integer N, which can also be negative)	1967	C<offset + N * interval> time (for some integer N, which can also be
1405	and then repeat, regardless of any time jumps.	1968	negative) and then repeat, regardless of any time jumps. The C<offset>
		1969	argument is merely an offset into the C<interval> periods.
1406		1970
1407	This can be used to create timers that do not drift with respect to system	1971	This can be used to create timers that do not drift with respect to the
1408	time, for example, here is a C<ev_periodic> that triggers each hour, on	1972	system clock, for example, here is an C<ev_periodic> that triggers each
1409	the hour:	1973	hour, on the hour (with respect to UTC):
1410		1974
1411	ev_periodic_set (&periodic, 0., 3600., 0);	1975	ev_periodic_set (&periodic, 0., 3600., 0);
1412		1976
1413	This doesn't mean there will always be 3600 seconds in between triggers,	1977	This doesn't mean there will always be 3600 seconds in between triggers,
1414	but only that the callback will be called when the system time shows a	1978	but only that the callback will be called when the system time shows a
1415	full hour (UTC), or more correctly, when the system time is evenly divisible	1979	full hour (UTC), or more correctly, when the system time is evenly divisible
1416	by 3600.	1980	by 3600.
1417		1981
1418	Another way to think about it (for the mathematically inclined) is that	1982	Another way to think about it (for the mathematically inclined) is that
1419	C<ev_periodic> will try to run the callback in this mode at the next possible	1983	C<ev_periodic> will try to run the callback in this mode at the next possible
1420	time where C<time = at (mod interval)>, regardless of any time jumps.	1984	time where C<time = offset (mod interval)>, regardless of any time jumps.
1421		1985
1422	For numerical stability it is preferable that the C<at> value is near	1986	For numerical stability it is preferable that the C<offset> value is near
1423	C<ev_now ()> (the current time), but there is no range requirement for	1987	C<ev_now ()> (the current time), but there is no range requirement for
1424	this value, and in fact is often specified as zero.	1988	this value, and in fact is often specified as zero.
1425		1989
1426	Note also that there is an upper limit to how often a timer can fire (CPU	1990	Note also that there is an upper limit to how often a timer can fire (CPU
1427	speed for example), so if C<interval> is very small then timing stability	1991	speed for example), so if C<interval> is very small then timing stability
1428	will of course deteriorate. Libev itself tries to be exact to be about one	1992	will of course deteriorate. Libev itself tries to be exact to be about one
1429	millisecond (if the OS supports it and the machine is fast enough).	1993	millisecond (if the OS supports it and the machine is fast enough).
1430		1994
1431	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1995	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1432		1996
1433	In this mode the values for C<interval> and C<at> are both being	1997	In this mode the values for C<interval> and C<offset> are both being
1434	ignored. Instead, each time the periodic watcher gets scheduled, the	1998	ignored. Instead, each time the periodic watcher gets scheduled, the
1435	reschedule callback will be called with the watcher as first, and the	1999	reschedule callback will be called with the watcher as first, and the
1436	current time as second argument.	2000	current time as second argument.
1437		2001
1438	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	2002	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1439	ever, or make ANY event loop modifications whatsoever>.	2003	or make ANY other event loop modifications whatsoever, unless explicitly
		2004	allowed by documentation here>.
1440		2005
1441	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	2006	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1442	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	2007	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1443	only event loop modification you are allowed to do).	2008	only event loop modification you are allowed to do).
1444		2009
1445	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	2010	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1446	*w, ev_tstamp now)>, e.g.:	2011	*w, ev_tstamp now)>, e.g.:
1447		2012
		2013	static ev_tstamp
1448	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	2014	my_rescheduler (ev_periodic *w, ev_tstamp now)
1449	{	2015	{
1450	return now + 60.;	2016	return now + 60.;
1451	}	2017	}
1452		2018
1453	It must return the next time to trigger, based on the passed time value	2019	It must return the next time to trigger, based on the passed time value
…		…
1473	a different time than the last time it was called (e.g. in a crond like	2039	a different time than the last time it was called (e.g. in a crond like
1474	program when the crontabs have changed).	2040	program when the crontabs have changed).
1475		2041
1476	=item ev_tstamp ev_periodic_at (ev_periodic *)	2042	=item ev_tstamp ev_periodic_at (ev_periodic *)
1477		2043
1478	When active, returns the absolute time that the watcher is supposed to	2044	When active, returns the absolute time that the watcher is supposed
1479	trigger next.	2045	to trigger next. This is not the same as the C<offset> argument to
		2046	C<ev_periodic_set>, but indeed works even in interval and manual
		2047	rescheduling modes.
1480		2048
1481	=item ev_tstamp offset [read-write]	2049	=item ev_tstamp offset [read-write]
1482		2050
1483	When repeating, this contains the offset value, otherwise this is the	2051	When repeating, this contains the offset value, otherwise this is the
1484	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	2052	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		2053	although libev might modify this value for better numerical stability).
1485		2054
1486	Can be modified any time, but changes only take effect when the periodic	2055	Can be modified any time, but changes only take effect when the periodic
1487	timer fires or C<ev_periodic_again> is being called.	2056	timer fires or C<ev_periodic_again> is being called.
1488		2057
1489	=item ev_tstamp interval [read-write]	2058	=item ev_tstamp interval [read-write]
1490		2059
1491	The current interval value. Can be modified any time, but changes only	2060	The current interval value. Can be modified any time, but changes only
1492	take effect when the periodic timer fires or C<ev_periodic_again> is being	2061	take effect when the periodic timer fires or C<ev_periodic_again> is being
1493	called.	2062	called.
1494		2063
1495	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	2064	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1496		2065
1497	The current reschedule callback, or C<0>, if this functionality is	2066	The current reschedule callback, or C<0>, if this functionality is
1498	switched off. Can be changed any time, but changes only take effect when	2067	switched off. Can be changed any time, but changes only take effect when
1499	the periodic timer fires or C<ev_periodic_again> is being called.	2068	the periodic timer fires or C<ev_periodic_again> is being called.
1500		2069
1501	=back	2070	=back
1502		2071
1503	=head3 Examples	2072	=head3 Examples
1504		2073
1505	Example: Call a callback every hour, or, more precisely, whenever the	2074	Example: Call a callback every hour, or, more precisely, whenever the
1506	system clock is divisible by 3600. The callback invocation times have	2075	system time is divisible by 3600. The callback invocation times have
1507	potentially a lot of jitter, but good long-term stability.	2076	potentially a lot of jitter, but good long-term stability.
1508		2077
1509	static void	2078	static void
1510	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	2079	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1511	{	2080	{
1512	... its now a full hour (UTC, or TAI or whatever your clock follows)	2081	... its now a full hour (UTC, or TAI or whatever your clock follows)
1513	}	2082	}
1514		2083
1515	struct ev_periodic hourly_tick;	2084	ev_periodic hourly_tick;
1516	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	2085	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1517	ev_periodic_start (loop, &hourly_tick);	2086	ev_periodic_start (loop, &hourly_tick);
1518		2087
1519	Example: The same as above, but use a reschedule callback to do it:	2088	Example: The same as above, but use a reschedule callback to do it:
1520		2089
1521	#include <math.h>	2090	#include <math.h>
1522		2091
1523	static ev_tstamp	2092	static ev_tstamp
1524	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	2093	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1525	{	2094	{
1526	return fmod (now, 3600.) + 3600.;	2095	return now + (3600. - fmod (now, 3600.));
1527	}	2096	}
1528		2097
1529	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	2098	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1530		2099
1531	Example: Call a callback every hour, starting now:	2100	Example: Call a callback every hour, starting now:
1532		2101
1533	struct ev_periodic hourly_tick;	2102	ev_periodic hourly_tick;
1534	ev_periodic_init (&hourly_tick, clock_cb,	2103	ev_periodic_init (&hourly_tick, clock_cb,
1535	fmod (ev_now (loop), 3600.), 3600., 0);	2104	fmod (ev_now (loop), 3600.), 3600., 0);
1536	ev_periodic_start (loop, &hourly_tick);	2105	ev_periodic_start (loop, &hourly_tick);
1537		2106
1538		2107
…		…
1541	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1542	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1543	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1544	normal event processing, like any other event.	2113	normal event processing, like any other event.
1545		2114
		2115	If you want signals to be delivered truly asynchronously, just use
		2116	C<sigaction> as you would do without libev and forget about sharing
		2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
		2119
1546	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1547	first watcher gets started will libev actually register a signal watcher	2126	When the first watcher gets started will libev actually register something
1548	with the kernel (thus it coexists with your own signal handlers as long	2127	with the kernel (thus it coexists with your own signal handlers as long as
1549	as you don't register any with libev). Similarly, when the last signal	2128	you don't register any with libev for the same signal).
1550	watcher for a signal is stopped libev will reset the signal handler to
1551	SIG_DFL (regardless of what it was set to before).
1552		2129
1553	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1554	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1555	interrupted. If you have a problem with system calls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1556	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1557	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1558		2160
1559	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1560		2162
1561	=over 4	2163	=over 4
1562		2164
…		…
1573		2175
1574	=back	2176	=back
1575		2177
1576	=head3 Examples	2178	=head3 Examples
1577		2179
1578	Example: Try to exit cleanly on SIGINT and SIGTERM.	2180	Example: Try to exit cleanly on SIGINT.
1579		2181
1580	static void	2182	static void
1581	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	2183	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1582	{	2184	{
1583	ev_unloop (loop, EVUNLOOP_ALL);	2185	ev_unloop (loop, EVUNLOOP_ALL);
1584	}	2186	}
1585		2187
1586	struct ev_signal signal_watcher;	2188	ev_signal signal_watcher;
1587	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	2189	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1588	ev_signal_start (loop, &sigint_cb);	2190	ev_signal_start (loop, &signal_watcher);
1589		2191
1590		2192
1591	=head2 C<ev_child> - watch out for process status changes	2193	=head2 C<ev_child> - watch out for process status changes
1592		2194
1593	Child watchers trigger when your process receives a SIGCHLD in response to	2195	Child watchers trigger when your process receives a SIGCHLD in response to
1594	some child status changes (most typically when a child of yours dies). It	2196	some child status changes (most typically when a child of yours dies or
1595	is permissible to install a child watcher I<after> the child has been	2197	exits). It is permissible to install a child watcher I<after> the child
1596	forked (which implies it might have already exited), as long as the event	2198	has been forked (which implies it might have already exited), as long
1597	loop isn't entered (or is continued from a watcher).	2199	as the event loop isn't entered (or is continued from a watcher), i.e.,
		2200	forking and then immediately registering a watcher for the child is fine,
		2201	but forking and registering a watcher a few event loop iterations later or
		2202	in the next callback invocation is not.
1598		2203
1599	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
1600	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
1601		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
1602	=head3 Process Interaction	2211	=head3 Process Interaction
1603		2212
1604	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
1605	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
1606	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
1607	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
1608	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
1609	children, even ones not watched.	2218	children, even ones not watched.
1610		2219
1611	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
1621	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
1622		2231
1623	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
1624	child terminates, so normally one needs to stop the watcher in the	2233	child terminates, so normally one needs to stop the watcher in the
1625	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
1626	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
1627		2237
1628	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
1629		2239
1630	=over 4	2240	=over 4
1631		2241
…		…
1663	its completion.	2273	its completion.
1664		2274
1665	ev_child cw;	2275	ev_child cw;
1666		2276
1667	static void	2277	static void
1668	child_cb (EV_P_ struct ev_child *w, int revents)	2278	child_cb (EV_P_ ev_child *w, int revents)
1669	{	2279	{
1670	ev_child_stop (EV_A_ w);	2280	ev_child_stop (EV_A_ w);
1671	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	2281	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1672	}	2282	}
1673		2283
…		…
1688		2298
1689		2299
1690	=head2 C<ev_stat> - did the file attributes just change?	2300	=head2 C<ev_stat> - did the file attributes just change?
1691		2301
1692	This watches a file system path for attribute changes. That is, it calls	2302	This watches a file system path for attribute changes. That is, it calls
1693	C<stat> regularly (or when the OS says it changed) and sees if it changed	2303	C<stat> on that path in regular intervals (or when the OS says it changed)
1694	compared to the last time, invoking the callback if it did.	2304	and sees if it changed compared to the last time, invoking the callback if
		2305	it did.
1695		2306
1696	The path does not need to exist: changing from "path exists" to "path does	2307	The path does not need to exist: changing from "path exists" to "path does
1697	not exist" is a status change like any other. The condition "path does	2308	not exist" is a status change like any other. The condition "path does not
1698	not exist" is signified by the C<st_nlink> field being zero (which is	2309	exist" (or more correctly "path cannot be stat'ed") is signified by the
1699	otherwise always forced to be at least one) and all the other fields of	2310	C<st_nlink> field being zero (which is otherwise always forced to be at
1700	the stat buffer having unspecified contents.	2311	least one) and all the other fields of the stat buffer having unspecified
		2312	contents.
1701		2313
1702	The path I<should> be absolute and I<must not> end in a slash. If it is	2314	The path I<must not> end in a slash or contain special components such as
		2315	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1703	relative and your working directory changes, the behaviour is undefined.	2316	your working directory changes, then the behaviour is undefined.
1704		2317
1705	Since there is no standard to do this, the portable implementation simply	2318	Since there is no portable change notification interface available, the
1706	calls C<stat (2)> regularly on the path to see if it changed somehow. You	2319	portable implementation simply calls C<stat(2)> regularly on the path
1707	can specify a recommended polling interval for this case. If you specify	2320	to see if it changed somehow. You can specify a recommended polling
1708	a polling interval of C<0> (highly recommended!) then a I<suitable,	2321	interval for this case. If you specify a polling interval of C<0> (highly
1709	unspecified default> value will be used (which you can expect to be around	2322	recommended!) then a I<suitable, unspecified default> value will be used
1710	five seconds, although this might change dynamically). Libev will also	2323	(which you can expect to be around five seconds, although this might
1711	impose a minimum interval which is currently around C<0.1>, but thats	2324	change dynamically). Libev will also impose a minimum interval which is
1712	usually overkill.	2325	currently around C<0.1>, but that's usually overkill.
1713		2326
1714	This watcher type is not meant for massive numbers of stat watchers,	2327	This watcher type is not meant for massive numbers of stat watchers,
1715	as even with OS-supported change notifications, this can be	2328	as even with OS-supported change notifications, this can be
1716	resource-intensive.	2329	resource-intensive.
1717		2330
1718	At the time of this writing, only the Linux inotify interface is	2331	At the time of this writing, the only OS-specific interface implemented
1719	implemented (implementing kqueue support is left as an exercise for the	2332	is the Linux inotify interface (implementing kqueue support is left as an
1720	reader, note, however, that the author sees no way of implementing ev_stat	2333	exercise for the reader. Note, however, that the author sees no way of
1721	semantics with kqueue). Inotify will be used to give hints only and should	2334	implementing C<ev_stat> semantics with kqueue, except as a hint).
1722	not change the semantics of C<ev_stat> watchers, which means that libev
1723	sometimes needs to fall back to regular polling again even with inotify,
1724	but changes are usually detected immediately, and if the file exists there
1725	will be no polling.
1726		2335
1727	=head3 ABI Issues (Largefile Support)	2336	=head3 ABI Issues (Largefile Support)
1728		2337
1729	Libev by default (unless the user overrides this) uses the default	2338	Libev by default (unless the user overrides this) uses the default
1730	compilation environment, which means that on systems with large file	2339	compilation environment, which means that on systems with large file
1731	support disabled by default, you get the 32 bit version of the stat	2340	support disabled by default, you get the 32 bit version of the stat
1732	structure. When using the library from programs that change the ABI to	2341	structure. When using the library from programs that change the ABI to
1733	use 64 bit file offsets the programs will fail. In that case you have to	2342	use 64 bit file offsets the programs will fail. In that case you have to
1734	compile libev with the same flags to get binary compatibility. This is	2343	compile libev with the same flags to get binary compatibility. This is
1735	obviously the case with any flags that change the ABI, but the problem is	2344	obviously the case with any flags that change the ABI, but the problem is
1736	most noticeably disabled with ev_stat and large file support.	2345	most noticeably displayed with ev_stat and large file support.
1737		2346
1738	The solution for this is to lobby your distribution maker to make large	2347	The solution for this is to lobby your distribution maker to make large
1739	file interfaces available by default (as e.g. FreeBSD does) and not	2348	file interfaces available by default (as e.g. FreeBSD does) and not
1740	optional. Libev cannot simply switch on large file support because it has	2349	optional. Libev cannot simply switch on large file support because it has
1741	to exchange stat structures with application programs compiled using the	2350	to exchange stat structures with application programs compiled using the
1742	default compilation environment.	2351	default compilation environment.
1743		2352
1744	=head3 Inotify	2353	=head3 Inotify and Kqueue
1745		2354
1746	When C<inotify (7)> support has been compiled into libev (generally only	2355	When C<inotify (7)> support has been compiled into libev and present at
1747	available on Linux) and present at runtime, it will be used to speed up	2356	runtime, it will be used to speed up change detection where possible. The
1748	change detection where possible. The inotify descriptor will be created lazily	2357	inotify descriptor will be created lazily when the first C<ev_stat>
1749	when the first C<ev_stat> watcher is being started.	2358	watcher is being started.
1750		2359
1751	Inotify presence does not change the semantics of C<ev_stat> watchers	2360	Inotify presence does not change the semantics of C<ev_stat> watchers
1752	except that changes might be detected earlier, and in some cases, to avoid	2361	except that changes might be detected earlier, and in some cases, to avoid
1753	making regular C<stat> calls. Even in the presence of inotify support	2362	making regular C<stat> calls. Even in the presence of inotify support
1754	there are many cases where libev has to resort to regular C<stat> polling.	2363	there are many cases where libev has to resort to regular C<stat> polling,
		2364	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2365	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2366	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2367	xfs are fully working) libev usually gets away without polling.
1755		2368
1756	(There is no support for kqueue, as apparently it cannot be used to	2369	There is no support for kqueue, as apparently it cannot be used to
1757	implement this functionality, due to the requirement of having a file	2370	implement this functionality, due to the requirement of having a file
1758	descriptor open on the object at all times).	2371	descriptor open on the object at all times, and detecting renames, unlinks
		2372	etc. is difficult.
		2373
		2374	=head3 C<stat ()> is a synchronous operation
		2375
		2376	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2377	the process. The exception are C<ev_stat> watchers - those call C<stat
		2378	()>, which is a synchronous operation.
		2379
		2380	For local paths, this usually doesn't matter: unless the system is very
		2381	busy or the intervals between stat's are large, a stat call will be fast,
		2382	as the path data is usually in memory already (except when starting the
		2383	watcher).
		2384
		2385	For networked file systems, calling C<stat ()> can block an indefinite
		2386	time due to network issues, and even under good conditions, a stat call
		2387	often takes multiple milliseconds.
		2388
		2389	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2390	paths, although this is fully supported by libev.
1759		2391
1760	=head3 The special problem of stat time resolution	2392	=head3 The special problem of stat time resolution
1761		2393
1762	The C<stat ()> system call only supports full-second resolution portably, and	2394	The C<stat ()> system call only supports full-second resolution portably,
1763	even on systems where the resolution is higher, many file systems still	2395	and even on systems where the resolution is higher, most file systems
1764	only support whole seconds.	2396	still only support whole seconds.
1765		2397
1766	That means that, if the time is the only thing that changes, you can	2398	That means that, if the time is the only thing that changes, you can
1767	easily miss updates: on the first update, C<ev_stat> detects a change and	2399	easily miss updates: on the first update, C<ev_stat> detects a change and
1768	calls your callback, which does something. When there is another update	2400	calls your callback, which does something. When there is another update
1769	within the same second, C<ev_stat> will be unable to detect it as the stat	2401	within the same second, C<ev_stat> will be unable to detect unless the
1770	data does not change.	2402	stat data does change in other ways (e.g. file size).
1771		2403
1772	The solution to this is to delay acting on a change for slightly more	2404	The solution to this is to delay acting on a change for slightly more
1773	than a second (or till slightly after the next full second boundary), using	2405	than a second (or till slightly after the next full second boundary), using
1774	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);	2406	a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02);
1775	ev_timer_again (loop, w)>).	2407	ev_timer_again (loop, w)>).
…		…
1795	C<path>. The C<interval> is a hint on how quickly a change is expected to	2427	C<path>. The C<interval> is a hint on how quickly a change is expected to
1796	be detected and should normally be specified as C<0> to let libev choose	2428	be detected and should normally be specified as C<0> to let libev choose
1797	a suitable value. The memory pointed to by C<path> must point to the same	2429	a suitable value. The memory pointed to by C<path> must point to the same
1798	path for as long as the watcher is active.	2430	path for as long as the watcher is active.
1799		2431
1800	The callback will receive C<EV_STAT> when a change was detected, relative	2432	The callback will receive an C<EV_STAT> event when a change was detected,
1801	to the attributes at the time the watcher was started (or the last change	2433	relative to the attributes at the time the watcher was started (or the
1802	was detected).	2434	last change was detected).
1803		2435
1804	=item ev_stat_stat (loop, ev_stat *)	2436	=item ev_stat_stat (loop, ev_stat *)
1805		2437
1806	Updates the stat buffer immediately with new values. If you change the	2438	Updates the stat buffer immediately with new values. If you change the
1807	watched path in your callback, you could call this function to avoid	2439	watched path in your callback, you could call this function to avoid
…		…
1890		2522
1891		2523
1892	=head2 C<ev_idle> - when you've got nothing better to do...	2524	=head2 C<ev_idle> - when you've got nothing better to do...
1893		2525
1894	Idle watchers trigger events when no other events of the same or higher	2526	Idle watchers trigger events when no other events of the same or higher
1895	priority are pending (prepare, check and other idle watchers do not	2527	priority are pending (prepare, check and other idle watchers do not count
1896	count).	2528	as receiving "events").
1897		2529
1898	That is, as long as your process is busy handling sockets or timeouts	2530	That is, as long as your process is busy handling sockets or timeouts
1899	(or even signals, imagine) of the same or higher priority it will not be	2531	(or even signals, imagine) of the same or higher priority it will not be
1900	triggered. But when your process is idle (or only lower-priority watchers	2532	triggered. But when your process is idle (or only lower-priority watchers
1901	are pending), the idle watchers are being called once per event loop	2533	are pending), the idle watchers are being called once per event loop
…		…
1912		2544
1913	=head3 Watcher-Specific Functions and Data Members	2545	=head3 Watcher-Specific Functions and Data Members
1914		2546
1915	=over 4	2547	=over 4
1916		2548
1917	=item ev_idle_init (ev_signal *, callback)	2549	=item ev_idle_init (ev_idle *, callback)
1918		2550
1919	Initialises and configures the idle watcher - it has no parameters of any	2551	Initialises and configures the idle watcher - it has no parameters of any
1920	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2552	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1921	believe me.	2553	believe me.
1922		2554
…		…
1926		2558
1927	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2559	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1928	callback, free it. Also, use no error checking, as usual.	2560	callback, free it. Also, use no error checking, as usual.
1929		2561
1930	static void	2562	static void
1931	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2563	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1932	{	2564	{
1933	free (w);	2565	free (w);
1934	// now do something you wanted to do when the program has	2566	// now do something you wanted to do when the program has
1935	// no longer anything immediate to do.	2567	// no longer anything immediate to do.
1936	}	2568	}
1937		2569
1938	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2570	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1939	ev_idle_init (idle_watcher, idle_cb);	2571	ev_idle_init (idle_watcher, idle_cb);
1940	ev_idle_start (loop, idle_cb);	2572	ev_idle_start (loop, idle_watcher);
1941		2573
1942		2574
1943	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2575	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1944		2576
1945	Prepare and check watchers are usually (but not always) used in tandem:	2577	Prepare and check watchers are usually (but not always) used in pairs:
1946	prepare watchers get invoked before the process blocks and check watchers	2578	prepare watchers get invoked before the process blocks and check watchers
1947	afterwards.	2579	afterwards.
1948		2580
1949	You I<must not> call C<ev_loop> or similar functions that enter	2581	You I<must not> call C<ev_loop> or similar functions that enter
1950	the current event loop from either C<ev_prepare> or C<ev_check>	2582	the current event loop from either C<ev_prepare> or C<ev_check>
…		…
1953	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,	2585	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
1954	C<ev_check> so if you have one watcher of each kind they will always be	2586	C<ev_check> so if you have one watcher of each kind they will always be
1955	called in pairs bracketing the blocking call.	2587	called in pairs bracketing the blocking call.
1956		2588
1957	Their main purpose is to integrate other event mechanisms into libev and	2589	Their main purpose is to integrate other event mechanisms into libev and
1958	their use is somewhat advanced. This could be used, for example, to track	2590	their use is somewhat advanced. They could be used, for example, to track
1959	variable changes, implement your own watchers, integrate net-snmp or a	2591	variable changes, implement your own watchers, integrate net-snmp or a
1960	coroutine library and lots more. They are also occasionally useful if	2592	coroutine library and lots more. They are also occasionally useful if
1961	you cache some data and want to flush it before blocking (for example,	2593	you cache some data and want to flush it before blocking (for example,
1962	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>	2594	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
1963	watcher).	2595	watcher).
1964		2596
1965	This is done by examining in each prepare call which file descriptors need	2597	This is done by examining in each prepare call which file descriptors
1966	to be watched by the other library, registering C<ev_io> watchers for	2598	need to be watched by the other library, registering C<ev_io> watchers
1967	them and starting an C<ev_timer> watcher for any timeouts (many libraries	2599	for them and starting an C<ev_timer> watcher for any timeouts (many
1968	provide just this functionality). Then, in the check watcher you check for	2600	libraries provide exactly this functionality). Then, in the check watcher,
1969	any events that occurred (by checking the pending status of all watchers	2601	you check for any events that occurred (by checking the pending status
1970	and stopping them) and call back into the library. The I/O and timer	2602	of all watchers and stopping them) and call back into the library. The
1971	callbacks will never actually be called (but must be valid nevertheless,	2603	I/O and timer callbacks will never actually be called (but must be valid
1972	because you never know, you know?).	2604	nevertheless, because you never know, you know?).
1973		2605
1974	As another example, the Perl Coro module uses these hooks to integrate	2606	As another example, the Perl Coro module uses these hooks to integrate
1975	coroutines into libev programs, by yielding to other active coroutines	2607	coroutines into libev programs, by yielding to other active coroutines
1976	during each prepare and only letting the process block if no coroutines	2608	during each prepare and only letting the process block if no coroutines
1977	are ready to run (it's actually more complicated: it only runs coroutines	2609	are ready to run (it's actually more complicated: it only runs coroutines
…		…
1980	loop from blocking if lower-priority coroutines are active, thus mapping	2612	loop from blocking if lower-priority coroutines are active, thus mapping
1981	low-priority coroutines to idle/background tasks).	2613	low-priority coroutines to idle/background tasks).
1982		2614
1983	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	2615	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1984	priority, to ensure that they are being run before any other watchers	2616	priority, to ensure that they are being run before any other watchers
		2617	after the poll (this doesn't matter for C<ev_prepare> watchers).
		2618
1985	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	2619	Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not
1986	too) should not activate ("feed") events into libev. While libev fully	2620	activate ("feed") events into libev. While libev fully supports this, they
1987	supports this, they might get executed before other C<ev_check> watchers	2621	might get executed before other C<ev_check> watchers did their job. As
1988	did their job. As C<ev_check> watchers are often used to embed other	2622	C<ev_check> watchers are often used to embed other (non-libev) event
1989	(non-libev) event loops those other event loops might be in an unusable	2623	loops those other event loops might be in an unusable state until their
1990	state until their C<ev_check> watcher ran (always remind yourself to	2624	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1991	coexist peacefully with others).	2625	others).
1992		2626
1993	=head3 Watcher-Specific Functions and Data Members	2627	=head3 Watcher-Specific Functions and Data Members
1994		2628
1995	=over 4	2629	=over 4
1996		2630
…		…
1998		2632
1999	=item ev_check_init (ev_check *, callback)	2633	=item ev_check_init (ev_check *, callback)
2000		2634
2001	Initialises and configures the prepare or check watcher - they have no	2635	Initialises and configures the prepare or check watcher - they have no
2002	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	2636	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
2003	macros, but using them is utterly, utterly and completely pointless.	2637	macros, but using them is utterly, utterly, utterly and completely
		2638	pointless.
2004		2639
2005	=back	2640	=back
2006		2641
2007	=head3 Examples	2642	=head3 Examples
2008		2643
…		…
2021		2656
2022	static ev_io iow [nfd];	2657	static ev_io iow [nfd];
2023	static ev_timer tw;	2658	static ev_timer tw;
2024		2659
2025	static void	2660	static void
2026	io_cb (ev_loop *loop, ev_io *w, int revents)	2661	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2027	{	2662	{
2028	}	2663	}
2029		2664
2030	// create io watchers for each fd and a timer before blocking	2665	// create io watchers for each fd and a timer before blocking
2031	static void	2666	static void
2032	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2667	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2033	{	2668	{
2034	int timeout = 3600000;	2669	int timeout = 3600000;
2035	struct pollfd fds [nfd];	2670	struct pollfd fds [nfd];
2036	// actual code will need to loop here and realloc etc.	2671	// actual code will need to loop here and realloc etc.
2037	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2672	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2038		2673
2039	/* the callback is illegal, but won't be called as we stop during check */	2674	/* the callback is illegal, but won't be called as we stop during check */
2040	ev_timer_init (&tw, 0, timeout * 1e-3);	2675	ev_timer_init (&tw, 0, timeout * 1e-3, 0.);
2041	ev_timer_start (loop, &tw);	2676	ev_timer_start (loop, &tw);
2042		2677
2043	// create one ev_io per pollfd	2678	// create one ev_io per pollfd
2044	for (int i = 0; i < nfd; ++i)	2679	for (int i = 0; i < nfd; ++i)
2045	{	2680	{
…		…
2052	}	2687	}
2053	}	2688	}
2054		2689
2055	// stop all watchers after blocking	2690	// stop all watchers after blocking
2056	static void	2691	static void
2057	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2692	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2058	{	2693	{
2059	ev_timer_stop (loop, &tw);	2694	ev_timer_stop (loop, &tw);
2060		2695
2061	for (int i = 0; i < nfd; ++i)	2696	for (int i = 0; i < nfd; ++i)
2062	{	2697	{
…		…
2101	}	2736	}
2102		2737
2103	// do not ever call adns_afterpoll	2738	// do not ever call adns_afterpoll
2104		2739
2105	Method 4: Do not use a prepare or check watcher because the module you	2740	Method 4: Do not use a prepare or check watcher because the module you
2106	want to embed is too inflexible to support it. Instead, you can override	2741	want to embed is not flexible enough to support it. Instead, you can
2107	their poll function. The drawback with this solution is that the main	2742	override their poll function. The drawback with this solution is that the
2108	loop is now no longer controllable by EV. The C<Glib::EV> module does	2743	main loop is now no longer controllable by EV. The C<Glib::EV> module uses
2109	this.	2744	this approach, effectively embedding EV as a client into the horrible
		2745	libglib event loop.
2110		2746
2111	static gint	2747	static gint
2112	event_poll_func (GPollFD *fds, guint nfds, gint timeout)	2748	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
2113	{	2749	{
2114	int got_events = 0;	2750	int got_events = 0;
…		…
2145	prioritise I/O.	2781	prioritise I/O.
2146		2782
2147	As an example for a bug workaround, the kqueue backend might only support	2783	As an example for a bug workaround, the kqueue backend might only support
2148	sockets on some platform, so it is unusable as generic backend, but you	2784	sockets on some platform, so it is unusable as generic backend, but you
2149	still want to make use of it because you have many sockets and it scales	2785	still want to make use of it because you have many sockets and it scales
2150	so nicely. In this case, you would create a kqueue-based loop and embed it	2786	so nicely. In this case, you would create a kqueue-based loop and embed
2151	into your default loop (which might use e.g. poll). Overall operation will	2787	it into your default loop (which might use e.g. poll). Overall operation
2152	be a bit slower because first libev has to poll and then call kevent, but	2788	will be a bit slower because first libev has to call C<poll> and then
2153	at least you can use both at what they are best.	2789	C<kevent>, but at least you can use both mechanisms for what they are
		2790	best: C<kqueue> for scalable sockets and C<poll> if you want it to work :)
2154		2791
2155	As for prioritising I/O: rarely you have the case where some fds have	2792	As for prioritising I/O: under rare circumstances you have the case where
2156	to be watched and handled very quickly (with low latency), and even	2793	some fds have to be watched and handled very quickly (with low latency),
2157	priorities and idle watchers might have too much overhead. In this case	2794	and even priorities and idle watchers might have too much overhead. In
2158	you would put all the high priority stuff in one loop and all the rest in	2795	this case you would put all the high priority stuff in one loop and all
2159	a second one, and embed the second one in the first.	2796	the rest in a second one, and embed the second one in the first.
2160		2797
2161	As long as the watcher is active, the callback will be invoked every time	2798	As long as the watcher is active, the callback will be invoked every
2162	there might be events pending in the embedded loop. The callback must then	2799	time there might be events pending in the embedded loop. The callback
2163	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2800	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2164	their callbacks (you could also start an idle watcher to give the embedded	2801	sweep and invoke their callbacks (the callback doesn't need to invoke the
2165	loop strictly lower priority for example). You can also set the callback	2802	C<ev_embed_sweep> function directly, it could also start an idle watcher
2166	to C<0>, in which case the embed watcher will automatically execute the	2803	to give the embedded loop strictly lower priority for example).
2167	embedded loop sweep.
2168		2804
2169	As long as the watcher is started it will automatically handle events. The	2805	You can also set the callback to C<0>, in which case the embed watcher
2170	callback will be invoked whenever some events have been handled. You can	2806	will automatically execute the embedded loop sweep whenever necessary.
2171	set the callback to C<0> to avoid having to specify one if you are not
2172	interested in that.
2173		2807
2174	Also, there have not currently been made special provisions for forking:	2808	Fork detection will be handled transparently while the C<ev_embed> watcher
2175	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2809	is active, i.e., the embedded loop will automatically be forked when the
2176	but you will also have to stop and restart any C<ev_embed> watchers	2810	embedding loop forks. In other cases, the user is responsible for calling
2177	yourself.	2811	C<ev_loop_fork> on the embedded loop.
2178		2812
2179	Unfortunately, not all backends are embeddable, only the ones returned by	2813	Unfortunately, not all backends are embeddable: only the ones returned by
2180	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2814	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2181	portable one.	2815	portable one.
2182		2816
2183	So when you want to use this feature you will always have to be prepared	2817	So when you want to use this feature you will always have to be prepared
2184	that you cannot get an embeddable loop. The recommended way to get around	2818	that you cannot get an embeddable loop. The recommended way to get around
2185	this is to have a separate variables for your embeddable loop, try to	2819	this is to have a separate variables for your embeddable loop, try to
2186	create it, and if that fails, use the normal loop for everything.	2820	create it, and if that fails, use the normal loop for everything.
		2821
		2822	=head3 C<ev_embed> and fork
		2823
		2824	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2825	automatically be applied to the embedded loop as well, so no special
		2826	fork handling is required in that case. When the watcher is not running,
		2827	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2828	as applicable.
2187		2829
2188	=head3 Watcher-Specific Functions and Data Members	2830	=head3 Watcher-Specific Functions and Data Members
2189		2831
2190	=over 4	2832	=over 4
2191		2833
…		…
2219	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2861	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2220	used).	2862	used).
2221		2863
2222	struct ev_loop *loop_hi = ev_default_init (0);	2864	struct ev_loop *loop_hi = ev_default_init (0);
2223	struct ev_loop *loop_lo = 0;	2865	struct ev_loop *loop_lo = 0;
2224	struct ev_embed embed;	2866	ev_embed embed;
2225		2867
2226	// see if there is a chance of getting one that works	2868	// see if there is a chance of getting one that works
2227	// (remember that a flags value of 0 means autodetection)	2869	// (remember that a flags value of 0 means autodetection)
2228	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2870	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2229	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2871	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2243	kqueue implementation). Store the kqueue/socket-only event loop in	2885	kqueue implementation). Store the kqueue/socket-only event loop in
2244	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2886	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2245		2887
2246	struct ev_loop *loop = ev_default_init (0);	2888	struct ev_loop *loop = ev_default_init (0);
2247	struct ev_loop *loop_socket = 0;	2889	struct ev_loop *loop_socket = 0;
2248	struct ev_embed embed;	2890	ev_embed embed;
2249		2891
2250	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2892	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2251	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2893	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2252	{	2894	{
2253	ev_embed_init (&embed, 0, loop_socket);	2895	ev_embed_init (&embed, 0, loop_socket);
…		…
2268	event loop blocks next and before C<ev_check> watchers are being called,	2910	event loop blocks next and before C<ev_check> watchers are being called,
2269	and only in the child after the fork. If whoever good citizen calling	2911	and only in the child after the fork. If whoever good citizen calling
2270	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2912	C<ev_default_fork> cheats and calls it in the wrong process, the fork
2271	handlers will be invoked, too, of course.	2913	handlers will be invoked, too, of course.
2272		2914
		2915	=head3 The special problem of life after fork - how is it possible?
		2916
		2917	Most uses of C<fork()> consist of forking, then some simple calls to ste
		2918	up/change the process environment, followed by a call to C<exec()>. This
		2919	sequence should be handled by libev without any problems.
		2920
		2921	This changes when the application actually wants to do event handling
		2922	in the child, or both parent in child, in effect "continuing" after the
		2923	fork.
		2924
		2925	The default mode of operation (for libev, with application help to detect
		2926	forks) is to duplicate all the state in the child, as would be expected
		2927	when I<either> the parent I<or> the child process continues.
		2928
		2929	When both processes want to continue using libev, then this is usually the
		2930	wrong result. In that case, usually one process (typically the parent) is
		2931	supposed to continue with all watchers in place as before, while the other
		2932	process typically wants to start fresh, i.e. without any active watchers.
		2933
		2934	The cleanest and most efficient way to achieve that with libev is to
		2935	simply create a new event loop, which of course will be "empty", and
		2936	use that for new watchers. This has the advantage of not touching more
		2937	memory than necessary, and thus avoiding the copy-on-write, and the
		2938	disadvantage of having to use multiple event loops (which do not support
		2939	signal watchers).
		2940
		2941	When this is not possible, or you want to use the default loop for
		2942	other reasons, then in the process that wants to start "fresh", call
		2943	C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying
		2944	the default loop will "orphan" (not stop) all registered watchers, so you
		2945	have to be careful not to execute code that modifies those watchers. Note
		2946	also that in that case, you have to re-register any signal watchers.
		2947
2273	=head3 Watcher-Specific Functions and Data Members	2948	=head3 Watcher-Specific Functions and Data Members
2274		2949
2275	=over 4	2950	=over 4
2276		2951
2277	=item ev_fork_init (ev_signal *, callback)	2952	=item ev_fork_init (ev_signal *, callback)
…		…
2309	is that the author does not know of a simple (or any) algorithm for a	2984	is that the author does not know of a simple (or any) algorithm for a
2310	multiple-writer-single-reader queue that works in all cases and doesn't	2985	multiple-writer-single-reader queue that works in all cases and doesn't
2311	need elaborate support such as pthreads.	2986	need elaborate support such as pthreads.
2312		2987
2313	That means that if you want to queue data, you have to provide your own	2988	That means that if you want to queue data, you have to provide your own
2314	queue. But at least I can tell you would implement locking around your	2989	queue. But at least I can tell you how to implement locking around your
2315	queue:	2990	queue:
2316		2991
2317	=over 4	2992	=over 4
2318		2993
2319	=item queueing from a signal handler context	2994	=item queueing from a signal handler context
2320		2995
2321	To implement race-free queueing, you simply add to the queue in the signal	2996	To implement race-free queueing, you simply add to the queue in the signal
2322	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2997	handler but you block the signal handler in the watcher callback. Here is
2323	some fictitious SIGUSR1 handler:	2998	an example that does that for some fictitious SIGUSR1 handler:
2324		2999
2325	static ev_async mysig;	3000	static ev_async mysig;
2326		3001
2327	static void	3002	static void
2328	sigusr1_handler (void)	3003	sigusr1_handler (void)
…		…
2394	=over 4	3069	=over 4
2395		3070
2396	=item ev_async_init (ev_async *, callback)	3071	=item ev_async_init (ev_async *, callback)
2397		3072
2398	Initialises and configures the async watcher - it has no parameters of any	3073	Initialises and configures the async watcher - it has no parameters of any
2399	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	3074	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2400	believe me.	3075	trust me.
2401		3076
2402	=item ev_async_send (loop, ev_async *)	3077	=item ev_async_send (loop, ev_async *)
2403		3078
2404	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	3079	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2405	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	3080	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2406	C<ev_feed_event>, this call is safe to do in other threads, signal or	3081	C<ev_feed_event>, this call is safe to do from other threads, signal or
2407	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	3082	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2408	section below on what exactly this means).	3083	section below on what exactly this means).
2409		3084
		3085	Note that, as with other watchers in libev, multiple events might get
		3086	compressed into a single callback invocation (another way to look at this
		3087	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		3088	reset when the event loop detects that).
		3089
2410	This call incurs the overhead of a system call only once per loop iteration,	3090	This call incurs the overhead of a system call only once per event loop
2411	so while the overhead might be noticeable, it doesn't apply to repeated	3091	iteration, so while the overhead might be noticeable, it doesn't apply to
2412	calls to C<ev_async_send>.	3092	repeated calls to C<ev_async_send> for the same event loop.
2413		3093
2414	=item bool = ev_async_pending (ev_async *)	3094	=item bool = ev_async_pending (ev_async *)
2415		3095
2416	Returns a non-zero value when C<ev_async_send> has been called on the	3096	Returns a non-zero value when C<ev_async_send> has been called on the
2417	watcher but the event has not yet been processed (or even noted) by the	3097	watcher but the event has not yet been processed (or even noted) by the
…		…
2420	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	3100	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2421	the loop iterates next and checks for the watcher to have become active,	3101	the loop iterates next and checks for the watcher to have become active,
2422	it will reset the flag again. C<ev_async_pending> can be used to very	3102	it will reset the flag again. C<ev_async_pending> can be used to very
2423	quickly check whether invoking the loop might be a good idea.	3103	quickly check whether invoking the loop might be a good idea.
2424		3104
2425	Not that this does I<not> check whether the watcher itself is pending, only	3105	Not that this does I<not> check whether the watcher itself is pending,
2426	whether it has been requested to make this watcher pending.	3106	only whether it has been requested to make this watcher pending: there
		3107	is a time window between the event loop checking and resetting the async
		3108	notification, and the callback being invoked.
2427		3109
2428	=back	3110	=back
2429		3111
2430		3112
2431	=head1 OTHER FUNCTIONS	3113	=head1 OTHER FUNCTIONS
…		…
2435	=over 4	3117	=over 4
2436		3118
2437	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	3119	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2438		3120
2439	This function combines a simple timer and an I/O watcher, calls your	3121	This function combines a simple timer and an I/O watcher, calls your
2440	callback on whichever event happens first and automatically stop both	3122	callback on whichever event happens first and automatically stops both
2441	watchers. This is useful if you want to wait for a single event on an fd	3123	watchers. This is useful if you want to wait for a single event on an fd
2442	or timeout without having to allocate/configure/start/stop/free one or	3124	or timeout without having to allocate/configure/start/stop/free one or
2443	more watchers yourself.	3125	more watchers yourself.
2444		3126
2445	If C<fd> is less than 0, then no I/O watcher will be started and events	3127	If C<fd> is less than 0, then no I/O watcher will be started and the
2446	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	3128	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2447	C<events> set will be created and started.	3129	the given C<fd> and C<events> set will be created and started.
2448		3130
2449	If C<timeout> is less than 0, then no timeout watcher will be	3131	If C<timeout> is less than 0, then no timeout watcher will be
2450	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	3132	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2451	repeat = 0) will be started. While C<0> is a valid timeout, it is of	3133	repeat = 0) will be started. C<0> is a valid timeout.
2452	dubious value.
2453		3134
2454	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	3135	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2455	passed an C<revents> set like normal event callbacks (a combination of	3136	passed an C<revents> set like normal event callbacks (a combination of
2456	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	3137	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2457	value passed to C<ev_once>:	3138	value passed to C<ev_once>. Note that it is possible to receive I<both>
		3139	a timeout and an io event at the same time - you probably should give io
		3140	events precedence.
		3141
		3142	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2458		3143
2459	static void stdin_ready (int revents, void *arg)	3144	static void stdin_ready (int revents, void *arg)
2460	{	3145	{
		3146	if (revents & EV_READ)
		3147	/* stdin might have data for us, joy! */;
2461	if (revents & EV_TIMEOUT)	3148	else if (revents & EV_TIMEOUT)
2462	/* doh, nothing entered */;	3149	/* doh, nothing entered */;
2463	else if (revents & EV_READ)
2464	/* stdin might have data for us, joy! */;
2465	}	3150	}
2466		3151
2467	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2468		3153
2469	=item ev_feed_event (ev_loop *, watcher *, int revents)
2470
2471	Feeds the given event set into the event loop, as if the specified event
2472	had happened for the specified watcher (which must be a pointer to an
2473	initialised but not necessarily started event watcher).
2474
2475	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2476		3155
2477	Feed an event on the given fd, as if a file descriptor backend detected	3156	Feed an event on the given fd, as if a file descriptor backend detected
2478	the given events it.	3157	the given events it.
2479		3158
2480	=item ev_feed_signal_event (ev_loop *loop, int signum)	3159	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2481		3160
2482	Feed an event as if the given signal occurred (C<loop> must be the default	3161	Feed an event as if the given signal occurred (C<loop> must be the default
2483	loop!).	3162	loop!).
2484		3163
2485	=back	3164	=back
…		…
2607		3286
2608	myclass obj;	3287	myclass obj;
2609	ev::io iow;	3288	ev::io iow;
2610	iow.set <myclass, &myclass::io_cb> (&obj);	3289	iow.set <myclass, &myclass::io_cb> (&obj);
2611		3290
		3291	=item w->set (object *)
		3292
		3293	This is an B<experimental> feature that might go away in a future version.
		3294
		3295	This is a variation of a method callback - leaving out the method to call
		3296	will default the method to C<operator ()>, which makes it possible to use
		3297	functor objects without having to manually specify the C<operator ()> all
		3298	the time. Incidentally, you can then also leave out the template argument
		3299	list.
		3300
		3301	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		3302	int revents)>.
		3303
		3304	See the method-C<set> above for more details.
		3305
		3306	Example: use a functor object as callback.
		3307
		3308	struct myfunctor
		3309	{
		3310	void operator() (ev::io &w, int revents)
		3311	{
		3312	...
		3313	}
		3314	}
		3315
		3316	myfunctor f;
		3317
		3318	ev::io w;
		3319	w.set (&f);
		3320
2612	=item w->set<function> (void *data = 0)	3321	=item w->set<function> (void *data = 0)
2613		3322
2614	Also sets a callback, but uses a static method or plain function as	3323	Also sets a callback, but uses a static method or plain function as
2615	callback. The optional C<data> argument will be stored in the watcher's	3324	callback. The optional C<data> argument will be stored in the watcher's
2616	C<data> member and is free for you to use.	3325	C<data> member and is free for you to use.
2617		3326
2618	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	3327	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2619		3328
2620	See the method-C<set> above for more details.	3329	See the method-C<set> above for more details.
2621		3330
2622	Example:	3331	Example: Use a plain function as callback.
2623		3332
2624	static void io_cb (ev::io &w, int revents) { }	3333	static void io_cb (ev::io &w, int revents) { }
2625	iow.set <io_cb> ();	3334	iow.set <io_cb> ();
2626		3335
2627	=item w->set (struct ev_loop *)	3336	=item w->set (struct ev_loop *)
…		…
2665	Example: Define a class with an IO and idle watcher, start one of them in	3374	Example: Define a class with an IO and idle watcher, start one of them in
2666	the constructor.	3375	the constructor.
2667		3376
2668	class myclass	3377	class myclass
2669	{	3378	{
2670	ev::io io; void io_cb (ev::io &w, int revents);	3379	ev::io io ; void io_cb (ev::io &w, int revents);
2671	ev:idle idle void idle_cb (ev::idle &w, int revents);	3380	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2672		3381
2673	myclass (int fd)	3382	myclass (int fd)
2674	{	3383	{
2675	io .set <myclass, &myclass::io_cb > (this);	3384	io .set <myclass, &myclass::io_cb > (this);
2676	idle.set <myclass, &myclass::idle_cb> (this);	3385	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2692	=item Perl	3401	=item Perl
2693		3402
2694	The EV module implements the full libev API and is actually used to test	3403	The EV module implements the full libev API and is actually used to test
2695	libev. EV is developed together with libev. Apart from the EV core module,	3404	libev. EV is developed together with libev. Apart from the EV core module,
2696	there are additional modules that implement libev-compatible interfaces	3405	there are additional modules that implement libev-compatible interfaces
2697	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	3406	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2698	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	3407	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		3408	and C<EV::Glib>).
2699		3409
2700	It can be found and installed via CPAN, its homepage is at	3410	It can be found and installed via CPAN, its homepage is at
2701	L<http://software.schmorp.de/pkg/EV>.	3411	L<http://software.schmorp.de/pkg/EV>.
2702		3412
2703	=item Python	3413	=item Python
2704		3414
2705	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3415	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2706	seems to be quite complete and well-documented. Note, however, that the	3416	seems to be quite complete and well-documented.
2707	patch they require for libev is outright dangerous as it breaks the ABI
2708	for everybody else, and therefore, should never be applied in an installed
2709	libev (if python requires an incompatible ABI then it needs to embed
2710	libev).
2711		3417
2712	=item Ruby	3418	=item Ruby
2713		3419
2714	Tony Arcieri has written a ruby extension that offers access to a subset	3420	Tony Arcieri has written a ruby extension that offers access to a subset
2715	of the libev API and adds file handle abstractions, asynchronous DNS and	3421	of the libev API and adds file handle abstractions, asynchronous DNS and
2716	more on top of it. It can be found via gem servers. Its homepage is at	3422	more on top of it. It can be found via gem servers. Its homepage is at
2717	L<http://rev.rubyforge.org/>.	3423	L<http://rev.rubyforge.org/>.
2718		3424
		3425	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3426	makes rev work even on mingw.
		3427
		3428	=item Haskell
		3429
		3430	A haskell binding to libev is available at
		3431	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3432
2719	=item D	3433	=item D
2720		3434
2721	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3435	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2722	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3436	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3437
		3438	=item Ocaml
		3439
		3440	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3442
		3443	=item Lua
		3444
		3445	Brian Maher has written a partial interface to libev
		3446	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3447	L<http://github.com/brimworks/lua-ev>.
2723		3448
2724	=back	3449	=back
2725		3450
2726		3451
2727	=head1 MACRO MAGIC	3452	=head1 MACRO MAGIC
…		…
2828		3553
2829	#define EV_STANDALONE 1	3554	#define EV_STANDALONE 1
2830	#include "ev.h"	3555	#include "ev.h"
2831		3556
2832	Both header files and implementation files can be compiled with a C++	3557	Both header files and implementation files can be compiled with a C++
2833	compiler (at least, thats a stated goal, and breakage will be treated	3558	compiler (at least, that's a stated goal, and breakage will be treated
2834	as a bug).	3559	as a bug).
2835		3560
2836	You need the following files in your source tree, or in a directory	3561	You need the following files in your source tree, or in a directory
2837	in your include path (e.g. in libev/ when using -Ilibev):	3562	in your include path (e.g. in libev/ when using -Ilibev):
2838		3563
…		…
2882		3607
2883	=head2 PREPROCESSOR SYMBOLS/MACROS	3608	=head2 PREPROCESSOR SYMBOLS/MACROS
2884		3609
2885	Libev can be configured via a variety of preprocessor symbols you have to	3610	Libev can be configured via a variety of preprocessor symbols you have to
2886	define before including any of its files. The default in the absence of	3611	define before including any of its files. The default in the absence of
2887	autoconf is noted for every option.	3612	autoconf is documented for every option.
2888		3613
2889	=over 4	3614	=over 4
2890		3615
2891	=item EV_STANDALONE	3616	=item EV_STANDALONE
2892		3617
…		…
2894	keeps libev from including F<config.h>, and it also defines dummy	3619	keeps libev from including F<config.h>, and it also defines dummy
2895	implementations for some libevent functions (such as logging, which is not	3620	implementations for some libevent functions (such as logging, which is not
2896	supported). It will also not define any of the structs usually found in	3621	supported). It will also not define any of the structs usually found in
2897	F<event.h> that are not directly supported by the libev core alone.	3622	F<event.h> that are not directly supported by the libev core alone.
2898		3623
		3624	In standalone mode, libev will still try to automatically deduce the
		3625	configuration, but has to be more conservative.
		3626
2899	=item EV_USE_MONOTONIC	3627	=item EV_USE_MONOTONIC
2900		3628
2901	If defined to be C<1>, libev will try to detect the availability of the	3629	If defined to be C<1>, libev will try to detect the availability of the
2902	monotonic clock option at both compile time and runtime. Otherwise no use	3630	monotonic clock option at both compile time and runtime. Otherwise no
2903	of the monotonic clock option will be attempted. If you enable this, you	3631	use of the monotonic clock option will be attempted. If you enable this,
2904	usually have to link against librt or something similar. Enabling it when	3632	you usually have to link against librt or something similar. Enabling it
2905	the functionality isn't available is safe, though, although you have	3633	when the functionality isn't available is safe, though, although you have
2906	to make sure you link against any libraries where the C<clock_gettime>	3634	to make sure you link against any libraries where the C<clock_gettime>
2907	function is hiding in (often F<-lrt>).	3635	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2908		3636
2909	=item EV_USE_REALTIME	3637	=item EV_USE_REALTIME
2910		3638
2911	If defined to be C<1>, libev will try to detect the availability of the	3639	If defined to be C<1>, libev will try to detect the availability of the
2912	real-time clock option at compile time (and assume its availability at	3640	real-time clock option at compile time (and assume its availability
2913	runtime if successful). Otherwise no use of the real-time clock option will	3641	at runtime if successful). Otherwise no use of the real-time clock
2914	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3642	option will be attempted. This effectively replaces C<gettimeofday>
2915	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3643	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2916	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3644	correctness. See the note about libraries in the description of
		3645	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3646	C<EV_USE_CLOCK_SYSCALL>.
		3647
		3648	=item EV_USE_CLOCK_SYSCALL
		3649
		3650	If defined to be C<1>, libev will try to use a direct syscall instead
		3651	of calling the system-provided C<clock_gettime> function. This option
		3652	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3653	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3654	programs needlessly. Using a direct syscall is slightly slower (in
		3655	theory), because no optimised vdso implementation can be used, but avoids
		3656	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3657	higher, as it simplifies linking (no need for C<-lrt>).
2917		3658
2918	=item EV_USE_NANOSLEEP	3659	=item EV_USE_NANOSLEEP
2919		3660
2920	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3661	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2921	and will use it for delays. Otherwise it will use C<select ()>.	3662	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2937		3678
2938	=item EV_SELECT_USE_FD_SET	3679	=item EV_SELECT_USE_FD_SET
2939		3680
2940	If defined to C<1>, then the select backend will use the system C<fd_set>	3681	If defined to C<1>, then the select backend will use the system C<fd_set>
2941	structure. This is useful if libev doesn't compile due to a missing	3682	structure. This is useful if libev doesn't compile due to a missing
2942	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3683	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
2943	exotic systems. This usually limits the range of file descriptors to some	3684	on exotic systems. This usually limits the range of file descriptors to
2944	low limit such as 1024 or might have other limitations (winsocket only	3685	some low limit such as 1024 or might have other limitations (winsocket
2945	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3686	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
2946	influence the size of the C<fd_set> used.	3687	configures the maximum size of the C<fd_set>.
2947		3688
2948	=item EV_SELECT_IS_WINSOCKET	3689	=item EV_SELECT_IS_WINSOCKET
2949		3690
2950	When defined to C<1>, the select backend will assume that	3691	When defined to C<1>, the select backend will assume that
2951	select/socket/connect etc. don't understand file descriptors but	3692	select/socket/connect etc. don't understand file descriptors but
…		…
2953	be used is the winsock select). This means that it will call	3694	be used is the winsock select). This means that it will call
2954	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3695	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2955	it is assumed that all these functions actually work on fds, even	3696	it is assumed that all these functions actually work on fds, even
2956	on win32. Should not be defined on non-win32 platforms.	3697	on win32. Should not be defined on non-win32 platforms.
2957		3698
2958	=item EV_FD_TO_WIN32_HANDLE	3699	=item EV_FD_TO_WIN32_HANDLE(fd)
2959		3700
2960	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3701	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2961	file descriptors to socket handles. When not defining this symbol (the	3702	file descriptors to socket handles. When not defining this symbol (the
2962	default), then libev will call C<_get_osfhandle>, which is usually	3703	default), then libev will call C<_get_osfhandle>, which is usually
2963	correct. In some cases, programs use their own file descriptor management,	3704	correct. In some cases, programs use their own file descriptor management,
2964	in which case they can provide this function to map fds to socket handles.	3705	in which case they can provide this function to map fds to socket handles.
		3706
		3707	=item EV_WIN32_HANDLE_TO_FD(handle)
		3708
		3709	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3710	using the standard C<_open_osfhandle> function. For programs implementing
		3711	their own fd to handle mapping, overwriting this function makes it easier
		3712	to do so. This can be done by defining this macro to an appropriate value.
		3713
		3714	=item EV_WIN32_CLOSE_FD(fd)
		3715
		3716	If programs implement their own fd to handle mapping on win32, then this
		3717	macro can be used to override the C<close> function, useful to unregister
		3718	file descriptors again. Note that the replacement function has to close
		3719	the underlying OS handle.
2965		3720
2966	=item EV_USE_POLL	3721	=item EV_USE_POLL
2967		3722
2968	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3723	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2969	backend. Otherwise it will be enabled on non-win32 platforms. It	3724	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3062	When doing priority-based operations, libev usually has to linearly search	3817	When doing priority-based operations, libev usually has to linearly search
3063	all the priorities, so having many of them (hundreds) uses a lot of space	3818	all the priorities, so having many of them (hundreds) uses a lot of space
3064	and time, so using the defaults of five priorities (-2 .. +2) is usually	3819	and time, so using the defaults of five priorities (-2 .. +2) is usually
3065	fine.	3820	fine.
3066		3821
3067	If your embedding application does not need any priorities, defining these both to	3822	If your embedding application does not need any priorities, defining these
3068	C<0> will save some memory and CPU.	3823	both to C<0> will save some memory and CPU.
3069		3824
3070	=item EV_PERIODIC_ENABLE	3825	=item EV_PERIODIC_ENABLE
3071		3826
3072	If undefined or defined to be C<1>, then periodic timers are supported. If	3827	If undefined or defined to be C<1>, then periodic timers are supported. If
3073	defined to be C<0>, then they are not. Disabling them saves a few kB of	3828	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3080	code.	3835	code.
3081		3836
3082	=item EV_EMBED_ENABLE	3837	=item EV_EMBED_ENABLE
3083		3838
3084	If undefined or defined to be C<1>, then embed watchers are supported. If	3839	If undefined or defined to be C<1>, then embed watchers are supported. If
3085	defined to be C<0>, then they are not.	3840	defined to be C<0>, then they are not. Embed watchers rely on most other
		3841	watcher types, which therefore must not be disabled.
3086		3842
3087	=item EV_STAT_ENABLE	3843	=item EV_STAT_ENABLE
3088		3844
3089	If undefined or defined to be C<1>, then stat watchers are supported. If	3845	If undefined or defined to be C<1>, then stat watchers are supported. If
3090	defined to be C<0>, then they are not.	3846	defined to be C<0>, then they are not.
…		…
3100	defined to be C<0>, then they are not.	3856	defined to be C<0>, then they are not.
3101		3857
3102	=item EV_MINIMAL	3858	=item EV_MINIMAL
3103		3859
3104	If you need to shave off some kilobytes of code at the expense of some	3860	If you need to shave off some kilobytes of code at the expense of some
3105	speed, define this symbol to C<1>. Currently this is used to override some	3861	speed (but with the full API), define this symbol to C<1>. Currently this
3106	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3862	is used to override some inlining decisions, saves roughly 30% code size
3107	much smaller 2-heap for timer management over the default 4-heap.	3863	on amd64. It also selects a much smaller 2-heap for timer management over
		3864	the default 4-heap.
		3865
		3866	You can save even more by disabling watcher types you do not need
		3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3868	(C<-DNDEBUG>) will usually reduce code size a lot.
		3869
		3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3871	provide a bare-bones event library. See C<ev.h> for details on what parts
		3872	of the API are still available, and do not complain if this subset changes
		3873	over time.
		3874
		3875	=item EV_NSIG
		3876
		3877	The highest supported signal number, +1 (or, the number of
		3878	signals): Normally, libev tries to deduce the maximum number of signals
		3879	automatically, but sometimes this fails, in which case it can be
		3880	specified. Also, using a lower number than detected (C<32> should be
		3881	good for about any system in existance) can save some memory, as libev
		3882	statically allocates some 12-24 bytes per signal number.
3108		3883
3109	=item EV_PID_HASHSIZE	3884	=item EV_PID_HASHSIZE
3110		3885
3111	C<ev_child> watchers use a small hash table to distribute workload by	3886	C<ev_child> watchers use a small hash table to distribute workload by
3112	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3887	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3122	two).	3897	two).
3123		3898
3124	=item EV_USE_4HEAP	3899	=item EV_USE_4HEAP
3125		3900
3126	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3901	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3127	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3902	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3128	to C<1>. The 4-heap uses more complicated (longer) code but has	3903	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3129	noticeably faster performance with many (thousands) of watchers.	3904	faster performance with many (thousands) of watchers.
3130		3905
3131	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3906	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3132	(disabled).	3907	(disabled).
3133		3908
3134	=item EV_HEAP_CACHE_AT	3909	=item EV_HEAP_CACHE_AT
3135		3910
3136	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3911	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3137	timer and periodics heap, libev can cache the timestamp (I<at>) within	3912	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3138	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3913	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3139	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3914	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3140	but avoids random read accesses on heap changes. This improves performance	3915	but avoids random read accesses on heap changes. This improves performance
3141	noticeably with with many (hundreds) of watchers.	3916	noticeably with many (hundreds) of watchers.
3142		3917
3143	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3918	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3144	(disabled).	3919	(disabled).
3145		3920
3146	=item EV_VERIFY	3921	=item EV_VERIFY
…		…
3152	called once per loop, which can slow down libev. If set to C<3>, then the	3927	called once per loop, which can slow down libev. If set to C<3>, then the
3153	verification code will be called very frequently, which will slow down	3928	verification code will be called very frequently, which will slow down
3154	libev considerably.	3929	libev considerably.
3155		3930
3156	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3931	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3157	C<0.>	3932	C<0>.
3158		3933
3159	=item EV_COMMON	3934	=item EV_COMMON
3160		3935
3161	By default, all watchers have a C<void *data> member. By redefining	3936	By default, all watchers have a C<void *data> member. By redefining
3162	this macro to a something else you can include more and other types of	3937	this macro to a something else you can include more and other types of
…		…
3179	and the way callbacks are invoked and set. Must expand to a struct member	3954	and the way callbacks are invoked and set. Must expand to a struct member
3180	definition and a statement, respectively. See the F<ev.h> header file for	3955	definition and a statement, respectively. See the F<ev.h> header file for
3181	their default definitions. One possible use for overriding these is to	3956	their default definitions. One possible use for overriding these is to
3182	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3957	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3183	method calls instead of plain function calls in C++.	3958	method calls instead of plain function calls in C++.
		3959
		3960	=back
3184		3961
3185	=head2 EXPORTED API SYMBOLS	3962	=head2 EXPORTED API SYMBOLS
3186		3963
3187	If you need to re-export the API (e.g. via a DLL) and you need a list of	3964	If you need to re-export the API (e.g. via a DLL) and you need a list of
3188	exported symbols, you can use the provided F<Symbol.*> files which list	3965	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3235	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	4012	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3236		4013
3237	#include "ev_cpp.h"	4014	#include "ev_cpp.h"
3238	#include "ev.c"	4015	#include "ev.c"
3239		4016
		4017	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3240		4018
3241	=head1 THREADS AND COROUTINES	4019	=head2 THREADS AND COROUTINES
3242		4020
3243	=head2 THREADS	4021	=head3 THREADS
3244		4022
3245	Libev itself is thread-safe (unless the opposite is specifically	4023	All libev functions are reentrant and thread-safe unless explicitly
3246	documented for a function), but it uses no locking itself. This means that	4024	documented otherwise, but libev implements no locking itself. This means
3247	you can use as many loops as you want in parallel, as long as only one	4025	that you can use as many loops as you want in parallel, as long as there
3248	thread ever calls into one libev function with the same loop parameter:	4026	are no concurrent calls into any libev function with the same loop
		4027	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3249	libev guarentees that different event loops share no data structures that	4028	of course): libev guarantees that different event loops share no data
3250	need locking.	4029	structures that need any locking.
3251		4030
3252	Or to put it differently: calls with different loop parameters can be done	4031	Or to put it differently: calls with different loop parameters can be done
3253	concurrently from multiple threads, calls with the same loop parameter	4032	concurrently from multiple threads, calls with the same loop parameter
3254	must be done serially (but can be done from different threads, as long as	4033	must be done serially (but can be done from different threads, as long as
3255	only one thread ever is inside a call at any point in time, e.g. by using	4034	only one thread ever is inside a call at any point in time, e.g. by using
3256	a mutex per loop).	4035	a mutex per loop).
3257		4036
3258	Specifically to support threads (and signal handlers), libev implements	4037	Specifically to support threads (and signal handlers), libev implements
3259	so-called C<ev_async> watchers, which allow some limited form of	4038	so-called C<ev_async> watchers, which allow some limited form of
3260	concurrency on the same event loop.	4039	concurrency on the same event loop, namely waking it up "from the
		4040	outside".
3261		4041
3262	If you want to know which design (one loop, locking, or multiple loops	4042	If you want to know which design (one loop, locking, or multiple loops
3263	without or something else still) is best for your problem, then I cannot	4043	without or something else still) is best for your problem, then I cannot
3264	help you. I can give some generic advice however:	4044	help you, but here is some generic advice:
3265		4045
3266	=over 4	4046	=over 4
3267		4047
3268	=item * most applications have a main thread: use the default libev loop	4048	=item * most applications have a main thread: use the default libev loop
3269	in that thread, or create a separate thread running only the default loop.	4049	in that thread, or create a separate thread running only the default loop.
…		…
3281		4061
3282	Choosing a model is hard - look around, learn, know that usually you can do	4062	Choosing a model is hard - look around, learn, know that usually you can do
3283	better than you currently do :-)	4063	better than you currently do :-)
3284		4064
3285	=item * often you need to talk to some other thread which blocks in the	4065	=item * often you need to talk to some other thread which blocks in the
		4066	event loop.
		4067
3286	event loop - C<ev_async> watchers can be used to wake them up from other	4068	C<ev_async> watchers can be used to wake them up from other threads safely
3287	threads safely (or from signal contexts...).	4069	(or from signal contexts...).
3288		4070
3289	=item * some watcher types are only supported in the default loop - use	4071	An example use would be to communicate signals or other events that only
3290	C<ev_async> watchers to tell your other loops about any such events.	4072	work in the default loop by registering the signal watcher with the
		4073	default loop and triggering an C<ev_async> watcher from the default loop
		4074	watcher callback into the event loop interested in the signal.
3291		4075
3292	=back	4076	=back
3293		4077
		4078	=head4 THREAD LOCKING EXAMPLE
		4079
		4080	Here is a fictitious example of how to run an event loop in a different
		4081	thread than where callbacks are being invoked and watchers are
		4082	created/added/removed.
		4083
		4084	For a real-world example, see the C<EV::Loop::Async> perl module,
		4085	which uses exactly this technique (which is suited for many high-level
		4086	languages).
		4087
		4088	The example uses a pthread mutex to protect the loop data, a condition
		4089	variable to wait for callback invocations, an async watcher to notify the
		4090	event loop thread and an unspecified mechanism to wake up the main thread.
		4091
		4092	First, you need to associate some data with the event loop:
		4093
		4094	typedef struct {
		4095	mutex_t lock; /* global loop lock */
		4096	ev_async async_w;
		4097	thread_t tid;
		4098	cond_t invoke_cv;
		4099	} userdata;
		4100
		4101	void prepare_loop (EV_P)
		4102	{
		4103	// for simplicity, we use a static userdata struct.
		4104	static userdata u;
		4105
		4106	ev_async_init (&u->async_w, async_cb);
		4107	ev_async_start (EV_A_ &u->async_w);
		4108
		4109	pthread_mutex_init (&u->lock, 0);
		4110	pthread_cond_init (&u->invoke_cv, 0);
		4111
		4112	// now associate this with the loop
		4113	ev_set_userdata (EV_A_ u);
		4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4116
		4117	// then create the thread running ev_loop
		4118	pthread_create (&u->tid, 0, l_run, EV_A);
		4119	}
		4120
		4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4122	solely to wake up the event loop so it takes notice of any new watchers
		4123	that might have been added:
		4124
		4125	static void
		4126	async_cb (EV_P_ ev_async *w, int revents)
		4127	{
		4128	// just used for the side effects
		4129	}
		4130
		4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4132	protecting the loop data, respectively.
		4133
		4134	static void
		4135	l_release (EV_P)
		4136	{
		4137	userdata *u = ev_userdata (EV_A);
		4138	pthread_mutex_unlock (&u->lock);
		4139	}
		4140
		4141	static void
		4142	l_acquire (EV_P)
		4143	{
		4144	userdata *u = ev_userdata (EV_A);
		4145	pthread_mutex_lock (&u->lock);
		4146	}
		4147
		4148	The event loop thread first acquires the mutex, and then jumps straight
		4149	into C<ev_loop>:
		4150
		4151	void *
		4152	l_run (void *thr_arg)
		4153	{
		4154	struct ev_loop *loop = (struct ev_loop *)thr_arg;
		4155
		4156	l_acquire (EV_A);
		4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4158	ev_loop (EV_A_ 0);
		4159	l_release (EV_A);
		4160
		4161	return 0;
		4162	}
		4163
		4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4165	signal the main thread via some unspecified mechanism (signals? pipe
		4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4167	have been called (in a while loop because a) spurious wakeups are possible
		4168	and b) skipping inter-thread-communication when there are no pending
		4169	watchers is very beneficial):
		4170
		4171	static void
		4172	l_invoke (EV_P)
		4173	{
		4174	userdata *u = ev_userdata (EV_A);
		4175
		4176	while (ev_pending_count (EV_A))
		4177	{
		4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4180	}
		4181	}
		4182
		4183	Now, whenever the main thread gets told to invoke pending watchers, it
		4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4185	thread to continue:
		4186
		4187	static void
		4188	real_invoke_pending (EV_P)
		4189	{
		4190	userdata *u = ev_userdata (EV_A);
		4191
		4192	pthread_mutex_lock (&u->lock);
		4193	ev_invoke_pending (EV_A);
		4194	pthread_cond_signal (&u->invoke_cv);
		4195	pthread_mutex_unlock (&u->lock);
		4196	}
		4197
		4198	Whenever you want to start/stop a watcher or do other modifications to an
		4199	event loop, you will now have to lock:
		4200
		4201	ev_timer timeout_watcher;
		4202	userdata *u = ev_userdata (EV_A);
		4203
		4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4205
		4206	pthread_mutex_lock (&u->lock);
		4207	ev_timer_start (EV_A_ &timeout_watcher);
		4208	ev_async_send (EV_A_ &u->async_w);
		4209	pthread_mutex_unlock (&u->lock);
		4210
		4211	Note that sending the C<ev_async> watcher is required because otherwise
		4212	an event loop currently blocking in the kernel will have no knowledge
		4213	about the newly added timer. By waking up the loop it will pick up any new
		4214	watchers in the next event loop iteration.
		4215
3294	=head2 COROUTINES	4216	=head3 COROUTINES
3295		4217
3296	Libev is much more accommodating to coroutines ("cooperative threads"):	4218	Libev is very accommodating to coroutines ("cooperative threads"):
3297	libev fully supports nesting calls to it's functions from different	4219	libev fully supports nesting calls to its functions from different
3298	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4220	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3299	different coroutines and switch freely between both coroutines running the	4221	different coroutines, and switch freely between both coroutines running
3300	loop, as long as you don't confuse yourself). The only exception is that	4222	the loop, as long as you don't confuse yourself). The only exception is
3301	you must not do this from C<ev_periodic> reschedule callbacks.	4223	that you must not do this from C<ev_periodic> reschedule callbacks.
3302		4224
3303	Care has been taken to ensure that libev does not keep local state inside	4225	Care has been taken to ensure that libev does not keep local state inside
3304	C<ev_loop>, and other calls do not usually allow coroutine switches.	4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		4227	they do not call any callbacks.
3305		4228
		4229	=head2 COMPILER WARNINGS
3306		4230
3307	=head1 COMPLEXITIES	4231	Depending on your compiler and compiler settings, you might get no or a
		4232	lot of warnings when compiling libev code. Some people are apparently
		4233	scared by this.
3308		4234
3309	In this section the complexities of (many of) the algorithms used inside	4235	However, these are unavoidable for many reasons. For one, each compiler
3310	libev will be explained. For complexity discussions about backends see the	4236	has different warnings, and each user has different tastes regarding
3311	documentation for C<ev_default_init>.	4237	warning options. "Warn-free" code therefore cannot be a goal except when
		4238	targeting a specific compiler and compiler-version.
3312		4239
3313	All of the following are about amortised time: If an array needs to be	4240	Another reason is that some compiler warnings require elaborate
3314	extended, libev needs to realloc and move the whole array, but this	4241	workarounds, or other changes to the code that make it less clear and less
3315	happens asymptotically never with higher number of elements, so O(1) might	4242	maintainable.
3316	mean it might do a lengthy realloc operation in rare cases, but on average
3317	it is much faster and asymptotically approaches constant time.
3318		4243
3319	=over 4	4244	And of course, some compiler warnings are just plain stupid, or simply
		4245	wrong (because they don't actually warn about the condition their message
		4246	seems to warn about). For example, certain older gcc versions had some
		4247	warnings that resulted an extreme number of false positives. These have
		4248	been fixed, but some people still insist on making code warn-free with
		4249	such buggy versions.
3320		4250
3321	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	4251	While libev is written to generate as few warnings as possible,
		4252	"warn-free" code is not a goal, and it is recommended not to build libev
		4253	with any compiler warnings enabled unless you are prepared to cope with
		4254	them (e.g. by ignoring them). Remember that warnings are just that:
		4255	warnings, not errors, or proof of bugs.
3322		4256
3323	This means that, when you have a watcher that triggers in one hour and
3324	there are 100 watchers that would trigger before that then inserting will
3325	have to skip roughly seven (C<ld 100>) of these watchers.
3326		4257
3327	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	4258	=head2 VALGRIND
3328		4259
3329	That means that changing a timer costs less than removing/adding them	4260	Valgrind has a special section here because it is a popular tool that is
3330	as only the relative motion in the event queue has to be paid for.	4261	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3331		4262
3332	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	4263	If you think you found a bug (memory leak, uninitialised data access etc.)
		4264	in libev, then check twice: If valgrind reports something like:
3333		4265
3334	These just add the watcher into an array or at the head of a list.	4266	==2274== definitely lost: 0 bytes in 0 blocks.
		4267	==2274== possibly lost: 0 bytes in 0 blocks.
		4268	==2274== still reachable: 256 bytes in 1 blocks.
3335		4269
3336	=item Stopping check/prepare/idle/fork/async watchers: O(1)	4270	Then there is no memory leak, just as memory accounted to global variables
		4271	is not a memleak - the memory is still being referenced, and didn't leak.
3337		4272
3338	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	4273	Similarly, under some circumstances, valgrind might report kernel bugs
		4274	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		4275	although an acceptable workaround has been found here), or it might be
		4276	confused.
3339		4277
3340	These watchers are stored in lists then need to be walked to find the	4278	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3341	correct watcher to remove. The lists are usually short (you don't usually	4279	make it into some kind of religion.
3342	have many watchers waiting for the same fd or signal).
3343		4280
3344	=item Finding the next timer in each loop iteration: O(1)	4281	If you are unsure about something, feel free to contact the mailing list
		4282	with the full valgrind report and an explanation on why you think this
		4283	is a bug in libev (best check the archives, too :). However, don't be
		4284	annoyed when you get a brisk "this is no bug" answer and take the chance
		4285	of learning how to interpret valgrind properly.
3345		4286
3346	By virtue of using a binary or 4-heap, the next timer is always found at a	4287	If you need, for some reason, empty reports from valgrind for your project
3347	fixed position in the storage array.	4288	I suggest using suppression lists.
3348		4289
3349	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3350		4290
3351	A change means an I/O watcher gets started or stopped, which requires	4291	=head1 PORTABILITY NOTES
3352	libev to recalculate its status (and possibly tell the kernel, depending
3353	on backend and whether C<ev_io_set> was used).
3354		4292
3355	=item Activating one watcher (putting it into the pending state): O(1)
3356
3357	=item Priority handling: O(number_of_priorities)
3358
3359	Priorities are implemented by allocating some space for each
3360	priority. When doing priority-based operations, libev usually has to
3361	linearly search all the priorities, but starting/stopping and activating
3362	watchers becomes O(1) w.r.t. priority handling.
3363
3364	=item Sending an ev_async: O(1)
3365
3366	=item Processing ev_async_send: O(number_of_async_watchers)
3367
3368	=item Processing signals: O(max_signal_number)
3369
3370	Sending involves a system call I<iff> there were no other C<ev_async_send>
3371	calls in the current loop iteration. Checking for async and signal events
3372	involves iterating over all running async watchers or all signal numbers.
3373
3374	=back
3375
3376
3377	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	4293	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3378		4294
3379	Win32 doesn't support any of the standards (e.g. POSIX) that libev	4295	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3380	requires, and its I/O model is fundamentally incompatible with the POSIX	4296	requires, and its I/O model is fundamentally incompatible with the POSIX
3381	model. Libev still offers limited functionality on this platform in	4297	model. Libev still offers limited functionality on this platform in
3382	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	4298	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3389	way (note also that glib is the slowest event library known to man).	4305	way (note also that glib is the slowest event library known to man).
3390		4306
3391	There is no supported compilation method available on windows except	4307	There is no supported compilation method available on windows except
3392	embedding it into other applications.	4308	embedding it into other applications.
3393		4309
		4310	Sensible signal handling is officially unsupported by Microsoft - libev
		4311	tries its best, but under most conditions, signals will simply not work.
		4312
3394	Not a libev limitation but worth mentioning: windows apparently doesn't	4313	Not a libev limitation but worth mentioning: windows apparently doesn't
3395	accept large writes: instead of resulting in a partial write, windows will	4314	accept large writes: instead of resulting in a partial write, windows will
3396	either accept everything or return C<ENOBUFS> if the buffer is too large,	4315	either accept everything or return C<ENOBUFS> if the buffer is too large,
3397	so make sure you only write small amounts into your sockets (less than a	4316	so make sure you only write small amounts into your sockets (less than a
3398	megabyte seems safe, but thsi apparently depends on the amount of memory	4317	megabyte seems safe, but this apparently depends on the amount of memory
3399	available).	4318	available).
3400		4319
3401	Due to the many, low, and arbitrary limits on the win32 platform and	4320	Due to the many, low, and arbitrary limits on the win32 platform and
3402	the abysmal performance of winsockets, using a large number of sockets	4321	the abysmal performance of winsockets, using a large number of sockets
3403	is not recommended (and not reasonable). If your program needs to use	4322	is not recommended (and not reasonable). If your program needs to use
3404	more than a hundred or so sockets, then likely it needs to use a totally	4323	more than a hundred or so sockets, then likely it needs to use a totally
3405	different implementation for windows, as libev offers the POSIX readiness	4324	different implementation for windows, as libev offers the POSIX readiness
3406	notification model, which cannot be implemented efficiently on windows	4325	notification model, which cannot be implemented efficiently on windows
3407	(Microsoft monopoly games).	4326	(due to Microsoft monopoly games).
3408		4327
3409	A typical way to use libev under windows is to embed it (see the embedding	4328	A typical way to use libev under windows is to embed it (see the embedding
3410	section for details) and use the following F<evwrap.h> header file instead	4329	section for details) and use the following F<evwrap.h> header file instead
3411	of F<ev.h>:	4330	of F<ev.h>:
3412		4331
…		…
3414	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	4333	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3415		4334
3416	#include "ev.h"	4335	#include "ev.h"
3417		4336
3418	And compile the following F<evwrap.c> file into your project (make sure	4337	And compile the following F<evwrap.c> file into your project (make sure
3419	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	4338	you do I<not> compile the F<ev.c> or any other embedded source files!):
3420		4339
3421	#include "evwrap.h"	4340	#include "evwrap.h"
3422	#include "ev.c"	4341	#include "ev.c"
3423		4342
3424	=over 4	4343	=over 4
…		…
3448		4367
3449	Early versions of winsocket's select only supported waiting for a maximum	4368	Early versions of winsocket's select only supported waiting for a maximum
3450	of C<64> handles (probably owning to the fact that all windows kernels	4369	of C<64> handles (probably owning to the fact that all windows kernels
3451	can only wait for C<64> things at the same time internally; Microsoft	4370	can only wait for C<64> things at the same time internally; Microsoft
3452	recommends spawning a chain of threads and wait for 63 handles and the	4371	recommends spawning a chain of threads and wait for 63 handles and the
3453	previous thread in each. Great).	4372	previous thread in each. Sounds great!).
3454		4373
3455	Newer versions support more handles, but you need to define C<FD_SETSIZE>	4374	Newer versions support more handles, but you need to define C<FD_SETSIZE>
3456	to some high number (e.g. C<2048>) before compiling the winsocket select	4375	to some high number (e.g. C<2048>) before compiling the winsocket select
3457	call (which might be in libev or elsewhere, for example, perl does its own	4376	call (which might be in libev or elsewhere, for example, perl and many
3458	select emulation on windows).	4377	other interpreters do their own select emulation on windows).
3459		4378
3460	Another limit is the number of file descriptors in the Microsoft runtime	4379	Another limit is the number of file descriptors in the Microsoft runtime
3461	libraries, which by default is C<64> (there must be a hidden I<64> fetish	4380	libraries, which by default is C<64> (there must be a hidden I<64>
3462	or something like this inside Microsoft). You can increase this by calling	4381	fetish or something like this inside Microsoft). You can increase this
3463	C<_setmaxstdio>, which can increase this limit to C<2048> (another	4382	by calling C<_setmaxstdio>, which can increase this limit to C<2048>
3464	arbitrary limit), but is broken in many versions of the Microsoft runtime	4383	(another arbitrary limit), but is broken in many versions of the Microsoft
3465	libraries.
3466
3467	This might get you to about C<512> or C<2048> sockets (depending on	4384	runtime libraries. This might get you to about C<512> or C<2048> sockets
3468	windows version and/or the phase of the moon). To get more, you need to	4385	(depending on windows version and/or the phase of the moon). To get more,
3469	wrap all I/O functions and provide your own fd management, but the cost of	4386	you need to wrap all I/O functions and provide your own fd management, but
3470	calling select (O(n²)) will likely make this unworkable.	4387	the cost of calling select (O(n²)) will likely make this unworkable.
3471		4388
3472	=back	4389	=back
3473		4390
3474
3475	=head1 PORTABILITY REQUIREMENTS	4391	=head2 PORTABILITY REQUIREMENTS
3476		4392
3477	In addition to a working ISO-C implementation, libev relies on a few	4393	In addition to a working ISO-C implementation and of course the
3478	additional extensions:	4394	backend-specific APIs, libev relies on a few additional extensions:
3479		4395
3480	=over 4	4396	=over 4
3481		4397
3482	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	4398	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3483	calling conventions regardless of C<ev_watcher_type *>.	4399	calling conventions regardless of C<ev_watcher_type *>.
…		…
3489	calls them using an C<ev_watcher *> internally.	4405	calls them using an C<ev_watcher *> internally.
3490		4406
3491	=item C<sig_atomic_t volatile> must be thread-atomic as well	4407	=item C<sig_atomic_t volatile> must be thread-atomic as well
3492		4408
3493	The type C<sig_atomic_t volatile> (or whatever is defined as	4409	The type C<sig_atomic_t volatile> (or whatever is defined as
3494	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	4410	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3495	threads. This is not part of the specification for C<sig_atomic_t>, but is	4411	threads. This is not part of the specification for C<sig_atomic_t>, but is
3496	believed to be sufficiently portable.	4412	believed to be sufficiently portable.
3497		4413
3498	=item C<sigprocmask> must work in a threaded environment	4414	=item C<sigprocmask> must work in a threaded environment
3499		4415
…		…
3508	except the initial one, and run the default loop in the initial thread as	4424	except the initial one, and run the default loop in the initial thread as
3509	well.	4425	well.
3510		4426
3511	=item C<long> must be large enough for common memory allocation sizes	4427	=item C<long> must be large enough for common memory allocation sizes
3512		4428
3513	To improve portability and simplify using libev, libev uses C<long>	4429	To improve portability and simplify its API, libev uses C<long> internally
3514	internally instead of C<size_t> when allocating its data structures. On	4430	instead of C<size_t> when allocating its data structures. On non-POSIX
3515	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	4431	systems (Microsoft...) this might be unexpectedly low, but is still at
3516	is still at least 31 bits everywhere, which is enough for hundreds of	4432	least 31 bits everywhere, which is enough for hundreds of millions of
3517	millions of watchers.	4433	watchers.
3518		4434
3519	=item C<double> must hold a time value in seconds with enough accuracy	4435	=item C<double> must hold a time value in seconds with enough accuracy
3520		4436
3521	The type C<double> is used to represent timestamps. It is required to	4437	The type C<double> is used to represent timestamps. It is required to
3522	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4438	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
3523	enough for at least into the year 4000. This requirement is fulfilled by	4439	enough for at least into the year 4000. This requirement is fulfilled by
3524	implementations implementing IEEE 754 (basically all existing ones).	4440	implementations implementing IEEE 754, which is basically all existing
		4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4442	2200.
3525		4443
3526	=back	4444	=back
3527		4445
3528	If you know of other additional requirements drop me a note.	4446	If you know of other additional requirements drop me a note.
3529		4447
3530		4448
3531	=head1 COMPILER WARNINGS	4449	=head1 ALGORITHMIC COMPLEXITIES
3532		4450
3533	Depending on your compiler and compiler settings, you might get no or a	4451	In this section the complexities of (many of) the algorithms used inside
3534	lot of warnings when compiling libev code. Some people are apparently	4452	libev will be documented. For complexity discussions about backends see
3535	scared by this.	4453	the documentation for C<ev_default_init>.
3536		4454
3537	However, these are unavoidable for many reasons. For one, each compiler	4455	All of the following are about amortised time: If an array needs to be
3538	has different warnings, and each user has different tastes regarding	4456	extended, libev needs to realloc and move the whole array, but this
3539	warning options. "Warn-free" code therefore cannot be a goal except when	4457	happens asymptotically rarer with higher number of elements, so O(1) might
3540	targeting a specific compiler and compiler-version.	4458	mean that libev does a lengthy realloc operation in rare cases, but on
		4459	average it is much faster and asymptotically approaches constant time.
3541		4460
3542	Another reason is that some compiler warnings require elaborate	4461	=over 4
3543	workarounds, or other changes to the code that make it less clear and less
3544	maintainable.
3545		4462
3546	And of course, some compiler warnings are just plain stupid, or simply	4463	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3547	wrong (because they don't actually warn about the condition their message
3548	seems to warn about).
3549		4464
3550	While libev is written to generate as few warnings as possible,	4465	This means that, when you have a watcher that triggers in one hour and
3551	"warn-free" code is not a goal, and it is recommended not to build libev	4466	there are 100 watchers that would trigger before that, then inserting will
3552	with any compiler warnings enabled unless you are prepared to cope with	4467	have to skip roughly seven (C<ld 100>) of these watchers.
3553	them (e.g. by ignoring them). Remember that warnings are just that:
3554	warnings, not errors, or proof of bugs.
3555		4468
		4469	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3556		4470
3557	=head1 VALGRIND	4471	That means that changing a timer costs less than removing/adding them,
		4472	as only the relative motion in the event queue has to be paid for.
3558		4473
3559	Valgrind has a special section here because it is a popular tool that is	4474	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3560	highly useful, but valgrind reports are very hard to interpret.
3561		4475
3562	If you think you found a bug (memory leak, uninitialised data access etc.)	4476	These just add the watcher into an array or at the head of a list.
3563	in libev, then check twice: If valgrind reports something like:
3564		4477
3565	==2274== definitely lost: 0 bytes in 0 blocks.	4478	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3566	==2274== possibly lost: 0 bytes in 0 blocks.
3567	==2274== still reachable: 256 bytes in 1 blocks.
3568		4479
3569	Then there is no memory leak. Similarly, under some circumstances,	4480	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3570	valgrind might report kernel bugs as if it were a bug in libev, or it
3571	might be confused (it is a very good tool, but only a tool).
3572		4481
3573	If you are unsure about something, feel free to contact the mailing list	4482	These watchers are stored in lists, so they need to be walked to find the
3574	with the full valgrind report and an explanation on why you think this is	4483	correct watcher to remove. The lists are usually short (you don't usually
3575	a bug in libev. However, don't be annoyed when you get a brisk "this is	4484	have many watchers waiting for the same fd or signal: one is typical, two
3576	no bug" answer and take the chance of learning how to interpret valgrind	4485	is rare).
3577	properly.
3578		4486
3579	If you need, for some reason, empty reports from valgrind for your project	4487	=item Finding the next timer in each loop iteration: O(1)
3580	I suggest using suppression lists.
3581		4488
		4489	By virtue of using a binary or 4-heap, the next timer is always found at a
		4490	fixed position in the storage array.
		4491
		4492	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		4493
		4494	A change means an I/O watcher gets started or stopped, which requires
		4495	libev to recalculate its status (and possibly tell the kernel, depending
		4496	on backend and whether C<ev_io_set> was used).
		4497
		4498	=item Activating one watcher (putting it into the pending state): O(1)
		4499
		4500	=item Priority handling: O(number_of_priorities)
		4501
		4502	Priorities are implemented by allocating some space for each
		4503	priority. When doing priority-based operations, libev usually has to
		4504	linearly search all the priorities, but starting/stopping and activating
		4505	watchers becomes O(1) with respect to priority handling.
		4506
		4507	=item Sending an ev_async: O(1)
		4508
		4509	=item Processing ev_async_send: O(number_of_async_watchers)
		4510
		4511	=item Processing signals: O(max_signal_number)
		4512
		4513	Sending involves a system call I<iff> there were no other C<ev_async_send>
		4514	calls in the current loop iteration. Checking for async and signal events
		4515	involves iterating over all running async watchers or all signal numbers.
		4516
		4517	=back
		4518
		4519
		4520	=head1 GLOSSARY
		4521
		4522	=over 4
		4523
		4524	=item active
		4525
		4526	A watcher is active as long as it has been started (has been attached to
		4527	an event loop) but not yet stopped (disassociated from the event loop).
		4528
		4529	=item application
		4530
		4531	In this document, an application is whatever is using libev.
		4532
		4533	=item callback
		4534
		4535	The address of a function that is called when some event has been
		4536	detected. Callbacks are being passed the event loop, the watcher that
		4537	received the event, and the actual event bitset.
		4538
		4539	=item callback invocation
		4540
		4541	The act of calling the callback associated with a watcher.
		4542
		4543	=item event
		4544
		4545	A change of state of some external event, such as data now being available
		4546	for reading on a file descriptor, time having passed or simply not having
		4547	any other events happening anymore.
		4548
		4549	In libev, events are represented as single bits (such as C<EV_READ> or
		4550	C<EV_TIMEOUT>).
		4551
		4552	=item event library
		4553
		4554	A software package implementing an event model and loop.
		4555
		4556	=item event loop
		4557
		4558	An entity that handles and processes external events and converts them
		4559	into callback invocations.
		4560
		4561	=item event model
		4562
		4563	The model used to describe how an event loop handles and processes
		4564	watchers and events.
		4565
		4566	=item pending
		4567
		4568	A watcher is pending as soon as the corresponding event has been detected,
		4569	and stops being pending as soon as the watcher will be invoked or its
		4570	pending status is explicitly cleared by the application.
		4571
		4572	A watcher can be pending, but not active. Stopping a watcher also clears
		4573	its pending status.
		4574
		4575	=item real time
		4576
		4577	The physical time that is observed. It is apparently strictly monotonic :)
		4578
		4579	=item wall-clock time
		4580
		4581	The time and date as shown on clocks. Unlike real time, it can actually
		4582	be wrong and jump forwards and backwards, e.g. when the you adjust your
		4583	clock.
		4584
		4585	=item watcher
		4586
		4587	A data structure that describes interest in certain events. Watchers need
		4588	to be started (attached to an event loop) before they can receive events.
		4589
		4590	=item watcher invocation
		4591
		4592	The act of calling the callback associated with a watcher.
		4593
		4594	=back
3582		4595
3583	=head1 AUTHOR	4596	=head1 AUTHOR
3584		4597
3585	Marc Lehmann <libev@schmorp.de>.	4598	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3586		4599

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