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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
53	The newest version of this document is also available as a html-formatted	53	The newest version of this document is also available as a html-formatted
54	web page you might find easier to navigate when reading it for the first	54	web page you might find easier to navigate when reading it for the first
55	time: L<http://cvs.schmorp.de/libev/ev.html>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
58	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
62	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
65	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
94	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
101	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
102	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
103	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
104		106
105	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
106		108
107	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
108	library in any way.	110	library in any way.
…		…
113		115
114	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
115	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
116	you actually want to know.	118	you actually want to know.
117		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
118	=item int ev_version_major ()	126	=item int ev_version_major ()
119		127
120	=item int ev_version_minor ()	128	=item int ev_version_minor ()
121		129
122	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
123	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
124	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
125	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126	version of the library your program was compiled against.	134	version of the library your program was compiled against.
127		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
128	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
129	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
130	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
131	not a problem.	142	not a problem.
132		143
133	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
134	version.	145	version.
…		…
249	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
250		261
251	If you don't know what event loop to use, use the one returned from this	262	If you don't know what event loop to use, use the one returned from this
252	function.	263	function.
253		264
		265	The default loop is the only loop that can handle C<ev_signal> and
		266	C<ev_child> watchers, and to do this, it always registers a handler
		267	for C<SIGCHLD>. If this is a problem for your app you can either
		268	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
		269	can simply overwrite the C<SIGCHLD> signal handler I<after> calling
		270	C<ev_default_init>.
		271
254	The flags argument can be used to specify special behaviour or specific	272	The flags argument can be used to specify special behaviour or specific
255	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).	273	backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
256		274
257	The following flags are supported:	275	The following flags are supported:
258		276
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		314
297	This is your standard select(2) backend. Not I<completely> standard, as	315	This is your standard select(2) backend. Not I<completely> standard, as
298	libev tries to roll its own fd_set with no limits on the number of fds,	316	libev tries to roll its own fd_set with no limits on the number of fds,
299	but if that fails, expect a fairly low limit on the number of fds when	317	but if that fails, expect a fairly low limit on the number of fds when
300	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	318	using this backend. It doesn't scale too well (O(highest_fd)), but its
301	the fastest backend for a low number of fds.	319	usually the fastest backend for a low number of (low-numbered :) fds.
		320
		321	To get good performance out of this backend you need a high amount of
		322	parallelity (most of the file descriptors should be busy). If you are
		323	writing a server, you should C<accept ()> in a loop to accept as many
		324	connections as possible during one iteration. You might also want to have
		325	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		326	readyness notifications you get per iteration.
302		327
303	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	328	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304		329
305	And this is your standard poll(2) backend. It's more complicated than	330	And this is your standard poll(2) backend. It's more complicated
306	select, but handles sparse fds better and has no artificial limit on the	331	than select, but handles sparse fds better and has no artificial
307	number of fds you can use (except it will slow down considerably with a	332	limit on the number of fds you can use (except it will slow down
308	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	333	considerably with a lot of inactive fds). It scales similarly to select,
		334	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		335	performance tips.
309		336
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		338
312	For few fds, this backend is a bit little slower than poll and select,	339	For few fds, this backend is a bit little slower than poll and select,
313	but it scales phenomenally better. While poll and select usually scale like	340	but it scales phenomenally better. While poll and select usually scale
314	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	341	like O(total_fds) where n is the total number of fds (or the highest fd),
315	either O(1) or O(active_fds).	342	epoll scales either O(1) or O(active_fds). The epoll design has a number
		343	of shortcomings, such as silently dropping events in some hard-to-detect
		344	cases and rewiring a syscall per fd change, no fork support and bad
		345	support for dup.
316		346
317	While stopping and starting an I/O watcher in the same iteration will	347	While stopping, setting and starting an I/O watcher in the same iteration
318	result in some caching, there is still a syscall per such incident	348	will result in some caching, there is still a syscall per such incident
319	(because the fd could point to a different file description now), so its	349	(because the fd could point to a different file description now), so its
320	best to avoid that. Also, dup()ed file descriptors might not work very	350	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321	well if you register events for both fds.	351	very well if you register events for both fds.
322		352
323	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
324	need to use non-blocking I/O or other means to avoid blocking when no data	354	need to use non-blocking I/O or other means to avoid blocking when no data
325	(or space) is available.	355	(or space) is available.
326		356
		357	Best performance from this backend is achieved by not unregistering all
		358	watchers for a file descriptor until it has been closed, if possible, i.e.
		359	keep at least one watcher active per fd at all times.
		360
		361	While nominally embeddeble in other event loops, this feature is broken in
		362	all kernel versions tested so far.
		363
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		365
329	Kqueue deserves special mention, as at the time of this writing, it	366	Kqueue deserves special mention, as at the time of this writing, it
330	was broken on all BSDs except NetBSD (usually it doesn't work with	367	was broken on all BSDs except NetBSD (usually it doesn't work reliably
331	anything but sockets and pipes, except on Darwin, where of course its	368	with anything but sockets and pipes, except on Darwin, where of course
332	completely useless). For this reason its not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
333	unless you explicitly specify it explicitly in the flags (i.e. using	370	unless you explicitly specify it explicitly in the flags (i.e. using
334	C<EVBACKEND_KQUEUE>).	371	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		372	system like NetBSD.
		373
		374	You still can embed kqueue into a normal poll or select backend and use it
		375	only for sockets (after having made sure that sockets work with kqueue on
		376	the target platform). See C<ev_embed> watchers for more info.
335		377
336	It scales in the same way as the epoll backend, but the interface to the	378	It scales in the same way as the epoll backend, but the interface to the
337	kernel is more efficient (which says nothing about its actual speed, of	379	kernel is more efficient (which says nothing about its actual speed, of
338	course). While starting and stopping an I/O watcher does not cause an	380	course). While stopping, setting and starting an I/O watcher does never
339	extra syscall as with epoll, it still adds up to four event changes per	381	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340	incident, so its best to avoid that.	382	two event changes per incident, support for C<fork ()> is very bad and it
		383	drops fds silently in similarly hard-to-detect cases.
		384
		385	This backend usually performs well under most conditions.
		386
		387	While nominally embeddable in other event loops, this doesn't work
		388	everywhere, so you might need to test for this. And since it is broken
		389	almost everywhere, you should only use it when you have a lot of sockets
		390	(for which it usually works), by embedding it into another event loop
		391	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		392	sockets.
341		393
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		395
344	This is not implemented yet (and might never be).	396	This is not implemented yet (and might never be, unless you send me an
		397	implementation). According to reports, C</dev/poll> only supports sockets
		398	and is not embeddable, which would limit the usefulness of this backend
		399	immensely.
345		400
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		402
348	This uses the Solaris 10 port mechanism. As with everything on Solaris,	403	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349	it's really slow, but it still scales very well (O(active_fds)).	404	it's really slow, but it still scales very well (O(active_fds)).
350		405
351	Please note that solaris ports can result in a lot of spurious	406	Please note that solaris event ports can deliver a lot of spurious
352	notifications, so you need to use non-blocking I/O or other means to avoid	407	notifications, so you need to use non-blocking I/O or other means to avoid
353	blocking when no data (or space) is available.	408	blocking when no data (or space) is available.
		409
		410	While this backend scales well, it requires one system call per active
		411	file descriptor per loop iteration. For small and medium numbers of file
		412	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		413	might perform better.
		414
		415	On the positive side, ignoring the spurious readyness notifications, this
		416	backend actually performed to specification in all tests and is fully
		417	embeddable, which is a rare feat among the OS-specific backends.
354		418
355	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
356		420
357	Try all backends (even potentially broken ones that wouldn't be tried	421	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	422	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		424
		425	It is definitely not recommended to use this flag.
		426
361	=back	427	=back
362		428
363	If one or more of these are ored into the flags value, then only these	429	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	430	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		432
368	The most typical usage is like this:	433	The most typical usage is like this:
369		434
370	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
399	Destroys the default loop again (frees all memory and kernel state	464	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	465	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	466	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	467	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	468	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	469	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	470	for example).
		471
		472	Note that certain global state, such as signal state, will not be freed by
		473	this function, and related watchers (such as signal and child watchers)
		474	would need to be stopped manually.
		475
		476	In general it is not advisable to call this function except in the
		477	rare occasion where you really need to free e.g. the signal handling
		478	pipe fds. If you need dynamically allocated loops it is better to use
		479	C<ev_loop_new> and C<ev_loop_destroy>).
406		480
407	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
408		482
409	Like C<ev_default_destroy>, but destroys an event loop created by an	483	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
411		485
412	=item ev_default_fork ()	486	=item ev_default_fork ()
413		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
414	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
415	one. Despite the name, you can call it anytime, but it makes most sense	490	name, you can call it anytime, but it makes most sense after forking, in
416	after forking, in either the parent or child process (or both, but that	491	the child process (or both child and parent, but that again makes little
417	again makes little sense).	492	sense). You I<must> call it in the child before using any of the libev
		493	functions, and it will only take effect at the next C<ev_loop> iteration.
418		494
419	You I<must> call this function in the child process after forking if and	495	On the other hand, you only need to call this function in the child
420	only if you want to use the event library in both processes. If you just	496	process if and only if you want to use the event library in the child. If
421	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
422		498
423	The function itself is quite fast and it's usually not a problem to call	499	The function itself is quite fast and it's usually not a problem to call
424	it just in case after a fork. To make this easy, the function will fit in	500	it just in case after a fork. To make this easy, the function will fit in
425	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
426		502
427	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
428		504
429	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
430	without calling this function, so if you force one of those backends you
431	do not need to care.
432
433	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
434		506
435	Like C<ev_default_fork>, but acts on an event loop created by	507	Like C<ev_default_fork>, but acts on an event loop created by
436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	508	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
437	after fork, and how you do this is entirely your own problem.	509	after fork, and how you do this is entirely your own problem.
		510
		511	=item int ev_is_default_loop (loop)
		512
		513	Returns true when the given loop actually is the default loop, false otherwise.
438		514
439	=item unsigned int ev_loop_count (loop)	515	=item unsigned int ev_loop_count (loop)
440		516
441	Returns the count of loop iterations for the loop, which is identical to	517	Returns the count of loop iterations for the loop, which is identical to
442	the number of times libev did poll for new events. It starts at C<0> and	518	the number of times libev did poll for new events. It starts at C<0> and
…		…
455		531
456	Returns the current "event loop time", which is the time the event loop	532	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	533	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	534	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	535	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	536	event occurring (or more correctly, libev finding out about it).
461		537
462	=item ev_loop (loop, int flags)	538	=item ev_loop (loop, int flags)
463		539
464	Finally, this is it, the event handler. This function usually is called	540	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	541	after you initialised all your watchers and you want to start handling
…		…
487	usually a better approach for this kind of thing.	563	usually a better approach for this kind of thing.
488		564
489	Here are the gory details of what C<ev_loop> does:	565	Here are the gory details of what C<ev_loop> does:
490		566
491	- Before the first iteration, call any pending watchers.	567	- Before the first iteration, call any pending watchers.
492	* If there are no active watchers (reference count is zero), return.	568	* If EVFLAG_FORKCHECK was used, check for a fork.
493	- Queue all prepare watchers and then call all outstanding watchers.	569	- If a fork was detected, queue and call all fork watchers.
		570	- Queue and call all prepare watchers.
494	- If we have been forked, recreate the kernel state.	571	- If we have been forked, recreate the kernel state.
495	- Update the kernel state with all outstanding changes.	572	- Update the kernel state with all outstanding changes.
496	- Update the "event loop time".	573	- Update the "event loop time".
497	- Calculate for how long to block.	574	- Calculate for how long to sleep or block, if at all
		575	(active idle watchers, EVLOOP_NONBLOCK or not having
		576	any active watchers at all will result in not sleeping).
		577	- Sleep if the I/O and timer collect interval say so.
498	- Block the process, waiting for any events.	578	- Block the process, waiting for any events.
499	- Queue all outstanding I/O (fd) events.	579	- Queue all outstanding I/O (fd) events.
500	- Update the "event loop time" and do time jump handling.	580	- Update the "event loop time" and do time jump handling.
501	- Queue all outstanding timers.	581	- Queue all outstanding timers.
502	- Queue all outstanding periodics.	582	- Queue all outstanding periodics.
503	- If no events are pending now, queue all idle watchers.	583	- If no events are pending now, queue all idle watchers.
504	- Queue all check watchers.	584	- Queue all check watchers.
505	- Call all queued watchers in reverse order (i.e. check watchers first).	585	- Call all queued watchers in reverse order (i.e. check watchers first).
506	Signals and child watchers are implemented as I/O watchers, and will	586	Signals and child watchers are implemented as I/O watchers, and will
507	be handled here by queueing them when their watcher gets executed.	587	be handled here by queueing them when their watcher gets executed.
508	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	588	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
509	were used, return, otherwise continue with step *.	589	were used, or there are no active watchers, return, otherwise
		590	continue with step *.
510		591
511	Example: Queue some jobs and then loop until no events are outsanding	592	Example: Queue some jobs and then loop until no events are outstanding
512	anymore.	593	anymore.
513		594
514	... queue jobs here, make sure they register event watchers as long	595	... queue jobs here, make sure they register event watchers as long
515	... as they still have work to do (even an idle watcher will do..)	596	... as they still have work to do (even an idle watcher will do..)
516	ev_loop (my_loop, 0);	597	ev_loop (my_loop, 0);
…		…
520		601
521	Can be used to make a call to C<ev_loop> return early (but only after it	602	Can be used to make a call to C<ev_loop> return early (but only after it
522	has processed all outstanding events). The C<how> argument must be either	603	has processed all outstanding events). The C<how> argument must be either
523	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	604	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
524	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	605	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		606
		607	This "unloop state" will be cleared when entering C<ev_loop> again.
525		608
526	=item ev_ref (loop)	609	=item ev_ref (loop)
527		610
528	=item ev_unref (loop)	611	=item ev_unref (loop)
529		612
…		…
534	returning, ev_unref() after starting, and ev_ref() before stopping it. For	617	returning, ev_unref() after starting, and ev_ref() before stopping it. For
535	example, libev itself uses this for its internal signal pipe: It is not	618	example, libev itself uses this for its internal signal pipe: It is not
536	visible to the libev user and should not keep C<ev_loop> from exiting if	619	visible to the libev user and should not keep C<ev_loop> from exiting if
537	no event watchers registered by it are active. It is also an excellent	620	no event watchers registered by it are active. It is also an excellent
538	way to do this for generic recurring timers or from within third-party	621	way to do this for generic recurring timers or from within third-party
539	libraries. Just remember to I<unref after start> and I<ref before stop>.	622	libraries. Just remember to I<unref after start> and I<ref before stop>
		623	(but only if the watcher wasn't active before, or was active before,
		624	respectively).
540		625
541	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	626	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
542	running when nothing else is active.	627	running when nothing else is active.
543		628
544	struct ev_signal exitsig;	629	struct ev_signal exitsig;
…		…
548		633
549	Example: For some weird reason, unregister the above signal handler again.	634	Example: For some weird reason, unregister the above signal handler again.
550		635
551	ev_ref (loop);	636	ev_ref (loop);
552	ev_signal_stop (loop, &exitsig);	637	ev_signal_stop (loop, &exitsig);
		638
		639	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		640
		641	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		642
		643	These advanced functions influence the time that libev will spend waiting
		644	for events. Both are by default C<0>, meaning that libev will try to
		645	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		646
		647	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		648	allows libev to delay invocation of I/O and timer/periodic callbacks to
		649	increase efficiency of loop iterations.
		650
		651	The background is that sometimes your program runs just fast enough to
		652	handle one (or very few) event(s) per loop iteration. While this makes
		653	the program responsive, it also wastes a lot of CPU time to poll for new
		654	events, especially with backends like C<select ()> which have a high
		655	overhead for the actual polling but can deliver many events at once.
		656
		657	By setting a higher I<io collect interval> you allow libev to spend more
		658	time collecting I/O events, so you can handle more events per iteration,
		659	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		660	C<ev_timer>) will be not affected. Setting this to a non-null value will
		661	introduce an additional C<ev_sleep ()> call into most loop iterations.
		662
		663	Likewise, by setting a higher I<timeout collect interval> you allow libev
		664	to spend more time collecting timeouts, at the expense of increased
		665	latency (the watcher callback will be called later). C<ev_io> watchers
		666	will not be affected. Setting this to a non-null value will not introduce
		667	any overhead in libev.
		668
		669	Many (busy) programs can usually benefit by setting the io collect
		670	interval to a value near C<0.1> or so, which is often enough for
		671	interactive servers (of course not for games), likewise for timeouts. It
		672	usually doesn't make much sense to set it to a lower value than C<0.01>,
		673	as this approsaches the timing granularity of most systems.
553		674
554	=back	675	=back
555		676
556		677
557	=head1 ANATOMY OF A WATCHER	678	=head1 ANATOMY OF A WATCHER
…		…
656		777
657	=item C<EV_FORK>	778	=item C<EV_FORK>
658		779
659	The event loop has been resumed in the child process after fork (see	780	The event loop has been resumed in the child process after fork (see
660	C<ev_fork>).	781	C<ev_fork>).
		782
		783	=item C<EV_ASYNC>
		784
		785	The given async watcher has been asynchronously notified (see C<ev_async>).
661		786
662	=item C<EV_ERROR>	787	=item C<EV_ERROR>
663		788
664	An unspecified error has occured, the watcher has been stopped. This might	789	An unspecified error has occured, the watcher has been stopped. This might
665	happen because the watcher could not be properly started because libev	790	happen because the watcher could not be properly started because libev
…		…
883	In general you can register as many read and/or write event watchers per	1008	In general you can register as many read and/or write event watchers per
884	fd as you want (as long as you don't confuse yourself). Setting all file	1009	fd as you want (as long as you don't confuse yourself). Setting all file
885	descriptors to non-blocking mode is also usually a good idea (but not	1010	descriptors to non-blocking mode is also usually a good idea (but not
886	required if you know what you are doing).	1011	required if you know what you are doing).
887		1012
888	You have to be careful with dup'ed file descriptors, though. Some backends
889	(the linux epoll backend is a notable example) cannot handle dup'ed file
890	descriptors correctly if you register interest in two or more fds pointing
891	to the same underlying file/socket/etc. description (that is, they share
892	the same underlying "file open").
893
894	If you must do this, then force the use of a known-to-be-good backend	1013	If you must do this, then force the use of a known-to-be-good backend
895	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1014	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
896	C<EVBACKEND_POLL>).	1015	C<EVBACKEND_POLL>).
897		1016
898	Another thing you have to watch out for is that it is quite easy to	1017	Another thing you have to watch out for is that it is quite easy to
…		…
908	play around with an Xlib connection), then you have to seperately re-test	1027	play around with an Xlib connection), then you have to seperately re-test
909	whether a file descriptor is really ready with a known-to-be good interface	1028	whether a file descriptor is really ready with a known-to-be good interface
910	such as poll (fortunately in our Xlib example, Xlib already does this on	1029	such as poll (fortunately in our Xlib example, Xlib already does this on
911	its own, so its quite safe to use).	1030	its own, so its quite safe to use).
912		1031
		1032	=head3 The special problem of disappearing file descriptors
		1033
		1034	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1035	descriptor (either by calling C<close> explicitly or by any other means,
		1036	such as C<dup>). The reason is that you register interest in some file
		1037	descriptor, but when it goes away, the operating system will silently drop
		1038	this interest. If another file descriptor with the same number then is
		1039	registered with libev, there is no efficient way to see that this is, in
		1040	fact, a different file descriptor.
		1041
		1042	To avoid having to explicitly tell libev about such cases, libev follows
		1043	the following policy: Each time C<ev_io_set> is being called, libev
		1044	will assume that this is potentially a new file descriptor, otherwise
		1045	it is assumed that the file descriptor stays the same. That means that
		1046	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1047	descriptor even if the file descriptor number itself did not change.
		1048
		1049	This is how one would do it normally anyway, the important point is that
		1050	the libev application should not optimise around libev but should leave
		1051	optimisations to libev.
		1052
		1053	=head3 The special problem of dup'ed file descriptors
		1054
		1055	Some backends (e.g. epoll), cannot register events for file descriptors,
		1056	but only events for the underlying file descriptions. That means when you
		1057	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1058	events for them, only one file descriptor might actually receive events.
		1059
		1060	There is no workaround possible except not registering events
		1061	for potentially C<dup ()>'ed file descriptors, or to resort to
		1062	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1063
		1064	=head3 The special problem of fork
		1065
		1066	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1067	useless behaviour. Libev fully supports fork, but needs to be told about
		1068	it in the child.
		1069
		1070	To support fork in your programs, you either have to call
		1071	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1072	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1073	C<EVBACKEND_POLL>.
		1074
		1075
		1076	=head3 Watcher-Specific Functions
		1077
913	=over 4	1078	=over 4
914		1079
915	=item ev_io_init (ev_io *, callback, int fd, int events)	1080	=item ev_io_init (ev_io *, callback, int fd, int events)
916		1081
917	=item ev_io_set (ev_io *, int fd, int events)	1082	=item ev_io_set (ev_io *, int fd, int events)
…		…
927	=item int events [read-only]	1092	=item int events [read-only]
928		1093
929	The events being watched.	1094	The events being watched.
930		1095
931	=back	1096	=back
		1097
		1098	=head3 Examples
932		1099
933	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1100	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
934	readable, but only once. Since it is likely line-buffered, you could	1101	readable, but only once. Since it is likely line-buffered, you could
935	attempt to read a whole line in the callback.	1102	attempt to read a whole line in the callback.
936		1103
…		…
970		1137
971	The callback is guarenteed to be invoked only when its timeout has passed,	1138	The callback is guarenteed to be invoked only when its timeout has passed,
972	but if multiple timers become ready during the same loop iteration then	1139	but if multiple timers become ready during the same loop iteration then
973	order of execution is undefined.	1140	order of execution is undefined.
974		1141
		1142	=head3 Watcher-Specific Functions and Data Members
		1143
975	=over 4	1144	=over 4
976		1145
977	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1146	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978		1147
979	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1148	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
987	configure a timer to trigger every 10 seconds, then it will trigger at	1156	configure a timer to trigger every 10 seconds, then it will trigger at
988	exactly 10 second intervals. If, however, your program cannot keep up with	1157	exactly 10 second intervals. If, however, your program cannot keep up with
989	the timer (because it takes longer than those 10 seconds to do stuff) the	1158	the timer (because it takes longer than those 10 seconds to do stuff) the
990	timer will not fire more than once per event loop iteration.	1159	timer will not fire more than once per event loop iteration.
991		1160
992	=item ev_timer_again (loop)	1161	=item ev_timer_again (loop, ev_timer *)
993		1162
994	This will act as if the timer timed out and restart it again if it is	1163	This will act as if the timer timed out and restart it again if it is
995	repeating. The exact semantics are:	1164	repeating. The exact semantics are:
996		1165
997	If the timer is pending, its pending status is cleared.	1166	If the timer is pending, its pending status is cleared.
…		…
1032	or C<ev_timer_again> is called and determines the next timeout (if any),	1201	or C<ev_timer_again> is called and determines the next timeout (if any),
1033	which is also when any modifications are taken into account.	1202	which is also when any modifications are taken into account.
1034		1203
1035	=back	1204	=back
1036		1205
		1206	=head3 Examples
		1207
1037	Example: Create a timer that fires after 60 seconds.	1208	Example: Create a timer that fires after 60 seconds.
1038		1209
1039	static void	1210	static void
1040	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1211	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1041	{	1212	{
…		…
1074	but on wallclock time (absolute time). You can tell a periodic watcher	1245	but on wallclock time (absolute time). You can tell a periodic watcher
1075	to trigger "at" some specific point in time. For example, if you tell a	1246	to trigger "at" some specific point in time. For example, if you tell a
1076	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1247	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1077	+ 10.>) and then reset your system clock to the last year, then it will	1248	+ 10.>) and then reset your system clock to the last year, then it will
1078	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1249	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1079	roughly 10 seconds later and of course not if you reset your system time	1250	roughly 10 seconds later).
1080	again).
1081		1251
1082	They can also be used to implement vastly more complex timers, such as	1252	They can also be used to implement vastly more complex timers, such as
1083	triggering an event on eahc midnight, local time.	1253	triggering an event on each midnight, local time or other, complicated,
		1254	rules.
1084		1255
1085	As with timers, the callback is guarenteed to be invoked only when the	1256	As with timers, the callback is guarenteed to be invoked only when the
1086	time (C<at>) has been passed, but if multiple periodic timers become ready	1257	time (C<at>) has been passed, but if multiple periodic timers become ready
1087	during the same loop iteration then order of execution is undefined.	1258	during the same loop iteration then order of execution is undefined.
1088		1259
		1260	=head3 Watcher-Specific Functions and Data Members
		1261
1089	=over 4	1262	=over 4
1090		1263
1091	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1264	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092		1265
1093	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1266	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1095	Lots of arguments, lets sort it out... There are basically three modes of	1268	Lots of arguments, lets sort it out... There are basically three modes of
1096	operation, and we will explain them from simplest to complex:	1269	operation, and we will explain them from simplest to complex:
1097		1270
1098	=over 4	1271	=over 4
1099		1272
1100	=item * absolute timer (interval = reschedule_cb = 0)	1273	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1101		1274
1102	In this configuration the watcher triggers an event at the wallclock time	1275	In this configuration the watcher triggers an event at the wallclock time
1103	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1276	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1104	that is, if it is to be run at January 1st 2011 then it will run when the	1277	that is, if it is to be run at January 1st 2011 then it will run when the
1105	system time reaches or surpasses this time.	1278	system time reaches or surpasses this time.
1106		1279
1107	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1280	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1108		1281
1109	In this mode the watcher will always be scheduled to time out at the next	1282	In this mode the watcher will always be scheduled to time out at the next
1110	C<at + N * interval> time (for some integer N) and then repeat, regardless	1283	C<at + N * interval> time (for some integer N, which can also be negative)
1111	of any time jumps.	1284	and then repeat, regardless of any time jumps.
1112		1285
1113	This can be used to create timers that do not drift with respect to system	1286	This can be used to create timers that do not drift with respect to system
1114	time:	1287	time:
1115		1288
1116	ev_periodic_set (&periodic, 0., 3600., 0);	1289	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1122		1295
1123	Another way to think about it (for the mathematically inclined) is that	1296	Another way to think about it (for the mathematically inclined) is that
1124	C<ev_periodic> will try to run the callback in this mode at the next possible	1297	C<ev_periodic> will try to run the callback in this mode at the next possible
1125	time where C<time = at (mod interval)>, regardless of any time jumps.	1298	time where C<time = at (mod interval)>, regardless of any time jumps.
1126		1299
		1300	For numerical stability it is preferable that the C<at> value is near
		1301	C<ev_now ()> (the current time), but there is no range requirement for
		1302	this value.
		1303
1127	=item * manual reschedule mode (reschedule_cb = callback)	1304	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1128		1305
1129	In this mode the values for C<interval> and C<at> are both being	1306	In this mode the values for C<interval> and C<at> are both being
1130	ignored. Instead, each time the periodic watcher gets scheduled, the	1307	ignored. Instead, each time the periodic watcher gets scheduled, the
1131	reschedule callback will be called with the watcher as first, and the	1308	reschedule callback will be called with the watcher as first, and the
1132	current time as second argument.	1309	current time as second argument.
1133		1310
1134	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1311	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1135	ever, or make any event loop modifications>. If you need to stop it,	1312	ever, or make any event loop modifications>. If you need to stop it,
1136	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1313	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1137	starting a prepare watcher).	1314	starting an C<ev_prepare> watcher, which is legal).
1138		1315
1139	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1316	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1140	ev_tstamp now)>, e.g.:	1317	ev_tstamp now)>, e.g.:
1141		1318
1142	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1319	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1165	Simply stops and restarts the periodic watcher again. This is only useful	1342	Simply stops and restarts the periodic watcher again. This is only useful
1166	when you changed some parameters or the reschedule callback would return	1343	when you changed some parameters or the reschedule callback would return
1167	a different time than the last time it was called (e.g. in a crond like	1344	a different time than the last time it was called (e.g. in a crond like
1168	program when the crontabs have changed).	1345	program when the crontabs have changed).
1169		1346
		1347	=item ev_tstamp offset [read-write]
		1348
		1349	When repeating, this contains the offset value, otherwise this is the
		1350	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1351
		1352	Can be modified any time, but changes only take effect when the periodic
		1353	timer fires or C<ev_periodic_again> is being called.
		1354
1170	=item ev_tstamp interval [read-write]	1355	=item ev_tstamp interval [read-write]
1171		1356
1172	The current interval value. Can be modified any time, but changes only	1357	The current interval value. Can be modified any time, but changes only
1173	take effect when the periodic timer fires or C<ev_periodic_again> is being	1358	take effect when the periodic timer fires or C<ev_periodic_again> is being
1174	called.	1359	called.
…		…
1177		1362
1178	The current reschedule callback, or C<0>, if this functionality is	1363	The current reschedule callback, or C<0>, if this functionality is
1179	switched off. Can be changed any time, but changes only take effect when	1364	switched off. Can be changed any time, but changes only take effect when
1180	the periodic timer fires or C<ev_periodic_again> is being called.	1365	the periodic timer fires or C<ev_periodic_again> is being called.
1181		1366
		1367	=item ev_tstamp at [read-only]
		1368
		1369	When active, contains the absolute time that the watcher is supposed to
		1370	trigger next.
		1371
1182	=back	1372	=back
		1373
		1374	=head3 Examples
1183		1375
1184	Example: Call a callback every hour, or, more precisely, whenever the	1376	Example: Call a callback every hour, or, more precisely, whenever the
1185	system clock is divisible by 3600. The callback invocation times have	1377	system clock is divisible by 3600. The callback invocation times have
1186	potentially a lot of jittering, but good long-term stability.	1378	potentially a lot of jittering, but good long-term stability.
1187		1379
…		…
1227	with the kernel (thus it coexists with your own signal handlers as long	1419	with the kernel (thus it coexists with your own signal handlers as long
1228	as you don't register any with libev). Similarly, when the last signal	1420	as you don't register any with libev). Similarly, when the last signal
1229	watcher for a signal is stopped libev will reset the signal handler to	1421	watcher for a signal is stopped libev will reset the signal handler to
1230	SIG_DFL (regardless of what it was set to before).	1422	SIG_DFL (regardless of what it was set to before).
1231		1423
		1424	=head3 Watcher-Specific Functions and Data Members
		1425
1232	=over 4	1426	=over 4
1233		1427
1234	=item ev_signal_init (ev_signal *, callback, int signum)	1428	=item ev_signal_init (ev_signal *, callback, int signum)
1235		1429
1236	=item ev_signal_set (ev_signal *, int signum)	1430	=item ev_signal_set (ev_signal *, int signum)
…		…
1242		1436
1243	The signal the watcher watches out for.	1437	The signal the watcher watches out for.
1244		1438
1245	=back	1439	=back
1246		1440
		1441	=head3 Examples
		1442
		1443	Example: Try to exit cleanly on SIGINT and SIGTERM.
		1444
		1445	static void
		1446	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
		1447	{
		1448	ev_unloop (loop, EVUNLOOP_ALL);
		1449	}
		1450
		1451	struct ev_signal signal_watcher;
		1452	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
		1453	ev_signal_start (loop, &sigint_cb);
		1454
1247		1455
1248	=head2 C<ev_child> - watch out for process status changes	1456	=head2 C<ev_child> - watch out for process status changes
1249		1457
1250	Child watchers trigger when your process receives a SIGCHLD in response to	1458	Child watchers trigger when your process receives a SIGCHLD in response to
1251	some child status changes (most typically when a child of yours dies).	1459	some child status changes (most typically when a child of yours dies). It
		1460	is permissible to install a child watcher I<after> the child has been
		1461	forked (which implies it might have already exited), as long as the event
		1462	loop isn't entered (or is continued from a watcher).
		1463
		1464	Only the default event loop is capable of handling signals, and therefore
		1465	you can only rgeister child watchers in the default event loop.
		1466
		1467	=head3 Process Interaction
		1468
		1469	Libev grabs C<SIGCHLD> as soon as the default event loop is
		1470	initialised. This is necessary to guarantee proper behaviour even if
		1471	the first child watcher is started after the child exits. The occurance
		1472	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
		1473	synchronously as part of the event loop processing. Libev always reaps all
		1474	children, even ones not watched.
		1475
		1476	=head3 Overriding the Built-In Processing
		1477
		1478	Libev offers no special support for overriding the built-in child
		1479	processing, but if your application collides with libev's default child
		1480	handler, you can override it easily by installing your own handler for
		1481	C<SIGCHLD> after initialising the default loop, and making sure the
		1482	default loop never gets destroyed. You are encouraged, however, to use an
		1483	event-based approach to child reaping and thus use libev's support for
		1484	that, so other libev users can use C<ev_child> watchers freely.
		1485
		1486	=head3 Watcher-Specific Functions and Data Members
1252		1487
1253	=over 4	1488	=over 4
1254		1489
1255	=item ev_child_init (ev_child *, callback, int pid)	1490	=item ev_child_init (ev_child *, callback, int pid, int trace)
1256		1491
1257	=item ev_child_set (ev_child *, int pid)	1492	=item ev_child_set (ev_child *, int pid, int trace)
1258		1493
1259	Configures the watcher to wait for status changes of process C<pid> (or	1494	Configures the watcher to wait for status changes of process C<pid> (or
1260	I<any> process if C<pid> is specified as C<0>). The callback can look	1495	I<any> process if C<pid> is specified as C<0>). The callback can look
1261	at the C<rstatus> member of the C<ev_child> watcher structure to see	1496	at the C<rstatus> member of the C<ev_child> watcher structure to see
1262	the status word (use the macros from C<sys/wait.h> and see your systems	1497	the status word (use the macros from C<sys/wait.h> and see your systems
1263	C<waitpid> documentation). The C<rpid> member contains the pid of the	1498	C<waitpid> documentation). The C<rpid> member contains the pid of the
1264	process causing the status change.	1499	process causing the status change. C<trace> must be either C<0> (only
		1500	activate the watcher when the process terminates) or C<1> (additionally
		1501	activate the watcher when the process is stopped or continued).
1265		1502
1266	=item int pid [read-only]	1503	=item int pid [read-only]
1267		1504
1268	The process id this watcher watches out for, or C<0>, meaning any process id.	1505	The process id this watcher watches out for, or C<0>, meaning any process id.
1269		1506
…		…
1276	The process exit/trace status caused by C<rpid> (see your systems	1513	The process exit/trace status caused by C<rpid> (see your systems
1277	C<waitpid> and C<sys/wait.h> documentation for details).	1514	C<waitpid> and C<sys/wait.h> documentation for details).
1278		1515
1279	=back	1516	=back
1280		1517
1281	Example: Try to exit cleanly on SIGINT and SIGTERM.	1518	=head3 Examples
		1519
		1520	Example: C<fork()> a new process and install a child handler to wait for
		1521	its completion.
		1522
		1523	ev_child cw;
1282		1524
1283	static void	1525	static void
1284	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1526	child_cb (EV_P_ struct ev_child *w, int revents)
1285	{	1527	{
1286	ev_unloop (loop, EVUNLOOP_ALL);	1528	ev_child_stop (EV_A_ w);
		1529	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1287	}	1530	}
1288		1531
1289	struct ev_signal signal_watcher;	1532	pid_t pid = fork ();
1290	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1533
1291	ev_signal_start (loop, &sigint_cb);	1534	if (pid < 0)
		1535	// error
		1536	else if (pid == 0)
		1537	{
		1538	// the forked child executes here
		1539	exit (1);
		1540	}
		1541	else
		1542	{
		1543	ev_child_init (&cw, child_cb, pid, 0);
		1544	ev_child_start (EV_DEFAULT_ &cw);
		1545	}
1292		1546
1293		1547
1294	=head2 C<ev_stat> - did the file attributes just change?	1548	=head2 C<ev_stat> - did the file attributes just change?
1295		1549
1296	This watches a filesystem path for attribute changes. That is, it calls	1550	This watches a filesystem path for attribute changes. That is, it calls
…		…
1325	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1579	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1326	to fall back to regular polling again even with inotify, but changes are	1580	to fall back to regular polling again even with inotify, but changes are
1327	usually detected immediately, and if the file exists there will be no	1581	usually detected immediately, and if the file exists there will be no
1328	polling.	1582	polling.
1329		1583
		1584	=head3 Inotify
		1585
		1586	When C<inotify (7)> support has been compiled into libev (generally only
		1587	available on Linux) and present at runtime, it will be used to speed up
		1588	change detection where possible. The inotify descriptor will be created lazily
		1589	when the first C<ev_stat> watcher is being started.
		1590
		1591	Inotify presense does not change the semantics of C<ev_stat> watchers
		1592	except that changes might be detected earlier, and in some cases, to avoid
		1593	making regular C<stat> calls. Even in the presense of inotify support
		1594	there are many cases where libev has to resort to regular C<stat> polling.
		1595
		1596	(There is no support for kqueue, as apparently it cannot be used to
		1597	implement this functionality, due to the requirement of having a file
		1598	descriptor open on the object at all times).
		1599
		1600	=head3 The special problem of stat time resolution
		1601
		1602	The C<stat ()> syscall only supports full-second resolution portably, and
		1603	even on systems where the resolution is higher, many filesystems still
		1604	only support whole seconds.
		1605
		1606	That means that, if the time is the only thing that changes, you might
		1607	miss updates: on the first update, C<ev_stat> detects a change and calls
		1608	your callback, which does something. When there is another update within
		1609	the same second, C<ev_stat> will be unable to detect it.
		1610
		1611	The solution to this is to delay acting on a change for a second (or till
		1612	the next second boundary), using a roughly one-second delay C<ev_timer>
		1613	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1614	is added to work around small timing inconsistencies of some operating
		1615	systems.
		1616
		1617	=head3 Watcher-Specific Functions and Data Members
		1618
1330	=over 4	1619	=over 4
1331		1620
1332	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1621	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1333		1622
1334	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1623	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1341		1630
1342	The callback will be receive C<EV_STAT> when a change was detected,	1631	The callback will be receive C<EV_STAT> when a change was detected,
1343	relative to the attributes at the time the watcher was started (or the	1632	relative to the attributes at the time the watcher was started (or the
1344	last change was detected).	1633	last change was detected).
1345		1634
1346	=item ev_stat_stat (ev_stat *)	1635	=item ev_stat_stat (loop, ev_stat *)
1347		1636
1348	Updates the stat buffer immediately with new values. If you change the	1637	Updates the stat buffer immediately with new values. If you change the
1349	watched path in your callback, you could call this fucntion to avoid	1638	watched path in your callback, you could call this fucntion to avoid
1350	detecting this change (while introducing a race condition). Can also be	1639	detecting this change (while introducing a race condition). Can also be
1351	useful simply to find out the new values.	1640	useful simply to find out the new values.
…		…
1369	=item const char *path [read-only]	1658	=item const char *path [read-only]
1370		1659
1371	The filesystem path that is being watched.	1660	The filesystem path that is being watched.
1372		1661
1373	=back	1662	=back
		1663
		1664	=head3 Examples
1374		1665
1375	Example: Watch C</etc/passwd> for attribute changes.	1666	Example: Watch C</etc/passwd> for attribute changes.
1376		1667
1377	static void	1668	static void
1378	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1669	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1391	}	1682	}
1392		1683
1393	...	1684	...
1394	ev_stat passwd;	1685	ev_stat passwd;
1395		1686
1396	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1687	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1397	ev_stat_start (loop, &passwd);	1688	ev_stat_start (loop, &passwd);
		1689
		1690	Example: Like above, but additionally use a one-second delay so we do not
		1691	miss updates (however, frequent updates will delay processing, too, so
		1692	one might do the work both on C<ev_stat> callback invocation I<and> on
		1693	C<ev_timer> callback invocation).
		1694
		1695	static ev_stat passwd;
		1696	static ev_timer timer;
		1697
		1698	static void
		1699	timer_cb (EV_P_ ev_timer *w, int revents)
		1700	{
		1701	ev_timer_stop (EV_A_ w);
		1702
		1703	/* now it's one second after the most recent passwd change */
		1704	}
		1705
		1706	static void
		1707	stat_cb (EV_P_ ev_stat *w, int revents)
		1708	{
		1709	/* reset the one-second timer */
		1710	ev_timer_again (EV_A_ &timer);
		1711	}
		1712
		1713	...
		1714	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1715	ev_stat_start (loop, &passwd);
		1716	ev_timer_init (&timer, timer_cb, 0., 1.01);
1398		1717
1399		1718
1400	=head2 C<ev_idle> - when you've got nothing better to do...	1719	=head2 C<ev_idle> - when you've got nothing better to do...
1401		1720
1402	Idle watchers trigger events when no other events of the same or higher	1721	Idle watchers trigger events when no other events of the same or higher
…		…
1416	Apart from keeping your process non-blocking (which is a useful	1735	Apart from keeping your process non-blocking (which is a useful
1417	effect on its own sometimes), idle watchers are a good place to do	1736	effect on its own sometimes), idle watchers are a good place to do
1418	"pseudo-background processing", or delay processing stuff to after the	1737	"pseudo-background processing", or delay processing stuff to after the
1419	event loop has handled all outstanding events.	1738	event loop has handled all outstanding events.
1420		1739
		1740	=head3 Watcher-Specific Functions and Data Members
		1741
1421	=over 4	1742	=over 4
1422		1743
1423	=item ev_idle_init (ev_signal *, callback)	1744	=item ev_idle_init (ev_signal *, callback)
1424		1745
1425	Initialises and configures the idle watcher - it has no parameters of any	1746	Initialises and configures the idle watcher - it has no parameters of any
1426	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1747	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1427	believe me.	1748	believe me.
1428		1749
1429	=back	1750	=back
		1751
		1752	=head3 Examples
1430		1753
1431	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1754	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1432	callback, free it. Also, use no error checking, as usual.	1755	callback, free it. Also, use no error checking, as usual.
1433		1756
1434	static void	1757	static void
1435	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1758	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1436	{	1759	{
1437	free (w);	1760	free (w);
1438	// now do something you wanted to do when the program has	1761	// now do something you wanted to do when the program has
1439	// no longer asnything immediate to do.	1762	// no longer anything immediate to do.
1440	}	1763	}
1441		1764
1442	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1765	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1443	ev_idle_init (idle_watcher, idle_cb);	1766	ev_idle_init (idle_watcher, idle_cb);
1444	ev_idle_start (loop, idle_cb);	1767	ev_idle_start (loop, idle_cb);
…		…
1486		1809
1487	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)	1810	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1488	priority, to ensure that they are being run before any other watchers	1811	priority, to ensure that they are being run before any other watchers
1489	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,	1812	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1490	too) should not activate ("feed") events into libev. While libev fully	1813	too) should not activate ("feed") events into libev. While libev fully
1491	supports this, they will be called before other C<ev_check> watchers did	1814	supports this, they will be called before other C<ev_check> watchers
1492	their job. As C<ev_check> watchers are often used to embed other event	1815	did their job. As C<ev_check> watchers are often used to embed other
1493	loops those other event loops might be in an unusable state until their	1816	(non-libev) event loops those other event loops might be in an unusable
1494	C<ev_check> watcher ran (always remind yourself to coexist peacefully with	1817	state until their C<ev_check> watcher ran (always remind yourself to
1495	others).	1818	coexist peacefully with others).
		1819
		1820	=head3 Watcher-Specific Functions and Data Members
1496		1821
1497	=over 4	1822	=over 4
1498		1823
1499	=item ev_prepare_init (ev_prepare *, callback)	1824	=item ev_prepare_init (ev_prepare *, callback)
1500		1825
…		…
1503	Initialises and configures the prepare or check watcher - they have no	1828	Initialises and configures the prepare or check watcher - they have no
1504	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1829	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1505	macros, but using them is utterly, utterly and completely pointless.	1830	macros, but using them is utterly, utterly and completely pointless.
1506		1831
1507	=back	1832	=back
		1833
		1834	=head3 Examples
1508		1835
1509	There are a number of principal ways to embed other event loops or modules	1836	There are a number of principal ways to embed other event loops or modules
1510	into libev. Here are some ideas on how to include libadns into libev	1837	into libev. Here are some ideas on how to include libadns into libev
1511	(there is a Perl module named C<EV::ADNS> that does this, which you could	1838	(there is a Perl module named C<EV::ADNS> that does this, which you could
1512	use for an actually working example. Another Perl module named C<EV::Glib>	1839	use for an actually working example. Another Perl module named C<EV::Glib>
…		…
1681	portable one.	2008	portable one.
1682		2009
1683	So when you want to use this feature you will always have to be prepared	2010	So when you want to use this feature you will always have to be prepared
1684	that you cannot get an embeddable loop. The recommended way to get around	2011	that you cannot get an embeddable loop. The recommended way to get around
1685	this is to have a separate variables for your embeddable loop, try to	2012	this is to have a separate variables for your embeddable loop, try to
1686	create it, and if that fails, use the normal loop for everything:	2013	create it, and if that fails, use the normal loop for everything.
		2014
		2015	=head3 Watcher-Specific Functions and Data Members
		2016
		2017	=over 4
		2018
		2019	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		2020
		2021	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		2022
		2023	Configures the watcher to embed the given loop, which must be
		2024	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		2025	invoked automatically, otherwise it is the responsibility of the callback
		2026	to invoke it (it will continue to be called until the sweep has been done,
		2027	if you do not want thta, you need to temporarily stop the embed watcher).
		2028
		2029	=item ev_embed_sweep (loop, ev_embed *)
		2030
		2031	Make a single, non-blocking sweep over the embedded loop. This works
		2032	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		2033	apropriate way for embedded loops.
		2034
		2035	=item struct ev_loop *other [read-only]
		2036
		2037	The embedded event loop.
		2038
		2039	=back
		2040
		2041	=head3 Examples
		2042
		2043	Example: Try to get an embeddable event loop and embed it into the default
		2044	event loop. If that is not possible, use the default loop. The default
		2045	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		2046	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		2047	used).
1687		2048
1688	struct ev_loop *loop_hi = ev_default_init (0);	2049	struct ev_loop *loop_hi = ev_default_init (0);
1689	struct ev_loop *loop_lo = 0;	2050	struct ev_loop *loop_lo = 0;
1690	struct ev_embed embed;	2051	struct ev_embed embed;
1691		2052
…		…
1702	ev_embed_start (loop_hi, &embed);	2063	ev_embed_start (loop_hi, &embed);
1703	}	2064	}
1704	else	2065	else
1705	loop_lo = loop_hi;	2066	loop_lo = loop_hi;
1706		2067
1707	=over 4	2068	Example: Check if kqueue is available but not recommended and create
		2069	a kqueue backend for use with sockets (which usually work with any
		2070	kqueue implementation). Store the kqueue/socket-only event loop in
		2071	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1708		2072
1709	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2073	struct ev_loop *loop = ev_default_init (0);
		2074	struct ev_loop *loop_socket = 0;
		2075	struct ev_embed embed;
		2076
		2077	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2078	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2079	{
		2080	ev_embed_init (&embed, 0, loop_socket);
		2081	ev_embed_start (loop, &embed);
		2082	}
1710		2083
1711	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2084	if (!loop_socket)
		2085	loop_socket = loop;
1712		2086
1713	Configures the watcher to embed the given loop, which must be	2087	// now use loop_socket for all sockets, and loop for everything else
1714	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1715	invoked automatically, otherwise it is the responsibility of the callback
1716	to invoke it (it will continue to be called until the sweep has been done,
1717	if you do not want thta, you need to temporarily stop the embed watcher).
1718
1719	=item ev_embed_sweep (loop, ev_embed *)
1720
1721	Make a single, non-blocking sweep over the embedded loop. This works
1722	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1723	apropriate way for embedded loops.
1724
1725	=item struct ev_loop *loop [read-only]
1726
1727	The embedded event loop.
1728
1729	=back
1730		2088
1731		2089
1732	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2090	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1733		2091
1734	Fork watchers are called when a C<fork ()> was detected (usually because	2092	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1737	event loop blocks next and before C<ev_check> watchers are being called,	2095	event loop blocks next and before C<ev_check> watchers are being called,
1738	and only in the child after the fork. If whoever good citizen calling	2096	and only in the child after the fork. If whoever good citizen calling
1739	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2097	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1740	handlers will be invoked, too, of course.	2098	handlers will be invoked, too, of course.
1741		2099
		2100	=head3 Watcher-Specific Functions and Data Members
		2101
1742	=over 4	2102	=over 4
1743		2103
1744	=item ev_fork_init (ev_signal *, callback)	2104	=item ev_fork_init (ev_signal *, callback)
1745		2105
1746	Initialises and configures the fork watcher - it has no parameters of any	2106	Initialises and configures the fork watcher - it has no parameters of any
1747	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2107	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1748	believe me.	2108	believe me.
		2109
		2110	=back
		2111
		2112
		2113	=head2 C<ev_async> - how to wake up another event loop
		2114
		2115	In general, you cannot use an C<ev_loop> from multiple threads or other
		2116	asynchronous sources such as signal handlers (as opposed to multiple event
		2117	loops - those are of course safe to use in different threads).
		2118
		2119	Sometimes, however, you need to wake up another event loop you do not
		2120	control, for example because it belongs to another thread. This is what
		2121	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2122	can signal it by calling C<ev_async_send>, which is thread- and signal
		2123	safe.
		2124
		2125	This functionality is very similar to C<ev_signal> watchers, as signals,
		2126	too, are asynchronous in nature, and signals, too, will be compressed
		2127	(i.e. the number of callback invocations may be less than the number of
		2128	C<ev_async_sent> calls).
		2129
		2130	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2131	just the default loop.
		2132
		2133	=head3 Queueing
		2134
		2135	C<ev_async> does not support queueing of data in any way. The reason
		2136	is that the author does not know of a simple (or any) algorithm for a
		2137	multiple-writer-single-reader queue that works in all cases and doesn't
		2138	need elaborate support such as pthreads.
		2139
		2140	That means that if you want to queue data, you have to provide your own
		2141	queue. But at least I can tell you would implement locking around your
		2142	queue:
		2143
		2144	=over 4
		2145
		2146	=item queueing from a signal handler context
		2147
		2148	To implement race-free queueing, you simply add to the queue in the signal
		2149	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2150	some fictitiuous SIGUSR1 handler:
		2151
		2152	static ev_async mysig;
		2153
		2154	static void
		2155	sigusr1_handler (void)
		2156	{
		2157	sometype data;
		2158
		2159	// no locking etc.
		2160	queue_put (data);
		2161	ev_async_send (EV_DEFAULT_ &mysig);
		2162	}
		2163
		2164	static void
		2165	mysig_cb (EV_P_ ev_async *w, int revents)
		2166	{
		2167	sometype data;
		2168	sigset_t block, prev;
		2169
		2170	sigemptyset (&block);
		2171	sigaddset (&block, SIGUSR1);
		2172	sigprocmask (SIG_BLOCK, &block, &prev);
		2173
		2174	while (queue_get (&data))
		2175	process (data);
		2176
		2177	if (sigismember (&prev, SIGUSR1)
		2178	sigprocmask (SIG_UNBLOCK, &block, 0);
		2179	}
		2180
		2181	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2182	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2183	either...).
		2184
		2185	=item queueing from a thread context
		2186
		2187	The strategy for threads is different, as you cannot (easily) block
		2188	threads but you can easily preempt them, so to queue safely you need to
		2189	employ a traditional mutex lock, such as in this pthread example:
		2190
		2191	static ev_async mysig;
		2192	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2193
		2194	static void
		2195	otherthread (void)
		2196	{
		2197	// only need to lock the actual queueing operation
		2198	pthread_mutex_lock (&mymutex);
		2199	queue_put (data);
		2200	pthread_mutex_unlock (&mymutex);
		2201
		2202	ev_async_send (EV_DEFAULT_ &mysig);
		2203	}
		2204
		2205	static void
		2206	mysig_cb (EV_P_ ev_async *w, int revents)
		2207	{
		2208	pthread_mutex_lock (&mymutex);
		2209
		2210	while (queue_get (&data))
		2211	process (data);
		2212
		2213	pthread_mutex_unlock (&mymutex);
		2214	}
		2215
		2216	=back
		2217
		2218
		2219	=head3 Watcher-Specific Functions and Data Members
		2220
		2221	=over 4
		2222
		2223	=item ev_async_init (ev_async *, callback)
		2224
		2225	Initialises and configures the async watcher - it has no parameters of any
		2226	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2227	believe me.
		2228
		2229	=item ev_async_send (loop, ev_async *)
		2230
		2231	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2232	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2233	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2234	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2235	section below on what exactly this means).
		2236
		2237	This call incurs the overhead of a syscall only once per loop iteration,
		2238	so while the overhead might be noticable, it doesn't apply to repeated
		2239	calls to C<ev_async_send>.
1749		2240
1750	=back	2241	=back
1751		2242
1752		2243
1753	=head1 OTHER FUNCTIONS	2244	=head1 OTHER FUNCTIONS
…		…
1962		2453
1963	=item w->stop ()	2454	=item w->stop ()
1964		2455
1965	Stops the watcher if it is active. Again, no C<loop> argument.	2456	Stops the watcher if it is active. Again, no C<loop> argument.
1966		2457
1967	=item w->again () C<ev::timer>, C<ev::periodic> only	2458	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1968		2459
1969	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2460	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1970	C<ev_TYPE_again> function.	2461	C<ev_TYPE_again> function.
1971		2462
1972	=item w->sweep () C<ev::embed> only	2463	=item w->sweep () (C<ev::embed> only)
1973		2464
1974	Invokes C<ev_embed_sweep>.	2465	Invokes C<ev_embed_sweep>.
1975		2466
1976	=item w->update () C<ev::stat> only	2467	=item w->update () (C<ev::stat> only)
1977		2468
1978	Invokes C<ev_stat_stat>.	2469	Invokes C<ev_stat_stat>.
1979		2470
1980	=back	2471	=back
1981		2472
…		…
1984	Example: Define a class with an IO and idle watcher, start one of them in	2475	Example: Define a class with an IO and idle watcher, start one of them in
1985	the constructor.	2476	the constructor.
1986		2477
1987	class myclass	2478	class myclass
1988	{	2479	{
1989	ev_io io; void io_cb (ev::io &w, int revents);	2480	ev::io io; void io_cb (ev::io &w, int revents);
1990	ev_idle idle void idle_cb (ev::idle &w, int revents);	2481	ev:idle idle void idle_cb (ev::idle &w, int revents);
1991		2482
1992	myclass ();	2483	myclass (int fd)
1993	}
1994
1995	myclass::myclass (int fd)
1996	{	2484	{
1997	io .set <myclass, &myclass::io_cb > (this);	2485	io .set <myclass, &myclass::io_cb > (this);
1998	idle.set <myclass, &myclass::idle_cb> (this);	2486	idle.set <myclass, &myclass::idle_cb> (this);
1999		2487
2000	io.start (fd, ev::READ);	2488	io.start (fd, ev::READ);
		2489	}
2001	}	2490	};
2002		2491
2003		2492
2004	=head1 MACRO MAGIC	2493	=head1 MACRO MAGIC
2005		2494
2006	Libev can be compiled with a variety of options, the most fundemantal is	2495	Libev can be compiled with a variety of options, the most fundamantal
2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2496	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2008	callbacks have an initial C<struct ev_loop *> argument.	2497	functions and callbacks have an initial C<struct ev_loop *> argument.
2009		2498
2010	To make it easier to write programs that cope with either variant, the	2499	To make it easier to write programs that cope with either variant, the
2011	following macros are defined:	2500	following macros are defined:
2012		2501
2013	=over 4	2502	=over 4
…		…
2067	Libev can (and often is) directly embedded into host	2556	Libev can (and often is) directly embedded into host
2068	applications. Examples of applications that embed it include the Deliantra	2557	applications. Examples of applications that embed it include the Deliantra
2069	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2558	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2070	and rxvt-unicode.	2559	and rxvt-unicode.
2071		2560
2072	The goal is to enable you to just copy the neecssary files into your	2561	The goal is to enable you to just copy the necessary files into your
2073	source directory without having to change even a single line in them, so	2562	source directory without having to change even a single line in them, so
2074	you can easily upgrade by simply copying (or having a checked-out copy of	2563	you can easily upgrade by simply copying (or having a checked-out copy of
2075	libev somewhere in your source tree).	2564	libev somewhere in your source tree).
2076		2565
2077	=head2 FILESETS	2566	=head2 FILESETS
…		…
2167		2656
2168	If defined to be C<1>, libev will try to detect the availability of the	2657	If defined to be C<1>, libev will try to detect the availability of the
2169	monotonic clock option at both compiletime and runtime. Otherwise no use	2658	monotonic clock option at both compiletime and runtime. Otherwise no use
2170	of the monotonic clock option will be attempted. If you enable this, you	2659	of the monotonic clock option will be attempted. If you enable this, you
2171	usually have to link against librt or something similar. Enabling it when	2660	usually have to link against librt or something similar. Enabling it when
2172	the functionality isn't available is safe, though, althoguh you have	2661	the functionality isn't available is safe, though, although you have
2173	to make sure you link against any libraries where the C<clock_gettime>	2662	to make sure you link against any libraries where the C<clock_gettime>
2174	function is hiding in (often F<-lrt>).	2663	function is hiding in (often F<-lrt>).
2175		2664
2176	=item EV_USE_REALTIME	2665	=item EV_USE_REALTIME
2177		2666
2178	If defined to be C<1>, libev will try to detect the availability of the	2667	If defined to be C<1>, libev will try to detect the availability of the
2179	realtime clock option at compiletime (and assume its availability at	2668	realtime clock option at compiletime (and assume its availability at
2180	runtime if successful). Otherwise no use of the realtime clock option will	2669	runtime if successful). Otherwise no use of the realtime clock option will
2181	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2670	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2182	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2671	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2183	in the description of C<EV_USE_MONOTONIC>, though.	2672	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2673
		2674	=item EV_USE_NANOSLEEP
		2675
		2676	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2677	and will use it for delays. Otherwise it will use C<select ()>.
2184		2678
2185	=item EV_USE_SELECT	2679	=item EV_USE_SELECT
2186		2680
2187	If undefined or defined to be C<1>, libev will compile in support for the	2681	If undefined or defined to be C<1>, libev will compile in support for the
2188	C<select>(2) backend. No attempt at autodetection will be done: if no	2682	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2206	wants osf handles on win32 (this is the case when the select to	2700	wants osf handles on win32 (this is the case when the select to
2207	be used is the winsock select). This means that it will call	2701	be used is the winsock select). This means that it will call
2208	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2702	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2209	it is assumed that all these functions actually work on fds, even	2703	it is assumed that all these functions actually work on fds, even
2210	on win32. Should not be defined on non-win32 platforms.	2704	on win32. Should not be defined on non-win32 platforms.
		2705
		2706	=item EV_FD_TO_WIN32_HANDLE
		2707
		2708	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2709	file descriptors to socket handles. When not defining this symbol (the
		2710	default), then libev will call C<_get_osfhandle>, which is usually
		2711	correct. In some cases, programs use their own file descriptor management,
		2712	in which case they can provide this function to map fds to socket handles.
2211		2713
2212	=item EV_USE_POLL	2714	=item EV_USE_POLL
2213		2715
2214	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2716	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2215	backend. Otherwise it will be enabled on non-win32 platforms. It	2717	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2249		2751
2250	If defined to be C<1>, libev will compile in support for the Linux inotify	2752	If defined to be C<1>, libev will compile in support for the Linux inotify
2251	interface to speed up C<ev_stat> watchers. Its actual availability will	2753	interface to speed up C<ev_stat> watchers. Its actual availability will
2252	be detected at runtime.	2754	be detected at runtime.
2253		2755
		2756	=item EV_ATOMIC_T
		2757
		2758	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2759	access is atomic with respect to other threads or signal contexts. No such
		2760	type is easily found in the C language, so you can provide your own type
		2761	that you know is safe for your purposes. It is used both for signal handler "locking"
		2762	as well as for signal and thread safety in C<ev_async> watchers.
		2763
		2764	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2765	(from F<signal.h>), which is usually good enough on most platforms.
		2766
2254	=item EV_H	2767	=item EV_H
2255		2768
2256	The name of the F<ev.h> header file used to include it. The default if	2769	The name of the F<ev.h> header file used to include it. The default if
2257	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2770	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2258	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2771	used to virtually rename the F<ev.h> header file in case of conflicts.
2259		2772
2260	=item EV_CONFIG_H	2773	=item EV_CONFIG_H
2261		2774
2262	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2775	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2263	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2776	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2264	C<EV_H>, above.	2777	C<EV_H>, above.
2265		2778
2266	=item EV_EVENT_H	2779	=item EV_EVENT_H
2267		2780
2268	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2781	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2269	of how the F<event.h> header can be found.	2782	of how the F<event.h> header can be found, the default is C<"event.h">.
2270		2783
2271	=item EV_PROTOTYPES	2784	=item EV_PROTOTYPES
2272		2785
2273	If defined to be C<0>, then F<ev.h> will not define any function	2786	If defined to be C<0>, then F<ev.h> will not define any function
2274	prototypes, but still define all the structs and other symbols. This is	2787	prototypes, but still define all the structs and other symbols. This is
…		…
2325	=item EV_FORK_ENABLE	2838	=item EV_FORK_ENABLE
2326		2839
2327	If undefined or defined to be C<1>, then fork watchers are supported. If	2840	If undefined or defined to be C<1>, then fork watchers are supported. If
2328	defined to be C<0>, then they are not.	2841	defined to be C<0>, then they are not.
2329		2842
		2843	=item EV_ASYNC_ENABLE
		2844
		2845	If undefined or defined to be C<1>, then async watchers are supported. If
		2846	defined to be C<0>, then they are not.
		2847
2330	=item EV_MINIMAL	2848	=item EV_MINIMAL
2331		2849
2332	If you need to shave off some kilobytes of code at the expense of some	2850	If you need to shave off some kilobytes of code at the expense of some
2333	speed, define this symbol to C<1>. Currently only used for gcc to override	2851	speed, define this symbol to C<1>. Currently only used for gcc to override
2334	some inlining decisions, saves roughly 30% codesize of amd64.	2852	some inlining decisions, saves roughly 30% codesize of amd64.
…		…
2340	than enough. If you need to manage thousands of children you might want to	2858	than enough. If you need to manage thousands of children you might want to
2341	increase this value (I<must> be a power of two).	2859	increase this value (I<must> be a power of two).
2342		2860
2343	=item EV_INOTIFY_HASHSIZE	2861	=item EV_INOTIFY_HASHSIZE
2344		2862
2345	C<ev_staz> watchers use a small hash table to distribute workload by	2863	C<ev_stat> watchers use a small hash table to distribute workload by
2346	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2864	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2347	usually more than enough. If you need to manage thousands of C<ev_stat>	2865	usually more than enough. If you need to manage thousands of C<ev_stat>
2348	watchers you might want to increase this value (I<must> be a power of	2866	watchers you might want to increase this value (I<must> be a power of
2349	two).	2867	two).
2350		2868
…		…
2367		2885
2368	=item ev_set_cb (ev, cb)	2886	=item ev_set_cb (ev, cb)
2369		2887
2370	Can be used to change the callback member declaration in each watcher,	2888	Can be used to change the callback member declaration in each watcher,
2371	and the way callbacks are invoked and set. Must expand to a struct member	2889	and the way callbacks are invoked and set. Must expand to a struct member
2372	definition and a statement, respectively. See the F<ev.v> header file for	2890	definition and a statement, respectively. See the F<ev.h> header file for
2373	their default definitions. One possible use for overriding these is to	2891	their default definitions. One possible use for overriding these is to
2374	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2892	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2375	method calls instead of plain function calls in C++.	2893	method calls instead of plain function calls in C++.
		2894
		2895	=head2 EXPORTED API SYMBOLS
		2896
		2897	If you need to re-export the API (e.g. via a dll) and you need a list of
		2898	exported symbols, you can use the provided F<Symbol.*> files which list
		2899	all public symbols, one per line:
		2900
		2901	Symbols.ev for libev proper
		2902	Symbols.event for the libevent emulation
		2903
		2904	This can also be used to rename all public symbols to avoid clashes with
		2905	multiple versions of libev linked together (which is obviously bad in
		2906	itself, but sometimes it is inconvinient to avoid this).
		2907
		2908	A sed command like this will create wrapper C<#define>'s that you need to
		2909	include before including F<ev.h>:
		2910
		2911	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2912
		2913	This would create a file F<wrap.h> which essentially looks like this:
		2914
		2915	#define ev_backend myprefix_ev_backend
		2916	#define ev_check_start myprefix_ev_check_start
		2917	#define ev_check_stop myprefix_ev_check_stop
		2918	...
2376		2919
2377	=head2 EXAMPLES	2920	=head2 EXAMPLES
2378		2921
2379	For a real-world example of a program the includes libev	2922	For a real-world example of a program the includes libev
2380	verbatim, you can have a look at the EV perl module	2923	verbatim, you can have a look at the EV perl module
…		…
2421		2964
2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2965	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2423		2966
2424	This means that, when you have a watcher that triggers in one hour and	2967	This means that, when you have a watcher that triggers in one hour and
2425	there are 100 watchers that would trigger before that then inserting will	2968	there are 100 watchers that would trigger before that then inserting will
2426	have to skip those 100 watchers.	2969	have to skip roughly seven (C<ld 100>) of these watchers.
2427		2970
2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2971	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2429		2972
2430	That means that for changing a timer costs less than removing/adding them	2973	That means that changing a timer costs less than removing/adding them
2431	as only the relative motion in the event queue has to be paid for.	2974	as only the relative motion in the event queue has to be paid for.
2432		2975
2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2976	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2434		2977
2435	These just add the watcher into an array or at the head of a list.	2978	These just add the watcher into an array or at the head of a list.
		2979
2436	=item Stopping check/prepare/idle watchers: O(1)	2980	=item Stopping check/prepare/idle/fork/async watchers: O(1)
2437		2981
2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2982	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2439		2983
2440	These watchers are stored in lists then need to be walked to find the	2984	These watchers are stored in lists then need to be walked to find the
2441	correct watcher to remove. The lists are usually short (you don't usually	2985	correct watcher to remove. The lists are usually short (you don't usually
2442	have many watchers waiting for the same fd or signal).	2986	have many watchers waiting for the same fd or signal).
2443		2987
2444	=item Finding the next timer per loop iteration: O(1)	2988	=item Finding the next timer in each loop iteration: O(1)
		2989
		2990	By virtue of using a binary heap, the next timer is always found at the
		2991	beginning of the storage array.
2445		2992
2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2993	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2447		2994
2448	A change means an I/O watcher gets started or stopped, which requires	2995	A change means an I/O watcher gets started or stopped, which requires
2449	libev to recalculate its status (and possibly tell the kernel).	2996	libev to recalculate its status (and possibly tell the kernel, depending
		2997	on backend and wether C<ev_io_set> was used).
2450		2998
2451	=item Activating one watcher: O(1)	2999	=item Activating one watcher (putting it into the pending state): O(1)
2452		3000
2453	=item Priority handling: O(number_of_priorities)	3001	=item Priority handling: O(number_of_priorities)
2454		3002
2455	Priorities are implemented by allocating some space for each	3003	Priorities are implemented by allocating some space for each
2456	priority. When doing priority-based operations, libev usually has to	3004	priority. When doing priority-based operations, libev usually has to
2457	linearly search all the priorities.	3005	linearly search all the priorities, but starting/stopping and activating
		3006	watchers becomes O(1) w.r.t. priority handling.
		3007
		3008	=item Sending an ev_async: O(1)
		3009
		3010	=item Processing ev_async_send: O(number_of_async_watchers)
		3011
		3012	=item Processing signals: O(max_signal_number)
		3013
		3014	Sending involves a syscall I<iff> there were no other C<ev_async_send>
		3015	calls in the current loop iteration. Checking for async and signal events
		3016	involves iterating over all running async watchers or all signal numbers.
2458		3017
2459	=back	3018	=back
2460		3019
2461		3020
		3021	=head1 Win32 platform limitations and workarounds
		3022
		3023	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		3024	requires, and its I/O model is fundamentally incompatible with the POSIX
		3025	model. Libev still offers limited functionality on this platform in
		3026	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		3027	descriptors. This only applies when using Win32 natively, not when using
		3028	e.g. cygwin.
		3029
		3030	There is no supported compilation method available on windows except
		3031	embedding it into other applications.
		3032
		3033	Due to the many, low, and arbitrary limits on the win32 platform and the
		3034	abysmal performance of winsockets, using a large number of sockets is not
		3035	recommended (and not reasonable). If your program needs to use more than
		3036	a hundred or so sockets, then likely it needs to use a totally different
		3037	implementation for windows, as libev offers the POSIX model, which cannot
		3038	be implemented efficiently on windows (microsoft monopoly games).
		3039
		3040	=over 4
		3041
		3042	=item The winsocket select function
		3043
		3044	The winsocket C<select> function doesn't follow POSIX in that it requires
		3045	socket I<handles> and not socket I<file descriptors>. This makes select
		3046	very inefficient, and also requires a mapping from file descriptors
		3047	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		3048	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		3049	symbols for more info.
		3050
		3051	The configuration for a "naked" win32 using the microsoft runtime
		3052	libraries and raw winsocket select is:
		3053
		3054	#define EV_USE_SELECT 1
		3055	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		3056
		3057	Note that winsockets handling of fd sets is O(n), so you can easily get a
		3058	complexity in the O(n²) range when using win32.
		3059
		3060	=item Limited number of file descriptors
		3061
		3062	Windows has numerous arbitrary (and low) limits on things. Early versions
		3063	of winsocket's select only supported waiting for a max. of C<64> handles
		3064	(probably owning to the fact that all windows kernels can only wait for
		3065	C<64> things at the same time internally; microsoft recommends spawning a
		3066	chain of threads and wait for 63 handles and the previous thread in each).
		3067
		3068	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		3069	to some high number (e.g. C<2048>) before compiling the winsocket select
		3070	call (which might be in libev or elsewhere, for example, perl does its own
		3071	select emulation on windows).
		3072
		3073	Another limit is the number of file descriptors in the microsoft runtime
		3074	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3075	or something like this inside microsoft). You can increase this by calling
		3076	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3077	arbitrary limit), but is broken in many versions of the microsoft runtime
		3078	libraries.
		3079
		3080	This might get you to about C<512> or C<2048> sockets (depending on
		3081	windows version and/or the phase of the moon). To get more, you need to
		3082	wrap all I/O functions and provide your own fd management, but the cost of
		3083	calling select (O(n²)) will likely make this unworkable.
		3084
		3085	=back
		3086
		3087
2462	=head1 AUTHOR	3088	=head1 AUTHOR
2463		3089
2464	Marc Lehmann <libev@schmorp.de>.	3090	Marc Lehmann <libev@schmorp.de>.
2465		3091

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