ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs.
Revision 1.126 by root, Fri Feb 1 13:46:26 2008 UTC

…		…
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;
…		…
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		52
		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
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
53	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
54	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
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
57	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
58	(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
59	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
61	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
62	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
63	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
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head2 FEATURES
67		71
68	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
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	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
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		82
79	It also is quite fast (see this	83	It also is quite fast (see this
80	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
81	for example).	85	for example).
82		86
83	=head1 CONVENTIONS	87	=head2 CONVENTIONS
84		88
85	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
86	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
87	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
88	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
89	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>
90	(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.
91		95
92	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
93		97
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	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
97	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
98	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
99	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.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
109		115
110	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
111	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
112	you actually want to know.	118	you actually want to know.
113		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
114	=item int ev_version_major ()	126	=item int ev_version_major ()
115		127
116	=item int ev_version_minor ()	128	=item int ev_version_minor ()
117		129
118	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
119	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
120	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
121	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
122	version of the library your program was compiled against.	134	version of the library your program was compiled against.
123		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
124	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,
125	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
126	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
127	not a problem.	142	not a problem.
128		143
129	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
130	version.	145	version.
…		…
163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164	recommended ones.	179	recommended ones.
165		180
166	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
167		182
168	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
169		184
170	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
171	identical to the realloc C function). It is used to allocate and free	186	semantics is identical - to the realloc C function). It is used to
172	memory (no surprises here). If it returns zero when memory needs to be	187	allocate and free memory (no surprises here). If it returns zero when
173	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
174	action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
175		191
176	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
177	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
178	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
179		195
…		…
244	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
245		261
246	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
247	function.	263	function.
248		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
249	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
250	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>).
251		274
252	The following flags are supported:	275	The following flags are supported:
253		276
…		…
265	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
266	override the flags completely if it is found in the environment. This is	289	override the flags completely if it is found in the environment. This is
267	useful to try out specific backends to test their performance, or to work	290	useful to try out specific backends to test their performance, or to work
268	around bugs.	291	around bugs.
269		292
		293	=item C<EVFLAG_FORKCHECK>
		294
		295	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		296	a fork, you can also make libev check for a fork in each iteration by
		297	enabling this flag.
		298
		299	This works by calling C<getpid ()> on every iteration of the loop,
		300	and thus this might slow down your event loop if you do a lot of loop
		301	iterations and little real work, but is usually not noticeable (on my
		302	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		303	without a syscall and thus I<very> fast, but my Linux system also has
		304	C<pthread_atfork> which is even faster).
		305
		306	The big advantage of this flag is that you can forget about fork (and
		307	forget about forgetting to tell libev about forking) when you use this
		308	flag.
		309
		310	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		311	environment variable.
		312
270	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
271		314
272	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
273	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,
274	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
275	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
276	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.
277		327
278	=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)
279		329
280	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
281	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
282	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
283	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.
284		336
285	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
286		338
287	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,
288	but it scales phenomenally better. While poll and select usually scale like	340	but it scales phenomenally better. While poll and select usually scale
289	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),
290	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.
291		346
292	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
293	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
294	(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
295	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
296	well if you register events for both fds.	351	very well if you register events for both fds.
297		352
298	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
299	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
300	(or space) is available.	355	(or space) is available.
301		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
302	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
303		365
304	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
305	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
306	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
307	completely useless). For this reason its not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
308	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
309	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.
310		377
311	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
312	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
313	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
314	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
315	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.
316		393
317	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
318		395
319	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.
320		400
321	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
322		402
323	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,
324	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)).
325		405
326	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
327	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
328	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.
329		418
330	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
331		420
332	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
333	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
334	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
335		424
		425	It is definitely not recommended to use this flag.
		426
336	=back	427	=back
337		428
338	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
339	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
340	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
341	order of their flag values :)
342		432
343	The most typical usage is like this:	433	The most typical usage is like this:
344		434
345	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
346	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
374	Destroys the default loop again (frees all memory and kernel state	464	Destroys the default loop again (frees all memory and kernel state
375	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
376	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
377	responsibility to either stop all watchers cleanly yoursef I<before>	467	responsibility to either stop all watchers cleanly yoursef I<before>
378	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
379	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
380	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>).
381		480
382	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
383		482
384	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
385	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
386		485
387	=item ev_default_fork ()	486	=item ev_default_fork ()
388		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
389	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
390	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
391	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
392	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.
393		494
394	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
395	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
396	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
397		498
398	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
399	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
400	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
401		502
402	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
403		504
404	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
405	without calling this function, so if you force one of those backends you
406	do not need to care.
407
408	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
409		506
410	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
411	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
412	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 unsigned int ev_loop_count (loop)
		512
		513	Returns the count of loop iterations for the loop, which is identical to
		514	the number of times libev did poll for new events. It starts at C<0> and
		515	happily wraps around with enough iterations.
		516
		517	This value can sometimes be useful as a generation counter of sorts (it
		518	"ticks" the number of loop iterations), as it roughly corresponds with
		519	C<ev_prepare> and C<ev_check> calls.
413		520
414	=item unsigned int ev_backend (loop)	521	=item unsigned int ev_backend (loop)
415		522
416	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	523	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
417	use.	524	use.
…		…
420		527
421	Returns the current "event loop time", which is the time the event loop	528	Returns the current "event loop time", which is the time the event loop
422	received events and started processing them. This timestamp does not	529	received events and started processing them. This timestamp does not
423	change as long as callbacks are being processed, and this is also the base	530	change as long as callbacks are being processed, and this is also the base
424	time used for relative timers. You can treat it as the timestamp of the	531	time used for relative timers. You can treat it as the timestamp of the
425	event occuring (or more correctly, libev finding out about it).	532	event occurring (or more correctly, libev finding out about it).
426		533
427	=item ev_loop (loop, int flags)	534	=item ev_loop (loop, int flags)
428		535
429	Finally, this is it, the event handler. This function usually is called	536	Finally, this is it, the event handler. This function usually is called
430	after you initialised all your watchers and you want to start handling	537	after you initialised all your watchers and you want to start handling
…		…
451	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	558	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
452	usually a better approach for this kind of thing.	559	usually a better approach for this kind of thing.
453		560
454	Here are the gory details of what C<ev_loop> does:	561	Here are the gory details of what C<ev_loop> does:
455		562
456	* If there are no active watchers (reference count is zero), return.	563	- Before the first iteration, call any pending watchers.
457	- Queue prepare watchers and then call all outstanding watchers.	564	* If EVFLAG_FORKCHECK was used, check for a fork.
		565	- If a fork was detected, queue and call all fork watchers.
		566	- Queue and call all prepare watchers.
458	- If we have been forked, recreate the kernel state.	567	- If we have been forked, recreate the kernel state.
459	- Update the kernel state with all outstanding changes.	568	- Update the kernel state with all outstanding changes.
460	- Update the "event loop time".	569	- Update the "event loop time".
461	- Calculate for how long to block.	570	- Calculate for how long to sleep or block, if at all
		571	(active idle watchers, EVLOOP_NONBLOCK or not having
		572	any active watchers at all will result in not sleeping).
		573	- Sleep if the I/O and timer collect interval say so.
462	- Block the process, waiting for any events.	574	- Block the process, waiting for any events.
463	- Queue all outstanding I/O (fd) events.	575	- Queue all outstanding I/O (fd) events.
464	- Update the "event loop time" and do time jump handling.	576	- Update the "event loop time" and do time jump handling.
465	- Queue all outstanding timers.	577	- Queue all outstanding timers.
466	- Queue all outstanding periodics.	578	- Queue all outstanding periodics.
467	- If no events are pending now, queue all idle watchers.	579	- If no events are pending now, queue all idle watchers.
468	- Queue all check watchers.	580	- Queue all check watchers.
469	- Call all queued watchers in reverse order (i.e. check watchers first).	581	- Call all queued watchers in reverse order (i.e. check watchers first).
470	Signals and child watchers are implemented as I/O watchers, and will	582	Signals and child watchers are implemented as I/O watchers, and will
471	be handled here by queueing them when their watcher gets executed.	583	be handled here by queueing them when their watcher gets executed.
472	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	584	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
473	were used, return, otherwise continue with step *.	585	were used, or there are no active watchers, return, otherwise
		586	continue with step *.
474		587
475	Example: Queue some jobs and then loop until no events are outsanding	588	Example: Queue some jobs and then loop until no events are outstanding
476	anymore.	589	anymore.
477		590
478	... queue jobs here, make sure they register event watchers as long	591	... queue jobs here, make sure they register event watchers as long
479	... as they still have work to do (even an idle watcher will do..)	592	... as they still have work to do (even an idle watcher will do..)
480	ev_loop (my_loop, 0);	593	ev_loop (my_loop, 0);
…		…
484		597
485	Can be used to make a call to C<ev_loop> return early (but only after it	598	Can be used to make a call to C<ev_loop> return early (but only after it
486	has processed all outstanding events). The C<how> argument must be either	599	has processed all outstanding events). The C<how> argument must be either
487	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	600	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
488	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	601	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		602
		603	This "unloop state" will be cleared when entering C<ev_loop> again.
489		604
490	=item ev_ref (loop)	605	=item ev_ref (loop)
491		606
492	=item ev_unref (loop)	607	=item ev_unref (loop)
493		608
…		…
498	returning, ev_unref() after starting, and ev_ref() before stopping it. For	613	returning, ev_unref() after starting, and ev_ref() before stopping it. For
499	example, libev itself uses this for its internal signal pipe: It is not	614	example, libev itself uses this for its internal signal pipe: It is not
500	visible to the libev user and should not keep C<ev_loop> from exiting if	615	visible to the libev user and should not keep C<ev_loop> from exiting if
501	no event watchers registered by it are active. It is also an excellent	616	no event watchers registered by it are active. It is also an excellent
502	way to do this for generic recurring timers or from within third-party	617	way to do this for generic recurring timers or from within third-party
503	libraries. Just remember to I<unref after start> and I<ref before stop>.	618	libraries. Just remember to I<unref after start> and I<ref before stop>
		619	(but only if the watcher wasn't active before, or was active before,
		620	respectively).
504		621
505	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	622	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
506	running when nothing else is active.	623	running when nothing else is active.
507		624
508	struct ev_signal exitsig;	625	struct ev_signal exitsig;
…		…
512		629
513	Example: For some weird reason, unregister the above signal handler again.	630	Example: For some weird reason, unregister the above signal handler again.
514		631
515	ev_ref (loop);	632	ev_ref (loop);
516	ev_signal_stop (loop, &exitsig);	633	ev_signal_stop (loop, &exitsig);
		634
		635	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		636
		637	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		638
		639	These advanced functions influence the time that libev will spend waiting
		640	for events. Both are by default C<0>, meaning that libev will try to
		641	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		642
		643	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		644	allows libev to delay invocation of I/O and timer/periodic callbacks to
		645	increase efficiency of loop iterations.
		646
		647	The background is that sometimes your program runs just fast enough to
		648	handle one (or very few) event(s) per loop iteration. While this makes
		649	the program responsive, it also wastes a lot of CPU time to poll for new
		650	events, especially with backends like C<select ()> which have a high
		651	overhead for the actual polling but can deliver many events at once.
		652
		653	By setting a higher I<io collect interval> you allow libev to spend more
		654	time collecting I/O events, so you can handle more events per iteration,
		655	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		656	C<ev_timer>) will be not affected. Setting this to a non-null value will
		657	introduce an additional C<ev_sleep ()> call into most loop iterations.
		658
		659	Likewise, by setting a higher I<timeout collect interval> you allow libev
		660	to spend more time collecting timeouts, at the expense of increased
		661	latency (the watcher callback will be called later). C<ev_io> watchers
		662	will not be affected. Setting this to a non-null value will not introduce
		663	any overhead in libev.
		664
		665	Many (busy) programs can usually benefit by setting the io collect
		666	interval to a value near C<0.1> or so, which is often enough for
		667	interactive servers (of course not for games), likewise for timeouts. It
		668	usually doesn't make much sense to set it to a lower value than C<0.01>,
		669	as this approsaches the timing granularity of most systems.
517		670
518	=back	671	=back
519		672
520		673
521	=head1 ANATOMY OF A WATCHER	674	=head1 ANATOMY OF A WATCHER
…		…
621	=item C<EV_FORK>	774	=item C<EV_FORK>
622		775
623	The event loop has been resumed in the child process after fork (see	776	The event loop has been resumed in the child process after fork (see
624	C<ev_fork>).	777	C<ev_fork>).
625		778
		779	=item C<EV_ASYNC>
		780
		781	The given async watcher has been asynchronously notified (see C<ev_async>).
		782
626	=item C<EV_ERROR>	783	=item C<EV_ERROR>
627		784
628	An unspecified error has occured, the watcher has been stopped. This might	785	An unspecified error has occured, the watcher has been stopped. This might
629	happen because the watcher could not be properly started because libev	786	happen because the watcher could not be properly started because libev
630	ran out of memory, a file descriptor was found to be closed or any other	787	ran out of memory, a file descriptor was found to be closed or any other
…		…
701	=item bool ev_is_pending (ev_TYPE *watcher)	858	=item bool ev_is_pending (ev_TYPE *watcher)
702		859
703	Returns a true value iff the watcher is pending, (i.e. it has outstanding	860	Returns a true value iff the watcher is pending, (i.e. it has outstanding
704	events but its callback has not yet been invoked). As long as a watcher	861	events but its callback has not yet been invoked). As long as a watcher
705	is pending (but not active) you must not call an init function on it (but	862	is pending (but not active) you must not call an init function on it (but
706	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	863	C<ev_TYPE_set> is safe), you must not change its priority, and you must
707	libev (e.g. you cnanot C<free ()> it).	864	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		865	it).
708		866
709	=item callback ev_cb (ev_TYPE *watcher)	867	=item callback ev_cb (ev_TYPE *watcher)
710		868
711	Returns the callback currently set on the watcher.	869	Returns the callback currently set on the watcher.
712		870
713	=item ev_cb_set (ev_TYPE *watcher, callback)	871	=item ev_cb_set (ev_TYPE *watcher, callback)
714		872
715	Change the callback. You can change the callback at virtually any time	873	Change the callback. You can change the callback at virtually any time
716	(modulo threads).	874	(modulo threads).
		875
		876	=item ev_set_priority (ev_TYPE *watcher, priority)
		877
		878	=item int ev_priority (ev_TYPE *watcher)
		879
		880	Set and query the priority of the watcher. The priority is a small
		881	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		882	(default: C<-2>). Pending watchers with higher priority will be invoked
		883	before watchers with lower priority, but priority will not keep watchers
		884	from being executed (except for C<ev_idle> watchers).
		885
		886	This means that priorities are I<only> used for ordering callback
		887	invocation after new events have been received. This is useful, for
		888	example, to reduce latency after idling, or more often, to bind two
		889	watchers on the same event and make sure one is called first.
		890
		891	If you need to suppress invocation when higher priority events are pending
		892	you need to look at C<ev_idle> watchers, which provide this functionality.
		893
		894	You I<must not> change the priority of a watcher as long as it is active or
		895	pending.
		896
		897	The default priority used by watchers when no priority has been set is
		898	always C<0>, which is supposed to not be too high and not be too low :).
		899
		900	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		901	fine, as long as you do not mind that the priority value you query might
		902	or might not have been adjusted to be within valid range.
		903
		904	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		905
		906	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		907	C<loop> nor C<revents> need to be valid as long as the watcher callback
		908	can deal with that fact.
		909
		910	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		911
		912	If the watcher is pending, this function returns clears its pending status
		913	and returns its C<revents> bitset (as if its callback was invoked). If the
		914	watcher isn't pending it does nothing and returns C<0>.
717		915
718	=back	916	=back
719		917
720		918
721	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	919	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
806	In general you can register as many read and/or write event watchers per	1004	In general you can register as many read and/or write event watchers per
807	fd as you want (as long as you don't confuse yourself). Setting all file	1005	fd as you want (as long as you don't confuse yourself). Setting all file
808	descriptors to non-blocking mode is also usually a good idea (but not	1006	descriptors to non-blocking mode is also usually a good idea (but not
809	required if you know what you are doing).	1007	required if you know what you are doing).
810		1008
811	You have to be careful with dup'ed file descriptors, though. Some backends
812	(the linux epoll backend is a notable example) cannot handle dup'ed file
813	descriptors correctly if you register interest in two or more fds pointing
814	to the same underlying file/socket/etc. description (that is, they share
815	the same underlying "file open").
816
817	If you must do this, then force the use of a known-to-be-good backend	1009	If you must do this, then force the use of a known-to-be-good backend
818	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1010	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
819	C<EVBACKEND_POLL>).	1011	C<EVBACKEND_POLL>).
820		1012
821	Another thing you have to watch out for is that it is quite easy to	1013	Another thing you have to watch out for is that it is quite easy to
…		…
827	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1019	it is best to always use non-blocking I/O: An extra C<read>(2) returning
828	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1020	C<EAGAIN> is far preferable to a program hanging until some data arrives.
829		1021
830	If you cannot run the fd in non-blocking mode (for example you should not	1022	If you cannot run the fd in non-blocking mode (for example you should not
831	play around with an Xlib connection), then you have to seperately re-test	1023	play around with an Xlib connection), then you have to seperately re-test
832	wether a file descriptor is really ready with a known-to-be good interface	1024	whether a file descriptor is really ready with a known-to-be good interface
833	such as poll (fortunately in our Xlib example, Xlib already does this on	1025	such as poll (fortunately in our Xlib example, Xlib already does this on
834	its own, so its quite safe to use).	1026	its own, so its quite safe to use).
		1027
		1028	=head3 The special problem of disappearing file descriptors
		1029
		1030	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1031	descriptor (either by calling C<close> explicitly or by any other means,
		1032	such as C<dup>). The reason is that you register interest in some file
		1033	descriptor, but when it goes away, the operating system will silently drop
		1034	this interest. If another file descriptor with the same number then is
		1035	registered with libev, there is no efficient way to see that this is, in
		1036	fact, a different file descriptor.
		1037
		1038	To avoid having to explicitly tell libev about such cases, libev follows
		1039	the following policy: Each time C<ev_io_set> is being called, libev
		1040	will assume that this is potentially a new file descriptor, otherwise
		1041	it is assumed that the file descriptor stays the same. That means that
		1042	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1043	descriptor even if the file descriptor number itself did not change.
		1044
		1045	This is how one would do it normally anyway, the important point is that
		1046	the libev application should not optimise around libev but should leave
		1047	optimisations to libev.
		1048
		1049	=head3 The special problem of dup'ed file descriptors
		1050
		1051	Some backends (e.g. epoll), cannot register events for file descriptors,
		1052	but only events for the underlying file descriptions. That means when you
		1053	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1054	events for them, only one file descriptor might actually receive events.
		1055
		1056	There is no workaround possible except not registering events
		1057	for potentially C<dup ()>'ed file descriptors, or to resort to
		1058	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1059
		1060	=head3 The special problem of fork
		1061
		1062	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1063	useless behaviour. Libev fully supports fork, but needs to be told about
		1064	it in the child.
		1065
		1066	To support fork in your programs, you either have to call
		1067	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1068	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1069	C<EVBACKEND_POLL>.
		1070
		1071
		1072	=head3 Watcher-Specific Functions
835		1073
836	=over 4	1074	=over 4
837		1075
838	=item ev_io_init (ev_io *, callback, int fd, int events)	1076	=item ev_io_init (ev_io *, callback, int fd, int events)
839		1077
…		…
850	=item int events [read-only]	1088	=item int events [read-only]
851		1089
852	The events being watched.	1090	The events being watched.
853		1091
854	=back	1092	=back
		1093
		1094	=head3 Examples
855		1095
856	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1096	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
857	readable, but only once. Since it is likely line-buffered, you could	1097	readable, but only once. Since it is likely line-buffered, you could
858	attempt to read a whole line in the callback.	1098	attempt to read a whole line in the callback.
859		1099
…		…
893		1133
894	The callback is guarenteed to be invoked only when its timeout has passed,	1134	The callback is guarenteed to be invoked only when its timeout has passed,
895	but if multiple timers become ready during the same loop iteration then	1135	but if multiple timers become ready during the same loop iteration then
896	order of execution is undefined.	1136	order of execution is undefined.
897		1137
		1138	=head3 Watcher-Specific Functions and Data Members
		1139
898	=over 4	1140	=over 4
899		1141
900	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1142	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
901		1143
902	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1144	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
915	=item ev_timer_again (loop)	1157	=item ev_timer_again (loop)
916		1158
917	This will act as if the timer timed out and restart it again if it is	1159	This will act as if the timer timed out and restart it again if it is
918	repeating. The exact semantics are:	1160	repeating. The exact semantics are:
919		1161
		1162	If the timer is pending, its pending status is cleared.
		1163
920	If the timer is started but nonrepeating, stop it.	1164	If the timer is started but nonrepeating, stop it (as if it timed out).
921		1165
922	If the timer is repeating, either start it if necessary (with the repeat	1166	If the timer is repeating, either start it if necessary (with the
923	value), or reset the running timer to the repeat value.	1167	C<repeat> value), or reset the running timer to the C<repeat> value.
924		1168
925	This sounds a bit complicated, but here is a useful and typical	1169	This sounds a bit complicated, but here is a useful and typical
926	example: Imagine you have a tcp connection and you want a so-called	1170	example: Imagine you have a tcp connection and you want a so-called idle
927	idle timeout, that is, you want to be called when there have been,	1171	timeout, that is, you want to be called when there have been, say, 60
928	say, 60 seconds of inactivity on the socket. The easiest way to do	1172	seconds of inactivity on the socket. The easiest way to do this is to
929	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1173	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
930	C<ev_timer_again> each time you successfully read or write some data. If	1174	C<ev_timer_again> each time you successfully read or write some data. If
931	you go into an idle state where you do not expect data to travel on the	1175	you go into an idle state where you do not expect data to travel on the
932	socket, you can stop the timer, and again will automatically restart it if	1176	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
933	need be.	1177	automatically restart it if need be.
934		1178
935	You can also ignore the C<after> value and C<ev_timer_start> altogether	1179	That means you can ignore the C<after> value and C<ev_timer_start>
936	and only ever use the C<repeat> value:	1180	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
937		1181
938	ev_timer_init (timer, callback, 0., 5.);	1182	ev_timer_init (timer, callback, 0., 5.);
939	ev_timer_again (loop, timer);	1183	ev_timer_again (loop, timer);
940	...	1184	...
941	timer->again = 17.;	1185	timer->again = 17.;
942	ev_timer_again (loop, timer);	1186	ev_timer_again (loop, timer);
943	...	1187	...
944	timer->again = 10.;	1188	timer->again = 10.;
945	ev_timer_again (loop, timer);	1189	ev_timer_again (loop, timer);
946		1190
947	This is more efficient then stopping/starting the timer eahc time you want	1191	This is more slightly efficient then stopping/starting the timer each time
948	to modify its timeout value.	1192	you want to modify its timeout value.
949		1193
950	=item ev_tstamp repeat [read-write]	1194	=item ev_tstamp repeat [read-write]
951		1195
952	The current C<repeat> value. Will be used each time the watcher times out	1196	The current C<repeat> value. Will be used each time the watcher times out
953	or C<ev_timer_again> is called and determines the next timeout (if any),	1197	or C<ev_timer_again> is called and determines the next timeout (if any),
954	which is also when any modifications are taken into account.	1198	which is also when any modifications are taken into account.
955		1199
956	=back	1200	=back
		1201
		1202	=head3 Examples
957		1203
958	Example: Create a timer that fires after 60 seconds.	1204	Example: Create a timer that fires after 60 seconds.
959		1205
960	static void	1206	static void
961	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1207	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
…		…
995	but on wallclock time (absolute time). You can tell a periodic watcher	1241	but on wallclock time (absolute time). You can tell a periodic watcher
996	to trigger "at" some specific point in time. For example, if you tell a	1242	to trigger "at" some specific point in time. For example, if you tell a
997	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1243	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
998	+ 10.>) and then reset your system clock to the last year, then it will	1244	+ 10.>) and then reset your system clock to the last year, then it will
999	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1245	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1000	roughly 10 seconds later and of course not if you reset your system time	1246	roughly 10 seconds later).
1001	again).
1002		1247
1003	They can also be used to implement vastly more complex timers, such as	1248	They can also be used to implement vastly more complex timers, such as
1004	triggering an event on eahc midnight, local time.	1249	triggering an event on each midnight, local time or other, complicated,
		1250	rules.
1005		1251
1006	As with timers, the callback is guarenteed to be invoked only when the	1252	As with timers, the callback is guarenteed to be invoked only when the
1007	time (C<at>) has been passed, but if multiple periodic timers become ready	1253	time (C<at>) has been passed, but if multiple periodic timers become ready
1008	during the same loop iteration then order of execution is undefined.	1254	during the same loop iteration then order of execution is undefined.
1009		1255
		1256	=head3 Watcher-Specific Functions and Data Members
		1257
1010	=over 4	1258	=over 4
1011		1259
1012	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1260	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1013		1261
1014	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1262	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1016	Lots of arguments, lets sort it out... There are basically three modes of	1264	Lots of arguments, lets sort it out... There are basically three modes of
1017	operation, and we will explain them from simplest to complex:	1265	operation, and we will explain them from simplest to complex:
1018		1266
1019	=over 4	1267	=over 4
1020		1268
1021	=item * absolute timer (interval = reschedule_cb = 0)	1269	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1022		1270
1023	In this configuration the watcher triggers an event at the wallclock time	1271	In this configuration the watcher triggers an event at the wallclock time
1024	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1272	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1025	that is, if it is to be run at January 1st 2011 then it will run when the	1273	that is, if it is to be run at January 1st 2011 then it will run when the
1026	system time reaches or surpasses this time.	1274	system time reaches or surpasses this time.
1027		1275
1028	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1276	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1029		1277
1030	In this mode the watcher will always be scheduled to time out at the next	1278	In this mode the watcher will always be scheduled to time out at the next
1031	C<at + N * interval> time (for some integer N) and then repeat, regardless	1279	C<at + N * interval> time (for some integer N, which can also be negative)
1032	of any time jumps.	1280	and then repeat, regardless of any time jumps.
1033		1281
1034	This can be used to create timers that do not drift with respect to system	1282	This can be used to create timers that do not drift with respect to system
1035	time:	1283	time:
1036		1284
1037	ev_periodic_set (&periodic, 0., 3600., 0);	1285	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1043		1291
1044	Another way to think about it (for the mathematically inclined) is that	1292	Another way to think about it (for the mathematically inclined) is that
1045	C<ev_periodic> will try to run the callback in this mode at the next possible	1293	C<ev_periodic> will try to run the callback in this mode at the next possible
1046	time where C<time = at (mod interval)>, regardless of any time jumps.	1294	time where C<time = at (mod interval)>, regardless of any time jumps.
1047		1295
		1296	For numerical stability it is preferable that the C<at> value is near
		1297	C<ev_now ()> (the current time), but there is no range requirement for
		1298	this value.
		1299
1048	=item * manual reschedule mode (reschedule_cb = callback)	1300	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1049		1301
1050	In this mode the values for C<interval> and C<at> are both being	1302	In this mode the values for C<interval> and C<at> are both being
1051	ignored. Instead, each time the periodic watcher gets scheduled, the	1303	ignored. Instead, each time the periodic watcher gets scheduled, the
1052	reschedule callback will be called with the watcher as first, and the	1304	reschedule callback will be called with the watcher as first, and the
1053	current time as second argument.	1305	current time as second argument.
1054		1306
1055	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1307	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1056	ever, or make any event loop modifications>. If you need to stop it,	1308	ever, or make any event loop modifications>. If you need to stop it,
1057	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1309	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1058	starting a prepare watcher).	1310	starting an C<ev_prepare> watcher, which is legal).
1059		1311
1060	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1312	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1061	ev_tstamp now)>, e.g.:	1313	ev_tstamp now)>, e.g.:
1062		1314
1063	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1315	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1086	Simply stops and restarts the periodic watcher again. This is only useful	1338	Simply stops and restarts the periodic watcher again. This is only useful
1087	when you changed some parameters or the reschedule callback would return	1339	when you changed some parameters or the reschedule callback would return
1088	a different time than the last time it was called (e.g. in a crond like	1340	a different time than the last time it was called (e.g. in a crond like
1089	program when the crontabs have changed).	1341	program when the crontabs have changed).
1090		1342
		1343	=item ev_tstamp offset [read-write]
		1344
		1345	When repeating, this contains the offset value, otherwise this is the
		1346	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1347
		1348	Can be modified any time, but changes only take effect when the periodic
		1349	timer fires or C<ev_periodic_again> is being called.
		1350
1091	=item ev_tstamp interval [read-write]	1351	=item ev_tstamp interval [read-write]
1092		1352
1093	The current interval value. Can be modified any time, but changes only	1353	The current interval value. Can be modified any time, but changes only
1094	take effect when the periodic timer fires or C<ev_periodic_again> is being	1354	take effect when the periodic timer fires or C<ev_periodic_again> is being
1095	called.	1355	called.
…		…
1098		1358
1099	The current reschedule callback, or C<0>, if this functionality is	1359	The current reschedule callback, or C<0>, if this functionality is
1100	switched off. Can be changed any time, but changes only take effect when	1360	switched off. Can be changed any time, but changes only take effect when
1101	the periodic timer fires or C<ev_periodic_again> is being called.	1361	the periodic timer fires or C<ev_periodic_again> is being called.
1102		1362
		1363	=item ev_tstamp at [read-only]
		1364
		1365	When active, contains the absolute time that the watcher is supposed to
		1366	trigger next.
		1367
1103	=back	1368	=back
		1369
		1370	=head3 Examples
1104		1371
1105	Example: Call a callback every hour, or, more precisely, whenever the	1372	Example: Call a callback every hour, or, more precisely, whenever the
1106	system clock is divisible by 3600. The callback invocation times have	1373	system clock is divisible by 3600. The callback invocation times have
1107	potentially a lot of jittering, but good long-term stability.	1374	potentially a lot of jittering, but good long-term stability.
1108		1375
…		…
1148	with the kernel (thus it coexists with your own signal handlers as long	1415	with the kernel (thus it coexists with your own signal handlers as long
1149	as you don't register any with libev). Similarly, when the last signal	1416	as you don't register any with libev). Similarly, when the last signal
1150	watcher for a signal is stopped libev will reset the signal handler to	1417	watcher for a signal is stopped libev will reset the signal handler to
1151	SIG_DFL (regardless of what it was set to before).	1418	SIG_DFL (regardless of what it was set to before).
1152		1419
		1420	=head3 Watcher-Specific Functions and Data Members
		1421
1153	=over 4	1422	=over 4
1154		1423
1155	=item ev_signal_init (ev_signal *, callback, int signum)	1424	=item ev_signal_init (ev_signal *, callback, int signum)
1156		1425
1157	=item ev_signal_set (ev_signal *, int signum)	1426	=item ev_signal_set (ev_signal *, int signum)
…		…
1169	=head2 C<ev_child> - watch out for process status changes	1438	=head2 C<ev_child> - watch out for process status changes
1170		1439
1171	Child watchers trigger when your process receives a SIGCHLD in response to	1440	Child watchers trigger when your process receives a SIGCHLD in response to
1172	some child status changes (most typically when a child of yours dies).	1441	some child status changes (most typically when a child of yours dies).
1173		1442
		1443	=head3 Watcher-Specific Functions and Data Members
		1444
1174	=over 4	1445	=over 4
1175		1446
1176	=item ev_child_init (ev_child *, callback, int pid)	1447	=item ev_child_init (ev_child *, callback, int pid, int trace)
1177		1448
1178	=item ev_child_set (ev_child *, int pid)	1449	=item ev_child_set (ev_child *, int pid, int trace)
1179		1450
1180	Configures the watcher to wait for status changes of process C<pid> (or	1451	Configures the watcher to wait for status changes of process C<pid> (or
1181	I<any> process if C<pid> is specified as C<0>). The callback can look	1452	I<any> process if C<pid> is specified as C<0>). The callback can look
1182	at the C<rstatus> member of the C<ev_child> watcher structure to see	1453	at the C<rstatus> member of the C<ev_child> watcher structure to see
1183	the status word (use the macros from C<sys/wait.h> and see your systems	1454	the status word (use the macros from C<sys/wait.h> and see your systems
1184	C<waitpid> documentation). The C<rpid> member contains the pid of the	1455	C<waitpid> documentation). The C<rpid> member contains the pid of the
1185	process causing the status change.	1456	process causing the status change. C<trace> must be either C<0> (only
		1457	activate the watcher when the process terminates) or C<1> (additionally
		1458	activate the watcher when the process is stopped or continued).
1186		1459
1187	=item int pid [read-only]	1460	=item int pid [read-only]
1188		1461
1189	The process id this watcher watches out for, or C<0>, meaning any process id.	1462	The process id this watcher watches out for, or C<0>, meaning any process id.
1190		1463
…		…
1196		1469
1197	The process exit/trace status caused by C<rpid> (see your systems	1470	The process exit/trace status caused by C<rpid> (see your systems
1198	C<waitpid> and C<sys/wait.h> documentation for details).	1471	C<waitpid> and C<sys/wait.h> documentation for details).
1199		1472
1200	=back	1473	=back
		1474
		1475	=head3 Examples
1201		1476
1202	Example: Try to exit cleanly on SIGINT and SIGTERM.	1477	Example: Try to exit cleanly on SIGINT and SIGTERM.
1203		1478
1204	static void	1479	static void
1205	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1480	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
…		…
1221	The path does not need to exist: changing from "path exists" to "path does	1496	The path does not need to exist: changing from "path exists" to "path does
1222	not exist" is a status change like any other. The condition "path does	1497	not exist" is a status change like any other. The condition "path does
1223	not exist" is signified by the C<st_nlink> field being zero (which is	1498	not exist" is signified by the C<st_nlink> field being zero (which is
1224	otherwise always forced to be at least one) and all the other fields of	1499	otherwise always forced to be at least one) and all the other fields of
1225	the stat buffer having unspecified contents.	1500	the stat buffer having unspecified contents.
		1501
		1502	The path I<should> be absolute and I<must not> end in a slash. If it is
		1503	relative and your working directory changes, the behaviour is undefined.
1226		1504
1227	Since there is no standard to do this, the portable implementation simply	1505	Since there is no standard to do this, the portable implementation simply
1228	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1506	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1229	can specify a recommended polling interval for this case. If you specify	1507	can specify a recommended polling interval for this case. If you specify
1230	a polling interval of C<0> (highly recommended!) then a I<suitable,	1508	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1243	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1521	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1244	to fall back to regular polling again even with inotify, but changes are	1522	to fall back to regular polling again even with inotify, but changes are
1245	usually detected immediately, and if the file exists there will be no	1523	usually detected immediately, and if the file exists there will be no
1246	polling.	1524	polling.
1247		1525
		1526	=head3 Inotify
		1527
		1528	When C<inotify (7)> support has been compiled into libev (generally only
		1529	available on Linux) and present at runtime, it will be used to speed up
		1530	change detection where possible. The inotify descriptor will be created lazily
		1531	when the first C<ev_stat> watcher is being started.
		1532
		1533	Inotify presense does not change the semantics of C<ev_stat> watchers
		1534	except that changes might be detected earlier, and in some cases, to avoid
		1535	making regular C<stat> calls. Even in the presense of inotify support
		1536	there are many cases where libev has to resort to regular C<stat> polling.
		1537
		1538	(There is no support for kqueue, as apparently it cannot be used to
		1539	implement this functionality, due to the requirement of having a file
		1540	descriptor open on the object at all times).
		1541
		1542	=head3 The special problem of stat time resolution
		1543
		1544	The C<stat ()> syscall only supports full-second resolution portably, and
		1545	even on systems where the resolution is higher, many filesystems still
		1546	only support whole seconds.
		1547
		1548	That means that, if the time is the only thing that changes, you might
		1549	miss updates: on the first update, C<ev_stat> detects a change and calls
		1550	your callback, which does something. When there is another update within
		1551	the same second, C<ev_stat> will be unable to detect it.
		1552
		1553	The solution to this is to delay acting on a change for a second (or till
		1554	the next second boundary), using a roughly one-second delay C<ev_timer>
		1555	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1556	is added to work around small timing inconsistencies of some operating
		1557	systems.
		1558
		1559	=head3 Watcher-Specific Functions and Data Members
		1560
1248	=over 4	1561	=over 4
1249		1562
1250	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1563	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1251		1564
1252	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)	1565	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
…		…
1287	=item const char *path [read-only]	1600	=item const char *path [read-only]
1288		1601
1289	The filesystem path that is being watched.	1602	The filesystem path that is being watched.
1290		1603
1291	=back	1604	=back
		1605
		1606	=head3 Examples
1292		1607
1293	Example: Watch C</etc/passwd> for attribute changes.	1608	Example: Watch C</etc/passwd> for attribute changes.
1294		1609
1295	static void	1610	static void
1296	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1611	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1309	}	1624	}
1310		1625
1311	...	1626	...
1312	ev_stat passwd;	1627	ev_stat passwd;
1313		1628
1314	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1629	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1315	ev_stat_start (loop, &passwd);	1630	ev_stat_start (loop, &passwd);
1316		1631
		1632	Example: Like above, but additionally use a one-second delay so we do not
		1633	miss updates (however, frequent updates will delay processing, too, so
		1634	one might do the work both on C<ev_stat> callback invocation I<and> on
		1635	C<ev_timer> callback invocation).
		1636
		1637	static ev_stat passwd;
		1638	static ev_timer timer;
		1639
		1640	static void
		1641	timer_cb (EV_P_ ev_timer *w, int revents)
		1642	{
		1643	ev_timer_stop (EV_A_ w);
		1644
		1645	/* now it's one second after the most recent passwd change */
		1646	}
		1647
		1648	static void
		1649	stat_cb (EV_P_ ev_stat *w, int revents)
		1650	{
		1651	/* reset the one-second timer */
		1652	ev_timer_again (EV_A_ &timer);
		1653	}
		1654
		1655	...
		1656	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1657	ev_stat_start (loop, &passwd);
		1658	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1659
1317		1660
1318	=head2 C<ev_idle> - when you've got nothing better to do...	1661	=head2 C<ev_idle> - when you've got nothing better to do...
1319		1662
1320	Idle watchers trigger events when there are no other events are pending	1663	Idle watchers trigger events when no other events of the same or higher
1321	(prepare, check and other idle watchers do not count). That is, as long	1664	priority are pending (prepare, check and other idle watchers do not
1322	as your process is busy handling sockets or timeouts (or even signals,	1665	count).
1323	imagine) it will not be triggered. But when your process is idle all idle	1666
1324	watchers are being called again and again, once per event loop iteration -	1667	That is, as long as your process is busy handling sockets or timeouts
		1668	(or even signals, imagine) of the same or higher priority it will not be
		1669	triggered. But when your process is idle (or only lower-priority watchers
		1670	are pending), the idle watchers are being called once per event loop
1325	until stopped, that is, or your process receives more events and becomes	1671	iteration - until stopped, that is, or your process receives more events
1326	busy.	1672	and becomes busy again with higher priority stuff.
1327		1673
1328	The most noteworthy effect is that as long as any idle watchers are	1674	The most noteworthy effect is that as long as any idle watchers are
1329	active, the process will not block when waiting for new events.	1675	active, the process will not block when waiting for new events.
1330		1676
1331	Apart from keeping your process non-blocking (which is a useful	1677	Apart from keeping your process non-blocking (which is a useful
1332	effect on its own sometimes), idle watchers are a good place to do	1678	effect on its own sometimes), idle watchers are a good place to do
1333	"pseudo-background processing", or delay processing stuff to after the	1679	"pseudo-background processing", or delay processing stuff to after the
1334	event loop has handled all outstanding events.	1680	event loop has handled all outstanding events.
1335		1681
		1682	=head3 Watcher-Specific Functions and Data Members
		1683
1336	=over 4	1684	=over 4
1337		1685
1338	=item ev_idle_init (ev_signal *, callback)	1686	=item ev_idle_init (ev_signal *, callback)
1339		1687
1340	Initialises and configures the idle watcher - it has no parameters of any	1688	Initialises and configures the idle watcher - it has no parameters of any
1341	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1689	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1342	believe me.	1690	believe me.
1343		1691
1344	=back	1692	=back
		1693
		1694	=head3 Examples
1345		1695
1346	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1696	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1347	callback, free it. Also, use no error checking, as usual.	1697	callback, free it. Also, use no error checking, as usual.
1348		1698
1349	static void	1699	static void
1350	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1700	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1351	{	1701	{
1352	free (w);	1702	free (w);
1353	// now do something you wanted to do when the program has	1703	// now do something you wanted to do when the program has
1354	// no longer asnything immediate to do.	1704	// no longer anything immediate to do.
1355	}	1705	}
1356		1706
1357	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1707	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1358	ev_idle_init (idle_watcher, idle_cb);	1708	ev_idle_init (idle_watcher, idle_cb);
1359	ev_idle_start (loop, idle_cb);	1709	ev_idle_start (loop, idle_cb);
…		…
1397	with priority higher than or equal to the event loop and one coroutine	1747	with priority higher than or equal to the event loop and one coroutine
1398	of lower priority, but only once, using idle watchers to keep the event	1748	of lower priority, but only once, using idle watchers to keep the event
1399	loop from blocking if lower-priority coroutines are active, thus mapping	1749	loop from blocking if lower-priority coroutines are active, thus mapping
1400	low-priority coroutines to idle/background tasks).	1750	low-priority coroutines to idle/background tasks).
1401		1751
		1752	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1753	priority, to ensure that they are being run before any other watchers
		1754	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1755	too) should not activate ("feed") events into libev. While libev fully
		1756	supports this, they will be called before other C<ev_check> watchers
		1757	did their job. As C<ev_check> watchers are often used to embed other
		1758	(non-libev) event loops those other event loops might be in an unusable
		1759	state until their C<ev_check> watcher ran (always remind yourself to
		1760	coexist peacefully with others).
		1761
		1762	=head3 Watcher-Specific Functions and Data Members
		1763
1402	=over 4	1764	=over 4
1403		1765
1404	=item ev_prepare_init (ev_prepare *, callback)	1766	=item ev_prepare_init (ev_prepare *, callback)
1405		1767
1406	=item ev_check_init (ev_check *, callback)	1768	=item ev_check_init (ev_check *, callback)
…		…
1409	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1771	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1410	macros, but using them is utterly, utterly and completely pointless.	1772	macros, but using them is utterly, utterly and completely pointless.
1411		1773
1412	=back	1774	=back
1413		1775
1414	Example: To include a library such as adns, you would add IO watchers	1776	=head3 Examples
1415	and a timeout watcher in a prepare handler, as required by libadns, and	1777
		1778	There are a number of principal ways to embed other event loops or modules
		1779	into libev. Here are some ideas on how to include libadns into libev
		1780	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1781	use for an actually working example. Another Perl module named C<EV::Glib>
		1782	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1783	into the Glib event loop).
		1784
		1785	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1416	in a check watcher, destroy them and call into libadns. What follows is	1786	and in a check watcher, destroy them and call into libadns. What follows
1417	pseudo-code only of course:	1787	is pseudo-code only of course. This requires you to either use a low
		1788	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1789	the callbacks for the IO/timeout watchers might not have been called yet.
1418		1790
1419	static ev_io iow [nfd];	1791	static ev_io iow [nfd];
1420	static ev_timer tw;	1792	static ev_timer tw;
1421		1793
1422	static void	1794	static void
1423	io_cb (ev_loop *loop, ev_io *w, int revents)	1795	io_cb (ev_loop *loop, ev_io *w, int revents)
1424	{	1796	{
1425	// set the relevant poll flags
1426	// could also call adns_processreadable etc. here
1427	struct pollfd *fd = (struct pollfd *)w->data;
1428	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1429	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1430	}	1797	}
1431		1798
1432	// create io watchers for each fd and a timer before blocking	1799	// create io watchers for each fd and a timer before blocking
1433	static void	1800	static void
1434	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1801	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1435	{	1802	{
1436	int timeout = 3600000;truct pollfd fds [nfd];	1803	int timeout = 3600000;
		1804	struct pollfd fds [nfd];
1437	// actual code will need to loop here and realloc etc.	1805	// actual code will need to loop here and realloc etc.
1438	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1806	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1439		1807
1440	/* the callback is illegal, but won't be called as we stop during check */	1808	/* the callback is illegal, but won't be called as we stop during check */
1441	ev_timer_init (&tw, 0, timeout * 1e-3);	1809	ev_timer_init (&tw, 0, timeout * 1e-3);
1442	ev_timer_start (loop, &tw);	1810	ev_timer_start (loop, &tw);
1443		1811
1444	// create on ev_io per pollfd	1812	// create one ev_io per pollfd
1445	for (int i = 0; i < nfd; ++i)	1813	for (int i = 0; i < nfd; ++i)
1446	{	1814	{
1447	ev_io_init (iow + i, io_cb, fds [i].fd,	1815	ev_io_init (iow + i, io_cb, fds [i].fd,
1448	((fds [i].events & POLLIN ? EV_READ : 0)	1816	((fds [i].events & POLLIN ? EV_READ : 0)
1449	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1817	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1450		1818
1451	fds [i].revents = 0;	1819	fds [i].revents = 0;
1452	iow [i].data = fds + i;
1453	ev_io_start (loop, iow + i);	1820	ev_io_start (loop, iow + i);
1454	}	1821	}
1455	}	1822	}
1456		1823
1457	// stop all watchers after blocking	1824	// stop all watchers after blocking
…		…
1459	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1826	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1460	{	1827	{
1461	ev_timer_stop (loop, &tw);	1828	ev_timer_stop (loop, &tw);
1462		1829
1463	for (int i = 0; i < nfd; ++i)	1830	for (int i = 0; i < nfd; ++i)
		1831	{
		1832	// set the relevant poll flags
		1833	// could also call adns_processreadable etc. here
		1834	struct pollfd *fd = fds + i;
		1835	int revents = ev_clear_pending (iow + i);
		1836	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1837	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1838
		1839	// now stop the watcher
1464	ev_io_stop (loop, iow + i);	1840	ev_io_stop (loop, iow + i);
		1841	}
1465		1842
1466	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1843	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1844	}
		1845
		1846	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1847	in the prepare watcher and would dispose of the check watcher.
		1848
		1849	Method 3: If the module to be embedded supports explicit event
		1850	notification (adns does), you can also make use of the actual watcher
		1851	callbacks, and only destroy/create the watchers in the prepare watcher.
		1852
		1853	static void
		1854	timer_cb (EV_P_ ev_timer *w, int revents)
		1855	{
		1856	adns_state ads = (adns_state)w->data;
		1857	update_now (EV_A);
		1858
		1859	adns_processtimeouts (ads, &tv_now);
		1860	}
		1861
		1862	static void
		1863	io_cb (EV_P_ ev_io *w, int revents)
		1864	{
		1865	adns_state ads = (adns_state)w->data;
		1866	update_now (EV_A);
		1867
		1868	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1869	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1870	}
		1871
		1872	// do not ever call adns_afterpoll
		1873
		1874	Method 4: Do not use a prepare or check watcher because the module you
		1875	want to embed is too inflexible to support it. Instead, youc na override
		1876	their poll function. The drawback with this solution is that the main
		1877	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1878	this.
		1879
		1880	static gint
		1881	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1882	{
		1883	int got_events = 0;
		1884
		1885	for (n = 0; n < nfds; ++n)
		1886	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1887
		1888	if (timeout >= 0)
		1889	// create/start timer
		1890
		1891	// poll
		1892	ev_loop (EV_A_ 0);
		1893
		1894	// stop timer again
		1895	if (timeout >= 0)
		1896	ev_timer_stop (EV_A_ &to);
		1897
		1898	// stop io watchers again - their callbacks should have set
		1899	for (n = 0; n < nfds; ++n)
		1900	ev_io_stop (EV_A_ iow [n]);
		1901
		1902	return got_events;
1467	}	1903	}
1468		1904
1469		1905
1470	=head2 C<ev_embed> - when one backend isn't enough...	1906	=head2 C<ev_embed> - when one backend isn't enough...
1471		1907
…		…
1514	portable one.	1950	portable one.
1515		1951
1516	So when you want to use this feature you will always have to be prepared	1952	So when you want to use this feature you will always have to be prepared
1517	that you cannot get an embeddable loop. The recommended way to get around	1953	that you cannot get an embeddable loop. The recommended way to get around
1518	this is to have a separate variables for your embeddable loop, try to	1954	this is to have a separate variables for your embeddable loop, try to
1519	create it, and if that fails, use the normal loop for everything:	1955	create it, and if that fails, use the normal loop for everything.
		1956
		1957	=head3 Watcher-Specific Functions and Data Members
		1958
		1959	=over 4
		1960
		1961	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1962
		1963	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1964
		1965	Configures the watcher to embed the given loop, which must be
		1966	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1967	invoked automatically, otherwise it is the responsibility of the callback
		1968	to invoke it (it will continue to be called until the sweep has been done,
		1969	if you do not want thta, you need to temporarily stop the embed watcher).
		1970
		1971	=item ev_embed_sweep (loop, ev_embed *)
		1972
		1973	Make a single, non-blocking sweep over the embedded loop. This works
		1974	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1975	apropriate way for embedded loops.
		1976
		1977	=item struct ev_loop *other [read-only]
		1978
		1979	The embedded event loop.
		1980
		1981	=back
		1982
		1983	=head3 Examples
		1984
		1985	Example: Try to get an embeddable event loop and embed it into the default
		1986	event loop. If that is not possible, use the default loop. The default
		1987	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1988	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1989	used).
1520		1990
1521	struct ev_loop *loop_hi = ev_default_init (0);	1991	struct ev_loop *loop_hi = ev_default_init (0);
1522	struct ev_loop *loop_lo = 0;	1992	struct ev_loop *loop_lo = 0;
1523	struct ev_embed embed;	1993	struct ev_embed embed;
1524		1994
…		…
1535	ev_embed_start (loop_hi, &embed);	2005	ev_embed_start (loop_hi, &embed);
1536	}	2006	}
1537	else	2007	else
1538	loop_lo = loop_hi;	2008	loop_lo = loop_hi;
1539		2009
1540	=over 4	2010	Example: Check if kqueue is available but not recommended and create
		2011	a kqueue backend for use with sockets (which usually work with any
		2012	kqueue implementation). Store the kqueue/socket-only event loop in
		2013	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1541		2014
1542	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2015	struct ev_loop *loop = ev_default_init (0);
		2016	struct ev_loop *loop_socket = 0;
		2017	struct ev_embed embed;
		2018
		2019	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2020	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2021	{
		2022	ev_embed_init (&embed, 0, loop_socket);
		2023	ev_embed_start (loop, &embed);
		2024	}
1543		2025
1544	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2026	if (!loop_socket)
		2027	loop_socket = loop;
1545		2028
1546	Configures the watcher to embed the given loop, which must be	2029	// now use loop_socket for all sockets, and loop for everything else
1547	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1548	invoked automatically, otherwise it is the responsibility of the callback
1549	to invoke it (it will continue to be called until the sweep has been done,
1550	if you do not want thta, you need to temporarily stop the embed watcher).
1551
1552	=item ev_embed_sweep (loop, ev_embed *)
1553
1554	Make a single, non-blocking sweep over the embedded loop. This works
1555	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1556	apropriate way for embedded loops.
1557
1558	=item struct ev_loop *loop [read-only]
1559
1560	The embedded event loop.
1561
1562	=back
1563		2030
1564		2031
1565	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2032	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1566		2033
1567	Fork watchers are called when a C<fork ()> was detected (usually because	2034	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1570	event loop blocks next and before C<ev_check> watchers are being called,	2037	event loop blocks next and before C<ev_check> watchers are being called,
1571	and only in the child after the fork. If whoever good citizen calling	2038	and only in the child after the fork. If whoever good citizen calling
1572	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2039	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1573	handlers will be invoked, too, of course.	2040	handlers will be invoked, too, of course.
1574		2041
		2042	=head3 Watcher-Specific Functions and Data Members
		2043
1575	=over 4	2044	=over 4
1576		2045
1577	=item ev_fork_init (ev_signal *, callback)	2046	=item ev_fork_init (ev_signal *, callback)
1578		2047
1579	Initialises and configures the fork watcher - it has no parameters of any	2048	Initialises and configures the fork watcher - it has no parameters of any
1580	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,	2049	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1581	believe me.	2050	believe me.
		2051
		2052	=back
		2053
		2054
		2055	=head2 C<ev_async> - how to wake up another event loop
		2056
		2057	In general, you cannot use an C<ev_loop> from multiple threads or other
		2058	asynchronous sources such as signal handlers (as opposed to multiple event
		2059	loops - those are of course safe to use in different threads).
		2060
		2061	Sometimes, however, you need to wake up another event loop you do not
		2062	control, for example because it belongs to another thread. This is what
		2063	C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
		2064	can signal it by calling C<ev_async_send>, which is thread- and signal
		2065	safe.
		2066
		2067	This functionality is very similar to C<ev_signal> watchers, as signals,
		2068	too, are asynchronous in nature, and signals, too, will be compressed
		2069	(i.e. the number of callback invocations may be less than the number of
		2070	C<ev_async_sent> calls).
		2071
		2072	Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
		2073	just the default loop.
		2074
		2075	=head3 Queueing
		2076
		2077	C<ev_async> does not support queueing of data in any way. The reason
		2078	is that the author does not know of a simple (or any) algorithm for a
		2079	multiple-writer-single-reader queue that works in all cases and doesn't
		2080	need elaborate support such as pthreads.
		2081
		2082	That means that if you want to queue data, you have to provide your own
		2083	queue. And here is how you would implement locking:
		2084
		2085	=over 4
		2086
		2087	=item queueing from a signal handler context
		2088
		2089	To implement race-free queueing, you simply add to the queue in the signal
		2090	handler but you block the signal handler in the watcher callback. Here is an example that does that for
		2091	some fictitiuous SIGUSR1 handler:
		2092
		2093	static ev_async mysig;
		2094
		2095	static void
		2096	sigusr1_handler (void)
		2097	{
		2098	sometype data;
		2099
		2100	// no locking etc.
		2101	queue_put (data);
		2102	ev_async_send (DEFAULT_ &mysig);
		2103	}
		2104
		2105	static void
		2106	mysig_cb (EV_P_ ev_async *w, int revents)
		2107	{
		2108	sometype data;
		2109	sigset_t block, prev;
		2110
		2111	sigemptyset (&block);
		2112	sigaddset (&block, SIGUSR1);
		2113	sigprocmask (SIG_BLOCK, &block, &prev);
		2114
		2115	while (queue_get (&data))
		2116	process (data);
		2117
		2118	if (sigismember (&prev, SIGUSR1)
		2119	sigprocmask (SIG_UNBLOCK, &block, 0);
		2120	}
		2121
		2122	(Note: pthreads in theory requires you to use C<pthread_setmask>
		2123	instead of C<sigprocmask> when you use threads, but libev doesn't do it
		2124	either...).
		2125
		2126	=item queueing from a thread context
		2127
		2128	The strategy for threads is different, as you cannot (easily) block
		2129	threads but you can easily preempt them, so to queue safely you need to
		2130	emply a traditional mutex lock, such as in this pthread example:
		2131
		2132	static ev_async mysig;
		2133	static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
		2134
		2135	static void
		2136	otherthread (void)
		2137	{
		2138	// only need to lock the actual queueing operation
		2139	pthread_mutex_lock (&mymutex);
		2140	queue_put (data);
		2141	pthread_mutex_unlock (&mymutex);
		2142
		2143	ev_async_send (DEFAULT_ &mysig);
		2144	}
		2145
		2146	static void
		2147	mysig_cb (EV_P_ ev_async *w, int revents)
		2148	{
		2149	pthread_mutex_lock (&mymutex);
		2150
		2151	while (queue_get (&data))
		2152	process (data);
		2153
		2154	pthread_mutex_unlock (&mymutex);
		2155	}
		2156
		2157	=back
		2158
		2159
		2160	=head3 Watcher-Specific Functions and Data Members
		2161
		2162	=over 4
		2163
		2164	=item ev_async_init (ev_async *, callback)
		2165
		2166	Initialises and configures the async watcher - it has no parameters of any
		2167	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
		2168	believe me.
		2169
		2170	=item ev_async_send (loop, ev_async *)
		2171
		2172	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
		2173	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
		2174	C<ev_feed_event>, this call is safe to do in other threads, signal or
		2175	similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
		2176	section below on what exactly this means).
		2177
		2178	This call incurs the overhead of a syscall only once per loop iteration,
		2179	so while the overhead might be noticable, it doesn't apply to repeated
		2180	calls to C<ev_async_send>.
1582		2181
1583	=back	2182	=back
1584		2183
1585		2184
1586	=head1 OTHER FUNCTIONS	2185	=head1 OTHER FUNCTIONS
…		…
1675		2274
1676	To use it,	2275	To use it,
1677		2276
1678	#include <ev++.h>	2277	#include <ev++.h>
1679		2278
1680	(it is not installed by default). This automatically includes F<ev.h>	2279	This automatically includes F<ev.h> and puts all of its definitions (many
1681	and puts all of its definitions (many of them macros) into the global	2280	of them macros) into the global namespace. All C++ specific things are
1682	namespace. All C++ specific things are put into the C<ev> namespace.	2281	put into the C<ev> namespace. It should support all the same embedding
		2282	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1683		2283
1684	It should support all the same embedding options as F<ev.h>, most notably	2284	Care has been taken to keep the overhead low. The only data member the C++
1685	C<EV_MULTIPLICITY>.	2285	classes add (compared to plain C-style watchers) is the event loop pointer
		2286	that the watcher is associated with (or no additional members at all if
		2287	you disable C<EV_MULTIPLICITY> when embedding libev).
		2288
		2289	Currently, functions, and static and non-static member functions can be
		2290	used as callbacks. Other types should be easy to add as long as they only
		2291	need one additional pointer for context. If you need support for other
		2292	types of functors please contact the author (preferably after implementing
		2293	it).
1686		2294
1687	Here is a list of things available in the C<ev> namespace:	2295	Here is a list of things available in the C<ev> namespace:
1688		2296
1689	=over 4	2297	=over 4
1690		2298
…		…
1706		2314
1707	All of those classes have these methods:	2315	All of those classes have these methods:
1708		2316
1709	=over 4	2317	=over 4
1710		2318
1711	=item ev::TYPE::TYPE (object *, object::method *)	2319	=item ev::TYPE::TYPE ()
1712		2320
1713	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2321	=item ev::TYPE::TYPE (struct ev_loop *)
1714		2322
1715	=item ev::TYPE::~TYPE	2323	=item ev::TYPE::~TYPE
1716		2324
1717	The constructor takes a pointer to an object and a method pointer to	2325	The constructor (optionally) takes an event loop to associate the watcher
1718	the event handler callback to call in this class. The constructor calls	2326	with. If it is omitted, it will use C<EV_DEFAULT>.
1719	C<ev_init> for you, which means you have to call the C<set> method	2327
1720	before starting it. If you do not specify a loop then the constructor	2328	The constructor calls C<ev_init> for you, which means you have to call the
1721	automatically associates the default loop with this watcher.	2329	C<set> method before starting it.
		2330
		2331	It will not set a callback, however: You have to call the templated C<set>
		2332	method to set a callback before you can start the watcher.
		2333
		2334	(The reason why you have to use a method is a limitation in C++ which does
		2335	not allow explicit template arguments for constructors).
1722		2336
1723	The destructor automatically stops the watcher if it is active.	2337	The destructor automatically stops the watcher if it is active.
		2338
		2339	=item w->set<class, &class::method> (object *)
		2340
		2341	This method sets the callback method to call. The method has to have a
		2342	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2343	first argument and the C<revents> as second. The object must be given as
		2344	parameter and is stored in the C<data> member of the watcher.
		2345
		2346	This method synthesizes efficient thunking code to call your method from
		2347	the C callback that libev requires. If your compiler can inline your
		2348	callback (i.e. it is visible to it at the place of the C<set> call and
		2349	your compiler is good :), then the method will be fully inlined into the
		2350	thunking function, making it as fast as a direct C callback.
		2351
		2352	Example: simple class declaration and watcher initialisation
		2353
		2354	struct myclass
		2355	{
		2356	void io_cb (ev::io &w, int revents) { }
		2357	}
		2358
		2359	myclass obj;
		2360	ev::io iow;
		2361	iow.set <myclass, &myclass::io_cb> (&obj);
		2362
		2363	=item w->set<function> (void *data = 0)
		2364
		2365	Also sets a callback, but uses a static method or plain function as
		2366	callback. The optional C<data> argument will be stored in the watcher's
		2367	C<data> member and is free for you to use.
		2368
		2369	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2370
		2371	See the method-C<set> above for more details.
		2372
		2373	Example:
		2374
		2375	static void io_cb (ev::io &w, int revents) { }
		2376	iow.set <io_cb> ();
1724		2377
1725	=item w->set (struct ev_loop *)	2378	=item w->set (struct ev_loop *)
1726		2379
1727	Associates a different C<struct ev_loop> with this watcher. You can only	2380	Associates a different C<struct ev_loop> with this watcher. You can only
1728	do this when the watcher is inactive (and not pending either).	2381	do this when the watcher is inactive (and not pending either).
1729		2382
1730	=item w->set ([args])	2383	=item w->set ([args])
1731		2384
1732	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2385	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1733	called at least once. Unlike the C counterpart, an active watcher gets	2386	called at least once. Unlike the C counterpart, an active watcher gets
1734	automatically stopped and restarted.	2387	automatically stopped and restarted when reconfiguring it with this
		2388	method.
1735		2389
1736	=item w->start ()	2390	=item w->start ()
1737		2391
1738	Starts the watcher. Note that there is no C<loop> argument as the	2392	Starts the watcher. Note that there is no C<loop> argument, as the
1739	constructor already takes the loop.	2393	constructor already stores the event loop.
1740		2394
1741	=item w->stop ()	2395	=item w->stop ()
1742		2396
1743	Stops the watcher if it is active. Again, no C<loop> argument.	2397	Stops the watcher if it is active. Again, no C<loop> argument.
1744		2398
1745	=item w->again () C<ev::timer>, C<ev::periodic> only	2399	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1746		2400
1747	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2401	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1748	C<ev_TYPE_again> function.	2402	C<ev_TYPE_again> function.
1749		2403
1750	=item w->sweep () C<ev::embed> only	2404	=item w->sweep () (C<ev::embed> only)
1751		2405
1752	Invokes C<ev_embed_sweep>.	2406	Invokes C<ev_embed_sweep>.
1753		2407
1754	=item w->update () C<ev::stat> only	2408	=item w->update () (C<ev::stat> only)
1755		2409
1756	Invokes C<ev_stat_stat>.	2410	Invokes C<ev_stat_stat>.
1757		2411
1758	=back	2412	=back
1759		2413
…		…
1762	Example: Define a class with an IO and idle watcher, start one of them in	2416	Example: Define a class with an IO and idle watcher, start one of them in
1763	the constructor.	2417	the constructor.
1764		2418
1765	class myclass	2419	class myclass
1766	{	2420	{
1767	ev_io io; void io_cb (ev::io &w, int revents);	2421	ev::io io; void io_cb (ev::io &w, int revents);
1768	ev_idle idle void idle_cb (ev::idle &w, int revents);	2422	ev:idle idle void idle_cb (ev::idle &w, int revents);
1769		2423
1770	myclass ();	2424	myclass (int fd)
1771	}
1772
1773	myclass::myclass (int fd)
1774	: io (this, &myclass::io_cb),
1775	idle (this, &myclass::idle_cb)
1776	{	2425	{
		2426	io .set <myclass, &myclass::io_cb > (this);
		2427	idle.set <myclass, &myclass::idle_cb> (this);
		2428
1777	io.start (fd, ev::READ);	2429	io.start (fd, ev::READ);
		2430	}
1778	}	2431	};
1779		2432
1780		2433
1781	=head1 MACRO MAGIC	2434	=head1 MACRO MAGIC
1782		2435
1783	Libev can be compiled with a variety of options, the most fundemantal is	2436	Libev can be compiled with a variety of options, the most fundamantal
1784	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2437	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1785	callbacks have an initial C<struct ev_loop *> argument.	2438	functions and callbacks have an initial C<struct ev_loop *> argument.
1786		2439
1787	To make it easier to write programs that cope with either variant, the	2440	To make it easier to write programs that cope with either variant, the
1788	following macros are defined:	2441	following macros are defined:
1789		2442
1790	=over 4	2443	=over 4
…		…
1822	Similar to the other two macros, this gives you the value of the default	2475	Similar to the other two macros, this gives you the value of the default
1823	loop, if multiple loops are supported ("ev loop default").	2476	loop, if multiple loops are supported ("ev loop default").
1824		2477
1825	=back	2478	=back
1826		2479
1827	Example: Declare and initialise a check watcher, working regardless of	2480	Example: Declare and initialise a check watcher, utilising the above
1828	wether multiple loops are supported or not.	2481	macros so it will work regardless of whether multiple loops are supported
		2482	or not.
1829		2483
1830	static void	2484	static void
1831	check_cb (EV_P_ ev_timer *w, int revents)	2485	check_cb (EV_P_ ev_timer *w, int revents)
1832	{	2486	{
1833	ev_check_stop (EV_A_ w);	2487	ev_check_stop (EV_A_ w);
…		…
1836	ev_check check;	2490	ev_check check;
1837	ev_check_init (&check, check_cb);	2491	ev_check_init (&check, check_cb);
1838	ev_check_start (EV_DEFAULT_ &check);	2492	ev_check_start (EV_DEFAULT_ &check);
1839	ev_loop (EV_DEFAULT_ 0);	2493	ev_loop (EV_DEFAULT_ 0);
1840		2494
1841
1842	=head1 EMBEDDING	2495	=head1 EMBEDDING
1843		2496
1844	Libev can (and often is) directly embedded into host	2497	Libev can (and often is) directly embedded into host
1845	applications. Examples of applications that embed it include the Deliantra	2498	applications. Examples of applications that embed it include the Deliantra
1846	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2499	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1847	and rxvt-unicode.	2500	and rxvt-unicode.
1848		2501
1849	The goal is to enable you to just copy the neecssary files into your	2502	The goal is to enable you to just copy the necessary files into your
1850	source directory without having to change even a single line in them, so	2503	source directory without having to change even a single line in them, so
1851	you can easily upgrade by simply copying (or having a checked-out copy of	2504	you can easily upgrade by simply copying (or having a checked-out copy of
1852	libev somewhere in your source tree).	2505	libev somewhere in your source tree).
1853		2506
1854	=head2 FILESETS	2507	=head2 FILESETS
…		…
1885	ev_vars.h	2538	ev_vars.h
1886	ev_wrap.h	2539	ev_wrap.h
1887		2540
1888	ev_win32.c required on win32 platforms only	2541	ev_win32.c required on win32 platforms only
1889		2542
1890	ev_select.c only when select backend is enabled (which is by default)	2543	ev_select.c only when select backend is enabled (which is enabled by default)
1891	ev_poll.c only when poll backend is enabled (disabled by default)	2544	ev_poll.c only when poll backend is enabled (disabled by default)
1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2545	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2546	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1894	ev_port.c only when the solaris port backend is enabled (disabled by default)	2547	ev_port.c only when the solaris port backend is enabled (disabled by default)
1895		2548
…		…
1944		2597
1945	If defined to be C<1>, libev will try to detect the availability of the	2598	If defined to be C<1>, libev will try to detect the availability of the
1946	monotonic clock option at both compiletime and runtime. Otherwise no use	2599	monotonic clock option at both compiletime and runtime. Otherwise no use
1947	of the monotonic clock option will be attempted. If you enable this, you	2600	of the monotonic clock option will be attempted. If you enable this, you
1948	usually have to link against librt or something similar. Enabling it when	2601	usually have to link against librt or something similar. Enabling it when
1949	the functionality isn't available is safe, though, althoguh you have	2602	the functionality isn't available is safe, though, although you have
1950	to make sure you link against any libraries where the C<clock_gettime>	2603	to make sure you link against any libraries where the C<clock_gettime>
1951	function is hiding in (often F<-lrt>).	2604	function is hiding in (often F<-lrt>).
1952		2605
1953	=item EV_USE_REALTIME	2606	=item EV_USE_REALTIME
1954		2607
1955	If defined to be C<1>, libev will try to detect the availability of the	2608	If defined to be C<1>, libev will try to detect the availability of the
1956	realtime clock option at compiletime (and assume its availability at	2609	realtime clock option at compiletime (and assume its availability at
1957	runtime if successful). Otherwise no use of the realtime clock option will	2610	runtime if successful). Otherwise no use of the realtime clock option will
1958	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2611	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1959	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2612	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1960	in the description of C<EV_USE_MONOTONIC>, though.	2613	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2614
		2615	=item EV_USE_NANOSLEEP
		2616
		2617	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2618	and will use it for delays. Otherwise it will use C<select ()>.
1961		2619
1962	=item EV_USE_SELECT	2620	=item EV_USE_SELECT
1963		2621
1964	If undefined or defined to be C<1>, libev will compile in support for the	2622	If undefined or defined to be C<1>, libev will compile in support for the
1965	C<select>(2) backend. No attempt at autodetection will be done: if no	2623	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1983	wants osf handles on win32 (this is the case when the select to	2641	wants osf handles on win32 (this is the case when the select to
1984	be used is the winsock select). This means that it will call	2642	be used is the winsock select). This means that it will call
1985	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2643	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1986	it is assumed that all these functions actually work on fds, even	2644	it is assumed that all these functions actually work on fds, even
1987	on win32. Should not be defined on non-win32 platforms.	2645	on win32. Should not be defined on non-win32 platforms.
		2646
		2647	=item EV_FD_TO_WIN32_HANDLE
		2648
		2649	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2650	file descriptors to socket handles. When not defining this symbol (the
		2651	default), then libev will call C<_get_osfhandle>, which is usually
		2652	correct. In some cases, programs use their own file descriptor management,
		2653	in which case they can provide this function to map fds to socket handles.
1988		2654
1989	=item EV_USE_POLL	2655	=item EV_USE_POLL
1990		2656
1991	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2657	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1992	backend. Otherwise it will be enabled on non-win32 platforms. It	2658	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2026		2692
2027	If defined to be C<1>, libev will compile in support for the Linux inotify	2693	If defined to be C<1>, libev will compile in support for the Linux inotify
2028	interface to speed up C<ev_stat> watchers. Its actual availability will	2694	interface to speed up C<ev_stat> watchers. Its actual availability will
2029	be detected at runtime.	2695	be detected at runtime.
2030		2696
		2697	=item EV_ATOMIC_T
		2698
		2699	Libev requires an integer type (suitable for storing C<0> or C<1>) whose
		2700	access is atomic with respect to other threads or signal contexts. No such
		2701	type is easily found in the C language, so you can provide your own type
		2702	that you know is safe for your purposes.
		2703
		2704	In the absense of this define, libev will use C<sig_atomic_t volatile>
		2705	(from F<signal.h>), which is usually good enough on most platforms.
		2706
2031	=item EV_H	2707	=item EV_H
2032		2708
2033	The name of the F<ev.h> header file used to include it. The default if	2709	The name of the F<ev.h> header file used to include it. The default if
2034	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2710	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2035	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2711	used to virtually rename the F<ev.h> header file in case of conflicts.
2036		2712
2037	=item EV_CONFIG_H	2713	=item EV_CONFIG_H
2038		2714
2039	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2715	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2040	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2716	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2041	C<EV_H>, above.	2717	C<EV_H>, above.
2042		2718
2043	=item EV_EVENT_H	2719	=item EV_EVENT_H
2044		2720
2045	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2721	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2046	of how the F<event.h> header can be found.	2722	of how the F<event.h> header can be found, the default is C<"event.h">.
2047		2723
2048	=item EV_PROTOTYPES	2724	=item EV_PROTOTYPES
2049		2725
2050	If defined to be C<0>, then F<ev.h> will not define any function	2726	If defined to be C<0>, then F<ev.h> will not define any function
2051	prototypes, but still define all the structs and other symbols. This is	2727	prototypes, but still define all the structs and other symbols. This is
…		…
2058	will have the C<struct ev_loop *> as first argument, and you can create	2734	will have the C<struct ev_loop *> as first argument, and you can create
2059	additional independent event loops. Otherwise there will be no support	2735	additional independent event loops. Otherwise there will be no support
2060	for multiple event loops and there is no first event loop pointer	2736	for multiple event loops and there is no first event loop pointer
2061	argument. Instead, all functions act on the single default loop.	2737	argument. Instead, all functions act on the single default loop.
2062		2738
		2739	=item EV_MINPRI
		2740
		2741	=item EV_MAXPRI
		2742
		2743	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2744	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2745	provide for more priorities by overriding those symbols (usually defined
		2746	to be C<-2> and C<2>, respectively).
		2747
		2748	When doing priority-based operations, libev usually has to linearly search
		2749	all the priorities, so having many of them (hundreds) uses a lot of space
		2750	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2751	fine.
		2752
		2753	If your embedding app does not need any priorities, defining these both to
		2754	C<0> will save some memory and cpu.
		2755
2063	=item EV_PERIODIC_ENABLE	2756	=item EV_PERIODIC_ENABLE
2064		2757
2065	If undefined or defined to be C<1>, then periodic timers are supported. If	2758	If undefined or defined to be C<1>, then periodic timers are supported. If
2066	defined to be C<0>, then they are not. Disabling them saves a few kB of	2759	defined to be C<0>, then they are not. Disabling them saves a few kB of
2067	code.	2760	code.
2068		2761
		2762	=item EV_IDLE_ENABLE
		2763
		2764	If undefined or defined to be C<1>, then idle watchers are supported. If
		2765	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2766	code.
		2767
2069	=item EV_EMBED_ENABLE	2768	=item EV_EMBED_ENABLE
2070		2769
2071	If undefined or defined to be C<1>, then embed watchers are supported. If	2770	If undefined or defined to be C<1>, then embed watchers are supported. If
2072	defined to be C<0>, then they are not.	2771	defined to be C<0>, then they are not.
2073		2772
…		…
2077	defined to be C<0>, then they are not.	2776	defined to be C<0>, then they are not.
2078		2777
2079	=item EV_FORK_ENABLE	2778	=item EV_FORK_ENABLE
2080		2779
2081	If undefined or defined to be C<1>, then fork watchers are supported. If	2780	If undefined or defined to be C<1>, then fork watchers are supported. If
		2781	defined to be C<0>, then they are not.
		2782
		2783	=item EV_ASYNC_ENABLE
		2784
		2785	If undefined or defined to be C<1>, then async watchers are supported. If
2082	defined to be C<0>, then they are not.	2786	defined to be C<0>, then they are not.
2083		2787
2084	=item EV_MINIMAL	2788	=item EV_MINIMAL
2085		2789
2086	If you need to shave off some kilobytes of code at the expense of some	2790	If you need to shave off some kilobytes of code at the expense of some
…		…
2094	than enough. If you need to manage thousands of children you might want to	2798	than enough. If you need to manage thousands of children you might want to
2095	increase this value (I<must> be a power of two).	2799	increase this value (I<must> be a power of two).
2096		2800
2097	=item EV_INOTIFY_HASHSIZE	2801	=item EV_INOTIFY_HASHSIZE
2098		2802
2099	C<ev_staz> watchers use a small hash table to distribute workload by	2803	C<ev_stat> watchers use a small hash table to distribute workload by
2100	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2804	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2101	usually more than enough. If you need to manage thousands of C<ev_stat>	2805	usually more than enough. If you need to manage thousands of C<ev_stat>
2102	watchers you might want to increase this value (I<must> be a power of	2806	watchers you might want to increase this value (I<must> be a power of
2103	two).	2807	two).
2104		2808
…		…
2121		2825
2122	=item ev_set_cb (ev, cb)	2826	=item ev_set_cb (ev, cb)
2123		2827
2124	Can be used to change the callback member declaration in each watcher,	2828	Can be used to change the callback member declaration in each watcher,
2125	and the way callbacks are invoked and set. Must expand to a struct member	2829	and the way callbacks are invoked and set. Must expand to a struct member
2126	definition and a statement, respectively. See the F<ev.v> header file for	2830	definition and a statement, respectively. See the F<ev.h> header file for
2127	their default definitions. One possible use for overriding these is to	2831	their default definitions. One possible use for overriding these is to
2128	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2832	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2129	method calls instead of plain function calls in C++.	2833	method calls instead of plain function calls in C++.
		2834
		2835	=head2 EXPORTED API SYMBOLS
		2836
		2837	If you need to re-export the API (e.g. via a dll) and you need a list of
		2838	exported symbols, you can use the provided F<Symbol.*> files which list
		2839	all public symbols, one per line:
		2840
		2841	Symbols.ev for libev proper
		2842	Symbols.event for the libevent emulation
		2843
		2844	This can also be used to rename all public symbols to avoid clashes with
		2845	multiple versions of libev linked together (which is obviously bad in
		2846	itself, but sometimes it is inconvinient to avoid this).
		2847
		2848	A sed command like this will create wrapper C<#define>'s that you need to
		2849	include before including F<ev.h>:
		2850
		2851	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2852
		2853	This would create a file F<wrap.h> which essentially looks like this:
		2854
		2855	#define ev_backend myprefix_ev_backend
		2856	#define ev_check_start myprefix_ev_check_start
		2857	#define ev_check_stop myprefix_ev_check_stop
		2858	...
2130		2859
2131	=head2 EXAMPLES	2860	=head2 EXAMPLES
2132		2861
2133	For a real-world example of a program the includes libev	2862	For a real-world example of a program the includes libev
2134	verbatim, you can have a look at the EV perl module	2863	verbatim, you can have a look at the EV perl module
…		…
2137	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2866	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2138	will be compiled. It is pretty complex because it provides its own header	2867	will be compiled. It is pretty complex because it provides its own header
2139	file.	2868	file.
2140		2869
2141	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2870	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2142	that everybody includes and which overrides some autoconf choices:	2871	that everybody includes and which overrides some configure choices:
2143		2872
		2873	#define EV_MINIMAL 1
2144	#define EV_USE_POLL 0	2874	#define EV_USE_POLL 0
2145	#define EV_MULTIPLICITY 0	2875	#define EV_MULTIPLICITY 0
2146	#define EV_PERIODICS 0	2876	#define EV_PERIODIC_ENABLE 0
		2877	#define EV_STAT_ENABLE 0
		2878	#define EV_FORK_ENABLE 0
2147	#define EV_CONFIG_H <config.h>	2879	#define EV_CONFIG_H <config.h>
		2880	#define EV_MINPRI 0
		2881	#define EV_MAXPRI 0
2148		2882
2149	#include "ev++.h"	2883	#include "ev++.h"
2150		2884
2151	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2885	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2152		2886
…		…
2158		2892
2159	In this section the complexities of (many of) the algorithms used inside	2893	In this section the complexities of (many of) the algorithms used inside
2160	libev will be explained. For complexity discussions about backends see the	2894	libev will be explained. For complexity discussions about backends see the
2161	documentation for C<ev_default_init>.	2895	documentation for C<ev_default_init>.
2162		2896
		2897	All of the following are about amortised time: If an array needs to be
		2898	extended, libev needs to realloc and move the whole array, but this
		2899	happens asymptotically never with higher number of elements, so O(1) might
		2900	mean it might do a lengthy realloc operation in rare cases, but on average
		2901	it is much faster and asymptotically approaches constant time.
		2902
2163	=over 4	2903	=over 4
2164		2904
2165	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2905	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2166		2906
		2907	This means that, when you have a watcher that triggers in one hour and
		2908	there are 100 watchers that would trigger before that then inserting will
		2909	have to skip roughly seven (C<ld 100>) of these watchers.
		2910
2167	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2911	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2912
		2913	That means that changing a timer costs less than removing/adding them
		2914	as only the relative motion in the event queue has to be paid for.
2168		2915
2169	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2916	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2170		2917
		2918	These just add the watcher into an array or at the head of a list.
		2919
2171	=item Stopping check/prepare/idle watchers: O(1)	2920	=item Stopping check/prepare/idle watchers: O(1)
2172		2921
2173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2922	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2174		2923
		2924	These watchers are stored in lists then need to be walked to find the
		2925	correct watcher to remove. The lists are usually short (you don't usually
		2926	have many watchers waiting for the same fd or signal).
		2927
2175	=item Finding the next timer per loop iteration: O(1)	2928	=item Finding the next timer in each loop iteration: O(1)
		2929
		2930	By virtue of using a binary heap, the next timer is always found at the
		2931	beginning of the storage array.
2176		2932
2177	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2933	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2178		2934
2179	=item Activating one watcher: O(1)	2935	A change means an I/O watcher gets started or stopped, which requires
		2936	libev to recalculate its status (and possibly tell the kernel, depending
		2937	on backend and wether C<ev_io_set> was used).
		2938
		2939	=item Activating one watcher (putting it into the pending state): O(1)
		2940
		2941	=item Priority handling: O(number_of_priorities)
		2942
		2943	Priorities are implemented by allocating some space for each
		2944	priority. When doing priority-based operations, libev usually has to
		2945	linearly search all the priorities, but starting/stopping and activating
		2946	watchers becomes O(1) w.r.t. prioritiy handling.
2180		2947
2181	=back	2948	=back
2182		2949
2183		2950
		2951	=head1 Win32 platform limitations and workarounds
		2952
		2953	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2954	requires, and its I/O model is fundamentally incompatible with the POSIX
		2955	model. Libev still offers limited functionality on this platform in
		2956	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2957	descriptors. This only applies when using Win32 natively, not when using
		2958	e.g. cygwin.
		2959
		2960	There is no supported compilation method available on windows except
		2961	embedding it into other applications.
		2962
		2963	Due to the many, low, and arbitrary limits on the win32 platform and the
		2964	abysmal performance of winsockets, using a large number of sockets is not
		2965	recommended (and not reasonable). If your program needs to use more than
		2966	a hundred or so sockets, then likely it needs to use a totally different
		2967	implementation for windows, as libev offers the POSIX model, which cannot
		2968	be implemented efficiently on windows (microsoft monopoly games).
		2969
		2970	=over 4
		2971
		2972	=item The winsocket select function
		2973
		2974	The winsocket C<select> function doesn't follow POSIX in that it requires
		2975	socket I<handles> and not socket I<file descriptors>. This makes select
		2976	very inefficient, and also requires a mapping from file descriptors
		2977	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2978	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2979	symbols for more info.
		2980
		2981	The configuration for a "naked" win32 using the microsoft runtime
		2982	libraries and raw winsocket select is:
		2983
		2984	#define EV_USE_SELECT 1
		2985	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2986
		2987	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2988	complexity in the O(n²) range when using win32.
		2989
		2990	=item Limited number of file descriptors
		2991
		2992	Windows has numerous arbitrary (and low) limits on things. Early versions
		2993	of winsocket's select only supported waiting for a max. of C<64> handles
		2994	(probably owning to the fact that all windows kernels can only wait for
		2995	C<64> things at the same time internally; microsoft recommends spawning a
		2996	chain of threads and wait for 63 handles and the previous thread in each).
		2997
		2998	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2999	to some high number (e.g. C<2048>) before compiling the winsocket select
		3000	call (which might be in libev or elsewhere, for example, perl does its own
		3001	select emulation on windows).
		3002
		3003	Another limit is the number of file descriptors in the microsoft runtime
		3004	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		3005	or something like this inside microsoft). You can increase this by calling
		3006	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		3007	arbitrary limit), but is broken in many versions of the microsoft runtime
		3008	libraries.
		3009
		3010	This might get you to about C<512> or C<2048> sockets (depending on
		3011	windows version and/or the phase of the moon). To get more, you need to
		3012	wrap all I/O functions and provide your own fd management, but the cost of
		3013	calling select (O(n²)) will likely make this unworkable.
		3014
		3015	=back
		3016
		3017
2184	=head1 AUTHOR	3018	=head1 AUTHOR
2185		3019
2186	Marc Lehmann <libev@schmorp.de>.	3020	Marc Lehmann <libev@schmorp.de>.
2187		3021

Diff Legend

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