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Revision 1.53 by root, Tue Nov 27 20:15:02 2007 UTC vs.
Revision 1.121 by root, Mon Jan 28 12:13:54 2008 UTC

…		…
2		2
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	/* this is the only header you need */
8	#include <ev.h>	7	#include <ev.h>
9		8
10	/* what follows is a fully working example program */	9	=head2 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
11	ev_io stdin_watcher;	13	ev_io stdin_watcher;
12	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
13		15
14	/* called when data readable on stdin */	16	/* called when data readable on stdin */
15	static void	17	static void
…		…
46	return 0;	48	return 0;
47	}	49	}
48		50
49	=head1 DESCRIPTION	51	=head1 DESCRIPTION
50		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
51	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
52	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
53	these event sources and provide your program with events.	59	these event sources and provide your program with events.
54		60
55	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
56	(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
57	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
59	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
60	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
61	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
62	watcher.	68	watcher.
63		69
64	=head1 FEATURES	70	=head2 FEATURES
65		71
66	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
67	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
68	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
69	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
70	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
71	fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
72	it to libevent for example).	85	for example).
73		86
74	=head1 CONVENTIONS	87	=head2 CONVENTIONS
75		88
76	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
77	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
78	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
79	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
80	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
81	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
82	will not have this argument.
83		95
84	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
85		97
86	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
87	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
88	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
89	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
90	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
91	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.
92		106
93	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
94		108
95	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
96	library in any way.	110	library in any way.
…		…
101		115
102	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
103	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
104	you actually want to know.	118	you actually want to know.
105		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
106	=item int ev_version_major ()	126	=item int ev_version_major ()
107		127
108	=item int ev_version_minor ()	128	=item int ev_version_minor ()
109		129
110	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
111	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
112	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
113	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
114	version of the library your program was compiled against.	134	version of the library your program was compiled against.
115		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
116	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,
117	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
118	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
119	not a problem.	142	not a problem.
120		143
121	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
122	version:	145	version.
123		146
124	assert (("libev version mismatch",	147	assert (("libev version mismatch",
125	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
126	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
127		150
…		…
155	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
156	recommended ones.	179	recommended ones.
157		180
158	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
159		182
160	=item ev_set_allocator (void *(*cb)(void *ptr, size_t size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
161		184
162	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
163	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
164	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
165	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
166	action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
167		191
168	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
169	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,
170	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.
171		195
172	Example: replace the libev allocator with one that waits a bit and then	196	Example: Replace the libev allocator with one that waits a bit and then
173	retries: better than mine).	197	retries).
174		198
175	static void *	199	static void *
176	persistent_realloc (void *ptr, size_t size)	200	persistent_realloc (void *ptr, size_t size)
177	{	201	{
178	for (;;)	202	for (;;)
…		…
197	callback is set, then libev will expect it to remedy the sitution, no	221	callback is set, then libev will expect it to remedy the sitution, no
198	matter what, when it returns. That is, libev will generally retry the	222	matter what, when it returns. That is, libev will generally retry the
199	requested operation, or, if the condition doesn't go away, do bad stuff	223	requested operation, or, if the condition doesn't go away, do bad stuff
200	(such as abort).	224	(such as abort).
201		225
202	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
203		227
204	static void	228	static void
205	fatal_error (const char *msg)	229	fatal_error (const char *msg)
206	{	230	{
207	perror (msg);	231	perror (msg);
…		…
236	flags. If that is troubling you, check C<ev_backend ()> afterwards).	260	flags. If that is troubling you, check C<ev_backend ()> afterwards).
237		261
238	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
239	function.	263	function.
240		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
241	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
242	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>).
243		274
244	The following flags are supported:	275	The following flags are supported:
245		276
…		…
257	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	288	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
258	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
259	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
260	around bugs.	291	around bugs.
261		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
262	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	313	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
263		314
264	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
265	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,
266	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
267	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
268	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.
269		327
270	=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)
271		329
272	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
273	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
274	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
275	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.
276		336
277	=item C<EVBACKEND_EPOLL> (value 4, Linux)	337	=item C<EVBACKEND_EPOLL> (value 4, Linux)
278		338
279	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,
280	but it scales phenomenally better. While poll and select usually scale like	340	but it scales phenomenally better. While poll and select usually scale
281	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),
282	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.
283		346
284	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
285	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
286	(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
287	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
288	well if you register events for both fds.	351	very well if you register events for both fds.
289		352
290	Please note that epoll sometimes generates spurious notifications, so you	353	Please note that epoll sometimes generates spurious notifications, so you
291	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
292	(or space) is available.	355	(or space) is available.
293		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
294	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	364	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
295		365
296	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
297	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
298	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
299	completely useless). For this reason its not being "autodetected"	369	it's completely useless). For this reason it's not being "autodetected"
300	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
301	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.
302		377
303	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
304	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
305	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
306	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
307	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.
308		393
309	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	394	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
310		395
311	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.
312		400
313	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	401	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
314		402
315	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,
316	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)).
317		405
318	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
319	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
320	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.
321		418
322	=item C<EVBACKEND_ALL>	419	=item C<EVBACKEND_ALL>
323		420
324	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
325	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
326	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	423	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
327		424
		425	It is definitely not recommended to use this flag.
		426
328	=back	427	=back
329		428
330	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
331	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
332	specified, most compiled-in backend will be tried, usually in reverse	431	specified, all backends in C<ev_recommended_backends ()> will be tried.
333	order of their flag values :)
334		432
335	The most typical usage is like this:	433	The most typical usage is like this:
336		434
337	if (!ev_default_loop (0))	435	if (!ev_default_loop (0))
338	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	436	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
353	Similar to C<ev_default_loop>, but always creates a new event loop that is	451	Similar to C<ev_default_loop>, but always creates a new event loop that is
354	always distinct from the default loop. Unlike the default loop, it cannot	452	always distinct from the default loop. Unlike the default loop, it cannot
355	handle signal and child watchers, and attempts to do so will be greeted by	453	handle signal and child watchers, and attempts to do so will be greeted by
356	undefined behaviour (or a failed assertion if assertions are enabled).	454	undefined behaviour (or a failed assertion if assertions are enabled).
357		455
358	Example: try to create a event loop that uses epoll and nothing else.	456	Example: Try to create a event loop that uses epoll and nothing else.
359		457
360	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	458	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
361	if (!epoller)	459	if (!epoller)
362	fatal ("no epoll found here, maybe it hides under your chair");	460	fatal ("no epoll found here, maybe it hides under your chair");
363		461
…		…
366	Destroys the default loop again (frees all memory and kernel state	464	Destroys the default loop again (frees all memory and kernel state
367	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
368	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
369	responsibility to either stop all watchers cleanly yoursef I<before>	467	responsibility to either stop all watchers cleanly yoursef I<before>
370	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
371	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
372	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>).
373		480
374	=item ev_loop_destroy (loop)	481	=item ev_loop_destroy (loop)
375		482
376	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
377	earlier call to C<ev_loop_new>.	484	earlier call to C<ev_loop_new>.
378		485
379	=item ev_default_fork ()	486	=item ev_default_fork ()
380		487
		488	This function sets a flag that causes subsequent C<ev_loop> iterations
381	This function reinitialises the kernel state for backends that have	489	to reinitialise the kernel state for backends that have one. Despite the
382	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
383	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
384	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.
385		494
386	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
387	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
388	fork+exec, you don't have to call it.	497	you just fork+exec, you don't have to call it at all.
389		498
390	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
391	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
392	quite nicely into a call to C<pthread_atfork>:	501	quite nicely into a call to C<pthread_atfork>:
393		502
394	pthread_atfork (0, 0, ev_default_fork);	503	pthread_atfork (0, 0, ev_default_fork);
395		504
396	At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
397	without calling this function, so if you force one of those backends you
398	do not need to care.
399
400	=item ev_loop_fork (loop)	505	=item ev_loop_fork (loop)
401		506
402	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
403	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
404	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.
405		520
406	=item unsigned int ev_backend (loop)	521	=item unsigned int ev_backend (loop)
407		522
408	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
409	use.	524	use.
…		…
412		527
413	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
414	received events and started processing them. This timestamp does not	529	received events and started processing them. This timestamp does not
415	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
416	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
417	event occuring (or more correctly, libev finding out about it).	532	event occurring (or more correctly, libev finding out about it).
418		533
419	=item ev_loop (loop, int flags)	534	=item ev_loop (loop, int flags)
420		535
421	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
422	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
…		…
443	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
444	usually a better approach for this kind of thing.	559	usually a better approach for this kind of thing.
445		560
446	Here are the gory details of what C<ev_loop> does:	561	Here are the gory details of what C<ev_loop> does:
447		562
448	* If there are no active watchers (reference count is zero), return.	563	- Before the first iteration, call any pending watchers.
449	- 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.
450	- If we have been forked, recreate the kernel state.	567	- If we have been forked, recreate the kernel state.
451	- Update the kernel state with all outstanding changes.	568	- Update the kernel state with all outstanding changes.
452	- Update the "event loop time".	569	- Update the "event loop time".
453	- 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.
454	- Block the process, waiting for any events.	574	- Block the process, waiting for any events.
455	- Queue all outstanding I/O (fd) events.	575	- Queue all outstanding I/O (fd) events.
456	- Update the "event loop time" and do time jump handling.	576	- Update the "event loop time" and do time jump handling.
457	- Queue all outstanding timers.	577	- Queue all outstanding timers.
458	- Queue all outstanding periodics.	578	- Queue all outstanding periodics.
459	- If no events are pending now, queue all idle watchers.	579	- If no events are pending now, queue all idle watchers.
460	- Queue all check watchers.	580	- Queue all check watchers.
461	- 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).
462	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
463	be handled here by queueing them when their watcher gets executed.	583	be handled here by queueing them when their watcher gets executed.
464	- 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
465	were used, return, otherwise continue with step *.	585	were used, or there are no active watchers, return, otherwise
		586	continue with step *.
466		587
467	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
468	anymore.	589	anymore.
469		590
470	... queue jobs here, make sure they register event watchers as long	591	... queue jobs here, make sure they register event watchers as long
471	... 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..)
472	ev_loop (my_loop, 0);	593	ev_loop (my_loop, 0);
…		…
476		597
477	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
478	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
479	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
480	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.
481		604
482	=item ev_ref (loop)	605	=item ev_ref (loop)
483		606
484	=item ev_unref (loop)	607	=item ev_unref (loop)
485		608
…		…
490	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
491	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
492	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
493	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
494	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
495	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).
496		621
497	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>
498	running when nothing else is active.	623	running when nothing else is active.
499		624
500	struct dv_signal exitsig;	625	struct ev_signal exitsig;
501	ev_signal_init (&exitsig, sig_cb, SIGINT);	626	ev_signal_init (&exitsig, sig_cb, SIGINT);
502	ev_signal_start (myloop, &exitsig);	627	ev_signal_start (loop, &exitsig);
503	evf_unref (myloop);	628	evf_unref (loop);
504		629
505	Example: for some weird reason, unregister the above signal handler again.	630	Example: For some weird reason, unregister the above signal handler again.
506		631
507	ev_ref (myloop);	632	ev_ref (loop);
508	ev_signal_stop (myloop, &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.
509		670
510	=back	671	=back
511		672
512		673
513	=head1 ANATOMY OF A WATCHER	674	=head1 ANATOMY OF A WATCHER
…		…
693	=item bool ev_is_pending (ev_TYPE *watcher)	854	=item bool ev_is_pending (ev_TYPE *watcher)
694		855
695	Returns a true value iff the watcher is pending, (i.e. it has outstanding	856	Returns a true value iff the watcher is pending, (i.e. it has outstanding
696	events but its callback has not yet been invoked). As long as a watcher	857	events but its callback has not yet been invoked). As long as a watcher
697	is pending (but not active) you must not call an init function on it (but	858	is pending (but not active) you must not call an init function on it (but
698	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	859	C<ev_TYPE_set> is safe), you must not change its priority, and you must
699	libev (e.g. you cnanot C<free ()> it).	860	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		861	it).
700		862
701	=item callback = ev_cb (ev_TYPE *watcher)	863	=item callback ev_cb (ev_TYPE *watcher)
702		864
703	Returns the callback currently set on the watcher.	865	Returns the callback currently set on the watcher.
704		866
705	=item ev_cb_set (ev_TYPE *watcher, callback)	867	=item ev_cb_set (ev_TYPE *watcher, callback)
706		868
707	Change the callback. You can change the callback at virtually any time	869	Change the callback. You can change the callback at virtually any time
708	(modulo threads).	870	(modulo threads).
		871
		872	=item ev_set_priority (ev_TYPE *watcher, priority)
		873
		874	=item int ev_priority (ev_TYPE *watcher)
		875
		876	Set and query the priority of the watcher. The priority is a small
		877	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		878	(default: C<-2>). Pending watchers with higher priority will be invoked
		879	before watchers with lower priority, but priority will not keep watchers
		880	from being executed (except for C<ev_idle> watchers).
		881
		882	This means that priorities are I<only> used for ordering callback
		883	invocation after new events have been received. This is useful, for
		884	example, to reduce latency after idling, or more often, to bind two
		885	watchers on the same event and make sure one is called first.
		886
		887	If you need to suppress invocation when higher priority events are pending
		888	you need to look at C<ev_idle> watchers, which provide this functionality.
		889
		890	You I<must not> change the priority of a watcher as long as it is active or
		891	pending.
		892
		893	The default priority used by watchers when no priority has been set is
		894	always C<0>, which is supposed to not be too high and not be too low :).
		895
		896	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		897	fine, as long as you do not mind that the priority value you query might
		898	or might not have been adjusted to be within valid range.
		899
		900	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		901
		902	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		903	C<loop> nor C<revents> need to be valid as long as the watcher callback
		904	can deal with that fact.
		905
		906	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		907
		908	If the watcher is pending, this function returns clears its pending status
		909	and returns its C<revents> bitset (as if its callback was invoked). If the
		910	watcher isn't pending it does nothing and returns C<0>.
709		911
710	=back	912	=back
711		913
712		914
713	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	915	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
734	{	936	{
735	struct my_io *w = (struct my_io *)w_;	937	struct my_io *w = (struct my_io *)w_;
736	...	938	...
737	}	939	}
738		940
739	More interesting and less C-conformant ways of catsing your callback type	941	More interesting and less C-conformant ways of casting your callback type
740	have been omitted....	942	instead have been omitted.
		943
		944	Another common scenario is having some data structure with multiple
		945	watchers:
		946
		947	struct my_biggy
		948	{
		949	int some_data;
		950	ev_timer t1;
		951	ev_timer t2;
		952	}
		953
		954	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		955	you need to use C<offsetof>:
		956
		957	#include <stddef.h>
		958
		959	static void
		960	t1_cb (EV_P_ struct ev_timer *w, int revents)
		961	{
		962	struct my_biggy big = (struct my_biggy *
		963	(((char *)w) - offsetof (struct my_biggy, t1));
		964	}
		965
		966	static void
		967	t2_cb (EV_P_ struct ev_timer *w, int revents)
		968	{
		969	struct my_biggy big = (struct my_biggy *
		970	(((char *)w) - offsetof (struct my_biggy, t2));
		971	}
741		972
742		973
743	=head1 WATCHER TYPES	974	=head1 WATCHER TYPES
744		975
745	This section describes each watcher in detail, but will not repeat	976	This section describes each watcher in detail, but will not repeat
…		…
769	In general you can register as many read and/or write event watchers per	1000	In general you can register as many read and/or write event watchers per
770	fd as you want (as long as you don't confuse yourself). Setting all file	1001	fd as you want (as long as you don't confuse yourself). Setting all file
771	descriptors to non-blocking mode is also usually a good idea (but not	1002	descriptors to non-blocking mode is also usually a good idea (but not
772	required if you know what you are doing).	1003	required if you know what you are doing).
773		1004
774	You have to be careful with dup'ed file descriptors, though. Some backends
775	(the linux epoll backend is a notable example) cannot handle dup'ed file
776	descriptors correctly if you register interest in two or more fds pointing
777	to the same underlying file/socket/etc. description (that is, they share
778	the same underlying "file open").
779
780	If you must do this, then force the use of a known-to-be-good backend	1005	If you must do this, then force the use of a known-to-be-good backend
781	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1006	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
782	C<EVBACKEND_POLL>).	1007	C<EVBACKEND_POLL>).
783		1008
784	Another thing you have to watch out for is that it is quite easy to	1009	Another thing you have to watch out for is that it is quite easy to
…		…
790	it is best to always use non-blocking I/O: An extra C<read>(2) returning	1015	it is best to always use non-blocking I/O: An extra C<read>(2) returning
791	C<EAGAIN> is far preferable to a program hanging until some data arrives.	1016	C<EAGAIN> is far preferable to a program hanging until some data arrives.
792		1017
793	If you cannot run the fd in non-blocking mode (for example you should not	1018	If you cannot run the fd in non-blocking mode (for example you should not
794	play around with an Xlib connection), then you have to seperately re-test	1019	play around with an Xlib connection), then you have to seperately re-test
795	wether a file descriptor is really ready with a known-to-be good interface	1020	whether a file descriptor is really ready with a known-to-be good interface
796	such as poll (fortunately in our Xlib example, Xlib already does this on	1021	such as poll (fortunately in our Xlib example, Xlib already does this on
797	its own, so its quite safe to use).	1022	its own, so its quite safe to use).
		1023
		1024	=head3 The special problem of disappearing file descriptors
		1025
		1026	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1027	descriptor (either by calling C<close> explicitly or by any other means,
		1028	such as C<dup>). The reason is that you register interest in some file
		1029	descriptor, but when it goes away, the operating system will silently drop
		1030	this interest. If another file descriptor with the same number then is
		1031	registered with libev, there is no efficient way to see that this is, in
		1032	fact, a different file descriptor.
		1033
		1034	To avoid having to explicitly tell libev about such cases, libev follows
		1035	the following policy: Each time C<ev_io_set> is being called, libev
		1036	will assume that this is potentially a new file descriptor, otherwise
		1037	it is assumed that the file descriptor stays the same. That means that
		1038	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1039	descriptor even if the file descriptor number itself did not change.
		1040
		1041	This is how one would do it normally anyway, the important point is that
		1042	the libev application should not optimise around libev but should leave
		1043	optimisations to libev.
		1044
		1045	=head3 The special problem of dup'ed file descriptors
		1046
		1047	Some backends (e.g. epoll), cannot register events for file descriptors,
		1048	but only events for the underlying file descriptions. That means when you
		1049	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1050	events for them, only one file descriptor might actually receive events.
		1051
		1052	There is no workaround possible except not registering events
		1053	for potentially C<dup ()>'ed file descriptors, or to resort to
		1054	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1055
		1056	=head3 The special problem of fork
		1057
		1058	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1059	useless behaviour. Libev fully supports fork, but needs to be told about
		1060	it in the child.
		1061
		1062	To support fork in your programs, you either have to call
		1063	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1064	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1065	C<EVBACKEND_POLL>.
		1066
		1067
		1068	=head3 Watcher-Specific Functions
798		1069
799	=over 4	1070	=over 4
800		1071
801	=item ev_io_init (ev_io *, callback, int fd, int events)	1072	=item ev_io_init (ev_io *, callback, int fd, int events)
802		1073
…		…
814		1085
815	The events being watched.	1086	The events being watched.
816		1087
817	=back	1088	=back
818		1089
		1090	=head3 Examples
		1091
819	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1092	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
820	readable, but only once. Since it is likely line-buffered, you could	1093	readable, but only once. Since it is likely line-buffered, you could
821	attempt to read a whole line in the callback:	1094	attempt to read a whole line in the callback.
822		1095
823	static void	1096	static void
824	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1097	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
825	{	1098	{
826	ev_io_stop (loop, w);	1099	ev_io_stop (loop, w);
…		…
856		1129
857	The callback is guarenteed to be invoked only when its timeout has passed,	1130	The callback is guarenteed to be invoked only when its timeout has passed,
858	but if multiple timers become ready during the same loop iteration then	1131	but if multiple timers become ready during the same loop iteration then
859	order of execution is undefined.	1132	order of execution is undefined.
860		1133
		1134	=head3 Watcher-Specific Functions and Data Members
		1135
861	=over 4	1136	=over 4
862		1137
863	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1138	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
864		1139
865	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1140	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
878	=item ev_timer_again (loop)	1153	=item ev_timer_again (loop)
879		1154
880	This will act as if the timer timed out and restart it again if it is	1155	This will act as if the timer timed out and restart it again if it is
881	repeating. The exact semantics are:	1156	repeating. The exact semantics are:
882		1157
		1158	If the timer is pending, its pending status is cleared.
		1159
883	If the timer is started but nonrepeating, stop it.	1160	If the timer is started but nonrepeating, stop it (as if it timed out).
884		1161
885	If the timer is repeating, either start it if necessary (with the repeat	1162	If the timer is repeating, either start it if necessary (with the
886	value), or reset the running timer to the repeat value.	1163	C<repeat> value), or reset the running timer to the C<repeat> value.
887		1164
888	This sounds a bit complicated, but here is a useful and typical	1165	This sounds a bit complicated, but here is a useful and typical
889	example: Imagine you have a tcp connection and you want a so-called	1166	example: Imagine you have a tcp connection and you want a so-called idle
890	idle timeout, that is, you want to be called when there have been,	1167	timeout, that is, you want to be called when there have been, say, 60
891	say, 60 seconds of inactivity on the socket. The easiest way to do	1168	seconds of inactivity on the socket. The easiest way to do this is to
892	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1169	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
893	C<ev_timer_again> each time you successfully read or write some data. If	1170	C<ev_timer_again> each time you successfully read or write some data. If
894	you go into an idle state where you do not expect data to travel on the	1171	you go into an idle state where you do not expect data to travel on the
895	socket, you can stop the timer, and again will automatically restart it if	1172	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
896	need be.	1173	automatically restart it if need be.
897		1174
898	You can also ignore the C<after> value and C<ev_timer_start> altogether	1175	That means you can ignore the C<after> value and C<ev_timer_start>
899	and only ever use the C<repeat> value:	1176	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
900		1177
901	ev_timer_init (timer, callback, 0., 5.);	1178	ev_timer_init (timer, callback, 0., 5.);
902	ev_timer_again (loop, timer);	1179	ev_timer_again (loop, timer);
903	...	1180	...
904	timer->again = 17.;	1181	timer->again = 17.;
905	ev_timer_again (loop, timer);	1182	ev_timer_again (loop, timer);
906	...	1183	...
907	timer->again = 10.;	1184	timer->again = 10.;
908	ev_timer_again (loop, timer);	1185	ev_timer_again (loop, timer);
909		1186
910	This is more efficient then stopping/starting the timer eahc time you want	1187	This is more slightly efficient then stopping/starting the timer each time
911	to modify its timeout value.	1188	you want to modify its timeout value.
912		1189
913	=item ev_tstamp repeat [read-write]	1190	=item ev_tstamp repeat [read-write]
914		1191
915	The current C<repeat> value. Will be used each time the watcher times out	1192	The current C<repeat> value. Will be used each time the watcher times out
916	or C<ev_timer_again> is called and determines the next timeout (if any),	1193	or C<ev_timer_again> is called and determines the next timeout (if any),
917	which is also when any modifications are taken into account.	1194	which is also when any modifications are taken into account.
918		1195
919	=back	1196	=back
920		1197
		1198	=head3 Examples
		1199
921	Example: create a timer that fires after 60 seconds.	1200	Example: Create a timer that fires after 60 seconds.
922		1201
923	static void	1202	static void
924	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1203	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
925	{	1204	{
926	.. one minute over, w is actually stopped right here	1205	.. one minute over, w is actually stopped right here
…		…
928		1207
929	struct ev_timer mytimer;	1208	struct ev_timer mytimer;
930	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1209	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
931	ev_timer_start (loop, &mytimer);	1210	ev_timer_start (loop, &mytimer);
932		1211
933	Example: create a timeout timer that times out after 10 seconds of	1212	Example: Create a timeout timer that times out after 10 seconds of
934	inactivity.	1213	inactivity.
935		1214
936	static void	1215	static void
937	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1216	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
938	{	1217	{
…		…
958	but on wallclock time (absolute time). You can tell a periodic watcher	1237	but on wallclock time (absolute time). You can tell a periodic watcher
959	to trigger "at" some specific point in time. For example, if you tell a	1238	to trigger "at" some specific point in time. For example, if you tell a
960	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1239	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
961	+ 10.>) and then reset your system clock to the last year, then it will	1240	+ 10.>) and then reset your system clock to the last year, then it will
962	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1241	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
963	roughly 10 seconds later and of course not if you reset your system time	1242	roughly 10 seconds later).
964	again).
965		1243
966	They can also be used to implement vastly more complex timers, such as	1244	They can also be used to implement vastly more complex timers, such as
967	triggering an event on eahc midnight, local time.	1245	triggering an event on each midnight, local time or other, complicated,
		1246	rules.
968		1247
969	As with timers, the callback is guarenteed to be invoked only when the	1248	As with timers, the callback is guarenteed to be invoked only when the
970	time (C<at>) has been passed, but if multiple periodic timers become ready	1249	time (C<at>) has been passed, but if multiple periodic timers become ready
971	during the same loop iteration then order of execution is undefined.	1250	during the same loop iteration then order of execution is undefined.
972		1251
		1252	=head3 Watcher-Specific Functions and Data Members
		1253
973	=over 4	1254	=over 4
974		1255
975	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1256	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
976		1257
977	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1258	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
979	Lots of arguments, lets sort it out... There are basically three modes of	1260	Lots of arguments, lets sort it out... There are basically three modes of
980	operation, and we will explain them from simplest to complex:	1261	operation, and we will explain them from simplest to complex:
981		1262
982	=over 4	1263	=over 4
983		1264
984	=item * absolute timer (interval = reschedule_cb = 0)	1265	=item * absolute timer (at = time, interval = reschedule_cb = 0)
985		1266
986	In this configuration the watcher triggers an event at the wallclock time	1267	In this configuration the watcher triggers an event at the wallclock time
987	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1268	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
988	that is, if it is to be run at January 1st 2011 then it will run when the	1269	that is, if it is to be run at January 1st 2011 then it will run when the
989	system time reaches or surpasses this time.	1270	system time reaches or surpasses this time.
990		1271
991	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1272	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
992		1273
993	In this mode the watcher will always be scheduled to time out at the next	1274	In this mode the watcher will always be scheduled to time out at the next
994	C<at + N * interval> time (for some integer N) and then repeat, regardless	1275	C<at + N * interval> time (for some integer N, which can also be negative)
995	of any time jumps.	1276	and then repeat, regardless of any time jumps.
996		1277
997	This can be used to create timers that do not drift with respect to system	1278	This can be used to create timers that do not drift with respect to system
998	time:	1279	time:
999		1280
1000	ev_periodic_set (&periodic, 0., 3600., 0);	1281	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1006		1287
1007	Another way to think about it (for the mathematically inclined) is that	1288	Another way to think about it (for the mathematically inclined) is that
1008	C<ev_periodic> will try to run the callback in this mode at the next possible	1289	C<ev_periodic> will try to run the callback in this mode at the next possible
1009	time where C<time = at (mod interval)>, regardless of any time jumps.	1290	time where C<time = at (mod interval)>, regardless of any time jumps.
1010		1291
		1292	For numerical stability it is preferable that the C<at> value is near
		1293	C<ev_now ()> (the current time), but there is no range requirement for
		1294	this value.
		1295
1011	=item * manual reschedule mode (reschedule_cb = callback)	1296	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1012		1297
1013	In this mode the values for C<interval> and C<at> are both being	1298	In this mode the values for C<interval> and C<at> are both being
1014	ignored. Instead, each time the periodic watcher gets scheduled, the	1299	ignored. Instead, each time the periodic watcher gets scheduled, the
1015	reschedule callback will be called with the watcher as first, and the	1300	reschedule callback will be called with the watcher as first, and the
1016	current time as second argument.	1301	current time as second argument.
1017		1302
1018	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1303	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1019	ever, or make any event loop modifications>. If you need to stop it,	1304	ever, or make any event loop modifications>. If you need to stop it,
1020	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1305	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1021	starting a prepare watcher).	1306	starting an C<ev_prepare> watcher, which is legal).
1022		1307
1023	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1308	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1024	ev_tstamp now)>, e.g.:	1309	ev_tstamp now)>, e.g.:
1025		1310
1026	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1311	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1049	Simply stops and restarts the periodic watcher again. This is only useful	1334	Simply stops and restarts the periodic watcher again. This is only useful
1050	when you changed some parameters or the reschedule callback would return	1335	when you changed some parameters or the reschedule callback would return
1051	a different time than the last time it was called (e.g. in a crond like	1336	a different time than the last time it was called (e.g. in a crond like
1052	program when the crontabs have changed).	1337	program when the crontabs have changed).
1053		1338
		1339	=item ev_tstamp offset [read-write]
		1340
		1341	When repeating, this contains the offset value, otherwise this is the
		1342	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1343
		1344	Can be modified any time, but changes only take effect when the periodic
		1345	timer fires or C<ev_periodic_again> is being called.
		1346
1054	=item ev_tstamp interval [read-write]	1347	=item ev_tstamp interval [read-write]
1055		1348
1056	The current interval value. Can be modified any time, but changes only	1349	The current interval value. Can be modified any time, but changes only
1057	take effect when the periodic timer fires or C<ev_periodic_again> is being	1350	take effect when the periodic timer fires or C<ev_periodic_again> is being
1058	called.	1351	called.
…		…
1061		1354
1062	The current reschedule callback, or C<0>, if this functionality is	1355	The current reschedule callback, or C<0>, if this functionality is
1063	switched off. Can be changed any time, but changes only take effect when	1356	switched off. Can be changed any time, but changes only take effect when
1064	the periodic timer fires or C<ev_periodic_again> is being called.	1357	the periodic timer fires or C<ev_periodic_again> is being called.
1065		1358
		1359	=item ev_tstamp at [read-only]
		1360
		1361	When active, contains the absolute time that the watcher is supposed to
		1362	trigger next.
		1363
1066	=back	1364	=back
1067		1365
		1366	=head3 Examples
		1367
1068	Example: call a callback every hour, or, more precisely, whenever the	1368	Example: Call a callback every hour, or, more precisely, whenever the
1069	system clock is divisible by 3600. The callback invocation times have	1369	system clock is divisible by 3600. The callback invocation times have
1070	potentially a lot of jittering, but good long-term stability.	1370	potentially a lot of jittering, but good long-term stability.
1071		1371
1072	static void	1372	static void
1073	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1373	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
1077		1377
1078	struct ev_periodic hourly_tick;	1378	struct ev_periodic hourly_tick;
1079	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1379	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1080	ev_periodic_start (loop, &hourly_tick);	1380	ev_periodic_start (loop, &hourly_tick);
1081		1381
1082	Example: the same as above, but use a reschedule callback to do it:	1382	Example: The same as above, but use a reschedule callback to do it:
1083		1383
1084	#include <math.h>	1384	#include <math.h>
1085		1385
1086	static ev_tstamp	1386	static ev_tstamp
1087	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1387	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
1089	return fmod (now, 3600.) + 3600.;	1389	return fmod (now, 3600.) + 3600.;
1090	}	1390	}
1091		1391
1092	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1392	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1093		1393
1094	Example: call a callback every hour, starting now:	1394	Example: Call a callback every hour, starting now:
1095		1395
1096	struct ev_periodic hourly_tick;	1396	struct ev_periodic hourly_tick;
1097	ev_periodic_init (&hourly_tick, clock_cb,	1397	ev_periodic_init (&hourly_tick, clock_cb,
1098	fmod (ev_now (loop), 3600.), 3600., 0);	1398	fmod (ev_now (loop), 3600.), 3600., 0);
1099	ev_periodic_start (loop, &hourly_tick);	1399	ev_periodic_start (loop, &hourly_tick);
…		…
1111	with the kernel (thus it coexists with your own signal handlers as long	1411	with the kernel (thus it coexists with your own signal handlers as long
1112	as you don't register any with libev). Similarly, when the last signal	1412	as you don't register any with libev). Similarly, when the last signal
1113	watcher for a signal is stopped libev will reset the signal handler to	1413	watcher for a signal is stopped libev will reset the signal handler to
1114	SIG_DFL (regardless of what it was set to before).	1414	SIG_DFL (regardless of what it was set to before).
1115		1415
		1416	=head3 Watcher-Specific Functions and Data Members
		1417
1116	=over 4	1418	=over 4
1117		1419
1118	=item ev_signal_init (ev_signal *, callback, int signum)	1420	=item ev_signal_init (ev_signal *, callback, int signum)
1119		1421
1120	=item ev_signal_set (ev_signal *, int signum)	1422	=item ev_signal_set (ev_signal *, int signum)
…		…
1132	=head2 C<ev_child> - watch out for process status changes	1434	=head2 C<ev_child> - watch out for process status changes
1133		1435
1134	Child watchers trigger when your process receives a SIGCHLD in response to	1436	Child watchers trigger when your process receives a SIGCHLD in response to
1135	some child status changes (most typically when a child of yours dies).	1437	some child status changes (most typically when a child of yours dies).
1136		1438
		1439	=head3 Watcher-Specific Functions and Data Members
		1440
1137	=over 4	1441	=over 4
1138		1442
1139	=item ev_child_init (ev_child *, callback, int pid)	1443	=item ev_child_init (ev_child *, callback, int pid, int trace)
1140		1444
1141	=item ev_child_set (ev_child *, int pid)	1445	=item ev_child_set (ev_child *, int pid, int trace)
1142		1446
1143	Configures the watcher to wait for status changes of process C<pid> (or	1447	Configures the watcher to wait for status changes of process C<pid> (or
1144	I<any> process if C<pid> is specified as C<0>). The callback can look	1448	I<any> process if C<pid> is specified as C<0>). The callback can look
1145	at the C<rstatus> member of the C<ev_child> watcher structure to see	1449	at the C<rstatus> member of the C<ev_child> watcher structure to see
1146	the status word (use the macros from C<sys/wait.h> and see your systems	1450	the status word (use the macros from C<sys/wait.h> and see your systems
1147	C<waitpid> documentation). The C<rpid> member contains the pid of the	1451	C<waitpid> documentation). The C<rpid> member contains the pid of the
1148	process causing the status change.	1452	process causing the status change. C<trace> must be either C<0> (only
		1453	activate the watcher when the process terminates) or C<1> (additionally
		1454	activate the watcher when the process is stopped or continued).
1149		1455
1150	=item int pid [read-only]	1456	=item int pid [read-only]
1151		1457
1152	The process id this watcher watches out for, or C<0>, meaning any process id.	1458	The process id this watcher watches out for, or C<0>, meaning any process id.
1153		1459
…		…
1160	The process exit/trace status caused by C<rpid> (see your systems	1466	The process exit/trace status caused by C<rpid> (see your systems
1161	C<waitpid> and C<sys/wait.h> documentation for details).	1467	C<waitpid> and C<sys/wait.h> documentation for details).
1162		1468
1163	=back	1469	=back
1164		1470
		1471	=head3 Examples
		1472
1165	Example: try to exit cleanly on SIGINT and SIGTERM.	1473	Example: Try to exit cleanly on SIGINT and SIGTERM.
1166		1474
1167	static void	1475	static void
1168	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1476	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1169	{	1477	{
1170	ev_unloop (loop, EVUNLOOP_ALL);	1478	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1185	not exist" is a status change like any other. The condition "path does	1493	not exist" is a status change like any other. The condition "path does
1186	not exist" is signified by the C<st_nlink> field being zero (which is	1494	not exist" is signified by the C<st_nlink> field being zero (which is
1187	otherwise always forced to be at least one) and all the other fields of	1495	otherwise always forced to be at least one) and all the other fields of
1188	the stat buffer having unspecified contents.	1496	the stat buffer having unspecified contents.
1189		1497
		1498	The path I<should> be absolute and I<must not> end in a slash. If it is
		1499	relative and your working directory changes, the behaviour is undefined.
		1500
1190	Since there is no standard to do this, the portable implementation simply	1501	Since there is no standard to do this, the portable implementation simply
1191	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1502	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1192	can specify a recommended polling interval for this case. If you specify	1503	can specify a recommended polling interval for this case. If you specify
1193	a polling interval of C<0> (highly recommended!) then a I<suitable,	1504	a polling interval of C<0> (highly recommended!) then a I<suitable,
1194	unspecified default> value will be used (which you can expect to be around	1505	unspecified default> value will be used (which you can expect to be around
1195	five seconds, although this might change dynamically). Libev will also	1506	five seconds, although this might change dynamically). Libev will also
1196	impose a minimum interval which is currently around C<0.1>, but thats	1507	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1198		1509
1199	This watcher type is not meant for massive numbers of stat watchers,	1510	This watcher type is not meant for massive numbers of stat watchers,
1200	as even with OS-supported change notifications, this can be	1511	as even with OS-supported change notifications, this can be
1201	resource-intensive.	1512	resource-intensive.
1202		1513
1203	At the time of this writing, no specific OS backends are implemented, but	1514	At the time of this writing, only the Linux inotify interface is
1204	if demand increases, at least a kqueue and inotify backend will be added.	1515	implemented (implementing kqueue support is left as an exercise for the
		1516	reader). Inotify will be used to give hints only and should not change the
		1517	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1518	to fall back to regular polling again even with inotify, but changes are
		1519	usually detected immediately, and if the file exists there will be no
		1520	polling.
		1521
		1522	=head3 Inotify
		1523
		1524	When C<inotify (7)> support has been compiled into libev (generally only
		1525	available on Linux) and present at runtime, it will be used to speed up
		1526	change detection where possible. The inotify descriptor will be created lazily
		1527	when the first C<ev_stat> watcher is being started.
		1528
		1529	Inotify presense does not change the semantics of C<ev_stat> watchers
		1530	except that changes might be detected earlier, and in some cases, to avoid
		1531	making regular C<stat> calls. Even in the presense of inotify support
		1532	there are many cases where libev has to resort to regular C<stat> polling.
		1533
		1534	(There is no support for kqueue, as apparently it cannot be used to
		1535	implement this functionality, due to the requirement of having a file
		1536	descriptor open on the object at all times).
		1537
		1538	=head3 The special problem of stat time resolution
		1539
		1540	The C<stat ()> syscall only supports full-second resolution portably, and
		1541	even on systems where the resolution is higher, many filesystems still
		1542	only support whole seconds.
		1543
		1544	That means that, if the time is the only thing that changes, you might
		1545	miss updates: on the first update, C<ev_stat> detects a change and calls
		1546	your callback, which does something. When there is another update within
		1547	the same second, C<ev_stat> will be unable to detect it.
		1548
		1549	The solution to this is to delay acting on a change for a second (or till
		1550	the next second boundary), using a roughly one-second delay C<ev_timer>
		1551	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1552	is added to work around small timing inconsistencies of some operating
		1553	systems.
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
1205		1556
1206	=over 4	1557	=over 4
1207		1558
1208	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)	1559	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1209		1560
…		…
1245	=item const char *path [read-only]	1596	=item const char *path [read-only]
1246		1597
1247	The filesystem path that is being watched.	1598	The filesystem path that is being watched.
1248		1599
1249	=back	1600	=back
		1601
		1602	=head3 Examples
1250		1603
1251	Example: Watch C</etc/passwd> for attribute changes.	1604	Example: Watch C</etc/passwd> for attribute changes.
1252		1605
1253	static void	1606	static void
1254	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)	1607	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
…		…
1267	}	1620	}
1268		1621
1269	...	1622	...
1270	ev_stat passwd;	1623	ev_stat passwd;
1271		1624
1272	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1625	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1273	ev_stat_start (loop, &passwd);	1626	ev_stat_start (loop, &passwd);
1274		1627
		1628	Example: Like above, but additionally use a one-second delay so we do not
		1629	miss updates (however, frequent updates will delay processing, too, so
		1630	one might do the work both on C<ev_stat> callback invocation I<and> on
		1631	C<ev_timer> callback invocation).
		1632
		1633	static ev_stat passwd;
		1634	static ev_timer timer;
		1635
		1636	static void
		1637	timer_cb (EV_P_ ev_timer *w, int revents)
		1638	{
		1639	ev_timer_stop (EV_A_ w);
		1640
		1641	/* now it's one second after the most recent passwd change */
		1642	}
		1643
		1644	static void
		1645	stat_cb (EV_P_ ev_stat *w, int revents)
		1646	{
		1647	/* reset the one-second timer */
		1648	ev_timer_again (EV_A_ &timer);
		1649	}
		1650
		1651	...
		1652	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1653	ev_stat_start (loop, &passwd);
		1654	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1655
1275		1656
1276	=head2 C<ev_idle> - when you've got nothing better to do...	1657	=head2 C<ev_idle> - when you've got nothing better to do...
1277		1658
1278	Idle watchers trigger events when there are no other events are pending	1659	Idle watchers trigger events when no other events of the same or higher
1279	(prepare, check and other idle watchers do not count). That is, as long	1660	priority are pending (prepare, check and other idle watchers do not
1280	as your process is busy handling sockets or timeouts (or even signals,	1661	count).
1281	imagine) it will not be triggered. But when your process is idle all idle	1662
1282	watchers are being called again and again, once per event loop iteration -	1663	That is, as long as your process is busy handling sockets or timeouts
		1664	(or even signals, imagine) of the same or higher priority it will not be
		1665	triggered. But when your process is idle (or only lower-priority watchers
		1666	are pending), the idle watchers are being called once per event loop
1283	until stopped, that is, or your process receives more events and becomes	1667	iteration - until stopped, that is, or your process receives more events
1284	busy.	1668	and becomes busy again with higher priority stuff.
1285		1669
1286	The most noteworthy effect is that as long as any idle watchers are	1670	The most noteworthy effect is that as long as any idle watchers are
1287	active, the process will not block when waiting for new events.	1671	active, the process will not block when waiting for new events.
1288		1672
1289	Apart from keeping your process non-blocking (which is a useful	1673	Apart from keeping your process non-blocking (which is a useful
1290	effect on its own sometimes), idle watchers are a good place to do	1674	effect on its own sometimes), idle watchers are a good place to do
1291	"pseudo-background processing", or delay processing stuff to after the	1675	"pseudo-background processing", or delay processing stuff to after the
1292	event loop has handled all outstanding events.	1676	event loop has handled all outstanding events.
1293		1677
		1678	=head3 Watcher-Specific Functions and Data Members
		1679
1294	=over 4	1680	=over 4
1295		1681
1296	=item ev_idle_init (ev_signal *, callback)	1682	=item ev_idle_init (ev_signal *, callback)
1297		1683
1298	Initialises and configures the idle watcher - it has no parameters of any	1684	Initialises and configures the idle watcher - it has no parameters of any
1299	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1685	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1300	believe me.	1686	believe me.
1301		1687
1302	=back	1688	=back
1303		1689
		1690	=head3 Examples
		1691
1304	Example: dynamically allocate an C<ev_idle>, start it, and in the	1692	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1305	callback, free it. Alos, use no error checking, as usual.	1693	callback, free it. Also, use no error checking, as usual.
1306		1694
1307	static void	1695	static void
1308	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1696	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1309	{	1697	{
1310	free (w);	1698	free (w);
1311	// now do something you wanted to do when the program has	1699	// now do something you wanted to do when the program has
1312	// no longer asnything immediate to do.	1700	// no longer anything immediate to do.
1313	}	1701	}
1314		1702
1315	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1703	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1316	ev_idle_init (idle_watcher, idle_cb);	1704	ev_idle_init (idle_watcher, idle_cb);
1317	ev_idle_start (loop, idle_cb);	1705	ev_idle_start (loop, idle_cb);
…		…
1355	with priority higher than or equal to the event loop and one coroutine	1743	with priority higher than or equal to the event loop and one coroutine
1356	of lower priority, but only once, using idle watchers to keep the event	1744	of lower priority, but only once, using idle watchers to keep the event
1357	loop from blocking if lower-priority coroutines are active, thus mapping	1745	loop from blocking if lower-priority coroutines are active, thus mapping
1358	low-priority coroutines to idle/background tasks).	1746	low-priority coroutines to idle/background tasks).
1359		1747
		1748	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1749	priority, to ensure that they are being run before any other watchers
		1750	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1751	too) should not activate ("feed") events into libev. While libev fully
		1752	supports this, they will be called before other C<ev_check> watchers
		1753	did their job. As C<ev_check> watchers are often used to embed other
		1754	(non-libev) event loops those other event loops might be in an unusable
		1755	state until their C<ev_check> watcher ran (always remind yourself to
		1756	coexist peacefully with others).
		1757
		1758	=head3 Watcher-Specific Functions and Data Members
		1759
1360	=over 4	1760	=over 4
1361		1761
1362	=item ev_prepare_init (ev_prepare *, callback)	1762	=item ev_prepare_init (ev_prepare *, callback)
1363		1763
1364	=item ev_check_init (ev_check *, callback)	1764	=item ev_check_init (ev_check *, callback)
…		…
1367	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1767	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1368	macros, but using them is utterly, utterly and completely pointless.	1768	macros, but using them is utterly, utterly and completely pointless.
1369		1769
1370	=back	1770	=back
1371		1771
1372	Example: To include a library such as adns, you would add IO watchers	1772	=head3 Examples
1373	and a timeout watcher in a prepare handler, as required by libadns, and	1773
		1774	There are a number of principal ways to embed other event loops or modules
		1775	into libev. Here are some ideas on how to include libadns into libev
		1776	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1777	use for an actually working example. Another Perl module named C<EV::Glib>
		1778	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1779	into the Glib event loop).
		1780
		1781	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1374	in a check watcher, destroy them and call into libadns. What follows is	1782	and in a check watcher, destroy them and call into libadns. What follows
1375	pseudo-code only of course:	1783	is pseudo-code only of course. This requires you to either use a low
		1784	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1785	the callbacks for the IO/timeout watchers might not have been called yet.
1376		1786
1377	static ev_io iow [nfd];	1787	static ev_io iow [nfd];
1378	static ev_timer tw;	1788	static ev_timer tw;
1379		1789
1380	static void	1790	static void
1381	io_cb (ev_loop *loop, ev_io *w, int revents)	1791	io_cb (ev_loop *loop, ev_io *w, int revents)
1382	{	1792	{
1383	// set the relevant poll flags
1384	// could also call adns_processreadable etc. here
1385	struct pollfd *fd = (struct pollfd *)w->data;
1386	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1387	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1388	}	1793	}
1389		1794
1390	// create io watchers for each fd and a timer before blocking	1795	// create io watchers for each fd and a timer before blocking
1391	static void	1796	static void
1392	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	1797	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1393	{	1798	{
1394	int timeout = 3600000;truct pollfd fds [nfd];	1799	int timeout = 3600000;
		1800	struct pollfd fds [nfd];
1395	// actual code will need to loop here and realloc etc.	1801	// actual code will need to loop here and realloc etc.
1396	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1802	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1397		1803
1398	/* the callback is illegal, but won't be called as we stop during check */	1804	/* the callback is illegal, but won't be called as we stop during check */
1399	ev_timer_init (&tw, 0, timeout * 1e-3);	1805	ev_timer_init (&tw, 0, timeout * 1e-3);
1400	ev_timer_start (loop, &tw);	1806	ev_timer_start (loop, &tw);
1401		1807
1402	// create on ev_io per pollfd	1808	// create one ev_io per pollfd
1403	for (int i = 0; i < nfd; ++i)	1809	for (int i = 0; i < nfd; ++i)
1404	{	1810	{
1405	ev_io_init (iow + i, io_cb, fds [i].fd,	1811	ev_io_init (iow + i, io_cb, fds [i].fd,
1406	((fds [i].events & POLLIN ? EV_READ : 0)	1812	((fds [i].events & POLLIN ? EV_READ : 0)
1407	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1813	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1408		1814
1409	fds [i].revents = 0;	1815	fds [i].revents = 0;
1410	iow [i].data = fds + i;
1411	ev_io_start (loop, iow + i);	1816	ev_io_start (loop, iow + i);
1412	}	1817	}
1413	}	1818	}
1414		1819
1415	// stop all watchers after blocking	1820	// stop all watchers after blocking
…		…
1417	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	1822	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1418	{	1823	{
1419	ev_timer_stop (loop, &tw);	1824	ev_timer_stop (loop, &tw);
1420		1825
1421	for (int i = 0; i < nfd; ++i)	1826	for (int i = 0; i < nfd; ++i)
		1827	{
		1828	// set the relevant poll flags
		1829	// could also call adns_processreadable etc. here
		1830	struct pollfd *fd = fds + i;
		1831	int revents = ev_clear_pending (iow + i);
		1832	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1833	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1834
		1835	// now stop the watcher
1422	ev_io_stop (loop, iow + i);	1836	ev_io_stop (loop, iow + i);
		1837	}
1423		1838
1424	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1839	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1840	}
		1841
		1842	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1843	in the prepare watcher and would dispose of the check watcher.
		1844
		1845	Method 3: If the module to be embedded supports explicit event
		1846	notification (adns does), you can also make use of the actual watcher
		1847	callbacks, and only destroy/create the watchers in the prepare watcher.
		1848
		1849	static void
		1850	timer_cb (EV_P_ ev_timer *w, int revents)
		1851	{
		1852	adns_state ads = (adns_state)w->data;
		1853	update_now (EV_A);
		1854
		1855	adns_processtimeouts (ads, &tv_now);
		1856	}
		1857
		1858	static void
		1859	io_cb (EV_P_ ev_io *w, int revents)
		1860	{
		1861	adns_state ads = (adns_state)w->data;
		1862	update_now (EV_A);
		1863
		1864	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1865	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1866	}
		1867
		1868	// do not ever call adns_afterpoll
		1869
		1870	Method 4: Do not use a prepare or check watcher because the module you
		1871	want to embed is too inflexible to support it. Instead, youc na override
		1872	their poll function. The drawback with this solution is that the main
		1873	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1874	this.
		1875
		1876	static gint
		1877	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1878	{
		1879	int got_events = 0;
		1880
		1881	for (n = 0; n < nfds; ++n)
		1882	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1883
		1884	if (timeout >= 0)
		1885	// create/start timer
		1886
		1887	// poll
		1888	ev_loop (EV_A_ 0);
		1889
		1890	// stop timer again
		1891	if (timeout >= 0)
		1892	ev_timer_stop (EV_A_ &to);
		1893
		1894	// stop io watchers again - their callbacks should have set
		1895	for (n = 0; n < nfds; ++n)
		1896	ev_io_stop (EV_A_ iow [n]);
		1897
		1898	return got_events;
1425	}	1899	}
1426		1900
1427		1901
1428	=head2 C<ev_embed> - when one backend isn't enough...	1902	=head2 C<ev_embed> - when one backend isn't enough...
1429		1903
…		…
1472	portable one.	1946	portable one.
1473		1947
1474	So when you want to use this feature you will always have to be prepared	1948	So when you want to use this feature you will always have to be prepared
1475	that you cannot get an embeddable loop. The recommended way to get around	1949	that you cannot get an embeddable loop. The recommended way to get around
1476	this is to have a separate variables for your embeddable loop, try to	1950	this is to have a separate variables for your embeddable loop, try to
1477	create it, and if that fails, use the normal loop for everything:	1951	create it, and if that fails, use the normal loop for everything.
		1952
		1953	=head3 Watcher-Specific Functions and Data Members
		1954
		1955	=over 4
		1956
		1957	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
		1958
		1959	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
		1960
		1961	Configures the watcher to embed the given loop, which must be
		1962	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1963	invoked automatically, otherwise it is the responsibility of the callback
		1964	to invoke it (it will continue to be called until the sweep has been done,
		1965	if you do not want thta, you need to temporarily stop the embed watcher).
		1966
		1967	=item ev_embed_sweep (loop, ev_embed *)
		1968
		1969	Make a single, non-blocking sweep over the embedded loop. This works
		1970	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1971	apropriate way for embedded loops.
		1972
		1973	=item struct ev_loop *other [read-only]
		1974
		1975	The embedded event loop.
		1976
		1977	=back
		1978
		1979	=head3 Examples
		1980
		1981	Example: Try to get an embeddable event loop and embed it into the default
		1982	event loop. If that is not possible, use the default loop. The default
		1983	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1984	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1985	used).
1478		1986
1479	struct ev_loop *loop_hi = ev_default_init (0);	1987	struct ev_loop *loop_hi = ev_default_init (0);
1480	struct ev_loop *loop_lo = 0;	1988	struct ev_loop *loop_lo = 0;
1481	struct ev_embed embed;	1989	struct ev_embed embed;
1482		1990
…		…
1493	ev_embed_start (loop_hi, &embed);	2001	ev_embed_start (loop_hi, &embed);
1494	}	2002	}
1495	else	2003	else
1496	loop_lo = loop_hi;	2004	loop_lo = loop_hi;
1497		2005
1498	=over 4	2006	Example: Check if kqueue is available but not recommended and create
		2007	a kqueue backend for use with sockets (which usually work with any
		2008	kqueue implementation). Store the kqueue/socket-only event loop in
		2009	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1499		2010
1500	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	2011	struct ev_loop *loop = ev_default_init (0);
		2012	struct ev_loop *loop_socket = 0;
		2013	struct ev_embed embed;
		2014
		2015	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2016	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2017	{
		2018	ev_embed_init (&embed, 0, loop_socket);
		2019	ev_embed_start (loop, &embed);
		2020	}
1501		2021
1502	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	2022	if (!loop_socket)
		2023	loop_socket = loop;
1503		2024
1504	Configures the watcher to embed the given loop, which must be	2025	// now use loop_socket for all sockets, and loop for everything else
1505	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1506	invoked automatically, otherwise it is the responsibility of the callback
1507	to invoke it (it will continue to be called until the sweep has been done,
1508	if you do not want thta, you need to temporarily stop the embed watcher).
1509
1510	=item ev_embed_sweep (loop, ev_embed *)
1511
1512	Make a single, non-blocking sweep over the embedded loop. This works
1513	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1514	apropriate way for embedded loops.
1515
1516	=item struct ev_loop *loop [read-only]
1517
1518	The embedded event loop.
1519
1520	=back
1521		2026
1522		2027
1523	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2028	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1524		2029
1525	Fork watchers are called when a C<fork ()> was detected (usually because	2030	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1528	event loop blocks next and before C<ev_check> watchers are being called,	2033	event loop blocks next and before C<ev_check> watchers are being called,
1529	and only in the child after the fork. If whoever good citizen calling	2034	and only in the child after the fork. If whoever good citizen calling
1530	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2035	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1531	handlers will be invoked, too, of course.	2036	handlers will be invoked, too, of course.
1532		2037
		2038	=head3 Watcher-Specific Functions and Data Members
		2039
1533	=over 4	2040	=over 4
1534		2041
1535	=item ev_fork_init (ev_signal *, callback)	2042	=item ev_fork_init (ev_signal *, callback)
1536		2043
1537	Initialises and configures the fork watcher - it has no parameters of any	2044	Initialises and configures the fork watcher - it has no parameters of any
…		…
1633		2140
1634	To use it,	2141	To use it,
1635		2142
1636	#include <ev++.h>	2143	#include <ev++.h>
1637		2144
1638	(it is not installed by default). This automatically includes F<ev.h>	2145	This automatically includes F<ev.h> and puts all of its definitions (many
1639	and puts all of its definitions (many of them macros) into the global	2146	of them macros) into the global namespace. All C++ specific things are
1640	namespace. All C++ specific things are put into the C<ev> namespace.	2147	put into the C<ev> namespace. It should support all the same embedding
		2148	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1641		2149
1642	It should support all the same embedding options as F<ev.h>, most notably	2150	Care has been taken to keep the overhead low. The only data member the C++
1643	C<EV_MULTIPLICITY>.	2151	classes add (compared to plain C-style watchers) is the event loop pointer
		2152	that the watcher is associated with (or no additional members at all if
		2153	you disable C<EV_MULTIPLICITY> when embedding libev).
		2154
		2155	Currently, functions, and static and non-static member functions can be
		2156	used as callbacks. Other types should be easy to add as long as they only
		2157	need one additional pointer for context. If you need support for other
		2158	types of functors please contact the author (preferably after implementing
		2159	it).
1644		2160
1645	Here is a list of things available in the C<ev> namespace:	2161	Here is a list of things available in the C<ev> namespace:
1646		2162
1647	=over 4	2163	=over 4
1648		2164
…		…
1664		2180
1665	All of those classes have these methods:	2181	All of those classes have these methods:
1666		2182
1667	=over 4	2183	=over 4
1668		2184
1669	=item ev::TYPE::TYPE (object *, object::method *)	2185	=item ev::TYPE::TYPE ()
1670		2186
1671	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2187	=item ev::TYPE::TYPE (struct ev_loop *)
1672		2188
1673	=item ev::TYPE::~TYPE	2189	=item ev::TYPE::~TYPE
1674		2190
1675	The constructor takes a pointer to an object and a method pointer to	2191	The constructor (optionally) takes an event loop to associate the watcher
1676	the event handler callback to call in this class. The constructor calls	2192	with. If it is omitted, it will use C<EV_DEFAULT>.
1677	C<ev_init> for you, which means you have to call the C<set> method	2193
1678	before starting it. If you do not specify a loop then the constructor	2194	The constructor calls C<ev_init> for you, which means you have to call the
1679	automatically associates the default loop with this watcher.	2195	C<set> method before starting it.
		2196
		2197	It will not set a callback, however: You have to call the templated C<set>
		2198	method to set a callback before you can start the watcher.
		2199
		2200	(The reason why you have to use a method is a limitation in C++ which does
		2201	not allow explicit template arguments for constructors).
1680		2202
1681	The destructor automatically stops the watcher if it is active.	2203	The destructor automatically stops the watcher if it is active.
		2204
		2205	=item w->set<class, &class::method> (object *)
		2206
		2207	This method sets the callback method to call. The method has to have a
		2208	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2209	first argument and the C<revents> as second. The object must be given as
		2210	parameter and is stored in the C<data> member of the watcher.
		2211
		2212	This method synthesizes efficient thunking code to call your method from
		2213	the C callback that libev requires. If your compiler can inline your
		2214	callback (i.e. it is visible to it at the place of the C<set> call and
		2215	your compiler is good :), then the method will be fully inlined into the
		2216	thunking function, making it as fast as a direct C callback.
		2217
		2218	Example: simple class declaration and watcher initialisation
		2219
		2220	struct myclass
		2221	{
		2222	void io_cb (ev::io &w, int revents) { }
		2223	}
		2224
		2225	myclass obj;
		2226	ev::io iow;
		2227	iow.set <myclass, &myclass::io_cb> (&obj);
		2228
		2229	=item w->set<function> (void *data = 0)
		2230
		2231	Also sets a callback, but uses a static method or plain function as
		2232	callback. The optional C<data> argument will be stored in the watcher's
		2233	C<data> member and is free for you to use.
		2234
		2235	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2236
		2237	See the method-C<set> above for more details.
		2238
		2239	Example:
		2240
		2241	static void io_cb (ev::io &w, int revents) { }
		2242	iow.set <io_cb> ();
1682		2243
1683	=item w->set (struct ev_loop *)	2244	=item w->set (struct ev_loop *)
1684		2245
1685	Associates a different C<struct ev_loop> with this watcher. You can only	2246	Associates a different C<struct ev_loop> with this watcher. You can only
1686	do this when the watcher is inactive (and not pending either).	2247	do this when the watcher is inactive (and not pending either).
1687		2248
1688	=item w->set ([args])	2249	=item w->set ([args])
1689		2250
1690	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2251	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1691	called at least once. Unlike the C counterpart, an active watcher gets	2252	called at least once. Unlike the C counterpart, an active watcher gets
1692	automatically stopped and restarted.	2253	automatically stopped and restarted when reconfiguring it with this
		2254	method.
1693		2255
1694	=item w->start ()	2256	=item w->start ()
1695		2257
1696	Starts the watcher. Note that there is no C<loop> argument as the	2258	Starts the watcher. Note that there is no C<loop> argument, as the
1697	constructor already takes the loop.	2259	constructor already stores the event loop.
1698		2260
1699	=item w->stop ()	2261	=item w->stop ()
1700		2262
1701	Stops the watcher if it is active. Again, no C<loop> argument.	2263	Stops the watcher if it is active. Again, no C<loop> argument.
1702		2264
1703	=item w->again () C<ev::timer>, C<ev::periodic> only	2265	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1704		2266
1705	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2267	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1706	C<ev_TYPE_again> function.	2268	C<ev_TYPE_again> function.
1707		2269
1708	=item w->sweep () C<ev::embed> only	2270	=item w->sweep () (C<ev::embed> only)
1709		2271
1710	Invokes C<ev_embed_sweep>.	2272	Invokes C<ev_embed_sweep>.
1711		2273
1712	=item w->update () C<ev::stat> only	2274	=item w->update () (C<ev::stat> only)
1713		2275
1714	Invokes C<ev_stat_stat>.	2276	Invokes C<ev_stat_stat>.
1715		2277
1716	=back	2278	=back
1717		2279
…		…
1720	Example: Define a class with an IO and idle watcher, start one of them in	2282	Example: Define a class with an IO and idle watcher, start one of them in
1721	the constructor.	2283	the constructor.
1722		2284
1723	class myclass	2285	class myclass
1724	{	2286	{
1725	ev_io io; void io_cb (ev::io &w, int revents);	2287	ev::io io; void io_cb (ev::io &w, int revents);
1726	ev_idle idle void idle_cb (ev::idle &w, int revents);	2288	ev:idle idle void idle_cb (ev::idle &w, int revents);
1727		2289
1728	myclass ();	2290	myclass (int fd)
1729	}
1730
1731	myclass::myclass (int fd)
1732	: io (this, &myclass::io_cb),
1733	idle (this, &myclass::idle_cb)
1734	{	2291	{
		2292	io .set <myclass, &myclass::io_cb > (this);
		2293	idle.set <myclass, &myclass::idle_cb> (this);
		2294
1735	io.start (fd, ev::READ);	2295	io.start (fd, ev::READ);
		2296	}
1736	}	2297	};
1737		2298
1738		2299
1739	=head1 MACRO MAGIC	2300	=head1 MACRO MAGIC
1740		2301
1741	Libev can be compiled with a variety of options, the most fundemantal is	2302	Libev can be compiled with a variety of options, the most fundamantal
1742	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2303	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1743	callbacks have an initial C<struct ev_loop *> argument.	2304	functions and callbacks have an initial C<struct ev_loop *> argument.
1744		2305
1745	To make it easier to write programs that cope with either variant, the	2306	To make it easier to write programs that cope with either variant, the
1746	following macros are defined:	2307	following macros are defined:
1747		2308
1748	=over 4	2309	=over 4
…		…
1780	Similar to the other two macros, this gives you the value of the default	2341	Similar to the other two macros, this gives you the value of the default
1781	loop, if multiple loops are supported ("ev loop default").	2342	loop, if multiple loops are supported ("ev loop default").
1782		2343
1783	=back	2344	=back
1784		2345
1785	Example: Declare and initialise a check watcher, working regardless of	2346	Example: Declare and initialise a check watcher, utilising the above
1786	wether multiple loops are supported or not.	2347	macros so it will work regardless of whether multiple loops are supported
		2348	or not.
1787		2349
1788	static void	2350	static void
1789	check_cb (EV_P_ ev_timer *w, int revents)	2351	check_cb (EV_P_ ev_timer *w, int revents)
1790	{	2352	{
1791	ev_check_stop (EV_A_ w);	2353	ev_check_stop (EV_A_ w);
…		…
1794	ev_check check;	2356	ev_check check;
1795	ev_check_init (&check, check_cb);	2357	ev_check_init (&check, check_cb);
1796	ev_check_start (EV_DEFAULT_ &check);	2358	ev_check_start (EV_DEFAULT_ &check);
1797	ev_loop (EV_DEFAULT_ 0);	2359	ev_loop (EV_DEFAULT_ 0);
1798		2360
1799
1800	=head1 EMBEDDING	2361	=head1 EMBEDDING
1801		2362
1802	Libev can (and often is) directly embedded into host	2363	Libev can (and often is) directly embedded into host
1803	applications. Examples of applications that embed it include the Deliantra	2364	applications. Examples of applications that embed it include the Deliantra
1804	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2365	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1805	and rxvt-unicode.	2366	and rxvt-unicode.
1806		2367
1807	The goal is to enable you to just copy the neecssary files into your	2368	The goal is to enable you to just copy the necessary files into your
1808	source directory without having to change even a single line in them, so	2369	source directory without having to change even a single line in them, so
1809	you can easily upgrade by simply copying (or having a checked-out copy of	2370	you can easily upgrade by simply copying (or having a checked-out copy of
1810	libev somewhere in your source tree).	2371	libev somewhere in your source tree).
1811		2372
1812	=head2 FILESETS	2373	=head2 FILESETS
…		…
1843	ev_vars.h	2404	ev_vars.h
1844	ev_wrap.h	2405	ev_wrap.h
1845		2406
1846	ev_win32.c required on win32 platforms only	2407	ev_win32.c required on win32 platforms only
1847		2408
1848	ev_select.c only when select backend is enabled (which is by default)	2409	ev_select.c only when select backend is enabled (which is enabled by default)
1849	ev_poll.c only when poll backend is enabled (disabled by default)	2410	ev_poll.c only when poll backend is enabled (disabled by default)
1850	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2411	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1851	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2412	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1852	ev_port.c only when the solaris port backend is enabled (disabled by default)	2413	ev_port.c only when the solaris port backend is enabled (disabled by default)
1853		2414
…		…
1902		2463
1903	If defined to be C<1>, libev will try to detect the availability of the	2464	If defined to be C<1>, libev will try to detect the availability of the
1904	monotonic clock option at both compiletime and runtime. Otherwise no use	2465	monotonic clock option at both compiletime and runtime. Otherwise no use
1905	of the monotonic clock option will be attempted. If you enable this, you	2466	of the monotonic clock option will be attempted. If you enable this, you
1906	usually have to link against librt or something similar. Enabling it when	2467	usually have to link against librt or something similar. Enabling it when
1907	the functionality isn't available is safe, though, althoguh you have	2468	the functionality isn't available is safe, though, although you have
1908	to make sure you link against any libraries where the C<clock_gettime>	2469	to make sure you link against any libraries where the C<clock_gettime>
1909	function is hiding in (often F<-lrt>).	2470	function is hiding in (often F<-lrt>).
1910		2471
1911	=item EV_USE_REALTIME	2472	=item EV_USE_REALTIME
1912		2473
1913	If defined to be C<1>, libev will try to detect the availability of the	2474	If defined to be C<1>, libev will try to detect the availability of the
1914	realtime clock option at compiletime (and assume its availability at	2475	realtime clock option at compiletime (and assume its availability at
1915	runtime if successful). Otherwise no use of the realtime clock option will	2476	runtime if successful). Otherwise no use of the realtime clock option will
1916	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2477	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1917	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2478	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1918	in the description of C<EV_USE_MONOTONIC>, though.	2479	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2480
		2481	=item EV_USE_NANOSLEEP
		2482
		2483	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2484	and will use it for delays. Otherwise it will use C<select ()>.
1919		2485
1920	=item EV_USE_SELECT	2486	=item EV_USE_SELECT
1921		2487
1922	If undefined or defined to be C<1>, libev will compile in support for the	2488	If undefined or defined to be C<1>, libev will compile in support for the
1923	C<select>(2) backend. No attempt at autodetection will be done: if no	2489	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1941	wants osf handles on win32 (this is the case when the select to	2507	wants osf handles on win32 (this is the case when the select to
1942	be used is the winsock select). This means that it will call	2508	be used is the winsock select). This means that it will call
1943	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2509	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
1944	it is assumed that all these functions actually work on fds, even	2510	it is assumed that all these functions actually work on fds, even
1945	on win32. Should not be defined on non-win32 platforms.	2511	on win32. Should not be defined on non-win32 platforms.
		2512
		2513	=item EV_FD_TO_WIN32_HANDLE
		2514
		2515	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2516	file descriptors to socket handles. When not defining this symbol (the
		2517	default), then libev will call C<_get_osfhandle>, which is usually
		2518	correct. In some cases, programs use their own file descriptor management,
		2519	in which case they can provide this function to map fds to socket handles.
1946		2520
1947	=item EV_USE_POLL	2521	=item EV_USE_POLL
1948		2522
1949	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2523	If defined to be C<1>, libev will compile in support for the C<poll>(2)
1950	backend. Otherwise it will be enabled on non-win32 platforms. It	2524	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
1978		2552
1979	=item EV_USE_DEVPOLL	2553	=item EV_USE_DEVPOLL
1980		2554
1981	reserved for future expansion, works like the USE symbols above.	2555	reserved for future expansion, works like the USE symbols above.
1982		2556
		2557	=item EV_USE_INOTIFY
		2558
		2559	If defined to be C<1>, libev will compile in support for the Linux inotify
		2560	interface to speed up C<ev_stat> watchers. Its actual availability will
		2561	be detected at runtime.
		2562
1983	=item EV_H	2563	=item EV_H
1984		2564
1985	The name of the F<ev.h> header file used to include it. The default if	2565	The name of the F<ev.h> header file used to include it. The default if
1986	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2566	undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
1987	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2567	used to virtually rename the F<ev.h> header file in case of conflicts.
1988		2568
1989	=item EV_CONFIG_H	2569	=item EV_CONFIG_H
1990		2570
1991	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2571	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
1992	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2572	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
1993	C<EV_H>, above.	2573	C<EV_H>, above.
1994		2574
1995	=item EV_EVENT_H	2575	=item EV_EVENT_H
1996		2576
1997	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2577	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
1998	of how the F<event.h> header can be found.	2578	of how the F<event.h> header can be found, the default is C<"event.h">.
1999		2579
2000	=item EV_PROTOTYPES	2580	=item EV_PROTOTYPES
2001		2581
2002	If defined to be C<0>, then F<ev.h> will not define any function	2582	If defined to be C<0>, then F<ev.h> will not define any function
2003	prototypes, but still define all the structs and other symbols. This is	2583	prototypes, but still define all the structs and other symbols. This is
…		…
2010	will have the C<struct ev_loop *> as first argument, and you can create	2590	will have the C<struct ev_loop *> as first argument, and you can create
2011	additional independent event loops. Otherwise there will be no support	2591	additional independent event loops. Otherwise there will be no support
2012	for multiple event loops and there is no first event loop pointer	2592	for multiple event loops and there is no first event loop pointer
2013	argument. Instead, all functions act on the single default loop.	2593	argument. Instead, all functions act on the single default loop.
2014		2594
		2595	=item EV_MINPRI
		2596
		2597	=item EV_MAXPRI
		2598
		2599	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2600	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2601	provide for more priorities by overriding those symbols (usually defined
		2602	to be C<-2> and C<2>, respectively).
		2603
		2604	When doing priority-based operations, libev usually has to linearly search
		2605	all the priorities, so having many of them (hundreds) uses a lot of space
		2606	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2607	fine.
		2608
		2609	If your embedding app does not need any priorities, defining these both to
		2610	C<0> will save some memory and cpu.
		2611
2015	=item EV_PERIODIC_ENABLE	2612	=item EV_PERIODIC_ENABLE
2016		2613
2017	If undefined or defined to be C<1>, then periodic timers are supported. If	2614	If undefined or defined to be C<1>, then periodic timers are supported. If
2018	defined to be C<0>, then they are not. Disabling them saves a few kB of	2615	defined to be C<0>, then they are not. Disabling them saves a few kB of
2019	code.	2616	code.
2020		2617
		2618	=item EV_IDLE_ENABLE
		2619
		2620	If undefined or defined to be C<1>, then idle watchers are supported. If
		2621	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2622	code.
		2623
2021	=item EV_EMBED_ENABLE	2624	=item EV_EMBED_ENABLE
2022		2625
2023	If undefined or defined to be C<1>, then embed watchers are supported. If	2626	If undefined or defined to be C<1>, then embed watchers are supported. If
2024	defined to be C<0>, then they are not.	2627	defined to be C<0>, then they are not.
2025		2628
…		…
2042	=item EV_PID_HASHSIZE	2645	=item EV_PID_HASHSIZE
2043		2646
2044	C<ev_child> watchers use a small hash table to distribute workload by	2647	C<ev_child> watchers use a small hash table to distribute workload by
2045	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2648	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2046	than enough. If you need to manage thousands of children you might want to	2649	than enough. If you need to manage thousands of children you might want to
2047	increase this value.	2650	increase this value (I<must> be a power of two).
		2651
		2652	=item EV_INOTIFY_HASHSIZE
		2653
		2654	C<ev_stat> watchers use a small hash table to distribute workload by
		2655	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2656	usually more than enough. If you need to manage thousands of C<ev_stat>
		2657	watchers you might want to increase this value (I<must> be a power of
		2658	two).
2048		2659
2049	=item EV_COMMON	2660	=item EV_COMMON
2050		2661
2051	By default, all watchers have a C<void *data> member. By redefining	2662	By default, all watchers have a C<void *data> member. By redefining
2052	this macro to a something else you can include more and other types of	2663	this macro to a something else you can include more and other types of
…		…
2065		2676
2066	=item ev_set_cb (ev, cb)	2677	=item ev_set_cb (ev, cb)
2067		2678
2068	Can be used to change the callback member declaration in each watcher,	2679	Can be used to change the callback member declaration in each watcher,
2069	and the way callbacks are invoked and set. Must expand to a struct member	2680	and the way callbacks are invoked and set. Must expand to a struct member
2070	definition and a statement, respectively. See the F<ev.v> header file for	2681	definition and a statement, respectively. See the F<ev.h> header file for
2071	their default definitions. One possible use for overriding these is to	2682	their default definitions. One possible use for overriding these is to
2072	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2683	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2073	method calls instead of plain function calls in C++.	2684	method calls instead of plain function calls in C++.
		2685
		2686	=head2 EXPORTED API SYMBOLS
		2687
		2688	If you need to re-export the API (e.g. via a dll) and you need a list of
		2689	exported symbols, you can use the provided F<Symbol.*> files which list
		2690	all public symbols, one per line:
		2691
		2692	Symbols.ev for libev proper
		2693	Symbols.event for the libevent emulation
		2694
		2695	This can also be used to rename all public symbols to avoid clashes with
		2696	multiple versions of libev linked together (which is obviously bad in
		2697	itself, but sometimes it is inconvinient to avoid this).
		2698
		2699	A sed command like this will create wrapper C<#define>'s that you need to
		2700	include before including F<ev.h>:
		2701
		2702	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2703
		2704	This would create a file F<wrap.h> which essentially looks like this:
		2705
		2706	#define ev_backend myprefix_ev_backend
		2707	#define ev_check_start myprefix_ev_check_start
		2708	#define ev_check_stop myprefix_ev_check_stop
		2709	...
2074		2710
2075	=head2 EXAMPLES	2711	=head2 EXAMPLES
2076		2712
2077	For a real-world example of a program the includes libev	2713	For a real-world example of a program the includes libev
2078	verbatim, you can have a look at the EV perl module	2714	verbatim, you can have a look at the EV perl module
…		…
2081	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2717	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2082	will be compiled. It is pretty complex because it provides its own header	2718	will be compiled. It is pretty complex because it provides its own header
2083	file.	2719	file.
2084		2720
2085	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2721	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2086	that everybody includes and which overrides some autoconf choices:	2722	that everybody includes and which overrides some configure choices:
2087		2723
		2724	#define EV_MINIMAL 1
2088	#define EV_USE_POLL 0	2725	#define EV_USE_POLL 0
2089	#define EV_MULTIPLICITY 0	2726	#define EV_MULTIPLICITY 0
2090	#define EV_PERIODICS 0	2727	#define EV_PERIODIC_ENABLE 0
		2728	#define EV_STAT_ENABLE 0
		2729	#define EV_FORK_ENABLE 0
2091	#define EV_CONFIG_H <config.h>	2730	#define EV_CONFIG_H <config.h>
		2731	#define EV_MINPRI 0
		2732	#define EV_MAXPRI 0
2092		2733
2093	#include "ev++.h"	2734	#include "ev++.h"
2094		2735
2095	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2736	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2096		2737
…		…
2102		2743
2103	In this section the complexities of (many of) the algorithms used inside	2744	In this section the complexities of (many of) the algorithms used inside
2104	libev will be explained. For complexity discussions about backends see the	2745	libev will be explained. For complexity discussions about backends see the
2105	documentation for C<ev_default_init>.	2746	documentation for C<ev_default_init>.
2106		2747
		2748	All of the following are about amortised time: If an array needs to be
		2749	extended, libev needs to realloc and move the whole array, but this
		2750	happens asymptotically never with higher number of elements, so O(1) might
		2751	mean it might do a lengthy realloc operation in rare cases, but on average
		2752	it is much faster and asymptotically approaches constant time.
		2753
2107	=over 4	2754	=over 4
2108		2755
2109	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2756	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2110		2757
		2758	This means that, when you have a watcher that triggers in one hour and
		2759	there are 100 watchers that would trigger before that then inserting will
		2760	have to skip roughly seven (C<ld 100>) of these watchers.
		2761
2111	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2762	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2763
		2764	That means that changing a timer costs less than removing/adding them
		2765	as only the relative motion in the event queue has to be paid for.
2112		2766
2113	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2767	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2114		2768
		2769	These just add the watcher into an array or at the head of a list.
		2770
2115	=item Stopping check/prepare/idle watchers: O(1)	2771	=item Stopping check/prepare/idle watchers: O(1)
2116		2772
2117	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2773	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2118		2774
		2775	These watchers are stored in lists then need to be walked to find the
		2776	correct watcher to remove. The lists are usually short (you don't usually
		2777	have many watchers waiting for the same fd or signal).
		2778
2119	=item Finding the next timer per loop iteration: O(1)	2779	=item Finding the next timer in each loop iteration: O(1)
		2780
		2781	By virtue of using a binary heap, the next timer is always found at the
		2782	beginning of the storage array.
2120		2783
2121	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2784	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2122		2785
2123	=item Activating one watcher: O(1)	2786	A change means an I/O watcher gets started or stopped, which requires
		2787	libev to recalculate its status (and possibly tell the kernel, depending
		2788	on backend and wether C<ev_io_set> was used).
		2789
		2790	=item Activating one watcher (putting it into the pending state): O(1)
		2791
		2792	=item Priority handling: O(number_of_priorities)
		2793
		2794	Priorities are implemented by allocating some space for each
		2795	priority. When doing priority-based operations, libev usually has to
		2796	linearly search all the priorities, but starting/stopping and activating
		2797	watchers becomes O(1) w.r.t. prioritiy handling.
2124		2798
2125	=back	2799	=back
2126		2800
2127		2801
		2802	=head1 Win32 platform limitations and workarounds
		2803
		2804	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2805	requires, and its I/O model is fundamentally incompatible with the POSIX
		2806	model. Libev still offers limited functionality on this platform in
		2807	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2808	descriptors. This only applies when using Win32 natively, not when using
		2809	e.g. cygwin.
		2810
		2811	There is no supported compilation method available on windows except
		2812	embedding it into other applications.
		2813
		2814	Due to the many, low, and arbitrary limits on the win32 platform and the
		2815	abysmal performance of winsockets, using a large number of sockets is not
		2816	recommended (and not reasonable). If your program needs to use more than
		2817	a hundred or so sockets, then likely it needs to use a totally different
		2818	implementation for windows, as libev offers the POSIX model, which cannot
		2819	be implemented efficiently on windows (microsoft monopoly games).
		2820
		2821	=over 4
		2822
		2823	=item The winsocket select function
		2824
		2825	The winsocket C<select> function doesn't follow POSIX in that it requires
		2826	socket I<handles> and not socket I<file descriptors>. This makes select
		2827	very inefficient, and also requires a mapping from file descriptors
		2828	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2829	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2830	symbols for more info.
		2831
		2832	The configuration for a "naked" win32 using the microsoft runtime
		2833	libraries and raw winsocket select is:
		2834
		2835	#define EV_USE_SELECT 1
		2836	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2837
		2838	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2839	complexity in the O(n²) range when using win32.
		2840
		2841	=item Limited number of file descriptors
		2842
		2843	Windows has numerous arbitrary (and low) limits on things. Early versions
		2844	of winsocket's select only supported waiting for a max. of C<64> handles
		2845	(probably owning to the fact that all windows kernels can only wait for
		2846	C<64> things at the same time internally; microsoft recommends spawning a
		2847	chain of threads and wait for 63 handles and the previous thread in each).
		2848
		2849	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2850	to some high number (e.g. C<2048>) before compiling the winsocket select
		2851	call (which might be in libev or elsewhere, for example, perl does its own
		2852	select emulation on windows).
		2853
		2854	Another limit is the number of file descriptors in the microsoft runtime
		2855	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2856	or something like this inside microsoft). You can increase this by calling
		2857	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2858	arbitrary limit), but is broken in many versions of the microsoft runtime
		2859	libraries.
		2860
		2861	This might get you to about C<512> or C<2048> sockets (depending on
		2862	windows version and/or the phase of the moon). To get more, you need to
		2863	wrap all I/O functions and provide your own fd management, but the cost of
		2864	calling select (O(n²)) will likely make this unworkable.
		2865
		2866	=back
		2867
		2868
2128	=head1 AUTHOR	2869	=head1 AUTHOR
2129		2870
2130	Marc Lehmann <libev@schmorp.de>.	2871	Marc Lehmann <libev@schmorp.de>.
2131		2872

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