ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.37 by root, Sat Nov 24 07:20:43 2007 UTC vs.
Revision 1.99 by root, Sat Dec 22 06:16:36 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		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
11	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
12	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
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
15	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
16	(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
17	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
21	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
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	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
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	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
31	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
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	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.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	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
49	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
50	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
51	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
52		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
53		106
54	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
55		108
56	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
57	library in any way.	110	library in any way.
…		…
62		115
63	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
64	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
65	you actually want to know.	118	you actually want to know.
66		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
67	=item int ev_version_major ()	126	=item int ev_version_major ()
68		127
69	=item int ev_version_minor ()	128	=item int ev_version_minor ()
70		129
71	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
72	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
73	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
74	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
75	version of the library your program was compiled against.	134	version of the library your program was compiled against.
76		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
77	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,
78	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
79	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
80	not a problem.	142	not a problem.
81		143
82	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
83	version:	145	version.
84		146
85	assert (("libev version mismatch",	147	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	148	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	149	&& ev_version_minor () >= EV_VERSION_MINOR));
88		150
…		…
118		180
119	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
120		182
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	183	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		184
123	Sets the allocation function to use (the prototype is similar to the	185	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	186	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	187	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	188	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
128		191
129	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
130	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,
131	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.
132		195
133	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
134	retries: better than mine).	197	retries).
135		198
136	static void *	199	static void *
137	persistent_realloc (void *ptr, long size)	200	persistent_realloc (void *ptr, size_t size)
138	{	201	{
139	for (;;)	202	for (;;)
140	{	203	{
141	void *newptr = realloc (ptr, size);	204	void *newptr = realloc (ptr, size);
142		205
…		…
158	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
159	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
160	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
161	(such as abort).	224	(such as abort).
162		225
163	Example: do the same thing as libev does internally:	226	Example: This is basically the same thing that libev does internally, too.
164		227
165	static void	228	static void
166	fatal_error (const char *msg)	229	fatal_error (const char *msg)
167	{	230	{
168	perror (msg);	231	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
221	around bugs.	284	around bugs.
222		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		307
225	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
…		…
236	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
237		320
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	321	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		322
240	For few fds, this backend is a bit little slower than poll and select,	323	For few fds, this backend is a bit little slower than poll and select,
241	but it scales phenomenally better. While poll and select usually scale like	324	but it scales phenomenally better. While poll and select usually scale
242	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	325	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	326	epoll scales either O(1) or O(active_fds). The epoll design has a number
		327	of shortcomings, such as silently dropping events in some hard-to-detect
		328	cases and rewiring a syscall per fd change, no fork support and bad
		329	support for dup:
244		330
245	While stopping and starting an I/O watcher in the same iteration will	331	While stopping, setting and starting an I/O watcher in the same iteration
246	result in some caching, there is still a syscall per such incident	332	will result in some caching, there is still a syscall per such incident
247	(because the fd could point to a different file description now), so its	333	(because the fd could point to a different file description now), so its
248	best to avoid that. Also, dup()ed file descriptors might not work very	334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	335	very well if you register events for both fds.
250		336
251	Please note that epoll sometimes generates spurious notifications, so you	337	Please note that epoll sometimes generates spurious notifications, so you
252	need to use non-blocking I/O or other means to avoid blocking when no data	338	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	339	(or space) is available.
254		340
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		342
257	Kqueue deserves special mention, as at the time of this writing, it	343	Kqueue deserves special mention, as at the time of this writing, it
258	was broken on all BSDs except NetBSD (usually it doesn't work with	344	was broken on I<all> BSDs (usually it doesn't work with anything but
259	anything but sockets and pipes, except on Darwin, where of course its	345	sockets and pipes, except on Darwin, where of course it's completely
		346	useless. On NetBSD, it seems to work for all the FD types I tested, so it
260	completely useless). For this reason its not being "autodetected"	347	is used by default there). For this reason it's not being "autodetected"
261	unless you explicitly specify it explicitly in the flags (i.e. using	348	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	349	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		350	system like NetBSD.
263		351
264	It scales in the same way as the epoll backend, but the interface to the	352	It scales in the same way as the epoll backend, but the interface to the
265	kernel is more efficient (which says nothing about its actual speed, of	353	kernel is more efficient (which says nothing about its actual speed,
266	course). While starting and stopping an I/O watcher does not cause an	354	of course). While stopping, setting and starting an I/O watcher does
267	extra syscall as with epoll, it still adds up to four event changes per	355	never cause an extra syscall as with epoll, it still adds up to two event
268	incident, so its best to avoid that.	356	changes per incident, support for C<fork ()> is very bad and it drops fds
		357	silently in similarly hard-to-detetc cases.
269		358
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	359	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		360
272	This is not implemented yet (and might never be).	361	This is not implemented yet (and might never be).
273		362
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	363	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		364
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	365	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
277	it's really slow, but it still scales very well (O(active_fds)).	366	it's really slow, but it still scales very well (O(active_fds)).
278		367
279	Please note that solaris ports can result in a lot of spurious	368	Please note that solaris event ports can deliver a lot of spurious
280	notifications, so you need to use non-blocking I/O or other means to avoid	369	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	370	blocking when no data (or space) is available.
282		371
283	=item C<EVBACKEND_ALL>	372	=item C<EVBACKEND_ALL>
284		373
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	403	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	404	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	405	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	406	undefined behaviour (or a failed assertion if assertions are enabled).
318		407
319	Example: try to create a event loop that uses epoll and nothing else.	408	Example: Try to create a event loop that uses epoll and nothing else.
320		409
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	410	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	411	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	412	fatal ("no epoll found here, maybe it hides under your chair");
324		413
…		…
327	Destroys the default loop again (frees all memory and kernel state	416	Destroys the default loop again (frees all memory and kernel state
328	etc.). None of the active event watchers will be stopped in the normal	417	etc.). None of the active event watchers will be stopped in the normal
329	sense, so e.g. C<ev_is_active> might still return true. It is your	418	sense, so e.g. C<ev_is_active> might still return true. It is your
330	responsibility to either stop all watchers cleanly yoursef I<before>	419	responsibility to either stop all watchers cleanly yoursef I<before>
331	calling this function, or cope with the fact afterwards (which is usually	420	calling this function, or cope with the fact afterwards (which is usually
332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	421	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	422	for example).
		423
		424	Note that certain global state, such as signal state, will not be freed by
		425	this function, and related watchers (such as signal and child watchers)
		426	would need to be stopped manually.
		427
		428	In general it is not advisable to call this function except in the
		429	rare occasion where you really need to free e.g. the signal handling
		430	pipe fds. If you need dynamically allocated loops it is better to use
		431	C<ev_loop_new> and C<ev_loop_destroy>).
334		432
335	=item ev_loop_destroy (loop)	433	=item ev_loop_destroy (loop)
336		434
337	Like C<ev_default_destroy>, but destroys an event loop created by an	435	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	436	earlier call to C<ev_loop_new>.
…		…
362		460
363	Like C<ev_default_fork>, but acts on an event loop created by	461	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	462	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	463	after fork, and how you do this is entirely your own problem.
366		464
		465	=item unsigned int ev_loop_count (loop)
		466
		467	Returns the count of loop iterations for the loop, which is identical to
		468	the number of times libev did poll for new events. It starts at C<0> and
		469	happily wraps around with enough iterations.
		470
		471	This value can sometimes be useful as a generation counter of sorts (it
		472	"ticks" the number of loop iterations), as it roughly corresponds with
		473	C<ev_prepare> and C<ev_check> calls.
		474
367	=item unsigned int ev_backend (loop)	475	=item unsigned int ev_backend (loop)
368		476
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	477	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	478	use.
371		479
…		…
373		481
374	Returns the current "event loop time", which is the time the event loop	482	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	483	received events and started processing them. This timestamp does not
376	change as long as callbacks are being processed, and this is also the base	484	change as long as callbacks are being processed, and this is also the base
377	time used for relative timers. You can treat it as the timestamp of the	485	time used for relative timers. You can treat it as the timestamp of the
378	event occuring (or more correctly, libev finding out about it).	486	event occurring (or more correctly, libev finding out about it).
379		487
380	=item ev_loop (loop, int flags)	488	=item ev_loop (loop, int flags)
381		489
382	Finally, this is it, the event handler. This function usually is called	490	Finally, this is it, the event handler. This function usually is called
383	after you initialised all your watchers and you want to start handling	491	after you initialised all your watchers and you want to start handling
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	512	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	513	usually a better approach for this kind of thing.
406		514
407	Here are the gory details of what C<ev_loop> does:	515	Here are the gory details of what C<ev_loop> does:
408		516
		517	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	518	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	519	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	520	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	521	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	522	- Update the "event loop time".
414	- Calculate for how long to block.	523	- Calculate for how long to block.
415	- Block the process, waiting for any events.	524	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	532	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	533	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	534	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	535	were used, return, otherwise continue with step *.
427		536
428	Example: queue some jobs and then loop until no events are outsanding	537	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	538	anymore.
430		539
431	... queue jobs here, make sure they register event watchers as long	540	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	541	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	542	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	562	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	563	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	564	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	565	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		566
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	567	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	568	running when nothing else is active.
460		569
461	struct dv_signal exitsig;	570	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	571	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	572	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	573	evf_unref (loop);
465		574
466	Example: for some weird reason, unregister the above signal handler again.	575	Example: For some weird reason, unregister the above signal handler again.
467		576
468	ev_ref (myloop);	577	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	578	ev_signal_stop (loop, &exitsig);
		579
		580	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		581
		582	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		583
		584	These advanced functions influence the time that libev will spend waiting
		585	for events. Both are by default C<0>, meaning that libev will try to
		586	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		587
		588	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		589	allows libev to delay invocation of I/O and timer/periodic callbacks to
		590	increase efficiency of loop iterations.
		591
		592	The background is that sometimes your program runs just fast enough to
		593	handle one (or very few) event(s) per loop iteration. While this makes
		594	the program responsive, it also wastes a lot of CPU time to poll for new
		595	events, especially with backends like C<select ()> which have a high
		596	overhead for the actual polling but can deliver many events at once.
		597
		598	By setting a higher I<io collect interval> you allow libev to spend more
		599	time collecting I/O events, so you can handle more events per iteration,
		600	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		601	C<ev_timer>) will be not affected. Setting this to a non-null bvalue will
		602	introduce an additional C<ev_sleep ()> call into most loop iterations.
		603
		604	Likewise, by setting a higher I<timeout collect interval> you allow libev
		605	to spend more time collecting timeouts, at the expense of increased
		606	latency (the watcher callback will be called later). C<ev_io> watchers
		607	will not be affected. Setting this to a non-null value will not introduce
		608	any overhead in libev.
		609
		610	Many (busy) programs can usually benefit by setting the io collect
		611	interval to a value near C<0.1> or so, which is often enough for
		612	interactive servers (of course not for games), likewise for timeouts. It
		613	usually doesn't make much sense to set it to a lower value than C<0.01>,
		614	as this approsaches the timing granularity of most systems.
470		615
471	=back	616	=back
		617
472		618
473	=head1 ANATOMY OF A WATCHER	619	=head1 ANATOMY OF A WATCHER
474		620
475	A watcher is a structure that you create and register to record your	621	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	622	interest in some event. For instance, if you want to wait for STDIN to
…		…
543	The signal specified in the C<ev_signal> watcher has been received by a thread.	689	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		690
545	=item C<EV_CHILD>	691	=item C<EV_CHILD>
546		692
547	The pid specified in the C<ev_child> watcher has received a status change.	693	The pid specified in the C<ev_child> watcher has received a status change.
		694
		695	=item C<EV_STAT>
		696
		697	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		698
549	=item C<EV_IDLE>	699	=item C<EV_IDLE>
550		700
551	The C<ev_idle> watcher has determined that you have nothing better to do.	701	The C<ev_idle> watcher has determined that you have nothing better to do.
552		702
…		…
560	received events. Callbacks of both watcher types can start and stop as	710	received events. Callbacks of both watcher types can start and stop as
561	many watchers as they want, and all of them will be taken into account	711	many watchers as they want, and all of them will be taken into account
562	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	712	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	713	C<ev_loop> from blocking).
564		714
		715	=item C<EV_EMBED>
		716
		717	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		718
		719	=item C<EV_FORK>
		720
		721	The event loop has been resumed in the child process after fork (see
		722	C<ev_fork>).
		723
565	=item C<EV_ERROR>	724	=item C<EV_ERROR>
566		725
567	An unspecified error has occured, the watcher has been stopped. This might	726	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	727	happen because the watcher could not be properly started because libev
569	ran out of memory, a file descriptor was found to be closed or any other	728	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	with the error from read() or write(). This will not work in multithreaded	735	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	736	programs, though, so beware.
578		737
579	=back	738	=back
580		739
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	740	=head2 GENERIC WATCHER FUNCTIONS
582		741
583	In the following description, C<TYPE> stands for the watcher type,	742	In the following description, C<TYPE> stands for the watcher type,
584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.	743	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		744
586	=over 4	745	=over 4
…		…
595	which rolls both calls into one.	754	which rolls both calls into one.
596		755
597	You can reinitialise a watcher at any time as long as it has been stopped	756	You can reinitialise a watcher at any time as long as it has been stopped
598	(or never started) and there are no pending events outstanding.	757	(or never started) and there are no pending events outstanding.
599		758
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	759	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	760	int revents)>.
602		761
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	762	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		763
605	This macro initialises the type-specific parts of a watcher. You need to	764	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	799	=item bool ev_is_pending (ev_TYPE *watcher)
641		800
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	801	Returns a true value iff the watcher is pending, (i.e. it has outstanding
643	events but its callback has not yet been invoked). As long as a watcher	802	events but its callback has not yet been invoked). As long as a watcher
644	is pending (but not active) you must not call an init function on it (but	803	is pending (but not active) you must not call an init function on it (but
645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	804	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	805	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		806	it).
647		807
648	=item callback = ev_cb (ev_TYPE *watcher)	808	=item callback ev_cb (ev_TYPE *watcher)
649		809
650	Returns the callback currently set on the watcher.	810	Returns the callback currently set on the watcher.
651		811
652	=item ev_cb_set (ev_TYPE *watcher, callback)	812	=item ev_cb_set (ev_TYPE *watcher, callback)
653		813
654	Change the callback. You can change the callback at virtually any time	814	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	815	(modulo threads).
		816
		817	=item ev_set_priority (ev_TYPE *watcher, priority)
		818
		819	=item int ev_priority (ev_TYPE *watcher)
		820
		821	Set and query the priority of the watcher. The priority is a small
		822	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		823	(default: C<-2>). Pending watchers with higher priority will be invoked
		824	before watchers with lower priority, but priority will not keep watchers
		825	from being executed (except for C<ev_idle> watchers).
		826
		827	This means that priorities are I<only> used for ordering callback
		828	invocation after new events have been received. This is useful, for
		829	example, to reduce latency after idling, or more often, to bind two
		830	watchers on the same event and make sure one is called first.
		831
		832	If you need to suppress invocation when higher priority events are pending
		833	you need to look at C<ev_idle> watchers, which provide this functionality.
		834
		835	You I<must not> change the priority of a watcher as long as it is active or
		836	pending.
		837
		838	The default priority used by watchers when no priority has been set is
		839	always C<0>, which is supposed to not be too high and not be too low :).
		840
		841	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		842	fine, as long as you do not mind that the priority value you query might
		843	or might not have been adjusted to be within valid range.
		844
		845	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		846
		847	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		848	C<loop> nor C<revents> need to be valid as long as the watcher callback
		849	can deal with that fact.
		850
		851	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		852
		853	If the watcher is pending, this function returns clears its pending status
		854	and returns its C<revents> bitset (as if its callback was invoked). If the
		855	watcher isn't pending it does nothing and returns C<0>.
656		856
657	=back	857	=back
658		858
659		859
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	860	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	881	{
682	struct my_io *w = (struct my_io *)w_;	882	struct my_io *w = (struct my_io *)w_;
683	...	883	...
684	}	884	}
685		885
686	More interesting and less C-conformant ways of catsing your callback type	886	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	887	instead have been omitted.
		888
		889	Another common scenario is having some data structure with multiple
		890	watchers:
		891
		892	struct my_biggy
		893	{
		894	int some_data;
		895	ev_timer t1;
		896	ev_timer t2;
		897	}
		898
		899	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		900	you need to use C<offsetof>:
		901
		902	#include <stddef.h>
		903
		904	static void
		905	t1_cb (EV_P_ struct ev_timer *w, int revents)
		906	{
		907	struct my_biggy big = (struct my_biggy *
		908	(((char *)w) - offsetof (struct my_biggy, t1));
		909	}
		910
		911	static void
		912	t2_cb (EV_P_ struct ev_timer *w, int revents)
		913	{
		914	struct my_biggy big = (struct my_biggy *
		915	(((char *)w) - offsetof (struct my_biggy, t2));
		916	}
688		917
689		918
690	=head1 WATCHER TYPES	919	=head1 WATCHER TYPES
691		920
692	This section describes each watcher in detail, but will not repeat	921	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	922	information given in the last section. Any initialisation/set macros,
		923	functions and members specific to the watcher type are explained.
694		924
		925	Members are additionally marked with either I<[read-only]>, meaning that,
		926	while the watcher is active, you can look at the member and expect some
		927	sensible content, but you must not modify it (you can modify it while the
		928	watcher is stopped to your hearts content), or I<[read-write]>, which
		929	means you can expect it to have some sensible content while the watcher
		930	is active, but you can also modify it. Modifying it may not do something
		931	sensible or take immediate effect (or do anything at all), but libev will
		932	not crash or malfunction in any way.
695		933
		934
696	=head2 C<ev_io> - is this file descriptor readable or writable	935	=head2 C<ev_io> - is this file descriptor readable or writable?
697		936
698	I/O watchers check whether a file descriptor is readable or writable	937	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	938	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	939	would not block the process and writing would at least be able to write
701	condition persists. Remember you can stop the watcher if you don't want to	940	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	941	receiving events as long as the condition persists. Remember you can stop
		942	the watcher if you don't want to act on the event and neither want to
		943	receive future events.
703		944
704	In general you can register as many read and/or write event watchers per	945	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	946	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	947	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	948	required if you know what you are doing).
708		949
709	You have to be careful with dup'ed file descriptors, though. Some backends	950	You have to be careful with dup'ed file descriptors, though. Some backends
710	(the linux epoll backend is a notable example) cannot handle dup'ed file	951	(the linux epoll backend is a notable example) cannot handle dup'ed file
711	descriptors correctly if you register interest in two or more fds pointing	952	descriptors correctly if you register interest in two or more fds pointing
712	to the same underlying file/socket etc. description (that is, they share	953	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	954	the same underlying "file open").
714		955
715	If you must do this, then force the use of a known-to-be-good backend	956	If you must do this, then force the use of a known-to-be-good backend
716	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	957	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	958	C<EVBACKEND_POLL>).
718		959
		960	Another thing you have to watch out for is that it is quite easy to
		961	receive "spurious" readyness notifications, that is your callback might
		962	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		963	because there is no data. Not only are some backends known to create a
		964	lot of those (for example solaris ports), it is very easy to get into
		965	this situation even with a relatively standard program structure. Thus
		966	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		967	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		968
		969	If you cannot run the fd in non-blocking mode (for example you should not
		970	play around with an Xlib connection), then you have to seperately re-test
		971	whether a file descriptor is really ready with a known-to-be good interface
		972	such as poll (fortunately in our Xlib example, Xlib already does this on
		973	its own, so its quite safe to use).
		974
		975	=head3 The special problem of disappearing file descriptors
		976
		977	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		978	descriptor (either by calling C<close> explicitly or by any other means,
		979	such as C<dup>). The reason is that you register interest in some file
		980	descriptor, but when it goes away, the operating system will silently drop
		981	this interest. If another file descriptor with the same number then is
		982	registered with libev, there is no efficient way to see that this is, in
		983	fact, a different file descriptor.
		984
		985	To avoid having to explicitly tell libev about such cases, libev follows
		986	the following policy: Each time C<ev_io_set> is being called, libev
		987	will assume that this is potentially a new file descriptor, otherwise
		988	it is assumed that the file descriptor stays the same. That means that
		989	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		990	descriptor even if the file descriptor number itself did not change.
		991
		992	This is how one would do it normally anyway, the important point is that
		993	the libev application should not optimise around libev but should leave
		994	optimisations to libev.
		995
		996	=head3 The special problem of dup'ed file descriptors
		997
		998	Some backends (e.g. epoll), cannot register events for file descriptors,
		999	but only events for the underlying file descriptions. That menas when you
		1000	have C<dup ()>'ed file descriptors and register events for them, only one
		1001	file descriptor might actually receive events.
		1002
		1003	There is no workaorund possible except not registering events
		1004	for potentially C<dup ()>'ed file descriptors or to resort to
		1005	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1006
		1007	=head3 The special problem of fork
		1008
		1009	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1010	useless behaviour. Libev fully supports fork, but needs to be told about
		1011	it in the child.
		1012
		1013	To support fork in your programs, you either have to call
		1014	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1015	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1016	C<EVBACKEND_POLL>.
		1017
		1018
		1019	=head3 Watcher-Specific Functions
		1020
719	=over 4	1021	=over 4
720		1022
721	=item ev_io_init (ev_io *, callback, int fd, int events)	1023	=item ev_io_init (ev_io *, callback, int fd, int events)
722		1024
723	=item ev_io_set (ev_io *, int fd, int events)	1025	=item ev_io_set (ev_io *, int fd, int events)
724		1026
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1027	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
726	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |	1028	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	1029	C<EV_READ | EV_WRITE> to receive the given events.
728		1030
729	Please note that most of the more scalable backend mechanisms (for example	1031	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	1032
731	for file descriptors, so you practically need to use non-blocking I/O (and	1033	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	1034
733	interface before doing I/O (XLib can do this), or force the use of either	1035	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	1036
735	problem. Also note that it is quite easy to have your callback invoked	1037	The events being watched.
736	when the readyness condition is no longer valid even when employing
737	typical ways of handling events, so its a good idea to use non-blocking
738	I/O unconditionally.
739		1038
740	=back	1039	=back
741		1040
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1041	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	1042	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	1043	attempt to read a whole line in the callback.
745		1044
746	static void	1045	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1046	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	1047	{
749	ev_io_stop (loop, w);	1048	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1055	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	1056	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	1057	ev_loop (loop, 0);
759		1058
760		1059
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	1060	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		1061
763	Timer watchers are simple relative timers that generate an event after a	1062	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	1063	given time, and optionally repeating in regular intervals after that.
765		1064
766	The timers are based on real time, that is, if you register an event that	1065	The timers are based on real time, that is, if you register an event that
…		…
779		1078
780	The callback is guarenteed to be invoked only when its timeout has passed,	1079	The callback is guarenteed to be invoked only when its timeout has passed,
781	but if multiple timers become ready during the same loop iteration then	1080	but if multiple timers become ready during the same loop iteration then
782	order of execution is undefined.	1081	order of execution is undefined.
783		1082
		1083	=head3 Watcher-Specific Functions and Data Members
		1084
784	=over 4	1085	=over 4
785		1086
786	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1087	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
787		1088
788	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1089	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
801	=item ev_timer_again (loop)	1102	=item ev_timer_again (loop)
802		1103
803	This will act as if the timer timed out and restart it again if it is	1104	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	1105	repeating. The exact semantics are:
805		1106
		1107	If the timer is pending, its pending status is cleared.
		1108
806	If the timer is started but nonrepeating, stop it.	1109	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1110
808	If the timer is repeating, either start it if necessary (with the repeat	1111	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1112	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1113
811	This sounds a bit complicated, but here is a useful and typical	1114	This sounds a bit complicated, but here is a useful and typical
812	example: Imagine you have a tcp connection and you want a so-called idle	1115	example: Imagine you have a tcp connection and you want a so-called idle
813	timeout, that is, you want to be called when there have been, say, 60	1116	timeout, that is, you want to be called when there have been, say, 60
814	seconds of inactivity on the socket. The easiest way to do this is to	1117	seconds of inactivity on the socket. The easiest way to do this is to
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1118	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
816	time you successfully read or write some data. If you go into an idle	1119	C<ev_timer_again> each time you successfully read or write some data. If
817	state where you do not expect data to travel on the socket, you can stop	1120	you go into an idle state where you do not expect data to travel on the
818	the timer, and again will automatically restart it if need be.	1121	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1122	automatically restart it if need be.
		1123
		1124	That means you can ignore the C<after> value and C<ev_timer_start>
		1125	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1126
		1127	ev_timer_init (timer, callback, 0., 5.);
		1128	ev_timer_again (loop, timer);
		1129	...
		1130	timer->again = 17.;
		1131	ev_timer_again (loop, timer);
		1132	...
		1133	timer->again = 10.;
		1134	ev_timer_again (loop, timer);
		1135
		1136	This is more slightly efficient then stopping/starting the timer each time
		1137	you want to modify its timeout value.
		1138
		1139	=item ev_tstamp repeat [read-write]
		1140
		1141	The current C<repeat> value. Will be used each time the watcher times out
		1142	or C<ev_timer_again> is called and determines the next timeout (if any),
		1143	which is also when any modifications are taken into account.
819		1144
820	=back	1145	=back
821		1146
822	Example: create a timer that fires after 60 seconds.	1147	Example: Create a timer that fires after 60 seconds.
823		1148
824	static void	1149	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1150	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1151	{
827	.. one minute over, w is actually stopped right here	1152	.. one minute over, w is actually stopped right here
…		…
829		1154
830	struct ev_timer mytimer;	1155	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1156	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1157	ev_timer_start (loop, &mytimer);
833		1158
834	Example: create a timeout timer that times out after 10 seconds of	1159	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1160	inactivity.
836		1161
837	static void	1162	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1163	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1164	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1173	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1174	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1175	ev_timer_again (&mytimer);
851		1176
852		1177
853	=head2 C<ev_periodic> - to cron or not to cron	1178	=head2 C<ev_periodic> - to cron or not to cron?
854		1179
855	Periodic watchers are also timers of a kind, but they are very versatile	1180	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1181	(and unfortunately a bit complex).
857		1182
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1183	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
859	but on wallclock time (absolute time). You can tell a periodic watcher	1184	but on wallclock time (absolute time). You can tell a periodic watcher
860	to trigger "at" some specific point in time. For example, if you tell a	1185	to trigger "at" some specific point in time. For example, if you tell a
861	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	1186	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
862	+ 10.>) and then reset your system clock to the last year, then it will	1187	+ 10.>) and then reset your system clock to the last year, then it will
863	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1188	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
864	roughly 10 seconds later and of course not if you reset your system time	1189	roughly 10 seconds later).
865	again).
866		1190
867	They can also be used to implement vastly more complex timers, such as	1191	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1192	triggering an event on each midnight, local time or other, complicated,
		1193	rules.
869		1194
870	As with timers, the callback is guarenteed to be invoked only when the	1195	As with timers, the callback is guarenteed to be invoked only when the
871	time (C<at>) has been passed, but if multiple periodic timers become ready	1196	time (C<at>) has been passed, but if multiple periodic timers become ready
872	during the same loop iteration then order of execution is undefined.	1197	during the same loop iteration then order of execution is undefined.
873		1198
		1199	=head3 Watcher-Specific Functions and Data Members
		1200
874	=over 4	1201	=over 4
875		1202
876	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1203	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
877		1204
878	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1205	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
880	Lots of arguments, lets sort it out... There are basically three modes of	1207	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1208	operation, and we will explain them from simplest to complex:
882		1209
883	=over 4	1210	=over 4
884		1211
885	=item * absolute timer (interval = reschedule_cb = 0)	1212	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1213
887	In this configuration the watcher triggers an event at the wallclock time	1214	In this configuration the watcher triggers an event at the wallclock time
888	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1215	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
889	that is, if it is to be run at January 1st 2011 then it will run when the	1216	that is, if it is to be run at January 1st 2011 then it will run when the
890	system time reaches or surpasses this time.	1217	system time reaches or surpasses this time.
891		1218
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1219	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1220
894	In this mode the watcher will always be scheduled to time out at the next	1221	In this mode the watcher will always be scheduled to time out at the next
895	C<at + N * interval> time (for some integer N) and then repeat, regardless	1222	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1223	and then repeat, regardless of any time jumps.
897		1224
898	This can be used to create timers that do not drift with respect to system	1225	This can be used to create timers that do not drift with respect to system
899	time:	1226	time:
900		1227
901	ev_periodic_set (&periodic, 0., 3600., 0);	1228	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1234
908	Another way to think about it (for the mathematically inclined) is that	1235	Another way to think about it (for the mathematically inclined) is that
909	C<ev_periodic> will try to run the callback in this mode at the next possible	1236	C<ev_periodic> will try to run the callback in this mode at the next possible
910	time where C<time = at (mod interval)>, regardless of any time jumps.	1237	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1238
		1239	For numerical stability it is preferable that the C<at> value is near
		1240	C<ev_now ()> (the current time), but there is no range requirement for
		1241	this value.
		1242
912	=item * manual reschedule mode (reschedule_cb = callback)	1243	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1244
914	In this mode the values for C<interval> and C<at> are both being	1245	In this mode the values for C<interval> and C<at> are both being
915	ignored. Instead, each time the periodic watcher gets scheduled, the	1246	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1247	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1248	current time as second argument.
918		1249
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1250	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
920	ever, or make any event loop modifications>. If you need to stop it,	1251	ever, or make any event loop modifications>. If you need to stop it,
921	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1252	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1253	starting an C<ev_prepare> watcher, which is legal).
923		1254
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1255	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1256	ev_tstamp now)>, e.g.:
926		1257
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1258	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1281	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1282	when you changed some parameters or the reschedule callback would return
952	a different time than the last time it was called (e.g. in a crond like	1283	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1284	program when the crontabs have changed).
954		1285
		1286	=item ev_tstamp offset [read-write]
		1287
		1288	When repeating, this contains the offset value, otherwise this is the
		1289	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1290
		1291	Can be modified any time, but changes only take effect when the periodic
		1292	timer fires or C<ev_periodic_again> is being called.
		1293
		1294	=item ev_tstamp interval [read-write]
		1295
		1296	The current interval value. Can be modified any time, but changes only
		1297	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1298	called.
		1299
		1300	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1301
		1302	The current reschedule callback, or C<0>, if this functionality is
		1303	switched off. Can be changed any time, but changes only take effect when
		1304	the periodic timer fires or C<ev_periodic_again> is being called.
		1305
		1306	=item ev_tstamp at [read-only]
		1307
		1308	When active, contains the absolute time that the watcher is supposed to
		1309	trigger next.
		1310
955	=back	1311	=back
956		1312
957	Example: call a callback every hour, or, more precisely, whenever the	1313	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1314	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1315	potentially a lot of jittering, but good long-term stability.
960		1316
961	static void	1317	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1318	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1322
967	struct ev_periodic hourly_tick;	1323	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1324	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1325	ev_periodic_start (loop, &hourly_tick);
970		1326
971	Example: the same as above, but use a reschedule callback to do it:	1327	Example: The same as above, but use a reschedule callback to do it:
972		1328
973	#include <math.h>	1329	#include <math.h>
974		1330
975	static ev_tstamp	1331	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1332	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1334	return fmod (now, 3600.) + 3600.;
979	}	1335	}
980		1336
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1337	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1338
983	Example: call a callback every hour, starting now:	1339	Example: Call a callback every hour, starting now:
984		1340
985	struct ev_periodic hourly_tick;	1341	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1342	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1343	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1344	ev_periodic_start (loop, &hourly_tick);
989		1345
990		1346
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1347	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1348
993	Signal watchers will trigger an event when the process receives a specific	1349	Signal watchers will trigger an event when the process receives a specific
994	signal one or more times. Even though signals are very asynchronous, libev	1350	signal one or more times. Even though signals are very asynchronous, libev
995	will try it's best to deliver signals synchronously, i.e. as part of the	1351	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1352	normal event processing, like any other event.
…		…
1000	with the kernel (thus it coexists with your own signal handlers as long	1356	with the kernel (thus it coexists with your own signal handlers as long
1001	as you don't register any with libev). Similarly, when the last signal	1357	as you don't register any with libev). Similarly, when the last signal
1002	watcher for a signal is stopped libev will reset the signal handler to	1358	watcher for a signal is stopped libev will reset the signal handler to
1003	SIG_DFL (regardless of what it was set to before).	1359	SIG_DFL (regardless of what it was set to before).
1004		1360
		1361	=head3 Watcher-Specific Functions and Data Members
		1362
1005	=over 4	1363	=over 4
1006		1364
1007	=item ev_signal_init (ev_signal *, callback, int signum)	1365	=item ev_signal_init (ev_signal *, callback, int signum)
1008		1366
1009	=item ev_signal_set (ev_signal *, int signum)	1367	=item ev_signal_set (ev_signal *, int signum)
1010		1368
1011	Configures the watcher to trigger on the given signal number (usually one	1369	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1370	of the C<SIGxxx> constants).
1013		1371
		1372	=item int signum [read-only]
		1373
		1374	The signal the watcher watches out for.
		1375
1014	=back	1376	=back
1015		1377
1016		1378
1017	=head2 C<ev_child> - wait for pid status changes	1379	=head2 C<ev_child> - watch out for process status changes
1018		1380
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1381	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1382	some child status changes (most typically when a child of yours dies).
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
1021		1385
1022	=over 4	1386	=over 4
1023		1387
1024	=item ev_child_init (ev_child *, callback, int pid)	1388	=item ev_child_init (ev_child *, callback, int pid)
1025		1389
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1394	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1395	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1396	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1397	process causing the status change.
1034		1398
		1399	=item int pid [read-only]
		1400
		1401	The process id this watcher watches out for, or C<0>, meaning any process id.
		1402
		1403	=item int rpid [read-write]
		1404
		1405	The process id that detected a status change.
		1406
		1407	=item int rstatus [read-write]
		1408
		1409	The process exit/trace status caused by C<rpid> (see your systems
		1410	C<waitpid> and C<sys/wait.h> documentation for details).
		1411
1035	=back	1412	=back
1036		1413
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1414	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1415
1039	static void	1416	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1417	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1418	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1419	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1422	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1423	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1424	ev_signal_start (loop, &sigint_cb);
1048		1425
1049		1426
		1427	=head2 C<ev_stat> - did the file attributes just change?
		1428
		1429	This watches a filesystem path for attribute changes. That is, it calls
		1430	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1431	compared to the last time, invoking the callback if it did.
		1432
		1433	The path does not need to exist: changing from "path exists" to "path does
		1434	not exist" is a status change like any other. The condition "path does
		1435	not exist" is signified by the C<st_nlink> field being zero (which is
		1436	otherwise always forced to be at least one) and all the other fields of
		1437	the stat buffer having unspecified contents.
		1438
		1439	The path I<should> be absolute and I<must not> end in a slash. If it is
		1440	relative and your working directory changes, the behaviour is undefined.
		1441
		1442	Since there is no standard to do this, the portable implementation simply
		1443	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1444	can specify a recommended polling interval for this case. If you specify
		1445	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1446	unspecified default> value will be used (which you can expect to be around
		1447	five seconds, although this might change dynamically). Libev will also
		1448	impose a minimum interval which is currently around C<0.1>, but thats
		1449	usually overkill.
		1450
		1451	This watcher type is not meant for massive numbers of stat watchers,
		1452	as even with OS-supported change notifications, this can be
		1453	resource-intensive.
		1454
		1455	At the time of this writing, only the Linux inotify interface is
		1456	implemented (implementing kqueue support is left as an exercise for the
		1457	reader). Inotify will be used to give hints only and should not change the
		1458	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1459	to fall back to regular polling again even with inotify, but changes are
		1460	usually detected immediately, and if the file exists there will be no
		1461	polling.
		1462
		1463	=head3 Watcher-Specific Functions and Data Members
		1464
		1465	=over 4
		1466
		1467	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1468
		1469	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1470
		1471	Configures the watcher to wait for status changes of the given
		1472	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1473	be detected and should normally be specified as C<0> to let libev choose
		1474	a suitable value. The memory pointed to by C<path> must point to the same
		1475	path for as long as the watcher is active.
		1476
		1477	The callback will be receive C<EV_STAT> when a change was detected,
		1478	relative to the attributes at the time the watcher was started (or the
		1479	last change was detected).
		1480
		1481	=item ev_stat_stat (ev_stat *)
		1482
		1483	Updates the stat buffer immediately with new values. If you change the
		1484	watched path in your callback, you could call this fucntion to avoid
		1485	detecting this change (while introducing a race condition). Can also be
		1486	useful simply to find out the new values.
		1487
		1488	=item ev_statdata attr [read-only]
		1489
		1490	The most-recently detected attributes of the file. Although the type is of
		1491	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1492	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1493	was some error while C<stat>ing the file.
		1494
		1495	=item ev_statdata prev [read-only]
		1496
		1497	The previous attributes of the file. The callback gets invoked whenever
		1498	C<prev> != C<attr>.
		1499
		1500	=item ev_tstamp interval [read-only]
		1501
		1502	The specified interval.
		1503
		1504	=item const char *path [read-only]
		1505
		1506	The filesystem path that is being watched.
		1507
		1508	=back
		1509
		1510	Example: Watch C</etc/passwd> for attribute changes.
		1511
		1512	static void
		1513	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1514	{
		1515	/* /etc/passwd changed in some way */
		1516	if (w->attr.st_nlink)
		1517	{
		1518	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1519	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1520	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1521	}
		1522	else
		1523	/* you shalt not abuse printf for puts */
		1524	puts ("wow, /etc/passwd is not there, expect problems. "
		1525	"if this is windows, they already arrived\n");
		1526	}
		1527
		1528	...
		1529	ev_stat passwd;
		1530
		1531	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1532	ev_stat_start (loop, &passwd);
		1533
		1534
1050	=head2 C<ev_idle> - when you've got nothing better to do	1535	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1536
1052	Idle watchers trigger events when there are no other events are pending	1537	Idle watchers trigger events when no other events of the same or higher
1053	(prepare, check and other idle watchers do not count). That is, as long	1538	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1539	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1540
1056	watchers are being called again and again, once per event loop iteration -	1541	That is, as long as your process is busy handling sockets or timeouts
		1542	(or even signals, imagine) of the same or higher priority it will not be
		1543	triggered. But when your process is idle (or only lower-priority watchers
		1544	are pending), the idle watchers are being called once per event loop
1057	until stopped, that is, or your process receives more events and becomes	1545	iteration - until stopped, that is, or your process receives more events
1058	busy.	1546	and becomes busy again with higher priority stuff.
1059		1547
1060	The most noteworthy effect is that as long as any idle watchers are	1548	The most noteworthy effect is that as long as any idle watchers are
1061	active, the process will not block when waiting for new events.	1549	active, the process will not block when waiting for new events.
1062		1550
1063	Apart from keeping your process non-blocking (which is a useful	1551	Apart from keeping your process non-blocking (which is a useful
1064	effect on its own sometimes), idle watchers are a good place to do	1552	effect on its own sometimes), idle watchers are a good place to do
1065	"pseudo-background processing", or delay processing stuff to after the	1553	"pseudo-background processing", or delay processing stuff to after the
1066	event loop has handled all outstanding events.	1554	event loop has handled all outstanding events.
1067		1555
		1556	=head3 Watcher-Specific Functions and Data Members
		1557
1068	=over 4	1558	=over 4
1069		1559
1070	=item ev_idle_init (ev_signal *, callback)	1560	=item ev_idle_init (ev_signal *, callback)
1071		1561
1072	Initialises and configures the idle watcher - it has no parameters of any	1562	Initialises and configures the idle watcher - it has no parameters of any
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1563	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1564	believe me.
1075		1565
1076	=back	1566	=back
1077		1567
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1568	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1569	callback, free it. Also, use no error checking, as usual.
1080		1570
1081	static void	1571	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1572	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1573	{
1084	free (w);	1574	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1579	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1580	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1581	ev_idle_start (loop, idle_cb);
1092		1582
1093		1583
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1584	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1585
1096	Prepare and check watchers are usually (but not always) used in tandem:	1586	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1587	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1588	afterwards.
1099		1589
		1590	You I<must not> call C<ev_loop> or similar functions that enter
		1591	the current event loop from either C<ev_prepare> or C<ev_check>
		1592	watchers. Other loops than the current one are fine, however. The
		1593	rationale behind this is that you do not need to check for recursion in
		1594	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1595	C<ev_check> so if you have one watcher of each kind they will always be
		1596	called in pairs bracketing the blocking call.
		1597
1100	Their main purpose is to integrate other event mechanisms into libev and	1598	Their main purpose is to integrate other event mechanisms into libev and
1101	their use is somewhat advanced. This could be used, for example, to track	1599	their use is somewhat advanced. This could be used, for example, to track
1102	variable changes, implement your own watchers, integrate net-snmp or a	1600	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1601	coroutine library and lots more. They are also occasionally useful if
		1602	you cache some data and want to flush it before blocking (for example,
		1603	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1604	watcher).
1104		1605
1105	This is done by examining in each prepare call which file descriptors need	1606	This is done by examining in each prepare call which file descriptors need
1106	to be watched by the other library, registering C<ev_io> watchers for	1607	to be watched by the other library, registering C<ev_io> watchers for
1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1608	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1108	provide just this functionality). Then, in the check watcher you check for	1609	provide just this functionality). Then, in the check watcher you check for
…		…
1118	with priority higher than or equal to the event loop and one coroutine	1619	with priority higher than or equal to the event loop and one coroutine
1119	of lower priority, but only once, using idle watchers to keep the event	1620	of lower priority, but only once, using idle watchers to keep the event
1120	loop from blocking if lower-priority coroutines are active, thus mapping	1621	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1622	low-priority coroutines to idle/background tasks).
1122		1623
		1624	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1625	priority, to ensure that they are being run before any other watchers
		1626	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1627	too) should not activate ("feed") events into libev. While libev fully
		1628	supports this, they will be called before other C<ev_check> watchers did
		1629	their job. As C<ev_check> watchers are often used to embed other event
		1630	loops those other event loops might be in an unusable state until their
		1631	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1632	others).
		1633
		1634	=head3 Watcher-Specific Functions and Data Members
		1635
1123	=over 4	1636	=over 4
1124		1637
1125	=item ev_prepare_init (ev_prepare *, callback)	1638	=item ev_prepare_init (ev_prepare *, callback)
1126		1639
1127	=item ev_check_init (ev_check *, callback)	1640	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1643	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1644	macros, but using them is utterly, utterly and completely pointless.
1132		1645
1133	=back	1646	=back
1134		1647
1135	Example: *TODO*.	1648	There are a number of principal ways to embed other event loops or modules
		1649	into libev. Here are some ideas on how to include libadns into libev
		1650	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1651	use for an actually working example. Another Perl module named C<EV::Glib>
		1652	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1653	into the Glib event loop).
1136		1654
		1655	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1656	and in a check watcher, destroy them and call into libadns. What follows
		1657	is pseudo-code only of course. This requires you to either use a low
		1658	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1659	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1660
		1661	static ev_io iow [nfd];
		1662	static ev_timer tw;
		1663
		1664	static void
		1665	io_cb (ev_loop *loop, ev_io *w, int revents)
		1666	{
		1667	}
		1668
		1669	// create io watchers for each fd and a timer before blocking
		1670	static void
		1671	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1672	{
		1673	int timeout = 3600000;
		1674	struct pollfd fds [nfd];
		1675	// actual code will need to loop here and realloc etc.
		1676	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1677
		1678	/* the callback is illegal, but won't be called as we stop during check */
		1679	ev_timer_init (&tw, 0, timeout * 1e-3);
		1680	ev_timer_start (loop, &tw);
		1681
		1682	// create one ev_io per pollfd
		1683	for (int i = 0; i < nfd; ++i)
		1684	{
		1685	ev_io_init (iow + i, io_cb, fds [i].fd,
		1686	((fds [i].events & POLLIN ? EV_READ : 0)
		1687	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1688
		1689	fds [i].revents = 0;
		1690	ev_io_start (loop, iow + i);
		1691	}
		1692	}
		1693
		1694	// stop all watchers after blocking
		1695	static void
		1696	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1697	{
		1698	ev_timer_stop (loop, &tw);
		1699
		1700	for (int i = 0; i < nfd; ++i)
		1701	{
		1702	// set the relevant poll flags
		1703	// could also call adns_processreadable etc. here
		1704	struct pollfd *fd = fds + i;
		1705	int revents = ev_clear_pending (iow + i);
		1706	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1707	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1708
		1709	// now stop the watcher
		1710	ev_io_stop (loop, iow + i);
		1711	}
		1712
		1713	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1714	}
		1715
		1716	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1717	in the prepare watcher and would dispose of the check watcher.
		1718
		1719	Method 3: If the module to be embedded supports explicit event
		1720	notification (adns does), you can also make use of the actual watcher
		1721	callbacks, and only destroy/create the watchers in the prepare watcher.
		1722
		1723	static void
		1724	timer_cb (EV_P_ ev_timer *w, int revents)
		1725	{
		1726	adns_state ads = (adns_state)w->data;
		1727	update_now (EV_A);
		1728
		1729	adns_processtimeouts (ads, &tv_now);
		1730	}
		1731
		1732	static void
		1733	io_cb (EV_P_ ev_io *w, int revents)
		1734	{
		1735	adns_state ads = (adns_state)w->data;
		1736	update_now (EV_A);
		1737
		1738	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1739	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1740	}
		1741
		1742	// do not ever call adns_afterpoll
		1743
		1744	Method 4: Do not use a prepare or check watcher because the module you
		1745	want to embed is too inflexible to support it. Instead, youc na override
		1746	their poll function. The drawback with this solution is that the main
		1747	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1748	this.
		1749
		1750	static gint
		1751	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1752	{
		1753	int got_events = 0;
		1754
		1755	for (n = 0; n < nfds; ++n)
		1756	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1757
		1758	if (timeout >= 0)
		1759	// create/start timer
		1760
		1761	// poll
		1762	ev_loop (EV_A_ 0);
		1763
		1764	// stop timer again
		1765	if (timeout >= 0)
		1766	ev_timer_stop (EV_A_ &to);
		1767
		1768	// stop io watchers again - their callbacks should have set
		1769	for (n = 0; n < nfds; ++n)
		1770	ev_io_stop (EV_A_ iow [n]);
		1771
		1772	return got_events;
		1773	}
		1774
		1775
1138	=head2 C<ev_embed> - when one backend isn't enough	1776	=head2 C<ev_embed> - when one backend isn't enough...
1139		1777
1140	This is a rather advanced watcher type that lets you embed one event loop	1778	This is a rather advanced watcher type that lets you embed one event loop
1141	into another (currently only C<ev_io> events are supported in the embedded	1779	into another (currently only C<ev_io> events are supported in the embedded
1142	loop, other types of watchers might be handled in a delayed or incorrect	1780	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1781	fashion and must not be used). (See portability notes, below).
1144		1782
1145	There are primarily two reasons you would want that: work around bugs and	1783	There are primarily two reasons you would want that: work around bugs and
1146	prioritise I/O.	1784	prioritise I/O.
1147		1785
1148	As an example for a bug workaround, the kqueue backend might only support	1786	As an example for a bug workaround, the kqueue backend might only support
…		…
1203	ev_embed_start (loop_hi, &embed);	1841	ev_embed_start (loop_hi, &embed);
1204	}	1842	}
1205	else	1843	else
1206	loop_lo = loop_hi;	1844	loop_lo = loop_hi;
1207		1845
		1846	=head2 Portability notes
		1847
		1848	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1849	tried, in various ways. Usually the embedded event loop will simply never
		1850	receive events, sometimes it will only trigger a few times, sometimes in a
		1851	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1852	will always eport the epoll fd as ready, even when no events are pending.
		1853
		1854	While libev allows embedding these backends (they are contained in
		1855	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1856	work.
		1857
		1858	When in doubt, create a dynamic event loop forced to use sockets (this
		1859	usually works) and possibly another thread and a pipe or so to report to
		1860	your main event loop.
		1861
		1862	=head3 Watcher-Specific Functions and Data Members
		1863
1208	=over 4	1864	=over 4
1209		1865
1210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1866	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1211		1867
1212	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	1868	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1221		1877
1222	Make a single, non-blocking sweep over the embedded loop. This works	1878	Make a single, non-blocking sweep over the embedded loop. This works
1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1879	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1880	apropriate way for embedded loops.
1225		1881
		1882	=item struct ev_loop *other [read-only]
		1883
		1884	The embedded event loop.
		1885
		1886	=back
		1887
		1888
		1889	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1890
		1891	Fork watchers are called when a C<fork ()> was detected (usually because
		1892	whoever is a good citizen cared to tell libev about it by calling
		1893	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1894	event loop blocks next and before C<ev_check> watchers are being called,
		1895	and only in the child after the fork. If whoever good citizen calling
		1896	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1897	handlers will be invoked, too, of course.
		1898
		1899	=head3 Watcher-Specific Functions and Data Members
		1900
		1901	=over 4
		1902
		1903	=item ev_fork_init (ev_signal *, callback)
		1904
		1905	Initialises and configures the fork watcher - it has no parameters of any
		1906	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1907	believe me.
		1908
1226	=back	1909	=back
1227		1910
1228		1911
1229	=head1 OTHER FUNCTIONS	1912	=head1 OTHER FUNCTIONS
1230		1913
…		…
1310		1993
1311	=back	1994	=back
1312		1995
1313	=head1 C++ SUPPORT	1996	=head1 C++ SUPPORT
1314		1997
1315	TBD.	1998	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1999	you to use some convinience methods to start/stop watchers and also change
		2000	the callback model to a model using method callbacks on objects.
		2001
		2002	To use it,
		2003
		2004	#include <ev++.h>
		2005
		2006	This automatically includes F<ev.h> and puts all of its definitions (many
		2007	of them macros) into the global namespace. All C++ specific things are
		2008	put into the C<ev> namespace. It should support all the same embedding
		2009	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
		2010
		2011	Care has been taken to keep the overhead low. The only data member the C++
		2012	classes add (compared to plain C-style watchers) is the event loop pointer
		2013	that the watcher is associated with (or no additional members at all if
		2014	you disable C<EV_MULTIPLICITY> when embedding libev).
		2015
		2016	Currently, functions, and static and non-static member functions can be
		2017	used as callbacks. Other types should be easy to add as long as they only
		2018	need one additional pointer for context. If you need support for other
		2019	types of functors please contact the author (preferably after implementing
		2020	it).
		2021
		2022	Here is a list of things available in the C<ev> namespace:
		2023
		2024	=over 4
		2025
		2026	=item C<ev::READ>, C<ev::WRITE> etc.
		2027
		2028	These are just enum values with the same values as the C<EV_READ> etc.
		2029	macros from F<ev.h>.
		2030
		2031	=item C<ev::tstamp>, C<ev::now>
		2032
		2033	Aliases to the same types/functions as with the C<ev_> prefix.
		2034
		2035	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		2036
		2037	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		2038	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		2039	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		2040	defines by many implementations.
		2041
		2042	All of those classes have these methods:
		2043
		2044	=over 4
		2045
		2046	=item ev::TYPE::TYPE ()
		2047
		2048	=item ev::TYPE::TYPE (struct ev_loop *)
		2049
		2050	=item ev::TYPE::~TYPE
		2051
		2052	The constructor (optionally) takes an event loop to associate the watcher
		2053	with. If it is omitted, it will use C<EV_DEFAULT>.
		2054
		2055	The constructor calls C<ev_init> for you, which means you have to call the
		2056	C<set> method before starting it.
		2057
		2058	It will not set a callback, however: You have to call the templated C<set>
		2059	method to set a callback before you can start the watcher.
		2060
		2061	(The reason why you have to use a method is a limitation in C++ which does
		2062	not allow explicit template arguments for constructors).
		2063
		2064	The destructor automatically stops the watcher if it is active.
		2065
		2066	=item w->set<class, &class::method> (object *)
		2067
		2068	This method sets the callback method to call. The method has to have a
		2069	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2070	first argument and the C<revents> as second. The object must be given as
		2071	parameter and is stored in the C<data> member of the watcher.
		2072
		2073	This method synthesizes efficient thunking code to call your method from
		2074	the C callback that libev requires. If your compiler can inline your
		2075	callback (i.e. it is visible to it at the place of the C<set> call and
		2076	your compiler is good :), then the method will be fully inlined into the
		2077	thunking function, making it as fast as a direct C callback.
		2078
		2079	Example: simple class declaration and watcher initialisation
		2080
		2081	struct myclass
		2082	{
		2083	void io_cb (ev::io &w, int revents) { }
		2084	}
		2085
		2086	myclass obj;
		2087	ev::io iow;
		2088	iow.set <myclass, &myclass::io_cb> (&obj);
		2089
		2090	=item w->set<function> (void *data = 0)
		2091
		2092	Also sets a callback, but uses a static method or plain function as
		2093	callback. The optional C<data> argument will be stored in the watcher's
		2094	C<data> member and is free for you to use.
		2095
		2096	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2097
		2098	See the method-C<set> above for more details.
		2099
		2100	Example:
		2101
		2102	static void io_cb (ev::io &w, int revents) { }
		2103	iow.set <io_cb> ();
		2104
		2105	=item w->set (struct ev_loop *)
		2106
		2107	Associates a different C<struct ev_loop> with this watcher. You can only
		2108	do this when the watcher is inactive (and not pending either).
		2109
		2110	=item w->set ([args])
		2111
		2112	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		2113	called at least once. Unlike the C counterpart, an active watcher gets
		2114	automatically stopped and restarted when reconfiguring it with this
		2115	method.
		2116
		2117	=item w->start ()
		2118
		2119	Starts the watcher. Note that there is no C<loop> argument, as the
		2120	constructor already stores the event loop.
		2121
		2122	=item w->stop ()
		2123
		2124	Stops the watcher if it is active. Again, no C<loop> argument.
		2125
		2126	=item w->again () (C<ev::timer>, C<ev::periodic> only)
		2127
		2128	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		2129	C<ev_TYPE_again> function.
		2130
		2131	=item w->sweep () (C<ev::embed> only)
		2132
		2133	Invokes C<ev_embed_sweep>.
		2134
		2135	=item w->update () (C<ev::stat> only)
		2136
		2137	Invokes C<ev_stat_stat>.
		2138
		2139	=back
		2140
		2141	=back
		2142
		2143	Example: Define a class with an IO and idle watcher, start one of them in
		2144	the constructor.
		2145
		2146	class myclass
		2147	{
		2148	ev_io io; void io_cb (ev::io &w, int revents);
		2149	ev_idle idle void idle_cb (ev::idle &w, int revents);
		2150
		2151	myclass ();
		2152	}
		2153
		2154	myclass::myclass (int fd)
		2155	{
		2156	io .set <myclass, &myclass::io_cb > (this);
		2157	idle.set <myclass, &myclass::idle_cb> (this);
		2158
		2159	io.start (fd, ev::READ);
		2160	}
		2161
		2162
		2163	=head1 MACRO MAGIC
		2164
		2165	Libev can be compiled with a variety of options, the most fundamantal
		2166	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2167	functions and callbacks have an initial C<struct ev_loop *> argument.
		2168
		2169	To make it easier to write programs that cope with either variant, the
		2170	following macros are defined:
		2171
		2172	=over 4
		2173
		2174	=item C<EV_A>, C<EV_A_>
		2175
		2176	This provides the loop I<argument> for functions, if one is required ("ev
		2177	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2178	C<EV_A_> is used when other arguments are following. Example:
		2179
		2180	ev_unref (EV_A);
		2181	ev_timer_add (EV_A_ watcher);
		2182	ev_loop (EV_A_ 0);
		2183
		2184	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2185	which is often provided by the following macro.
		2186
		2187	=item C<EV_P>, C<EV_P_>
		2188
		2189	This provides the loop I<parameter> for functions, if one is required ("ev
		2190	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2191	C<EV_P_> is used when other parameters are following. Example:
		2192
		2193	// this is how ev_unref is being declared
		2194	static void ev_unref (EV_P);
		2195
		2196	// this is how you can declare your typical callback
		2197	static void cb (EV_P_ ev_timer *w, int revents)
		2198
		2199	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2200	suitable for use with C<EV_A>.
		2201
		2202	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2203
		2204	Similar to the other two macros, this gives you the value of the default
		2205	loop, if multiple loops are supported ("ev loop default").
		2206
		2207	=back
		2208
		2209	Example: Declare and initialise a check watcher, utilising the above
		2210	macros so it will work regardless of whether multiple loops are supported
		2211	or not.
		2212
		2213	static void
		2214	check_cb (EV_P_ ev_timer *w, int revents)
		2215	{
		2216	ev_check_stop (EV_A_ w);
		2217	}
		2218
		2219	ev_check check;
		2220	ev_check_init (&check, check_cb);
		2221	ev_check_start (EV_DEFAULT_ &check);
		2222	ev_loop (EV_DEFAULT_ 0);
		2223
		2224	=head1 EMBEDDING
		2225
		2226	Libev can (and often is) directly embedded into host
		2227	applications. Examples of applications that embed it include the Deliantra
		2228	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
		2229	and rxvt-unicode.
		2230
		2231	The goal is to enable you to just copy the necessary files into your
		2232	source directory without having to change even a single line in them, so
		2233	you can easily upgrade by simply copying (or having a checked-out copy of
		2234	libev somewhere in your source tree).
		2235
		2236	=head2 FILESETS
		2237
		2238	Depending on what features you need you need to include one or more sets of files
		2239	in your app.
		2240
		2241	=head3 CORE EVENT LOOP
		2242
		2243	To include only the libev core (all the C<ev_*> functions), with manual
		2244	configuration (no autoconf):
		2245
		2246	#define EV_STANDALONE 1
		2247	#include "ev.c"
		2248
		2249	This will automatically include F<ev.h>, too, and should be done in a
		2250	single C source file only to provide the function implementations. To use
		2251	it, do the same for F<ev.h> in all files wishing to use this API (best
		2252	done by writing a wrapper around F<ev.h> that you can include instead and
		2253	where you can put other configuration options):
		2254
		2255	#define EV_STANDALONE 1
		2256	#include "ev.h"
		2257
		2258	Both header files and implementation files can be compiled with a C++
		2259	compiler (at least, thats a stated goal, and breakage will be treated
		2260	as a bug).
		2261
		2262	You need the following files in your source tree, or in a directory
		2263	in your include path (e.g. in libev/ when using -Ilibev):
		2264
		2265	ev.h
		2266	ev.c
		2267	ev_vars.h
		2268	ev_wrap.h
		2269
		2270	ev_win32.c required on win32 platforms only
		2271
		2272	ev_select.c only when select backend is enabled (which is enabled by default)
		2273	ev_poll.c only when poll backend is enabled (disabled by default)
		2274	ev_epoll.c only when the epoll backend is enabled (disabled by default)
		2275	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
		2276	ev_port.c only when the solaris port backend is enabled (disabled by default)
		2277
		2278	F<ev.c> includes the backend files directly when enabled, so you only need
		2279	to compile this single file.
		2280
		2281	=head3 LIBEVENT COMPATIBILITY API
		2282
		2283	To include the libevent compatibility API, also include:
		2284
		2285	#include "event.c"
		2286
		2287	in the file including F<ev.c>, and:
		2288
		2289	#include "event.h"
		2290
		2291	in the files that want to use the libevent API. This also includes F<ev.h>.
		2292
		2293	You need the following additional files for this:
		2294
		2295	event.h
		2296	event.c
		2297
		2298	=head3 AUTOCONF SUPPORT
		2299
		2300	Instead of using C<EV_STANDALONE=1> and providing your config in
		2301	whatever way you want, you can also C<m4_include([libev.m4])> in your
		2302	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
		2303	include F<config.h> and configure itself accordingly.
		2304
		2305	For this of course you need the m4 file:
		2306
		2307	libev.m4
		2308
		2309	=head2 PREPROCESSOR SYMBOLS/MACROS
		2310
		2311	Libev can be configured via a variety of preprocessor symbols you have to define
		2312	before including any of its files. The default is not to build for multiplicity
		2313	and only include the select backend.
		2314
		2315	=over 4
		2316
		2317	=item EV_STANDALONE
		2318
		2319	Must always be C<1> if you do not use autoconf configuration, which
		2320	keeps libev from including F<config.h>, and it also defines dummy
		2321	implementations for some libevent functions (such as logging, which is not
		2322	supported). It will also not define any of the structs usually found in
		2323	F<event.h> that are not directly supported by the libev core alone.
		2324
		2325	=item EV_USE_MONOTONIC
		2326
		2327	If defined to be C<1>, libev will try to detect the availability of the
		2328	monotonic clock option at both compiletime and runtime. Otherwise no use
		2329	of the monotonic clock option will be attempted. If you enable this, you
		2330	usually have to link against librt or something similar. Enabling it when
		2331	the functionality isn't available is safe, though, although you have
		2332	to make sure you link against any libraries where the C<clock_gettime>
		2333	function is hiding in (often F<-lrt>).
		2334
		2335	=item EV_USE_REALTIME
		2336
		2337	If defined to be C<1>, libev will try to detect the availability of the
		2338	realtime clock option at compiletime (and assume its availability at
		2339	runtime if successful). Otherwise no use of the realtime clock option will
		2340	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
		2341	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
		2342	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2343
		2344	=item EV_USE_NANOSLEEP
		2345
		2346	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2347	and will use it for delays. Otherwise it will use C<select ()>.
		2348
		2349	=item EV_USE_SELECT
		2350
		2351	If undefined or defined to be C<1>, libev will compile in support for the
		2352	C<select>(2) backend. No attempt at autodetection will be done: if no
		2353	other method takes over, select will be it. Otherwise the select backend
		2354	will not be compiled in.
		2355
		2356	=item EV_SELECT_USE_FD_SET
		2357
		2358	If defined to C<1>, then the select backend will use the system C<fd_set>
		2359	structure. This is useful if libev doesn't compile due to a missing
		2360	C<NFDBITS> or C<fd_mask> definition or it misguesses the bitset layout on
		2361	exotic systems. This usually limits the range of file descriptors to some
		2362	low limit such as 1024 or might have other limitations (winsocket only
		2363	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might
		2364	influence the size of the C<fd_set> used.
		2365
		2366	=item EV_SELECT_IS_WINSOCKET
		2367
		2368	When defined to C<1>, the select backend will assume that
		2369	select/socket/connect etc. don't understand file descriptors but
		2370	wants osf handles on win32 (this is the case when the select to
		2371	be used is the winsock select). This means that it will call
		2372	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
		2373	it is assumed that all these functions actually work on fds, even
		2374	on win32. Should not be defined on non-win32 platforms.
		2375
		2376	=item EV_USE_POLL
		2377
		2378	If defined to be C<1>, libev will compile in support for the C<poll>(2)
		2379	backend. Otherwise it will be enabled on non-win32 platforms. It
		2380	takes precedence over select.
		2381
		2382	=item EV_USE_EPOLL
		2383
		2384	If defined to be C<1>, libev will compile in support for the Linux
		2385	C<epoll>(7) backend. Its availability will be detected at runtime,
		2386	otherwise another method will be used as fallback. This is the
		2387	preferred backend for GNU/Linux systems.
		2388
		2389	=item EV_USE_KQUEUE
		2390
		2391	If defined to be C<1>, libev will compile in support for the BSD style
		2392	C<kqueue>(2) backend. Its actual availability will be detected at runtime,
		2393	otherwise another method will be used as fallback. This is the preferred
		2394	backend for BSD and BSD-like systems, although on most BSDs kqueue only
		2395	supports some types of fds correctly (the only platform we found that
		2396	supports ptys for example was NetBSD), so kqueue might be compiled in, but
		2397	not be used unless explicitly requested. The best way to use it is to find
		2398	out whether kqueue supports your type of fd properly and use an embedded
		2399	kqueue loop.
		2400
		2401	=item EV_USE_PORT
		2402
		2403	If defined to be C<1>, libev will compile in support for the Solaris
		2404	10 port style backend. Its availability will be detected at runtime,
		2405	otherwise another method will be used as fallback. This is the preferred
		2406	backend for Solaris 10 systems.
		2407
		2408	=item EV_USE_DEVPOLL
		2409
		2410	reserved for future expansion, works like the USE symbols above.
		2411
		2412	=item EV_USE_INOTIFY
		2413
		2414	If defined to be C<1>, libev will compile in support for the Linux inotify
		2415	interface to speed up C<ev_stat> watchers. Its actual availability will
		2416	be detected at runtime.
		2417
		2418	=item EV_H
		2419
		2420	The name of the F<ev.h> header file used to include it. The default if
		2421	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
		2422	can be used to virtually rename the F<ev.h> header file in case of conflicts.
		2423
		2424	=item EV_CONFIG_H
		2425
		2426	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
		2427	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
		2428	C<EV_H>, above.
		2429
		2430	=item EV_EVENT_H
		2431
		2432	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
		2433	of how the F<event.h> header can be found.
		2434
		2435	=item EV_PROTOTYPES
		2436
		2437	If defined to be C<0>, then F<ev.h> will not define any function
		2438	prototypes, but still define all the structs and other symbols. This is
		2439	occasionally useful if you want to provide your own wrapper functions
		2440	around libev functions.
		2441
		2442	=item EV_MULTIPLICITY
		2443
		2444	If undefined or defined to C<1>, then all event-loop-specific functions
		2445	will have the C<struct ev_loop *> as first argument, and you can create
		2446	additional independent event loops. Otherwise there will be no support
		2447	for multiple event loops and there is no first event loop pointer
		2448	argument. Instead, all functions act on the single default loop.
		2449
		2450	=item EV_MINPRI
		2451
		2452	=item EV_MAXPRI
		2453
		2454	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2455	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2456	provide for more priorities by overriding those symbols (usually defined
		2457	to be C<-2> and C<2>, respectively).
		2458
		2459	When doing priority-based operations, libev usually has to linearly search
		2460	all the priorities, so having many of them (hundreds) uses a lot of space
		2461	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2462	fine.
		2463
		2464	If your embedding app does not need any priorities, defining these both to
		2465	C<0> will save some memory and cpu.
		2466
		2467	=item EV_PERIODIC_ENABLE
		2468
		2469	If undefined or defined to be C<1>, then periodic timers are supported. If
		2470	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2471	code.
		2472
		2473	=item EV_IDLE_ENABLE
		2474
		2475	If undefined or defined to be C<1>, then idle watchers are supported. If
		2476	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2477	code.
		2478
		2479	=item EV_EMBED_ENABLE
		2480
		2481	If undefined or defined to be C<1>, then embed watchers are supported. If
		2482	defined to be C<0>, then they are not.
		2483
		2484	=item EV_STAT_ENABLE
		2485
		2486	If undefined or defined to be C<1>, then stat watchers are supported. If
		2487	defined to be C<0>, then they are not.
		2488
		2489	=item EV_FORK_ENABLE
		2490
		2491	If undefined or defined to be C<1>, then fork watchers are supported. If
		2492	defined to be C<0>, then they are not.
		2493
		2494	=item EV_MINIMAL
		2495
		2496	If you need to shave off some kilobytes of code at the expense of some
		2497	speed, define this symbol to C<1>. Currently only used for gcc to override
		2498	some inlining decisions, saves roughly 30% codesize of amd64.
		2499
		2500	=item EV_PID_HASHSIZE
		2501
		2502	C<ev_child> watchers use a small hash table to distribute workload by
		2503	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2504	than enough. If you need to manage thousands of children you might want to
		2505	increase this value (I<must> be a power of two).
		2506
		2507	=item EV_INOTIFY_HASHSIZE
		2508
		2509	C<ev_staz> watchers use a small hash table to distribute workload by
		2510	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2511	usually more than enough. If you need to manage thousands of C<ev_stat>
		2512	watchers you might want to increase this value (I<must> be a power of
		2513	two).
		2514
		2515	=item EV_COMMON
		2516
		2517	By default, all watchers have a C<void *data> member. By redefining
		2518	this macro to a something else you can include more and other types of
		2519	members. You have to define it each time you include one of the files,
		2520	though, and it must be identical each time.
		2521
		2522	For example, the perl EV module uses something like this:
		2523
		2524	#define EV_COMMON \
		2525	SV *self; /* contains this struct */ \
		2526	SV *cb_sv, *fh /* note no trailing ";" */
		2527
		2528	=item EV_CB_DECLARE (type)
		2529
		2530	=item EV_CB_INVOKE (watcher, revents)
		2531
		2532	=item ev_set_cb (ev, cb)
		2533
		2534	Can be used to change the callback member declaration in each watcher,
		2535	and the way callbacks are invoked and set. Must expand to a struct member
		2536	definition and a statement, respectively. See the F<ev.h> header file for
		2537	their default definitions. One possible use for overriding these is to
		2538	avoid the C<struct ev_loop *> as first argument in all cases, or to use
		2539	method calls instead of plain function calls in C++.
		2540
		2541	=head2 EXPORTED API SYMBOLS
		2542
		2543	If you need to re-export the API (e.g. via a dll) and you need a list of
		2544	exported symbols, you can use the provided F<Symbol.*> files which list
		2545	all public symbols, one per line:
		2546
		2547	Symbols.ev for libev proper
		2548	Symbols.event for the libevent emulation
		2549
		2550	This can also be used to rename all public symbols to avoid clashes with
		2551	multiple versions of libev linked together (which is obviously bad in
		2552	itself, but sometimes it is inconvinient to avoid this).
		2553
		2554	A sed command like this will create wrapper C<#define>'s that you need to
		2555	include before including F<ev.h>:
		2556
		2557	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2558
		2559	This would create a file F<wrap.h> which essentially looks like this:
		2560
		2561	#define ev_backend myprefix_ev_backend
		2562	#define ev_check_start myprefix_ev_check_start
		2563	#define ev_check_stop myprefix_ev_check_stop
		2564	...
		2565
		2566	=head2 EXAMPLES
		2567
		2568	For a real-world example of a program the includes libev
		2569	verbatim, you can have a look at the EV perl module
		2570	(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
		2571	the F<libev/> subdirectory and includes them in the F<EV/EVAPI.h> (public
		2572	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
		2573	will be compiled. It is pretty complex because it provides its own header
		2574	file.
		2575
		2576	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
		2577	that everybody includes and which overrides some configure choices:
		2578
		2579	#define EV_MINIMAL 1
		2580	#define EV_USE_POLL 0
		2581	#define EV_MULTIPLICITY 0
		2582	#define EV_PERIODIC_ENABLE 0
		2583	#define EV_STAT_ENABLE 0
		2584	#define EV_FORK_ENABLE 0
		2585	#define EV_CONFIG_H <config.h>
		2586	#define EV_MINPRI 0
		2587	#define EV_MAXPRI 0
		2588
		2589	#include "ev++.h"
		2590
		2591	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
		2592
		2593	#include "ev_cpp.h"
		2594	#include "ev.c"
		2595
		2596
		2597	=head1 COMPLEXITIES
		2598
		2599	In this section the complexities of (many of) the algorithms used inside
		2600	libev will be explained. For complexity discussions about backends see the
		2601	documentation for C<ev_default_init>.
		2602
		2603	All of the following are about amortised time: If an array needs to be
		2604	extended, libev needs to realloc and move the whole array, but this
		2605	happens asymptotically never with higher number of elements, so O(1) might
		2606	mean it might do a lengthy realloc operation in rare cases, but on average
		2607	it is much faster and asymptotically approaches constant time.
		2608
		2609	=over 4
		2610
		2611	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2612
		2613	This means that, when you have a watcher that triggers in one hour and
		2614	there are 100 watchers that would trigger before that then inserting will
		2615	have to skip those 100 watchers.
		2616
		2617	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2618
		2619	That means that for changing a timer costs less than removing/adding them
		2620	as only the relative motion in the event queue has to be paid for.
		2621
		2622	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2623
		2624	These just add the watcher into an array or at the head of a list.
		2625	=item Stopping check/prepare/idle watchers: O(1)
		2626
		2627	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2628
		2629	These watchers are stored in lists then need to be walked to find the
		2630	correct watcher to remove. The lists are usually short (you don't usually
		2631	have many watchers waiting for the same fd or signal).
		2632
		2633	=item Finding the next timer per loop iteration: O(1)
		2634
		2635	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2636
		2637	A change means an I/O watcher gets started or stopped, which requires
		2638	libev to recalculate its status (and possibly tell the kernel).
		2639
		2640	=item Activating one watcher: O(1)
		2641
		2642	=item Priority handling: O(number_of_priorities)
		2643
		2644	Priorities are implemented by allocating some space for each
		2645	priority. When doing priority-based operations, libev usually has to
		2646	linearly search all the priorities.
		2647
		2648	=back
		2649
1316		2650
1317	=head1 AUTHOR	2651	=head1 AUTHOR
1318		2652
1319	Marc Lehmann <libev@schmorp.de>.	2653	Marc Lehmann <libev@schmorp.de>.
1320		2654

Diff Legend

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