ViewVC Help

View File | Revision Log | Show Annotations | Download File

/cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.41 by root, Sat Nov 24 10:19:14 2007 UTC vs.
Revision 1.98 by root, Sat Dec 22 06:10:25 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.
		602
		603	Likewise, by setting a higher I<timeout collect interval> you allow libev
		604	to spend more time collecting timeouts, at the expense of increased
		605	latency (the watcher callback will be called later). C<ev_io> watchers
		606	will not be affected.
		607
		608	Many (busy) programs can usually benefit by setting the io collect
		609	interval to a value near C<0.1> or so, which is often enough for
		610	interactive servers (of course not for games), likewise for timeouts. It
		611	usually doesn't make much sense to set it to a lower value than C<0.01>,
		612	as this approsaches the timing granularity of most systems.
470		613
471	=back	614	=back
		615
472		616
473	=head1 ANATOMY OF A WATCHER	617	=head1 ANATOMY OF A WATCHER
474		618
475	A watcher is a structure that you create and register to record your	619	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	620	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.	687	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		688
545	=item C<EV_CHILD>	689	=item C<EV_CHILD>
546		690
547	The pid specified in the C<ev_child> watcher has received a status change.	691	The pid specified in the C<ev_child> watcher has received a status change.
		692
		693	=item C<EV_STAT>
		694
		695	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		696
549	=item C<EV_IDLE>	697	=item C<EV_IDLE>
550		698
551	The C<ev_idle> watcher has determined that you have nothing better to do.	699	The C<ev_idle> watcher has determined that you have nothing better to do.
552		700
…		…
560	received events. Callbacks of both watcher types can start and stop as	708	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	709	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	710	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	711	C<ev_loop> from blocking).
564		712
		713	=item C<EV_EMBED>
		714
		715	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		716
		717	=item C<EV_FORK>
		718
		719	The event loop has been resumed in the child process after fork (see
		720	C<ev_fork>).
		721
565	=item C<EV_ERROR>	722	=item C<EV_ERROR>
566		723
567	An unspecified error has occured, the watcher has been stopped. This might	724	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	725	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	726	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	733	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	734	programs, though, so beware.
578		735
579	=back	736	=back
580		737
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	738	=head2 GENERIC WATCHER FUNCTIONS
582		739
583	In the following description, C<TYPE> stands for the watcher type,	740	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.	741	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		742
586	=over 4	743	=over 4
…		…
595	which rolls both calls into one.	752	which rolls both calls into one.
596		753
597	You can reinitialise a watcher at any time as long as it has been stopped	754	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.	755	(or never started) and there are no pending events outstanding.
599		756
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	757	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	758	int revents)>.
602		759
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	760	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		761
605	This macro initialises the type-specific parts of a watcher. You need to	762	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	797	=item bool ev_is_pending (ev_TYPE *watcher)
641		798
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	799	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	800	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	801	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	802	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	803	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		804	it).
647		805
648	=item callback = ev_cb (ev_TYPE *watcher)	806	=item callback ev_cb (ev_TYPE *watcher)
649		807
650	Returns the callback currently set on the watcher.	808	Returns the callback currently set on the watcher.
651		809
652	=item ev_cb_set (ev_TYPE *watcher, callback)	810	=item ev_cb_set (ev_TYPE *watcher, callback)
653		811
654	Change the callback. You can change the callback at virtually any time	812	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	813	(modulo threads).
		814
		815	=item ev_set_priority (ev_TYPE *watcher, priority)
		816
		817	=item int ev_priority (ev_TYPE *watcher)
		818
		819	Set and query the priority of the watcher. The priority is a small
		820	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		821	(default: C<-2>). Pending watchers with higher priority will be invoked
		822	before watchers with lower priority, but priority will not keep watchers
		823	from being executed (except for C<ev_idle> watchers).
		824
		825	This means that priorities are I<only> used for ordering callback
		826	invocation after new events have been received. This is useful, for
		827	example, to reduce latency after idling, or more often, to bind two
		828	watchers on the same event and make sure one is called first.
		829
		830	If you need to suppress invocation when higher priority events are pending
		831	you need to look at C<ev_idle> watchers, which provide this functionality.
		832
		833	You I<must not> change the priority of a watcher as long as it is active or
		834	pending.
		835
		836	The default priority used by watchers when no priority has been set is
		837	always C<0>, which is supposed to not be too high and not be too low :).
		838
		839	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		840	fine, as long as you do not mind that the priority value you query might
		841	or might not have been adjusted to be within valid range.
		842
		843	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		844
		845	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		846	C<loop> nor C<revents> need to be valid as long as the watcher callback
		847	can deal with that fact.
		848
		849	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		850
		851	If the watcher is pending, this function returns clears its pending status
		852	and returns its C<revents> bitset (as if its callback was invoked). If the
		853	watcher isn't pending it does nothing and returns C<0>.
656		854
657	=back	855	=back
658		856
659		857
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	858	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	879	{
682	struct my_io *w = (struct my_io *)w_;	880	struct my_io *w = (struct my_io *)w_;
683	...	881	...
684	}	882	}
685		883
686	More interesting and less C-conformant ways of catsing your callback type	884	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	885	instead have been omitted.
		886
		887	Another common scenario is having some data structure with multiple
		888	watchers:
		889
		890	struct my_biggy
		891	{
		892	int some_data;
		893	ev_timer t1;
		894	ev_timer t2;
		895	}
		896
		897	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		898	you need to use C<offsetof>:
		899
		900	#include <stddef.h>
		901
		902	static void
		903	t1_cb (EV_P_ struct ev_timer *w, int revents)
		904	{
		905	struct my_biggy big = (struct my_biggy *
		906	(((char *)w) - offsetof (struct my_biggy, t1));
		907	}
		908
		909	static void
		910	t2_cb (EV_P_ struct ev_timer *w, int revents)
		911	{
		912	struct my_biggy big = (struct my_biggy *
		913	(((char *)w) - offsetof (struct my_biggy, t2));
		914	}
688		915
689		916
690	=head1 WATCHER TYPES	917	=head1 WATCHER TYPES
691		918
692	This section describes each watcher in detail, but will not repeat	919	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	920	information given in the last section. Any initialisation/set macros,
		921	functions and members specific to the watcher type are explained.
694		922
		923	Members are additionally marked with either I<[read-only]>, meaning that,
		924	while the watcher is active, you can look at the member and expect some
		925	sensible content, but you must not modify it (you can modify it while the
		926	watcher is stopped to your hearts content), or I<[read-write]>, which
		927	means you can expect it to have some sensible content while the watcher
		928	is active, but you can also modify it. Modifying it may not do something
		929	sensible or take immediate effect (or do anything at all), but libev will
		930	not crash or malfunction in any way.
695		931
		932
696	=head2 C<ev_io> - is this file descriptor readable or writable	933	=head2 C<ev_io> - is this file descriptor readable or writable?
697		934
698	I/O watchers check whether a file descriptor is readable or writable	935	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	936	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	937	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	938	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	939	receiving events as long as the condition persists. Remember you can stop
		940	the watcher if you don't want to act on the event and neither want to
		941	receive future events.
703		942
704	In general you can register as many read and/or write event watchers per	943	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	944	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	945	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	946	required if you know what you are doing).
708		947
709	You have to be careful with dup'ed file descriptors, though. Some backends	948	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	949	(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	950	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	951	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	952	the same underlying "file open").
714		953
715	If you must do this, then force the use of a known-to-be-good backend	954	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	955	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	956	C<EVBACKEND_POLL>).
718		957
		958	Another thing you have to watch out for is that it is quite easy to
		959	receive "spurious" readyness notifications, that is your callback might
		960	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		961	because there is no data. Not only are some backends known to create a
		962	lot of those (for example solaris ports), it is very easy to get into
		963	this situation even with a relatively standard program structure. Thus
		964	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		965	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		966
		967	If you cannot run the fd in non-blocking mode (for example you should not
		968	play around with an Xlib connection), then you have to seperately re-test
		969	whether a file descriptor is really ready with a known-to-be good interface
		970	such as poll (fortunately in our Xlib example, Xlib already does this on
		971	its own, so its quite safe to use).
		972
		973	=head3 The special problem of disappearing file descriptors
		974
		975	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		976	descriptor (either by calling C<close> explicitly or by any other means,
		977	such as C<dup>). The reason is that you register interest in some file
		978	descriptor, but when it goes away, the operating system will silently drop
		979	this interest. If another file descriptor with the same number then is
		980	registered with libev, there is no efficient way to see that this is, in
		981	fact, a different file descriptor.
		982
		983	To avoid having to explicitly tell libev about such cases, libev follows
		984	the following policy: Each time C<ev_io_set> is being called, libev
		985	will assume that this is potentially a new file descriptor, otherwise
		986	it is assumed that the file descriptor stays the same. That means that
		987	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		988	descriptor even if the file descriptor number itself did not change.
		989
		990	This is how one would do it normally anyway, the important point is that
		991	the libev application should not optimise around libev but should leave
		992	optimisations to libev.
		993
		994	=head3 The special problem of dup'ed file descriptors
		995
		996	Some backends (e.g. epoll), cannot register events for file descriptors,
		997	but only events for the underlying file descriptions. That menas when you
		998	have C<dup ()>'ed file descriptors and register events for them, only one
		999	file descriptor might actually receive events.
		1000
		1001	There is no workaorund possible except not registering events
		1002	for potentially C<dup ()>'ed file descriptors or to resort to
		1003	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1004
		1005	=head3 The special problem of fork
		1006
		1007	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1008	useless behaviour. Libev fully supports fork, but needs to be told about
		1009	it in the child.
		1010
		1011	To support fork in your programs, you either have to call
		1012	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1013	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1014	C<EVBACKEND_POLL>.
		1015
		1016
		1017	=head3 Watcher-Specific Functions
		1018
719	=over 4	1019	=over 4
720		1020
721	=item ev_io_init (ev_io *, callback, int fd, int events)	1021	=item ev_io_init (ev_io *, callback, int fd, int events)
722		1022
723	=item ev_io_set (ev_io *, int fd, int events)	1023	=item ev_io_set (ev_io *, int fd, int events)
724		1024
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	1025	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 |	1026	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	1027	C<EV_READ | EV_WRITE> to receive the given events.
728		1028
729	Please note that most of the more scalable backend mechanisms (for example	1029	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	1030
731	for file descriptors, so you practically need to use non-blocking I/O (and	1031	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	1032
733	interface before doing I/O (XLib can do this), or force the use of either	1033	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	1034
735	problem. Also note that it is quite easy to have your callback invoked	1035	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		1036
740	=back	1037	=back
741		1038
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	1039	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	1040	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	1041	attempt to read a whole line in the callback.
745		1042
746	static void	1043	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1044	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	1045	{
749	ev_io_stop (loop, w);	1046	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1053	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	1054	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	1055	ev_loop (loop, 0);
759		1056
760		1057
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	1058	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		1059
763	Timer watchers are simple relative timers that generate an event after a	1060	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	1061	given time, and optionally repeating in regular intervals after that.
765		1062
766	The timers are based on real time, that is, if you register an event that	1063	The timers are based on real time, that is, if you register an event that
…		…
779		1076
780	The callback is guarenteed to be invoked only when its timeout has passed,	1077	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	1078	but if multiple timers become ready during the same loop iteration then
782	order of execution is undefined.	1079	order of execution is undefined.
783		1080
		1081	=head3 Watcher-Specific Functions and Data Members
		1082
784	=over 4	1083	=over 4
785		1084
786	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1085	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
787		1086
788	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1087	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
801	=item ev_timer_again (loop)	1100	=item ev_timer_again (loop)
802		1101
803	This will act as if the timer timed out and restart it again if it is	1102	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	1103	repeating. The exact semantics are:
805		1104
		1105	If the timer is pending, its pending status is cleared.
		1106
806	If the timer is started but nonrepeating, stop it.	1107	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1108
808	If the timer is repeating, either start it if necessary (with the repeat	1109	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1110	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1111
811	This sounds a bit complicated, but here is a useful and typical	1112	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	1113	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	1114	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	1115	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	1116	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	1117	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	1118	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.	1119	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1120	automatically restart it if need be.
		1121
		1122	That means you can ignore the C<after> value and C<ev_timer_start>
		1123	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1124
		1125	ev_timer_init (timer, callback, 0., 5.);
		1126	ev_timer_again (loop, timer);
		1127	...
		1128	timer->again = 17.;
		1129	ev_timer_again (loop, timer);
		1130	...
		1131	timer->again = 10.;
		1132	ev_timer_again (loop, timer);
		1133
		1134	This is more slightly efficient then stopping/starting the timer each time
		1135	you want to modify its timeout value.
		1136
		1137	=item ev_tstamp repeat [read-write]
		1138
		1139	The current C<repeat> value. Will be used each time the watcher times out
		1140	or C<ev_timer_again> is called and determines the next timeout (if any),
		1141	which is also when any modifications are taken into account.
819		1142
820	=back	1143	=back
821		1144
822	Example: create a timer that fires after 60 seconds.	1145	Example: Create a timer that fires after 60 seconds.
823		1146
824	static void	1147	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1148	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1149	{
827	.. one minute over, w is actually stopped right here	1150	.. one minute over, w is actually stopped right here
…		…
829		1152
830	struct ev_timer mytimer;	1153	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1154	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1155	ev_timer_start (loop, &mytimer);
833		1156
834	Example: create a timeout timer that times out after 10 seconds of	1157	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1158	inactivity.
836		1159
837	static void	1160	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1161	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1162	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1171	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1172	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1173	ev_timer_again (&mytimer);
851		1174
852		1175
853	=head2 C<ev_periodic> - to cron or not to cron	1176	=head2 C<ev_periodic> - to cron or not to cron?
854		1177
855	Periodic watchers are also timers of a kind, but they are very versatile	1178	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1179	(and unfortunately a bit complex).
857		1180
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1181	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	1182	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	1183	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 ()	1184	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	1185	+ 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	1186	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	1187	roughly 10 seconds later).
865	again).
866		1188
867	They can also be used to implement vastly more complex timers, such as	1189	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1190	triggering an event on each midnight, local time or other, complicated,
		1191	rules.
869		1192
870	As with timers, the callback is guarenteed to be invoked only when the	1193	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	1194	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.	1195	during the same loop iteration then order of execution is undefined.
873		1196
		1197	=head3 Watcher-Specific Functions and Data Members
		1198
874	=over 4	1199	=over 4
875		1200
876	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1201	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
877		1202
878	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1203	=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	1205	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1206	operation, and we will explain them from simplest to complex:
882		1207
883	=over 4	1208	=over 4
884		1209
885	=item * absolute timer (interval = reschedule_cb = 0)	1210	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1211
887	In this configuration the watcher triggers an event at the wallclock time	1212	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,	1213	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	1214	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.	1215	system time reaches or surpasses this time.
891		1216
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1217	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1218
894	In this mode the watcher will always be scheduled to time out at the next	1219	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	1220	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1221	and then repeat, regardless of any time jumps.
897		1222
898	This can be used to create timers that do not drift with respect to system	1223	This can be used to create timers that do not drift with respect to system
899	time:	1224	time:
900		1225
901	ev_periodic_set (&periodic, 0., 3600., 0);	1226	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1232
908	Another way to think about it (for the mathematically inclined) is that	1233	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	1234	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.	1235	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1236
		1237	For numerical stability it is preferable that the C<at> value is near
		1238	C<ev_now ()> (the current time), but there is no range requirement for
		1239	this value.
		1240
912	=item * manual reschedule mode (reschedule_cb = callback)	1241	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1242
914	In this mode the values for C<interval> and C<at> are both being	1243	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	1244	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1245	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1246	current time as second argument.
918		1247
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1248	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,	1249	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	1250	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1251	starting an C<ev_prepare> watcher, which is legal).
923		1252
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1253	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1254	ev_tstamp now)>, e.g.:
926		1255
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1256	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	1279	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1280	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	1281	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1282	program when the crontabs have changed).
954		1283
		1284	=item ev_tstamp offset [read-write]
		1285
		1286	When repeating, this contains the offset value, otherwise this is the
		1287	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1288
		1289	Can be modified any time, but changes only take effect when the periodic
		1290	timer fires or C<ev_periodic_again> is being called.
		1291
		1292	=item ev_tstamp interval [read-write]
		1293
		1294	The current interval value. Can be modified any time, but changes only
		1295	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1296	called.
		1297
		1298	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1299
		1300	The current reschedule callback, or C<0>, if this functionality is
		1301	switched off. Can be changed any time, but changes only take effect when
		1302	the periodic timer fires or C<ev_periodic_again> is being called.
		1303
		1304	=item ev_tstamp at [read-only]
		1305
		1306	When active, contains the absolute time that the watcher is supposed to
		1307	trigger next.
		1308
955	=back	1309	=back
956		1310
957	Example: call a callback every hour, or, more precisely, whenever the	1311	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1312	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1313	potentially a lot of jittering, but good long-term stability.
960		1314
961	static void	1315	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1316	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1320
967	struct ev_periodic hourly_tick;	1321	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1322	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1323	ev_periodic_start (loop, &hourly_tick);
970		1324
971	Example: the same as above, but use a reschedule callback to do it:	1325	Example: The same as above, but use a reschedule callback to do it:
972		1326
973	#include <math.h>	1327	#include <math.h>
974		1328
975	static ev_tstamp	1329	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1330	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1332	return fmod (now, 3600.) + 3600.;
979	}	1333	}
980		1334
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1335	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1336
983	Example: call a callback every hour, starting now:	1337	Example: Call a callback every hour, starting now:
984		1338
985	struct ev_periodic hourly_tick;	1339	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1340	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1341	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1342	ev_periodic_start (loop, &hourly_tick);
989		1343
990		1344
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1345	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1346
993	Signal watchers will trigger an event when the process receives a specific	1347	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	1348	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	1349	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1350	normal event processing, like any other event.
…		…
1000	with the kernel (thus it coexists with your own signal handlers as long	1354	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	1355	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	1356	watcher for a signal is stopped libev will reset the signal handler to
1003	SIG_DFL (regardless of what it was set to before).	1357	SIG_DFL (regardless of what it was set to before).
1004		1358
		1359	=head3 Watcher-Specific Functions and Data Members
		1360
1005	=over 4	1361	=over 4
1006		1362
1007	=item ev_signal_init (ev_signal *, callback, int signum)	1363	=item ev_signal_init (ev_signal *, callback, int signum)
1008		1364
1009	=item ev_signal_set (ev_signal *, int signum)	1365	=item ev_signal_set (ev_signal *, int signum)
1010		1366
1011	Configures the watcher to trigger on the given signal number (usually one	1367	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1368	of the C<SIGxxx> constants).
1013		1369
		1370	=item int signum [read-only]
		1371
		1372	The signal the watcher watches out for.
		1373
1014	=back	1374	=back
1015		1375
1016		1376
1017	=head2 C<ev_child> - wait for pid status changes	1377	=head2 C<ev_child> - watch out for process status changes
1018		1378
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1379	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).	1380	some child status changes (most typically when a child of yours dies).
		1381
		1382	=head3 Watcher-Specific Functions and Data Members
1021		1383
1022	=over 4	1384	=over 4
1023		1385
1024	=item ev_child_init (ev_child *, callback, int pid)	1386	=item ev_child_init (ev_child *, callback, int pid)
1025		1387
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1392	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	1393	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	1394	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1395	process causing the status change.
1034		1396
		1397	=item int pid [read-only]
		1398
		1399	The process id this watcher watches out for, or C<0>, meaning any process id.
		1400
		1401	=item int rpid [read-write]
		1402
		1403	The process id that detected a status change.
		1404
		1405	=item int rstatus [read-write]
		1406
		1407	The process exit/trace status caused by C<rpid> (see your systems
		1408	C<waitpid> and C<sys/wait.h> documentation for details).
		1409
1035	=back	1410	=back
1036		1411
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1412	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1413
1039	static void	1414	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1415	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1416	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1417	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1420	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1421	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1422	ev_signal_start (loop, &sigint_cb);
1048		1423
1049		1424
		1425	=head2 C<ev_stat> - did the file attributes just change?
		1426
		1427	This watches a filesystem path for attribute changes. That is, it calls
		1428	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1429	compared to the last time, invoking the callback if it did.
		1430
		1431	The path does not need to exist: changing from "path exists" to "path does
		1432	not exist" is a status change like any other. The condition "path does
		1433	not exist" is signified by the C<st_nlink> field being zero (which is
		1434	otherwise always forced to be at least one) and all the other fields of
		1435	the stat buffer having unspecified contents.
		1436
		1437	The path I<should> be absolute and I<must not> end in a slash. If it is
		1438	relative and your working directory changes, the behaviour is undefined.
		1439
		1440	Since there is no standard to do this, the portable implementation simply
		1441	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1442	can specify a recommended polling interval for this case. If you specify
		1443	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1444	unspecified default> value will be used (which you can expect to be around
		1445	five seconds, although this might change dynamically). Libev will also
		1446	impose a minimum interval which is currently around C<0.1>, but thats
		1447	usually overkill.
		1448
		1449	This watcher type is not meant for massive numbers of stat watchers,
		1450	as even with OS-supported change notifications, this can be
		1451	resource-intensive.
		1452
		1453	At the time of this writing, only the Linux inotify interface is
		1454	implemented (implementing kqueue support is left as an exercise for the
		1455	reader). Inotify will be used to give hints only and should not change the
		1456	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1457	to fall back to regular polling again even with inotify, but changes are
		1458	usually detected immediately, and if the file exists there will be no
		1459	polling.
		1460
		1461	=head3 Watcher-Specific Functions and Data Members
		1462
		1463	=over 4
		1464
		1465	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1466
		1467	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1468
		1469	Configures the watcher to wait for status changes of the given
		1470	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1471	be detected and should normally be specified as C<0> to let libev choose
		1472	a suitable value. The memory pointed to by C<path> must point to the same
		1473	path for as long as the watcher is active.
		1474
		1475	The callback will be receive C<EV_STAT> when a change was detected,
		1476	relative to the attributes at the time the watcher was started (or the
		1477	last change was detected).
		1478
		1479	=item ev_stat_stat (ev_stat *)
		1480
		1481	Updates the stat buffer immediately with new values. If you change the
		1482	watched path in your callback, you could call this fucntion to avoid
		1483	detecting this change (while introducing a race condition). Can also be
		1484	useful simply to find out the new values.
		1485
		1486	=item ev_statdata attr [read-only]
		1487
		1488	The most-recently detected attributes of the file. Although the type is of
		1489	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1490	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1491	was some error while C<stat>ing the file.
		1492
		1493	=item ev_statdata prev [read-only]
		1494
		1495	The previous attributes of the file. The callback gets invoked whenever
		1496	C<prev> != C<attr>.
		1497
		1498	=item ev_tstamp interval [read-only]
		1499
		1500	The specified interval.
		1501
		1502	=item const char *path [read-only]
		1503
		1504	The filesystem path that is being watched.
		1505
		1506	=back
		1507
		1508	Example: Watch C</etc/passwd> for attribute changes.
		1509
		1510	static void
		1511	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1512	{
		1513	/* /etc/passwd changed in some way */
		1514	if (w->attr.st_nlink)
		1515	{
		1516	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1517	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1518	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1519	}
		1520	else
		1521	/* you shalt not abuse printf for puts */
		1522	puts ("wow, /etc/passwd is not there, expect problems. "
		1523	"if this is windows, they already arrived\n");
		1524	}
		1525
		1526	...
		1527	ev_stat passwd;
		1528
		1529	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1530	ev_stat_start (loop, &passwd);
		1531
		1532
1050	=head2 C<ev_idle> - when you've got nothing better to do	1533	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1534
1052	Idle watchers trigger events when there are no other events are pending	1535	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	1536	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1537	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1538
1056	watchers are being called again and again, once per event loop iteration -	1539	That is, as long as your process is busy handling sockets or timeouts
		1540	(or even signals, imagine) of the same or higher priority it will not be
		1541	triggered. But when your process is idle (or only lower-priority watchers
		1542	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	1543	iteration - until stopped, that is, or your process receives more events
1058	busy.	1544	and becomes busy again with higher priority stuff.
1059		1545
1060	The most noteworthy effect is that as long as any idle watchers are	1546	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.	1547	active, the process will not block when waiting for new events.
1062		1548
1063	Apart from keeping your process non-blocking (which is a useful	1549	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	1550	effect on its own sometimes), idle watchers are a good place to do
1065	"pseudo-background processing", or delay processing stuff to after the	1551	"pseudo-background processing", or delay processing stuff to after the
1066	event loop has handled all outstanding events.	1552	event loop has handled all outstanding events.
1067		1553
		1554	=head3 Watcher-Specific Functions and Data Members
		1555
1068	=over 4	1556	=over 4
1069		1557
1070	=item ev_idle_init (ev_signal *, callback)	1558	=item ev_idle_init (ev_signal *, callback)
1071		1559
1072	Initialises and configures the idle watcher - it has no parameters of any	1560	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,	1561	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1562	believe me.
1075		1563
1076	=back	1564	=back
1077		1565
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1566	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1567	callback, free it. Also, use no error checking, as usual.
1080		1568
1081	static void	1569	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1570	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1571	{
1084	free (w);	1572	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1577	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1578	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1579	ev_idle_start (loop, idle_cb);
1092		1580
1093		1581
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1582	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1583
1096	Prepare and check watchers are usually (but not always) used in tandem:	1584	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1585	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1586	afterwards.
1099		1587
		1588	You I<must not> call C<ev_loop> or similar functions that enter
		1589	the current event loop from either C<ev_prepare> or C<ev_check>
		1590	watchers. Other loops than the current one are fine, however. The
		1591	rationale behind this is that you do not need to check for recursion in
		1592	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1593	C<ev_check> so if you have one watcher of each kind they will always be
		1594	called in pairs bracketing the blocking call.
		1595
1100	Their main purpose is to integrate other event mechanisms into libev and	1596	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	1597	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	1598	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1599	coroutine library and lots more. They are also occasionally useful if
		1600	you cache some data and want to flush it before blocking (for example,
		1601	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1602	watcher).
1104		1603
1105	This is done by examining in each prepare call which file descriptors need	1604	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	1605	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	1606	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	1607	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	1617	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	1618	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	1619	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1620	low-priority coroutines to idle/background tasks).
1122		1621
		1622	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1623	priority, to ensure that they are being run before any other watchers
		1624	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1625	too) should not activate ("feed") events into libev. While libev fully
		1626	supports this, they will be called before other C<ev_check> watchers did
		1627	their job. As C<ev_check> watchers are often used to embed other event
		1628	loops those other event loops might be in an unusable state until their
		1629	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1630	others).
		1631
		1632	=head3 Watcher-Specific Functions and Data Members
		1633
1123	=over 4	1634	=over 4
1124		1635
1125	=item ev_prepare_init (ev_prepare *, callback)	1636	=item ev_prepare_init (ev_prepare *, callback)
1126		1637
1127	=item ev_check_init (ev_check *, callback)	1638	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1641	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.	1642	macros, but using them is utterly, utterly and completely pointless.
1132		1643
1133	=back	1644	=back
1134		1645
1135	Example: *TODO*.	1646	There are a number of principal ways to embed other event loops or modules
		1647	into libev. Here are some ideas on how to include libadns into libev
		1648	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1649	use for an actually working example. Another Perl module named C<EV::Glib>
		1650	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1651	into the Glib event loop).
1136		1652
		1653	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1654	and in a check watcher, destroy them and call into libadns. What follows
		1655	is pseudo-code only of course. This requires you to either use a low
		1656	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1657	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1658
		1659	static ev_io iow [nfd];
		1660	static ev_timer tw;
		1661
		1662	static void
		1663	io_cb (ev_loop *loop, ev_io *w, int revents)
		1664	{
		1665	}
		1666
		1667	// create io watchers for each fd and a timer before blocking
		1668	static void
		1669	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1670	{
		1671	int timeout = 3600000;
		1672	struct pollfd fds [nfd];
		1673	// actual code will need to loop here and realloc etc.
		1674	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1675
		1676	/* the callback is illegal, but won't be called as we stop during check */
		1677	ev_timer_init (&tw, 0, timeout * 1e-3);
		1678	ev_timer_start (loop, &tw);
		1679
		1680	// create one ev_io per pollfd
		1681	for (int i = 0; i < nfd; ++i)
		1682	{
		1683	ev_io_init (iow + i, io_cb, fds [i].fd,
		1684	((fds [i].events & POLLIN ? EV_READ : 0)
		1685	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1686
		1687	fds [i].revents = 0;
		1688	ev_io_start (loop, iow + i);
		1689	}
		1690	}
		1691
		1692	// stop all watchers after blocking
		1693	static void
		1694	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1695	{
		1696	ev_timer_stop (loop, &tw);
		1697
		1698	for (int i = 0; i < nfd; ++i)
		1699	{
		1700	// set the relevant poll flags
		1701	// could also call adns_processreadable etc. here
		1702	struct pollfd *fd = fds + i;
		1703	int revents = ev_clear_pending (iow + i);
		1704	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1705	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1706
		1707	// now stop the watcher
		1708	ev_io_stop (loop, iow + i);
		1709	}
		1710
		1711	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1712	}
		1713
		1714	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1715	in the prepare watcher and would dispose of the check watcher.
		1716
		1717	Method 3: If the module to be embedded supports explicit event
		1718	notification (adns does), you can also make use of the actual watcher
		1719	callbacks, and only destroy/create the watchers in the prepare watcher.
		1720
		1721	static void
		1722	timer_cb (EV_P_ ev_timer *w, int revents)
		1723	{
		1724	adns_state ads = (adns_state)w->data;
		1725	update_now (EV_A);
		1726
		1727	adns_processtimeouts (ads, &tv_now);
		1728	}
		1729
		1730	static void
		1731	io_cb (EV_P_ ev_io *w, int revents)
		1732	{
		1733	adns_state ads = (adns_state)w->data;
		1734	update_now (EV_A);
		1735
		1736	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1737	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1738	}
		1739
		1740	// do not ever call adns_afterpoll
		1741
		1742	Method 4: Do not use a prepare or check watcher because the module you
		1743	want to embed is too inflexible to support it. Instead, youc na override
		1744	their poll function. The drawback with this solution is that the main
		1745	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1746	this.
		1747
		1748	static gint
		1749	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1750	{
		1751	int got_events = 0;
		1752
		1753	for (n = 0; n < nfds; ++n)
		1754	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1755
		1756	if (timeout >= 0)
		1757	// create/start timer
		1758
		1759	// poll
		1760	ev_loop (EV_A_ 0);
		1761
		1762	// stop timer again
		1763	if (timeout >= 0)
		1764	ev_timer_stop (EV_A_ &to);
		1765
		1766	// stop io watchers again - their callbacks should have set
		1767	for (n = 0; n < nfds; ++n)
		1768	ev_io_stop (EV_A_ iow [n]);
		1769
		1770	return got_events;
		1771	}
		1772
		1773
1138	=head2 C<ev_embed> - when one backend isn't enough	1774	=head2 C<ev_embed> - when one backend isn't enough...
1139		1775
1140	This is a rather advanced watcher type that lets you embed one event loop	1776	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	1777	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	1778	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1779	fashion and must not be used). (See portability notes, below).
1144		1780
1145	There are primarily two reasons you would want that: work around bugs and	1781	There are primarily two reasons you would want that: work around bugs and
1146	prioritise I/O.	1782	prioritise I/O.
1147		1783
1148	As an example for a bug workaround, the kqueue backend might only support	1784	As an example for a bug workaround, the kqueue backend might only support
…		…
1203	ev_embed_start (loop_hi, &embed);	1839	ev_embed_start (loop_hi, &embed);
1204	}	1840	}
1205	else	1841	else
1206	loop_lo = loop_hi;	1842	loop_lo = loop_hi;
1207		1843
		1844	=head2 Portability notes
		1845
		1846	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1847	tried, in various ways. Usually the embedded event loop will simply never
		1848	receive events, sometimes it will only trigger a few times, sometimes in a
		1849	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1850	will always eport the epoll fd as ready, even when no events are pending.
		1851
		1852	While libev allows embedding these backends (they are contained in
		1853	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1854	work.
		1855
		1856	When in doubt, create a dynamic event loop forced to use sockets (this
		1857	usually works) and possibly another thread and a pipe or so to report to
		1858	your main event loop.
		1859
		1860	=head3 Watcher-Specific Functions and Data Members
		1861
1208	=over 4	1862	=over 4
1209		1863
1210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1864	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1211		1865
1212	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	1866	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1221		1875
1222	Make a single, non-blocking sweep over the embedded loop. This works	1876	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	1877	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1878	apropriate way for embedded loops.
1225		1879
		1880	=item struct ev_loop *other [read-only]
		1881
		1882	The embedded event loop.
		1883
		1884	=back
		1885
		1886
		1887	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1888
		1889	Fork watchers are called when a C<fork ()> was detected (usually because
		1890	whoever is a good citizen cared to tell libev about it by calling
		1891	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1892	event loop blocks next and before C<ev_check> watchers are being called,
		1893	and only in the child after the fork. If whoever good citizen calling
		1894	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1895	handlers will be invoked, too, of course.
		1896
		1897	=head3 Watcher-Specific Functions and Data Members
		1898
		1899	=over 4
		1900
		1901	=item ev_fork_init (ev_signal *, callback)
		1902
		1903	Initialises and configures the fork watcher - it has no parameters of any
		1904	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1905	believe me.
		1906
1226	=back	1907	=back
1227		1908
1228		1909
1229	=head1 OTHER FUNCTIONS	1910	=head1 OTHER FUNCTIONS
1230		1911
…		…
1318		1999
1319	To use it,	2000	To use it,
1320		2001
1321	#include <ev++.h>	2002	#include <ev++.h>
1322		2003
1323	(it is not installed by default). This automatically includes F<ev.h>	2004	This automatically includes F<ev.h> and puts all of its definitions (many
1324	and puts all of its definitions (many of them macros) into the global	2005	of them macros) into the global namespace. All C++ specific things are
1325	namespace. All C++ specific things are put into the C<ev> namespace.	2006	put into the C<ev> namespace. It should support all the same embedding
		2007	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		2008
1327	It should support all the same embedding options as F<ev.h>, most notably	2009	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	2010	classes add (compared to plain C-style watchers) is the event loop pointer
		2011	that the watcher is associated with (or no additional members at all if
		2012	you disable C<EV_MULTIPLICITY> when embedding libev).
		2013
		2014	Currently, functions, and static and non-static member functions can be
		2015	used as callbacks. Other types should be easy to add as long as they only
		2016	need one additional pointer for context. If you need support for other
		2017	types of functors please contact the author (preferably after implementing
		2018	it).
1329		2019
1330	Here is a list of things available in the C<ev> namespace:	2020	Here is a list of things available in the C<ev> namespace:
1331		2021
1332	=over 4	2022	=over 4
1333		2023
…		…
1349		2039
1350	All of those classes have these methods:	2040	All of those classes have these methods:
1351		2041
1352	=over 4	2042	=over 4
1353		2043
1354	=item ev::TYPE::TYPE (object *, object::method *)	2044	=item ev::TYPE::TYPE ()
1355		2045
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2046	=item ev::TYPE::TYPE (struct ev_loop *)
1357		2047
1358	=item ev::TYPE::~TYPE	2048	=item ev::TYPE::~TYPE
1359		2049
1360	The constructor takes a pointer to an object and a method pointer to	2050	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	2051	with. If it is omitted, it will use C<EV_DEFAULT>.
1362	C<ev_init> for you, which means you have to call the C<set> method	2052
1363	before starting it. If you do not specify a loop then the constructor	2053	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	2054	C<set> method before starting it.
		2055
		2056	It will not set a callback, however: You have to call the templated C<set>
		2057	method to set a callback before you can start the watcher.
		2058
		2059	(The reason why you have to use a method is a limitation in C++ which does
		2060	not allow explicit template arguments for constructors).
1365		2061
1366	The destructor automatically stops the watcher if it is active.	2062	The destructor automatically stops the watcher if it is active.
		2063
		2064	=item w->set<class, &class::method> (object *)
		2065
		2066	This method sets the callback method to call. The method has to have a
		2067	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2068	first argument and the C<revents> as second. The object must be given as
		2069	parameter and is stored in the C<data> member of the watcher.
		2070
		2071	This method synthesizes efficient thunking code to call your method from
		2072	the C callback that libev requires. If your compiler can inline your
		2073	callback (i.e. it is visible to it at the place of the C<set> call and
		2074	your compiler is good :), then the method will be fully inlined into the
		2075	thunking function, making it as fast as a direct C callback.
		2076
		2077	Example: simple class declaration and watcher initialisation
		2078
		2079	struct myclass
		2080	{
		2081	void io_cb (ev::io &w, int revents) { }
		2082	}
		2083
		2084	myclass obj;
		2085	ev::io iow;
		2086	iow.set <myclass, &myclass::io_cb> (&obj);
		2087
		2088	=item w->set<function> (void *data = 0)
		2089
		2090	Also sets a callback, but uses a static method or plain function as
		2091	callback. The optional C<data> argument will be stored in the watcher's
		2092	C<data> member and is free for you to use.
		2093
		2094	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2095
		2096	See the method-C<set> above for more details.
		2097
		2098	Example:
		2099
		2100	static void io_cb (ev::io &w, int revents) { }
		2101	iow.set <io_cb> ();
1367		2102
1368	=item w->set (struct ev_loop *)	2103	=item w->set (struct ev_loop *)
1369		2104
1370	Associates a different C<struct ev_loop> with this watcher. You can only	2105	Associates a different C<struct ev_loop> with this watcher. You can only
1371	do this when the watcher is inactive (and not pending either).	2106	do this when the watcher is inactive (and not pending either).
1372		2107
1373	=item w->set ([args])	2108	=item w->set ([args])
1374		2109
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2110	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1376	called at least once. Unlike the C counterpart, an active watcher gets	2111	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	2112	automatically stopped and restarted when reconfiguring it with this
		2113	method.
1378		2114
1379	=item w->start ()	2115	=item w->start ()
1380		2116
1381	Starts the watcher. Note that there is no C<loop> argument as the	2117	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	2118	constructor already stores the event loop.
1383		2119
1384	=item w->stop ()	2120	=item w->stop ()
1385		2121
1386	Stops the watcher if it is active. Again, no C<loop> argument.	2122	Stops the watcher if it is active. Again, no C<loop> argument.
1387		2123
1388	=item w->again () C<ev::timer>, C<ev::periodic> only	2124	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1389		2125
1390	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2126	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1391	C<ev_TYPE_again> function.	2127	C<ev_TYPE_again> function.
1392		2128
1393	=item w->sweep () C<ev::embed> only	2129	=item w->sweep () (C<ev::embed> only)
1394		2130
1395	Invokes C<ev_embed_sweep>.	2131	Invokes C<ev_embed_sweep>.
		2132
		2133	=item w->update () (C<ev::stat> only)
		2134
		2135	Invokes C<ev_stat_stat>.
1396		2136
1397	=back	2137	=back
1398		2138
1399	=back	2139	=back
1400		2140
…		…
1408		2148
1409	myclass ();	2149	myclass ();
1410	}	2150	}
1411		2151
1412	myclass::myclass (int fd)	2152	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	2153	{
		2154	io .set <myclass, &myclass::io_cb > (this);
		2155	idle.set <myclass, &myclass::idle_cb> (this);
		2156
1416	io.start (fd, ev::READ);	2157	io.start (fd, ev::READ);
1417	}	2158	}
		2159
		2160
		2161	=head1 MACRO MAGIC
		2162
		2163	Libev can be compiled with a variety of options, the most fundamantal
		2164	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2165	functions and callbacks have an initial C<struct ev_loop *> argument.
		2166
		2167	To make it easier to write programs that cope with either variant, the
		2168	following macros are defined:
		2169
		2170	=over 4
		2171
		2172	=item C<EV_A>, C<EV_A_>
		2173
		2174	This provides the loop I<argument> for functions, if one is required ("ev
		2175	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2176	C<EV_A_> is used when other arguments are following. Example:
		2177
		2178	ev_unref (EV_A);
		2179	ev_timer_add (EV_A_ watcher);
		2180	ev_loop (EV_A_ 0);
		2181
		2182	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2183	which is often provided by the following macro.
		2184
		2185	=item C<EV_P>, C<EV_P_>
		2186
		2187	This provides the loop I<parameter> for functions, if one is required ("ev
		2188	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2189	C<EV_P_> is used when other parameters are following. Example:
		2190
		2191	// this is how ev_unref is being declared
		2192	static void ev_unref (EV_P);
		2193
		2194	// this is how you can declare your typical callback
		2195	static void cb (EV_P_ ev_timer *w, int revents)
		2196
		2197	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2198	suitable for use with C<EV_A>.
		2199
		2200	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2201
		2202	Similar to the other two macros, this gives you the value of the default
		2203	loop, if multiple loops are supported ("ev loop default").
		2204
		2205	=back
		2206
		2207	Example: Declare and initialise a check watcher, utilising the above
		2208	macros so it will work regardless of whether multiple loops are supported
		2209	or not.
		2210
		2211	static void
		2212	check_cb (EV_P_ ev_timer *w, int revents)
		2213	{
		2214	ev_check_stop (EV_A_ w);
		2215	}
		2216
		2217	ev_check check;
		2218	ev_check_init (&check, check_cb);
		2219	ev_check_start (EV_DEFAULT_ &check);
		2220	ev_loop (EV_DEFAULT_ 0);
1418		2221
1419	=head1 EMBEDDING	2222	=head1 EMBEDDING
1420		2223
1421	Libev can (and often is) directly embedded into host	2224	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	2225	applications. Examples of applications that embed it include the Deliantra
1423	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2226	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1424	and rxvt-unicode.	2227	and rxvt-unicode.
1425		2228
1426	The goal is to enable you to just copy the neecssary files into your	2229	The goal is to enable you to just copy the necessary files into your
1427	source directory without having to change even a single line in them, so	2230	source directory without having to change even a single line in them, so
1428	you can easily upgrade by simply copying (or having a checked-out copy of	2231	you can easily upgrade by simply copying (or having a checked-out copy of
1429	libev somewhere in your source tree).	2232	libev somewhere in your source tree).
1430		2233
1431	=head2 FILESETS	2234	=head2 FILESETS
…		…
1462	ev_vars.h	2265	ev_vars.h
1463	ev_wrap.h	2266	ev_wrap.h
1464		2267
1465	ev_win32.c required on win32 platforms only	2268	ev_win32.c required on win32 platforms only
1466		2269
1467	ev_select.c only when select backend is enabled (which is is by default)	2270	ev_select.c only when select backend is enabled (which is enabled by default)
1468	ev_poll.c only when poll backend is enabled (disabled by default)	2271	ev_poll.c only when poll backend is enabled (disabled by default)
1469	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2272	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1470	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2273	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1471	ev_port.c only when the solaris port backend is enabled (disabled by default)	2274	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		2275
1473	F<ev.c> includes the backend files directly when enabled, so you only need	2276	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	2277	to compile this single file.
1475		2278
1476	=head3 LIBEVENT COMPATIBILITY API	2279	=head3 LIBEVENT COMPATIBILITY API
1477		2280
1478	To include the libevent compatibility API, also include:	2281	To include the libevent compatibility API, also include:
1479		2282
…		…
1492		2295
1493	=head3 AUTOCONF SUPPORT	2296	=head3 AUTOCONF SUPPORT
1494		2297
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	2298	Instead of using C<EV_STANDALONE=1> and providing your config in
1496	whatever way you want, you can also C<m4_include([libev.m4])> in your	2299	whatever way you want, you can also C<m4_include([libev.m4])> in your
1497	F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include	2300	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	2301	include F<config.h> and configure itself accordingly.
1499		2302
1500	For this of course you need the m4 file:	2303	For this of course you need the m4 file:
1501		2304
1502	libev.m4	2305	libev.m4
1503		2306
…		…
1521		2324
1522	If defined to be C<1>, libev will try to detect the availability of the	2325	If defined to be C<1>, libev will try to detect the availability of the
1523	monotonic clock option at both compiletime and runtime. Otherwise no use	2326	monotonic clock option at both compiletime and runtime. Otherwise no use
1524	of the monotonic clock option will be attempted. If you enable this, you	2327	of the monotonic clock option will be attempted. If you enable this, you
1525	usually have to link against librt or something similar. Enabling it when	2328	usually have to link against librt or something similar. Enabling it when
1526	the functionality isn't available is safe, though, althoguh you have	2329	the functionality isn't available is safe, though, although you have
1527	to make sure you link against any libraries where the C<clock_gettime>	2330	to make sure you link against any libraries where the C<clock_gettime>
1528	function is hiding in (often F<-lrt>).	2331	function is hiding in (often F<-lrt>).
1529		2332
1530	=item EV_USE_REALTIME	2333	=item EV_USE_REALTIME
1531		2334
1532	If defined to be C<1>, libev will try to detect the availability of the	2335	If defined to be C<1>, libev will try to detect the availability of the
1533	realtime clock option at compiletime (and assume its availability at	2336	realtime clock option at compiletime (and assume its availability at
1534	runtime if successful). Otherwise no use of the realtime clock option will	2337	runtime if successful). Otherwise no use of the realtime clock option will
1535	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2338	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1536	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2339	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1537	in the description of C<EV_USE_MONOTONIC>, though.	2340	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2341
		2342	=item EV_USE_NANOSLEEP
		2343
		2344	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2345	and will use it for delays. Otherwise it will use C<select ()>.
1538		2346
1539	=item EV_USE_SELECT	2347	=item EV_USE_SELECT
1540		2348
1541	If undefined or defined to be C<1>, libev will compile in support for the	2349	If undefined or defined to be C<1>, libev will compile in support for the
1542	C<select>(2) backend. No attempt at autodetection will be done: if no	2350	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1597		2405
1598	=item EV_USE_DEVPOLL	2406	=item EV_USE_DEVPOLL
1599		2407
1600	reserved for future expansion, works like the USE symbols above.	2408	reserved for future expansion, works like the USE symbols above.
1601		2409
		2410	=item EV_USE_INOTIFY
		2411
		2412	If defined to be C<1>, libev will compile in support for the Linux inotify
		2413	interface to speed up C<ev_stat> watchers. Its actual availability will
		2414	be detected at runtime.
		2415
1602	=item EV_H	2416	=item EV_H
1603		2417
1604	The name of the F<ev.h> header file used to include it. The default if	2418	The name of the F<ev.h> header file used to include it. The default if
1605	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2419	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1606	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2420	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2443	will have the C<struct ev_loop *> as first argument, and you can create
1630	additional independent event loops. Otherwise there will be no support	2444	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2445	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2446	argument. Instead, all functions act on the single default loop.
1633		2447
		2448	=item EV_MINPRI
		2449
		2450	=item EV_MAXPRI
		2451
		2452	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2453	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2454	provide for more priorities by overriding those symbols (usually defined
		2455	to be C<-2> and C<2>, respectively).
		2456
		2457	When doing priority-based operations, libev usually has to linearly search
		2458	all the priorities, so having many of them (hundreds) uses a lot of space
		2459	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2460	fine.
		2461
		2462	If your embedding app does not need any priorities, defining these both to
		2463	C<0> will save some memory and cpu.
		2464
1634	=item EV_PERIODICS	2465	=item EV_PERIODIC_ENABLE
1635		2466
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2467	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2468	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2469	code.
		2470
		2471	=item EV_IDLE_ENABLE
		2472
		2473	If undefined or defined to be C<1>, then idle watchers are supported. If
		2474	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2475	code.
		2476
		2477	=item EV_EMBED_ENABLE
		2478
		2479	If undefined or defined to be C<1>, then embed watchers are supported. If
		2480	defined to be C<0>, then they are not.
		2481
		2482	=item EV_STAT_ENABLE
		2483
		2484	If undefined or defined to be C<1>, then stat watchers are supported. If
		2485	defined to be C<0>, then they are not.
		2486
		2487	=item EV_FORK_ENABLE
		2488
		2489	If undefined or defined to be C<1>, then fork watchers are supported. If
		2490	defined to be C<0>, then they are not.
		2491
		2492	=item EV_MINIMAL
		2493
		2494	If you need to shave off some kilobytes of code at the expense of some
		2495	speed, define this symbol to C<1>. Currently only used for gcc to override
		2496	some inlining decisions, saves roughly 30% codesize of amd64.
		2497
		2498	=item EV_PID_HASHSIZE
		2499
		2500	C<ev_child> watchers use a small hash table to distribute workload by
		2501	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2502	than enough. If you need to manage thousands of children you might want to
		2503	increase this value (I<must> be a power of two).
		2504
		2505	=item EV_INOTIFY_HASHSIZE
		2506
		2507	C<ev_staz> watchers use a small hash table to distribute workload by
		2508	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2509	usually more than enough. If you need to manage thousands of C<ev_stat>
		2510	watchers you might want to increase this value (I<must> be a power of
		2511	two).
1638		2512
1639	=item EV_COMMON	2513	=item EV_COMMON
1640		2514
1641	By default, all watchers have a C<void *data> member. By redefining	2515	By default, all watchers have a C<void *data> member. By redefining
1642	this macro to a something else you can include more and other types of	2516	this macro to a something else you can include more and other types of
…		…
1647		2521
1648	#define EV_COMMON \	2522	#define EV_COMMON \
1649	SV *self; /* contains this struct */ \	2523	SV *self; /* contains this struct */ \
1650	SV *cb_sv, *fh /* note no trailing ";" */	2524	SV *cb_sv, *fh /* note no trailing ";" */
1651		2525
1652	=item EV_CB_DECLARE(type)	2526	=item EV_CB_DECLARE (type)
1653		2527
1654	=item EV_CB_INVOKE(watcher,revents)	2528	=item EV_CB_INVOKE (watcher, revents)
1655		2529
1656	=item ev_set_cb(ev,cb)	2530	=item ev_set_cb (ev, cb)
1657		2531
1658	Can be used to change the callback member declaration in each watcher,	2532	Can be used to change the callback member declaration in each watcher,
1659	and the way callbacks are invoked and set. Must expand to a struct member	2533	and the way callbacks are invoked and set. Must expand to a struct member
1660	definition and a statement, respectively. See the F<ev.v> header file for	2534	definition and a statement, respectively. See the F<ev.h> header file for
1661	their default definitions. One possible use for overriding these is to	2535	their default definitions. One possible use for overriding these is to
1662	avoid the ev_loop pointer as first argument in all cases, or to use method	2536	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2537	method calls instead of plain function calls in C++.
		2538
		2539	=head2 EXPORTED API SYMBOLS
		2540
		2541	If you need to re-export the API (e.g. via a dll) and you need a list of
		2542	exported symbols, you can use the provided F<Symbol.*> files which list
		2543	all public symbols, one per line:
		2544
		2545	Symbols.ev for libev proper
		2546	Symbols.event for the libevent emulation
		2547
		2548	This can also be used to rename all public symbols to avoid clashes with
		2549	multiple versions of libev linked together (which is obviously bad in
		2550	itself, but sometimes it is inconvinient to avoid this).
		2551
		2552	A sed command like this will create wrapper C<#define>'s that you need to
		2553	include before including F<ev.h>:
		2554
		2555	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2556
		2557	This would create a file F<wrap.h> which essentially looks like this:
		2558
		2559	#define ev_backend myprefix_ev_backend
		2560	#define ev_check_start myprefix_ev_check_start
		2561	#define ev_check_stop myprefix_ev_check_stop
		2562	...
1664		2563
1665	=head2 EXAMPLES	2564	=head2 EXAMPLES
1666		2565
1667	For a real-world example of a program the includes libev	2566	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2567	verbatim, you can have a look at the EV perl module
…		…
1671	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2570	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1672	will be compiled. It is pretty complex because it provides its own header	2571	will be compiled. It is pretty complex because it provides its own header
1673	file.	2572	file.
1674		2573
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2574	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1676	that everybody includes and which overrides some autoconf choices:	2575	that everybody includes and which overrides some configure choices:
1677		2576
		2577	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	2578	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	2579	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	2580	#define EV_PERIODIC_ENABLE 0
		2581	#define EV_STAT_ENABLE 0
		2582	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	2583	#define EV_CONFIG_H <config.h>
		2584	#define EV_MINPRI 0
		2585	#define EV_MAXPRI 0
1682		2586
1683	#include "ev++.h"	2587	#include "ev++.h"
1684		2588
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2589	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2590
1687	#include "ev_cpp.h"	2591	#include "ev_cpp.h"
1688	#include "ev.c"	2592	#include "ev.c"
1689		2593
		2594
		2595	=head1 COMPLEXITIES
		2596
		2597	In this section the complexities of (many of) the algorithms used inside
		2598	libev will be explained. For complexity discussions about backends see the
		2599	documentation for C<ev_default_init>.
		2600
		2601	All of the following are about amortised time: If an array needs to be
		2602	extended, libev needs to realloc and move the whole array, but this
		2603	happens asymptotically never with higher number of elements, so O(1) might
		2604	mean it might do a lengthy realloc operation in rare cases, but on average
		2605	it is much faster and asymptotically approaches constant time.
		2606
		2607	=over 4
		2608
		2609	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2610
		2611	This means that, when you have a watcher that triggers in one hour and
		2612	there are 100 watchers that would trigger before that then inserting will
		2613	have to skip those 100 watchers.
		2614
		2615	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2616
		2617	That means that for changing a timer costs less than removing/adding them
		2618	as only the relative motion in the event queue has to be paid for.
		2619
		2620	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2621
		2622	These just add the watcher into an array or at the head of a list.
		2623	=item Stopping check/prepare/idle watchers: O(1)
		2624
		2625	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2626
		2627	These watchers are stored in lists then need to be walked to find the
		2628	correct watcher to remove. The lists are usually short (you don't usually
		2629	have many watchers waiting for the same fd or signal).
		2630
		2631	=item Finding the next timer per loop iteration: O(1)
		2632
		2633	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2634
		2635	A change means an I/O watcher gets started or stopped, which requires
		2636	libev to recalculate its status (and possibly tell the kernel).
		2637
		2638	=item Activating one watcher: O(1)
		2639
		2640	=item Priority handling: O(number_of_priorities)
		2641
		2642	Priorities are implemented by allocating some space for each
		2643	priority. When doing priority-based operations, libev usually has to
		2644	linearly search all the priorities.
		2645
		2646	=back
		2647
		2648
1690	=head1 AUTHOR	2649	=head1 AUTHOR
1691		2650
1692	Marc Lehmann <libev@schmorp.de>.	2651	Marc Lehmann <libev@schmorp.de>.
1693		2652

Diff Legend

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