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…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		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.
…		…
66		119
67	=item int ev_version_major ()	120	=item int ev_version_major ()
68		121
69	=item int ev_version_minor ()	122	=item int ev_version_minor ()
70		123
71	You can find out the major and minor version numbers of the library	124	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	125	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	126	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	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	128	version of the library your program was compiled against.
76		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
77	Usually, it's a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	136	not a problem.
81		137
82	Example: make sure we haven't accidentally been linked against the wrong	138	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	139	version.
84		140
85	assert (("libev version mismatch",	141	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	142	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	143	&& ev_version_minor () >= EV_VERSION_MINOR));
88		144
…		…
118		174
119	See the description of C<ev_embed> watchers for more info.	175	See the description of C<ev_embed> watchers for more info.
120		176
121	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	177	=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122		178
123	Sets the allocation function to use (the prototype is similar to the	179	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	180	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	181	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	182	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	183	potentially destructive action. The default is your system realloc
		184	function.
128		185
129	You could override this function in high-availability programs to, say,	186	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,	187	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.	188	or even to sleep a while and retry until some memory is available.
132		189
133	Example: replace the libev allocator with one that waits a bit and then	190	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	191	retries).
135		192
136	static void *	193	static void *
137	persistent_realloc (void *ptr, long size)	194	persistent_realloc (void *ptr, size_t size)
138	{	195	{
139	for (;;)	196	for (;;)
140	{	197	{
141	void *newptr = realloc (ptr, size);	198	void *newptr = realloc (ptr, size);
142		199
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	215	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	216	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	217	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	218	(such as abort).
162		219
163	Example: do the same thing as libev does internally:	220	Example: This is basically the same thing that libev does internally, too.
164		221
165	static void	222	static void
166	fatal_error (const char *msg)	223	fatal_error (const char *msg)
167	{	224	{
168	perror (msg);	225	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	276	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	277	useful to try out specific backends to test their performance, or to work
221	around bugs.	278	around bugs.
222		279
		280	=item C<EVFLAG_FORKCHECK>
		281
		282	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		283	a fork, you can also make libev check for a fork in each iteration by
		284	enabling this flag.
		285
		286	This works by calling C<getpid ()> on every iteration of the loop,
		287	and thus this might slow down your event loop if you do a lot of loop
		288	iterations and little real work, but is usually not noticeable (on my
		289	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		290	without a syscall and thus I<very> fast, but my Linux system also has
		291	C<pthread_atfork> which is even faster).
		292
		293	The big advantage of this flag is that you can forget about fork (and
		294	forget about forgetting to tell libev about forking) when you use this
		295	flag.
		296
		297	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		298	environment variable.
		299
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		301
225	This is your standard select(2) backend. Not I<completely> standard, as	302	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,	303	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	304	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).	313	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
237		314
238	=item C<EVBACKEND_EPOLL> (value 4, Linux)	315	=item C<EVBACKEND_EPOLL> (value 4, Linux)
239		316
240	For few fds, this backend is a bit little slower than poll and select,	317	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	318	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	319	like O(total_fds) where n is the total number of fds (or the highest fd),
243	either O(1) or O(active_fds).	320	epoll scales either O(1) or O(active_fds). The epoll design has a number
		321	of shortcomings, such as silently dropping events in some hard-to-detect
		322	cases and rewuiring a syscall per fd change, no fork support and bad
		323	support for dup:
244		324
245	While stopping and starting an I/O watcher in the same iteration will	325	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	326	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	327	(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	328	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
249	well if you register events for both fds.	329	very well if you register events for both fds.
250		330
251	Please note that epoll sometimes generates spurious notifications, so you	331	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	332	need to use non-blocking I/O or other means to avoid blocking when no data
253	(or space) is available.	333	(or space) is available.
254		334
255	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	335	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
256		336
257	Kqueue deserves special mention, as at the time of this writing, it	337	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	338	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	339	sockets and pipes, except on Darwin, where of course it's completely
		340	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"	341	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	342	unless you explicitly specify it explicitly in the flags (i.e. using
262	C<EVBACKEND_KQUEUE>).	343	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		344	system like NetBSD.
263		345
264	It scales in the same way as the epoll backend, but the interface to the	346	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	347	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	348	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	349	never cause an extra syscall as with epoll, it still adds up to two event
268	incident, so its best to avoid that.	350	changes per incident, support for C<fork ()> is very bad and it drops fds
		351	silently in similarly hard-to-detetc cases.
269		352
270	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	353	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
271		354
272	This is not implemented yet (and might never be).	355	This is not implemented yet (and might never be).
273		356
274	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	357	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
275		358
276	This uses the Solaris 10 port mechanism. As with everything on Solaris,	359	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)).	360	it's really slow, but it still scales very well (O(active_fds)).
278		361
279	Please note that solaris ports can result in a lot of spurious	362	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	363	notifications, so you need to use non-blocking I/O or other means to avoid
281	blocking when no data (or space) is available.	364	blocking when no data (or space) is available.
282		365
283	=item C<EVBACKEND_ALL>	366	=item C<EVBACKEND_ALL>
284		367
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	397	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	398	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	399	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).	400	undefined behaviour (or a failed assertion if assertions are enabled).
318		401
319	Example: try to create a event loop that uses epoll and nothing else.	402	Example: Try to create a event loop that uses epoll and nothing else.
320		403
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);	404	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322	if (!epoller)	405	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	406	fatal ("no epoll found here, maybe it hides under your chair");
324		407
…		…
327	Destroys the default loop again (frees all memory and kernel state	410	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	411	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	412	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>	413	responsibility to either stop all watchers cleanly yoursef I<before>
331	calling this function, or cope with the fact afterwards (which is usually	414	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	415	the easiest thing, you can just ignore the watchers and/or C<free ()> them
333	for example).	416	for example).
		417
		418	Note that certain global state, such as signal state, will not be freed by
		419	this function, and related watchers (such as signal and child watchers)
		420	would need to be stopped manually.
		421
		422	In general it is not advisable to call this function except in the
		423	rare occasion where you really need to free e.g. the signal handling
		424	pipe fds. If you need dynamically allocated loops it is better to use
		425	C<ev_loop_new> and C<ev_loop_destroy>).
334		426
335	=item ev_loop_destroy (loop)	427	=item ev_loop_destroy (loop)
336		428
337	Like C<ev_default_destroy>, but destroys an event loop created by an	429	Like C<ev_default_destroy>, but destroys an event loop created by an
338	earlier call to C<ev_loop_new>.	430	earlier call to C<ev_loop_new>.
…		…
362		454
363	Like C<ev_default_fork>, but acts on an event loop created by	455	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	456	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.	457	after fork, and how you do this is entirely your own problem.
366		458
		459	=item unsigned int ev_loop_count (loop)
		460
		461	Returns the count of loop iterations for the loop, which is identical to
		462	the number of times libev did poll for new events. It starts at C<0> and
		463	happily wraps around with enough iterations.
		464
		465	This value can sometimes be useful as a generation counter of sorts (it
		466	"ticks" the number of loop iterations), as it roughly corresponds with
		467	C<ev_prepare> and C<ev_check> calls.
		468
367	=item unsigned int ev_backend (loop)	469	=item unsigned int ev_backend (loop)
368		470
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	471	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	472	use.
371		473
…		…
373		475
374	Returns the current "event loop time", which is the time the event loop	476	Returns the current "event loop time", which is the time the event loop
375	received events and started processing them. This timestamp does not	477	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	478	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	479	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).	480	event occurring (or more correctly, libev finding out about it).
379		481
380	=item ev_loop (loop, int flags)	482	=item ev_loop (loop, int flags)
381		483
382	Finally, this is it, the event handler. This function usually is called	484	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	485	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	506	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	507	usually a better approach for this kind of thing.
406		508
407	Here are the gory details of what C<ev_loop> does:	509	Here are the gory details of what C<ev_loop> does:
408		510
		511	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	512	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	513	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	514	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	515	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	516	- Update the "event loop time".
414	- Calculate for how long to block.	517	- Calculate for how long to block.
415	- Block the process, waiting for any events.	518	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	526	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	527	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	528	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	529	were used, return, otherwise continue with step *.
427		530
428	Example: queue some jobs and then loop until no events are outsanding	531	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	532	anymore.
430		533
431	... queue jobs here, make sure they register event watchers as long	534	... 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..)	535	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	536	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	556	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	557	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	558	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>.	559	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		560
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	561	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	562	running when nothing else is active.
460		563
461	struct dv_signal exitsig;	564	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	565	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	566	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	567	evf_unref (loop);
465		568
466	Example: for some weird reason, unregister the above signal handler again.	569	Example: For some weird reason, unregister the above signal handler again.
467		570
468	ev_ref (myloop);	571	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	572	ev_signal_stop (loop, &exitsig);
470		573
471	=back	574	=back
		575
472		576
473	=head1 ANATOMY OF A WATCHER	577	=head1 ANATOMY OF A WATCHER
474		578
475	A watcher is a structure that you create and register to record your	579	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	580	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.	647	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		648
545	=item C<EV_CHILD>	649	=item C<EV_CHILD>
546		650
547	The pid specified in the C<ev_child> watcher has received a status change.	651	The pid specified in the C<ev_child> watcher has received a status change.
		652
		653	=item C<EV_STAT>
		654
		655	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		656
549	=item C<EV_IDLE>	657	=item C<EV_IDLE>
550		658
551	The C<ev_idle> watcher has determined that you have nothing better to do.	659	The C<ev_idle> watcher has determined that you have nothing better to do.
552		660
…		…
560	received events. Callbacks of both watcher types can start and stop as	668	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	669	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	670	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	671	C<ev_loop> from blocking).
564		672
		673	=item C<EV_EMBED>
		674
		675	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		676
		677	=item C<EV_FORK>
		678
		679	The event loop has been resumed in the child process after fork (see
		680	C<ev_fork>).
		681
565	=item C<EV_ERROR>	682	=item C<EV_ERROR>
566		683
567	An unspecified error has occured, the watcher has been stopped. This might	684	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	685	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	686	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	693	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	694	programs, though, so beware.
578		695
579	=back	696	=back
580		697
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	698	=head2 GENERIC WATCHER FUNCTIONS
582		699
583	In the following description, C<TYPE> stands for the watcher type,	700	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.	701	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		702
586	=over 4	703	=over 4
…		…
595	which rolls both calls into one.	712	which rolls both calls into one.
596		713
597	You can reinitialise a watcher at any time as long as it has been stopped	714	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.	715	(or never started) and there are no pending events outstanding.
599		716
600	The callbakc is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	717	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,
601	int revents)>.	718	int revents)>.
602		719
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	720	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		721
605	This macro initialises the type-specific parts of a watcher. You need to	722	This macro initialises the type-specific parts of a watcher. You need to
…		…
640	=item bool ev_is_pending (ev_TYPE *watcher)	757	=item bool ev_is_pending (ev_TYPE *watcher)
641		758
642	Returns a true value iff the watcher is pending, (i.e. it has outstanding	759	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	760	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	761	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	762	C<ev_TYPE_set> is safe), you must not change its priority, and you must
646	libev (e.g. you cnanot C<free ()> it).	763	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		764	it).
647		765
648	=item callback = ev_cb (ev_TYPE *watcher)	766	=item callback ev_cb (ev_TYPE *watcher)
649		767
650	Returns the callback currently set on the watcher.	768	Returns the callback currently set on the watcher.
651		769
652	=item ev_cb_set (ev_TYPE *watcher, callback)	770	=item ev_cb_set (ev_TYPE *watcher, callback)
653		771
654	Change the callback. You can change the callback at virtually any time	772	Change the callback. You can change the callback at virtually any time
655	(modulo threads).	773	(modulo threads).
		774
		775	=item ev_set_priority (ev_TYPE *watcher, priority)
		776
		777	=item int ev_priority (ev_TYPE *watcher)
		778
		779	Set and query the priority of the watcher. The priority is a small
		780	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		781	(default: C<-2>). Pending watchers with higher priority will be invoked
		782	before watchers with lower priority, but priority will not keep watchers
		783	from being executed (except for C<ev_idle> watchers).
		784
		785	This means that priorities are I<only> used for ordering callback
		786	invocation after new events have been received. This is useful, for
		787	example, to reduce latency after idling, or more often, to bind two
		788	watchers on the same event and make sure one is called first.
		789
		790	If you need to suppress invocation when higher priority events are pending
		791	you need to look at C<ev_idle> watchers, which provide this functionality.
		792
		793	You I<must not> change the priority of a watcher as long as it is active or
		794	pending.
		795
		796	The default priority used by watchers when no priority has been set is
		797	always C<0>, which is supposed to not be too high and not be too low :).
		798
		799	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		800	fine, as long as you do not mind that the priority value you query might
		801	or might not have been adjusted to be within valid range.
		802
		803	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		804
		805	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		806	C<loop> nor C<revents> need to be valid as long as the watcher callback
		807	can deal with that fact.
		808
		809	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		810
		811	If the watcher is pending, this function returns clears its pending status
		812	and returns its C<revents> bitset (as if its callback was invoked). If the
		813	watcher isn't pending it does nothing and returns C<0>.
656		814
657	=back	815	=back
658		816
659		817
660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	818	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
681	{	839	{
682	struct my_io *w = (struct my_io *)w_;	840	struct my_io *w = (struct my_io *)w_;
683	...	841	...
684	}	842	}
685		843
686	More interesting and less C-conformant ways of catsing your callback type	844	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	845	instead have been omitted.
		846
		847	Another common scenario is having some data structure with multiple
		848	watchers:
		849
		850	struct my_biggy
		851	{
		852	int some_data;
		853	ev_timer t1;
		854	ev_timer t2;
		855	}
		856
		857	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		858	you need to use C<offsetof>:
		859
		860	#include <stddef.h>
		861
		862	static void
		863	t1_cb (EV_P_ struct ev_timer *w, int revents)
		864	{
		865	struct my_biggy big = (struct my_biggy *
		866	(((char *)w) - offsetof (struct my_biggy, t1));
		867	}
		868
		869	static void
		870	t2_cb (EV_P_ struct ev_timer *w, int revents)
		871	{
		872	struct my_biggy big = (struct my_biggy *
		873	(((char *)w) - offsetof (struct my_biggy, t2));
		874	}
688		875
689		876
690	=head1 WATCHER TYPES	877	=head1 WATCHER TYPES
691		878
692	This section describes each watcher in detail, but will not repeat	879	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	880	information given in the last section. Any initialisation/set macros,
		881	functions and members specific to the watcher type are explained.
694		882
		883	Members are additionally marked with either I<[read-only]>, meaning that,
		884	while the watcher is active, you can look at the member and expect some
		885	sensible content, but you must not modify it (you can modify it while the
		886	watcher is stopped to your hearts content), or I<[read-write]>, which
		887	means you can expect it to have some sensible content while the watcher
		888	is active, but you can also modify it. Modifying it may not do something
		889	sensible or take immediate effect (or do anything at all), but libev will
		890	not crash or malfunction in any way.
695		891
		892
696	=head2 C<ev_io> - is this file descriptor readable or writable	893	=head2 C<ev_io> - is this file descriptor readable or writable?
697		894
698	I/O watchers check whether a file descriptor is readable or writable	895	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	896	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	897	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	898	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	899	receiving events as long as the condition persists. Remember you can stop
		900	the watcher if you don't want to act on the event and neither want to
		901	receive future events.
703		902
704	In general you can register as many read and/or write event watchers per	903	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	904	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	905	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	906	required if you know what you are doing).
708		907
709	You have to be careful with dup'ed file descriptors, though. Some backends	908	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	909	(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	910	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	911	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	912	the same underlying "file open").
714		913
715	If you must do this, then force the use of a known-to-be-good backend	914	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	915	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	916	C<EVBACKEND_POLL>).
718		917
		918	Another thing you have to watch out for is that it is quite easy to
		919	receive "spurious" readyness notifications, that is your callback might
		920	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		921	because there is no data. Not only are some backends known to create a
		922	lot of those (for example solaris ports), it is very easy to get into
		923	this situation even with a relatively standard program structure. Thus
		924	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		925	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		926
		927	If you cannot run the fd in non-blocking mode (for example you should not
		928	play around with an Xlib connection), then you have to seperately re-test
		929	whether a file descriptor is really ready with a known-to-be good interface
		930	such as poll (fortunately in our Xlib example, Xlib already does this on
		931	its own, so its quite safe to use).
		932
		933	=head3 The special problem of disappearing file descriptors
		934
		935	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		936	descriptor (either by calling C<close> explicitly or by any other means,
		937	such as C<dup>). The reason is that you register interest in some file
		938	descriptor, but when it goes away, the operating system will silently drop
		939	this interest. If another file descriptor with the same number then is
		940	registered with libev, there is no efficient way to see that this is, in
		941	fact, a different file descriptor.
		942
		943	To avoid having to explicitly tell libev about such cases, libev follows
		944	the following policy: Each time C<ev_io_set> is being called, libev
		945	will assume that this is potentially a new file descriptor, otherwise
		946	it is assumed that the file descriptor stays the same. That means that
		947	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		948	descriptor even if the file descriptor number itself did not change.
		949
		950	This is how one would do it normally anyway, the important point is that
		951	the libev application should not optimise around libev but should leave
		952	optimisations to libev.
		953
		954	=head3 The special problem of dup'ed file descriptors
		955
		956	Some backends (e.g. epoll), cannot register events for file descriptors,
		957	but only events for the underlying file descriptions. That menas when you
		958	have C<dup ()>'ed file descriptors and register events for them, only one
		959	file descriptor might actually receive events.
		960
		961	There is no workaorund possible except not registering events
		962	for potentially C<dup ()>'ed file descriptors or to resort to
		963	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		964
		965	=head3 The special problem of fork
		966
		967	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		968	useless behaviour. Libev fully supports fork, but needs to be told about
		969	it in the child.
		970
		971	To support fork in your programs, you either have to call
		972	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		973	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		974	C<EVBACKEND_POLL>.
		975
		976
		977	=head3 Watcher-Specific Functions
		978
719	=over 4	979	=over 4
720		980
721	=item ev_io_init (ev_io *, callback, int fd, int events)	981	=item ev_io_init (ev_io *, callback, int fd, int events)
722		982
723	=item ev_io_set (ev_io *, int fd, int events)	983	=item ev_io_set (ev_io *, int fd, int events)
724		984
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	985	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 |	986	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	987	C<EV_READ | EV_WRITE> to receive the given events.
728		988
729	Please note that most of the more scalable backend mechanisms (for example	989	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	990
731	for file descriptors, so you practically need to use non-blocking I/O (and	991	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	992
733	interface before doing I/O (XLib can do this), or force the use of either	993	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	994
735	problem. Also note that it is quite easy to have your callback invoked	995	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		996
740	=back	997	=back
741		998
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	999	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	1000	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	1001	attempt to read a whole line in the callback.
745		1002
746	static void	1003	static void
747	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1004	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
748	{	1005	{
749	ev_io_stop (loop, w);	1006	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1013	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	1014	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	1015	ev_loop (loop, 0);
759		1016
760		1017
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	1018	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		1019
763	Timer watchers are simple relative timers that generate an event after a	1020	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	1021	given time, and optionally repeating in regular intervals after that.
765		1022
766	The timers are based on real time, that is, if you register an event that	1023	The timers are based on real time, that is, if you register an event that
…		…
779		1036
780	The callback is guarenteed to be invoked only when its timeout has passed,	1037	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	1038	but if multiple timers become ready during the same loop iteration then
782	order of execution is undefined.	1039	order of execution is undefined.
783		1040
		1041	=head3 Watcher-Specific Functions and Data Members
		1042
784	=over 4	1043	=over 4
785		1044
786	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1045	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
787		1046
788	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1047	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
801	=item ev_timer_again (loop)	1060	=item ev_timer_again (loop)
802		1061
803	This will act as if the timer timed out and restart it again if it is	1062	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	1063	repeating. The exact semantics are:
805		1064
		1065	If the timer is pending, its pending status is cleared.
		1066
806	If the timer is started but nonrepeating, stop it.	1067	If the timer is started but nonrepeating, stop it (as if it timed out).
807		1068
808	If the timer is repeating, either start it if necessary (with the repeat	1069	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	1070	C<repeat> value), or reset the running timer to the C<repeat> value.
810		1071
811	This sounds a bit complicated, but here is a useful and typical	1072	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	1073	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	1074	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	1075	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	1076	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	1077	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	1078	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.	1079	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1080	automatically restart it if need be.
		1081
		1082	That means you can ignore the C<after> value and C<ev_timer_start>
		1083	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1084
		1085	ev_timer_init (timer, callback, 0., 5.);
		1086	ev_timer_again (loop, timer);
		1087	...
		1088	timer->again = 17.;
		1089	ev_timer_again (loop, timer);
		1090	...
		1091	timer->again = 10.;
		1092	ev_timer_again (loop, timer);
		1093
		1094	This is more slightly efficient then stopping/starting the timer each time
		1095	you want to modify its timeout value.
		1096
		1097	=item ev_tstamp repeat [read-write]
		1098
		1099	The current C<repeat> value. Will be used each time the watcher times out
		1100	or C<ev_timer_again> is called and determines the next timeout (if any),
		1101	which is also when any modifications are taken into account.
819		1102
820	=back	1103	=back
821		1104
822	Example: create a timer that fires after 60 seconds.	1105	Example: Create a timer that fires after 60 seconds.
823		1106
824	static void	1107	static void
825	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1108	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
826	{	1109	{
827	.. one minute over, w is actually stopped right here	1110	.. one minute over, w is actually stopped right here
…		…
829		1112
830	struct ev_timer mytimer;	1113	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1114	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	1115	ev_timer_start (loop, &mytimer);
833		1116
834	Example: create a timeout timer that times out after 10 seconds of	1117	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	1118	inactivity.
836		1119
837	static void	1120	static void
838	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1121	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
839	{	1122	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1131	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1132	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1133	ev_timer_again (&mytimer);
851		1134
852		1135
853	=head2 C<ev_periodic> - to cron or not to cron	1136	=head2 C<ev_periodic> - to cron or not to cron?
854		1137
855	Periodic watchers are also timers of a kind, but they are very versatile	1138	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1139	(and unfortunately a bit complex).
857		1140
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1141	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	1142	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	1143	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 ()	1144	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	1145	+ 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	1146	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	1147	roughly 10 seconds later).
865	again).
866		1148
867	They can also be used to implement vastly more complex timers, such as	1149	They can also be used to implement vastly more complex timers, such as
868	triggering an event on eahc midnight, local time.	1150	triggering an event on each midnight, local time or other, complicated,
		1151	rules.
869		1152
870	As with timers, the callback is guarenteed to be invoked only when the	1153	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	1154	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.	1155	during the same loop iteration then order of execution is undefined.
873		1156
		1157	=head3 Watcher-Specific Functions and Data Members
		1158
874	=over 4	1159	=over 4
875		1160
876	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1161	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
877		1162
878	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1163	=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	1165	Lots of arguments, lets sort it out... There are basically three modes of
881	operation, and we will explain them from simplest to complex:	1166	operation, and we will explain them from simplest to complex:
882		1167
883	=over 4	1168	=over 4
884		1169
885	=item * absolute timer (interval = reschedule_cb = 0)	1170	=item * absolute timer (at = time, interval = reschedule_cb = 0)
886		1171
887	In this configuration the watcher triggers an event at the wallclock time	1172	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,	1173	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	1174	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.	1175	system time reaches or surpasses this time.
891		1176
892	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1177	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
893		1178
894	In this mode the watcher will always be scheduled to time out at the next	1179	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	1180	C<at + N * interval> time (for some integer N, which can also be negative)
896	of any time jumps.	1181	and then repeat, regardless of any time jumps.
897		1182
898	This can be used to create timers that do not drift with respect to system	1183	This can be used to create timers that do not drift with respect to system
899	time:	1184	time:
900		1185
901	ev_periodic_set (&periodic, 0., 3600., 0);	1186	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
907		1192
908	Another way to think about it (for the mathematically inclined) is that	1193	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	1194	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.	1195	time where C<time = at (mod interval)>, regardless of any time jumps.
911		1196
		1197	For numerical stability it is preferable that the C<at> value is near
		1198	C<ev_now ()> (the current time), but there is no range requirement for
		1199	this value.
		1200
912	=item * manual reschedule mode (reschedule_cb = callback)	1201	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
913		1202
914	In this mode the values for C<interval> and C<at> are both being	1203	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	1204	ignored. Instead, each time the periodic watcher gets scheduled, the
916	reschedule callback will be called with the watcher as first, and the	1205	reschedule callback will be called with the watcher as first, and the
917	current time as second argument.	1206	current time as second argument.
918		1207
919	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1208	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,	1209	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	1210	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
922	starting a prepare watcher).	1211	starting an C<ev_prepare> watcher, which is legal).
923		1212
924	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,	1213	Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
925	ev_tstamp now)>, e.g.:	1214	ev_tstamp now)>, e.g.:
926		1215
927	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1216	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	1239	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1240	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	1241	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1242	program when the crontabs have changed).
954		1243
		1244	=item ev_tstamp offset [read-write]
		1245
		1246	When repeating, this contains the offset value, otherwise this is the
		1247	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1248
		1249	Can be modified any time, but changes only take effect when the periodic
		1250	timer fires or C<ev_periodic_again> is being called.
		1251
		1252	=item ev_tstamp interval [read-write]
		1253
		1254	The current interval value. Can be modified any time, but changes only
		1255	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1256	called.
		1257
		1258	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
		1259
		1260	The current reschedule callback, or C<0>, if this functionality is
		1261	switched off. Can be changed any time, but changes only take effect when
		1262	the periodic timer fires or C<ev_periodic_again> is being called.
		1263
		1264	=item ev_tstamp at [read-only]
		1265
		1266	When active, contains the absolute time that the watcher is supposed to
		1267	trigger next.
		1268
955	=back	1269	=back
956		1270
957	Example: call a callback every hour, or, more precisely, whenever the	1271	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1272	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1273	potentially a lot of jittering, but good long-term stability.
960		1274
961	static void	1275	static void
962	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1276	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
…		…
966		1280
967	struct ev_periodic hourly_tick;	1281	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1282	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1283	ev_periodic_start (loop, &hourly_tick);
970		1284
971	Example: the same as above, but use a reschedule callback to do it:	1285	Example: The same as above, but use a reschedule callback to do it:
972		1286
973	#include <math.h>	1287	#include <math.h>
974		1288
975	static ev_tstamp	1289	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1290	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1292	return fmod (now, 3600.) + 3600.;
979	}	1293	}
980		1294
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1295	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1296
983	Example: call a callback every hour, starting now:	1297	Example: Call a callback every hour, starting now:
984		1298
985	struct ev_periodic hourly_tick;	1299	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1300	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1301	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1302	ev_periodic_start (loop, &hourly_tick);
989		1303
990		1304
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1305	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1306
993	Signal watchers will trigger an event when the process receives a specific	1307	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	1308	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	1309	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1310	normal event processing, like any other event.
…		…
1000	with the kernel (thus it coexists with your own signal handlers as long	1314	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	1315	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	1316	watcher for a signal is stopped libev will reset the signal handler to
1003	SIG_DFL (regardless of what it was set to before).	1317	SIG_DFL (regardless of what it was set to before).
1004		1318
		1319	=head3 Watcher-Specific Functions and Data Members
		1320
1005	=over 4	1321	=over 4
1006		1322
1007	=item ev_signal_init (ev_signal *, callback, int signum)	1323	=item ev_signal_init (ev_signal *, callback, int signum)
1008		1324
1009	=item ev_signal_set (ev_signal *, int signum)	1325	=item ev_signal_set (ev_signal *, int signum)
1010		1326
1011	Configures the watcher to trigger on the given signal number (usually one	1327	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1328	of the C<SIGxxx> constants).
1013		1329
		1330	=item int signum [read-only]
		1331
		1332	The signal the watcher watches out for.
		1333
1014	=back	1334	=back
1015		1335
1016		1336
1017	=head2 C<ev_child> - wait for pid status changes	1337	=head2 C<ev_child> - watch out for process status changes
1018		1338
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1339	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).	1340	some child status changes (most typically when a child of yours dies).
		1341
		1342	=head3 Watcher-Specific Functions and Data Members
1021		1343
1022	=over 4	1344	=over 4
1023		1345
1024	=item ev_child_init (ev_child *, callback, int pid)	1346	=item ev_child_init (ev_child *, callback, int pid)
1025		1347
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1352	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	1353	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	1354	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1355	process causing the status change.
1034		1356
		1357	=item int pid [read-only]
		1358
		1359	The process id this watcher watches out for, or C<0>, meaning any process id.
		1360
		1361	=item int rpid [read-write]
		1362
		1363	The process id that detected a status change.
		1364
		1365	=item int rstatus [read-write]
		1366
		1367	The process exit/trace status caused by C<rpid> (see your systems
		1368	C<waitpid> and C<sys/wait.h> documentation for details).
		1369
1035	=back	1370	=back
1036		1371
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1372	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1373
1039	static void	1374	static void
1040	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1375	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1041	{	1376	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1377	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1380	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1381	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1382	ev_signal_start (loop, &sigint_cb);
1048		1383
1049		1384
		1385	=head2 C<ev_stat> - did the file attributes just change?
		1386
		1387	This watches a filesystem path for attribute changes. That is, it calls
		1388	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1389	compared to the last time, invoking the callback if it did.
		1390
		1391	The path does not need to exist: changing from "path exists" to "path does
		1392	not exist" is a status change like any other. The condition "path does
		1393	not exist" is signified by the C<st_nlink> field being zero (which is
		1394	otherwise always forced to be at least one) and all the other fields of
		1395	the stat buffer having unspecified contents.
		1396
		1397	The path I<should> be absolute and I<must not> end in a slash. If it is
		1398	relative and your working directory changes, the behaviour is undefined.
		1399
		1400	Since there is no standard to do this, the portable implementation simply
		1401	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1402	can specify a recommended polling interval for this case. If you specify
		1403	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1404	unspecified default> value will be used (which you can expect to be around
		1405	five seconds, although this might change dynamically). Libev will also
		1406	impose a minimum interval which is currently around C<0.1>, but thats
		1407	usually overkill.
		1408
		1409	This watcher type is not meant for massive numbers of stat watchers,
		1410	as even with OS-supported change notifications, this can be
		1411	resource-intensive.
		1412
		1413	At the time of this writing, only the Linux inotify interface is
		1414	implemented (implementing kqueue support is left as an exercise for the
		1415	reader). Inotify will be used to give hints only and should not change the
		1416	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1417	to fall back to regular polling again even with inotify, but changes are
		1418	usually detected immediately, and if the file exists there will be no
		1419	polling.
		1420
		1421	=head3 Watcher-Specific Functions and Data Members
		1422
		1423	=over 4
		1424
		1425	=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
		1426
		1427	=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
		1428
		1429	Configures the watcher to wait for status changes of the given
		1430	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1431	be detected and should normally be specified as C<0> to let libev choose
		1432	a suitable value. The memory pointed to by C<path> must point to the same
		1433	path for as long as the watcher is active.
		1434
		1435	The callback will be receive C<EV_STAT> when a change was detected,
		1436	relative to the attributes at the time the watcher was started (or the
		1437	last change was detected).
		1438
		1439	=item ev_stat_stat (ev_stat *)
		1440
		1441	Updates the stat buffer immediately with new values. If you change the
		1442	watched path in your callback, you could call this fucntion to avoid
		1443	detecting this change (while introducing a race condition). Can also be
		1444	useful simply to find out the new values.
		1445
		1446	=item ev_statdata attr [read-only]
		1447
		1448	The most-recently detected attributes of the file. Although the type is of
		1449	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1450	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1451	was some error while C<stat>ing the file.
		1452
		1453	=item ev_statdata prev [read-only]
		1454
		1455	The previous attributes of the file. The callback gets invoked whenever
		1456	C<prev> != C<attr>.
		1457
		1458	=item ev_tstamp interval [read-only]
		1459
		1460	The specified interval.
		1461
		1462	=item const char *path [read-only]
		1463
		1464	The filesystem path that is being watched.
		1465
		1466	=back
		1467
		1468	Example: Watch C</etc/passwd> for attribute changes.
		1469
		1470	static void
		1471	passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
		1472	{
		1473	/* /etc/passwd changed in some way */
		1474	if (w->attr.st_nlink)
		1475	{
		1476	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1477	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1478	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1479	}
		1480	else
		1481	/* you shalt not abuse printf for puts */
		1482	puts ("wow, /etc/passwd is not there, expect problems. "
		1483	"if this is windows, they already arrived\n");
		1484	}
		1485
		1486	...
		1487	ev_stat passwd;
		1488
		1489	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1490	ev_stat_start (loop, &passwd);
		1491
		1492
1050	=head2 C<ev_idle> - when you've got nothing better to do	1493	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1494
1052	Idle watchers trigger events when there are no other events are pending	1495	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	1496	priority are pending (prepare, check and other idle watchers do not
1054	as your process is busy handling sockets or timeouts (or even signals,	1497	count).
1055	imagine) it will not be triggered. But when your process is idle all idle	1498
1056	watchers are being called again and again, once per event loop iteration -	1499	That is, as long as your process is busy handling sockets or timeouts
		1500	(or even signals, imagine) of the same or higher priority it will not be
		1501	triggered. But when your process is idle (or only lower-priority watchers
		1502	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	1503	iteration - until stopped, that is, or your process receives more events
1058	busy.	1504	and becomes busy again with higher priority stuff.
1059		1505
1060	The most noteworthy effect is that as long as any idle watchers are	1506	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.	1507	active, the process will not block when waiting for new events.
1062		1508
1063	Apart from keeping your process non-blocking (which is a useful	1509	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	1510	effect on its own sometimes), idle watchers are a good place to do
1065	"pseudo-background processing", or delay processing stuff to after the	1511	"pseudo-background processing", or delay processing stuff to after the
1066	event loop has handled all outstanding events.	1512	event loop has handled all outstanding events.
1067		1513
		1514	=head3 Watcher-Specific Functions and Data Members
		1515
1068	=over 4	1516	=over 4
1069		1517
1070	=item ev_idle_init (ev_signal *, callback)	1518	=item ev_idle_init (ev_signal *, callback)
1071		1519
1072	Initialises and configures the idle watcher - it has no parameters of any	1520	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,	1521	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1522	believe me.
1075		1523
1076	=back	1524	=back
1077		1525
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1526	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1527	callback, free it. Also, use no error checking, as usual.
1080		1528
1081	static void	1529	static void
1082	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	1530	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1083	{	1531	{
1084	free (w);	1532	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1537	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1538	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1539	ev_idle_start (loop, idle_cb);
1092		1540
1093		1541
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1542	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1543
1096	Prepare and check watchers are usually (but not always) used in tandem:	1544	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1545	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1546	afterwards.
1099		1547
		1548	You I<must not> call C<ev_loop> or similar functions that enter
		1549	the current event loop from either C<ev_prepare> or C<ev_check>
		1550	watchers. Other loops than the current one are fine, however. The
		1551	rationale behind this is that you do not need to check for recursion in
		1552	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1553	C<ev_check> so if you have one watcher of each kind they will always be
		1554	called in pairs bracketing the blocking call.
		1555
1100	Their main purpose is to integrate other event mechanisms into libev and	1556	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	1557	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	1558	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1559	coroutine library and lots more. They are also occasionally useful if
		1560	you cache some data and want to flush it before blocking (for example,
		1561	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1562	watcher).
1104		1563
1105	This is done by examining in each prepare call which file descriptors need	1564	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	1565	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	1566	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	1567	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	1577	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	1578	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	1579	loop from blocking if lower-priority coroutines are active, thus mapping
1121	low-priority coroutines to idle/background tasks).	1580	low-priority coroutines to idle/background tasks).
1122		1581
		1582	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1583	priority, to ensure that they are being run before any other watchers
		1584	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1585	too) should not activate ("feed") events into libev. While libev fully
		1586	supports this, they will be called before other C<ev_check> watchers did
		1587	their job. As C<ev_check> watchers are often used to embed other event
		1588	loops those other event loops might be in an unusable state until their
		1589	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1590	others).
		1591
		1592	=head3 Watcher-Specific Functions and Data Members
		1593
1123	=over 4	1594	=over 4
1124		1595
1125	=item ev_prepare_init (ev_prepare *, callback)	1596	=item ev_prepare_init (ev_prepare *, callback)
1126		1597
1127	=item ev_check_init (ev_check *, callback)	1598	=item ev_check_init (ev_check *, callback)
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1601	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.	1602	macros, but using them is utterly, utterly and completely pointless.
1132		1603
1133	=back	1604	=back
1134		1605
1135	Example: *TODO*.	1606	There are a number of principal ways to embed other event loops or modules
		1607	into libev. Here are some ideas on how to include libadns into libev
		1608	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1609	use for an actually working example. Another Perl module named C<EV::Glib>
		1610	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1611	into the Glib event loop).
1136		1612
		1613	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
		1614	and in a check watcher, destroy them and call into libadns. What follows
		1615	is pseudo-code only of course. This requires you to either use a low
		1616	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1617	the callbacks for the IO/timeout watchers might not have been called yet.
1137		1618
		1619	static ev_io iow [nfd];
		1620	static ev_timer tw;
		1621
		1622	static void
		1623	io_cb (ev_loop *loop, ev_io *w, int revents)
		1624	{
		1625	}
		1626
		1627	// create io watchers for each fd and a timer before blocking
		1628	static void
		1629	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
		1630	{
		1631	int timeout = 3600000;
		1632	struct pollfd fds [nfd];
		1633	// actual code will need to loop here and realloc etc.
		1634	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1635
		1636	/* the callback is illegal, but won't be called as we stop during check */
		1637	ev_timer_init (&tw, 0, timeout * 1e-3);
		1638	ev_timer_start (loop, &tw);
		1639
		1640	// create one ev_io per pollfd
		1641	for (int i = 0; i < nfd; ++i)
		1642	{
		1643	ev_io_init (iow + i, io_cb, fds [i].fd,
		1644	((fds [i].events & POLLIN ? EV_READ : 0)
		1645	| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1646
		1647	fds [i].revents = 0;
		1648	ev_io_start (loop, iow + i);
		1649	}
		1650	}
		1651
		1652	// stop all watchers after blocking
		1653	static void
		1654	adns_check_cb (ev_loop *loop, ev_check *w, int revents)
		1655	{
		1656	ev_timer_stop (loop, &tw);
		1657
		1658	for (int i = 0; i < nfd; ++i)
		1659	{
		1660	// set the relevant poll flags
		1661	// could also call adns_processreadable etc. here
		1662	struct pollfd *fd = fds + i;
		1663	int revents = ev_clear_pending (iow + i);
		1664	if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
		1665	if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
		1666
		1667	// now stop the watcher
		1668	ev_io_stop (loop, iow + i);
		1669	}
		1670
		1671	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1672	}
		1673
		1674	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1675	in the prepare watcher and would dispose of the check watcher.
		1676
		1677	Method 3: If the module to be embedded supports explicit event
		1678	notification (adns does), you can also make use of the actual watcher
		1679	callbacks, and only destroy/create the watchers in the prepare watcher.
		1680
		1681	static void
		1682	timer_cb (EV_P_ ev_timer *w, int revents)
		1683	{
		1684	adns_state ads = (adns_state)w->data;
		1685	update_now (EV_A);
		1686
		1687	adns_processtimeouts (ads, &tv_now);
		1688	}
		1689
		1690	static void
		1691	io_cb (EV_P_ ev_io *w, int revents)
		1692	{
		1693	adns_state ads = (adns_state)w->data;
		1694	update_now (EV_A);
		1695
		1696	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1697	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1698	}
		1699
		1700	// do not ever call adns_afterpoll
		1701
		1702	Method 4: Do not use a prepare or check watcher because the module you
		1703	want to embed is too inflexible to support it. Instead, youc na override
		1704	their poll function. The drawback with this solution is that the main
		1705	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1706	this.
		1707
		1708	static gint
		1709	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1710	{
		1711	int got_events = 0;
		1712
		1713	for (n = 0; n < nfds; ++n)
		1714	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1715
		1716	if (timeout >= 0)
		1717	// create/start timer
		1718
		1719	// poll
		1720	ev_loop (EV_A_ 0);
		1721
		1722	// stop timer again
		1723	if (timeout >= 0)
		1724	ev_timer_stop (EV_A_ &to);
		1725
		1726	// stop io watchers again - their callbacks should have set
		1727	for (n = 0; n < nfds; ++n)
		1728	ev_io_stop (EV_A_ iow [n]);
		1729
		1730	return got_events;
		1731	}
		1732
		1733
1138	=head2 C<ev_embed> - when one backend isn't enough	1734	=head2 C<ev_embed> - when one backend isn't enough...
1139		1735
1140	This is a rather advanced watcher type that lets you embed one event loop	1736	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	1737	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	1738	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1739	fashion and must not be used). (See portability notes, below).
1144		1740
1145	There are primarily two reasons you would want that: work around bugs and	1741	There are primarily two reasons you would want that: work around bugs and
1146	prioritise I/O.	1742	prioritise I/O.
1147		1743
1148	As an example for a bug workaround, the kqueue backend might only support	1744	As an example for a bug workaround, the kqueue backend might only support
…		…
1203	ev_embed_start (loop_hi, &embed);	1799	ev_embed_start (loop_hi, &embed);
1204	}	1800	}
1205	else	1801	else
1206	loop_lo = loop_hi;	1802	loop_lo = loop_hi;
1207		1803
		1804	=head2 Portability notes
		1805
		1806	Kqueue is nominally embeddable, but this is broken on all BSDs that I
		1807	tried, in various ways. Usually the embedded event loop will simply never
		1808	receive events, sometimes it will only trigger a few times, sometimes in a
		1809	loop. Epoll is also nominally embeddable, but many Linux kernel versions
		1810	will always eport the epoll fd as ready, even when no events are pending.
		1811
		1812	While libev allows embedding these backends (they are contained in
		1813	C<ev_embeddable_backends ()>), take extreme care that it will actually
		1814	work.
		1815
		1816	When in doubt, create a dynamic event loop forced to use sockets (this
		1817	usually works) and possibly another thread and a pipe or so to report to
		1818	your main event loop.
		1819
		1820	=head3 Watcher-Specific Functions and Data Members
		1821
1208	=over 4	1822	=over 4
1209		1823
1210	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)	1824	=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1211		1825
1212	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)	1826	=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
…		…
1221		1835
1222	Make a single, non-blocking sweep over the embedded loop. This works	1836	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	1837	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1838	apropriate way for embedded loops.
1225		1839
		1840	=item struct ev_loop *other [read-only]
		1841
		1842	The embedded event loop.
		1843
		1844	=back
		1845
		1846
		1847	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1848
		1849	Fork watchers are called when a C<fork ()> was detected (usually because
		1850	whoever is a good citizen cared to tell libev about it by calling
		1851	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1852	event loop blocks next and before C<ev_check> watchers are being called,
		1853	and only in the child after the fork. If whoever good citizen calling
		1854	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1855	handlers will be invoked, too, of course.
		1856
		1857	=head3 Watcher-Specific Functions and Data Members
		1858
		1859	=over 4
		1860
		1861	=item ev_fork_init (ev_signal *, callback)
		1862
		1863	Initialises and configures the fork watcher - it has no parameters of any
		1864	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1865	believe me.
		1866
1226	=back	1867	=back
1227		1868
1228		1869
1229	=head1 OTHER FUNCTIONS	1870	=head1 OTHER FUNCTIONS
1230		1871
…		…
1318		1959
1319	To use it,	1960	To use it,
1320		1961
1321	#include <ev++.h>	1962	#include <ev++.h>
1322		1963
1323	(it is not installed by default). This automatically includes F<ev.h>	1964	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	1965	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.	1966	put into the C<ev> namespace. It should support all the same embedding
		1967	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1326		1968
1327	It should support all the same embedding options as F<ev.h>, most notably	1969	Care has been taken to keep the overhead low. The only data member the C++
1328	C<EV_MULTIPLICITY>.	1970	classes add (compared to plain C-style watchers) is the event loop pointer
		1971	that the watcher is associated with (or no additional members at all if
		1972	you disable C<EV_MULTIPLICITY> when embedding libev).
		1973
		1974	Currently, functions, and static and non-static member functions can be
		1975	used as callbacks. Other types should be easy to add as long as they only
		1976	need one additional pointer for context. If you need support for other
		1977	types of functors please contact the author (preferably after implementing
		1978	it).
1329		1979
1330	Here is a list of things available in the C<ev> namespace:	1980	Here is a list of things available in the C<ev> namespace:
1331		1981
1332	=over 4	1982	=over 4
1333		1983
…		…
1349		1999
1350	All of those classes have these methods:	2000	All of those classes have these methods:
1351		2001
1352	=over 4	2002	=over 4
1353		2003
1354	=item ev::TYPE::TYPE (object *, object::method *)	2004	=item ev::TYPE::TYPE ()
1355		2005
1356	=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)	2006	=item ev::TYPE::TYPE (struct ev_loop *)
1357		2007
1358	=item ev::TYPE::~TYPE	2008	=item ev::TYPE::~TYPE
1359		2009
1360	The constructor takes a pointer to an object and a method pointer to	2010	The constructor (optionally) takes an event loop to associate the watcher
1361	the event handler callback to call in this class. The constructor calls	2011	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	2012
1363	before starting it. If you do not specify a loop then the constructor	2013	The constructor calls C<ev_init> for you, which means you have to call the
1364	automatically associates the default loop with this watcher.	2014	C<set> method before starting it.
		2015
		2016	It will not set a callback, however: You have to call the templated C<set>
		2017	method to set a callback before you can start the watcher.
		2018
		2019	(The reason why you have to use a method is a limitation in C++ which does
		2020	not allow explicit template arguments for constructors).
1365		2021
1366	The destructor automatically stops the watcher if it is active.	2022	The destructor automatically stops the watcher if it is active.
		2023
		2024	=item w->set<class, &class::method> (object *)
		2025
		2026	This method sets the callback method to call. The method has to have a
		2027	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2028	first argument and the C<revents> as second. The object must be given as
		2029	parameter and is stored in the C<data> member of the watcher.
		2030
		2031	This method synthesizes efficient thunking code to call your method from
		2032	the C callback that libev requires. If your compiler can inline your
		2033	callback (i.e. it is visible to it at the place of the C<set> call and
		2034	your compiler is good :), then the method will be fully inlined into the
		2035	thunking function, making it as fast as a direct C callback.
		2036
		2037	Example: simple class declaration and watcher initialisation
		2038
		2039	struct myclass
		2040	{
		2041	void io_cb (ev::io &w, int revents) { }
		2042	}
		2043
		2044	myclass obj;
		2045	ev::io iow;
		2046	iow.set <myclass, &myclass::io_cb> (&obj);
		2047
		2048	=item w->set<function> (void *data = 0)
		2049
		2050	Also sets a callback, but uses a static method or plain function as
		2051	callback. The optional C<data> argument will be stored in the watcher's
		2052	C<data> member and is free for you to use.
		2053
		2054	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2055
		2056	See the method-C<set> above for more details.
		2057
		2058	Example:
		2059
		2060	static void io_cb (ev::io &w, int revents) { }
		2061	iow.set <io_cb> ();
1367		2062
1368	=item w->set (struct ev_loop *)	2063	=item w->set (struct ev_loop *)
1369		2064
1370	Associates a different C<struct ev_loop> with this watcher. You can only	2065	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).	2066	do this when the watcher is inactive (and not pending either).
1372		2067
1373	=item w->set ([args])	2068	=item w->set ([args])
1374		2069
1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2070	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	2071	called at least once. Unlike the C counterpart, an active watcher gets
1377	automatically stopped and restarted.	2072	automatically stopped and restarted when reconfiguring it with this
		2073	method.
1378		2074
1379	=item w->start ()	2075	=item w->start ()
1380		2076
1381	Starts the watcher. Note that there is no C<loop> argument as the	2077	Starts the watcher. Note that there is no C<loop> argument, as the
1382	constructor already takes the loop.	2078	constructor already stores the event loop.
1383		2079
1384	=item w->stop ()	2080	=item w->stop ()
1385		2081
1386	Stops the watcher if it is active. Again, no C<loop> argument.	2082	Stops the watcher if it is active. Again, no C<loop> argument.
1387		2083
1388	=item w->again () C<ev::timer>, C<ev::periodic> only	2084	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1389		2085
1390	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2086	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1391	C<ev_TYPE_again> function.	2087	C<ev_TYPE_again> function.
1392		2088
1393	=item w->sweep () C<ev::embed> only	2089	=item w->sweep () (C<ev::embed> only)
1394		2090
1395	Invokes C<ev_embed_sweep>.	2091	Invokes C<ev_embed_sweep>.
		2092
		2093	=item w->update () (C<ev::stat> only)
		2094
		2095	Invokes C<ev_stat_stat>.
1396		2096
1397	=back	2097	=back
1398		2098
1399	=back	2099	=back
1400		2100
…		…
1408		2108
1409	myclass ();	2109	myclass ();
1410	}	2110	}
1411		2111
1412	myclass::myclass (int fd)	2112	myclass::myclass (int fd)
1413	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)
1415	{	2113	{
		2114	io .set <myclass, &myclass::io_cb > (this);
		2115	idle.set <myclass, &myclass::idle_cb> (this);
		2116
1416	io.start (fd, ev::READ);	2117	io.start (fd, ev::READ);
1417	}	2118	}
		2119
		2120
		2121	=head1 MACRO MAGIC
		2122
		2123	Libev can be compiled with a variety of options, the most fundamantal
		2124	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2125	functions and callbacks have an initial C<struct ev_loop *> argument.
		2126
		2127	To make it easier to write programs that cope with either variant, the
		2128	following macros are defined:
		2129
		2130	=over 4
		2131
		2132	=item C<EV_A>, C<EV_A_>
		2133
		2134	This provides the loop I<argument> for functions, if one is required ("ev
		2135	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2136	C<EV_A_> is used when other arguments are following. Example:
		2137
		2138	ev_unref (EV_A);
		2139	ev_timer_add (EV_A_ watcher);
		2140	ev_loop (EV_A_ 0);
		2141
		2142	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2143	which is often provided by the following macro.
		2144
		2145	=item C<EV_P>, C<EV_P_>
		2146
		2147	This provides the loop I<parameter> for functions, if one is required ("ev
		2148	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2149	C<EV_P_> is used when other parameters are following. Example:
		2150
		2151	// this is how ev_unref is being declared
		2152	static void ev_unref (EV_P);
		2153
		2154	// this is how you can declare your typical callback
		2155	static void cb (EV_P_ ev_timer *w, int revents)
		2156
		2157	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2158	suitable for use with C<EV_A>.
		2159
		2160	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2161
		2162	Similar to the other two macros, this gives you the value of the default
		2163	loop, if multiple loops are supported ("ev loop default").
		2164
		2165	=back
		2166
		2167	Example: Declare and initialise a check watcher, utilising the above
		2168	macros so it will work regardless of whether multiple loops are supported
		2169	or not.
		2170
		2171	static void
		2172	check_cb (EV_P_ ev_timer *w, int revents)
		2173	{
		2174	ev_check_stop (EV_A_ w);
		2175	}
		2176
		2177	ev_check check;
		2178	ev_check_init (&check, check_cb);
		2179	ev_check_start (EV_DEFAULT_ &check);
		2180	ev_loop (EV_DEFAULT_ 0);
1418		2181
1419	=head1 EMBEDDING	2182	=head1 EMBEDDING
1420		2183
1421	Libev can (and often is) directly embedded into host	2184	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	2185	applications. Examples of applications that embed it include the Deliantra
1423	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2186	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1424	and rxvt-unicode.	2187	and rxvt-unicode.
1425		2188
1426	The goal is to enable you to just copy the neecssary files into your	2189	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	2190	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	2191	you can easily upgrade by simply copying (or having a checked-out copy of
1429	libev somewhere in your source tree).	2192	libev somewhere in your source tree).
1430		2193
1431	=head2 FILESETS	2194	=head2 FILESETS
…		…
1462	ev_vars.h	2225	ev_vars.h
1463	ev_wrap.h	2226	ev_wrap.h
1464		2227
1465	ev_win32.c required on win32 platforms only	2228	ev_win32.c required on win32 platforms only
1466		2229
1467	ev_select.c only when select backend is enabled (which is is by default)	2230	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)	2231	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)	2232	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)	2233	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)	2234	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		2235
1473	F<ev.c> includes the backend files directly when enabled, so you only need	2236	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	2237	to compile this single file.
1475		2238
1476	=head3 LIBEVENT COMPATIBILITY API	2239	=head3 LIBEVENT COMPATIBILITY API
1477		2240
1478	To include the libevent compatibility API, also include:	2241	To include the libevent compatibility API, also include:
1479		2242
…		…
1492		2255
1493	=head3 AUTOCONF SUPPORT	2256	=head3 AUTOCONF SUPPORT
1494		2257
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	2258	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	2259	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	2260	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	2261	include F<config.h> and configure itself accordingly.
1499		2262
1500	For this of course you need the m4 file:	2263	For this of course you need the m4 file:
1501		2264
1502	libev.m4	2265	libev.m4
1503		2266
…		…
1521		2284
1522	If defined to be C<1>, libev will try to detect the availability of the	2285	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	2286	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	2287	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	2288	usually have to link against librt or something similar. Enabling it when
1526	the functionality isn't available is safe, though, althoguh you have	2289	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>	2290	to make sure you link against any libraries where the C<clock_gettime>
1528	function is hiding in (often F<-lrt>).	2291	function is hiding in (often F<-lrt>).
1529		2292
1530	=item EV_USE_REALTIME	2293	=item EV_USE_REALTIME
1531		2294
1532	If defined to be C<1>, libev will try to detect the availability of the	2295	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	2296	realtime clock option at compiletime (and assume its availability at
1534	runtime if successful). Otherwise no use of the realtime clock option will	2297	runtime if successful). Otherwise no use of the realtime clock option will
1535	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2298	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	2299	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1537	in the description of C<EV_USE_MONOTONIC>, though.	2300	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
1538		2301
1539	=item EV_USE_SELECT	2302	=item EV_USE_SELECT
1540		2303
1541	If undefined or defined to be C<1>, libev will compile in support for the	2304	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	2305	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1583	otherwise another method will be used as fallback. This is the preferred	2346	otherwise another method will be used as fallback. This is the preferred
1584	backend for BSD and BSD-like systems, although on most BSDs kqueue only	2347	backend for BSD and BSD-like systems, although on most BSDs kqueue only
1585	supports some types of fds correctly (the only platform we found that	2348	supports some types of fds correctly (the only platform we found that
1586	supports ptys for example was NetBSD), so kqueue might be compiled in, but	2349	supports ptys for example was NetBSD), so kqueue might be compiled in, but
1587	not be used unless explicitly requested. The best way to use it is to find	2350	not be used unless explicitly requested. The best way to use it is to find
1588	out wether kqueue supports your type of fd properly and use an embedded	2351	out whether kqueue supports your type of fd properly and use an embedded
1589	kqueue loop.	2352	kqueue loop.
1590		2353
1591	=item EV_USE_PORT	2354	=item EV_USE_PORT
1592		2355
1593	If defined to be C<1>, libev will compile in support for the Solaris	2356	If defined to be C<1>, libev will compile in support for the Solaris
…		…
1596	backend for Solaris 10 systems.	2359	backend for Solaris 10 systems.
1597		2360
1598	=item EV_USE_DEVPOLL	2361	=item EV_USE_DEVPOLL
1599		2362
1600	reserved for future expansion, works like the USE symbols above.	2363	reserved for future expansion, works like the USE symbols above.
		2364
		2365	=item EV_USE_INOTIFY
		2366
		2367	If defined to be C<1>, libev will compile in support for the Linux inotify
		2368	interface to speed up C<ev_stat> watchers. Its actual availability will
		2369	be detected at runtime.
1601		2370
1602	=item EV_H	2371	=item EV_H
1603		2372
1604	The name of the F<ev.h> header file used to include it. The default if	2373	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	2374	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2398	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	2399	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2400	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2401	argument. Instead, all functions act on the single default loop.
1633		2402
		2403	=item EV_MINPRI
		2404
		2405	=item EV_MAXPRI
		2406
		2407	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2408	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2409	provide for more priorities by overriding those symbols (usually defined
		2410	to be C<-2> and C<2>, respectively).
		2411
		2412	When doing priority-based operations, libev usually has to linearly search
		2413	all the priorities, so having many of them (hundreds) uses a lot of space
		2414	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2415	fine.
		2416
		2417	If your embedding app does not need any priorities, defining these both to
		2418	C<0> will save some memory and cpu.
		2419
1634	=item EV_PERIODICS	2420	=item EV_PERIODIC_ENABLE
1635		2421
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2422	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2423	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2424	code.
		2425
		2426	=item EV_IDLE_ENABLE
		2427
		2428	If undefined or defined to be C<1>, then idle watchers are supported. If
		2429	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2430	code.
		2431
		2432	=item EV_EMBED_ENABLE
		2433
		2434	If undefined or defined to be C<1>, then embed watchers are supported. If
		2435	defined to be C<0>, then they are not.
		2436
		2437	=item EV_STAT_ENABLE
		2438
		2439	If undefined or defined to be C<1>, then stat watchers are supported. If
		2440	defined to be C<0>, then they are not.
		2441
		2442	=item EV_FORK_ENABLE
		2443
		2444	If undefined or defined to be C<1>, then fork watchers are supported. If
		2445	defined to be C<0>, then they are not.
		2446
		2447	=item EV_MINIMAL
		2448
		2449	If you need to shave off some kilobytes of code at the expense of some
		2450	speed, define this symbol to C<1>. Currently only used for gcc to override
		2451	some inlining decisions, saves roughly 30% codesize of amd64.
		2452
		2453	=item EV_PID_HASHSIZE
		2454
		2455	C<ev_child> watchers use a small hash table to distribute workload by
		2456	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2457	than enough. If you need to manage thousands of children you might want to
		2458	increase this value (I<must> be a power of two).
		2459
		2460	=item EV_INOTIFY_HASHSIZE
		2461
		2462	C<ev_staz> watchers use a small hash table to distribute workload by
		2463	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2464	usually more than enough. If you need to manage thousands of C<ev_stat>
		2465	watchers you might want to increase this value (I<must> be a power of
		2466	two).
1638		2467
1639	=item EV_COMMON	2468	=item EV_COMMON
1640		2469
1641	By default, all watchers have a C<void *data> member. By redefining	2470	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	2471	this macro to a something else you can include more and other types of
…		…
1647		2476
1648	#define EV_COMMON \	2477	#define EV_COMMON \
1649	SV *self; /* contains this struct */ \	2478	SV *self; /* contains this struct */ \
1650	SV *cb_sv, *fh /* note no trailing ";" */	2479	SV *cb_sv, *fh /* note no trailing ";" */
1651		2480
1652	=item EV_CB_DECLARE(type)	2481	=item EV_CB_DECLARE (type)
1653		2482
1654	=item EV_CB_INVOKE(watcher,revents)	2483	=item EV_CB_INVOKE (watcher, revents)
1655		2484
1656	=item ev_set_cb(ev,cb)	2485	=item ev_set_cb (ev, cb)
1657		2486
1658	Can be used to change the callback member declaration in each watcher,	2487	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	2488	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	2489	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	2490	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	2491	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2492	method calls instead of plain function calls in C++.
		2493
		2494	=head2 EXPORTED API SYMBOLS
		2495
		2496	If you need to re-export the API (e.g. via a dll) and you need a list of
		2497	exported symbols, you can use the provided F<Symbol.*> files which list
		2498	all public symbols, one per line:
		2499
		2500	Symbols.ev for libev proper
		2501	Symbols.event for the libevent emulation
		2502
		2503	This can also be used to rename all public symbols to avoid clashes with
		2504	multiple versions of libev linked together (which is obviously bad in
		2505	itself, but sometimes it is inconvinient to avoid this).
		2506
		2507	A sed command like this will create wrapper C<#define>'s that you need to
		2508	include before including F<ev.h>:
		2509
		2510	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2511
		2512	This would create a file F<wrap.h> which essentially looks like this:
		2513
		2514	#define ev_backend myprefix_ev_backend
		2515	#define ev_check_start myprefix_ev_check_start
		2516	#define ev_check_stop myprefix_ev_check_stop
		2517	...
1664		2518
1665	=head2 EXAMPLES	2519	=head2 EXAMPLES
1666		2520
1667	For a real-world example of a program the includes libev	2521	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2522	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	2525	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	2526	will be compiled. It is pretty complex because it provides its own header
1673	file.	2527	file.
1674		2528
1675	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2529	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:	2530	that everybody includes and which overrides some configure choices:
1677		2531
		2532	#define EV_MINIMAL 1
1678	#define EV_USE_POLL 0	2533	#define EV_USE_POLL 0
1679	#define EV_MULTIPLICITY 0	2534	#define EV_MULTIPLICITY 0
1680	#define EV_PERIODICS 0	2535	#define EV_PERIODIC_ENABLE 0
		2536	#define EV_STAT_ENABLE 0
		2537	#define EV_FORK_ENABLE 0
1681	#define EV_CONFIG_H <config.h>	2538	#define EV_CONFIG_H <config.h>
		2539	#define EV_MINPRI 0
		2540	#define EV_MAXPRI 0
1682		2541
1683	#include "ev++.h"	2542	#include "ev++.h"
1684		2543
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2544	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2545
1687	#include "rxvttoolkit.h"	2546	#include "ev_cpp.h"
1688
1689	/* darwin has problems with its header files in C++, requiring this namespace juggling */
1690	using namespace ev;
1691
1692	#include "ev.c"	2547	#include "ev.c"
		2548
		2549
		2550	=head1 COMPLEXITIES
		2551
		2552	In this section the complexities of (many of) the algorithms used inside
		2553	libev will be explained. For complexity discussions about backends see the
		2554	documentation for C<ev_default_init>.
		2555
		2556	All of the following are about amortised time: If an array needs to be
		2557	extended, libev needs to realloc and move the whole array, but this
		2558	happens asymptotically never with higher number of elements, so O(1) might
		2559	mean it might do a lengthy realloc operation in rare cases, but on average
		2560	it is much faster and asymptotically approaches constant time.
		2561
		2562	=over 4
		2563
		2564	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2565
		2566	This means that, when you have a watcher that triggers in one hour and
		2567	there are 100 watchers that would trigger before that then inserting will
		2568	have to skip those 100 watchers.
		2569
		2570	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2571
		2572	That means that for changing a timer costs less than removing/adding them
		2573	as only the relative motion in the event queue has to be paid for.
		2574
		2575	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2576
		2577	These just add the watcher into an array or at the head of a list.
		2578	=item Stopping check/prepare/idle watchers: O(1)
		2579
		2580	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2581
		2582	These watchers are stored in lists then need to be walked to find the
		2583	correct watcher to remove. The lists are usually short (you don't usually
		2584	have many watchers waiting for the same fd or signal).
		2585
		2586	=item Finding the next timer per loop iteration: O(1)
		2587
		2588	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2589
		2590	A change means an I/O watcher gets started or stopped, which requires
		2591	libev to recalculate its status (and possibly tell the kernel).
		2592
		2593	=item Activating one watcher: O(1)
		2594
		2595	=item Priority handling: O(number_of_priorities)
		2596
		2597	Priorities are implemented by allocating some space for each
		2598	priority. When doing priority-based operations, libev usually has to
		2599	linearly search all the priorities.
		2600
		2601	=back
1693		2602
1694		2603
1695	=head1 AUTHOR	2604	=head1 AUTHOR
1696		2605
1697	Marc Lehmann <libev@schmorp.de>.	2606	Marc Lehmann <libev@schmorp.de>.

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