[ViewVC] Diff of: cvs/libev/ev.pod

Comparing libev/ev.pod (file contents):
Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs.
Revision 1.109 by root, Mon Dec 24 13:19:12 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
9	=head1 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	#include <ev.h>	11	#include <ev.h>
12		12
13	ev_io stdin_watcher;	13	ev_io stdin_watcher;
14	ev_timer timeout_watcher;	14	ev_timer timeout_watcher;
…		…
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
52		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occurring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
57	To do this, it must take more or less complete control over your process	61	To do this, it must take more or less complete control over your process
58	(or thread) by executing the I<event loop> handler, and will then	62	(or thread) by executing the I<event loop> handler, and will then
59	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
61	You register interest in certain events by registering so-called I<event	65	You register interest in certain events by registering so-called I<event
62	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
63	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
64	watcher.	68	watcher.
65		69
66	=head1 FEATURES	70	=head2 FEATURES
67		71
68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
78		82
79	It also is quite fast (see this	83	It also is quite fast (see this
80	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
81	for example).	85	for example).
82		86
83	=head1 CONVENTIONS	87	=head2 CONVENTIONS
84		88
85	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
86	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
87	various configuration options please have a look at B<EMBED> section in	91	various configuration options please have a look at B<EMBED> section in
88	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
89	loops, then all functions taking an initial argument of name C<loop>	93	loops, then all functions taking an initial argument of name C<loop>
90	(which is always of type C<struct ev_loop *>) will not have this argument.	94	(which is always of type C<struct ev_loop *>) will not have this argument.
91		95
92	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
93		97
94	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
95	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
96	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
97	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
98	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
99	it, you should treat it as such.	103	it, you should treat it as some floatingpoint value. Unlike the name
		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
100		106
101	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
102		108
103	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
104	library in any way.	110	library in any way.
…		…
109		115
110	Returns the current time as libev would use it. Please note that the	116	Returns the current time as libev would use it. Please note that the
111	C<ev_now> function is usually faster and also often returns the timestamp	117	C<ev_now> function is usually faster and also often returns the timestamp
112	you actually want to know.	118	you actually want to know.
113		119
		120	=item ev_sleep (ev_tstamp interval)
		121
		122	Sleep for the given interval: The current thread will be blocked until
		123	either it is interrupted or the given time interval has passed. Basically
		124	this is a subsecond-resolution C<sleep ()>.
		125
114	=item int ev_version_major ()	126	=item int ev_version_major ()
115		127
116	=item int ev_version_minor ()	128	=item int ev_version_minor ()
117		129
118	You can find out the major and minor version numbers of the library	130	You can find out the major and minor ABI version numbers of the library
119	you linked against by calling the functions C<ev_version_major> and	131	you linked against by calling the functions C<ev_version_major> and
120	C<ev_version_minor>. If you want, you can compare against the global	132	C<ev_version_minor>. If you want, you can compare against the global
121	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	133	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122	version of the library your program was compiled against.	134	version of the library your program was compiled against.
123		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
124	Usually, it's a good idea to terminate if the major versions mismatch,	139	Usually, it's a good idea to terminate if the major versions mismatch,
125	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
126	compatible to older versions, so a larger minor version alone is usually	141	compatible to older versions, so a larger minor version alone is usually
127	not a problem.	142	not a problem.
128		143
129	Example: Make sure we haven't accidentally been linked against the wrong	144	Example: Make sure we haven't accidentally been linked against the wrong
130	version.	145	version.
…		…
163	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164	recommended ones.	179	recommended ones.
165		180
166	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
167		182
168	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	183	=item ev_set_allocator (void (cb)(void *ptr, long size))
169		184
170	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
171	identical to the realloc C function). It is used to allocate and free	186	semantics is identical - to the realloc C function). It is used to
172	memory (no surprises here). If it returns zero when memory needs to be	187	allocate and free memory (no surprises here). If it returns zero when
173	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
174	action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
175		191
176	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
177	free some memory if it cannot allocate memory, to use a special allocator,	193	free some memory if it cannot allocate memory, to use a special allocator,
178	or even to sleep a while and retry until some memory is available.	194	or even to sleep a while and retry until some memory is available.
179		195
…		…
265	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
266	override the flags completely if it is found in the environment. This is	282	override the flags completely if it is found in the environment. This is
267	useful to try out specific backends to test their performance, or to work	283	useful to try out specific backends to test their performance, or to work
268	around bugs.	284	around bugs.
269		285
		286	=item C<EVFLAG_FORKCHECK>
		287
		288	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		289	a fork, you can also make libev check for a fork in each iteration by
		290	enabling this flag.
		291
		292	This works by calling C<getpid ()> on every iteration of the loop,
		293	and thus this might slow down your event loop if you do a lot of loop
		294	iterations and little real work, but is usually not noticeable (on my
		295	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		296	without a syscall and thus I<very> fast, but my Linux system also has
		297	C<pthread_atfork> which is even faster).
		298
		299	The big advantage of this flag is that you can forget about fork (and
		300	forget about forgetting to tell libev about forking) when you use this
		301	flag.
		302
		303	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		304	environment variable.
		305
270	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
271		307
272	This is your standard select(2) backend. Not I<completely> standard, as	308	This is your standard select(2) backend. Not I<completely> standard, as
273	libev tries to roll its own fd_set with no limits on the number of fds,	309	libev tries to roll its own fd_set with no limits on the number of fds,
274	but if that fails, expect a fairly low limit on the number of fds when	310	but if that fails, expect a fairly low limit on the number of fds when
275	using this backend. It doesn't scale too well (O(highest_fd)), but its usually	311	using this backend. It doesn't scale too well (O(highest_fd)), but its
276	the fastest backend for a low number of fds.	312	usually the fastest backend for a low number of (low-numbered :) fds.
		313
		314	To get good performance out of this backend you need a high amount of
		315	parallelity (most of the file descriptors should be busy). If you are
		316	writing a server, you should C<accept ()> in a loop to accept as many
		317	connections as possible during one iteration. You might also want to have
		318	a look at C<ev_set_io_collect_interval ()> to increase the amount of
		319	readyness notifications you get per iteration.
277		320
278	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)	321	=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
279		322
280	And this is your standard poll(2) backend. It's more complicated than	323	And this is your standard poll(2) backend. It's more complicated
281	select, but handles sparse fds better and has no artificial limit on the	324	than select, but handles sparse fds better and has no artificial
282	number of fds you can use (except it will slow down considerably with a	325	limit on the number of fds you can use (except it will slow down
283	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	326	considerably with a lot of inactive fds). It scales similarly to select,
		327	i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
		328	performance tips.
284		329
285	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
286		331
287	For few fds, this backend is a bit little slower than poll and select,	332	For few fds, this backend is a bit little slower than poll and select,
288	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
289	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	334	like O(total_fds) where n is the total number of fds (or the highest fd),
290	either O(1) or O(active_fds).	335	epoll scales either O(1) or O(active_fds). The epoll design has a number
		336	of shortcomings, such as silently dropping events in some hard-to-detect
		337	cases and rewiring a syscall per fd change, no fork support and bad
		338	support for dup.
291		339
292	While stopping and starting an I/O watcher in the same iteration will	340	While stopping, setting and starting an I/O watcher in the same iteration
293	result in some caching, there is still a syscall per such incident	341	will result in some caching, there is still a syscall per such incident
294	(because the fd could point to a different file description now), so its	342	(because the fd could point to a different file description now), so its
295	best to avoid that. Also, dup()ed file descriptors might not work very	343	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
296	well if you register events for both fds.	344	very well if you register events for both fds.
297		345
298	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
299	need to use non-blocking I/O or other means to avoid blocking when no data	347	need to use non-blocking I/O or other means to avoid blocking when no data
300	(or space) is available.	348	(or space) is available.
301		349
		350	Best performance from this backend is achieved by not unregistering all
		351	watchers for a file descriptor until it has been closed, if possible, i.e.
		352	keep at least one watcher active per fd at all times.
		353
		354	While nominally embeddeble in other event loops, this feature is broken in
		355	all kernel versions tested so far.
		356
302	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
303		358
304	Kqueue deserves special mention, as at the time of this writing, it	359	Kqueue deserves special mention, as at the time of this writing, it
305	was broken on all BSDs except NetBSD (usually it doesn't work with	360	was broken on all BSDs except NetBSD (usually it doesn't work reliably
306	anything but sockets and pipes, except on Darwin, where of course its	361	with anything but sockets and pipes, except on Darwin, where of course
307	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
308	unless you explicitly specify it explicitly in the flags (i.e. using	363	unless you explicitly specify it explicitly in the flags (i.e. using
309	C<EVBACKEND_KQUEUE>).	364	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		365	system like NetBSD.
		366
		367	You still can embed kqueue into a normal poll or select backend and use it
		368	only for sockets (after having made sure that sockets work with kqueue on
		369	the target platform). See C<ev_embed> watchers for more info.
310		370
311	It scales in the same way as the epoll backend, but the interface to the	371	It scales in the same way as the epoll backend, but the interface to the
312	kernel is more efficient (which says nothing about its actual speed, of	372	kernel is more efficient (which says nothing about its actual speed, of
313	course). While starting and stopping an I/O watcher does not cause an	373	course). While stopping, setting and starting an I/O watcher does never
314	extra syscall as with epoll, it still adds up to four event changes per	374	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
315	incident, so its best to avoid that.	375	two event changes per incident, support for C<fork ()> is very bad and it
		376	drops fds silently in similarly hard-to-detect cases.
		377
		378	This backend usually performs well under most conditions.
		379
		380	While nominally embeddable in other event loops, this doesn't work
		381	everywhere, so you might need to test for this. And since it is broken
		382	almost everywhere, you should only use it when you have a lot of sockets
		383	(for which it usually works), by embedding it into another event loop
		384	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
		385	sockets.
316		386
317	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
318		388
319	This is not implemented yet (and might never be).	389	This is not implemented yet (and might never be, unless you send me an
		390	implementation). According to reports, C</dev/poll> only supports sockets
		391	and is not embeddable, which would limit the usefulness of this backend
		392	immensely.
320		393
321	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
322		395
323	This uses the Solaris 10 port mechanism. As with everything on Solaris,	396	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
324	it's really slow, but it still scales very well (O(active_fds)).	397	it's really slow, but it still scales very well (O(active_fds)).
325		398
326	Please note that solaris ports can result in a lot of spurious	399	Please note that solaris event ports can deliver a lot of spurious
327	notifications, so you need to use non-blocking I/O or other means to avoid	400	notifications, so you need to use non-blocking I/O or other means to avoid
328	blocking when no data (or space) is available.	401	blocking when no data (or space) is available.
		402
		403	While this backend scales well, it requires one system call per active
		404	file descriptor per loop iteration. For small and medium numbers of file
		405	descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
		406	might perform better.
329		407
330	=item C<EVBACKEND_ALL>	408	=item C<EVBACKEND_ALL>
331		409
332	Try all backends (even potentially broken ones that wouldn't be tried	410	Try all backends (even potentially broken ones that wouldn't be tried
333	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	411	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
334	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	412	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
		413
		414	It is definitely not recommended to use this flag.
335		415
336	=back	416	=back
337		417
338	If one or more of these are ored into the flags value, then only these	418	If one or more of these are ored into the flags value, then only these
339	backends will be tried (in the reverse order as given here). If none are	419	backends will be tried (in the reverse order as given here). If none are
…		…
374	Destroys the default loop again (frees all memory and kernel state	454	Destroys the default loop again (frees all memory and kernel state
375	etc.). None of the active event watchers will be stopped in the normal	455	etc.). None of the active event watchers will be stopped in the normal
376	sense, so e.g. C<ev_is_active> might still return true. It is your	456	sense, so e.g. C<ev_is_active> might still return true. It is your
377	responsibility to either stop all watchers cleanly yoursef I<before>	457	responsibility to either stop all watchers cleanly yoursef I<before>
378	calling this function, or cope with the fact afterwards (which is usually	458	calling this function, or cope with the fact afterwards (which is usually
379	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	459	the easiest thing, you can just ignore the watchers and/or C<free ()> them
380	for example).	460	for example).
		461
		462	Note that certain global state, such as signal state, will not be freed by
		463	this function, and related watchers (such as signal and child watchers)
		464	would need to be stopped manually.
		465
		466	In general it is not advisable to call this function except in the
		467	rare occasion where you really need to free e.g. the signal handling
		468	pipe fds. If you need dynamically allocated loops it is better to use
		469	C<ev_loop_new> and C<ev_loop_destroy>).
381		470
382	=item ev_loop_destroy (loop)	471	=item ev_loop_destroy (loop)
383		472
384	Like C<ev_default_destroy>, but destroys an event loop created by an	473	Like C<ev_default_destroy>, but destroys an event loop created by an
385	earlier call to C<ev_loop_new>.	474	earlier call to C<ev_loop_new>.
…		…
409		498
410	Like C<ev_default_fork>, but acts on an event loop created by	499	Like C<ev_default_fork>, but acts on an event loop created by
411	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	500	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
412	after fork, and how you do this is entirely your own problem.	501	after fork, and how you do this is entirely your own problem.
413		502
		503	=item unsigned int ev_loop_count (loop)
		504
		505	Returns the count of loop iterations for the loop, which is identical to
		506	the number of times libev did poll for new events. It starts at C<0> and
		507	happily wraps around with enough iterations.
		508
		509	This value can sometimes be useful as a generation counter of sorts (it
		510	"ticks" the number of loop iterations), as it roughly corresponds with
		511	C<ev_prepare> and C<ev_check> calls.
		512
414	=item unsigned int ev_backend (loop)	513	=item unsigned int ev_backend (loop)
415		514
416	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	515	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
417	use.	516	use.
418		517
…		…
420		519
421	Returns the current "event loop time", which is the time the event loop	520	Returns the current "event loop time", which is the time the event loop
422	received events and started processing them. This timestamp does not	521	received events and started processing them. This timestamp does not
423	change as long as callbacks are being processed, and this is also the base	522	change as long as callbacks are being processed, and this is also the base
424	time used for relative timers. You can treat it as the timestamp of the	523	time used for relative timers. You can treat it as the timestamp of the
425	event occuring (or more correctly, libev finding out about it).	524	event occurring (or more correctly, libev finding out about it).
426		525
427	=item ev_loop (loop, int flags)	526	=item ev_loop (loop, int flags)
428		527
429	Finally, this is it, the event handler. This function usually is called	528	Finally, this is it, the event handler. This function usually is called
430	after you initialised all your watchers and you want to start handling	529	after you initialised all your watchers and you want to start handling
…		…
451	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	550	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
452	usually a better approach for this kind of thing.	551	usually a better approach for this kind of thing.
453		552
454	Here are the gory details of what C<ev_loop> does:	553	Here are the gory details of what C<ev_loop> does:
455		554
		555	- Before the first iteration, call any pending watchers.
456	* If there are no active watchers (reference count is zero), return.	556	* If there are no active watchers (reference count is zero), return.
457	- Queue prepare watchers and then call all outstanding watchers.	557	- Queue all prepare watchers and then call all outstanding watchers.
458	- If we have been forked, recreate the kernel state.	558	- If we have been forked, recreate the kernel state.
459	- Update the kernel state with all outstanding changes.	559	- Update the kernel state with all outstanding changes.
460	- Update the "event loop time".	560	- Update the "event loop time".
461	- Calculate for how long to block.	561	- Calculate for how long to block.
462	- Block the process, waiting for any events.	562	- Block the process, waiting for any events.
…		…
513	Example: For some weird reason, unregister the above signal handler again.	613	Example: For some weird reason, unregister the above signal handler again.
514		614
515	ev_ref (loop);	615	ev_ref (loop);
516	ev_signal_stop (loop, &exitsig);	616	ev_signal_stop (loop, &exitsig);
517		617
		618	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		619
		620	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		621
		622	These advanced functions influence the time that libev will spend waiting
		623	for events. Both are by default C<0>, meaning that libev will try to
		624	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		625
		626	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		627	allows libev to delay invocation of I/O and timer/periodic callbacks to
		628	increase efficiency of loop iterations.
		629
		630	The background is that sometimes your program runs just fast enough to
		631	handle one (or very few) event(s) per loop iteration. While this makes
		632	the program responsive, it also wastes a lot of CPU time to poll for new
		633	events, especially with backends like C<select ()> which have a high
		634	overhead for the actual polling but can deliver many events at once.
		635
		636	By setting a higher I<io collect interval> you allow libev to spend more
		637	time collecting I/O events, so you can handle more events per iteration,
		638	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		639	C<ev_timer>) will be not affected. Setting this to a non-null value will
		640	introduce an additional C<ev_sleep ()> call into most loop iterations.
		641
		642	Likewise, by setting a higher I<timeout collect interval> you allow libev
		643	to spend more time collecting timeouts, at the expense of increased
		644	latency (the watcher callback will be called later). C<ev_io> watchers
		645	will not be affected. Setting this to a non-null value will not introduce
		646	any overhead in libev.
		647
		648	Many (busy) programs can usually benefit by setting the io collect
		649	interval to a value near C<0.1> or so, which is often enough for
		650	interactive servers (of course not for games), likewise for timeouts. It
		651	usually doesn't make much sense to set it to a lower value than C<0.01>,
		652	as this approsaches the timing granularity of most systems.
		653
518	=back	654	=back
519		655
520		656
521	=head1 ANATOMY OF A WATCHER	657	=head1 ANATOMY OF A WATCHER
522		658
…		…
701	=item bool ev_is_pending (ev_TYPE *watcher)	837	=item bool ev_is_pending (ev_TYPE *watcher)
702		838
703	Returns a true value iff the watcher is pending, (i.e. it has outstanding	839	Returns a true value iff the watcher is pending, (i.e. it has outstanding
704	events but its callback has not yet been invoked). As long as a watcher	840	events but its callback has not yet been invoked). As long as a watcher
705	is pending (but not active) you must not call an init function on it (but	841	is pending (but not active) you must not call an init function on it (but
706	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	842	C<ev_TYPE_set> is safe), you must not change its priority, and you must
707	libev (e.g. you cnanot C<free ()> it).	843	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		844	it).
708		845
709	=item callback ev_cb (ev_TYPE *watcher)	846	=item callback ev_cb (ev_TYPE *watcher)
710		847
711	Returns the callback currently set on the watcher.	848	Returns the callback currently set on the watcher.
712		849
713	=item ev_cb_set (ev_TYPE *watcher, callback)	850	=item ev_cb_set (ev_TYPE *watcher, callback)
714		851
715	Change the callback. You can change the callback at virtually any time	852	Change the callback. You can change the callback at virtually any time
716	(modulo threads).	853	(modulo threads).
		854
		855	=item ev_set_priority (ev_TYPE *watcher, priority)
		856
		857	=item int ev_priority (ev_TYPE *watcher)
		858
		859	Set and query the priority of the watcher. The priority is a small
		860	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		861	(default: C<-2>). Pending watchers with higher priority will be invoked
		862	before watchers with lower priority, but priority will not keep watchers
		863	from being executed (except for C<ev_idle> watchers).
		864
		865	This means that priorities are I<only> used for ordering callback
		866	invocation after new events have been received. This is useful, for
		867	example, to reduce latency after idling, or more often, to bind two
		868	watchers on the same event and make sure one is called first.
		869
		870	If you need to suppress invocation when higher priority events are pending
		871	you need to look at C<ev_idle> watchers, which provide this functionality.
		872
		873	You I<must not> change the priority of a watcher as long as it is active or
		874	pending.
		875
		876	The default priority used by watchers when no priority has been set is
		877	always C<0>, which is supposed to not be too high and not be too low :).
		878
		879	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		880	fine, as long as you do not mind that the priority value you query might
		881	or might not have been adjusted to be within valid range.
		882
		883	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		884
		885	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		886	C<loop> nor C<revents> need to be valid as long as the watcher callback
		887	can deal with that fact.
		888
		889	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		890
		891	If the watcher is pending, this function returns clears its pending status
		892	and returns its C<revents> bitset (as if its callback was invoked). If the
		893	watcher isn't pending it does nothing and returns C<0>.
717		894
718	=back	895	=back
719		896
720		897
721	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	898	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
806	In general you can register as many read and/or write event watchers per	983	In general you can register as many read and/or write event watchers per
807	fd as you want (as long as you don't confuse yourself). Setting all file	984	fd as you want (as long as you don't confuse yourself). Setting all file
808	descriptors to non-blocking mode is also usually a good idea (but not	985	descriptors to non-blocking mode is also usually a good idea (but not
809	required if you know what you are doing).	986	required if you know what you are doing).
810		987
811	You have to be careful with dup'ed file descriptors, though. Some backends
812	(the linux epoll backend is a notable example) cannot handle dup'ed file
813	descriptors correctly if you register interest in two or more fds pointing
814	to the same underlying file/socket/etc. description (that is, they share
815	the same underlying "file open").
816
817	If you must do this, then force the use of a known-to-be-good backend	988	If you must do this, then force the use of a known-to-be-good backend
818	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	989	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
819	C<EVBACKEND_POLL>).	990	C<EVBACKEND_POLL>).
820		991
821	Another thing you have to watch out for is that it is quite easy to	992	Another thing you have to watch out for is that it is quite easy to
…		…
827	it is best to always use non-blocking I/O: An extra C<read>(2) returning	998	it is best to always use non-blocking I/O: An extra C<read>(2) returning
828	C<EAGAIN> is far preferable to a program hanging until some data arrives.	999	C<EAGAIN> is far preferable to a program hanging until some data arrives.
829		1000
830	If you cannot run the fd in non-blocking mode (for example you should not	1001	If you cannot run the fd in non-blocking mode (for example you should not
831	play around with an Xlib connection), then you have to seperately re-test	1002	play around with an Xlib connection), then you have to seperately re-test
832	wether a file descriptor is really ready with a known-to-be good interface	1003	whether a file descriptor is really ready with a known-to-be good interface
833	such as poll (fortunately in our Xlib example, Xlib already does this on	1004	such as poll (fortunately in our Xlib example, Xlib already does this on
834	its own, so its quite safe to use).	1005	its own, so its quite safe to use).
		1006
		1007	=head3 The special problem of disappearing file descriptors
		1008
		1009	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1010	descriptor (either by calling C<close> explicitly or by any other means,
		1011	such as C<dup>). The reason is that you register interest in some file
		1012	descriptor, but when it goes away, the operating system will silently drop
		1013	this interest. If another file descriptor with the same number then is
		1014	registered with libev, there is no efficient way to see that this is, in
		1015	fact, a different file descriptor.
		1016
		1017	To avoid having to explicitly tell libev about such cases, libev follows
		1018	the following policy: Each time C<ev_io_set> is being called, libev
		1019	will assume that this is potentially a new file descriptor, otherwise
		1020	it is assumed that the file descriptor stays the same. That means that
		1021	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1022	descriptor even if the file descriptor number itself did not change.
		1023
		1024	This is how one would do it normally anyway, the important point is that
		1025	the libev application should not optimise around libev but should leave
		1026	optimisations to libev.
		1027
		1028	=head3 The special problem of dup'ed file descriptors
		1029
		1030	Some backends (e.g. epoll), cannot register events for file descriptors,
		1031	but only events for the underlying file descriptions. That means when you
		1032	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1033	events for them, only one file descriptor might actually receive events.
		1034
		1035	There is no workaround possible except not registering events
		1036	for potentially C<dup ()>'ed file descriptors, or to resort to
		1037	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1038
		1039	=head3 The special problem of fork
		1040
		1041	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1042	useless behaviour. Libev fully supports fork, but needs to be told about
		1043	it in the child.
		1044
		1045	To support fork in your programs, you either have to call
		1046	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1047	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1048	C<EVBACKEND_POLL>.
		1049
		1050
		1051	=head3 Watcher-Specific Functions
835		1052
836	=over 4	1053	=over 4
837		1054
838	=item ev_io_init (ev_io *, callback, int fd, int events)	1055	=item ev_io_init (ev_io *, callback, int fd, int events)
839		1056
…		…
893		1110
894	The callback is guarenteed to be invoked only when its timeout has passed,	1111	The callback is guarenteed to be invoked only when its timeout has passed,
895	but if multiple timers become ready during the same loop iteration then	1112	but if multiple timers become ready during the same loop iteration then
896	order of execution is undefined.	1113	order of execution is undefined.
897		1114
		1115	=head3 Watcher-Specific Functions and Data Members
		1116
898	=over 4	1117	=over 4
899		1118
900	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1119	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
901		1120
902	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1121	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
915	=item ev_timer_again (loop)	1134	=item ev_timer_again (loop)
916		1135
917	This will act as if the timer timed out and restart it again if it is	1136	This will act as if the timer timed out and restart it again if it is
918	repeating. The exact semantics are:	1137	repeating. The exact semantics are:
919		1138
		1139	If the timer is pending, its pending status is cleared.
		1140
920	If the timer is started but nonrepeating, stop it.	1141	If the timer is started but nonrepeating, stop it (as if it timed out).
921		1142
922	If the timer is repeating, either start it if necessary (with the repeat	1143	If the timer is repeating, either start it if necessary (with the
923	value), or reset the running timer to the repeat value.	1144	C<repeat> value), or reset the running timer to the C<repeat> value.
924		1145
925	This sounds a bit complicated, but here is a useful and typical	1146	This sounds a bit complicated, but here is a useful and typical
926	example: Imagine you have a tcp connection and you want a so-called	1147	example: Imagine you have a tcp connection and you want a so-called idle
927	idle timeout, that is, you want to be called when there have been,	1148	timeout, that is, you want to be called when there have been, say, 60
928	say, 60 seconds of inactivity on the socket. The easiest way to do	1149	seconds of inactivity on the socket. The easiest way to do this is to
929	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1150	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
930	C<ev_timer_again> each time you successfully read or write some data. If	1151	C<ev_timer_again> each time you successfully read or write some data. If
931	you go into an idle state where you do not expect data to travel on the	1152	you go into an idle state where you do not expect data to travel on the
932	socket, you can stop the timer, and again will automatically restart it if	1153	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
933	need be.	1154	automatically restart it if need be.
934		1155
935	You can also ignore the C<after> value and C<ev_timer_start> altogether	1156	That means you can ignore the C<after> value and C<ev_timer_start>
936	and only ever use the C<repeat> value:	1157	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
937		1158
938	ev_timer_init (timer, callback, 0., 5.);	1159	ev_timer_init (timer, callback, 0., 5.);
939	ev_timer_again (loop, timer);	1160	ev_timer_again (loop, timer);
940	...	1161	...
941	timer->again = 17.;	1162	timer->again = 17.;
942	ev_timer_again (loop, timer);	1163	ev_timer_again (loop, timer);
943	...	1164	...
944	timer->again = 10.;	1165	timer->again = 10.;
945	ev_timer_again (loop, timer);	1166	ev_timer_again (loop, timer);
946		1167
947	This is more efficient then stopping/starting the timer eahc time you want	1168	This is more slightly efficient then stopping/starting the timer each time
948	to modify its timeout value.	1169	you want to modify its timeout value.
949		1170
950	=item ev_tstamp repeat [read-write]	1171	=item ev_tstamp repeat [read-write]
951		1172
952	The current C<repeat> value. Will be used each time the watcher times out	1173	The current C<repeat> value. Will be used each time the watcher times out
953	or C<ev_timer_again> is called and determines the next timeout (if any),	1174	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
995	but on wallclock time (absolute time). You can tell a periodic watcher	1216	but on wallclock time (absolute time). You can tell a periodic watcher
996	to trigger "at" some specific point in time. For example, if you tell a	1217	to trigger "at" some specific point in time. For example, if you tell a
997	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1218	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
998	+ 10.>) and then reset your system clock to the last year, then it will	1219	+ 10.>) and then reset your system clock to the last year, then it will
999	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1220	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1000	roughly 10 seconds later and of course not if you reset your system time	1221	roughly 10 seconds later).
1001	again).
1002		1222
1003	They can also be used to implement vastly more complex timers, such as	1223	They can also be used to implement vastly more complex timers, such as
1004	triggering an event on eahc midnight, local time.	1224	triggering an event on each midnight, local time or other, complicated,
		1225	rules.
1005		1226
1006	As with timers, the callback is guarenteed to be invoked only when the	1227	As with timers, the callback is guarenteed to be invoked only when the
1007	time (C<at>) has been passed, but if multiple periodic timers become ready	1228	time (C<at>) has been passed, but if multiple periodic timers become ready
1008	during the same loop iteration then order of execution is undefined.	1229	during the same loop iteration then order of execution is undefined.
1009		1230
		1231	=head3 Watcher-Specific Functions and Data Members
		1232
1010	=over 4	1233	=over 4
1011		1234
1012	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1235	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1013		1236
1014	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1237	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1016	Lots of arguments, lets sort it out... There are basically three modes of	1239	Lots of arguments, lets sort it out... There are basically three modes of
1017	operation, and we will explain them from simplest to complex:	1240	operation, and we will explain them from simplest to complex:
1018		1241
1019	=over 4	1242	=over 4
1020		1243
1021	=item * absolute timer (interval = reschedule_cb = 0)	1244	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1022		1245
1023	In this configuration the watcher triggers an event at the wallclock time	1246	In this configuration the watcher triggers an event at the wallclock time
1024	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1247	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1025	that is, if it is to be run at January 1st 2011 then it will run when the	1248	that is, if it is to be run at January 1st 2011 then it will run when the
1026	system time reaches or surpasses this time.	1249	system time reaches or surpasses this time.
1027		1250
1028	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1251	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1029		1252
1030	In this mode the watcher will always be scheduled to time out at the next	1253	In this mode the watcher will always be scheduled to time out at the next
1031	C<at + N * interval> time (for some integer N) and then repeat, regardless	1254	C<at + N * interval> time (for some integer N, which can also be negative)
1032	of any time jumps.	1255	and then repeat, regardless of any time jumps.
1033		1256
1034	This can be used to create timers that do not drift with respect to system	1257	This can be used to create timers that do not drift with respect to system
1035	time:	1258	time:
1036		1259
1037	ev_periodic_set (&periodic, 0., 3600., 0);	1260	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1043		1266
1044	Another way to think about it (for the mathematically inclined) is that	1267	Another way to think about it (for the mathematically inclined) is that
1045	C<ev_periodic> will try to run the callback in this mode at the next possible	1268	C<ev_periodic> will try to run the callback in this mode at the next possible
1046	time where C<time = at (mod interval)>, regardless of any time jumps.	1269	time where C<time = at (mod interval)>, regardless of any time jumps.
1047		1270
		1271	For numerical stability it is preferable that the C<at> value is near
		1272	C<ev_now ()> (the current time), but there is no range requirement for
		1273	this value.
		1274
1048	=item * manual reschedule mode (reschedule_cb = callback)	1275	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1049		1276
1050	In this mode the values for C<interval> and C<at> are both being	1277	In this mode the values for C<interval> and C<at> are both being
1051	ignored. Instead, each time the periodic watcher gets scheduled, the	1278	ignored. Instead, each time the periodic watcher gets scheduled, the
1052	reschedule callback will be called with the watcher as first, and the	1279	reschedule callback will be called with the watcher as first, and the
1053	current time as second argument.	1280	current time as second argument.
1054		1281
1055	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1282	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1056	ever, or make any event loop modifications>. If you need to stop it,	1283	ever, or make any event loop modifications>. If you need to stop it,
1057	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1284	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1058	starting a prepare watcher).	1285	starting an C<ev_prepare> watcher, which is legal).
1059		1286
1060	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1287	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1061	ev_tstamp now)>, e.g.:	1288	ev_tstamp now)>, e.g.:
1062		1289
1063	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1290	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1086	Simply stops and restarts the periodic watcher again. This is only useful	1313	Simply stops and restarts the periodic watcher again. This is only useful
1087	when you changed some parameters or the reschedule callback would return	1314	when you changed some parameters or the reschedule callback would return
1088	a different time than the last time it was called (e.g. in a crond like	1315	a different time than the last time it was called (e.g. in a crond like
1089	program when the crontabs have changed).	1316	program when the crontabs have changed).
1090		1317
		1318	=item ev_tstamp offset [read-write]
		1319
		1320	When repeating, this contains the offset value, otherwise this is the
		1321	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1322
		1323	Can be modified any time, but changes only take effect when the periodic
		1324	timer fires or C<ev_periodic_again> is being called.
		1325
1091	=item ev_tstamp interval [read-write]	1326	=item ev_tstamp interval [read-write]
1092		1327
1093	The current interval value. Can be modified any time, but changes only	1328	The current interval value. Can be modified any time, but changes only
1094	take effect when the periodic timer fires or C<ev_periodic_again> is being	1329	take effect when the periodic timer fires or C<ev_periodic_again> is being
1095	called.	1330	called.
…		…
1097	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1332	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1098		1333
1099	The current reschedule callback, or C<0>, if this functionality is	1334	The current reschedule callback, or C<0>, if this functionality is
1100	switched off. Can be changed any time, but changes only take effect when	1335	switched off. Can be changed any time, but changes only take effect when
1101	the periodic timer fires or C<ev_periodic_again> is being called.	1336	the periodic timer fires or C<ev_periodic_again> is being called.
		1337
		1338	=item ev_tstamp at [read-only]
		1339
		1340	When active, contains the absolute time that the watcher is supposed to
		1341	trigger next.
1102		1342
1103	=back	1343	=back
1104		1344
1105	Example: Call a callback every hour, or, more precisely, whenever the	1345	Example: Call a callback every hour, or, more precisely, whenever the
1106	system clock is divisible by 3600. The callback invocation times have	1346	system clock is divisible by 3600. The callback invocation times have
…		…
1148	with the kernel (thus it coexists with your own signal handlers as long	1388	with the kernel (thus it coexists with your own signal handlers as long
1149	as you don't register any with libev). Similarly, when the last signal	1389	as you don't register any with libev). Similarly, when the last signal
1150	watcher for a signal is stopped libev will reset the signal handler to	1390	watcher for a signal is stopped libev will reset the signal handler to
1151	SIG_DFL (regardless of what it was set to before).	1391	SIG_DFL (regardless of what it was set to before).
1152		1392
		1393	=head3 Watcher-Specific Functions and Data Members
		1394
1153	=over 4	1395	=over 4
1154		1396
1155	=item ev_signal_init (ev_signal *, callback, int signum)	1397	=item ev_signal_init (ev_signal *, callback, int signum)
1156		1398
1157	=item ev_signal_set (ev_signal *, int signum)	1399	=item ev_signal_set (ev_signal *, int signum)
…		…
1168		1410
1169	=head2 C<ev_child> - watch out for process status changes	1411	=head2 C<ev_child> - watch out for process status changes
1170		1412
1171	Child watchers trigger when your process receives a SIGCHLD in response to	1413	Child watchers trigger when your process receives a SIGCHLD in response to
1172	some child status changes (most typically when a child of yours dies).	1414	some child status changes (most typically when a child of yours dies).
		1415
		1416	=head3 Watcher-Specific Functions and Data Members
1173		1417
1174	=over 4	1418	=over 4
1175		1419
1176	=item ev_child_init (ev_child *, callback, int pid)	1420	=item ev_child_init (ev_child *, callback, int pid)
1177		1421
…		…
1221	The path does not need to exist: changing from "path exists" to "path does	1465	The path does not need to exist: changing from "path exists" to "path does
1222	not exist" is a status change like any other. The condition "path does	1466	not exist" is a status change like any other. The condition "path does
1223	not exist" is signified by the C<st_nlink> field being zero (which is	1467	not exist" is signified by the C<st_nlink> field being zero (which is
1224	otherwise always forced to be at least one) and all the other fields of	1468	otherwise always forced to be at least one) and all the other fields of
1225	the stat buffer having unspecified contents.	1469	the stat buffer having unspecified contents.
		1470
		1471	The path I<should> be absolute and I<must not> end in a slash. If it is
		1472	relative and your working directory changes, the behaviour is undefined.
1226		1473
1227	Since there is no standard to do this, the portable implementation simply	1474	Since there is no standard to do this, the portable implementation simply
1228	calls C<stat (2)> regularly on the path to see if it changed somehow. You	1475	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1229	can specify a recommended polling interval for this case. If you specify	1476	can specify a recommended polling interval for this case. If you specify
1230	a polling interval of C<0> (highly recommended!) then a I<suitable,	1477	a polling interval of C<0> (highly recommended!) then a I<suitable,
…		…
1243	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1490	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1244	to fall back to regular polling again even with inotify, but changes are	1491	to fall back to regular polling again even with inotify, but changes are
1245	usually detected immediately, and if the file exists there will be no	1492	usually detected immediately, and if the file exists there will be no
1246	polling.	1493	polling.
1247		1494
		1495	=head3 Inotify
		1496
		1497	When C<inotify (7)> support has been compiled into libev (generally only
		1498	available on Linux) and present at runtime, it will be used to speed up
		1499	change detection where possible. The inotify descriptor will be created lazily
		1500	when the first C<ev_stat> watcher is being started.
		1501
		1502	Inotify presense does not change the semantics of C<ev_stat> watchers
		1503	except that changes might be detected earlier, and in some cases, to avoid
		1504	making regular C<stat> calls. Even in the presense of inotify support
		1505	there are many cases where libev has to resort to regular C<stat> polling.
		1506
		1507	(There is no support for kqueue, as apparently it cannot be used to
		1508	implement this functionality, due to the requirement of having a file
		1509	descriptor open on the object at all times).
		1510
		1511	=head3 The special problem of stat time resolution
		1512
		1513	The C<stat ()> syscall only supports full-second resolution portably, and
		1514	even on systems where the resolution is higher, many filesystems still
		1515	only support whole seconds.
		1516
		1517	That means that, if the time is the only thing that changes, you might
		1518	miss updates: on the first update, C<ev_stat> detects a change and calls
		1519	your callback, which does something. When there is another update within
		1520	the same second, C<ev_stat> will be unable to detect it.
		1521
		1522	The solution to this is to delay acting on a change for a second (or till
		1523	the next second boundary), using a roughly one-second delay C<ev_timer>
		1524	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1525	is added to work around small timing inconsistencies of some operating
		1526	systems.
		1527
		1528	=head3 Watcher-Specific Functions and Data Members
		1529
1248	=over 4	1530	=over 4
1249		1531
1250	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1532	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1251		1533
1252	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)	1534	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
…		…
1287	=item const char *path [read-only]	1569	=item const char *path [read-only]
1288		1570
1289	The filesystem path that is being watched.	1571	The filesystem path that is being watched.
1290		1572
1291	=back	1573	=back
		1574
		1575	=head3 Examples
1292		1576
1293	Example: Watch C</etc/passwd> for attribute changes.	1577	Example: Watch C</etc/passwd> for attribute changes.
1294		1578
1295	static void	1579	static void
1296	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1580	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1309	}	1593	}
1310		1594
1311	...	1595	...
1312	ev_stat passwd;	1596	ev_stat passwd;
1313		1597
1314	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1598	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1315	ev_stat_start (loop, &passwd);	1599	ev_stat_start (loop, &passwd);
1316		1600
		1601	Example: Like above, but additionally use a one-second delay so we do not
		1602	miss updates (however, frequent updates will delay processing, too, so
		1603	one might do the work both on C<ev_stat> callback invocation I<and> on
		1604	C<ev_timer> callback invocation).
		1605
		1606	static ev_stat passwd;
		1607	static ev_timer timer;
		1608
		1609	static void
		1610	timer_cb (EV_P_ ev_timer *w, int revents)
		1611	{
		1612	ev_timer_stop (EV_A_ w);
		1613
		1614	/* now it's one second after the most recent passwd change */
		1615	}
		1616
		1617	static void
		1618	stat_cb (EV_P_ ev_stat *w, int revents)
		1619	{
		1620	/* reset the one-second timer */
		1621	ev_timer_again (EV_A_ &timer);
		1622	}
		1623
		1624	...
		1625	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1626	ev_stat_start (loop, &passwd);
		1627	ev_timer_init (&timer, timer_cb, 0., 1.01);
		1628
1317		1629
1318	=head2 C<ev_idle> - when you've got nothing better to do...	1630	=head2 C<ev_idle> - when you've got nothing better to do...
1319		1631
1320	Idle watchers trigger events when there are no other events are pending	1632	Idle watchers trigger events when no other events of the same or higher
1321	(prepare, check and other idle watchers do not count). That is, as long	1633	priority are pending (prepare, check and other idle watchers do not
1322	as your process is busy handling sockets or timeouts (or even signals,	1634	count).
1323	imagine) it will not be triggered. But when your process is idle all idle	1635
1324	watchers are being called again and again, once per event loop iteration -	1636	That is, as long as your process is busy handling sockets or timeouts
		1637	(or even signals, imagine) of the same or higher priority it will not be
		1638	triggered. But when your process is idle (or only lower-priority watchers
		1639	are pending), the idle watchers are being called once per event loop
1325	until stopped, that is, or your process receives more events and becomes	1640	iteration - until stopped, that is, or your process receives more events
1326	busy.	1641	and becomes busy again with higher priority stuff.
1327		1642
1328	The most noteworthy effect is that as long as any idle watchers are	1643	The most noteworthy effect is that as long as any idle watchers are
1329	active, the process will not block when waiting for new events.	1644	active, the process will not block when waiting for new events.
1330		1645
1331	Apart from keeping your process non-blocking (which is a useful	1646	Apart from keeping your process non-blocking (which is a useful
1332	effect on its own sometimes), idle watchers are a good place to do	1647	effect on its own sometimes), idle watchers are a good place to do
1333	"pseudo-background processing", or delay processing stuff to after the	1648	"pseudo-background processing", or delay processing stuff to after the
1334	event loop has handled all outstanding events.	1649	event loop has handled all outstanding events.
		1650
		1651	=head3 Watcher-Specific Functions and Data Members
1335		1652
1336	=over 4	1653	=over 4
1337		1654
1338	=item ev_idle_init (ev_signal *, callback)	1655	=item ev_idle_init (ev_signal *, callback)
1339		1656
…		…
1397	with priority higher than or equal to the event loop and one coroutine	1714	with priority higher than or equal to the event loop and one coroutine
1398	of lower priority, but only once, using idle watchers to keep the event	1715	of lower priority, but only once, using idle watchers to keep the event
1399	loop from blocking if lower-priority coroutines are active, thus mapping	1716	loop from blocking if lower-priority coroutines are active, thus mapping
1400	low-priority coroutines to idle/background tasks).	1717	low-priority coroutines to idle/background tasks).
1401		1718
		1719	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1720	priority, to ensure that they are being run before any other watchers
		1721	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1722	too) should not activate ("feed") events into libev. While libev fully
		1723	supports this, they will be called before other C<ev_check> watchers
		1724	did their job. As C<ev_check> watchers are often used to embed other
		1725	(non-libev) event loops those other event loops might be in an unusable
		1726	state until their C<ev_check> watcher ran (always remind yourself to
		1727	coexist peacefully with others).
		1728
		1729	=head3 Watcher-Specific Functions and Data Members
		1730
1402	=over 4	1731	=over 4
1403		1732
1404	=item ev_prepare_init (ev_prepare *, callback)	1733	=item ev_prepare_init (ev_prepare *, callback)
1405		1734
1406	=item ev_check_init (ev_check *, callback)	1735	=item ev_check_init (ev_check *, callback)
…		…
1409	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1738	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1410	macros, but using them is utterly, utterly and completely pointless.	1739	macros, but using them is utterly, utterly and completely pointless.
1411		1740
1412	=back	1741	=back
1413		1742
1414	Example: To include a library such as adns, you would add IO watchers	1743	There are a number of principal ways to embed other event loops or modules
1415	and a timeout watcher in a prepare handler, as required by libadns, and	1744	into libev. Here are some ideas on how to include libadns into libev
		1745	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1746	use for an actually working example. Another Perl module named C<EV::Glib>
		1747	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1748	into the Glib event loop).
		1749
		1750	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1416	in a check watcher, destroy them and call into libadns. What follows is	1751	and in a check watcher, destroy them and call into libadns. What follows
1417	pseudo-code only of course:	1752	is pseudo-code only of course. This requires you to either use a low
		1753	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1754	the callbacks for the IO/timeout watchers might not have been called yet.
1418		1755
1419	static ev_io iow [nfd];	1756	static ev_io iow [nfd];
1420	static ev_timer tw;	1757	static ev_timer tw;
1421		1758
1422	static void	1759	static void
1423	io_cb (ev_loop loop, ev_io w, int revents)	1760	io_cb (ev_loop loop, ev_io w, int revents)
1424	{	1761	{
1425	// set the relevant poll flags
1426	// could also call adns_processreadable etc. here
1427	struct pollfd fd = (struct pollfd )w->data;
1428	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1429	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1430	}	1762	}
1431		1763
1432	// create io watchers for each fd and a timer before blocking	1764	// create io watchers for each fd and a timer before blocking
1433	static void	1765	static void
1434	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1766	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1435	{	1767	{
1436	int timeout = 3600000;truct pollfd fds [nfd];	1768	int timeout = 3600000;
		1769	struct pollfd fds [nfd];
1437	// actual code will need to loop here and realloc etc.	1770	// actual code will need to loop here and realloc etc.
1438	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1771	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1439		1772
1440	/* the callback is illegal, but won't be called as we stop during check */	1773	/* the callback is illegal, but won't be called as we stop during check */
1441	ev_timer_init (&tw, 0, timeout * 1e-3);	1774	ev_timer_init (&tw, 0, timeout * 1e-3);
1442	ev_timer_start (loop, &tw);	1775	ev_timer_start (loop, &tw);
1443		1776
1444	// create on ev_io per pollfd	1777	// create one ev_io per pollfd
1445	for (int i = 0; i < nfd; ++i)	1778	for (int i = 0; i < nfd; ++i)
1446	{	1779	{
1447	ev_io_init (iow + i, io_cb, fds [i].fd,	1780	ev_io_init (iow + i, io_cb, fds [i].fd,
1448	((fds [i].events & POLLIN ? EV_READ : 0)	1781	((fds [i].events & POLLIN ? EV_READ : 0)
1449	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1782	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1450		1783
1451	fds [i].revents = 0;	1784	fds [i].revents = 0;
1452	iow [i].data = fds + i;
1453	ev_io_start (loop, iow + i);	1785	ev_io_start (loop, iow + i);
1454	}	1786	}
1455	}	1787	}
1456		1788
1457	// stop all watchers after blocking	1789	// stop all watchers after blocking
…		…
1459	adns_check_cb (ev_loop loop, ev_check w, int revents)	1791	adns_check_cb (ev_loop loop, ev_check w, int revents)
1460	{	1792	{
1461	ev_timer_stop (loop, &tw);	1793	ev_timer_stop (loop, &tw);
1462		1794
1463	for (int i = 0; i < nfd; ++i)	1795	for (int i = 0; i < nfd; ++i)
		1796	{
		1797	// set the relevant poll flags
		1798	// could also call adns_processreadable etc. here
		1799	struct pollfd *fd = fds + i;
		1800	int revents = ev_clear_pending (iow + i);
		1801	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1802	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1803
		1804	// now stop the watcher
1464	ev_io_stop (loop, iow + i);	1805	ev_io_stop (loop, iow + i);
		1806	}
1465		1807
1466	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1808	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1809	}
		1810
		1811	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1812	in the prepare watcher and would dispose of the check watcher.
		1813
		1814	Method 3: If the module to be embedded supports explicit event
		1815	notification (adns does), you can also make use of the actual watcher
		1816	callbacks, and only destroy/create the watchers in the prepare watcher.
		1817
		1818	static void
		1819	timer_cb (EV_P_ ev_timer *w, int revents)
		1820	{
		1821	adns_state ads = (adns_state)w->data;
		1822	update_now (EV_A);
		1823
		1824	adns_processtimeouts (ads, &tv_now);
		1825	}
		1826
		1827	static void
		1828	io_cb (EV_P_ ev_io *w, int revents)
		1829	{
		1830	adns_state ads = (adns_state)w->data;
		1831	update_now (EV_A);
		1832
		1833	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1834	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1835	}
		1836
		1837	// do not ever call adns_afterpoll
		1838
		1839	Method 4: Do not use a prepare or check watcher because the module you
		1840	want to embed is too inflexible to support it. Instead, youc na override
		1841	their poll function. The drawback with this solution is that the main
		1842	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1843	this.
		1844
		1845	static gint
		1846	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1847	{
		1848	int got_events = 0;
		1849
		1850	for (n = 0; n < nfds; ++n)
		1851	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1852
		1853	if (timeout >= 0)
		1854	// create/start timer
		1855
		1856	// poll
		1857	ev_loop (EV_A_ 0);
		1858
		1859	// stop timer again
		1860	if (timeout >= 0)
		1861	ev_timer_stop (EV_A_ &to);
		1862
		1863	// stop io watchers again - their callbacks should have set
		1864	for (n = 0; n < nfds; ++n)
		1865	ev_io_stop (EV_A_ iow [n]);
		1866
		1867	return got_events;
1467	}	1868	}
1468		1869
1469		1870
1470	=head2 C<ev_embed> - when one backend isn't enough...	1871	=head2 C<ev_embed> - when one backend isn't enough...
1471		1872
…		…
1535	ev_embed_start (loop_hi, &embed);	1936	ev_embed_start (loop_hi, &embed);
1536	}	1937	}
1537	else	1938	else
1538	loop_lo = loop_hi;	1939	loop_lo = loop_hi;
1539		1940
		1941	=head3 Watcher-Specific Functions and Data Members
		1942
1540	=over 4	1943	=over 4
1541		1944
1542	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1945	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1543		1946
1544	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1947	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1553		1956
1554	Make a single, non-blocking sweep over the embedded loop. This works	1957	Make a single, non-blocking sweep over the embedded loop. This works
1555	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1958	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1556	apropriate way for embedded loops.	1959	apropriate way for embedded loops.
1557		1960
1558	=item struct ev_loop *loop [read-only]	1961	=item struct ev_loop *other [read-only]
1559		1962
1560	The embedded event loop.	1963	The embedded event loop.
1561		1964
1562	=back	1965	=back
1563		1966
…		…
1570	event loop blocks next and before C<ev_check> watchers are being called,	1973	event loop blocks next and before C<ev_check> watchers are being called,
1571	and only in the child after the fork. If whoever good citizen calling	1974	and only in the child after the fork. If whoever good citizen calling
1572	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1975	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1573	handlers will be invoked, too, of course.	1976	handlers will be invoked, too, of course.
1574		1977
		1978	=head3 Watcher-Specific Functions and Data Members
		1979
1575	=over 4	1980	=over 4
1576		1981
1577	=item ev_fork_init (ev_signal *, callback)	1982	=item ev_fork_init (ev_signal *, callback)
1578		1983
1579	Initialises and configures the fork watcher - it has no parameters of any	1984	Initialises and configures the fork watcher - it has no parameters of any
…		…
1675		2080
1676	To use it,	2081	To use it,
1677		2082
1678	#include <ev++.h>	2083	#include <ev++.h>
1679		2084
1680	(it is not installed by default). This automatically includes F<ev.h>	2085	This automatically includes F<ev.h> and puts all of its definitions (many
1681	and puts all of its definitions (many of them macros) into the global	2086	of them macros) into the global namespace. All C++ specific things are
1682	namespace. All C++ specific things are put into the C<ev> namespace.	2087	put into the C<ev> namespace. It should support all the same embedding
		2088	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1683		2089
1684	It should support all the same embedding options as F<ev.h>, most notably	2090	Care has been taken to keep the overhead low. The only data member the C++
1685	C<EV_MULTIPLICITY>.	2091	classes add (compared to plain C-style watchers) is the event loop pointer
		2092	that the watcher is associated with (or no additional members at all if
		2093	you disable C<EV_MULTIPLICITY> when embedding libev).
		2094
		2095	Currently, functions, and static and non-static member functions can be
		2096	used as callbacks. Other types should be easy to add as long as they only
		2097	need one additional pointer for context. If you need support for other
		2098	types of functors please contact the author (preferably after implementing
		2099	it).
1686		2100
1687	Here is a list of things available in the C<ev> namespace:	2101	Here is a list of things available in the C<ev> namespace:
1688		2102
1689	=over 4	2103	=over 4
1690		2104
…		…
1706		2120
1707	All of those classes have these methods:	2121	All of those classes have these methods:
1708		2122
1709	=over 4	2123	=over 4
1710		2124
1711	=item ev::TYPE::TYPE (object , object::method )	2125	=item ev::TYPE::TYPE ()
1712		2126
1713	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2127	=item ev::TYPE::TYPE (struct ev_loop *)
1714		2128
1715	=item ev::TYPE::~TYPE	2129	=item ev::TYPE::~TYPE
1716		2130
1717	The constructor takes a pointer to an object and a method pointer to	2131	The constructor (optionally) takes an event loop to associate the watcher
1718	the event handler callback to call in this class. The constructor calls	2132	with. If it is omitted, it will use C<EV_DEFAULT>.
1719	C<ev_init> for you, which means you have to call the C<set> method	2133
1720	before starting it. If you do not specify a loop then the constructor	2134	The constructor calls C<ev_init> for you, which means you have to call the
1721	automatically associates the default loop with this watcher.	2135	C<set> method before starting it.
		2136
		2137	It will not set a callback, however: You have to call the templated C<set>
		2138	method to set a callback before you can start the watcher.
		2139
		2140	(The reason why you have to use a method is a limitation in C++ which does
		2141	not allow explicit template arguments for constructors).
1722		2142
1723	The destructor automatically stops the watcher if it is active.	2143	The destructor automatically stops the watcher if it is active.
		2144
		2145	=item w->set<class, &class::method> (object *)
		2146
		2147	This method sets the callback method to call. The method has to have a
		2148	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2149	first argument and the C<revents> as second. The object must be given as
		2150	parameter and is stored in the C<data> member of the watcher.
		2151
		2152	This method synthesizes efficient thunking code to call your method from
		2153	the C callback that libev requires. If your compiler can inline your
		2154	callback (i.e. it is visible to it at the place of the C<set> call and
		2155	your compiler is good :), then the method will be fully inlined into the
		2156	thunking function, making it as fast as a direct C callback.
		2157
		2158	Example: simple class declaration and watcher initialisation
		2159
		2160	struct myclass
		2161	{
		2162	void io_cb (ev::io &w, int revents) { }
		2163	}
		2164
		2165	myclass obj;
		2166	ev::io iow;
		2167	iow.set <myclass, &myclass::io_cb> (&obj);
		2168
		2169	=item w->set<function> (void *data = 0)
		2170
		2171	Also sets a callback, but uses a static method or plain function as
		2172	callback. The optional C<data> argument will be stored in the watcher's
		2173	C<data> member and is free for you to use.
		2174
		2175	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2176
		2177	See the method-C<set> above for more details.
		2178
		2179	Example:
		2180
		2181	static void io_cb (ev::io &w, int revents) { }
		2182	iow.set <io_cb> ();
1724		2183
1725	=item w->set (struct ev_loop *)	2184	=item w->set (struct ev_loop *)
1726		2185
1727	Associates a different C<struct ev_loop> with this watcher. You can only	2186	Associates a different C<struct ev_loop> with this watcher. You can only
1728	do this when the watcher is inactive (and not pending either).	2187	do this when the watcher is inactive (and not pending either).
1729		2188
1730	=item w->set ([args])	2189	=item w->set ([args])
1731		2190
1732	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2191	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1733	called at least once. Unlike the C counterpart, an active watcher gets	2192	called at least once. Unlike the C counterpart, an active watcher gets
1734	automatically stopped and restarted.	2193	automatically stopped and restarted when reconfiguring it with this
		2194	method.
1735		2195
1736	=item w->start ()	2196	=item w->start ()
1737		2197
1738	Starts the watcher. Note that there is no C<loop> argument as the	2198	Starts the watcher. Note that there is no C<loop> argument, as the
1739	constructor already takes the loop.	2199	constructor already stores the event loop.
1740		2200
1741	=item w->stop ()	2201	=item w->stop ()
1742		2202
1743	Stops the watcher if it is active. Again, no C<loop> argument.	2203	Stops the watcher if it is active. Again, no C<loop> argument.
1744		2204
1745	=item w->again () C<ev::timer>, C<ev::periodic> only	2205	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1746		2206
1747	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2207	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1748	C<ev_TYPE_again> function.	2208	C<ev_TYPE_again> function.
1749		2209
1750	=item w->sweep () C<ev::embed> only	2210	=item w->sweep () (C<ev::embed> only)
1751		2211
1752	Invokes C<ev_embed_sweep>.	2212	Invokes C<ev_embed_sweep>.
1753		2213
1754	=item w->update () C<ev::stat> only	2214	=item w->update () (C<ev::stat> only)
1755		2215
1756	Invokes C<ev_stat_stat>.	2216	Invokes C<ev_stat_stat>.
1757		2217
1758	=back	2218	=back
1759		2219
…		…
1769		2229
1770	myclass ();	2230	myclass ();
1771	}	2231	}
1772		2232
1773	myclass::myclass (int fd)	2233	myclass::myclass (int fd)
1774	: io (this, &myclass::io_cb),
1775	idle (this, &myclass::idle_cb)
1776	{	2234	{
		2235	io .set <myclass, &myclass::io_cb > (this);
		2236	idle.set <myclass, &myclass::idle_cb> (this);
		2237
1777	io.start (fd, ev::READ);	2238	io.start (fd, ev::READ);
1778	}	2239	}
1779		2240
1780		2241
1781	=head1 MACRO MAGIC	2242	=head1 MACRO MAGIC
1782		2243
1783	Libev can be compiled with a variety of options, the most fundemantal is	2244	Libev can be compiled with a variety of options, the most fundamantal
1784	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2245	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1785	callbacks have an initial C<struct ev_loop *> argument.	2246	functions and callbacks have an initial C<struct ev_loop *> argument.
1786		2247
1787	To make it easier to write programs that cope with either variant, the	2248	To make it easier to write programs that cope with either variant, the
1788	following macros are defined:	2249	following macros are defined:
1789		2250
1790	=over 4	2251	=over 4
…		…
1822	Similar to the other two macros, this gives you the value of the default	2283	Similar to the other two macros, this gives you the value of the default
1823	loop, if multiple loops are supported ("ev loop default").	2284	loop, if multiple loops are supported ("ev loop default").
1824		2285
1825	=back	2286	=back
1826		2287
1827	Example: Declare and initialise a check watcher, working regardless of	2288	Example: Declare and initialise a check watcher, utilising the above
1828	wether multiple loops are supported or not.	2289	macros so it will work regardless of whether multiple loops are supported
		2290	or not.
1829		2291
1830	static void	2292	static void
1831	check_cb (EV_P_ ev_timer *w, int revents)	2293	check_cb (EV_P_ ev_timer *w, int revents)
1832	{	2294	{
1833	ev_check_stop (EV_A_ w);	2295	ev_check_stop (EV_A_ w);
…		…
1836	ev_check check;	2298	ev_check check;
1837	ev_check_init (&check, check_cb);	2299	ev_check_init (&check, check_cb);
1838	ev_check_start (EV_DEFAULT_ &check);	2300	ev_check_start (EV_DEFAULT_ &check);
1839	ev_loop (EV_DEFAULT_ 0);	2301	ev_loop (EV_DEFAULT_ 0);
1840		2302
1841
1842	=head1 EMBEDDING	2303	=head1 EMBEDDING
1843		2304
1844	Libev can (and often is) directly embedded into host	2305	Libev can (and often is) directly embedded into host
1845	applications. Examples of applications that embed it include the Deliantra	2306	applications. Examples of applications that embed it include the Deliantra
1846	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2307	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1847	and rxvt-unicode.	2308	and rxvt-unicode.
1848		2309
1849	The goal is to enable you to just copy the neecssary files into your	2310	The goal is to enable you to just copy the necessary files into your
1850	source directory without having to change even a single line in them, so	2311	source directory without having to change even a single line in them, so
1851	you can easily upgrade by simply copying (or having a checked-out copy of	2312	you can easily upgrade by simply copying (or having a checked-out copy of
1852	libev somewhere in your source tree).	2313	libev somewhere in your source tree).
1853		2314
1854	=head2 FILESETS	2315	=head2 FILESETS
…		…
1885	ev_vars.h	2346	ev_vars.h
1886	ev_wrap.h	2347	ev_wrap.h
1887		2348
1888	ev_win32.c required on win32 platforms only	2349	ev_win32.c required on win32 platforms only
1889		2350
1890	ev_select.c only when select backend is enabled (which is by default)	2351	ev_select.c only when select backend is enabled (which is enabled by default)
1891	ev_poll.c only when poll backend is enabled (disabled by default)	2352	ev_poll.c only when poll backend is enabled (disabled by default)
1892	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2353	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1893	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2354	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1894	ev_port.c only when the solaris port backend is enabled (disabled by default)	2355	ev_port.c only when the solaris port backend is enabled (disabled by default)
1895		2356
…		…
1944		2405
1945	If defined to be C<1>, libev will try to detect the availability of the	2406	If defined to be C<1>, libev will try to detect the availability of the
1946	monotonic clock option at both compiletime and runtime. Otherwise no use	2407	monotonic clock option at both compiletime and runtime. Otherwise no use
1947	of the monotonic clock option will be attempted. If you enable this, you	2408	of the monotonic clock option will be attempted. If you enable this, you
1948	usually have to link against librt or something similar. Enabling it when	2409	usually have to link against librt or something similar. Enabling it when
1949	the functionality isn't available is safe, though, althoguh you have	2410	the functionality isn't available is safe, though, although you have
1950	to make sure you link against any libraries where the C<clock_gettime>	2411	to make sure you link against any libraries where the C<clock_gettime>
1951	function is hiding in (often F<-lrt>).	2412	function is hiding in (often F<-lrt>).
1952		2413
1953	=item EV_USE_REALTIME	2414	=item EV_USE_REALTIME
1954		2415
1955	If defined to be C<1>, libev will try to detect the availability of the	2416	If defined to be C<1>, libev will try to detect the availability of the
1956	realtime clock option at compiletime (and assume its availability at	2417	realtime clock option at compiletime (and assume its availability at
1957	runtime if successful). Otherwise no use of the realtime clock option will	2418	runtime if successful). Otherwise no use of the realtime clock option will
1958	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2419	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1959	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2420	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1960	in the description of C<EV_USE_MONOTONIC>, though.	2421	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2422
		2423	=item EV_USE_NANOSLEEP
		2424
		2425	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2426	and will use it for delays. Otherwise it will use C<select ()>.
1961		2427
1962	=item EV_USE_SELECT	2428	=item EV_USE_SELECT
1963		2429
1964	If undefined or defined to be C<1>, libev will compile in support for the	2430	If undefined or defined to be C<1>, libev will compile in support for the
1965	C<select>(2) backend. No attempt at autodetection will be done: if no	2431	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2058	will have the C<struct ev_loop *> as first argument, and you can create	2524	will have the C<struct ev_loop *> as first argument, and you can create
2059	additional independent event loops. Otherwise there will be no support	2525	additional independent event loops. Otherwise there will be no support
2060	for multiple event loops and there is no first event loop pointer	2526	for multiple event loops and there is no first event loop pointer
2061	argument. Instead, all functions act on the single default loop.	2527	argument. Instead, all functions act on the single default loop.
2062		2528
		2529	=item EV_MINPRI
		2530
		2531	=item EV_MAXPRI
		2532
		2533	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2534	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2535	provide for more priorities by overriding those symbols (usually defined
		2536	to be C<-2> and C<2>, respectively).
		2537
		2538	When doing priority-based operations, libev usually has to linearly search
		2539	all the priorities, so having many of them (hundreds) uses a lot of space
		2540	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2541	fine.
		2542
		2543	If your embedding app does not need any priorities, defining these both to
		2544	C<0> will save some memory and cpu.
		2545
2063	=item EV_PERIODIC_ENABLE	2546	=item EV_PERIODIC_ENABLE
2064		2547
2065	If undefined or defined to be C<1>, then periodic timers are supported. If	2548	If undefined or defined to be C<1>, then periodic timers are supported. If
		2549	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2550	code.
		2551
		2552	=item EV_IDLE_ENABLE
		2553
		2554	If undefined or defined to be C<1>, then idle watchers are supported. If
2066	defined to be C<0>, then they are not. Disabling them saves a few kB of	2555	defined to be C<0>, then they are not. Disabling them saves a few kB of
2067	code.	2556	code.
2068		2557
2069	=item EV_EMBED_ENABLE	2558	=item EV_EMBED_ENABLE
2070		2559
…		…
2094	than enough. If you need to manage thousands of children you might want to	2583	than enough. If you need to manage thousands of children you might want to
2095	increase this value (I<must> be a power of two).	2584	increase this value (I<must> be a power of two).
2096		2585
2097	=item EV_INOTIFY_HASHSIZE	2586	=item EV_INOTIFY_HASHSIZE
2098		2587
2099	C<ev_staz> watchers use a small hash table to distribute workload by	2588	C<ev_stat> watchers use a small hash table to distribute workload by
2100	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2589	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2101	usually more than enough. If you need to manage thousands of C<ev_stat>	2590	usually more than enough. If you need to manage thousands of C<ev_stat>
2102	watchers you might want to increase this value (I<must> be a power of	2591	watchers you might want to increase this value (I<must> be a power of
2103	two).	2592	two).
2104		2593
…		…
2121		2610
2122	=item ev_set_cb (ev, cb)	2611	=item ev_set_cb (ev, cb)
2123		2612
2124	Can be used to change the callback member declaration in each watcher,	2613	Can be used to change the callback member declaration in each watcher,
2125	and the way callbacks are invoked and set. Must expand to a struct member	2614	and the way callbacks are invoked and set. Must expand to a struct member
2126	definition and a statement, respectively. See the F<ev.v> header file for	2615	definition and a statement, respectively. See the F<ev.h> header file for
2127	their default definitions. One possible use for overriding these is to	2616	their default definitions. One possible use for overriding these is to
2128	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2617	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2129	method calls instead of plain function calls in C++.	2618	method calls instead of plain function calls in C++.
		2619
		2620	=head2 EXPORTED API SYMBOLS
		2621
		2622	If you need to re-export the API (e.g. via a dll) and you need a list of
		2623	exported symbols, you can use the provided F<Symbol.*> files which list
		2624	all public symbols, one per line:
		2625
		2626	Symbols.ev for libev proper
		2627	Symbols.event for the libevent emulation
		2628
		2629	This can also be used to rename all public symbols to avoid clashes with
		2630	multiple versions of libev linked together (which is obviously bad in
		2631	itself, but sometimes it is inconvinient to avoid this).
		2632
		2633	A sed command like this will create wrapper C<#define>'s that you need to
		2634	include before including F<ev.h>:
		2635
		2636	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2637
		2638	This would create a file F<wrap.h> which essentially looks like this:
		2639
		2640	#define ev_backend myprefix_ev_backend
		2641	#define ev_check_start myprefix_ev_check_start
		2642	#define ev_check_stop myprefix_ev_check_stop
		2643	...
2130		2644
2131	=head2 EXAMPLES	2645	=head2 EXAMPLES
2132		2646
2133	For a real-world example of a program the includes libev	2647	For a real-world example of a program the includes libev
2134	verbatim, you can have a look at the EV perl module	2648	verbatim, you can have a look at the EV perl module
…		…
2137	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2651	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2138	will be compiled. It is pretty complex because it provides its own header	2652	will be compiled. It is pretty complex because it provides its own header
2139	file.	2653	file.
2140		2654
2141	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2655	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2142	that everybody includes and which overrides some autoconf choices:	2656	that everybody includes and which overrides some configure choices:
2143		2657
		2658	#define EV_MINIMAL 1
2144	#define EV_USE_POLL 0	2659	#define EV_USE_POLL 0
2145	#define EV_MULTIPLICITY 0	2660	#define EV_MULTIPLICITY 0
2146	#define EV_PERIODICS 0	2661	#define EV_PERIODIC_ENABLE 0
		2662	#define EV_STAT_ENABLE 0
		2663	#define EV_FORK_ENABLE 0
2147	#define EV_CONFIG_H <config.h>	2664	#define EV_CONFIG_H <config.h>
		2665	#define EV_MINPRI 0
		2666	#define EV_MAXPRI 0
2148		2667
2149	#include "ev++.h"	2668	#include "ev++.h"
2150		2669
2151	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2670	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2152		2671
…		…
2158		2677
2159	In this section the complexities of (many of) the algorithms used inside	2678	In this section the complexities of (many of) the algorithms used inside
2160	libev will be explained. For complexity discussions about backends see the	2679	libev will be explained. For complexity discussions about backends see the
2161	documentation for C<ev_default_init>.	2680	documentation for C<ev_default_init>.
2162		2681
		2682	All of the following are about amortised time: If an array needs to be
		2683	extended, libev needs to realloc and move the whole array, but this
		2684	happens asymptotically never with higher number of elements, so O(1) might
		2685	mean it might do a lengthy realloc operation in rare cases, but on average
		2686	it is much faster and asymptotically approaches constant time.
		2687
2163	=over 4	2688	=over 4
2164		2689
2165	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2690	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2166		2691
		2692	This means that, when you have a watcher that triggers in one hour and
		2693	there are 100 watchers that would trigger before that then inserting will
		2694	have to skip roughly seven (C<ld 100>) of these watchers.
		2695
2167	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2696	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
		2697
		2698	That means that changing a timer costs less than removing/adding them
		2699	as only the relative motion in the event queue has to be paid for.
2168		2700
2169	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2701	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2170		2702
		2703	These just add the watcher into an array or at the head of a list.
		2704
2171	=item Stopping check/prepare/idle watchers: O(1)	2705	=item Stopping check/prepare/idle watchers: O(1)
2172		2706
2173	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2707	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2174		2708
		2709	These watchers are stored in lists then need to be walked to find the
		2710	correct watcher to remove. The lists are usually short (you don't usually
		2711	have many watchers waiting for the same fd or signal).
		2712
2175	=item Finding the next timer per loop iteration: O(1)	2713	=item Finding the next timer in each loop iteration: O(1)
		2714
		2715	By virtue of using a binary heap, the next timer is always found at the
		2716	beginning of the storage array.
2176		2717
2177	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2718	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2178		2719
2179	=item Activating one watcher: O(1)	2720	A change means an I/O watcher gets started or stopped, which requires
		2721	libev to recalculate its status (and possibly tell the kernel, depending
		2722	on backend and wether C<ev_io_set> was used).
		2723
		2724	=item Activating one watcher (putting it into the pending state): O(1)
		2725
		2726	=item Priority handling: O(number_of_priorities)
		2727
		2728	Priorities are implemented by allocating some space for each
		2729	priority. When doing priority-based operations, libev usually has to
		2730	linearly search all the priorities, but starting/stopping and activating
		2731	watchers becomes O(1) w.r.t. prioritiy handling.
2180		2732
2181	=back	2733	=back
2182		2734
2183		2735
2184	=head1 AUTHOR	2736	=head1 AUTHOR

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Comparing libev/ev.pod (file contents): Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs. Revision 1.109 by root, Mon Dec 24 13:19:12 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.58 by root, Wed Nov 28 11:31:34 2007 UTC vs.
Revision 1.109 by root, Mon Dec 24 13:19:12 2007 UTC