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

Comparing libev/ev.pod (file contents):
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs.
Revision 1.101 by ayin, Sat Dec 22 14:11:25 2007 UTC

…		…
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.
…		…
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	=head1 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>), relative timers (C<ev_timer>),	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
		75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71	absolute timers with customised rescheduling (C<ev_periodic>), synchronous	76	with customised rescheduling (C<ev_periodic>), synchronous signals
72	signals (C<ev_signal>), process status change events (C<ev_child>), and	77	(C<ev_signal>), process status change events (C<ev_child>), and event
73	event watchers dealing with the event loop mechanism itself (C<ev_idle>,	78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
74	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75	file watchers (C<ev_stat>) and even limited support for fork events	80	file watchers (C<ev_stat>) and even limited support for fork events
76	(C<ev_fork>).	81	(C<ev_fork>).
77		82
78	It also is quite fast (see this	83	It also is quite fast (see this
…		…
93	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
94	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
95	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
96	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
97	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
98	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.
99		106
100	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
101		108
102	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
103	library in any way.	110	library in any way.
…		…
108		115
109	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
110	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
111	you actually want to know.	118	you actually want to know.
112		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
113	=item int ev_version_major ()	126	=item int ev_version_major ()
114		127
115	=item int ev_version_minor ()	128	=item int ev_version_minor ()
116		129
117	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
118	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
119	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
120	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
121	version of the library your program was compiled against.	134	version of the library your program was compiled against.
122		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
123	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,
124	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
125	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
126	not a problem.	142	not a problem.
127		143
128	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
129	version.	145	version.
…		…
162	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	178	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163	recommended ones.	179	recommended ones.
164		180
165	See the description of C<ev_embed> watchers for more info.	181	See the description of C<ev_embed> watchers for more info.
166		182
167	=item ev_set_allocator (void (cb)(void *ptr, size_t size))	183	=item ev_set_allocator (void (cb)(void *ptr, long size))
168		184
169	Sets the allocation function to use (the prototype and semantics are	185	Sets the allocation function to use (the prototype is similar - the
170	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
171	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
172	allocated, the library might abort or take some potentially destructive	188	memory needs to be allocated, the library might abort or take some
173	action. The default is your system realloc function.	189	potentially destructive action. The default is your system realloc
		190	function.
174		191
175	You could override this function in high-availability programs to, say,	192	You could override this function in high-availability programs to, say,
176	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,
177	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.
178		195
…		…
264	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	281	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
265	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
266	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
267	around bugs.	284	around bugs.
268		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
269	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
270		307
271	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
272	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,
273	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
…		…
282	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).	319	lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
283		320
284	=item C<EVBACKEND_EPOLL> (value 4, Linux)	321	=item C<EVBACKEND_EPOLL> (value 4, Linux)
285		322
286	For few fds, this backend is a bit little slower than poll and select,	323	For few fds, this backend is a bit little slower than poll and select,
287	but it scales phenomenally better. While poll and select usually scale like	324	but it scales phenomenally better. While poll and select usually scale
288	O(total_fds) where n is the total number of fds (or the highest fd), epoll scales	325	like O(total_fds) where n is the total number of fds (or the highest fd),
289	either O(1) or O(active_fds).	326	epoll scales either O(1) or O(active_fds). The epoll design has a number
		327	of shortcomings, such as silently dropping events in some hard-to-detect
		328	cases and rewiring a syscall per fd change, no fork support and bad
		329	support for dup:
290		330
291	While stopping and starting an I/O watcher in the same iteration will	331	While stopping, setting and starting an I/O watcher in the same iteration
292	result in some caching, there is still a syscall per such incident	332	will result in some caching, there is still a syscall per such incident
293	(because the fd could point to a different file description now), so its	333	(because the fd could point to a different file description now), so its
294	best to avoid that. Also, dup()ed file descriptors might not work very	334	best to avoid that. Also, C<dup ()>'ed file descriptors might not work
295	well if you register events for both fds.	335	very well if you register events for both fds.
296		336
297	Please note that epoll sometimes generates spurious notifications, so you	337	Please note that epoll sometimes generates spurious notifications, so you
298	need to use non-blocking I/O or other means to avoid blocking when no data	338	need to use non-blocking I/O or other means to avoid blocking when no data
299	(or space) is available.	339	(or space) is available.
300		340
301	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	341	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
302		342
303	Kqueue deserves special mention, as at the time of this writing, it	343	Kqueue deserves special mention, as at the time of this writing, it
304	was broken on all BSDs except NetBSD (usually it doesn't work with	344	was broken on all BSDs except NetBSD (usually it doesn't work reliably
305	anything but sockets and pipes, except on Darwin, where of course its	345	with anything but sockets and pipes, except on Darwin, where of course
306	completely useless). For this reason its not being "autodetected"	346	it's completely useless). For this reason it's not being "autodetected"
307	unless you explicitly specify it explicitly in the flags (i.e. using	347	unless you explicitly specify it explicitly in the flags (i.e. using
308	C<EVBACKEND_KQUEUE>).	348	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		349	system like NetBSD.
		350
		351	You still can embed kqueue into a normal poll or select backend and use it
		352	only for sockets (after having made sure that sockets work with kqueue on
		353	the target platform). See C<ev_embed> watchers for more info.
309		354
310	It scales in the same way as the epoll backend, but the interface to the	355	It scales in the same way as the epoll backend, but the interface to the
311	kernel is more efficient (which says nothing about its actual speed, of	356	kernel is more efficient (which says nothing about its actual speed, of
312	course). While starting and stopping an I/O watcher does not cause an	357	course). While stopping, setting and starting an I/O watcher does never
313	extra syscall as with epoll, it still adds up to four event changes per	358	cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
314	incident, so its best to avoid that.	359	two event changes per incident, support for C<fork ()> is very bad and it
		360	drops fds silently in similarly hard-to-detect cases.
315		361
316	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	362	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
317		363
318	This is not implemented yet (and might never be).	364	This is not implemented yet (and might never be).
319		365
320	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	366	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
321		367
322	This uses the Solaris 10 port mechanism. As with everything on Solaris,	368	This uses the Solaris 10 event port mechanism. As with everything on Solaris,
323	it's really slow, but it still scales very well (O(active_fds)).	369	it's really slow, but it still scales very well (O(active_fds)).
324		370
325	Please note that solaris ports can result in a lot of spurious	371	Please note that solaris event ports can deliver a lot of spurious
326	notifications, so you need to use non-blocking I/O or other means to avoid	372	notifications, so you need to use non-blocking I/O or other means to avoid
327	blocking when no data (or space) is available.	373	blocking when no data (or space) is available.
328		374
329	=item C<EVBACKEND_ALL>	375	=item C<EVBACKEND_ALL>
330		376
…		…
373	Destroys the default loop again (frees all memory and kernel state	419	Destroys the default loop again (frees all memory and kernel state
374	etc.). None of the active event watchers will be stopped in the normal	420	etc.). None of the active event watchers will be stopped in the normal
375	sense, so e.g. C<ev_is_active> might still return true. It is your	421	sense, so e.g. C<ev_is_active> might still return true. It is your
376	responsibility to either stop all watchers cleanly yoursef I<before>	422	responsibility to either stop all watchers cleanly yoursef I<before>
377	calling this function, or cope with the fact afterwards (which is usually	423	calling this function, or cope with the fact afterwards (which is usually
378	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	424	the easiest thing, you can just ignore the watchers and/or C<free ()> them
379	for example).	425	for example).
		426
		427	Note that certain global state, such as signal state, will not be freed by
		428	this function, and related watchers (such as signal and child watchers)
		429	would need to be stopped manually.
		430
		431	In general it is not advisable to call this function except in the
		432	rare occasion where you really need to free e.g. the signal handling
		433	pipe fds. If you need dynamically allocated loops it is better to use
		434	C<ev_loop_new> and C<ev_loop_destroy>).
380		435
381	=item ev_loop_destroy (loop)	436	=item ev_loop_destroy (loop)
382		437
383	Like C<ev_default_destroy>, but destroys an event loop created by an	438	Like C<ev_default_destroy>, but destroys an event loop created by an
384	earlier call to C<ev_loop_new>.	439	earlier call to C<ev_loop_new>.
…		…
408		463
409	Like C<ev_default_fork>, but acts on an event loop created by	464	Like C<ev_default_fork>, but acts on an event loop created by
410	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	465	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
411	after fork, and how you do this is entirely your own problem.	466	after fork, and how you do this is entirely your own problem.
412		467
		468	=item unsigned int ev_loop_count (loop)
		469
		470	Returns the count of loop iterations for the loop, which is identical to
		471	the number of times libev did poll for new events. It starts at C<0> and
		472	happily wraps around with enough iterations.
		473
		474	This value can sometimes be useful as a generation counter of sorts (it
		475	"ticks" the number of loop iterations), as it roughly corresponds with
		476	C<ev_prepare> and C<ev_check> calls.
		477
413	=item unsigned int ev_backend (loop)	478	=item unsigned int ev_backend (loop)
414		479
415	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	480	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
416	use.	481	use.
417		482
…		…
419		484
420	Returns the current "event loop time", which is the time the event loop	485	Returns the current "event loop time", which is the time the event loop
421	received events and started processing them. This timestamp does not	486	received events and started processing them. This timestamp does not
422	change as long as callbacks are being processed, and this is also the base	487	change as long as callbacks are being processed, and this is also the base
423	time used for relative timers. You can treat it as the timestamp of the	488	time used for relative timers. You can treat it as the timestamp of the
424	event occuring (or more correctly, libev finding out about it).	489	event occurring (or more correctly, libev finding out about it).
425		490
426	=item ev_loop (loop, int flags)	491	=item ev_loop (loop, int flags)
427		492
428	Finally, this is it, the event handler. This function usually is called	493	Finally, this is it, the event handler. This function usually is called
429	after you initialised all your watchers and you want to start handling	494	after you initialised all your watchers and you want to start handling
…		…
450	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	515	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
451	usually a better approach for this kind of thing.	516	usually a better approach for this kind of thing.
452		517
453	Here are the gory details of what C<ev_loop> does:	518	Here are the gory details of what C<ev_loop> does:
454		519
		520	- Before the first iteration, call any pending watchers.
455	* If there are no active watchers (reference count is zero), return.	521	* If there are no active watchers (reference count is zero), return.
456	- Queue prepare watchers and then call all outstanding watchers.	522	- Queue all prepare watchers and then call all outstanding watchers.
457	- If we have been forked, recreate the kernel state.	523	- If we have been forked, recreate the kernel state.
458	- Update the kernel state with all outstanding changes.	524	- Update the kernel state with all outstanding changes.
459	- Update the "event loop time".	525	- Update the "event loop time".
460	- Calculate for how long to block.	526	- Calculate for how long to block.
461	- Block the process, waiting for any events.	527	- Block the process, waiting for any events.
…		…
512	Example: For some weird reason, unregister the above signal handler again.	578	Example: For some weird reason, unregister the above signal handler again.
513		579
514	ev_ref (loop);	580	ev_ref (loop);
515	ev_signal_stop (loop, &exitsig);	581	ev_signal_stop (loop, &exitsig);
516		582
		583	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		584
		585	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		586
		587	These advanced functions influence the time that libev will spend waiting
		588	for events. Both are by default C<0>, meaning that libev will try to
		589	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		590
		591	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		592	allows libev to delay invocation of I/O and timer/periodic callbacks to
		593	increase efficiency of loop iterations.
		594
		595	The background is that sometimes your program runs just fast enough to
		596	handle one (or very few) event(s) per loop iteration. While this makes
		597	the program responsive, it also wastes a lot of CPU time to poll for new
		598	events, especially with backends like C<select ()> which have a high
		599	overhead for the actual polling but can deliver many events at once.
		600
		601	By setting a higher I<io collect interval> you allow libev to spend more
		602	time collecting I/O events, so you can handle more events per iteration,
		603	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		604	C<ev_timer>) will be not affected. Setting this to a non-null value will
		605	introduce an additional C<ev_sleep ()> call into most loop iterations.
		606
		607	Likewise, by setting a higher I<timeout collect interval> you allow libev
		608	to spend more time collecting timeouts, at the expense of increased
		609	latency (the watcher callback will be called later). C<ev_io> watchers
		610	will not be affected. Setting this to a non-null value will not introduce
		611	any overhead in libev.
		612
		613	Many (busy) programs can usually benefit by setting the io collect
		614	interval to a value near C<0.1> or so, which is often enough for
		615	interactive servers (of course not for games), likewise for timeouts. It
		616	usually doesn't make much sense to set it to a lower value than C<0.01>,
		617	as this approsaches the timing granularity of most systems.
		618
517	=back	619	=back
518		620
519		621
520	=head1 ANATOMY OF A WATCHER	622	=head1 ANATOMY OF A WATCHER
521		623
…		…
700	=item bool ev_is_pending (ev_TYPE *watcher)	802	=item bool ev_is_pending (ev_TYPE *watcher)
701		803
702	Returns a true value iff the watcher is pending, (i.e. it has outstanding	804	Returns a true value iff the watcher is pending, (i.e. it has outstanding
703	events but its callback has not yet been invoked). As long as a watcher	805	events but its callback has not yet been invoked). As long as a watcher
704	is pending (but not active) you must not call an init function on it (but	806	is pending (but not active) you must not call an init function on it (but
705	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	807	C<ev_TYPE_set> is safe), you must not change its priority, and you must
706	libev (e.g. you cnanot C<free ()> it).	808	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		809	it).
707		810
708	=item callback = ev_cb (ev_TYPE *watcher)	811	=item callback ev_cb (ev_TYPE *watcher)
709		812
710	Returns the callback currently set on the watcher.	813	Returns the callback currently set on the watcher.
711		814
712	=item ev_cb_set (ev_TYPE *watcher, callback)	815	=item ev_cb_set (ev_TYPE *watcher, callback)
713		816
714	Change the callback. You can change the callback at virtually any time	817	Change the callback. You can change the callback at virtually any time
715	(modulo threads).	818	(modulo threads).
		819
		820	=item ev_set_priority (ev_TYPE *watcher, priority)
		821
		822	=item int ev_priority (ev_TYPE *watcher)
		823
		824	Set and query the priority of the watcher. The priority is a small
		825	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		826	(default: C<-2>). Pending watchers with higher priority will be invoked
		827	before watchers with lower priority, but priority will not keep watchers
		828	from being executed (except for C<ev_idle> watchers).
		829
		830	This means that priorities are I<only> used for ordering callback
		831	invocation after new events have been received. This is useful, for
		832	example, to reduce latency after idling, or more often, to bind two
		833	watchers on the same event and make sure one is called first.
		834
		835	If you need to suppress invocation when higher priority events are pending
		836	you need to look at C<ev_idle> watchers, which provide this functionality.
		837
		838	You I<must not> change the priority of a watcher as long as it is active or
		839	pending.
		840
		841	The default priority used by watchers when no priority has been set is
		842	always C<0>, which is supposed to not be too high and not be too low :).
		843
		844	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		845	fine, as long as you do not mind that the priority value you query might
		846	or might not have been adjusted to be within valid range.
		847
		848	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		849
		850	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		851	C<loop> nor C<revents> need to be valid as long as the watcher callback
		852	can deal with that fact.
		853
		854	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		855
		856	If the watcher is pending, this function returns clears its pending status
		857	and returns its C<revents> bitset (as if its callback was invoked). If the
		858	watcher isn't pending it does nothing and returns C<0>.
716		859
717	=back	860	=back
718		861
719		862
720	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	863	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
741	{	884	{
742	struct my_io w = (struct my_io )w_;	885	struct my_io w = (struct my_io )w_;
743	...	886	...
744	}	887	}
745		888
746	More interesting and less C-conformant ways of catsing your callback type	889	More interesting and less C-conformant ways of casting your callback type
747	have been omitted....	890	instead have been omitted.
		891
		892	Another common scenario is having some data structure with multiple
		893	watchers:
		894
		895	struct my_biggy
		896	{
		897	int some_data;
		898	ev_timer t1;
		899	ev_timer t2;
		900	}
		901
		902	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		903	you need to use C<offsetof>:
		904
		905	#include <stddef.h>
		906
		907	static void
		908	t1_cb (EV_P_ struct ev_timer *w, int revents)
		909	{
		910	struct my_biggy big = (struct my_biggy *
		911	(((char *)w) - offsetof (struct my_biggy, t1));
		912	}
		913
		914	static void
		915	t2_cb (EV_P_ struct ev_timer *w, int revents)
		916	{
		917	struct my_biggy big = (struct my_biggy *
		918	(((char *)w) - offsetof (struct my_biggy, t2));
		919	}
748		920
749		921
750	=head1 WATCHER TYPES	922	=head1 WATCHER TYPES
751		923
752	This section describes each watcher in detail, but will not repeat	924	This section describes each watcher in detail, but will not repeat
…		…
797	it is best to always use non-blocking I/O: An extra C<read>(2) returning	969	it is best to always use non-blocking I/O: An extra C<read>(2) returning
798	C<EAGAIN> is far preferable to a program hanging until some data arrives.	970	C<EAGAIN> is far preferable to a program hanging until some data arrives.
799		971
800	If you cannot run the fd in non-blocking mode (for example you should not	972	If you cannot run the fd in non-blocking mode (for example you should not
801	play around with an Xlib connection), then you have to seperately re-test	973	play around with an Xlib connection), then you have to seperately re-test
802	wether a file descriptor is really ready with a known-to-be good interface	974	whether a file descriptor is really ready with a known-to-be good interface
803	such as poll (fortunately in our Xlib example, Xlib already does this on	975	such as poll (fortunately in our Xlib example, Xlib already does this on
804	its own, so its quite safe to use).	976	its own, so its quite safe to use).
		977
		978	=head3 The special problem of disappearing file descriptors
		979
		980	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		981	descriptor (either by calling C<close> explicitly or by any other means,
		982	such as C<dup>). The reason is that you register interest in some file
		983	descriptor, but when it goes away, the operating system will silently drop
		984	this interest. If another file descriptor with the same number then is
		985	registered with libev, there is no efficient way to see that this is, in
		986	fact, a different file descriptor.
		987
		988	To avoid having to explicitly tell libev about such cases, libev follows
		989	the following policy: Each time C<ev_io_set> is being called, libev
		990	will assume that this is potentially a new file descriptor, otherwise
		991	it is assumed that the file descriptor stays the same. That means that
		992	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		993	descriptor even if the file descriptor number itself did not change.
		994
		995	This is how one would do it normally anyway, the important point is that
		996	the libev application should not optimise around libev but should leave
		997	optimisations to libev.
		998
		999	=head3 The special problem of dup'ed file descriptors
		1000
		1001	Some backends (e.g. epoll), cannot register events for file descriptors,
		1002	but only events for the underlying file descriptions. That menas when you
		1003	have C<dup ()>'ed file descriptors and register events for them, only one
		1004	file descriptor might actually receive events.
		1005
		1006	There is no workaorund possible except not registering events
		1007	for potentially C<dup ()>'ed file descriptors or to resort to
		1008	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1009
		1010	=head3 The special problem of fork
		1011
		1012	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1013	useless behaviour. Libev fully supports fork, but needs to be told about
		1014	it in the child.
		1015
		1016	To support fork in your programs, you either have to call
		1017	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1018	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1019	C<EVBACKEND_POLL>.
		1020
		1021
		1022	=head3 Watcher-Specific Functions
805		1023
806	=over 4	1024	=over 4
807		1025
808	=item ev_io_init (ev_io *, callback, int fd, int events)	1026	=item ev_io_init (ev_io *, callback, int fd, int events)
809		1027
…		…
863		1081
864	The callback is guarenteed to be invoked only when its timeout has passed,	1082	The callback is guarenteed to be invoked only when its timeout has passed,
865	but if multiple timers become ready during the same loop iteration then	1083	but if multiple timers become ready during the same loop iteration then
866	order of execution is undefined.	1084	order of execution is undefined.
867		1085
		1086	=head3 Watcher-Specific Functions and Data Members
		1087
868	=over 4	1088	=over 4
869		1089
870	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1090	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
871		1091
872	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1092	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
885	=item ev_timer_again (loop)	1105	=item ev_timer_again (loop)
886		1106
887	This will act as if the timer timed out and restart it again if it is	1107	This will act as if the timer timed out and restart it again if it is
888	repeating. The exact semantics are:	1108	repeating. The exact semantics are:
889		1109
		1110	If the timer is pending, its pending status is cleared.
		1111
890	If the timer is started but nonrepeating, stop it.	1112	If the timer is started but nonrepeating, stop it (as if it timed out).
891		1113
892	If the timer is repeating, either start it if necessary (with the repeat	1114	If the timer is repeating, either start it if necessary (with the
893	value), or reset the running timer to the repeat value.	1115	C<repeat> value), or reset the running timer to the C<repeat> value.
894		1116
895	This sounds a bit complicated, but here is a useful and typical	1117	This sounds a bit complicated, but here is a useful and typical
896	example: Imagine you have a tcp connection and you want a so-called	1118	example: Imagine you have a tcp connection and you want a so-called idle
897	idle timeout, that is, you want to be called when there have been,	1119	timeout, that is, you want to be called when there have been, say, 60
898	say, 60 seconds of inactivity on the socket. The easiest way to do	1120	seconds of inactivity on the socket. The easiest way to do this is to
899	this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling	1121	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
900	C<ev_timer_again> each time you successfully read or write some data. If	1122	C<ev_timer_again> each time you successfully read or write some data. If
901	you go into an idle state where you do not expect data to travel on the	1123	you go into an idle state where you do not expect data to travel on the
902	socket, you can stop the timer, and again will automatically restart it if	1124	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
903	need be.	1125	automatically restart it if need be.
904		1126
905	You can also ignore the C<after> value and C<ev_timer_start> altogether	1127	That means you can ignore the C<after> value and C<ev_timer_start>
906	and only ever use the C<repeat> value:	1128	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
907		1129
908	ev_timer_init (timer, callback, 0., 5.);	1130	ev_timer_init (timer, callback, 0., 5.);
909	ev_timer_again (loop, timer);	1131	ev_timer_again (loop, timer);
910	...	1132	...
911	timer->again = 17.;	1133	timer->again = 17.;
912	ev_timer_again (loop, timer);	1134	ev_timer_again (loop, timer);
913	...	1135	...
914	timer->again = 10.;	1136	timer->again = 10.;
915	ev_timer_again (loop, timer);	1137	ev_timer_again (loop, timer);
916		1138
917	This is more efficient then stopping/starting the timer eahc time you want	1139	This is more slightly efficient then stopping/starting the timer each time
918	to modify its timeout value.	1140	you want to modify its timeout value.
919		1141
920	=item ev_tstamp repeat [read-write]	1142	=item ev_tstamp repeat [read-write]
921		1143
922	The current C<repeat> value. Will be used each time the watcher times out	1144	The current C<repeat> value. Will be used each time the watcher times out
923	or C<ev_timer_again> is called and determines the next timeout (if any),	1145	or C<ev_timer_again> is called and determines the next timeout (if any),
…		…
965	but on wallclock time (absolute time). You can tell a periodic watcher	1187	but on wallclock time (absolute time). You can tell a periodic watcher
966	to trigger "at" some specific point in time. For example, if you tell a	1188	to trigger "at" some specific point in time. For example, if you tell a
967	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1189	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
968	+ 10.>) and then reset your system clock to the last year, then it will	1190	+ 10.>) and then reset your system clock to the last year, then it will
969	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1191	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
970	roughly 10 seconds later and of course not if you reset your system time	1192	roughly 10 seconds later).
971	again).
972		1193
973	They can also be used to implement vastly more complex timers, such as	1194	They can also be used to implement vastly more complex timers, such as
974	triggering an event on eahc midnight, local time.	1195	triggering an event on each midnight, local time or other, complicated,
		1196	rules.
975		1197
976	As with timers, the callback is guarenteed to be invoked only when the	1198	As with timers, the callback is guarenteed to be invoked only when the
977	time (C<at>) has been passed, but if multiple periodic timers become ready	1199	time (C<at>) has been passed, but if multiple periodic timers become ready
978	during the same loop iteration then order of execution is undefined.	1200	during the same loop iteration then order of execution is undefined.
979		1201
		1202	=head3 Watcher-Specific Functions and Data Members
		1203
980	=over 4	1204	=over 4
981		1205
982	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1206	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
983		1207
984	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1208	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
986	Lots of arguments, lets sort it out... There are basically three modes of	1210	Lots of arguments, lets sort it out... There are basically three modes of
987	operation, and we will explain them from simplest to complex:	1211	operation, and we will explain them from simplest to complex:
988		1212
989	=over 4	1213	=over 4
990		1214
991	=item * absolute timer (interval = reschedule_cb = 0)	1215	=item * absolute timer (at = time, interval = reschedule_cb = 0)
992		1216
993	In this configuration the watcher triggers an event at the wallclock time	1217	In this configuration the watcher triggers an event at the wallclock time
994	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1218	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
995	that is, if it is to be run at January 1st 2011 then it will run when the	1219	that is, if it is to be run at January 1st 2011 then it will run when the
996	system time reaches or surpasses this time.	1220	system time reaches or surpasses this time.
997		1221
998	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1222	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
999		1223
1000	In this mode the watcher will always be scheduled to time out at the next	1224	In this mode the watcher will always be scheduled to time out at the next
1001	C<at + N * interval> time (for some integer N) and then repeat, regardless	1225	C<at + N * interval> time (for some integer N, which can also be negative)
1002	of any time jumps.	1226	and then repeat, regardless of any time jumps.
1003		1227
1004	This can be used to create timers that do not drift with respect to system	1228	This can be used to create timers that do not drift with respect to system
1005	time:	1229	time:
1006		1230
1007	ev_periodic_set (&periodic, 0., 3600., 0);	1231	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1013		1237
1014	Another way to think about it (for the mathematically inclined) is that	1238	Another way to think about it (for the mathematically inclined) is that
1015	C<ev_periodic> will try to run the callback in this mode at the next possible	1239	C<ev_periodic> will try to run the callback in this mode at the next possible
1016	time where C<time = at (mod interval)>, regardless of any time jumps.	1240	time where C<time = at (mod interval)>, regardless of any time jumps.
1017		1241
		1242	For numerical stability it is preferable that the C<at> value is near
		1243	C<ev_now ()> (the current time), but there is no range requirement for
		1244	this value.
		1245
1018	=item * manual reschedule mode (reschedule_cb = callback)	1246	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1019		1247
1020	In this mode the values for C<interval> and C<at> are both being	1248	In this mode the values for C<interval> and C<at> are both being
1021	ignored. Instead, each time the periodic watcher gets scheduled, the	1249	ignored. Instead, each time the periodic watcher gets scheduled, the
1022	reschedule callback will be called with the watcher as first, and the	1250	reschedule callback will be called with the watcher as first, and the
1023	current time as second argument.	1251	current time as second argument.
1024		1252
1025	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1253	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1026	ever, or make any event loop modifications>. If you need to stop it,	1254	ever, or make any event loop modifications>. If you need to stop it,
1027	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1255	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1028	starting a prepare watcher).	1256	starting an C<ev_prepare> watcher, which is legal).
1029		1257
1030	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1258	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1031	ev_tstamp now)>, e.g.:	1259	ev_tstamp now)>, e.g.:
1032		1260
1033	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1261	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1056	Simply stops and restarts the periodic watcher again. This is only useful	1284	Simply stops and restarts the periodic watcher again. This is only useful
1057	when you changed some parameters or the reschedule callback would return	1285	when you changed some parameters or the reschedule callback would return
1058	a different time than the last time it was called (e.g. in a crond like	1286	a different time than the last time it was called (e.g. in a crond like
1059	program when the crontabs have changed).	1287	program when the crontabs have changed).
1060		1288
		1289	=item ev_tstamp offset [read-write]
		1290
		1291	When repeating, this contains the offset value, otherwise this is the
		1292	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1293
		1294	Can be modified any time, but changes only take effect when the periodic
		1295	timer fires or C<ev_periodic_again> is being called.
		1296
1061	=item ev_tstamp interval [read-write]	1297	=item ev_tstamp interval [read-write]
1062		1298
1063	The current interval value. Can be modified any time, but changes only	1299	The current interval value. Can be modified any time, but changes only
1064	take effect when the periodic timer fires or C<ev_periodic_again> is being	1300	take effect when the periodic timer fires or C<ev_periodic_again> is being
1065	called.	1301	called.
…		…
1067	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1303	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
1068		1304
1069	The current reschedule callback, or C<0>, if this functionality is	1305	The current reschedule callback, or C<0>, if this functionality is
1070	switched off. Can be changed any time, but changes only take effect when	1306	switched off. Can be changed any time, but changes only take effect when
1071	the periodic timer fires or C<ev_periodic_again> is being called.	1307	the periodic timer fires or C<ev_periodic_again> is being called.
		1308
		1309	=item ev_tstamp at [read-only]
		1310
		1311	When active, contains the absolute time that the watcher is supposed to
		1312	trigger next.
1072		1313
1073	=back	1314	=back
1074		1315
1075	Example: Call a callback every hour, or, more precisely, whenever the	1316	Example: Call a callback every hour, or, more precisely, whenever the
1076	system clock is divisible by 3600. The callback invocation times have	1317	system clock is divisible by 3600. The callback invocation times have
…		…
1118	with the kernel (thus it coexists with your own signal handlers as long	1359	with the kernel (thus it coexists with your own signal handlers as long
1119	as you don't register any with libev). Similarly, when the last signal	1360	as you don't register any with libev). Similarly, when the last signal
1120	watcher for a signal is stopped libev will reset the signal handler to	1361	watcher for a signal is stopped libev will reset the signal handler to
1121	SIG_DFL (regardless of what it was set to before).	1362	SIG_DFL (regardless of what it was set to before).
1122		1363
		1364	=head3 Watcher-Specific Functions and Data Members
		1365
1123	=over 4	1366	=over 4
1124		1367
1125	=item ev_signal_init (ev_signal *, callback, int signum)	1368	=item ev_signal_init (ev_signal *, callback, int signum)
1126		1369
1127	=item ev_signal_set (ev_signal *, int signum)	1370	=item ev_signal_set (ev_signal *, int signum)
…		…
1138		1381
1139	=head2 C<ev_child> - watch out for process status changes	1382	=head2 C<ev_child> - watch out for process status changes
1140		1383
1141	Child watchers trigger when your process receives a SIGCHLD in response to	1384	Child watchers trigger when your process receives a SIGCHLD in response to
1142	some child status changes (most typically when a child of yours dies).	1385	some child status changes (most typically when a child of yours dies).
		1386
		1387	=head3 Watcher-Specific Functions and Data Members
1143		1388
1144	=over 4	1389	=over 4
1145		1390
1146	=item ev_child_init (ev_child *, callback, int pid)	1391	=item ev_child_init (ev_child *, callback, int pid)
1147		1392
…		…
1192	not exist" is a status change like any other. The condition "path does	1437	not exist" is a status change like any other. The condition "path does
1193	not exist" is signified by the C<st_nlink> field being zero (which is	1438	not exist" is signified by the C<st_nlink> field being zero (which is
1194	otherwise always forced to be at least one) and all the other fields of	1439	otherwise always forced to be at least one) and all the other fields of
1195	the stat buffer having unspecified contents.	1440	the stat buffer having unspecified contents.
1196		1441
		1442	The path I<should> be absolute and I<must not> end in a slash. If it is
		1443	relative and your working directory changes, the behaviour is undefined.
		1444
1197	Since there is no standard to do this, the portable implementation simply	1445	Since there is no standard to do this, the portable implementation simply
1198	calls C<stat (2)> regulalry on the path to see if it changed somehow. You	1446	calls C<stat (2)> regularly on the path to see if it changed somehow. You
1199	can specify a recommended polling interval for this case. If you specify	1447	can specify a recommended polling interval for this case. If you specify
1200	a polling interval of C<0> (highly recommended!) then a I<suitable,	1448	a polling interval of C<0> (highly recommended!) then a I<suitable,
1201	unspecified default> value will be used (which you can expect to be around	1449	unspecified default> value will be used (which you can expect to be around
1202	five seconds, although this might change dynamically). Libev will also	1450	five seconds, although this might change dynamically). Libev will also
1203	impose a minimum interval which is currently around C<0.1>, but thats	1451	impose a minimum interval which is currently around C<0.1>, but thats
…		…
1205		1453
1206	This watcher type is not meant for massive numbers of stat watchers,	1454	This watcher type is not meant for massive numbers of stat watchers,
1207	as even with OS-supported change notifications, this can be	1455	as even with OS-supported change notifications, this can be
1208	resource-intensive.	1456	resource-intensive.
1209		1457
1210	At the time of this writing, no specific OS backends are implemented, but	1458	At the time of this writing, only the Linux inotify interface is
1211	if demand increases, at least a kqueue and inotify backend will be added.	1459	implemented (implementing kqueue support is left as an exercise for the
		1460	reader). Inotify will be used to give hints only and should not change the
		1461	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1462	to fall back to regular polling again even with inotify, but changes are
		1463	usually detected immediately, and if the file exists there will be no
		1464	polling.
		1465
		1466	=head3 Watcher-Specific Functions and Data Members
1212		1467
1213	=over 4	1468	=over 4
1214		1469
1215	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1470	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1216		1471
…		…
1280	ev_stat_start (loop, &passwd);	1535	ev_stat_start (loop, &passwd);
1281		1536
1282		1537
1283	=head2 C<ev_idle> - when you've got nothing better to do...	1538	=head2 C<ev_idle> - when you've got nothing better to do...
1284		1539
1285	Idle watchers trigger events when there are no other events are pending	1540	Idle watchers trigger events when no other events of the same or higher
1286	(prepare, check and other idle watchers do not count). That is, as long	1541	priority are pending (prepare, check and other idle watchers do not
1287	as your process is busy handling sockets or timeouts (or even signals,	1542	count).
1288	imagine) it will not be triggered. But when your process is idle all idle	1543
1289	watchers are being called again and again, once per event loop iteration -	1544	That is, as long as your process is busy handling sockets or timeouts
		1545	(or even signals, imagine) of the same or higher priority it will not be
		1546	triggered. But when your process is idle (or only lower-priority watchers
		1547	are pending), the idle watchers are being called once per event loop
1290	until stopped, that is, or your process receives more events and becomes	1548	iteration - until stopped, that is, or your process receives more events
1291	busy.	1549	and becomes busy again with higher priority stuff.
1292		1550
1293	The most noteworthy effect is that as long as any idle watchers are	1551	The most noteworthy effect is that as long as any idle watchers are
1294	active, the process will not block when waiting for new events.	1552	active, the process will not block when waiting for new events.
1295		1553
1296	Apart from keeping your process non-blocking (which is a useful	1554	Apart from keeping your process non-blocking (which is a useful
1297	effect on its own sometimes), idle watchers are a good place to do	1555	effect on its own sometimes), idle watchers are a good place to do
1298	"pseudo-background processing", or delay processing stuff to after the	1556	"pseudo-background processing", or delay processing stuff to after the
1299	event loop has handled all outstanding events.	1557	event loop has handled all outstanding events.
		1558
		1559	=head3 Watcher-Specific Functions and Data Members
1300		1560
1301	=over 4	1561	=over 4
1302		1562
1303	=item ev_idle_init (ev_signal *, callback)	1563	=item ev_idle_init (ev_signal *, callback)
1304		1564
…		…
1362	with priority higher than or equal to the event loop and one coroutine	1622	with priority higher than or equal to the event loop and one coroutine
1363	of lower priority, but only once, using idle watchers to keep the event	1623	of lower priority, but only once, using idle watchers to keep the event
1364	loop from blocking if lower-priority coroutines are active, thus mapping	1624	loop from blocking if lower-priority coroutines are active, thus mapping
1365	low-priority coroutines to idle/background tasks).	1625	low-priority coroutines to idle/background tasks).
1366		1626
		1627	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1628	priority, to ensure that they are being run before any other watchers
		1629	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1630	too) should not activate ("feed") events into libev. While libev fully
		1631	supports this, they will be called before other C<ev_check> watchers
		1632	did their job. As C<ev_check> watchers are often used to embed other
		1633	(non-libev) event loops those other event loops might be in an unusable
		1634	state until their C<ev_check> watcher ran (always remind yourself to
		1635	coexist peacefully with others).
		1636
		1637	=head3 Watcher-Specific Functions and Data Members
		1638
1367	=over 4	1639	=over 4
1368		1640
1369	=item ev_prepare_init (ev_prepare *, callback)	1641	=item ev_prepare_init (ev_prepare *, callback)
1370		1642
1371	=item ev_check_init (ev_check *, callback)	1643	=item ev_check_init (ev_check *, callback)
…		…
1374	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1646	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1375	macros, but using them is utterly, utterly and completely pointless.	1647	macros, but using them is utterly, utterly and completely pointless.
1376		1648
1377	=back	1649	=back
1378		1650
1379	Example: To include a library such as adns, you would add IO watchers	1651	There are a number of principal ways to embed other event loops or modules
1380	and a timeout watcher in a prepare handler, as required by libadns, and	1652	into libev. Here are some ideas on how to include libadns into libev
		1653	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1654	use for an actually working example. Another Perl module named C<EV::Glib>
		1655	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1656	into the Glib event loop).
		1657
		1658	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1381	in a check watcher, destroy them and call into libadns. What follows is	1659	and in a check watcher, destroy them and call into libadns. What follows
1382	pseudo-code only of course:	1660	is pseudo-code only of course. This requires you to either use a low
		1661	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1662	the callbacks for the IO/timeout watchers might not have been called yet.
1383		1663
1384	static ev_io iow [nfd];	1664	static ev_io iow [nfd];
1385	static ev_timer tw;	1665	static ev_timer tw;
1386		1666
1387	static void	1667	static void
1388	io_cb (ev_loop loop, ev_io w, int revents)	1668	io_cb (ev_loop loop, ev_io w, int revents)
1389	{	1669	{
1390	// set the relevant poll flags
1391	// could also call adns_processreadable etc. here
1392	struct pollfd fd = (struct pollfd )w->data;
1393	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1394	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1395	}	1670	}
1396		1671
1397	// create io watchers for each fd and a timer before blocking	1672	// create io watchers for each fd and a timer before blocking
1398	static void	1673	static void
1399	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1674	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1400	{	1675	{
1401	int timeout = 3600000;truct pollfd fds [nfd];	1676	int timeout = 3600000;
		1677	struct pollfd fds [nfd];
1402	// actual code will need to loop here and realloc etc.	1678	// actual code will need to loop here and realloc etc.
1403	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1679	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1404		1680
1405	/* the callback is illegal, but won't be called as we stop during check */	1681	/* the callback is illegal, but won't be called as we stop during check */
1406	ev_timer_init (&tw, 0, timeout * 1e-3);	1682	ev_timer_init (&tw, 0, timeout * 1e-3);
1407	ev_timer_start (loop, &tw);	1683	ev_timer_start (loop, &tw);
1408		1684
1409	// create on ev_io per pollfd	1685	// create one ev_io per pollfd
1410	for (int i = 0; i < nfd; ++i)	1686	for (int i = 0; i < nfd; ++i)
1411	{	1687	{
1412	ev_io_init (iow + i, io_cb, fds [i].fd,	1688	ev_io_init (iow + i, io_cb, fds [i].fd,
1413	((fds [i].events & POLLIN ? EV_READ : 0)	1689	((fds [i].events & POLLIN ? EV_READ : 0)
1414	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1690	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1415		1691
1416	fds [i].revents = 0;	1692	fds [i].revents = 0;
1417	iow [i].data = fds + i;
1418	ev_io_start (loop, iow + i);	1693	ev_io_start (loop, iow + i);
1419	}	1694	}
1420	}	1695	}
1421		1696
1422	// stop all watchers after blocking	1697	// stop all watchers after blocking
…		…
1424	adns_check_cb (ev_loop loop, ev_check w, int revents)	1699	adns_check_cb (ev_loop loop, ev_check w, int revents)
1425	{	1700	{
1426	ev_timer_stop (loop, &tw);	1701	ev_timer_stop (loop, &tw);
1427		1702
1428	for (int i = 0; i < nfd; ++i)	1703	for (int i = 0; i < nfd; ++i)
		1704	{
		1705	// set the relevant poll flags
		1706	// could also call adns_processreadable etc. here
		1707	struct pollfd *fd = fds + i;
		1708	int revents = ev_clear_pending (iow + i);
		1709	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1710	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1711
		1712	// now stop the watcher
1429	ev_io_stop (loop, iow + i);	1713	ev_io_stop (loop, iow + i);
		1714	}
1430		1715
1431	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1716	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1717	}
		1718
		1719	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1720	in the prepare watcher and would dispose of the check watcher.
		1721
		1722	Method 3: If the module to be embedded supports explicit event
		1723	notification (adns does), you can also make use of the actual watcher
		1724	callbacks, and only destroy/create the watchers in the prepare watcher.
		1725
		1726	static void
		1727	timer_cb (EV_P_ ev_timer *w, int revents)
		1728	{
		1729	adns_state ads = (adns_state)w->data;
		1730	update_now (EV_A);
		1731
		1732	adns_processtimeouts (ads, &tv_now);
		1733	}
		1734
		1735	static void
		1736	io_cb (EV_P_ ev_io *w, int revents)
		1737	{
		1738	adns_state ads = (adns_state)w->data;
		1739	update_now (EV_A);
		1740
		1741	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1742	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1743	}
		1744
		1745	// do not ever call adns_afterpoll
		1746
		1747	Method 4: Do not use a prepare or check watcher because the module you
		1748	want to embed is too inflexible to support it. Instead, youc na override
		1749	their poll function. The drawback with this solution is that the main
		1750	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1751	this.
		1752
		1753	static gint
		1754	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1755	{
		1756	int got_events = 0;
		1757
		1758	for (n = 0; n < nfds; ++n)
		1759	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1760
		1761	if (timeout >= 0)
		1762	// create/start timer
		1763
		1764	// poll
		1765	ev_loop (EV_A_ 0);
		1766
		1767	// stop timer again
		1768	if (timeout >= 0)
		1769	ev_timer_stop (EV_A_ &to);
		1770
		1771	// stop io watchers again - their callbacks should have set
		1772	for (n = 0; n < nfds; ++n)
		1773	ev_io_stop (EV_A_ iow [n]);
		1774
		1775	return got_events;
1432	}	1776	}
1433		1777
1434		1778
1435	=head2 C<ev_embed> - when one backend isn't enough...	1779	=head2 C<ev_embed> - when one backend isn't enough...
1436		1780
…		…
1500	ev_embed_start (loop_hi, &embed);	1844	ev_embed_start (loop_hi, &embed);
1501	}	1845	}
1502	else	1846	else
1503	loop_lo = loop_hi;	1847	loop_lo = loop_hi;
1504		1848
		1849	=head3 Watcher-Specific Functions and Data Members
		1850
1505	=over 4	1851	=over 4
1506		1852
1507	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1853	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1508		1854
1509	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1855	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1518		1864
1519	Make a single, non-blocking sweep over the embedded loop. This works	1865	Make a single, non-blocking sweep over the embedded loop. This works
1520	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1866	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1521	apropriate way for embedded loops.	1867	apropriate way for embedded loops.
1522		1868
1523	=item struct ev_loop *loop [read-only]	1869	=item struct ev_loop *other [read-only]
1524		1870
1525	The embedded event loop.	1871	The embedded event loop.
1526		1872
1527	=back	1873	=back
1528		1874
…		…
1535	event loop blocks next and before C<ev_check> watchers are being called,	1881	event loop blocks next and before C<ev_check> watchers are being called,
1536	and only in the child after the fork. If whoever good citizen calling	1882	and only in the child after the fork. If whoever good citizen calling
1537	C<ev_default_fork> cheats and calls it in the wrong process, the fork	1883	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1538	handlers will be invoked, too, of course.	1884	handlers will be invoked, too, of course.
1539		1885
		1886	=head3 Watcher-Specific Functions and Data Members
		1887
1540	=over 4	1888	=over 4
1541		1889
1542	=item ev_fork_init (ev_signal *, callback)	1890	=item ev_fork_init (ev_signal *, callback)
1543		1891
1544	Initialises and configures the fork watcher - it has no parameters of any	1892	Initialises and configures the fork watcher - it has no parameters of any
…		…
1640		1988
1641	To use it,	1989	To use it,
1642		1990
1643	#include <ev++.h>	1991	#include <ev++.h>
1644		1992
1645	(it is not installed by default). This automatically includes F<ev.h>	1993	This automatically includes F<ev.h> and puts all of its definitions (many
1646	and puts all of its definitions (many of them macros) into the global	1994	of them macros) into the global namespace. All C++ specific things are
1647	namespace. All C++ specific things are put into the C<ev> namespace.	1995	put into the C<ev> namespace. It should support all the same embedding
		1996	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1648		1997
1649	It should support all the same embedding options as F<ev.h>, most notably	1998	Care has been taken to keep the overhead low. The only data member the C++
1650	C<EV_MULTIPLICITY>.	1999	classes add (compared to plain C-style watchers) is the event loop pointer
		2000	that the watcher is associated with (or no additional members at all if
		2001	you disable C<EV_MULTIPLICITY> when embedding libev).
		2002
		2003	Currently, functions, and static and non-static member functions can be
		2004	used as callbacks. Other types should be easy to add as long as they only
		2005	need one additional pointer for context. If you need support for other
		2006	types of functors please contact the author (preferably after implementing
		2007	it).
1651		2008
1652	Here is a list of things available in the C<ev> namespace:	2009	Here is a list of things available in the C<ev> namespace:
1653		2010
1654	=over 4	2011	=over 4
1655		2012
…		…
1671		2028
1672	All of those classes have these methods:	2029	All of those classes have these methods:
1673		2030
1674	=over 4	2031	=over 4
1675		2032
1676	=item ev::TYPE::TYPE (object , object::method )	2033	=item ev::TYPE::TYPE ()
1677		2034
1678	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	2035	=item ev::TYPE::TYPE (struct ev_loop *)
1679		2036
1680	=item ev::TYPE::~TYPE	2037	=item ev::TYPE::~TYPE
1681		2038
1682	The constructor takes a pointer to an object and a method pointer to	2039	The constructor (optionally) takes an event loop to associate the watcher
1683	the event handler callback to call in this class. The constructor calls	2040	with. If it is omitted, it will use C<EV_DEFAULT>.
1684	C<ev_init> for you, which means you have to call the C<set> method	2041
1685	before starting it. If you do not specify a loop then the constructor	2042	The constructor calls C<ev_init> for you, which means you have to call the
1686	automatically associates the default loop with this watcher.	2043	C<set> method before starting it.
		2044
		2045	It will not set a callback, however: You have to call the templated C<set>
		2046	method to set a callback before you can start the watcher.
		2047
		2048	(The reason why you have to use a method is a limitation in C++ which does
		2049	not allow explicit template arguments for constructors).
1687		2050
1688	The destructor automatically stops the watcher if it is active.	2051	The destructor automatically stops the watcher if it is active.
		2052
		2053	=item w->set<class, &class::method> (object *)
		2054
		2055	This method sets the callback method to call. The method has to have a
		2056	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		2057	first argument and the C<revents> as second. The object must be given as
		2058	parameter and is stored in the C<data> member of the watcher.
		2059
		2060	This method synthesizes efficient thunking code to call your method from
		2061	the C callback that libev requires. If your compiler can inline your
		2062	callback (i.e. it is visible to it at the place of the C<set> call and
		2063	your compiler is good :), then the method will be fully inlined into the
		2064	thunking function, making it as fast as a direct C callback.
		2065
		2066	Example: simple class declaration and watcher initialisation
		2067
		2068	struct myclass
		2069	{
		2070	void io_cb (ev::io &w, int revents) { }
		2071	}
		2072
		2073	myclass obj;
		2074	ev::io iow;
		2075	iow.set <myclass, &myclass::io_cb> (&obj);
		2076
		2077	=item w->set<function> (void *data = 0)
		2078
		2079	Also sets a callback, but uses a static method or plain function as
		2080	callback. The optional C<data> argument will be stored in the watcher's
		2081	C<data> member and is free for you to use.
		2082
		2083	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2084
		2085	See the method-C<set> above for more details.
		2086
		2087	Example:
		2088
		2089	static void io_cb (ev::io &w, int revents) { }
		2090	iow.set <io_cb> ();
1689		2091
1690	=item w->set (struct ev_loop *)	2092	=item w->set (struct ev_loop *)
1691		2093
1692	Associates a different C<struct ev_loop> with this watcher. You can only	2094	Associates a different C<struct ev_loop> with this watcher. You can only
1693	do this when the watcher is inactive (and not pending either).	2095	do this when the watcher is inactive (and not pending either).
1694		2096
1695	=item w->set ([args])	2097	=item w->set ([args])
1696		2098
1697	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2099	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1698	called at least once. Unlike the C counterpart, an active watcher gets	2100	called at least once. Unlike the C counterpart, an active watcher gets
1699	automatically stopped and restarted.	2101	automatically stopped and restarted when reconfiguring it with this
		2102	method.
1700		2103
1701	=item w->start ()	2104	=item w->start ()
1702		2105
1703	Starts the watcher. Note that there is no C<loop> argument as the	2106	Starts the watcher. Note that there is no C<loop> argument, as the
1704	constructor already takes the loop.	2107	constructor already stores the event loop.
1705		2108
1706	=item w->stop ()	2109	=item w->stop ()
1707		2110
1708	Stops the watcher if it is active. Again, no C<loop> argument.	2111	Stops the watcher if it is active. Again, no C<loop> argument.
1709		2112
1710	=item w->again () C<ev::timer>, C<ev::periodic> only	2113	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1711		2114
1712	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2115	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1713	C<ev_TYPE_again> function.	2116	C<ev_TYPE_again> function.
1714		2117
1715	=item w->sweep () C<ev::embed> only	2118	=item w->sweep () (C<ev::embed> only)
1716		2119
1717	Invokes C<ev_embed_sweep>.	2120	Invokes C<ev_embed_sweep>.
1718		2121
1719	=item w->update () C<ev::stat> only	2122	=item w->update () (C<ev::stat> only)
1720		2123
1721	Invokes C<ev_stat_stat>.	2124	Invokes C<ev_stat_stat>.
1722		2125
1723	=back	2126	=back
1724		2127
…		…
1734		2137
1735	myclass ();	2138	myclass ();
1736	}	2139	}
1737		2140
1738	myclass::myclass (int fd)	2141	myclass::myclass (int fd)
1739	: io (this, &myclass::io_cb),
1740	idle (this, &myclass::idle_cb)
1741	{	2142	{
		2143	io .set <myclass, &myclass::io_cb > (this);
		2144	idle.set <myclass, &myclass::idle_cb> (this);
		2145
1742	io.start (fd, ev::READ);	2146	io.start (fd, ev::READ);
1743	}	2147	}
1744		2148
1745		2149
1746	=head1 MACRO MAGIC	2150	=head1 MACRO MAGIC
1747		2151
1748	Libev can be compiled with a variety of options, the most fundemantal is	2152	Libev can be compiled with a variety of options, the most fundamantal
1749	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2153	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1750	callbacks have an initial C<struct ev_loop *> argument.	2154	functions and callbacks have an initial C<struct ev_loop *> argument.
1751		2155
1752	To make it easier to write programs that cope with either variant, the	2156	To make it easier to write programs that cope with either variant, the
1753	following macros are defined:	2157	following macros are defined:
1754		2158
1755	=over 4	2159	=over 4
…		…
1787	Similar to the other two macros, this gives you the value of the default	2191	Similar to the other two macros, this gives you the value of the default
1788	loop, if multiple loops are supported ("ev loop default").	2192	loop, if multiple loops are supported ("ev loop default").
1789		2193
1790	=back	2194	=back
1791		2195
1792	Example: Declare and initialise a check watcher, working regardless of	2196	Example: Declare and initialise a check watcher, utilising the above
1793	wether multiple loops are supported or not.	2197	macros so it will work regardless of whether multiple loops are supported
		2198	or not.
1794		2199
1795	static void	2200	static void
1796	check_cb (EV_P_ ev_timer *w, int revents)	2201	check_cb (EV_P_ ev_timer *w, int revents)
1797	{	2202	{
1798	ev_check_stop (EV_A_ w);	2203	ev_check_stop (EV_A_ w);
…		…
1801	ev_check check;	2206	ev_check check;
1802	ev_check_init (&check, check_cb);	2207	ev_check_init (&check, check_cb);
1803	ev_check_start (EV_DEFAULT_ &check);	2208	ev_check_start (EV_DEFAULT_ &check);
1804	ev_loop (EV_DEFAULT_ 0);	2209	ev_loop (EV_DEFAULT_ 0);
1805		2210
1806
1807	=head1 EMBEDDING	2211	=head1 EMBEDDING
1808		2212
1809	Libev can (and often is) directly embedded into host	2213	Libev can (and often is) directly embedded into host
1810	applications. Examples of applications that embed it include the Deliantra	2214	applications. Examples of applications that embed it include the Deliantra
1811	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2215	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1812	and rxvt-unicode.	2216	and rxvt-unicode.
1813		2217
1814	The goal is to enable you to just copy the neecssary files into your	2218	The goal is to enable you to just copy the necessary files into your
1815	source directory without having to change even a single line in them, so	2219	source directory without having to change even a single line in them, so
1816	you can easily upgrade by simply copying (or having a checked-out copy of	2220	you can easily upgrade by simply copying (or having a checked-out copy of
1817	libev somewhere in your source tree).	2221	libev somewhere in your source tree).
1818		2222
1819	=head2 FILESETS	2223	=head2 FILESETS
…		…
1850	ev_vars.h	2254	ev_vars.h
1851	ev_wrap.h	2255	ev_wrap.h
1852		2256
1853	ev_win32.c required on win32 platforms only	2257	ev_win32.c required on win32 platforms only
1854		2258
1855	ev_select.c only when select backend is enabled (which is by default)	2259	ev_select.c only when select backend is enabled (which is enabled by default)
1856	ev_poll.c only when poll backend is enabled (disabled by default)	2260	ev_poll.c only when poll backend is enabled (disabled by default)
1857	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2261	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1858	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2262	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1859	ev_port.c only when the solaris port backend is enabled (disabled by default)	2263	ev_port.c only when the solaris port backend is enabled (disabled by default)
1860		2264
…		…
1909		2313
1910	If defined to be C<1>, libev will try to detect the availability of the	2314	If defined to be C<1>, libev will try to detect the availability of the
1911	monotonic clock option at both compiletime and runtime. Otherwise no use	2315	monotonic clock option at both compiletime and runtime. Otherwise no use
1912	of the monotonic clock option will be attempted. If you enable this, you	2316	of the monotonic clock option will be attempted. If you enable this, you
1913	usually have to link against librt or something similar. Enabling it when	2317	usually have to link against librt or something similar. Enabling it when
1914	the functionality isn't available is safe, though, althoguh you have	2318	the functionality isn't available is safe, though, although you have
1915	to make sure you link against any libraries where the C<clock_gettime>	2319	to make sure you link against any libraries where the C<clock_gettime>
1916	function is hiding in (often F<-lrt>).	2320	function is hiding in (often F<-lrt>).
1917		2321
1918	=item EV_USE_REALTIME	2322	=item EV_USE_REALTIME
1919		2323
1920	If defined to be C<1>, libev will try to detect the availability of the	2324	If defined to be C<1>, libev will try to detect the availability of the
1921	realtime clock option at compiletime (and assume its availability at	2325	realtime clock option at compiletime (and assume its availability at
1922	runtime if successful). Otherwise no use of the realtime clock option will	2326	runtime if successful). Otherwise no use of the realtime clock option will
1923	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2327	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
1924	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2328	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
1925	in the description of C<EV_USE_MONOTONIC>, though.	2329	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2330
		2331	=item EV_USE_NANOSLEEP
		2332
		2333	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2334	and will use it for delays. Otherwise it will use C<select ()>.
1926		2335
1927	=item EV_USE_SELECT	2336	=item EV_USE_SELECT
1928		2337
1929	If undefined or defined to be C<1>, libev will compile in support for the	2338	If undefined or defined to be C<1>, libev will compile in support for the
1930	C<select>(2) backend. No attempt at autodetection will be done: if no	2339	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
1985		2394
1986	=item EV_USE_DEVPOLL	2395	=item EV_USE_DEVPOLL
1987		2396
1988	reserved for future expansion, works like the USE symbols above.	2397	reserved for future expansion, works like the USE symbols above.
1989		2398
		2399	=item EV_USE_INOTIFY
		2400
		2401	If defined to be C<1>, libev will compile in support for the Linux inotify
		2402	interface to speed up C<ev_stat> watchers. Its actual availability will
		2403	be detected at runtime.
		2404
1990	=item EV_H	2405	=item EV_H
1991		2406
1992	The name of the F<ev.h> header file used to include it. The default if	2407	The name of the F<ev.h> header file used to include it. The default if
1993	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2408	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1994	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2409	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
2017	will have the C<struct ev_loop *> as first argument, and you can create	2432	will have the C<struct ev_loop *> as first argument, and you can create
2018	additional independent event loops. Otherwise there will be no support	2433	additional independent event loops. Otherwise there will be no support
2019	for multiple event loops and there is no first event loop pointer	2434	for multiple event loops and there is no first event loop pointer
2020	argument. Instead, all functions act on the single default loop.	2435	argument. Instead, all functions act on the single default loop.
2021		2436
		2437	=item EV_MINPRI
		2438
		2439	=item EV_MAXPRI
		2440
		2441	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2442	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2443	provide for more priorities by overriding those symbols (usually defined
		2444	to be C<-2> and C<2>, respectively).
		2445
		2446	When doing priority-based operations, libev usually has to linearly search
		2447	all the priorities, so having many of them (hundreds) uses a lot of space
		2448	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2449	fine.
		2450
		2451	If your embedding app does not need any priorities, defining these both to
		2452	C<0> will save some memory and cpu.
		2453
2022	=item EV_PERIODIC_ENABLE	2454	=item EV_PERIODIC_ENABLE
2023		2455
2024	If undefined or defined to be C<1>, then periodic timers are supported. If	2456	If undefined or defined to be C<1>, then periodic timers are supported. If
2025	defined to be C<0>, then they are not. Disabling them saves a few kB of	2457	defined to be C<0>, then they are not. Disabling them saves a few kB of
2026	code.	2458	code.
2027		2459
		2460	=item EV_IDLE_ENABLE
		2461
		2462	If undefined or defined to be C<1>, then idle watchers are supported. If
		2463	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2464	code.
		2465
2028	=item EV_EMBED_ENABLE	2466	=item EV_EMBED_ENABLE
2029		2467
2030	If undefined or defined to be C<1>, then embed watchers are supported. If	2468	If undefined or defined to be C<1>, then embed watchers are supported. If
2031	defined to be C<0>, then they are not.	2469	defined to be C<0>, then they are not.
2032		2470
…		…
2049	=item EV_PID_HASHSIZE	2487	=item EV_PID_HASHSIZE
2050		2488
2051	C<ev_child> watchers use a small hash table to distribute workload by	2489	C<ev_child> watchers use a small hash table to distribute workload by
2052	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	2490	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2053	than enough. If you need to manage thousands of children you might want to	2491	than enough. If you need to manage thousands of children you might want to
2054	increase this value.	2492	increase this value (I<must> be a power of two).
		2493
		2494	=item EV_INOTIFY_HASHSIZE
		2495
		2496	C<ev_staz> watchers use a small hash table to distribute workload by
		2497	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2498	usually more than enough. If you need to manage thousands of C<ev_stat>
		2499	watchers you might want to increase this value (I<must> be a power of
		2500	two).
2055		2501
2056	=item EV_COMMON	2502	=item EV_COMMON
2057		2503
2058	By default, all watchers have a C<void *data> member. By redefining	2504	By default, all watchers have a C<void *data> member. By redefining
2059	this macro to a something else you can include more and other types of	2505	this macro to a something else you can include more and other types of
…		…
2072		2518
2073	=item ev_set_cb (ev, cb)	2519	=item ev_set_cb (ev, cb)
2074		2520
2075	Can be used to change the callback member declaration in each watcher,	2521	Can be used to change the callback member declaration in each watcher,
2076	and the way callbacks are invoked and set. Must expand to a struct member	2522	and the way callbacks are invoked and set. Must expand to a struct member
2077	definition and a statement, respectively. See the F<ev.v> header file for	2523	definition and a statement, respectively. See the F<ev.h> header file for
2078	their default definitions. One possible use for overriding these is to	2524	their default definitions. One possible use for overriding these is to
2079	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2525	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2080	method calls instead of plain function calls in C++.	2526	method calls instead of plain function calls in C++.
		2527
		2528	=head2 EXPORTED API SYMBOLS
		2529
		2530	If you need to re-export the API (e.g. via a dll) and you need a list of
		2531	exported symbols, you can use the provided F<Symbol.*> files which list
		2532	all public symbols, one per line:
		2533
		2534	Symbols.ev for libev proper
		2535	Symbols.event for the libevent emulation
		2536
		2537	This can also be used to rename all public symbols to avoid clashes with
		2538	multiple versions of libev linked together (which is obviously bad in
		2539	itself, but sometimes it is inconvinient to avoid this).
		2540
		2541	A sed command like this will create wrapper C<#define>'s that you need to
		2542	include before including F<ev.h>:
		2543
		2544	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2545
		2546	This would create a file F<wrap.h> which essentially looks like this:
		2547
		2548	#define ev_backend myprefix_ev_backend
		2549	#define ev_check_start myprefix_ev_check_start
		2550	#define ev_check_stop myprefix_ev_check_stop
		2551	...
2081		2552
2082	=head2 EXAMPLES	2553	=head2 EXAMPLES
2083		2554
2084	For a real-world example of a program the includes libev	2555	For a real-world example of a program the includes libev
2085	verbatim, you can have a look at the EV perl module	2556	verbatim, you can have a look at the EV perl module
…		…
2088	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2559	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2089	will be compiled. It is pretty complex because it provides its own header	2560	will be compiled. It is pretty complex because it provides its own header
2090	file.	2561	file.
2091		2562
2092	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2563	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2093	that everybody includes and which overrides some autoconf choices:	2564	that everybody includes and which overrides some configure choices:
2094		2565
		2566	#define EV_MINIMAL 1
2095	#define EV_USE_POLL 0	2567	#define EV_USE_POLL 0
2096	#define EV_MULTIPLICITY 0	2568	#define EV_MULTIPLICITY 0
2097	#define EV_PERIODICS 0	2569	#define EV_PERIODIC_ENABLE 0
		2570	#define EV_STAT_ENABLE 0
		2571	#define EV_FORK_ENABLE 0
2098	#define EV_CONFIG_H <config.h>	2572	#define EV_CONFIG_H <config.h>
		2573	#define EV_MINPRI 0
		2574	#define EV_MAXPRI 0
2099		2575
2100	#include "ev++.h"	2576	#include "ev++.h"
2101		2577
2102	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2578	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2103		2579
…		…
2109		2585
2110	In this section the complexities of (many of) the algorithms used inside	2586	In this section the complexities of (many of) the algorithms used inside
2111	libev will be explained. For complexity discussions about backends see the	2587	libev will be explained. For complexity discussions about backends see the
2112	documentation for C<ev_default_init>.	2588	documentation for C<ev_default_init>.
2113		2589
		2590	All of the following are about amortised time: If an array needs to be
		2591	extended, libev needs to realloc and move the whole array, but this
		2592	happens asymptotically never with higher number of elements, so O(1) might
		2593	mean it might do a lengthy realloc operation in rare cases, but on average
		2594	it is much faster and asymptotically approaches constant time.
		2595
2114	=over 4	2596	=over 4
2115		2597
2116	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2598	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2117		2599
		2600	This means that, when you have a watcher that triggers in one hour and
		2601	there are 100 watchers that would trigger before that then inserting will
		2602	have to skip those 100 watchers.
		2603
2118	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2604	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2119		2605
		2606	That means that for changing a timer costs less than removing/adding them
		2607	as only the relative motion in the event queue has to be paid for.
		2608
2120	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2609	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2121		2610
		2611	These just add the watcher into an array or at the head of a list.
2122	=item Stopping check/prepare/idle watchers: O(1)	2612	=item Stopping check/prepare/idle watchers: O(1)
2123		2613
2124	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2614	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2615
		2616	These watchers are stored in lists then need to be walked to find the
		2617	correct watcher to remove. The lists are usually short (you don't usually
		2618	have many watchers waiting for the same fd or signal).
2125		2619
2126	=item Finding the next timer per loop iteration: O(1)	2620	=item Finding the next timer per loop iteration: O(1)
2127		2621
2128	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2622	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2129		2623
		2624	A change means an I/O watcher gets started or stopped, which requires
		2625	libev to recalculate its status (and possibly tell the kernel).
		2626
2130	=item Activating one watcher: O(1)	2627	=item Activating one watcher: O(1)
2131		2628
		2629	=item Priority handling: O(number_of_priorities)
		2630
		2631	Priorities are implemented by allocating some space for each
		2632	priority. When doing priority-based operations, libev usually has to
		2633	linearly search all the priorities.
		2634
2132	=back	2635	=back
2133		2636
2134		2637
2135	=head1 AUTHOR	2638	=head1 AUTHOR
2136		2639

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Comparing libev/ev.pod (file contents): Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs. Revision 1.101 by ayin, Sat Dec 22 14:11:25 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs.
Revision 1.101 by ayin, Sat Dec 22 14:11:25 2007 UTC