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

Comparing libev/ev.pod (file contents):
Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs.
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 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;
…		…
53	The newest version of this document is also available as a html-formatted	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	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>.	55	time: L<http://cvs.schmorp.de/libev/ev.html>.
56		56
57	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
58	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
59	these event sources and provide your program with events.	59	these event sources and provide your program with events.
60		60
61	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
62	(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
63	communicate events via a callback mechanism.	63	communicate events via a callback mechanism.
…		…
65	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
66	watchers>, which are relatively small C structures you initialise with the	66	watchers>, which are relatively small C structures you initialise with the
67	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
68	watcher.	68	watcher.
69		69
70	=head1 FEATURES	70	=head2 FEATURES
71		71
72	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
73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74	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
75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
…		…
82		82
83	It also is quite fast (see this	83	It also is quite fast (see this
84	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
85	for example).	85	for example).
86		86
87	=head1 CONVENTIONS	87	=head2 CONVENTIONS
88		88
89	Libev is very configurable. In this manual the default configuration will	89	Libev is very configurable. In this manual the default configuration will
90	be described, which supports multiple event loops. For more info about	90	be described, which supports multiple event loops. For more info about
91	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
92	this manual. If libev was configured without support for multiple event	92	this manual. If libev was configured without support for multiple event
93	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>
94	(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.
95		95
96	=head1 TIME REPRESENTATION	96	=head2 TIME REPRESENTATION
97		97
98	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
99	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
100	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
101	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
102	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
103	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.
104		106
105	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
106		108
107	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
108	library in any way.	110	library in any way.
…		…
113		115
114	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
115	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
116	you actually want to know.	118	you actually want to know.
117		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
118	=item int ev_version_major ()	126	=item int ev_version_major ()
119		127
120	=item int ev_version_minor ()	128	=item int ev_version_minor ()
121		129
122	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
123	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
124	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
125	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
126	version of the library your program was compiled against.	134	version of the library your program was compiled against.
127		135
		136	These version numbers refer to the ABI version of the library, not the
		137	release version.
		138
128	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,
129	as this indicates an incompatible change. Minor versions are usually	140	as this indicates an incompatible change. Minor versions are usually
130	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
131	not a problem.	142	not a problem.
132		143
133	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
134	version.	145	version.
…		…
295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	306	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296		307
297	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
298	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,
299	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
300	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
301	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.
302		320
303	=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)
304		322
305	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
306	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
307	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
308	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.
309		329
310	=item C<EVBACKEND_EPOLL> (value 4, Linux)	330	=item C<EVBACKEND_EPOLL> (value 4, Linux)
311		331
312	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,
313	but it scales phenomenally better. While poll and select usually scale like	333	but it scales phenomenally better. While poll and select usually scale
314	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),
315	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.
316		339
317	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
318	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
319	(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
320	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
321	well if you register events for both fds.	344	very well if you register events for both fds.
322		345
323	Please note that epoll sometimes generates spurious notifications, so you	346	Please note that epoll sometimes generates spurious notifications, so you
324	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
325	(or space) is available.	348	(or space) is available.
326		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
327	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	357	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328		358
329	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
330	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
331	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
332	completely useless). For this reason its not being "autodetected"	362	it's completely useless). For this reason it's not being "autodetected"
333	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
334	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.
335		370
336	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
337	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
338	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
339	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
340	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.
341		386
342	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)	387	=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343		388
344	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.
345		393
346	=item C<EVBACKEND_PORT> (value 32, Solaris 10)	394	=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347		395
348	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,
349	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)).
350		398
351	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
352	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
353	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.
		407
		408	On the positive side, ignoring the spurious readyness notifications, this
		409	backend actually performed to specification in all tests and is fully
		410	embeddable, which is a rare feat among the OS-specific backends.
354		411
355	=item C<EVBACKEND_ALL>	412	=item C<EVBACKEND_ALL>
356		413
357	Try all backends (even potentially broken ones that wouldn't be tried	414	Try all backends (even potentially broken ones that wouldn't be tried
358	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as	415	with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.	416	C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360		417
		418	It is definitely not recommended to use this flag.
		419
361	=back	420	=back
362		421
363	If one or more of these are ored into the flags value, then only these	422	If one or more of these are ored into the flags value, then only these
364	backends will be tried (in the reverse order as given here). If none are	423	backends will be tried (in the reverse order as listed here). If none are
365	specified, most compiled-in backend will be tried, usually in reverse	424	specified, all backends in C<ev_recommended_backends ()> will be tried.
366	order of their flag values :)
367		425
368	The most typical usage is like this:	426	The most typical usage is like this:
369		427
370	if (!ev_default_loop (0))	428	if (!ev_default_loop (0))
371	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	429	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
399	Destroys the default loop again (frees all memory and kernel state	457	Destroys the default loop again (frees all memory and kernel state
400	etc.). None of the active event watchers will be stopped in the normal	458	etc.). None of the active event watchers will be stopped in the normal
401	sense, so e.g. C<ev_is_active> might still return true. It is your	459	sense, so e.g. C<ev_is_active> might still return true. It is your
402	responsibility to either stop all watchers cleanly yoursef I<before>	460	responsibility to either stop all watchers cleanly yoursef I<before>
403	calling this function, or cope with the fact afterwards (which is usually	461	calling this function, or cope with the fact afterwards (which is usually
404	the easiest thing, youc na just ignore the watchers and/or C<free ()> them	462	the easiest thing, you can just ignore the watchers and/or C<free ()> them
405	for example).	463	for example).
		464
		465	Note that certain global state, such as signal state, will not be freed by
		466	this function, and related watchers (such as signal and child watchers)
		467	would need to be stopped manually.
		468
		469	In general it is not advisable to call this function except in the
		470	rare occasion where you really need to free e.g. the signal handling
		471	pipe fds. If you need dynamically allocated loops it is better to use
		472	C<ev_loop_new> and C<ev_loop_destroy>).
406		473
407	=item ev_loop_destroy (loop)	474	=item ev_loop_destroy (loop)
408		475
409	Like C<ev_default_destroy>, but destroys an event loop created by an	476	Like C<ev_default_destroy>, but destroys an event loop created by an
410	earlier call to C<ev_loop_new>.	477	earlier call to C<ev_loop_new>.
…		…
455		522
456	Returns the current "event loop time", which is the time the event loop	523	Returns the current "event loop time", which is the time the event loop
457	received events and started processing them. This timestamp does not	524	received events and started processing them. This timestamp does not
458	change as long as callbacks are being processed, and this is also the base	525	change as long as callbacks are being processed, and this is also the base
459	time used for relative timers. You can treat it as the timestamp of the	526	time used for relative timers. You can treat it as the timestamp of the
460	event occuring (or more correctly, libev finding out about it).	527	event occurring (or more correctly, libev finding out about it).
461		528
462	=item ev_loop (loop, int flags)	529	=item ev_loop (loop, int flags)
463		530
464	Finally, this is it, the event handler. This function usually is called	531	Finally, this is it, the event handler. This function usually is called
465	after you initialised all your watchers and you want to start handling	532	after you initialised all your watchers and you want to start handling
…		…
486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	553	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487	usually a better approach for this kind of thing.	554	usually a better approach for this kind of thing.
488		555
489	Here are the gory details of what C<ev_loop> does:	556	Here are the gory details of what C<ev_loop> does:
490		557
491	* If there are no active watchers (reference count is zero), return.	558	- Before the first iteration, call any pending watchers.
492	- Queue prepare watchers and then call all outstanding watchers.	559	* If EVFLAG_FORKCHECK was used, check for a fork.
		560	- If a fork was detected, queue and call all fork watchers.
		561	- Queue and call all prepare watchers.
493	- If we have been forked, recreate the kernel state.	562	- If we have been forked, recreate the kernel state.
494	- Update the kernel state with all outstanding changes.	563	- Update the kernel state with all outstanding changes.
495	- Update the "event loop time".	564	- Update the "event loop time".
496	- Calculate for how long to block.	565	- Calculate for how long to sleep or block, if at all
		566	(active idle watchers, EVLOOP_NONBLOCK or not having
		567	any active watchers at all will result in not sleeping).
		568	- Sleep if the I/O and timer collect interval say so.
497	- Block the process, waiting for any events.	569	- Block the process, waiting for any events.
498	- Queue all outstanding I/O (fd) events.	570	- Queue all outstanding I/O (fd) events.
499	- Update the "event loop time" and do time jump handling.	571	- Update the "event loop time" and do time jump handling.
500	- Queue all outstanding timers.	572	- Queue all outstanding timers.
501	- Queue all outstanding periodics.	573	- Queue all outstanding periodics.
502	- If no events are pending now, queue all idle watchers.	574	- If no events are pending now, queue all idle watchers.
503	- Queue all check watchers.	575	- Queue all check watchers.
504	- Call all queued watchers in reverse order (i.e. check watchers first).	576	- Call all queued watchers in reverse order (i.e. check watchers first).
505	Signals and child watchers are implemented as I/O watchers, and will	577	Signals and child watchers are implemented as I/O watchers, and will
506	be handled here by queueing them when their watcher gets executed.	578	be handled here by queueing them when their watcher gets executed.
507	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	579	- If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
508	were used, return, otherwise continue with step *.	580	were used, or there are no active watchers, return, otherwise
		581	continue with step *.
509		582
510	Example: Queue some jobs and then loop until no events are outsanding	583	Example: Queue some jobs and then loop until no events are outstanding
511	anymore.	584	anymore.
512		585
513	... queue jobs here, make sure they register event watchers as long	586	... queue jobs here, make sure they register event watchers as long
514	... as they still have work to do (even an idle watcher will do..)	587	... as they still have work to do (even an idle watcher will do..)
515	ev_loop (my_loop, 0);	588	ev_loop (my_loop, 0);
…		…
519		592
520	Can be used to make a call to C<ev_loop> return early (but only after it	593	Can be used to make a call to C<ev_loop> return early (but only after it
521	has processed all outstanding events). The C<how> argument must be either	594	has processed all outstanding events). The C<how> argument must be either
522	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	595	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
523	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	596	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
		597
		598	This "unloop state" will be cleared when entering C<ev_loop> again.
524		599
525	=item ev_ref (loop)	600	=item ev_ref (loop)
526		601
527	=item ev_unref (loop)	602	=item ev_unref (loop)
528		603
…		…
533	returning, ev_unref() after starting, and ev_ref() before stopping it. For	608	returning, ev_unref() after starting, and ev_ref() before stopping it. For
534	example, libev itself uses this for its internal signal pipe: It is not	609	example, libev itself uses this for its internal signal pipe: It is not
535	visible to the libev user and should not keep C<ev_loop> from exiting if	610	visible to the libev user and should not keep C<ev_loop> from exiting if
536	no event watchers registered by it are active. It is also an excellent	611	no event watchers registered by it are active. It is also an excellent
537	way to do this for generic recurring timers or from within third-party	612	way to do this for generic recurring timers or from within third-party
538	libraries. Just remember to I<unref after start> and I<ref before stop>.	613	libraries. Just remember to I<unref after start> and I<ref before stop>
		614	(but only if the watcher wasn't active before, or was active before,
		615	respectively).
539		616
540	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	617	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
541	running when nothing else is active.	618	running when nothing else is active.
542		619
543	struct ev_signal exitsig;	620	struct ev_signal exitsig;
…		…
547		624
548	Example: For some weird reason, unregister the above signal handler again.	625	Example: For some weird reason, unregister the above signal handler again.
549		626
550	ev_ref (loop);	627	ev_ref (loop);
551	ev_signal_stop (loop, &exitsig);	628	ev_signal_stop (loop, &exitsig);
		629
		630	=item ev_set_io_collect_interval (loop, ev_tstamp interval)
		631
		632	=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
		633
		634	These advanced functions influence the time that libev will spend waiting
		635	for events. Both are by default C<0>, meaning that libev will try to
		636	invoke timer/periodic callbacks and I/O callbacks with minimum latency.
		637
		638	Setting these to a higher value (the C<interval> I<must> be >= C<0>)
		639	allows libev to delay invocation of I/O and timer/periodic callbacks to
		640	increase efficiency of loop iterations.
		641
		642	The background is that sometimes your program runs just fast enough to
		643	handle one (or very few) event(s) per loop iteration. While this makes
		644	the program responsive, it also wastes a lot of CPU time to poll for new
		645	events, especially with backends like C<select ()> which have a high
		646	overhead for the actual polling but can deliver many events at once.
		647
		648	By setting a higher I<io collect interval> you allow libev to spend more
		649	time collecting I/O events, so you can handle more events per iteration,
		650	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
		651	C<ev_timer>) will be not affected. Setting this to a non-null value will
		652	introduce an additional C<ev_sleep ()> call into most loop iterations.
		653
		654	Likewise, by setting a higher I<timeout collect interval> you allow libev
		655	to spend more time collecting timeouts, at the expense of increased
		656	latency (the watcher callback will be called later). C<ev_io> watchers
		657	will not be affected. Setting this to a non-null value will not introduce
		658	any overhead in libev.
		659
		660	Many (busy) programs can usually benefit by setting the io collect
		661	interval to a value near C<0.1> or so, which is often enough for
		662	interactive servers (of course not for games), likewise for timeouts. It
		663	usually doesn't make much sense to set it to a lower value than C<0.01>,
		664	as this approsaches the timing granularity of most systems.
552		665
553	=back	666	=back
554		667
555		668
556	=head1 ANATOMY OF A WATCHER	669	=head1 ANATOMY OF A WATCHER
…		…
882	In general you can register as many read and/or write event watchers per	995	In general you can register as many read and/or write event watchers per
883	fd as you want (as long as you don't confuse yourself). Setting all file	996	fd as you want (as long as you don't confuse yourself). Setting all file
884	descriptors to non-blocking mode is also usually a good idea (but not	997	descriptors to non-blocking mode is also usually a good idea (but not
885	required if you know what you are doing).	998	required if you know what you are doing).
886		999
887	You have to be careful with dup'ed file descriptors, though. Some backends
888	(the linux epoll backend is a notable example) cannot handle dup'ed file
889	descriptors correctly if you register interest in two or more fds pointing
890	to the same underlying file/socket/etc. description (that is, they share
891	the same underlying "file open").
892
893	If you must do this, then force the use of a known-to-be-good backend	1000	If you must do this, then force the use of a known-to-be-good backend
894	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	1001	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
895	C<EVBACKEND_POLL>).	1002	C<EVBACKEND_POLL>).
896		1003
897	Another thing you have to watch out for is that it is quite easy to	1004	Another thing you have to watch out for is that it is quite easy to
…		…
907	play around with an Xlib connection), then you have to seperately re-test	1014	play around with an Xlib connection), then you have to seperately re-test
908	whether a file descriptor is really ready with a known-to-be good interface	1015	whether a file descriptor is really ready with a known-to-be good interface
909	such as poll (fortunately in our Xlib example, Xlib already does this on	1016	such as poll (fortunately in our Xlib example, Xlib already does this on
910	its own, so its quite safe to use).	1017	its own, so its quite safe to use).
911		1018
		1019	=head3 The special problem of disappearing file descriptors
		1020
		1021	Some backends (e.g. kqueue, epoll) need to be told about closing a file
		1022	descriptor (either by calling C<close> explicitly or by any other means,
		1023	such as C<dup>). The reason is that you register interest in some file
		1024	descriptor, but when it goes away, the operating system will silently drop
		1025	this interest. If another file descriptor with the same number then is
		1026	registered with libev, there is no efficient way to see that this is, in
		1027	fact, a different file descriptor.
		1028
		1029	To avoid having to explicitly tell libev about such cases, libev follows
		1030	the following policy: Each time C<ev_io_set> is being called, libev
		1031	will assume that this is potentially a new file descriptor, otherwise
		1032	it is assumed that the file descriptor stays the same. That means that
		1033	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		1034	descriptor even if the file descriptor number itself did not change.
		1035
		1036	This is how one would do it normally anyway, the important point is that
		1037	the libev application should not optimise around libev but should leave
		1038	optimisations to libev.
		1039
		1040	=head3 The special problem of dup'ed file descriptors
		1041
		1042	Some backends (e.g. epoll), cannot register events for file descriptors,
		1043	but only events for the underlying file descriptions. That means when you
		1044	have C<dup ()>'ed file descriptors or weirder constellations, and register
		1045	events for them, only one file descriptor might actually receive events.
		1046
		1047	There is no workaround possible except not registering events
		1048	for potentially C<dup ()>'ed file descriptors, or to resort to
		1049	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
		1050
		1051	=head3 The special problem of fork
		1052
		1053	Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
		1054	useless behaviour. Libev fully supports fork, but needs to be told about
		1055	it in the child.
		1056
		1057	To support fork in your programs, you either have to call
		1058	C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
		1059	enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
		1060	C<EVBACKEND_POLL>.
		1061
		1062
		1063	=head3 Watcher-Specific Functions
		1064
912	=over 4	1065	=over 4
913		1066
914	=item ev_io_init (ev_io *, callback, int fd, int events)	1067	=item ev_io_init (ev_io *, callback, int fd, int events)
915		1068
916	=item ev_io_set (ev_io *, int fd, int events)	1069	=item ev_io_set (ev_io *, int fd, int events)
…		…
926	=item int events [read-only]	1079	=item int events [read-only]
927		1080
928	The events being watched.	1081	The events being watched.
929		1082
930	=back	1083	=back
		1084
		1085	=head3 Examples
931		1086
932	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1087	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
933	readable, but only once. Since it is likely line-buffered, you could	1088	readable, but only once. Since it is likely line-buffered, you could
934	attempt to read a whole line in the callback.	1089	attempt to read a whole line in the callback.
935		1090
…		…
968	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);	1123	ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
969		1124
970	The callback is guarenteed to be invoked only when its timeout has passed,	1125	The callback is guarenteed to be invoked only when its timeout has passed,
971	but if multiple timers become ready during the same loop iteration then	1126	but if multiple timers become ready during the same loop iteration then
972	order of execution is undefined.	1127	order of execution is undefined.
		1128
		1129	=head3 Watcher-Specific Functions and Data Members
973		1130
974	=over 4	1131	=over 4
975		1132
976	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1133	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
977		1134
…		…
1031	or C<ev_timer_again> is called and determines the next timeout (if any),	1188	or C<ev_timer_again> is called and determines the next timeout (if any),
1032	which is also when any modifications are taken into account.	1189	which is also when any modifications are taken into account.
1033		1190
1034	=back	1191	=back
1035		1192
		1193	=head3 Examples
		1194
1036	Example: Create a timer that fires after 60 seconds.	1195	Example: Create a timer that fires after 60 seconds.
1037		1196
1038	static void	1197	static void
1039	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1198	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
1040	{	1199	{
…		…
1073	but on wallclock time (absolute time). You can tell a periodic watcher	1232	but on wallclock time (absolute time). You can tell a periodic watcher
1074	to trigger "at" some specific point in time. For example, if you tell a	1233	to trigger "at" some specific point in time. For example, if you tell a
1075	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1234	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1076	+ 10.>) and then reset your system clock to the last year, then it will	1235	+ 10.>) and then reset your system clock to the last year, then it will
1077	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1236	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1078	roughly 10 seconds later and of course not if you reset your system time	1237	roughly 10 seconds later).
1079	again).
1080		1238
1081	They can also be used to implement vastly more complex timers, such as	1239	They can also be used to implement vastly more complex timers, such as
1082	triggering an event on eahc midnight, local time.	1240	triggering an event on each midnight, local time or other, complicated,
		1241	rules.
1083		1242
1084	As with timers, the callback is guarenteed to be invoked only when the	1243	As with timers, the callback is guarenteed to be invoked only when the
1085	time (C<at>) has been passed, but if multiple periodic timers become ready	1244	time (C<at>) has been passed, but if multiple periodic timers become ready
1086	during the same loop iteration then order of execution is undefined.	1245	during the same loop iteration then order of execution is undefined.
1087		1246
		1247	=head3 Watcher-Specific Functions and Data Members
		1248
1088	=over 4	1249	=over 4
1089		1250
1090	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1251	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1091		1252
1092	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1253	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
1094	Lots of arguments, lets sort it out... There are basically three modes of	1255	Lots of arguments, lets sort it out... There are basically three modes of
1095	operation, and we will explain them from simplest to complex:	1256	operation, and we will explain them from simplest to complex:
1096		1257
1097	=over 4	1258	=over 4
1098		1259
1099	=item * absolute timer (interval = reschedule_cb = 0)	1260	=item * absolute timer (at = time, interval = reschedule_cb = 0)
1100		1261
1101	In this configuration the watcher triggers an event at the wallclock time	1262	In this configuration the watcher triggers an event at the wallclock time
1102	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1263	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1103	that is, if it is to be run at January 1st 2011 then it will run when the	1264	that is, if it is to be run at January 1st 2011 then it will run when the
1104	system time reaches or surpasses this time.	1265	system time reaches or surpasses this time.
1105		1266
1106	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1267	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1107		1268
1108	In this mode the watcher will always be scheduled to time out at the next	1269	In this mode the watcher will always be scheduled to time out at the next
1109	C<at + N * interval> time (for some integer N) and then repeat, regardless	1270	C<at + N * interval> time (for some integer N, which can also be negative)
1110	of any time jumps.	1271	and then repeat, regardless of any time jumps.
1111		1272
1112	This can be used to create timers that do not drift with respect to system	1273	This can be used to create timers that do not drift with respect to system
1113	time:	1274	time:
1114		1275
1115	ev_periodic_set (&periodic, 0., 3600., 0);	1276	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
1121		1282
1122	Another way to think about it (for the mathematically inclined) is that	1283	Another way to think about it (for the mathematically inclined) is that
1123	C<ev_periodic> will try to run the callback in this mode at the next possible	1284	C<ev_periodic> will try to run the callback in this mode at the next possible
1124	time where C<time = at (mod interval)>, regardless of any time jumps.	1285	time where C<time = at (mod interval)>, regardless of any time jumps.
1125		1286
		1287	For numerical stability it is preferable that the C<at> value is near
		1288	C<ev_now ()> (the current time), but there is no range requirement for
		1289	this value.
		1290
1126	=item * manual reschedule mode (reschedule_cb = callback)	1291	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1127		1292
1128	In this mode the values for C<interval> and C<at> are both being	1293	In this mode the values for C<interval> and C<at> are both being
1129	ignored. Instead, each time the periodic watcher gets scheduled, the	1294	ignored. Instead, each time the periodic watcher gets scheduled, the
1130	reschedule callback will be called with the watcher as first, and the	1295	reschedule callback will be called with the watcher as first, and the
1131	current time as second argument.	1296	current time as second argument.
1132		1297
1133	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1298	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1134	ever, or make any event loop modifications>. If you need to stop it,	1299	ever, or make any event loop modifications>. If you need to stop it,
1135	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1300	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1136	starting a prepare watcher).	1301	starting an C<ev_prepare> watcher, which is legal).
1137		1302
1138	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1303	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
1139	ev_tstamp now)>, e.g.:	1304	ev_tstamp now)>, e.g.:
1140		1305
1141	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1306	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
1164	Simply stops and restarts the periodic watcher again. This is only useful	1329	Simply stops and restarts the periodic watcher again. This is only useful
1165	when you changed some parameters or the reschedule callback would return	1330	when you changed some parameters or the reschedule callback would return
1166	a different time than the last time it was called (e.g. in a crond like	1331	a different time than the last time it was called (e.g. in a crond like
1167	program when the crontabs have changed).	1332	program when the crontabs have changed).
1168		1333
		1334	=item ev_tstamp offset [read-write]
		1335
		1336	When repeating, this contains the offset value, otherwise this is the
		1337	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1338
		1339	Can be modified any time, but changes only take effect when the periodic
		1340	timer fires or C<ev_periodic_again> is being called.
		1341
1169	=item ev_tstamp interval [read-write]	1342	=item ev_tstamp interval [read-write]
1170		1343
1171	The current interval value. Can be modified any time, but changes only	1344	The current interval value. Can be modified any time, but changes only
1172	take effect when the periodic timer fires or C<ev_periodic_again> is being	1345	take effect when the periodic timer fires or C<ev_periodic_again> is being
1173	called.	1346	called.
…		…
1176		1349
1177	The current reschedule callback, or C<0>, if this functionality is	1350	The current reschedule callback, or C<0>, if this functionality is
1178	switched off. Can be changed any time, but changes only take effect when	1351	switched off. Can be changed any time, but changes only take effect when
1179	the periodic timer fires or C<ev_periodic_again> is being called.	1352	the periodic timer fires or C<ev_periodic_again> is being called.
1180		1353
		1354	=item ev_tstamp at [read-only]
		1355
		1356	When active, contains the absolute time that the watcher is supposed to
		1357	trigger next.
		1358
1181	=back	1359	=back
		1360
		1361	=head3 Examples
1182		1362
1183	Example: Call a callback every hour, or, more precisely, whenever the	1363	Example: Call a callback every hour, or, more precisely, whenever the
1184	system clock is divisible by 3600. The callback invocation times have	1364	system clock is divisible by 3600. The callback invocation times have
1185	potentially a lot of jittering, but good long-term stability.	1365	potentially a lot of jittering, but good long-term stability.
1186		1366
…		…
1226	with the kernel (thus it coexists with your own signal handlers as long	1406	with the kernel (thus it coexists with your own signal handlers as long
1227	as you don't register any with libev). Similarly, when the last signal	1407	as you don't register any with libev). Similarly, when the last signal
1228	watcher for a signal is stopped libev will reset the signal handler to	1408	watcher for a signal is stopped libev will reset the signal handler to
1229	SIG_DFL (regardless of what it was set to before).	1409	SIG_DFL (regardless of what it was set to before).
1230		1410
		1411	=head3 Watcher-Specific Functions and Data Members
		1412
1231	=over 4	1413	=over 4
1232		1414
1233	=item ev_signal_init (ev_signal *, callback, int signum)	1415	=item ev_signal_init (ev_signal *, callback, int signum)
1234		1416
1235	=item ev_signal_set (ev_signal *, int signum)	1417	=item ev_signal_set (ev_signal *, int signum)
…		…
1246		1428
1247	=head2 C<ev_child> - watch out for process status changes	1429	=head2 C<ev_child> - watch out for process status changes
1248		1430
1249	Child watchers trigger when your process receives a SIGCHLD in response to	1431	Child watchers trigger when your process receives a SIGCHLD in response to
1250	some child status changes (most typically when a child of yours dies).	1432	some child status changes (most typically when a child of yours dies).
		1433
		1434	=head3 Watcher-Specific Functions and Data Members
1251		1435
1252	=over 4	1436	=over 4
1253		1437
1254	=item ev_child_init (ev_child *, callback, int pid)	1438	=item ev_child_init (ev_child *, callback, int pid)
1255		1439
…		…
1274		1458
1275	The process exit/trace status caused by C<rpid> (see your systems	1459	The process exit/trace status caused by C<rpid> (see your systems
1276	C<waitpid> and C<sys/wait.h> documentation for details).	1460	C<waitpid> and C<sys/wait.h> documentation for details).
1277		1461
1278	=back	1462	=back
		1463
		1464	=head3 Examples
1279		1465
1280	Example: Try to exit cleanly on SIGINT and SIGTERM.	1466	Example: Try to exit cleanly on SIGINT and SIGTERM.
1281		1467
1282	static void	1468	static void
1283	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1469	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
…		…
1324	semantics of C<ev_stat> watchers, which means that libev sometimes needs	1510	semantics of C<ev_stat> watchers, which means that libev sometimes needs
1325	to fall back to regular polling again even with inotify, but changes are	1511	to fall back to regular polling again even with inotify, but changes are
1326	usually detected immediately, and if the file exists there will be no	1512	usually detected immediately, and if the file exists there will be no
1327	polling.	1513	polling.
1328		1514
		1515	=head3 Inotify
		1516
		1517	When C<inotify (7)> support has been compiled into libev (generally only
		1518	available on Linux) and present at runtime, it will be used to speed up
		1519	change detection where possible. The inotify descriptor will be created lazily
		1520	when the first C<ev_stat> watcher is being started.
		1521
		1522	Inotify presense does not change the semantics of C<ev_stat> watchers
		1523	except that changes might be detected earlier, and in some cases, to avoid
		1524	making regular C<stat> calls. Even in the presense of inotify support
		1525	there are many cases where libev has to resort to regular C<stat> polling.
		1526
		1527	(There is no support for kqueue, as apparently it cannot be used to
		1528	implement this functionality, due to the requirement of having a file
		1529	descriptor open on the object at all times).
		1530
		1531	=head3 The special problem of stat time resolution
		1532
		1533	The C<stat ()> syscall only supports full-second resolution portably, and
		1534	even on systems where the resolution is higher, many filesystems still
		1535	only support whole seconds.
		1536
		1537	That means that, if the time is the only thing that changes, you might
		1538	miss updates: on the first update, C<ev_stat> detects a change and calls
		1539	your callback, which does something. When there is another update within
		1540	the same second, C<ev_stat> will be unable to detect it.
		1541
		1542	The solution to this is to delay acting on a change for a second (or till
		1543	the next second boundary), using a roughly one-second delay C<ev_timer>
		1544	(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
		1545	is added to work around small timing inconsistencies of some operating
		1546	systems.
		1547
		1548	=head3 Watcher-Specific Functions and Data Members
		1549
1329	=over 4	1550	=over 4
1330		1551
1331	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)	1552	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
1332		1553
1333	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)	1554	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
…		…
1368	=item const char *path [read-only]	1589	=item const char *path [read-only]
1369		1590
1370	The filesystem path that is being watched.	1591	The filesystem path that is being watched.
1371		1592
1372	=back	1593	=back
		1594
		1595	=head3 Examples
1373		1596
1374	Example: Watch C</etc/passwd> for attribute changes.	1597	Example: Watch C</etc/passwd> for attribute changes.
1375		1598
1376	static void	1599	static void
1377	passwd_cb (struct ev_loop loop, ev_stat w, int revents)	1600	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
…		…
1390	}	1613	}
1391		1614
1392	...	1615	...
1393	ev_stat passwd;	1616	ev_stat passwd;
1394		1617
1395	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");	1618	ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1396	ev_stat_start (loop, &passwd);	1619	ev_stat_start (loop, &passwd);
		1620
		1621	Example: Like above, but additionally use a one-second delay so we do not
		1622	miss updates (however, frequent updates will delay processing, too, so
		1623	one might do the work both on C<ev_stat> callback invocation I<and> on
		1624	C<ev_timer> callback invocation).
		1625
		1626	static ev_stat passwd;
		1627	static ev_timer timer;
		1628
		1629	static void
		1630	timer_cb (EV_P_ ev_timer *w, int revents)
		1631	{
		1632	ev_timer_stop (EV_A_ w);
		1633
		1634	/* now it's one second after the most recent passwd change */
		1635	}
		1636
		1637	static void
		1638	stat_cb (EV_P_ ev_stat *w, int revents)
		1639	{
		1640	/* reset the one-second timer */
		1641	ev_timer_again (EV_A_ &timer);
		1642	}
		1643
		1644	...
		1645	ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
		1646	ev_stat_start (loop, &passwd);
		1647	ev_timer_init (&timer, timer_cb, 0., 1.01);
1397		1648
1398		1649
1399	=head2 C<ev_idle> - when you've got nothing better to do...	1650	=head2 C<ev_idle> - when you've got nothing better to do...
1400		1651
1401	Idle watchers trigger events when no other events of the same or higher	1652	Idle watchers trigger events when no other events of the same or higher
…		…
1415	Apart from keeping your process non-blocking (which is a useful	1666	Apart from keeping your process non-blocking (which is a useful
1416	effect on its own sometimes), idle watchers are a good place to do	1667	effect on its own sometimes), idle watchers are a good place to do
1417	"pseudo-background processing", or delay processing stuff to after the	1668	"pseudo-background processing", or delay processing stuff to after the
1418	event loop has handled all outstanding events.	1669	event loop has handled all outstanding events.
1419		1670
		1671	=head3 Watcher-Specific Functions and Data Members
		1672
1420	=over 4	1673	=over 4
1421		1674
1422	=item ev_idle_init (ev_signal *, callback)	1675	=item ev_idle_init (ev_signal *, callback)
1423		1676
1424	Initialises and configures the idle watcher - it has no parameters of any	1677	Initialises and configures the idle watcher - it has no parameters of any
1425	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1678	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1426	believe me.	1679	believe me.
1427		1680
1428	=back	1681	=back
		1682
		1683	=head3 Examples
1429		1684
1430	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	1685	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1431	callback, free it. Also, use no error checking, as usual.	1686	callback, free it. Also, use no error checking, as usual.
1432		1687
1433	static void	1688	static void
…		…
1481	with priority higher than or equal to the event loop and one coroutine	1736	with priority higher than or equal to the event loop and one coroutine
1482	of lower priority, but only once, using idle watchers to keep the event	1737	of lower priority, but only once, using idle watchers to keep the event
1483	loop from blocking if lower-priority coroutines are active, thus mapping	1738	loop from blocking if lower-priority coroutines are active, thus mapping
1484	low-priority coroutines to idle/background tasks).	1739	low-priority coroutines to idle/background tasks).
1485		1740
		1741	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1742	priority, to ensure that they are being run before any other watchers
		1743	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1744	too) should not activate ("feed") events into libev. While libev fully
		1745	supports this, they will be called before other C<ev_check> watchers
		1746	did their job. As C<ev_check> watchers are often used to embed other
		1747	(non-libev) event loops those other event loops might be in an unusable
		1748	state until their C<ev_check> watcher ran (always remind yourself to
		1749	coexist peacefully with others).
		1750
		1751	=head3 Watcher-Specific Functions and Data Members
		1752
1486	=over 4	1753	=over 4
1487		1754
1488	=item ev_prepare_init (ev_prepare *, callback)	1755	=item ev_prepare_init (ev_prepare *, callback)
1489		1756
1490	=item ev_check_init (ev_check *, callback)	1757	=item ev_check_init (ev_check *, callback)
…		…
1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1760	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1494	macros, but using them is utterly, utterly and completely pointless.	1761	macros, but using them is utterly, utterly and completely pointless.
1495		1762
1496	=back	1763	=back
1497		1764
1498	Example: To include a library such as adns, you would add IO watchers	1765	=head3 Examples
1499	and a timeout watcher in a prepare handler, as required by libadns, and	1766
		1767	There are a number of principal ways to embed other event loops or modules
		1768	into libev. Here are some ideas on how to include libadns into libev
		1769	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1770	use for an actually working example. Another Perl module named C<EV::Glib>
		1771	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1772	into the Glib event loop).
		1773
		1774	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1500	in a check watcher, destroy them and call into libadns. What follows is	1775	and in a check watcher, destroy them and call into libadns. What follows
1501	pseudo-code only of course:	1776	is pseudo-code only of course. This requires you to either use a low
		1777	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1778	the callbacks for the IO/timeout watchers might not have been called yet.
1502		1779
1503	static ev_io iow [nfd];	1780	static ev_io iow [nfd];
1504	static ev_timer tw;	1781	static ev_timer tw;
1505		1782
1506	static void	1783	static void
1507	io_cb (ev_loop loop, ev_io w, int revents)	1784	io_cb (ev_loop loop, ev_io w, int revents)
1508	{	1785	{
1509	// set the relevant poll flags
1510	// could also call adns_processreadable etc. here
1511	struct pollfd fd = (struct pollfd )w->data;
1512	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1513	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1514	}	1786	}
1515		1787
1516	// create io watchers for each fd and a timer before blocking	1788	// create io watchers for each fd and a timer before blocking
1517	static void	1789	static void
1518	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1790	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1524		1796
1525	/* the callback is illegal, but won't be called as we stop during check */	1797	/* the callback is illegal, but won't be called as we stop during check */
1526	ev_timer_init (&tw, 0, timeout * 1e-3);	1798	ev_timer_init (&tw, 0, timeout * 1e-3);
1527	ev_timer_start (loop, &tw);	1799	ev_timer_start (loop, &tw);
1528		1800
1529	// create on ev_io per pollfd	1801	// create one ev_io per pollfd
1530	for (int i = 0; i < nfd; ++i)	1802	for (int i = 0; i < nfd; ++i)
1531	{	1803	{
1532	ev_io_init (iow + i, io_cb, fds [i].fd,	1804	ev_io_init (iow + i, io_cb, fds [i].fd,
1533	((fds [i].events & POLLIN ? EV_READ : 0)	1805	((fds [i].events & POLLIN ? EV_READ : 0)
1534	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1806	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1535		1807
1536	fds [i].revents = 0;	1808	fds [i].revents = 0;
1537	iow [i].data = fds + i;
1538	ev_io_start (loop, iow + i);	1809	ev_io_start (loop, iow + i);
1539	}	1810	}
1540	}	1811	}
1541		1812
1542	// stop all watchers after blocking	1813	// stop all watchers after blocking
…		…
1544	adns_check_cb (ev_loop loop, ev_check w, int revents)	1815	adns_check_cb (ev_loop loop, ev_check w, int revents)
1545	{	1816	{
1546	ev_timer_stop (loop, &tw);	1817	ev_timer_stop (loop, &tw);
1547		1818
1548	for (int i = 0; i < nfd; ++i)	1819	for (int i = 0; i < nfd; ++i)
		1820	{
		1821	// set the relevant poll flags
		1822	// could also call adns_processreadable etc. here
		1823	struct pollfd *fd = fds + i;
		1824	int revents = ev_clear_pending (iow + i);
		1825	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1826	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1827
		1828	// now stop the watcher
1549	ev_io_stop (loop, iow + i);	1829	ev_io_stop (loop, iow + i);
		1830	}
1550		1831
1551	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1832	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1833	}
		1834
		1835	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1836	in the prepare watcher and would dispose of the check watcher.
		1837
		1838	Method 3: If the module to be embedded supports explicit event
		1839	notification (adns does), you can also make use of the actual watcher
		1840	callbacks, and only destroy/create the watchers in the prepare watcher.
		1841
		1842	static void
		1843	timer_cb (EV_P_ ev_timer *w, int revents)
		1844	{
		1845	adns_state ads = (adns_state)w->data;
		1846	update_now (EV_A);
		1847
		1848	adns_processtimeouts (ads, &tv_now);
		1849	}
		1850
		1851	static void
		1852	io_cb (EV_P_ ev_io *w, int revents)
		1853	{
		1854	adns_state ads = (adns_state)w->data;
		1855	update_now (EV_A);
		1856
		1857	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1858	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1859	}
		1860
		1861	// do not ever call adns_afterpoll
		1862
		1863	Method 4: Do not use a prepare or check watcher because the module you
		1864	want to embed is too inflexible to support it. Instead, youc na override
		1865	their poll function. The drawback with this solution is that the main
		1866	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1867	this.
		1868
		1869	static gint
		1870	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1871	{
		1872	int got_events = 0;
		1873
		1874	for (n = 0; n < nfds; ++n)
		1875	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1876
		1877	if (timeout >= 0)
		1878	// create/start timer
		1879
		1880	// poll
		1881	ev_loop (EV_A_ 0);
		1882
		1883	// stop timer again
		1884	if (timeout >= 0)
		1885	ev_timer_stop (EV_A_ &to);
		1886
		1887	// stop io watchers again - their callbacks should have set
		1888	for (n = 0; n < nfds; ++n)
		1889	ev_io_stop (EV_A_ iow [n]);
		1890
		1891	return got_events;
1552	}	1892	}
1553		1893
1554		1894
1555	=head2 C<ev_embed> - when one backend isn't enough...	1895	=head2 C<ev_embed> - when one backend isn't enough...
1556		1896
…		…
1599	portable one.	1939	portable one.
1600		1940
1601	So when you want to use this feature you will always have to be prepared	1941	So when you want to use this feature you will always have to be prepared
1602	that you cannot get an embeddable loop. The recommended way to get around	1942	that you cannot get an embeddable loop. The recommended way to get around
1603	this is to have a separate variables for your embeddable loop, try to	1943	this is to have a separate variables for your embeddable loop, try to
1604	create it, and if that fails, use the normal loop for everything:	1944	create it, and if that fails, use the normal loop for everything.
		1945
		1946	=head3 Watcher-Specific Functions and Data Members
		1947
		1948	=over 4
		1949
		1950	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1951
		1952	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1953
		1954	Configures the watcher to embed the given loop, which must be
		1955	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1956	invoked automatically, otherwise it is the responsibility of the callback
		1957	to invoke it (it will continue to be called until the sweep has been done,
		1958	if you do not want thta, you need to temporarily stop the embed watcher).
		1959
		1960	=item ev_embed_sweep (loop, ev_embed *)
		1961
		1962	Make a single, non-blocking sweep over the embedded loop. This works
		1963	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1964	apropriate way for embedded loops.
		1965
		1966	=item struct ev_loop *other [read-only]
		1967
		1968	The embedded event loop.
		1969
		1970	=back
		1971
		1972	=head3 Examples
		1973
		1974	Example: Try to get an embeddable event loop and embed it into the default
		1975	event loop. If that is not possible, use the default loop. The default
		1976	loop is stored in C<loop_hi>, while the mebeddable loop is stored in
		1977	C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
		1978	used).
1605		1979
1606	struct ev_loop *loop_hi = ev_default_init (0);	1980	struct ev_loop *loop_hi = ev_default_init (0);
1607	struct ev_loop *loop_lo = 0;	1981	struct ev_loop *loop_lo = 0;
1608	struct ev_embed embed;	1982	struct ev_embed embed;
1609		1983
…		…
1620	ev_embed_start (loop_hi, &embed);	1994	ev_embed_start (loop_hi, &embed);
1621	}	1995	}
1622	else	1996	else
1623	loop_lo = loop_hi;	1997	loop_lo = loop_hi;
1624		1998
1625	=over 4	1999	Example: Check if kqueue is available but not recommended and create
		2000	a kqueue backend for use with sockets (which usually work with any
		2001	kqueue implementation). Store the kqueue/socket-only event loop in
		2002	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1626		2003
1627	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2004	struct ev_loop *loop = ev_default_init (0);
		2005	struct ev_loop *loop_socket = 0;
		2006	struct ev_embed embed;
		2007
		2008	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
		2009	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
		2010	{
		2011	ev_embed_init (&embed, 0, loop_socket);
		2012	ev_embed_start (loop, &embed);
		2013	}
1628		2014
1629	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	2015	if (!loop_socket)
		2016	loop_socket = loop;
1630		2017
1631	Configures the watcher to embed the given loop, which must be	2018	// now use loop_socket for all sockets, and loop for everything else
1632	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1633	invoked automatically, otherwise it is the responsibility of the callback
1634	to invoke it (it will continue to be called until the sweep has been done,
1635	if you do not want thta, you need to temporarily stop the embed watcher).
1636
1637	=item ev_embed_sweep (loop, ev_embed *)
1638
1639	Make a single, non-blocking sweep over the embedded loop. This works
1640	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1641	apropriate way for embedded loops.
1642
1643	=item struct ev_loop *loop [read-only]
1644
1645	The embedded event loop.
1646
1647	=back
1648		2019
1649		2020
1650	=head2 C<ev_fork> - the audacity to resume the event loop after a fork	2021	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1651		2022
1652	Fork watchers are called when a C<fork ()> was detected (usually because	2023	Fork watchers are called when a C<fork ()> was detected (usually because
…		…
1655	event loop blocks next and before C<ev_check> watchers are being called,	2026	event loop blocks next and before C<ev_check> watchers are being called,
1656	and only in the child after the fork. If whoever good citizen calling	2027	and only in the child after the fork. If whoever good citizen calling
1657	C<ev_default_fork> cheats and calls it in the wrong process, the fork	2028	C<ev_default_fork> cheats and calls it in the wrong process, the fork
1658	handlers will be invoked, too, of course.	2029	handlers will be invoked, too, of course.
1659		2030
		2031	=head3 Watcher-Specific Functions and Data Members
		2032
1660	=over 4	2033	=over 4
1661		2034
1662	=item ev_fork_init (ev_signal *, callback)	2035	=item ev_fork_init (ev_signal *, callback)
1663		2036
1664	Initialises and configures the fork watcher - it has no parameters of any	2037	Initialises and configures the fork watcher - it has no parameters of any
…		…
1844		2217
1845	myclass obj;	2218	myclass obj;
1846	ev::io iow;	2219	ev::io iow;
1847	iow.set <myclass, &myclass::io_cb> (&obj);	2220	iow.set <myclass, &myclass::io_cb> (&obj);
1848		2221
1849	=item w->set (void (function)(watcher &w, int), void data = 0)	2222	=item w->set<function> (void *data = 0)
1850		2223
1851	Also sets a callback, but uses a static method or plain function as	2224	Also sets a callback, but uses a static method or plain function as
1852	callback. The optional C<data> argument will be stored in the watcher's	2225	callback. The optional C<data> argument will be stored in the watcher's
1853	C<data> member and is free for you to use.	2226	C<data> member and is free for you to use.
1854		2227
		2228	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2229
1855	See the method-C<set> above for more details.	2230	See the method-C<set> above for more details.
		2231
		2232	Example:
		2233
		2234	static void io_cb (ev::io &w, int revents) { }
		2235	iow.set <io_cb> ();
1856		2236
1857	=item w->set (struct ev_loop *)	2237	=item w->set (struct ev_loop *)
1858		2238
1859	Associates a different C<struct ev_loop> with this watcher. You can only	2239	Associates a different C<struct ev_loop> with this watcher. You can only
1860	do this when the watcher is inactive (and not pending either).	2240	do this when the watcher is inactive (and not pending either).
…		…
1873		2253
1874	=item w->stop ()	2254	=item w->stop ()
1875		2255
1876	Stops the watcher if it is active. Again, no C<loop> argument.	2256	Stops the watcher if it is active. Again, no C<loop> argument.
1877		2257
1878	=item w->again () C<ev::timer>, C<ev::periodic> only	2258	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1879		2259
1880	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2260	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1881	C<ev_TYPE_again> function.	2261	C<ev_TYPE_again> function.
1882		2262
1883	=item w->sweep () C<ev::embed> only	2263	=item w->sweep () (C<ev::embed> only)
1884		2264
1885	Invokes C<ev_embed_sweep>.	2265	Invokes C<ev_embed_sweep>.
1886		2266
1887	=item w->update () C<ev::stat> only	2267	=item w->update () (C<ev::stat> only)
1888		2268
1889	Invokes C<ev_stat_stat>.	2269	Invokes C<ev_stat_stat>.
1890		2270
1891	=back	2271	=back
1892		2272
…		…
1912	}	2292	}
1913		2293
1914		2294
1915	=head1 MACRO MAGIC	2295	=head1 MACRO MAGIC
1916		2296
1917	Libev can be compiled with a variety of options, the most fundemantal is	2297	Libev can be compiled with a variety of options, the most fundamantal
1918	C<EV_MULTIPLICITY>. This option determines whether (most) functions and	2298	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1919	callbacks have an initial C<struct ev_loop *> argument.	2299	functions and callbacks have an initial C<struct ev_loop *> argument.
1920		2300
1921	To make it easier to write programs that cope with either variant, the	2301	To make it easier to write programs that cope with either variant, the
1922	following macros are defined:	2302	following macros are defined:
1923		2303
1924	=over 4	2304	=over 4
…		…
1978	Libev can (and often is) directly embedded into host	2358	Libev can (and often is) directly embedded into host
1979	applications. Examples of applications that embed it include the Deliantra	2359	applications. Examples of applications that embed it include the Deliantra
1980	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)	2360	Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
1981	and rxvt-unicode.	2361	and rxvt-unicode.
1982		2362
1983	The goal is to enable you to just copy the neecssary files into your	2363	The goal is to enable you to just copy the necessary files into your
1984	source directory without having to change even a single line in them, so	2364	source directory without having to change even a single line in them, so
1985	you can easily upgrade by simply copying (or having a checked-out copy of	2365	you can easily upgrade by simply copying (or having a checked-out copy of
1986	libev somewhere in your source tree).	2366	libev somewhere in your source tree).
1987		2367
1988	=head2 FILESETS	2368	=head2 FILESETS
…		…
2078		2458
2079	If defined to be C<1>, libev will try to detect the availability of the	2459	If defined to be C<1>, libev will try to detect the availability of the
2080	monotonic clock option at both compiletime and runtime. Otherwise no use	2460	monotonic clock option at both compiletime and runtime. Otherwise no use
2081	of the monotonic clock option will be attempted. If you enable this, you	2461	of the monotonic clock option will be attempted. If you enable this, you
2082	usually have to link against librt or something similar. Enabling it when	2462	usually have to link against librt or something similar. Enabling it when
2083	the functionality isn't available is safe, though, althoguh you have	2463	the functionality isn't available is safe, though, although you have
2084	to make sure you link against any libraries where the C<clock_gettime>	2464	to make sure you link against any libraries where the C<clock_gettime>
2085	function is hiding in (often F<-lrt>).	2465	function is hiding in (often F<-lrt>).
2086		2466
2087	=item EV_USE_REALTIME	2467	=item EV_USE_REALTIME
2088		2468
2089	If defined to be C<1>, libev will try to detect the availability of the	2469	If defined to be C<1>, libev will try to detect the availability of the
2090	realtime clock option at compiletime (and assume its availability at	2470	realtime clock option at compiletime (and assume its availability at
2091	runtime if successful). Otherwise no use of the realtime clock option will	2471	runtime if successful). Otherwise no use of the realtime clock option will
2092	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	2472	be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2093	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries	2473	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2094	in the description of C<EV_USE_MONOTONIC>, though.	2474	note about libraries in the description of C<EV_USE_MONOTONIC>, though.
		2475
		2476	=item EV_USE_NANOSLEEP
		2477
		2478	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
		2479	and will use it for delays. Otherwise it will use C<select ()>.
2095		2480
2096	=item EV_USE_SELECT	2481	=item EV_USE_SELECT
2097		2482
2098	If undefined or defined to be C<1>, libev will compile in support for the	2483	If undefined or defined to be C<1>, libev will compile in support for the
2099	C<select>(2) backend. No attempt at autodetection will be done: if no	2484	C<select>(2) backend. No attempt at autodetection will be done: if no
…		…
2117	wants osf handles on win32 (this is the case when the select to	2502	wants osf handles on win32 (this is the case when the select to
2118	be used is the winsock select). This means that it will call	2503	be used is the winsock select). This means that it will call
2119	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	2504	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2120	it is assumed that all these functions actually work on fds, even	2505	it is assumed that all these functions actually work on fds, even
2121	on win32. Should not be defined on non-win32 platforms.	2506	on win32. Should not be defined on non-win32 platforms.
		2507
		2508	=item EV_FD_TO_WIN32_HANDLE
		2509
		2510	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
		2511	file descriptors to socket handles. When not defining this symbol (the
		2512	default), then libev will call C<_get_osfhandle>, which is usually
		2513	correct. In some cases, programs use their own file descriptor management,
		2514	in which case they can provide this function to map fds to socket handles.
2122		2515
2123	=item EV_USE_POLL	2516	=item EV_USE_POLL
2124		2517
2125	If defined to be C<1>, libev will compile in support for the C<poll>(2)	2518	If defined to be C<1>, libev will compile in support for the C<poll>(2)
2126	backend. Otherwise it will be enabled on non-win32 platforms. It	2519	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
2163	be detected at runtime.	2556	be detected at runtime.
2164		2557
2165	=item EV_H	2558	=item EV_H
2166		2559
2167	The name of the F<ev.h> header file used to include it. The default if	2560	The name of the F<ev.h> header file used to include it. The default if
2168	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2561	undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2169	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2562	virtually rename the F<ev.h> header file in case of conflicts.
2170		2563
2171	=item EV_CONFIG_H	2564	=item EV_CONFIG_H
2172		2565
2173	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override	2566	If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2174	F<ev.c>'s idea of where to find the F<config.h> file, similarly to	2567	F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2175	C<EV_H>, above.	2568	C<EV_H>, above.
2176		2569
2177	=item EV_EVENT_H	2570	=item EV_EVENT_H
2178		2571
2179	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea	2572	Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2180	of how the F<event.h> header can be found.	2573	of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2181		2574
2182	=item EV_PROTOTYPES	2575	=item EV_PROTOTYPES
2183		2576
2184	If defined to be C<0>, then F<ev.h> will not define any function	2577	If defined to be C<0>, then F<ev.h> will not define any function
2185	prototypes, but still define all the structs and other symbols. This is	2578	prototypes, but still define all the structs and other symbols. This is
…		…
2251	than enough. If you need to manage thousands of children you might want to	2644	than enough. If you need to manage thousands of children you might want to
2252	increase this value (I<must> be a power of two).	2645	increase this value (I<must> be a power of two).
2253		2646
2254	=item EV_INOTIFY_HASHSIZE	2647	=item EV_INOTIFY_HASHSIZE
2255		2648
2256	C<ev_staz> watchers use a small hash table to distribute workload by	2649	C<ev_stat> watchers use a small hash table to distribute workload by
2257	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),	2650	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2258	usually more than enough. If you need to manage thousands of C<ev_stat>	2651	usually more than enough. If you need to manage thousands of C<ev_stat>
2259	watchers you might want to increase this value (I<must> be a power of	2652	watchers you might want to increase this value (I<must> be a power of
2260	two).	2653	two).
2261		2654
…		…
2278		2671
2279	=item ev_set_cb (ev, cb)	2672	=item ev_set_cb (ev, cb)
2280		2673
2281	Can be used to change the callback member declaration in each watcher,	2674	Can be used to change the callback member declaration in each watcher,
2282	and the way callbacks are invoked and set. Must expand to a struct member	2675	and the way callbacks are invoked and set. Must expand to a struct member
2283	definition and a statement, respectively. See the F<ev.v> header file for	2676	definition and a statement, respectively. See the F<ev.h> header file for
2284	their default definitions. One possible use for overriding these is to	2677	their default definitions. One possible use for overriding these is to
2285	avoid the C<struct ev_loop *> as first argument in all cases, or to use	2678	avoid the C<struct ev_loop *> as first argument in all cases, or to use
2286	method calls instead of plain function calls in C++.	2679	method calls instead of plain function calls in C++.
		2680
		2681	=head2 EXPORTED API SYMBOLS
		2682
		2683	If you need to re-export the API (e.g. via a dll) and you need a list of
		2684	exported symbols, you can use the provided F<Symbol.*> files which list
		2685	all public symbols, one per line:
		2686
		2687	Symbols.ev for libev proper
		2688	Symbols.event for the libevent emulation
		2689
		2690	This can also be used to rename all public symbols to avoid clashes with
		2691	multiple versions of libev linked together (which is obviously bad in
		2692	itself, but sometimes it is inconvinient to avoid this).
		2693
		2694	A sed command like this will create wrapper C<#define>'s that you need to
		2695	include before including F<ev.h>:
		2696
		2697	<Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
		2698
		2699	This would create a file F<wrap.h> which essentially looks like this:
		2700
		2701	#define ev_backend myprefix_ev_backend
		2702	#define ev_check_start myprefix_ev_check_start
		2703	#define ev_check_stop myprefix_ev_check_stop
		2704	...
2287		2705
2288	=head2 EXAMPLES	2706	=head2 EXAMPLES
2289		2707
2290	For a real-world example of a program the includes libev	2708	For a real-world example of a program the includes libev
2291	verbatim, you can have a look at the EV perl module	2709	verbatim, you can have a look at the EV perl module
…		…
2332		2750
2333	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2751	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2334		2752
2335	This means that, when you have a watcher that triggers in one hour and	2753	This means that, when you have a watcher that triggers in one hour and
2336	there are 100 watchers that would trigger before that then inserting will	2754	there are 100 watchers that would trigger before that then inserting will
2337	have to skip those 100 watchers.	2755	have to skip roughly seven (C<ld 100>) of these watchers.
2338		2756
2339	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2757	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2340		2758
2341	That means that for changing a timer costs less than removing/adding them	2759	That means that changing a timer costs less than removing/adding them
2342	as only the relative motion in the event queue has to be paid for.	2760	as only the relative motion in the event queue has to be paid for.
2343		2761
2344	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2762	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2345		2763
2346	These just add the watcher into an array or at the head of a list.	2764	These just add the watcher into an array or at the head of a list.
		2765
2347	=item Stopping check/prepare/idle watchers: O(1)	2766	=item Stopping check/prepare/idle watchers: O(1)
2348		2767
2349	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2768	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2350		2769
2351	These watchers are stored in lists then need to be walked to find the	2770	These watchers are stored in lists then need to be walked to find the
2352	correct watcher to remove. The lists are usually short (you don't usually	2771	correct watcher to remove. The lists are usually short (you don't usually
2353	have many watchers waiting for the same fd or signal).	2772	have many watchers waiting for the same fd or signal).
2354		2773
2355	=item Finding the next timer per loop iteration: O(1)	2774	=item Finding the next timer in each loop iteration: O(1)
		2775
		2776	By virtue of using a binary heap, the next timer is always found at the
		2777	beginning of the storage array.
2356		2778
2357	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2779	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2358		2780
2359	A change means an I/O watcher gets started or stopped, which requires	2781	A change means an I/O watcher gets started or stopped, which requires
2360	libev to recalculate its status (and possibly tell the kernel).	2782	libev to recalculate its status (and possibly tell the kernel, depending
		2783	on backend and wether C<ev_io_set> was used).
2361		2784
2362	=item Activating one watcher: O(1)	2785	=item Activating one watcher (putting it into the pending state): O(1)
2363		2786
2364	=item Priority handling: O(number_of_priorities)	2787	=item Priority handling: O(number_of_priorities)
2365		2788
2366	Priorities are implemented by allocating some space for each	2789	Priorities are implemented by allocating some space for each
2367	priority. When doing priority-based operations, libev usually has to	2790	priority. When doing priority-based operations, libev usually has to
2368	linearly search all the priorities.	2791	linearly search all the priorities, but starting/stopping and activating
		2792	watchers becomes O(1) w.r.t. prioritiy handling.
2369		2793
2370	=back	2794	=back
2371		2795
2372		2796
		2797	=head1 Win32 platform limitations and workarounds
		2798
		2799	Win32 doesn't support any of the standards (e.g. POSIX) that libev
		2800	requires, and its I/O model is fundamentally incompatible with the POSIX
		2801	model. Libev still offers limited functionality on this platform in
		2802	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
		2803	descriptors. This only applies when using Win32 natively, not when using
		2804	e.g. cygwin.
		2805
		2806	There is no supported compilation method available on windows except
		2807	embedding it into other applications.
		2808
		2809	Due to the many, low, and arbitrary limits on the win32 platform and the
		2810	abysmal performance of winsockets, using a large number of sockets is not
		2811	recommended (and not reasonable). If your program needs to use more than
		2812	a hundred or so sockets, then likely it needs to use a totally different
		2813	implementation for windows, as libev offers the POSIX model, which cannot
		2814	be implemented efficiently on windows (microsoft monopoly games).
		2815
		2816	=over 4
		2817
		2818	=item The winsocket select function
		2819
		2820	The winsocket C<select> function doesn't follow POSIX in that it requires
		2821	socket I<handles> and not socket I<file descriptors>. This makes select
		2822	very inefficient, and also requires a mapping from file descriptors
		2823	to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
		2824	C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
		2825	symbols for more info.
		2826
		2827	The configuration for a "naked" win32 using the microsoft runtime
		2828	libraries and raw winsocket select is:
		2829
		2830	#define EV_USE_SELECT 1
		2831	#define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
		2832
		2833	Note that winsockets handling of fd sets is O(n), so you can easily get a
		2834	complexity in the O(n²) range when using win32.
		2835
		2836	=item Limited number of file descriptors
		2837
		2838	Windows has numerous arbitrary (and low) limits on things. Early versions
		2839	of winsocket's select only supported waiting for a max. of C<64> handles
		2840	(probably owning to the fact that all windows kernels can only wait for
		2841	C<64> things at the same time internally; microsoft recommends spawning a
		2842	chain of threads and wait for 63 handles and the previous thread in each).
		2843
		2844	Newer versions support more handles, but you need to define C<FD_SETSIZE>
		2845	to some high number (e.g. C<2048>) before compiling the winsocket select
		2846	call (which might be in libev or elsewhere, for example, perl does its own
		2847	select emulation on windows).
		2848
		2849	Another limit is the number of file descriptors in the microsoft runtime
		2850	libraries, which by default is C<64> (there must be a hidden I<64> fetish
		2851	or something like this inside microsoft). You can increase this by calling
		2852	C<_setmaxstdio>, which can increase this limit to C<2048> (another
		2853	arbitrary limit), but is broken in many versions of the microsoft runtime
		2854	libraries.
		2855
		2856	This might get you to about C<512> or C<2048> sockets (depending on
		2857	windows version and/or the phase of the moon). To get more, you need to
		2858	wrap all I/O functions and provide your own fd management, but the cost of
		2859	calling select (O(n²)) will likely make this unworkable.
		2860
		2861	=back
		2862
		2863
2373	=head1 AUTHOR	2864	=head1 AUTHOR
2374		2865
2375	Marc Lehmann <libev@schmorp.de>.	2866	Marc Lehmann <libev@schmorp.de>.
2376		2867

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Comparing libev/ev.pod (file contents): Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs. Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.74 by root, Sat Dec 8 14:12:08 2007 UTC vs.
Revision 1.117 by root, Wed Jan 9 04:15:39 2008 UTC