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

Comparing libev/ev.pod (file contents):
Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

…		…
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
8		8
		9	=head1 EXAMPLE PROGRAM
		10
		11	#include <ev.h>
		12
		13	ev_io stdin_watcher;
		14	ev_timer timeout_watcher;
		15
		16	/* called when data readable on stdin */
		17	static void
		18	stdin_cb (EV_P_ struct ev_io *w, int revents)
		19	{
		20	/* puts ("stdin ready"); */
		21	ev_io_stop (EV_A_ w); /* just a syntax example */
		22	ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
		23	}
		24
		25	static void
		26	timeout_cb (EV_P_ struct ev_timer *w, int revents)
		27	{
		28	/* puts ("timeout"); */
		29	ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
		30	}
		31
		32	int
		33	main (void)
		34	{
		35	struct ev_loop *loop = ev_default_loop (0);
		36
		37	/* initialise an io watcher, then start it */
		38	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
		39	ev_io_start (loop, &stdin_watcher);
		40
		41	/* simple non-repeating 5.5 second timeout */
		42	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		43	ev_timer_start (loop, &timeout_watcher);
		44
		45	/* loop till timeout or data ready */
		46	ev_loop (loop, 0);
		47
		48	return 0;
		49	}
		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		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>.
10		56
11	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
12	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
13	these event sources and provide your program with events.	59	these event sources and provide your program with events.
14		60
…		…
21	details of the event, and then hand it over to libev by I<starting> the	67	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	68	watcher.
23		69
24	=head1 FEATURES	70	=head1 FEATURES
25		71
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	72	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	73	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	74	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	75	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	76	with customised rescheduling (C<ev_periodic>), synchronous signals
		77	(C<ev_signal>), process status change events (C<ev_child>), and event
		78	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		79	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		80	file watchers (C<ev_stat>) and even limited support for fork events
		81	(C<ev_fork>).
		82
		83	It also is quite fast (see this
31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	84	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	85	for example).
33		86
34	=head1 CONVENTIONS	87	=head1 CONVENTIONS
35		88
36	Libev is very configurable. In this manual the default configuration	89	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	90	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	91	various configuration options please have a look at B<EMBED> section in
39	F<README.embed> in the libev distribution. If libev was configured without	92	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	93	loops, then all functions taking an initial argument of name C<loop>
41	argument of name C<loop> (which is always of type C<struct ev_loop *>)	94	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		95
44	=head1 TIME REPRESENTATION	96	=head1 TIME REPRESENTATION
45		97
46	Libev represents time as a single floating point number, representing the	98	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	99	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	100	the beginning of 1970, details are complicated, don't ask). This type is
49	called C<ev_tstamp>, which is what you should use too. It usually aliases	101	called C<ev_tstamp>, which is what you should use too. It usually aliases
50	to the C<double> type in C, and when you need to do any calculations on	102	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	103	it, you should treat it as such.
52		104
53
54	=head1 GLOBAL FUNCTIONS	105	=head1 GLOBAL FUNCTIONS
55		106
56	These functions can be called anytime, even before initialising the	107	These functions can be called anytime, even before initialising the
57	library in any way.	108	library in any way.
58		109
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	128	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	129	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	130	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	131	not a problem.
81		132
82	Example: make sure we haven't accidentally been linked against the wrong	133	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	134	version.
84		135
85	assert (("libev version mismatch",	136	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	137	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	138	&& ev_version_minor () >= EV_VERSION_MINOR));
88		139
…		…
118		169
119	See the description of C<ev_embed> watchers for more info.	170	See the description of C<ev_embed> watchers for more info.
120		171
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	172	=item ev_set_allocator (void (cb)(void *ptr, long size))
122		173
123	Sets the allocation function to use (the prototype is similar to the	174	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	175	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	176	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	177	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	178	potentially destructive action. The default is your system realloc
		179	function.
128		180
129	You could override this function in high-availability programs to, say,	181	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	182	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	183	or even to sleep a while and retry until some memory is available.
132		184
133	Example: replace the libev allocator with one that waits a bit and then	185	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	186	retries).
135		187
136	static void *	188	static void *
137	persistent_realloc (void *ptr, long size)	189	persistent_realloc (void *ptr, size_t size)
138	{	190	{
139	for (;;)	191	for (;;)
140	{	192	{
141	void *newptr = realloc (ptr, size);	193	void *newptr = realloc (ptr, size);
142		194
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	210	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	211	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	212	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	213	(such as abort).
162		214
163	Example: do the same thing as libev does internally:	215	Example: This is basically the same thing that libev does internally, too.
164		216
165	static void	217	static void
166	fatal_error (const char *msg)	218	fatal_error (const char *msg)
167	{	219	{
168	perror (msg);	220	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	270	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	271	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	272	useful to try out specific backends to test their performance, or to work
221	around bugs.	273	around bugs.
222		274
		275	=item C<EVFLAG_FORKCHECK>
		276
		277	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		278	a fork, you can also make libev check for a fork in each iteration by
		279	enabling this flag.
		280
		281	This works by calling C<getpid ()> on every iteration of the loop,
		282	and thus this might slow down your event loop if you do a lot of loop
		283	iterations and little real work, but is usually not noticeable (on my
		284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		285	without a syscall and thus I<very> fast, but my Linux system also has
		286	C<pthread_atfork> which is even faster).
		287
		288	The big advantage of this flag is that you can forget about fork (and
		289	forget about forgetting to tell libev about forking) when you use this
		290	flag.
		291
		292	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		293	environment variable.
		294
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	295	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		296
225	This is your standard select(2) backend. Not I<completely> standard, as	297	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	298	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	299	but if that fails, expect a fairly low limit on the number of fds when
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	386	Similar to C<ev_default_loop>, but always creates a new event loop that is
315	always distinct from the default loop. Unlike the default loop, it cannot	387	always distinct from the default loop. Unlike the default loop, it cannot
316	handle signal and child watchers, and attempts to do so will be greeted by	388	handle signal and child watchers, and attempts to do so will be greeted by
317	undefined behaviour (or a failed assertion if assertions are enabled).	389	undefined behaviour (or a failed assertion if assertions are enabled).
318		390
319	Example: try to create a event loop that uses epoll and nothing else.	391	Example: Try to create a event loop that uses epoll and nothing else.
320		392
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	393	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	394	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	395	fatal ("no epoll found here, maybe it hides under your chair");
324		396
…		…
362		434
363	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
364	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
365	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
366		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
		448
367	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
368		450
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	452	use.
371		453
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
406		488
407	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
408		490
		491	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	496	- Update the "event loop time".
414	- Calculate for how long to block.	497	- Calculate for how long to block.
415	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	506	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	507	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	508	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	509	were used, return, otherwise continue with step *.
427		510
428	Example: queue some jobs and then loop until no events are outsanding	511	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	512	anymore.
430		513
431	... queue jobs here, make sure they register event watchers as long	514	... queue jobs here, make sure they register event watchers as long
432	... as they still have work to do (even an idle watcher will do..)	515	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	516	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	536	visible to the libev user and should not keep C<ev_loop> from exiting if
454	no event watchers registered by it are active. It is also an excellent	537	no event watchers registered by it are active. It is also an excellent
455	way to do this for generic recurring timers or from within third-party	538	way to do this for generic recurring timers or from within third-party
456	libraries. Just remember to I<unref after start> and I<ref before stop>.	539	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		540
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	541	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	542	running when nothing else is active.
460		543
461	struct dv_signal exitsig;	544	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	545	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	546	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	547	evf_unref (loop);
465		548
466	Example: for some weird reason, unregister the above signal handler again.	549	Example: For some weird reason, unregister the above signal handler again.
467		550
468	ev_ref (myloop);	551	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	552	ev_signal_stop (loop, &exitsig);
470		553
471	=back	554	=back
472		555
473		556
474	=head1 ANATOMY OF A WATCHER	557	=head1 ANATOMY OF A WATCHER
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	627	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		628
546	=item C<EV_CHILD>	629	=item C<EV_CHILD>
547		630
548	The pid specified in the C<ev_child> watcher has received a status change.	631	The pid specified in the C<ev_child> watcher has received a status change.
		632
		633	=item C<EV_STAT>
		634
		635	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		636
550	=item C<EV_IDLE>	637	=item C<EV_IDLE>
551		638
552	The C<ev_idle> watcher has determined that you have nothing better to do.	639	The C<ev_idle> watcher has determined that you have nothing better to do.
553		640
…		…
561	received events. Callbacks of both watcher types can start and stop as	648	received events. Callbacks of both watcher types can start and stop as
562	many watchers as they want, and all of them will be taken into account	649	many watchers as they want, and all of them will be taken into account
563	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	650	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	651	C<ev_loop> from blocking).
565		652
		653	=item C<EV_EMBED>
		654
		655	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		656
		657	=item C<EV_FORK>
		658
		659	The event loop has been resumed in the child process after fork (see
		660	C<ev_fork>).
		661
566	=item C<EV_ERROR>	662	=item C<EV_ERROR>
567		663
568	An unspecified error has occured, the watcher has been stopped. This might	664	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	665	happen because the watcher could not be properly started because libev
570	ran out of memory, a file descriptor was found to be closed or any other	666	ran out of memory, a file descriptor was found to be closed or any other
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
642		738
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	739	Returns a true value iff the watcher is pending, (i.e. it has outstanding
644	events but its callback has not yet been invoked). As long as a watcher	740	events but its callback has not yet been invoked). As long as a watcher
645	is pending (but not active) you must not call an init function on it (but	741	is pending (but not active) you must not call an init function on it (but
646	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	742	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	743	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		744	it).
648		745
649	=item callback = ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
650		747
651	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
652		749
653	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
654		751
655	Change the callback. You can change the callback at virtually any time	752	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	753	(modulo threads).
		754
		755	=item ev_set_priority (ev_TYPE *watcher, priority)
		756
		757	=item int ev_priority (ev_TYPE *watcher)
		758
		759	Set and query the priority of the watcher. The priority is a small
		760	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		761	(default: C<-2>). Pending watchers with higher priority will be invoked
		762	before watchers with lower priority, but priority will not keep watchers
		763	from being executed (except for C<ev_idle> watchers).
		764
		765	This means that priorities are I<only> used for ordering callback
		766	invocation after new events have been received. This is useful, for
		767	example, to reduce latency after idling, or more often, to bind two
		768	watchers on the same event and make sure one is called first.
		769
		770	If you need to suppress invocation when higher priority events are pending
		771	you need to look at C<ev_idle> watchers, which provide this functionality.
		772
		773	You I<must not> change the priority of a watcher as long as it is active or
		774	pending.
		775
		776	The default priority used by watchers when no priority has been set is
		777	always C<0>, which is supposed to not be too high and not be too low :).
		778
		779	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		780	fine, as long as you do not mind that the priority value you query might
		781	or might not have been adjusted to be within valid range.
		782
		783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		784
		785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		786	C<loop> nor C<revents> need to be valid as long as the watcher callback
		787	can deal with that fact.
		788
		789	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		790
		791	If the watcher is pending, this function returns clears its pending status
		792	and returns its C<revents> bitset (as if its callback was invoked). If the
		793	watcher isn't pending it does nothing and returns C<0>.
657		794
658	=back	795	=back
659		796
660		797
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
682	{	819	{
683	struct my_io w = (struct my_io )w_;	820	struct my_io w = (struct my_io )w_;
684	...	821	...
685	}	822	}
686		823
687	More interesting and less C-conformant ways of catsing your callback type	824	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	825	instead have been omitted.
		826
		827	Another common scenario is having some data structure with multiple
		828	watchers:
		829
		830	struct my_biggy
		831	{
		832	int some_data;
		833	ev_timer t1;
		834	ev_timer t2;
		835	}
		836
		837	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		838	you need to use C<offsetof>:
		839
		840	#include <stddef.h>
		841
		842	static void
		843	t1_cb (EV_P_ struct ev_timer *w, int revents)
		844	{
		845	struct my_biggy big = (struct my_biggy *
		846	(((char *)w) - offsetof (struct my_biggy, t1));
		847	}
		848
		849	static void
		850	t2_cb (EV_P_ struct ev_timer *w, int revents)
		851	{
		852	struct my_biggy big = (struct my_biggy *
		853	(((char *)w) - offsetof (struct my_biggy, t2));
		854	}
689		855
690		856
691	=head1 WATCHER TYPES	857	=head1 WATCHER TYPES
692		858
693	This section describes each watcher in detail, but will not repeat	859	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	860	information given in the last section. Any initialisation/set macros,
		861	functions and members specific to the watcher type are explained.
		862
		863	Members are additionally marked with either I<[read-only]>, meaning that,
		864	while the watcher is active, you can look at the member and expect some
		865	sensible content, but you must not modify it (you can modify it while the
		866	watcher is stopped to your hearts content), or I<[read-write]>, which
		867	means you can expect it to have some sensible content while the watcher
		868	is active, but you can also modify it. Modifying it may not do something
		869	sensible or take immediate effect (or do anything at all), but libev will
		870	not crash or malfunction in any way.
695		871
696		872
697	=head2 C<ev_io> - is this file descriptor readable or writable?	873	=head2 C<ev_io> - is this file descriptor readable or writable?
698		874
699	I/O watchers check whether a file descriptor is readable or writable	875	I/O watchers check whether a file descriptor is readable or writable
…		…
728	it is best to always use non-blocking I/O: An extra C<read>(2) returning	904	it is best to always use non-blocking I/O: An extra C<read>(2) returning
729	C<EAGAIN> is far preferable to a program hanging until some data arrives.	905	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		906
731	If you cannot run the fd in non-blocking mode (for example you should not	907	If you cannot run the fd in non-blocking mode (for example you should not
732	play around with an Xlib connection), then you have to seperately re-test	908	play around with an Xlib connection), then you have to seperately re-test
733	wether a file descriptor is really ready with a known-to-be good interface	909	whether a file descriptor is really ready with a known-to-be good interface
734	such as poll (fortunately in our Xlib example, Xlib already does this on	910	such as poll (fortunately in our Xlib example, Xlib already does this on
735	its own, so its quite safe to use).	911	its own, so its quite safe to use).
736		912
737	=over 4	913	=over 4
738		914
…		…
742		918
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	919	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
744	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or	920	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
745	C<EV_READ \| EV_WRITE> to receive the given events.	921	C<EV_READ \| EV_WRITE> to receive the given events.
746		922
		923	=item int fd [read-only]
		924
		925	The file descriptor being watched.
		926
		927	=item int events [read-only]
		928
		929	The events being watched.
		930
747	=back	931	=back
748		932
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	933	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
750	readable, but only once. Since it is likely line-buffered, you could	934	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	935	attempt to read a whole line in the callback.
752		936
753	static void	937	static void
754	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	938	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
755	{	939	{
756	ev_io_stop (loop, w);	940	ev_io_stop (loop, w);
…		…
808	=item ev_timer_again (loop)	992	=item ev_timer_again (loop)
809		993
810	This will act as if the timer timed out and restart it again if it is	994	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	995	repeating. The exact semantics are:
812		996
		997	If the timer is pending, its pending status is cleared.
		998
813	If the timer is started but nonrepeating, stop it.	999	If the timer is started but nonrepeating, stop it (as if it timed out).
814		1000
815	If the timer is repeating, either start it if necessary (with the repeat	1001	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1002	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1003
818	This sounds a bit complicated, but here is a useful and typical	1004	This sounds a bit complicated, but here is a useful and typical
819	example: Imagine you have a tcp connection and you want a so-called idle	1005	example: Imagine you have a tcp connection and you want a so-called idle
820	timeout, that is, you want to be called when there have been, say, 60	1006	timeout, that is, you want to be called when there have been, say, 60
821	seconds of inactivity on the socket. The easiest way to do this is to	1007	seconds of inactivity on the socket. The easiest way to do this is to
822	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	1008	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
823	time you successfully read or write some data. If you go into an idle	1009	C<ev_timer_again> each time you successfully read or write some data. If
824	state where you do not expect data to travel on the socket, you can stop	1010	you go into an idle state where you do not expect data to travel on the
825	the timer, and again will automatically restart it if need be.	1011	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1012	automatically restart it if need be.
		1013
		1014	That means you can ignore the C<after> value and C<ev_timer_start>
		1015	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1016
		1017	ev_timer_init (timer, callback, 0., 5.);
		1018	ev_timer_again (loop, timer);
		1019	...
		1020	timer->again = 17.;
		1021	ev_timer_again (loop, timer);
		1022	...
		1023	timer->again = 10.;
		1024	ev_timer_again (loop, timer);
		1025
		1026	This is more slightly efficient then stopping/starting the timer each time
		1027	you want to modify its timeout value.
		1028
		1029	=item ev_tstamp repeat [read-write]
		1030
		1031	The current C<repeat> value. Will be used each time the watcher times out
		1032	or C<ev_timer_again> is called and determines the next timeout (if any),
		1033	which is also when any modifications are taken into account.
826		1034
827	=back	1035	=back
828		1036
829	Example: create a timer that fires after 60 seconds.	1037	Example: Create a timer that fires after 60 seconds.
830		1038
831	static void	1039	static void
832	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1040	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
833	{	1041	{
834	.. one minute over, w is actually stopped right here	1042	.. one minute over, w is actually stopped right here
…		…
836		1044
837	struct ev_timer mytimer;	1045	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1046	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1047	ev_timer_start (loop, &mytimer);
840		1048
841	Example: create a timeout timer that times out after 10 seconds of	1049	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1050	inactivity.
843		1051
844	static void	1052	static void
845	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1053	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
846	{	1054	{
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1165	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1166	when you changed some parameters or the reschedule callback would return
959	a different time than the last time it was called (e.g. in a crond like	1167	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1168	program when the crontabs have changed).
961		1169
		1170	=item ev_tstamp interval [read-write]
		1171
		1172	The current interval value. Can be modified any time, but changes only
		1173	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1174	called.
		1175
		1176	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1177
		1178	The current reschedule callback, or C<0>, if this functionality is
		1179	switched off. Can be changed any time, but changes only take effect when
		1180	the periodic timer fires or C<ev_periodic_again> is being called.
		1181
962	=back	1182	=back
963		1183
964	Example: call a callback every hour, or, more precisely, whenever the	1184	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1185	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1186	potentially a lot of jittering, but good long-term stability.
967		1187
968	static void	1188	static void
969	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1189	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
973		1193
974	struct ev_periodic hourly_tick;	1194	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1195	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1196	ev_periodic_start (loop, &hourly_tick);
977		1197
978	Example: the same as above, but use a reschedule callback to do it:	1198	Example: The same as above, but use a reschedule callback to do it:
979		1199
980	#include <math.h>	1200	#include <math.h>
981		1201
982	static ev_tstamp	1202	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1203	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
985	return fmod (now, 3600.) + 3600.;	1205	return fmod (now, 3600.) + 3600.;
986	}	1206	}
987		1207
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1208	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1209
990	Example: call a callback every hour, starting now:	1210	Example: Call a callback every hour, starting now:
991		1211
992	struct ev_periodic hourly_tick;	1212	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1213	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1214	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1215	ev_periodic_start (loop, &hourly_tick);
…		…
1016	=item ev_signal_set (ev_signal *, int signum)	1236	=item ev_signal_set (ev_signal *, int signum)
1017		1237
1018	Configures the watcher to trigger on the given signal number (usually one	1238	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1239	of the C<SIGxxx> constants).
1020		1240
		1241	=item int signum [read-only]
		1242
		1243	The signal the watcher watches out for.
		1244
1021	=back	1245	=back
1022		1246
1023		1247
1024	=head2 C<ev_child> - watch out for process status changes	1248	=head2 C<ev_child> - watch out for process status changes
1025		1249
…		…
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1261	at the C<rstatus> member of the C<ev_child> watcher structure to see
1038	the status word (use the macros from C<sys/wait.h> and see your systems	1262	the status word (use the macros from C<sys/wait.h> and see your systems
1039	C<waitpid> documentation). The C<rpid> member contains the pid of the	1263	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1264	process causing the status change.
1041		1265
		1266	=item int pid [read-only]
		1267
		1268	The process id this watcher watches out for, or C<0>, meaning any process id.
		1269
		1270	=item int rpid [read-write]
		1271
		1272	The process id that detected a status change.
		1273
		1274	=item int rstatus [read-write]
		1275
		1276	The process exit/trace status caused by C<rpid> (see your systems
		1277	C<waitpid> and C<sys/wait.h> documentation for details).
		1278
1042	=back	1279	=back
1043		1280
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1281	Example: Try to exit cleanly on SIGINT and SIGTERM.
1045		1282
1046	static void	1283	static void
1047	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1284	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1048	{	1285	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1286	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1052	struct ev_signal signal_watcher;	1289	struct ev_signal signal_watcher;
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1290	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1054	ev_signal_start (loop, &sigint_cb);	1291	ev_signal_start (loop, &sigint_cb);
1055		1292
1056		1293
		1294	=head2 C<ev_stat> - did the file attributes just change?
		1295
		1296	This watches a filesystem path for attribute changes. That is, it calls
		1297	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1298	compared to the last time, invoking the callback if it did.
		1299
		1300	The path does not need to exist: changing from "path exists" to "path does
		1301	not exist" is a status change like any other. The condition "path does
		1302	not exist" is signified by the C<st_nlink> field being zero (which is
		1303	otherwise always forced to be at least one) and all the other fields of
		1304	the stat buffer having unspecified contents.
		1305
		1306	The path I<should> be absolute and I<must not> end in a slash. If it is
		1307	relative and your working directory changes, the behaviour is undefined.
		1308
		1309	Since there is no standard to do this, the portable implementation simply
		1310	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1311	can specify a recommended polling interval for this case. If you specify
		1312	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1313	unspecified default> value will be used (which you can expect to be around
		1314	five seconds, although this might change dynamically). Libev will also
		1315	impose a minimum interval which is currently around C<0.1>, but thats
		1316	usually overkill.
		1317
		1318	This watcher type is not meant for massive numbers of stat watchers,
		1319	as even with OS-supported change notifications, this can be
		1320	resource-intensive.
		1321
		1322	At the time of this writing, only the Linux inotify interface is
		1323	implemented (implementing kqueue support is left as an exercise for the
		1324	reader). Inotify will be used to give hints only and should not change the
		1325	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1326	to fall back to regular polling again even with inotify, but changes are
		1327	usually detected immediately, and if the file exists there will be no
		1328	polling.
		1329
		1330	=over 4
		1331
		1332	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1333
		1334	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1335
		1336	Configures the watcher to wait for status changes of the given
		1337	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1338	be detected and should normally be specified as C<0> to let libev choose
		1339	a suitable value. The memory pointed to by C<path> must point to the same
		1340	path for as long as the watcher is active.
		1341
		1342	The callback will be receive C<EV_STAT> when a change was detected,
		1343	relative to the attributes at the time the watcher was started (or the
		1344	last change was detected).
		1345
		1346	=item ev_stat_stat (ev_stat *)
		1347
		1348	Updates the stat buffer immediately with new values. If you change the
		1349	watched path in your callback, you could call this fucntion to avoid
		1350	detecting this change (while introducing a race condition). Can also be
		1351	useful simply to find out the new values.
		1352
		1353	=item ev_statdata attr [read-only]
		1354
		1355	The most-recently detected attributes of the file. Although the type is of
		1356	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1357	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1358	was some error while C<stat>ing the file.
		1359
		1360	=item ev_statdata prev [read-only]
		1361
		1362	The previous attributes of the file. The callback gets invoked whenever
		1363	C<prev> != C<attr>.
		1364
		1365	=item ev_tstamp interval [read-only]
		1366
		1367	The specified interval.
		1368
		1369	=item const char *path [read-only]
		1370
		1371	The filesystem path that is being watched.
		1372
		1373	=back
		1374
		1375	Example: Watch C</etc/passwd> for attribute changes.
		1376
		1377	static void
		1378	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1379	{
		1380	/* /etc/passwd changed in some way */
		1381	if (w->attr.st_nlink)
		1382	{
		1383	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1384	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1385	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1386	}
		1387	else
		1388	/* you shalt not abuse printf for puts */
		1389	puts ("wow, /etc/passwd is not there, expect problems. "
		1390	"if this is windows, they already arrived\n");
		1391	}
		1392
		1393	...
		1394	ev_stat passwd;
		1395
		1396	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1397	ev_stat_start (loop, &passwd);
		1398
		1399
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1400	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1401
1059	Idle watchers trigger events when there are no other events are pending	1402	Idle watchers trigger events when no other events of the same or higher
1060	(prepare, check and other idle watchers do not count). That is, as long	1403	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1404	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1405
1063	watchers are being called again and again, once per event loop iteration -	1406	That is, as long as your process is busy handling sockets or timeouts
		1407	(or even signals, imagine) of the same or higher priority it will not be
		1408	triggered. But when your process is idle (or only lower-priority watchers
		1409	are pending), the idle watchers are being called once per event loop
1064	until stopped, that is, or your process receives more events and becomes	1410	iteration - until stopped, that is, or your process receives more events
1065	busy.	1411	and becomes busy again with higher priority stuff.
1066		1412
1067	The most noteworthy effect is that as long as any idle watchers are	1413	The most noteworthy effect is that as long as any idle watchers are
1068	active, the process will not block when waiting for new events.	1414	active, the process will not block when waiting for new events.
1069		1415
1070	Apart from keeping your process non-blocking (which is a useful	1416	Apart from keeping your process non-blocking (which is a useful
…		…
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1426	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1427	believe me.
1082		1428
1083	=back	1429	=back
1084		1430
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1431	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1432	callback, free it. Also, use no error checking, as usual.
1087		1433
1088	static void	1434	static void
1089	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1435	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1090	{	1436	{
1091	free (w);	1437	free (w);
…		…
1136	with priority higher than or equal to the event loop and one coroutine	1482	with priority higher than or equal to the event loop and one coroutine
1137	of lower priority, but only once, using idle watchers to keep the event	1483	of lower priority, but only once, using idle watchers to keep the event
1138	loop from blocking if lower-priority coroutines are active, thus mapping	1484	loop from blocking if lower-priority coroutines are active, thus mapping
1139	low-priority coroutines to idle/background tasks).	1485	low-priority coroutines to idle/background tasks).
1140		1486
		1487	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1488	priority, to ensure that they are being run before any other watchers
		1489	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1490	too) should not activate ("feed") events into libev. While libev fully
		1491	supports this, they will be called before other C<ev_check> watchers did
		1492	their job. As C<ev_check> watchers are often used to embed other event
		1493	loops those other event loops might be in an unusable state until their
		1494	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1495	others).
		1496
1141	=over 4	1497	=over 4
1142		1498
1143	=item ev_prepare_init (ev_prepare *, callback)	1499	=item ev_prepare_init (ev_prepare *, callback)
1144		1500
1145	=item ev_check_init (ev_check *, callback)	1501	=item ev_check_init (ev_check *, callback)
…		…
1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1504	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1149	macros, but using them is utterly, utterly and completely pointless.	1505	macros, but using them is utterly, utterly and completely pointless.
1150		1506
1151	=back	1507	=back
1152		1508
1153	Example: To include a library such as adns, you would add IO watchers	1509	There are a number of principal ways to embed other event loops or modules
1154	and a timeout watcher in a prepare handler, as required by libadns, and	1510	into libev. Here are some ideas on how to include libadns into libev
		1511	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1512	use for an actually working example. Another Perl module named C<EV::Glib>
		1513	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1514	into the Glib event loop).
		1515
		1516	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1155	in a check watcher, destroy them and call into libadns. What follows is	1517	and in a check watcher, destroy them and call into libadns. What follows
1156	pseudo-code only of course:	1518	is pseudo-code only of course. This requires you to either use a low
		1519	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1520	the callbacks for the IO/timeout watchers might not have been called yet.
1157		1521
1158	static ev_io iow [nfd];	1522	static ev_io iow [nfd];
1159	static ev_timer tw;	1523	static ev_timer tw;
1160		1524
1161	static void	1525	static void
1162	io_cb (ev_loop loop, ev_io w, int revents)	1526	io_cb (ev_loop loop, ev_io w, int revents)
1163	{	1527	{
1164	// set the relevant poll flags
1165	// could also call adns_processreadable etc. here
1166	struct pollfd fd = (struct pollfd )w->data;
1167	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1168	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1169	}	1528	}
1170		1529
1171	// create io watchers for each fd and a timer before blocking	1530	// create io watchers for each fd and a timer before blocking
1172	static void	1531	static void
1173	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1532	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1174	{	1533	{
1175	int timeout = 3600000;truct pollfd fds [nfd];	1534	int timeout = 3600000;
		1535	struct pollfd fds [nfd];
1176	// actual code will need to loop here and realloc etc.	1536	// actual code will need to loop here and realloc etc.
1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1537	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1178		1538
1179	/* the callback is illegal, but won't be called as we stop during check */	1539	/* the callback is illegal, but won't be called as we stop during check */
1180	ev_timer_init (&tw, 0, timeout * 1e-3);	1540	ev_timer_init (&tw, 0, timeout * 1e-3);
1181	ev_timer_start (loop, &tw);	1541	ev_timer_start (loop, &tw);
1182		1542
1183	// create on ev_io per pollfd	1543	// create one ev_io per pollfd
1184	for (int i = 0; i < nfd; ++i)	1544	for (int i = 0; i < nfd; ++i)
1185	{	1545	{
1186	ev_io_init (iow + i, io_cb, fds [i].fd,	1546	ev_io_init (iow + i, io_cb, fds [i].fd,
1187	((fds [i].events & POLLIN ? EV_READ : 0)	1547	((fds [i].events & POLLIN ? EV_READ : 0)
1188	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1548	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1189		1549
1190	fds [i].revents = 0;	1550	fds [i].revents = 0;
1191	iow [i].data = fds + i;
1192	ev_io_start (loop, iow + i);	1551	ev_io_start (loop, iow + i);
1193	}	1552	}
1194	}	1553	}
1195		1554
1196	// stop all watchers after blocking	1555	// stop all watchers after blocking
…		…
1198	adns_check_cb (ev_loop loop, ev_check w, int revents)	1557	adns_check_cb (ev_loop loop, ev_check w, int revents)
1199	{	1558	{
1200	ev_timer_stop (loop, &tw);	1559	ev_timer_stop (loop, &tw);
1201		1560
1202	for (int i = 0; i < nfd; ++i)	1561	for (int i = 0; i < nfd; ++i)
		1562	{
		1563	// set the relevant poll flags
		1564	// could also call adns_processreadable etc. here
		1565	struct pollfd *fd = fds + i;
		1566	int revents = ev_clear_pending (iow + i);
		1567	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1568	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1569
		1570	// now stop the watcher
1203	ev_io_stop (loop, iow + i);	1571	ev_io_stop (loop, iow + i);
		1572	}
1204		1573
1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1574	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1575	}
		1576
		1577	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1578	in the prepare watcher and would dispose of the check watcher.
		1579
		1580	Method 3: If the module to be embedded supports explicit event
		1581	notification (adns does), you can also make use of the actual watcher
		1582	callbacks, and only destroy/create the watchers in the prepare watcher.
		1583
		1584	static void
		1585	timer_cb (EV_P_ ev_timer *w, int revents)
		1586	{
		1587	adns_state ads = (adns_state)w->data;
		1588	update_now (EV_A);
		1589
		1590	adns_processtimeouts (ads, &tv_now);
		1591	}
		1592
		1593	static void
		1594	io_cb (EV_P_ ev_io *w, int revents)
		1595	{
		1596	adns_state ads = (adns_state)w->data;
		1597	update_now (EV_A);
		1598
		1599	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1600	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1601	}
		1602
		1603	// do not ever call adns_afterpoll
		1604
		1605	Method 4: Do not use a prepare or check watcher because the module you
		1606	want to embed is too inflexible to support it. Instead, youc na override
		1607	their poll function. The drawback with this solution is that the main
		1608	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1609	this.
		1610
		1611	static gint
		1612	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1613	{
		1614	int got_events = 0;
		1615
		1616	for (n = 0; n < nfds; ++n)
		1617	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1618
		1619	if (timeout >= 0)
		1620	// create/start timer
		1621
		1622	// poll
		1623	ev_loop (EV_A_ 0);
		1624
		1625	// stop timer again
		1626	if (timeout >= 0)
		1627	ev_timer_stop (EV_A_ &to);
		1628
		1629	// stop io watchers again - their callbacks should have set
		1630	for (n = 0; n < nfds; ++n)
		1631	ev_io_stop (EV_A_ iow [n]);
		1632
		1633	return got_events;
1206	}	1634	}
1207		1635
1208		1636
1209	=head2 C<ev_embed> - when one backend isn't enough...	1637	=head2 C<ev_embed> - when one backend isn't enough...
1210		1638
…		…
1292		1720
1293	Make a single, non-blocking sweep over the embedded loop. This works	1721	Make a single, non-blocking sweep over the embedded loop. This works
1294	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1722	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1295	apropriate way for embedded loops.	1723	apropriate way for embedded loops.
1296		1724
		1725	=item struct ev_loop *loop [read-only]
		1726
		1727	The embedded event loop.
		1728
		1729	=back
		1730
		1731
		1732	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1733
		1734	Fork watchers are called when a C<fork ()> was detected (usually because
		1735	whoever is a good citizen cared to tell libev about it by calling
		1736	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1737	event loop blocks next and before C<ev_check> watchers are being called,
		1738	and only in the child after the fork. If whoever good citizen calling
		1739	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1740	handlers will be invoked, too, of course.
		1741
		1742	=over 4
		1743
		1744	=item ev_fork_init (ev_signal *, callback)
		1745
		1746	Initialises and configures the fork watcher - it has no parameters of any
		1747	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1748	believe me.
		1749
1297	=back	1750	=back
1298		1751
1299		1752
1300	=head1 OTHER FUNCTIONS	1753	=head1 OTHER FUNCTIONS
1301		1754
…		…
1389		1842
1390	To use it,	1843	To use it,
1391		1844
1392	#include <ev++.h>	1845	#include <ev++.h>
1393		1846
1394	(it is not installed by default). This automatically includes F<ev.h>	1847	This automatically includes F<ev.h> and puts all of its definitions (many
1395	and puts all of its definitions (many of them macros) into the global	1848	of them macros) into the global namespace. All C++ specific things are
1396	namespace. All C++ specific things are put into the C<ev> namespace.	1849	put into the C<ev> namespace. It should support all the same embedding
		1850	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1397		1851
1398	It should support all the same embedding options as F<ev.h>, most notably	1852	Care has been taken to keep the overhead low. The only data member the C++
1399	C<EV_MULTIPLICITY>.	1853	classes add (compared to plain C-style watchers) is the event loop pointer
		1854	that the watcher is associated with (or no additional members at all if
		1855	you disable C<EV_MULTIPLICITY> when embedding libev).
		1856
		1857	Currently, functions, and static and non-static member functions can be
		1858	used as callbacks. Other types should be easy to add as long as they only
		1859	need one additional pointer for context. If you need support for other
		1860	types of functors please contact the author (preferably after implementing
		1861	it).
1400		1862
1401	Here is a list of things available in the C<ev> namespace:	1863	Here is a list of things available in the C<ev> namespace:
1402		1864
1403	=over 4	1865	=over 4
1404		1866
…		…
1420		1882
1421	All of those classes have these methods:	1883	All of those classes have these methods:
1422		1884
1423	=over 4	1885	=over 4
1424		1886
1425	=item ev::TYPE::TYPE (object , object::method )	1887	=item ev::TYPE::TYPE ()
1426		1888
1427	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1889	=item ev::TYPE::TYPE (struct ev_loop *)
1428		1890
1429	=item ev::TYPE::~TYPE	1891	=item ev::TYPE::~TYPE
1430		1892
1431	The constructor takes a pointer to an object and a method pointer to	1893	The constructor (optionally) takes an event loop to associate the watcher
1432	the event handler callback to call in this class. The constructor calls	1894	with. If it is omitted, it will use C<EV_DEFAULT>.
1433	C<ev_init> for you, which means you have to call the C<set> method	1895
1434	before starting it. If you do not specify a loop then the constructor	1896	The constructor calls C<ev_init> for you, which means you have to call the
1435	automatically associates the default loop with this watcher.	1897	C<set> method before starting it.
		1898
		1899	It will not set a callback, however: You have to call the templated C<set>
		1900	method to set a callback before you can start the watcher.
		1901
		1902	(The reason why you have to use a method is a limitation in C++ which does
		1903	not allow explicit template arguments for constructors).
1436		1904
1437	The destructor automatically stops the watcher if it is active.	1905	The destructor automatically stops the watcher if it is active.
		1906
		1907	=item w->set<class, &class::method> (object *)
		1908
		1909	This method sets the callback method to call. The method has to have a
		1910	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1911	first argument and the C<revents> as second. The object must be given as
		1912	parameter and is stored in the C<data> member of the watcher.
		1913
		1914	This method synthesizes efficient thunking code to call your method from
		1915	the C callback that libev requires. If your compiler can inline your
		1916	callback (i.e. it is visible to it at the place of the C<set> call and
		1917	your compiler is good :), then the method will be fully inlined into the
		1918	thunking function, making it as fast as a direct C callback.
		1919
		1920	Example: simple class declaration and watcher initialisation
		1921
		1922	struct myclass
		1923	{
		1924	void io_cb (ev::io &w, int revents) { }
		1925	}
		1926
		1927	myclass obj;
		1928	ev::io iow;
		1929	iow.set <myclass, &myclass::io_cb> (&obj);
		1930
		1931	=item w->set<function> (void *data = 0)
		1932
		1933	Also sets a callback, but uses a static method or plain function as
		1934	callback. The optional C<data> argument will be stored in the watcher's
		1935	C<data> member and is free for you to use.
		1936
		1937	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1938
		1939	See the method-C<set> above for more details.
		1940
		1941	Example:
		1942
		1943	static void io_cb (ev::io &w, int revents) { }
		1944	iow.set <io_cb> ();
1438		1945
1439	=item w->set (struct ev_loop *)	1946	=item w->set (struct ev_loop *)
1440		1947
1441	Associates a different C<struct ev_loop> with this watcher. You can only	1948	Associates a different C<struct ev_loop> with this watcher. You can only
1442	do this when the watcher is inactive (and not pending either).	1949	do this when the watcher is inactive (and not pending either).
1443		1950
1444	=item w->set ([args])	1951	=item w->set ([args])
1445		1952
1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1953	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1447	called at least once. Unlike the C counterpart, an active watcher gets	1954	called at least once. Unlike the C counterpart, an active watcher gets
1448	automatically stopped and restarted.	1955	automatically stopped and restarted when reconfiguring it with this
		1956	method.
1449		1957
1450	=item w->start ()	1958	=item w->start ()
1451		1959
1452	Starts the watcher. Note that there is no C<loop> argument as the	1960	Starts the watcher. Note that there is no C<loop> argument, as the
1453	constructor already takes the loop.	1961	constructor already stores the event loop.
1454		1962
1455	=item w->stop ()	1963	=item w->stop ()
1456		1964
1457	Stops the watcher if it is active. Again, no C<loop> argument.	1965	Stops the watcher if it is active. Again, no C<loop> argument.
1458		1966
…		…
1463		1971
1464	=item w->sweep () C<ev::embed> only	1972	=item w->sweep () C<ev::embed> only
1465		1973
1466	Invokes C<ev_embed_sweep>.	1974	Invokes C<ev_embed_sweep>.
1467		1975
		1976	=item w->update () C<ev::stat> only
		1977
		1978	Invokes C<ev_stat_stat>.
		1979
1468	=back	1980	=back
1469		1981
1470	=back	1982	=back
1471		1983
1472	Example: Define a class with an IO and idle watcher, start one of them in	1984	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1479		1991
1480	myclass ();	1992	myclass ();
1481	}	1993	}
1482		1994
1483	myclass::myclass (int fd)	1995	myclass::myclass (int fd)
1484	: io (this, &myclass::io_cb),
1485	idle (this, &myclass::idle_cb)
1486	{	1996	{
		1997	io .set <myclass, &myclass::io_cb > (this);
		1998	idle.set <myclass, &myclass::idle_cb> (this);
		1999
1487	io.start (fd, ev::READ);	2000	io.start (fd, ev::READ);
1488	}	2001	}
		2002
		2003
		2004	=head1 MACRO MAGIC
		2005
		2006	Libev can be compiled with a variety of options, the most fundemantal is
		2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
		2008	callbacks have an initial C<struct ev_loop *> argument.
		2009
		2010	To make it easier to write programs that cope with either variant, the
		2011	following macros are defined:
		2012
		2013	=over 4
		2014
		2015	=item C<EV_A>, C<EV_A_>
		2016
		2017	This provides the loop I<argument> for functions, if one is required ("ev
		2018	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2019	C<EV_A_> is used when other arguments are following. Example:
		2020
		2021	ev_unref (EV_A);
		2022	ev_timer_add (EV_A_ watcher);
		2023	ev_loop (EV_A_ 0);
		2024
		2025	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2026	which is often provided by the following macro.
		2027
		2028	=item C<EV_P>, C<EV_P_>
		2029
		2030	This provides the loop I<parameter> for functions, if one is required ("ev
		2031	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2032	C<EV_P_> is used when other parameters are following. Example:
		2033
		2034	// this is how ev_unref is being declared
		2035	static void ev_unref (EV_P);
		2036
		2037	// this is how you can declare your typical callback
		2038	static void cb (EV_P_ ev_timer *w, int revents)
		2039
		2040	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2041	suitable for use with C<EV_A>.
		2042
		2043	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2044
		2045	Similar to the other two macros, this gives you the value of the default
		2046	loop, if multiple loops are supported ("ev loop default").
		2047
		2048	=back
		2049
		2050	Example: Declare and initialise a check watcher, utilising the above
		2051	macros so it will work regardless of whether multiple loops are supported
		2052	or not.
		2053
		2054	static void
		2055	check_cb (EV_P_ ev_timer *w, int revents)
		2056	{
		2057	ev_check_stop (EV_A_ w);
		2058	}
		2059
		2060	ev_check check;
		2061	ev_check_init (&check, check_cb);
		2062	ev_check_start (EV_DEFAULT_ &check);
		2063	ev_loop (EV_DEFAULT_ 0);
1489		2064
1490	=head1 EMBEDDING	2065	=head1 EMBEDDING
1491		2066
1492	Libev can (and often is) directly embedded into host	2067	Libev can (and often is) directly embedded into host
1493	applications. Examples of applications that embed it include the Deliantra	2068	applications. Examples of applications that embed it include the Deliantra
…		…
1533	ev_vars.h	2108	ev_vars.h
1534	ev_wrap.h	2109	ev_wrap.h
1535		2110
1536	ev_win32.c required on win32 platforms only	2111	ev_win32.c required on win32 platforms only
1537		2112
1538	ev_select.c only when select backend is enabled (which is by default)	2113	ev_select.c only when select backend is enabled (which is enabled by default)
1539	ev_poll.c only when poll backend is enabled (disabled by default)	2114	ev_poll.c only when poll backend is enabled (disabled by default)
1540	ev_epoll.c only when the epoll backend is enabled (disabled by default)	2115	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1541	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	2116	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1542	ev_port.c only when the solaris port backend is enabled (disabled by default)	2117	ev_port.c only when the solaris port backend is enabled (disabled by default)
1543		2118
…		…
1668		2243
1669	=item EV_USE_DEVPOLL	2244	=item EV_USE_DEVPOLL
1670		2245
1671	reserved for future expansion, works like the USE symbols above.	2246	reserved for future expansion, works like the USE symbols above.
1672		2247
		2248	=item EV_USE_INOTIFY
		2249
		2250	If defined to be C<1>, libev will compile in support for the Linux inotify
		2251	interface to speed up C<ev_stat> watchers. Its actual availability will
		2252	be detected at runtime.
		2253
1673	=item EV_H	2254	=item EV_H
1674		2255
1675	The name of the F<ev.h> header file used to include it. The default if	2256	The name of the F<ev.h> header file used to include it. The default if
1676	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2257	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1677	can be used to virtually rename the F<ev.h> header file in case of conflicts.	2258	can be used to virtually rename the F<ev.h> header file in case of conflicts.
…		…
1700	will have the C<struct ev_loop *> as first argument, and you can create	2281	will have the C<struct ev_loop *> as first argument, and you can create
1701	additional independent event loops. Otherwise there will be no support	2282	additional independent event loops. Otherwise there will be no support
1702	for multiple event loops and there is no first event loop pointer	2283	for multiple event loops and there is no first event loop pointer
1703	argument. Instead, all functions act on the single default loop.	2284	argument. Instead, all functions act on the single default loop.
1704		2285
		2286	=item EV_MINPRI
		2287
		2288	=item EV_MAXPRI
		2289
		2290	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2291	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2292	provide for more priorities by overriding those symbols (usually defined
		2293	to be C<-2> and C<2>, respectively).
		2294
		2295	When doing priority-based operations, libev usually has to linearly search
		2296	all the priorities, so having many of them (hundreds) uses a lot of space
		2297	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2298	fine.
		2299
		2300	If your embedding app does not need any priorities, defining these both to
		2301	C<0> will save some memory and cpu.
		2302
1705	=item EV_PERIODICS	2303	=item EV_PERIODIC_ENABLE
1706		2304
1707	If undefined or defined to be C<1>, then periodic timers are supported,	2305	If undefined or defined to be C<1>, then periodic timers are supported. If
1708	otherwise not. This saves a few kb of code.	2306	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2307	code.
		2308
		2309	=item EV_IDLE_ENABLE
		2310
		2311	If undefined or defined to be C<1>, then idle watchers are supported. If
		2312	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2313	code.
		2314
		2315	=item EV_EMBED_ENABLE
		2316
		2317	If undefined or defined to be C<1>, then embed watchers are supported. If
		2318	defined to be C<0>, then they are not.
		2319
		2320	=item EV_STAT_ENABLE
		2321
		2322	If undefined or defined to be C<1>, then stat watchers are supported. If
		2323	defined to be C<0>, then they are not.
		2324
		2325	=item EV_FORK_ENABLE
		2326
		2327	If undefined or defined to be C<1>, then fork watchers are supported. If
		2328	defined to be C<0>, then they are not.
		2329
		2330	=item EV_MINIMAL
		2331
		2332	If you need to shave off some kilobytes of code at the expense of some
		2333	speed, define this symbol to C<1>. Currently only used for gcc to override
		2334	some inlining decisions, saves roughly 30% codesize of amd64.
		2335
		2336	=item EV_PID_HASHSIZE
		2337
		2338	C<ev_child> watchers use a small hash table to distribute workload by
		2339	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2340	than enough. If you need to manage thousands of children you might want to
		2341	increase this value (I<must> be a power of two).
		2342
		2343	=item EV_INOTIFY_HASHSIZE
		2344
		2345	C<ev_staz> watchers use a small hash table to distribute workload by
		2346	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2347	usually more than enough. If you need to manage thousands of C<ev_stat>
		2348	watchers you might want to increase this value (I<must> be a power of
		2349	two).
1709		2350
1710	=item EV_COMMON	2351	=item EV_COMMON
1711		2352
1712	By default, all watchers have a C<void *data> member. By redefining	2353	By default, all watchers have a C<void *data> member. By redefining
1713	this macro to a something else you can include more and other types of	2354	this macro to a something else you can include more and other types of
…		…
1742	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file	2383	interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1743	will be compiled. It is pretty complex because it provides its own header	2384	will be compiled. It is pretty complex because it provides its own header
1744	file.	2385	file.
1745		2386
1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2387	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1747	that everybody includes and which overrides some autoconf choices:	2388	that everybody includes and which overrides some configure choices:
1748		2389
		2390	#define EV_MINIMAL 1
1749	#define EV_USE_POLL 0	2391	#define EV_USE_POLL 0
1750	#define EV_MULTIPLICITY 0	2392	#define EV_MULTIPLICITY 0
1751	#define EV_PERIODICS 0	2393	#define EV_PERIODIC_ENABLE 0
		2394	#define EV_STAT_ENABLE 0
		2395	#define EV_FORK_ENABLE 0
1752	#define EV_CONFIG_H <config.h>	2396	#define EV_CONFIG_H <config.h>
		2397	#define EV_MINPRI 0
		2398	#define EV_MAXPRI 0
1753		2399
1754	#include "ev++.h"	2400	#include "ev++.h"
1755		2401
1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2402	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1757		2403
…		…
1763		2409
1764	In this section the complexities of (many of) the algorithms used inside	2410	In this section the complexities of (many of) the algorithms used inside
1765	libev will be explained. For complexity discussions about backends see the	2411	libev will be explained. For complexity discussions about backends see the
1766	documentation for C<ev_default_init>.	2412	documentation for C<ev_default_init>.
1767		2413
		2414	All of the following are about amortised time: If an array needs to be
		2415	extended, libev needs to realloc and move the whole array, but this
		2416	happens asymptotically never with higher number of elements, so O(1) might
		2417	mean it might do a lengthy realloc operation in rare cases, but on average
		2418	it is much faster and asymptotically approaches constant time.
		2419
1768	=over 4	2420	=over 4
1769		2421
1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1771		2423
		2424	This means that, when you have a watcher that triggers in one hour and
		2425	there are 100 watchers that would trigger before that then inserting will
		2426	have to skip those 100 watchers.
		2427
1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
1773		2429
		2430	That means that for changing a timer costs less than removing/adding them
		2431	as only the relative motion in the event queue has to be paid for.
		2432
1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
1775		2434
		2435	These just add the watcher into an array or at the head of a list.
1776	=item Stopping check/prepare/idle watchers: O(1)	2436	=item Stopping check/prepare/idle watchers: O(1)
1777		2437
1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2439
		2440	These watchers are stored in lists then need to be walked to find the
		2441	correct watcher to remove. The lists are usually short (you don't usually
		2442	have many watchers waiting for the same fd or signal).
1779		2443
1780	=item Finding the next timer per loop iteration: O(1)	2444	=item Finding the next timer per loop iteration: O(1)
1781		2445
1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1783		2447
		2448	A change means an I/O watcher gets started or stopped, which requires
		2449	libev to recalculate its status (and possibly tell the kernel).
		2450
1784	=item Activating one watcher: O(1)	2451	=item Activating one watcher: O(1)
1785		2452
		2453	=item Priority handling: O(number_of_priorities)
		2454
		2455	Priorities are implemented by allocating some space for each
		2456	priority. When doing priority-based operations, libev usually has to
		2457	linearly search all the priorities.
		2458
1786	=back	2459	=back
1787		2460
1788		2461
1789	=head1 AUTHOR	2462	=head1 AUTHOR
1790		2463

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Comparing libev/ev.pod (file contents): Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs. Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.46 by root, Mon Nov 26 10:20:43 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC