[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 1.86 by root, Tue Dec 18 01:20:33 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 some floatingpoint value. Unlike the name
52		104	component C<stamp> might indicate, it is also used for time differences
		105	throughout libev.
53		106
54	=head1 GLOBAL FUNCTIONS	107	=head1 GLOBAL FUNCTIONS
55		108
56	These functions can be called anytime, even before initialising the	109	These functions can be called anytime, even before initialising the
57	library in any way.	110	library in any way.
…		…
66		119
67	=item int ev_version_major ()	120	=item int ev_version_major ()
68		121
69	=item int ev_version_minor ()	122	=item int ev_version_minor ()
70		123
71	You can find out the major and minor version numbers of the library	124	You can find out the major and minor ABI version numbers of the library
72	you linked against by calling the functions C<ev_version_major> and	125	you linked against by calling the functions C<ev_version_major> and
73	C<ev_version_minor>. If you want, you can compare against the global	126	C<ev_version_minor>. If you want, you can compare against the global
74	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the	127	symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
75	version of the library your program was compiled against.	128	version of the library your program was compiled against.
76		129
		130	These version numbers refer to the ABI version of the library, not the
		131	release version.
		132
77	Usually, it's a good idea to terminate if the major versions mismatch,	133	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	134	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	135	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	136	not a problem.
81		137
82	Example: make sure we haven't accidentally been linked against the wrong	138	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	139	version.
84		140
85	assert (("libev version mismatch",	141	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	142	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	143	&& ev_version_minor () >= EV_VERSION_MINOR));
88		144
…		…
118		174
119	See the description of C<ev_embed> watchers for more info.	175	See the description of C<ev_embed> watchers for more info.
120		176
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	177	=item ev_set_allocator (void (cb)(void *ptr, long size))
122		178
123	Sets the allocation function to use (the prototype is similar to the	179	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	180	semantics is identical - to the realloc C function). It is used to
125	and free memory (no surprises here). If it returns zero when memory	181	allocate and free memory (no surprises here). If it returns zero when
126	needs to be allocated, the library might abort or take some potentially	182	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	183	potentially destructive action. The default is your system realloc
		184	function.
128		185
129	You could override this function in high-availability programs to, say,	186	You could override this function in high-availability programs to, say,
130	free some memory if it cannot allocate memory, to use a special allocator,	187	free some memory if it cannot allocate memory, to use a special allocator,
131	or even to sleep a while and retry until some memory is available.	188	or even to sleep a while and retry until some memory is available.
132		189
133	Example: replace the libev allocator with one that waits a bit and then	190	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	191	retries).
135		192
136	static void *	193	static void *
137	persistent_realloc (void *ptr, long size)	194	persistent_realloc (void *ptr, size_t size)
138	{	195	{
139	for (;;)	196	for (;;)
140	{	197	{
141	void *newptr = realloc (ptr, size);	198	void *newptr = realloc (ptr, size);
142		199
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	215	callback is set, then libev will expect it to remedy the sitution, no
159	matter what, when it returns. That is, libev will generally retry the	216	matter what, when it returns. That is, libev will generally retry the
160	requested operation, or, if the condition doesn't go away, do bad stuff	217	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	218	(such as abort).
162		219
163	Example: do the same thing as libev does internally:	220	Example: This is basically the same thing that libev does internally, too.
164		221
165	static void	222	static void
166	fatal_error (const char *msg)	223	fatal_error (const char *msg)
167	{	224	{
168	perror (msg);	225	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	275	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	276	override the flags completely if it is found in the environment. This is
220	useful to try out specific backends to test their performance, or to work	277	useful to try out specific backends to test their performance, or to work
221	around bugs.	278	around bugs.
222		279
		280	=item C<EVFLAG_FORKCHECK>
		281
		282	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		283	a fork, you can also make libev check for a fork in each iteration by
		284	enabling this flag.
		285
		286	This works by calling C<getpid ()> on every iteration of the loop,
		287	and thus this might slow down your event loop if you do a lot of loop
		288	iterations and little real work, but is usually not noticeable (on my
		289	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		290	without a syscall and thus I<very> fast, but my Linux system also has
		291	C<pthread_atfork> which is even faster).
		292
		293	The big advantage of this flag is that you can forget about fork (and
		294	forget about forgetting to tell libev about forking) when you use this
		295	flag.
		296
		297	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		298	environment variable.
		299
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	300	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		301
225	This is your standard select(2) backend. Not I<completely> standard, as	302	This is your standard select(2) backend. Not I<completely> standard, as
226	libev tries to roll its own fd_set with no limits on the number of fds,	303	libev tries to roll its own fd_set with no limits on the number of fds,
227	but if that fails, expect a fairly low limit on the number of fds when	304	but if that fails, expect a fairly low limit on the number of fds when
…		…
314	Similar to C<ev_default_loop>, but always creates a new event loop that is	391	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	392	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	393	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).	394	undefined behaviour (or a failed assertion if assertions are enabled).
318		395
319	Example: try to create a event loop that uses epoll and nothing else.	396	Example: Try to create a event loop that uses epoll and nothing else.
320		397
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	398	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	399	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	400	fatal ("no epoll found here, maybe it hides under your chair");
324		401
…		…
362		439
363	Like C<ev_default_fork>, but acts on an event loop created by	440	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	441	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.	442	after fork, and how you do this is entirely your own problem.
366		443
		444	=item unsigned int ev_loop_count (loop)
		445
		446	Returns the count of loop iterations for the loop, which is identical to
		447	the number of times libev did poll for new events. It starts at C<0> and
		448	happily wraps around with enough iterations.
		449
		450	This value can sometimes be useful as a generation counter of sorts (it
		451	"ticks" the number of loop iterations), as it roughly corresponds with
		452	C<ev_prepare> and C<ev_check> calls.
		453
367	=item unsigned int ev_backend (loop)	454	=item unsigned int ev_backend (loop)
368		455
369	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	456	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
370	use.	457	use.
371		458
…		…
404	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	491	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
405	usually a better approach for this kind of thing.	492	usually a better approach for this kind of thing.
406		493
407	Here are the gory details of what C<ev_loop> does:	494	Here are the gory details of what C<ev_loop> does:
408		495
		496	- Before the first iteration, call any pending watchers.
409	* If there are no active watchers (reference count is zero), return.	497	* If there are no active watchers (reference count is zero), return.
410	- Queue prepare watchers and then call all outstanding watchers.	498	- Queue all prepare watchers and then call all outstanding watchers.
411	- If we have been forked, recreate the kernel state.	499	- If we have been forked, recreate the kernel state.
412	- Update the kernel state with all outstanding changes.	500	- Update the kernel state with all outstanding changes.
413	- Update the "event loop time".	501	- Update the "event loop time".
414	- Calculate for how long to block.	502	- Calculate for how long to block.
415	- Block the process, waiting for any events.	503	- Block the process, waiting for any events.
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	511	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	512	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	513	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	514	were used, return, otherwise continue with step *.
427		515
428	Example: queue some jobs and then loop until no events are outsanding	516	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	517	anymore.
430		518
431	... queue jobs here, make sure they register event watchers as long	519	... 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..)	520	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	521	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	541	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	542	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	543	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>.	544	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		545
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	546	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	547	running when nothing else is active.
460		548
461	struct dv_signal exitsig;	549	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	550	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	551	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	552	evf_unref (loop);
465		553
466	Example: for some weird reason, unregister the above signal handler again.	554	Example: For some weird reason, unregister the above signal handler again.
467		555
468	ev_ref (myloop);	556	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	557	ev_signal_stop (loop, &exitsig);
470		558
471	=back	559	=back
472		560
473		561
474	=head1 ANATOMY OF A WATCHER	562	=head1 ANATOMY OF A WATCHER
…		…
544	The signal specified in the C<ev_signal> watcher has been received by a thread.	632	The signal specified in the C<ev_signal> watcher has been received by a thread.
545		633
546	=item C<EV_CHILD>	634	=item C<EV_CHILD>
547		635
548	The pid specified in the C<ev_child> watcher has received a status change.	636	The pid specified in the C<ev_child> watcher has received a status change.
		637
		638	=item C<EV_STAT>
		639
		640	The path specified in the C<ev_stat> watcher changed its attributes somehow.
549		641
550	=item C<EV_IDLE>	642	=item C<EV_IDLE>
551		643
552	The C<ev_idle> watcher has determined that you have nothing better to do.	644	The C<ev_idle> watcher has determined that you have nothing better to do.
553		645
…		…
561	received events. Callbacks of both watcher types can start and stop as	653	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	654	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	655	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
564	C<ev_loop> from blocking).	656	C<ev_loop> from blocking).
565		657
		658	=item C<EV_EMBED>
		659
		660	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		661
		662	=item C<EV_FORK>
		663
		664	The event loop has been resumed in the child process after fork (see
		665	C<ev_fork>).
		666
566	=item C<EV_ERROR>	667	=item C<EV_ERROR>
567		668
568	An unspecified error has occured, the watcher has been stopped. This might	669	An unspecified error has occured, the watcher has been stopped. This might
569	happen because the watcher could not be properly started because libev	670	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	671	ran out of memory, a file descriptor was found to be closed or any other
…		…
641	=item bool ev_is_pending (ev_TYPE *watcher)	742	=item bool ev_is_pending (ev_TYPE *watcher)
642		743
643	Returns a true value iff the watcher is pending, (i.e. it has outstanding	744	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	745	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	746	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	747	C<ev_TYPE_set> is safe), you must not change its priority, and you must
647	libev (e.g. you cnanot C<free ()> it).	748	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		749	it).
648		750
649	=item callback = ev_cb (ev_TYPE *watcher)	751	=item callback ev_cb (ev_TYPE *watcher)
650		752
651	Returns the callback currently set on the watcher.	753	Returns the callback currently set on the watcher.
652		754
653	=item ev_cb_set (ev_TYPE *watcher, callback)	755	=item ev_cb_set (ev_TYPE *watcher, callback)
654		756
655	Change the callback. You can change the callback at virtually any time	757	Change the callback. You can change the callback at virtually any time
656	(modulo threads).	758	(modulo threads).
		759
		760	=item ev_set_priority (ev_TYPE *watcher, priority)
		761
		762	=item int ev_priority (ev_TYPE *watcher)
		763
		764	Set and query the priority of the watcher. The priority is a small
		765	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		766	(default: C<-2>). Pending watchers with higher priority will be invoked
		767	before watchers with lower priority, but priority will not keep watchers
		768	from being executed (except for C<ev_idle> watchers).
		769
		770	This means that priorities are I<only> used for ordering callback
		771	invocation after new events have been received. This is useful, for
		772	example, to reduce latency after idling, or more often, to bind two
		773	watchers on the same event and make sure one is called first.
		774
		775	If you need to suppress invocation when higher priority events are pending
		776	you need to look at C<ev_idle> watchers, which provide this functionality.
		777
		778	You I<must not> change the priority of a watcher as long as it is active or
		779	pending.
		780
		781	The default priority used by watchers when no priority has been set is
		782	always C<0>, which is supposed to not be too high and not be too low :).
		783
		784	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		785	fine, as long as you do not mind that the priority value you query might
		786	or might not have been adjusted to be within valid range.
		787
		788	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		789
		790	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		791	C<loop> nor C<revents> need to be valid as long as the watcher callback
		792	can deal with that fact.
		793
		794	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		795
		796	If the watcher is pending, this function returns clears its pending status
		797	and returns its C<revents> bitset (as if its callback was invoked). If the
		798	watcher isn't pending it does nothing and returns C<0>.
657		799
658	=back	800	=back
659		801
660		802
661	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	803	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
682	{	824	{
683	struct my_io w = (struct my_io )w_;	825	struct my_io w = (struct my_io )w_;
684	...	826	...
685	}	827	}
686		828
687	More interesting and less C-conformant ways of catsing your callback type	829	More interesting and less C-conformant ways of casting your callback type
688	have been omitted....	830	instead have been omitted.
		831
		832	Another common scenario is having some data structure with multiple
		833	watchers:
		834
		835	struct my_biggy
		836	{
		837	int some_data;
		838	ev_timer t1;
		839	ev_timer t2;
		840	}
		841
		842	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		843	you need to use C<offsetof>:
		844
		845	#include <stddef.h>
		846
		847	static void
		848	t1_cb (EV_P_ struct ev_timer *w, int revents)
		849	{
		850	struct my_biggy big = (struct my_biggy *
		851	(((char *)w) - offsetof (struct my_biggy, t1));
		852	}
		853
		854	static void
		855	t2_cb (EV_P_ struct ev_timer *w, int revents)
		856	{
		857	struct my_biggy big = (struct my_biggy *
		858	(((char *)w) - offsetof (struct my_biggy, t2));
		859	}
689		860
690		861
691	=head1 WATCHER TYPES	862	=head1 WATCHER TYPES
692		863
693	This section describes each watcher in detail, but will not repeat	864	This section describes each watcher in detail, but will not repeat
694	information given in the last section.	865	information given in the last section. Any initialisation/set macros,
		866	functions and members specific to the watcher type are explained.
		867
		868	Members are additionally marked with either I<[read-only]>, meaning that,
		869	while the watcher is active, you can look at the member and expect some
		870	sensible content, but you must not modify it (you can modify it while the
		871	watcher is stopped to your hearts content), or I<[read-write]>, which
		872	means you can expect it to have some sensible content while the watcher
		873	is active, but you can also modify it. Modifying it may not do something
		874	sensible or take immediate effect (or do anything at all), but libev will
		875	not crash or malfunction in any way.
695		876
696		877
697	=head2 C<ev_io> - is this file descriptor readable or writable?	878	=head2 C<ev_io> - is this file descriptor readable or writable?
698		879
699	I/O watchers check whether a file descriptor is readable or writable	880	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	909	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.	910	C<EAGAIN> is far preferable to a program hanging until some data arrives.
730		911
731	If you cannot run the fd in non-blocking mode (for example you should not	912	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	913	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	914	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	915	such as poll (fortunately in our Xlib example, Xlib already does this on
735	its own, so its quite safe to use).	916	its own, so its quite safe to use).
		917
		918	=head3 The special problem of disappearing file descriptors
		919
		920	Some backends (e.g kqueue, epoll) need to be told about closing a file
		921	descriptor (either by calling C<close> explicitly or by any other means,
		922	such as C<dup>). The reason is that you register interest in some file
		923	descriptor, but when it goes away, the operating system will silently drop
		924	this interest. If another file descriptor with the same number then is
		925	registered with libev, there is no efficient way to see that this is, in
		926	fact, a different file descriptor.
		927
		928	To avoid having to explicitly tell libev about such cases, libev follows
		929	the following policy: Each time C<ev_io_set> is being called, libev
		930	will assume that this is potentially a new file descriptor, otherwise
		931	it is assumed that the file descriptor stays the same. That means that
		932	you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
		933	descriptor even if the file descriptor number itself did not change.
		934
		935	This is how one would do it normally anyway, the important point is that
		936	the libev application should not optimise around libev but should leave
		937	optimisations to libev.
		938
		939
		940	=head3 Watcher-Specific Functions
736		941
737	=over 4	942	=over 4
738		943
739	=item ev_io_init (ev_io *, callback, int fd, int events)	944	=item ev_io_init (ev_io *, callback, int fd, int events)
740		945
…		…
742		947
743	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to	948	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	949	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.	950	C<EV_READ \| EV_WRITE> to receive the given events.
746		951
		952	=item int fd [read-only]
		953
		954	The file descriptor being watched.
		955
		956	=item int events [read-only]
		957
		958	The events being watched.
		959
747	=back	960	=back
748		961
749	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	962	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	963	readable, but only once. Since it is likely line-buffered, you could
751	attempt to read a whole line in the callback:	964	attempt to read a whole line in the callback.
752		965
753	static void	966	static void
754	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	967	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
755	{	968	{
756	ev_io_stop (loop, w);	969	ev_io_stop (loop, w);
…		…
786		999
787	The callback is guarenteed to be invoked only when its timeout has passed,	1000	The callback is guarenteed to be invoked only when its timeout has passed,
788	but if multiple timers become ready during the same loop iteration then	1001	but if multiple timers become ready during the same loop iteration then
789	order of execution is undefined.	1002	order of execution is undefined.
790		1003
		1004	=head3 Watcher-Specific Functions and Data Members
		1005
791	=over 4	1006	=over 4
792		1007
793	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1008	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
794		1009
795	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)	1010	=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
…		…
808	=item ev_timer_again (loop)	1023	=item ev_timer_again (loop)
809		1024
810	This will act as if the timer timed out and restart it again if it is	1025	This will act as if the timer timed out and restart it again if it is
811	repeating. The exact semantics are:	1026	repeating. The exact semantics are:
812		1027
		1028	If the timer is pending, its pending status is cleared.
		1029
813	If the timer is started but nonrepeating, stop it.	1030	If the timer is started but nonrepeating, stop it (as if it timed out).
814		1031
815	If the timer is repeating, either start it if necessary (with the repeat	1032	If the timer is repeating, either start it if necessary (with the
816	value), or reset the running timer to the repeat value.	1033	C<repeat> value), or reset the running timer to the C<repeat> value.
817		1034
818	This sounds a bit complicated, but here is a useful and typical	1035	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	1036	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	1037	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	1038	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	1039	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	1040	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	1041	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.	1042	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		1043	automatically restart it if need be.
		1044
		1045	That means you can ignore the C<after> value and C<ev_timer_start>
		1046	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		1047
		1048	ev_timer_init (timer, callback, 0., 5.);
		1049	ev_timer_again (loop, timer);
		1050	...
		1051	timer->again = 17.;
		1052	ev_timer_again (loop, timer);
		1053	...
		1054	timer->again = 10.;
		1055	ev_timer_again (loop, timer);
		1056
		1057	This is more slightly efficient then stopping/starting the timer each time
		1058	you want to modify its timeout value.
		1059
		1060	=item ev_tstamp repeat [read-write]
		1061
		1062	The current C<repeat> value. Will be used each time the watcher times out
		1063	or C<ev_timer_again> is called and determines the next timeout (if any),
		1064	which is also when any modifications are taken into account.
826		1065
827	=back	1066	=back
828		1067
829	Example: create a timer that fires after 60 seconds.	1068	Example: Create a timer that fires after 60 seconds.
830		1069
831	static void	1070	static void
832	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1071	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
833	{	1072	{
834	.. one minute over, w is actually stopped right here	1073	.. one minute over, w is actually stopped right here
…		…
836		1075
837	struct ev_timer mytimer;	1076	struct ev_timer mytimer;
838	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1077	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
839	ev_timer_start (loop, &mytimer);	1078	ev_timer_start (loop, &mytimer);
840		1079
841	Example: create a timeout timer that times out after 10 seconds of	1080	Example: Create a timeout timer that times out after 10 seconds of
842	inactivity.	1081	inactivity.
843		1082
844	static void	1083	static void
845	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1084	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
846	{	1085	{
…		…
866	but on wallclock time (absolute time). You can tell a periodic watcher	1105	but on wallclock time (absolute time). You can tell a periodic watcher
867	to trigger "at" some specific point in time. For example, if you tell a	1106	to trigger "at" some specific point in time. For example, if you tell a
868	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()	1107	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
869	+ 10.>) and then reset your system clock to the last year, then it will	1108	+ 10.>) and then reset your system clock to the last year, then it will
870	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	1109	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
871	roughly 10 seconds later and of course not if you reset your system time	1110	roughly 10 seconds later).
872	again).
873		1111
874	They can also be used to implement vastly more complex timers, such as	1112	They can also be used to implement vastly more complex timers, such as
875	triggering an event on eahc midnight, local time.	1113	triggering an event on each midnight, local time or other, complicated,
		1114	rules.
876		1115
877	As with timers, the callback is guarenteed to be invoked only when the	1116	As with timers, the callback is guarenteed to be invoked only when the
878	time (C<at>) has been passed, but if multiple periodic timers become ready	1117	time (C<at>) has been passed, but if multiple periodic timers become ready
879	during the same loop iteration then order of execution is undefined.	1118	during the same loop iteration then order of execution is undefined.
880		1119
		1120	=head3 Watcher-Specific Functions and Data Members
		1121
881	=over 4	1122	=over 4
882		1123
883	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1124	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
884		1125
885	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1126	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
…		…
887	Lots of arguments, lets sort it out... There are basically three modes of	1128	Lots of arguments, lets sort it out... There are basically three modes of
888	operation, and we will explain them from simplest to complex:	1129	operation, and we will explain them from simplest to complex:
889		1130
890	=over 4	1131	=over 4
891		1132
892	=item * absolute timer (interval = reschedule_cb = 0)	1133	=item * absolute timer (at = time, interval = reschedule_cb = 0)
893		1134
894	In this configuration the watcher triggers an event at the wallclock time	1135	In this configuration the watcher triggers an event at the wallclock time
895	C<at> and doesn't repeat. It will not adjust when a time jump occurs,	1136	C<at> and doesn't repeat. It will not adjust when a time jump occurs,
896	that is, if it is to be run at January 1st 2011 then it will run when the	1137	that is, if it is to be run at January 1st 2011 then it will run when the
897	system time reaches or surpasses this time.	1138	system time reaches or surpasses this time.
898		1139
899	=item * non-repeating interval timer (interval > 0, reschedule_cb = 0)	1140	=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
900		1141
901	In this mode the watcher will always be scheduled to time out at the next	1142	In this mode the watcher will always be scheduled to time out at the next
902	C<at + N * interval> time (for some integer N) and then repeat, regardless	1143	C<at + N * interval> time (for some integer N, which can also be negative)
903	of any time jumps.	1144	and then repeat, regardless of any time jumps.
904		1145
905	This can be used to create timers that do not drift with respect to system	1146	This can be used to create timers that do not drift with respect to system
906	time:	1147	time:
907		1148
908	ev_periodic_set (&periodic, 0., 3600., 0);	1149	ev_periodic_set (&periodic, 0., 3600., 0);
…		…
914		1155
915	Another way to think about it (for the mathematically inclined) is that	1156	Another way to think about it (for the mathematically inclined) is that
916	C<ev_periodic> will try to run the callback in this mode at the next possible	1157	C<ev_periodic> will try to run the callback in this mode at the next possible
917	time where C<time = at (mod interval)>, regardless of any time jumps.	1158	time where C<time = at (mod interval)>, regardless of any time jumps.
918		1159
		1160	For numerical stability it is preferable that the C<at> value is near
		1161	C<ev_now ()> (the current time), but there is no range requirement for
		1162	this value.
		1163
919	=item * manual reschedule mode (reschedule_cb = callback)	1164	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
920		1165
921	In this mode the values for C<interval> and C<at> are both being	1166	In this mode the values for C<interval> and C<at> are both being
922	ignored. Instead, each time the periodic watcher gets scheduled, the	1167	ignored. Instead, each time the periodic watcher gets scheduled, the
923	reschedule callback will be called with the watcher as first, and the	1168	reschedule callback will be called with the watcher as first, and the
924	current time as second argument.	1169	current time as second argument.
925		1170
926	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1171	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
927	ever, or make any event loop modifications>. If you need to stop it,	1172	ever, or make any event loop modifications>. If you need to stop it,
928	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by	1173	return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
929	starting a prepare watcher).	1174	starting an C<ev_prepare> watcher, which is legal).
930		1175
931	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,	1176	Its prototype is C<ev_tstamp (reschedule_cb)(struct ev_periodic w,
932	ev_tstamp now)>, e.g.:	1177	ev_tstamp now)>, e.g.:
933		1178
934	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1179	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
…		…
957	Simply stops and restarts the periodic watcher again. This is only useful	1202	Simply stops and restarts the periodic watcher again. This is only useful
958	when you changed some parameters or the reschedule callback would return	1203	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	1204	a different time than the last time it was called (e.g. in a crond like
960	program when the crontabs have changed).	1205	program when the crontabs have changed).
961		1206
		1207	=item ev_tstamp offset [read-write]
		1208
		1209	When repeating, this contains the offset value, otherwise this is the
		1210	absolute point in time (the C<at> value passed to C<ev_periodic_set>).
		1211
		1212	Can be modified any time, but changes only take effect when the periodic
		1213	timer fires or C<ev_periodic_again> is being called.
		1214
		1215	=item ev_tstamp interval [read-write]
		1216
		1217	The current interval value. Can be modified any time, but changes only
		1218	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1219	called.
		1220
		1221	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1222
		1223	The current reschedule callback, or C<0>, if this functionality is
		1224	switched off. Can be changed any time, but changes only take effect when
		1225	the periodic timer fires or C<ev_periodic_again> is being called.
		1226
		1227	=item ev_tstamp at [read-only]
		1228
		1229	When active, contains the absolute time that the watcher is supposed to
		1230	trigger next.
		1231
962	=back	1232	=back
963		1233
964	Example: call a callback every hour, or, more precisely, whenever the	1234	Example: Call a callback every hour, or, more precisely, whenever the
965	system clock is divisible by 3600. The callback invocation times have	1235	system clock is divisible by 3600. The callback invocation times have
966	potentially a lot of jittering, but good long-term stability.	1236	potentially a lot of jittering, but good long-term stability.
967		1237
968	static void	1238	static void
969	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1239	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
973		1243
974	struct ev_periodic hourly_tick;	1244	struct ev_periodic hourly_tick;
975	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1245	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
976	ev_periodic_start (loop, &hourly_tick);	1246	ev_periodic_start (loop, &hourly_tick);
977		1247
978	Example: the same as above, but use a reschedule callback to do it:	1248	Example: The same as above, but use a reschedule callback to do it:
979		1249
980	#include <math.h>	1250	#include <math.h>
981		1251
982	static ev_tstamp	1252	static ev_tstamp
983	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1253	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
985	return fmod (now, 3600.) + 3600.;	1255	return fmod (now, 3600.) + 3600.;
986	}	1256	}
987		1257
988	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1258	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
989		1259
990	Example: call a callback every hour, starting now:	1260	Example: Call a callback every hour, starting now:
991		1261
992	struct ev_periodic hourly_tick;	1262	struct ev_periodic hourly_tick;
993	ev_periodic_init (&hourly_tick, clock_cb,	1263	ev_periodic_init (&hourly_tick, clock_cb,
994	fmod (ev_now (loop), 3600.), 3600., 0);	1264	fmod (ev_now (loop), 3600.), 3600., 0);
995	ev_periodic_start (loop, &hourly_tick);	1265	ev_periodic_start (loop, &hourly_tick);
…		…
1007	with the kernel (thus it coexists with your own signal handlers as long	1277	with the kernel (thus it coexists with your own signal handlers as long
1008	as you don't register any with libev). Similarly, when the last signal	1278	as you don't register any with libev). Similarly, when the last signal
1009	watcher for a signal is stopped libev will reset the signal handler to	1279	watcher for a signal is stopped libev will reset the signal handler to
1010	SIG_DFL (regardless of what it was set to before).	1280	SIG_DFL (regardless of what it was set to before).
1011		1281
		1282	=head3 Watcher-Specific Functions and Data Members
		1283
1012	=over 4	1284	=over 4
1013		1285
1014	=item ev_signal_init (ev_signal *, callback, int signum)	1286	=item ev_signal_init (ev_signal *, callback, int signum)
1015		1287
1016	=item ev_signal_set (ev_signal *, int signum)	1288	=item ev_signal_set (ev_signal *, int signum)
1017		1289
1018	Configures the watcher to trigger on the given signal number (usually one	1290	Configures the watcher to trigger on the given signal number (usually one
1019	of the C<SIGxxx> constants).	1291	of the C<SIGxxx> constants).
1020		1292
		1293	=item int signum [read-only]
		1294
		1295	The signal the watcher watches out for.
		1296
1021	=back	1297	=back
1022		1298
1023		1299
1024	=head2 C<ev_child> - watch out for process status changes	1300	=head2 C<ev_child> - watch out for process status changes
1025		1301
1026	Child watchers trigger when your process receives a SIGCHLD in response to	1302	Child watchers trigger when your process receives a SIGCHLD in response to
1027	some child status changes (most typically when a child of yours dies).	1303	some child status changes (most typically when a child of yours dies).
		1304
		1305	=head3 Watcher-Specific Functions and Data Members
1028		1306
1029	=over 4	1307	=over 4
1030		1308
1031	=item ev_child_init (ev_child *, callback, int pid)	1309	=item ev_child_init (ev_child *, callback, int pid)
1032		1310
…		…
1037	at the C<rstatus> member of the C<ev_child> watcher structure to see	1315	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	1316	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	1317	C<waitpid> documentation). The C<rpid> member contains the pid of the
1040	process causing the status change.	1318	process causing the status change.
1041		1319
		1320	=item int pid [read-only]
		1321
		1322	The process id this watcher watches out for, or C<0>, meaning any process id.
		1323
		1324	=item int rpid [read-write]
		1325
		1326	The process id that detected a status change.
		1327
		1328	=item int rstatus [read-write]
		1329
		1330	The process exit/trace status caused by C<rpid> (see your systems
		1331	C<waitpid> and C<sys/wait.h> documentation for details).
		1332
1042	=back	1333	=back
1043		1334
1044	Example: try to exit cleanly on SIGINT and SIGTERM.	1335	Example: Try to exit cleanly on SIGINT and SIGTERM.
1045		1336
1046	static void	1337	static void
1047	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1338	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1048	{	1339	{
1049	ev_unloop (loop, EVUNLOOP_ALL);	1340	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1052	struct ev_signal signal_watcher;	1343	struct ev_signal signal_watcher;
1053	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1344	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1054	ev_signal_start (loop, &sigint_cb);	1345	ev_signal_start (loop, &sigint_cb);
1055		1346
1056		1347
		1348	=head2 C<ev_stat> - did the file attributes just change?
		1349
		1350	This watches a filesystem path for attribute changes. That is, it calls
		1351	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1352	compared to the last time, invoking the callback if it did.
		1353
		1354	The path does not need to exist: changing from "path exists" to "path does
		1355	not exist" is a status change like any other. The condition "path does
		1356	not exist" is signified by the C<st_nlink> field being zero (which is
		1357	otherwise always forced to be at least one) and all the other fields of
		1358	the stat buffer having unspecified contents.
		1359
		1360	The path I<should> be absolute and I<must not> end in a slash. If it is
		1361	relative and your working directory changes, the behaviour is undefined.
		1362
		1363	Since there is no standard to do this, the portable implementation simply
		1364	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1365	can specify a recommended polling interval for this case. If you specify
		1366	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1367	unspecified default> value will be used (which you can expect to be around
		1368	five seconds, although this might change dynamically). Libev will also
		1369	impose a minimum interval which is currently around C<0.1>, but thats
		1370	usually overkill.
		1371
		1372	This watcher type is not meant for massive numbers of stat watchers,
		1373	as even with OS-supported change notifications, this can be
		1374	resource-intensive.
		1375
		1376	At the time of this writing, only the Linux inotify interface is
		1377	implemented (implementing kqueue support is left as an exercise for the
		1378	reader). Inotify will be used to give hints only and should not change the
		1379	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1380	to fall back to regular polling again even with inotify, but changes are
		1381	usually detected immediately, and if the file exists there will be no
		1382	polling.
		1383
		1384	=head3 Watcher-Specific Functions and Data Members
		1385
		1386	=over 4
		1387
		1388	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1389
		1390	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1391
		1392	Configures the watcher to wait for status changes of the given
		1393	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1394	be detected and should normally be specified as C<0> to let libev choose
		1395	a suitable value. The memory pointed to by C<path> must point to the same
		1396	path for as long as the watcher is active.
		1397
		1398	The callback will be receive C<EV_STAT> when a change was detected,
		1399	relative to the attributes at the time the watcher was started (or the
		1400	last change was detected).
		1401
		1402	=item ev_stat_stat (ev_stat *)
		1403
		1404	Updates the stat buffer immediately with new values. If you change the
		1405	watched path in your callback, you could call this fucntion to avoid
		1406	detecting this change (while introducing a race condition). Can also be
		1407	useful simply to find out the new values.
		1408
		1409	=item ev_statdata attr [read-only]
		1410
		1411	The most-recently detected attributes of the file. Although the type is of
		1412	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1413	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1414	was some error while C<stat>ing the file.
		1415
		1416	=item ev_statdata prev [read-only]
		1417
		1418	The previous attributes of the file. The callback gets invoked whenever
		1419	C<prev> != C<attr>.
		1420
		1421	=item ev_tstamp interval [read-only]
		1422
		1423	The specified interval.
		1424
		1425	=item const char *path [read-only]
		1426
		1427	The filesystem path that is being watched.
		1428
		1429	=back
		1430
		1431	Example: Watch C</etc/passwd> for attribute changes.
		1432
		1433	static void
		1434	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1435	{
		1436	/* /etc/passwd changed in some way */
		1437	if (w->attr.st_nlink)
		1438	{
		1439	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1440	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1441	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1442	}
		1443	else
		1444	/* you shalt not abuse printf for puts */
		1445	puts ("wow, /etc/passwd is not there, expect problems. "
		1446	"if this is windows, they already arrived\n");
		1447	}
		1448
		1449	...
		1450	ev_stat passwd;
		1451
		1452	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1453	ev_stat_start (loop, &passwd);
		1454
		1455
1057	=head2 C<ev_idle> - when you've got nothing better to do...	1456	=head2 C<ev_idle> - when you've got nothing better to do...
1058		1457
1059	Idle watchers trigger events when there are no other events are pending	1458	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	1459	priority are pending (prepare, check and other idle watchers do not
1061	as your process is busy handling sockets or timeouts (or even signals,	1460	count).
1062	imagine) it will not be triggered. But when your process is idle all idle	1461
1063	watchers are being called again and again, once per event loop iteration -	1462	That is, as long as your process is busy handling sockets or timeouts
		1463	(or even signals, imagine) of the same or higher priority it will not be
		1464	triggered. But when your process is idle (or only lower-priority watchers
		1465	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	1466	iteration - until stopped, that is, or your process receives more events
1065	busy.	1467	and becomes busy again with higher priority stuff.
1066		1468
1067	The most noteworthy effect is that as long as any idle watchers are	1469	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.	1470	active, the process will not block when waiting for new events.
1069		1471
1070	Apart from keeping your process non-blocking (which is a useful	1472	Apart from keeping your process non-blocking (which is a useful
1071	effect on its own sometimes), idle watchers are a good place to do	1473	effect on its own sometimes), idle watchers are a good place to do
1072	"pseudo-background processing", or delay processing stuff to after the	1474	"pseudo-background processing", or delay processing stuff to after the
1073	event loop has handled all outstanding events.	1475	event loop has handled all outstanding events.
1074		1476
		1477	=head3 Watcher-Specific Functions and Data Members
		1478
1075	=over 4	1479	=over 4
1076		1480
1077	=item ev_idle_init (ev_signal *, callback)	1481	=item ev_idle_init (ev_signal *, callback)
1078		1482
1079	Initialises and configures the idle watcher - it has no parameters of any	1483	Initialises and configures the idle watcher - it has no parameters of any
1080	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1484	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1081	believe me.	1485	believe me.
1082		1486
1083	=back	1487	=back
1084		1488
1085	Example: dynamically allocate an C<ev_idle>, start it, and in the	1489	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1086	callback, free it. Alos, use no error checking, as usual.	1490	callback, free it. Also, use no error checking, as usual.
1087		1491
1088	static void	1492	static void
1089	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1493	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1090	{	1494	{
1091	free (w);	1495	free (w);
…		…
1136	with priority higher than or equal to the event loop and one coroutine	1540	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	1541	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	1542	loop from blocking if lower-priority coroutines are active, thus mapping
1139	low-priority coroutines to idle/background tasks).	1543	low-priority coroutines to idle/background tasks).
1140		1544
		1545	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1546	priority, to ensure that they are being run before any other watchers
		1547	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1548	too) should not activate ("feed") events into libev. While libev fully
		1549	supports this, they will be called before other C<ev_check> watchers did
		1550	their job. As C<ev_check> watchers are often used to embed other event
		1551	loops those other event loops might be in an unusable state until their
		1552	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1553	others).
		1554
		1555	=head3 Watcher-Specific Functions and Data Members
		1556
1141	=over 4	1557	=over 4
1142		1558
1143	=item ev_prepare_init (ev_prepare *, callback)	1559	=item ev_prepare_init (ev_prepare *, callback)
1144		1560
1145	=item ev_check_init (ev_check *, callback)	1561	=item ev_check_init (ev_check *, callback)
…		…
1148	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1564	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.	1565	macros, but using them is utterly, utterly and completely pointless.
1150		1566
1151	=back	1567	=back
1152		1568
1153	Example: To include a library such as adns, you would add IO watchers	1569	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	1570	into libev. Here are some ideas on how to include libadns into libev
		1571	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1572	use for an actually working example. Another Perl module named C<EV::Glib>
		1573	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1574	into the Glib event loop).
		1575
		1576	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	1577	and in a check watcher, destroy them and call into libadns. What follows
1156	pseudo-code only of course:	1578	is pseudo-code only of course. This requires you to either use a low
		1579	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1580	the callbacks for the IO/timeout watchers might not have been called yet.
1157		1581
1158	static ev_io iow [nfd];	1582	static ev_io iow [nfd];
1159	static ev_timer tw;	1583	static ev_timer tw;
1160		1584
1161	static void	1585	static void
1162	io_cb (ev_loop loop, ev_io w, int revents)	1586	io_cb (ev_loop loop, ev_io w, int revents)
1163	{	1587	{
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	}	1588	}
1170		1589
1171	// create io watchers for each fd and a timer before blocking	1590	// create io watchers for each fd and a timer before blocking
1172	static void	1591	static void
1173	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1592	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
1174	{	1593	{
1175	int timeout = 3600000;truct pollfd fds [nfd];	1594	int timeout = 3600000;
		1595	struct pollfd fds [nfd];
1176	// actual code will need to loop here and realloc etc.	1596	// actual code will need to loop here and realloc etc.
1177	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	1597	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1178		1598
1179	/* the callback is illegal, but won't be called as we stop during check */	1599	/* the callback is illegal, but won't be called as we stop during check */
1180	ev_timer_init (&tw, 0, timeout * 1e-3);	1600	ev_timer_init (&tw, 0, timeout * 1e-3);
1181	ev_timer_start (loop, &tw);	1601	ev_timer_start (loop, &tw);
1182		1602
1183	// create on ev_io per pollfd	1603	// create one ev_io per pollfd
1184	for (int i = 0; i < nfd; ++i)	1604	for (int i = 0; i < nfd; ++i)
1185	{	1605	{
1186	ev_io_init (iow + i, io_cb, fds [i].fd,	1606	ev_io_init (iow + i, io_cb, fds [i].fd,
1187	((fds [i].events & POLLIN ? EV_READ : 0)	1607	((fds [i].events & POLLIN ? EV_READ : 0)
1188	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1608	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1189		1609
1190	fds [i].revents = 0;	1610	fds [i].revents = 0;
1191	iow [i].data = fds + i;
1192	ev_io_start (loop, iow + i);	1611	ev_io_start (loop, iow + i);
1193	}	1612	}
1194	}	1613	}
1195		1614
1196	// stop all watchers after blocking	1615	// stop all watchers after blocking
…		…
1198	adns_check_cb (ev_loop loop, ev_check w, int revents)	1617	adns_check_cb (ev_loop loop, ev_check w, int revents)
1199	{	1618	{
1200	ev_timer_stop (loop, &tw);	1619	ev_timer_stop (loop, &tw);
1201		1620
1202	for (int i = 0; i < nfd; ++i)	1621	for (int i = 0; i < nfd; ++i)
		1622	{
		1623	// set the relevant poll flags
		1624	// could also call adns_processreadable etc. here
		1625	struct pollfd *fd = fds + i;
		1626	int revents = ev_clear_pending (iow + i);
		1627	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1628	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1629
		1630	// now stop the watcher
1203	ev_io_stop (loop, iow + i);	1631	ev_io_stop (loop, iow + i);
		1632	}
1204		1633
1205	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1634	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1635	}
		1636
		1637	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1638	in the prepare watcher and would dispose of the check watcher.
		1639
		1640	Method 3: If the module to be embedded supports explicit event
		1641	notification (adns does), you can also make use of the actual watcher
		1642	callbacks, and only destroy/create the watchers in the prepare watcher.
		1643
		1644	static void
		1645	timer_cb (EV_P_ ev_timer *w, int revents)
		1646	{
		1647	adns_state ads = (adns_state)w->data;
		1648	update_now (EV_A);
		1649
		1650	adns_processtimeouts (ads, &tv_now);
		1651	}
		1652
		1653	static void
		1654	io_cb (EV_P_ ev_io *w, int revents)
		1655	{
		1656	adns_state ads = (adns_state)w->data;
		1657	update_now (EV_A);
		1658
		1659	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1660	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1661	}
		1662
		1663	// do not ever call adns_afterpoll
		1664
		1665	Method 4: Do not use a prepare or check watcher because the module you
		1666	want to embed is too inflexible to support it. Instead, youc na override
		1667	their poll function. The drawback with this solution is that the main
		1668	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1669	this.
		1670
		1671	static gint
		1672	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1673	{
		1674	int got_events = 0;
		1675
		1676	for (n = 0; n < nfds; ++n)
		1677	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1678
		1679	if (timeout >= 0)
		1680	// create/start timer
		1681
		1682	// poll
		1683	ev_loop (EV_A_ 0);
		1684
		1685	// stop timer again
		1686	if (timeout >= 0)
		1687	ev_timer_stop (EV_A_ &to);
		1688
		1689	// stop io watchers again - their callbacks should have set
		1690	for (n = 0; n < nfds; ++n)
		1691	ev_io_stop (EV_A_ iow [n]);
		1692
		1693	return got_events;
1206	}	1694	}
1207		1695
1208		1696
1209	=head2 C<ev_embed> - when one backend isn't enough...	1697	=head2 C<ev_embed> - when one backend isn't enough...
1210		1698
…		…
1274	ev_embed_start (loop_hi, &embed);	1762	ev_embed_start (loop_hi, &embed);
1275	}	1763	}
1276	else	1764	else
1277	loop_lo = loop_hi;	1765	loop_lo = loop_hi;
1278		1766
		1767	=head3 Watcher-Specific Functions and Data Members
		1768
1279	=over 4	1769	=over 4
1280		1770
1281	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	1771	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
1282		1772
1283	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)	1773	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
…		…
1292		1782
1293	Make a single, non-blocking sweep over the embedded loop. This works	1783	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	1784	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1295	apropriate way for embedded loops.	1785	apropriate way for embedded loops.
1296		1786
		1787	=item struct ev_loop *loop [read-only]
		1788
		1789	The embedded event loop.
		1790
		1791	=back
		1792
		1793
		1794	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1795
		1796	Fork watchers are called when a C<fork ()> was detected (usually because
		1797	whoever is a good citizen cared to tell libev about it by calling
		1798	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1799	event loop blocks next and before C<ev_check> watchers are being called,
		1800	and only in the child after the fork. If whoever good citizen calling
		1801	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1802	handlers will be invoked, too, of course.
		1803
		1804	=head3 Watcher-Specific Functions and Data Members
		1805
		1806	=over 4
		1807
		1808	=item ev_fork_init (ev_signal *, callback)
		1809
		1810	Initialises and configures the fork watcher - it has no parameters of any
		1811	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1812	believe me.
		1813
1297	=back	1814	=back
1298		1815
1299		1816
1300	=head1 OTHER FUNCTIONS	1817	=head1 OTHER FUNCTIONS
1301		1818
…		…
1389		1906
1390	To use it,	1907	To use it,
1391		1908
1392	#include <ev++.h>	1909	#include <ev++.h>
1393		1910
1394	(it is not installed by default). This automatically includes F<ev.h>	1911	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	1912	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.	1913	put into the C<ev> namespace. It should support all the same embedding
		1914	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1397		1915
1398	It should support all the same embedding options as F<ev.h>, most notably	1916	Care has been taken to keep the overhead low. The only data member the C++
1399	C<EV_MULTIPLICITY>.	1917	classes add (compared to plain C-style watchers) is the event loop pointer
		1918	that the watcher is associated with (or no additional members at all if
		1919	you disable C<EV_MULTIPLICITY> when embedding libev).
		1920
		1921	Currently, functions, and static and non-static member functions can be
		1922	used as callbacks. Other types should be easy to add as long as they only
		1923	need one additional pointer for context. If you need support for other
		1924	types of functors please contact the author (preferably after implementing
		1925	it).
1400		1926
1401	Here is a list of things available in the C<ev> namespace:	1927	Here is a list of things available in the C<ev> namespace:
1402		1928
1403	=over 4	1929	=over 4
1404		1930
…		…
1420		1946
1421	All of those classes have these methods:	1947	All of those classes have these methods:
1422		1948
1423	=over 4	1949	=over 4
1424		1950
1425	=item ev::TYPE::TYPE (object , object::method )	1951	=item ev::TYPE::TYPE ()
1426		1952
1427	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1953	=item ev::TYPE::TYPE (struct ev_loop *)
1428		1954
1429	=item ev::TYPE::~TYPE	1955	=item ev::TYPE::~TYPE
1430		1956
1431	The constructor takes a pointer to an object and a method pointer to	1957	The constructor (optionally) takes an event loop to associate the watcher
1432	the event handler callback to call in this class. The constructor calls	1958	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	1959
1434	before starting it. If you do not specify a loop then the constructor	1960	The constructor calls C<ev_init> for you, which means you have to call the
1435	automatically associates the default loop with this watcher.	1961	C<set> method before starting it.
		1962
		1963	It will not set a callback, however: You have to call the templated C<set>
		1964	method to set a callback before you can start the watcher.
		1965
		1966	(The reason why you have to use a method is a limitation in C++ which does
		1967	not allow explicit template arguments for constructors).
1436		1968
1437	The destructor automatically stops the watcher if it is active.	1969	The destructor automatically stops the watcher if it is active.
		1970
		1971	=item w->set<class, &class::method> (object *)
		1972
		1973	This method sets the callback method to call. The method has to have a
		1974	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1975	first argument and the C<revents> as second. The object must be given as
		1976	parameter and is stored in the C<data> member of the watcher.
		1977
		1978	This method synthesizes efficient thunking code to call your method from
		1979	the C callback that libev requires. If your compiler can inline your
		1980	callback (i.e. it is visible to it at the place of the C<set> call and
		1981	your compiler is good :), then the method will be fully inlined into the
		1982	thunking function, making it as fast as a direct C callback.
		1983
		1984	Example: simple class declaration and watcher initialisation
		1985
		1986	struct myclass
		1987	{
		1988	void io_cb (ev::io &w, int revents) { }
		1989	}
		1990
		1991	myclass obj;
		1992	ev::io iow;
		1993	iow.set <myclass, &myclass::io_cb> (&obj);
		1994
		1995	=item w->set<function> (void *data = 0)
		1996
		1997	Also sets a callback, but uses a static method or plain function as
		1998	callback. The optional C<data> argument will be stored in the watcher's
		1999	C<data> member and is free for you to use.
		2000
		2001	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		2002
		2003	See the method-C<set> above for more details.
		2004
		2005	Example:
		2006
		2007	static void io_cb (ev::io &w, int revents) { }
		2008	iow.set <io_cb> ();
1438		2009
1439	=item w->set (struct ev_loop *)	2010	=item w->set (struct ev_loop *)
1440		2011
1441	Associates a different C<struct ev_loop> with this watcher. You can only	2012	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).	2013	do this when the watcher is inactive (and not pending either).
1443		2014
1444	=item w->set ([args])	2015	=item w->set ([args])
1445		2016
1446	Basically the same as C<ev_TYPE_set>, with the same args. Must be	2017	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	2018	called at least once. Unlike the C counterpart, an active watcher gets
1448	automatically stopped and restarted.	2019	automatically stopped and restarted when reconfiguring it with this
		2020	method.
1449		2021
1450	=item w->start ()	2022	=item w->start ()
1451		2023
1452	Starts the watcher. Note that there is no C<loop> argument as the	2024	Starts the watcher. Note that there is no C<loop> argument, as the
1453	constructor already takes the loop.	2025	constructor already stores the event loop.
1454		2026
1455	=item w->stop ()	2027	=item w->stop ()
1456		2028
1457	Stops the watcher if it is active. Again, no C<loop> argument.	2029	Stops the watcher if it is active. Again, no C<loop> argument.
1458		2030
1459	=item w->again () C<ev::timer>, C<ev::periodic> only	2031	=item w->again () (C<ev::timer>, C<ev::periodic> only)
1460		2032
1461	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding	2033	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1462	C<ev_TYPE_again> function.	2034	C<ev_TYPE_again> function.
1463		2035
1464	=item w->sweep () C<ev::embed> only	2036	=item w->sweep () (C<ev::embed> only)
1465		2037
1466	Invokes C<ev_embed_sweep>.	2038	Invokes C<ev_embed_sweep>.
		2039
		2040	=item w->update () (C<ev::stat> only)
		2041
		2042	Invokes C<ev_stat_stat>.
1467		2043
1468	=back	2044	=back
1469		2045
1470	=back	2046	=back
1471		2047
…		…
1479		2055
1480	myclass ();	2056	myclass ();
1481	}	2057	}
1482		2058
1483	myclass::myclass (int fd)	2059	myclass::myclass (int fd)
1484	: io (this, &myclass::io_cb),
1485	idle (this, &myclass::idle_cb)
1486	{	2060	{
		2061	io .set <myclass, &myclass::io_cb > (this);
		2062	idle.set <myclass, &myclass::idle_cb> (this);
		2063
1487	io.start (fd, ev::READ);	2064	io.start (fd, ev::READ);
1488	}	2065	}
		2066
		2067
		2068	=head1 MACRO MAGIC
		2069
		2070	Libev can be compiled with a variety of options, the most fundamantal
		2071	of which is C<EV_MULTIPLICITY>. This option determines whether (most)
		2072	functions and callbacks have an initial C<struct ev_loop *> argument.
		2073
		2074	To make it easier to write programs that cope with either variant, the
		2075	following macros are defined:
		2076
		2077	=over 4
		2078
		2079	=item C<EV_A>, C<EV_A_>
		2080
		2081	This provides the loop I<argument> for functions, if one is required ("ev
		2082	loop argument"). The C<EV_A> form is used when this is the sole argument,
		2083	C<EV_A_> is used when other arguments are following. Example:
		2084
		2085	ev_unref (EV_A);
		2086	ev_timer_add (EV_A_ watcher);
		2087	ev_loop (EV_A_ 0);
		2088
		2089	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		2090	which is often provided by the following macro.
		2091
		2092	=item C<EV_P>, C<EV_P_>
		2093
		2094	This provides the loop I<parameter> for functions, if one is required ("ev
		2095	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		2096	C<EV_P_> is used when other parameters are following. Example:
		2097
		2098	// this is how ev_unref is being declared
		2099	static void ev_unref (EV_P);
		2100
		2101	// this is how you can declare your typical callback
		2102	static void cb (EV_P_ ev_timer *w, int revents)
		2103
		2104	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		2105	suitable for use with C<EV_A>.
		2106
		2107	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		2108
		2109	Similar to the other two macros, this gives you the value of the default
		2110	loop, if multiple loops are supported ("ev loop default").
		2111
		2112	=back
		2113
		2114	Example: Declare and initialise a check watcher, utilising the above
		2115	macros so it will work regardless of whether multiple loops are supported
		2116	or not.
		2117
		2118	static void
		2119	check_cb (EV_P_ ev_timer *w, int revents)
		2120	{
		2121	ev_check_stop (EV_A_ w);
		2122	}
		2123
		2124	ev_check check;
		2125	ev_check_init (&check, check_cb);
		2126	ev_check_start (EV_DEFAULT_ &check);
		2127	ev_loop (EV_DEFAULT_ 0);
1489		2128
1490	=head1 EMBEDDING	2129	=head1 EMBEDDING
1491		2130
1492	Libev can (and often is) directly embedded into host	2131	Libev can (and often is) directly embedded into host
1493	applications. Examples of applications that embed it include the Deliantra	2132	applications. Examples of applications that embed it include the Deliantra
…		…
1533	ev_vars.h	2172	ev_vars.h
1534	ev_wrap.h	2173	ev_wrap.h
1535		2174
1536	ev_win32.c required on win32 platforms only	2175	ev_win32.c required on win32 platforms only
1537		2176
1538	ev_select.c only when select backend is enabled (which is by default)	2177	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)	2178	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)	2179	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)	2180	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)	2181	ev_port.c only when the solaris port backend is enabled (disabled by default)
1543		2182
…		…
1668		2307
1669	=item EV_USE_DEVPOLL	2308	=item EV_USE_DEVPOLL
1670		2309
1671	reserved for future expansion, works like the USE symbols above.	2310	reserved for future expansion, works like the USE symbols above.
1672		2311
		2312	=item EV_USE_INOTIFY
		2313
		2314	If defined to be C<1>, libev will compile in support for the Linux inotify
		2315	interface to speed up C<ev_stat> watchers. Its actual availability will
		2316	be detected at runtime.
		2317
1673	=item EV_H	2318	=item EV_H
1674		2319
1675	The name of the F<ev.h> header file used to include it. The default if	2320	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	2321	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.	2322	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	2345	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	2346	additional independent event loops. Otherwise there will be no support
1702	for multiple event loops and there is no first event loop pointer	2347	for multiple event loops and there is no first event loop pointer
1703	argument. Instead, all functions act on the single default loop.	2348	argument. Instead, all functions act on the single default loop.
1704		2349
		2350	=item EV_MINPRI
		2351
		2352	=item EV_MAXPRI
		2353
		2354	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2355	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2356	provide for more priorities by overriding those symbols (usually defined
		2357	to be C<-2> and C<2>, respectively).
		2358
		2359	When doing priority-based operations, libev usually has to linearly search
		2360	all the priorities, so having many of them (hundreds) uses a lot of space
		2361	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2362	fine.
		2363
		2364	If your embedding app does not need any priorities, defining these both to
		2365	C<0> will save some memory and cpu.
		2366
1705	=item EV_PERIODICS	2367	=item EV_PERIODIC_ENABLE
1706		2368
1707	If undefined or defined to be C<1>, then periodic timers are supported,	2369	If undefined or defined to be C<1>, then periodic timers are supported. If
1708	otherwise not. This saves a few kb of code.	2370	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2371	code.
		2372
		2373	=item EV_IDLE_ENABLE
		2374
		2375	If undefined or defined to be C<1>, then idle watchers are supported. If
		2376	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2377	code.
		2378
		2379	=item EV_EMBED_ENABLE
		2380
		2381	If undefined or defined to be C<1>, then embed watchers are supported. If
		2382	defined to be C<0>, then they are not.
		2383
		2384	=item EV_STAT_ENABLE
		2385
		2386	If undefined or defined to be C<1>, then stat watchers are supported. If
		2387	defined to be C<0>, then they are not.
		2388
		2389	=item EV_FORK_ENABLE
		2390
		2391	If undefined or defined to be C<1>, then fork watchers are supported. If
		2392	defined to be C<0>, then they are not.
		2393
		2394	=item EV_MINIMAL
		2395
		2396	If you need to shave off some kilobytes of code at the expense of some
		2397	speed, define this symbol to C<1>. Currently only used for gcc to override
		2398	some inlining decisions, saves roughly 30% codesize of amd64.
		2399
		2400	=item EV_PID_HASHSIZE
		2401
		2402	C<ev_child> watchers use a small hash table to distribute workload by
		2403	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2404	than enough. If you need to manage thousands of children you might want to
		2405	increase this value (I<must> be a power of two).
		2406
		2407	=item EV_INOTIFY_HASHSIZE
		2408
		2409	C<ev_staz> watchers use a small hash table to distribute workload by
		2410	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2411	usually more than enough. If you need to manage thousands of C<ev_stat>
		2412	watchers you might want to increase this value (I<must> be a power of
		2413	two).
1709		2414
1710	=item EV_COMMON	2415	=item EV_COMMON
1711		2416
1712	By default, all watchers have a C<void *data> member. By redefining	2417	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	2418	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	2447	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	2448	will be compiled. It is pretty complex because it provides its own header
1744	file.	2449	file.
1745		2450
1746	The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file	2451	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:	2452	that everybody includes and which overrides some configure choices:
1748		2453
		2454	#define EV_MINIMAL 1
1749	#define EV_USE_POLL 0	2455	#define EV_USE_POLL 0
1750	#define EV_MULTIPLICITY 0	2456	#define EV_MULTIPLICITY 0
1751	#define EV_PERIODICS 0	2457	#define EV_PERIODIC_ENABLE 0
		2458	#define EV_STAT_ENABLE 0
		2459	#define EV_FORK_ENABLE 0
1752	#define EV_CONFIG_H <config.h>	2460	#define EV_CONFIG_H <config.h>
		2461	#define EV_MINPRI 0
		2462	#define EV_MAXPRI 0
1753		2463
1754	#include "ev++.h"	2464	#include "ev++.h"
1755		2465
1756	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2466	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1757		2467
…		…
1763		2473
1764	In this section the complexities of (many of) the algorithms used inside	2474	In this section the complexities of (many of) the algorithms used inside
1765	libev will be explained. For complexity discussions about backends see the	2475	libev will be explained. For complexity discussions about backends see the
1766	documentation for C<ev_default_init>.	2476	documentation for C<ev_default_init>.
1767		2477
		2478	All of the following are about amortised time: If an array needs to be
		2479	extended, libev needs to realloc and move the whole array, but this
		2480	happens asymptotically never with higher number of elements, so O(1) might
		2481	mean it might do a lengthy realloc operation in rare cases, but on average
		2482	it is much faster and asymptotically approaches constant time.
		2483
1768	=over 4	2484	=over 4
1769		2485
1770	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2486	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
1771		2487
		2488	This means that, when you have a watcher that triggers in one hour and
		2489	there are 100 watchers that would trigger before that then inserting will
		2490	have to skip those 100 watchers.
		2491
1772	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2492	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
1773		2493
		2494	That means that for changing a timer costs less than removing/adding them
		2495	as only the relative motion in the event queue has to be paid for.
		2496
1774	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2497	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
1775		2498
		2499	These just add the watcher into an array or at the head of a list.
1776	=item Stopping check/prepare/idle watchers: O(1)	2500	=item Stopping check/prepare/idle watchers: O(1)
1777		2501
1778	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))	2502	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2503
		2504	These watchers are stored in lists then need to be walked to find the
		2505	correct watcher to remove. The lists are usually short (you don't usually
		2506	have many watchers waiting for the same fd or signal).
1779		2507
1780	=item Finding the next timer per loop iteration: O(1)	2508	=item Finding the next timer per loop iteration: O(1)
1781		2509
1782	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2510	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1783		2511
		2512	A change means an I/O watcher gets started or stopped, which requires
		2513	libev to recalculate its status (and possibly tell the kernel).
		2514
1784	=item Activating one watcher: O(1)	2515	=item Activating one watcher: O(1)
1785		2516
		2517	=item Priority handling: O(number_of_priorities)
		2518
		2519	Priorities are implemented by allocating some space for each
		2520	priority. When doing priority-based operations, libev usually has to
		2521	linearly search all the priorities.
		2522
1786	=back	2523	=back
1787		2524
1788		2525
1789	=head1 AUTHOR	2526	=head1 AUTHOR
1790		2527

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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 1.86 by root, Tue Dec 18 01:20:33 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 1.86 by root, Tue Dec 18 01:20:33 2007 UTC