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

Comparing libev/ev.pod (file contents):
Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs.
Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC

…		…
3	libev - a high performance full-featured event loop written in C	3	libev - a high performance full-featured event loop written in C
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	#include <ev.h>	7	#include <ev.h>
		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	}
8		50
9	=head1 DESCRIPTION	51	=head1 DESCRIPTION
10		52
11	Libev is an event loop: you register interest in certain events (such as a	53	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	54	file descriptor being readable or a timeout occuring), and it will manage
…		…
21	details of the event, and then hand it over to libev by I<starting> the	63	details of the event, and then hand it over to libev by I<starting> the
22	watcher.	64	watcher.
23		65
24	=head1 FEATURES	66	=head1 FEATURES
25		67
26	Libev supports select, poll, the linux-specific epoll and the bsd-specific	68	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27	kqueue mechanisms for file descriptor events, relative timers, absolute	69	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28	timers with customised rescheduling, signal events, process status change	70	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29	events (related to SIGCHLD), and event watchers dealing with the event	71	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30	loop mechanism itself (idle, prepare and check watchers). It also is quite	72	with customised rescheduling (C<ev_periodic>), synchronous signals
		73	(C<ev_signal>), process status change events (C<ev_child>), and event
		74	watchers dealing with the event loop mechanism itself (C<ev_idle>,
		75	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
		76	file watchers (C<ev_stat>) and even limited support for fork events
		77	(C<ev_fork>).
		78
		79	It also is quite fast (see this
31	fast (see this L<benchmark\|http://libev.schmorp.de/bench.html> comparing	80	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
32	it to libevent for example).	81	for example).
33		82
34	=head1 CONVENTIONS	83	=head1 CONVENTIONS
35		84
36	Libev is very configurable. In this manual the default configuration	85	Libev is very configurable. In this manual the default configuration will
37	will be described, which supports multiple event loops. For more info	86	be described, which supports multiple event loops. For more info about
38	about various configuration options please have a look at the file	87	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	88	this manual. If libev was configured without support for multiple event
40	support for multiple event loops, then all functions taking an initial	89	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 *>)	90	(which is always of type C<struct ev_loop *>) will not have this argument.
42	will not have this argument.
43		91
44	=head1 TIME REPRESENTATION	92	=head1 TIME REPRESENTATION
45		93
46	Libev represents time as a single floating point number, representing the	94	Libev represents time as a single floating point number, representing the
47	(fractional) number of seconds since the (POSIX) epoch (somewhere near	95	(fractional) number of seconds since the (POSIX) epoch (somewhere near
48	the beginning of 1970, details are complicated, don't ask). This type is	96	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	97	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	98	to the C<double> type in C, and when you need to do any calculations on
51	it, you should treat it as such.	99	it, you should treat it as such.
52		100
53
54	=head1 GLOBAL FUNCTIONS	101	=head1 GLOBAL FUNCTIONS
55		102
56	These functions can be called anytime, even before initialising the	103	These functions can be called anytime, even before initialising the
57	library in any way.	104	library in any way.
58		105
…		…
77	Usually, it's a good idea to terminate if the major versions mismatch,	124	Usually, it's a good idea to terminate if the major versions mismatch,
78	as this indicates an incompatible change. Minor versions are usually	125	as this indicates an incompatible change. Minor versions are usually
79	compatible to older versions, so a larger minor version alone is usually	126	compatible to older versions, so a larger minor version alone is usually
80	not a problem.	127	not a problem.
81		128
82	Example: make sure we haven't accidentally been linked against the wrong	129	Example: Make sure we haven't accidentally been linked against the wrong
83	version:	130	version.
84		131
85	assert (("libev version mismatch",	132	assert (("libev version mismatch",
86	ev_version_major () == EV_VERSION_MAJOR	133	ev_version_major () == EV_VERSION_MAJOR
87	&& ev_version_minor () >= EV_VERSION_MINOR));	134	&& ev_version_minor () >= EV_VERSION_MINOR));
88		135
…		…
118		165
119	See the description of C<ev_embed> watchers for more info.	166	See the description of C<ev_embed> watchers for more info.
120		167
121	=item ev_set_allocator (void (cb)(void *ptr, long size))	168	=item ev_set_allocator (void (cb)(void *ptr, long size))
122		169
123	Sets the allocation function to use (the prototype is similar to the	170	Sets the allocation function to use (the prototype is similar - the
124	realloc C function, the semantics are identical). It is used to allocate	171	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	172	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	173	memory needs to be allocated, the library might abort or take some
127	destructive action. The default is your system realloc function.	174	potentially destructive action. The default is your system realloc
		175	function.
128		176
129	You could override this function in high-availability programs to, say,	177	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,	178	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.	179	or even to sleep a while and retry until some memory is available.
132		180
133	Example: replace the libev allocator with one that waits a bit and then	181	Example: Replace the libev allocator with one that waits a bit and then
134	retries: better than mine).	182	retries).
135		183
136	static void *	184	static void *
137	persistent_realloc (void *ptr, long size)	185	persistent_realloc (void *ptr, size_t size)
138	{	186	{
139	for (;;)	187	for (;;)
140	{	188	{
141	void *newptr = realloc (ptr, size);	189	void *newptr = realloc (ptr, size);
142		190
…		…
158	callback is set, then libev will expect it to remedy the sitution, no	206	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	207	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	208	requested operation, or, if the condition doesn't go away, do bad stuff
161	(such as abort).	209	(such as abort).
162		210
163	Example: do the same thing as libev does internally:	211	Example: This is basically the same thing that libev does internally, too.
164		212
165	static void	213	static void
166	fatal_error (const char *msg)	214	fatal_error (const char *msg)
167	{	215	{
168	perror (msg);	216	perror (msg);
…		…
218	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will	266	C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219	override the flags completely if it is found in the environment. This is	267	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	268	useful to try out specific backends to test their performance, or to work
221	around bugs.	269	around bugs.
222		270
		271	=item C<EVFLAG_FORKCHECK>
		272
		273	Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
		274	a fork, you can also make libev check for a fork in each iteration by
		275	enabling this flag.
		276
		277	This works by calling C<getpid ()> on every iteration of the loop,
		278	and thus this might slow down your event loop if you do a lot of loop
		279	iterations and little real work, but is usually not noticable (on my
		280	Linux system for example, C<getpid> is actually a simple 5-insn sequence
		281	without a syscall and thus I<very> fast, but my Linux system also has
		282	C<pthread_atfork> which is even faster).
		283
		284	The big advantage of this flag is that you can forget about fork (and
		285	forget about forgetting to tell libev about forking) when you use this
		286	flag.
		287
		288	This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
		289	environment variable.
		290
223	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	291	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224		292
225	This is your standard select(2) backend. Not I<completely> standard, as	293	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,	294	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	295	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	382	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	383	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	384	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).	385	undefined behaviour (or a failed assertion if assertions are enabled).
318		386
319	Example: try to create a event loop that uses epoll and nothing else.	387	Example: Try to create a event loop that uses epoll and nothing else.
320		388
321	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);	389	struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL \| EVFLAG_NOENV);
322	if (!epoller)	390	if (!epoller)
323	fatal ("no epoll found here, maybe it hides under your chair");	391	fatal ("no epoll found here, maybe it hides under your chair");
324		392
…		…
423	Signals and child watchers are implemented as I/O watchers, and will	491	Signals and child watchers are implemented as I/O watchers, and will
424	be handled here by queueing them when their watcher gets executed.	492	be handled here by queueing them when their watcher gets executed.
425	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK	493	- If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426	were used, return, otherwise continue with step *.	494	were used, return, otherwise continue with step *.
427		495
428	Example: queue some jobs and then loop until no events are outsanding	496	Example: Queue some jobs and then loop until no events are outsanding
429	anymore.	497	anymore.
430		498
431	... queue jobs here, make sure they register event watchers as long	499	... 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..)	500	... as they still have work to do (even an idle watcher will do..)
433	ev_loop (my_loop, 0);	501	ev_loop (my_loop, 0);
…		…
453	visible to the libev user and should not keep C<ev_loop> from exiting if	521	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	522	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	523	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>.	524	libraries. Just remember to I<unref after start> and I<ref before stop>.
457		525
458	Example: create a signal watcher, but keep it from keeping C<ev_loop>	526	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459	running when nothing else is active.	527	running when nothing else is active.
460		528
461	struct dv_signal exitsig;	529	struct ev_signal exitsig;
462	ev_signal_init (&exitsig, sig_cb, SIGINT);	530	ev_signal_init (&exitsig, sig_cb, SIGINT);
463	ev_signal_start (myloop, &exitsig);	531	ev_signal_start (loop, &exitsig);
464	evf_unref (myloop);	532	evf_unref (loop);
465		533
466	Example: for some weird reason, unregister the above signal handler again.	534	Example: For some weird reason, unregister the above signal handler again.
467		535
468	ev_ref (myloop);	536	ev_ref (loop);
469	ev_signal_stop (myloop, &exitsig);	537	ev_signal_stop (loop, &exitsig);
470		538
471	=back	539	=back
		540
472		541
473	=head1 ANATOMY OF A WATCHER	542	=head1 ANATOMY OF A WATCHER
474		543
475	A watcher is a structure that you create and register to record your	544	A watcher is a structure that you create and register to record your
476	interest in some event. For instance, if you want to wait for STDIN to	545	interest in some event. For instance, if you want to wait for STDIN to
…		…
543	The signal specified in the C<ev_signal> watcher has been received by a thread.	612	The signal specified in the C<ev_signal> watcher has been received by a thread.
544		613
545	=item C<EV_CHILD>	614	=item C<EV_CHILD>
546		615
547	The pid specified in the C<ev_child> watcher has received a status change.	616	The pid specified in the C<ev_child> watcher has received a status change.
		617
		618	=item C<EV_STAT>
		619
		620	The path specified in the C<ev_stat> watcher changed its attributes somehow.
548		621
549	=item C<EV_IDLE>	622	=item C<EV_IDLE>
550		623
551	The C<ev_idle> watcher has determined that you have nothing better to do.	624	The C<ev_idle> watcher has determined that you have nothing better to do.
552		625
…		…
560	received events. Callbacks of both watcher types can start and stop as	633	received events. Callbacks of both watcher types can start and stop as
561	many watchers as they want, and all of them will be taken into account	634	many watchers as they want, and all of them will be taken into account
562	(for example, a C<ev_prepare> watcher might start an idle watcher to keep	635	(for example, a C<ev_prepare> watcher might start an idle watcher to keep
563	C<ev_loop> from blocking).	636	C<ev_loop> from blocking).
564		637
		638	=item C<EV_EMBED>
		639
		640	The embedded event loop specified in the C<ev_embed> watcher needs attention.
		641
		642	=item C<EV_FORK>
		643
		644	The event loop has been resumed in the child process after fork (see
		645	C<ev_fork>).
		646
565	=item C<EV_ERROR>	647	=item C<EV_ERROR>
566		648
567	An unspecified error has occured, the watcher has been stopped. This might	649	An unspecified error has occured, the watcher has been stopped. This might
568	happen because the watcher could not be properly started because libev	650	happen because the watcher could not be properly started because libev
569	ran out of memory, a file descriptor was found to be closed or any other	651	ran out of memory, a file descriptor was found to be closed or any other
…		…
576	with the error from read() or write(). This will not work in multithreaded	658	with the error from read() or write(). This will not work in multithreaded
577	programs, though, so beware.	659	programs, though, so beware.
578		660
579	=back	661	=back
580		662
581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS	663	=head2 GENERIC WATCHER FUNCTIONS
582		664
583	In the following description, C<TYPE> stands for the watcher type,	665	In the following description, C<TYPE> stands for the watcher type,
584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.	666	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
585		667
586	=over 4	668	=over 4
…		…
595	which rolls both calls into one.	677	which rolls both calls into one.
596		678
597	You can reinitialise a watcher at any time as long as it has been stopped	679	You can reinitialise a watcher at any time as long as it has been stopped
598	(or never started) and there are no pending events outstanding.	680	(or never started) and there are no pending events outstanding.
599		681
600	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	682	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
601	int revents)>.	683	int revents)>.
602		684
603	=item C<ev_TYPE_set> (ev_TYPE *, [args])	685	=item C<ev_TYPE_set> (ev_TYPE *, [args])
604		686
605	This macro initialises the type-specific parts of a watcher. You need to	687	This macro initialises the type-specific parts of a watcher. You need to
…		…
643	events but its callback has not yet been invoked). As long as a watcher	725	events but its callback has not yet been invoked). As long as a watcher
644	is pending (but not active) you must not call an init function on it (but	726	is pending (but not active) you must not call an init function on it (but
645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	727	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
646	libev (e.g. you cnanot C<free ()> it).	728	libev (e.g. you cnanot C<free ()> it).
647		729
648	=item callback = ev_cb (ev_TYPE *watcher)	730	=item callback ev_cb (ev_TYPE *watcher)
649		731
650	Returns the callback currently set on the watcher.	732	Returns the callback currently set on the watcher.
651		733
652	=item ev_cb_set (ev_TYPE *watcher, callback)	734	=item ev_cb_set (ev_TYPE *watcher, callback)
653		735
…		…
681	{	763	{
682	struct my_io w = (struct my_io )w_;	764	struct my_io w = (struct my_io )w_;
683	...	765	...
684	}	766	}
685		767
686	More interesting and less C-conformant ways of catsing your callback type	768	More interesting and less C-conformant ways of casting your callback type
687	have been omitted....	769	instead have been omitted.
		770
		771	Another common scenario is having some data structure with multiple
		772	watchers:
		773
		774	struct my_biggy
		775	{
		776	int some_data;
		777	ev_timer t1;
		778	ev_timer t2;
		779	}
		780
		781	In this case getting the pointer to C<my_biggy> is a bit more complicated,
		782	you need to use C<offsetof>:
		783
		784	#include <stddef.h>
		785
		786	static void
		787	t1_cb (EV_P_ struct ev_timer *w, int revents)
		788	{
		789	struct my_biggy big = (struct my_biggy *
		790	(((char *)w) - offsetof (struct my_biggy, t1));
		791	}
		792
		793	static void
		794	t2_cb (EV_P_ struct ev_timer *w, int revents)
		795	{
		796	struct my_biggy big = (struct my_biggy *
		797	(((char *)w) - offsetof (struct my_biggy, t2));
		798	}
688		799
689		800
690	=head1 WATCHER TYPES	801	=head1 WATCHER TYPES
691		802
692	This section describes each watcher in detail, but will not repeat	803	This section describes each watcher in detail, but will not repeat
693	information given in the last section.	804	information given in the last section. Any initialisation/set macros,
		805	functions and members specific to the watcher type are explained.
694		806
		807	Members are additionally marked with either I<[read-only]>, meaning that,
		808	while the watcher is active, you can look at the member and expect some
		809	sensible content, but you must not modify it (you can modify it while the
		810	watcher is stopped to your hearts content), or I<[read-write]>, which
		811	means you can expect it to have some sensible content while the watcher
		812	is active, but you can also modify it. Modifying it may not do something
		813	sensible or take immediate effect (or do anything at all), but libev will
		814	not crash or malfunction in any way.
695		815
		816
696	=head2 C<ev_io> - is this file descriptor readable or writable	817	=head2 C<ev_io> - is this file descriptor readable or writable?
697		818
698	I/O watchers check whether a file descriptor is readable or writable	819	I/O watchers check whether a file descriptor is readable or writable
699	in each iteration of the event loop (This behaviour is called	820	in each iteration of the event loop, or, more precisely, when reading
700	level-triggering because you keep receiving events as long as the	821	would not block the process and writing would at least be able to write
701	condition persists. Remember you can stop the watcher if you don't want to	822	some data. This behaviour is called level-triggering because you keep
702	act on the event and neither want to receive future events).	823	receiving events as long as the condition persists. Remember you can stop
		824	the watcher if you don't want to act on the event and neither want to
		825	receive future events.
703		826
704	In general you can register as many read and/or write event watchers per	827	In general you can register as many read and/or write event watchers per
705	fd as you want (as long as you don't confuse yourself). Setting all file	828	fd as you want (as long as you don't confuse yourself). Setting all file
706	descriptors to non-blocking mode is also usually a good idea (but not	829	descriptors to non-blocking mode is also usually a good idea (but not
707	required if you know what you are doing).	830	required if you know what you are doing).
708		831
709	You have to be careful with dup'ed file descriptors, though. Some backends	832	You have to be careful with dup'ed file descriptors, though. Some backends
710	(the linux epoll backend is a notable example) cannot handle dup'ed file	833	(the linux epoll backend is a notable example) cannot handle dup'ed file
711	descriptors correctly if you register interest in two or more fds pointing	834	descriptors correctly if you register interest in two or more fds pointing
712	to the same underlying file/socket etc. description (that is, they share	835	to the same underlying file/socket/etc. description (that is, they share
713	the same underlying "file open").	836	the same underlying "file open").
714		837
715	If you must do this, then force the use of a known-to-be-good backend	838	If you must do this, then force the use of a known-to-be-good backend
716	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and	839	(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
717	C<EVBACKEND_POLL>).	840	C<EVBACKEND_POLL>).
718		841
		842	Another thing you have to watch out for is that it is quite easy to
		843	receive "spurious" readyness notifications, that is your callback might
		844	be called with C<EV_READ> but a subsequent C<read>(2) will actually block
		845	because there is no data. Not only are some backends known to create a
		846	lot of those (for example solaris ports), it is very easy to get into
		847	this situation even with a relatively standard program structure. Thus
		848	it is best to always use non-blocking I/O: An extra C<read>(2) returning
		849	C<EAGAIN> is far preferable to a program hanging until some data arrives.
		850
		851	If you cannot run the fd in non-blocking mode (for example you should not
		852	play around with an Xlib connection), then you have to seperately re-test
		853	wether a file descriptor is really ready with a known-to-be good interface
		854	such as poll (fortunately in our Xlib example, Xlib already does this on
		855	its own, so its quite safe to use).
		856
719	=over 4	857	=over 4
720		858
721	=item ev_io_init (ev_io *, callback, int fd, int events)	859	=item ev_io_init (ev_io *, callback, int fd, int events)
722		860
723	=item ev_io_set (ev_io *, int fd, int events)	861	=item ev_io_set (ev_io *, int fd, int events)
724		862
725	Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive	863	Configures an C<ev_io> watcher. The C<fd> is the file descriptor to
726	events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ \|	864	rceeive events for and events is either C<EV_READ>, C<EV_WRITE> or
727	EV_WRITE> to receive the given events.	865	C<EV_READ \| EV_WRITE> to receive the given events.
728		866
729	Please note that most of the more scalable backend mechanisms (for example	867	=item int fd [read-only]
730	epoll and solaris ports) can result in spurious readyness notifications	868
731	for file descriptors, so you practically need to use non-blocking I/O (and	869	The file descriptor being watched.
732	treat callback invocation as hint only), or retest separately with a safe	870
733	interface before doing I/O (XLib can do this), or force the use of either	871	=item int events [read-only]
734	C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>, which don't suffer from this	872
735	problem. Also note that it is quite easy to have your callback invoked	873	The events being watched.
736	when the readyness condition is no longer valid even when employing
737	typical ways of handling events, so its a good idea to use non-blocking
738	I/O unconditionally.
739		874
740	=back	875	=back
741		876
742	Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well	877	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
743	readable, but only once. Since it is likely line-buffered, you could	878	readable, but only once. Since it is likely line-buffered, you could
744	attempt to read a whole line in the callback:	879	attempt to read a whole line in the callback.
745		880
746	static void	881	static void
747	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	882	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)
748	{	883	{
749	ev_io_stop (loop, w);	884	ev_io_stop (loop, w);
…		…
756	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	891	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
757	ev_io_start (loop, &stdin_readable);	892	ev_io_start (loop, &stdin_readable);
758	ev_loop (loop, 0);	893	ev_loop (loop, 0);
759		894
760		895
761	=head2 C<ev_timer> - relative and optionally recurring timeouts	896	=head2 C<ev_timer> - relative and optionally repeating timeouts
762		897
763	Timer watchers are simple relative timers that generate an event after a	898	Timer watchers are simple relative timers that generate an event after a
764	given time, and optionally repeating in regular intervals after that.	899	given time, and optionally repeating in regular intervals after that.
765		900
766	The timers are based on real time, that is, if you register an event that	901	The timers are based on real time, that is, if you register an event that
…		…
801	=item ev_timer_again (loop)	936	=item ev_timer_again (loop)
802		937
803	This will act as if the timer timed out and restart it again if it is	938	This will act as if the timer timed out and restart it again if it is
804	repeating. The exact semantics are:	939	repeating. The exact semantics are:
805		940
		941	If the timer is pending, its pending status is cleared.
		942
806	If the timer is started but nonrepeating, stop it.	943	If the timer is started but nonrepeating, stop it (as if it timed out).
807		944
808	If the timer is repeating, either start it if necessary (with the repeat	945	If the timer is repeating, either start it if necessary (with the
809	value), or reset the running timer to the repeat value.	946	C<repeat> value), or reset the running timer to the C<repeat> value.
810		947
811	This sounds a bit complicated, but here is a useful and typical	948	This sounds a bit complicated, but here is a useful and typical
812	example: Imagine you have a tcp connection and you want a so-called idle	949	example: Imagine you have a tcp connection and you want a so-called idle
813	timeout, that is, you want to be called when there have been, say, 60	950	timeout, that is, you want to be called when there have been, say, 60
814	seconds of inactivity on the socket. The easiest way to do this is to	951	seconds of inactivity on the socket. The easiest way to do this is to
815	configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each	952	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
816	time you successfully read or write some data. If you go into an idle	953	C<ev_timer_again> each time you successfully read or write some data. If
817	state where you do not expect data to travel on the socket, you can stop	954	you go into an idle state where you do not expect data to travel on the
818	the timer, and again will automatically restart it if need be.	955	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
		956	automatically restart it if need be.
		957
		958	That means you can ignore the C<after> value and C<ev_timer_start>
		959	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
		960
		961	ev_timer_init (timer, callback, 0., 5.);
		962	ev_timer_again (loop, timer);
		963	...
		964	timer->again = 17.;
		965	ev_timer_again (loop, timer);
		966	...
		967	timer->again = 10.;
		968	ev_timer_again (loop, timer);
		969
		970	This is more slightly efficient then stopping/starting the timer each time
		971	you want to modify its timeout value.
		972
		973	=item ev_tstamp repeat [read-write]
		974
		975	The current C<repeat> value. Will be used each time the watcher times out
		976	or C<ev_timer_again> is called and determines the next timeout (if any),
		977	which is also when any modifications are taken into account.
819		978
820	=back	979	=back
821		980
822	Example: create a timer that fires after 60 seconds.	981	Example: Create a timer that fires after 60 seconds.
823		982
824	static void	983	static void
825	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	984	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)
826	{	985	{
827	.. one minute over, w is actually stopped right here	986	.. one minute over, w is actually stopped right here
…		…
829		988
830	struct ev_timer mytimer;	989	struct ev_timer mytimer;
831	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	990	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
832	ev_timer_start (loop, &mytimer);	991	ev_timer_start (loop, &mytimer);
833		992
834	Example: create a timeout timer that times out after 10 seconds of	993	Example: Create a timeout timer that times out after 10 seconds of
835	inactivity.	994	inactivity.
836		995
837	static void	996	static void
838	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	997	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)
839	{	998	{
…		…
848	// and in some piece of code that gets executed on any "activity":	1007	// and in some piece of code that gets executed on any "activity":
849	// reset the timeout to start ticking again at 10 seconds	1008	// reset the timeout to start ticking again at 10 seconds
850	ev_timer_again (&mytimer);	1009	ev_timer_again (&mytimer);
851		1010
852		1011
853	=head2 C<ev_periodic> - to cron or not to cron	1012	=head2 C<ev_periodic> - to cron or not to cron?
854		1013
855	Periodic watchers are also timers of a kind, but they are very versatile	1014	Periodic watchers are also timers of a kind, but they are very versatile
856	(and unfortunately a bit complex).	1015	(and unfortunately a bit complex).
857		1016
858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1017	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
…		…
950	Simply stops and restarts the periodic watcher again. This is only useful	1109	Simply stops and restarts the periodic watcher again. This is only useful
951	when you changed some parameters or the reschedule callback would return	1110	when you changed some parameters or the reschedule callback would return
952	a different time than the last time it was called (e.g. in a crond like	1111	a different time than the last time it was called (e.g. in a crond like
953	program when the crontabs have changed).	1112	program when the crontabs have changed).
954		1113
		1114	=item ev_tstamp interval [read-write]
		1115
		1116	The current interval value. Can be modified any time, but changes only
		1117	take effect when the periodic timer fires or C<ev_periodic_again> is being
		1118	called.
		1119
		1120	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]
		1121
		1122	The current reschedule callback, or C<0>, if this functionality is
		1123	switched off. Can be changed any time, but changes only take effect when
		1124	the periodic timer fires or C<ev_periodic_again> is being called.
		1125
955	=back	1126	=back
956		1127
957	Example: call a callback every hour, or, more precisely, whenever the	1128	Example: Call a callback every hour, or, more precisely, whenever the
958	system clock is divisible by 3600. The callback invocation times have	1129	system clock is divisible by 3600. The callback invocation times have
959	potentially a lot of jittering, but good long-term stability.	1130	potentially a lot of jittering, but good long-term stability.
960		1131
961	static void	1132	static void
962	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1133	clock_cb (struct ev_loop loop, struct ev_io w, int revents)
…		…
966		1137
967	struct ev_periodic hourly_tick;	1138	struct ev_periodic hourly_tick;
968	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1139	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
969	ev_periodic_start (loop, &hourly_tick);	1140	ev_periodic_start (loop, &hourly_tick);
970		1141
971	Example: the same as above, but use a reschedule callback to do it:	1142	Example: The same as above, but use a reschedule callback to do it:
972		1143
973	#include <math.h>	1144	#include <math.h>
974		1145
975	static ev_tstamp	1146	static ev_tstamp
976	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1147	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
…		…
978	return fmod (now, 3600.) + 3600.;	1149	return fmod (now, 3600.) + 3600.;
979	}	1150	}
980		1151
981	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1152	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
982		1153
983	Example: call a callback every hour, starting now:	1154	Example: Call a callback every hour, starting now:
984		1155
985	struct ev_periodic hourly_tick;	1156	struct ev_periodic hourly_tick;
986	ev_periodic_init (&hourly_tick, clock_cb,	1157	ev_periodic_init (&hourly_tick, clock_cb,
987	fmod (ev_now (loop), 3600.), 3600., 0);	1158	fmod (ev_now (loop), 3600.), 3600., 0);
988	ev_periodic_start (loop, &hourly_tick);	1159	ev_periodic_start (loop, &hourly_tick);
989		1160
990		1161
991	=head2 C<ev_signal> - signal me when a signal gets signalled	1162	=head2 C<ev_signal> - signal me when a signal gets signalled!
992		1163
993	Signal watchers will trigger an event when the process receives a specific	1164	Signal watchers will trigger an event when the process receives a specific
994	signal one or more times. Even though signals are very asynchronous, libev	1165	signal one or more times. Even though signals are very asynchronous, libev
995	will try it's best to deliver signals synchronously, i.e. as part of the	1166	will try it's best to deliver signals synchronously, i.e. as part of the
996	normal event processing, like any other event.	1167	normal event processing, like any other event.
…		…
1009	=item ev_signal_set (ev_signal *, int signum)	1180	=item ev_signal_set (ev_signal *, int signum)
1010		1181
1011	Configures the watcher to trigger on the given signal number (usually one	1182	Configures the watcher to trigger on the given signal number (usually one
1012	of the C<SIGxxx> constants).	1183	of the C<SIGxxx> constants).
1013		1184
		1185	=item int signum [read-only]
		1186
		1187	The signal the watcher watches out for.
		1188
1014	=back	1189	=back
1015		1190
1016		1191
1017	=head2 C<ev_child> - wait for pid status changes	1192	=head2 C<ev_child> - watch out for process status changes
1018		1193
1019	Child watchers trigger when your process receives a SIGCHLD in response to	1194	Child watchers trigger when your process receives a SIGCHLD in response to
1020	some child status changes (most typically when a child of yours dies).	1195	some child status changes (most typically when a child of yours dies).
1021		1196
1022	=over 4	1197	=over 4
…		…
1030	at the C<rstatus> member of the C<ev_child> watcher structure to see	1205	at the C<rstatus> member of the C<ev_child> watcher structure to see
1031	the status word (use the macros from C<sys/wait.h> and see your systems	1206	the status word (use the macros from C<sys/wait.h> and see your systems
1032	C<waitpid> documentation). The C<rpid> member contains the pid of the	1207	C<waitpid> documentation). The C<rpid> member contains the pid of the
1033	process causing the status change.	1208	process causing the status change.
1034		1209
		1210	=item int pid [read-only]
		1211
		1212	The process id this watcher watches out for, or C<0>, meaning any process id.
		1213
		1214	=item int rpid [read-write]
		1215
		1216	The process id that detected a status change.
		1217
		1218	=item int rstatus [read-write]
		1219
		1220	The process exit/trace status caused by C<rpid> (see your systems
		1221	C<waitpid> and C<sys/wait.h> documentation for details).
		1222
1035	=back	1223	=back
1036		1224
1037	Example: try to exit cleanly on SIGINT and SIGTERM.	1225	Example: Try to exit cleanly on SIGINT and SIGTERM.
1038		1226
1039	static void	1227	static void
1040	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1228	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1041	{	1229	{
1042	ev_unloop (loop, EVUNLOOP_ALL);	1230	ev_unloop (loop, EVUNLOOP_ALL);
…		…
1045	struct ev_signal signal_watcher;	1233	struct ev_signal signal_watcher;
1046	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1234	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1047	ev_signal_start (loop, &sigint_cb);	1235	ev_signal_start (loop, &sigint_cb);
1048		1236
1049		1237
		1238	=head2 C<ev_stat> - did the file attributes just change?
		1239
		1240	This watches a filesystem path for attribute changes. That is, it calls
		1241	C<stat> regularly (or when the OS says it changed) and sees if it changed
		1242	compared to the last time, invoking the callback if it did.
		1243
		1244	The path does not need to exist: changing from "path exists" to "path does
		1245	not exist" is a status change like any other. The condition "path does
		1246	not exist" is signified by the C<st_nlink> field being zero (which is
		1247	otherwise always forced to be at least one) and all the other fields of
		1248	the stat buffer having unspecified contents.
		1249
		1250	The path I<should> be absolute and I<must not> end in a slash. If it is
		1251	relative and your working directory changes, the behaviour is undefined.
		1252
		1253	Since there is no standard to do this, the portable implementation simply
		1254	calls C<stat (2)> regularly on the path to see if it changed somehow. You
		1255	can specify a recommended polling interval for this case. If you specify
		1256	a polling interval of C<0> (highly recommended!) then a I<suitable,
		1257	unspecified default> value will be used (which you can expect to be around
		1258	five seconds, although this might change dynamically). Libev will also
		1259	impose a minimum interval which is currently around C<0.1>, but thats
		1260	usually overkill.
		1261
		1262	This watcher type is not meant for massive numbers of stat watchers,
		1263	as even with OS-supported change notifications, this can be
		1264	resource-intensive.
		1265
		1266	At the time of this writing, only the Linux inotify interface is
		1267	implemented (implementing kqueue support is left as an exercise for the
		1268	reader). Inotify will be used to give hints only and should not change the
		1269	semantics of C<ev_stat> watchers, which means that libev sometimes needs
		1270	to fall back to regular polling again even with inotify, but changes are
		1271	usually detected immediately, and if the file exists there will be no
		1272	polling.
		1273
		1274	=over 4
		1275
		1276	=item ev_stat_init (ev_stat , callback, const char path, ev_tstamp interval)
		1277
		1278	=item ev_stat_set (ev_stat , const char path, ev_tstamp interval)
		1279
		1280	Configures the watcher to wait for status changes of the given
		1281	C<path>. The C<interval> is a hint on how quickly a change is expected to
		1282	be detected and should normally be specified as C<0> to let libev choose
		1283	a suitable value. The memory pointed to by C<path> must point to the same
		1284	path for as long as the watcher is active.
		1285
		1286	The callback will be receive C<EV_STAT> when a change was detected,
		1287	relative to the attributes at the time the watcher was started (or the
		1288	last change was detected).
		1289
		1290	=item ev_stat_stat (ev_stat *)
		1291
		1292	Updates the stat buffer immediately with new values. If you change the
		1293	watched path in your callback, you could call this fucntion to avoid
		1294	detecting this change (while introducing a race condition). Can also be
		1295	useful simply to find out the new values.
		1296
		1297	=item ev_statdata attr [read-only]
		1298
		1299	The most-recently detected attributes of the file. Although the type is of
		1300	C<ev_statdata>, this is usually the (or one of the) C<struct stat> types
		1301	suitable for your system. If the C<st_nlink> member is C<0>, then there
		1302	was some error while C<stat>ing the file.
		1303
		1304	=item ev_statdata prev [read-only]
		1305
		1306	The previous attributes of the file. The callback gets invoked whenever
		1307	C<prev> != C<attr>.
		1308
		1309	=item ev_tstamp interval [read-only]
		1310
		1311	The specified interval.
		1312
		1313	=item const char *path [read-only]
		1314
		1315	The filesystem path that is being watched.
		1316
		1317	=back
		1318
		1319	Example: Watch C</etc/passwd> for attribute changes.
		1320
		1321	static void
		1322	passwd_cb (struct ev_loop loop, ev_stat w, int revents)
		1323	{
		1324	/* /etc/passwd changed in some way */
		1325	if (w->attr.st_nlink)
		1326	{
		1327	printf ("passwd current size %ld\n", (long)w->attr.st_size);
		1328	printf ("passwd current atime %ld\n", (long)w->attr.st_mtime);
		1329	printf ("passwd current mtime %ld\n", (long)w->attr.st_mtime);
		1330	}
		1331	else
		1332	/* you shalt not abuse printf for puts */
		1333	puts ("wow, /etc/passwd is not there, expect problems. "
		1334	"if this is windows, they already arrived\n");
		1335	}
		1336
		1337	...
		1338	ev_stat passwd;
		1339
		1340	ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
		1341	ev_stat_start (loop, &passwd);
		1342
		1343
1050	=head2 C<ev_idle> - when you've got nothing better to do	1344	=head2 C<ev_idle> - when you've got nothing better to do...
1051		1345
1052	Idle watchers trigger events when there are no other events are pending	1346	Idle watchers trigger events when there are no other events are pending
1053	(prepare, check and other idle watchers do not count). That is, as long	1347	(prepare, check and other idle watchers do not count). That is, as long
1054	as your process is busy handling sockets or timeouts (or even signals,	1348	as your process is busy handling sockets or timeouts (or even signals,
1055	imagine) it will not be triggered. But when your process is idle all idle	1349	imagine) it will not be triggered. But when your process is idle all idle
…		…
1073	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	1367	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1074	believe me.	1368	believe me.
1075		1369
1076	=back	1370	=back
1077		1371
1078	Example: dynamically allocate an C<ev_idle>, start it, and in the	1372	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1079	callback, free it. Alos, use no error checking, as usual.	1373	callback, free it. Also, use no error checking, as usual.
1080		1374
1081	static void	1375	static void
1082	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	1376	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)
1083	{	1377	{
1084	free (w);	1378	free (w);
…		…
1089	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	1383	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1090	ev_idle_init (idle_watcher, idle_cb);	1384	ev_idle_init (idle_watcher, idle_cb);
1091	ev_idle_start (loop, idle_cb);	1385	ev_idle_start (loop, idle_cb);
1092		1386
1093		1387
1094	=head2 C<ev_prepare> and C<ev_check> - customise your event loop	1388	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
1095		1389
1096	Prepare and check watchers are usually (but not always) used in tandem:	1390	Prepare and check watchers are usually (but not always) used in tandem:
1097	prepare watchers get invoked before the process blocks and check watchers	1391	prepare watchers get invoked before the process blocks and check watchers
1098	afterwards.	1392	afterwards.
1099		1393
		1394	You I<must not> call C<ev_loop> or similar functions that enter
		1395	the current event loop from either C<ev_prepare> or C<ev_check>
		1396	watchers. Other loops than the current one are fine, however. The
		1397	rationale behind this is that you do not need to check for recursion in
		1398	those watchers, i.e. the sequence will always be C<ev_prepare>, blocking,
		1399	C<ev_check> so if you have one watcher of each kind they will always be
		1400	called in pairs bracketing the blocking call.
		1401
1100	Their main purpose is to integrate other event mechanisms into libev and	1402	Their main purpose is to integrate other event mechanisms into libev and
1101	their use is somewhat advanced. This could be used, for example, to track	1403	their use is somewhat advanced. This could be used, for example, to track
1102	variable changes, implement your own watchers, integrate net-snmp or a	1404	variable changes, implement your own watchers, integrate net-snmp or a
1103	coroutine library and lots more.	1405	coroutine library and lots more. They are also occasionally useful if
		1406	you cache some data and want to flush it before blocking (for example,
		1407	in X programs you might want to do an C<XFlush ()> in an C<ev_prepare>
		1408	watcher).
1104		1409
1105	This is done by examining in each prepare call which file descriptors need	1410	This is done by examining in each prepare call which file descriptors need
1106	to be watched by the other library, registering C<ev_io> watchers for	1411	to be watched by the other library, registering C<ev_io> watchers for
1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1412	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1108	provide just this functionality). Then, in the check watcher you check for	1413	provide just this functionality). Then, in the check watcher you check for
…		…
1130	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1435	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1131	macros, but using them is utterly, utterly and completely pointless.	1436	macros, but using them is utterly, utterly and completely pointless.
1132		1437
1133	=back	1438	=back
1134		1439
1135	Example: TODO.	1440	Example: To include a library such as adns, you would add IO watchers
		1441	and a timeout watcher in a prepare handler, as required by libadns, and
		1442	in a check watcher, destroy them and call into libadns. What follows is
		1443	pseudo-code only of course:
1136		1444
		1445	static ev_io iow [nfd];
		1446	static ev_timer tw;
1137		1447
		1448	static void
		1449	io_cb (ev_loop loop, ev_io w, int revents)
		1450	{
		1451	// set the relevant poll flags
		1452	// could also call adns_processreadable etc. here
		1453	struct pollfd fd = (struct pollfd )w->data;
		1454	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1455	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1456	}
		1457
		1458	// create io watchers for each fd and a timer before blocking
		1459	static void
		1460	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
		1461	{
		1462	int timeout = 3600000;truct pollfd fds [nfd];
		1463	// actual code will need to loop here and realloc etc.
		1464	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
		1465
		1466	/* the callback is illegal, but won't be called as we stop during check */
		1467	ev_timer_init (&tw, 0, timeout * 1e-3);
		1468	ev_timer_start (loop, &tw);
		1469
		1470	// create on ev_io per pollfd
		1471	for (int i = 0; i < nfd; ++i)
		1472	{
		1473	ev_io_init (iow + i, io_cb, fds [i].fd,
		1474	((fds [i].events & POLLIN ? EV_READ : 0)
		1475	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
		1476
		1477	fds [i].revents = 0;
		1478	iow [i].data = fds + i;
		1479	ev_io_start (loop, iow + i);
		1480	}
		1481	}
		1482
		1483	// stop all watchers after blocking
		1484	static void
		1485	adns_check_cb (ev_loop loop, ev_check w, int revents)
		1486	{
		1487	ev_timer_stop (loop, &tw);
		1488
		1489	for (int i = 0; i < nfd; ++i)
		1490	ev_io_stop (loop, iow + i);
		1491
		1492	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1493	}
		1494
		1495
1138	=head2 C<ev_embed> - when one backend isn't enough	1496	=head2 C<ev_embed> - when one backend isn't enough...
1139		1497
1140	This is a rather advanced watcher type that lets you embed one event loop	1498	This is a rather advanced watcher type that lets you embed one event loop
1141	into another (currently only C<ev_io> events are supported in the embedded	1499	into another (currently only C<ev_io> events are supported in the embedded
1142	loop, other types of watchers might be handled in a delayed or incorrect	1500	loop, other types of watchers might be handled in a delayed or incorrect
1143	fashion and must not be used).	1501	fashion and must not be used).
…		…
1221		1579
1222	Make a single, non-blocking sweep over the embedded loop. This works	1580	Make a single, non-blocking sweep over the embedded loop. This works
1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most	1581	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1224	apropriate way for embedded loops.	1582	apropriate way for embedded loops.
1225		1583
		1584	=item struct ev_loop *loop [read-only]
		1585
		1586	The embedded event loop.
		1587
		1588	=back
		1589
		1590
		1591	=head2 C<ev_fork> - the audacity to resume the event loop after a fork
		1592
		1593	Fork watchers are called when a C<fork ()> was detected (usually because
		1594	whoever is a good citizen cared to tell libev about it by calling
		1595	C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
		1596	event loop blocks next and before C<ev_check> watchers are being called,
		1597	and only in the child after the fork. If whoever good citizen calling
		1598	C<ev_default_fork> cheats and calls it in the wrong process, the fork
		1599	handlers will be invoked, too, of course.
		1600
		1601	=over 4
		1602
		1603	=item ev_fork_init (ev_signal *, callback)
		1604
		1605	Initialises and configures the fork watcher - it has no parameters of any
		1606	kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
		1607	believe me.
		1608
1226	=back	1609	=back
1227		1610
1228		1611
1229	=head1 OTHER FUNCTIONS	1612	=head1 OTHER FUNCTIONS
1230		1613
…		…
1392		1775
1393	=item w->sweep () C<ev::embed> only	1776	=item w->sweep () C<ev::embed> only
1394		1777
1395	Invokes C<ev_embed_sweep>.	1778	Invokes C<ev_embed_sweep>.
1396		1779
		1780	=item w->update () C<ev::stat> only
		1781
		1782	Invokes C<ev_stat_stat>.
		1783
1397	=back	1784	=back
1398		1785
1399	=back	1786	=back
1400		1787
1401	Example: Define a class with an IO and idle watcher, start one of them in	1788	Example: Define a class with an IO and idle watcher, start one of them in
…		…
1413	: io (this, &myclass::io_cb),	1800	: io (this, &myclass::io_cb),
1414	idle (this, &myclass::idle_cb)	1801	idle (this, &myclass::idle_cb)
1415	{	1802	{
1416	io.start (fd, ev::READ);	1803	io.start (fd, ev::READ);
1417	}	1804	}
		1805
		1806
		1807	=head1 MACRO MAGIC
		1808
		1809	Libev can be compiled with a variety of options, the most fundemantal is
		1810	C<EV_MULTIPLICITY>. This option determines wether (most) functions and
		1811	callbacks have an initial C<struct ev_loop *> argument.
		1812
		1813	To make it easier to write programs that cope with either variant, the
		1814	following macros are defined:
		1815
		1816	=over 4
		1817
		1818	=item C<EV_A>, C<EV_A_>
		1819
		1820	This provides the loop I<argument> for functions, if one is required ("ev
		1821	loop argument"). The C<EV_A> form is used when this is the sole argument,
		1822	C<EV_A_> is used when other arguments are following. Example:
		1823
		1824	ev_unref (EV_A);
		1825	ev_timer_add (EV_A_ watcher);
		1826	ev_loop (EV_A_ 0);
		1827
		1828	It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
		1829	which is often provided by the following macro.
		1830
		1831	=item C<EV_P>, C<EV_P_>
		1832
		1833	This provides the loop I<parameter> for functions, if one is required ("ev
		1834	loop parameter"). The C<EV_P> form is used when this is the sole parameter,
		1835	C<EV_P_> is used when other parameters are following. Example:
		1836
		1837	// this is how ev_unref is being declared
		1838	static void ev_unref (EV_P);
		1839
		1840	// this is how you can declare your typical callback
		1841	static void cb (EV_P_ ev_timer *w, int revents)
		1842
		1843	It declares a parameter C<loop> of type C<struct ev_loop *>, quite
		1844	suitable for use with C<EV_A>.
		1845
		1846	=item C<EV_DEFAULT>, C<EV_DEFAULT_>
		1847
		1848	Similar to the other two macros, this gives you the value of the default
		1849	loop, if multiple loops are supported ("ev loop default").
		1850
		1851	=back
		1852
		1853	Example: Declare and initialise a check watcher, working regardless of
		1854	wether multiple loops are supported or not.
		1855
		1856	static void
		1857	check_cb (EV_P_ ev_timer *w, int revents)
		1858	{
		1859	ev_check_stop (EV_A_ w);
		1860	}
		1861
		1862	ev_check check;
		1863	ev_check_init (&check, check_cb);
		1864	ev_check_start (EV_DEFAULT_ &check);
		1865	ev_loop (EV_DEFAULT_ 0);
		1866
1418		1867
1419	=head1 EMBEDDING	1868	=head1 EMBEDDING
1420		1869
1421	Libev can (and often is) directly embedded into host	1870	Libev can (and often is) directly embedded into host
1422	applications. Examples of applications that embed it include the Deliantra	1871	applications. Examples of applications that embed it include the Deliantra
…		…
1462	ev_vars.h	1911	ev_vars.h
1463	ev_wrap.h	1912	ev_wrap.h
1464		1913
1465	ev_win32.c required on win32 platforms only	1914	ev_win32.c required on win32 platforms only
1466		1915
1467	ev_select.c only when select backend is enabled (which is is by default)	1916	ev_select.c only when select backend is enabled (which is by default)
1468	ev_poll.c only when poll backend is enabled (disabled by default)	1917	ev_poll.c only when poll backend is enabled (disabled by default)
1469	ev_epoll.c only when the epoll backend is enabled (disabled by default)	1918	ev_epoll.c only when the epoll backend is enabled (disabled by default)
1470	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)	1919	ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1471	ev_port.c only when the solaris port backend is enabled (disabled by default)	1920	ev_port.c only when the solaris port backend is enabled (disabled by default)
1472		1921
1473	F<ev.c> includes the backend files directly when enabled, so you only need	1922	F<ev.c> includes the backend files directly when enabled, so you only need
1474	to compile a single file.	1923	to compile this single file.
1475		1924
1476	=head3 LIBEVENT COMPATIBILITY API	1925	=head3 LIBEVENT COMPATIBILITY API
1477		1926
1478	To include the libevent compatibility API, also include:	1927	To include the libevent compatibility API, also include:
1479		1928
…		…
1492		1941
1493	=head3 AUTOCONF SUPPORT	1942	=head3 AUTOCONF SUPPORT
1494		1943
1495	Instead of using C<EV_STANDALONE=1> and providing your config in	1944	Instead of using C<EV_STANDALONE=1> and providing your config in
1496	whatever way you want, you can also C<m4_include([libev.m4])> in your	1945	whatever way you want, you can also C<m4_include([libev.m4])> in your
1497	F<configure.ac> and leave C<EV_STANDALONE> off. F<ev.c> will then include	1946	F<configure.ac> and leave C<EV_STANDALONE> undefined. F<ev.c> will then
1498	F<config.h> and configure itself accordingly.	1947	include F<config.h> and configure itself accordingly.
1499		1948
1500	For this of course you need the m4 file:	1949	For this of course you need the m4 file:
1501		1950
1502	libev.m4	1951	libev.m4
1503		1952
…		…
1583	otherwise another method will be used as fallback. This is the preferred	2032	otherwise another method will be used as fallback. This is the preferred
1584	backend for BSD and BSD-like systems, although on most BSDs kqueue only	2033	backend for BSD and BSD-like systems, although on most BSDs kqueue only
1585	supports some types of fds correctly (the only platform we found that	2034	supports some types of fds correctly (the only platform we found that
1586	supports ptys for example was NetBSD), so kqueue might be compiled in, but	2035	supports ptys for example was NetBSD), so kqueue might be compiled in, but
1587	not be used unless explicitly requested. The best way to use it is to find	2036	not be used unless explicitly requested. The best way to use it is to find
1588	out wether kqueue supports your type of fd properly and use an embedded	2037	out whether kqueue supports your type of fd properly and use an embedded
1589	kqueue loop.	2038	kqueue loop.
1590		2039
1591	=item EV_USE_PORT	2040	=item EV_USE_PORT
1592		2041
1593	If defined to be C<1>, libev will compile in support for the Solaris	2042	If defined to be C<1>, libev will compile in support for the Solaris
…		…
1596	backend for Solaris 10 systems.	2045	backend for Solaris 10 systems.
1597		2046
1598	=item EV_USE_DEVPOLL	2047	=item EV_USE_DEVPOLL
1599		2048
1600	reserved for future expansion, works like the USE symbols above.	2049	reserved for future expansion, works like the USE symbols above.
		2050
		2051	=item EV_USE_INOTIFY
		2052
		2053	If defined to be C<1>, libev will compile in support for the Linux inotify
		2054	interface to speed up C<ev_stat> watchers. Its actual availability will
		2055	be detected at runtime.
1601		2056
1602	=item EV_H	2057	=item EV_H
1603		2058
1604	The name of the F<ev.h> header file used to include it. The default if	2059	The name of the F<ev.h> header file used to include it. The default if
1605	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This	2060	undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
…		…
1629	will have the C<struct ev_loop *> as first argument, and you can create	2084	will have the C<struct ev_loop *> as first argument, and you can create
1630	additional independent event loops. Otherwise there will be no support	2085	additional independent event loops. Otherwise there will be no support
1631	for multiple event loops and there is no first event loop pointer	2086	for multiple event loops and there is no first event loop pointer
1632	argument. Instead, all functions act on the single default loop.	2087	argument. Instead, all functions act on the single default loop.
1633		2088
1634	=item EV_PERIODICS	2089	=item EV_PERIODIC_ENABLE
1635		2090
1636	If undefined or defined to be C<1>, then periodic timers are supported,	2091	If undefined or defined to be C<1>, then periodic timers are supported. If
1637	otherwise not. This saves a few kb of code.	2092	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2093	code.
		2094
		2095	=item EV_EMBED_ENABLE
		2096
		2097	If undefined or defined to be C<1>, then embed watchers are supported. If
		2098	defined to be C<0>, then they are not.
		2099
		2100	=item EV_STAT_ENABLE
		2101
		2102	If undefined or defined to be C<1>, then stat watchers are supported. If
		2103	defined to be C<0>, then they are not.
		2104
		2105	=item EV_FORK_ENABLE
		2106
		2107	If undefined or defined to be C<1>, then fork watchers are supported. If
		2108	defined to be C<0>, then they are not.
		2109
		2110	=item EV_MINIMAL
		2111
		2112	If you need to shave off some kilobytes of code at the expense of some
		2113	speed, define this symbol to C<1>. Currently only used for gcc to override
		2114	some inlining decisions, saves roughly 30% codesize of amd64.
		2115
		2116	=item EV_PID_HASHSIZE
		2117
		2118	C<ev_child> watchers use a small hash table to distribute workload by
		2119	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
		2120	than enough. If you need to manage thousands of children you might want to
		2121	increase this value (I<must> be a power of two).
		2122
		2123	=item EV_INOTIFY_HASHSIZE
		2124
		2125	C<ev_staz> watchers use a small hash table to distribute workload by
		2126	inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
		2127	usually more than enough. If you need to manage thousands of C<ev_stat>
		2128	watchers you might want to increase this value (I<must> be a power of
		2129	two).
1638		2130
1639	=item EV_COMMON	2131	=item EV_COMMON
1640		2132
1641	By default, all watchers have a C<void *data> member. By redefining	2133	By default, all watchers have a C<void *data> member. By redefining
1642	this macro to a something else you can include more and other types of	2134	this macro to a something else you can include more and other types of
…		…
1647		2139
1648	#define EV_COMMON \	2140	#define EV_COMMON \
1649	SV self; / contains this struct */ \	2141	SV self; / contains this struct */ \
1650	SV cb_sv, fh /* note no trailing ";" */	2142	SV cb_sv, fh /* note no trailing ";" */
1651		2143
1652	=item EV_CB_DECLARE(type)	2144	=item EV_CB_DECLARE (type)
1653		2145
1654	=item EV_CB_INVOKE(watcher,revents)	2146	=item EV_CB_INVOKE (watcher, revents)
1655		2147
1656	=item ev_set_cb(ev,cb)	2148	=item ev_set_cb (ev, cb)
1657		2149
1658	Can be used to change the callback member declaration in each watcher,	2150	Can be used to change the callback member declaration in each watcher,
1659	and the way callbacks are invoked and set. Must expand to a struct member	2151	and the way callbacks are invoked and set. Must expand to a struct member
1660	definition and a statement, respectively. See the F<ev.v> header file for	2152	definition and a statement, respectively. See the F<ev.v> header file for
1661	their default definitions. One possible use for overriding these is to	2153	their default definitions. One possible use for overriding these is to
1662	avoid the ev_loop pointer as first argument in all cases, or to use method	2154	avoid the C<struct ev_loop *> as first argument in all cases, or to use
1663	calls instead of plain function calls in C++.	2155	method calls instead of plain function calls in C++.
1664		2156
1665	=head2 EXAMPLES	2157	=head2 EXAMPLES
1666		2158
1667	For a real-world example of a program the includes libev	2159	For a real-world example of a program the includes libev
1668	verbatim, you can have a look at the EV perl module	2160	verbatim, you can have a look at the EV perl module
…		…
1685	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	2177	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1686		2178
1687	#include "ev_cpp.h"	2179	#include "ev_cpp.h"
1688	#include "ev.c"	2180	#include "ev.c"
1689		2181
		2182
		2183	=head1 COMPLEXITIES
		2184
		2185	In this section the complexities of (many of) the algorithms used inside
		2186	libev will be explained. For complexity discussions about backends see the
		2187	documentation for C<ev_default_init>.
		2188
		2189	=over 4
		2190
		2191	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
		2192
		2193	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
		2194
		2195	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
		2196
		2197	=item Stopping check/prepare/idle watchers: O(1)
		2198
		2199	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
		2200
		2201	=item Finding the next timer per loop iteration: O(1)
		2202
		2203	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		2204
		2205	=item Activating one watcher: O(1)
		2206
		2207	=back
		2208
		2209
1690	=head1 AUTHOR	2210	=head1 AUTHOR
1691		2211
1692	Marc Lehmann <libev@schmorp.de>.	2212	Marc Lehmann <libev@schmorp.de>.
1693		2213

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Comparing libev/ev.pod (file contents): Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs. Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.40 by root, Sat Nov 24 10:15:16 2007 UTC vs.
Revision 1.62 by root, Thu Nov 29 17:28:13 2007 UTC