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Revision 1.229 by root, Wed Apr 15 17:49:27 2009 UTC

…		…
9	=head2 EXAMPLE PROGRAM	9	=head2 EXAMPLE PROGRAM
10		10
11	// a single header file is required	11	// a single header file is required
12	#include <ev.h>	12	#include <ev.h>
13		13
		14	#include <stdio.h> // for puts
		15
14	// every watcher type has its own typedef'd struct	16	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	17	// with the name ev_TYPE
16	ev_io stdin_watcher;	18	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	19	ev_timer timeout_watcher;
18		20
19	// all watcher callbacks have a similar signature	21	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	22	// this callback is called when data is readable on stdin
21	static void	23	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	24	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	25	{
24	puts ("stdin ready");	26	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	27	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	28	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	29	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	32	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	33	}
32		34
33	// another callback, this time for a time-out	35	// another callback, this time for a time-out
34	static void	36	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	37	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	38	{
37	puts ("timeout");	39	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	40	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	41	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	42	}
…		…
103	Libev is very configurable. In this manual the default (and most common)	105	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	106	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	107	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	108	B<EMBED> section in this manual. If libev was configured without support
107	for multiple event loops, then all functions taking an initial argument of	109	for multiple event loops, then all functions taking an initial argument of
108	name C<loop> (which is always of type C<struct ev_loop *>) will not have	110	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	111	this argument.
110		112
111	=head2 TIME REPRESENTATION	113	=head2 TIME REPRESENTATION
112		114
113	Libev represents time as a single floating point number, representing the	115	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	216	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	217	recommended ones.
216		218
217	See the description of C<ev_embed> watchers for more info.	219	See the description of C<ev_embed> watchers for more info.
218		220
219	=item ev_set_allocator (void *(*cb)(void *ptr, long size))	221	=item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]
220		222
221	Sets the allocation function to use (the prototype is similar - the	223	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	224	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	225	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	226	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	252	}
251		253
252	...	254	...
253	ev_set_allocator (persistent_realloc);	255	ev_set_allocator (persistent_realloc);
254		256
255	=item ev_set_syserr_cb (void (*cb)(const char *msg));	257	=item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]
256		258
257	Set the callback function to call on a retryable system call error (such	259	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	260	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	261	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	262	callback is set, then libev will expect it to remedy the situation, no
…		…
276		278
277	=back	279	=back
278		280
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	281	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		282
281	An event loop is described by a C<struct ev_loop *>. The library knows two	283	An event loop is described by a C<struct ev_loop *> (the C<struct>
282	types of such loops, the I<default> loop, which supports signals and child	284	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	285	I<function>).
		286
		287	The library knows two types of such loops, the I<default> loop, which
		288	supports signals and child events, and dynamically created loops which do
		289	not.
284		290
285	=over 4	291	=over 4
286		292
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	293	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		294
…		…
294	If you don't know what event loop to use, use the one returned from this	300	If you don't know what event loop to use, use the one returned from this
295	function.	301	function.
296		302
297	Note that this function is I<not> thread-safe, so if you want to use it	303	Note that this function is I<not> thread-safe, so if you want to use it
298	from multiple threads, you have to lock (note also that this is unlikely,	304	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	305	as loops cannot be shared easily between threads anyway).
300		306
301	The default loop is the only loop that can handle C<ev_signal> and	307	The default loop is the only loop that can handle C<ev_signal> and
302	C<ev_child> watchers, and to do this, it always registers a handler	308	C<ev_child> watchers, and to do this, it always registers a handler
303	for C<SIGCHLD>. If this is a problem for your application you can either	309	for C<SIGCHLD>. If this is a problem for your application you can either
304	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you	310	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	386	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		387
382	For few fds, this backend is a bit little slower than poll and select,	388	For few fds, this backend is a bit little slower than poll and select,
383	but it scales phenomenally better. While poll and select usually scale	389	but it scales phenomenally better. While poll and select usually scale
384	like O(total_fds) where n is the total number of fds (or the highest fd),	390	like O(total_fds) where n is the total number of fds (or the highest fd),
385	epoll scales either O(1) or O(active_fds). The epoll design has a number	391	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	392
387	cases and requiring a system call per fd change, no fork support and bad	393	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	394	of the more advanced event mechanisms: mere annoyances include silently
		395	dropping file descriptors, requiring a system call per change per file
		396	descriptor (and unnecessary guessing of parameters), problems with dup and
		397	so on. The biggest issue is fork races, however - if a program forks then
		398	I<both> parent and child process have to recreate the epoll set, which can
		399	take considerable time (one syscall per file descriptor) and is of course
		400	hard to detect.
		401
		402	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		403	of course I<doesn't>, and epoll just loves to report events for totally
		404	I<different> file descriptors (even already closed ones, so one cannot
		405	even remove them from the set) than registered in the set (especially
		406	on SMP systems). Libev tries to counter these spurious notifications by
		407	employing an additional generation counter and comparing that against the
		408	events to filter out spurious ones, recreating the set when required.
389		409
390	While stopping, setting and starting an I/O watcher in the same iteration	410	While stopping, setting and starting an I/O watcher in the same iteration
391	will result in some caching, there is still a system call per such incident	411	will result in some caching, there is still a system call per such
392	(because the fd could point to a different file description now), so its	412	incident (because the same I<file descriptor> could point to a different
393	best to avoid that. Also, C<dup ()>'ed file descriptors might not work	413	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	414	file descriptors might not work very well if you register events for both
395		415	file descriptors.
396	Please note that epoll sometimes generates spurious notifications, so you
397	need to use non-blocking I/O or other means to avoid blocking when no data
398	(or space) is available.
399		416
400	Best performance from this backend is achieved by not unregistering all	417	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	418	watchers for a file descriptor until it has been closed, if possible,
402	i.e. keep at least one watcher active per fd at all times. Stopping and	419	i.e. keep at least one watcher active per fd at all times. Stopping and
403	starting a watcher (without re-setting it) also usually doesn't cause	420	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	421	extra overhead. A fork can both result in spurious notifications as well
		422	as in libev having to destroy and recreate the epoll object, which can
		423	take considerable time and thus should be avoided.
		424
		425	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		426	faster than epoll for maybe up to a hundred file descriptors, depending on
		427	the usage. So sad.
405		428
406	While nominally embeddable in other event loops, this feature is broken in	429	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	430	all kernel versions tested so far.
408		431
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	432	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	433	C<EVBACKEND_POLL>.
411		434
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	435	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		436
414	Kqueue deserves special mention, as at the time of this writing, it was	437	Kqueue deserves special mention, as at the time of this writing, it
415	broken on all BSDs except NetBSD (usually it doesn't work reliably with	438	was broken on all BSDs except NetBSD (usually it doesn't work reliably
416	anything but sockets and pipes, except on Darwin, where of course it's	439	with anything but sockets and pipes, except on Darwin, where of course
417	completely useless). For this reason it's not being "auto-detected" unless	440	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	441	is by design, these kqueue bugs can (and eventually will) be fixed
419	libev was compiled on a known-to-be-good (-enough) system like NetBSD.	442	without API changes to existing programs. For this reason it's not being
		443	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		444	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		445	system like NetBSD.
420		446
421	You still can embed kqueue into a normal poll or select backend and use it	447	You still can embed kqueue into a normal poll or select backend and use it
422	only for sockets (after having made sure that sockets work with kqueue on	448	only for sockets (after having made sure that sockets work with kqueue on
423	the target platform). See C<ev_embed> watchers for more info.	449	the target platform). See C<ev_embed> watchers for more info.
424		450
425	It scales in the same way as the epoll backend, but the interface to the	451	It scales in the same way as the epoll backend, but the interface to the
426	kernel is more efficient (which says nothing about its actual speed, of	452	kernel is more efficient (which says nothing about its actual speed, of
427	course). While stopping, setting and starting an I/O watcher does never	453	course). While stopping, setting and starting an I/O watcher does never
428	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to	454	cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to
429	two event changes per incident. Support for C<fork ()> is very bad and it	455	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	456	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		457	cases
431		458
432	This backend usually performs well under most conditions.	459	This backend usually performs well under most conditions.
433		460
434	While nominally embeddable in other event loops, this doesn't work	461	While nominally embeddable in other event loops, this doesn't work
435	everywhere, so you might need to test for this. And since it is broken	462	everywhere, so you might need to test for this. And since it is broken
436	almost everywhere, you should only use it when you have a lot of sockets	463	almost everywhere, you should only use it when you have a lot of sockets
437	(for which it usually works), by embedding it into another event loop	464	(for which it usually works), by embedding it into another event loop
438	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it,	465	(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course
439	using it only for sockets.	466	also broken on OS X)) and, did I mention it, using it only for sockets.
440		467
441	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with	468	This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with
442	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with	469	C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with
443	C<NOTE_EOF>.	470	C<NOTE_EOF>.
444		471
…		…
464	might perform better.	491	might perform better.
465		492
466	On the positive side, with the exception of the spurious readiness	493	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	494	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	495	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	496	OS-specific backends (I vastly prefer correctness over speed hacks).
470		497
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	498	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	499	C<EVBACKEND_POLL>.
473		500
474	=item C<EVBACKEND_ALL>	501	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	554	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	555	calling this function, or cope with the fact afterwards (which is usually
529	the easiest thing, you can just ignore the watchers and/or C<free ()> them	556	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	557	for example).
531		558
532	Note that certain global state, such as signal state, will not be freed by	559	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	560	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	561	as signal and child watchers) would need to be stopped manually.
535		562
536	In general it is not advisable to call this function except in the	563	In general it is not advisable to call this function except in the
537	rare occasion where you really need to free e.g. the signal handling	564	rare occasion where you really need to free e.g. the signal handling
538	pipe fds. If you need dynamically allocated loops it is better to use	565	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	566	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	658	the loop.
632		659
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	660	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
634	necessary) and will handle those and any already outstanding ones. It	661	necessary) and will handle those and any already outstanding ones. It
635	will block your process until at least one new event arrives (which could	662	will block your process until at least one new event arrives (which could
636	be an event internal to libev itself, so there is no guarentee that a	663	be an event internal to libev itself, so there is no guarantee that a
637	user-registered callback will be called), and will return after one	664	user-registered callback will be called), and will return after one
638	iteration of the loop.	665	iteration of the loop.
639		666
640	This is useful if you are waiting for some external event in conjunction	667	This is useful if you are waiting for some external event in conjunction
641	with something not expressible using other libev watchers (i.e. "roll your	668	with something not expressible using other libev watchers (i.e. "roll your
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	712	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	713	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		714
688	This "unloop state" will be cleared when entering C<ev_loop> again.	715	This "unloop state" will be cleared when entering C<ev_loop> again.
689		716
		717	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		718
690	=item ev_ref (loop)	719	=item ev_ref (loop)
691		720
692	=item ev_unref (loop)	721	=item ev_unref (loop)
693		722
694	Ref/unref can be used to add or remove a reference count on the event	723	Ref/unref can be used to add or remove a reference count on the event
…		…
697		726
698	If you have a watcher you never unregister that should not keep C<ev_loop>	727	If you have a watcher you never unregister that should not keep C<ev_loop>
699	from returning, call ev_unref() after starting, and ev_ref() before	728	from returning, call ev_unref() after starting, and ev_ref() before
700	stopping it.	729	stopping it.
701		730
702	As an example, libev itself uses this for its internal signal pipe: It is	731	As an example, libev itself uses this for its internal signal pipe: It
703	not visible to the libev user and should not keep C<ev_loop> from exiting	732	is not visible to the libev user and should not keep C<ev_loop> from
704	if no event watchers registered by it are active. It is also an excellent	733	exiting if no event watchers registered by it are active. It is also an
705	way to do this for generic recurring timers or from within third-party	734	excellent way to do this for generic recurring timers or from within
706	libraries. Just remember to I<unref after start> and I<ref before stop>	735	third-party libraries. Just remember to I<unref after start> and I<ref
707	(but only if the watcher wasn't active before, or was active before,	736	before stop> (but only if the watcher wasn't active before, or was active
708	respectively).	737	before, respectively. Note also that libev might stop watchers itself
		738	(e.g. non-repeating timers) in which case you have to C<ev_ref>
		739	in the callback).
709		740
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	741	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	742	running when nothing else is active.
712		743
713	struct ev_signal exitsig;	744	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	745	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	746	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	747	evf_unref (loop);
717		748
718	Example: For some weird reason, unregister the above signal handler again.	749	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	797	they fire on, say, one-second boundaries only.
767		798
768	=item ev_loop_verify (loop)	799	=item ev_loop_verify (loop)
769		800
770	This function only does something when C<EV_VERIFY> support has been	801	This function only does something when C<EV_VERIFY> support has been
771	compiled in. which is the default for non-minimal builds. It tries to go	802	compiled in, which is the default for non-minimal builds. It tries to go
772	through all internal structures and checks them for validity. If anything	803	through all internal structures and checks them for validity. If anything
773	is found to be inconsistent, it will print an error message to standard	804	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	805	error and call C<abort ()>.
775		806
776	This can be used to catch bugs inside libev itself: under normal	807	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	811	=back
781		812
782		813
783	=head1 ANATOMY OF A WATCHER	814	=head1 ANATOMY OF A WATCHER
784		815
		816	In the following description, uppercase C<TYPE> in names stands for the
		817	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		818	watchers and C<ev_io_start> for I/O watchers.
		819
785	A watcher is a structure that you create and register to record your	820	A watcher is a structure that you create and register to record your
786	interest in some event. For instance, if you want to wait for STDIN to	821	interest in some event. For instance, if you want to wait for STDIN to
787	become readable, you would create an C<ev_io> watcher for that:	822	become readable, you would create an C<ev_io> watcher for that:
788		823
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	824	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	825	{
791	ev_io_stop (w);	826	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	827	ev_unloop (loop, EVUNLOOP_ALL);
793	}	828	}
794		829
795	struct ev_loop *loop = ev_default_loop (0);	830	struct ev_loop *loop = ev_default_loop (0);
		831
796	struct ev_io stdin_watcher;	832	ev_io stdin_watcher;
		833
797	ev_init (&stdin_watcher, my_cb);	834	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	835	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	836	ev_io_start (loop, &stdin_watcher);
		837
800	ev_loop (loop, 0);	838	ev_loop (loop, 0);
801		839
802	As you can see, you are responsible for allocating the memory for your	840	As you can see, you are responsible for allocating the memory for your
803	watcher structures (and it is usually a bad idea to do this on the stack,	841	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	842	stack).
		843
		844	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		845	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		846
806	Each watcher structure must be initialised by a call to C<ev_init	847	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	848	(watcher *, callback)>, which expects a callback to be provided. This
808	callback gets invoked each time the event occurs (or, in the case of I/O	849	callback gets invoked each time the event occurs (or, in the case of I/O
809	watchers, each time the event loop detects that the file descriptor given	850	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	851	is readable and/or writable).
811		852
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	853	Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >>
813	with arguments specific to this watcher type. There is also a macro	854	macro to configure it, with arguments specific to the watcher type. There
814	to combine initialisation and setting in one call: C<< ev_<type>_init	855	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	856	ev_TYPE_init (watcher *, callback, ...) >>.
816		857
817	To make the watcher actually watch out for events, you have to start it	858	To make the watcher actually watch out for events, you have to start it
818	with a watcher-specific start function (C<< ev_<type>_start (loop, watcher	859	with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher
819	*) >>), and you can stop watching for events at any time by calling the	860	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	861	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		862
822	As long as your watcher is active (has been started but not stopped) you	863	As long as your watcher is active (has been started but not stopped) you
823	must not touch the values stored in it. Most specifically you must never	864	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	865	reinitialise it or call its C<ev_TYPE_set> macro.
825		866
826	Each and every callback receives the event loop pointer as first, the	867	Each and every callback receives the event loop pointer as first, the
827	registered watcher structure as second, and a bitset of received events as	868	registered watcher structure as second, and a bitset of received events as
828	third argument.	869	third argument.
829		870
…		…
887		928
888	=item C<EV_ASYNC>	929	=item C<EV_ASYNC>
889		930
890	The given async watcher has been asynchronously notified (see C<ev_async>).	931	The given async watcher has been asynchronously notified (see C<ev_async>).
891		932
		933	=item C<EV_CUSTOM>
		934
		935	Not ever sent (or otherwise used) by libev itself, but can be freely used
		936	by libev users to signal watchers (e.g. via C<ev_feed_event>).
		937
892	=item C<EV_ERROR>	938	=item C<EV_ERROR>
893		939
894	An unspecified error has occurred, the watcher has been stopped. This might	940	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	941	happen because the watcher could not be properly started because libev
896	ran out of memory, a file descriptor was found to be closed or any other	942	ran out of memory, a file descriptor was found to be closed or any other
		943	problem. Libev considers these application bugs.
		944
897	problem. You best act on it by reporting the problem and somehow coping	945	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	946	watcher being stopped. Note that well-written programs should not receive
		947	an error ever, so when your watcher receives it, this usually indicates a
		948	bug in your program.
899		949
900	Libev will usually signal a few "dummy" events together with an error, for	950	Libev will usually signal a few "dummy" events together with an error, for
901	example it might indicate that a fd is readable or writable, and if your	951	example it might indicate that a fd is readable or writable, and if your
902	callbacks is well-written it can just attempt the operation and cope with	952	callbacks is well-written it can just attempt the operation and cope with
903	the error from read() or write(). This will not work in multi-threaded	953	the error from read() or write(). This will not work in multi-threaded
…		…
906		956
907	=back	957	=back
908		958
909	=head2 GENERIC WATCHER FUNCTIONS	959	=head2 GENERIC WATCHER FUNCTIONS
910		960
911	In the following description, C<TYPE> stands for the watcher type,
912	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
913
914	=over 4	961	=over 4
915		962
916	=item C<ev_init> (ev_TYPE *watcher, callback)	963	=item C<ev_init> (ev_TYPE *watcher, callback)
917		964
918	This macro initialises the generic portion of a watcher. The contents	965	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	970	which rolls both calls into one.
924		971
925	You can reinitialise a watcher at any time as long as it has been stopped	972	You can reinitialise a watcher at any time as long as it has been stopped
926	(or never started) and there are no pending events outstanding.	973	(or never started) and there are no pending events outstanding.
927		974
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	975	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	976	int revents)>.
930		977
931	Example: Initialise an C<ev_io> watcher in two steps.	978	Example: Initialise an C<ev_io> watcher in two steps.
932		979
933	ev_io w;	980	ev_io w;
…		…
967		1014
968	ev_io_start (EV_DEFAULT_UC, &w);	1015	ev_io_start (EV_DEFAULT_UC, &w);
969		1016
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1017	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1018
972	Stops the given watcher again (if active) and clears the pending	1019	Stops the given watcher if active, and clears the pending status (whether
		1020	the watcher was active or not).
		1021
973	status. It is possible that stopped watchers are pending (for example,	1022	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1023	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	1024	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	1025	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	1026	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1027
979	=item bool ev_is_active (ev_TYPE *watcher)	1028	=item bool ev_is_active (ev_TYPE *watcher)
980		1029
981	Returns a true value iff the watcher is active (i.e. it has been started	1030	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	1031	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1024	The default priority used by watchers when no priority has been set is	1073	The default priority used by watchers when no priority has been set is
1025	always C<0>, which is supposed to not be too high and not be too low :).	1074	always C<0>, which is supposed to not be too high and not be too low :).
1026		1075
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1076	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
1028	fine, as long as you do not mind that the priority value you query might	1077	fine, as long as you do not mind that the priority value you query might
1029	or might not have been adjusted to be within valid range.	1078	or might not have been clamped to the valid range.
1030		1079
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1080	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1081
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1082	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
1034	C<loop> nor C<revents> need to be valid as long as the watcher callback	1083	C<loop> nor C<revents> need to be valid as long as the watcher callback
…		…
1056	member, you can also "subclass" the watcher type and provide your own	1105	member, you can also "subclass" the watcher type and provide your own
1057	data:	1106	data:
1058		1107
1059	struct my_io	1108	struct my_io
1060	{	1109	{
1061	struct ev_io io;	1110	ev_io io;
1062	int otherfd;	1111	int otherfd;
1063	void *somedata;	1112	void *somedata;
1064	struct whatever *mostinteresting;	1113	struct whatever *mostinteresting;
1065	};	1114	};
1066		1115
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1118	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1119
1071	And since your callback will be called with a pointer to the watcher, you	1120	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1121	can cast it back to your own type:
1073		1122
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1123	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1124	{
1076	struct my_io *w = (struct my_io *)w_;	1125	struct my_io *w = (struct my_io *)w_;
1077	...	1126	...
1078	}	1127	}
1079		1128
…		…
1097	programmers):	1146	programmers):
1098		1147
1099	#include <stddef.h>	1148	#include <stddef.h>
1100		1149
1101	static void	1150	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1151	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1152	{
1104	struct my_biggy big = (struct my_biggy *	1153	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1154	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1155	}
1107		1156
1108	static void	1157	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1158	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1159	{
1111	struct my_biggy big = (struct my_biggy *	1160	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1161	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1162	}
1114		1163
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1298	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250	readable, but only once. Since it is likely line-buffered, you could	1299	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1300	attempt to read a whole line in the callback.
1252		1301
1253	static void	1302	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1303	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1304	{
1256	ev_io_stop (loop, w);	1305	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1306	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1307	}
1259		1308
1260	...	1309	...
1261	struct ev_loop *loop = ev_default_init (0);	1310	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1311	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1312	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1313	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1314	ev_loop (loop, 0);
1266		1315
1267		1316
…		…
1278		1327
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1328	The callback is guaranteed to be invoked only I<after> its timeout has
1280	passed, but if multiple timers become ready during the same loop iteration	1329	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1330	then order of execution is undefined.
1282		1331
		1332	=head3 Be smart about timeouts
		1333
		1334	Many real-world problems involve some kind of timeout, usually for error
		1335	recovery. A typical example is an HTTP request - if the other side hangs,
		1336	you want to raise some error after a while.
		1337
		1338	What follows are some ways to handle this problem, from obvious and
		1339	inefficient to smart and efficient.
		1340
		1341	In the following, a 60 second activity timeout is assumed - a timeout that
		1342	gets reset to 60 seconds each time there is activity (e.g. each time some
		1343	data or other life sign was received).
		1344
		1345	=over 4
		1346
		1347	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1348
		1349	This is the most obvious, but not the most simple way: In the beginning,
		1350	start the watcher:
		1351
		1352	ev_timer_init (timer, callback, 60., 0.);
		1353	ev_timer_start (loop, timer);
		1354
		1355	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1356	and start it again:
		1357
		1358	ev_timer_stop (loop, timer);
		1359	ev_timer_set (timer, 60., 0.);
		1360	ev_timer_start (loop, timer);
		1361
		1362	This is relatively simple to implement, but means that each time there is
		1363	some activity, libev will first have to remove the timer from its internal
		1364	data structure and then add it again. Libev tries to be fast, but it's
		1365	still not a constant-time operation.
		1366
		1367	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1368
		1369	This is the easiest way, and involves using C<ev_timer_again> instead of
		1370	C<ev_timer_start>.
		1371
		1372	To implement this, configure an C<ev_timer> with a C<repeat> value
		1373	of C<60> and then call C<ev_timer_again> at start and each time you
		1374	successfully read or write some data. If you go into an idle state where
		1375	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1376	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1377
		1378	That means you can ignore both the C<ev_timer_start> function and the
		1379	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1380	member and C<ev_timer_again>.
		1381
		1382	At start:
		1383
		1384	ev_timer_init (timer, callback);
		1385	timer->repeat = 60.;
		1386	ev_timer_again (loop, timer);
		1387
		1388	Each time there is some activity:
		1389
		1390	ev_timer_again (loop, timer);
		1391
		1392	It is even possible to change the time-out on the fly, regardless of
		1393	whether the watcher is active or not:
		1394
		1395	timer->repeat = 30.;
		1396	ev_timer_again (loop, timer);
		1397
		1398	This is slightly more efficient then stopping/starting the timer each time
		1399	you want to modify its timeout value, as libev does not have to completely
		1400	remove and re-insert the timer from/into its internal data structure.
		1401
		1402	It is, however, even simpler than the "obvious" way to do it.
		1403
		1404	=item 3. Let the timer time out, but then re-arm it as required.
		1405
		1406	This method is more tricky, but usually most efficient: Most timeouts are
		1407	relatively long compared to the intervals between other activity - in
		1408	our example, within 60 seconds, there are usually many I/O events with
		1409	associated activity resets.
		1410
		1411	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1412	but remember the time of last activity, and check for a real timeout only
		1413	within the callback:
		1414
		1415	ev_tstamp last_activity; // time of last activity
		1416
		1417	static void
		1418	callback (EV_P_ ev_timer *w, int revents)
		1419	{
		1420	ev_tstamp now = ev_now (EV_A);
		1421	ev_tstamp timeout = last_activity + 60.;
		1422
		1423	// if last_activity + 60. is older than now, we did time out
		1424	if (timeout < now)
		1425	{
		1426	// timeout occured, take action
		1427	}
		1428	else
		1429	{
		1430	// callback was invoked, but there was some activity, re-arm
		1431	// the watcher to fire in last_activity + 60, which is
		1432	// guaranteed to be in the future, so "again" is positive:
		1433	w->repeat = timeout - now;
		1434	ev_timer_again (EV_A_ w);
		1435	}
		1436	}
		1437
		1438	To summarise the callback: first calculate the real timeout (defined
		1439	as "60 seconds after the last activity"), then check if that time has
		1440	been reached, which means something I<did>, in fact, time out. Otherwise
		1441	the callback was invoked too early (C<timeout> is in the future), so
		1442	re-schedule the timer to fire at that future time, to see if maybe we have
		1443	a timeout then.
		1444
		1445	Note how C<ev_timer_again> is used, taking advantage of the
		1446	C<ev_timer_again> optimisation when the timer is already running.
		1447
		1448	This scheme causes more callback invocations (about one every 60 seconds
		1449	minus half the average time between activity), but virtually no calls to
		1450	libev to change the timeout.
		1451
		1452	To start the timer, simply initialise the watcher and set C<last_activity>
		1453	to the current time (meaning we just have some activity :), then call the
		1454	callback, which will "do the right thing" and start the timer:
		1455
		1456	ev_timer_init (timer, callback);
		1457	last_activity = ev_now (loop);
		1458	callback (loop, timer, EV_TIMEOUT);
		1459
		1460	And when there is some activity, simply store the current time in
		1461	C<last_activity>, no libev calls at all:
		1462
		1463	last_actiivty = ev_now (loop);
		1464
		1465	This technique is slightly more complex, but in most cases where the
		1466	time-out is unlikely to be triggered, much more efficient.
		1467
		1468	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1469	callback :) - just change the timeout and invoke the callback, which will
		1470	fix things for you.
		1471
		1472	=item 4. Wee, just use a double-linked list for your timeouts.
		1473
		1474	If there is not one request, but many thousands (millions...), all
		1475	employing some kind of timeout with the same timeout value, then one can
		1476	do even better:
		1477
		1478	When starting the timeout, calculate the timeout value and put the timeout
		1479	at the I<end> of the list.
		1480
		1481	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1482	the list is expected to fire (for example, using the technique #3).
		1483
		1484	When there is some activity, remove the timer from the list, recalculate
		1485	the timeout, append it to the end of the list again, and make sure to
		1486	update the C<ev_timer> if it was taken from the beginning of the list.
		1487
		1488	This way, one can manage an unlimited number of timeouts in O(1) time for
		1489	starting, stopping and updating the timers, at the expense of a major
		1490	complication, and having to use a constant timeout. The constant timeout
		1491	ensures that the list stays sorted.
		1492
		1493	=back
		1494
		1495	So which method the best?
		1496
		1497	Method #2 is a simple no-brain-required solution that is adequate in most
		1498	situations. Method #3 requires a bit more thinking, but handles many cases
		1499	better, and isn't very complicated either. In most case, choosing either
		1500	one is fine, with #3 being better in typical situations.
		1501
		1502	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1503	rather complicated, but extremely efficient, something that really pays
		1504	off after the first million or so of active timers, i.e. it's usually
		1505	overkill :)
		1506
1283	=head3 The special problem of time updates	1507	=head3 The special problem of time updates
1284		1508
1285	Establishing the current time is a costly operation (it usually takes at	1509	Establishing the current time is a costly operation (it usually takes at
1286	least two system calls): EV therefore updates its idea of the current	1510	least two system calls): EV therefore updates its idea of the current
1287	time only before and after C<ev_loop> collects new events, which causes a	1511	time only before and after C<ev_loop> collects new events, which causes a
…		…
1330	If the timer is started but non-repeating, stop it (as if it timed out).	1554	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1555
1332	If the timer is repeating, either start it if necessary (with the	1556	If the timer is repeating, either start it if necessary (with the
1333	C<repeat> value), or reset the running timer to the C<repeat> value.	1557	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1558
1335	This sounds a bit complicated, but here is a useful and typical	1559	This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336	example: Imagine you have a TCP connection and you want a so-called idle	1560	usage example.
1337	timeout, that is, you want to be called when there have been, say, 60
1338	seconds of inactivity on the socket. The easiest way to do this is to
1339	configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340	C<ev_timer_again> each time you successfully read or write some data. If
1341	you go into an idle state where you do not expect data to travel on the
1342	socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343	automatically restart it if need be.
1344
1345	That means you can ignore the C<after> value and C<ev_timer_start>
1346	altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348	ev_timer_init (timer, callback, 0., 5.);
1349	ev_timer_again (loop, timer);
1350	...
1351	timer->again = 17.;
1352	ev_timer_again (loop, timer);
1353	...
1354	timer->again = 10.;
1355	ev_timer_again (loop, timer);
1356
1357	This is more slightly efficient then stopping/starting the timer each time
1358	you want to modify its timeout value.
1359
1360	Note, however, that it is often even more efficient to remember the
1361	time of the last activity and let the timer time-out naturally. In the
1362	callback, you then check whether the time-out is real, or, if there was
1363	some activity, you reschedule the watcher to time-out in "last_activity +
1364	timeout - ev_now ()" seconds.
1365		1561
1366	=item ev_tstamp repeat [read-write]	1562	=item ev_tstamp repeat [read-write]
1367		1563
1368	The current C<repeat> value. Will be used each time the watcher times out	1564	The current C<repeat> value. Will be used each time the watcher times out
1369	or C<ev_timer_again> is called, and determines the next timeout (if any),	1565	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1570	=head3 Examples
1375		1571
1376	Example: Create a timer that fires after 60 seconds.	1572	Example: Create a timer that fires after 60 seconds.
1377		1573
1378	static void	1574	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1576	{
1381	.. one minute over, w is actually stopped right here	1577	.. one minute over, w is actually stopped right here
1382	}	1578	}
1383		1579
1384	struct ev_timer mytimer;	1580	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1581	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1582	ev_timer_start (loop, &mytimer);
1387		1583
1388	Example: Create a timeout timer that times out after 10 seconds of	1584	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1585	inactivity.
1390		1586
1391	static void	1587	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1588	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1589	{
1394	.. ten seconds without any activity	1590	.. ten seconds without any activity
1395	}	1591	}
1396		1592
1397	struct ev_timer mytimer;	1593	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1594	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1595	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1596	ev_loop (loop, 0);
1401		1597
1402	// and in some piece of code that gets executed on any "activity":	1598	// and in some piece of code that gets executed on any "activity":
…		…
1407	=head2 C<ev_periodic> - to cron or not to cron?	1603	=head2 C<ev_periodic> - to cron or not to cron?
1408		1604
1409	Periodic watchers are also timers of a kind, but they are very versatile	1605	Periodic watchers are also timers of a kind, but they are very versatile
1410	(and unfortunately a bit complex).	1606	(and unfortunately a bit complex).
1411		1607
1412	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	1608	Unlike C<ev_timer>, periodic watchers are not based on real time (or
1413	but on wall clock time (absolute time). You can tell a periodic watcher	1609	relative time, the physical time that passes) but on wall clock time
1414	to trigger after some specific point in time. For example, if you tell a	1610	(absolute time, the thing you can read on your calender or clock). The
1415	periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now ()	1611	difference is that wall clock time can run faster or slower than real
1416	+ 10.>, that is, an absolute time not a delay) and then reset your system	1612	time, and time jumps are not uncommon (e.g. when you adjust your
1417	clock to January of the previous year, then it will take more than year	1613	wrist-watch).
1418	to trigger the event (unlike an C<ev_timer>, which would still trigger
1419	roughly 10 seconds later as it uses a relative timeout).
1420		1614
		1615	You can tell a periodic watcher to trigger after some specific point
		1616	in time: for example, if you tell a periodic watcher to trigger "in 10
		1617	seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time
		1618	not a delay) and then reset your system clock to January of the previous
		1619	year, then it will take a year or more to trigger the event (unlike an
		1620	C<ev_timer>, which would still trigger roughly 10 seconds after starting
		1621	it, as it uses a relative timeout).
		1622
1421	C<ev_periodic>s can also be used to implement vastly more complex timers,	1623	C<ev_periodic> watchers can also be used to implement vastly more complex
1422	such as triggering an event on each "midnight, local time", or other	1624	timers, such as triggering an event on each "midnight, local time", or
1423	complicated rules.	1625	other complicated rules. This cannot be done with C<ev_timer> watchers, as
		1626	those cannot react to time jumps.
1424		1627
1425	As with timers, the callback is guaranteed to be invoked only when the	1628	As with timers, the callback is guaranteed to be invoked only when the
1426	time (C<at>) has passed, but if multiple periodic timers become ready	1629	point in time where it is supposed to trigger has passed, but if multiple
1427	during the same loop iteration, then order of execution is undefined.	1630	periodic timers become ready during the same loop iteration, then order of
		1631	execution is undefined.
1428		1632
1429	=head3 Watcher-Specific Functions and Data Members	1633	=head3 Watcher-Specific Functions and Data Members
1430		1634
1431	=over 4	1635	=over 4
1432		1636
1433	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)	1637	=item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1434		1638
1435	=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)	1639	=item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb)
1436		1640
1437	Lots of arguments, lets sort it out... There are basically three modes of	1641	Lots of arguments, let's sort it out... There are basically three modes of
1438	operation, and we will explain them from simplest to most complex:	1642	operation, and we will explain them from simplest to most complex:
1439		1643
1440	=over 4	1644	=over 4
1441		1645
1442	=item * absolute timer (at = time, interval = reschedule_cb = 0)	1646	=item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0)
1443		1647
1444	In this configuration the watcher triggers an event after the wall clock	1648	In this configuration the watcher triggers an event after the wall clock
1445	time C<at> has passed. It will not repeat and will not adjust when a time	1649	time C<offset> has passed. It will not repeat and will not adjust when a
1446	jump occurs, that is, if it is to be run at January 1st 2011 then it will	1650	time jump occurs, that is, if it is to be run at January 1st 2011 then it
1447	only run when the system clock reaches or surpasses this time.	1651	will be stopped and invoked when the system clock reaches or surpasses
		1652	this point in time.
1448		1653
1449	=item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)	1654	=item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0)
1450		1655
1451	In this mode the watcher will always be scheduled to time out at the next	1656	In this mode the watcher will always be scheduled to time out at the next
1452	C<at + N * interval> time (for some integer N, which can also be negative)	1657	C<offset + N * interval> time (for some integer N, which can also be
1453	and then repeat, regardless of any time jumps.	1658	negative) and then repeat, regardless of any time jumps. The C<offset>
		1659	argument is merely an offset into the C<interval> periods.
1454		1660
1455	This can be used to create timers that do not drift with respect to the	1661	This can be used to create timers that do not drift with respect to the
1456	system clock, for example, here is a C<ev_periodic> that triggers each	1662	system clock, for example, here is an C<ev_periodic> that triggers each
1457	hour, on the hour:	1663	hour, on the hour (with respect to UTC):
1458		1664
1459	ev_periodic_set (&periodic, 0., 3600., 0);	1665	ev_periodic_set (&periodic, 0., 3600., 0);
1460		1666
1461	This doesn't mean there will always be 3600 seconds in between triggers,	1667	This doesn't mean there will always be 3600 seconds in between triggers,
1462	but only that the callback will be called when the system time shows a	1668	but only that the callback will be called when the system time shows a
1463	full hour (UTC), or more correctly, when the system time is evenly divisible	1669	full hour (UTC), or more correctly, when the system time is evenly divisible
1464	by 3600.	1670	by 3600.
1465		1671
1466	Another way to think about it (for the mathematically inclined) is that	1672	Another way to think about it (for the mathematically inclined) is that
1467	C<ev_periodic> will try to run the callback in this mode at the next possible	1673	C<ev_periodic> will try to run the callback in this mode at the next possible
1468	time where C<time = at (mod interval)>, regardless of any time jumps.	1674	time where C<time = offset (mod interval)>, regardless of any time jumps.
1469		1675
1470	For numerical stability it is preferable that the C<at> value is near	1676	For numerical stability it is preferable that the C<offset> value is near
1471	C<ev_now ()> (the current time), but there is no range requirement for	1677	C<ev_now ()> (the current time), but there is no range requirement for
1472	this value, and in fact is often specified as zero.	1678	this value, and in fact is often specified as zero.
1473		1679
1474	Note also that there is an upper limit to how often a timer can fire (CPU	1680	Note also that there is an upper limit to how often a timer can fire (CPU
1475	speed for example), so if C<interval> is very small then timing stability	1681	speed for example), so if C<interval> is very small then timing stability
1476	will of course deteriorate. Libev itself tries to be exact to be about one	1682	will of course deteriorate. Libev itself tries to be exact to be about one
1477	millisecond (if the OS supports it and the machine is fast enough).	1683	millisecond (if the OS supports it and the machine is fast enough).
1478		1684
1479	=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)	1685	=item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback)
1480		1686
1481	In this mode the values for C<interval> and C<at> are both being	1687	In this mode the values for C<interval> and C<offset> are both being
1482	ignored. Instead, each time the periodic watcher gets scheduled, the	1688	ignored. Instead, each time the periodic watcher gets scheduled, the
1483	reschedule callback will be called with the watcher as first, and the	1689	reschedule callback will be called with the watcher as first, and the
1484	current time as second argument.	1690	current time as second argument.
1485		1691
1486	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,	1692	NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever,
1487	ever, or make ANY event loop modifications whatsoever>.	1693	or make ANY other event loop modifications whatsoever, unless explicitly
		1694	allowed by documentation here>.
1488		1695
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1696	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the	1697	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1698	only event loop modification you are allowed to do).
1492		1699
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1700	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1701	*w, ev_tstamp now)>, e.g.:
1495		1702
		1703	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1704	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1705	{
1498	return now + 60.;	1706	return now + 60.;
1499	}	1707	}
1500		1708
1501	It must return the next time to trigger, based on the passed time value	1709	It must return the next time to trigger, based on the passed time value
…		…
1521	a different time than the last time it was called (e.g. in a crond like	1729	a different time than the last time it was called (e.g. in a crond like
1522	program when the crontabs have changed).	1730	program when the crontabs have changed).
1523		1731
1524	=item ev_tstamp ev_periodic_at (ev_periodic *)	1732	=item ev_tstamp ev_periodic_at (ev_periodic *)
1525		1733
1526	When active, returns the absolute time that the watcher is supposed to	1734	When active, returns the absolute time that the watcher is supposed
1527	trigger next.	1735	to trigger next. This is not the same as the C<offset> argument to
		1736	C<ev_periodic_set>, but indeed works even in interval and manual
		1737	rescheduling modes.
1528		1738
1529	=item ev_tstamp offset [read-write]	1739	=item ev_tstamp offset [read-write]
1530		1740
1531	When repeating, this contains the offset value, otherwise this is the	1741	When repeating, this contains the offset value, otherwise this is the
1532	absolute point in time (the C<at> value passed to C<ev_periodic_set>).	1742	absolute point in time (the C<offset> value passed to C<ev_periodic_set>,
		1743	although libev might modify this value for better numerical stability).
1533		1744
1534	Can be modified any time, but changes only take effect when the periodic	1745	Can be modified any time, but changes only take effect when the periodic
1535	timer fires or C<ev_periodic_again> is being called.	1746	timer fires or C<ev_periodic_again> is being called.
1536		1747
1537	=item ev_tstamp interval [read-write]	1748	=item ev_tstamp interval [read-write]
1538		1749
1539	The current interval value. Can be modified any time, but changes only	1750	The current interval value. Can be modified any time, but changes only
1540	take effect when the periodic timer fires or C<ev_periodic_again> is being	1751	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1752	called.
1542		1753
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1754	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1755
1545	The current reschedule callback, or C<0>, if this functionality is	1756	The current reschedule callback, or C<0>, if this functionality is
1546	switched off. Can be changed any time, but changes only take effect when	1757	switched off. Can be changed any time, but changes only take effect when
1547	the periodic timer fires or C<ev_periodic_again> is being called.	1758	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1759
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1764	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1765	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1766	potentially a lot of jitter, but good long-term stability.
1556		1767
1557	static void	1768	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1769	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1770	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1771	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1772	}
1562		1773
1563	struct ev_periodic hourly_tick;	1774	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1775	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1776	ev_periodic_start (loop, &hourly_tick);
1566		1777
1567	Example: The same as above, but use a reschedule callback to do it:	1778	Example: The same as above, but use a reschedule callback to do it:
1568		1779
1569	#include <math.h>	1780	#include <math.h>
1570		1781
1571	static ev_tstamp	1782	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1783	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1784	{
1574	return now + (3600. - fmod (now, 3600.));	1785	return now + (3600. - fmod (now, 3600.));
1575	}	1786	}
1576		1787
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1788	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1789
1579	Example: Call a callback every hour, starting now:	1790	Example: Call a callback every hour, starting now:
1580		1791
1581	struct ev_periodic hourly_tick;	1792	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1793	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1794	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1795	ev_periodic_start (loop, &hourly_tick);
1585		1796
1586		1797
…		…
1625		1836
1626	=back	1837	=back
1627		1838
1628	=head3 Examples	1839	=head3 Examples
1629		1840
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1841	Example: Try to exit cleanly on SIGINT.
1631		1842
1632	static void	1843	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1844	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	1845	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1846	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1847	}
1637		1848
1638	struct ev_signal signal_watcher;	1849	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1850	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1851	ev_signal_start (loop, &signal_watcher);
1641		1852
1642		1853
1643	=head2 C<ev_child> - watch out for process status changes	1854	=head2 C<ev_child> - watch out for process status changes
1644		1855
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1856	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1929	its completion.
1719		1930
1720	ev_child cw;	1931	ev_child cw;
1721		1932
1722	static void	1933	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1934	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1935	{
1725	ev_child_stop (EV_A_ w);	1936	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1937	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1938	}
1728		1939
…		…
1743		1954
1744		1955
1745	=head2 C<ev_stat> - did the file attributes just change?	1956	=head2 C<ev_stat> - did the file attributes just change?
1746		1957
1747	This watches a file system path for attribute changes. That is, it calls	1958	This watches a file system path for attribute changes. That is, it calls
1748	C<stat> regularly (or when the OS says it changed) and sees if it changed	1959	C<stat> on that path in regular intervals (or when the OS says it changed)
1749	compared to the last time, invoking the callback if it did.	1960	and sees if it changed compared to the last time, invoking the callback if
		1961	it did.
1750		1962
1751	The path does not need to exist: changing from "path exists" to "path does	1963	The path does not need to exist: changing from "path exists" to "path does
1752	not exist" is a status change like any other. The condition "path does	1964	not exist" is a status change like any other. The condition "path does not
1753	not exist" is signified by the C<st_nlink> field being zero (which is	1965	exist" (or more correctly "path cannot be stat'ed") is signified by the
1754	otherwise always forced to be at least one) and all the other fields of	1966	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1967	least one) and all the other fields of the stat buffer having unspecified
		1968	contents.
1756		1969
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1970	The path I<must not> end in a slash or contain special components such as
		1971	C<.> or C<..>. The path I<should> be absolute: If it is relative and
1758	relative and your working directory changes, the behaviour is undefined.	1972	your working directory changes, then the behaviour is undefined.
1759		1973
1760	Since there is no standard kernel interface to do this, the portable	1974	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	1975	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	1976	to see if it changed somehow. You can specify a recommended polling
1763	this case. If you specify a polling interval of C<0> (highly recommended!)	1977	interval for this case. If you specify a polling interval of C<0> (highly
1764	then a I<suitable, unspecified default> value will be used (which	1978	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	1979	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	1980	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	1981	currently around C<0.1>, but that's usually overkill.
1768		1982
1769	This watcher type is not meant for massive numbers of stat watchers,	1983	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	1984	as even with OS-supported change notifications, this can be
1771	resource-intensive.	1985	resource-intensive.
1772		1986
1773	At the time of this writing, the only OS-specific interface implemented	1987	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	1988	is the Linux inotify interface (implementing kqueue support is left as an
1775	an exercise for the reader. Note, however, that the author sees no way	1989	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	1990	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		1991
1778	=head3 ABI Issues (Largefile Support)	1992	=head3 ABI Issues (Largefile Support)
1779		1993
1780	Libev by default (unless the user overrides this) uses the default	1994	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	1995	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	1996	support disabled by default, you get the 32 bit version of the stat
1783	structure. When using the library from programs that change the ABI to	1997	structure. When using the library from programs that change the ABI to
1784	use 64 bit file offsets the programs will fail. In that case you have to	1998	use 64 bit file offsets the programs will fail. In that case you have to
1785	compile libev with the same flags to get binary compatibility. This is	1999	compile libev with the same flags to get binary compatibility. This is
1786	obviously the case with any flags that change the ABI, but the problem is	2000	obviously the case with any flags that change the ABI, but the problem is
1787	most noticeably disabled with ev_stat and large file support.	2001	most noticeably displayed with ev_stat and large file support.
1788		2002
1789	The solution for this is to lobby your distribution maker to make large	2003	The solution for this is to lobby your distribution maker to make large
1790	file interfaces available by default (as e.g. FreeBSD does) and not	2004	file interfaces available by default (as e.g. FreeBSD does) and not
1791	optional. Libev cannot simply switch on large file support because it has	2005	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	2006	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	2007	default compilation environment.
1794		2008
1795	=head3 Inotify and Kqueue	2009	=head3 Inotify and Kqueue
1796		2010
1797	When C<inotify (7)> support has been compiled into libev (generally only	2011	When C<inotify (7)> support has been compiled into libev and present at
1798	available with Linux) and present at runtime, it will be used to speed up	2012	runtime, it will be used to speed up change detection where possible. The
1799	change detection where possible. The inotify descriptor will be created lazily	2013	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	2014	watcher is being started.
1801		2015
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	2016	Inotify presence does not change the semantics of C<ev_stat> watchers
1803	except that changes might be detected earlier, and in some cases, to avoid	2017	except that changes might be detected earlier, and in some cases, to avoid
1804	making regular C<stat> calls. Even in the presence of inotify support	2018	making regular C<stat> calls. Even in the presence of inotify support
1805	there are many cases where libev has to resort to regular C<stat> polling,	2019	there are many cases where libev has to resort to regular C<stat> polling,
1806	but as long as the path exists, libev usually gets away without polling.	2020	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		2021	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		2022	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2023	xfs are fully working) libev usually gets away without polling.
1807		2024
1808	There is no support for kqueue, as apparently it cannot be used to	2025	There is no support for kqueue, as apparently it cannot be used to
1809	implement this functionality, due to the requirement of having a file	2026	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2027	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2028	etc. is difficult.
1812		2029
		2030	=head3 C<stat ()> is a synchronous operation
		2031
		2032	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2033	the process. The exception are C<ev_stat> watchers - those call C<stat
		2034	()>, which is a synchronous operation.
		2035
		2036	For local paths, this usually doesn't matter: unless the system is very
		2037	busy or the intervals between stat's are large, a stat call will be fast,
		2038	as the path data is usually in memory already (except when starting the
		2039	watcher).
		2040
		2041	For networked file systems, calling C<stat ()> can block an indefinite
		2042	time due to network issues, and even under good conditions, a stat call
		2043	often takes multiple milliseconds.
		2044
		2045	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2046	paths, although this is fully supported by libev.
		2047
1813	=head3 The special problem of stat time resolution	2048	=head3 The special problem of stat time resolution
1814		2049
1815	The C<stat ()> system call only supports full-second resolution portably, and	2050	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2051	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2052	still only support whole seconds.
1818		2053
1819	That means that, if the time is the only thing that changes, you can	2054	That means that, if the time is the only thing that changes, you can
1820	easily miss updates: on the first update, C<ev_stat> detects a change and	2055	easily miss updates: on the first update, C<ev_stat> detects a change and
1821	calls your callback, which does something. When there is another update	2056	calls your callback, which does something. When there is another update
1822	within the same second, C<ev_stat> will be unable to detect unless the	2057	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1965		2200
1966	=head3 Watcher-Specific Functions and Data Members	2201	=head3 Watcher-Specific Functions and Data Members
1967		2202
1968	=over 4	2203	=over 4
1969		2204
1970	=item ev_idle_init (ev_signal *, callback)	2205	=item ev_idle_init (ev_idle *, callback)
1971		2206
1972	Initialises and configures the idle watcher - it has no parameters of any	2207	Initialises and configures the idle watcher - it has no parameters of any
1973	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,	2208	kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1974	believe me.	2209	believe me.
1975		2210
…		…
1979		2214
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2215	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2216	callback, free it. Also, use no error checking, as usual.
1982		2217
1983	static void	2218	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2219	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2220	{
1986	free (w);	2221	free (w);
1987	// now do something you wanted to do when the program has	2222	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2223	// no longer anything immediate to do.
1989	}	2224	}
1990		2225
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2226	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2227	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2228	ev_idle_start (loop, idle_cb);
1994		2229
1995		2230
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2231	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2312
2078	static ev_io iow [nfd];	2313	static ev_io iow [nfd];
2079	static ev_timer tw;	2314	static ev_timer tw;
2080		2315
2081	static void	2316	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2317	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2318	{
2084	}	2319	}
2085		2320
2086	// create io watchers for each fd and a timer before blocking	2321	// create io watchers for each fd and a timer before blocking
2087	static void	2322	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2323	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2324	{
2090	int timeout = 3600000;	2325	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2326	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2327	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2328	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2343	}
2109	}	2344	}
2110		2345
2111	// stop all watchers after blocking	2346	// stop all watchers after blocking
2112	static void	2347	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2348	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2349	{
2115	ev_timer_stop (loop, &tw);	2350	ev_timer_stop (loop, &tw);
2116		2351
2117	for (int i = 0; i < nfd; ++i)	2352	for (int i = 0; i < nfd; ++i)
2118	{	2353	{
…		…
2214	some fds have to be watched and handled very quickly (with low latency),	2449	some fds have to be watched and handled very quickly (with low latency),
2215	and even priorities and idle watchers might have too much overhead. In	2450	and even priorities and idle watchers might have too much overhead. In
2216	this case you would put all the high priority stuff in one loop and all	2451	this case you would put all the high priority stuff in one loop and all
2217	the rest in a second one, and embed the second one in the first.	2452	the rest in a second one, and embed the second one in the first.
2218		2453
2219	As long as the watcher is active, the callback will be invoked every time	2454	As long as the watcher is active, the callback will be invoked every
2220	there might be events pending in the embedded loop. The callback must then	2455	time there might be events pending in the embedded loop. The callback
2221	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke	2456	must then call C<ev_embed_sweep (mainloop, watcher)> to make a single
2222	their callbacks (you could also start an idle watcher to give the embedded	2457	sweep and invoke their callbacks (the callback doesn't need to invoke the
2223	loop strictly lower priority for example). You can also set the callback	2458	C<ev_embed_sweep> function directly, it could also start an idle watcher
2224	to C<0>, in which case the embed watcher will automatically execute the	2459	to give the embedded loop strictly lower priority for example).
2225	embedded loop sweep.
2226		2460
2227	As long as the watcher is started it will automatically handle events. The	2461	You can also set the callback to C<0>, in which case the embed watcher
2228	callback will be invoked whenever some events have been handled. You can	2462	will automatically execute the embedded loop sweep whenever necessary.
2229	set the callback to C<0> to avoid having to specify one if you are not
2230	interested in that.
2231		2463
2232	Also, there have not currently been made special provisions for forking:	2464	Fork detection will be handled transparently while the C<ev_embed> watcher
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2465	is active, i.e., the embedded loop will automatically be forked when the
2234	but you will also have to stop and restart any C<ev_embed> watchers	2466	embedding loop forks. In other cases, the user is responsible for calling
2235	yourself - but you can use a fork watcher to handle this automatically,	2467	C<ev_loop_fork> on the embedded loop.
2236	and future versions of libev might do just that.
2237		2468
2238	Unfortunately, not all backends are embeddable: only the ones returned by	2469	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2470	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2471	portable one.
2241		2472
2242	So when you want to use this feature you will always have to be prepared	2473	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2474	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2475	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2476	create it, and if that fails, use the normal loop for everything.
		2477
		2478	=head3 C<ev_embed> and fork
		2479
		2480	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2481	automatically be applied to the embedded loop as well, so no special
		2482	fork handling is required in that case. When the watcher is not running,
		2483	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2484	as applicable.
2246		2485
2247	=head3 Watcher-Specific Functions and Data Members	2486	=head3 Watcher-Specific Functions and Data Members
2248		2487
2249	=over 4	2488	=over 4
2250		2489
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2517	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2518	used).
2280		2519
2281	struct ev_loop *loop_hi = ev_default_init (0);	2520	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2521	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2522	ev_embed embed;
2284		2523
2285	// see if there is a chance of getting one that works	2524	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2525	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2526	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2527	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2541	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2542	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2543
2305	struct ev_loop *loop = ev_default_init (0);	2544	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2545	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2546	ev_embed embed;
2308		2547
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2548	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2549	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2550	{
2312	ev_embed_init (&embed, 0, loop_socket);	2551	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2615	=over 4
2377		2616
2378	=item queueing from a signal handler context	2617	=item queueing from a signal handler context
2379		2618
2380	To implement race-free queueing, you simply add to the queue in the signal	2619	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2620	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2621	an example that does that for some fictitious SIGUSR1 handler:
2383		2622
2384	static ev_async mysig;	2623	static ev_async mysig;
2385		2624
2386	static void	2625	static void
2387	sigusr1_handler (void)	2626	sigusr1_handler (void)
…		…
2453	=over 4	2692	=over 4
2454		2693
2455	=item ev_async_init (ev_async *, callback)	2694	=item ev_async_init (ev_async *, callback)
2456		2695
2457	Initialises and configures the async watcher - it has no parameters of any	2696	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2697	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	2698	trust me.
2460		2699
2461	=item ev_async_send (loop, ev_async *)	2700	=item ev_async_send (loop, ev_async *)
2462		2701
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2702	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2703	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do from other threads, signal or	2704	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2705	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2706	section below on what exactly this means).
2468		2707
		2708	Note that, as with other watchers in libev, multiple events might get
		2709	compressed into a single callback invocation (another way to look at this
		2710	is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>,
		2711	reset when the event loop detects that).
		2712
2469	This call incurs the overhead of a system call only once per loop iteration,	2713	This call incurs the overhead of a system call only once per event loop
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2714	iteration, so while the overhead might be noticeable, it doesn't apply to
2471	calls to C<ev_async_send>.	2715	repeated calls to C<ev_async_send> for the same event loop.
2472		2716
2473	=item bool = ev_async_pending (ev_async *)	2717	=item bool = ev_async_pending (ev_async *)
2474		2718
2475	Returns a non-zero value when C<ev_async_send> has been called on the	2719	Returns a non-zero value when C<ev_async_send> has been called on the
2476	watcher but the event has not yet been processed (or even noted) by the	2720	watcher but the event has not yet been processed (or even noted) by the
…		…
2479	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When	2723	C<ev_async_send> sets a flag in the watcher and wakes up the loop. When
2480	the loop iterates next and checks for the watcher to have become active,	2724	the loop iterates next and checks for the watcher to have become active,
2481	it will reset the flag again. C<ev_async_pending> can be used to very	2725	it will reset the flag again. C<ev_async_pending> can be used to very
2482	quickly check whether invoking the loop might be a good idea.	2726	quickly check whether invoking the loop might be a good idea.
2483		2727
2484	Not that this does I<not> check whether the watcher itself is pending, only	2728	Not that this does I<not> check whether the watcher itself is pending,
2485	whether it has been requested to make this watcher pending.	2729	only whether it has been requested to make this watcher pending: there
		2730	is a time window between the event loop checking and resetting the async
		2731	notification, and the callback being invoked.
2486		2732
2487	=back	2733	=back
2488		2734
2489		2735
2490	=head1 OTHER FUNCTIONS	2736	=head1 OTHER FUNCTIONS
…		…
2494	=over 4	2740	=over 4
2495		2741
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2742	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2743
2498	This function combines a simple timer and an I/O watcher, calls your	2744	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2745	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2746	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2747	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2748	more watchers yourself.
2503		2749
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2750	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2751	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2752	the given C<fd> and C<events> set will be created and started.
2507		2753
2508	If C<timeout> is less than 0, then no timeout watcher will be	2754	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2755	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2756	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2757
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2758	The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	2759	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2760	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2761	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2762	a timeout and an io event at the same time - you probably should give io
		2763	events precedence.
		2764
		2765	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2766
2518	static void stdin_ready (int revents, void *arg)	2767	static void stdin_ready (int revents, void *arg)
2519	{	2768	{
		2769	if (revents & EV_READ)
		2770	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2771	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2772	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2773	}
2525		2774
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2775	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2776
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)	2777	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2529		2778
2530	Feeds the given event set into the event loop, as if the specified event	2779	Feeds the given event set into the event loop, as if the specified event
2531	had happened for the specified watcher (which must be a pointer to an	2780	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2781	initialised but not necessarily started event watcher).
2533		2782
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2783	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2784
2536	Feed an event on the given fd, as if a file descriptor backend detected	2785	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2786	the given events it.
2538		2787
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2788	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2789
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2790	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2791	loop!).
2543		2792
2544	=back	2793	=back
…		…
2665	}	2914	}
2666		2915
2667	myclass obj;	2916	myclass obj;
2668	ev::io iow;	2917	ev::io iow;
2669	iow.set <myclass, &myclass::io_cb> (&obj);	2918	iow.set <myclass, &myclass::io_cb> (&obj);
		2919
		2920	=item w->set (object *)
		2921
		2922	This is an B<experimental> feature that might go away in a future version.
		2923
		2924	This is a variation of a method callback - leaving out the method to call
		2925	will default the method to C<operator ()>, which makes it possible to use
		2926	functor objects without having to manually specify the C<operator ()> all
		2927	the time. Incidentally, you can then also leave out the template argument
		2928	list.
		2929
		2930	The C<operator ()> method prototype must be C<void operator ()(watcher &w,
		2931	int revents)>.
		2932
		2933	See the method-C<set> above for more details.
		2934
		2935	Example: use a functor object as callback.
		2936
		2937	struct myfunctor
		2938	{
		2939	void operator() (ev::io &w, int revents)
		2940	{
		2941	...
		2942	}
		2943	}
		2944
		2945	myfunctor f;
		2946
		2947	ev::io w;
		2948	w.set (&f);
2670		2949
2671	=item w->set<function> (void *data = 0)	2950	=item w->set<function> (void *data = 0)
2672		2951
2673	Also sets a callback, but uses a static method or plain function as	2952	Also sets a callback, but uses a static method or plain function as
2674	callback. The optional C<data> argument will be stored in the watcher's	2953	callback. The optional C<data> argument will be stored in the watcher's
…		…
2761	L<http://software.schmorp.de/pkg/EV>.	3040	L<http://software.schmorp.de/pkg/EV>.
2762		3041
2763	=item Python	3042	=item Python
2764		3043
2765	Python bindings can be found at L<http://code.google.com/p/pyev/>. It	3044	Python bindings can be found at L<http://code.google.com/p/pyev/>. It
2766	seems to be quite complete and well-documented. Note, however, that the	3045	seems to be quite complete and well-documented.
2767	patch they require for libev is outright dangerous as it breaks the ABI
2768	for everybody else, and therefore, should never be applied in an installed
2769	libev (if python requires an incompatible ABI then it needs to embed
2770	libev).
2771		3046
2772	=item Ruby	3047	=item Ruby
2773		3048
2774	Tony Arcieri has written a ruby extension that offers access to a subset	3049	Tony Arcieri has written a ruby extension that offers access to a subset
2775	of the libev API and adds file handle abstractions, asynchronous DNS and	3050	of the libev API and adds file handle abstractions, asynchronous DNS and
2776	more on top of it. It can be found via gem servers. Its homepage is at	3051	more on top of it. It can be found via gem servers. Its homepage is at
2777	L<http://rev.rubyforge.org/>.	3052	L<http://rev.rubyforge.org/>.
2778		3053
		3054	Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190>
		3055	makes rev work even on mingw.
		3056
		3057	=item Haskell
		3058
		3059	A haskell binding to libev is available at
		3060	L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>.
		3061
2779	=item D	3062	=item D
2780		3063
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3064	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2782	be found at L<http://proj.llucax.com.ar/wiki/evd>.	3065	be found at L<http://proj.llucax.com.ar/wiki/evd>.
		3066
		3067	=item Ocaml
		3068
		3069	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3070	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
2783		3071
2784	=back	3072	=back
2785		3073
2786		3074
2787	=head1 MACRO MAGIC	3075	=head1 MACRO MAGIC
…		…
2888		3176
2889	#define EV_STANDALONE 1	3177	#define EV_STANDALONE 1
2890	#include "ev.h"	3178	#include "ev.h"
2891		3179
2892	Both header files and implementation files can be compiled with a C++	3180	Both header files and implementation files can be compiled with a C++
2893	compiler (at least, thats a stated goal, and breakage will be treated	3181	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3182	as a bug).
2895		3183
2896	You need the following files in your source tree, or in a directory	3184	You need the following files in your source tree, or in a directory
2897	in your include path (e.g. in libev/ when using -Ilibev):	3185	in your include path (e.g. in libev/ when using -Ilibev):
2898		3186
…		…
2954	keeps libev from including F<config.h>, and it also defines dummy	3242	keeps libev from including F<config.h>, and it also defines dummy
2955	implementations for some libevent functions (such as logging, which is not	3243	implementations for some libevent functions (such as logging, which is not
2956	supported). It will also not define any of the structs usually found in	3244	supported). It will also not define any of the structs usually found in
2957	F<event.h> that are not directly supported by the libev core alone.	3245	F<event.h> that are not directly supported by the libev core alone.
2958		3246
		3247	In stanbdalone mode, libev will still try to automatically deduce the
		3248	configuration, but has to be more conservative.
		3249
2959	=item EV_USE_MONOTONIC	3250	=item EV_USE_MONOTONIC
2960		3251
2961	If defined to be C<1>, libev will try to detect the availability of the	3252	If defined to be C<1>, libev will try to detect the availability of the
2962	monotonic clock option at both compile time and runtime. Otherwise no use	3253	monotonic clock option at both compile time and runtime. Otherwise no
2963	of the monotonic clock option will be attempted. If you enable this, you	3254	use of the monotonic clock option will be attempted. If you enable this,
2964	usually have to link against librt or something similar. Enabling it when	3255	you usually have to link against librt or something similar. Enabling it
2965	the functionality isn't available is safe, though, although you have	3256	when the functionality isn't available is safe, though, although you have
2966	to make sure you link against any libraries where the C<clock_gettime>	3257	to make sure you link against any libraries where the C<clock_gettime>
2967	function is hiding in (often F<-lrt>).	3258	function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>.
2968		3259
2969	=item EV_USE_REALTIME	3260	=item EV_USE_REALTIME
2970		3261
2971	If defined to be C<1>, libev will try to detect the availability of the	3262	If defined to be C<1>, libev will try to detect the availability of the
2972	real-time clock option at compile time (and assume its availability at	3263	real-time clock option at compile time (and assume its availability
2973	runtime if successful). Otherwise no use of the real-time clock option will	3264	at runtime if successful). Otherwise no use of the real-time clock
2974	be attempted. This effectively replaces C<gettimeofday> by C<clock_get	3265	option will be attempted. This effectively replaces C<gettimeofday>
2975	(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the	3266	by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect
2976	note about libraries in the description of C<EV_USE_MONOTONIC>, though.	3267	correctness. See the note about libraries in the description of
		3268	C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of
		3269	C<EV_USE_CLOCK_SYSCALL>.
		3270
		3271	=item EV_USE_CLOCK_SYSCALL
		3272
		3273	If defined to be C<1>, libev will try to use a direct syscall instead
		3274	of calling the system-provided C<clock_gettime> function. This option
		3275	exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt>
		3276	unconditionally pulls in C<libpthread>, slowing down single-threaded
		3277	programs needlessly. Using a direct syscall is slightly slower (in
		3278	theory), because no optimised vdso implementation can be used, but avoids
		3279	the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or
		3280	higher, as it simplifies linking (no need for C<-lrt>).
2977		3281
2978	=item EV_USE_NANOSLEEP	3282	=item EV_USE_NANOSLEEP
2979		3283
2980	If defined to be C<1>, libev will assume that C<nanosleep ()> is available	3284	If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2981	and will use it for delays. Otherwise it will use C<select ()>.	3285	and will use it for delays. Otherwise it will use C<select ()>.
…		…
2997		3301
2998	=item EV_SELECT_USE_FD_SET	3302	=item EV_SELECT_USE_FD_SET
2999		3303
3000	If defined to C<1>, then the select backend will use the system C<fd_set>	3304	If defined to C<1>, then the select backend will use the system C<fd_set>
3001	structure. This is useful if libev doesn't compile due to a missing	3305	structure. This is useful if libev doesn't compile due to a missing
3002	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on	3306	C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout
3003	exotic systems. This usually limits the range of file descriptors to some	3307	on exotic systems. This usually limits the range of file descriptors to
3004	low limit such as 1024 or might have other limitations (winsocket only	3308	some low limit such as 1024 or might have other limitations (winsocket
3005	allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might	3309	only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation,
3006	influence the size of the C<fd_set> used.	3310	configures the maximum size of the C<fd_set>.
3007		3311
3008	=item EV_SELECT_IS_WINSOCKET	3312	=item EV_SELECT_IS_WINSOCKET
3009		3313
3010	When defined to C<1>, the select backend will assume that	3314	When defined to C<1>, the select backend will assume that
3011	select/socket/connect etc. don't understand file descriptors but	3315	select/socket/connect etc. don't understand file descriptors but
…		…
3241	definition and a statement, respectively. See the F<ev.h> header file for	3545	definition and a statement, respectively. See the F<ev.h> header file for
3242	their default definitions. One possible use for overriding these is to	3546	their default definitions. One possible use for overriding these is to
3243	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3547	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3244	method calls instead of plain function calls in C++.	3548	method calls instead of plain function calls in C++.
3245		3549
		3550	=back
		3551
3246	=head2 EXPORTED API SYMBOLS	3552	=head2 EXPORTED API SYMBOLS
3247		3553
3248	If you need to re-export the API (e.g. via a DLL) and you need a list of	3554	If you need to re-export the API (e.g. via a DLL) and you need a list of
3249	exported symbols, you can use the provided F<Symbol.*> files which list	3555	exported symbols, you can use the provided F<Symbol.*> files which list
3250	all public symbols, one per line:	3556	all public symbols, one per line:
…		…
3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3602	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3297		3603
3298	#include "ev_cpp.h"	3604	#include "ev_cpp.h"
3299	#include "ev.c"	3605	#include "ev.c"
3300		3606
		3607	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3301		3608
3302	=head1 THREADS AND COROUTINES	3609	=head2 THREADS AND COROUTINES
3303		3610
3304	=head2 THREADS	3611	=head3 THREADS
3305		3612
3306	Libev itself is thread-safe (unless the opposite is specifically	3613	All libev functions are reentrant and thread-safe unless explicitly
3307	documented for a function), but it uses no locking itself. This means that	3614	documented otherwise, but libev implements no locking itself. This means
3308	you can use as many loops as you want in parallel, as long as only one	3615	that you can use as many loops as you want in parallel, as long as there
3309	thread ever calls into one libev function with the same loop parameter:	3616	are no concurrent calls into any libev function with the same loop
		3617	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3310	libev guarantees that different event loops share no data structures that	3618	of course): libev guarantees that different event loops share no data
3311	need locking.	3619	structures that need any locking.
3312		3620
3313	Or to put it differently: calls with different loop parameters can be done	3621	Or to put it differently: calls with different loop parameters can be done
3314	concurrently from multiple threads, calls with the same loop parameter	3622	concurrently from multiple threads, calls with the same loop parameter
3315	must be done serially (but can be done from different threads, as long as	3623	must be done serially (but can be done from different threads, as long as
3316	only one thread ever is inside a call at any point in time, e.g. by using	3624	only one thread ever is inside a call at any point in time, e.g. by using
3317	a mutex per loop).	3625	a mutex per loop).
3318		3626
3319	Specifically to support threads (and signal handlers), libev implements	3627	Specifically to support threads (and signal handlers), libev implements
3320	so-called C<ev_async> watchers, which allow some limited form of	3628	so-called C<ev_async> watchers, which allow some limited form of
3321	concurrency on the same event loop.	3629	concurrency on the same event loop, namely waking it up "from the
		3630	outside".
3322		3631
3323	If you want to know which design (one loop, locking, or multiple loops	3632	If you want to know which design (one loop, locking, or multiple loops
3324	without or something else still) is best for your problem, then I cannot	3633	without or something else still) is best for your problem, then I cannot
3325	help you. I can give some generic advice however:	3634	help you, but here is some generic advice:
3326		3635
3327	=over 4	3636	=over 4
3328		3637
3329	=item * most applications have a main thread: use the default libev loop	3638	=item * most applications have a main thread: use the default libev loop
3330	in that thread, or create a separate thread running only the default loop.	3639	in that thread, or create a separate thread running only the default loop.
…		…
3354	default loop and triggering an C<ev_async> watcher from the default loop	3663	default loop and triggering an C<ev_async> watcher from the default loop
3355	watcher callback into the event loop interested in the signal.	3664	watcher callback into the event loop interested in the signal.
3356		3665
3357	=back	3666	=back
3358		3667
3359	=head2 COROUTINES	3668	=head3 COROUTINES
3360		3669
3361	Libev is much more accommodating to coroutines ("cooperative threads"):	3670	Libev is very accommodating to coroutines ("cooperative threads"):
3362	libev fully supports nesting calls to it's functions from different	3671	libev fully supports nesting calls to its functions from different
3363	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3672	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3364	different coroutines and switch freely between both coroutines running the	3673	different coroutines, and switch freely between both coroutines running the
3365	loop, as long as you don't confuse yourself). The only exception is that	3674	loop, as long as you don't confuse yourself). The only exception is that
3366	you must not do this from C<ev_periodic> reschedule callbacks.	3675	you must not do this from C<ev_periodic> reschedule callbacks.
3367		3676
3368	Care has been taken to ensure that libev does not keep local state inside	3677	Care has been taken to ensure that libev does not keep local state inside
3369	C<ev_loop>, and other calls do not usually allow coroutine switches.	3678	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3679	they do not call any callbacks.
3370		3680
		3681	=head2 COMPILER WARNINGS
3371		3682
3372	=head1 COMPLEXITIES	3683	Depending on your compiler and compiler settings, you might get no or a
		3684	lot of warnings when compiling libev code. Some people are apparently
		3685	scared by this.
3373		3686
3374	In this section the complexities of (many of) the algorithms used inside	3687	However, these are unavoidable for many reasons. For one, each compiler
3375	libev will be explained. For complexity discussions about backends see the	3688	has different warnings, and each user has different tastes regarding
3376	documentation for C<ev_default_init>.	3689	warning options. "Warn-free" code therefore cannot be a goal except when
		3690	targeting a specific compiler and compiler-version.
3377		3691
3378	All of the following are about amortised time: If an array needs to be	3692	Another reason is that some compiler warnings require elaborate
3379	extended, libev needs to realloc and move the whole array, but this	3693	workarounds, or other changes to the code that make it less clear and less
3380	happens asymptotically never with higher number of elements, so O(1) might	3694	maintainable.
3381	mean it might do a lengthy realloc operation in rare cases, but on average
3382	it is much faster and asymptotically approaches constant time.
3383		3695
3384	=over 4	3696	And of course, some compiler warnings are just plain stupid, or simply
		3697	wrong (because they don't actually warn about the condition their message
		3698	seems to warn about). For example, certain older gcc versions had some
		3699	warnings that resulted an extreme number of false positives. These have
		3700	been fixed, but some people still insist on making code warn-free with
		3701	such buggy versions.
3385		3702
3386	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3703	While libev is written to generate as few warnings as possible,
		3704	"warn-free" code is not a goal, and it is recommended not to build libev
		3705	with any compiler warnings enabled unless you are prepared to cope with
		3706	them (e.g. by ignoring them). Remember that warnings are just that:
		3707	warnings, not errors, or proof of bugs.
3387		3708
3388	This means that, when you have a watcher that triggers in one hour and
3389	there are 100 watchers that would trigger before that then inserting will
3390	have to skip roughly seven (C<ld 100>) of these watchers.
3391		3709
3392	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3710	=head2 VALGRIND
3393		3711
3394	That means that changing a timer costs less than removing/adding them	3712	Valgrind has a special section here because it is a popular tool that is
3395	as only the relative motion in the event queue has to be paid for.	3713	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3396		3714
3397	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3715	If you think you found a bug (memory leak, uninitialised data access etc.)
		3716	in libev, then check twice: If valgrind reports something like:
3398		3717
3399	These just add the watcher into an array or at the head of a list.	3718	==2274== definitely lost: 0 bytes in 0 blocks.
		3719	==2274== possibly lost: 0 bytes in 0 blocks.
		3720	==2274== still reachable: 256 bytes in 1 blocks.
3400		3721
3401	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3722	Then there is no memory leak, just as memory accounted to global variables
		3723	is not a memleak - the memory is still being referenced, and didn't leak.
3402		3724
3403	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3725	Similarly, under some circumstances, valgrind might report kernel bugs
		3726	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3727	although an acceptable workaround has been found here), or it might be
		3728	confused.
3404		3729
3405	These watchers are stored in lists then need to be walked to find the	3730	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3406	correct watcher to remove. The lists are usually short (you don't usually	3731	make it into some kind of religion.
3407	have many watchers waiting for the same fd or signal).
3408		3732
3409	=item Finding the next timer in each loop iteration: O(1)	3733	If you are unsure about something, feel free to contact the mailing list
		3734	with the full valgrind report and an explanation on why you think this
		3735	is a bug in libev (best check the archives, too :). However, don't be
		3736	annoyed when you get a brisk "this is no bug" answer and take the chance
		3737	of learning how to interpret valgrind properly.
3410		3738
3411	By virtue of using a binary or 4-heap, the next timer is always found at a	3739	If you need, for some reason, empty reports from valgrind for your project
3412	fixed position in the storage array.	3740	I suggest using suppression lists.
3413		3741
3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3415		3742
3416	A change means an I/O watcher gets started or stopped, which requires	3743	=head1 PORTABILITY NOTES
3417	libev to recalculate its status (and possibly tell the kernel, depending
3418	on backend and whether C<ev_io_set> was used).
3419		3744
3420	=item Activating one watcher (putting it into the pending state): O(1)
3421
3422	=item Priority handling: O(number_of_priorities)
3423
3424	Priorities are implemented by allocating some space for each
3425	priority. When doing priority-based operations, libev usually has to
3426	linearly search all the priorities, but starting/stopping and activating
3427	watchers becomes O(1) with respect to priority handling.
3428
3429	=item Sending an ev_async: O(1)
3430
3431	=item Processing ev_async_send: O(number_of_async_watchers)
3432
3433	=item Processing signals: O(max_signal_number)
3434
3435	Sending involves a system call I<iff> there were no other C<ev_async_send>
3436	calls in the current loop iteration. Checking for async and signal events
3437	involves iterating over all running async watchers or all signal numbers.
3438
3439	=back
3440
3441
3442	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3745	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3443		3746
3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3747	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3445	requires, and its I/O model is fundamentally incompatible with the POSIX	3748	requires, and its I/O model is fundamentally incompatible with the POSIX
3446	model. Libev still offers limited functionality on this platform in	3749	model. Libev still offers limited functionality on this platform in
3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3750	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3534	wrap all I/O functions and provide your own fd management, but the cost of	3837	wrap all I/O functions and provide your own fd management, but the cost of
3535	calling select (O(n²)) will likely make this unworkable.	3838	calling select (O(n²)) will likely make this unworkable.
3536		3839
3537	=back	3840	=back
3538		3841
3539
3540	=head1 PORTABILITY REQUIREMENTS	3842	=head2 PORTABILITY REQUIREMENTS
3541		3843
3542	In addition to a working ISO-C implementation, libev relies on a few	3844	In addition to a working ISO-C implementation and of course the
3543	additional extensions:	3845	backend-specific APIs, libev relies on a few additional extensions:
3544		3846
3545	=over 4	3847	=over 4
3546		3848
3547	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3849	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3548	calling conventions regardless of C<ev_watcher_type *>.	3850	calling conventions regardless of C<ev_watcher_type *>.
…		…
3573	except the initial one, and run the default loop in the initial thread as	3875	except the initial one, and run the default loop in the initial thread as
3574	well.	3876	well.
3575		3877
3576	=item C<long> must be large enough for common memory allocation sizes	3878	=item C<long> must be large enough for common memory allocation sizes
3577		3879
3578	To improve portability and simplify using libev, libev uses C<long>	3880	To improve portability and simplify its API, libev uses C<long> internally
3579	internally instead of C<size_t> when allocating its data structures. On	3881	instead of C<size_t> when allocating its data structures. On non-POSIX
3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3882	systems (Microsoft...) this might be unexpectedly low, but is still at
3581	is still at least 31 bits everywhere, which is enough for hundreds of	3883	least 31 bits everywhere, which is enough for hundreds of millions of
3582	millions of watchers.	3884	watchers.
3583		3885
3584	=item C<double> must hold a time value in seconds with enough accuracy	3886	=item C<double> must hold a time value in seconds with enough accuracy
3585		3887
3586	The type C<double> is used to represent timestamps. It is required to	3888	The type C<double> is used to represent timestamps. It is required to
3587	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3889	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3591	=back	3893	=back
3592		3894
3593	If you know of other additional requirements drop me a note.	3895	If you know of other additional requirements drop me a note.
3594		3896
3595		3897
3596	=head1 COMPILER WARNINGS	3898	=head1 ALGORITHMIC COMPLEXITIES
3597		3899
3598	Depending on your compiler and compiler settings, you might get no or a	3900	In this section the complexities of (many of) the algorithms used inside
3599	lot of warnings when compiling libev code. Some people are apparently	3901	libev will be documented. For complexity discussions about backends see
3600	scared by this.	3902	the documentation for C<ev_default_init>.
3601		3903
3602	However, these are unavoidable for many reasons. For one, each compiler	3904	All of the following are about amortised time: If an array needs to be
3603	has different warnings, and each user has different tastes regarding	3905	extended, libev needs to realloc and move the whole array, but this
3604	warning options. "Warn-free" code therefore cannot be a goal except when	3906	happens asymptotically rarer with higher number of elements, so O(1) might
3605	targeting a specific compiler and compiler-version.	3907	mean that libev does a lengthy realloc operation in rare cases, but on
		3908	average it is much faster and asymptotically approaches constant time.
3606		3909
3607	Another reason is that some compiler warnings require elaborate	3910	=over 4
3608	workarounds, or other changes to the code that make it less clear and less
3609	maintainable.
3610		3911
3611	And of course, some compiler warnings are just plain stupid, or simply	3912	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3612	wrong (because they don't actually warn about the condition their message
3613	seems to warn about).
3614		3913
3615	While libev is written to generate as few warnings as possible,	3914	This means that, when you have a watcher that triggers in one hour and
3616	"warn-free" code is not a goal, and it is recommended not to build libev	3915	there are 100 watchers that would trigger before that, then inserting will
3617	with any compiler warnings enabled unless you are prepared to cope with	3916	have to skip roughly seven (C<ld 100>) of these watchers.
3618	them (e.g. by ignoring them). Remember that warnings are just that:
3619	warnings, not errors, or proof of bugs.
3620		3917
		3918	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3621		3919
3622	=head1 VALGRIND	3920	That means that changing a timer costs less than removing/adding them,
		3921	as only the relative motion in the event queue has to be paid for.
3623		3922
3624	Valgrind has a special section here because it is a popular tool that is	3923	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3625	highly useful, but valgrind reports are very hard to interpret.
3626		3924
3627	If you think you found a bug (memory leak, uninitialised data access etc.)	3925	These just add the watcher into an array or at the head of a list.
3628	in libev, then check twice: If valgrind reports something like:
3629		3926
3630	==2274== definitely lost: 0 bytes in 0 blocks.	3927	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3631	==2274== possibly lost: 0 bytes in 0 blocks.
3632	==2274== still reachable: 256 bytes in 1 blocks.
3633		3928
3634	Then there is no memory leak. Similarly, under some circumstances,	3929	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3635	valgrind might report kernel bugs as if it were a bug in libev, or it
3636	might be confused (it is a very good tool, but only a tool).
3637		3930
3638	If you are unsure about something, feel free to contact the mailing list	3931	These watchers are stored in lists, so they need to be walked to find the
3639	with the full valgrind report and an explanation on why you think this is	3932	correct watcher to remove. The lists are usually short (you don't usually
3640	a bug in libev. However, don't be annoyed when you get a brisk "this is	3933	have many watchers waiting for the same fd or signal: one is typical, two
3641	no bug" answer and take the chance of learning how to interpret valgrind	3934	is rare).
3642	properly.
3643		3935
3644	If you need, for some reason, empty reports from valgrind for your project	3936	=item Finding the next timer in each loop iteration: O(1)
3645	I suggest using suppression lists.	3937
		3938	By virtue of using a binary or 4-heap, the next timer is always found at a
		3939	fixed position in the storage array.
		3940
		3941	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3942
		3943	A change means an I/O watcher gets started or stopped, which requires
		3944	libev to recalculate its status (and possibly tell the kernel, depending
		3945	on backend and whether C<ev_io_set> was used).
		3946
		3947	=item Activating one watcher (putting it into the pending state): O(1)
		3948
		3949	=item Priority handling: O(number_of_priorities)
		3950
		3951	Priorities are implemented by allocating some space for each
		3952	priority. When doing priority-based operations, libev usually has to
		3953	linearly search all the priorities, but starting/stopping and activating
		3954	watchers becomes O(1) with respect to priority handling.
		3955
		3956	=item Sending an ev_async: O(1)
		3957
		3958	=item Processing ev_async_send: O(number_of_async_watchers)
		3959
		3960	=item Processing signals: O(max_signal_number)
		3961
		3962	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3963	calls in the current loop iteration. Checking for async and signal events
		3964	involves iterating over all running async watchers or all signal numbers.
		3965
		3966	=back
3646		3967
3647		3968
3648	=head1 AUTHOR	3969	=head1 AUTHOR
3649		3970
3650	Marc Lehmann <libev@schmorp.de>.	3971	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3651		3972

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