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

Comparing libev/ev.pod (file contents):
Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs.
Revision 1.216 by root, Thu Nov 13 15:55:38 2008 UTC

…		…
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	// every watcher type has its own typedef'd struct	14	// every watcher type has its own typedef'd struct
15	// with the name ev_<type>	15	// with the name ev_TYPE
16	ev_io stdin_watcher;	16	ev_io stdin_watcher;
17	ev_timer timeout_watcher;	17	ev_timer timeout_watcher;
18		18
19	// all watcher callbacks have a similar signature	19	// all watcher callbacks have a similar signature
20	// this callback is called when data is readable on stdin	20	// this callback is called when data is readable on stdin
21	static void	21	static void
22	stdin_cb (EV_P_ struct ev_io *w, int revents)	22	stdin_cb (EV_P_ ev_io *w, int revents)
23	{	23	{
24	puts ("stdin ready");	24	puts ("stdin ready");
25	// for one-shot events, one must manually stop the watcher	25	// for one-shot events, one must manually stop the watcher
26	// with its corresponding stop function.	26	// with its corresponding stop function.
27	ev_io_stop (EV_A_ w);	27	ev_io_stop (EV_A_ w);
…		…
30	ev_unloop (EV_A_ EVUNLOOP_ALL);	30	ev_unloop (EV_A_ EVUNLOOP_ALL);
31	}	31	}
32		32
33	// another callback, this time for a time-out	33	// another callback, this time for a time-out
34	static void	34	static void
35	timeout_cb (EV_P_ struct ev_timer *w, int revents)	35	timeout_cb (EV_P_ ev_timer *w, int revents)
36	{	36	{
37	puts ("timeout");	37	puts ("timeout");
38	// this causes the innermost ev_loop to stop iterating	38	// this causes the innermost ev_loop to stop iterating
39	ev_unloop (EV_A_ EVUNLOOP_ONE);	39	ev_unloop (EV_A_ EVUNLOOP_ONE);
40	}	40	}
41		41
42	int	42	int
43	main (void)	43	main (void)
44	{	44	{
45	// use the default event loop unless you have special needs	45	// use the default event loop unless you have special needs
46	struct ev_loop *loop = ev_default_loop (0);	46	ev_loop *loop = ev_default_loop (0);
47		47
48	// initialise an io watcher, then start it	48	// initialise an io watcher, then start it
49	// this one will watch for stdin to become readable	49	// this one will watch for stdin to become readable
50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);	50	ev_io_init (&stdin_watcher, stdin_cb, /STDIN_FILENO/ 0, EV_READ);
51	ev_io_start (loop, &stdin_watcher);	51	ev_io_start (loop, &stdin_watcher);
…		…
103	Libev is very configurable. In this manual the default (and most common)	103	Libev is very configurable. In this manual the default (and most common)
104	configuration will be described, which supports multiple event loops. For	104	configuration will be described, which supports multiple event loops. For
105	more info about various configuration options please have a look at	105	more info about various configuration options please have a look at
106	B<EMBED> section in this manual. If libev was configured without support	106	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	107	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	108	name C<loop> (which is always of type C<ev_loop *>) will not have
109	this argument.	109	this argument.
110		110
111	=head2 TIME REPRESENTATION	111	=head2 TIME REPRESENTATION
112		112
113	Libev represents time as a single floating point number, representing the	113	Libev represents time as a single floating point number, representing the
…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	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	222	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	223	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	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	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	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	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	260	callback is set, then libev will expect it to remedy the situation, no
…		…
276		276
277	=back	277	=back
278		278
279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP	279	=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280		280
281	An event loop is described by a C<struct ev_loop *>. The library knows two	281	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	282	is I<not> optional in this case, as there is also an C<ev_loop>
283	events, and dynamically created loops which do not.	283	I<function>).
		284
		285	The library knows two types of such loops, the I<default> loop, which
		286	supports signals and child events, and dynamically created loops which do
		287	not.
284		288
285	=over 4	289	=over 4
286		290
287	=item struct ev_loop *ev_default_loop (unsigned int flags)	291	=item struct ev_loop *ev_default_loop (unsigned int flags)
288		292
…		…
294	If you don't know what event loop to use, use the one returned from this	298	If you don't know what event loop to use, use the one returned from this
295	function.	299	function.
296		300
297	Note that this function is I<not> thread-safe, so if you want to use it	301	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,	302	from multiple threads, you have to lock (note also that this is unlikely,
299	as loops cannot bes hared easily between threads anyway).	303	as loops cannot be shared easily between threads anyway).
300		304
301	The default loop is the only loop that can handle C<ev_signal> and	305	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	306	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	307	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	308	create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
…		…
380	=item C<EVBACKEND_EPOLL> (value 4, Linux)	384	=item C<EVBACKEND_EPOLL> (value 4, Linux)
381		385
382	For few fds, this backend is a bit little slower than poll and select,	386	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	387	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),	388	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	389	epoll scales either O(1) or O(active_fds).
386	of shortcomings, such as silently dropping events in some hard-to-detect	390
387	cases and requiring a system call per fd change, no fork support and bad	391	The epoll mechanism deserves honorable mention as the most misdesigned
388	support for dup.	392	of the more advanced event mechanisms: mere annoyances include silently
		393	dropping file descriptors, requiring a system call per change per file
		394	descriptor (and unnecessary guessing of parameters), problems with dup and
		395	so on. The biggest issue is fork races, however - if a program forks then
		396	I<both> parent and child process have to recreate the epoll set, which can
		397	take considerable time (one syscall per file descriptor) and is of course
		398	hard to detect.
		399
		400	Epoll is also notoriously buggy - embedding epoll fds I<should> work, but
		401	of course I<doesn't>, and epoll just loves to report events for totally
		402	I<different> file descriptors (even already closed ones, so one cannot
		403	even remove them from the set) than registered in the set (especially
		404	on SMP systems). Libev tries to counter these spurious notifications by
		405	employing an additional generation counter and comparing that against the
		406	events to filter out spurious ones, recreating the set when required.
389		407
390	While stopping, setting and starting an I/O watcher in the same iteration	408	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	409	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	410	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	411	I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
394	very well if you register events for both fds.	412	file descriptors might not work very well if you register events for both
395		413	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		414
400	Best performance from this backend is achieved by not unregistering all	415	Best performance from this backend is achieved by not unregistering all
401	watchers for a file descriptor until it has been closed, if possible,	416	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	417	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	418	starting a watcher (without re-setting it) also usually doesn't cause
404	extra overhead.	419	extra overhead. A fork can both result in spurious notifications as well
		420	as in libev having to destroy and recreate the epoll object, which can
		421	take considerable time and thus should be avoided.
		422
		423	All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or
		424	faster than epoll for maybe up to a hundred file descriptors, depending on
		425	the usage. So sad.
405		426
406	While nominally embeddable in other event loops, this feature is broken in	427	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	428	all kernel versions tested so far.
408		429
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	430	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	431	C<EVBACKEND_POLL>.
411		432
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	433	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		434
414	Kqueue deserves special mention, as at the time of this writing, it was	435	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	436	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	437	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	438	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	439	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.	440	without API changes to existing programs. For this reason it's not being
		441	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		442	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		443	system like NetBSD.
420		444
421	You still can embed kqueue into a normal poll or select backend and use it	445	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	446	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.	447	the target platform). See C<ev_embed> watchers for more info.
424		448
425	It scales in the same way as the epoll backend, but the interface to the	449	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	450	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	451	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	452	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	453	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	454	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		455	cases
431		456
432	This backend usually performs well under most conditions.	457	This backend usually performs well under most conditions.
433		458
434	While nominally embeddable in other event loops, this doesn't work	459	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	460	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	489	might perform better.
465		490
466	On the positive side, with the exception of the spurious readiness	491	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	492	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	493	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	494	OS-specific backends (I vastly prefer correctness over speed hacks).
470		495
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	496	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	497	C<EVBACKEND_POLL>.
473		498
474	=item C<EVBACKEND_ALL>	499	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	552	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	553	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	554	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	555	for example).
531		556
532	Note that certain global state, such as signal state, will not be freed by	557	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	558	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	559	as signal and child watchers) would need to be stopped manually.
535		560
536	In general it is not advisable to call this function except in the	561	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	562	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	563	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	564	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	656	the loop.
632		657
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	658	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	659	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	660	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	661	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	662	user-registered callback will be called), and will return after one
638	iteration of the loop.	663	iteration of the loop.
639		664
640	This is useful if you are waiting for some external event in conjunction	665	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	666	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	710	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.	711	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		712
688	This "unloop state" will be cleared when entering C<ev_loop> again.	713	This "unloop state" will be cleared when entering C<ev_loop> again.
689		714
		715	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		716
690	=item ev_ref (loop)	717	=item ev_ref (loop)
691		718
692	=item ev_unref (loop)	719	=item ev_unref (loop)
693		720
694	Ref/unref can be used to add or remove a reference count on the event	721	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	735	respectively).
709		736
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	737	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	738	running when nothing else is active.
712		739
713	struct ev_signal exitsig;	740	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	741	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	742	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	743	evf_unref (loop);
717		744
718	Example: For some weird reason, unregister the above signal handler again.	745	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	793	they fire on, say, one-second boundaries only.
767		794
768	=item ev_loop_verify (loop)	795	=item ev_loop_verify (loop)
769		796
770	This function only does something when C<EV_VERIFY> support has been	797	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	798	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	799	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	800	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	801	error and call C<abort ()>.
775		802
776	This can be used to catch bugs inside libev itself: under normal	803	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	807	=back
781		808
782		809
783	=head1 ANATOMY OF A WATCHER	810	=head1 ANATOMY OF A WATCHER
784		811
		812	In the following description, uppercase C<TYPE> in names stands for the
		813	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		814	watchers and C<ev_io_start> for I/O watchers.
		815
785	A watcher is a structure that you create and register to record your	816	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	817	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:	818	become readable, you would create an C<ev_io> watcher for that:
788		819
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	820	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	821	{
791	ev_io_stop (w);	822	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	823	ev_unloop (loop, EVUNLOOP_ALL);
793	}	824	}
794		825
795	struct ev_loop *loop = ev_default_loop (0);	826	struct ev_loop *loop = ev_default_loop (0);
		827
796	struct ev_io stdin_watcher;	828	ev_io stdin_watcher;
		829
797	ev_init (&stdin_watcher, my_cb);	830	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	831	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	832	ev_io_start (loop, &stdin_watcher);
		833
800	ev_loop (loop, 0);	834	ev_loop (loop, 0);
801		835
802	As you can see, you are responsible for allocating the memory for your	836	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,	837	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	838	stack).
		839
		840	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		841	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		842
806	Each watcher structure must be initialised by a call to C<ev_init	843	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	844	(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	845	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	846	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	847	is readable and/or writable).
811		848
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	849	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	850	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	851	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	852	ev_TYPE_init (watcher *, callback, ...) >>.
816		853
817	To make the watcher actually watch out for events, you have to start it	854	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	855	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	856	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	857	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		858
822	As long as your watcher is active (has been started but not stopped) you	859	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	860	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	861	reinitialise it or call its C<ev_TYPE_set> macro.
825		862
826	Each and every callback receives the event loop pointer as first, the	863	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	864	registered watcher structure as second, and a bitset of received events as
828	third argument.	865	third argument.
829		866
…		…
892	=item C<EV_ERROR>	929	=item C<EV_ERROR>
893		930
894	An unspecified error has occurred, the watcher has been stopped. This might	931	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	932	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	933	ran out of memory, a file descriptor was found to be closed or any other
		934	problem. Libev considers these application bugs.
		935
897	problem. You best act on it by reporting the problem and somehow coping	936	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	937	watcher being stopped. Note that well-written programs should not receive
		938	an error ever, so when your watcher receives it, this usually indicates a
		939	bug in your program.
899		940
900	Libev will usually signal a few "dummy" events together with an error, for	941	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	942	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	943	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	944	the error from read() or write(). This will not work in multi-threaded
…		…
906		947
907	=back	948	=back
908		949
909	=head2 GENERIC WATCHER FUNCTIONS	950	=head2 GENERIC WATCHER FUNCTIONS
910		951
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	952	=over 4
915		953
916	=item C<ev_init> (ev_TYPE *watcher, callback)	954	=item C<ev_init> (ev_TYPE *watcher, callback)
917		955
918	This macro initialises the generic portion of a watcher. The contents	956	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	961	which rolls both calls into one.
924		962
925	You can reinitialise a watcher at any time as long as it has been stopped	963	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.	964	(or never started) and there are no pending events outstanding.
927		965
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	966	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	967	int revents)>.
930		968
931	Example: Initialise an C<ev_io> watcher in two steps.	969	Example: Initialise an C<ev_io> watcher in two steps.
932		970
933	ev_io w;	971	ev_io w;
…		…
967		1005
968	ev_io_start (EV_DEFAULT_UC, &w);	1006	ev_io_start (EV_DEFAULT_UC, &w);
969		1007
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1008	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		1009
972	Stops the given watcher again (if active) and clears the pending	1010	Stops the given watcher if active, and clears the pending status (whether
		1011	the watcher was active or not).
		1012
973	status. It is possible that stopped watchers are pending (for example,	1013	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1014	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	1015	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	1016	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.	1017	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1018
979	=item bool ev_is_active (ev_TYPE *watcher)	1019	=item bool ev_is_active (ev_TYPE *watcher)
980		1020
981	Returns a true value iff the watcher is active (i.e. it has been started	1021	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	1022	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	1064	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 :).	1065	always C<0>, which is supposed to not be too high and not be too low :).
1026		1066
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1067	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	1068	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.	1069	or might not have been clamped to the valid range.
1030		1070
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1071	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1072
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1073	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	1074	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	1096	member, you can also "subclass" the watcher type and provide your own
1057	data:	1097	data:
1058		1098
1059	struct my_io	1099	struct my_io
1060	{	1100	{
1061	struct ev_io io;	1101	ev_io io;
1062	int otherfd;	1102	int otherfd;
1063	void *somedata;	1103	void *somedata;
1064	struct whatever *mostinteresting;	1104	struct whatever *mostinteresting;
1065	};	1105	};
1066		1106
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1109	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1110
1071	And since your callback will be called with a pointer to the watcher, you	1111	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1112	can cast it back to your own type:
1073		1113
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1114	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1115	{
1076	struct my_io w = (struct my_io )w_;	1116	struct my_io w = (struct my_io )w_;
1077	...	1117	...
1078	}	1118	}
1079		1119
…		…
1097	programmers):	1137	programmers):
1098		1138
1099	#include <stddef.h>	1139	#include <stddef.h>
1100		1140
1101	static void	1141	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1142	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1143	{
1104	struct my_biggy big = (struct my_biggy *	1144	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1145	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1146	}
1107		1147
1108	static void	1148	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1149	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1150	{
1111	struct my_biggy big = (struct my_biggy *	1151	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1152	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1153	}
1114		1154
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1289	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	1290	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1291	attempt to read a whole line in the callback.
1252		1292
1253	static void	1293	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1294	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1295	{
1256	ev_io_stop (loop, w);	1296	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1297	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1298	}
1259		1299
1260	...	1300	...
1261	struct ev_loop *loop = ev_default_init (0);	1301	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1302	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1303	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1304	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1305	ev_loop (loop, 0);
1266		1306
1267		1307
…		…
1278		1318
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1319	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	1320	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1321	then order of execution is undefined.
1282		1322
		1323	=head3 Be smart about timeouts
		1324
		1325	Many real-world problems involve some kind of timeout, usually for error
		1326	recovery. A typical example is an HTTP request - if the other side hangs,
		1327	you want to raise some error after a while.
		1328
		1329	What follows are some ways to handle this problem, from obvious and
		1330	inefficient to smart and efficient.
		1331
		1332	In the following, a 60 second activity timeout is assumed - a timeout that
		1333	gets reset to 60 seconds each time there is activity (e.g. each time some
		1334	data or other life sign was received).
		1335
		1336	=over 4
		1337
		1338	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1339
		1340	This is the most obvious, but not the most simple way: In the beginning,
		1341	start the watcher:
		1342
		1343	ev_timer_init (timer, callback, 60., 0.);
		1344	ev_timer_start (loop, timer);
		1345
		1346	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1347	and start it again:
		1348
		1349	ev_timer_stop (loop, timer);
		1350	ev_timer_set (timer, 60., 0.);
		1351	ev_timer_start (loop, timer);
		1352
		1353	This is relatively simple to implement, but means that each time there is
		1354	some activity, libev will first have to remove the timer from its internal
		1355	data structure and then add it again. Libev tries to be fast, but it's
		1356	still not a constant-time operation.
		1357
		1358	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1359
		1360	This is the easiest way, and involves using C<ev_timer_again> instead of
		1361	C<ev_timer_start>.
		1362
		1363	To implement this, configure an C<ev_timer> with a C<repeat> value
		1364	of C<60> and then call C<ev_timer_again> at start and each time you
		1365	successfully read or write some data. If you go into an idle state where
		1366	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1367	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1368
		1369	That means you can ignore both the C<ev_timer_start> function and the
		1370	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1371	member and C<ev_timer_again>.
		1372
		1373	At start:
		1374
		1375	ev_timer_init (timer, callback);
		1376	timer->repeat = 60.;
		1377	ev_timer_again (loop, timer);
		1378
		1379	Each time there is some activity:
		1380
		1381	ev_timer_again (loop, timer);
		1382
		1383	It is even possible to change the time-out on the fly, regardless of
		1384	whether the watcher is active or not:
		1385
		1386	timer->repeat = 30.;
		1387	ev_timer_again (loop, timer);
		1388
		1389	This is slightly more efficient then stopping/starting the timer each time
		1390	you want to modify its timeout value, as libev does not have to completely
		1391	remove and re-insert the timer from/into its internal data structure.
		1392
		1393	It is, however, even simpler than the "obvious" way to do it.
		1394
		1395	=item 3. Let the timer time out, but then re-arm it as required.
		1396
		1397	This method is more tricky, but usually most efficient: Most timeouts are
		1398	relatively long compared to the intervals between other activity - in
		1399	our example, within 60 seconds, there are usually many I/O events with
		1400	associated activity resets.
		1401
		1402	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1403	but remember the time of last activity, and check for a real timeout only
		1404	within the callback:
		1405
		1406	ev_tstamp last_activity; // time of last activity
		1407
		1408	static void
		1409	callback (EV_P_ ev_timer *w, int revents)
		1410	{
		1411	ev_tstamp now = ev_now (EV_A);
		1412	ev_tstamp timeout = last_activity + 60.;
		1413
		1414	// if last_activity + 60. is older than now, we did time out
		1415	if (timeout < now)
		1416	{
		1417	// timeout occured, take action
		1418	}
		1419	else
		1420	{
		1421	// callback was invoked, but there was some activity, re-arm
		1422	// the watcher to fire in last_activity + 60, which is
		1423	// guaranteed to be in the future, so "again" is positive:
		1424	w->repeat = timeout - now;
		1425	ev_timer_again (EV_A_ w);
		1426	}
		1427	}
		1428
		1429	To summarise the callback: first calculate the real timeout (defined
		1430	as "60 seconds after the last activity"), then check if that time has
		1431	been reached, which means something I<did>, in fact, time out. Otherwise
		1432	the callback was invoked too early (C<timeout> is in the future), so
		1433	re-schedule the timer to fire at that future time, to see if maybe we have
		1434	a timeout then.
		1435
		1436	Note how C<ev_timer_again> is used, taking advantage of the
		1437	C<ev_timer_again> optimisation when the timer is already running.
		1438
		1439	This scheme causes more callback invocations (about one every 60 seconds
		1440	minus half the average time between activity), but virtually no calls to
		1441	libev to change the timeout.
		1442
		1443	To start the timer, simply initialise the watcher and set C<last_activity>
		1444	to the current time (meaning we just have some activity :), then call the
		1445	callback, which will "do the right thing" and start the timer:
		1446
		1447	ev_timer_init (timer, callback);
		1448	last_activity = ev_now (loop);
		1449	callback (loop, timer, EV_TIMEOUT);
		1450
		1451	And when there is some activity, simply store the current time in
		1452	C<last_activity>, no libev calls at all:
		1453
		1454	last_actiivty = ev_now (loop);
		1455
		1456	This technique is slightly more complex, but in most cases where the
		1457	time-out is unlikely to be triggered, much more efficient.
		1458
		1459	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1460	callback :) - just change the timeout and invoke the callback, which will
		1461	fix things for you.
		1462
		1463	=item 4. Wee, just use a double-linked list for your timeouts.
		1464
		1465	If there is not one request, but many thousands (millions...), all
		1466	employing some kind of timeout with the same timeout value, then one can
		1467	do even better:
		1468
		1469	When starting the timeout, calculate the timeout value and put the timeout
		1470	at the I<end> of the list.
		1471
		1472	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1473	the list is expected to fire (for example, using the technique #3).
		1474
		1475	When there is some activity, remove the timer from the list, recalculate
		1476	the timeout, append it to the end of the list again, and make sure to
		1477	update the C<ev_timer> if it was taken from the beginning of the list.
		1478
		1479	This way, one can manage an unlimited number of timeouts in O(1) time for
		1480	starting, stopping and updating the timers, at the expense of a major
		1481	complication, and having to use a constant timeout. The constant timeout
		1482	ensures that the list stays sorted.
		1483
		1484	=back
		1485
		1486	So which method the best?
		1487
		1488	Method #2 is a simple no-brain-required solution that is adequate in most
		1489	situations. Method #3 requires a bit more thinking, but handles many cases
		1490	better, and isn't very complicated either. In most case, choosing either
		1491	one is fine, with #3 being better in typical situations.
		1492
		1493	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1494	rather complicated, but extremely efficient, something that really pays
		1495	off after the first million or so of active timers, i.e. it's usually
		1496	overkill :)
		1497
1283	=head3 The special problem of time updates	1498	=head3 The special problem of time updates
1284		1499
1285	Establishing the current time is a costly operation (it usually takes at	1500	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	1501	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	1502	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).	1545	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1546
1332	If the timer is repeating, either start it if necessary (with the	1547	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.	1548	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1549
1335	This sounds a bit complicated, but here is a useful and typical	1550	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	1551	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		1552
1366	=item ev_tstamp repeat [read-write]	1553	=item ev_tstamp repeat [read-write]
1367		1554
1368	The current C<repeat> value. Will be used each time the watcher times out	1555	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),	1556	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1561	=head3 Examples
1375		1562
1376	Example: Create a timer that fires after 60 seconds.	1563	Example: Create a timer that fires after 60 seconds.
1377		1564
1378	static void	1565	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1566	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1567	{
1381	.. one minute over, w is actually stopped right here	1568	.. one minute over, w is actually stopped right here
1382	}	1569	}
1383		1570
1384	struct ev_timer mytimer;	1571	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1572	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1573	ev_timer_start (loop, &mytimer);
1387		1574
1388	Example: Create a timeout timer that times out after 10 seconds of	1575	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1576	inactivity.
1390		1577
1391	static void	1578	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1579	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1580	{
1394	.. ten seconds without any activity	1581	.. ten seconds without any activity
1395	}	1582	}
1396		1583
1397	struct ev_timer mytimer;	1584	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1585	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1586	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1587	ev_loop (loop, 0);
1401		1588
1402	// and in some piece of code that gets executed on any "activity":	1589	// and in some piece of code that gets executed on any "activity":
…		…
1488		1675
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1676	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	1677	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1678	only event loop modification you are allowed to do).
1492		1679
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1680	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1681	*w, ev_tstamp now)>, e.g.:
1495		1682
		1683	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1684	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1685	{
1498	return now + 60.;	1686	return now + 60.;
1499	}	1687	}
1500		1688
1501	It must return the next time to trigger, based on the passed time value	1689	It must return the next time to trigger, based on the passed time value
…		…
1538		1726
1539	The current interval value. Can be modified any time, but changes only	1727	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	1728	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1729	called.
1542		1730
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1731	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1732
1545	The current reschedule callback, or C<0>, if this functionality is	1733	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	1734	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.	1735	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1736
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1741	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1742	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1743	potentially a lot of jitter, but good long-term stability.
1556		1744
1557	static void	1745	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1746	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1747	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1748	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1749	}
1562		1750
1563	struct ev_periodic hourly_tick;	1751	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1752	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1753	ev_periodic_start (loop, &hourly_tick);
1566		1754
1567	Example: The same as above, but use a reschedule callback to do it:	1755	Example: The same as above, but use a reschedule callback to do it:
1568		1756
1569	#include <math.h>	1757	#include <math.h>
1570		1758
1571	static ev_tstamp	1759	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1760	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1761	{
1574	return now + (3600. - fmod (now, 3600.));	1762	return now + (3600. - fmod (now, 3600.));
1575	}	1763	}
1576		1764
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1765	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1766
1579	Example: Call a callback every hour, starting now:	1767	Example: Call a callback every hour, starting now:
1580		1768
1581	struct ev_periodic hourly_tick;	1769	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1770	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1771	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1772	ev_periodic_start (loop, &hourly_tick);
1585		1773
1586		1774
…		…
1625		1813
1626	=back	1814	=back
1627		1815
1628	=head3 Examples	1816	=head3 Examples
1629		1817
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1818	Example: Try to exit cleanly on SIGINT.
1631		1819
1632	static void	1820	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1821	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1822	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1823	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1824	}
1637		1825
1638	struct ev_signal signal_watcher;	1826	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1827	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1828	ev_signal_start (loop, &signal_watcher);
1641		1829
1642		1830
1643	=head2 C<ev_child> - watch out for process status changes	1831	=head2 C<ev_child> - watch out for process status changes
1644		1832
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1833	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1906	its completion.
1719		1907
1720	ev_child cw;	1908	ev_child cw;
1721		1909
1722	static void	1910	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1911	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1912	{
1725	ev_child_stop (EV_A_ w);	1913	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1914	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1915	}
1728		1916
…		…
1743		1931
1744		1932
1745	=head2 C<ev_stat> - did the file attributes just change?	1933	=head2 C<ev_stat> - did the file attributes just change?
1746		1934
1747	This watches a file system path for attribute changes. That is, it calls	1935	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	1936	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.	1937	and sees if it changed compared to the last time, invoking the callback if
		1938	it did.
1750		1939
1751	The path does not need to exist: changing from "path exists" to "path does	1940	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	1941	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	1942	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	1943	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1944	least one) and all the other fields of the stat buffer having unspecified
		1945	contents.
1756		1946
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1947	The path I<must not> end in a slash or contain special components such as
		1948	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.	1949	your working directory changes, then the behaviour is undefined.
1759		1950
1760	Since there is no standard kernel interface to do this, the portable	1951	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	1952	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	1953	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!)	1954	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	1955	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	1956	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	1957	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	1958	currently around C<0.1>, but that's usually overkill.
1768		1959
1769	This watcher type is not meant for massive numbers of stat watchers,	1960	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	1961	as even with OS-supported change notifications, this can be
1771	resource-intensive.	1962	resource-intensive.
1772		1963
1773	At the time of this writing, the only OS-specific interface implemented	1964	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	1965	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	1966	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	1967	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		1968
1778	=head3 ABI Issues (Largefile Support)	1969	=head3 ABI Issues (Largefile Support)
1779		1970
1780	Libev by default (unless the user overrides this) uses the default	1971	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	1972	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	1973	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	1974	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	1975	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	1976	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	1977	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.	1978	most noticeably displayed with ev_stat and large file support.
1788		1979
1789	The solution for this is to lobby your distribution maker to make large	1980	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	1981	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	1982	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	1983	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1984	default compilation environment.
1794		1985
1795	=head3 Inotify and Kqueue	1986	=head3 Inotify and Kqueue
1796		1987
1797	When C<inotify (7)> support has been compiled into libev (generally only	1988	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	1989	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	1990	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	1991	watcher is being started.
1801		1992
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1993	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	1994	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	1995	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,	1996	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.	1997	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1998	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1999	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		2000	xfs are fully working) libev usually gets away without polling.
1807		2001
1808	There is no support for kqueue, as apparently it cannot be used to	2002	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	2003	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2004	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2005	etc. is difficult.
1812		2006
		2007	=head3 C<stat ()> is a synchronous operation
		2008
		2009	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2010	the process. The exception are C<ev_stat> watchers - those call C<stat
		2011	()>, which is a synchronous operation.
		2012
		2013	For local paths, this usually doesn't matter: unless the system is very
		2014	busy or the intervals between stat's are large, a stat call will be fast,
		2015	as the path data is suually in memory already (except when starting the
		2016	watcher).
		2017
		2018	For networked file systems, calling C<stat ()> can block an indefinite
		2019	time due to network issues, and even under good conditions, a stat call
		2020	often takes multiple milliseconds.
		2021
		2022	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2023	paths, although this is fully supported by libev.
		2024
1813	=head3 The special problem of stat time resolution	2025	=head3 The special problem of stat time resolution
1814		2026
1815	The C<stat ()> system call only supports full-second resolution portably, and	2027	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2028	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2029	still only support whole seconds.
1818		2030
1819	That means that, if the time is the only thing that changes, you can	2031	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	2032	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	2033	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	2034	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1979		2191
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2192	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2193	callback, free it. Also, use no error checking, as usual.
1982		2194
1983	static void	2195	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2196	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2197	{
1986	free (w);	2198	free (w);
1987	// now do something you wanted to do when the program has	2199	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2200	// no longer anything immediate to do.
1989	}	2201	}
1990		2202
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2203	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2204	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2205	ev_idle_start (loop, idle_cb);
1994		2206
1995		2207
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2208	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2289
2078	static ev_io iow [nfd];	2290	static ev_io iow [nfd];
2079	static ev_timer tw;	2291	static ev_timer tw;
2080		2292
2081	static void	2293	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2294	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2295	{
2084	}	2296	}
2085		2297
2086	// create io watchers for each fd and a timer before blocking	2298	// create io watchers for each fd and a timer before blocking
2087	static void	2299	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2300	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2301	{
2090	int timeout = 3600000;	2302	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2303	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2304	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2305	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2320	}
2109	}	2321	}
2110		2322
2111	// stop all watchers after blocking	2323	// stop all watchers after blocking
2112	static void	2324	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2325	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2326	{
2115	ev_timer_stop (loop, &tw);	2327	ev_timer_stop (loop, &tw);
2116		2328
2117	for (int i = 0; i < nfd; ++i)	2329	for (int i = 0; i < nfd; ++i)
2118	{	2330	{
…		…
2242	So when you want to use this feature you will always have to be prepared	2454	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	2455	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	2456	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.	2457	create it, and if that fails, use the normal loop for everything.
2246		2458
		2459	=head3 C<ev_embed> and fork
		2460
		2461	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2462	automatically be applied to the embedded loop as well, so no special
		2463	fork handling is required in that case. When the watcher is not running,
		2464	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2465	as applicable.
		2466
2247	=head3 Watcher-Specific Functions and Data Members	2467	=head3 Watcher-Specific Functions and Data Members
2248		2468
2249	=over 4	2469	=over 4
2250		2470
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2471	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2498	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2499	used).
2280		2500
2281	struct ev_loop *loop_hi = ev_default_init (0);	2501	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2502	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2503	ev_embed embed;
2284		2504
2285	// see if there is a chance of getting one that works	2505	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2506	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2507	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2508	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2522	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2523	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2524
2305	struct ev_loop *loop = ev_default_init (0);	2525	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2526	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2527	ev_embed embed;
2308		2528
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2529	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2530	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2531	{
2312	ev_embed_init (&embed, 0, loop_socket);	2532	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2596	=over 4
2377		2597
2378	=item queueing from a signal handler context	2598	=item queueing from a signal handler context
2379		2599
2380	To implement race-free queueing, you simply add to the queue in the signal	2600	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	2601	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2602	an example that does that for some fictitious SIGUSR1 handler:
2383		2603
2384	static ev_async mysig;	2604	static ev_async mysig;
2385		2605
2386	static void	2606	static void
2387	sigusr1_handler (void)	2607	sigusr1_handler (void)
…		…
2453	=over 4	2673	=over 4
2454		2674
2455	=item ev_async_init (ev_async *, callback)	2675	=item ev_async_init (ev_async *, callback)
2456		2676
2457	Initialises and configures the async watcher - it has no parameters of any	2677	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,	2678	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	2679	trust me.
2460		2680
2461	=item ev_async_send (loop, ev_async *)	2681	=item ev_async_send (loop, ev_async *)
2462		2682
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2683	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
…		…
2494	=over 4	2714	=over 4
2495		2715
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2716	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2717
2498	This function combines a simple timer and an I/O watcher, calls your	2718	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2719	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	2720	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	2721	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2722	more watchers yourself.
2503		2723
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2724	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	2725	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2726	the given C<fd> and C<events> set will be created and started.
2507		2727
2508	If C<timeout> is less than 0, then no timeout watcher will be	2728	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	2729	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	2730	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2731
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2732	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	2733	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>	2734	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2735	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2736	a timeout and an io event at the same time - you probably should give io
		2737	events precedence.
		2738
		2739	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2740
2518	static void stdin_ready (int revents, void *arg)	2741	static void stdin_ready (int revents, void *arg)
2519	{	2742	{
		2743	if (revents & EV_READ)
		2744	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2745	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2746	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2747	}
2525		2748
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2749	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2750
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2751	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2752
2530	Feeds the given event set into the event loop, as if the specified event	2753	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	2754	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2755	initialised but not necessarily started event watcher).
2533		2756
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2757	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2758
2536	Feed an event on the given fd, as if a file descriptor backend detected	2759	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2760	the given events it.
2538		2761
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2762	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2763
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2764	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2765	loop!).
2543		2766
2544	=back	2767	=back
…		…
2779	=item D	3002	=item D
2780		3003
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3004	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>.	3005	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2783		3006
		3007	=item Ocaml
		3008
		3009	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3010	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3011
2784	=back	3012	=back
2785		3013
2786		3014
2787	=head1 MACRO MAGIC	3015	=head1 MACRO MAGIC
2788		3016
…		…
2888		3116
2889	#define EV_STANDALONE 1	3117	#define EV_STANDALONE 1
2890	#include "ev.h"	3118	#include "ev.h"
2891		3119
2892	Both header files and implementation files can be compiled with a C++	3120	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	3121	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3122	as a bug).
2895		3123
2896	You need the following files in your source tree, or in a directory	3124	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):	3125	in your include path (e.g. in libev/ when using -Ilibev):
2898		3126
…		…
3241	definition and a statement, respectively. See the F<ev.h> header file for	3469	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	3470	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	3471	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++.	3472	method calls instead of plain function calls in C++.
3245		3473
		3474	=back
		3475
3246	=head2 EXPORTED API SYMBOLS	3476	=head2 EXPORTED API SYMBOLS
3247		3477
3248	If you need to re-export the API (e.g. via a DLL) and you need a list of	3478	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	3479	exported symbols, you can use the provided F<Symbol.*> files which list
3250	all public symbols, one per line:	3480	all public symbols, one per line:
…		…
3296	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3526	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3297		3527
3298	#include "ev_cpp.h"	3528	#include "ev_cpp.h"
3299	#include "ev.c"	3529	#include "ev.c"
3300		3530
		3531	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3301		3532
3302	=head1 THREADS AND COROUTINES	3533	=head2 THREADS AND COROUTINES
3303		3534
3304	=head2 THREADS	3535	=head3 THREADS
3305		3536
3306	Libev itself is thread-safe (unless the opposite is specifically	3537	All libev functions are reentrant and thread-safe unless explicitly
3307	documented for a function), but it uses no locking itself. This means that	3538	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	3539	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:	3540	are no concurrent calls into any libev function with the same loop
		3541	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3310	libev guarantees that different event loops share no data structures that	3542	of course): libev guarantees that different event loops share no data
3311	need locking.	3543	structures that need any locking.
3312		3544
3313	Or to put it differently: calls with different loop parameters can be done	3545	Or to put it differently: calls with different loop parameters can be done
3314	concurrently from multiple threads, calls with the same loop parameter	3546	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	3547	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	3548	only one thread ever is inside a call at any point in time, e.g. by using
3317	a mutex per loop).	3549	a mutex per loop).
3318		3550
3319	Specifically to support threads (and signal handlers), libev implements	3551	Specifically to support threads (and signal handlers), libev implements
3320	so-called C<ev_async> watchers, which allow some limited form of	3552	so-called C<ev_async> watchers, which allow some limited form of
3321	concurrency on the same event loop.	3553	concurrency on the same event loop, namely waking it up "from the
		3554	outside".
3322		3555
3323	If you want to know which design (one loop, locking, or multiple loops	3556	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	3557	without or something else still) is best for your problem, then I cannot
3325	help you. I can give some generic advice however:	3558	help you, but here is some generic advice:
3326		3559
3327	=over 4	3560	=over 4
3328		3561
3329	=item * most applications have a main thread: use the default libev loop	3562	=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.	3563	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	3587	default loop and triggering an C<ev_async> watcher from the default loop
3355	watcher callback into the event loop interested in the signal.	3588	watcher callback into the event loop interested in the signal.
3356		3589
3357	=back	3590	=back
3358		3591
3359	=head2 COROUTINES	3592	=head3 COROUTINES
3360		3593
3361	Libev is much more accommodating to coroutines ("cooperative threads"):	3594	Libev is very accommodating to coroutines ("cooperative threads"):
3362	libev fully supports nesting calls to it's functions from different	3595	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	3596	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	3597	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	3598	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.	3599	you must not do this from C<ev_periodic> reschedule callbacks.
3367		3600
3368	Care has been taken to ensure that libev does not keep local state inside	3601	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.	3602	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3603	they do not call any callbacks.
3370		3604
		3605	=head2 COMPILER WARNINGS
3371		3606
3372	=head1 COMPLEXITIES	3607	Depending on your compiler and compiler settings, you might get no or a
		3608	lot of warnings when compiling libev code. Some people are apparently
		3609	scared by this.
3373		3610
3374	In this section the complexities of (many of) the algorithms used inside	3611	However, these are unavoidable for many reasons. For one, each compiler
3375	libev will be explained. For complexity discussions about backends see the	3612	has different warnings, and each user has different tastes regarding
3376	documentation for C<ev_default_init>.	3613	warning options. "Warn-free" code therefore cannot be a goal except when
		3614	targeting a specific compiler and compiler-version.
3377		3615
3378	All of the following are about amortised time: If an array needs to be	3616	Another reason is that some compiler warnings require elaborate
3379	extended, libev needs to realloc and move the whole array, but this	3617	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	3618	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		3619
3384	=over 4	3620	And of course, some compiler warnings are just plain stupid, or simply
		3621	wrong (because they don't actually warn about the condition their message
		3622	seems to warn about). For example, certain older gcc versions had some
		3623	warnings that resulted an extreme number of false positives. These have
		3624	been fixed, but some people still insist on making code warn-free with
		3625	such buggy versions.
3385		3626
3386	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3627	While libev is written to generate as few warnings as possible,
		3628	"warn-free" code is not a goal, and it is recommended not to build libev
		3629	with any compiler warnings enabled unless you are prepared to cope with
		3630	them (e.g. by ignoring them). Remember that warnings are just that:
		3631	warnings, not errors, or proof of bugs.
3387		3632
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		3633
3392	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3634	=head2 VALGRIND
3393		3635
3394	That means that changing a timer costs less than removing/adding them	3636	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.	3637	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3396		3638
3397	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3639	If you think you found a bug (memory leak, uninitialised data access etc.)
		3640	in libev, then check twice: If valgrind reports something like:
3398		3641
3399	These just add the watcher into an array or at the head of a list.	3642	==2274== definitely lost: 0 bytes in 0 blocks.
		3643	==2274== possibly lost: 0 bytes in 0 blocks.
		3644	==2274== still reachable: 256 bytes in 1 blocks.
3400		3645
3401	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3646	Then there is no memory leak, just as memory accounted to global variables
		3647	is not a memleak - the memory is still being referenced, and didn't leak.
3402		3648
3403	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3649	Similarly, under some circumstances, valgrind might report kernel bugs
		3650	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3651	although an acceptable workaround has been found here), or it might be
		3652	confused.
3404		3653
3405	These watchers are stored in lists then need to be walked to find the	3654	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	3655	make it into some kind of religion.
3407	have many watchers waiting for the same fd or signal).
3408		3656
3409	=item Finding the next timer in each loop iteration: O(1)	3657	If you are unsure about something, feel free to contact the mailing list
		3658	with the full valgrind report and an explanation on why you think this
		3659	is a bug in libev (best check the archives, too :). However, don't be
		3660	annoyed when you get a brisk "this is no bug" answer and take the chance
		3661	of learning how to interpret valgrind properly.
3410		3662
3411	By virtue of using a binary or 4-heap, the next timer is always found at a	3663	If you need, for some reason, empty reports from valgrind for your project
3412	fixed position in the storage array.	3664	I suggest using suppression lists.
3413		3665
3414	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3415		3666
3416	A change means an I/O watcher gets started or stopped, which requires	3667	=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		3668
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	3669	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3443		3670
3444	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3671	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	3672	requires, and its I/O model is fundamentally incompatible with the POSIX
3446	model. Libev still offers limited functionality on this platform in	3673	model. Libev still offers limited functionality on this platform in
3447	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3674	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	3761	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.	3762	calling select (O(n²)) will likely make this unworkable.
3536		3763
3537	=back	3764	=back
3538		3765
3539
3540	=head1 PORTABILITY REQUIREMENTS	3766	=head2 PORTABILITY REQUIREMENTS
3541		3767
3542	In addition to a working ISO-C implementation, libev relies on a few	3768	In addition to a working ISO-C implementation and of course the
3543	additional extensions:	3769	backend-specific APIs, libev relies on a few additional extensions:
3544		3770
3545	=over 4	3771	=over 4
3546		3772
3547	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3773	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3548	calling conventions regardless of C<ev_watcher_type *>.	3774	calling conventions regardless of C<ev_watcher_type *>.
…		…
3573	except the initial one, and run the default loop in the initial thread as	3799	except the initial one, and run the default loop in the initial thread as
3574	well.	3800	well.
3575		3801
3576	=item C<long> must be large enough for common memory allocation sizes	3802	=item C<long> must be large enough for common memory allocation sizes
3577		3803
3578	To improve portability and simplify using libev, libev uses C<long>	3804	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	3805	instead of C<size_t> when allocating its data structures. On non-POSIX
3580	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3806	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	3807	least 31 bits everywhere, which is enough for hundreds of millions of
3582	millions of watchers.	3808	watchers.
3583		3809
3584	=item C<double> must hold a time value in seconds with enough accuracy	3810	=item C<double> must hold a time value in seconds with enough accuracy
3585		3811
3586	The type C<double> is used to represent timestamps. It is required to	3812	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	3813	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3591	=back	3817	=back
3592		3818
3593	If you know of other additional requirements drop me a note.	3819	If you know of other additional requirements drop me a note.
3594		3820
3595		3821
3596	=head1 COMPILER WARNINGS	3822	=head1 ALGORITHMIC COMPLEXITIES
3597		3823
3598	Depending on your compiler and compiler settings, you might get no or a	3824	In this section the complexities of (many of) the algorithms used inside
3599	lot of warnings when compiling libev code. Some people are apparently	3825	libev will be documented. For complexity discussions about backends see
3600	scared by this.	3826	the documentation for C<ev_default_init>.
3601		3827
3602	However, these are unavoidable for many reasons. For one, each compiler	3828	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	3829	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	3830	happens asymptotically rarer with higher number of elements, so O(1) might
3605	targeting a specific compiler and compiler-version.	3831	mean that libev does a lengthy realloc operation in rare cases, but on
		3832	average it is much faster and asymptotically approaches constant time.
3606		3833
3607	Another reason is that some compiler warnings require elaborate	3834	=over 4
3608	workarounds, or other changes to the code that make it less clear and less
3609	maintainable.
3610		3835
3611	And of course, some compiler warnings are just plain stupid, or simply	3836	=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		3837
3615	While libev is written to generate as few warnings as possible,	3838	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	3839	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	3840	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		3841
		3842	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3621		3843
3622	=head1 VALGRIND	3844	That means that changing a timer costs less than removing/adding them,
		3845	as only the relative motion in the event queue has to be paid for.
3623		3846
3624	Valgrind has a special section here because it is a popular tool that is	3847	=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		3848
3627	If you think you found a bug (memory leak, uninitialised data access etc.)	3849	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		3850
3630	==2274== definitely lost: 0 bytes in 0 blocks.	3851	=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		3852
3634	Then there is no memory leak. Similarly, under some circumstances,	3853	=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		3854
3638	If you are unsure about something, feel free to contact the mailing list	3855	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	3856	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	3857	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	3858	is rare).
3642	properly.
3643		3859
3644	If you need, for some reason, empty reports from valgrind for your project	3860	=item Finding the next timer in each loop iteration: O(1)
3645	I suggest using suppression lists.	3861
		3862	By virtue of using a binary or 4-heap, the next timer is always found at a
		3863	fixed position in the storage array.
		3864
		3865	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3866
		3867	A change means an I/O watcher gets started or stopped, which requires
		3868	libev to recalculate its status (and possibly tell the kernel, depending
		3869	on backend and whether C<ev_io_set> was used).
		3870
		3871	=item Activating one watcher (putting it into the pending state): O(1)
		3872
		3873	=item Priority handling: O(number_of_priorities)
		3874
		3875	Priorities are implemented by allocating some space for each
		3876	priority. When doing priority-based operations, libev usually has to
		3877	linearly search all the priorities, but starting/stopping and activating
		3878	watchers becomes O(1) with respect to priority handling.
		3879
		3880	=item Sending an ev_async: O(1)
		3881
		3882	=item Processing ev_async_send: O(number_of_async_watchers)
		3883
		3884	=item Processing signals: O(max_signal_number)
		3885
		3886	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3887	calls in the current loop iteration. Checking for async and signal events
		3888	involves iterating over all running async watchers or all signal numbers.
		3889
		3890	=back
3646		3891
3647		3892
3648	=head1 AUTHOR	3893	=head1 AUTHOR
3649		3894
3650	Marc Lehmann <libev@schmorp.de>.	3895	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3651		3896

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Comparing libev/ev.pod (file contents): Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs. Revision 1.216 by root, Thu Nov 13 15:55:38 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.184 by root, Tue Sep 23 09:11:14 2008 UTC vs.
Revision 1.216 by root, Thu Nov 13 15:55:38 2008 UTC