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

Comparing libev/ev.pod (file contents):
Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs.
Revision 1.213 by root, Wed Nov 5 02:48:45 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 practise, C<EVBACKEND_SELECT> is as fast or faster
		424	then epoll for maybe up to a hundred file descriptors. So sad.
405		425
406	While nominally embeddable in other event loops, this feature is broken in	426	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	427	all kernel versions tested so far.
408		428
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	429	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	430	C<EVBACKEND_POLL>.
411		431
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	432	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		433
414	Kqueue deserves special mention, as at the time of this writing, it was	434	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	435	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	436	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	437	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	438	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.	439	without API changes to existing programs. For this reason it's not being
		440	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		441	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		442	system like NetBSD.
420		443
421	You still can embed kqueue into a normal poll or select backend and use it	444	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	445	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.	446	the target platform). See C<ev_embed> watchers for more info.
424		447
425	It scales in the same way as the epoll backend, but the interface to the	448	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	449	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	450	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	451	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	452	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	453	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		454	cases
431		455
432	This backend usually performs well under most conditions.	456	This backend usually performs well under most conditions.
433		457
434	While nominally embeddable in other event loops, this doesn't work	458	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	459	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	488	might perform better.
465		489
466	On the positive side, with the exception of the spurious readiness	490	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	491	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	492	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	493	OS-specific backends (I vastly prefer correctness over speed hacks).
470		494
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	495	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	496	C<EVBACKEND_POLL>.
473		497
474	=item C<EVBACKEND_ALL>	498	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	551	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	552	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	553	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	554	for example).
531		555
532	Note that certain global state, such as signal state, will not be freed by	556	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	557	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	558	as signal and child watchers) would need to be stopped manually.
535		559
536	In general it is not advisable to call this function except in the	560	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	561	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	562	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	563	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	655	the loop.
632		656
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	657	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	658	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	659	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	660	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	661	user-registered callback will be called), and will return after one
638	iteration of the loop.	662	iteration of the loop.
639		663
640	This is useful if you are waiting for some external event in conjunction	664	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	665	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	709	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.	710	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		711
688	This "unloop state" will be cleared when entering C<ev_loop> again.	712	This "unloop state" will be cleared when entering C<ev_loop> again.
689		713
		714	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		715
690	=item ev_ref (loop)	716	=item ev_ref (loop)
691		717
692	=item ev_unref (loop)	718	=item ev_unref (loop)
693		719
694	Ref/unref can be used to add or remove a reference count on the event	720	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	734	respectively).
709		735
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	736	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	737	running when nothing else is active.
712		738
713	struct ev_signal exitsig;	739	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	740	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	741	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	742	evf_unref (loop);
717		743
718	Example: For some weird reason, unregister the above signal handler again.	744	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	792	they fire on, say, one-second boundaries only.
767		793
768	=item ev_loop_verify (loop)	794	=item ev_loop_verify (loop)
769		795
770	This function only does something when C<EV_VERIFY> support has been	796	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	797	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	798	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	799	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	800	error and call C<abort ()>.
775		801
776	This can be used to catch bugs inside libev itself: under normal	802	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	806	=back
781		807
782		808
783	=head1 ANATOMY OF A WATCHER	809	=head1 ANATOMY OF A WATCHER
784		810
		811	In the following description, uppercase C<TYPE> in names stands for the
		812	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		813	watchers and C<ev_io_start> for I/O watchers.
		814
785	A watcher is a structure that you create and register to record your	815	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	816	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:	817	become readable, you would create an C<ev_io> watcher for that:
788		818
789	static void my_cb (struct ev_loop loop, struct ev_io w, int revents)	819	static void my_cb (struct ev_loop loop, ev_io w, int revents)
790	{	820	{
791	ev_io_stop (w);	821	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	822	ev_unloop (loop, EVUNLOOP_ALL);
793	}	823	}
794		824
795	struct ev_loop *loop = ev_default_loop (0);	825	struct ev_loop *loop = ev_default_loop (0);
		826
796	struct ev_io stdin_watcher;	827	ev_io stdin_watcher;
		828
797	ev_init (&stdin_watcher, my_cb);	829	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	830	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	831	ev_io_start (loop, &stdin_watcher);
		832
800	ev_loop (loop, 0);	833	ev_loop (loop, 0);
801		834
802	As you can see, you are responsible for allocating the memory for your	835	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,	836	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	837	stack).
		838
		839	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		840	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		841
806	Each watcher structure must be initialised by a call to C<ev_init	842	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	843	(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	844	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	845	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	846	is readable and/or writable).
811		847
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	848	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	849	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	850	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	851	ev_TYPE_init (watcher *, callback, ...) >>.
816		852
817	To make the watcher actually watch out for events, you have to start it	853	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	854	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	855	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	856	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		857
822	As long as your watcher is active (has been started but not stopped) you	858	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	859	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	860	reinitialise it or call its C<ev_TYPE_set> macro.
825		861
826	Each and every callback receives the event loop pointer as first, the	862	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	863	registered watcher structure as second, and a bitset of received events as
828	third argument.	864	third argument.
829		865
…		…
892	=item C<EV_ERROR>	928	=item C<EV_ERROR>
893		929
894	An unspecified error has occurred, the watcher has been stopped. This might	930	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	931	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	932	ran out of memory, a file descriptor was found to be closed or any other
		933	problem. Libev considers these application bugs.
		934
897	problem. You best act on it by reporting the problem and somehow coping	935	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	936	watcher being stopped. Note that well-written programs should not receive
		937	an error ever, so when your watcher receives it, this usually indicates a
		938	bug in your program.
899		939
900	Libev will usually signal a few "dummy" events together with an error, for	940	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	941	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	942	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	943	the error from read() or write(). This will not work in multi-threaded
…		…
906		946
907	=back	947	=back
908		948
909	=head2 GENERIC WATCHER FUNCTIONS	949	=head2 GENERIC WATCHER FUNCTIONS
910		950
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	951	=over 4
915		952
916	=item C<ev_init> (ev_TYPE *watcher, callback)	953	=item C<ev_init> (ev_TYPE *watcher, callback)
917		954
918	This macro initialises the generic portion of a watcher. The contents	955	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	960	which rolls both calls into one.
924		961
925	You can reinitialise a watcher at any time as long as it has been stopped	962	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.	963	(or never started) and there are no pending events outstanding.
927		964
928	The callback is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,	965	The callback is always of type C<void ()(struct ev_loop loop, ev_TYPE *watcher,
929	int revents)>.	966	int revents)>.
930		967
931	Example: Initialise an C<ev_io> watcher in two steps.	968	Example: Initialise an C<ev_io> watcher in two steps.
932		969
933	ev_io w;	970	ev_io w;
…		…
967		1004
968	ev_io_start (EV_DEFAULT_UC, &w);	1005	ev_io_start (EV_DEFAULT_UC, &w);
969		1006
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1007	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		1008
972	Stops the given watcher again (if active) and clears the pending	1009	Stops the given watcher if active, and clears the pending status (whether
		1010	the watcher was active or not).
		1011
973	status. It is possible that stopped watchers are pending (for example,	1012	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1013	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	1014	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	1015	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.	1016	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1017
979	=item bool ev_is_active (ev_TYPE *watcher)	1018	=item bool ev_is_active (ev_TYPE *watcher)
980		1019
981	Returns a true value iff the watcher is active (i.e. it has been started	1020	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	1021	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	1063	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 :).	1064	always C<0>, which is supposed to not be too high and not be too low :).
1026		1065
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1066	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	1067	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.	1068	or might not have been clamped to the valid range.
1030		1069
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1070	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1071
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1072	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	1073	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	1095	member, you can also "subclass" the watcher type and provide your own
1057	data:	1096	data:
1058		1097
1059	struct my_io	1098	struct my_io
1060	{	1099	{
1061	struct ev_io io;	1100	ev_io io;
1062	int otherfd;	1101	int otherfd;
1063	void *somedata;	1102	void *somedata;
1064	struct whatever *mostinteresting;	1103	struct whatever *mostinteresting;
1065	};	1104	};
1066		1105
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1108	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1109
1071	And since your callback will be called with a pointer to the watcher, you	1110	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1111	can cast it back to your own type:
1073		1112
1074	static void my_cb (struct ev_loop loop, struct ev_io w_, int revents)	1113	static void my_cb (struct ev_loop loop, ev_io w_, int revents)
1075	{	1114	{
1076	struct my_io w = (struct my_io )w_;	1115	struct my_io w = (struct my_io )w_;
1077	...	1116	...
1078	}	1117	}
1079		1118
…		…
1097	programmers):	1136	programmers):
1098		1137
1099	#include <stddef.h>	1138	#include <stddef.h>
1100		1139
1101	static void	1140	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1141	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1142	{
1104	struct my_biggy big = (struct my_biggy *	1143	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1144	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1145	}
1107		1146
1108	static void	1147	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1148	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1149	{
1111	struct my_biggy big = (struct my_biggy *	1150	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1151	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1152	}
1114		1153
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1288	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	1289	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1290	attempt to read a whole line in the callback.
1252		1291
1253	static void	1292	static void
1254	stdin_readable_cb (struct ev_loop loop, struct ev_io w, int revents)	1293	stdin_readable_cb (struct ev_loop loop, ev_io w, int revents)
1255	{	1294	{
1256	ev_io_stop (loop, w);	1295	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1296	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1297	}
1259		1298
1260	...	1299	...
1261	struct ev_loop *loop = ev_default_init (0);	1300	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1301	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1302	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1303	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1304	ev_loop (loop, 0);
1266		1305
1267		1306
…		…
1278		1317
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1318	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	1319	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1320	then order of execution is undefined.
1282		1321
		1322	=head3 Be smart about timeouts
		1323
		1324	Many real-world problems involve some kind of timeout, usually for error
		1325	recovery. A typical example is an HTTP request - if the other side hangs,
		1326	you want to raise some error after a while.
		1327
		1328	What follows are some ways to handle this problem, from obvious and
		1329	inefficient to smart and efficient.
		1330
		1331	In the following, a 60 second activity timeout is assumed - a timeout that
		1332	gets reset to 60 seconds each time there is activity (e.g. each time some
		1333	data or other life sign was received).
		1334
		1335	=over 4
		1336
		1337	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1338
		1339	This is the most obvious, but not the most simple way: In the beginning,
		1340	start the watcher:
		1341
		1342	ev_timer_init (timer, callback, 60., 0.);
		1343	ev_timer_start (loop, timer);
		1344
		1345	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1346	and start it again:
		1347
		1348	ev_timer_stop (loop, timer);
		1349	ev_timer_set (timer, 60., 0.);
		1350	ev_timer_start (loop, timer);
		1351
		1352	This is relatively simple to implement, but means that each time there is
		1353	some activity, libev will first have to remove the timer from its internal
		1354	data structure and then add it again. Libev tries to be fast, but it's
		1355	still not a constant-time operation.
		1356
		1357	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1358
		1359	This is the easiest way, and involves using C<ev_timer_again> instead of
		1360	C<ev_timer_start>.
		1361
		1362	To implement this, configure an C<ev_timer> with a C<repeat> value
		1363	of C<60> and then call C<ev_timer_again> at start and each time you
		1364	successfully read or write some data. If you go into an idle state where
		1365	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1366	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1367
		1368	That means you can ignore both the C<ev_timer_start> function and the
		1369	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1370	member and C<ev_timer_again>.
		1371
		1372	At start:
		1373
		1374	ev_timer_init (timer, callback);
		1375	timer->repeat = 60.;
		1376	ev_timer_again (loop, timer);
		1377
		1378	Each time there is some activity:
		1379
		1380	ev_timer_again (loop, timer);
		1381
		1382	It is even possible to change the time-out on the fly, regardless of
		1383	whether the watcher is active or not:
		1384
		1385	timer->repeat = 30.;
		1386	ev_timer_again (loop, timer);
		1387
		1388	This is slightly more efficient then stopping/starting the timer each time
		1389	you want to modify its timeout value, as libev does not have to completely
		1390	remove and re-insert the timer from/into its internal data structure.
		1391
		1392	It is, however, even simpler than the "obvious" way to do it.
		1393
		1394	=item 3. Let the timer time out, but then re-arm it as required.
		1395
		1396	This method is more tricky, but usually most efficient: Most timeouts are
		1397	relatively long compared to the intervals between other activity - in
		1398	our example, within 60 seconds, there are usually many I/O events with
		1399	associated activity resets.
		1400
		1401	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1402	but remember the time of last activity, and check for a real timeout only
		1403	within the callback:
		1404
		1405	ev_tstamp last_activity; // time of last activity
		1406
		1407	static void
		1408	callback (EV_P_ ev_timer *w, int revents)
		1409	{
		1410	ev_tstamp now = ev_now (EV_A);
		1411	ev_tstamp timeout = last_activity + 60.;
		1412
		1413	// if last_activity + 60. is older than now, we did time out
		1414	if (timeout < now)
		1415	{
		1416	// timeout occured, take action
		1417	}
		1418	else
		1419	{
		1420	// callback was invoked, but there was some activity, re-arm
		1421	// the watcher to fire in last_activity + 60, which is
		1422	// guaranteed to be in the future, so "again" is positive:
		1423	w->again = timeout - now;
		1424	ev_timer_again (EV_A_ w);
		1425	}
		1426	}
		1427
		1428	To summarise the callback: first calculate the real timeout (defined
		1429	as "60 seconds after the last activity"), then check if that time has
		1430	been reached, which means something I<did>, in fact, time out. Otherwise
		1431	the callback was invoked too early (C<timeout> is in the future), so
		1432	re-schedule the timer to fire at that future time, to see if maybe we have
		1433	a timeout then.
		1434
		1435	Note how C<ev_timer_again> is used, taking advantage of the
		1436	C<ev_timer_again> optimisation when the timer is already running.
		1437
		1438	This scheme causes more callback invocations (about one every 60 seconds
		1439	minus half the average time between activity), but virtually no calls to
		1440	libev to change the timeout.
		1441
		1442	To start the timer, simply initialise the watcher and set C<last_activity>
		1443	to the current time (meaning we just have some activity :), then call the
		1444	callback, which will "do the right thing" and start the timer:
		1445
		1446	ev_timer_init (timer, callback);
		1447	last_activity = ev_now (loop);
		1448	callback (loop, timer, EV_TIMEOUT);
		1449
		1450	And when there is some activity, simply store the current time in
		1451	C<last_activity>, no libev calls at all:
		1452
		1453	last_actiivty = ev_now (loop);
		1454
		1455	This technique is slightly more complex, but in most cases where the
		1456	time-out is unlikely to be triggered, much more efficient.
		1457
		1458	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1459	callback :) - just change the timeout and invoke the callback, which will
		1460	fix things for you.
		1461
		1462	=item 4. Wee, just use a double-linked list for your timeouts.
		1463
		1464	If there is not one request, but many thousands (millions...), all
		1465	employing some kind of timeout with the same timeout value, then one can
		1466	do even better:
		1467
		1468	When starting the timeout, calculate the timeout value and put the timeout
		1469	at the I<end> of the list.
		1470
		1471	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1472	the list is expected to fire (for example, using the technique #3).
		1473
		1474	When there is some activity, remove the timer from the list, recalculate
		1475	the timeout, append it to the end of the list again, and make sure to
		1476	update the C<ev_timer> if it was taken from the beginning of the list.
		1477
		1478	This way, one can manage an unlimited number of timeouts in O(1) time for
		1479	starting, stopping and updating the timers, at the expense of a major
		1480	complication, and having to use a constant timeout. The constant timeout
		1481	ensures that the list stays sorted.
		1482
		1483	=back
		1484
		1485	So which method the best?
		1486
		1487	Method #2 is a simple no-brain-required solution that is adequate in most
		1488	situations. Method #3 requires a bit more thinking, but handles many cases
		1489	better, and isn't very complicated either. In most case, choosing either
		1490	one is fine, with #3 being better in typical situations.
		1491
		1492	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1493	rather complicated, but extremely efficient, something that really pays
		1494	off after the first million or so of active timers, i.e. it's usually
		1495	overkill :)
		1496
1283	=head3 The special problem of time updates	1497	=head3 The special problem of time updates
1284		1498
1285	Establishing the current time is a costly operation (it usually takes at	1499	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	1500	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	1501	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).	1544	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1545
1332	If the timer is repeating, either start it if necessary (with the	1546	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.	1547	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1548
1335	This sounds a bit complicated, but here is a useful and typical	1549	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	1550	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		1551
1366	=item ev_tstamp repeat [read-write]	1552	=item ev_tstamp repeat [read-write]
1367		1553
1368	The current C<repeat> value. Will be used each time the watcher times out	1554	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),	1555	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1560	=head3 Examples
1375		1561
1376	Example: Create a timer that fires after 60 seconds.	1562	Example: Create a timer that fires after 60 seconds.
1377		1563
1378	static void	1564	static void
1379	one_minute_cb (struct ev_loop loop, struct ev_timer w, int revents)	1565	one_minute_cb (struct ev_loop loop, ev_timer w, int revents)
1380	{	1566	{
1381	.. one minute over, w is actually stopped right here	1567	.. one minute over, w is actually stopped right here
1382	}	1568	}
1383		1569
1384	struct ev_timer mytimer;	1570	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1571	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1572	ev_timer_start (loop, &mytimer);
1387		1573
1388	Example: Create a timeout timer that times out after 10 seconds of	1574	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1575	inactivity.
1390		1576
1391	static void	1577	static void
1392	timeout_cb (struct ev_loop loop, struct ev_timer w, int revents)	1578	timeout_cb (struct ev_loop loop, ev_timer w, int revents)
1393	{	1579	{
1394	.. ten seconds without any activity	1580	.. ten seconds without any activity
1395	}	1581	}
1396		1582
1397	struct ev_timer mytimer;	1583	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1584	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1585	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1586	ev_loop (loop, 0);
1401		1587
1402	// and in some piece of code that gets executed on any "activity":	1588	// and in some piece of code that gets executed on any "activity":
…		…
1488		1674
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1675	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	1676	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1677	only event loop modification you are allowed to do).
1492		1678
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1679	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1680	*w, ev_tstamp now)>, e.g.:
1495		1681
		1682	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1683	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1684	{
1498	return now + 60.;	1685	return now + 60.;
1499	}	1686	}
1500		1687
1501	It must return the next time to trigger, based on the passed time value	1688	It must return the next time to trigger, based on the passed time value
…		…
1538		1725
1539	The current interval value. Can be modified any time, but changes only	1726	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	1727	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1728	called.
1542		1729
1543	=item ev_tstamp (reschedule_cb)(struct ev_periodic w, ev_tstamp now) [read-write]	1730	=item ev_tstamp (reschedule_cb)(ev_periodic w, ev_tstamp now) [read-write]
1544		1731
1545	The current reschedule callback, or C<0>, if this functionality is	1732	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	1733	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.	1734	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1735
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1740	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1741	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1742	potentially a lot of jitter, but good long-term stability.
1556		1743
1557	static void	1744	static void
1558	clock_cb (struct ev_loop loop, struct ev_io w, int revents)	1745	clock_cb (struct ev_loop loop, ev_io w, int revents)
1559	{	1746	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1747	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1748	}
1562		1749
1563	struct ev_periodic hourly_tick;	1750	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1751	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1752	ev_periodic_start (loop, &hourly_tick);
1566		1753
1567	Example: The same as above, but use a reschedule callback to do it:	1754	Example: The same as above, but use a reschedule callback to do it:
1568		1755
1569	#include <math.h>	1756	#include <math.h>
1570		1757
1571	static ev_tstamp	1758	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1759	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1760	{
1574	return now + (3600. - fmod (now, 3600.));	1761	return now + (3600. - fmod (now, 3600.));
1575	}	1762	}
1576		1763
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1764	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1765
1579	Example: Call a callback every hour, starting now:	1766	Example: Call a callback every hour, starting now:
1580		1767
1581	struct ev_periodic hourly_tick;	1768	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1769	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1770	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1771	ev_periodic_start (loop, &hourly_tick);
1585		1772
1586		1773
…		…
1625		1812
1626	=back	1813	=back
1627		1814
1628	=head3 Examples	1815	=head3 Examples
1629		1816
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1817	Example: Try to exit cleanly on SIGINT.
1631		1818
1632	static void	1819	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1820	sigint_cb (struct ev_loop loop, ev_signal w, int revents)
1634	{	1821	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1822	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1823	}
1637		1824
1638	struct ev_signal signal_watcher;	1825	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1826	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1827	ev_signal_start (loop, &signal_watcher);
1641		1828
1642		1829
1643	=head2 C<ev_child> - watch out for process status changes	1830	=head2 C<ev_child> - watch out for process status changes
1644		1831
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1832	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1905	its completion.
1719		1906
1720	ev_child cw;	1907	ev_child cw;
1721		1908
1722	static void	1909	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1910	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1911	{
1725	ev_child_stop (EV_A_ w);	1912	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1913	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1914	}
1728		1915
…		…
1743		1930
1744		1931
1745	=head2 C<ev_stat> - did the file attributes just change?	1932	=head2 C<ev_stat> - did the file attributes just change?
1746		1933
1747	This watches a file system path for attribute changes. That is, it calls	1934	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	1935	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.	1936	and sees if it changed compared to the last time, invoking the callback if
		1937	it did.
1750		1938
1751	The path does not need to exist: changing from "path exists" to "path does	1939	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	1940	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	1941	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	1942	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1943	least one) and all the other fields of the stat buffer having unspecified
		1944	contents.
1756		1945
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1946	The path I<must not> end in a slash or contain special components such as
		1947	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.	1948	your working directory changes, then the behaviour is undefined.
1759		1949
1760	Since there is no standard kernel interface to do this, the portable	1950	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	1951	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	1952	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!)	1953	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	1954	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	1955	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	1956	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	1957	currently around C<0.1>, but that's usually overkill.
1768		1958
1769	This watcher type is not meant for massive numbers of stat watchers,	1959	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	1960	as even with OS-supported change notifications, this can be
1771	resource-intensive.	1961	resource-intensive.
1772		1962
1773	At the time of this writing, the only OS-specific interface implemented	1963	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	1964	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	1965	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	1966	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		1967
1778	=head3 ABI Issues (Largefile Support)	1968	=head3 ABI Issues (Largefile Support)
1779		1969
1780	Libev by default (unless the user overrides this) uses the default	1970	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	1971	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	1972	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	1973	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	1974	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	1975	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	1976	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.	1977	most noticeably displayed with ev_stat and large file support.
1788		1978
1789	The solution for this is to lobby your distribution maker to make large	1979	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	1980	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	1981	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	1982	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1983	default compilation environment.
1794		1984
1795	=head3 Inotify and Kqueue	1985	=head3 Inotify and Kqueue
1796		1986
1797	When C<inotify (7)> support has been compiled into libev (generally only	1987	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	1988	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	1989	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	1990	watcher is being started.
1801		1991
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1992	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	1993	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	1994	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,	1995	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.	1996	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1997	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1998	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1999	xfs are fully working) libev usually gets away without polling.
1807		2000
1808	There is no support for kqueue, as apparently it cannot be used to	2001	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	2002	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2003	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2004	etc. is difficult.
1812		2005
		2006	=head3 C<stat ()> is a synchronous operation
		2007
		2008	Libev doesn't normally do any kind of I/O itself, and so is not blocking
		2009	the process. The exception are C<ev_stat> watchers - those call C<stat
		2010	()>, which is a synchronous operation.
		2011
		2012	For local paths, this usually doesn't matter: unless the system is very
		2013	busy or the intervals between stat's are large, a stat call will be fast,
		2014	as the path data is suually in memory already (except when starting the
		2015	watcher).
		2016
		2017	For networked file systems, calling C<stat ()> can block an indefinite
		2018	time due to network issues, and even under good conditions, a stat call
		2019	often takes multiple milliseconds.
		2020
		2021	Therefore, it is best to avoid using C<ev_stat> watchers on networked
		2022	paths, although this is fully supported by libev.
		2023
1813	=head3 The special problem of stat time resolution	2024	=head3 The special problem of stat time resolution
1814		2025
1815	The C<stat ()> system call only supports full-second resolution portably, and	2026	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2027	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2028	still only support whole seconds.
1818		2029
1819	That means that, if the time is the only thing that changes, you can	2030	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	2031	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	2032	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	2033	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1979		2190
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2191	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2192	callback, free it. Also, use no error checking, as usual.
1982		2193
1983	static void	2194	static void
1984	idle_cb (struct ev_loop loop, struct ev_idle w, int revents)	2195	idle_cb (struct ev_loop loop, ev_idle w, int revents)
1985	{	2196	{
1986	free (w);	2197	free (w);
1987	// now do something you wanted to do when the program has	2198	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2199	// no longer anything immediate to do.
1989	}	2200	}
1990		2201
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2202	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2203	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2204	ev_idle_start (loop, idle_cb);
1994		2205
1995		2206
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2207	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2288
2078	static ev_io iow [nfd];	2289	static ev_io iow [nfd];
2079	static ev_timer tw;	2290	static ev_timer tw;
2080		2291
2081	static void	2292	static void
2082	io_cb (ev_loop loop, ev_io w, int revents)	2293	io_cb (struct ev_loop loop, ev_io w, int revents)
2083	{	2294	{
2084	}	2295	}
2085		2296
2086	// create io watchers for each fd and a timer before blocking	2297	// create io watchers for each fd and a timer before blocking
2087	static void	2298	static void
2088	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	2299	adns_prepare_cb (struct ev_loop loop, ev_prepare w, int revents)
2089	{	2300	{
2090	int timeout = 3600000;	2301	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2302	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2303	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2304	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2319	}
2109	}	2320	}
2110		2321
2111	// stop all watchers after blocking	2322	// stop all watchers after blocking
2112	static void	2323	static void
2113	adns_check_cb (ev_loop loop, ev_check w, int revents)	2324	adns_check_cb (struct ev_loop loop, ev_check w, int revents)
2114	{	2325	{
2115	ev_timer_stop (loop, &tw);	2326	ev_timer_stop (loop, &tw);
2116		2327
2117	for (int i = 0; i < nfd; ++i)	2328	for (int i = 0; i < nfd; ++i)
2118	{	2329	{
…		…
2242	So when you want to use this feature you will always have to be prepared	2453	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	2454	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	2455	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.	2456	create it, and if that fails, use the normal loop for everything.
2246		2457
		2458	=head3 C<ev_embed> and fork
		2459
		2460	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2461	automatically be applied to the embedded loop as well, so no special
		2462	fork handling is required in that case. When the watcher is not running,
		2463	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2464	as applicable.
		2465
2247	=head3 Watcher-Specific Functions and Data Members	2466	=head3 Watcher-Specific Functions and Data Members
2248		2467
2249	=over 4	2468	=over 4
2250		2469
2251	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)	2470	=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	2497	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2498	used).
2280		2499
2281	struct ev_loop *loop_hi = ev_default_init (0);	2500	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2501	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2502	ev_embed embed;
2284		2503
2285	// see if there is a chance of getting one that works	2504	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2505	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2506	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2507	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2521	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2522	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2523
2305	struct ev_loop *loop = ev_default_init (0);	2524	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2525	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2526	ev_embed embed;
2308		2527
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2528	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2529	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2530	{
2312	ev_embed_init (&embed, 0, loop_socket);	2531	ev_embed_init (&embed, 0, loop_socket);
…		…
2376	=over 4	2595	=over 4
2377		2596
2378	=item queueing from a signal handler context	2597	=item queueing from a signal handler context
2379		2598
2380	To implement race-free queueing, you simply add to the queue in the signal	2599	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	2600	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2601	an example that does that for some fictitious SIGUSR1 handler:
2383		2602
2384	static ev_async mysig;	2603	static ev_async mysig;
2385		2604
2386	static void	2605	static void
2387	sigusr1_handler (void)	2606	sigusr1_handler (void)
…		…
2453	=over 4	2672	=over 4
2454		2673
2455	=item ev_async_init (ev_async *, callback)	2674	=item ev_async_init (ev_async *, callback)
2456		2675
2457	Initialises and configures the async watcher - it has no parameters of any	2676	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,	2677	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	trust me.	2678	trust me.
2460		2679
2461	=item ev_async_send (loop, ev_async *)	2680	=item ev_async_send (loop, ev_async *)
2462		2681
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2682	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
…		…
2494	=over 4	2713	=over 4
2495		2714
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2715	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2716
2498	This function combines a simple timer and an I/O watcher, calls your	2717	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2718	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	2719	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	2720	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2721	more watchers yourself.
2503		2722
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2723	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	2724	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2725	the given C<fd> and C<events> set will be created and started.
2507		2726
2508	If C<timeout> is less than 0, then no timeout watcher will be	2727	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	2728	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	2729	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2730
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2731	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	2732	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>	2733	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2734	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2735	a timeout and an io event at the same time - you probably should give io
		2736	events precedence.
		2737
		2738	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2739
2518	static void stdin_ready (int revents, void *arg)	2740	static void stdin_ready (int revents, void *arg)
2519	{	2741	{
		2742	if (revents & EV_READ)
		2743	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2744	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2745	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2746	}
2525		2747
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2748	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2749
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2750	=item ev_feed_event (struct ev_loop , watcher , int revents)
2529		2751
2530	Feeds the given event set into the event loop, as if the specified event	2752	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	2753	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2754	initialised but not necessarily started event watcher).
2533		2755
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2756	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2757
2536	Feed an event on the given fd, as if a file descriptor backend detected	2758	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2759	the given events it.
2538		2760
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2761	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2762
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2763	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2764	loop!).
2543		2765
2544	=back	2766	=back
…		…
2779	=item D	3001	=item D
2780		3002
2781	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	3003	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>.	3004	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2783		3005
		3006	=item Ocaml
		3007
		3008	Erkki Seppala has written Ocaml bindings for libev, to be found at
		3009	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		3010
2784	=back	3011	=back
2785		3012
2786		3013
2787	=head1 MACRO MAGIC	3014	=head1 MACRO MAGIC
2788		3015
…		…
2888		3115
2889	#define EV_STANDALONE 1	3116	#define EV_STANDALONE 1
2890	#include "ev.h"	3117	#include "ev.h"
2891		3118
2892	Both header files and implementation files can be compiled with a C++	3119	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	3120	compiler (at least, that's a stated goal, and breakage will be treated
2894	as a bug).	3121	as a bug).
2895		3122
2896	You need the following files in your source tree, or in a directory	3123	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):	3124	in your include path (e.g. in libev/ when using -Ilibev):
2898		3125
…		…
3298	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3525	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3299		3526
3300	#include "ev_cpp.h"	3527	#include "ev_cpp.h"
3301	#include "ev.c"	3528	#include "ev.c"
3302		3529
		3530	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3303		3531
3304	=head1 THREADS AND COROUTINES	3532	=head2 THREADS AND COROUTINES
3305		3533
3306	=head2 THREADS	3534	=head3 THREADS
3307		3535
3308	Libev itself is thread-safe (unless the opposite is specifically	3536	All libev functions are reentrant and thread-safe unless explicitly
3309	documented for a function), but it uses no locking itself. This means that	3537	documented otherwise, but libev implements no locking itself. This means
3310	you can use as many loops as you want in parallel, as long as only one	3538	that you can use as many loops as you want in parallel, as long as there
3311	thread ever calls into one libev function with the same loop parameter:	3539	are no concurrent calls into any libev function with the same loop
		3540	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3312	libev guarantees that different event loops share no data structures that	3541	of course): libev guarantees that different event loops share no data
3313	need locking.	3542	structures that need any locking.
3314		3543
3315	Or to put it differently: calls with different loop parameters can be done	3544	Or to put it differently: calls with different loop parameters can be done
3316	concurrently from multiple threads, calls with the same loop parameter	3545	concurrently from multiple threads, calls with the same loop parameter
3317	must be done serially (but can be done from different threads, as long as	3546	must be done serially (but can be done from different threads, as long as
3318	only one thread ever is inside a call at any point in time, e.g. by using	3547	only one thread ever is inside a call at any point in time, e.g. by using
3319	a mutex per loop).	3548	a mutex per loop).
3320		3549
3321	Specifically to support threads (and signal handlers), libev implements	3550	Specifically to support threads (and signal handlers), libev implements
3322	so-called C<ev_async> watchers, which allow some limited form of	3551	so-called C<ev_async> watchers, which allow some limited form of
3323	concurrency on the same event loop.	3552	concurrency on the same event loop, namely waking it up "from the
		3553	outside".
3324		3554
3325	If you want to know which design (one loop, locking, or multiple loops	3555	If you want to know which design (one loop, locking, or multiple loops
3326	without or something else still) is best for your problem, then I cannot	3556	without or something else still) is best for your problem, then I cannot
3327	help you. I can give some generic advice however:	3557	help you, but here is some generic advice:
3328		3558
3329	=over 4	3559	=over 4
3330		3560
3331	=item * most applications have a main thread: use the default libev loop	3561	=item * most applications have a main thread: use the default libev loop
3332	in that thread, or create a separate thread running only the default loop.	3562	in that thread, or create a separate thread running only the default loop.
…		…
3356	default loop and triggering an C<ev_async> watcher from the default loop	3586	default loop and triggering an C<ev_async> watcher from the default loop
3357	watcher callback into the event loop interested in the signal.	3587	watcher callback into the event loop interested in the signal.
3358		3588
3359	=back	3589	=back
3360		3590
3361	=head2 COROUTINES	3591	=head3 COROUTINES
3362		3592
3363	Libev is much more accommodating to coroutines ("cooperative threads"):	3593	Libev is very accommodating to coroutines ("cooperative threads"):
3364	libev fully supports nesting calls to it's functions from different	3594	libev fully supports nesting calls to its functions from different
3365	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3595	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3366	different coroutines and switch freely between both coroutines running the	3596	different coroutines, and switch freely between both coroutines running the
3367	loop, as long as you don't confuse yourself). The only exception is that	3597	loop, as long as you don't confuse yourself). The only exception is that
3368	you must not do this from C<ev_periodic> reschedule callbacks.	3598	you must not do this from C<ev_periodic> reschedule callbacks.
3369		3599
3370	Care has been taken to ensure that libev does not keep local state inside	3600	Care has been taken to ensure that libev does not keep local state inside
3371	C<ev_loop>, and other calls do not usually allow coroutine switches.	3601	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3602	they do not call any callbacks.
3372		3603
		3604	=head2 COMPILER WARNINGS
3373		3605
3374	=head1 COMPLEXITIES	3606	Depending on your compiler and compiler settings, you might get no or a
		3607	lot of warnings when compiling libev code. Some people are apparently
		3608	scared by this.
3375		3609
3376	In this section the complexities of (many of) the algorithms used inside	3610	However, these are unavoidable for many reasons. For one, each compiler
3377	libev will be explained. For complexity discussions about backends see the	3611	has different warnings, and each user has different tastes regarding
3378	documentation for C<ev_default_init>.	3612	warning options. "Warn-free" code therefore cannot be a goal except when
		3613	targeting a specific compiler and compiler-version.
3379		3614
3380	All of the following are about amortised time: If an array needs to be	3615	Another reason is that some compiler warnings require elaborate
3381	extended, libev needs to realloc and move the whole array, but this	3616	workarounds, or other changes to the code that make it less clear and less
3382	happens asymptotically never with higher number of elements, so O(1) might	3617	maintainable.
3383	mean it might do a lengthy realloc operation in rare cases, but on average
3384	it is much faster and asymptotically approaches constant time.
3385		3618
3386	=over 4	3619	And of course, some compiler warnings are just plain stupid, or simply
		3620	wrong (because they don't actually warn about the condition their message
		3621	seems to warn about). For example, certain older gcc versions had some
		3622	warnings that resulted an extreme number of false positives. These have
		3623	been fixed, but some people still insist on making code warn-free with
		3624	such buggy versions.
3387		3625
3388	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3626	While libev is written to generate as few warnings as possible,
		3627	"warn-free" code is not a goal, and it is recommended not to build libev
		3628	with any compiler warnings enabled unless you are prepared to cope with
		3629	them (e.g. by ignoring them). Remember that warnings are just that:
		3630	warnings, not errors, or proof of bugs.
3389		3631
3390	This means that, when you have a watcher that triggers in one hour and
3391	there are 100 watchers that would trigger before that then inserting will
3392	have to skip roughly seven (C<ld 100>) of these watchers.
3393		3632
3394	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3633	=head2 VALGRIND
3395		3634
3396	That means that changing a timer costs less than removing/adding them	3635	Valgrind has a special section here because it is a popular tool that is
3397	as only the relative motion in the event queue has to be paid for.	3636	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3398		3637
3399	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3638	If you think you found a bug (memory leak, uninitialised data access etc.)
		3639	in libev, then check twice: If valgrind reports something like:
3400		3640
3401	These just add the watcher into an array or at the head of a list.	3641	==2274== definitely lost: 0 bytes in 0 blocks.
		3642	==2274== possibly lost: 0 bytes in 0 blocks.
		3643	==2274== still reachable: 256 bytes in 1 blocks.
3402		3644
3403	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3645	Then there is no memory leak, just as memory accounted to global variables
		3646	is not a memleak - the memory is still being referenced, and didn't leak.
3404		3647
3405	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3648	Similarly, under some circumstances, valgrind might report kernel bugs
		3649	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3650	although an acceptable workaround has been found here), or it might be
		3651	confused.
3406		3652
3407	These watchers are stored in lists then need to be walked to find the	3653	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3408	correct watcher to remove. The lists are usually short (you don't usually	3654	make it into some kind of religion.
3409	have many watchers waiting for the same fd or signal).
3410		3655
3411	=item Finding the next timer in each loop iteration: O(1)	3656	If you are unsure about something, feel free to contact the mailing list
		3657	with the full valgrind report and an explanation on why you think this
		3658	is a bug in libev (best check the archives, too :). However, don't be
		3659	annoyed when you get a brisk "this is no bug" answer and take the chance
		3660	of learning how to interpret valgrind properly.
3412		3661
3413	By virtue of using a binary or 4-heap, the next timer is always found at a	3662	If you need, for some reason, empty reports from valgrind for your project
3414	fixed position in the storage array.	3663	I suggest using suppression lists.
3415		3664
3416	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3417		3665
3418	A change means an I/O watcher gets started or stopped, which requires	3666	=head1 PORTABILITY NOTES
3419	libev to recalculate its status (and possibly tell the kernel, depending
3420	on backend and whether C<ev_io_set> was used).
3421		3667
3422	=item Activating one watcher (putting it into the pending state): O(1)
3423
3424	=item Priority handling: O(number_of_priorities)
3425
3426	Priorities are implemented by allocating some space for each
3427	priority. When doing priority-based operations, libev usually has to
3428	linearly search all the priorities, but starting/stopping and activating
3429	watchers becomes O(1) with respect to priority handling.
3430
3431	=item Sending an ev_async: O(1)
3432
3433	=item Processing ev_async_send: O(number_of_async_watchers)
3434
3435	=item Processing signals: O(max_signal_number)
3436
3437	Sending involves a system call I<iff> there were no other C<ev_async_send>
3438	calls in the current loop iteration. Checking for async and signal events
3439	involves iterating over all running async watchers or all signal numbers.
3440
3441	=back
3442
3443
3444	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3668	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3445		3669
3446	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3670	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3447	requires, and its I/O model is fundamentally incompatible with the POSIX	3671	requires, and its I/O model is fundamentally incompatible with the POSIX
3448	model. Libev still offers limited functionality on this platform in	3672	model. Libev still offers limited functionality on this platform in
3449	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3673	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3536	wrap all I/O functions and provide your own fd management, but the cost of	3760	wrap all I/O functions and provide your own fd management, but the cost of
3537	calling select (O(n²)) will likely make this unworkable.	3761	calling select (O(n²)) will likely make this unworkable.
3538		3762
3539	=back	3763	=back
3540		3764
3541
3542	=head1 PORTABILITY REQUIREMENTS	3765	=head2 PORTABILITY REQUIREMENTS
3543		3766
3544	In addition to a working ISO-C implementation, libev relies on a few	3767	In addition to a working ISO-C implementation and of course the
3545	additional extensions:	3768	backend-specific APIs, libev relies on a few additional extensions:
3546		3769
3547	=over 4	3770	=over 4
3548		3771
3549	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3772	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3550	calling conventions regardless of C<ev_watcher_type *>.	3773	calling conventions regardless of C<ev_watcher_type *>.
…		…
3575	except the initial one, and run the default loop in the initial thread as	3798	except the initial one, and run the default loop in the initial thread as
3576	well.	3799	well.
3577		3800
3578	=item C<long> must be large enough for common memory allocation sizes	3801	=item C<long> must be large enough for common memory allocation sizes
3579		3802
3580	To improve portability and simplify using libev, libev uses C<long>	3803	To improve portability and simplify its API, libev uses C<long> internally
3581	internally instead of C<size_t> when allocating its data structures. On	3804	instead of C<size_t> when allocating its data structures. On non-POSIX
3582	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3805	systems (Microsoft...) this might be unexpectedly low, but is still at
3583	is still at least 31 bits everywhere, which is enough for hundreds of	3806	least 31 bits everywhere, which is enough for hundreds of millions of
3584	millions of watchers.	3807	watchers.
3585		3808
3586	=item C<double> must hold a time value in seconds with enough accuracy	3809	=item C<double> must hold a time value in seconds with enough accuracy
3587		3810
3588	The type C<double> is used to represent timestamps. It is required to	3811	The type C<double> is used to represent timestamps. It is required to
3589	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3812	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3593	=back	3816	=back
3594		3817
3595	If you know of other additional requirements drop me a note.	3818	If you know of other additional requirements drop me a note.
3596		3819
3597		3820
3598	=head1 COMPILER WARNINGS	3821	=head1 ALGORITHMIC COMPLEXITIES
3599		3822
3600	Depending on your compiler and compiler settings, you might get no or a	3823	In this section the complexities of (many of) the algorithms used inside
3601	lot of warnings when compiling libev code. Some people are apparently	3824	libev will be documented. For complexity discussions about backends see
3602	scared by this.	3825	the documentation for C<ev_default_init>.
3603		3826
3604	However, these are unavoidable for many reasons. For one, each compiler	3827	All of the following are about amortised time: If an array needs to be
3605	has different warnings, and each user has different tastes regarding	3828	extended, libev needs to realloc and move the whole array, but this
3606	warning options. "Warn-free" code therefore cannot be a goal except when	3829	happens asymptotically rarer with higher number of elements, so O(1) might
3607	targeting a specific compiler and compiler-version.	3830	mean that libev does a lengthy realloc operation in rare cases, but on
		3831	average it is much faster and asymptotically approaches constant time.
3608		3832
3609	Another reason is that some compiler warnings require elaborate	3833	=over 4
3610	workarounds, or other changes to the code that make it less clear and less
3611	maintainable.
3612		3834
3613	And of course, some compiler warnings are just plain stupid, or simply	3835	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3614	wrong (because they don't actually warn about the condition their message
3615	seems to warn about).
3616		3836
3617	While libev is written to generate as few warnings as possible,	3837	This means that, when you have a watcher that triggers in one hour and
3618	"warn-free" code is not a goal, and it is recommended not to build libev	3838	there are 100 watchers that would trigger before that, then inserting will
3619	with any compiler warnings enabled unless you are prepared to cope with	3839	have to skip roughly seven (C<ld 100>) of these watchers.
3620	them (e.g. by ignoring them). Remember that warnings are just that:
3621	warnings, not errors, or proof of bugs.
3622		3840
		3841	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3623		3842
3624	=head1 VALGRIND	3843	That means that changing a timer costs less than removing/adding them,
		3844	as only the relative motion in the event queue has to be paid for.
3625		3845
3626	Valgrind has a special section here because it is a popular tool that is	3846	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3627	highly useful, but valgrind reports are very hard to interpret.
3628		3847
3629	If you think you found a bug (memory leak, uninitialised data access etc.)	3848	These just add the watcher into an array or at the head of a list.
3630	in libev, then check twice: If valgrind reports something like:
3631		3849
3632	==2274== definitely lost: 0 bytes in 0 blocks.	3850	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3633	==2274== possibly lost: 0 bytes in 0 blocks.
3634	==2274== still reachable: 256 bytes in 1 blocks.
3635		3851
3636	Then there is no memory leak. Similarly, under some circumstances,	3852	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3637	valgrind might report kernel bugs as if it were a bug in libev, or it
3638	might be confused (it is a very good tool, but only a tool).
3639		3853
3640	If you are unsure about something, feel free to contact the mailing list	3854	These watchers are stored in lists, so they need to be walked to find the
3641	with the full valgrind report and an explanation on why you think this is	3855	correct watcher to remove. The lists are usually short (you don't usually
3642	a bug in libev. However, don't be annoyed when you get a brisk "this is	3856	have many watchers waiting for the same fd or signal: one is typical, two
3643	no bug" answer and take the chance of learning how to interpret valgrind	3857	is rare).
3644	properly.
3645		3858
3646	If you need, for some reason, empty reports from valgrind for your project	3859	=item Finding the next timer in each loop iteration: O(1)
3647	I suggest using suppression lists.	3860
		3861	By virtue of using a binary or 4-heap, the next timer is always found at a
		3862	fixed position in the storage array.
		3863
		3864	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3865
		3866	A change means an I/O watcher gets started or stopped, which requires
		3867	libev to recalculate its status (and possibly tell the kernel, depending
		3868	on backend and whether C<ev_io_set> was used).
		3869
		3870	=item Activating one watcher (putting it into the pending state): O(1)
		3871
		3872	=item Priority handling: O(number_of_priorities)
		3873
		3874	Priorities are implemented by allocating some space for each
		3875	priority. When doing priority-based operations, libev usually has to
		3876	linearly search all the priorities, but starting/stopping and activating
		3877	watchers becomes O(1) with respect to priority handling.
		3878
		3879	=item Sending an ev_async: O(1)
		3880
		3881	=item Processing ev_async_send: O(number_of_async_watchers)
		3882
		3883	=item Processing signals: O(max_signal_number)
		3884
		3885	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3886	calls in the current loop iteration. Checking for async and signal events
		3887	involves iterating over all running async watchers or all signal numbers.
		3888
		3889	=back
3648		3890
3649		3891
3650	=head1 AUTHOR	3892	=head1 AUTHOR
3651		3893
3652	Marc Lehmann <libev@schmorp.de>.	3894	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3653		3895

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.pod (file contents): Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs. Revision 1.213 by root, Wed Nov 5 02:48:45 2008 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.185 by root, Tue Sep 23 09:13:59 2008 UTC vs.
Revision 1.213 by root, Wed Nov 5 02:48:45 2008 UTC