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Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.211 by root, Mon Nov 3 14:34:16 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.
405		422
406	While nominally embeddable in other event loops, this feature is broken in	423	While nominally embeddable in other event loops, this feature is broken in
407	all kernel versions tested so far.	424	all kernel versions tested so far.
408		425
409	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	426	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
410	C<EVBACKEND_POLL>.	427	C<EVBACKEND_POLL>.
411		428
412	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)	429	=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
413		430
414	Kqueue deserves special mention, as at the time of this writing, it was	431	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	432	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	433	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	434	it's completely useless). Unlike epoll, however, whose brokenness
418	you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or	435	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.	436	without API changes to existing programs. For this reason it's not being
		437	"auto-detected" unless you explicitly specify it in the flags (i.e. using
		438	C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
		439	system like NetBSD.
420		440
421	You still can embed kqueue into a normal poll or select backend and use it	441	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	442	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.	443	the target platform). See C<ev_embed> watchers for more info.
424		444
425	It scales in the same way as the epoll backend, but the interface to the	445	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	446	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	447	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	448	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	449	two event changes per incident. Support for C<fork ()> is very bad (but
430	drops fds silently in similarly hard-to-detect cases.	450	sane, unlike epoll) and it drops fds silently in similarly hard-to-detect
		451	cases
431		452
432	This backend usually performs well under most conditions.	453	This backend usually performs well under most conditions.
433		454
434	While nominally embeddable in other event loops, this doesn't work	455	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	456	everywhere, so you might need to test for this. And since it is broken
…		…
464	might perform better.	485	might perform better.
465		486
466	On the positive side, with the exception of the spurious readiness	487	On the positive side, with the exception of the spurious readiness
467	notifications, this backend actually performed fully to specification	488	notifications, this backend actually performed fully to specification
468	in all tests and is fully embeddable, which is a rare feat among the	489	in all tests and is fully embeddable, which is a rare feat among the
469	OS-specific backends.	490	OS-specific backends (I vastly prefer correctness over speed hacks).
470		491
471	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as	492	This backend maps C<EV_READ> and C<EV_WRITE> in the same way as
472	C<EVBACKEND_POLL>.	493	C<EVBACKEND_POLL>.
473		494
474	=item C<EVBACKEND_ALL>	495	=item C<EVBACKEND_ALL>
…		…
527	responsibility to either stop all watchers cleanly yourself I<before>	548	responsibility to either stop all watchers cleanly yourself I<before>
528	calling this function, or cope with the fact afterwards (which is usually	549	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	550	the easiest thing, you can just ignore the watchers and/or C<free ()> them
530	for example).	551	for example).
531		552
532	Note that certain global state, such as signal state, will not be freed by	553	Note that certain global state, such as signal state (and installed signal
533	this function, and related watchers (such as signal and child watchers)	554	handlers), will not be freed by this function, and related watchers (such
534	would need to be stopped manually.	555	as signal and child watchers) would need to be stopped manually.
535		556
536	In general it is not advisable to call this function except in the	557	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	558	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	559	pipe fds. If you need dynamically allocated loops it is better to use
539	C<ev_loop_new> and C<ev_loop_destroy>).	560	C<ev_loop_new> and C<ev_loop_destroy>).
…		…
631	the loop.	652	the loop.
632		653
633	A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if	654	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	655	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	656	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	657	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	658	user-registered callback will be called), and will return after one
638	iteration of the loop.	659	iteration of the loop.
639		660
640	This is useful if you are waiting for some external event in conjunction	661	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	662	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	706	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.	707	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		708
688	This "unloop state" will be cleared when entering C<ev_loop> again.	709	This "unloop state" will be cleared when entering C<ev_loop> again.
689		710
		711	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		712
690	=item ev_ref (loop)	713	=item ev_ref (loop)
691		714
692	=item ev_unref (loop)	715	=item ev_unref (loop)
693		716
694	Ref/unref can be used to add or remove a reference count on the event	717	Ref/unref can be used to add or remove a reference count on the event
…		…
708	respectively).	731	respectively).
709		732
710	Example: Create a signal watcher, but keep it from keeping C<ev_loop>	733	Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711	running when nothing else is active.	734	running when nothing else is active.
712		735
713	struct ev_signal exitsig;	736	ev_signal exitsig;
714	ev_signal_init (&exitsig, sig_cb, SIGINT);	737	ev_signal_init (&exitsig, sig_cb, SIGINT);
715	ev_signal_start (loop, &exitsig);	738	ev_signal_start (loop, &exitsig);
716	evf_unref (loop);	739	evf_unref (loop);
717		740
718	Example: For some weird reason, unregister the above signal handler again.	741	Example: For some weird reason, unregister the above signal handler again.
…		…
766	they fire on, say, one-second boundaries only.	789	they fire on, say, one-second boundaries only.
767		790
768	=item ev_loop_verify (loop)	791	=item ev_loop_verify (loop)
769		792
770	This function only does something when C<EV_VERIFY> support has been	793	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	794	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	795	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	796	is found to be inconsistent, it will print an error message to standard
774	error and call C<abort ()>.	797	error and call C<abort ()>.
775		798
776	This can be used to catch bugs inside libev itself: under normal	799	This can be used to catch bugs inside libev itself: under normal
…		…
780	=back	803	=back
781		804
782		805
783	=head1 ANATOMY OF A WATCHER	806	=head1 ANATOMY OF A WATCHER
784		807
		808	In the following description, uppercase C<TYPE> in names stands for the
		809	watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer
		810	watchers and C<ev_io_start> for I/O watchers.
		811
785	A watcher is a structure that you create and register to record your	812	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	813	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:	814	become readable, you would create an C<ev_io> watcher for that:
788		815
789	static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)	816	static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790	{	817	{
791	ev_io_stop (w);	818	ev_io_stop (w);
792	ev_unloop (loop, EVUNLOOP_ALL);	819	ev_unloop (loop, EVUNLOOP_ALL);
793	}	820	}
794		821
795	struct ev_loop *loop = ev_default_loop (0);	822	struct ev_loop *loop = ev_default_loop (0);
		823
796	struct ev_io stdin_watcher;	824	ev_io stdin_watcher;
		825
797	ev_init (&stdin_watcher, my_cb);	826	ev_init (&stdin_watcher, my_cb);
798	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);	827	ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799	ev_io_start (loop, &stdin_watcher);	828	ev_io_start (loop, &stdin_watcher);
		829
800	ev_loop (loop, 0);	830	ev_loop (loop, 0);
801		831
802	As you can see, you are responsible for allocating the memory for your	832	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,	833	watcher structures (and it is I<usually> a bad idea to do this on the
804	although this can sometimes be quite valid).	834	stack).
		835
		836	Each watcher has an associated watcher structure (called C<struct ev_TYPE>
		837	or simply C<ev_TYPE>, as typedefs are provided for all watcher structs).
805		838
806	Each watcher structure must be initialised by a call to C<ev_init	839	Each watcher structure must be initialised by a call to C<ev_init
807	(watcher *, callback)>, which expects a callback to be provided. This	840	(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	841	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	842	watchers, each time the event loop detects that the file descriptor given
810	is readable and/or writable).	843	is readable and/or writable).
811		844
812	Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro	845	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	846	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	847	is also a macro to combine initialisation and setting in one call: C<<
815	(watcher *, callback, ...) >>.	848	ev_TYPE_init (watcher *, callback, ...) >>.
816		849
817	To make the watcher actually watch out for events, you have to start it	850	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	851	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	852	*) >>), and you can stop watching for events at any time by calling the
820	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	853	corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>.
821		854
822	As long as your watcher is active (has been started but not stopped) you	855	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	856	must not touch the values stored in it. Most specifically you must never
824	reinitialise it or call its C<set> macro.	857	reinitialise it or call its C<ev_TYPE_set> macro.
825		858
826	Each and every callback receives the event loop pointer as first, the	859	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	860	registered watcher structure as second, and a bitset of received events as
828	third argument.	861	third argument.
829		862
…		…
892	=item C<EV_ERROR>	925	=item C<EV_ERROR>
893		926
894	An unspecified error has occurred, the watcher has been stopped. This might	927	An unspecified error has occurred, the watcher has been stopped. This might
895	happen because the watcher could not be properly started because libev	928	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	929	ran out of memory, a file descriptor was found to be closed or any other
		930	problem. Libev considers these application bugs.
		931
897	problem. You best act on it by reporting the problem and somehow coping	932	You best act on it by reporting the problem and somehow coping with the
898	with the watcher being stopped.	933	watcher being stopped. Note that well-written programs should not receive
		934	an error ever, so when your watcher receives it, this usually indicates a
		935	bug in your program.
899		936
900	Libev will usually signal a few "dummy" events together with an error, for	937	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	938	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	939	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	940	the error from read() or write(). This will not work in multi-threaded
…		…
906		943
907	=back	944	=back
908		945
909	=head2 GENERIC WATCHER FUNCTIONS	946	=head2 GENERIC WATCHER FUNCTIONS
910		947
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	948	=over 4
915		949
916	=item C<ev_init> (ev_TYPE *watcher, callback)	950	=item C<ev_init> (ev_TYPE *watcher, callback)
917		951
918	This macro initialises the generic portion of a watcher. The contents	952	This macro initialises the generic portion of a watcher. The contents
…		…
923	which rolls both calls into one.	957	which rolls both calls into one.
924		958
925	You can reinitialise a watcher at any time as long as it has been stopped	959	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.	960	(or never started) and there are no pending events outstanding.
927		961
928	The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher,	962	The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929	int revents)>.	963	int revents)>.
930		964
931	Example: Initialise an C<ev_io> watcher in two steps.	965	Example: Initialise an C<ev_io> watcher in two steps.
932		966
933	ev_io w;	967	ev_io w;
…		…
967		1001
968	ev_io_start (EV_DEFAULT_UC, &w);	1002	ev_io_start (EV_DEFAULT_UC, &w);
969		1003
970	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)	1004	=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971		1005
972	Stops the given watcher again (if active) and clears the pending	1006	Stops the given watcher if active, and clears the pending status (whether
		1007	the watcher was active or not).
		1008
973	status. It is possible that stopped watchers are pending (for example,	1009	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	1010	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	1011	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	1012	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.	1013	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		1014
979	=item bool ev_is_active (ev_TYPE *watcher)	1015	=item bool ev_is_active (ev_TYPE *watcher)
980		1016
981	Returns a true value iff the watcher is active (i.e. it has been started	1017	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	1018	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	1060	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 :).	1061	always C<0>, which is supposed to not be too high and not be too low :).
1026		1062
1027	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	1063	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	1064	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.	1065	or might not have been clamped to the valid range.
1030		1066
1031	=item ev_invoke (loop, ev_TYPE *watcher, int revents)	1067	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
1032		1068
1033	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither	1069	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	1070	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	1092	member, you can also "subclass" the watcher type and provide your own
1057	data:	1093	data:
1058		1094
1059	struct my_io	1095	struct my_io
1060	{	1096	{
1061	struct ev_io io;	1097	ev_io io;
1062	int otherfd;	1098	int otherfd;
1063	void *somedata;	1099	void *somedata;
1064	struct whatever *mostinteresting;	1100	struct whatever *mostinteresting;
1065	};	1101	};
1066		1102
…		…
1069	ev_io_init (&w.io, my_cb, fd, EV_READ);	1105	ev_io_init (&w.io, my_cb, fd, EV_READ);
1070		1106
1071	And since your callback will be called with a pointer to the watcher, you	1107	And since your callback will be called with a pointer to the watcher, you
1072	can cast it back to your own type:	1108	can cast it back to your own type:
1073		1109
1074	static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)	1110	static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075	{	1111	{
1076	struct my_io *w = (struct my_io *)w_;	1112	struct my_io *w = (struct my_io *)w_;
1077	...	1113	...
1078	}	1114	}
1079		1115
…		…
1097	programmers):	1133	programmers):
1098		1134
1099	#include <stddef.h>	1135	#include <stddef.h>
1100		1136
1101	static void	1137	static void
1102	t1_cb (EV_P_ struct ev_timer *w, int revents)	1138	t1_cb (EV_P_ ev_timer *w, int revents)
1103	{	1139	{
1104	struct my_biggy big = (struct my_biggy *	1140	struct my_biggy big = (struct my_biggy *
1105	(((char *)w) - offsetof (struct my_biggy, t1));	1141	(((char *)w) - offsetof (struct my_biggy, t1));
1106	}	1142	}
1107		1143
1108	static void	1144	static void
1109	t2_cb (EV_P_ struct ev_timer *w, int revents)	1145	t2_cb (EV_P_ ev_timer *w, int revents)
1110	{	1146	{
1111	struct my_biggy big = (struct my_biggy *	1147	struct my_biggy big = (struct my_biggy *
1112	(((char *)w) - offsetof (struct my_biggy, t2));	1148	(((char *)w) - offsetof (struct my_biggy, t2));
1113	}	1149	}
1114		1150
…		…
1249	Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well	1285	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	1286	readable, but only once. Since it is likely line-buffered, you could
1251	attempt to read a whole line in the callback.	1287	attempt to read a whole line in the callback.
1252		1288
1253	static void	1289	static void
1254	stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1290	stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255	{	1291	{
1256	ev_io_stop (loop, w);	1292	ev_io_stop (loop, w);
1257	.. read from stdin here (or from w->fd) and handle any I/O errors	1293	.. read from stdin here (or from w->fd) and handle any I/O errors
1258	}	1294	}
1259		1295
1260	...	1296	...
1261	struct ev_loop *loop = ev_default_init (0);	1297	struct ev_loop *loop = ev_default_init (0);
1262	struct ev_io stdin_readable;	1298	ev_io stdin_readable;
1263	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);	1299	ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264	ev_io_start (loop, &stdin_readable);	1300	ev_io_start (loop, &stdin_readable);
1265	ev_loop (loop, 0);	1301	ev_loop (loop, 0);
1266		1302
1267		1303
…		…
1278		1314
1279	The callback is guaranteed to be invoked only I<after> its timeout has	1315	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	1316	passed, but if multiple timers become ready during the same loop iteration
1281	then order of execution is undefined.	1317	then order of execution is undefined.
1282		1318
		1319	=head3 Be smart about timeouts
		1320
		1321	Many real-world problems involve some kind of timeout, usually for error
		1322	recovery. A typical example is an HTTP request - if the other side hangs,
		1323	you want to raise some error after a while.
		1324
		1325	What follows are some ways to handle this problem, from obvious and
		1326	inefficient to smart and efficient.
		1327
		1328	In the following, a 60 second activity timeout is assumed - a timeout that
		1329	gets reset to 60 seconds each time there is activity (e.g. each time some
		1330	data or other life sign was received).
		1331
		1332	=over 4
		1333
		1334	=item 1. Use a timer and stop, reinitialise and start it on activity.
		1335
		1336	This is the most obvious, but not the most simple way: In the beginning,
		1337	start the watcher:
		1338
		1339	ev_timer_init (timer, callback, 60., 0.);
		1340	ev_timer_start (loop, timer);
		1341
		1342	Then, each time there is some activity, C<ev_timer_stop> it, initialise it
		1343	and start it again:
		1344
		1345	ev_timer_stop (loop, timer);
		1346	ev_timer_set (timer, 60., 0.);
		1347	ev_timer_start (loop, timer);
		1348
		1349	This is relatively simple to implement, but means that each time there is
		1350	some activity, libev will first have to remove the timer from its internal
		1351	data structure and then add it again. Libev tries to be fast, but it's
		1352	still not a constant-time operation.
		1353
		1354	=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
		1355
		1356	This is the easiest way, and involves using C<ev_timer_again> instead of
		1357	C<ev_timer_start>.
		1358
		1359	To implement this, configure an C<ev_timer> with a C<repeat> value
		1360	of C<60> and then call C<ev_timer_again> at start and each time you
		1361	successfully read or write some data. If you go into an idle state where
		1362	you do not expect data to travel on the socket, you can C<ev_timer_stop>
		1363	the timer, and C<ev_timer_again> will automatically restart it if need be.
		1364
		1365	That means you can ignore both the C<ev_timer_start> function and the
		1366	C<after> argument to C<ev_timer_set>, and only ever use the C<repeat>
		1367	member and C<ev_timer_again>.
		1368
		1369	At start:
		1370
		1371	ev_timer_init (timer, callback);
		1372	timer->repeat = 60.;
		1373	ev_timer_again (loop, timer);
		1374
		1375	Each time there is some activity:
		1376
		1377	ev_timer_again (loop, timer);
		1378
		1379	It is even possible to change the time-out on the fly, regardless of
		1380	whether the watcher is active or not:
		1381
		1382	timer->repeat = 30.;
		1383	ev_timer_again (loop, timer);
		1384
		1385	This is slightly more efficient then stopping/starting the timer each time
		1386	you want to modify its timeout value, as libev does not have to completely
		1387	remove and re-insert the timer from/into its internal data structure.
		1388
		1389	It is, however, even simpler than the "obvious" way to do it.
		1390
		1391	=item 3. Let the timer time out, but then re-arm it as required.
		1392
		1393	This method is more tricky, but usually most efficient: Most timeouts are
		1394	relatively long compared to the intervals between other activity - in
		1395	our example, within 60 seconds, there are usually many I/O events with
		1396	associated activity resets.
		1397
		1398	In this case, it would be more efficient to leave the C<ev_timer> alone,
		1399	but remember the time of last activity, and check for a real timeout only
		1400	within the callback:
		1401
		1402	ev_tstamp last_activity; // time of last activity
		1403
		1404	static void
		1405	callback (EV_P_ ev_timer *w, int revents)
		1406	{
		1407	ev_tstamp now = ev_now (EV_A);
		1408	ev_tstamp timeout = last_activity + 60.;
		1409
		1410	// if last_activity + 60. is older than now, we did time out
		1411	if (timeout < now)
		1412	{
		1413	// timeout occured, take action
		1414	}
		1415	else
		1416	{
		1417	// callback was invoked, but there was some activity, re-arm
		1418	// the watcher to fire in last_activity + 60, which is
		1419	// guaranteed to be in the future, so "again" is positive:
		1420	w->again = timeout - now;
		1421	ev_timer_again (EV_A_ w);
		1422	}
		1423	}
		1424
		1425	To summarise the callback: first calculate the real timeout (defined
		1426	as "60 seconds after the last activity"), then check if that time has
		1427	been reached, which means something I<did>, in fact, time out. Otherwise
		1428	the callback was invoked too early (C<timeout> is in the future), so
		1429	re-schedule the timer to fire at that future time, to see if maybe we have
		1430	a timeout then.
		1431
		1432	Note how C<ev_timer_again> is used, taking advantage of the
		1433	C<ev_timer_again> optimisation when the timer is already running.
		1434
		1435	This scheme causes more callback invocations (about one every 60 seconds
		1436	minus half the average time between activity), but virtually no calls to
		1437	libev to change the timeout.
		1438
		1439	To start the timer, simply initialise the watcher and set C<last_activity>
		1440	to the current time (meaning we just have some activity :), then call the
		1441	callback, which will "do the right thing" and start the timer:
		1442
		1443	ev_timer_init (timer, callback);
		1444	last_activity = ev_now (loop);
		1445	callback (loop, timer, EV_TIMEOUT);
		1446
		1447	And when there is some activity, simply store the current time in
		1448	C<last_activity>, no libev calls at all:
		1449
		1450	last_actiivty = ev_now (loop);
		1451
		1452	This technique is slightly more complex, but in most cases where the
		1453	time-out is unlikely to be triggered, much more efficient.
		1454
		1455	Changing the timeout is trivial as well (if it isn't hard-coded in the
		1456	callback :) - just change the timeout and invoke the callback, which will
		1457	fix things for you.
		1458
		1459	=item 4. Wee, just use a double-linked list for your timeouts.
		1460
		1461	If there is not one request, but many thousands (millions...), all
		1462	employing some kind of timeout with the same timeout value, then one can
		1463	do even better:
		1464
		1465	When starting the timeout, calculate the timeout value and put the timeout
		1466	at the I<end> of the list.
		1467
		1468	Then use an C<ev_timer> to fire when the timeout at the I<beginning> of
		1469	the list is expected to fire (for example, using the technique #3).
		1470
		1471	When there is some activity, remove the timer from the list, recalculate
		1472	the timeout, append it to the end of the list again, and make sure to
		1473	update the C<ev_timer> if it was taken from the beginning of the list.
		1474
		1475	This way, one can manage an unlimited number of timeouts in O(1) time for
		1476	starting, stopping and updating the timers, at the expense of a major
		1477	complication, and having to use a constant timeout. The constant timeout
		1478	ensures that the list stays sorted.
		1479
		1480	=back
		1481
		1482	So which method the best?
		1483
		1484	Method #2 is a simple no-brain-required solution that is adequate in most
		1485	situations. Method #3 requires a bit more thinking, but handles many cases
		1486	better, and isn't very complicated either. In most case, choosing either
		1487	one is fine, with #3 being better in typical situations.
		1488
		1489	Method #1 is almost always a bad idea, and buys you nothing. Method #4 is
		1490	rather complicated, but extremely efficient, something that really pays
		1491	off after the first million or so of active timers, i.e. it's usually
		1492	overkill :)
		1493
1283	=head3 The special problem of time updates	1494	=head3 The special problem of time updates
1284		1495
1285	Establishing the current time is a costly operation (it usually takes at	1496	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	1497	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	1498	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).	1541	If the timer is started but non-repeating, stop it (as if it timed out).
1331		1542
1332	If the timer is repeating, either start it if necessary (with the	1543	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.	1544	C<repeat> value), or reset the running timer to the C<repeat> value.
1334		1545
1335	This sounds a bit complicated, but here is a useful and typical	1546	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	1547	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		1548
1366	=item ev_tstamp repeat [read-write]	1549	=item ev_tstamp repeat [read-write]
1367		1550
1368	The current C<repeat> value. Will be used each time the watcher times out	1551	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),	1552	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1374	=head3 Examples	1557	=head3 Examples
1375		1558
1376	Example: Create a timer that fires after 60 seconds.	1559	Example: Create a timer that fires after 60 seconds.
1377		1560
1378	static void	1561	static void
1379	one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1562	one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380	{	1563	{
1381	.. one minute over, w is actually stopped right here	1564	.. one minute over, w is actually stopped right here
1382	}	1565	}
1383		1566
1384	struct ev_timer mytimer;	1567	ev_timer mytimer;
1385	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);	1568	ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386	ev_timer_start (loop, &mytimer);	1569	ev_timer_start (loop, &mytimer);
1387		1570
1388	Example: Create a timeout timer that times out after 10 seconds of	1571	Example: Create a timeout timer that times out after 10 seconds of
1389	inactivity.	1572	inactivity.
1390		1573
1391	static void	1574	static void
1392	timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)	1575	timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393	{	1576	{
1394	.. ten seconds without any activity	1577	.. ten seconds without any activity
1395	}	1578	}
1396		1579
1397	struct ev_timer mytimer;	1580	ev_timer mytimer;
1398	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */	1581	ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399	ev_timer_again (&mytimer); /* start timer */	1582	ev_timer_again (&mytimer); /* start timer */
1400	ev_loop (loop, 0);	1583	ev_loop (loop, 0);
1401		1584
1402	// and in some piece of code that gets executed on any "activity":	1585	// and in some piece of code that gets executed on any "activity":
…		…
1488		1671
1489	If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop	1672	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	1673	it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491	only event loop modification you are allowed to do).	1674	only event loop modification you are allowed to do).
1492		1675
1493	The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic	1676	The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494	*w, ev_tstamp now)>, e.g.:	1677	*w, ev_tstamp now)>, e.g.:
1495		1678
		1679	static ev_tstamp
1496	static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)	1680	my_rescheduler (ev_periodic *w, ev_tstamp now)
1497	{	1681	{
1498	return now + 60.;	1682	return now + 60.;
1499	}	1683	}
1500		1684
1501	It must return the next time to trigger, based on the passed time value	1685	It must return the next time to trigger, based on the passed time value
…		…
1538		1722
1539	The current interval value. Can be modified any time, but changes only	1723	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	1724	take effect when the periodic timer fires or C<ev_periodic_again> is being
1541	called.	1725	called.
1542		1726
1543	=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]	1727	=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544		1728
1545	The current reschedule callback, or C<0>, if this functionality is	1729	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	1730	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.	1731	the periodic timer fires or C<ev_periodic_again> is being called.
1548		1732
…		…
1553	Example: Call a callback every hour, or, more precisely, whenever the	1737	Example: Call a callback every hour, or, more precisely, whenever the
1554	system time is divisible by 3600. The callback invocation times have	1738	system time is divisible by 3600. The callback invocation times have
1555	potentially a lot of jitter, but good long-term stability.	1739	potentially a lot of jitter, but good long-term stability.
1556		1740
1557	static void	1741	static void
1558	clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)	1742	clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559	{	1743	{
1560	... its now a full hour (UTC, or TAI or whatever your clock follows)	1744	... its now a full hour (UTC, or TAI or whatever your clock follows)
1561	}	1745	}
1562		1746
1563	struct ev_periodic hourly_tick;	1747	ev_periodic hourly_tick;
1564	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);	1748	ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565	ev_periodic_start (loop, &hourly_tick);	1749	ev_periodic_start (loop, &hourly_tick);
1566		1750
1567	Example: The same as above, but use a reschedule callback to do it:	1751	Example: The same as above, but use a reschedule callback to do it:
1568		1752
1569	#include <math.h>	1753	#include <math.h>
1570		1754
1571	static ev_tstamp	1755	static ev_tstamp
1572	my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)	1756	my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573	{	1757	{
1574	return now + (3600. - fmod (now, 3600.));	1758	return now + (3600. - fmod (now, 3600.));
1575	}	1759	}
1576		1760
1577	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);	1761	ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578		1762
1579	Example: Call a callback every hour, starting now:	1763	Example: Call a callback every hour, starting now:
1580		1764
1581	struct ev_periodic hourly_tick;	1765	ev_periodic hourly_tick;
1582	ev_periodic_init (&hourly_tick, clock_cb,	1766	ev_periodic_init (&hourly_tick, clock_cb,
1583	fmod (ev_now (loop), 3600.), 3600., 0);	1767	fmod (ev_now (loop), 3600.), 3600., 0);
1584	ev_periodic_start (loop, &hourly_tick);	1768	ev_periodic_start (loop, &hourly_tick);
1585		1769
1586		1770
…		…
1625		1809
1626	=back	1810	=back
1627		1811
1628	=head3 Examples	1812	=head3 Examples
1629		1813
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1814	Example: Try to exit cleanly on SIGINT.
1631		1815
1632	static void	1816	static void
1633	sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)	1817	sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634	{	1818	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1819	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1820	}
1637		1821
1638	struct ev_signal signal_watcher;	1822	ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1823	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1824	ev_signal_start (loop, &signal_watcher);
1641		1825
1642		1826
1643	=head2 C<ev_child> - watch out for process status changes	1827	=head2 C<ev_child> - watch out for process status changes
1644		1828
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1829	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
1718	its completion.	1902	its completion.
1719		1903
1720	ev_child cw;	1904	ev_child cw;
1721		1905
1722	static void	1906	static void
1723	child_cb (EV_P_ struct ev_child *w, int revents)	1907	child_cb (EV_P_ ev_child *w, int revents)
1724	{	1908	{
1725	ev_child_stop (EV_A_ w);	1909	ev_child_stop (EV_A_ w);
1726	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);	1910	printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727	}	1911	}
1728		1912
…		…
1743		1927
1744		1928
1745	=head2 C<ev_stat> - did the file attributes just change?	1929	=head2 C<ev_stat> - did the file attributes just change?
1746		1930
1747	This watches a file system path for attribute changes. That is, it calls	1931	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	1932	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.	1933	and sees if it changed compared to the last time, invoking the callback if
		1934	it did.
1750		1935
1751	The path does not need to exist: changing from "path exists" to "path does	1936	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	1937	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	1938	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	1939	C<st_nlink> field being zero (which is otherwise always forced to be at
1755	the stat buffer having unspecified contents.	1940	least one) and all the other fields of the stat buffer having unspecified
		1941	contents.
1756		1942
1757	The path I<should> be absolute and I<must not> end in a slash. If it is	1943	The path I<must not> end in a slash or contain special components such as
		1944	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.	1945	your working directory changes, then the behaviour is undefined.
1759		1946
1760	Since there is no standard kernel interface to do this, the portable	1947	Since there is no portable change notification interface available, the
1761	implementation simply calls C<stat (2)> regularly on the path to see if	1948	portable implementation simply calls C<stat(2)> regularly on the path
1762	it changed somehow. You can specify a recommended polling interval for	1949	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!)	1950	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	1951	recommended!) then a I<suitable, unspecified default> value will be used
1765	you can expect to be around five seconds, although this might change	1952	(which you can expect to be around five seconds, although this might
1766	dynamically). Libev will also impose a minimum interval which is currently	1953	change dynamically). Libev will also impose a minimum interval which is
1767	around C<0.1>, but thats usually overkill.	1954	currently around C<0.1>, but that's usually overkill.
1768		1955
1769	This watcher type is not meant for massive numbers of stat watchers,	1956	This watcher type is not meant for massive numbers of stat watchers,
1770	as even with OS-supported change notifications, this can be	1957	as even with OS-supported change notifications, this can be
1771	resource-intensive.	1958	resource-intensive.
1772		1959
1773	At the time of this writing, the only OS-specific interface implemented	1960	At the time of this writing, the only OS-specific interface implemented
1774	is the Linux inotify interface (implementing kqueue support is left as	1961	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	1962	exercise for the reader. Note, however, that the author sees no way of
1776	of implementing C<ev_stat> semantics with kqueue).	1963	implementing C<ev_stat> semantics with kqueue, except as a hint).
1777		1964
1778	=head3 ABI Issues (Largefile Support)	1965	=head3 ABI Issues (Largefile Support)
1779		1966
1780	Libev by default (unless the user overrides this) uses the default	1967	Libev by default (unless the user overrides this) uses the default
1781	compilation environment, which means that on systems with large file	1968	compilation environment, which means that on systems with large file
1782	support disabled by default, you get the 32 bit version of the stat	1969	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	1970	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	1971	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	1972	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	1973	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.	1974	most noticeably displayed with ev_stat and large file support.
1788		1975
1789	The solution for this is to lobby your distribution maker to make large	1976	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	1977	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	1978	optional. Libev cannot simply switch on large file support because it has
1792	to exchange stat structures with application programs compiled using the	1979	to exchange stat structures with application programs compiled using the
1793	default compilation environment.	1980	default compilation environment.
1794		1981
1795	=head3 Inotify and Kqueue	1982	=head3 Inotify and Kqueue
1796		1983
1797	When C<inotify (7)> support has been compiled into libev (generally only	1984	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	1985	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	1986	inotify descriptor will be created lazily when the first C<ev_stat>
1800	when the first C<ev_stat> watcher is being started.	1987	watcher is being started.
1801		1988
1802	Inotify presence does not change the semantics of C<ev_stat> watchers	1989	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	1990	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	1991	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,	1992	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.	1993	but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too
		1994	many bugs), the path exists (i.e. stat succeeds), and the path resides on
		1995	a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and
		1996	xfs are fully working) libev usually gets away without polling.
1807		1997
1808	There is no support for kqueue, as apparently it cannot be used to	1998	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	1999	implement this functionality, due to the requirement of having a file
1810	descriptor open on the object at all times, and detecting renames, unlinks	2000	descriptor open on the object at all times, and detecting renames, unlinks
1811	etc. is difficult.	2001	etc. is difficult.
1812		2002
1813	=head3 The special problem of stat time resolution	2003	=head3 The special problem of stat time resolution
1814		2004
1815	The C<stat ()> system call only supports full-second resolution portably, and	2005	The C<stat ()> system call only supports full-second resolution portably,
1816	even on systems where the resolution is higher, most file systems still	2006	and even on systems where the resolution is higher, most file systems
1817	only support whole seconds.	2007	still only support whole seconds.
1818		2008
1819	That means that, if the time is the only thing that changes, you can	2009	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	2010	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	2011	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	2012	within the same second, C<ev_stat> will be unable to detect unless the
…		…
1979		2169
1980	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the	2170	Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981	callback, free it. Also, use no error checking, as usual.	2171	callback, free it. Also, use no error checking, as usual.
1982		2172
1983	static void	2173	static void
1984	idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)	2174	idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985	{	2175	{
1986	free (w);	2176	free (w);
1987	// now do something you wanted to do when the program has	2177	// now do something you wanted to do when the program has
1988	// no longer anything immediate to do.	2178	// no longer anything immediate to do.
1989	}	2179	}
1990		2180
1991	struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));	2181	ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992	ev_idle_init (idle_watcher, idle_cb);	2182	ev_idle_init (idle_watcher, idle_cb);
1993	ev_idle_start (loop, idle_cb);	2183	ev_idle_start (loop, idle_cb);
1994		2184
1995		2185
1996	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!	2186	=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
…		…
2077		2267
2078	static ev_io iow [nfd];	2268	static ev_io iow [nfd];
2079	static ev_timer tw;	2269	static ev_timer tw;
2080		2270
2081	static void	2271	static void
2082	io_cb (ev_loop *loop, ev_io *w, int revents)	2272	io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083	{	2273	{
2084	}	2274	}
2085		2275
2086	// create io watchers for each fd and a timer before blocking	2276	// create io watchers for each fd and a timer before blocking
2087	static void	2277	static void
2088	adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)	2278	adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089	{	2279	{
2090	int timeout = 3600000;	2280	int timeout = 3600000;
2091	struct pollfd fds [nfd];	2281	struct pollfd fds [nfd];
2092	// actual code will need to loop here and realloc etc.	2282	// actual code will need to loop here and realloc etc.
2093	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));	2283	adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
…		…
2108	}	2298	}
2109	}	2299	}
2110		2300
2111	// stop all watchers after blocking	2301	// stop all watchers after blocking
2112	static void	2302	static void
2113	adns_check_cb (ev_loop *loop, ev_check *w, int revents)	2303	adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114	{	2304	{
2115	ev_timer_stop (loop, &tw);	2305	ev_timer_stop (loop, &tw);
2116		2306
2117	for (int i = 0; i < nfd; ++i)	2307	for (int i = 0; i < nfd; ++i)
2118	{	2308	{
…		…
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2423	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2234	but you will also have to stop and restart any C<ev_embed> watchers	2424	but you will also have to stop and restart any C<ev_embed> watchers
2235	yourself - but you can use a fork watcher to handle this automatically,	2425	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2426	and future versions of libev might do just that.
2237		2427
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2428	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2429	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2430	portable one.
2241		2431
2242	So when you want to use this feature you will always have to be prepared	2432	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	2433	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	2434	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.	2435	create it, and if that fails, use the normal loop for everything.
		2436
		2437	=head3 C<ev_embed> and fork
		2438
		2439	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2440	automatically be applied to the embedded loop as well, so no special
		2441	fork handling is required in that case. When the watcher is not running,
		2442	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2443	as applicable.
2246		2444
2247	=head3 Watcher-Specific Functions and Data Members	2445	=head3 Watcher-Specific Functions and Data Members
2248		2446
2249	=over 4	2447	=over 4
2250		2448
…		…
2278	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be	2476	C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2279	used).	2477	used).
2280		2478
2281	struct ev_loop *loop_hi = ev_default_init (0);	2479	struct ev_loop *loop_hi = ev_default_init (0);
2282	struct ev_loop *loop_lo = 0;	2480	struct ev_loop *loop_lo = 0;
2283	struct ev_embed embed;	2481	ev_embed embed;
2284		2482
2285	// see if there is a chance of getting one that works	2483	// see if there is a chance of getting one that works
2286	// (remember that a flags value of 0 means autodetection)	2484	// (remember that a flags value of 0 means autodetection)
2287	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()	2485	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2288	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())	2486	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
…		…
2302	kqueue implementation). Store the kqueue/socket-only event loop in	2500	kqueue implementation). Store the kqueue/socket-only event loop in
2303	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).	2501	C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2304		2502
2305	struct ev_loop *loop = ev_default_init (0);	2503	struct ev_loop *loop = ev_default_init (0);
2306	struct ev_loop *loop_socket = 0;	2504	struct ev_loop *loop_socket = 0;
2307	struct ev_embed embed;	2505	ev_embed embed;
2308		2506
2309	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)	2507	if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2310	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))	2508	if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2311	{	2509	{
2312	ev_embed_init (&embed, 0, loop_socket);	2510	ev_embed_init (&embed, 0, loop_socket);
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2566	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2567	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2568	need elaborate support such as pthreads.
2371		2569
2372	That means that if you want to queue data, you have to provide your own	2570	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2571	queue. But at least I can tell you how to implement locking around your
2374	queue:	2572	queue:
2375		2573
2376	=over 4	2574	=over 4
2377		2575
2378	=item queueing from a signal handler context	2576	=item queueing from a signal handler context
2379		2577
2380	To implement race-free queueing, you simply add to the queue in the signal	2578	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	2579	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2580	an example that does that for some fictitious SIGUSR1 handler:
2383		2581
2384	static ev_async mysig;	2582	static ev_async mysig;
2385		2583
2386	static void	2584	static void
2387	sigusr1_handler (void)	2585	sigusr1_handler (void)
…		…
2453	=over 4	2651	=over 4
2454		2652
2455	=item ev_async_init (ev_async *, callback)	2653	=item ev_async_init (ev_async *, callback)
2456		2654
2457	Initialises and configures the async watcher - it has no parameters of any	2655	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,	2656	kind. There is a C<ev_async_set> macro, but using it is utterly pointless,
2459	believe me.	2657	trust me.
2460		2658
2461	=item ev_async_send (loop, ev_async *)	2659	=item ev_async_send (loop, ev_async *)
2462		2660
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2661	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2662	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2663	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2664	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2665	section below on what exactly this means).
2468		2666
2469	This call incurs the overhead of a system call only once per loop iteration,	2667	This call incurs the overhead of a system call only once per loop iteration,
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2668	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2692	=over 4
2495		2693
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2694	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2695
2498	This function combines a simple timer and an I/O watcher, calls your	2696	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2697	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	2698	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	2699	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2700	more watchers yourself.
2503		2701
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2702	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	2703	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2704	the given C<fd> and C<events> set will be created and started.
2507		2705
2508	If C<timeout> is less than 0, then no timeout watcher will be	2706	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	2707	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	2708	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2709
2513	The callback has the type C<void (*cb)(int revents, void *arg)> and gets	2710	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	2711	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>	2712	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2713	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2714	a timeout and an io event at the same time - you probably should give io
		2715	events precedence.
		2716
		2717	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2718
2518	static void stdin_ready (int revents, void *arg)	2719	static void stdin_ready (int revents, void *arg)
2519	{	2720	{
		2721	if (revents & EV_READ)
		2722	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2723	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2724	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2725	}
2525		2726
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2727	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2728
2528	=item ev_feed_event (ev_loop *, watcher *, int revents)	2729	=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2529		2730
2530	Feeds the given event set into the event loop, as if the specified event	2731	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	2732	had happened for the specified watcher (which must be a pointer to an
2532	initialised but not necessarily started event watcher).	2733	initialised but not necessarily started event watcher).
2533		2734
2534	=item ev_feed_fd_event (ev_loop *, int fd, int revents)	2735	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2535		2736
2536	Feed an event on the given fd, as if a file descriptor backend detected	2737	Feed an event on the given fd, as if a file descriptor backend detected
2537	the given events it.	2738	the given events it.
2538		2739
2539	=item ev_feed_signal_event (ev_loop *loop, int signum)	2740	=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2540		2741
2541	Feed an event as if the given signal occurred (C<loop> must be the default	2742	Feed an event as if the given signal occurred (C<loop> must be the default
2542	loop!).	2743	loop!).
2543		2744
2544	=back	2745	=back
…		…
2676		2877
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2878	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2879
2679	See the method-C<set> above for more details.	2880	See the method-C<set> above for more details.
2680		2881
2681	Example:	2882	Example: Use a plain function as callback.
2682		2883
2683	static void io_cb (ev::io &w, int revents) { }	2884	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2885	iow.set <io_cb> ();
2685		2886
2686	=item w->set (struct ev_loop *)	2887	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2925	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2926	the constructor.
2726		2927
2727	class myclass	2928	class myclass
2728	{	2929	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2930	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2931	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2932
2732	myclass (int fd)	2933	myclass (int fd)
2733	{	2934	{
2734	io .set <myclass, &myclass::io_cb > (this);	2935	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2936	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2952	=item Perl
2752		2953
2753	The EV module implements the full libev API and is actually used to test	2954	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	2955	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2956	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2957	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2958	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2959	and C<EV::Glib>).
2758		2960
2759	It can be found and installed via CPAN, its homepage is at	2961	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2962	L<http://software.schmorp.de/pkg/EV>.
2761		2963
2762	=item Python	2964	=item Python
…		…
2778	=item D	2980	=item D
2779		2981
2780	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to	2982	Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to
2781	be found at L<http://proj.llucax.com.ar/wiki/evd>.	2983	be found at L<http://proj.llucax.com.ar/wiki/evd>.
2782		2984
		2985	=item Ocaml
		2986
		2987	Erkki Seppala has written Ocaml bindings for libev, to be found at
		2988	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
		2989
2783	=back	2990	=back
2784		2991
2785		2992
2786	=head1 MACRO MAGIC	2993	=head1 MACRO MAGIC
2787		2994
…		…
2887		3094
2888	#define EV_STANDALONE 1	3095	#define EV_STANDALONE 1
2889	#include "ev.h"	3096	#include "ev.h"
2890		3097
2891	Both header files and implementation files can be compiled with a C++	3098	Both header files and implementation files can be compiled with a C++
2892	compiler (at least, thats a stated goal, and breakage will be treated	3099	compiler (at least, that's a stated goal, and breakage will be treated
2893	as a bug).	3100	as a bug).
2894		3101
2895	You need the following files in your source tree, or in a directory	3102	You need the following files in your source tree, or in a directory
2896	in your include path (e.g. in libev/ when using -Ilibev):	3103	in your include path (e.g. in libev/ when using -Ilibev):
2897		3104
…		…
2941		3148
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	3149	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		3150
2944	Libev can be configured via a variety of preprocessor symbols you have to	3151	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	3152	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	3153	autoconf is documented for every option.
2947		3154
2948	=over 4	3155	=over 4
2949		3156
2950	=item EV_STANDALONE	3157	=item EV_STANDALONE
2951		3158
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3328	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3329	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3330	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3331	fine.
3125		3332
3126	If your embedding application does not need any priorities, defining these both to	3333	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3334	both to C<0> will save some memory and CPU.
3128		3335
3129	=item EV_PERIODIC_ENABLE	3336	=item EV_PERIODIC_ENABLE
3130		3337
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3338	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3339	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3346	code.
3140		3347
3141	=item EV_EMBED_ENABLE	3348	=item EV_EMBED_ENABLE
3142		3349
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3350	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3351	defined to be C<0>, then they are not. Embed watchers rely on most other
		3352	watcher types, which therefore must not be disabled.
3145		3353
3146	=item EV_STAT_ENABLE	3354	=item EV_STAT_ENABLE
3147		3355
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3356	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3357	defined to be C<0>, then they are not.
…		…
3181	two).	3389	two).
3182		3390
3183	=item EV_USE_4HEAP	3391	=item EV_USE_4HEAP
3184		3392
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3393	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3394	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3395	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3396	faster performance with many (thousands) of watchers.
3189		3397
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3398	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3399	(disabled).
3192		3400
3193	=item EV_HEAP_CACHE_AT	3401	=item EV_HEAP_CACHE_AT
3194		3402
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3403	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3404	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3405	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3406	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3407	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3408	noticeably with many (hundreds) of watchers.
3201		3409
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3410	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3411	(disabled).
3204		3412
3205	=item EV_VERIFY	3413	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3419	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3420	verification code will be called very frequently, which will slow down
3213	libev considerably.	3421	libev considerably.
3214		3422
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3423	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3424	C<0>.
3217		3425
3218	=item EV_COMMON	3426	=item EV_COMMON
3219		3427
3220	By default, all watchers have a C<void *data> member. By redefining	3428	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3429	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3446	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3447	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3448	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3449	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3450	method calls instead of plain function calls in C++.
		3451
		3452	=back
3243		3453
3244	=head2 EXPORTED API SYMBOLS	3454	=head2 EXPORTED API SYMBOLS
3245		3455
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3456	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3457	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3504	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3505
3296	#include "ev_cpp.h"	3506	#include "ev_cpp.h"
3297	#include "ev.c"	3507	#include "ev.c"
3298		3508
		3509	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3510
3300	=head1 THREADS AND COROUTINES	3511	=head2 THREADS AND COROUTINES
3301		3512
3302	=head2 THREADS	3513	=head3 THREADS
3303		3514
3304	Libev itself is thread-safe (unless the opposite is specifically	3515	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3516	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3517	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3518	are no concurrent calls into any libev function with the same loop
		3519	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3520	of course): libev guarantees that different event loops share no data
3309	need locking.	3521	structures that need any locking.
3310		3522
3311	Or to put it differently: calls with different loop parameters can be done	3523	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3524	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3525	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3526	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3527	a mutex per loop).
3316		3528
3317	Specifically to support threads (and signal handlers), libev implements	3529	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3530	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3531	concurrency on the same event loop, namely waking it up "from the
		3532	outside".
3320		3533
3321	If you want to know which design (one loop, locking, or multiple loops	3534	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3535	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3536	help you, but here is some generic advice:
3324		3537
3325	=over 4	3538	=over 4
3326		3539
3327	=item * most applications have a main thread: use the default libev loop	3540	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3541	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3565	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3566	watcher callback into the event loop interested in the signal.
3354		3567
3355	=back	3568	=back
3356		3569
3357	=head2 COROUTINES	3570	=head3 COROUTINES
3358		3571
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3572	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3573	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3574	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3575	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3576	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3577	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3578
3366	Care has been taken to ensure that libev does not keep local state inside	3579	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	3580	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3581	they do not call any callbacks.
3368		3582
		3583	=head2 COMPILER WARNINGS
3369		3584
3370	=head1 COMPLEXITIES	3585	Depending on your compiler and compiler settings, you might get no or a
		3586	lot of warnings when compiling libev code. Some people are apparently
		3587	scared by this.
3371		3588
3372	In this section the complexities of (many of) the algorithms used inside	3589	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3590	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3591	warning options. "Warn-free" code therefore cannot be a goal except when
		3592	targeting a specific compiler and compiler-version.
3375		3593
3376	All of the following are about amortised time: If an array needs to be	3594	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3595	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	3596	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3597
3382	=over 4	3598	And of course, some compiler warnings are just plain stupid, or simply
		3599	wrong (because they don't actually warn about the condition their message
		3600	seems to warn about). For example, certain older gcc versions had some
		3601	warnings that resulted an extreme number of false positives. These have
		3602	been fixed, but some people still insist on making code warn-free with
		3603	such buggy versions.
3383		3604
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3605	While libev is written to generate as few warnings as possible,
		3606	"warn-free" code is not a goal, and it is recommended not to build libev
		3607	with any compiler warnings enabled unless you are prepared to cope with
		3608	them (e.g. by ignoring them). Remember that warnings are just that:
		3609	warnings, not errors, or proof of bugs.
3385		3610
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3611
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3612	=head2 VALGRIND
3391		3613
3392	That means that changing a timer costs less than removing/adding them	3614	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	3615	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3616
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3617	If you think you found a bug (memory leak, uninitialised data access etc.)
		3618	in libev, then check twice: If valgrind reports something like:
3396		3619
3397	These just add the watcher into an array or at the head of a list.	3620	==2274== definitely lost: 0 bytes in 0 blocks.
		3621	==2274== possibly lost: 0 bytes in 0 blocks.
		3622	==2274== still reachable: 256 bytes in 1 blocks.
3398		3623
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3624	Then there is no memory leak, just as memory accounted to global variables
		3625	is not a memleak - the memory is still being referenced, and didn't leak.
3400		3626
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3627	Similarly, under some circumstances, valgrind might report kernel bugs
		3628	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3629	although an acceptable workaround has been found here), or it might be
		3630	confused.
3402		3631
3403	These watchers are stored in lists then need to be walked to find the	3632	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	3633	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3634
3407	=item Finding the next timer in each loop iteration: O(1)	3635	If you are unsure about something, feel free to contact the mailing list
		3636	with the full valgrind report and an explanation on why you think this
		3637	is a bug in libev (best check the archives, too :). However, don't be
		3638	annoyed when you get a brisk "this is no bug" answer and take the chance
		3639	of learning how to interpret valgrind properly.
3408		3640
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3641	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3642	I suggest using suppression lists.
3411		3643
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3644
3414	A change means an I/O watcher gets started or stopped, which requires	3645	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3646
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3647	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3648
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3649	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	3650	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3651	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3652	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3663
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3664	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3665	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3666	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3667	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3668	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3669	available).
3463		3670
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3671	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3672	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3673	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3684	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3685
3479	#include "ev.h"	3686	#include "ev.h"
3480		3687
3481	And compile the following F<evwrap.c> file into your project (make sure	3688	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3689	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3690
3484	#include "evwrap.h"	3691	#include "evwrap.h"
3485	#include "ev.c"	3692	#include "ev.c"
3486		3693
3487	=over 4	3694	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3739	wrap all I/O functions and provide your own fd management, but the cost of
3533	calling select (O(n²)) will likely make this unworkable.	3740	calling select (O(n²)) will likely make this unworkable.
3534		3741
3535	=back	3742	=back
3536		3743
3537
3538	=head1 PORTABILITY REQUIREMENTS	3744	=head2 PORTABILITY REQUIREMENTS
3539		3745
3540	In addition to a working ISO-C implementation, libev relies on a few	3746	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3747	backend-specific APIs, libev relies on a few additional extensions:
3542		3748
3543	=over 4	3749	=over 4
3544		3750
3545	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible	3751	=item C<void (*)(ev_watcher_type *, int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3752	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3758	calls them using an C<ev_watcher *> internally.
3553		3759
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3760	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3761
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3762	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3763	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3764	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3765	believed to be sufficiently portable.
3560		3766
3561	=item C<sigprocmask> must work in a threaded environment	3767	=item C<sigprocmask> must work in a threaded environment
3562		3768
…		…
3571	except the initial one, and run the default loop in the initial thread as	3777	except the initial one, and run the default loop in the initial thread as
3572	well.	3778	well.
3573		3779
3574	=item C<long> must be large enough for common memory allocation sizes	3780	=item C<long> must be large enough for common memory allocation sizes
3575		3781
3576	To improve portability and simplify using libev, libev uses C<long>	3782	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3783	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3784	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3785	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3786	watchers.
3581		3787
3582	=item C<double> must hold a time value in seconds with enough accuracy	3788	=item C<double> must hold a time value in seconds with enough accuracy
3583		3789
3584	The type C<double> is used to represent timestamps. It is required to	3790	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3791	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3795	=back
3590		3796
3591	If you know of other additional requirements drop me a note.	3797	If you know of other additional requirements drop me a note.
3592		3798
3593		3799
3594	=head1 COMPILER WARNINGS	3800	=head1 ALGORITHMIC COMPLEXITIES
3595		3801
3596	Depending on your compiler and compiler settings, you might get no or a	3802	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3803	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3804	the documentation for C<ev_default_init>.
3599		3805
3600	However, these are unavoidable for many reasons. For one, each compiler	3806	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	3807	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3808	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3809	mean that libev does a lengthy realloc operation in rare cases, but on
		3810	average it is much faster and asymptotically approaches constant time.
3604		3811
3605	Another reason is that some compiler warnings require elaborate	3812	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3813
3609	And of course, some compiler warnings are just plain stupid, or simply	3814	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3815
3613	While libev is written to generate as few warnings as possible,	3816	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	3817	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	3818	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3819
		3820	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3821
3620	=head1 VALGRIND	3822	That means that changing a timer costs less than removing/adding them,
		3823	as only the relative motion in the event queue has to be paid for.
3621		3824
3622	Valgrind has a special section here because it is a popular tool that is	3825	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3826
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3827	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		3828
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3829	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3830
3632	Then there is no memory leak. Similarly, under some circumstances,	3831	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3832
3636	If you are unsure about something, feel free to contact the mailing list	3833	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	3834	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	3835	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	3836	is rare).
3640	properly.
3641		3837
3642	If you need, for some reason, empty reports from valgrind for your project	3838	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3839
		3840	By virtue of using a binary or 4-heap, the next timer is always found at a
		3841	fixed position in the storage array.
		3842
		3843	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3844
		3845	A change means an I/O watcher gets started or stopped, which requires
		3846	libev to recalculate its status (and possibly tell the kernel, depending
		3847	on backend and whether C<ev_io_set> was used).
		3848
		3849	=item Activating one watcher (putting it into the pending state): O(1)
		3850
		3851	=item Priority handling: O(number_of_priorities)
		3852
		3853	Priorities are implemented by allocating some space for each
		3854	priority. When doing priority-based operations, libev usually has to
		3855	linearly search all the priorities, but starting/stopping and activating
		3856	watchers becomes O(1) with respect to priority handling.
		3857
		3858	=item Sending an ev_async: O(1)
		3859
		3860	=item Processing ev_async_send: O(number_of_async_watchers)
		3861
		3862	=item Processing signals: O(max_signal_number)
		3863
		3864	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3865	calls in the current loop iteration. Checking for async and signal events
		3866	involves iterating over all running async watchers or all signal numbers.
		3867
		3868	=back
3644		3869
3645		3870
3646	=head1 AUTHOR	3871	=head1 AUTHOR
3647		3872
3648	Marc Lehmann <libev@schmorp.de>.	3873	Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson.
3649		3874

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