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

Comparing libev/ev.pod (file contents):
Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs.
Revision 1.271 by root, Fri Sep 18 21:16:10 2009 UTC

…		…
98	=head2 FEATURES	98	=head2 FEATURES
99		99
100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the	100	Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms	101	BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface	102	for file descriptor events (C<ev_io>), the Linux C<inotify> interface
103	(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers	103	(for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner
104	with customised rescheduling (C<ev_periodic>), synchronous signals	104	inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative
105	(C<ev_signal>), process status change events (C<ev_child>), and event	105	timers (C<ev_timer>), absolute timers with customised rescheduling
106	watchers dealing with the event loop mechanism itself (C<ev_idle>,	106	(C<ev_periodic>), synchronous signals (C<ev_signal>), process status
107	C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as	107	change events (C<ev_child>), and event watchers dealing with the event
108	file watchers (C<ev_stat>) and even limited support for fork events	108	loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and
109	(C<ev_fork>).	109	C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even
		110	limited support for fork events (C<ev_fork>).
110		111
111	It also is quite fast (see this	112	It also is quite fast (see this
112	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent	113	L<benchmark\|http://libev.schmorp.de/bench.html> comparing it to libevent
113	for example).	114	for example).
114		115
…		…
361	forget about forgetting to tell libev about forking) when you use this	362	forget about forgetting to tell libev about forking) when you use this
362	flag.	363	flag.
363		364
364	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>	365	This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS>
365	environment variable.	366	environment variable.
		367
		368	=item C<EVFLAG_NOINOTIFY>
		369
		370	When this flag is specified, then libev will not attempt to use the
		371	I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and
		372	testing, this flag can be useful to conserve inotify file descriptors, as
		373	otherwise each loop using C<ev_stat> watchers consumes one inotify handle.
		374
		375	=item C<EVFLAG_NOSIGFD>
		376
		377	When this flag is specified, then libev will not attempt to use the
		378	I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is
		379	probably only useful to work around any bugs in libev. Consequently, this
		380	flag might go away once the signalfd functionality is considered stable,
		381	so it's useful mostly in environment variables and not in program code.
366		382
367	=item C<EVBACKEND_SELECT> (value 1, portable select backend)	383	=item C<EVBACKEND_SELECT> (value 1, portable select backend)
368		384
369	This is your standard select(2) backend. Not I<completely> standard, as	385	This is your standard select(2) backend. Not I<completely> standard, as
370	libev tries to roll its own fd_set with no limits on the number of fds,	386	libev tries to roll its own fd_set with no limits on the number of fds,
…		…
518		534
519	It is definitely not recommended to use this flag.	535	It is definitely not recommended to use this flag.
520		536
521	=back	537	=back
522		538
523	If one or more of these are or'ed into the flags value, then only these	539	If one or more of the backend flags are or'ed into the flags value,
524	backends will be tried (in the reverse order as listed here). If none are	540	then only these backends will be tried (in the reverse order as listed
525	specified, all backends in C<ev_recommended_backends ()> will be tried.	541	here). If none are specified, all backends in C<ev_recommended_backends
		542	()> will be tried.
526		543
527	Example: This is the most typical usage.	544	Example: This is the most typical usage.
528		545
529	if (!ev_default_loop (0))	546	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	547	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	590	as signal and child watchers) would need to be stopped manually.
574		591
575	In general it is not advisable to call this function except in the	592	In general it is not advisable to call this function except in the
576	rare occasion where you really need to free e.g. the signal handling	593	rare occasion where you really need to free e.g. the signal handling
577	pipe fds. If you need dynamically allocated loops it is better to use	594	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	595	C<ev_loop_new> and C<ev_loop_destroy>.
579		596
580	=item ev_loop_destroy (loop)	597	=item ev_loop_destroy (loop)
581		598
582	Like C<ev_default_destroy>, but destroys an event loop created by an	599	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	600	earlier call to C<ev_loop_new>.
…		…
687	event loop time (see C<ev_now_update>).	704	event loop time (see C<ev_now_update>).
688		705
689	=item ev_loop (loop, int flags)	706	=item ev_loop (loop, int flags)
690		707
691	Finally, this is it, the event handler. This function usually is called	708	Finally, this is it, the event handler. This function usually is called
692	after you initialised all your watchers and you want to start handling	709	after you have initialised all your watchers and you want to start
693	events.	710	handling events.
694		711
695	If the flags argument is specified as C<0>, it will not return until	712	If the flags argument is specified as C<0>, it will not return until
696	either no event watchers are active anymore or C<ev_unloop> was called.	713	either no event watchers are active anymore or C<ev_unloop> was called.
697		714
698	Please note that an explicit C<ev_unloop> is usually better than	715	Please note that an explicit C<ev_unloop> is usually better than
…		…
856	more often than 100 times per second:	873	more often than 100 times per second:
857		874
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	875	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	876	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		877
		878	=item ev_invoke_pending (loop)
		879
		880	This call will simply invoke all pending watchers while resetting their
		881	pending state. Normally, C<ev_loop> does this automatically when required,
		882	but when overriding the invoke callback this call comes handy.
		883
		884	=item int ev_pending_count (loop)
		885
		886	Returns the number of pending watchers - zero indicates that no watchers
		887	are pending.
		888
		889	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		890
		891	This overrides the invoke pending functionality of the loop: Instead of
		892	invoking all pending watchers when there are any, C<ev_loop> will call
		893	this callback instead. This is useful, for example, when you want to
		894	invoke the actual watchers inside another context (another thread etc.).
		895
		896	If you want to reset the callback, use C<ev_invoke_pending> as new
		897	callback.
		898
		899	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		900
		901	Sometimes you want to share the same loop between multiple threads. This
		902	can be done relatively simply by putting mutex_lock/unlock calls around
		903	each call to a libev function.
		904
		905	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		906	wait for it to return. One way around this is to wake up the loop via
		907	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		908	and I<acquire> callbacks on the loop.
		909
		910	When set, then C<release> will be called just before the thread is
		911	suspended waiting for new events, and C<acquire> is called just
		912	afterwards.
		913
		914	Ideally, C<release> will just call your mutex_unlock function, and
		915	C<acquire> will just call the mutex_lock function again.
		916
		917	While event loop modifications are allowed between invocations of
		918	C<release> and C<acquire> (that's their only purpose after all), no
		919	modifications done will affect the event loop, i.e. adding watchers will
		920	have no effect on the set of file descriptors being watched, or the time
		921	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		922	to take note of any changes you made.
		923
		924	In theory, threads executing C<ev_loop> will be async-cancel safe between
		925	invocations of C<release> and C<acquire>.
		926
		927	See also the locking example in the C<THREADS> section later in this
		928	document.
		929
		930	=item ev_set_userdata (loop, void *data)
		931
		932	=item ev_userdata (loop)
		933
		934	Set and retrieve a single C<void *> associated with a loop. When
		935	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		936	C<0.>
		937
		938	These two functions can be used to associate arbitrary data with a loop,
		939	and are intended solely for the C<invoke_pending_cb>, C<release> and
		940	C<acquire> callbacks described above, but of course can be (ab-)used for
		941	any other purpose as well.
		942
861	=item ev_loop_verify (loop)	943	=item ev_loop_verify (loop)
862		944
863	This function only does something when C<EV_VERIFY> support has been	945	This function only does something when C<EV_VERIFY> support has been
864	compiled in, which is the default for non-minimal builds. It tries to go	946	compiled in, which is the default for non-minimal builds. It tries to go
865	through all internal structures and checks them for validity. If anything	947	through all internal structures and checks them for validity. If anything
…		…
1690		1772
1691	If the event loop is suspended for a long time, you can also force an	1773	If the event loop is suspended for a long time, you can also force an
1692	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1774	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1693	()>.	1775	()>.
1694		1776
		1777	=head3 The special problems of suspended animation
		1778
		1779	When you leave the server world it is quite customary to hit machines that
		1780	can suspend/hibernate - what happens to the clocks during such a suspend?
		1781
		1782	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1783	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1784	to run until the system is suspended, but they will not advance while the
		1785	system is suspended. That means, on resume, it will be as if the program
		1786	was frozen for a few seconds, but the suspend time will not be counted
		1787	towards C<ev_timer> when a monotonic clock source is used. The real time
		1788	clock advanced as expected, but if it is used as sole clocksource, then a
		1789	long suspend would be detected as a time jump by libev, and timers would
		1790	be adjusted accordingly.
		1791
		1792	I would not be surprised to see different behaviour in different between
		1793	operating systems, OS versions or even different hardware.
		1794
		1795	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1796	time jump in the monotonic clocks and the realtime clock. If the program
		1797	is suspended for a very long time, and monotonic clock sources are in use,
		1798	then you can expect C<ev_timer>s to expire as the full suspension time
		1799	will be counted towards the timers. When no monotonic clock source is in
		1800	use, then libev will again assume a timejump and adjust accordingly.
		1801
		1802	It might be beneficial for this latter case to call C<ev_suspend>
		1803	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1804	deterministic behaviour in this case (you can do nothing against
		1805	C<SIGSTOP>).
		1806
1695	=head3 Watcher-Specific Functions and Data Members	1807	=head3 Watcher-Specific Functions and Data Members
1696		1808
1697	=over 4	1809	=over 4
1698		1810
1699	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1811	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1724	If the timer is repeating, either start it if necessary (with the	1836	If the timer is repeating, either start it if necessary (with the
1725	C<repeat> value), or reset the running timer to the C<repeat> value.	1837	C<repeat> value), or reset the running timer to the C<repeat> value.
1726		1838
1727	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1839	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1728	usage example.	1840	usage example.
		1841
		1842	=item ev_timer_remaining (loop, ev_timer *)
		1843
		1844	Returns the remaining time until a timer fires. If the timer is active,
		1845	then this time is relative to the current event loop time, otherwise it's
		1846	the timeout value currently configured.
		1847
		1848	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1849	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1850	will return C<4>. When the timer expires and is restarted, it will return
		1851	roughly C<7> (likely slightly less as callback invocation takes some time,
		1852	too), and so on.
1729		1853
1730	=item ev_tstamp repeat [read-write]	1854	=item ev_tstamp repeat [read-write]
1731		1855
1732	The current C<repeat> value. Will be used each time the watcher times out	1856	The current C<repeat> value. Will be used each time the watcher times out
1733	or C<ev_timer_again> is called, and determines the next timeout (if any),	1857	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1969	Signal watchers will trigger an event when the process receives a specific	2093	Signal watchers will trigger an event when the process receives a specific
1970	signal one or more times. Even though signals are very asynchronous, libev	2094	signal one or more times. Even though signals are very asynchronous, libev
1971	will try it's best to deliver signals synchronously, i.e. as part of the	2095	will try it's best to deliver signals synchronously, i.e. as part of the
1972	normal event processing, like any other event.	2096	normal event processing, like any other event.
1973		2097
1974	If you want signals asynchronously, just use C<sigaction> as you would	2098	If you want signals to be delivered truly asynchronously, just use
1975	do without libev and forget about sharing the signal. You can even use	2099	C<sigaction> as you would do without libev and forget about sharing
1976	C<ev_async> from a signal handler to synchronously wake up an event loop.	2100	the signal. You can even use C<ev_async> from a signal handler to
		2101	synchronously wake up an event loop.
1977		2102
1978	You can configure as many watchers as you like per signal. Only when the	2103	You can configure as many watchers as you like for the same signal, but
		2104	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2105	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2106	C<SIGINT> in both the default loop and another loop at the same time. At
		2107	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2108
1979	first watcher gets started will libev actually register a signal handler	2109	When the first watcher gets started will libev actually register something
1980	with the kernel (thus it coexists with your own signal handlers as long as	2110	with the kernel (thus it coexists with your own signal handlers as long as
1981	you don't register any with libev for the same signal). Similarly, when	2111	you don't register any with libev for the same signal).
1982	the last signal watcher for a signal is stopped, libev will reset the
1983	signal handler to SIG_DFL (regardless of what it was set to before).
1984		2112
1985	If possible and supported, libev will install its handlers with	2113	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2114	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	interrupted. If you have a problem with system calls getting interrupted by	2115	not be unduly interrupted. If you have a problem with system calls getting
1988	signals you can block all signals in an C<ev_check> watcher and unblock	2116	interrupted by signals you can block all signals in an C<ev_check> watcher
1989	them in an C<ev_prepare> watcher.	2117	and unblock them in an C<ev_prepare> watcher.
		2118
		2119	=head3 The special problem of inheritance over execve
		2120
		2121	Both the signal mask (C<sigprocmask>) and the signal disposition
		2122	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2123	stopping it again), that is, libev might or might not block the signal,
		2124	and might or might not set or restore the installed signal handler.
		2125
		2126	While this does not matter for the signal disposition (libev never
		2127	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2128	C<execve>), this matters for the signal mask: many programs do not expect
		2129	certain signals to be blocked.
		2130
		2131	This means that before calling C<exec> (from the child) you should reset
		2132	the signal mask to whatever "default" you expect (all clear is a good
		2133	choice usually).
		2134
		2135	The simplest way to ensure that the signal mask is reset in the child is
		2136	to install a fork handler with C<pthread_atfork> that resets it. That will
		2137	catch fork calls done by libraries (such as the libc) as well.
		2138
		2139	In current versions of libev, you can also ensure that the signal mask is
		2140	not blocking any signals (except temporarily, so thread users watch out)
		2141	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2142	is not guaranteed for future versions, however.
1990		2143
1991	=head3 Watcher-Specific Functions and Data Members	2144	=head3 Watcher-Specific Functions and Data Members
1992		2145
1993	=over 4	2146	=over 4
1994		2147
…		…
2039	libev)	2192	libev)
2040		2193
2041	=head3 Process Interaction	2194	=head3 Process Interaction
2042		2195
2043	Libev grabs C<SIGCHLD> as soon as the default event loop is	2196	Libev grabs C<SIGCHLD> as soon as the default event loop is
2044	initialised. This is necessary to guarantee proper behaviour even if	2197	initialised. This is necessary to guarantee proper behaviour even if the
2045	the first child watcher is started after the child exits. The occurrence	2198	first child watcher is started after the child exits. The occurrence
2046	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2199	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2047	synchronously as part of the event loop processing. Libev always reaps all	2200	synchronously as part of the event loop processing. Libev always reaps all
2048	children, even ones not watched.	2201	children, even ones not watched.
2049		2202
2050	=head3 Overriding the Built-In Processing	2203	=head3 Overriding the Built-In Processing
…		…
2060	=head3 Stopping the Child Watcher	2213	=head3 Stopping the Child Watcher
2061		2214
2062	Currently, the child watcher never gets stopped, even when the	2215	Currently, the child watcher never gets stopped, even when the
2063	child terminates, so normally one needs to stop the watcher in the	2216	child terminates, so normally one needs to stop the watcher in the
2064	callback. Future versions of libev might stop the watcher automatically	2217	callback. Future versions of libev might stop the watcher automatically
2065	when a child exit is detected.	2218	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2219	problem).
2066		2220
2067	=head3 Watcher-Specific Functions and Data Members	2221	=head3 Watcher-Specific Functions and Data Members
2068		2222
2069	=over 4	2223	=over 4
2070		2224
…		…
3273	=item Ocaml	3427	=item Ocaml
3274		3428
3275	Erkki Seppala has written Ocaml bindings for libev, to be found at	3429	Erkki Seppala has written Ocaml bindings for libev, to be found at
3276	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3430	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3277		3431
		3432	=item Lua
		3433
		3434	Brian Maher has written a partial interface to libev
		3435	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3436	L<http://github.com/brimworks/lua-ev>.
		3437
3278	=back	3438	=back
3279		3439
3280		3440
3281	=head1 MACRO MAGIC	3441	=head1 MACRO MAGIC
3282		3442
…		…
3448	keeps libev from including F<config.h>, and it also defines dummy	3608	keeps libev from including F<config.h>, and it also defines dummy
3449	implementations for some libevent functions (such as logging, which is not	3609	implementations for some libevent functions (such as logging, which is not
3450	supported). It will also not define any of the structs usually found in	3610	supported). It will also not define any of the structs usually found in
3451	F<event.h> that are not directly supported by the libev core alone.	3611	F<event.h> that are not directly supported by the libev core alone.
3452		3612
3453	In stanbdalone mode, libev will still try to automatically deduce the	3613	In standalone mode, libev will still try to automatically deduce the
3454	configuration, but has to be more conservative.	3614	configuration, but has to be more conservative.
3455		3615
3456	=item EV_USE_MONOTONIC	3616	=item EV_USE_MONOTONIC
3457		3617
3458	If defined to be C<1>, libev will try to detect the availability of the	3618	If defined to be C<1>, libev will try to detect the availability of the
…		…
3523	be used is the winsock select). This means that it will call	3683	be used is the winsock select). This means that it will call
3524	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3684	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3525	it is assumed that all these functions actually work on fds, even	3685	it is assumed that all these functions actually work on fds, even
3526	on win32. Should not be defined on non-win32 platforms.	3686	on win32. Should not be defined on non-win32 platforms.
3527		3687
3528	=item EV_FD_TO_WIN32_HANDLE	3688	=item EV_FD_TO_WIN32_HANDLE(fd)
3529		3689
3530	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3690	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3531	file descriptors to socket handles. When not defining this symbol (the	3691	file descriptors to socket handles. When not defining this symbol (the
3532	default), then libev will call C<_get_osfhandle>, which is usually	3692	default), then libev will call C<_get_osfhandle>, which is usually
3533	correct. In some cases, programs use their own file descriptor management,	3693	correct. In some cases, programs use their own file descriptor management,
3534	in which case they can provide this function to map fds to socket handles.	3694	in which case they can provide this function to map fds to socket handles.
		3695
		3696	=item EV_WIN32_HANDLE_TO_FD(handle)
		3697
		3698	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3699	using the standard C<_open_osfhandle> function. For programs implementing
		3700	their own fd to handle mapping, overwriting this function makes it easier
		3701	to do so. This can be done by defining this macro to an appropriate value.
		3702
		3703	=item EV_WIN32_CLOSE_FD(fd)
		3704
		3705	If programs implement their own fd to handle mapping on win32, then this
		3706	macro can be used to override the C<close> function, useful to unregister
		3707	file descriptors again. Note that the replacement function has to close
		3708	the underlying OS handle.
3535		3709
3536	=item EV_USE_POLL	3710	=item EV_USE_POLL
3537		3711
3538	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3712	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3539	backend. Otherwise it will be enabled on non-win32 platforms. It	3713	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3671	defined to be C<0>, then they are not.	3845	defined to be C<0>, then they are not.
3672		3846
3673	=item EV_MINIMAL	3847	=item EV_MINIMAL
3674		3848
3675	If you need to shave off some kilobytes of code at the expense of some	3849	If you need to shave off some kilobytes of code at the expense of some
3676	speed, define this symbol to C<1>. Currently this is used to override some	3850	speed (but with the full API), define this symbol to C<1>. Currently this
3677	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3851	is used to override some inlining decisions, saves roughly 30% code size
3678	much smaller 2-heap for timer management over the default 4-heap.	3852	on amd64. It also selects a much smaller 2-heap for timer management over
		3853	the default 4-heap.
		3854
		3855	You can save even more by disabling watcher types you do not need
		3856	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3857	(C<-DNDEBUG>) will usually reduce code size a lot.
		3858
		3859	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3860	provide a bare-bones event library. See C<ev.h> for details on what parts
		3861	of the API are still available, and do not complain if this subset changes
		3862	over time.
		3863
		3864	=item EV_NSIG
		3865
		3866	The highest supported signal number, +1 (or, the number of
		3867	signals): Normally, libev tries to deduce the maximum number of signals
		3868	automatically, but sometimes this fails, in which case it can be
		3869	specified. Also, using a lower number than detected (C<32> should be
		3870	good for about any system in existance) can save some memory, as libev
		3871	statically allocates some 12-24 bytes per signal number.
3679		3872
3680	=item EV_PID_HASHSIZE	3873	=item EV_PID_HASHSIZE
3681		3874
3682	C<ev_child> watchers use a small hash table to distribute workload by	3875	C<ev_child> watchers use a small hash table to distribute workload by
3683	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3876	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3869	default loop and triggering an C<ev_async> watcher from the default loop	4062	default loop and triggering an C<ev_async> watcher from the default loop
3870	watcher callback into the event loop interested in the signal.	4063	watcher callback into the event loop interested in the signal.
3871		4064
3872	=back	4065	=back
3873		4066
		4067	=head4 THREAD LOCKING EXAMPLE
		4068
		4069	Here is a fictitious example of how to run an event loop in a different
		4070	thread than where callbacks are being invoked and watchers are
		4071	created/added/removed.
		4072
		4073	For a real-world example, see the C<EV::Loop::Async> perl module,
		4074	which uses exactly this technique (which is suited for many high-level
		4075	languages).
		4076
		4077	The example uses a pthread mutex to protect the loop data, a condition
		4078	variable to wait for callback invocations, an async watcher to notify the
		4079	event loop thread and an unspecified mechanism to wake up the main thread.
		4080
		4081	First, you need to associate some data with the event loop:
		4082
		4083	typedef struct {
		4084	mutex_t lock; /* global loop lock */
		4085	ev_async async_w;
		4086	thread_t tid;
		4087	cond_t invoke_cv;
		4088	} userdata;
		4089
		4090	void prepare_loop (EV_P)
		4091	{
		4092	// for simplicity, we use a static userdata struct.
		4093	static userdata u;
		4094
		4095	ev_async_init (&u->async_w, async_cb);
		4096	ev_async_start (EV_A_ &u->async_w);
		4097
		4098	pthread_mutex_init (&u->lock, 0);
		4099	pthread_cond_init (&u->invoke_cv, 0);
		4100
		4101	// now associate this with the loop
		4102	ev_set_userdata (EV_A_ u);
		4103	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4104	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4105
		4106	// then create the thread running ev_loop
		4107	pthread_create (&u->tid, 0, l_run, EV_A);
		4108	}
		4109
		4110	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4111	solely to wake up the event loop so it takes notice of any new watchers
		4112	that might have been added:
		4113
		4114	static void
		4115	async_cb (EV_P_ ev_async *w, int revents)
		4116	{
		4117	// just used for the side effects
		4118	}
		4119
		4120	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4121	protecting the loop data, respectively.
		4122
		4123	static void
		4124	l_release (EV_P)
		4125	{
		4126	userdata *u = ev_userdata (EV_A);
		4127	pthread_mutex_unlock (&u->lock);
		4128	}
		4129
		4130	static void
		4131	l_acquire (EV_P)
		4132	{
		4133	userdata *u = ev_userdata (EV_A);
		4134	pthread_mutex_lock (&u->lock);
		4135	}
		4136
		4137	The event loop thread first acquires the mutex, and then jumps straight
		4138	into C<ev_loop>:
		4139
		4140	void *
		4141	l_run (void *thr_arg)
		4142	{
		4143	struct ev_loop loop = (struct ev_loop )thr_arg;
		4144
		4145	l_acquire (EV_A);
		4146	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4147	ev_loop (EV_A_ 0);
		4148	l_release (EV_A);
		4149
		4150	return 0;
		4151	}
		4152
		4153	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4154	signal the main thread via some unspecified mechanism (signals? pipe
		4155	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4156	have been called (in a while loop because a) spurious wakeups are possible
		4157	and b) skipping inter-thread-communication when there are no pending
		4158	watchers is very beneficial):
		4159
		4160	static void
		4161	l_invoke (EV_P)
		4162	{
		4163	userdata *u = ev_userdata (EV_A);
		4164
		4165	while (ev_pending_count (EV_A))
		4166	{
		4167	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4168	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4169	}
		4170	}
		4171
		4172	Now, whenever the main thread gets told to invoke pending watchers, it
		4173	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4174	thread to continue:
		4175
		4176	static void
		4177	real_invoke_pending (EV_P)
		4178	{
		4179	userdata *u = ev_userdata (EV_A);
		4180
		4181	pthread_mutex_lock (&u->lock);
		4182	ev_invoke_pending (EV_A);
		4183	pthread_cond_signal (&u->invoke_cv);
		4184	pthread_mutex_unlock (&u->lock);
		4185	}
		4186
		4187	Whenever you want to start/stop a watcher or do other modifications to an
		4188	event loop, you will now have to lock:
		4189
		4190	ev_timer timeout_watcher;
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4194
		4195	pthread_mutex_lock (&u->lock);
		4196	ev_timer_start (EV_A_ &timeout_watcher);
		4197	ev_async_send (EV_A_ &u->async_w);
		4198	pthread_mutex_unlock (&u->lock);
		4199
		4200	Note that sending the C<ev_async> watcher is required because otherwise
		4201	an event loop currently blocking in the kernel will have no knowledge
		4202	about the newly added timer. By waking up the loop it will pick up any new
		4203	watchers in the next event loop iteration.
		4204
3874	=head3 COROUTINES	4205	=head3 COROUTINES
3875		4206
3876	Libev is very accommodating to coroutines ("cooperative threads"):	4207	Libev is very accommodating to coroutines ("cooperative threads"):
3877	libev fully supports nesting calls to its functions from different	4208	libev fully supports nesting calls to its functions from different
3878	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4209	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3879	different coroutines, and switch freely between both coroutines running the	4210	different coroutines, and switch freely between both coroutines running
3880	loop, as long as you don't confuse yourself). The only exception is that	4211	the loop, as long as you don't confuse yourself). The only exception is
3881	you must not do this from C<ev_periodic> reschedule callbacks.	4212	that you must not do this from C<ev_periodic> reschedule callbacks.
3882		4213
3883	Care has been taken to ensure that libev does not keep local state inside	4214	Care has been taken to ensure that libev does not keep local state inside
3884	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4215	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3885	they do not call any callbacks.	4216	they do not call any callbacks.
3886		4217

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Comparing libev/ev.pod (file contents): Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs. Revision 1.271 by root, Fri Sep 18 21:16:10 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.249 by root, Wed Jul 8 04:29:31 2009 UTC vs.
Revision 1.271 by root, Fri Sep 18 21:16:10 2009 UTC