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

Comparing libev/ev.pod (file contents):
Revision 1.244 by root, Mon Jun 29 04:41:34 2009 UTC vs.
Revision 1.273 by root, Tue Nov 24 14:46:59 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
…		…
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.
366		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.
		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,
371	but if that fails, expect a fairly low limit on the number of fds when	387	but if that fails, expect a fairly low limit on the number of fds when
…		…
394		410
395	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and	411	This backend maps C<EV_READ> to C<POLLIN \| POLLERR \| POLLHUP>, and
396	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.	412	C<EV_WRITE> to C<POLLOUT \| POLLERR \| POLLHUP>.
397		413
398	=item C<EVBACKEND_EPOLL> (value 4, Linux)	414	=item C<EVBACKEND_EPOLL> (value 4, Linux)
		415
		416	Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9
		417	kernels).
399		418
400	For few fds, this backend is a bit little slower than poll and select,	419	For few fds, this backend is a bit little slower than poll and select,
401	but it scales phenomenally better. While poll and select usually scale	420	but it scales phenomenally better. While poll and select usually scale
402	like O(total_fds) where n is the total number of fds (or the highest fd),	421	like O(total_fds) where n is the total number of fds (or the highest fd),
403	epoll scales either O(1) or O(active_fds).	422	epoll scales either O(1) or O(active_fds).
…		…
518		537
519	It is definitely not recommended to use this flag.	538	It is definitely not recommended to use this flag.
520		539
521	=back	540	=back
522		541
523	If one or more of these are or'ed into the flags value, then only these	542	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	543	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.	544	here). If none are specified, all backends in C<ev_recommended_backends
		545	()> will be tried.
526		546
527	Example: This is the most typical usage.	547	Example: This is the most typical usage.
528		548
529	if (!ev_default_loop (0))	549	if (!ev_default_loop (0))
530	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");	550	fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
…		…
573	as signal and child watchers) would need to be stopped manually.	593	as signal and child watchers) would need to be stopped manually.
574		594
575	In general it is not advisable to call this function except in the	595	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	596	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	597	pipe fds. If you need dynamically allocated loops it is better to use
578	C<ev_loop_new> and C<ev_loop_destroy>).	598	C<ev_loop_new> and C<ev_loop_destroy>.
579		599
580	=item ev_loop_destroy (loop)	600	=item ev_loop_destroy (loop)
581		601
582	Like C<ev_default_destroy>, but destroys an event loop created by an	602	Like C<ev_default_destroy>, but destroys an event loop created by an
583	earlier call to C<ev_loop_new>.	603	earlier call to C<ev_loop_new>.
…		…
621		641
622	This value can sometimes be useful as a generation counter of sorts (it	642	This value can sometimes be useful as a generation counter of sorts (it
623	"ticks" the number of loop iterations), as it roughly corresponds with	643	"ticks" the number of loop iterations), as it roughly corresponds with
624	C<ev_prepare> and C<ev_check> calls.	644	C<ev_prepare> and C<ev_check> calls.
625		645
		646	=item unsigned int ev_loop_depth (loop)
		647
		648	Returns the number of times C<ev_loop> was entered minus the number of
		649	times C<ev_loop> was exited, in other words, the recursion depth.
		650
		651	Outside C<ev_loop>, this number is zero. In a callback, this number is
		652	C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
		653	in which case it is higher.
		654
		655	Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
		656	etc.), doesn't count as exit.
		657
626	=item unsigned int ev_backend (loop)	658	=item unsigned int ev_backend (loop)
627		659
628	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	660	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
629	use.	661	use.
630		662
…		…
675	event loop time (see C<ev_now_update>).	707	event loop time (see C<ev_now_update>).
676		708
677	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
678		710
679	Finally, this is it, the event handler. This function usually is called	711	Finally, this is it, the event handler. This function usually is called
680	after you initialised all your watchers and you want to start handling	712	after you have initialised all your watchers and you want to start
681	events.	713	handling events.
682		714
683	If the flags argument is specified as C<0>, it will not return until	715	If the flags argument is specified as C<0>, it will not return until
684	either no event watchers are active anymore or C<ev_unloop> was called.	716	either no event watchers are active anymore or C<ev_unloop> was called.
685		717
686	Please note that an explicit C<ev_unloop> is usually better than	718	Please note that an explicit C<ev_unloop> is usually better than
…		…
811		843
812	By setting a higher I<io collect interval> you allow libev to spend more	844	By setting a higher I<io collect interval> you allow libev to spend more
813	time collecting I/O events, so you can handle more events per iteration,	845	time collecting I/O events, so you can handle more events per iteration,
814	at the cost of increasing latency. Timeouts (both C<ev_periodic> and	846	at the cost of increasing latency. Timeouts (both C<ev_periodic> and
815	C<ev_timer>) will be not affected. Setting this to a non-null value will	847	C<ev_timer>) will be not affected. Setting this to a non-null value will
816	introduce an additional C<ev_sleep ()> call into most loop iterations.	848	introduce an additional C<ev_sleep ()> call into most loop iterations. The
		849	sleep time ensures that libev will not poll for I/O events more often then
		850	once per this interval, on average.
817		851
818	Likewise, by setting a higher I<timeout collect interval> you allow libev	852	Likewise, by setting a higher I<timeout collect interval> you allow libev
819	to spend more time collecting timeouts, at the expense of increased	853	to spend more time collecting timeouts, at the expense of increased
820	latency/jitter/inexactness (the watcher callback will be called	854	latency/jitter/inexactness (the watcher callback will be called
821	later). C<ev_io> watchers will not be affected. Setting this to a non-null	855	later). C<ev_io> watchers will not be affected. Setting this to a non-null
…		…
823		857
824	Many (busy) programs can usually benefit by setting the I/O collect	858	Many (busy) programs can usually benefit by setting the I/O collect
825	interval to a value near C<0.1> or so, which is often enough for	859	interval to a value near C<0.1> or so, which is often enough for
826	interactive servers (of course not for games), likewise for timeouts. It	860	interactive servers (of course not for games), likewise for timeouts. It
827	usually doesn't make much sense to set it to a lower value than C<0.01>,	861	usually doesn't make much sense to set it to a lower value than C<0.01>,
828	as this approaches the timing granularity of most systems.	862	as this approaches the timing granularity of most systems. Note that if
		863	you do transactions with the outside world and you can't increase the
		864	parallelity, then this setting will limit your transaction rate (if you
		865	need to poll once per transaction and the I/O collect interval is 0.01,
		866	then you can't do more than 100 transations per second).
829		867
830	Setting the I<timeout collect interval> can improve the opportunity for	868	Setting the I<timeout collect interval> can improve the opportunity for
831	saving power, as the program will "bundle" timer callback invocations that	869	saving power, as the program will "bundle" timer callback invocations that
832	are "near" in time together, by delaying some, thus reducing the number of	870	are "near" in time together, by delaying some, thus reducing the number of
833	times the process sleeps and wakes up again. Another useful technique to	871	times the process sleeps and wakes up again. Another useful technique to
834	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure	872	reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure
835	they fire on, say, one-second boundaries only.	873	they fire on, say, one-second boundaries only.
		874
		875	Example: we only need 0.1s timeout granularity, and we wish not to poll
		876	more often than 100 times per second:
		877
		878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
		879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
		880
		881	=item ev_invoke_pending (loop)
		882
		883	This call will simply invoke all pending watchers while resetting their
		884	pending state. Normally, C<ev_loop> does this automatically when required,
		885	but when overriding the invoke callback this call comes handy.
		886
		887	=item int ev_pending_count (loop)
		888
		889	Returns the number of pending watchers - zero indicates that no watchers
		890	are pending.
		891
		892	=item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P))
		893
		894	This overrides the invoke pending functionality of the loop: Instead of
		895	invoking all pending watchers when there are any, C<ev_loop> will call
		896	this callback instead. This is useful, for example, when you want to
		897	invoke the actual watchers inside another context (another thread etc.).
		898
		899	If you want to reset the callback, use C<ev_invoke_pending> as new
		900	callback.
		901
		902	=item ev_set_loop_release_cb (loop, void (release)(EV_P), void (acquire)(EV_P))
		903
		904	Sometimes you want to share the same loop between multiple threads. This
		905	can be done relatively simply by putting mutex_lock/unlock calls around
		906	each call to a libev function.
		907
		908	However, C<ev_loop> can run an indefinite time, so it is not feasible to
		909	wait for it to return. One way around this is to wake up the loop via
		910	C<ev_unloop> and C<av_async_send>, another way is to set these I<release>
		911	and I<acquire> callbacks on the loop.
		912
		913	When set, then C<release> will be called just before the thread is
		914	suspended waiting for new events, and C<acquire> is called just
		915	afterwards.
		916
		917	Ideally, C<release> will just call your mutex_unlock function, and
		918	C<acquire> will just call the mutex_lock function again.
		919
		920	While event loop modifications are allowed between invocations of
		921	C<release> and C<acquire> (that's their only purpose after all), no
		922	modifications done will affect the event loop, i.e. adding watchers will
		923	have no effect on the set of file descriptors being watched, or the time
		924	waited. USe an C<ev_async> watcher to wake up C<ev_loop> when you want it
		925	to take note of any changes you made.
		926
		927	In theory, threads executing C<ev_loop> will be async-cancel safe between
		928	invocations of C<release> and C<acquire>.
		929
		930	See also the locking example in the C<THREADS> section later in this
		931	document.
		932
		933	=item ev_set_userdata (loop, void *data)
		934
		935	=item ev_userdata (loop)
		936
		937	Set and retrieve a single C<void *> associated with a loop. When
		938	C<ev_set_userdata> has never been called, then C<ev_userdata> returns
		939	C<0.>
		940
		941	These two functions can be used to associate arbitrary data with a loop,
		942	and are intended solely for the C<invoke_pending_cb>, C<release> and
		943	C<acquire> callbacks described above, but of course can be (ab-)used for
		944	any other purpose as well.
836		945
837	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
838		947
839	This function only does something when C<EV_VERIFY> support has been	948	This function only does something when C<EV_VERIFY> support has been
840	compiled in, which is the default for non-minimal builds. It tries to go	949	compiled in, which is the default for non-minimal builds. It tries to go
…		…
1126	returns its C<revents> bitset (as if its callback was invoked). If the	1235	returns its C<revents> bitset (as if its callback was invoked). If the
1127	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1128		1237
1129	Sometimes it can be useful to "poll" a watcher instead of waiting for its	1238	Sometimes it can be useful to "poll" a watcher instead of waiting for its
1130	callback to be invoked, which can be accomplished with this function.	1239	callback to be invoked, which can be accomplished with this function.
		1240
		1241	=item ev_feed_event (struct ev_loop , watcher , int revents)
		1242
		1243	Feeds the given event set into the event loop, as if the specified event
		1244	had happened for the specified watcher (which must be a pointer to an
		1245	initialised but not necessarily started event watcher). Obviously you must
		1246	not free the watcher as long as it has pending events.
		1247
		1248	Stopping the watcher, letting libev invoke it, or calling
		1249	C<ev_clear_pending> will clear the pending event, even if the watcher was
		1250	not started in the first place.
		1251
		1252	See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related
		1253	functions that do not need a watcher.
1131		1254
1132	=back	1255	=back
1133		1256
1134		1257
1135	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1468		1591
1469	The callback is guaranteed to be invoked only I<after> its timeout has	1592	The callback is guaranteed to be invoked only I<after> its timeout has
1470	passed (not I<at>, so on systems with very low-resolution clocks this	1593	passed (not I<at>, so on systems with very low-resolution clocks this
1471	might introduce a small delay). If multiple timers become ready during the	1594	might introduce a small delay). If multiple timers become ready during the
1472	same loop iteration then the ones with earlier time-out values are invoked	1595	same loop iteration then the ones with earlier time-out values are invoked
1473	before ones with later time-out values (but this is no longer true when a	1596	before ones of the same priority with later time-out values (but this is
1474	callback calls C<ev_loop> recursively).	1597	no longer true when a callback calls C<ev_loop> recursively).
1475		1598
1476	=head3 Be smart about timeouts	1599	=head3 Be smart about timeouts
1477		1600
1478	Many real-world problems involve some kind of timeout, usually for error	1601	Many real-world problems involve some kind of timeout, usually for error
1479	recovery. A typical example is an HTTP request - if the other side hangs,	1602	recovery. A typical example is an HTTP request - if the other side hangs,
…		…
1666		1789
1667	If the event loop is suspended for a long time, you can also force an	1790	If the event loop is suspended for a long time, you can also force an
1668	update of the time returned by C<ev_now ()> by calling C<ev_now_update	1791	update of the time returned by C<ev_now ()> by calling C<ev_now_update
1669	()>.	1792	()>.
1670		1793
		1794	=head3 The special problems of suspended animation
		1795
		1796	When you leave the server world it is quite customary to hit machines that
		1797	can suspend/hibernate - what happens to the clocks during such a suspend?
		1798
		1799	Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes
		1800	all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue
		1801	to run until the system is suspended, but they will not advance while the
		1802	system is suspended. That means, on resume, it will be as if the program
		1803	was frozen for a few seconds, but the suspend time will not be counted
		1804	towards C<ev_timer> when a monotonic clock source is used. The real time
		1805	clock advanced as expected, but if it is used as sole clocksource, then a
		1806	long suspend would be detected as a time jump by libev, and timers would
		1807	be adjusted accordingly.
		1808
		1809	I would not be surprised to see different behaviour in different between
		1810	operating systems, OS versions or even different hardware.
		1811
		1812	The other form of suspend (job control, or sending a SIGSTOP) will see a
		1813	time jump in the monotonic clocks and the realtime clock. If the program
		1814	is suspended for a very long time, and monotonic clock sources are in use,
		1815	then you can expect C<ev_timer>s to expire as the full suspension time
		1816	will be counted towards the timers. When no monotonic clock source is in
		1817	use, then libev will again assume a timejump and adjust accordingly.
		1818
		1819	It might be beneficial for this latter case to call C<ev_suspend>
		1820	and C<ev_resume> in code that handles C<SIGTSTP>, to at least get
		1821	deterministic behaviour in this case (you can do nothing against
		1822	C<SIGSTOP>).
		1823
1671	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1672		1825
1673	=over 4	1826	=over 4
1674		1827
1675	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)	1828	=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
…		…
1700	If the timer is repeating, either start it if necessary (with the	1853	If the timer is repeating, either start it if necessary (with the
1701	C<repeat> value), or reset the running timer to the C<repeat> value.	1854	C<repeat> value), or reset the running timer to the C<repeat> value.
1702		1855
1703	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a	1856	This sounds a bit complicated, see L<Be smart about timeouts>, above, for a
1704	usage example.	1857	usage example.
		1858
		1859	=item ev_timer_remaining (loop, ev_timer *)
		1860
		1861	Returns the remaining time until a timer fires. If the timer is active,
		1862	then this time is relative to the current event loop time, otherwise it's
		1863	the timeout value currently configured.
		1864
		1865	That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
		1866	C<5>. When the timer is started and one second passes, C<ev_timer_remain>
		1867	will return C<4>. When the timer expires and is restarted, it will return
		1868	roughly C<7> (likely slightly less as callback invocation takes some time,
		1869	too), and so on.
1705		1870
1706	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1707		1872
1708	The current C<repeat> value. Will be used each time the watcher times out	1873	The current C<repeat> value. Will be used each time the watcher times out
1709	or C<ev_timer_again> is called, and determines the next timeout (if any),	1874	or C<ev_timer_again> is called, and determines the next timeout (if any),
…		…
1945	Signal watchers will trigger an event when the process receives a specific	2110	Signal watchers will trigger an event when the process receives a specific
1946	signal one or more times. Even though signals are very asynchronous, libev	2111	signal one or more times. Even though signals are very asynchronous, libev
1947	will try it's best to deliver signals synchronously, i.e. as part of the	2112	will try it's best to deliver signals synchronously, i.e. as part of the
1948	normal event processing, like any other event.	2113	normal event processing, like any other event.
1949		2114
1950	If you want signals asynchronously, just use C<sigaction> as you would	2115	If you want signals to be delivered truly asynchronously, just use
1951	do without libev and forget about sharing the signal. You can even use	2116	C<sigaction> as you would do without libev and forget about sharing
1952	C<ev_async> from a signal handler to synchronously wake up an event loop.	2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
1953		2119
1954	You can configure as many watchers as you like per signal. Only when the	2120	You can configure as many watchers as you like for the same signal, but
		2121	only within the same loop, i.e. you can watch for C<SIGINT> in your
		2122	default loop and for C<SIGIO> in another loop, but you cannot watch for
		2123	C<SIGINT> in both the default loop and another loop at the same time. At
		2124	the moment, C<SIGCHLD> is permanently tied to the default loop.
		2125
1955	first watcher gets started will libev actually register a signal handler	2126	When the first watcher gets started will libev actually register something
1956	with the kernel (thus it coexists with your own signal handlers as long as	2127	with the kernel (thus it coexists with your own signal handlers as long as
1957	you don't register any with libev for the same signal). Similarly, when	2128	you don't register any with libev for the same signal).
1958	the last signal watcher for a signal is stopped, libev will reset the
1959	signal handler to SIG_DFL (regardless of what it was set to before).
1960		2129
1961	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1962	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1963	interrupted. If you have a problem with system calls getting interrupted by	2132	not be unduly interrupted. If you have a problem with system calls getting
1964	signals you can block all signals in an C<ev_check> watcher and unblock	2133	interrupted by signals you can block all signals in an C<ev_check> watcher
1965	them in an C<ev_prepare> watcher.	2134	and unblock them in an C<ev_prepare> watcher.
		2135
		2136	=head3 The special problem of inheritance over execve
		2137
		2138	Both the signal mask (C<sigprocmask>) and the signal disposition
		2139	(C<sigaction>) are unspecified after starting a signal watcher (and after
		2140	stopping it again), that is, libev might or might not block the signal,
		2141	and might or might not set or restore the installed signal handler.
		2142
		2143	While this does not matter for the signal disposition (libev never
		2144	sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on
		2145	C<execve>), this matters for the signal mask: many programs do not expect
		2146	certain signals to be blocked.
		2147
		2148	This means that before calling C<exec> (from the child) you should reset
		2149	the signal mask to whatever "default" you expect (all clear is a good
		2150	choice usually).
		2151
		2152	The simplest way to ensure that the signal mask is reset in the child is
		2153	to install a fork handler with C<pthread_atfork> that resets it. That will
		2154	catch fork calls done by libraries (such as the libc) as well.
		2155
		2156	In current versions of libev, you can also ensure that the signal mask is
		2157	not blocking any signals (except temporarily, so thread users watch out)
		2158	by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This
		2159	is not guaranteed for future versions, however.
1966		2160
1967	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1968		2162
1969	=over 4	2163	=over 4
1970		2164
…		…
2008	in the next callback invocation is not.	2202	in the next callback invocation is not.
2009		2203
2010	Only the default event loop is capable of handling signals, and therefore	2204	Only the default event loop is capable of handling signals, and therefore
2011	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
2012		2206
		2207	Due to some design glitches inside libev, child watchers will always be
		2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
		2210
2013	=head3 Process Interaction	2211	=head3 Process Interaction
2014		2212
2015	Libev grabs C<SIGCHLD> as soon as the default event loop is	2213	Libev grabs C<SIGCHLD> as soon as the default event loop is
2016	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
2017	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
2018	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2019	synchronously as part of the event loop processing. Libev always reaps all	2217	synchronously as part of the event loop processing. Libev always reaps all
2020	children, even ones not watched.	2218	children, even ones not watched.
2021		2219
2022	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
2032	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
2033		2231
2034	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
2035	child terminates, so normally one needs to stop the watcher in the	2233	child terminates, so normally one needs to stop the watcher in the
2036	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
2037	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
2038		2237
2039	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
2040		2239
2041	=over 4	2240	=over 4
2042		2241
…		…
2950	/* doh, nothing entered */;	3149	/* doh, nothing entered */;
2951	}	3150	}
2952		3151
2953	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3152	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2954		3153
2955	=item ev_feed_event (struct ev_loop , watcher , int revents)
2956
2957	Feeds the given event set into the event loop, as if the specified event
2958	had happened for the specified watcher (which must be a pointer to an
2959	initialised but not necessarily started event watcher).
2960
2961	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3154	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2962		3155
2963	Feed an event on the given fd, as if a file descriptor backend detected	3156	Feed an event on the given fd, as if a file descriptor backend detected
2964	the given events it.	3157	the given events it.
2965		3158
…		…
3245	=item Ocaml	3438	=item Ocaml
3246		3439
3247	Erkki Seppala has written Ocaml bindings for libev, to be found at	3440	Erkki Seppala has written Ocaml bindings for libev, to be found at
3248	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3441	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3249		3442
		3443	=item Lua
		3444
		3445	Brian Maher has written a partial interface to libev
		3446	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3447	L<http://github.com/brimworks/lua-ev>.
		3448
3250	=back	3449	=back
3251		3450
3252		3451
3253	=head1 MACRO MAGIC	3452	=head1 MACRO MAGIC
3254		3453
…		…
3420	keeps libev from including F<config.h>, and it also defines dummy	3619	keeps libev from including F<config.h>, and it also defines dummy
3421	implementations for some libevent functions (such as logging, which is not	3620	implementations for some libevent functions (such as logging, which is not
3422	supported). It will also not define any of the structs usually found in	3621	supported). It will also not define any of the structs usually found in
3423	F<event.h> that are not directly supported by the libev core alone.	3622	F<event.h> that are not directly supported by the libev core alone.
3424		3623
3425	In stanbdalone mode, libev will still try to automatically deduce the	3624	In standalone mode, libev will still try to automatically deduce the
3426	configuration, but has to be more conservative.	3625	configuration, but has to be more conservative.
3427		3626
3428	=item EV_USE_MONOTONIC	3627	=item EV_USE_MONOTONIC
3429		3628
3430	If defined to be C<1>, libev will try to detect the availability of the	3629	If defined to be C<1>, libev will try to detect the availability of the
…		…
3495	be used is the winsock select). This means that it will call	3694	be used is the winsock select). This means that it will call
3496	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3695	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3497	it is assumed that all these functions actually work on fds, even	3696	it is assumed that all these functions actually work on fds, even
3498	on win32. Should not be defined on non-win32 platforms.	3697	on win32. Should not be defined on non-win32 platforms.
3499		3698
3500	=item EV_FD_TO_WIN32_HANDLE	3699	=item EV_FD_TO_WIN32_HANDLE(fd)
3501		3700
3502	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3701	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3503	file descriptors to socket handles. When not defining this symbol (the	3702	file descriptors to socket handles. When not defining this symbol (the
3504	default), then libev will call C<_get_osfhandle>, which is usually	3703	default), then libev will call C<_get_osfhandle>, which is usually
3505	correct. In some cases, programs use their own file descriptor management,	3704	correct. In some cases, programs use their own file descriptor management,
3506	in which case they can provide this function to map fds to socket handles.	3705	in which case they can provide this function to map fds to socket handles.
		3706
		3707	=item EV_WIN32_HANDLE_TO_FD(handle)
		3708
		3709	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3710	using the standard C<_open_osfhandle> function. For programs implementing
		3711	their own fd to handle mapping, overwriting this function makes it easier
		3712	to do so. This can be done by defining this macro to an appropriate value.
		3713
		3714	=item EV_WIN32_CLOSE_FD(fd)
		3715
		3716	If programs implement their own fd to handle mapping on win32, then this
		3717	macro can be used to override the C<close> function, useful to unregister
		3718	file descriptors again. Note that the replacement function has to close
		3719	the underlying OS handle.
3507		3720
3508	=item EV_USE_POLL	3721	=item EV_USE_POLL
3509		3722
3510	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3723	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3511	backend. Otherwise it will be enabled on non-win32 platforms. It	3724	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3643	defined to be C<0>, then they are not.	3856	defined to be C<0>, then they are not.
3644		3857
3645	=item EV_MINIMAL	3858	=item EV_MINIMAL
3646		3859
3647	If you need to shave off some kilobytes of code at the expense of some	3860	If you need to shave off some kilobytes of code at the expense of some
3648	speed, define this symbol to C<1>. Currently this is used to override some	3861	speed (but with the full API), define this symbol to C<1>. Currently this
3649	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3862	is used to override some inlining decisions, saves roughly 30% code size
3650	much smaller 2-heap for timer management over the default 4-heap.	3863	on amd64. It also selects a much smaller 2-heap for timer management over
		3864	the default 4-heap.
		3865
		3866	You can save even more by disabling watcher types you do not need
		3867	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3868	(C<-DNDEBUG>) will usually reduce code size a lot.
		3869
		3870	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3871	provide a bare-bones event library. See C<ev.h> for details on what parts
		3872	of the API are still available, and do not complain if this subset changes
		3873	over time.
		3874
		3875	=item EV_NSIG
		3876
		3877	The highest supported signal number, +1 (or, the number of
		3878	signals): Normally, libev tries to deduce the maximum number of signals
		3879	automatically, but sometimes this fails, in which case it can be
		3880	specified. Also, using a lower number than detected (C<32> should be
		3881	good for about any system in existance) can save some memory, as libev
		3882	statically allocates some 12-24 bytes per signal number.
3651		3883
3652	=item EV_PID_HASHSIZE	3884	=item EV_PID_HASHSIZE
3653		3885
3654	C<ev_child> watchers use a small hash table to distribute workload by	3886	C<ev_child> watchers use a small hash table to distribute workload by
3655	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3887	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3841	default loop and triggering an C<ev_async> watcher from the default loop	4073	default loop and triggering an C<ev_async> watcher from the default loop
3842	watcher callback into the event loop interested in the signal.	4074	watcher callback into the event loop interested in the signal.
3843		4075
3844	=back	4076	=back
3845		4077
		4078	=head4 THREAD LOCKING EXAMPLE
		4079
		4080	Here is a fictitious example of how to run an event loop in a different
		4081	thread than where callbacks are being invoked and watchers are
		4082	created/added/removed.
		4083
		4084	For a real-world example, see the C<EV::Loop::Async> perl module,
		4085	which uses exactly this technique (which is suited for many high-level
		4086	languages).
		4087
		4088	The example uses a pthread mutex to protect the loop data, a condition
		4089	variable to wait for callback invocations, an async watcher to notify the
		4090	event loop thread and an unspecified mechanism to wake up the main thread.
		4091
		4092	First, you need to associate some data with the event loop:
		4093
		4094	typedef struct {
		4095	mutex_t lock; /* global loop lock */
		4096	ev_async async_w;
		4097	thread_t tid;
		4098	cond_t invoke_cv;
		4099	} userdata;
		4100
		4101	void prepare_loop (EV_P)
		4102	{
		4103	// for simplicity, we use a static userdata struct.
		4104	static userdata u;
		4105
		4106	ev_async_init (&u->async_w, async_cb);
		4107	ev_async_start (EV_A_ &u->async_w);
		4108
		4109	pthread_mutex_init (&u->lock, 0);
		4110	pthread_cond_init (&u->invoke_cv, 0);
		4111
		4112	// now associate this with the loop
		4113	ev_set_userdata (EV_A_ u);
		4114	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4115	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4116
		4117	// then create the thread running ev_loop
		4118	pthread_create (&u->tid, 0, l_run, EV_A);
		4119	}
		4120
		4121	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4122	solely to wake up the event loop so it takes notice of any new watchers
		4123	that might have been added:
		4124
		4125	static void
		4126	async_cb (EV_P_ ev_async *w, int revents)
		4127	{
		4128	// just used for the side effects
		4129	}
		4130
		4131	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4132	protecting the loop data, respectively.
		4133
		4134	static void
		4135	l_release (EV_P)
		4136	{
		4137	userdata *u = ev_userdata (EV_A);
		4138	pthread_mutex_unlock (&u->lock);
		4139	}
		4140
		4141	static void
		4142	l_acquire (EV_P)
		4143	{
		4144	userdata *u = ev_userdata (EV_A);
		4145	pthread_mutex_lock (&u->lock);
		4146	}
		4147
		4148	The event loop thread first acquires the mutex, and then jumps straight
		4149	into C<ev_loop>:
		4150
		4151	void *
		4152	l_run (void *thr_arg)
		4153	{
		4154	struct ev_loop loop = (struct ev_loop )thr_arg;
		4155
		4156	l_acquire (EV_A);
		4157	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4158	ev_loop (EV_A_ 0);
		4159	l_release (EV_A);
		4160
		4161	return 0;
		4162	}
		4163
		4164	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4165	signal the main thread via some unspecified mechanism (signals? pipe
		4166	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4167	have been called (in a while loop because a) spurious wakeups are possible
		4168	and b) skipping inter-thread-communication when there are no pending
		4169	watchers is very beneficial):
		4170
		4171	static void
		4172	l_invoke (EV_P)
		4173	{
		4174	userdata *u = ev_userdata (EV_A);
		4175
		4176	while (ev_pending_count (EV_A))
		4177	{
		4178	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4179	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4180	}
		4181	}
		4182
		4183	Now, whenever the main thread gets told to invoke pending watchers, it
		4184	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4185	thread to continue:
		4186
		4187	static void
		4188	real_invoke_pending (EV_P)
		4189	{
		4190	userdata *u = ev_userdata (EV_A);
		4191
		4192	pthread_mutex_lock (&u->lock);
		4193	ev_invoke_pending (EV_A);
		4194	pthread_cond_signal (&u->invoke_cv);
		4195	pthread_mutex_unlock (&u->lock);
		4196	}
		4197
		4198	Whenever you want to start/stop a watcher or do other modifications to an
		4199	event loop, you will now have to lock:
		4200
		4201	ev_timer timeout_watcher;
		4202	userdata *u = ev_userdata (EV_A);
		4203
		4204	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4205
		4206	pthread_mutex_lock (&u->lock);
		4207	ev_timer_start (EV_A_ &timeout_watcher);
		4208	ev_async_send (EV_A_ &u->async_w);
		4209	pthread_mutex_unlock (&u->lock);
		4210
		4211	Note that sending the C<ev_async> watcher is required because otherwise
		4212	an event loop currently blocking in the kernel will have no knowledge
		4213	about the newly added timer. By waking up the loop it will pick up any new
		4214	watchers in the next event loop iteration.
		4215
3846	=head3 COROUTINES	4216	=head3 COROUTINES
3847		4217
3848	Libev is very accommodating to coroutines ("cooperative threads"):	4218	Libev is very accommodating to coroutines ("cooperative threads"):
3849	libev fully supports nesting calls to its functions from different	4219	libev fully supports nesting calls to its functions from different
3850	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4220	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3851	different coroutines, and switch freely between both coroutines running the	4221	different coroutines, and switch freely between both coroutines running
3852	loop, as long as you don't confuse yourself). The only exception is that	4222	the loop, as long as you don't confuse yourself). The only exception is
3853	you must not do this from C<ev_periodic> reschedule callbacks.	4223	that you must not do this from C<ev_periodic> reschedule callbacks.
3854		4224
3855	Care has been taken to ensure that libev does not keep local state inside	4225	Care has been taken to ensure that libev does not keep local state inside
3856	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4226	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3857	they do not call any callbacks.	4227	they do not call any callbacks.
3858		4228
…		…
4065	=item C<double> must hold a time value in seconds with enough accuracy	4435	=item C<double> must hold a time value in seconds with enough accuracy
4066		4436
4067	The type C<double> is used to represent timestamps. It is required to	4437	The type C<double> is used to represent timestamps. It is required to
4068	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	4438	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
4069	enough for at least into the year 4000. This requirement is fulfilled by	4439	enough for at least into the year 4000. This requirement is fulfilled by
4070	implementations implementing IEEE 754 (basically all existing ones).	4440	implementations implementing IEEE 754, which is basically all existing
		4441	ones. With IEEE 754 doubles, you get microsecond accuracy until at least
		4442	2200.
4071		4443
4072	=back	4444	=back
4073		4445
4074	If you know of other additional requirements drop me a note.	4446	If you know of other additional requirements drop me a note.
4075		4447

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Comparing libev/ev.pod (file contents): Revision 1.244 by root, Mon Jun 29 04:41:34 2009 UTC vs. Revision 1.273 by root, Tue Nov 24 14:46:59 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.244 by root, Mon Jun 29 04:41:34 2009 UTC vs.
Revision 1.273 by root, Tue Nov 24 14:46:59 2009 UTC