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

Comparing libev/ev.pod (file contents):
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.275 by root, Sat Dec 26 09:21:54 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
…		…
117	Libev is very configurable. In this manual the default (and most common)	118	Libev is very configurable. In this manual the default (and most common)
118	configuration will be described, which supports multiple event loops. For	119	configuration will be described, which supports multiple event loops. For
119	more info about various configuration options please have a look at	120	more info about various configuration options please have a look at
120	B<EMBED> section in this manual. If libev was configured without support	121	B<EMBED> section in this manual. If libev was configured without support
121	for multiple event loops, then all functions taking an initial argument of	122	for multiple event loops, then all functions taking an initial argument of
122	name C<loop> (which is always of type C<ev_loop *>) will not have	123	name C<loop> (which is always of type C<struct ev_loop *>) will not have
123	this argument.	124	this argument.
124		125
125	=head2 TIME REPRESENTATION	126	=head2 TIME REPRESENTATION
126		127
127	Libev represents time as a single floating point number, representing	128	Libev represents time as a single floating point number, representing
…		…
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>.
…		…
687	event loop time (see C<ev_now_update>).	707	event loop time (see C<ev_now_update>).
688		708
689	=item ev_loop (loop, int flags)	709	=item ev_loop (loop, int flags)
690		710
691	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
692	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
693	events.	713	handling events.
694		714
695	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
696	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.
697		717
698	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
…		…
856	more often than 100 times per second:	876	more often than 100 times per second:
857		877
858	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);	878	ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1);
859	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);	879	ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01);
860		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.
		945
861	=item ev_loop_verify (loop)	946	=item ev_loop_verify (loop)
862		947
863	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
864	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
865	through all internal structures and checks them for validity. If anything	950	through all internal structures and checks them for validity. If anything
…		…
1041		1126
1042	ev_io w;	1127	ev_io w;
1043	ev_init (&w, my_cb);	1128	ev_init (&w, my_cb);
1044	ev_io_set (&w, STDIN_FILENO, EV_READ);	1129	ev_io_set (&w, STDIN_FILENO, EV_READ);
1045		1130
1046	=item C<ev_TYPE_set> (ev_TYPE *, [args])	1131	=item C<ev_TYPE_set> (ev_TYPE *watcher, [args])
1047		1132
1048	This macro initialises the type-specific parts of a watcher. You need to	1133	This macro initialises the type-specific parts of a watcher. You need to
1049	call C<ev_init> at least once before you call this macro, but you can	1134	call C<ev_init> at least once before you call this macro, but you can
1050	call C<ev_TYPE_set> any number of times. You must not, however, call this	1135	call C<ev_TYPE_set> any number of times. You must not, however, call this
1051	macro on a watcher that is active (it can be pending, however, which is a	1136	macro on a watcher that is active (it can be pending, however, which is a
…		…
1064		1149
1065	Example: Initialise and set an C<ev_io> watcher in one step.	1150	Example: Initialise and set an C<ev_io> watcher in one step.
1066		1151
1067	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);	1152	ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ);
1068		1153
1069	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)	1154	=item C<ev_TYPE_start> (loop, ev_TYPE *watcher)
1070		1155
1071	Starts (activates) the given watcher. Only active watchers will receive	1156	Starts (activates) the given watcher. Only active watchers will receive
1072	events. If the watcher is already active nothing will happen.	1157	events. If the watcher is already active nothing will happen.
1073		1158
1074	Example: Start the C<ev_io> watcher that is being abused as example in this	1159	Example: Start the C<ev_io> watcher that is being abused as example in this
1075	whole section.	1160	whole section.
1076		1161
1077	ev_io_start (EV_DEFAULT_UC, &w);	1162	ev_io_start (EV_DEFAULT_UC, &w);
1078		1163
1079	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	1164	=item C<ev_TYPE_stop> (loop, ev_TYPE *watcher)
1080		1165
1081	Stops the given watcher if active, and clears the pending status (whether	1166	Stops the given watcher if active, and clears the pending status (whether
1082	the watcher was active or not).	1167	the watcher was active or not).
1083		1168
1084	It is possible that stopped watchers are pending - for example,	1169	It is possible that stopped watchers are pending - for example,
…		…
1109	=item ev_cb_set (ev_TYPE *watcher, callback)	1194	=item ev_cb_set (ev_TYPE *watcher, callback)
1110		1195
1111	Change the callback. You can change the callback at virtually any time	1196	Change the callback. You can change the callback at virtually any time
1112	(modulo threads).	1197	(modulo threads).
1113		1198
1114	=item ev_set_priority (ev_TYPE *watcher, priority)	1199	=item ev_set_priority (ev_TYPE *watcher, int priority)
1115		1200
1116	=item int ev_priority (ev_TYPE *watcher)	1201	=item int ev_priority (ev_TYPE *watcher)
1117		1202
1118	Set and query the priority of the watcher. The priority is a small	1203	Set and query the priority of the watcher. The priority is a small
1119	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>	1204	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
…		…
1150	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
1151	watcher isn't pending it does nothing and returns C<0>.	1236	watcher isn't pending it does nothing and returns C<0>.
1152		1237
1153	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
1154	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 (loop, ev_TYPE *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.
1155		1254
1156	=back	1255	=back
1157		1256
1158		1257
1159	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	1258	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1690		1789
1691	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
1692	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
1693	()>.	1792	()>.
1694		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
1695	=head3 Watcher-Specific Functions and Data Members	1824	=head3 Watcher-Specific Functions and Data Members
1696		1825
1697	=over 4	1826	=over 4
1698		1827
1699	=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)
…		…
1724	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
1725	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.
1726		1855
1727	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
1728	usage example.	1857	usage example.
		1858
		1859	=item ev_tstamp 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.
1729		1870
1730	=item ev_tstamp repeat [read-write]	1871	=item ev_tstamp repeat [read-write]
1731		1872
1732	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
1733	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),
…		…
1969	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
1970	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
1971	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
1972	normal event processing, like any other event.	2113	normal event processing, like any other event.
1973		2114
1974	If you want signals asynchronously, just use C<sigaction> as you would	2115	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	2116	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.	2117	the signal. You can even use C<ev_async> from a signal handler to
		2118	synchronously wake up an event loop.
1977		2119
1978	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
1979	first watcher gets started will libev actually register a signal handler	2126	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	2127	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	2128	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		2129
1985	If possible and supported, libev will install its handlers with	2130	If possible and supported, libev will install its handlers with
1986	C<SA_RESTART> behaviour enabled, so system calls should not be unduly	2131	C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should
1987	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
1988	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
1989	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.
1990		2160
1991	=head3 Watcher-Specific Functions and Data Members	2161	=head3 Watcher-Specific Functions and Data Members
1992		2162
1993	=over 4	2163	=over 4
1994		2164
…		…
2033		2203
2034	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
2035	you can only register child watchers in the default event loop.	2205	you can only register child watchers in the default event loop.
2036		2206
2037	Due to some design glitches inside libev, child watchers will always be	2207	Due to some design glitches inside libev, child watchers will always be
2038	handled at maximum priority (their priority is set to EV_MAXPRI by libev)	2208	handled at maximum priority (their priority is set to C<EV_MAXPRI> by
		2209	libev)
2039		2210
2040	=head3 Process Interaction	2211	=head3 Process Interaction
2041		2212
2042	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
2043	initialised. This is necessary to guarantee proper behaviour even if	2214	initialised. This is necessary to guarantee proper behaviour even if the
2044	the first child watcher is started after the child exits. The occurrence	2215	first child watcher is started after the child exits. The occurrence
2045	of C<SIGCHLD> is recorded asynchronously, but child reaping is done	2216	of C<SIGCHLD> is recorded asynchronously, but child reaping is done
2046	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
2047	children, even ones not watched.	2218	children, even ones not watched.
2048		2219
2049	=head3 Overriding the Built-In Processing	2220	=head3 Overriding the Built-In Processing
…		…
2059	=head3 Stopping the Child Watcher	2230	=head3 Stopping the Child Watcher
2060		2231
2061	Currently, the child watcher never gets stopped, even when the	2232	Currently, the child watcher never gets stopped, even when the
2062	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
2063	callback. Future versions of libev might stop the watcher automatically	2234	callback. Future versions of libev might stop the watcher automatically
2064	when a child exit is detected.	2235	when a child exit is detected (calling C<ev_child_stop> twice is not a
		2236	problem).
2065		2237
2066	=head3 Watcher-Specific Functions and Data Members	2238	=head3 Watcher-Specific Functions and Data Members
2067		2239
2068	=over 4	2240	=over 4
2069		2241
…		…
2809	=head3 Queueing	2981	=head3 Queueing
2810		2982
2811	C<ev_async> does not support queueing of data in any way. The reason	2983	C<ev_async> does not support queueing of data in any way. The reason
2812	is that the author does not know of a simple (or any) algorithm for a	2984	is that the author does not know of a simple (or any) algorithm for a
2813	multiple-writer-single-reader queue that works in all cases and doesn't	2985	multiple-writer-single-reader queue that works in all cases and doesn't
2814	need elaborate support such as pthreads.	2986	need elaborate support such as pthreads or unportable memory access
		2987	semantics.
2815		2988
2816	That means that if you want to queue data, you have to provide your own	2989	That means that if you want to queue data, you have to provide your own
2817	queue. But at least I can tell you how to implement locking around your	2990	queue. But at least I can tell you how to implement locking around your
2818	queue:	2991	queue:
2819		2992
…		…
2977	/* doh, nothing entered */;	3150	/* doh, nothing entered */;
2978	}	3151	}
2979		3152
2980	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	3153	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2981		3154
2982	=item ev_feed_event (struct ev_loop , watcher , int revents)
2983
2984	Feeds the given event set into the event loop, as if the specified event
2985	had happened for the specified watcher (which must be a pointer to an
2986	initialised but not necessarily started event watcher).
2987
2988	=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)	3155	=item ev_feed_fd_event (loop, int fd, int revents)
2989		3156
2990	Feed an event on the given fd, as if a file descriptor backend detected	3157	Feed an event on the given fd, as if a file descriptor backend detected
2991	the given events it.	3158	the given events it.
2992		3159
2993	=item ev_feed_signal_event (struct ev_loop *loop, int signum)	3160	=item ev_feed_signal_event (loop, int signum)
2994		3161
2995	Feed an event as if the given signal occurred (C<loop> must be the default	3162	Feed an event as if the given signal occurred (C<loop> must be the default
2996	loop!).	3163	loop!).
2997		3164
2998	=back	3165	=back
…		…
3078		3245
3079	=over 4	3246	=over 4
3080		3247
3081	=item ev::TYPE::TYPE ()	3248	=item ev::TYPE::TYPE ()
3082		3249
3083	=item ev::TYPE::TYPE (struct ev_loop *)	3250	=item ev::TYPE::TYPE (loop)
3084		3251
3085	=item ev::TYPE::~TYPE	3252	=item ev::TYPE::~TYPE
3086		3253
3087	The constructor (optionally) takes an event loop to associate the watcher	3254	The constructor (optionally) takes an event loop to associate the watcher
3088	with. If it is omitted, it will use C<EV_DEFAULT>.	3255	with. If it is omitted, it will use C<EV_DEFAULT>.
…		…
3165	Example: Use a plain function as callback.	3332	Example: Use a plain function as callback.
3166		3333
3167	static void io_cb (ev::io &w, int revents) { }	3334	static void io_cb (ev::io &w, int revents) { }
3168	iow.set <io_cb> ();	3335	iow.set <io_cb> ();
3169		3336
3170	=item w->set (struct ev_loop *)	3337	=item w->set (loop)
3171		3338
3172	Associates a different C<struct ev_loop> with this watcher. You can only	3339	Associates a different C<struct ev_loop> with this watcher. You can only
3173	do this when the watcher is inactive (and not pending either).	3340	do this when the watcher is inactive (and not pending either).
3174		3341
3175	=item w->set ([arguments])	3342	=item w->set ([arguments])
…		…
3272	=item Ocaml	3439	=item Ocaml
3273		3440
3274	Erkki Seppala has written Ocaml bindings for libev, to be found at	3441	Erkki Seppala has written Ocaml bindings for libev, to be found at
3275	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.	3442	L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3276		3443
		3444	=item Lua
		3445
		3446	Brian Maher has written a partial interface to libev
		3447	for lua (only C<ev_io> and C<ev_timer>), to be found at
		3448	L<http://github.com/brimworks/lua-ev>.
		3449
3277	=back	3450	=back
3278		3451
3279		3452
3280	=head1 MACRO MAGIC	3453	=head1 MACRO MAGIC
3281		3454
…		…
3447	keeps libev from including F<config.h>, and it also defines dummy	3620	keeps libev from including F<config.h>, and it also defines dummy
3448	implementations for some libevent functions (such as logging, which is not	3621	implementations for some libevent functions (such as logging, which is not
3449	supported). It will also not define any of the structs usually found in	3622	supported). It will also not define any of the structs usually found in
3450	F<event.h> that are not directly supported by the libev core alone.	3623	F<event.h> that are not directly supported by the libev core alone.
3451		3624
3452	In stanbdalone mode, libev will still try to automatically deduce the	3625	In standalone mode, libev will still try to automatically deduce the
3453	configuration, but has to be more conservative.	3626	configuration, but has to be more conservative.
3454		3627
3455	=item EV_USE_MONOTONIC	3628	=item EV_USE_MONOTONIC
3456		3629
3457	If defined to be C<1>, libev will try to detect the availability of the	3630	If defined to be C<1>, libev will try to detect the availability of the
…		…
3522	be used is the winsock select). This means that it will call	3695	be used is the winsock select). This means that it will call
3523	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,	3696	C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
3524	it is assumed that all these functions actually work on fds, even	3697	it is assumed that all these functions actually work on fds, even
3525	on win32. Should not be defined on non-win32 platforms.	3698	on win32. Should not be defined on non-win32 platforms.
3526		3699
3527	=item EV_FD_TO_WIN32_HANDLE	3700	=item EV_FD_TO_WIN32_HANDLE(fd)
3528		3701
3529	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map	3702	If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
3530	file descriptors to socket handles. When not defining this symbol (the	3703	file descriptors to socket handles. When not defining this symbol (the
3531	default), then libev will call C<_get_osfhandle>, which is usually	3704	default), then libev will call C<_get_osfhandle>, which is usually
3532	correct. In some cases, programs use their own file descriptor management,	3705	correct. In some cases, programs use their own file descriptor management,
3533	in which case they can provide this function to map fds to socket handles.	3706	in which case they can provide this function to map fds to socket handles.
		3707
		3708	=item EV_WIN32_HANDLE_TO_FD(handle)
		3709
		3710	If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors
		3711	using the standard C<_open_osfhandle> function. For programs implementing
		3712	their own fd to handle mapping, overwriting this function makes it easier
		3713	to do so. This can be done by defining this macro to an appropriate value.
		3714
		3715	=item EV_WIN32_CLOSE_FD(fd)
		3716
		3717	If programs implement their own fd to handle mapping on win32, then this
		3718	macro can be used to override the C<close> function, useful to unregister
		3719	file descriptors again. Note that the replacement function has to close
		3720	the underlying OS handle.
3534		3721
3535	=item EV_USE_POLL	3722	=item EV_USE_POLL
3536		3723
3537	If defined to be C<1>, libev will compile in support for the C<poll>(2)	3724	If defined to be C<1>, libev will compile in support for the C<poll>(2)
3538	backend. Otherwise it will be enabled on non-win32 platforms. It	3725	backend. Otherwise it will be enabled on non-win32 platforms. It
…		…
3670	defined to be C<0>, then they are not.	3857	defined to be C<0>, then they are not.
3671		3858
3672	=item EV_MINIMAL	3859	=item EV_MINIMAL
3673		3860
3674	If you need to shave off some kilobytes of code at the expense of some	3861	If you need to shave off some kilobytes of code at the expense of some
3675	speed, define this symbol to C<1>. Currently this is used to override some	3862	speed (but with the full API), define this symbol to C<1>. Currently this
3676	inlining decisions, saves roughly 30% code size on amd64. It also selects a	3863	is used to override some inlining decisions, saves roughly 30% code size
3677	much smaller 2-heap for timer management over the default 4-heap.	3864	on amd64. It also selects a much smaller 2-heap for timer management over
		3865	the default 4-heap.
		3866
		3867	You can save even more by disabling watcher types you do not need
		3868	and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert>
		3869	(C<-DNDEBUG>) will usually reduce code size a lot.
		3870
		3871	Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to
		3872	provide a bare-bones event library. See C<ev.h> for details on what parts
		3873	of the API are still available, and do not complain if this subset changes
		3874	over time.
		3875
		3876	=item EV_NSIG
		3877
		3878	The highest supported signal number, +1 (or, the number of
		3879	signals): Normally, libev tries to deduce the maximum number of signals
		3880	automatically, but sometimes this fails, in which case it can be
		3881	specified. Also, using a lower number than detected (C<32> should be
		3882	good for about any system in existance) can save some memory, as libev
		3883	statically allocates some 12-24 bytes per signal number.
3678		3884
3679	=item EV_PID_HASHSIZE	3885	=item EV_PID_HASHSIZE
3680		3886
3681	C<ev_child> watchers use a small hash table to distribute workload by	3887	C<ev_child> watchers use a small hash table to distribute workload by
3682	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more	3888	pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
…		…
3868	default loop and triggering an C<ev_async> watcher from the default loop	4074	default loop and triggering an C<ev_async> watcher from the default loop
3869	watcher callback into the event loop interested in the signal.	4075	watcher callback into the event loop interested in the signal.
3870		4076
3871	=back	4077	=back
3872		4078
		4079	=head4 THREAD LOCKING EXAMPLE
		4080
		4081	Here is a fictitious example of how to run an event loop in a different
		4082	thread than where callbacks are being invoked and watchers are
		4083	created/added/removed.
		4084
		4085	For a real-world example, see the C<EV::Loop::Async> perl module,
		4086	which uses exactly this technique (which is suited for many high-level
		4087	languages).
		4088
		4089	The example uses a pthread mutex to protect the loop data, a condition
		4090	variable to wait for callback invocations, an async watcher to notify the
		4091	event loop thread and an unspecified mechanism to wake up the main thread.
		4092
		4093	First, you need to associate some data with the event loop:
		4094
		4095	typedef struct {
		4096	mutex_t lock; /* global loop lock */
		4097	ev_async async_w;
		4098	thread_t tid;
		4099	cond_t invoke_cv;
		4100	} userdata;
		4101
		4102	void prepare_loop (EV_P)
		4103	{
		4104	// for simplicity, we use a static userdata struct.
		4105	static userdata u;
		4106
		4107	ev_async_init (&u->async_w, async_cb);
		4108	ev_async_start (EV_A_ &u->async_w);
		4109
		4110	pthread_mutex_init (&u->lock, 0);
		4111	pthread_cond_init (&u->invoke_cv, 0);
		4112
		4113	// now associate this with the loop
		4114	ev_set_userdata (EV_A_ u);
		4115	ev_set_invoke_pending_cb (EV_A_ l_invoke);
		4116	ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
		4117
		4118	// then create the thread running ev_loop
		4119	pthread_create (&u->tid, 0, l_run, EV_A);
		4120	}
		4121
		4122	The callback for the C<ev_async> watcher does nothing: the watcher is used
		4123	solely to wake up the event loop so it takes notice of any new watchers
		4124	that might have been added:
		4125
		4126	static void
		4127	async_cb (EV_P_ ev_async *w, int revents)
		4128	{
		4129	// just used for the side effects
		4130	}
		4131
		4132	The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex
		4133	protecting the loop data, respectively.
		4134
		4135	static void
		4136	l_release (EV_P)
		4137	{
		4138	userdata *u = ev_userdata (EV_A);
		4139	pthread_mutex_unlock (&u->lock);
		4140	}
		4141
		4142	static void
		4143	l_acquire (EV_P)
		4144	{
		4145	userdata *u = ev_userdata (EV_A);
		4146	pthread_mutex_lock (&u->lock);
		4147	}
		4148
		4149	The event loop thread first acquires the mutex, and then jumps straight
		4150	into C<ev_loop>:
		4151
		4152	void *
		4153	l_run (void *thr_arg)
		4154	{
		4155	struct ev_loop loop = (struct ev_loop )thr_arg;
		4156
		4157	l_acquire (EV_A);
		4158	pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0);
		4159	ev_loop (EV_A_ 0);
		4160	l_release (EV_A);
		4161
		4162	return 0;
		4163	}
		4164
		4165	Instead of invoking all pending watchers, the C<l_invoke> callback will
		4166	signal the main thread via some unspecified mechanism (signals? pipe
		4167	writes? C<Async::Interrupt>?) and then waits until all pending watchers
		4168	have been called (in a while loop because a) spurious wakeups are possible
		4169	and b) skipping inter-thread-communication when there are no pending
		4170	watchers is very beneficial):
		4171
		4172	static void
		4173	l_invoke (EV_P)
		4174	{
		4175	userdata *u = ev_userdata (EV_A);
		4176
		4177	while (ev_pending_count (EV_A))
		4178	{
		4179	wake_up_other_thread_in_some_magic_or_not_so_magic_way ();
		4180	pthread_cond_wait (&u->invoke_cv, &u->lock);
		4181	}
		4182	}
		4183
		4184	Now, whenever the main thread gets told to invoke pending watchers, it
		4185	will grab the lock, call C<ev_invoke_pending> and then signal the loop
		4186	thread to continue:
		4187
		4188	static void
		4189	real_invoke_pending (EV_P)
		4190	{
		4191	userdata *u = ev_userdata (EV_A);
		4192
		4193	pthread_mutex_lock (&u->lock);
		4194	ev_invoke_pending (EV_A);
		4195	pthread_cond_signal (&u->invoke_cv);
		4196	pthread_mutex_unlock (&u->lock);
		4197	}
		4198
		4199	Whenever you want to start/stop a watcher or do other modifications to an
		4200	event loop, you will now have to lock:
		4201
		4202	ev_timer timeout_watcher;
		4203	userdata *u = ev_userdata (EV_A);
		4204
		4205	ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
		4206
		4207	pthread_mutex_lock (&u->lock);
		4208	ev_timer_start (EV_A_ &timeout_watcher);
		4209	ev_async_send (EV_A_ &u->async_w);
		4210	pthread_mutex_unlock (&u->lock);
		4211
		4212	Note that sending the C<ev_async> watcher is required because otherwise
		4213	an event loop currently blocking in the kernel will have no knowledge
		4214	about the newly added timer. By waking up the loop it will pick up any new
		4215	watchers in the next event loop iteration.
		4216
3873	=head3 COROUTINES	4217	=head3 COROUTINES
3874		4218
3875	Libev is very accommodating to coroutines ("cooperative threads"):	4219	Libev is very accommodating to coroutines ("cooperative threads"):
3876	libev fully supports nesting calls to its functions from different	4220	libev fully supports nesting calls to its functions from different
3877	coroutines (e.g. you can call C<ev_loop> on the same loop from two	4221	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3878	different coroutines, and switch freely between both coroutines running the	4222	different coroutines, and switch freely between both coroutines running
3879	loop, as long as you don't confuse yourself). The only exception is that	4223	the loop, as long as you don't confuse yourself). The only exception is
3880	you must not do this from C<ev_periodic> reschedule callbacks.	4224	that you must not do this from C<ev_periodic> reschedule callbacks.
3881		4225
3882	Care has been taken to ensure that libev does not keep local state inside	4226	Care has been taken to ensure that libev does not keep local state inside
3883	C<ev_loop>, and other calls do not usually allow for coroutine switches as	4227	C<ev_loop>, and other calls do not usually allow for coroutine switches as
3884	they do not call any callbacks.	4228	they do not call any callbacks.
3885		4229

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Comparing libev/ev.pod (file contents): Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs. Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.248 by root, Wed Jul 8 04:14:34 2009 UTC vs.
Revision 1.275 by root, Sat Dec 26 09:21:54 2009 UTC