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

Comparing libev/ev.pod (file contents):
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC

…		…
106	returned by C<ev_supported_backends>, as for example kqueue is broken on	106	returned by C<ev_supported_backends>, as for example kqueue is broken on
107	most BSDs and will not be autodetected unless you explicitly request it	107	most BSDs and will not be autodetected unless you explicitly request it
108	(assuming you know what you are doing). This is the set of backends that	108	(assuming you know what you are doing). This is the set of backends that
109	libev will probe for if you specify no backends explicitly.	109	libev will probe for if you specify no backends explicitly.
110		110
		111	=item unsigned int ev_embeddable_backends ()
		112
		113	Returns the set of backends that are embeddable in other event loops. This
		114	is the theoretical, all-platform, value. To find which backends
		115	might be supported on the current system, you would need to look at
		116	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
		117	recommended ones.
		118
		119	See the description of C<ev_embed> watchers for more info.
		120
111	=item ev_set_allocator (void (cb)(void *ptr, long size))	121	=item ev_set_allocator (void (cb)(void *ptr, long size))
112		122
113	Sets the allocation function to use (the prototype is similar to the	123	Sets the allocation function to use (the prototype is similar to the
114	realloc C function, the semantics are identical). It is used to allocate	124	realloc C function, the semantics are identical). It is used to allocate
115	and free memory (no surprises here). If it returns zero when memory	125	and free memory (no surprises here). If it returns zero when memory
…		…
313	fatal ("no epoll found here, maybe it hides under your chair");	323	fatal ("no epoll found here, maybe it hides under your chair");
314		324
315	=item ev_default_destroy ()	325	=item ev_default_destroy ()
316		326
317	Destroys the default loop again (frees all memory and kernel state	327	Destroys the default loop again (frees all memory and kernel state
318	etc.). This stops all registered event watchers (by not touching them in	328	etc.). None of the active event watchers will be stopped in the normal
319	any way whatsoever, although you cannot rely on this :).	329	sense, so e.g. C<ev_is_active> might still return true. It is your
		330	responsibility to either stop all watchers cleanly yoursef I<before>
		331	calling this function, or cope with the fact afterwards (which is usually
		332	the easiest thing, youc na just ignore the watchers and/or C<free ()> them
		333	for example).
320		334
321	=item ev_loop_destroy (loop)	335	=item ev_loop_destroy (loop)
322		336
323	Like C<ev_default_destroy>, but destroys an event loop created by an	337	Like C<ev_default_destroy>, but destroys an event loop created by an
324	earlier call to C<ev_loop_new>.	338	earlier call to C<ev_loop_new>.
…		…
495	*) >>), and you can stop watching for events at any time by calling the	509	*) >>), and you can stop watching for events at any time by calling the
496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	510	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
497		511
498	As long as your watcher is active (has been started but not stopped) you	512	As long as your watcher is active (has been started but not stopped) you
499	must not touch the values stored in it. Most specifically you must never	513	must not touch the values stored in it. Most specifically you must never
500	reinitialise it or call its set macro.	514	reinitialise it or call its C<set> macro.
501
502	You can check whether an event is active by calling the C<ev_is_active
503	(watcher *)> macro. To see whether an event is outstanding (but the
504	callback for it has not been called yet) you can use the C<ev_is_pending
505	(watcher *)> macro.
506		515
507	Each and every callback receives the event loop pointer as first, the	516	Each and every callback receives the event loop pointer as first, the
508	registered watcher structure as second, and a bitset of received events as	517	registered watcher structure as second, and a bitset of received events as
509	third argument.	518	third argument.
510		519
…		…
566	your callbacks is well-written it can just attempt the operation and cope	575	your callbacks is well-written it can just attempt the operation and cope
567	with the error from read() or write(). This will not work in multithreaded	576	with the error from read() or write(). This will not work in multithreaded
568	programs, though, so beware.	577	programs, though, so beware.
569		578
570	=back	579	=back
		580
		581	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS
		582
		583	In the following description, C<TYPE> stands for the watcher type,
		584	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		585
		586	=over 4
		587
		588	=item C<ev_init> (ev_TYPE *watcher, callback)
		589
		590	This macro initialises the generic portion of a watcher. The contents
		591	of the watcher object can be arbitrary (so C<malloc> will do). Only
		592	the generic parts of the watcher are initialised, you I<need> to call
		593	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		594	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		595	which rolls both calls into one.
		596
		597	You can reinitialise a watcher at any time as long as it has been stopped
		598	(or never started) and there are no pending events outstanding.
		599
		600	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
		601	int revents)>.
		602
		603	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		604
		605	This macro initialises the type-specific parts of a watcher. You need to
		606	call C<ev_init> at least once before you call this macro, but you can
		607	call C<ev_TYPE_set> any number of times. You must not, however, call this
		608	macro on a watcher that is active (it can be pending, however, which is a
		609	difference to the C<ev_init> macro).
		610
		611	Although some watcher types do not have type-specific arguments
		612	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		613
		614	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		615
		616	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		617	calls into a single call. This is the most convinient method to initialise
		618	a watcher. The same limitations apply, of course.
		619
		620	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
		621
		622	Starts (activates) the given watcher. Only active watchers will receive
		623	events. If the watcher is already active nothing will happen.
		624
		625	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
		626
		627	Stops the given watcher again (if active) and clears the pending
		628	status. It is possible that stopped watchers are pending (for example,
		629	non-repeating timers are being stopped when they become pending), but
		630	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		631	you want to free or reuse the memory used by the watcher it is therefore a
		632	good idea to always call its C<ev_TYPE_stop> function.
		633
		634	=item bool ev_is_active (ev_TYPE *watcher)
		635
		636	Returns a true value iff the watcher is active (i.e. it has been started
		637	and not yet been stopped). As long as a watcher is active you must not modify
		638	it.
		639
		640	=item bool ev_is_pending (ev_TYPE *watcher)
		641
		642	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		643	events but its callback has not yet been invoked). As long as a watcher
		644	is pending (but not active) you must not call an init function on it (but
		645	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		646	libev (e.g. you cnanot C<free ()> it).
		647
		648	=item callback = ev_cb (ev_TYPE *watcher)
		649
		650	Returns the callback currently set on the watcher.
		651
		652	=item ev_cb_set (ev_TYPE *watcher, callback)
		653
		654	Change the callback. You can change the callback at virtually any time
		655	(modulo threads).
		656
		657	=back
		658
571		659
572	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	660	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
573		661
574	Each watcher has, by default, a member C<void *data> that you can change	662	Each watcher has, by default, a member C<void *data> that you can change
575	and read at any time, libev will completely ignore it. This can be used	663	and read at any time, libev will completely ignore it. This can be used
…		…
768	(and unfortunately a bit complex).	856	(and unfortunately a bit complex).
769		857
770	Unlike C<ev_timer>'s, they are not based on real time (or relative time)	858	Unlike C<ev_timer>'s, they are not based on real time (or relative time)
771	but on wallclock time (absolute time). You can tell a periodic watcher	859	but on wallclock time (absolute time). You can tell a periodic watcher
772	to trigger "at" some specific point in time. For example, if you tell a	860	to trigger "at" some specific point in time. For example, if you tell a
773	periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()	861	periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
774	+ 10.>) and then reset your system clock to the last year, then it will	862	+ 10.>) and then reset your system clock to the last year, then it will
775	take a year to trigger the event (unlike an C<ev_timer>, which would trigger	863	take a year to trigger the event (unlike an C<ev_timer>, which would trigger
776	roughly 10 seconds later and of course not if you reset your system time	864	roughly 10 seconds later and of course not if you reset your system time
777	again).	865	again).
778		866
…		…
922		1010
923	Configures the watcher to trigger on the given signal number (usually one	1011	Configures the watcher to trigger on the given signal number (usually one
924	of the C<SIGxxx> constants).	1012	of the C<SIGxxx> constants).
925		1013
926	=back	1014	=back
		1015
927		1016
928	=head2 C<ev_child> - wait for pid status changes	1017	=head2 C<ev_child> - wait for pid status changes
929		1018
930	Child watchers trigger when your process receives a SIGCHLD in response to	1019	Child watchers trigger when your process receives a SIGCHLD in response to
931	some child status changes (most typically when a child of yours dies).	1020	some child status changes (most typically when a child of yours dies).
…		…
1006		1095
1007	Prepare and check watchers are usually (but not always) used in tandem:	1096	Prepare and check watchers are usually (but not always) used in tandem:
1008	prepare watchers get invoked before the process blocks and check watchers	1097	prepare watchers get invoked before the process blocks and check watchers
1009	afterwards.	1098	afterwards.
1010		1099
1011	Their main purpose is to integrate other event mechanisms into libev. This	1100	Their main purpose is to integrate other event mechanisms into libev and
1012	could be used, for example, to track variable changes, implement your own	1101	their use is somewhat advanced. This could be used, for example, to track
1013	watchers, integrate net-snmp or a coroutine library and lots more.	1102	variable changes, implement your own watchers, integrate net-snmp or a
		1103	coroutine library and lots more.
1014		1104
1015	This is done by examining in each prepare call which file descriptors need	1105	This is done by examining in each prepare call which file descriptors need
1016	to be watched by the other library, registering C<ev_io> watchers for	1106	to be watched by the other library, registering C<ev_io> watchers for
1017	them and starting an C<ev_timer> watcher for any timeouts (many libraries	1107	them and starting an C<ev_timer> watcher for any timeouts (many libraries
1018	provide just this functionality). Then, in the check watcher you check for	1108	provide just this functionality). Then, in the check watcher you check for
…		…
1043	=back	1133	=back
1044		1134
1045	Example: TODO.	1135	Example: TODO.
1046		1136
1047		1137
		1138	=head2 C<ev_embed> - when one backend isn't enough
		1139
		1140	This is a rather advanced watcher type that lets you embed one event loop
		1141	into another (currently only C<ev_io> events are supported in the embedded
		1142	loop, other types of watchers might be handled in a delayed or incorrect
		1143	fashion and must not be used).
		1144
		1145	There are primarily two reasons you would want that: work around bugs and
		1146	prioritise I/O.
		1147
		1148	As an example for a bug workaround, the kqueue backend might only support
		1149	sockets on some platform, so it is unusable as generic backend, but you
		1150	still want to make use of it because you have many sockets and it scales
		1151	so nicely. In this case, you would create a kqueue-based loop and embed it
		1152	into your default loop (which might use e.g. poll). Overall operation will
		1153	be a bit slower because first libev has to poll and then call kevent, but
		1154	at least you can use both at what they are best.
		1155
		1156	As for prioritising I/O: rarely you have the case where some fds have
		1157	to be watched and handled very quickly (with low latency), and even
		1158	priorities and idle watchers might have too much overhead. In this case
		1159	you would put all the high priority stuff in one loop and all the rest in
		1160	a second one, and embed the second one in the first.
		1161
		1162	As long as the watcher is active, the callback will be invoked every time
		1163	there might be events pending in the embedded loop. The callback must then
		1164	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1165	their callbacks (you could also start an idle watcher to give the embedded
		1166	loop strictly lower priority for example). You can also set the callback
		1167	to C<0>, in which case the embed watcher will automatically execute the
		1168	embedded loop sweep.
		1169
		1170	As long as the watcher is started it will automatically handle events. The
		1171	callback will be invoked whenever some events have been handled. You can
		1172	set the callback to C<0> to avoid having to specify one if you are not
		1173	interested in that.
		1174
		1175	Also, there have not currently been made special provisions for forking:
		1176	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1177	but you will also have to stop and restart any C<ev_embed> watchers
		1178	yourself.
		1179
		1180	Unfortunately, not all backends are embeddable, only the ones returned by
		1181	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1182	portable one.
		1183
		1184	So when you want to use this feature you will always have to be prepared
		1185	that you cannot get an embeddable loop. The recommended way to get around
		1186	this is to have a separate variables for your embeddable loop, try to
		1187	create it, and if that fails, use the normal loop for everything:
		1188
		1189	struct ev_loop *loop_hi = ev_default_init (0);
		1190	struct ev_loop *loop_lo = 0;
		1191	struct ev_embed embed;
		1192
		1193	// see if there is a chance of getting one that works
		1194	// (remember that a flags value of 0 means autodetection)
		1195	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1196	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1197	: 0;
		1198
		1199	// if we got one, then embed it, otherwise default to loop_hi
		1200	if (loop_lo)
		1201	{
		1202	ev_embed_init (&embed, 0, loop_lo);
		1203	ev_embed_start (loop_hi, &embed);
		1204	}
		1205	else
		1206	loop_lo = loop_hi;
		1207
		1208	=over 4
		1209
		1210	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1211
		1212	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1213
		1214	Configures the watcher to embed the given loop, which must be
		1215	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1216	invoked automatically, otherwise it is the responsibility of the callback
		1217	to invoke it (it will continue to be called until the sweep has been done,
		1218	if you do not want thta, you need to temporarily stop the embed watcher).
		1219
		1220	=item ev_embed_sweep (loop, ev_embed *)
		1221
		1222	Make a single, non-blocking sweep over the embedded loop. This works
		1223	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1224	apropriate way for embedded loops.
		1225
		1226	=back
		1227
		1228
1048	=head1 OTHER FUNCTIONS	1229	=head1 OTHER FUNCTIONS
1049		1230
1050	There are some other functions of possible interest. Described. Here. Now.	1231	There are some other functions of possible interest. Described. Here. Now.
1051		1232
1052	=over 4	1233	=over 4
…		…
1081	/* stdin might have data for us, joy! */;	1262	/* stdin might have data for us, joy! */;
1082	}	1263	}
1083		1264
1084	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1265	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1085		1266
1086	=item ev_feed_event (loop, watcher, int events)	1267	=item ev_feed_event (ev_loop , watcher , int revents)
1087		1268
1088	Feeds the given event set into the event loop, as if the specified event	1269	Feeds the given event set into the event loop, as if the specified event
1089	had happened for the specified watcher (which must be a pointer to an	1270	had happened for the specified watcher (which must be a pointer to an
1090	initialised but not necessarily started event watcher).	1271	initialised but not necessarily started event watcher).
1091		1272
1092	=item ev_feed_fd_event (loop, int fd, int revents)	1273	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
1093		1274
1094	Feed an event on the given fd, as if a file descriptor backend detected	1275	Feed an event on the given fd, as if a file descriptor backend detected
1095	the given events it.	1276	the given events it.
1096		1277
1097	=item ev_feed_signal_event (loop, int signum)	1278	=item ev_feed_signal_event (ev_loop *loop, int signum)
1098		1279
1099	Feed an event as if the given signal occured (loop must be the default loop!).	1280	Feed an event as if the given signal occured (C<loop> must be the default
		1281	loop!).
1100		1282
1101	=back	1283	=back
1102		1284
1103		1285
1104	=head1 LIBEVENT EMULATION	1286	=head1 LIBEVENT EMULATION
…		…
1128		1310
1129	=back	1311	=back
1130		1312
1131	=head1 C++ SUPPORT	1313	=head1 C++ SUPPORT
1132		1314
1133	TBD.	1315	Libev comes with some simplistic wrapper classes for C++ that mainly allow
		1316	you to use some convinience methods to start/stop watchers and also change
		1317	the callback model to a model using method callbacks on objects.
		1318
		1319	To use it,
		1320
		1321	#include <ev++.h>
		1322
		1323	(it is not installed by default). This automatically includes F<ev.h>
		1324	and puts all of its definitions (many of them macros) into the global
		1325	namespace. All C++ specific things are put into the C<ev> namespace.
		1326
		1327	It should support all the same embedding options as F<ev.h>, most notably
		1328	C<EV_MULTIPLICITY>.
		1329
		1330	Here is a list of things available in the C<ev> namespace:
		1331
		1332	=over 4
		1333
		1334	=item C<ev::READ>, C<ev::WRITE> etc.
		1335
		1336	These are just enum values with the same values as the C<EV_READ> etc.
		1337	macros from F<ev.h>.
		1338
		1339	=item C<ev::tstamp>, C<ev::now>
		1340
		1341	Aliases to the same types/functions as with the C<ev_> prefix.
		1342
		1343	=item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc.
		1344
		1345	For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of
		1346	the same name in the C<ev> namespace, with the exception of C<ev_signal>
		1347	which is called C<ev::sig> to avoid clashes with the C<signal> macro
		1348	defines by many implementations.
		1349
		1350	All of those classes have these methods:
		1351
		1352	=over 4
		1353
		1354	=item ev::TYPE::TYPE (object , object::method )
		1355
		1356	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)
		1357
		1358	=item ev::TYPE::~TYPE
		1359
		1360	The constructor takes a pointer to an object and a method pointer to
		1361	the event handler callback to call in this class. The constructor calls
		1362	C<ev_init> for you, which means you have to call the C<set> method
		1363	before starting it. If you do not specify a loop then the constructor
		1364	automatically associates the default loop with this watcher.
		1365
		1366	The destructor automatically stops the watcher if it is active.
		1367
		1368	=item w->set (struct ev_loop *)
		1369
		1370	Associates a different C<struct ev_loop> with this watcher. You can only
		1371	do this when the watcher is inactive (and not pending either).
		1372
		1373	=item w->set ([args])
		1374
		1375	Basically the same as C<ev_TYPE_set>, with the same args. Must be
		1376	called at least once. Unlike the C counterpart, an active watcher gets
		1377	automatically stopped and restarted.
		1378
		1379	=item w->start ()
		1380
		1381	Starts the watcher. Note that there is no C<loop> argument as the
		1382	constructor already takes the loop.
		1383
		1384	=item w->stop ()
		1385
		1386	Stops the watcher if it is active. Again, no C<loop> argument.
		1387
		1388	=item w->again () C<ev::timer>, C<ev::periodic> only
		1389
		1390	For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
		1391	C<ev_TYPE_again> function.
		1392
		1393	=item w->sweep () C<ev::embed> only
		1394
		1395	Invokes C<ev_embed_sweep>.
		1396
		1397	=back
		1398
		1399	=back
		1400
		1401	Example: Define a class with an IO and idle watcher, start one of them in
		1402	the constructor.
		1403
		1404	class myclass
		1405	{
		1406	ev_io io; void io_cb (ev::io &w, int revents);
		1407	ev_idle idle void idle_cb (ev::idle &w, int revents);
		1408
		1409	myclass ();
		1410	}
		1411
		1412	myclass::myclass (int fd)
		1413	: io (this, &myclass::io_cb),
		1414	idle (this, &myclass::idle_cb)
		1415	{
		1416	io.start (fd, ev::READ);
		1417	}
1134		1418
1135	=head1 AUTHOR	1419	=head1 AUTHOR
1136		1420
1137	Marc Lehmann <libev@schmorp.de>.	1421	Marc Lehmann <libev@schmorp.de>.
1138		1422

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Comparing libev/ev.pod (file contents): Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC vs. Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.34 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.38 by root, Sat Nov 24 09:48:38 2007 UTC