[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 1.36 by root, Sat Nov 24 07:14:26 2007 UTC

…		…
105	recommended for this platform. This set is often smaller than the one	105	recommended for this platform. This set is often smaller than the one
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
		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.
110		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
…		…
495	*) >>), and you can stop watching for events at any time by calling the	505	*) >>), and you can stop watching for events at any time by calling the
496	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.	506	corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>.
497		507
498	As long as your watcher is active (has been started but not stopped) you	508	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	509	must not touch the values stored in it. Most specifically you must never
500	reinitialise it or call its set macro.	510	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		511
507	Each and every callback receives the event loop pointer as first, the	512	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	513	registered watcher structure as second, and a bitset of received events as
509	third argument.	514	third argument.
510		515
…		…
566	your callbacks is well-written it can just attempt the operation and cope	571	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	572	with the error from read() or write(). This will not work in multithreaded
568	programs, though, so beware.	573	programs, though, so beware.
569		574
570	=back	575	=back
		576
		577	=head2 SUMMARY OF GENERIC WATCHER FUNCTIONS
		578
		579	In the following description, C<TYPE> stands for the watcher type,
		580	e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers.
		581
		582	=over 4
		583
		584	=item C<ev_init> (ev_TYPE *watcher, callback)
		585
		586	This macro initialises the generic portion of a watcher. The contents
		587	of the watcher object can be arbitrary (so C<malloc> will do). Only
		588	the generic parts of the watcher are initialised, you I<need> to call
		589	the type-specific C<ev_TYPE_set> macro afterwards to initialise the
		590	type-specific parts. For each type there is also a C<ev_TYPE_init> macro
		591	which rolls both calls into one.
		592
		593	You can reinitialise a watcher at any time as long as it has been stopped
		594	(or never started) and there are no pending events outstanding.
		595
		596	The callbakc is always of type C<void ()(ev_loop loop, ev_TYPE *watcher,
		597	int revents)>.
		598
		599	=item C<ev_TYPE_set> (ev_TYPE *, [args])
		600
		601	This macro initialises the type-specific parts of a watcher. You need to
		602	call C<ev_init> at least once before you call this macro, but you can
		603	call C<ev_TYPE_set> any number of times. You must not, however, call this
		604	macro on a watcher that is active (it can be pending, however, which is a
		605	difference to the C<ev_init> macro).
		606
		607	Although some watcher types do not have type-specific arguments
		608	(e.g. C<ev_prepare>) you still need to call its C<set> macro.
		609
		610	=item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args])
		611
		612	This convinience macro rolls both C<ev_init> and C<ev_TYPE_set> macro
		613	calls into a single call. This is the most convinient method to initialise
		614	a watcher. The same limitations apply, of course.
		615
		616	=item C<ev_TYPE_start> (loop , ev_TYPE watcher)
		617
		618	Starts (activates) the given watcher. Only active watchers will receive
		619	events. If the watcher is already active nothing will happen.
		620
		621	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
		622
		623	Stops the given watcher again (if active) and clears the pending
		624	status. It is possible that stopped watchers are pending (for example,
		625	non-repeating timers are being stopped when they become pending), but
		626	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If
		627	you want to free or reuse the memory used by the watcher it is therefore a
		628	good idea to always call its C<ev_TYPE_stop> function.
		629
		630	=item bool ev_is_active (ev_TYPE *watcher)
		631
		632	Returns a true value iff the watcher is active (i.e. it has been started
		633	and not yet been stopped). As long as a watcher is active you must not modify
		634	it.
		635
		636	=item bool ev_is_pending (ev_TYPE *watcher)
		637
		638	Returns a true value iff the watcher is pending, (i.e. it has outstanding
		639	events but its callback has not yet been invoked). As long as a watcher
		640	is pending (but not active) you must not call an init function on it (but
		641	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
		642	libev (e.g. you cnanot C<free ()> it).
		643
		644	=item callback = ev_cb (ev_TYPE *watcher)
		645
		646	Returns the callback currently set on the watcher.
		647
		648	=item ev_cb_set (ev_TYPE *watcher, callback)
		649
		650	Change the callback. You can change the callback at virtually any time
		651	(modulo threads).
		652
		653	=back
		654
571		655
572	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	656	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
573		657
574	Each watcher has, by default, a member C<void *data> that you can change	658	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	659	and read at any time, libev will completely ignore it. This can be used
…		…
923	Configures the watcher to trigger on the given signal number (usually one	1007	Configures the watcher to trigger on the given signal number (usually one
924	of the C<SIGxxx> constants).	1008	of the C<SIGxxx> constants).
925		1009
926	=back	1010	=back
927		1011
		1012
928	=head2 C<ev_child> - wait for pid status changes	1013	=head2 C<ev_child> - wait for pid status changes
929		1014
930	Child watchers trigger when your process receives a SIGCHLD in response to	1015	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).	1016	some child status changes (most typically when a child of yours dies).
932		1017
…		…
1006		1091
1007	Prepare and check watchers are usually (but not always) used in tandem:	1092	Prepare and check watchers are usually (but not always) used in tandem:
1008	prepare watchers get invoked before the process blocks and check watchers	1093	prepare watchers get invoked before the process blocks and check watchers
1009	afterwards.	1094	afterwards.
1010		1095
1011	Their main purpose is to integrate other event mechanisms into libev. This	1096	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	1097	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.	1098	variable changes, implement your own watchers, integrate net-snmp or a
		1099	coroutine library and lots more.
1014		1100
1015	This is done by examining in each prepare call which file descriptors need	1101	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	1102	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	1103	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	1104	provide just this functionality). Then, in the check watcher you check for
…		…
1043	=back	1129	=back
1044		1130
1045	Example: TODO.	1131	Example: TODO.
1046		1132
1047		1133
		1134	=head2 C<ev_embed> - when one backend isn't enough
		1135
		1136	This is a rather advanced watcher type that lets you embed one event loop
		1137	into another (currently only C<ev_io> events are supported in the embedded
		1138	loop, other types of watchers might be handled in a delayed or incorrect
		1139	fashion and must not be used).
		1140
		1141	There are primarily two reasons you would want that: work around bugs and
		1142	prioritise I/O.
		1143
		1144	As an example for a bug workaround, the kqueue backend might only support
		1145	sockets on some platform, so it is unusable as generic backend, but you
		1146	still want to make use of it because you have many sockets and it scales
		1147	so nicely. In this case, you would create a kqueue-based loop and embed it
		1148	into your default loop (which might use e.g. poll). Overall operation will
		1149	be a bit slower because first libev has to poll and then call kevent, but
		1150	at least you can use both at what they are best.
		1151
		1152	As for prioritising I/O: rarely you have the case where some fds have
		1153	to be watched and handled very quickly (with low latency), and even
		1154	priorities and idle watchers might have too much overhead. In this case
		1155	you would put all the high priority stuff in one loop and all the rest in
		1156	a second one, and embed the second one in the first.
		1157
		1158	As long as the watcher is active, the callback will be invoked every time
		1159	there might be events pending in the embedded loop. The callback must then
		1160	call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke
		1161	their callbacks (you could also start an idle watcher to give the embedded
		1162	loop strictly lower priority for example). You can also set the callback
		1163	to C<0>, in which case the embed watcher will automatically execute the
		1164	embedded loop sweep.
		1165
		1166	As long as the watcher is started it will automatically handle events. The
		1167	callback will be invoked whenever some events have been handled. You can
		1168	set the callback to C<0> to avoid having to specify one if you are not
		1169	interested in that.
		1170
		1171	Also, there have not currently been made special provisions for forking:
		1172	when you fork, you not only have to call C<ev_loop_fork> on both loops,
		1173	but you will also have to stop and restart any C<ev_embed> watchers
		1174	yourself.
		1175
		1176	Unfortunately, not all backends are embeddable, only the ones returned by
		1177	C<ev_embeddable_backends> are, which, unfortunately, does not include any
		1178	portable one.
		1179
		1180	So when you want to use this feature you will always have to be prepared
		1181	that you cannot get an embeddable loop. The recommended way to get around
		1182	this is to have a separate variables for your embeddable loop, try to
		1183	create it, and if that fails, use the normal loop for everything:
		1184
		1185	struct ev_loop *loop_hi = ev_default_init (0);
		1186	struct ev_loop *loop_lo = 0;
		1187	struct ev_embed embed;
		1188
		1189	// see if there is a chance of getting one that works
		1190	// (remember that a flags value of 0 means autodetection)
		1191	loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
		1192	? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
		1193	: 0;
		1194
		1195	// if we got one, then embed it, otherwise default to loop_hi
		1196	if (loop_lo)
		1197	{
		1198	ev_embed_init (&embed, 0, loop_lo);
		1199	ev_embed_start (loop_hi, &embed);
		1200	}
		1201	else
		1202	loop_lo = loop_hi;
		1203
		1204	=over 4
		1205
		1206	=item ev_embed_init (ev_embed , callback, struct ev_loop embedded_loop)
		1207
		1208	=item ev_embed_set (ev_embed , callback, struct ev_loop embedded_loop)
		1209
		1210	Configures the watcher to embed the given loop, which must be
		1211	embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
		1212	invoked automatically, otherwise it is the responsibility of the callback
		1213	to invoke it (it will continue to be called until the sweep has been done,
		1214	if you do not want thta, you need to temporarily stop the embed watcher).
		1215
		1216	=item ev_embed_sweep (loop, ev_embed *)
		1217
		1218	Make a single, non-blocking sweep over the embedded loop. This works
		1219	similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
		1220	apropriate way for embedded loops.
		1221
		1222	=back
		1223
		1224
1048	=head1 OTHER FUNCTIONS	1225	=head1 OTHER FUNCTIONS
1049		1226
1050	There are some other functions of possible interest. Described. Here. Now.	1227	There are some other functions of possible interest. Described. Here. Now.
1051		1228
1052	=over 4	1229	=over 4
…		…
1081	/* stdin might have data for us, joy! */;	1258	/* stdin might have data for us, joy! */;
1082	}	1259	}
1083		1260
1084	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	1261	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1085		1262
1086	=item ev_feed_event (loop, watcher, int events)	1263	=item ev_feed_event (ev_loop , watcher , int revents)
1087		1264
1088	Feeds the given event set into the event loop, as if the specified event	1265	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	1266	had happened for the specified watcher (which must be a pointer to an
1090	initialised but not necessarily started event watcher).	1267	initialised but not necessarily started event watcher).
1091		1268
1092	=item ev_feed_fd_event (loop, int fd, int revents)	1269	=item ev_feed_fd_event (ev_loop *, int fd, int revents)
1093		1270
1094	Feed an event on the given fd, as if a file descriptor backend detected	1271	Feed an event on the given fd, as if a file descriptor backend detected
1095	the given events it.	1272	the given events it.
1096		1273
1097	=item ev_feed_signal_event (loop, int signum)	1274	=item ev_feed_signal_event (ev_loop *loop, int signum)
1098		1275
1099	Feed an event as if the given signal occured (loop must be the default loop!).	1276	Feed an event as if the given signal occured (C<loop> must be the default
		1277	loop!).
1100		1278
1101	=back	1279	=back
1102		1280
1103		1281
1104	=head1 LIBEVENT EMULATION	1282	=head1 LIBEVENT EMULATION

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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 1.36 by root, Sat Nov 24 07:14:26 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 1.36 by root, Sat Nov 24 07:14:26 2007 UTC