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

Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC

…		…
47		47
48	return 0;	48	return 0;
49	}	49	}
50		50
51	=head1 DESCRIPTION	51	=head1 DESCRIPTION
		52
		53	The newest version of this document is also available as a html-formatted
		54	web page you might find easier to navigate when reading it for the first
		55	time: L<http://cvs.schmorp.de/libev/ev.html>.
52		56
53	Libev is an event loop: you register interest in certain events (such as a	57	Libev is an event loop: you register interest in certain events (such as a
54	file descriptor being readable or a timeout occuring), and it will manage	58	file descriptor being readable or a timeout occuring), and it will manage
55	these event sources and provide your program with events.	59	these event sources and provide your program with events.
56		60
…		…
274	a fork, you can also make libev check for a fork in each iteration by	278	a fork, you can also make libev check for a fork in each iteration by
275	enabling this flag.	279	enabling this flag.
276		280
277	This works by calling C<getpid ()> on every iteration of the loop,	281	This works by calling C<getpid ()> on every iteration of the loop,
278	and thus this might slow down your event loop if you do a lot of loop	282	and thus this might slow down your event loop if you do a lot of loop
279	iterations and little real work, but is usually not noticable (on my	283	iterations and little real work, but is usually not noticeable (on my
280	Linux system for example, C<getpid> is actually a simple 5-insn sequence	284	Linux system for example, C<getpid> is actually a simple 5-insn sequence
281	without a syscall and thus I<very> fast, but my Linux system also has	285	without a syscall and thus I<very> fast, but my Linux system also has
282	C<pthread_atfork> which is even faster).	286	C<pthread_atfork> which is even faster).
283		287
284	The big advantage of this flag is that you can forget about fork (and	288	The big advantage of this flag is that you can forget about fork (and
…		…
429	=item ev_loop_fork (loop)	433	=item ev_loop_fork (loop)
430		434
431	Like C<ev_default_fork>, but acts on an event loop created by	435	Like C<ev_default_fork>, but acts on an event loop created by
432	C<ev_loop_new>. Yes, you have to call this on every allocated event loop	436	C<ev_loop_new>. Yes, you have to call this on every allocated event loop
433	after fork, and how you do this is entirely your own problem.	437	after fork, and how you do this is entirely your own problem.
		438
		439	=item unsigned int ev_loop_count (loop)
		440
		441	Returns the count of loop iterations for the loop, which is identical to
		442	the number of times libev did poll for new events. It starts at C<0> and
		443	happily wraps around with enough iterations.
		444
		445	This value can sometimes be useful as a generation counter of sorts (it
		446	"ticks" the number of loop iterations), as it roughly corresponds with
		447	C<ev_prepare> and C<ev_check> calls.
434		448
435	=item unsigned int ev_backend (loop)	449	=item unsigned int ev_backend (loop)
436		450
437	Returns one of the C<EVBACKEND_*> flags indicating the event backend in	451	Returns one of the C<EVBACKEND_*> flags indicating the event backend in
438	use.	452	use.
…		…
734	=item ev_cb_set (ev_TYPE *watcher, callback)	748	=item ev_cb_set (ev_TYPE *watcher, callback)
735		749
736	Change the callback. You can change the callback at virtually any time	750	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	751	(modulo threads).
738		752
		753	=item ev_set_priority (ev_TYPE *watcher, priority)
		754
		755	=item int ev_priority (ev_TYPE *watcher)
		756
		757	Set and query the priority of the watcher. The priority is a small
		758	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		759	(default: C<-2>). Pending watchers with higher priority will be invoked
		760	before watchers with lower priority, but priority will not keep watchers
		761	from being executed (except for C<ev_idle> watchers).
		762
		763	This means that priorities are I<only> used for ordering callback
		764	invocation after new events have been received. This is useful, for
		765	example, to reduce latency after idling, or more often, to bind two
		766	watchers on the same event and make sure one is called first.
		767
		768	If you need to suppress invocation when higher priority events are pending
		769	you need to look at C<ev_idle> watchers, which provide this functionality.
		770
		771	The default priority used by watchers when no priority has been set is
		772	always C<0>, which is supposed to not be too high and not be too low :).
		773
		774	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		775	fine, as long as you do not mind that the priority value you query might
		776	or might not have been adjusted to be within valid range.
		777
739	=back	778	=back
740		779
741		780
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	781	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
743		782
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	887	it is best to always use non-blocking I/O: An extra C<read>(2) returning
849	C<EAGAIN> is far preferable to a program hanging until some data arrives.	888	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		889
851	If you cannot run the fd in non-blocking mode (for example you should not	890	If you cannot run the fd in non-blocking mode (for example you should not
852	play around with an Xlib connection), then you have to seperately re-test	891	play around with an Xlib connection), then you have to seperately re-test
853	wether a file descriptor is really ready with a known-to-be good interface	892	whether a file descriptor is really ready with a known-to-be good interface
854	such as poll (fortunately in our Xlib example, Xlib already does this on	893	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	894	its own, so its quite safe to use).
856		895
857	=over 4	896	=over 4
858		897
…		…
1341	ev_stat_start (loop, &passwd);	1380	ev_stat_start (loop, &passwd);
1342		1381
1343		1382
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1383	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1384
1346	Idle watchers trigger events when there are no other events are pending	1385	Idle watchers trigger events when no other events of the same or higher
1347	(prepare, check and other idle watchers do not count). That is, as long	1386	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1387	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1388
1350	watchers are being called again and again, once per event loop iteration -	1389	That is, as long as your process is busy handling sockets or timeouts
		1390	(or even signals, imagine) of the same or higher priority it will not be
		1391	triggered. But when your process is idle (or only lower-priority watchers
		1392	are pending), the idle watchers are being called once per event loop
1351	until stopped, that is, or your process receives more events and becomes	1393	iteration - until stopped, that is, or your process receives more events
1352	busy.	1394	and becomes busy again with higher priority stuff.
1353		1395
1354	The most noteworthy effect is that as long as any idle watchers are	1396	The most noteworthy effect is that as long as any idle watchers are
1355	active, the process will not block when waiting for new events.	1397	active, the process will not block when waiting for new events.
1356		1398
1357	Apart from keeping your process non-blocking (which is a useful	1399	Apart from keeping your process non-blocking (which is a useful
…		…
1806		1848
1807		1849
1808	=head1 MACRO MAGIC	1850	=head1 MACRO MAGIC
1809		1851
1810	Libev can be compiled with a variety of options, the most fundemantal is	1852	Libev can be compiled with a variety of options, the most fundemantal is
1811	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	1853	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1812	callbacks have an initial C<struct ev_loop *> argument.	1854	callbacks have an initial C<struct ev_loop *> argument.
1813		1855
1814	To make it easier to write programs that cope with either variant, the	1856	To make it easier to write programs that cope with either variant, the
1815	following macros are defined:	1857	following macros are defined:
1816		1858
…		…
1850	loop, if multiple loops are supported ("ev loop default").	1892	loop, if multiple loops are supported ("ev loop default").
1851		1893
1852	=back	1894	=back
1853		1895
1854	Example: Declare and initialise a check watcher, utilising the above	1896	Example: Declare and initialise a check watcher, utilising the above
1855	macros so it will work regardless of wether multiple loops are supported	1897	macros so it will work regardless of whether multiple loops are supported
1856	or not.	1898	or not.
1857		1899
1858	static void	1900	static void
1859	check_cb (EV_P_ ev_timer *w, int revents)	1901	check_cb (EV_P_ ev_timer *w, int revents)
1860	{	1902	{
…		…
2085	will have the C<struct ev_loop *> as first argument, and you can create	2127	will have the C<struct ev_loop *> as first argument, and you can create
2086	additional independent event loops. Otherwise there will be no support	2128	additional independent event loops. Otherwise there will be no support
2087	for multiple event loops and there is no first event loop pointer	2129	for multiple event loops and there is no first event loop pointer
2088	argument. Instead, all functions act on the single default loop.	2130	argument. Instead, all functions act on the single default loop.
2089		2131
		2132	=item EV_MINPRI
		2133
		2134	=item EV_MAXPRI
		2135
		2136	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2137	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2138	provide for more priorities by overriding those symbols (usually defined
		2139	to be C<-2> and C<2>, respectively).
		2140
		2141	When doing priority-based operations, libev usually has to linearly search
		2142	all the priorities, so having many of them (hundreds) uses a lot of space
		2143	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2144	fine.
		2145
		2146	If your embedding app does not need any priorities, defining these both to
		2147	C<0> will save some memory and cpu.
		2148
2090	=item EV_PERIODIC_ENABLE	2149	=item EV_PERIODIC_ENABLE
2091		2150
2092	If undefined or defined to be C<1>, then periodic timers are supported. If	2151	If undefined or defined to be C<1>, then periodic timers are supported. If
		2152	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2153	code.
		2154
		2155	=item EV_IDLE_ENABLE
		2156
		2157	If undefined or defined to be C<1>, then idle watchers are supported. If
2093	defined to be C<0>, then they are not. Disabling them saves a few kB of	2158	defined to be C<0>, then they are not. Disabling them saves a few kB of
2094	code.	2159	code.
2095		2160
2096	=item EV_EMBED_ENABLE	2161	=item EV_EMBED_ENABLE
2097		2162
…		…
2190		2255
2191	In this section the complexities of (many of) the algorithms used inside	2256	In this section the complexities of (many of) the algorithms used inside
2192	libev will be explained. For complexity discussions about backends see the	2257	libev will be explained. For complexity discussions about backends see the
2193	documentation for C<ev_default_init>.	2258	documentation for C<ev_default_init>.
2194		2259
		2260	All of the following are about amortised time: If an array needs to be
		2261	extended, libev needs to realloc and move the whole array, but this
		2262	happens asymptotically never with higher number of elements, so O(1) might
		2263	mean it might do a lengthy realloc operation in rare cases, but on average
		2264	it is much faster and asymptotically approaches constant time.
		2265
2195	=over 4	2266	=over 4
2196		2267
2197	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2268	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2198		2269
		2270	This means that, when you have a watcher that triggers in one hour and
		2271	there are 100 watchers that would trigger before that then inserting will
		2272	have to skip those 100 watchers.
		2273
2199	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2274	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2200		2275
		2276	That means that for changing a timer costs less than removing/adding them
		2277	as only the relative motion in the event queue has to be paid for.
		2278
2201	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2279	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2202		2280
		2281	These just add the watcher into an array or at the head of a list.
2203	=item Stopping check/prepare/idle watchers: O(1)	2282	=item Stopping check/prepare/idle watchers: O(1)
2204		2283
2205	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2284	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2206		2285
		2286	These watchers are stored in lists then need to be walked to find the
		2287	correct watcher to remove. The lists are usually short (you don't usually
		2288	have many watchers waiting for the same fd or signal).
		2289
2207	=item Finding the next timer per loop iteration: O(1)	2290	=item Finding the next timer per loop iteration: O(1)
2208		2291
2209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2292	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2210		2293
		2294	A change means an I/O watcher gets started or stopped, which requires
		2295	libev to recalculate its status (and possibly tell the kernel).
		2296
2211	=item Activating one watcher: O(1)	2297	=item Activating one watcher: O(1)
2212		2298
		2299	=item Priority handling: O(number_of_priorities)
		2300
		2301	Priorities are implemented by allocating some space for each
		2302	priority. When doing priority-based operations, libev usually has to
		2303	linearly search all the priorities.
		2304
2213	=back	2305	=back
2214		2306
2215		2307
2216	=head1 AUTHOR	2308	=head1 AUTHOR
2217		2309

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Comparing libev/ev.pod (file contents): Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs. Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC vs.
Revision 1.70 by root, Fri Dec 7 19:23:48 2007 UTC