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

Comparing libev/ev.pod (file contents):
Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 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
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	736	=item bool ev_is_pending (ev_TYPE *watcher)
733		737
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	738	Returns a true value iff the watcher is pending, (i.e. it has outstanding
735	events but its callback has not yet been invoked). As long as a watcher	739	events but its callback has not yet been invoked). As long as a watcher
736	is pending (but not active) you must not call an init function on it (but	740	is pending (but not active) you must not call an init function on it (but
737	C<ev_TYPE_set> is safe) and you must make sure the watcher is available to	741	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	742	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		743	it).
739		744
740	=item callback ev_cb (ev_TYPE *watcher)	745	=item callback ev_cb (ev_TYPE *watcher)
741		746
742	Returns the callback currently set on the watcher.	747	Returns the callback currently set on the watcher.
743		748
…		…
762	watchers on the same event and make sure one is called first.	767	watchers on the same event and make sure one is called first.
763		768
764	If you need to suppress invocation when higher priority events are pending	769	If you need to suppress invocation when higher priority events are pending
765	you need to look at C<ev_idle> watchers, which provide this functionality.	770	you need to look at C<ev_idle> watchers, which provide this functionality.
766		771
		772	You I<must not> change the priority of a watcher as long as it is active or
		773	pending.
		774
767	The default priority used by watchers when no priority has been set is	775	The default priority used by watchers when no priority has been set is
768	always C<0>, which is supposed to not be too high and not be too low :).	776	always C<0>, which is supposed to not be too high and not be too low :).
769		777
770	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is	778	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
771	fine, as long as you do not mind that the priority value you query might	779	fine, as long as you do not mind that the priority value you query might
772	or might not have been adjusted to be within valid range.	780	or might not have been adjusted to be within valid range.
		781
		782	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		783
		784	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		785	C<loop> nor C<revents> need to be valid as long as the watcher callback
		786	can deal with that fact.
		787
		788	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		789
		790	If the watcher is pending, this function returns clears its pending status
		791	and returns its C<revents> bitset (as if its callback was invoked). If the
		792	watcher isn't pending it does nothing and returns C<0>.
773		793
774	=back	794	=back
775		795
776		796
777	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
1473	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1493	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1474	macros, but using them is utterly, utterly and completely pointless.	1494	macros, but using them is utterly, utterly and completely pointless.
1475		1495
1476	=back	1496	=back
1477		1497
1478	Example: To include a library such as adns, you would add IO watchers	1498	There are a number of principal ways to embed other event loops or modules
1479	and a timeout watcher in a prepare handler, as required by libadns, and	1499	into libev. Here are some ideas on how to include libadns into libev
		1500	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1501	use for an actually working example. Another Perl module named C<EV::Glib>
		1502	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1503	into the Glib event loop).
		1504
		1505	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1480	in a check watcher, destroy them and call into libadns. What follows is	1506	and in a check watcher, destroy them and call into libadns. What follows
1481	pseudo-code only of course:	1507	is pseudo-code only of course. This requires you to either use a low
		1508	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1509	the callbacks for the IO/timeout watchers might not have been called yet.
1482		1510
1483	static ev_io iow [nfd];	1511	static ev_io iow [nfd];
1484	static ev_timer tw;	1512	static ev_timer tw;
1485		1513
1486	static void	1514	static void
1487	io_cb (ev_loop loop, ev_io w, int revents)	1515	io_cb (ev_loop loop, ev_io w, int revents)
1488	{	1516	{
1489	// set the relevant poll flags
1490	// could also call adns_processreadable etc. here
1491	struct pollfd fd = (struct pollfd )w->data;
1492	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1493	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1494	}	1517	}
1495		1518
1496	// create io watchers for each fd and a timer before blocking	1519	// create io watchers for each fd and a timer before blocking
1497	static void	1520	static void
1498	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1521	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1504		1527
1505	/* the callback is illegal, but won't be called as we stop during check */	1528	/* the callback is illegal, but won't be called as we stop during check */
1506	ev_timer_init (&tw, 0, timeout * 1e-3);	1529	ev_timer_init (&tw, 0, timeout * 1e-3);
1507	ev_timer_start (loop, &tw);	1530	ev_timer_start (loop, &tw);
1508		1531
1509	// create on ev_io per pollfd	1532	// create one ev_io per pollfd
1510	for (int i = 0; i < nfd; ++i)	1533	for (int i = 0; i < nfd; ++i)
1511	{	1534	{
1512	ev_io_init (iow + i, io_cb, fds [i].fd,	1535	ev_io_init (iow + i, io_cb, fds [i].fd,
1513	((fds [i].events & POLLIN ? EV_READ : 0)	1536	((fds [i].events & POLLIN ? EV_READ : 0)
1514	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1537	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1515		1538
1516	fds [i].revents = 0;	1539	fds [i].revents = 0;
1517	iow [i].data = fds + i;
1518	ev_io_start (loop, iow + i);	1540	ev_io_start (loop, iow + i);
1519	}	1541	}
1520	}	1542	}
1521		1543
1522	// stop all watchers after blocking	1544	// stop all watchers after blocking
…		…
1524	adns_check_cb (ev_loop loop, ev_check w, int revents)	1546	adns_check_cb (ev_loop loop, ev_check w, int revents)
1525	{	1547	{
1526	ev_timer_stop (loop, &tw);	1548	ev_timer_stop (loop, &tw);
1527		1549
1528	for (int i = 0; i < nfd; ++i)	1550	for (int i = 0; i < nfd; ++i)
		1551	{
		1552	// set the relevant poll flags
		1553	// could also call adns_processreadable etc. here
		1554	struct pollfd *fd = fds + i;
		1555	int revents = ev_clear_pending (iow + i);
		1556	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1557	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1558
		1559	// now stop the watcher
1529	ev_io_stop (loop, iow + i);	1560	ev_io_stop (loop, iow + i);
		1561	}
1530		1562
1531	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1563	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1564	}
		1565
		1566	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1567	in the prepare watcher and would dispose of the check watcher.
		1568
		1569	Method 3: If the module to be embedded supports explicit event
		1570	notification (adns does), you can also make use of the actual watcher
		1571	callbacks, and only destroy/create the watchers in the prepare watcher.
		1572
		1573	static void
		1574	timer_cb (EV_P_ ev_timer *w, int revents)
		1575	{
		1576	adns_state ads = (adns_state)w->data;
		1577	update_now (EV_A);
		1578
		1579	adns_processtimeouts (ads, &tv_now);
		1580	}
		1581
		1582	static void
		1583	io_cb (EV_P_ ev_io *w, int revents)
		1584	{
		1585	adns_state ads = (adns_state)w->data;
		1586	update_now (EV_A);
		1587
		1588	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1589	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1590	}
		1591
		1592	// do not ever call adns_afterpoll
		1593
		1594	Method 4: Do not use a prepare or check watcher because the module you
		1595	want to embed is too inflexible to support it. Instead, youc na override
		1596	their poll function. The drawback with this solution is that the main
		1597	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1598	this.
		1599
		1600	static gint
		1601	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1602	{
		1603	int got_events = 0;
		1604
		1605	for (n = 0; n < nfds; ++n)
		1606	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1607
		1608	if (timeout >= 0)
		1609	// create/start timer
		1610
		1611	// poll
		1612	ev_loop (EV_A_ 0);
		1613
		1614	// stop timer again
		1615	if (timeout >= 0)
		1616	ev_timer_stop (EV_A_ &to);
		1617
		1618	// stop io watchers again - their callbacks should have set
		1619	for (n = 0; n < nfds; ++n)
		1620	ev_io_stop (EV_A_ iow [n]);
		1621
		1622	return got_events;
1532	}	1623	}
1533		1624
1534		1625
1535	=head2 C<ev_embed> - when one backend isn't enough...	1626	=head2 C<ev_embed> - when one backend isn't enough...
1536		1627
…		…
1740		1831
1741	To use it,	1832	To use it,
1742		1833
1743	#include <ev++.h>	1834	#include <ev++.h>
1744		1835
1745	(it is not installed by default). This automatically includes F<ev.h>	1836	This automatically includes F<ev.h> and puts all of its definitions (many
1746	and puts all of its definitions (many of them macros) into the global	1837	of them macros) into the global namespace. All C++ specific things are
1747	namespace. All C++ specific things are put into the C<ev> namespace.	1838	put into the C<ev> namespace. It should support all the same embedding
		1839	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		1840
1749	It should support all the same embedding options as F<ev.h>, most notably	1841	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	1842	classes add (compared to plain C-style watchers) is the event loop pointer
		1843	that the watcher is associated with (or no additional members at all if
		1844	you disable C<EV_MULTIPLICITY> when embedding libev).
		1845
		1846	Currently, functions, and static and non-static member functions can be
		1847	used as callbacks. Other types should be easy to add as long as they only
		1848	need one additional pointer for context. If you need support for other
		1849	types of functors please contact the author (preferably after implementing
		1850	it).
1751		1851
1752	Here is a list of things available in the C<ev> namespace:	1852	Here is a list of things available in the C<ev> namespace:
1753		1853
1754	=over 4	1854	=over 4
1755		1855
…		…
1771		1871
1772	All of those classes have these methods:	1872	All of those classes have these methods:
1773		1873
1774	=over 4	1874	=over 4
1775		1875
1776	=item ev::TYPE::TYPE (object , object::method )	1876	=item ev::TYPE::TYPE ()
1777		1877
1778	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1878	=item ev::TYPE::TYPE (struct ev_loop *)
1779		1879
1780	=item ev::TYPE::~TYPE	1880	=item ev::TYPE::~TYPE
1781		1881
1782	The constructor takes a pointer to an object and a method pointer to	1882	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	1883	with. If it is omitted, it will use C<EV_DEFAULT>.
1784	C<ev_init> for you, which means you have to call the C<set> method	1884
1785	before starting it. If you do not specify a loop then the constructor	1885	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	1886	C<set> method before starting it.
		1887
		1888	It will not set a callback, however: You have to call the templated C<set>
		1889	method to set a callback before you can start the watcher.
		1890
		1891	(The reason why you have to use a method is a limitation in C++ which does
		1892	not allow explicit template arguments for constructors).
1787		1893
1788	The destructor automatically stops the watcher if it is active.	1894	The destructor automatically stops the watcher if it is active.
		1895
		1896	=item w->set<class, &class::method> (object *)
		1897
		1898	This method sets the callback method to call. The method has to have a
		1899	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1900	first argument and the C<revents> as second. The object must be given as
		1901	parameter and is stored in the C<data> member of the watcher.
		1902
		1903	This method synthesizes efficient thunking code to call your method from
		1904	the C callback that libev requires. If your compiler can inline your
		1905	callback (i.e. it is visible to it at the place of the C<set> call and
		1906	your compiler is good :), then the method will be fully inlined into the
		1907	thunking function, making it as fast as a direct C callback.
		1908
		1909	Example: simple class declaration and watcher initialisation
		1910
		1911	struct myclass
		1912	{
		1913	void io_cb (ev::io &w, int revents) { }
		1914	}
		1915
		1916	myclass obj;
		1917	ev::io iow;
		1918	iow.set <myclass, &myclass::io_cb> (&obj);
		1919
		1920	=item w->set<function> (void *data = 0)
		1921
		1922	Also sets a callback, but uses a static method or plain function as
		1923	callback. The optional C<data> argument will be stored in the watcher's
		1924	C<data> member and is free for you to use.
		1925
		1926	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1927
		1928	See the method-C<set> above for more details.
		1929
		1930	Example:
		1931
		1932	static void io_cb (ev::io &w, int revents) { }
		1933	iow.set <io_cb> ();
1789		1934
1790	=item w->set (struct ev_loop *)	1935	=item w->set (struct ev_loop *)
1791		1936
1792	Associates a different C<struct ev_loop> with this watcher. You can only	1937	Associates a different C<struct ev_loop> with this watcher. You can only
1793	do this when the watcher is inactive (and not pending either).	1938	do this when the watcher is inactive (and not pending either).
1794		1939
1795	=item w->set ([args])	1940	=item w->set ([args])
1796		1941
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1942	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1798	called at least once. Unlike the C counterpart, an active watcher gets	1943	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	1944	automatically stopped and restarted when reconfiguring it with this
		1945	method.
1800		1946
1801	=item w->start ()	1947	=item w->start ()
1802		1948
1803	Starts the watcher. Note that there is no C<loop> argument as the	1949	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	1950	constructor already stores the event loop.
1805		1951
1806	=item w->stop ()	1952	=item w->stop ()
1807		1953
1808	Stops the watcher if it is active. Again, no C<loop> argument.	1954	Stops the watcher if it is active. Again, no C<loop> argument.
1809		1955
…		…
1834		1980
1835	myclass ();	1981	myclass ();
1836	}	1982	}
1837		1983
1838	myclass::myclass (int fd)	1984	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	1985	{
		1986	io .set <myclass, &myclass::io_cb > (this);
		1987	idle.set <myclass, &myclass::idle_cb> (this);
		1988
1842	io.start (fd, ev::READ);	1989	io.start (fd, ev::READ);
1843	}	1990	}
1844		1991
1845		1992
1846	=head1 MACRO MAGIC	1993	=head1 MACRO MAGIC
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2270	will have the C<struct ev_loop *> as first argument, and you can create
2124	additional independent event loops. Otherwise there will be no support	2271	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2272	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2273	argument. Instead, all functions act on the single default loop.
2127		2274
		2275	=item EV_MINPRI
		2276
		2277	=item EV_MAXPRI
		2278
		2279	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2280	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2281	provide for more priorities by overriding those symbols (usually defined
		2282	to be C<-2> and C<2>, respectively).
		2283
		2284	When doing priority-based operations, libev usually has to linearly search
		2285	all the priorities, so having many of them (hundreds) uses a lot of space
		2286	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2287	fine.
		2288
		2289	If your embedding app does not need any priorities, defining these both to
		2290	C<0> will save some memory and cpu.
		2291
2128	=item EV_PERIODIC_ENABLE	2292	=item EV_PERIODIC_ENABLE
2129		2293
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2294	If undefined or defined to be C<1>, then periodic timers are supported. If
2131	defined to be C<0>, then they are not. Disabling them saves a few kB of	2295	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2296	code.
…		…
2234		2398
2235	In this section the complexities of (many of) the algorithms used inside	2399	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	2400	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2401	documentation for C<ev_default_init>.
2238		2402
		2403	All of the following are about amortised time: If an array needs to be
		2404	extended, libev needs to realloc and move the whole array, but this
		2405	happens asymptotically never with higher number of elements, so O(1) might
		2406	mean it might do a lengthy realloc operation in rare cases, but on average
		2407	it is much faster and asymptotically approaches constant time.
		2408
2239	=over 4	2409	=over 4
2240		2410
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2411	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		2412
		2413	This means that, when you have a watcher that triggers in one hour and
		2414	there are 100 watchers that would trigger before that then inserting will
		2415	have to skip those 100 watchers.
		2416
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2417	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2244		2418
		2419	That means that for changing a timer costs less than removing/adding them
		2420	as only the relative motion in the event queue has to be paid for.
		2421
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2422	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2423
		2424	These just add the watcher into an array or at the head of a list.
2247	=item Stopping check/prepare/idle watchers: O(1)	2425	=item Stopping check/prepare/idle watchers: O(1)
2248		2426
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2427	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		2428
		2429	These watchers are stored in lists then need to be walked to find the
		2430	correct watcher to remove. The lists are usually short (you don't usually
		2431	have many watchers waiting for the same fd or signal).
		2432
2251	=item Finding the next timer per loop iteration: O(1)	2433	=item Finding the next timer per loop iteration: O(1)
2252		2434
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2435	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		2436
		2437	A change means an I/O watcher gets started or stopped, which requires
		2438	libev to recalculate its status (and possibly tell the kernel).
		2439
2255	=item Activating one watcher: O(1)	2440	=item Activating one watcher: O(1)
2256		2441
		2442	=item Priority handling: O(number_of_priorities)
		2443
		2444	Priorities are implemented by allocating some space for each
		2445	priority. When doing priority-based operations, libev usually has to
		2446	linearly search all the priorities.
		2447
2257	=back	2448	=back
2258		2449
2259		2450
2260	=head1 AUTHOR	2451	=head1 AUTHOR
2261		2452

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Comparing libev/ev.pod (file contents): Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs. Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.68 by root, Fri Dec 7 18:09:43 2007 UTC vs.
Revision 1.76 by root, Sat Dec 8 15:30:30 2007 UTC