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

Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 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
…		…
482	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is	486	libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
483	usually a better approach for this kind of thing.	487	usually a better approach for this kind of thing.
484		488
485	Here are the gory details of what C<ev_loop> does:	489	Here are the gory details of what C<ev_loop> does:
486		490
		491	- Before the first iteration, call any pending watchers.
487	* If there are no active watchers (reference count is zero), return.	492	* If there are no active watchers (reference count is zero), return.
488	- Queue prepare watchers and then call all outstanding watchers.	493	- Queue all prepare watchers and then call all outstanding watchers.
489	- If we have been forked, recreate the kernel state.	494	- If we have been forked, recreate the kernel state.
490	- Update the kernel state with all outstanding changes.	495	- Update the kernel state with all outstanding changes.
491	- Update the "event loop time".	496	- Update the "event loop time".
492	- Calculate for how long to block.	497	- Calculate for how long to block.
493	- Block the process, waiting for any events.	498	- Block the process, waiting for any events.
…		…
732	=item bool ev_is_pending (ev_TYPE *watcher)	737	=item bool ev_is_pending (ev_TYPE *watcher)
733		738
734	Returns a true value iff the watcher is pending, (i.e. it has outstanding	739	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	740	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	741	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	742	C<ev_TYPE_set> is safe), you must not change its priority, and you must
738	libev (e.g. you cnanot C<free ()> it).	743	make sure the watcher is available to libev (e.g. you cannot C<free ()>
		744	it).
739		745
740	=item callback ev_cb (ev_TYPE *watcher)	746	=item callback ev_cb (ev_TYPE *watcher)
741		747
742	Returns the callback currently set on the watcher.	748	Returns the callback currently set on the watcher.
743		749
744	=item ev_cb_set (ev_TYPE *watcher, callback)	750	=item ev_cb_set (ev_TYPE *watcher, callback)
745		751
746	Change the callback. You can change the callback at virtually any time	752	Change the callback. You can change the callback at virtually any time
747	(modulo threads).	753	(modulo threads).
		754
		755	=item ev_set_priority (ev_TYPE *watcher, priority)
		756
		757	=item int ev_priority (ev_TYPE *watcher)
		758
		759	Set and query the priority of the watcher. The priority is a small
		760	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		761	(default: C<-2>). Pending watchers with higher priority will be invoked
		762	before watchers with lower priority, but priority will not keep watchers
		763	from being executed (except for C<ev_idle> watchers).
		764
		765	This means that priorities are I<only> used for ordering callback
		766	invocation after new events have been received. This is useful, for
		767	example, to reduce latency after idling, or more often, to bind two
		768	watchers on the same event and make sure one is called first.
		769
		770	If you need to suppress invocation when higher priority events are pending
		771	you need to look at C<ev_idle> watchers, which provide this functionality.
		772
		773	You I<must not> change the priority of a watcher as long as it is active or
		774	pending.
		775
		776	The default priority used by watchers when no priority has been set is
		777	always C<0>, which is supposed to not be too high and not be too low :).
		778
		779	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		780	fine, as long as you do not mind that the priority value you query might
		781	or might not have been adjusted to be within valid range.
		782
		783	=item ev_invoke (loop, ev_TYPE *watcher, int revents)
		784
		785	Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
		786	C<loop> nor C<revents> need to be valid as long as the watcher callback
		787	can deal with that fact.
		788
		789	=item int ev_clear_pending (loop, ev_TYPE *watcher)
		790
		791	If the watcher is pending, this function returns clears its pending status
		792	and returns its C<revents> bitset (as if its callback was invoked). If the
		793	watcher isn't pending it does nothing and returns C<0>.
748		794
749	=back	795	=back
750		796
751		797
752	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	798	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
858	it is best to always use non-blocking I/O: An extra C<read>(2) returning	904	it is best to always use non-blocking I/O: An extra C<read>(2) returning
859	C<EAGAIN> is far preferable to a program hanging until some data arrives.	905	C<EAGAIN> is far preferable to a program hanging until some data arrives.
860		906
861	If you cannot run the fd in non-blocking mode (for example you should not	907	If you cannot run the fd in non-blocking mode (for example you should not
862	play around with an Xlib connection), then you have to seperately re-test	908	play around with an Xlib connection), then you have to seperately re-test
863	wether a file descriptor is really ready with a known-to-be good interface	909	whether a file descriptor is really ready with a known-to-be good interface
864	such as poll (fortunately in our Xlib example, Xlib already does this on	910	such as poll (fortunately in our Xlib example, Xlib already does this on
865	its own, so its quite safe to use).	911	its own, so its quite safe to use).
866		912
867	=over 4	913	=over 4
868		914
…		…
1351	ev_stat_start (loop, &passwd);	1397	ev_stat_start (loop, &passwd);
1352		1398
1353		1399
1354	=head2 C<ev_idle> - when you've got nothing better to do...	1400	=head2 C<ev_idle> - when you've got nothing better to do...
1355		1401
1356	Idle watchers trigger events when there are no other events are pending	1402	Idle watchers trigger events when no other events of the same or higher
1357	(prepare, check and other idle watchers do not count). That is, as long	1403	priority are pending (prepare, check and other idle watchers do not
1358	as your process is busy handling sockets or timeouts (or even signals,	1404	count).
1359	imagine) it will not be triggered. But when your process is idle all idle	1405
1360	watchers are being called again and again, once per event loop iteration -	1406	That is, as long as your process is busy handling sockets or timeouts
		1407	(or even signals, imagine) of the same or higher priority it will not be
		1408	triggered. But when your process is idle (or only lower-priority watchers
		1409	are pending), the idle watchers are being called once per event loop
1361	until stopped, that is, or your process receives more events and becomes	1410	iteration - until stopped, that is, or your process receives more events
1362	busy.	1411	and becomes busy again with higher priority stuff.
1363		1412
1364	The most noteworthy effect is that as long as any idle watchers are	1413	The most noteworthy effect is that as long as any idle watchers are
1365	active, the process will not block when waiting for new events.	1414	active, the process will not block when waiting for new events.
1366		1415
1367	Apart from keeping your process non-blocking (which is a useful	1416	Apart from keeping your process non-blocking (which is a useful
…		…
1433	with priority higher than or equal to the event loop and one coroutine	1482	with priority higher than or equal to the event loop and one coroutine
1434	of lower priority, but only once, using idle watchers to keep the event	1483	of lower priority, but only once, using idle watchers to keep the event
1435	loop from blocking if lower-priority coroutines are active, thus mapping	1484	loop from blocking if lower-priority coroutines are active, thus mapping
1436	low-priority coroutines to idle/background tasks).	1485	low-priority coroutines to idle/background tasks).
1437		1486
		1487	It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
		1488	priority, to ensure that they are being run before any other watchers
		1489	after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
		1490	too) should not activate ("feed") events into libev. While libev fully
		1491	supports this, they will be called before other C<ev_check> watchers did
		1492	their job. As C<ev_check> watchers are often used to embed other event
		1493	loops those other event loops might be in an unusable state until their
		1494	C<ev_check> watcher ran (always remind yourself to coexist peacefully with
		1495	others).
		1496
1438	=over 4	1497	=over 4
1439		1498
1440	=item ev_prepare_init (ev_prepare *, callback)	1499	=item ev_prepare_init (ev_prepare *, callback)
1441		1500
1442	=item ev_check_init (ev_check *, callback)	1501	=item ev_check_init (ev_check *, callback)
…		…
1445	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>	1504	parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1446	macros, but using them is utterly, utterly and completely pointless.	1505	macros, but using them is utterly, utterly and completely pointless.
1447		1506
1448	=back	1507	=back
1449		1508
1450	Example: To include a library such as adns, you would add IO watchers	1509	There are a number of principal ways to embed other event loops or modules
1451	and a timeout watcher in a prepare handler, as required by libadns, and	1510	into libev. Here are some ideas on how to include libadns into libev
		1511	(there is a Perl module named C<EV::ADNS> that does this, which you could
		1512	use for an actually working example. Another Perl module named C<EV::Glib>
		1513	embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
		1514	into the Glib event loop).
		1515
		1516	Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1452	in a check watcher, destroy them and call into libadns. What follows is	1517	and in a check watcher, destroy them and call into libadns. What follows
1453	pseudo-code only of course:	1518	is pseudo-code only of course. This requires you to either use a low
		1519	priority for the check watcher or use C<ev_clear_pending> explicitly, as
		1520	the callbacks for the IO/timeout watchers might not have been called yet.
1454		1521
1455	static ev_io iow [nfd];	1522	static ev_io iow [nfd];
1456	static ev_timer tw;	1523	static ev_timer tw;
1457		1524
1458	static void	1525	static void
1459	io_cb (ev_loop loop, ev_io w, int revents)	1526	io_cb (ev_loop loop, ev_io w, int revents)
1460	{	1527	{
1461	// set the relevant poll flags
1462	// could also call adns_processreadable etc. here
1463	struct pollfd fd = (struct pollfd )w->data;
1464	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
1465	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
1466	}	1528	}
1467		1529
1468	// create io watchers for each fd and a timer before blocking	1530	// create io watchers for each fd and a timer before blocking
1469	static void	1531	static void
1470	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)	1532	adns_prepare_cb (ev_loop loop, ev_prepare w, int revents)
…		…
1476		1538
1477	/* the callback is illegal, but won't be called as we stop during check */	1539	/* the callback is illegal, but won't be called as we stop during check */
1478	ev_timer_init (&tw, 0, timeout * 1e-3);	1540	ev_timer_init (&tw, 0, timeout * 1e-3);
1479	ev_timer_start (loop, &tw);	1541	ev_timer_start (loop, &tw);
1480		1542
1481	// create on ev_io per pollfd	1543	// create one ev_io per pollfd
1482	for (int i = 0; i < nfd; ++i)	1544	for (int i = 0; i < nfd; ++i)
1483	{	1545	{
1484	ev_io_init (iow + i, io_cb, fds [i].fd,	1546	ev_io_init (iow + i, io_cb, fds [i].fd,
1485	((fds [i].events & POLLIN ? EV_READ : 0)	1547	((fds [i].events & POLLIN ? EV_READ : 0)
1486	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));	1548	\| (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487		1549
1488	fds [i].revents = 0;	1550	fds [i].revents = 0;
1489	iow [i].data = fds + i;
1490	ev_io_start (loop, iow + i);	1551	ev_io_start (loop, iow + i);
1491	}	1552	}
1492	}	1553	}
1493		1554
1494	// stop all watchers after blocking	1555	// stop all watchers after blocking
…		…
1496	adns_check_cb (ev_loop loop, ev_check w, int revents)	1557	adns_check_cb (ev_loop loop, ev_check w, int revents)
1497	{	1558	{
1498	ev_timer_stop (loop, &tw);	1559	ev_timer_stop (loop, &tw);
1499		1560
1500	for (int i = 0; i < nfd; ++i)	1561	for (int i = 0; i < nfd; ++i)
		1562	{
		1563	// set the relevant poll flags
		1564	// could also call adns_processreadable etc. here
		1565	struct pollfd *fd = fds + i;
		1566	int revents = ev_clear_pending (iow + i);
		1567	if (revents & EV_READ ) fd->revents \|= fd->events & POLLIN;
		1568	if (revents & EV_WRITE) fd->revents \|= fd->events & POLLOUT;
		1569
		1570	// now stop the watcher
1501	ev_io_stop (loop, iow + i);	1571	ev_io_stop (loop, iow + i);
		1572	}
1502		1573
1503	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));	1574	adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
		1575	}
		1576
		1577	Method 2: This would be just like method 1, but you run C<adns_afterpoll>
		1578	in the prepare watcher and would dispose of the check watcher.
		1579
		1580	Method 3: If the module to be embedded supports explicit event
		1581	notification (adns does), you can also make use of the actual watcher
		1582	callbacks, and only destroy/create the watchers in the prepare watcher.
		1583
		1584	static void
		1585	timer_cb (EV_P_ ev_timer *w, int revents)
		1586	{
		1587	adns_state ads = (adns_state)w->data;
		1588	update_now (EV_A);
		1589
		1590	adns_processtimeouts (ads, &tv_now);
		1591	}
		1592
		1593	static void
		1594	io_cb (EV_P_ ev_io *w, int revents)
		1595	{
		1596	adns_state ads = (adns_state)w->data;
		1597	update_now (EV_A);
		1598
		1599	if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
		1600	if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
		1601	}
		1602
		1603	// do not ever call adns_afterpoll
		1604
		1605	Method 4: Do not use a prepare or check watcher because the module you
		1606	want to embed is too inflexible to support it. Instead, youc na override
		1607	their poll function. The drawback with this solution is that the main
		1608	loop is now no longer controllable by EV. The C<Glib::EV> module does
		1609	this.
		1610
		1611	static gint
		1612	event_poll_func (GPollFD *fds, guint nfds, gint timeout)
		1613	{
		1614	int got_events = 0;
		1615
		1616	for (n = 0; n < nfds; ++n)
		1617	// create/start io watcher that sets the relevant bits in fds[n] and increment got_events
		1618
		1619	if (timeout >= 0)
		1620	// create/start timer
		1621
		1622	// poll
		1623	ev_loop (EV_A_ 0);
		1624
		1625	// stop timer again
		1626	if (timeout >= 0)
		1627	ev_timer_stop (EV_A_ &to);
		1628
		1629	// stop io watchers again - their callbacks should have set
		1630	for (n = 0; n < nfds; ++n)
		1631	ev_io_stop (EV_A_ iow [n]);
		1632
		1633	return got_events;
1504	}	1634	}
1505		1635
1506		1636
1507	=head2 C<ev_embed> - when one backend isn't enough...	1637	=head2 C<ev_embed> - when one backend isn't enough...
1508		1638
…		…
1712		1842
1713	To use it,	1843	To use it,
1714		1844
1715	#include <ev++.h>	1845	#include <ev++.h>
1716		1846
1717	(it is not installed by default). This automatically includes F<ev.h>	1847	This automatically includes F<ev.h> and puts all of its definitions (many
1718	and puts all of its definitions (many of them macros) into the global	1848	of them macros) into the global namespace. All C++ specific things are
1719	namespace. All C++ specific things are put into the C<ev> namespace.	1849	put into the C<ev> namespace. It should support all the same embedding
		1850	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720		1851
1721	It should support all the same embedding options as F<ev.h>, most notably	1852	Care has been taken to keep the overhead low. The only data member the C++
1722	C<EV_MULTIPLICITY>.	1853	classes add (compared to plain C-style watchers) is the event loop pointer
		1854	that the watcher is associated with (or no additional members at all if
		1855	you disable C<EV_MULTIPLICITY> when embedding libev).
		1856
		1857	Currently, functions, and static and non-static member functions can be
		1858	used as callbacks. Other types should be easy to add as long as they only
		1859	need one additional pointer for context. If you need support for other
		1860	types of functors please contact the author (preferably after implementing
		1861	it).
1723		1862
1724	Here is a list of things available in the C<ev> namespace:	1863	Here is a list of things available in the C<ev> namespace:
1725		1864
1726	=over 4	1865	=over 4
1727		1866
…		…
1743		1882
1744	All of those classes have these methods:	1883	All of those classes have these methods:
1745		1884
1746	=over 4	1885	=over 4
1747		1886
1748	=item ev::TYPE::TYPE (object , object::method )	1887	=item ev::TYPE::TYPE ()
1749		1888
1750	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1889	=item ev::TYPE::TYPE (struct ev_loop *)
1751		1890
1752	=item ev::TYPE::~TYPE	1891	=item ev::TYPE::~TYPE
1753		1892
1754	The constructor takes a pointer to an object and a method pointer to	1893	The constructor (optionally) takes an event loop to associate the watcher
1755	the event handler callback to call in this class. The constructor calls	1894	with. If it is omitted, it will use C<EV_DEFAULT>.
1756	C<ev_init> for you, which means you have to call the C<set> method	1895
1757	before starting it. If you do not specify a loop then the constructor	1896	The constructor calls C<ev_init> for you, which means you have to call the
1758	automatically associates the default loop with this watcher.	1897	C<set> method before starting it.
		1898
		1899	It will not set a callback, however: You have to call the templated C<set>
		1900	method to set a callback before you can start the watcher.
		1901
		1902	(The reason why you have to use a method is a limitation in C++ which does
		1903	not allow explicit template arguments for constructors).
1759		1904
1760	The destructor automatically stops the watcher if it is active.	1905	The destructor automatically stops the watcher if it is active.
		1906
		1907	=item w->set<class, &class::method> (object *)
		1908
		1909	This method sets the callback method to call. The method has to have a
		1910	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1911	first argument and the C<revents> as second. The object must be given as
		1912	parameter and is stored in the C<data> member of the watcher.
		1913
		1914	This method synthesizes efficient thunking code to call your method from
		1915	the C callback that libev requires. If your compiler can inline your
		1916	callback (i.e. it is visible to it at the place of the C<set> call and
		1917	your compiler is good :), then the method will be fully inlined into the
		1918	thunking function, making it as fast as a direct C callback.
		1919
		1920	Example: simple class declaration and watcher initialisation
		1921
		1922	struct myclass
		1923	{
		1924	void io_cb (ev::io &w, int revents) { }
		1925	}
		1926
		1927	myclass obj;
		1928	ev::io iow;
		1929	iow.set <myclass, &myclass::io_cb> (&obj);
		1930
		1931	=item w->set<function> (void *data = 0)
		1932
		1933	Also sets a callback, but uses a static method or plain function as
		1934	callback. The optional C<data> argument will be stored in the watcher's
		1935	C<data> member and is free for you to use.
		1936
		1937	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1938
		1939	See the method-C<set> above for more details.
		1940
		1941	Example:
		1942
		1943	static void io_cb (ev::io &w, int revents) { }
		1944	iow.set <io_cb> ();
1761		1945
1762	=item w->set (struct ev_loop *)	1946	=item w->set (struct ev_loop *)
1763		1947
1764	Associates a different C<struct ev_loop> with this watcher. You can only	1948	Associates a different C<struct ev_loop> with this watcher. You can only
1765	do this when the watcher is inactive (and not pending either).	1949	do this when the watcher is inactive (and not pending either).
1766		1950
1767	=item w->set ([args])	1951	=item w->set ([args])
1768		1952
1769	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1953	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1770	called at least once. Unlike the C counterpart, an active watcher gets	1954	called at least once. Unlike the C counterpart, an active watcher gets
1771	automatically stopped and restarted.	1955	automatically stopped and restarted when reconfiguring it with this
		1956	method.
1772		1957
1773	=item w->start ()	1958	=item w->start ()
1774		1959
1775	Starts the watcher. Note that there is no C<loop> argument as the	1960	Starts the watcher. Note that there is no C<loop> argument, as the
1776	constructor already takes the loop.	1961	constructor already stores the event loop.
1777		1962
1778	=item w->stop ()	1963	=item w->stop ()
1779		1964
1780	Stops the watcher if it is active. Again, no C<loop> argument.	1965	Stops the watcher if it is active. Again, no C<loop> argument.
1781		1966
…		…
1806		1991
1807	myclass ();	1992	myclass ();
1808	}	1993	}
1809		1994
1810	myclass::myclass (int fd)	1995	myclass::myclass (int fd)
1811	: io (this, &myclass::io_cb),
1812	idle (this, &myclass::idle_cb)
1813	{	1996	{
		1997	io .set <myclass, &myclass::io_cb > (this);
		1998	idle.set <myclass, &myclass::idle_cb> (this);
		1999
1814	io.start (fd, ev::READ);	2000	io.start (fd, ev::READ);
1815	}	2001	}
1816		2002
1817		2003
1818	=head1 MACRO MAGIC	2004	=head1 MACRO MAGIC
1819		2005
1820	Libev can be compiled with a variety of options, the most fundemantal is	2006	Libev can be compiled with a variety of options, the most fundemantal is
1821	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	2007	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1822	callbacks have an initial C<struct ev_loop *> argument.	2008	callbacks have an initial C<struct ev_loop *> argument.
1823		2009
1824	To make it easier to write programs that cope with either variant, the	2010	To make it easier to write programs that cope with either variant, the
1825	following macros are defined:	2011	following macros are defined:
1826		2012
…		…
1860	loop, if multiple loops are supported ("ev loop default").	2046	loop, if multiple loops are supported ("ev loop default").
1861		2047
1862	=back	2048	=back
1863		2049
1864	Example: Declare and initialise a check watcher, utilising the above	2050	Example: Declare and initialise a check watcher, utilising the above
1865	macros so it will work regardless of wether multiple loops are supported	2051	macros so it will work regardless of whether multiple loops are supported
1866	or not.	2052	or not.
1867		2053
1868	static void	2054	static void
1869	check_cb (EV_P_ ev_timer *w, int revents)	2055	check_cb (EV_P_ ev_timer *w, int revents)
1870	{	2056	{
…		…
2095	will have the C<struct ev_loop *> as first argument, and you can create	2281	will have the C<struct ev_loop *> as first argument, and you can create
2096	additional independent event loops. Otherwise there will be no support	2282	additional independent event loops. Otherwise there will be no support
2097	for multiple event loops and there is no first event loop pointer	2283	for multiple event loops and there is no first event loop pointer
2098	argument. Instead, all functions act on the single default loop.	2284	argument. Instead, all functions act on the single default loop.
2099		2285
		2286	=item EV_MINPRI
		2287
		2288	=item EV_MAXPRI
		2289
		2290	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2291	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2292	provide for more priorities by overriding those symbols (usually defined
		2293	to be C<-2> and C<2>, respectively).
		2294
		2295	When doing priority-based operations, libev usually has to linearly search
		2296	all the priorities, so having many of them (hundreds) uses a lot of space
		2297	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2298	fine.
		2299
		2300	If your embedding app does not need any priorities, defining these both to
		2301	C<0> will save some memory and cpu.
		2302
2100	=item EV_PERIODIC_ENABLE	2303	=item EV_PERIODIC_ENABLE
2101		2304
2102	If undefined or defined to be C<1>, then periodic timers are supported. If	2305	If undefined or defined to be C<1>, then periodic timers are supported. If
		2306	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2307	code.
		2308
		2309	=item EV_IDLE_ENABLE
		2310
		2311	If undefined or defined to be C<1>, then idle watchers are supported. If
2103	defined to be C<0>, then they are not. Disabling them saves a few kB of	2312	defined to be C<0>, then they are not. Disabling them saves a few kB of
2104	code.	2313	code.
2105		2314
2106	=item EV_EMBED_ENABLE	2315	=item EV_EMBED_ENABLE
2107		2316
…		…
2200		2409
2201	In this section the complexities of (many of) the algorithms used inside	2410	In this section the complexities of (many of) the algorithms used inside
2202	libev will be explained. For complexity discussions about backends see the	2411	libev will be explained. For complexity discussions about backends see the
2203	documentation for C<ev_default_init>.	2412	documentation for C<ev_default_init>.
2204		2413
		2414	All of the following are about amortised time: If an array needs to be
		2415	extended, libev needs to realloc and move the whole array, but this
		2416	happens asymptotically never with higher number of elements, so O(1) might
		2417	mean it might do a lengthy realloc operation in rare cases, but on average
		2418	it is much faster and asymptotically approaches constant time.
		2419
2205	=over 4	2420	=over 4
2206		2421
2207	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2422	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208		2423
		2424	This means that, when you have a watcher that triggers in one hour and
		2425	there are 100 watchers that would trigger before that then inserting will
		2426	have to skip those 100 watchers.
		2427
2209	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2428	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210		2429
		2430	That means that for changing a timer costs less than removing/adding them
		2431	as only the relative motion in the event queue has to be paid for.
		2432
2211	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2433	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212		2434
		2435	These just add the watcher into an array or at the head of a list.
2213	=item Stopping check/prepare/idle watchers: O(1)	2436	=item Stopping check/prepare/idle watchers: O(1)
2214		2437
2215	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2438	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216		2439
		2440	These watchers are stored in lists then need to be walked to find the
		2441	correct watcher to remove. The lists are usually short (you don't usually
		2442	have many watchers waiting for the same fd or signal).
		2443
2217	=item Finding the next timer per loop iteration: O(1)	2444	=item Finding the next timer per loop iteration: O(1)
2218		2445
2219	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2446	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220		2447
		2448	A change means an I/O watcher gets started or stopped, which requires
		2449	libev to recalculate its status (and possibly tell the kernel).
		2450
2221	=item Activating one watcher: O(1)	2451	=item Activating one watcher: O(1)
2222		2452
		2453	=item Priority handling: O(number_of_priorities)
		2454
		2455	Priorities are implemented by allocating some space for each
		2456	priority. When doing priority-based operations, libev usually has to
		2457	linearly search all the priorities.
		2458
2223	=back	2459	=back
2224		2460
2225		2461
2226	=head1 AUTHOR	2462	=head1 AUTHOR
2227		2463

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing libev/ev.pod (file contents): Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs. Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.66 by root, Mon Dec 3 13:41:25 2007 UTC vs.
Revision 1.77 by root, Sat Dec 8 22:11:14 2007 UTC