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

Comparing libev/ev.pod (file contents):
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs.
Revision 1.73 by root, Sat Dec 8 03:53:36 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
…		…
761	example, to reduce latency after idling, or more often, to bind two	766	example, to reduce latency after idling, or more often, to bind two
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.
		771
		772	You I<must not> change the priority of a watcher as long as it is active or
		773	pending.
766		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
…		…
883	it is best to always use non-blocking I/O: An extra C<read>(2) returning	891	it is best to always use non-blocking I/O: An extra C<read>(2) returning
884	C<EAGAIN> is far preferable to a program hanging until some data arrives.	892	C<EAGAIN> is far preferable to a program hanging until some data arrives.
885		893
886	If you cannot run the fd in non-blocking mode (for example you should not	894	If you cannot run the fd in non-blocking mode (for example you should not
887	play around with an Xlib connection), then you have to seperately re-test	895	play around with an Xlib connection), then you have to seperately re-test
888	wether a file descriptor is really ready with a known-to-be good interface	896	whether a file descriptor is really ready with a known-to-be good interface
889	such as poll (fortunately in our Xlib example, Xlib already does this on	897	such as poll (fortunately in our Xlib example, Xlib already does this on
890	its own, so its quite safe to use).	898	its own, so its quite safe to use).
891		899
892	=over 4	900	=over 4
893		901
…		…
1740		1748
1741	To use it,	1749	To use it,
1742		1750
1743	#include <ev++.h>	1751	#include <ev++.h>
1744		1752
1745	(it is not installed by default). This automatically includes F<ev.h>	1753	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	1754	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.	1755	put into the C<ev> namespace. It should support all the same embedding
		1756	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1748		1757
1749	It should support all the same embedding options as F<ev.h>, most notably	1758	Care has been taken to keep the overhead low. The only data member the C++
1750	C<EV_MULTIPLICITY>.	1759	classes add (compared to plain C-style watchers) is the event loop pointer
		1760	that the watcher is associated with (or no additional members at all if
		1761	you disable C<EV_MULTIPLICITY> when embedding libev).
		1762
		1763	Currently, functions, and static and non-static member functions can be
		1764	used as callbacks. Other types should be easy to add as long as they only
		1765	need one additional pointer for context. If you need support for other
		1766	types of functors please contact the author (preferably after implementing
		1767	it).
1751		1768
1752	Here is a list of things available in the C<ev> namespace:	1769	Here is a list of things available in the C<ev> namespace:
1753		1770
1754	=over 4	1771	=over 4
1755		1772
…		…
1771		1788
1772	All of those classes have these methods:	1789	All of those classes have these methods:
1773		1790
1774	=over 4	1791	=over 4
1775		1792
1776	=item ev::TYPE::TYPE (object , object::method )	1793	=item ev::TYPE::TYPE ()
1777		1794
1778	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1795	=item ev::TYPE::TYPE (struct ev_loop *)
1779		1796
1780	=item ev::TYPE::~TYPE	1797	=item ev::TYPE::~TYPE
1781		1798
1782	The constructor takes a pointer to an object and a method pointer to	1799	The constructor (optionally) takes an event loop to associate the watcher
1783	the event handler callback to call in this class. The constructor calls	1800	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	1801
1785	before starting it. If you do not specify a loop then the constructor	1802	The constructor calls C<ev_init> for you, which means you have to call the
1786	automatically associates the default loop with this watcher.	1803	C<set> method before starting it.
		1804
		1805	It will not set a callback, however: You have to call the templated C<set>
		1806	method to set a callback before you can start the watcher.
		1807
		1808	(The reason why you have to use a method is a limitation in C++ which does
		1809	not allow explicit template arguments for constructors).
1787		1810
1788	The destructor automatically stops the watcher if it is active.	1811	The destructor automatically stops the watcher if it is active.
		1812
		1813	=item w->set<class, &class::method> (object *)
		1814
		1815	This method sets the callback method to call. The method has to have a
		1816	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1817	first argument and the C<revents> as second. The object must be given as
		1818	parameter and is stored in the C<data> member of the watcher.
		1819
		1820	This method synthesizes efficient thunking code to call your method from
		1821	the C callback that libev requires. If your compiler can inline your
		1822	callback (i.e. it is visible to it at the place of the C<set> call and
		1823	your compiler is good :), then the method will be fully inlined into the
		1824	thunking function, making it as fast as a direct C callback.
		1825
		1826	Example: simple class declaration and watcher initialisation
		1827
		1828	struct myclass
		1829	{
		1830	void io_cb (ev::io &w, int revents) { }
		1831	}
		1832
		1833	myclass obj;
		1834	ev::io iow;
		1835	iow.set <myclass, &myclass::io_cb> (&obj);
		1836
		1837	=item w->set (void (function)(watcher &w, int), void data = 0)
		1838
		1839	Also sets a callback, but uses a static method or plain function as
		1840	callback. The optional C<data> argument will be stored in the watcher's
		1841	C<data> member and is free for you to use.
		1842
		1843	See the method-C<set> above for more details.
1789		1844
1790	=item w->set (struct ev_loop *)	1845	=item w->set (struct ev_loop *)
1791		1846
1792	Associates a different C<struct ev_loop> with this watcher. You can only	1847	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).	1848	do this when the watcher is inactive (and not pending either).
1794		1849
1795	=item w->set ([args])	1850	=item w->set ([args])
1796		1851
1797	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1852	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	1853	called at least once. Unlike the C counterpart, an active watcher gets
1799	automatically stopped and restarted.	1854	automatically stopped and restarted when reconfiguring it with this
		1855	method.
1800		1856
1801	=item w->start ()	1857	=item w->start ()
1802		1858
1803	Starts the watcher. Note that there is no C<loop> argument as the	1859	Starts the watcher. Note that there is no C<loop> argument, as the
1804	constructor already takes the loop.	1860	constructor already stores the event loop.
1805		1861
1806	=item w->stop ()	1862	=item w->stop ()
1807		1863
1808	Stops the watcher if it is active. Again, no C<loop> argument.	1864	Stops the watcher if it is active. Again, no C<loop> argument.
1809		1865
…		…
1834		1890
1835	myclass ();	1891	myclass ();
1836	}	1892	}
1837		1893
1838	myclass::myclass (int fd)	1894	myclass::myclass (int fd)
1839	: io (this, &myclass::io_cb),
1840	idle (this, &myclass::idle_cb)
1841	{	1895	{
		1896	io .set <myclass, &myclass::io_cb > (this);
		1897	idle.set <myclass, &myclass::idle_cb> (this);
		1898
1842	io.start (fd, ev::READ);	1899	io.start (fd, ev::READ);
1843	}	1900	}
1844		1901
1845		1902
1846	=head1 MACRO MAGIC	1903	=head1 MACRO MAGIC
1847		1904
1848	Libev can be compiled with a variety of options, the most fundemantal is	1905	Libev can be compiled with a variety of options, the most fundemantal is
1849	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	1906	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1850	callbacks have an initial C<struct ev_loop *> argument.	1907	callbacks have an initial C<struct ev_loop *> argument.
1851		1908
1852	To make it easier to write programs that cope with either variant, the	1909	To make it easier to write programs that cope with either variant, the
1853	following macros are defined:	1910	following macros are defined:
1854		1911
…		…
1888	loop, if multiple loops are supported ("ev loop default").	1945	loop, if multiple loops are supported ("ev loop default").
1889		1946
1890	=back	1947	=back
1891		1948
1892	Example: Declare and initialise a check watcher, utilising the above	1949	Example: Declare and initialise a check watcher, utilising the above
1893	macros so it will work regardless of wether multiple loops are supported	1950	macros so it will work regardless of whether multiple loops are supported
1894	or not.	1951	or not.
1895		1952
1896	static void	1953	static void
1897	check_cb (EV_P_ ev_timer *w, int revents)	1954	check_cb (EV_P_ ev_timer *w, int revents)
1898	{	1955	{
…		…
2123	will have the C<struct ev_loop *> as first argument, and you can create	2180	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	2181	additional independent event loops. Otherwise there will be no support
2125	for multiple event loops and there is no first event loop pointer	2182	for multiple event loops and there is no first event loop pointer
2126	argument. Instead, all functions act on the single default loop.	2183	argument. Instead, all functions act on the single default loop.
2127		2184
		2185	=item EV_MINPRI
		2186
		2187	=item EV_MAXPRI
		2188
		2189	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2190	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2191	provide for more priorities by overriding those symbols (usually defined
		2192	to be C<-2> and C<2>, respectively).
		2193
		2194	When doing priority-based operations, libev usually has to linearly search
		2195	all the priorities, so having many of them (hundreds) uses a lot of space
		2196	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2197	fine.
		2198
		2199	If your embedding app does not need any priorities, defining these both to
		2200	C<0> will save some memory and cpu.
		2201
2128	=item EV_PERIODIC_ENABLE	2202	=item EV_PERIODIC_ENABLE
2129		2203
2130	If undefined or defined to be C<1>, then periodic timers are supported. If	2204	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	2205	defined to be C<0>, then they are not. Disabling them saves a few kB of
2132	code.	2206	code.
…		…
2234		2308
2235	In this section the complexities of (many of) the algorithms used inside	2309	In this section the complexities of (many of) the algorithms used inside
2236	libev will be explained. For complexity discussions about backends see the	2310	libev will be explained. For complexity discussions about backends see the
2237	documentation for C<ev_default_init>.	2311	documentation for C<ev_default_init>.
2238		2312
		2313	All of the following are about amortised time: If an array needs to be
		2314	extended, libev needs to realloc and move the whole array, but this
		2315	happens asymptotically never with higher number of elements, so O(1) might
		2316	mean it might do a lengthy realloc operation in rare cases, but on average
		2317	it is much faster and asymptotically approaches constant time.
		2318
2239	=over 4	2319	=over 4
2240		2320
2241	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2321	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2242		2322
		2323	This means that, when you have a watcher that triggers in one hour and
		2324	there are 100 watchers that would trigger before that then inserting will
		2325	have to skip those 100 watchers.
		2326
2243	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2327	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2244		2328
		2329	That means that for changing a timer costs less than removing/adding them
		2330	as only the relative motion in the event queue has to be paid for.
		2331
2245	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2332	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2246		2333
		2334	These just add the watcher into an array or at the head of a list.
2247	=item Stopping check/prepare/idle watchers: O(1)	2335	=item Stopping check/prepare/idle watchers: O(1)
2248		2336
2249	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2337	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2250		2338
		2339	These watchers are stored in lists then need to be walked to find the
		2340	correct watcher to remove. The lists are usually short (you don't usually
		2341	have many watchers waiting for the same fd or signal).
		2342
2251	=item Finding the next timer per loop iteration: O(1)	2343	=item Finding the next timer per loop iteration: O(1)
2252		2344
2253	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2345	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2254		2346
		2347	A change means an I/O watcher gets started or stopped, which requires
		2348	libev to recalculate its status (and possibly tell the kernel).
		2349
2255	=item Activating one watcher: O(1)	2350	=item Activating one watcher: O(1)
2256		2351
		2352	=item Priority handling: O(number_of_priorities)
		2353
		2354	Priorities are implemented by allocating some space for each
		2355	priority. When doing priority-based operations, libev usually has to
		2356	linearly search all the priorities.
		2357
2257	=back	2358	=back
2258		2359
2259		2360
2260	=head1 AUTHOR	2361	=head1 AUTHOR
2261		2362

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Comparing libev/ev.pod (file contents): Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs. Revision 1.73 by root, Sat Dec 8 03:53:36 2007 UTC

Diff Legend

Comparing libev/ev.pod (file contents):
Revision 1.67 by root, Fri Dec 7 16:44:12 2007 UTC vs.
Revision 1.73 by root, Sat Dec 8 03:53:36 2007 UTC