[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 1.75 by root, Sat Dec 8 14:27:39 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.
…		…
722	=item bool ev_is_pending (ev_TYPE *watcher)	736	=item bool ev_is_pending (ev_TYPE *watcher)
723		737
724	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
725	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
726	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
727	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
728	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).
729		744
730	=item callback ev_cb (ev_TYPE *watcher)	745	=item callback ev_cb (ev_TYPE *watcher)
731		746
732	Returns the callback currently set on the watcher.	747	Returns the callback currently set on the watcher.
733		748
734	=item ev_cb_set (ev_TYPE *watcher, callback)	749	=item ev_cb_set (ev_TYPE *watcher, callback)
735		750
736	Change the callback. You can change the callback at virtually any time	751	Change the callback. You can change the callback at virtually any time
737	(modulo threads).	752	(modulo threads).
		753
		754	=item ev_set_priority (ev_TYPE *watcher, priority)
		755
		756	=item int ev_priority (ev_TYPE *watcher)
		757
		758	Set and query the priority of the watcher. The priority is a small
		759	integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
		760	(default: C<-2>). Pending watchers with higher priority will be invoked
		761	before watchers with lower priority, but priority will not keep watchers
		762	from being executed (except for C<ev_idle> watchers).
		763
		764	This means that priorities are I<only> used for ordering callback
		765	invocation after new events have been received. This is useful, for
		766	example, to reduce latency after idling, or more often, to bind two
		767	watchers on the same event and make sure one is called first.
		768
		769	If you need to suppress invocation when higher priority events are pending
		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.
		774
		775	The default priority used by watchers when no priority has been set is
		776	always C<0>, which is supposed to not be too high and not be too low :).
		777
		778	Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
		779	fine, as long as you do not mind that the priority value you query might
		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>.
738		793
739	=back	794	=back
740		795
741		796
742	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER	797	=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
…		…
848	it is best to always use non-blocking I/O: An extra C<read>(2) returning	903	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.	904	C<EAGAIN> is far preferable to a program hanging until some data arrives.
850		905
851	If you cannot run the fd in non-blocking mode (for example you should not	906	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	907	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	908	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	909	such as poll (fortunately in our Xlib example, Xlib already does this on
855	its own, so its quite safe to use).	910	its own, so its quite safe to use).
856		911
857	=over 4	912	=over 4
858		913
…		…
1341	ev_stat_start (loop, &passwd);	1396	ev_stat_start (loop, &passwd);
1342		1397
1343		1398
1344	=head2 C<ev_idle> - when you've got nothing better to do...	1399	=head2 C<ev_idle> - when you've got nothing better to do...
1345		1400
1346	Idle watchers trigger events when there are no other events are pending	1401	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	1402	priority are pending (prepare, check and other idle watchers do not
1348	as your process is busy handling sockets or timeouts (or even signals,	1403	count).
1349	imagine) it will not be triggered. But when your process is idle all idle	1404
1350	watchers are being called again and again, once per event loop iteration -	1405	That is, as long as your process is busy handling sockets or timeouts
		1406	(or even signals, imagine) of the same or higher priority it will not be
		1407	triggered. But when your process is idle (or only lower-priority watchers
		1408	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	1409	iteration - until stopped, that is, or your process receives more events
1352	busy.	1410	and becomes busy again with higher priority stuff.
1353		1411
1354	The most noteworthy effect is that as long as any idle watchers are	1412	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.	1413	active, the process will not block when waiting for new events.
1356		1414
1357	Apart from keeping your process non-blocking (which is a useful	1415	Apart from keeping your process non-blocking (which is a useful
…		…
1702		1760
1703	To use it,	1761	To use it,
1704		1762
1705	#include <ev++.h>	1763	#include <ev++.h>
1706		1764
1707	(it is not installed by default). This automatically includes F<ev.h>	1765	This automatically includes F<ev.h> and puts all of its definitions (many
1708	and puts all of its definitions (many of them macros) into the global	1766	of them macros) into the global namespace. All C++ specific things are
1709	namespace. All C++ specific things are put into the C<ev> namespace.	1767	put into the C<ev> namespace. It should support all the same embedding
		1768	options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1710		1769
1711	It should support all the same embedding options as F<ev.h>, most notably	1770	Care has been taken to keep the overhead low. The only data member the C++
1712	C<EV_MULTIPLICITY>.	1771	classes add (compared to plain C-style watchers) is the event loop pointer
		1772	that the watcher is associated with (or no additional members at all if
		1773	you disable C<EV_MULTIPLICITY> when embedding libev).
		1774
		1775	Currently, functions, and static and non-static member functions can be
		1776	used as callbacks. Other types should be easy to add as long as they only
		1777	need one additional pointer for context. If you need support for other
		1778	types of functors please contact the author (preferably after implementing
		1779	it).
1713		1780
1714	Here is a list of things available in the C<ev> namespace:	1781	Here is a list of things available in the C<ev> namespace:
1715		1782
1716	=over 4	1783	=over 4
1717		1784
…		…
1733		1800
1734	All of those classes have these methods:	1801	All of those classes have these methods:
1735		1802
1736	=over 4	1803	=over 4
1737		1804
1738	=item ev::TYPE::TYPE (object , object::method )	1805	=item ev::TYPE::TYPE ()
1739		1806
1740	=item ev::TYPE::TYPE (object , object::method , struct ev_loop *)	1807	=item ev::TYPE::TYPE (struct ev_loop *)
1741		1808
1742	=item ev::TYPE::~TYPE	1809	=item ev::TYPE::~TYPE
1743		1810
1744	The constructor takes a pointer to an object and a method pointer to	1811	The constructor (optionally) takes an event loop to associate the watcher
1745	the event handler callback to call in this class. The constructor calls	1812	with. If it is omitted, it will use C<EV_DEFAULT>.
1746	C<ev_init> for you, which means you have to call the C<set> method	1813
1747	before starting it. If you do not specify a loop then the constructor	1814	The constructor calls C<ev_init> for you, which means you have to call the
1748	automatically associates the default loop with this watcher.	1815	C<set> method before starting it.
		1816
		1817	It will not set a callback, however: You have to call the templated C<set>
		1818	method to set a callback before you can start the watcher.
		1819
		1820	(The reason why you have to use a method is a limitation in C++ which does
		1821	not allow explicit template arguments for constructors).
1749		1822
1750	The destructor automatically stops the watcher if it is active.	1823	The destructor automatically stops the watcher if it is active.
		1824
		1825	=item w->set<class, &class::method> (object *)
		1826
		1827	This method sets the callback method to call. The method has to have a
		1828	signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
		1829	first argument and the C<revents> as second. The object must be given as
		1830	parameter and is stored in the C<data> member of the watcher.
		1831
		1832	This method synthesizes efficient thunking code to call your method from
		1833	the C callback that libev requires. If your compiler can inline your
		1834	callback (i.e. it is visible to it at the place of the C<set> call and
		1835	your compiler is good :), then the method will be fully inlined into the
		1836	thunking function, making it as fast as a direct C callback.
		1837
		1838	Example: simple class declaration and watcher initialisation
		1839
		1840	struct myclass
		1841	{
		1842	void io_cb (ev::io &w, int revents) { }
		1843	}
		1844
		1845	myclass obj;
		1846	ev::io iow;
		1847	iow.set <myclass, &myclass::io_cb> (&obj);
		1848
		1849	=item w->set<function> (void *data = 0)
		1850
		1851	Also sets a callback, but uses a static method or plain function as
		1852	callback. The optional C<data> argument will be stored in the watcher's
		1853	C<data> member and is free for you to use.
		1854
		1855	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
		1856
		1857	See the method-C<set> above for more details.
		1858
		1859	Example:
		1860
		1861	static void io_cb (ev::io &w, int revents) { }
		1862	iow.set <io_cb> ();
1751		1863
1752	=item w->set (struct ev_loop *)	1864	=item w->set (struct ev_loop *)
1753		1865
1754	Associates a different C<struct ev_loop> with this watcher. You can only	1866	Associates a different C<struct ev_loop> with this watcher. You can only
1755	do this when the watcher is inactive (and not pending either).	1867	do this when the watcher is inactive (and not pending either).
1756		1868
1757	=item w->set ([args])	1869	=item w->set ([args])
1758		1870
1759	Basically the same as C<ev_TYPE_set>, with the same args. Must be	1871	Basically the same as C<ev_TYPE_set>, with the same args. Must be
1760	called at least once. Unlike the C counterpart, an active watcher gets	1872	called at least once. Unlike the C counterpart, an active watcher gets
1761	automatically stopped and restarted.	1873	automatically stopped and restarted when reconfiguring it with this
		1874	method.
1762		1875
1763	=item w->start ()	1876	=item w->start ()
1764		1877
1765	Starts the watcher. Note that there is no C<loop> argument as the	1878	Starts the watcher. Note that there is no C<loop> argument, as the
1766	constructor already takes the loop.	1879	constructor already stores the event loop.
1767		1880
1768	=item w->stop ()	1881	=item w->stop ()
1769		1882
1770	Stops the watcher if it is active. Again, no C<loop> argument.	1883	Stops the watcher if it is active. Again, no C<loop> argument.
1771		1884
…		…
1796		1909
1797	myclass ();	1910	myclass ();
1798	}	1911	}
1799		1912
1800	myclass::myclass (int fd)	1913	myclass::myclass (int fd)
1801	: io (this, &myclass::io_cb),
1802	idle (this, &myclass::idle_cb)
1803	{	1914	{
		1915	io .set <myclass, &myclass::io_cb > (this);
		1916	idle.set <myclass, &myclass::idle_cb> (this);
		1917
1804	io.start (fd, ev::READ);	1918	io.start (fd, ev::READ);
1805	}	1919	}
1806		1920
1807		1921
1808	=head1 MACRO MAGIC	1922	=head1 MACRO MAGIC
1809		1923
1810	Libev can be compiled with a variety of options, the most fundemantal is	1924	Libev can be compiled with a variety of options, the most fundemantal is
1811	C<EV_MULTIPLICITY>. This option determines wether (most) functions and	1925	C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1812	callbacks have an initial C<struct ev_loop *> argument.	1926	callbacks have an initial C<struct ev_loop *> argument.
1813		1927
1814	To make it easier to write programs that cope with either variant, the	1928	To make it easier to write programs that cope with either variant, the
1815	following macros are defined:	1929	following macros are defined:
1816		1930
…		…
1850	loop, if multiple loops are supported ("ev loop default").	1964	loop, if multiple loops are supported ("ev loop default").
1851		1965
1852	=back	1966	=back
1853		1967
1854	Example: Declare and initialise a check watcher, utilising the above	1968	Example: Declare and initialise a check watcher, utilising the above
1855	macros so it will work regardless of wether multiple loops are supported	1969	macros so it will work regardless of whether multiple loops are supported
1856	or not.	1970	or not.
1857		1971
1858	static void	1972	static void
1859	check_cb (EV_P_ ev_timer *w, int revents)	1973	check_cb (EV_P_ ev_timer *w, int revents)
1860	{	1974	{
…		…
2085	will have the C<struct ev_loop *> as first argument, and you can create	2199	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	2200	additional independent event loops. Otherwise there will be no support
2087	for multiple event loops and there is no first event loop pointer	2201	for multiple event loops and there is no first event loop pointer
2088	argument. Instead, all functions act on the single default loop.	2202	argument. Instead, all functions act on the single default loop.
2089		2203
		2204	=item EV_MINPRI
		2205
		2206	=item EV_MAXPRI
		2207
		2208	The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
		2209	C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
		2210	provide for more priorities by overriding those symbols (usually defined
		2211	to be C<-2> and C<2>, respectively).
		2212
		2213	When doing priority-based operations, libev usually has to linearly search
		2214	all the priorities, so having many of them (hundreds) uses a lot of space
		2215	and time, so using the defaults of five priorities (-2 .. +2) is usually
		2216	fine.
		2217
		2218	If your embedding app does not need any priorities, defining these both to
		2219	C<0> will save some memory and cpu.
		2220
2090	=item EV_PERIODIC_ENABLE	2221	=item EV_PERIODIC_ENABLE
2091		2222
2092	If undefined or defined to be C<1>, then periodic timers are supported. If	2223	If undefined or defined to be C<1>, then periodic timers are supported. If
		2224	defined to be C<0>, then they are not. Disabling them saves a few kB of
		2225	code.
		2226
		2227	=item EV_IDLE_ENABLE
		2228
		2229	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	2230	defined to be C<0>, then they are not. Disabling them saves a few kB of
2094	code.	2231	code.
2095		2232
2096	=item EV_EMBED_ENABLE	2233	=item EV_EMBED_ENABLE
2097		2234
…		…
2190		2327
2191	In this section the complexities of (many of) the algorithms used inside	2328	In this section the complexities of (many of) the algorithms used inside
2192	libev will be explained. For complexity discussions about backends see the	2329	libev will be explained. For complexity discussions about backends see the
2193	documentation for C<ev_default_init>.	2330	documentation for C<ev_default_init>.
2194		2331
		2332	All of the following are about amortised time: If an array needs to be
		2333	extended, libev needs to realloc and move the whole array, but this
		2334	happens asymptotically never with higher number of elements, so O(1) might
		2335	mean it might do a lengthy realloc operation in rare cases, but on average
		2336	it is much faster and asymptotically approaches constant time.
		2337
2195	=over 4	2338	=over 4
2196		2339
2197	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	2340	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2198		2341
		2342	This means that, when you have a watcher that triggers in one hour and
		2343	there are 100 watchers that would trigger before that then inserting will
		2344	have to skip those 100 watchers.
		2345
2199	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)	2346	=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2200		2347
		2348	That means that for changing a timer costs less than removing/adding them
		2349	as only the relative motion in the event queue has to be paid for.
		2350
2201	=item Starting io/check/prepare/idle/signal/child watchers: O(1)	2351	=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2202		2352
		2353	These just add the watcher into an array or at the head of a list.
2203	=item Stopping check/prepare/idle watchers: O(1)	2354	=item Stopping check/prepare/idle watchers: O(1)
2204		2355
2205	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	2356	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2206		2357
		2358	These watchers are stored in lists then need to be walked to find the
		2359	correct watcher to remove. The lists are usually short (you don't usually
		2360	have many watchers waiting for the same fd or signal).
		2361
2207	=item Finding the next timer per loop iteration: O(1)	2362	=item Finding the next timer per loop iteration: O(1)
2208		2363
2209	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)	2364	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2210		2365
		2366	A change means an I/O watcher gets started or stopped, which requires
		2367	libev to recalculate its status (and possibly tell the kernel).
		2368
2211	=item Activating one watcher: O(1)	2369	=item Activating one watcher: O(1)
2212		2370
		2371	=item Priority handling: O(number_of_priorities)
		2372
		2373	Priorities are implemented by allocating some space for each
		2374	priority. When doing priority-based operations, libev usually has to
		2375	linearly search all the priorities.
		2376
2213	=back	2377	=back
2214		2378
2215		2379
2216	=head1 AUTHOR	2380	=head1 AUTHOR
2217		2381

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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 1.75 by root, Sat Dec 8 14:27:39 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 1.75 by root, Sat Dec 8 14:27:39 2007 UTC