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

Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC

…		…
214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for	214	C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
215	recommended ones.	215	recommended ones.
216		216
217	See the description of C<ev_embed> watchers for more info.	217	See the description of C<ev_embed> watchers for more info.
218		218
219	=item ev_set_allocator (void (cb)(void *ptr, long size))	219	=item ev_set_allocator (void (cb)(void *ptr, long size)) [NOT REENTRANT]
220		220
221	Sets the allocation function to use (the prototype is similar - the	221	Sets the allocation function to use (the prototype is similar - the
222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is	222	semantics are identical to the C<realloc> C89/SuS/POSIX function). It is
223	used to allocate and free memory (no surprises here). If it returns zero	223	used to allocate and free memory (no surprises here). If it returns zero
224	when memory needs to be allocated (C<size != 0>), the library might abort	224	when memory needs to be allocated (C<size != 0>), the library might abort
…		…
250	}	250	}
251		251
252	...	252	...
253	ev_set_allocator (persistent_realloc);	253	ev_set_allocator (persistent_realloc);
254		254
255	=item ev_set_syserr_cb (void (cb)(const char msg));	255	=item ev_set_syserr_cb (void (cb)(const char msg)); [NOT REENTRANT]
256		256
257	Set the callback function to call on a retryable system call error (such	257	Set the callback function to call on a retryable system call error (such
258	as failed select, poll, epoll_wait). The message is a printable string	258	as failed select, poll, epoll_wait). The message is a printable string
259	indicating the system call or subsystem causing the problem. If this	259	indicating the system call or subsystem causing the problem. If this
260	callback is set, then libev will expect it to remedy the situation, no	260	callback is set, then libev will expect it to remedy the situation, no
…		…
685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or	685	C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.	686	C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687		687
688	This "unloop state" will be cleared when entering C<ev_loop> again.	688	This "unloop state" will be cleared when entering C<ev_loop> again.
689		689
		690	It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
		691
690	=item ev_ref (loop)	692	=item ev_ref (loop)
691		693
692	=item ev_unref (loop)	694	=item ev_unref (loop)
693		695
694	Ref/unref can be used to add or remove a reference count on the event	696	Ref/unref can be used to add or remove a reference count on the event
…		…
967		969
968	ev_io_start (EV_DEFAULT_UC, &w);	970	ev_io_start (EV_DEFAULT_UC, &w);
969		971
970	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)	972	=item C<ev_TYPE_stop> (loop , ev_TYPE watcher)
971		973
972	Stops the given watcher again (if active) and clears the pending	974	Stops the given watcher if active, and clears the pending status (whether
		975	the watcher was active or not).
		976
973	status. It is possible that stopped watchers are pending (for example,	977	It is possible that stopped watchers are pending - for example,
974	non-repeating timers are being stopped when they become pending), but	978	non-repeating timers are being stopped when they become pending - but
975	C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If	979	calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976	you want to free or reuse the memory used by the watcher it is therefore a	980	pending. If you want to free or reuse the memory used by the watcher it is
977	good idea to always call its C<ev_TYPE_stop> function.	981	therefore a good idea to always call its C<ev_TYPE_stop> function.
978		982
979	=item bool ev_is_active (ev_TYPE *watcher)	983	=item bool ev_is_active (ev_TYPE *watcher)
980		984
981	Returns a true value iff the watcher is active (i.e. it has been started	985	Returns a true value iff the watcher is active (i.e. it has been started
982	and not yet been stopped). As long as a watcher is active you must not modify	986	and not yet been stopped). As long as a watcher is active you must not modify
…		…
1625		1629
1626	=back	1630	=back
1627		1631
1628	=head3 Examples	1632	=head3 Examples
1629		1633
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1634	Example: Try to exit cleanly on SIGINT.
1631		1635
1632	static void	1636	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1637	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1634	{	1638	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1639	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1640	}
1637		1641
1638	struct ev_signal signal_watcher;	1642	struct ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1643	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1644	ev_signal_start (loop, &signal_watcher);
1641		1645
1642		1646
1643	=head2 C<ev_child> - watch out for process status changes	1647	=head2 C<ev_child> - watch out for process status changes
1644		1648
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1649	Child watchers trigger when your process receives a SIGCHLD in response to
…		…
2233	when you fork, you not only have to call C<ev_loop_fork> on both loops,	2237	when you fork, you not only have to call C<ev_loop_fork> on both loops,
2234	but you will also have to stop and restart any C<ev_embed> watchers	2238	but you will also have to stop and restart any C<ev_embed> watchers
2235	yourself - but you can use a fork watcher to handle this automatically,	2239	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2240	and future versions of libev might do just that.
2237		2241
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2242	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2243	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2244	portable one.
2241		2245
2242	So when you want to use this feature you will always have to be prepared	2246	So when you want to use this feature you will always have to be prepared
2243	that you cannot get an embeddable loop. The recommended way to get around	2247	that you cannot get an embeddable loop. The recommended way to get around
2244	this is to have a separate variables for your embeddable loop, try to	2248	this is to have a separate variables for your embeddable loop, try to
2245	create it, and if that fails, use the normal loop for everything.	2249	create it, and if that fails, use the normal loop for everything.
		2250
		2251	=head3 C<ev_embed> and fork
		2252
		2253	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2254	automatically be applied to the embedded loop as well, so no special
		2255	fork handling is required in that case. When the watcher is not running,
		2256	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2257	as applicable.
2246		2258
2247	=head3 Watcher-Specific Functions and Data Members	2259	=head3 Watcher-Specific Functions and Data Members
2248		2260
2249	=over 4	2261	=over 4
2250		2262
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2380	is that the author does not know of a simple (or any) algorithm for a
2369	multiple-writer-single-reader queue that works in all cases and doesn't	2381	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2382	need elaborate support such as pthreads.
2371		2383
2372	That means that if you want to queue data, you have to provide your own	2384	That means that if you want to queue data, you have to provide your own
2373	queue. But at least I can tell you would implement locking around your	2385	queue. But at least I can tell you how to implement locking around your
2374	queue:	2386	queue:
2375		2387
2376	=over 4	2388	=over 4
2377		2389
2378	=item queueing from a signal handler context	2390	=item queueing from a signal handler context
2379		2391
2380	To implement race-free queueing, you simply add to the queue in the signal	2392	To implement race-free queueing, you simply add to the queue in the signal
2381	handler but you block the signal handler in the watcher callback. Here is an example that does that for	2393	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2394	an example that does that for some fictitious SIGUSR1 handler:
2383		2395
2384	static ev_async mysig;	2396	static ev_async mysig;
2385		2397
2386	static void	2398	static void
2387	sigusr1_handler (void)	2399	sigusr1_handler (void)
…		…
2454		2466
2455	=item ev_async_init (ev_async *, callback)	2467	=item ev_async_init (ev_async *, callback)
2456		2468
2457	Initialises and configures the async watcher - it has no parameters of any	2469	Initialises and configures the async watcher - it has no parameters of any
2458	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,	2470	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2471	trust me.
2460		2472
2461	=item ev_async_send (loop, ev_async *)	2473	=item ev_async_send (loop, ev_async *)
2462		2474
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2475	Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2464	an C<EV_ASYNC> event on the watcher into the event loop. Unlike	2476	an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2465	C<ev_feed_event>, this call is safe to do in other threads, signal or	2477	C<ev_feed_event>, this call is safe to do from other threads, signal or
2466	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding	2478	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2479	section below on what exactly this means).
2468		2480
2469	This call incurs the overhead of a system call only once per loop iteration,	2481	This call incurs the overhead of a system call only once per loop iteration,
2470	so while the overhead might be noticeable, it doesn't apply to repeated	2482	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2506	=over 4
2495		2507
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2508	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2509
2498	This function combines a simple timer and an I/O watcher, calls your	2510	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2511	callback on whichever event happens first and automatically stops both
2500	watchers. This is useful if you want to wait for a single event on an fd	2512	watchers. This is useful if you want to wait for a single event on an fd
2501	or timeout without having to allocate/configure/start/stop/free one or	2513	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2514	more watchers yourself.
2503		2515
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2516	If C<fd> is less than 0, then no I/O watcher will be started and the
2505	is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and	2517	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2518	the given C<fd> and C<events> set will be created and started.
2507		2519
2508	If C<timeout> is less than 0, then no timeout watcher will be	2520	If C<timeout> is less than 0, then no timeout watcher will be
2509	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and	2521	started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2510	repeat = 0) will be started. While C<0> is a valid timeout, it is of	2522	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2523
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2524	The callback has the type C<void (cb)(int revents, void arg)> and gets
2514	passed an C<revents> set like normal event callbacks (a combination of	2525	passed an C<revents> set like normal event callbacks (a combination of
2515	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>	2526	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2527	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2528	a timeout and an io event at the same time - you probably should give io
		2529	events precedence.
		2530
		2531	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2532
2518	static void stdin_ready (int revents, void *arg)	2533	static void stdin_ready (int revents, void *arg)
2519	{	2534	{
		2535	if (revents & EV_READ)
		2536	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2537	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2538	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2539	}
2525		2540
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2541	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2542
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2543	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
2676		2691
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2692	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2693
2679	See the method-C<set> above for more details.	2694	See the method-C<set> above for more details.
2680		2695
2681	Example:	2696	Example: Use a plain function as callback.
2682		2697
2683	static void io_cb (ev::io &w, int revents) { }	2698	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2699	iow.set <io_cb> ();
2685		2700
2686	=item w->set (struct ev_loop *)	2701	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2739	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2740	the constructor.
2726		2741
2727	class myclass	2742	class myclass
2728	{	2743	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2744	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2745	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2746
2732	myclass (int fd)	2747	myclass (int fd)
2733	{	2748	{
2734	io .set <myclass, &myclass::io_cb > (this);	2749	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2750	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2766	=item Perl
2752		2767
2753	The EV module implements the full libev API and is actually used to test	2768	The EV module implements the full libev API and is actually used to test
2754	libev. EV is developed together with libev. Apart from the EV core module,	2769	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2770	there are additional modules that implement libev-compatible interfaces
2756	to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the	2771	to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays),
2757	C<libglib> event core (C<Glib::EV> and C<EV::Glib>).	2772	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2773	and C<EV::Glib>).
2758		2774
2759	It can be found and installed via CPAN, its homepage is at	2775	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2776	L<http://software.schmorp.de/pkg/EV>.
2761		2777
2762	=item Python	2778	=item Python
…		…
2941		2957
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	2958	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		2959
2944	Libev can be configured via a variety of preprocessor symbols you have to	2960	Libev can be configured via a variety of preprocessor symbols you have to
2945	define before including any of its files. The default in the absence of	2961	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	2962	autoconf is documented for every option.
2947		2963
2948	=over 4	2964	=over 4
2949		2965
2950	=item EV_STANDALONE	2966	=item EV_STANDALONE
2951		2967
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3137	When doing priority-based operations, libev usually has to linearly search
3122	all the priorities, so having many of them (hundreds) uses a lot of space	3138	all the priorities, so having many of them (hundreds) uses a lot of space
3123	and time, so using the defaults of five priorities (-2 .. +2) is usually	3139	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3140	fine.
3125		3141
3126	If your embedding application does not need any priorities, defining these both to	3142	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3143	both to C<0> will save some memory and CPU.
3128		3144
3129	=item EV_PERIODIC_ENABLE	3145	=item EV_PERIODIC_ENABLE
3130		3146
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3147	If undefined or defined to be C<1>, then periodic timers are supported. If
3132	defined to be C<0>, then they are not. Disabling them saves a few kB of	3148	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3155	code.
3140		3156
3141	=item EV_EMBED_ENABLE	3157	=item EV_EMBED_ENABLE
3142		3158
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3159	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3160	defined to be C<0>, then they are not. Embed watchers rely on most other
		3161	watcher types, which therefore must not be disabled.
3145		3162
3146	=item EV_STAT_ENABLE	3163	=item EV_STAT_ENABLE
3147		3164
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3165	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3166	defined to be C<0>, then they are not.
…		…
3181	two).	3198	two).
3182		3199
3183	=item EV_USE_4HEAP	3200	=item EV_USE_4HEAP
3184		3201
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3202	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3186	timer and periodics heap, libev uses a 4-heap when this symbol is defined	3203	timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3187	to C<1>. The 4-heap uses more complicated (longer) code but has	3204	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3205	faster performance with many (thousands) of watchers.
3189		3206
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3207	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3208	(disabled).
3192		3209
3193	=item EV_HEAP_CACHE_AT	3210	=item EV_HEAP_CACHE_AT
3194		3211
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3212	Heaps are not very cache-efficient. To improve the cache-efficiency of the
3196	timer and periodics heap, libev can cache the timestamp (I<at>) within	3213	timer and periodics heaps, libev can cache the timestamp (I<at>) within
3197	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),	3214	the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3198	which uses 8-12 bytes more per watcher and a few hundred bytes more code,	3215	which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3199	but avoids random read accesses on heap changes. This improves performance	3216	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3217	noticeably with many (hundreds) of watchers.
3201		3218
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3219	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3220	(disabled).
3204		3221
3205	=item EV_VERIFY	3222	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3228	called once per loop, which can slow down libev. If set to C<3>, then the
3212	verification code will be called very frequently, which will slow down	3229	verification code will be called very frequently, which will slow down
3213	libev considerably.	3230	libev considerably.
3214		3231
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3232	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3233	C<0>.
3217		3234
3218	=item EV_COMMON	3235	=item EV_COMMON
3219		3236
3220	By default, all watchers have a C<void *data> member. By redefining	3237	By default, all watchers have a C<void *data> member. By redefining
3221	this macro to a something else you can include more and other types of	3238	this macro to a something else you can include more and other types of
…		…
3238	and the way callbacks are invoked and set. Must expand to a struct member	3255	and the way callbacks are invoked and set. Must expand to a struct member
3239	definition and a statement, respectively. See the F<ev.h> header file for	3256	definition and a statement, respectively. See the F<ev.h> header file for
3240	their default definitions. One possible use for overriding these is to	3257	their default definitions. One possible use for overriding these is to
3241	avoid the C<struct ev_loop *> as first argument in all cases, or to use	3258	avoid the C<struct ev_loop *> as first argument in all cases, or to use
3242	method calls instead of plain function calls in C++.	3259	method calls instead of plain function calls in C++.
		3260
		3261	=back
3243		3262
3244	=head2 EXPORTED API SYMBOLS	3263	=head2 EXPORTED API SYMBOLS
3245		3264
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3265	If you need to re-export the API (e.g. via a DLL) and you need a list of
3247	exported symbols, you can use the provided F<Symbol.*> files which list	3266	exported symbols, you can use the provided F<Symbol.*> files which list
…		…
3294	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:	3313	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3314
3296	#include "ev_cpp.h"	3315	#include "ev_cpp.h"
3297	#include "ev.c"	3316	#include "ev.c"
3298		3317
		3318	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3319
3300	=head1 THREADS AND COROUTINES	3320	=head2 THREADS AND COROUTINES
3301		3321
3302	=head2 THREADS	3322	=head3 THREADS
3303		3323
3304	Libev itself is thread-safe (unless the opposite is specifically	3324	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3325	documented otherwise, but libev implements no locking itself. This means
3306	you can use as many loops as you want in parallel, as long as only one	3326	that you can use as many loops as you want in parallel, as long as there
3307	thread ever calls into one libev function with the same loop parameter:	3327	are no concurrent calls into any libev function with the same loop
		3328	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3329	of course): libev guarantees that different event loops share no data
3309	need locking.	3330	structures that need any locking.
3310		3331
3311	Or to put it differently: calls with different loop parameters can be done	3332	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3333	concurrently from multiple threads, calls with the same loop parameter
3313	must be done serially (but can be done from different threads, as long as	3334	must be done serially (but can be done from different threads, as long as
3314	only one thread ever is inside a call at any point in time, e.g. by using	3335	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3336	a mutex per loop).
3316		3337
3317	Specifically to support threads (and signal handlers), libev implements	3338	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3339	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3340	concurrency on the same event loop, namely waking it up "from the
		3341	outside".
3320		3342
3321	If you want to know which design (one loop, locking, or multiple loops	3343	If you want to know which design (one loop, locking, or multiple loops
3322	without or something else still) is best for your problem, then I cannot	3344	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3345	help you, but here is some generic advice:
3324		3346
3325	=over 4	3347	=over 4
3326		3348
3327	=item * most applications have a main thread: use the default libev loop	3349	=item * most applications have a main thread: use the default libev loop
3328	in that thread, or create a separate thread running only the default loop.	3350	in that thread, or create a separate thread running only the default loop.
…		…
3352	default loop and triggering an C<ev_async> watcher from the default loop	3374	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3375	watcher callback into the event loop interested in the signal.
3354		3376
3355	=back	3377	=back
3356		3378
3357	=head2 COROUTINES	3379	=head3 COROUTINES
3358		3380
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3381	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3382	libev fully supports nesting calls to its functions from different
3361	coroutines (e.g. you can call C<ev_loop> on the same loop from two	3383	coroutines (e.g. you can call C<ev_loop> on the same loop from two
3362	different coroutines and switch freely between both coroutines running the	3384	different coroutines, and switch freely between both coroutines running the
3363	loop, as long as you don't confuse yourself). The only exception is that	3385	loop, as long as you don't confuse yourself). The only exception is that
3364	you must not do this from C<ev_periodic> reschedule callbacks.	3386	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3387
3366	Care has been taken to ensure that libev does not keep local state inside	3388	Care has been taken to ensure that libev does not keep local state inside
3367	C<ev_loop>, and other calls do not usually allow coroutine switches.	3389	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3390	they do not clal any callbacks.
3368		3391
		3392	=head2 COMPILER WARNINGS
3369		3393
3370	=head1 COMPLEXITIES	3394	Depending on your compiler and compiler settings, you might get no or a
		3395	lot of warnings when compiling libev code. Some people are apparently
		3396	scared by this.
3371		3397
3372	In this section the complexities of (many of) the algorithms used inside	3398	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3399	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3400	warning options. "Warn-free" code therefore cannot be a goal except when
		3401	targeting a specific compiler and compiler-version.
3375		3402
3376	All of the following are about amortised time: If an array needs to be	3403	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3404	workarounds, or other changes to the code that make it less clear and less
3378	happens asymptotically never with higher number of elements, so O(1) might	3405	maintainable.
3379	mean it might do a lengthy realloc operation in rare cases, but on average
3380	it is much faster and asymptotically approaches constant time.
3381		3406
3382	=over 4	3407	And of course, some compiler warnings are just plain stupid, or simply
		3408	wrong (because they don't actually warn about the condition their message
		3409	seems to warn about). For example, certain older gcc versions had some
		3410	warnings that resulted an extreme number of false positives. These have
		3411	been fixed, but some people still insist on making code warn-free with
		3412	such buggy versions.
3383		3413
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3414	While libev is written to generate as few warnings as possible,
		3415	"warn-free" code is not a goal, and it is recommended not to build libev
		3416	with any compiler warnings enabled unless you are prepared to cope with
		3417	them (e.g. by ignoring them). Remember that warnings are just that:
		3418	warnings, not errors, or proof of bugs.
3385		3419
3386	This means that, when you have a watcher that triggers in one hour and
3387	there are 100 watchers that would trigger before that then inserting will
3388	have to skip roughly seven (C<ld 100>) of these watchers.
3389		3420
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3421	=head2 VALGRIND
3391		3422
3392	That means that changing a timer costs less than removing/adding them	3423	Valgrind has a special section here because it is a popular tool that is
3393	as only the relative motion in the event queue has to be paid for.	3424	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3425
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3426	If you think you found a bug (memory leak, uninitialised data access etc.)
		3427	in libev, then check twice: If valgrind reports something like:
3396		3428
3397	These just add the watcher into an array or at the head of a list.	3429	==2274== definitely lost: 0 bytes in 0 blocks.
		3430	==2274== possibly lost: 0 bytes in 0 blocks.
		3431	==2274== still reachable: 256 bytes in 1 blocks.
3398		3432
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3433	Then there is no memory leak, just as memory accounted to global variables
		3434	is not a memleak - the memory is still being refernced, and didn't leak.
3400		3435
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3436	Similarly, under some circumstances, valgrind might report kernel bugs
		3437	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3438	although an acceptable workaround has been found here), or it might be
		3439	confused.
3402		3440
3403	These watchers are stored in lists then need to be walked to find the	3441	Keep in mind that valgrind is a very good tool, but only a tool. Don't
3404	correct watcher to remove. The lists are usually short (you don't usually	3442	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3443
3407	=item Finding the next timer in each loop iteration: O(1)	3444	If you are unsure about something, feel free to contact the mailing list
		3445	with the full valgrind report and an explanation on why you think this
		3446	is a bug in libev (best check the archives, too :). However, don't be
		3447	annoyed when you get a brisk "this is no bug" answer and take the chance
		3448	of learning how to interpret valgrind properly.
3408		3449
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3450	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3451	I suggest using suppression lists.
3411		3452
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3453
3414	A change means an I/O watcher gets started or stopped, which requires	3454	=head1 PORTABILITY NOTES
3415	libev to recalculate its status (and possibly tell the kernel, depending
3416	on backend and whether C<ev_io_set> was used).
3417		3455
3418	=item Activating one watcher (putting it into the pending state): O(1)
3419
3420	=item Priority handling: O(number_of_priorities)
3421
3422	Priorities are implemented by allocating some space for each
3423	priority. When doing priority-based operations, libev usually has to
3424	linearly search all the priorities, but starting/stopping and activating
3425	watchers becomes O(1) w.r.t. priority handling.
3426
3427	=item Sending an ev_async: O(1)
3428
3429	=item Processing ev_async_send: O(number_of_async_watchers)
3430
3431	=item Processing signals: O(max_signal_number)
3432
3433	Sending involves a system call I<iff> there were no other C<ev_async_send>
3434	calls in the current loop iteration. Checking for async and signal events
3435	involves iterating over all running async watchers or all signal numbers.
3436
3437	=back
3438
3439
3440	=head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS	3456	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3457
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3458	Win32 doesn't support any of the standards (e.g. POSIX) that libev
3443	requires, and its I/O model is fundamentally incompatible with the POSIX	3459	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3460	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3461	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3472
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3473	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3474	accept large writes: instead of resulting in a partial write, windows will
3459	either accept everything or return C<ENOBUFS> if the buffer is too large,	3475	either accept everything or return C<ENOBUFS> if the buffer is too large,
3460	so make sure you only write small amounts into your sockets (less than a	3476	so make sure you only write small amounts into your sockets (less than a
3461	megabyte seems safe, but thsi apparently depends on the amount of memory	3477	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3478	available).
3463		3479
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3480	Due to the many, low, and arbitrary limits on the win32 platform and
3465	the abysmal performance of winsockets, using a large number of sockets	3481	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3482	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3493	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3494
3479	#include "ev.h"	3495	#include "ev.h"
3480		3496
3481	And compile the following F<evwrap.c> file into your project (make sure	3497	And compile the following F<evwrap.c> file into your project (make sure
3482	you do I<not> compile the F<ev.c> or any other embedded soruce files!):	3498	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3499
3484	#include "evwrap.h"	3500	#include "evwrap.h"
3485	#include "ev.c"	3501	#include "ev.c"
3486		3502
3487	=over 4	3503	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3548	wrap all I/O functions and provide your own fd management, but the cost of
3533	calling select (O(n²)) will likely make this unworkable.	3549	calling select (O(n²)) will likely make this unworkable.
3534		3550
3535	=back	3551	=back
3536		3552
3537
3538	=head1 PORTABILITY REQUIREMENTS	3553	=head2 PORTABILITY REQUIREMENTS
3539		3554
3540	In addition to a working ISO-C implementation, libev relies on a few	3555	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3556	backend-specific APIs, libev relies on a few additional extensions:
3542		3557
3543	=over 4	3558	=over 4
3544		3559
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3560	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3561	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3567	calls them using an C<ev_watcher *> internally.
3553		3568
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3569	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3570
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3571	The type C<sig_atomic_t volatile> (or whatever is defined as
3557	C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different	3572	C<EV_ATOMIC_T>) must be atomic with respect to accesses from different
3558	threads. This is not part of the specification for C<sig_atomic_t>, but is	3573	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3574	believed to be sufficiently portable.
3560		3575
3561	=item C<sigprocmask> must work in a threaded environment	3576	=item C<sigprocmask> must work in a threaded environment
3562		3577
…		…
3571	except the initial one, and run the default loop in the initial thread as	3586	except the initial one, and run the default loop in the initial thread as
3572	well.	3587	well.
3573		3588
3574	=item C<long> must be large enough for common memory allocation sizes	3589	=item C<long> must be large enough for common memory allocation sizes
3575		3590
3576	To improve portability and simplify using libev, libev uses C<long>	3591	To improve portability and simplify its API, libev uses C<long> internally
3577	internally instead of C<size_t> when allocating its data structures. On	3592	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3593	systems (Microsoft...) this might be unexpectedly low, but is still at
3579	is still at least 31 bits everywhere, which is enough for hundreds of	3594	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3595	watchers.
3581		3596
3582	=item C<double> must hold a time value in seconds with enough accuracy	3597	=item C<double> must hold a time value in seconds with enough accuracy
3583		3598
3584	The type C<double> is used to represent timestamps. It is required to	3599	The type C<double> is used to represent timestamps. It is required to
3585	have at least 51 bits of mantissa (and 9 bits of exponent), which is good	3600	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3604	=back
3590		3605
3591	If you know of other additional requirements drop me a note.	3606	If you know of other additional requirements drop me a note.
3592		3607
3593		3608
3594	=head1 COMPILER WARNINGS	3609	=head1 ALGORITHMIC COMPLEXITIES
3595		3610
3596	Depending on your compiler and compiler settings, you might get no or a	3611	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3612	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3613	the documentation for C<ev_default_init>.
3599		3614
3600	However, these are unavoidable for many reasons. For one, each compiler	3615	All of the following are about amortised time: If an array needs to be
3601	has different warnings, and each user has different tastes regarding	3616	extended, libev needs to realloc and move the whole array, but this
3602	warning options. "Warn-free" code therefore cannot be a goal except when	3617	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3618	mean that libev does a lengthy realloc operation in rare cases, but on
		3619	average it is much faster and asymptotically approaches constant time.
3604		3620
3605	Another reason is that some compiler warnings require elaborate	3621	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3622
3609	And of course, some compiler warnings are just plain stupid, or simply	3623	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
3610	wrong (because they don't actually warn about the condition their message
3611	seems to warn about).
3612		3624
3613	While libev is written to generate as few warnings as possible,	3625	This means that, when you have a watcher that triggers in one hour and
3614	"warn-free" code is not a goal, and it is recommended not to build libev	3626	there are 100 watchers that would trigger before that, then inserting will
3615	with any compiler warnings enabled unless you are prepared to cope with	3627	have to skip roughly seven (C<ld 100>) of these watchers.
3616	them (e.g. by ignoring them). Remember that warnings are just that:
3617	warnings, not errors, or proof of bugs.
3618		3628
		3629	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3630
3620	=head1 VALGRIND	3631	That means that changing a timer costs less than removing/adding them,
		3632	as only the relative motion in the event queue has to be paid for.
3621		3633
3622	Valgrind has a special section here because it is a popular tool that is	3634	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
3623	highly useful, but valgrind reports are very hard to interpret.
3624		3635
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3636	These just add the watcher into an array or at the head of a list.
3626	in libev, then check twice: If valgrind reports something like:
3627		3637
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3638	=item Stopping check/prepare/idle/fork/async watchers: O(1)
3629	==2274== possibly lost: 0 bytes in 0 blocks.
3630	==2274== still reachable: 256 bytes in 1 blocks.
3631		3639
3632	Then there is no memory leak. Similarly, under some circumstances,	3640	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
3633	valgrind might report kernel bugs as if it were a bug in libev, or it
3634	might be confused (it is a very good tool, but only a tool).
3635		3641
3636	If you are unsure about something, feel free to contact the mailing list	3642	These watchers are stored in lists, so they need to be walked to find the
3637	with the full valgrind report and an explanation on why you think this is	3643	correct watcher to remove. The lists are usually short (you don't usually
3638	a bug in libev. However, don't be annoyed when you get a brisk "this is	3644	have many watchers waiting for the same fd or signal: one is typical, two
3639	no bug" answer and take the chance of learning how to interpret valgrind	3645	is rare).
3640	properly.
3641		3646
3642	If you need, for some reason, empty reports from valgrind for your project	3647	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3648
		3649	By virtue of using a binary or 4-heap, the next timer is always found at a
		3650	fixed position in the storage array.
		3651
		3652	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3653
		3654	A change means an I/O watcher gets started or stopped, which requires
		3655	libev to recalculate its status (and possibly tell the kernel, depending
		3656	on backend and whether C<ev_io_set> was used).
		3657
		3658	=item Activating one watcher (putting it into the pending state): O(1)
		3659
		3660	=item Priority handling: O(number_of_priorities)
		3661
		3662	Priorities are implemented by allocating some space for each
		3663	priority. When doing priority-based operations, libev usually has to
		3664	linearly search all the priorities, but starting/stopping and activating
		3665	watchers becomes O(1) with respect to priority handling.
		3666
		3667	=item Sending an ev_async: O(1)
		3668
		3669	=item Processing ev_async_send: O(number_of_async_watchers)
		3670
		3671	=item Processing signals: O(max_signal_number)
		3672
		3673	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3674	calls in the current loop iteration. Checking for async and signal events
		3675	involves iterating over all running async watchers or all signal numbers.
		3676
		3677	=back
3644		3678
3645		3679
3646	=head1 AUTHOR	3680	=head1 AUTHOR
3647		3681
3648	Marc Lehmann <libev@schmorp.de>.	3682	Marc Lehmann <libev@schmorp.de>.

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Comparing libev/ev.pod (file contents): Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs. Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC

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Comparing libev/ev.pod (file contents):
Revision 1.183 by root, Tue Sep 23 08:37:38 2008 UTC vs.
Revision 1.195 by root, Mon Oct 20 17:50:48 2008 UTC