[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 1.194 by root, Mon Oct 20 16:08:36 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
…		…
1625		1627
1626	=back	1628	=back
1627		1629
1628	=head3 Examples	1630	=head3 Examples
1629		1631
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1632	Example: Try to exit cleanly on SIGINT.
1631		1633
1632	static void	1634	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1635	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1634	{	1636	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1637	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1638	}
1637		1639
1638	struct ev_signal signal_watcher;	1640	struct ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1641	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1642	ev_signal_start (loop, &signal_watcher);
1641		1643
1642		1644
1643	=head2 C<ev_child> - watch out for process status changes	1645	=head2 C<ev_child> - watch out for process status changes
1644		1646
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1647	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,	2235	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	2236	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,	2237	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2238	and future versions of libev might do just that.
2237		2239
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2240	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2241	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2242	portable one.
2241		2243
2242	So when you want to use this feature you will always have to be prepared	2244	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	2245	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	2246	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.	2247	create it, and if that fails, use the normal loop for everything.
		2248
		2249	=head3 C<ev_embed> and fork
		2250
		2251	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2252	automatically be applied to the embedded loop as well, so no special
		2253	fork handling is required in that case. When the watcher is not running,
		2254	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2255	as applicable.
2246		2256
2247	=head3 Watcher-Specific Functions and Data Members	2257	=head3 Watcher-Specific Functions and Data Members
2248		2258
2249	=over 4	2259	=over 4
2250		2260
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2378	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	2379	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2380	need elaborate support such as pthreads.
2371		2381
2372	That means that if you want to queue data, you have to provide your own	2382	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	2383	queue. But at least I can tell you how to implement locking around your
2374	queue:	2384	queue:
2375		2385
2376	=over 4	2386	=over 4
2377		2387
2378	=item queueing from a signal handler context	2388	=item queueing from a signal handler context
2379		2389
2380	To implement race-free queueing, you simply add to the queue in the signal	2390	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	2391	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2392	an example that does that for some fictitious SIGUSR1 handler:
2383		2393
2384	static ev_async mysig;	2394	static ev_async mysig;
2385		2395
2386	static void	2396	static void
2387	sigusr1_handler (void)	2397	sigusr1_handler (void)
…		…
2454		2464
2455	=item ev_async_init (ev_async *, callback)	2465	=item ev_async_init (ev_async *, callback)
2456		2466
2457	Initialises and configures the async watcher - it has no parameters of any	2467	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,	2468	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2469	trust me.
2460		2470
2461	=item ev_async_send (loop, ev_async *)	2471	=item ev_async_send (loop, ev_async *)
2462		2472
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2473	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	2474	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	2475	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	2476	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2477	section below on what exactly this means).
2468		2478
2469	This call incurs the overhead of a system call only once per loop iteration,	2479	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	2480	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2504	=over 4
2495		2505
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2506	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2507
2498	This function combines a simple timer and an I/O watcher, calls your	2508	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2509	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	2510	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	2511	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2512	more watchers yourself.
2503		2513
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2514	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	2515	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2516	the given C<fd> and C<events> set will be created and started.
2507		2517
2508	If C<timeout> is less than 0, then no timeout watcher will be	2518	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	2519	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	2520	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2521
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2522	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	2523	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>	2524	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2525	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2526	a timeout and an io event at the same time - you probably should give io
		2527	events precedence.
		2528
		2529	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2530
2518	static void stdin_ready (int revents, void *arg)	2531	static void stdin_ready (int revents, void *arg)
2519	{	2532	{
		2533	if (revents & EV_READ)
		2534	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2535	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2536	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2537	}
2525		2538
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2539	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2540
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2541	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
2676		2689
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2690	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2691
2679	See the method-C<set> above for more details.	2692	See the method-C<set> above for more details.
2680		2693
2681	Example:	2694	Example: Use a plain function as callback.
2682		2695
2683	static void io_cb (ev::io &w, int revents) { }	2696	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2697	iow.set <io_cb> ();
2685		2698
2686	=item w->set (struct ev_loop *)	2699	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2737	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2738	the constructor.
2726		2739
2727	class myclass	2740	class myclass
2728	{	2741	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2742	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2743	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2744
2732	myclass (int fd)	2745	myclass (int fd)
2733	{	2746	{
2734	io .set <myclass, &myclass::io_cb > (this);	2747	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2748	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2764	=item Perl
2752		2765
2753	The EV module implements the full libev API and is actually used to test	2766	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,	2767	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2768	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	2769	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>).	2770	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2771	and C<EV::Glib>).
2758		2772
2759	It can be found and installed via CPAN, its homepage is at	2773	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2774	L<http://software.schmorp.de/pkg/EV>.
2761		2775
2762	=item Python	2776	=item Python
…		…
2941		2955
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	2956	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		2957
2944	Libev can be configured via a variety of preprocessor symbols you have to	2958	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	2959	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	2960	autoconf is documented for every option.
2947		2961
2948	=over 4	2962	=over 4
2949		2963
2950	=item EV_STANDALONE	2964	=item EV_STANDALONE
2951		2965
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3135	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	3136	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	3137	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3138	fine.
3125		3139
3126	If your embedding application does not need any priorities, defining these both to	3140	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3141	both to C<0> will save some memory and CPU.
3128		3142
3129	=item EV_PERIODIC_ENABLE	3143	=item EV_PERIODIC_ENABLE
3130		3144
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3145	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	3146	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3153	code.
3140		3154
3141	=item EV_EMBED_ENABLE	3155	=item EV_EMBED_ENABLE
3142		3156
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3157	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3158	defined to be C<0>, then they are not. Embed watchers rely on most other
		3159	watcher types, which therefore must not be disabled.
3145		3160
3146	=item EV_STAT_ENABLE	3161	=item EV_STAT_ENABLE
3147		3162
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3163	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3164	defined to be C<0>, then they are not.
…		…
3181	two).	3196	two).
3182		3197
3183	=item EV_USE_4HEAP	3198	=item EV_USE_4HEAP
3184		3199
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3200	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	3201	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	3202	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3203	faster performance with many (thousands) of watchers.
3189		3204
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3205	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3206	(disabled).
3192		3207
3193	=item EV_HEAP_CACHE_AT	3208	=item EV_HEAP_CACHE_AT
3194		3209
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3210	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	3211	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>),	3212	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,	3213	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	3214	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3215	noticeably with many (hundreds) of watchers.
3201		3216
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3217	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3218	(disabled).
3204		3219
3205	=item EV_VERIFY	3220	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3226	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	3227	verification code will be called very frequently, which will slow down
3213	libev considerably.	3228	libev considerably.
3214		3229
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3230	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3231	C<0>.
3217		3232
3218	=item EV_COMMON	3233	=item EV_COMMON
3219		3234
3220	By default, all watchers have a C<void *data> member. By redefining	3235	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	3236	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	3253	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	3254	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	3255	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	3256	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++.	3257	method calls instead of plain function calls in C++.
		3258
		3259	=back
3243		3260
3244	=head2 EXPORTED API SYMBOLS	3261	=head2 EXPORTED API SYMBOLS
3245		3262
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3263	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	3264	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:	3311	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3312
3296	#include "ev_cpp.h"	3313	#include "ev_cpp.h"
3297	#include "ev.c"	3314	#include "ev.c"
3298		3315
		3316	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3317
3300	=head1 THREADS AND COROUTINES	3318	=head2 THREADS AND COROUTINES
3301		3319
3302	=head2 THREADS	3320	=head3 THREADS
3303		3321
3304	Libev itself is thread-safe (unless the opposite is specifically	3322	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3323	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	3324	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:	3325	are no concurrent calls into any libev function with the same loop
		3326	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3327	of course): libev guarantees that different event loops share no data
3309	need locking.	3328	structures that need any locking.
3310		3329
3311	Or to put it differently: calls with different loop parameters can be done	3330	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3331	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	3332	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	3333	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3334	a mutex per loop).
3316		3335
3317	Specifically to support threads (and signal handlers), libev implements	3336	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3337	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3338	concurrency on the same event loop, namely waking it up "from the
		3339	outside".
3320		3340
3321	If you want to know which design (one loop, locking, or multiple loops	3341	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	3342	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3343	help you, but here is some generic advice:
3324		3344
3325	=over 4	3345	=over 4
3326		3346
3327	=item * most applications have a main thread: use the default libev loop	3347	=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.	3348	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	3372	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3373	watcher callback into the event loop interested in the signal.
3354		3374
3355	=back	3375	=back
3356		3376
3357	=head2 COROUTINES	3377	=head3 COROUTINES
3358		3378
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3379	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3380	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	3381	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	3382	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	3383	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.	3384	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3385
3366	Care has been taken to ensure that libev does not keep local state inside	3386	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.	3387	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3388	they do not clal any callbacks.
3368		3389
		3390	=head2 COMPILER WARNINGS
3369		3391
3370	=head1 COMPLEXITIES	3392	Depending on your compiler and compiler settings, you might get no or a
		3393	lot of warnings when compiling libev code. Some people are apparently
		3394	scared by this.
3371		3395
3372	In this section the complexities of (many of) the algorithms used inside	3396	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3397	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3398	warning options. "Warn-free" code therefore cannot be a goal except when
		3399	targeting a specific compiler and compiler-version.
3375		3400
3376	All of the following are about amortised time: If an array needs to be	3401	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3402	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	3403	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		3404
3382	=over 4	3405	And of course, some compiler warnings are just plain stupid, or simply
		3406	wrong (because they don't actually warn about the condition their message
		3407	seems to warn about). For example, certain older gcc versions had some
		3408	warnings that resulted an extreme number of false positives. These have
		3409	been fixed, but some people still insist on making code warn-free with
		3410	such buggy versions.
3383		3411
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3412	While libev is written to generate as few warnings as possible,
		3413	"warn-free" code is not a goal, and it is recommended not to build libev
		3414	with any compiler warnings enabled unless you are prepared to cope with
		3415	them (e.g. by ignoring them). Remember that warnings are just that:
		3416	warnings, not errors, or proof of bugs.
3385		3417
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		3418
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3419	=head2 VALGRIND
3391		3420
3392	That means that changing a timer costs less than removing/adding them	3421	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.	3422	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3423
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3424	If you think you found a bug (memory leak, uninitialised data access etc.)
		3425	in libev, then check twice: If valgrind reports something like:
3396		3426
3397	These just add the watcher into an array or at the head of a list.	3427	==2274== definitely lost: 0 bytes in 0 blocks.
		3428	==2274== possibly lost: 0 bytes in 0 blocks.
		3429	==2274== still reachable: 256 bytes in 1 blocks.
3398		3430
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3431	Then there is no memory leak, just as memory accounted to global variables
		3432	is not a memleak - the memory is still being refernced, and didn't leak.
3400		3433
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3434	Similarly, under some circumstances, valgrind might report kernel bugs
		3435	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3436	although an acceptable workaround has been found here), or it might be
		3437	confused.
3402		3438
3403	These watchers are stored in lists then need to be walked to find the	3439	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	3440	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3441
3407	=item Finding the next timer in each loop iteration: O(1)	3442	If you are unsure about something, feel free to contact the mailing list
		3443	with the full valgrind report and an explanation on why you think this
		3444	is a bug in libev (best check the archives, too :). However, don't be
		3445	annoyed when you get a brisk "this is no bug" answer and take the chance
		3446	of learning how to interpret valgrind properly.
3408		3447
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3448	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3449	I suggest using suppression lists.
3411		3450
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3451
3414	A change means an I/O watcher gets started or stopped, which requires	3452	=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		3453
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	3454	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3455
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3456	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	3457	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3458	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3459	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3470
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3471	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3472	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,	3473	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	3474	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	3475	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3476	available).
3463		3477
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3478	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	3479	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3480	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3491	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3492
3479	#include "ev.h"	3493	#include "ev.h"
3480		3494
3481	And compile the following F<evwrap.c> file into your project (make sure	3495	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!):	3496	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3497
3484	#include "evwrap.h"	3498	#include "evwrap.h"
3485	#include "ev.c"	3499	#include "ev.c"
3486		3500
3487	=over 4	3501	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3546	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.	3547	calling select (O(n²)) will likely make this unworkable.
3534		3548
3535	=back	3549	=back
3536		3550
3537
3538	=head1 PORTABILITY REQUIREMENTS	3551	=head2 PORTABILITY REQUIREMENTS
3539		3552
3540	In addition to a working ISO-C implementation, libev relies on a few	3553	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3554	backend-specific APIs, libev relies on a few additional extensions:
3542		3555
3543	=over 4	3556	=over 4
3544		3557
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3558	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3559	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3565	calls them using an C<ev_watcher *> internally.
3553		3566
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3567	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3568
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3569	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	3570	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	3571	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3572	believed to be sufficiently portable.
3560		3573
3561	=item C<sigprocmask> must work in a threaded environment	3574	=item C<sigprocmask> must work in a threaded environment
3562		3575
…		…
3571	except the initial one, and run the default loop in the initial thread as	3584	except the initial one, and run the default loop in the initial thread as
3572	well.	3585	well.
3573		3586
3574	=item C<long> must be large enough for common memory allocation sizes	3587	=item C<long> must be large enough for common memory allocation sizes
3575		3588
3576	To improve portability and simplify using libev, libev uses C<long>	3589	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	3590	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3591	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	3592	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3593	watchers.
3581		3594
3582	=item C<double> must hold a time value in seconds with enough accuracy	3595	=item C<double> must hold a time value in seconds with enough accuracy
3583		3596
3584	The type C<double> is used to represent timestamps. It is required to	3597	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	3598	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3602	=back
3590		3603
3591	If you know of other additional requirements drop me a note.	3604	If you know of other additional requirements drop me a note.
3592		3605
3593		3606
3594	=head1 COMPILER WARNINGS	3607	=head1 ALGORITHMIC COMPLEXITIES
3595		3608
3596	Depending on your compiler and compiler settings, you might get no or a	3609	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3610	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3611	the documentation for C<ev_default_init>.
3599		3612
3600	However, these are unavoidable for many reasons. For one, each compiler	3613	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	3614	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	3615	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3616	mean that libev does a lengthy realloc operation in rare cases, but on
		3617	average it is much faster and asymptotically approaches constant time.
3604		3618
3605	Another reason is that some compiler warnings require elaborate	3619	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3620
3609	And of course, some compiler warnings are just plain stupid, or simply	3621	=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		3622
3613	While libev is written to generate as few warnings as possible,	3623	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	3624	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	3625	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		3626
		3627	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3628
3620	=head1 VALGRIND	3629	That means that changing a timer costs less than removing/adding them,
		3630	as only the relative motion in the event queue has to be paid for.
3621		3631
3622	Valgrind has a special section here because it is a popular tool that is	3632	=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		3633
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3634	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		3635
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3636	=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		3637
3632	Then there is no memory leak. Similarly, under some circumstances,	3638	=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		3639
3636	If you are unsure about something, feel free to contact the mailing list	3640	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	3641	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	3642	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	3643	is rare).
3640	properly.
3641		3644
3642	If you need, for some reason, empty reports from valgrind for your project	3645	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3646
		3647	By virtue of using a binary or 4-heap, the next timer is always found at a
		3648	fixed position in the storage array.
		3649
		3650	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3651
		3652	A change means an I/O watcher gets started or stopped, which requires
		3653	libev to recalculate its status (and possibly tell the kernel, depending
		3654	on backend and whether C<ev_io_set> was used).
		3655
		3656	=item Activating one watcher (putting it into the pending state): O(1)
		3657
		3658	=item Priority handling: O(number_of_priorities)
		3659
		3660	Priorities are implemented by allocating some space for each
		3661	priority. When doing priority-based operations, libev usually has to
		3662	linearly search all the priorities, but starting/stopping and activating
		3663	watchers becomes O(1) with respect to priority handling.
		3664
		3665	=item Sending an ev_async: O(1)
		3666
		3667	=item Processing ev_async_send: O(number_of_async_watchers)
		3668
		3669	=item Processing signals: O(max_signal_number)
		3670
		3671	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3672	calls in the current loop iteration. Checking for async and signal events
		3673	involves iterating over all running async watchers or all signal numbers.
		3674
		3675	=back
3644		3676
3645		3677
3646	=head1 AUTHOR	3678	=head1 AUTHOR
3647		3679
3648	Marc Lehmann <libev@schmorp.de>.	3680	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 1.194 by root, Mon Oct 20 16:08:36 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 1.194 by root, Mon Oct 20 16:08:36 2008 UTC