[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 1.193 by root, Wed Oct 1 04:25:25 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
…		…
1625		1625
1626	=back	1626	=back
1627		1627
1628	=head3 Examples	1628	=head3 Examples
1629		1629
1630	Example: Try to exit cleanly on SIGINT and SIGTERM.	1630	Example: Try to exit cleanly on SIGINT.
1631		1631
1632	static void	1632	static void
1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)	1633	sigint_cb (struct ev_loop loop, struct ev_signal w, int revents)
1634	{	1634	{
1635	ev_unloop (loop, EVUNLOOP_ALL);	1635	ev_unloop (loop, EVUNLOOP_ALL);
1636	}	1636	}
1637		1637
1638	struct ev_signal signal_watcher;	1638	struct ev_signal signal_watcher;
1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);	1639	ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640	ev_signal_start (loop, &sigint_cb);	1640	ev_signal_start (loop, &signal_watcher);
1641		1641
1642		1642
1643	=head2 C<ev_child> - watch out for process status changes	1643	=head2 C<ev_child> - watch out for process status changes
1644		1644
1645	Child watchers trigger when your process receives a SIGCHLD in response to	1645	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,	2233	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	2234	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,	2235	yourself - but you can use a fork watcher to handle this automatically,
2236	and future versions of libev might do just that.	2236	and future versions of libev might do just that.
2237		2237
2238	Unfortunately, not all backends are embeddable, only the ones returned by	2238	Unfortunately, not all backends are embeddable: only the ones returned by
2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any	2239	C<ev_embeddable_backends> are, which, unfortunately, does not include any
2240	portable one.	2240	portable one.
2241		2241
2242	So when you want to use this feature you will always have to be prepared	2242	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	2243	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	2244	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.	2245	create it, and if that fails, use the normal loop for everything.
		2246
		2247	=head3 C<ev_embed> and fork
		2248
		2249	While the C<ev_embed> watcher is running, forks in the embedding loop will
		2250	automatically be applied to the embedded loop as well, so no special
		2251	fork handling is required in that case. When the watcher is not running,
		2252	however, it is still the task of the libev user to call C<ev_loop_fork ()>
		2253	as applicable.
2246		2254
2247	=head3 Watcher-Specific Functions and Data Members	2255	=head3 Watcher-Specific Functions and Data Members
2248		2256
2249	=over 4	2257	=over 4
2250		2258
…		…
2368	is that the author does not know of a simple (or any) algorithm for a	2376	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	2377	multiple-writer-single-reader queue that works in all cases and doesn't
2370	need elaborate support such as pthreads.	2378	need elaborate support such as pthreads.
2371		2379
2372	That means that if you want to queue data, you have to provide your own	2380	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	2381	queue. But at least I can tell you how to implement locking around your
2374	queue:	2382	queue:
2375		2383
2376	=over 4	2384	=over 4
2377		2385
2378	=item queueing from a signal handler context	2386	=item queueing from a signal handler context
2379		2387
2380	To implement race-free queueing, you simply add to the queue in the signal	2388	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	2389	handler but you block the signal handler in the watcher callback. Here is
2382	some fictitious SIGUSR1 handler:	2390	an example that does that for some fictitious SIGUSR1 handler:
2383		2391
2384	static ev_async mysig;	2392	static ev_async mysig;
2385		2393
2386	static void	2394	static void
2387	sigusr1_handler (void)	2395	sigusr1_handler (void)
…		…
2454		2462
2455	=item ev_async_init (ev_async *, callback)	2463	=item ev_async_init (ev_async *, callback)
2456		2464
2457	Initialises and configures the async watcher - it has no parameters of any	2465	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,	2466	kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2459	believe me.	2467	trust me.
2460		2468
2461	=item ev_async_send (loop, ev_async *)	2469	=item ev_async_send (loop, ev_async *)
2462		2470
2463	Sends/signals/activates the given C<ev_async> watcher, that is, feeds	2471	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	2472	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	2473	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	2474	similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding
2467	section below on what exactly this means).	2475	section below on what exactly this means).
2468		2476
2469	This call incurs the overhead of a system call only once per loop iteration,	2477	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	2478	so while the overhead might be noticeable, it doesn't apply to repeated
…		…
2494	=over 4	2502	=over 4
2495		2503
2496	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)	2504	=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2497		2505
2498	This function combines a simple timer and an I/O watcher, calls your	2506	This function combines a simple timer and an I/O watcher, calls your
2499	callback on whichever event happens first and automatically stop both	2507	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	2508	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	2509	or timeout without having to allocate/configure/start/stop/free one or
2502	more watchers yourself.	2510	more watchers yourself.
2503		2511
2504	If C<fd> is less than 0, then no I/O watcher will be started and events	2512	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	2513	C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2506	C<events> set will be created and started.	2514	the given C<fd> and C<events> set will be created and started.
2507		2515
2508	If C<timeout> is less than 0, then no timeout watcher will be	2516	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	2517	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	2518	repeat = 0) will be started. C<0> is a valid timeout.
2511	dubious value.
2512		2519
2513	The callback has the type C<void (cb)(int revents, void arg)> and gets	2520	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	2521	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>	2522	C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2516	value passed to C<ev_once>:	2523	value passed to C<ev_once>. Note that it is possible to receive I<both>
		2524	a timeout and an io event at the same time - you probably should give io
		2525	events precedence.
		2526
		2527	Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2517		2528
2518	static void stdin_ready (int revents, void *arg)	2529	static void stdin_ready (int revents, void *arg)
2519	{	2530	{
		2531	if (revents & EV_READ)
		2532	/* stdin might have data for us, joy! */;
2520	if (revents & EV_TIMEOUT)	2533	else if (revents & EV_TIMEOUT)
2521	/* doh, nothing entered */;	2534	/* doh, nothing entered */;
2522	else if (revents & EV_READ)
2523	/* stdin might have data for us, joy! */;
2524	}	2535	}
2525		2536
2526	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);	2537	ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2527		2538
2528	=item ev_feed_event (ev_loop , watcher , int revents)	2539	=item ev_feed_event (ev_loop , watcher , int revents)
…		…
2676		2687
2677	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.	2688	The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2678		2689
2679	See the method-C<set> above for more details.	2690	See the method-C<set> above for more details.
2680		2691
2681	Example:	2692	Example: Use a plain function as callback.
2682		2693
2683	static void io_cb (ev::io &w, int revents) { }	2694	static void io_cb (ev::io &w, int revents) { }
2684	iow.set <io_cb> ();	2695	iow.set <io_cb> ();
2685		2696
2686	=item w->set (struct ev_loop *)	2697	=item w->set (struct ev_loop *)
…		…
2724	Example: Define a class with an IO and idle watcher, start one of them in	2735	Example: Define a class with an IO and idle watcher, start one of them in
2725	the constructor.	2736	the constructor.
2726		2737
2727	class myclass	2738	class myclass
2728	{	2739	{
2729	ev::io io; void io_cb (ev::io &w, int revents);	2740	ev::io io ; void io_cb (ev::io &w, int revents);
2730	ev:idle idle void idle_cb (ev::idle &w, int revents);	2741	ev::idle idle; void idle_cb (ev::idle &w, int revents);
2731		2742
2732	myclass (int fd)	2743	myclass (int fd)
2733	{	2744	{
2734	io .set <myclass, &myclass::io_cb > (this);	2745	io .set <myclass, &myclass::io_cb > (this);
2735	idle.set <myclass, &myclass::idle_cb> (this);	2746	idle.set <myclass, &myclass::idle_cb> (this);
…		…
2751	=item Perl	2762	=item Perl
2752		2763
2753	The EV module implements the full libev API and is actually used to test	2764	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,	2765	libev. EV is developed together with libev. Apart from the EV core module,
2755	there are additional modules that implement libev-compatible interfaces	2766	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	2767	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>).	2768	C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV>
		2769	and C<EV::Glib>).
2758		2770
2759	It can be found and installed via CPAN, its homepage is at	2771	It can be found and installed via CPAN, its homepage is at
2760	L<http://software.schmorp.de/pkg/EV>.	2772	L<http://software.schmorp.de/pkg/EV>.
2761		2773
2762	=item Python	2774	=item Python
…		…
2941		2953
2942	=head2 PREPROCESSOR SYMBOLS/MACROS	2954	=head2 PREPROCESSOR SYMBOLS/MACROS
2943		2955
2944	Libev can be configured via a variety of preprocessor symbols you have to	2956	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	2957	define before including any of its files. The default in the absence of
2946	autoconf is noted for every option.	2958	autoconf is documented for every option.
2947		2959
2948	=over 4	2960	=over 4
2949		2961
2950	=item EV_STANDALONE	2962	=item EV_STANDALONE
2951		2963
…		…
3121	When doing priority-based operations, libev usually has to linearly search	3133	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	3134	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	3135	and time, so using the defaults of five priorities (-2 .. +2) is usually
3124	fine.	3136	fine.
3125		3137
3126	If your embedding application does not need any priorities, defining these both to	3138	If your embedding application does not need any priorities, defining these
3127	C<0> will save some memory and CPU.	3139	both to C<0> will save some memory and CPU.
3128		3140
3129	=item EV_PERIODIC_ENABLE	3141	=item EV_PERIODIC_ENABLE
3130		3142
3131	If undefined or defined to be C<1>, then periodic timers are supported. If	3143	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	3144	defined to be C<0>, then they are not. Disabling them saves a few kB of
…		…
3139	code.	3151	code.
3140		3152
3141	=item EV_EMBED_ENABLE	3153	=item EV_EMBED_ENABLE
3142		3154
3143	If undefined or defined to be C<1>, then embed watchers are supported. If	3155	If undefined or defined to be C<1>, then embed watchers are supported. If
3144	defined to be C<0>, then they are not.	3156	defined to be C<0>, then they are not. Embed watchers rely on most other
		3157	watcher types, which therefore must not be disabled.
3145		3158
3146	=item EV_STAT_ENABLE	3159	=item EV_STAT_ENABLE
3147		3160
3148	If undefined or defined to be C<1>, then stat watchers are supported. If	3161	If undefined or defined to be C<1>, then stat watchers are supported. If
3149	defined to be C<0>, then they are not.	3162	defined to be C<0>, then they are not.
…		…
3181	two).	3194	two).
3182		3195
3183	=item EV_USE_4HEAP	3196	=item EV_USE_4HEAP
3184		3197
3185	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3198	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	3199	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	3200	to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3188	noticeably faster performance with many (thousands) of watchers.	3201	faster performance with many (thousands) of watchers.
3189		3202
3190	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3203	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3191	(disabled).	3204	(disabled).
3192		3205
3193	=item EV_HEAP_CACHE_AT	3206	=item EV_HEAP_CACHE_AT
3194		3207
3195	Heaps are not very cache-efficient. To improve the cache-efficiency of the	3208	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	3209	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>),	3210	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,	3211	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	3212	but avoids random read accesses on heap changes. This improves performance
3200	noticeably with with many (hundreds) of watchers.	3213	noticeably with many (hundreds) of watchers.
3201		3214
3202	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>	3215	The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0>
3203	(disabled).	3216	(disabled).
3204		3217
3205	=item EV_VERIFY	3218	=item EV_VERIFY
…		…
3211	called once per loop, which can slow down libev. If set to C<3>, then the	3224	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	3225	verification code will be called very frequently, which will slow down
3213	libev considerably.	3226	libev considerably.
3214		3227
3215	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be	3228	The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be
3216	C<0.>	3229	C<0>.
3217		3230
3218	=item EV_COMMON	3231	=item EV_COMMON
3219		3232
3220	By default, all watchers have a C<void *data> member. By redefining	3233	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	3234	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	3251	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	3252	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	3253	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	3254	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++.	3255	method calls instead of plain function calls in C++.
		3256
		3257	=back
3243		3258
3244	=head2 EXPORTED API SYMBOLS	3259	=head2 EXPORTED API SYMBOLS
3245		3260
3246	If you need to re-export the API (e.g. via a DLL) and you need a list of	3261	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	3262	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:	3309	And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
3295		3310
3296	#include "ev_cpp.h"	3311	#include "ev_cpp.h"
3297	#include "ev.c"	3312	#include "ev.c"
3298		3313
		3314	=head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES
3299		3315
3300	=head1 THREADS AND COROUTINES	3316	=head2 THREADS AND COROUTINES
3301		3317
3302	=head2 THREADS	3318	=head3 THREADS
3303		3319
3304	Libev itself is thread-safe (unless the opposite is specifically	3320	All libev functions are reentrant and thread-safe unless explicitly
3305	documented for a function), but it uses no locking itself. This means that	3321	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	3322	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:	3323	are no concurrent calls into any libev function with the same loop
		3324	parameter (C<ev_default_*> calls have an implicit default loop parameter,
3308	libev guarentees that different event loops share no data structures that	3325	of course): libev guarantees that different event loops share no data
3309	need locking.	3326	structures that need any locking.
3310		3327
3311	Or to put it differently: calls with different loop parameters can be done	3328	Or to put it differently: calls with different loop parameters can be done
3312	concurrently from multiple threads, calls with the same loop parameter	3329	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	3330	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	3331	only one thread ever is inside a call at any point in time, e.g. by using
3315	a mutex per loop).	3332	a mutex per loop).
3316		3333
3317	Specifically to support threads (and signal handlers), libev implements	3334	Specifically to support threads (and signal handlers), libev implements
3318	so-called C<ev_async> watchers, which allow some limited form of	3335	so-called C<ev_async> watchers, which allow some limited form of
3319	concurrency on the same event loop.	3336	concurrency on the same event loop, namely waking it up "from the
		3337	outside".
3320		3338
3321	If you want to know which design (one loop, locking, or multiple loops	3339	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	3340	without or something else still) is best for your problem, then I cannot
3323	help you. I can give some generic advice however:	3341	help you, but here is some generic advice:
3324		3342
3325	=over 4	3343	=over 4
3326		3344
3327	=item * most applications have a main thread: use the default libev loop	3345	=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.	3346	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	3370	default loop and triggering an C<ev_async> watcher from the default loop
3353	watcher callback into the event loop interested in the signal.	3371	watcher callback into the event loop interested in the signal.
3354		3372
3355	=back	3373	=back
3356		3374
3357	=head2 COROUTINES	3375	=head3 COROUTINES
3358		3376
3359	Libev is much more accommodating to coroutines ("cooperative threads"):	3377	Libev is very accommodating to coroutines ("cooperative threads"):
3360	libev fully supports nesting calls to it's functions from different	3378	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	3379	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	3380	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	3381	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.	3382	you must not do this from C<ev_periodic> reschedule callbacks.
3365		3383
3366	Care has been taken to ensure that libev does not keep local state inside	3384	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.	3385	C<ev_loop>, and other calls do not usually allow for coroutine switches as
		3386	they do not clal any callbacks.
3368		3387
		3388	=head2 COMPILER WARNINGS
3369		3389
3370	=head1 COMPLEXITIES	3390	Depending on your compiler and compiler settings, you might get no or a
		3391	lot of warnings when compiling libev code. Some people are apparently
		3392	scared by this.
3371		3393
3372	In this section the complexities of (many of) the algorithms used inside	3394	However, these are unavoidable for many reasons. For one, each compiler
3373	libev will be explained. For complexity discussions about backends see the	3395	has different warnings, and each user has different tastes regarding
3374	documentation for C<ev_default_init>.	3396	warning options. "Warn-free" code therefore cannot be a goal except when
		3397	targeting a specific compiler and compiler-version.
3375		3398
3376	All of the following are about amortised time: If an array needs to be	3399	Another reason is that some compiler warnings require elaborate
3377	extended, libev needs to realloc and move the whole array, but this	3400	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	3401	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		3402
3382	=over 4	3403	And of course, some compiler warnings are just plain stupid, or simply
		3404	wrong (because they don't actually warn about the condition their message
		3405	seems to warn about). For example, certain older gcc versions had some
		3406	warnings that resulted an extreme number of false positives. These have
		3407	been fixed, but some people still insist on making code warn-free with
		3408	such buggy versions.
3383		3409
3384	=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)	3410	While libev is written to generate as few warnings as possible,
		3411	"warn-free" code is not a goal, and it is recommended not to build libev
		3412	with any compiler warnings enabled unless you are prepared to cope with
		3413	them (e.g. by ignoring them). Remember that warnings are just that:
		3414	warnings, not errors, or proof of bugs.
3385		3415
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		3416
3390	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)	3417	=head2 VALGRIND
3391		3418
3392	That means that changing a timer costs less than removing/adding them	3419	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.	3420	highly useful. Unfortunately, valgrind reports are very hard to interpret.
3394		3421
3395	=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)	3422	If you think you found a bug (memory leak, uninitialised data access etc.)
		3423	in libev, then check twice: If valgrind reports something like:
3396		3424
3397	These just add the watcher into an array or at the head of a list.	3425	==2274== definitely lost: 0 bytes in 0 blocks.
		3426	==2274== possibly lost: 0 bytes in 0 blocks.
		3427	==2274== still reachable: 256 bytes in 1 blocks.
3398		3428
3399	=item Stopping check/prepare/idle/fork/async watchers: O(1)	3429	Then there is no memory leak, just as memory accounted to global variables
		3430	is not a memleak - the memory is still being refernced, and didn't leak.
3400		3431
3401	=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))	3432	Similarly, under some circumstances, valgrind might report kernel bugs
		3433	as if it were a bug in libev (e.g. in realloc or in the poll backend,
		3434	although an acceptable workaround has been found here), or it might be
		3435	confused.
3402		3436
3403	These watchers are stored in lists then need to be walked to find the	3437	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	3438	make it into some kind of religion.
3405	have many watchers waiting for the same fd or signal).
3406		3439
3407	=item Finding the next timer in each loop iteration: O(1)	3440	If you are unsure about something, feel free to contact the mailing list
		3441	with the full valgrind report and an explanation on why you think this
		3442	is a bug in libev (best check the archives, too :). However, don't be
		3443	annoyed when you get a brisk "this is no bug" answer and take the chance
		3444	of learning how to interpret valgrind properly.
3408		3445
3409	By virtue of using a binary or 4-heap, the next timer is always found at a	3446	If you need, for some reason, empty reports from valgrind for your project
3410	fixed position in the storage array.	3447	I suggest using suppression lists.
3411		3448
3412	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
3413		3449
3414	A change means an I/O watcher gets started or stopped, which requires	3450	=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		3451
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	3452	=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
3441		3453
3442	Win32 doesn't support any of the standards (e.g. POSIX) that libev	3454	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	3455	requires, and its I/O model is fundamentally incompatible with the POSIX
3444	model. Libev still offers limited functionality on this platform in	3456	model. Libev still offers limited functionality on this platform in
3445	the form of the C<EVBACKEND_SELECT> backend, and only supports socket	3457	the form of the C<EVBACKEND_SELECT> backend, and only supports socket
…		…
3456		3468
3457	Not a libev limitation but worth mentioning: windows apparently doesn't	3469	Not a libev limitation but worth mentioning: windows apparently doesn't
3458	accept large writes: instead of resulting in a partial write, windows will	3470	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,	3471	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	3472	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	3473	megabyte seems safe, but this apparently depends on the amount of memory
3462	available).	3474	available).
3463		3475
3464	Due to the many, low, and arbitrary limits on the win32 platform and	3476	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	3477	the abysmal performance of winsockets, using a large number of sockets
3466	is not recommended (and not reasonable). If your program needs to use	3478	is not recommended (and not reasonable). If your program needs to use
…		…
3477	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */	3489	#define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */
3478		3490
3479	#include "ev.h"	3491	#include "ev.h"
3480		3492
3481	And compile the following F<evwrap.c> file into your project (make sure	3493	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!):	3494	you do I<not> compile the F<ev.c> or any other embedded source files!):
3483		3495
3484	#include "evwrap.h"	3496	#include "evwrap.h"
3485	#include "ev.c"	3497	#include "ev.c"
3486		3498
3487	=over 4	3499	=over 4
…		…
3532	wrap all I/O functions and provide your own fd management, but the cost of	3544	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.	3545	calling select (O(n²)) will likely make this unworkable.
3534		3546
3535	=back	3547	=back
3536		3548
3537
3538	=head1 PORTABILITY REQUIREMENTS	3549	=head2 PORTABILITY REQUIREMENTS
3539		3550
3540	In addition to a working ISO-C implementation, libev relies on a few	3551	In addition to a working ISO-C implementation and of course the
3541	additional extensions:	3552	backend-specific APIs, libev relies on a few additional extensions:
3542		3553
3543	=over 4	3554	=over 4
3544		3555
3545	=item C<void ()(ev_watcher_type , int revents)> must have compatible	3556	=item C<void ()(ev_watcher_type , int revents)> must have compatible
3546	calling conventions regardless of C<ev_watcher_type *>.	3557	calling conventions regardless of C<ev_watcher_type *>.
…		…
3552	calls them using an C<ev_watcher *> internally.	3563	calls them using an C<ev_watcher *> internally.
3553		3564
3554	=item C<sig_atomic_t volatile> must be thread-atomic as well	3565	=item C<sig_atomic_t volatile> must be thread-atomic as well
3555		3566
3556	The type C<sig_atomic_t volatile> (or whatever is defined as	3567	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	3568	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	3569	threads. This is not part of the specification for C<sig_atomic_t>, but is
3559	believed to be sufficiently portable.	3570	believed to be sufficiently portable.
3560		3571
3561	=item C<sigprocmask> must work in a threaded environment	3572	=item C<sigprocmask> must work in a threaded environment
3562		3573
…		…
3571	except the initial one, and run the default loop in the initial thread as	3582	except the initial one, and run the default loop in the initial thread as
3572	well.	3583	well.
3573		3584
3574	=item C<long> must be large enough for common memory allocation sizes	3585	=item C<long> must be large enough for common memory allocation sizes
3575		3586
3576	To improve portability and simplify using libev, libev uses C<long>	3587	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	3588	instead of C<size_t> when allocating its data structures. On non-POSIX
3578	non-POSIX systems (Microsoft...) this might be unexpectedly low, but	3589	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	3590	least 31 bits everywhere, which is enough for hundreds of millions of
3580	millions of watchers.	3591	watchers.
3581		3592
3582	=item C<double> must hold a time value in seconds with enough accuracy	3593	=item C<double> must hold a time value in seconds with enough accuracy
3583		3594
3584	The type C<double> is used to represent timestamps. It is required to	3595	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	3596	have at least 51 bits of mantissa (and 9 bits of exponent), which is good
…		…
3589	=back	3600	=back
3590		3601
3591	If you know of other additional requirements drop me a note.	3602	If you know of other additional requirements drop me a note.
3592		3603
3593		3604
3594	=head1 COMPILER WARNINGS	3605	=head1 ALGORITHMIC COMPLEXITIES
3595		3606
3596	Depending on your compiler and compiler settings, you might get no or a	3607	In this section the complexities of (many of) the algorithms used inside
3597	lot of warnings when compiling libev code. Some people are apparently	3608	libev will be documented. For complexity discussions about backends see
3598	scared by this.	3609	the documentation for C<ev_default_init>.
3599		3610
3600	However, these are unavoidable for many reasons. For one, each compiler	3611	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	3612	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	3613	happens asymptotically rarer with higher number of elements, so O(1) might
3603	targeting a specific compiler and compiler-version.	3614	mean that libev does a lengthy realloc operation in rare cases, but on
		3615	average it is much faster and asymptotically approaches constant time.
3604		3616
3605	Another reason is that some compiler warnings require elaborate	3617	=over 4
3606	workarounds, or other changes to the code that make it less clear and less
3607	maintainable.
3608		3618
3609	And of course, some compiler warnings are just plain stupid, or simply	3619	=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		3620
3613	While libev is written to generate as few warnings as possible,	3621	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	3622	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	3623	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		3624
		3625	=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
3619		3626
3620	=head1 VALGRIND	3627	That means that changing a timer costs less than removing/adding them,
		3628	as only the relative motion in the event queue has to be paid for.
3621		3629
3622	Valgrind has a special section here because it is a popular tool that is	3630	=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		3631
3625	If you think you found a bug (memory leak, uninitialised data access etc.)	3632	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		3633
3628	==2274== definitely lost: 0 bytes in 0 blocks.	3634	=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		3635
3632	Then there is no memory leak. Similarly, under some circumstances,	3636	=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		3637
3636	If you are unsure about something, feel free to contact the mailing list	3638	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	3639	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	3640	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	3641	is rare).
3640	properly.
3641		3642
3642	If you need, for some reason, empty reports from valgrind for your project	3643	=item Finding the next timer in each loop iteration: O(1)
3643	I suggest using suppression lists.	3644
		3645	By virtue of using a binary or 4-heap, the next timer is always found at a
		3646	fixed position in the storage array.
		3647
		3648	=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
		3649
		3650	A change means an I/O watcher gets started or stopped, which requires
		3651	libev to recalculate its status (and possibly tell the kernel, depending
		3652	on backend and whether C<ev_io_set> was used).
		3653
		3654	=item Activating one watcher (putting it into the pending state): O(1)
		3655
		3656	=item Priority handling: O(number_of_priorities)
		3657
		3658	Priorities are implemented by allocating some space for each
		3659	priority. When doing priority-based operations, libev usually has to
		3660	linearly search all the priorities, but starting/stopping and activating
		3661	watchers becomes O(1) with respect to priority handling.
		3662
		3663	=item Sending an ev_async: O(1)
		3664
		3665	=item Processing ev_async_send: O(number_of_async_watchers)
		3666
		3667	=item Processing signals: O(max_signal_number)
		3668
		3669	Sending involves a system call I<iff> there were no other C<ev_async_send>
		3670	calls in the current loop iteration. Checking for async and signal events
		3671	involves iterating over all running async watchers or all signal numbers.
		3672
		3673	=back
3644		3674
3645		3675
3646	=head1 AUTHOR	3676	=head1 AUTHOR
3647		3677
3648	Marc Lehmann <libev@schmorp.de>.	3678	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 1.193 by root, Wed Oct 1 04:25:25 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 1.193 by root, Wed Oct 1 04:25:25 2008 UTC