… | |
… | |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
243 | |
243 | |
244 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
245 | |
245 | |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
247 | |
247 | |
248 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
250 | used to allocate and free memory (no surprises here). If it returns zero |
250 | used to allocate and free memory (no surprises here). If it returns zero |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
277 | } |
277 | } |
278 | |
278 | |
279 | ... |
279 | ... |
280 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
281 | |
281 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
283 | |
283 | |
284 | Set the callback function to call on a retryable system call error (such |
284 | Set the callback function to call on a retryable system call error (such |
285 | as failed select, poll, epoll_wait). The message is a printable string |
285 | as failed select, poll, epoll_wait). The message is a printable string |
286 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
287 | callback is set, then libev will expect it to remedy the situation, no |
287 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
355 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
356 | |
356 | |
357 | This will create and initialise a new event loop object. If the loop |
357 | This will create and initialise a new event loop object. If the loop |
358 | could not be initialised, returns false. |
358 | could not be initialised, returns false. |
359 | |
359 | |
360 | Note that this function I<is> thread-safe, and one common way to use |
360 | This function is thread-safe, and one common way to use libev with |
361 | libev with threads is indeed to create one loop per thread, and using the |
361 | threads is indeed to create one loop per thread, and using the default |
362 | default loop in the "main" or "initial" thread. |
362 | loop in the "main" or "initial" thread. |
363 | |
363 | |
364 | The flags argument can be used to specify special behaviour or specific |
364 | The flags argument can be used to specify special behaviour or specific |
365 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
365 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
366 | |
366 | |
367 | The following flags are supported: |
367 | The following flags are supported: |
… | |
… | |
402 | environment variable. |
402 | environment variable. |
403 | |
403 | |
404 | =item C<EVFLAG_NOINOTIFY> |
404 | =item C<EVFLAG_NOINOTIFY> |
405 | |
405 | |
406 | When this flag is specified, then libev will not attempt to use the |
406 | When this flag is specified, then libev will not attempt to use the |
407 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
407 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
408 | testing, this flag can be useful to conserve inotify file descriptors, as |
408 | testing, this flag can be useful to conserve inotify file descriptors, as |
409 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
409 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
410 | |
410 | |
411 | =item C<EVFLAG_SIGNALFD> |
411 | =item C<EVFLAG_SIGNALFD> |
412 | |
412 | |
413 | When this flag is specified, then libev will attempt to use the |
413 | When this flag is specified, then libev will attempt to use the |
414 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
414 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
415 | delivers signals synchronously, which makes it both faster and might make |
415 | delivers signals synchronously, which makes it both faster and might make |
416 | it possible to get the queued signal data. It can also simplify signal |
416 | it possible to get the queued signal data. It can also simplify signal |
417 | handling with threads, as long as you properly block signals in your |
417 | handling with threads, as long as you properly block signals in your |
418 | threads that are not interested in handling them. |
418 | threads that are not interested in handling them. |
419 | |
419 | |
… | |
… | |
463 | epoll scales either O(1) or O(active_fds). |
463 | epoll scales either O(1) or O(active_fds). |
464 | |
464 | |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
466 | of the more advanced event mechanisms: mere annoyances include silently |
466 | of the more advanced event mechanisms: mere annoyances include silently |
467 | dropping file descriptors, requiring a system call per change per file |
467 | dropping file descriptors, requiring a system call per change per file |
468 | descriptor (and unnecessary guessing of parameters), problems with dup and |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
469 | returning before the timeout value, resulting in additional iterations |
|
|
470 | (and only giving 5ms accuracy while select on the same platform gives |
469 | so on. The biggest issue is fork races, however - if a program forks then |
471 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
470 | I<both> parent and child process have to recreate the epoll set, which can |
472 | forks then I<both> parent and child process have to recreate the epoll |
471 | take considerable time (one syscall per file descriptor) and is of course |
473 | set, which can take considerable time (one syscall per file descriptor) |
472 | hard to detect. |
474 | and is of course hard to detect. |
473 | |
475 | |
474 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
476 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
475 | of course I<doesn't>, and epoll just loves to report events for totally |
477 | of course I<doesn't>, and epoll just loves to report events for totally |
476 | I<different> file descriptors (even already closed ones, so one cannot |
478 | I<different> file descriptors (even already closed ones, so one cannot |
477 | even remove them from the set) than registered in the set (especially |
479 | even remove them from the set) than registered in the set (especially |
… | |
… | |
479 | employing an additional generation counter and comparing that against the |
481 | employing an additional generation counter and comparing that against the |
480 | events to filter out spurious ones, recreating the set when required. Last |
482 | events to filter out spurious ones, recreating the set when required. Last |
481 | not least, it also refuses to work with some file descriptors which work |
483 | not least, it also refuses to work with some file descriptors which work |
482 | perfectly fine with C<select> (files, many character devices...). |
484 | perfectly fine with C<select> (files, many character devices...). |
483 | |
485 | |
|
|
486 | Epoll is truly the train wreck analog among event poll mechanisms. |
|
|
487 | |
484 | While stopping, setting and starting an I/O watcher in the same iteration |
488 | While stopping, setting and starting an I/O watcher in the same iteration |
485 | will result in some caching, there is still a system call per such |
489 | will result in some caching, there is still a system call per such |
486 | incident (because the same I<file descriptor> could point to a different |
490 | incident (because the same I<file descriptor> could point to a different |
487 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
491 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
488 | file descriptors might not work very well if you register events for both |
492 | file descriptors might not work very well if you register events for both |
… | |
… | |
615 | This function is normally used on loop objects allocated by |
619 | This function is normally used on loop objects allocated by |
616 | C<ev_loop_new>, but it can also be used on the default loop returned by |
620 | C<ev_loop_new>, but it can also be used on the default loop returned by |
617 | C<ev_default_loop>, in which case it is not thread-safe. |
621 | C<ev_default_loop>, in which case it is not thread-safe. |
618 | |
622 | |
619 | Note that it is not advisable to call this function on the default loop |
623 | Note that it is not advisable to call this function on the default loop |
620 | except in the rare occasion where you really need to free it's resources. |
624 | except in the rare occasion where you really need to free its resources. |
621 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
625 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
622 | and C<ev_loop_destroy>. |
626 | and C<ev_loop_destroy>. |
623 | |
627 | |
624 | =item ev_loop_fork (loop) |
628 | =item ev_loop_fork (loop) |
625 | |
629 | |
… | |
… | |
673 | prepare and check phases. |
677 | prepare and check phases. |
674 | |
678 | |
675 | =item unsigned int ev_depth (loop) |
679 | =item unsigned int ev_depth (loop) |
676 | |
680 | |
677 | Returns the number of times C<ev_run> was entered minus the number of |
681 | Returns the number of times C<ev_run> was entered minus the number of |
678 | times C<ev_run> was exited, in other words, the recursion depth. |
682 | times C<ev_run> was exited normally, in other words, the recursion depth. |
679 | |
683 | |
680 | Outside C<ev_run>, this number is zero. In a callback, this number is |
684 | Outside C<ev_run>, this number is zero. In a callback, this number is |
681 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
685 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
682 | in which case it is higher. |
686 | in which case it is higher. |
683 | |
687 | |
684 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
688 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
685 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
689 | throwing an exception etc.), doesn't count as "exit" - consider this |
686 | ungentleman-like behaviour unless it's really convenient. |
690 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
691 | convenient, in which case it is fully supported. |
687 | |
692 | |
688 | =item unsigned int ev_backend (loop) |
693 | =item unsigned int ev_backend (loop) |
689 | |
694 | |
690 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
695 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
691 | use. |
696 | use. |
… | |
… | |
752 | relying on all watchers to be stopped when deciding when a program has |
757 | relying on all watchers to be stopped when deciding when a program has |
753 | finished (especially in interactive programs), but having a program |
758 | finished (especially in interactive programs), but having a program |
754 | that automatically loops as long as it has to and no longer by virtue |
759 | that automatically loops as long as it has to and no longer by virtue |
755 | of relying on its watchers stopping correctly, that is truly a thing of |
760 | of relying on its watchers stopping correctly, that is truly a thing of |
756 | beauty. |
761 | beauty. |
|
|
762 | |
|
|
763 | This function is also I<mostly> exception-safe - you can break out of |
|
|
764 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
765 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
766 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
757 | |
767 | |
758 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
768 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
759 | those events and any already outstanding ones, but will not wait and |
769 | those events and any already outstanding ones, but will not wait and |
760 | block your process in case there are no events and will return after one |
770 | block your process in case there are no events and will return after one |
761 | iteration of the loop. This is sometimes useful to poll and handle new |
771 | iteration of the loop. This is sometimes useful to poll and handle new |
… | |
… | |
823 | Can be used to make a call to C<ev_run> return early (but only after it |
833 | Can be used to make a call to C<ev_run> return early (but only after it |
824 | has processed all outstanding events). The C<how> argument must be either |
834 | has processed all outstanding events). The C<how> argument must be either |
825 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
835 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
826 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
836 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
827 | |
837 | |
828 | This "unloop state" will be cleared when entering C<ev_run> again. |
838 | This "break state" will be cleared on the next call to C<ev_run>. |
829 | |
839 | |
830 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
840 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
841 | which case it will have no effect. |
831 | |
842 | |
832 | =item ev_ref (loop) |
843 | =item ev_ref (loop) |
833 | |
844 | |
834 | =item ev_unref (loop) |
845 | =item ev_unref (loop) |
835 | |
846 | |
… | |
… | |
978 | See also the locking example in the C<THREADS> section later in this |
989 | See also the locking example in the C<THREADS> section later in this |
979 | document. |
990 | document. |
980 | |
991 | |
981 | =item ev_set_userdata (loop, void *data) |
992 | =item ev_set_userdata (loop, void *data) |
982 | |
993 | |
983 | =item ev_userdata (loop) |
994 | =item void *ev_userdata (loop) |
984 | |
995 | |
985 | Set and retrieve a single C<void *> associated with a loop. When |
996 | Set and retrieve a single C<void *> associated with a loop. When |
986 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
997 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
987 | C<0.> |
998 | C<0>. |
988 | |
999 | |
989 | These two functions can be used to associate arbitrary data with a loop, |
1000 | These two functions can be used to associate arbitrary data with a loop, |
990 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1001 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
991 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1002 | C<acquire> callbacks described above, but of course can be (ab-)used for |
992 | any other purpose as well. |
1003 | any other purpose as well. |
… | |
… | |
2256 | |
2267 | |
2257 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2268 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2258 | |
2269 | |
2259 | Signal watchers will trigger an event when the process receives a specific |
2270 | Signal watchers will trigger an event when the process receives a specific |
2260 | signal one or more times. Even though signals are very asynchronous, libev |
2271 | signal one or more times. Even though signals are very asynchronous, libev |
2261 | will try it's best to deliver signals synchronously, i.e. as part of the |
2272 | will try its best to deliver signals synchronously, i.e. as part of the |
2262 | normal event processing, like any other event. |
2273 | normal event processing, like any other event. |
2263 | |
2274 | |
2264 | If you want signals to be delivered truly asynchronously, just use |
2275 | If you want signals to be delivered truly asynchronously, just use |
2265 | C<sigaction> as you would do without libev and forget about sharing |
2276 | C<sigaction> as you would do without libev and forget about sharing |
2266 | the signal. You can even use C<ev_async> from a signal handler to |
2277 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
3356 | loop!). |
3367 | loop!). |
3357 | |
3368 | |
3358 | =back |
3369 | =back |
3359 | |
3370 | |
3360 | |
3371 | |
|
|
3372 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3373 | |
|
|
3374 | This section explains some common idioms that are not immediately |
|
|
3375 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3376 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3377 | |
|
|
3378 | =over 4 |
|
|
3379 | |
|
|
3380 | =item Model/nested event loop invocations and exit conditions. |
|
|
3381 | |
|
|
3382 | Often (especially in GUI toolkits) there are places where you have |
|
|
3383 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3384 | invoking C<ev_run>. |
|
|
3385 | |
|
|
3386 | This brings the problem of exiting - a callback might want to finish the |
|
|
3387 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3388 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3389 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3390 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3391 | |
|
|
3392 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3393 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3394 | triggered, using C<EVRUN_ONCE>: |
|
|
3395 | |
|
|
3396 | // main loop |
|
|
3397 | int exit_main_loop = 0; |
|
|
3398 | |
|
|
3399 | while (!exit_main_loop) |
|
|
3400 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3401 | |
|
|
3402 | // in a model watcher |
|
|
3403 | int exit_nested_loop = 0; |
|
|
3404 | |
|
|
3405 | while (!exit_nested_loop) |
|
|
3406 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3407 | |
|
|
3408 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3409 | |
|
|
3410 | // exit modal loop |
|
|
3411 | exit_nested_loop = 1; |
|
|
3412 | |
|
|
3413 | // exit main program, after modal loop is finished |
|
|
3414 | exit_main_loop = 1; |
|
|
3415 | |
|
|
3416 | // exit both |
|
|
3417 | exit_main_loop = exit_nested_loop = 1; |
|
|
3418 | |
|
|
3419 | =back |
|
|
3420 | |
|
|
3421 | |
3361 | =head1 LIBEVENT EMULATION |
3422 | =head1 LIBEVENT EMULATION |
3362 | |
3423 | |
3363 | Libev offers a compatibility emulation layer for libevent. It cannot |
3424 | Libev offers a compatibility emulation layer for libevent. It cannot |
3364 | emulate the internals of libevent, so here are some usage hints: |
3425 | emulate the internals of libevent, so here are some usage hints: |
3365 | |
3426 | |
3366 | =over 4 |
3427 | =over 4 |
|
|
3428 | |
|
|
3429 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3430 | |
|
|
3431 | This was the newest libevent version available when libev was implemented, |
|
|
3432 | and is still mostly uncanged in 2010. |
3367 | |
3433 | |
3368 | =item * Use it by including <event.h>, as usual. |
3434 | =item * Use it by including <event.h>, as usual. |
3369 | |
3435 | |
3370 | =item * The following members are fully supported: ev_base, ev_callback, |
3436 | =item * The following members are fully supported: ev_base, ev_callback, |
3371 | ev_arg, ev_fd, ev_res, ev_events. |
3437 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3377 | =item * Priorities are not currently supported. Initialising priorities |
3443 | =item * Priorities are not currently supported. Initialising priorities |
3378 | will fail and all watchers will have the same priority, even though there |
3444 | will fail and all watchers will have the same priority, even though there |
3379 | is an ev_pri field. |
3445 | is an ev_pri field. |
3380 | |
3446 | |
3381 | =item * In libevent, the last base created gets the signals, in libev, the |
3447 | =item * In libevent, the last base created gets the signals, in libev, the |
3382 | first base created (== the default loop) gets the signals. |
3448 | base that registered the signal gets the signals. |
3383 | |
3449 | |
3384 | =item * Other members are not supported. |
3450 | =item * Other members are not supported. |
3385 | |
3451 | |
3386 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3452 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3387 | to use the libev header file and library. |
3453 | to use the libev header file and library. |