… | |
… | |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
14 | // every watcher type has its own typedef'd struct |
14 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
15 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
16 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
18 | |
18 | |
19 | // all watcher callbacks have a similar signature |
19 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
20 | // this callback is called when data is readable on stdin |
21 | static void |
21 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
23 | { |
24 | puts ("stdin ready"); |
24 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
25 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
26 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
27 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
31 | } |
32 | |
32 | |
33 | // another callback, this time for a time-out |
33 | // another callback, this time for a time-out |
34 | static void |
34 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
36 | { |
37 | puts ("timeout"); |
37 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
38 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
40 | } |
41 | |
41 | |
42 | int |
42 | int |
43 | main (void) |
43 | main (void) |
44 | { |
44 | { |
45 | // use the default event loop unless you have special needs |
45 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
46 | ev_loop *loop = ev_default_loop (0); |
47 | |
47 | |
48 | // initialise an io watcher, then start it |
48 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
49 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
103 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
104 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
105 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
106 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
107 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
109 | this argument. |
110 | |
110 | |
111 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
112 | |
112 | |
113 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
… | |
… | |
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 |
… | |
… | |
276 | |
276 | |
277 | =back |
277 | =back |
278 | |
278 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
280 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
282 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
283 | I<function>). |
|
|
284 | |
|
|
285 | The library knows two types of such loops, the I<default> loop, which |
|
|
286 | supports signals and child events, and dynamically created loops which do |
|
|
287 | not. |
284 | |
288 | |
285 | =over 4 |
289 | =over 4 |
286 | |
290 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
291 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
292 | |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
363 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
364 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
365 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
366 | readiness notifications you get per iteration. |
363 | |
367 | |
|
|
368 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
369 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
370 | C<exceptfds> set on that platform). |
|
|
371 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
372 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
373 | |
366 | And this is your standard poll(2) backend. It's more complicated |
374 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
375 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
376 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
377 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
378 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
379 | performance tips. |
|
|
380 | |
|
|
381 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
382 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
372 | |
383 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
374 | |
385 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
386 | For few fds, this backend is a bit little slower than poll and select, |
376 | but it scales phenomenally better. While poll and select usually scale |
387 | but it scales phenomenally better. While poll and select usually scale |
… | |
… | |
389 | Please note that epoll sometimes generates spurious notifications, so you |
400 | Please note that epoll sometimes generates spurious notifications, so you |
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
401 | need to use non-blocking I/O or other means to avoid blocking when no data |
391 | (or space) is available. |
402 | (or space) is available. |
392 | |
403 | |
393 | Best performance from this backend is achieved by not unregistering all |
404 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
405 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
406 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
407 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
408 | extra overhead. |
396 | |
409 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
410 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
411 | all kernel versions tested so far. |
399 | |
412 | |
|
|
413 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
414 | C<EVBACKEND_POLL>. |
|
|
415 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
416 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
417 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
418 | Kqueue deserves special mention, as at the time of this writing, it was |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
419 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
404 | with anything but sockets and pipes, except on Darwin, where of course |
420 | anything but sockets and pipes, except on Darwin, where of course it's |
405 | it's completely useless). For this reason it's not being "auto-detected" |
421 | completely useless). For this reason it's not being "auto-detected" unless |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
422 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
423 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
408 | system like NetBSD. |
|
|
409 | |
424 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
425 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
426 | only for sockets (after having made sure that sockets work with kqueue on |
412 | the target platform). See C<ev_embed> watchers for more info. |
427 | the target platform). See C<ev_embed> watchers for more info. |
413 | |
428 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
429 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
430 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
431 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
432 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
433 | two event changes per incident. Support for C<fork ()> is very bad and it |
419 | drops fds silently in similarly hard-to-detect cases. |
434 | drops fds silently in similarly hard-to-detect cases. |
420 | |
435 | |
421 | This backend usually performs well under most conditions. |
436 | This backend usually performs well under most conditions. |
422 | |
437 | |
423 | While nominally embeddable in other event loops, this doesn't work |
438 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
439 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
440 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
441 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
442 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
428 | sockets. |
443 | using it only for sockets. |
|
|
444 | |
|
|
445 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
446 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
447 | C<NOTE_EOF>. |
429 | |
448 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
449 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
450 | |
432 | This is not implemented yet (and might never be, unless you send me an |
451 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
452 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
465 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
466 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
467 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
468 | might perform better. |
450 | |
469 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
470 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
471 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
472 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
473 | OS-specific backends. |
|
|
474 | |
|
|
475 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
476 | C<EVBACKEND_POLL>. |
454 | |
477 | |
455 | =item C<EVBACKEND_ALL> |
478 | =item C<EVBACKEND_ALL> |
456 | |
479 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
480 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
481 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
464 | |
487 | |
465 | If one or more of these are or'ed into the flags value, then only these |
488 | If one or more of these are or'ed into the flags value, then only these |
466 | backends will be tried (in the reverse order as listed here). If none are |
489 | backends will be tried (in the reverse order as listed here). If none are |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
490 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
468 | |
491 | |
469 | The most typical usage is like this: |
492 | Example: This is the most typical usage. |
470 | |
493 | |
471 | if (!ev_default_loop (0)) |
494 | if (!ev_default_loop (0)) |
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
495 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
473 | |
496 | |
474 | Restrict libev to the select and poll backends, and do not allow |
497 | Example: Restrict libev to the select and poll backends, and do not allow |
475 | environment settings to be taken into account: |
498 | environment settings to be taken into account: |
476 | |
499 | |
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
500 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
478 | |
501 | |
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
502 | Example: Use whatever libev has to offer, but make sure that kqueue is |
480 | available (warning, breaks stuff, best use only with your own private |
503 | used if available (warning, breaks stuff, best use only with your own |
481 | event loop and only if you know the OS supports your types of fds): |
504 | private event loop and only if you know the OS supports your types of |
|
|
505 | fds): |
482 | |
506 | |
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
507 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
484 | |
508 | |
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
509 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
486 | |
510 | |
… | |
… | |
544 | |
568 | |
545 | =item ev_loop_fork (loop) |
569 | =item ev_loop_fork (loop) |
546 | |
570 | |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
571 | Like C<ev_default_fork>, but acts on an event loop created by |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
572 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
549 | after fork, and how you do this is entirely your own problem. |
573 | after fork that you want to re-use in the child, and how you do this is |
|
|
574 | entirely your own problem. |
550 | |
575 | |
551 | =item int ev_is_default_loop (loop) |
576 | =item int ev_is_default_loop (loop) |
552 | |
577 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
578 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
579 | otherwise. |
554 | |
580 | |
555 | =item unsigned int ev_loop_count (loop) |
581 | =item unsigned int ev_loop_count (loop) |
556 | |
582 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
583 | Returns the count of loop iterations for the loop, which is identical to |
558 | the number of times libev did poll for new events. It starts at C<0> and |
584 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
599 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
600 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
601 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
602 | event occurring (or more correctly, libev finding out about it). |
577 | |
603 | |
|
|
604 | =item ev_now_update (loop) |
|
|
605 | |
|
|
606 | Establishes the current time by querying the kernel, updating the time |
|
|
607 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
608 | is usually done automatically within C<ev_loop ()>. |
|
|
609 | |
|
|
610 | This function is rarely useful, but when some event callback runs for a |
|
|
611 | very long time without entering the event loop, updating libev's idea of |
|
|
612 | the current time is a good idea. |
|
|
613 | |
|
|
614 | See also "The special problem of time updates" in the C<ev_timer> section. |
|
|
615 | |
578 | =item ev_loop (loop, int flags) |
616 | =item ev_loop (loop, int flags) |
579 | |
617 | |
580 | Finally, this is it, the event handler. This function usually is called |
618 | Finally, this is it, the event handler. This function usually is called |
581 | after you initialised all your watchers and you want to start handling |
619 | after you initialised all your watchers and you want to start handling |
582 | events. |
620 | events. |
… | |
… | |
584 | If the flags argument is specified as C<0>, it will not return until |
622 | If the flags argument is specified as C<0>, it will not return until |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
623 | either no event watchers are active anymore or C<ev_unloop> was called. |
586 | |
624 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
625 | Please note that an explicit C<ev_unloop> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
626 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
627 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
628 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
629 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
630 | beauty. |
592 | |
631 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
632 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
633 | those events and any already outstanding ones, but will not block your |
595 | case there are no events and will return after one iteration of the loop. |
634 | process in case there are no events and will return after one iteration of |
|
|
635 | the loop. |
596 | |
636 | |
597 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
637 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
598 | necessary) and will handle those and any outstanding ones. It will block |
638 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
639 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
640 | be an event internal to libev itself, so there is no guarentee that a |
601 | external event in conjunction with something not expressible using other |
641 | user-registered callback will be called), and will return after one |
|
|
642 | iteration of the loop. |
|
|
643 | |
|
|
644 | This is useful if you are waiting for some external event in conjunction |
|
|
645 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
646 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
647 | usually a better approach for this kind of thing. |
604 | |
648 | |
605 | Here are the gory details of what C<ev_loop> does: |
649 | Here are the gory details of what C<ev_loop> does: |
606 | |
650 | |
607 | - Before the first iteration, call any pending watchers. |
651 | - Before the first iteration, call any pending watchers. |
… | |
… | |
617 | any active watchers at all will result in not sleeping). |
661 | any active watchers at all will result in not sleeping). |
618 | - Sleep if the I/O and timer collect interval say so. |
662 | - Sleep if the I/O and timer collect interval say so. |
619 | - Block the process, waiting for any events. |
663 | - Block the process, waiting for any events. |
620 | - Queue all outstanding I/O (fd) events. |
664 | - Queue all outstanding I/O (fd) events. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
665 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
622 | - Queue all outstanding timers. |
666 | - Queue all expired timers. |
623 | - Queue all outstanding periodics. |
667 | - Queue all expired periodics. |
624 | - Unless any events are pending now, queue all idle watchers. |
668 | - Unless any events are pending now, queue all idle watchers. |
625 | - Queue all check watchers. |
669 | - Queue all check watchers. |
626 | - Call all queued watchers in reverse order (i.e. check watchers first). |
670 | - Call all queued watchers in reverse order (i.e. check watchers first). |
627 | Signals and child watchers are implemented as I/O watchers, and will |
671 | Signals and child watchers are implemented as I/O watchers, and will |
628 | be handled here by queueing them when their watcher gets executed. |
672 | be handled here by queueing them when their watcher gets executed. |
… | |
… | |
645 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
689 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
646 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
690 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
647 | |
691 | |
648 | This "unloop state" will be cleared when entering C<ev_loop> again. |
692 | This "unloop state" will be cleared when entering C<ev_loop> again. |
649 | |
693 | |
|
|
694 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
695 | |
650 | =item ev_ref (loop) |
696 | =item ev_ref (loop) |
651 | |
697 | |
652 | =item ev_unref (loop) |
698 | =item ev_unref (loop) |
653 | |
699 | |
654 | Ref/unref can be used to add or remove a reference count on the event |
700 | Ref/unref can be used to add or remove a reference count on the event |
655 | loop: Every watcher keeps one reference, and as long as the reference |
701 | loop: Every watcher keeps one reference, and as long as the reference |
656 | count is nonzero, C<ev_loop> will not return on its own. If you have |
702 | count is nonzero, C<ev_loop> will not return on its own. |
|
|
703 | |
657 | a watcher you never unregister that should not keep C<ev_loop> from |
704 | If you have a watcher you never unregister that should not keep C<ev_loop> |
658 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
705 | from returning, call ev_unref() after starting, and ev_ref() before |
|
|
706 | stopping it. |
|
|
707 | |
659 | example, libev itself uses this for its internal signal pipe: It is not |
708 | As an example, libev itself uses this for its internal signal pipe: It is |
660 | visible to the libev user and should not keep C<ev_loop> from exiting if |
709 | not visible to the libev user and should not keep C<ev_loop> from exiting |
661 | no event watchers registered by it are active. It is also an excellent |
710 | if no event watchers registered by it are active. It is also an excellent |
662 | way to do this for generic recurring timers or from within third-party |
711 | way to do this for generic recurring timers or from within third-party |
663 | libraries. Just remember to I<unref after start> and I<ref before stop> |
712 | libraries. Just remember to I<unref after start> and I<ref before stop> |
664 | (but only if the watcher wasn't active before, or was active before, |
713 | (but only if the watcher wasn't active before, or was active before, |
665 | respectively). |
714 | respectively). |
666 | |
715 | |
667 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
716 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
668 | running when nothing else is active. |
717 | running when nothing else is active. |
669 | |
718 | |
670 | struct ev_signal exitsig; |
719 | ev_signal exitsig; |
671 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
720 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
672 | ev_signal_start (loop, &exitsig); |
721 | ev_signal_start (loop, &exitsig); |
673 | evf_unref (loop); |
722 | evf_unref (loop); |
674 | |
723 | |
675 | Example: For some weird reason, unregister the above signal handler again. |
724 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
689 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
738 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
739 | allows libev to delay invocation of I/O and timer/periodic callbacks |
691 | to increase efficiency of loop iterations (or to increase power-saving |
740 | to increase efficiency of loop iterations (or to increase power-saving |
692 | opportunities). |
741 | opportunities). |
693 | |
742 | |
694 | The background is that sometimes your program runs just fast enough to |
743 | The idea is that sometimes your program runs just fast enough to handle |
695 | handle one (or very few) event(s) per loop iteration. While this makes |
744 | one (or very few) event(s) per loop iteration. While this makes the |
696 | the program responsive, it also wastes a lot of CPU time to poll for new |
745 | program responsive, it also wastes a lot of CPU time to poll for new |
697 | events, especially with backends like C<select ()> which have a high |
746 | events, especially with backends like C<select ()> which have a high |
698 | overhead for the actual polling but can deliver many events at once. |
747 | overhead for the actual polling but can deliver many events at once. |
699 | |
748 | |
700 | By setting a higher I<io collect interval> you allow libev to spend more |
749 | By setting a higher I<io collect interval> you allow libev to spend more |
701 | time collecting I/O events, so you can handle more events per iteration, |
750 | time collecting I/O events, so you can handle more events per iteration, |
… | |
… | |
703 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
752 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
704 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
753 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
705 | |
754 | |
706 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
755 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
707 | to spend more time collecting timeouts, at the expense of increased |
756 | to spend more time collecting timeouts, at the expense of increased |
708 | latency (the watcher callback will be called later). C<ev_io> watchers |
757 | latency/jitter/inexactness (the watcher callback will be called |
709 | will not be affected. Setting this to a non-null value will not introduce |
758 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
710 | any overhead in libev. |
759 | value will not introduce any overhead in libev. |
711 | |
760 | |
712 | Many (busy) programs can usually benefit by setting the I/O collect |
761 | Many (busy) programs can usually benefit by setting the I/O collect |
713 | interval to a value near C<0.1> or so, which is often enough for |
762 | interval to a value near C<0.1> or so, which is often enough for |
714 | interactive servers (of course not for games), likewise for timeouts. It |
763 | interactive servers (of course not for games), likewise for timeouts. It |
715 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
764 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
… | |
… | |
723 | they fire on, say, one-second boundaries only. |
772 | they fire on, say, one-second boundaries only. |
724 | |
773 | |
725 | =item ev_loop_verify (loop) |
774 | =item ev_loop_verify (loop) |
726 | |
775 | |
727 | This function only does something when C<EV_VERIFY> support has been |
776 | This function only does something when C<EV_VERIFY> support has been |
728 | compiled in. It tries to go through all internal structures and checks |
777 | compiled in, which is the default for non-minimal builds. It tries to go |
729 | them for validity. If anything is found to be inconsistent, it will print |
778 | through all internal structures and checks them for validity. If anything |
730 | an error message to standard error and call C<abort ()>. |
779 | is found to be inconsistent, it will print an error message to standard |
|
|
780 | error and call C<abort ()>. |
731 | |
781 | |
732 | This can be used to catch bugs inside libev itself: under normal |
782 | This can be used to catch bugs inside libev itself: under normal |
733 | circumstances, this function will never abort as of course libev keeps its |
783 | circumstances, this function will never abort as of course libev keeps its |
734 | data structures consistent. |
784 | data structures consistent. |
735 | |
785 | |
736 | =back |
786 | =back |
737 | |
787 | |
738 | |
788 | |
739 | =head1 ANATOMY OF A WATCHER |
789 | =head1 ANATOMY OF A WATCHER |
740 | |
790 | |
|
|
791 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
792 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
793 | watchers and C<ev_io_start> for I/O watchers. |
|
|
794 | |
741 | A watcher is a structure that you create and register to record your |
795 | A watcher is a structure that you create and register to record your |
742 | interest in some event. For instance, if you want to wait for STDIN to |
796 | interest in some event. For instance, if you want to wait for STDIN to |
743 | become readable, you would create an C<ev_io> watcher for that: |
797 | become readable, you would create an C<ev_io> watcher for that: |
744 | |
798 | |
745 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
799 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
746 | { |
800 | { |
747 | ev_io_stop (w); |
801 | ev_io_stop (w); |
748 | ev_unloop (loop, EVUNLOOP_ALL); |
802 | ev_unloop (loop, EVUNLOOP_ALL); |
749 | } |
803 | } |
750 | |
804 | |
751 | struct ev_loop *loop = ev_default_loop (0); |
805 | struct ev_loop *loop = ev_default_loop (0); |
|
|
806 | |
752 | struct ev_io stdin_watcher; |
807 | ev_io stdin_watcher; |
|
|
808 | |
753 | ev_init (&stdin_watcher, my_cb); |
809 | ev_init (&stdin_watcher, my_cb); |
754 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
810 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
755 | ev_io_start (loop, &stdin_watcher); |
811 | ev_io_start (loop, &stdin_watcher); |
|
|
812 | |
756 | ev_loop (loop, 0); |
813 | ev_loop (loop, 0); |
757 | |
814 | |
758 | As you can see, you are responsible for allocating the memory for your |
815 | As you can see, you are responsible for allocating the memory for your |
759 | watcher structures (and it is usually a bad idea to do this on the stack, |
816 | watcher structures (and it is I<usually> a bad idea to do this on the |
760 | although this can sometimes be quite valid). |
817 | stack). |
|
|
818 | |
|
|
819 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
820 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
761 | |
821 | |
762 | Each watcher structure must be initialised by a call to C<ev_init |
822 | Each watcher structure must be initialised by a call to C<ev_init |
763 | (watcher *, callback)>, which expects a callback to be provided. This |
823 | (watcher *, callback)>, which expects a callback to be provided. This |
764 | callback gets invoked each time the event occurs (or, in the case of I/O |
824 | callback gets invoked each time the event occurs (or, in the case of I/O |
765 | watchers, each time the event loop detects that the file descriptor given |
825 | watchers, each time the event loop detects that the file descriptor given |
766 | is readable and/or writable). |
826 | is readable and/or writable). |
767 | |
827 | |
768 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
828 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
769 | with arguments specific to this watcher type. There is also a macro |
829 | macro to configure it, with arguments specific to the watcher type. There |
770 | to combine initialisation and setting in one call: C<< ev_<type>_init |
830 | is also a macro to combine initialisation and setting in one call: C<< |
771 | (watcher *, callback, ...) >>. |
831 | ev_TYPE_init (watcher *, callback, ...) >>. |
772 | |
832 | |
773 | To make the watcher actually watch out for events, you have to start it |
833 | To make the watcher actually watch out for events, you have to start it |
774 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
834 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
775 | *) >>), and you can stop watching for events at any time by calling the |
835 | *) >>), and you can stop watching for events at any time by calling the |
776 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
836 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
777 | |
837 | |
778 | As long as your watcher is active (has been started but not stopped) you |
838 | As long as your watcher is active (has been started but not stopped) you |
779 | must not touch the values stored in it. Most specifically you must never |
839 | must not touch the values stored in it. Most specifically you must never |
780 | reinitialise it or call its C<set> macro. |
840 | reinitialise it or call its C<ev_TYPE_set> macro. |
781 | |
841 | |
782 | Each and every callback receives the event loop pointer as first, the |
842 | Each and every callback receives the event loop pointer as first, the |
783 | registered watcher structure as second, and a bitset of received events as |
843 | registered watcher structure as second, and a bitset of received events as |
784 | third argument. |
844 | third argument. |
785 | |
845 | |
… | |
… | |
848 | =item C<EV_ERROR> |
908 | =item C<EV_ERROR> |
849 | |
909 | |
850 | An unspecified error has occurred, the watcher has been stopped. This might |
910 | An unspecified error has occurred, the watcher has been stopped. This might |
851 | happen because the watcher could not be properly started because libev |
911 | happen because the watcher could not be properly started because libev |
852 | ran out of memory, a file descriptor was found to be closed or any other |
912 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
913 | problem. Libev considers these application bugs. |
|
|
914 | |
853 | problem. You best act on it by reporting the problem and somehow coping |
915 | You best act on it by reporting the problem and somehow coping with the |
854 | with the watcher being stopped. |
916 | watcher being stopped. Note that well-written programs should not receive |
|
|
917 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
918 | bug in your program. |
855 | |
919 | |
856 | Libev will usually signal a few "dummy" events together with an error, |
920 | Libev will usually signal a few "dummy" events together with an error, for |
857 | for example it might indicate that a fd is readable or writable, and if |
921 | example it might indicate that a fd is readable or writable, and if your |
858 | your callbacks is well-written it can just attempt the operation and cope |
922 | callbacks is well-written it can just attempt the operation and cope with |
859 | with the error from read() or write(). This will not work in multi-threaded |
923 | the error from read() or write(). This will not work in multi-threaded |
860 | programs, though, so beware. |
924 | programs, though, as the fd could already be closed and reused for another |
|
|
925 | thing, so beware. |
861 | |
926 | |
862 | =back |
927 | =back |
863 | |
928 | |
864 | =head2 GENERIC WATCHER FUNCTIONS |
929 | =head2 GENERIC WATCHER FUNCTIONS |
865 | |
|
|
866 | In the following description, C<TYPE> stands for the watcher type, |
|
|
867 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
868 | |
930 | |
869 | =over 4 |
931 | =over 4 |
870 | |
932 | |
871 | =item C<ev_init> (ev_TYPE *watcher, callback) |
933 | =item C<ev_init> (ev_TYPE *watcher, callback) |
872 | |
934 | |
… | |
… | |
878 | which rolls both calls into one. |
940 | which rolls both calls into one. |
879 | |
941 | |
880 | You can reinitialise a watcher at any time as long as it has been stopped |
942 | You can reinitialise a watcher at any time as long as it has been stopped |
881 | (or never started) and there are no pending events outstanding. |
943 | (or never started) and there are no pending events outstanding. |
882 | |
944 | |
883 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
945 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
884 | int revents)>. |
946 | int revents)>. |
|
|
947 | |
|
|
948 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
949 | |
|
|
950 | ev_io w; |
|
|
951 | ev_init (&w, my_cb); |
|
|
952 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
885 | |
953 | |
886 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
954 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
887 | |
955 | |
888 | This macro initialises the type-specific parts of a watcher. You need to |
956 | This macro initialises the type-specific parts of a watcher. You need to |
889 | call C<ev_init> at least once before you call this macro, but you can |
957 | call C<ev_init> at least once before you call this macro, but you can |
… | |
… | |
892 | difference to the C<ev_init> macro). |
960 | difference to the C<ev_init> macro). |
893 | |
961 | |
894 | Although some watcher types do not have type-specific arguments |
962 | Although some watcher types do not have type-specific arguments |
895 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
963 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
896 | |
964 | |
|
|
965 | See C<ev_init>, above, for an example. |
|
|
966 | |
897 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
967 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
898 | |
968 | |
899 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
969 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
900 | calls into a single call. This is the most convenient method to initialise |
970 | calls into a single call. This is the most convenient method to initialise |
901 | a watcher. The same limitations apply, of course. |
971 | a watcher. The same limitations apply, of course. |
902 | |
972 | |
|
|
973 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
974 | |
|
|
975 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
976 | |
903 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
977 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
904 | |
978 | |
905 | Starts (activates) the given watcher. Only active watchers will receive |
979 | Starts (activates) the given watcher. Only active watchers will receive |
906 | events. If the watcher is already active nothing will happen. |
980 | events. If the watcher is already active nothing will happen. |
907 | |
981 | |
|
|
982 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
983 | whole section. |
|
|
984 | |
|
|
985 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
986 | |
908 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
987 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
909 | |
988 | |
910 | Stops the given watcher again (if active) and clears the pending |
989 | Stops the given watcher if active, and clears the pending status (whether |
|
|
990 | the watcher was active or not). |
|
|
991 | |
911 | status. It is possible that stopped watchers are pending (for example, |
992 | It is possible that stopped watchers are pending - for example, |
912 | non-repeating timers are being stopped when they become pending), but |
993 | non-repeating timers are being stopped when they become pending - but |
913 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
994 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
914 | you want to free or reuse the memory used by the watcher it is therefore a |
995 | pending. If you want to free or reuse the memory used by the watcher it is |
915 | good idea to always call its C<ev_TYPE_stop> function. |
996 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
916 | |
997 | |
917 | =item bool ev_is_active (ev_TYPE *watcher) |
998 | =item bool ev_is_active (ev_TYPE *watcher) |
918 | |
999 | |
919 | Returns a true value iff the watcher is active (i.e. it has been started |
1000 | Returns a true value iff the watcher is active (i.e. it has been started |
920 | and not yet been stopped). As long as a watcher is active you must not modify |
1001 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
968 | |
1049 | |
969 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1050 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
970 | |
1051 | |
971 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1052 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
972 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1053 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
973 | can deal with that fact. |
1054 | can deal with that fact, as both are simply passed through to the |
|
|
1055 | callback. |
974 | |
1056 | |
975 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1057 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
976 | |
1058 | |
977 | If the watcher is pending, this function returns clears its pending status |
1059 | If the watcher is pending, this function clears its pending status and |
978 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1060 | returns its C<revents> bitset (as if its callback was invoked). If the |
979 | watcher isn't pending it does nothing and returns C<0>. |
1061 | watcher isn't pending it does nothing and returns C<0>. |
980 | |
1062 | |
|
|
1063 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1064 | callback to be invoked, which can be accomplished with this function. |
|
|
1065 | |
981 | =back |
1066 | =back |
982 | |
1067 | |
983 | |
1068 | |
984 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1069 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
985 | |
1070 | |
986 | Each watcher has, by default, a member C<void *data> that you can change |
1071 | Each watcher has, by default, a member C<void *data> that you can change |
987 | and read at any time, libev will completely ignore it. This can be used |
1072 | and read at any time: libev will completely ignore it. This can be used |
988 | to associate arbitrary data with your watcher. If you need more data and |
1073 | to associate arbitrary data with your watcher. If you need more data and |
989 | don't want to allocate memory and store a pointer to it in that data |
1074 | don't want to allocate memory and store a pointer to it in that data |
990 | member, you can also "subclass" the watcher type and provide your own |
1075 | member, you can also "subclass" the watcher type and provide your own |
991 | data: |
1076 | data: |
992 | |
1077 | |
993 | struct my_io |
1078 | struct my_io |
994 | { |
1079 | { |
995 | struct ev_io io; |
1080 | ev_io io; |
996 | int otherfd; |
1081 | int otherfd; |
997 | void *somedata; |
1082 | void *somedata; |
998 | struct whatever *mostinteresting; |
1083 | struct whatever *mostinteresting; |
999 | } |
1084 | }; |
|
|
1085 | |
|
|
1086 | ... |
|
|
1087 | struct my_io w; |
|
|
1088 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1000 | |
1089 | |
1001 | And since your callback will be called with a pointer to the watcher, you |
1090 | And since your callback will be called with a pointer to the watcher, you |
1002 | can cast it back to your own type: |
1091 | can cast it back to your own type: |
1003 | |
1092 | |
1004 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1093 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1005 | { |
1094 | { |
1006 | struct my_io *w = (struct my_io *)w_; |
1095 | struct my_io *w = (struct my_io *)w_; |
1007 | ... |
1096 | ... |
1008 | } |
1097 | } |
1009 | |
1098 | |
1010 | More interesting and less C-conformant ways of casting your callback type |
1099 | More interesting and less C-conformant ways of casting your callback type |
1011 | instead have been omitted. |
1100 | instead have been omitted. |
1012 | |
1101 | |
1013 | Another common scenario is having some data structure with multiple |
1102 | Another common scenario is to use some data structure with multiple |
1014 | watchers: |
1103 | embedded watchers: |
1015 | |
1104 | |
1016 | struct my_biggy |
1105 | struct my_biggy |
1017 | { |
1106 | { |
1018 | int some_data; |
1107 | int some_data; |
1019 | ev_timer t1; |
1108 | ev_timer t1; |
1020 | ev_timer t2; |
1109 | ev_timer t2; |
1021 | } |
1110 | } |
1022 | |
1111 | |
1023 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1112 | In this case getting the pointer to C<my_biggy> is a bit more |
1024 | you need to use C<offsetof>: |
1113 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1114 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1115 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1116 | programmers): |
1025 | |
1117 | |
1026 | #include <stddef.h> |
1118 | #include <stddef.h> |
1027 | |
1119 | |
1028 | static void |
1120 | static void |
1029 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1121 | t1_cb (EV_P_ ev_timer *w, int revents) |
1030 | { |
1122 | { |
1031 | struct my_biggy big = (struct my_biggy * |
1123 | struct my_biggy big = (struct my_biggy * |
1032 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1124 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1033 | } |
1125 | } |
1034 | |
1126 | |
1035 | static void |
1127 | static void |
1036 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1128 | t2_cb (EV_P_ ev_timer *w, int revents) |
1037 | { |
1129 | { |
1038 | struct my_biggy big = (struct my_biggy * |
1130 | struct my_biggy big = (struct my_biggy * |
1039 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1131 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1040 | } |
1132 | } |
1041 | |
1133 | |
… | |
… | |
1069 | In general you can register as many read and/or write event watchers per |
1161 | In general you can register as many read and/or write event watchers per |
1070 | fd as you want (as long as you don't confuse yourself). Setting all file |
1162 | fd as you want (as long as you don't confuse yourself). Setting all file |
1071 | descriptors to non-blocking mode is also usually a good idea (but not |
1163 | descriptors to non-blocking mode is also usually a good idea (but not |
1072 | required if you know what you are doing). |
1164 | required if you know what you are doing). |
1073 | |
1165 | |
1074 | If you must do this, then force the use of a known-to-be-good backend |
1166 | If you cannot use non-blocking mode, then force the use of a |
1075 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1167 | known-to-be-good backend (at the time of this writing, this includes only |
1076 | C<EVBACKEND_POLL>). |
1168 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1077 | |
1169 | |
1078 | Another thing you have to watch out for is that it is quite easy to |
1170 | Another thing you have to watch out for is that it is quite easy to |
1079 | receive "spurious" readiness notifications, that is your callback might |
1171 | receive "spurious" readiness notifications, that is your callback might |
1080 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1172 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1081 | because there is no data. Not only are some backends known to create a |
1173 | because there is no data. Not only are some backends known to create a |
1082 | lot of those (for example Solaris ports), it is very easy to get into |
1174 | lot of those (for example Solaris ports), it is very easy to get into |
1083 | this situation even with a relatively standard program structure. Thus |
1175 | this situation even with a relatively standard program structure. Thus |
1084 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1176 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1085 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1177 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1086 | |
1178 | |
1087 | If you cannot run the fd in non-blocking mode (for example you should not |
1179 | If you cannot run the fd in non-blocking mode (for example you should |
1088 | play around with an Xlib connection), then you have to separately re-test |
1180 | not play around with an Xlib connection), then you have to separately |
1089 | whether a file descriptor is really ready with a known-to-be good interface |
1181 | re-test whether a file descriptor is really ready with a known-to-be good |
1090 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1182 | interface such as poll (fortunately in our Xlib example, Xlib already |
1091 | its own, so its quite safe to use). |
1183 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1184 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1185 | indefinitely. |
|
|
1186 | |
|
|
1187 | But really, best use non-blocking mode. |
1092 | |
1188 | |
1093 | =head3 The special problem of disappearing file descriptors |
1189 | =head3 The special problem of disappearing file descriptors |
1094 | |
1190 | |
1095 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1191 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1096 | descriptor (either by calling C<close> explicitly or by any other means, |
1192 | descriptor (either due to calling C<close> explicitly or any other means, |
1097 | such as C<dup>). The reason is that you register interest in some file |
1193 | such as C<dup2>). The reason is that you register interest in some file |
1098 | descriptor, but when it goes away, the operating system will silently drop |
1194 | descriptor, but when it goes away, the operating system will silently drop |
1099 | this interest. If another file descriptor with the same number then is |
1195 | this interest. If another file descriptor with the same number then is |
1100 | registered with libev, there is no efficient way to see that this is, in |
1196 | registered with libev, there is no efficient way to see that this is, in |
1101 | fact, a different file descriptor. |
1197 | fact, a different file descriptor. |
1102 | |
1198 | |
… | |
… | |
1133 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1229 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1134 | C<EVBACKEND_POLL>. |
1230 | C<EVBACKEND_POLL>. |
1135 | |
1231 | |
1136 | =head3 The special problem of SIGPIPE |
1232 | =head3 The special problem of SIGPIPE |
1137 | |
1233 | |
1138 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1234 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1139 | when reading from a pipe whose other end has been closed, your program |
1235 | when writing to a pipe whose other end has been closed, your program gets |
1140 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1236 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1141 | programs this is sensible behaviour, for daemons, this is usually |
1237 | this is sensible behaviour, for daemons, this is usually undesirable. |
1142 | undesirable. |
|
|
1143 | |
1238 | |
1144 | So when you encounter spurious, unexplained daemon exits, make sure you |
1239 | So when you encounter spurious, unexplained daemon exits, make sure you |
1145 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1240 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1146 | somewhere, as that would have given you a big clue). |
1241 | somewhere, as that would have given you a big clue). |
1147 | |
1242 | |
… | |
… | |
1153 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1248 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1154 | |
1249 | |
1155 | =item ev_io_set (ev_io *, int fd, int events) |
1250 | =item ev_io_set (ev_io *, int fd, int events) |
1156 | |
1251 | |
1157 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1252 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1158 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1253 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1159 | C<EV_READ | EV_WRITE> to receive the given events. |
1254 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1160 | |
1255 | |
1161 | =item int fd [read-only] |
1256 | =item int fd [read-only] |
1162 | |
1257 | |
1163 | The file descriptor being watched. |
1258 | The file descriptor being watched. |
1164 | |
1259 | |
… | |
… | |
1173 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1268 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1174 | readable, but only once. Since it is likely line-buffered, you could |
1269 | readable, but only once. Since it is likely line-buffered, you could |
1175 | attempt to read a whole line in the callback. |
1270 | attempt to read a whole line in the callback. |
1176 | |
1271 | |
1177 | static void |
1272 | static void |
1178 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1273 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1179 | { |
1274 | { |
1180 | ev_io_stop (loop, w); |
1275 | ev_io_stop (loop, w); |
1181 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1276 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1182 | } |
1277 | } |
1183 | |
1278 | |
1184 | ... |
1279 | ... |
1185 | struct ev_loop *loop = ev_default_init (0); |
1280 | struct ev_loop *loop = ev_default_init (0); |
1186 | struct ev_io stdin_readable; |
1281 | ev_io stdin_readable; |
1187 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1282 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1188 | ev_io_start (loop, &stdin_readable); |
1283 | ev_io_start (loop, &stdin_readable); |
1189 | ev_loop (loop, 0); |
1284 | ev_loop (loop, 0); |
1190 | |
1285 | |
1191 | |
1286 | |
… | |
… | |
1194 | Timer watchers are simple relative timers that generate an event after a |
1289 | Timer watchers are simple relative timers that generate an event after a |
1195 | given time, and optionally repeating in regular intervals after that. |
1290 | given time, and optionally repeating in regular intervals after that. |
1196 | |
1291 | |
1197 | The timers are based on real time, that is, if you register an event that |
1292 | The timers are based on real time, that is, if you register an event that |
1198 | times out after an hour and you reset your system clock to January last |
1293 | times out after an hour and you reset your system clock to January last |
1199 | year, it will still time out after (roughly) and hour. "Roughly" because |
1294 | year, it will still time out after (roughly) one hour. "Roughly" because |
1200 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1295 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1201 | monotonic clock option helps a lot here). |
1296 | monotonic clock option helps a lot here). |
|
|
1297 | |
|
|
1298 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1299 | passed, but if multiple timers become ready during the same loop iteration |
|
|
1300 | then order of execution is undefined. |
|
|
1301 | |
|
|
1302 | =head3 Be smart about timeouts |
|
|
1303 | |
|
|
1304 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1305 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1306 | you want to raise some error after a while. |
|
|
1307 | |
|
|
1308 | What follows are some ways to handle this problem, from obvious and |
|
|
1309 | inefficient to smart and efficient. |
|
|
1310 | |
|
|
1311 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1312 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1313 | data or other life sign was received). |
|
|
1314 | |
|
|
1315 | =over 4 |
|
|
1316 | |
|
|
1317 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1318 | |
|
|
1319 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1320 | start the watcher: |
|
|
1321 | |
|
|
1322 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1323 | ev_timer_start (loop, timer); |
|
|
1324 | |
|
|
1325 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1326 | and start it again: |
|
|
1327 | |
|
|
1328 | ev_timer_stop (loop, timer); |
|
|
1329 | ev_timer_set (timer, 60., 0.); |
|
|
1330 | ev_timer_start (loop, timer); |
|
|
1331 | |
|
|
1332 | This is relatively simple to implement, but means that each time there is |
|
|
1333 | some activity, libev will first have to remove the timer from its internal |
|
|
1334 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1335 | still not a constant-time operation. |
|
|
1336 | |
|
|
1337 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1338 | |
|
|
1339 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1340 | C<ev_timer_start>. |
|
|
1341 | |
|
|
1342 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1343 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1344 | successfully read or write some data. If you go into an idle state where |
|
|
1345 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1346 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1347 | |
|
|
1348 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1349 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1350 | member and C<ev_timer_again>. |
|
|
1351 | |
|
|
1352 | At start: |
|
|
1353 | |
|
|
1354 | ev_timer_init (timer, callback); |
|
|
1355 | timer->repeat = 60.; |
|
|
1356 | ev_timer_again (loop, timer); |
|
|
1357 | |
|
|
1358 | Each time there is some activity: |
|
|
1359 | |
|
|
1360 | ev_timer_again (loop, timer); |
|
|
1361 | |
|
|
1362 | It is even possible to change the time-out on the fly, regardless of |
|
|
1363 | whether the watcher is active or not: |
|
|
1364 | |
|
|
1365 | timer->repeat = 30.; |
|
|
1366 | ev_timer_again (loop, timer); |
|
|
1367 | |
|
|
1368 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1369 | you want to modify its timeout value, as libev does not have to completely |
|
|
1370 | remove and re-insert the timer from/into its internal data structure. |
|
|
1371 | |
|
|
1372 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1373 | |
|
|
1374 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1375 | |
|
|
1376 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1377 | relatively long compared to the intervals between other activity - in |
|
|
1378 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1379 | associated activity resets. |
|
|
1380 | |
|
|
1381 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1382 | but remember the time of last activity, and check for a real timeout only |
|
|
1383 | within the callback: |
|
|
1384 | |
|
|
1385 | ev_tstamp last_activity; // time of last activity |
|
|
1386 | |
|
|
1387 | static void |
|
|
1388 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1389 | { |
|
|
1390 | ev_tstamp now = ev_now (EV_A); |
|
|
1391 | ev_tstamp timeout = last_activity + 60.; |
|
|
1392 | |
|
|
1393 | // if last_activity + 60. is older than now, we did time out |
|
|
1394 | if (timeout < now) |
|
|
1395 | { |
|
|
1396 | // timeout occured, take action |
|
|
1397 | } |
|
|
1398 | else |
|
|
1399 | { |
|
|
1400 | // callback was invoked, but there was some activity, re-arm |
|
|
1401 | // the watcher to fire in last_activity + 60, which is |
|
|
1402 | // guaranteed to be in the future, so "again" is positive: |
|
|
1403 | w->again = timeout - now; |
|
|
1404 | ev_timer_again (EV_A_ w); |
|
|
1405 | } |
|
|
1406 | } |
|
|
1407 | |
|
|
1408 | To summarise the callback: first calculate the real timeout (defined |
|
|
1409 | as "60 seconds after the last activity"), then check if that time has |
|
|
1410 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1411 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1412 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1413 | a timeout then. |
|
|
1414 | |
|
|
1415 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1416 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1417 | |
|
|
1418 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1419 | minus half the average time between activity), but virtually no calls to |
|
|
1420 | libev to change the timeout. |
|
|
1421 | |
|
|
1422 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1423 | to the current time (meaning we just have some activity :), then call the |
|
|
1424 | callback, which will "do the right thing" and start the timer: |
|
|
1425 | |
|
|
1426 | ev_timer_init (timer, callback); |
|
|
1427 | last_activity = ev_now (loop); |
|
|
1428 | callback (loop, timer, EV_TIMEOUT); |
|
|
1429 | |
|
|
1430 | And when there is some activity, simply store the current time in |
|
|
1431 | C<last_activity>, no libev calls at all: |
|
|
1432 | |
|
|
1433 | last_actiivty = ev_now (loop); |
|
|
1434 | |
|
|
1435 | This technique is slightly more complex, but in most cases where the |
|
|
1436 | time-out is unlikely to be triggered, much more efficient. |
|
|
1437 | |
|
|
1438 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1439 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1440 | fix things for you. |
|
|
1441 | |
|
|
1442 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1443 | |
|
|
1444 | If there is not one request, but many thousands (millions...), all |
|
|
1445 | employing some kind of timeout with the same timeout value, then one can |
|
|
1446 | do even better: |
|
|
1447 | |
|
|
1448 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1449 | at the I<end> of the list. |
|
|
1450 | |
|
|
1451 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1452 | the list is expected to fire (for example, using the technique #3). |
|
|
1453 | |
|
|
1454 | When there is some activity, remove the timer from the list, recalculate |
|
|
1455 | the timeout, append it to the end of the list again, and make sure to |
|
|
1456 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1457 | |
|
|
1458 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1459 | starting, stopping and updating the timers, at the expense of a major |
|
|
1460 | complication, and having to use a constant timeout. The constant timeout |
|
|
1461 | ensures that the list stays sorted. |
|
|
1462 | |
|
|
1463 | =back |
|
|
1464 | |
|
|
1465 | So which method the best? |
|
|
1466 | |
|
|
1467 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1468 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1469 | better, and isn't very complicated either. In most case, choosing either |
|
|
1470 | one is fine, with #3 being better in typical situations. |
|
|
1471 | |
|
|
1472 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1473 | rather complicated, but extremely efficient, something that really pays |
|
|
1474 | off after the first million or so of active timers, i.e. it's usually |
|
|
1475 | overkill :) |
|
|
1476 | |
|
|
1477 | =head3 The special problem of time updates |
|
|
1478 | |
|
|
1479 | Establishing the current time is a costly operation (it usually takes at |
|
|
1480 | least two system calls): EV therefore updates its idea of the current |
|
|
1481 | time only before and after C<ev_loop> collects new events, which causes a |
|
|
1482 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1483 | lots of events in one iteration. |
1202 | |
1484 | |
1203 | The relative timeouts are calculated relative to the C<ev_now ()> |
1485 | The relative timeouts are calculated relative to the C<ev_now ()> |
1204 | time. This is usually the right thing as this timestamp refers to the time |
1486 | time. This is usually the right thing as this timestamp refers to the time |
1205 | of the event triggering whatever timeout you are modifying/starting. If |
1487 | of the event triggering whatever timeout you are modifying/starting. If |
1206 | you suspect event processing to be delayed and you I<need> to base the timeout |
1488 | you suspect event processing to be delayed and you I<need> to base the |
1207 | on the current time, use something like this to adjust for this: |
1489 | timeout on the current time, use something like this to adjust for this: |
1208 | |
1490 | |
1209 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1491 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1210 | |
1492 | |
1211 | The callback is guaranteed to be invoked only after its timeout has passed, |
1493 | If the event loop is suspended for a long time, you can also force an |
1212 | but if multiple timers become ready during the same loop iteration then |
1494 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1213 | order of execution is undefined. |
1495 | ()>. |
1214 | |
1496 | |
1215 | =head3 Watcher-Specific Functions and Data Members |
1497 | =head3 Watcher-Specific Functions and Data Members |
1216 | |
1498 | |
1217 | =over 4 |
1499 | =over 4 |
1218 | |
1500 | |
… | |
… | |
1242 | If the timer is started but non-repeating, stop it (as if it timed out). |
1524 | If the timer is started but non-repeating, stop it (as if it timed out). |
1243 | |
1525 | |
1244 | If the timer is repeating, either start it if necessary (with the |
1526 | If the timer is repeating, either start it if necessary (with the |
1245 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1527 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1246 | |
1528 | |
1247 | This sounds a bit complicated, but here is a useful and typical |
1529 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1248 | example: Imagine you have a TCP connection and you want a so-called idle |
1530 | usage example. |
1249 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1250 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1251 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1252 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1253 | you go into an idle state where you do not expect data to travel on the |
|
|
1254 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1255 | automatically restart it if need be. |
|
|
1256 | |
|
|
1257 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1258 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1259 | |
|
|
1260 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1261 | ev_timer_again (loop, timer); |
|
|
1262 | ... |
|
|
1263 | timer->again = 17.; |
|
|
1264 | ev_timer_again (loop, timer); |
|
|
1265 | ... |
|
|
1266 | timer->again = 10.; |
|
|
1267 | ev_timer_again (loop, timer); |
|
|
1268 | |
|
|
1269 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1270 | you want to modify its timeout value. |
|
|
1271 | |
1531 | |
1272 | =item ev_tstamp repeat [read-write] |
1532 | =item ev_tstamp repeat [read-write] |
1273 | |
1533 | |
1274 | The current C<repeat> value. Will be used each time the watcher times out |
1534 | The current C<repeat> value. Will be used each time the watcher times out |
1275 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1535 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1276 | which is also when any modifications are taken into account. |
1536 | which is also when any modifications are taken into account. |
1277 | |
1537 | |
1278 | =back |
1538 | =back |
1279 | |
1539 | |
1280 | =head3 Examples |
1540 | =head3 Examples |
1281 | |
1541 | |
1282 | Example: Create a timer that fires after 60 seconds. |
1542 | Example: Create a timer that fires after 60 seconds. |
1283 | |
1543 | |
1284 | static void |
1544 | static void |
1285 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1545 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1286 | { |
1546 | { |
1287 | .. one minute over, w is actually stopped right here |
1547 | .. one minute over, w is actually stopped right here |
1288 | } |
1548 | } |
1289 | |
1549 | |
1290 | struct ev_timer mytimer; |
1550 | ev_timer mytimer; |
1291 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1551 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1292 | ev_timer_start (loop, &mytimer); |
1552 | ev_timer_start (loop, &mytimer); |
1293 | |
1553 | |
1294 | Example: Create a timeout timer that times out after 10 seconds of |
1554 | Example: Create a timeout timer that times out after 10 seconds of |
1295 | inactivity. |
1555 | inactivity. |
1296 | |
1556 | |
1297 | static void |
1557 | static void |
1298 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1558 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1299 | { |
1559 | { |
1300 | .. ten seconds without any activity |
1560 | .. ten seconds without any activity |
1301 | } |
1561 | } |
1302 | |
1562 | |
1303 | struct ev_timer mytimer; |
1563 | ev_timer mytimer; |
1304 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1564 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1305 | ev_timer_again (&mytimer); /* start timer */ |
1565 | ev_timer_again (&mytimer); /* start timer */ |
1306 | ev_loop (loop, 0); |
1566 | ev_loop (loop, 0); |
1307 | |
1567 | |
1308 | // and in some piece of code that gets executed on any "activity": |
1568 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1324 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1584 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1325 | roughly 10 seconds later as it uses a relative timeout). |
1585 | roughly 10 seconds later as it uses a relative timeout). |
1326 | |
1586 | |
1327 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1587 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1328 | such as triggering an event on each "midnight, local time", or other |
1588 | such as triggering an event on each "midnight, local time", or other |
1329 | complicated, rules. |
1589 | complicated rules. |
1330 | |
1590 | |
1331 | As with timers, the callback is guaranteed to be invoked only when the |
1591 | As with timers, the callback is guaranteed to be invoked only when the |
1332 | time (C<at>) has passed, but if multiple periodic timers become ready |
1592 | time (C<at>) has passed, but if multiple periodic timers become ready |
1333 | during the same loop iteration then order of execution is undefined. |
1593 | during the same loop iteration, then order of execution is undefined. |
1334 | |
1594 | |
1335 | =head3 Watcher-Specific Functions and Data Members |
1595 | =head3 Watcher-Specific Functions and Data Members |
1336 | |
1596 | |
1337 | =over 4 |
1597 | =over 4 |
1338 | |
1598 | |
1339 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1599 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1340 | |
1600 | |
1341 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1601 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1342 | |
1602 | |
1343 | Lots of arguments, lets sort it out... There are basically three modes of |
1603 | Lots of arguments, lets sort it out... There are basically three modes of |
1344 | operation, and we will explain them from simplest to complex: |
1604 | operation, and we will explain them from simplest to most complex: |
1345 | |
1605 | |
1346 | =over 4 |
1606 | =over 4 |
1347 | |
1607 | |
1348 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1608 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1349 | |
1609 | |
1350 | In this configuration the watcher triggers an event after the wall clock |
1610 | In this configuration the watcher triggers an event after the wall clock |
1351 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1611 | time C<at> has passed. It will not repeat and will not adjust when a time |
1352 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1612 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1353 | run when the system time reaches or surpasses this time. |
1613 | only run when the system clock reaches or surpasses this time. |
1354 | |
1614 | |
1355 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1615 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1356 | |
1616 | |
1357 | In this mode the watcher will always be scheduled to time out at the next |
1617 | In this mode the watcher will always be scheduled to time out at the next |
1358 | C<at + N * interval> time (for some integer N, which can also be negative) |
1618 | C<at + N * interval> time (for some integer N, which can also be negative) |
1359 | and then repeat, regardless of any time jumps. |
1619 | and then repeat, regardless of any time jumps. |
1360 | |
1620 | |
1361 | This can be used to create timers that do not drift with respect to system |
1621 | This can be used to create timers that do not drift with respect to the |
1362 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
1622 | system clock, for example, here is a C<ev_periodic> that triggers each |
1363 | the hour: |
1623 | hour, on the hour: |
1364 | |
1624 | |
1365 | ev_periodic_set (&periodic, 0., 3600., 0); |
1625 | ev_periodic_set (&periodic, 0., 3600., 0); |
1366 | |
1626 | |
1367 | This doesn't mean there will always be 3600 seconds in between triggers, |
1627 | This doesn't mean there will always be 3600 seconds in between triggers, |
1368 | but only that the callback will be called when the system time shows a |
1628 | but only that the callback will be called when the system time shows a |
… | |
… | |
1394 | |
1654 | |
1395 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1655 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1396 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1656 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1397 | only event loop modification you are allowed to do). |
1657 | only event loop modification you are allowed to do). |
1398 | |
1658 | |
1399 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1659 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1400 | *w, ev_tstamp now)>, e.g.: |
1660 | *w, ev_tstamp now)>, e.g.: |
1401 | |
1661 | |
|
|
1662 | static ev_tstamp |
1402 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1663 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1403 | { |
1664 | { |
1404 | return now + 60.; |
1665 | return now + 60.; |
1405 | } |
1666 | } |
1406 | |
1667 | |
1407 | It must return the next time to trigger, based on the passed time value |
1668 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1444 | |
1705 | |
1445 | The current interval value. Can be modified any time, but changes only |
1706 | The current interval value. Can be modified any time, but changes only |
1446 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1707 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1447 | called. |
1708 | called. |
1448 | |
1709 | |
1449 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1710 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1450 | |
1711 | |
1451 | The current reschedule callback, or C<0>, if this functionality is |
1712 | The current reschedule callback, or C<0>, if this functionality is |
1452 | switched off. Can be changed any time, but changes only take effect when |
1713 | switched off. Can be changed any time, but changes only take effect when |
1453 | the periodic timer fires or C<ev_periodic_again> is being called. |
1714 | the periodic timer fires or C<ev_periodic_again> is being called. |
1454 | |
1715 | |
1455 | =back |
1716 | =back |
1456 | |
1717 | |
1457 | =head3 Examples |
1718 | =head3 Examples |
1458 | |
1719 | |
1459 | Example: Call a callback every hour, or, more precisely, whenever the |
1720 | Example: Call a callback every hour, or, more precisely, whenever the |
1460 | system clock is divisible by 3600. The callback invocation times have |
1721 | system time is divisible by 3600. The callback invocation times have |
1461 | potentially a lot of jitter, but good long-term stability. |
1722 | potentially a lot of jitter, but good long-term stability. |
1462 | |
1723 | |
1463 | static void |
1724 | static void |
1464 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1725 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1465 | { |
1726 | { |
1466 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1727 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1467 | } |
1728 | } |
1468 | |
1729 | |
1469 | struct ev_periodic hourly_tick; |
1730 | ev_periodic hourly_tick; |
1470 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1731 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1471 | ev_periodic_start (loop, &hourly_tick); |
1732 | ev_periodic_start (loop, &hourly_tick); |
1472 | |
1733 | |
1473 | Example: The same as above, but use a reschedule callback to do it: |
1734 | Example: The same as above, but use a reschedule callback to do it: |
1474 | |
1735 | |
1475 | #include <math.h> |
1736 | #include <math.h> |
1476 | |
1737 | |
1477 | static ev_tstamp |
1738 | static ev_tstamp |
1478 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1739 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1479 | { |
1740 | { |
1480 | return fmod (now, 3600.) + 3600.; |
1741 | return now + (3600. - fmod (now, 3600.)); |
1481 | } |
1742 | } |
1482 | |
1743 | |
1483 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1744 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1484 | |
1745 | |
1485 | Example: Call a callback every hour, starting now: |
1746 | Example: Call a callback every hour, starting now: |
1486 | |
1747 | |
1487 | struct ev_periodic hourly_tick; |
1748 | ev_periodic hourly_tick; |
1488 | ev_periodic_init (&hourly_tick, clock_cb, |
1749 | ev_periodic_init (&hourly_tick, clock_cb, |
1489 | fmod (ev_now (loop), 3600.), 3600., 0); |
1750 | fmod (ev_now (loop), 3600.), 3600., 0); |
1490 | ev_periodic_start (loop, &hourly_tick); |
1751 | ev_periodic_start (loop, &hourly_tick); |
1491 | |
1752 | |
1492 | |
1753 | |
… | |
… | |
1495 | Signal watchers will trigger an event when the process receives a specific |
1756 | Signal watchers will trigger an event when the process receives a specific |
1496 | signal one or more times. Even though signals are very asynchronous, libev |
1757 | signal one or more times. Even though signals are very asynchronous, libev |
1497 | will try it's best to deliver signals synchronously, i.e. as part of the |
1758 | will try it's best to deliver signals synchronously, i.e. as part of the |
1498 | normal event processing, like any other event. |
1759 | normal event processing, like any other event. |
1499 | |
1760 | |
|
|
1761 | If you want signals asynchronously, just use C<sigaction> as you would |
|
|
1762 | do without libev and forget about sharing the signal. You can even use |
|
|
1763 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
|
|
1764 | |
1500 | You can configure as many watchers as you like per signal. Only when the |
1765 | You can configure as many watchers as you like per signal. Only when the |
1501 | first watcher gets started will libev actually register a signal watcher |
1766 | first watcher gets started will libev actually register a signal handler |
1502 | with the kernel (thus it coexists with your own signal handlers as long |
1767 | with the kernel (thus it coexists with your own signal handlers as long as |
1503 | as you don't register any with libev). Similarly, when the last signal |
1768 | you don't register any with libev for the same signal). Similarly, when |
1504 | watcher for a signal is stopped libev will reset the signal handler to |
1769 | the last signal watcher for a signal is stopped, libev will reset the |
1505 | SIG_DFL (regardless of what it was set to before). |
1770 | signal handler to SIG_DFL (regardless of what it was set to before). |
1506 | |
1771 | |
1507 | If possible and supported, libev will install its handlers with |
1772 | If possible and supported, libev will install its handlers with |
1508 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1773 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
1509 | interrupted. If you have a problem with system calls getting interrupted by |
1774 | interrupted. If you have a problem with system calls getting interrupted by |
1510 | signals you can block all signals in an C<ev_check> watcher and unblock |
1775 | signals you can block all signals in an C<ev_check> watcher and unblock |
… | |
… | |
1527 | |
1792 | |
1528 | =back |
1793 | =back |
1529 | |
1794 | |
1530 | =head3 Examples |
1795 | =head3 Examples |
1531 | |
1796 | |
1532 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1797 | Example: Try to exit cleanly on SIGINT. |
1533 | |
1798 | |
1534 | static void |
1799 | static void |
1535 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1800 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1536 | { |
1801 | { |
1537 | ev_unloop (loop, EVUNLOOP_ALL); |
1802 | ev_unloop (loop, EVUNLOOP_ALL); |
1538 | } |
1803 | } |
1539 | |
1804 | |
1540 | struct ev_signal signal_watcher; |
1805 | ev_signal signal_watcher; |
1541 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1806 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1542 | ev_signal_start (loop, &sigint_cb); |
1807 | ev_signal_start (loop, &signal_watcher); |
1543 | |
1808 | |
1544 | |
1809 | |
1545 | =head2 C<ev_child> - watch out for process status changes |
1810 | =head2 C<ev_child> - watch out for process status changes |
1546 | |
1811 | |
1547 | Child watchers trigger when your process receives a SIGCHLD in response to |
1812 | Child watchers trigger when your process receives a SIGCHLD in response to |
1548 | some child status changes (most typically when a child of yours dies). It |
1813 | some child status changes (most typically when a child of yours dies or |
1549 | is permissible to install a child watcher I<after> the child has been |
1814 | exits). It is permissible to install a child watcher I<after> the child |
1550 | forked (which implies it might have already exited), as long as the event |
1815 | has been forked (which implies it might have already exited), as long |
1551 | loop isn't entered (or is continued from a watcher). |
1816 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
1817 | forking and then immediately registering a watcher for the child is fine, |
|
|
1818 | but forking and registering a watcher a few event loop iterations later is |
|
|
1819 | not. |
1552 | |
1820 | |
1553 | Only the default event loop is capable of handling signals, and therefore |
1821 | Only the default event loop is capable of handling signals, and therefore |
1554 | you can only register child watchers in the default event loop. |
1822 | you can only register child watchers in the default event loop. |
1555 | |
1823 | |
1556 | =head3 Process Interaction |
1824 | =head3 Process Interaction |
… | |
… | |
1569 | handler, you can override it easily by installing your own handler for |
1837 | handler, you can override it easily by installing your own handler for |
1570 | C<SIGCHLD> after initialising the default loop, and making sure the |
1838 | C<SIGCHLD> after initialising the default loop, and making sure the |
1571 | default loop never gets destroyed. You are encouraged, however, to use an |
1839 | default loop never gets destroyed. You are encouraged, however, to use an |
1572 | event-based approach to child reaping and thus use libev's support for |
1840 | event-based approach to child reaping and thus use libev's support for |
1573 | that, so other libev users can use C<ev_child> watchers freely. |
1841 | that, so other libev users can use C<ev_child> watchers freely. |
|
|
1842 | |
|
|
1843 | =head3 Stopping the Child Watcher |
|
|
1844 | |
|
|
1845 | Currently, the child watcher never gets stopped, even when the |
|
|
1846 | child terminates, so normally one needs to stop the watcher in the |
|
|
1847 | callback. Future versions of libev might stop the watcher automatically |
|
|
1848 | when a child exit is detected. |
1574 | |
1849 | |
1575 | =head3 Watcher-Specific Functions and Data Members |
1850 | =head3 Watcher-Specific Functions and Data Members |
1576 | |
1851 | |
1577 | =over 4 |
1852 | =over 4 |
1578 | |
1853 | |
… | |
… | |
1610 | its completion. |
1885 | its completion. |
1611 | |
1886 | |
1612 | ev_child cw; |
1887 | ev_child cw; |
1613 | |
1888 | |
1614 | static void |
1889 | static void |
1615 | child_cb (EV_P_ struct ev_child *w, int revents) |
1890 | child_cb (EV_P_ ev_child *w, int revents) |
1616 | { |
1891 | { |
1617 | ev_child_stop (EV_A_ w); |
1892 | ev_child_stop (EV_A_ w); |
1618 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1893 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1619 | } |
1894 | } |
1620 | |
1895 | |
… | |
… | |
1647 | the stat buffer having unspecified contents. |
1922 | the stat buffer having unspecified contents. |
1648 | |
1923 | |
1649 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1924 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1650 | relative and your working directory changes, the behaviour is undefined. |
1925 | relative and your working directory changes, the behaviour is undefined. |
1651 | |
1926 | |
1652 | Since there is no standard to do this, the portable implementation simply |
1927 | Since there is no standard kernel interface to do this, the portable |
1653 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
1928 | implementation simply calls C<stat (2)> regularly on the path to see if |
1654 | can specify a recommended polling interval for this case. If you specify |
1929 | it changed somehow. You can specify a recommended polling interval for |
1655 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
1930 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1656 | unspecified default> value will be used (which you can expect to be around |
1931 | then a I<suitable, unspecified default> value will be used (which |
1657 | five seconds, although this might change dynamically). Libev will also |
1932 | you can expect to be around five seconds, although this might change |
1658 | impose a minimum interval which is currently around C<0.1>, but thats |
1933 | dynamically). Libev will also impose a minimum interval which is currently |
1659 | usually overkill. |
1934 | around C<0.1>, but thats usually overkill. |
1660 | |
1935 | |
1661 | This watcher type is not meant for massive numbers of stat watchers, |
1936 | This watcher type is not meant for massive numbers of stat watchers, |
1662 | as even with OS-supported change notifications, this can be |
1937 | as even with OS-supported change notifications, this can be |
1663 | resource-intensive. |
1938 | resource-intensive. |
1664 | |
1939 | |
1665 | At the time of this writing, only the Linux inotify interface is |
1940 | At the time of this writing, the only OS-specific interface implemented |
1666 | implemented (implementing kqueue support is left as an exercise for the |
1941 | is the Linux inotify interface (implementing kqueue support is left as |
1667 | reader, note, however, that the author sees no way of implementing ev_stat |
1942 | an exercise for the reader. Note, however, that the author sees no way |
1668 | semantics with kqueue). Inotify will be used to give hints only and should |
1943 | of implementing C<ev_stat> semantics with kqueue). |
1669 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1670 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1671 | but changes are usually detected immediately, and if the file exists there |
|
|
1672 | will be no polling. |
|
|
1673 | |
1944 | |
1674 | =head3 ABI Issues (Largefile Support) |
1945 | =head3 ABI Issues (Largefile Support) |
1675 | |
1946 | |
1676 | Libev by default (unless the user overrides this) uses the default |
1947 | Libev by default (unless the user overrides this) uses the default |
1677 | compilation environment, which means that on systems with large file |
1948 | compilation environment, which means that on systems with large file |
… | |
… | |
1686 | file interfaces available by default (as e.g. FreeBSD does) and not |
1957 | file interfaces available by default (as e.g. FreeBSD does) and not |
1687 | optional. Libev cannot simply switch on large file support because it has |
1958 | optional. Libev cannot simply switch on large file support because it has |
1688 | to exchange stat structures with application programs compiled using the |
1959 | to exchange stat structures with application programs compiled using the |
1689 | default compilation environment. |
1960 | default compilation environment. |
1690 | |
1961 | |
1691 | =head3 Inotify |
1962 | =head3 Inotify and Kqueue |
1692 | |
1963 | |
1693 | When C<inotify (7)> support has been compiled into libev (generally only |
1964 | When C<inotify (7)> support has been compiled into libev (generally |
|
|
1965 | only available with Linux 2.6.25 or above due to bugs in earlier |
1694 | available on Linux) and present at runtime, it will be used to speed up |
1966 | implementations) and present at runtime, it will be used to speed up |
1695 | change detection where possible. The inotify descriptor will be created lazily |
1967 | change detection where possible. The inotify descriptor will be created |
1696 | when the first C<ev_stat> watcher is being started. |
1968 | lazily when the first C<ev_stat> watcher is being started. |
1697 | |
1969 | |
1698 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1970 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1699 | except that changes might be detected earlier, and in some cases, to avoid |
1971 | except that changes might be detected earlier, and in some cases, to avoid |
1700 | making regular C<stat> calls. Even in the presence of inotify support |
1972 | making regular C<stat> calls. Even in the presence of inotify support |
1701 | there are many cases where libev has to resort to regular C<stat> polling. |
1973 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
1974 | but as long as the path exists, libev usually gets away without polling. |
1702 | |
1975 | |
1703 | (There is no support for kqueue, as apparently it cannot be used to |
1976 | There is no support for kqueue, as apparently it cannot be used to |
1704 | implement this functionality, due to the requirement of having a file |
1977 | implement this functionality, due to the requirement of having a file |
1705 | descriptor open on the object at all times). |
1978 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
1979 | etc. is difficult. |
1706 | |
1980 | |
1707 | =head3 The special problem of stat time resolution |
1981 | =head3 The special problem of stat time resolution |
1708 | |
1982 | |
1709 | The C<stat ()> system call only supports full-second resolution portably, and |
1983 | The C<stat ()> system call only supports full-second resolution portably, and |
1710 | even on systems where the resolution is higher, many file systems still |
1984 | even on systems where the resolution is higher, most file systems still |
1711 | only support whole seconds. |
1985 | only support whole seconds. |
1712 | |
1986 | |
1713 | That means that, if the time is the only thing that changes, you can |
1987 | That means that, if the time is the only thing that changes, you can |
1714 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1988 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1715 | calls your callback, which does something. When there is another update |
1989 | calls your callback, which does something. When there is another update |
1716 | within the same second, C<ev_stat> will be unable to detect it as the stat |
1990 | within the same second, C<ev_stat> will be unable to detect unless the |
1717 | data does not change. |
1991 | stat data does change in other ways (e.g. file size). |
1718 | |
1992 | |
1719 | The solution to this is to delay acting on a change for slightly more |
1993 | The solution to this is to delay acting on a change for slightly more |
1720 | than a second (or till slightly after the next full second boundary), using |
1994 | than a second (or till slightly after the next full second boundary), using |
1721 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1995 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1722 | ev_timer_again (loop, w)>). |
1996 | ev_timer_again (loop, w)>). |
… | |
… | |
1742 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2016 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1743 | be detected and should normally be specified as C<0> to let libev choose |
2017 | be detected and should normally be specified as C<0> to let libev choose |
1744 | a suitable value. The memory pointed to by C<path> must point to the same |
2018 | a suitable value. The memory pointed to by C<path> must point to the same |
1745 | path for as long as the watcher is active. |
2019 | path for as long as the watcher is active. |
1746 | |
2020 | |
1747 | The callback will receive C<EV_STAT> when a change was detected, relative |
2021 | The callback will receive an C<EV_STAT> event when a change was detected, |
1748 | to the attributes at the time the watcher was started (or the last change |
2022 | relative to the attributes at the time the watcher was started (or the |
1749 | was detected). |
2023 | last change was detected). |
1750 | |
2024 | |
1751 | =item ev_stat_stat (loop, ev_stat *) |
2025 | =item ev_stat_stat (loop, ev_stat *) |
1752 | |
2026 | |
1753 | Updates the stat buffer immediately with new values. If you change the |
2027 | Updates the stat buffer immediately with new values. If you change the |
1754 | watched path in your callback, you could call this function to avoid |
2028 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1837 | |
2111 | |
1838 | |
2112 | |
1839 | =head2 C<ev_idle> - when you've got nothing better to do... |
2113 | =head2 C<ev_idle> - when you've got nothing better to do... |
1840 | |
2114 | |
1841 | Idle watchers trigger events when no other events of the same or higher |
2115 | Idle watchers trigger events when no other events of the same or higher |
1842 | priority are pending (prepare, check and other idle watchers do not |
2116 | priority are pending (prepare, check and other idle watchers do not count |
1843 | count). |
2117 | as receiving "events"). |
1844 | |
2118 | |
1845 | That is, as long as your process is busy handling sockets or timeouts |
2119 | That is, as long as your process is busy handling sockets or timeouts |
1846 | (or even signals, imagine) of the same or higher priority it will not be |
2120 | (or even signals, imagine) of the same or higher priority it will not be |
1847 | triggered. But when your process is idle (or only lower-priority watchers |
2121 | triggered. But when your process is idle (or only lower-priority watchers |
1848 | are pending), the idle watchers are being called once per event loop |
2122 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1873 | |
2147 | |
1874 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2148 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1875 | callback, free it. Also, use no error checking, as usual. |
2149 | callback, free it. Also, use no error checking, as usual. |
1876 | |
2150 | |
1877 | static void |
2151 | static void |
1878 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2152 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1879 | { |
2153 | { |
1880 | free (w); |
2154 | free (w); |
1881 | // now do something you wanted to do when the program has |
2155 | // now do something you wanted to do when the program has |
1882 | // no longer anything immediate to do. |
2156 | // no longer anything immediate to do. |
1883 | } |
2157 | } |
1884 | |
2158 | |
1885 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2159 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1886 | ev_idle_init (idle_watcher, idle_cb); |
2160 | ev_idle_init (idle_watcher, idle_cb); |
1887 | ev_idle_start (loop, idle_cb); |
2161 | ev_idle_start (loop, idle_cb); |
1888 | |
2162 | |
1889 | |
2163 | |
1890 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2164 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1891 | |
2165 | |
1892 | Prepare and check watchers are usually (but not always) used in tandem: |
2166 | Prepare and check watchers are usually (but not always) used in pairs: |
1893 | prepare watchers get invoked before the process blocks and check watchers |
2167 | prepare watchers get invoked before the process blocks and check watchers |
1894 | afterwards. |
2168 | afterwards. |
1895 | |
2169 | |
1896 | You I<must not> call C<ev_loop> or similar functions that enter |
2170 | You I<must not> call C<ev_loop> or similar functions that enter |
1897 | the current event loop from either C<ev_prepare> or C<ev_check> |
2171 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1900 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2174 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1901 | C<ev_check> so if you have one watcher of each kind they will always be |
2175 | C<ev_check> so if you have one watcher of each kind they will always be |
1902 | called in pairs bracketing the blocking call. |
2176 | called in pairs bracketing the blocking call. |
1903 | |
2177 | |
1904 | Their main purpose is to integrate other event mechanisms into libev and |
2178 | Their main purpose is to integrate other event mechanisms into libev and |
1905 | their use is somewhat advanced. This could be used, for example, to track |
2179 | their use is somewhat advanced. They could be used, for example, to track |
1906 | variable changes, implement your own watchers, integrate net-snmp or a |
2180 | variable changes, implement your own watchers, integrate net-snmp or a |
1907 | coroutine library and lots more. They are also occasionally useful if |
2181 | coroutine library and lots more. They are also occasionally useful if |
1908 | you cache some data and want to flush it before blocking (for example, |
2182 | you cache some data and want to flush it before blocking (for example, |
1909 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2183 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1910 | watcher). |
2184 | watcher). |
1911 | |
2185 | |
1912 | This is done by examining in each prepare call which file descriptors need |
2186 | This is done by examining in each prepare call which file descriptors |
1913 | to be watched by the other library, registering C<ev_io> watchers for |
2187 | need to be watched by the other library, registering C<ev_io> watchers |
1914 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2188 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1915 | provide just this functionality). Then, in the check watcher you check for |
2189 | libraries provide exactly this functionality). Then, in the check watcher, |
1916 | any events that occurred (by checking the pending status of all watchers |
2190 | you check for any events that occurred (by checking the pending status |
1917 | and stopping them) and call back into the library. The I/O and timer |
2191 | of all watchers and stopping them) and call back into the library. The |
1918 | callbacks will never actually be called (but must be valid nevertheless, |
2192 | I/O and timer callbacks will never actually be called (but must be valid |
1919 | because you never know, you know?). |
2193 | nevertheless, because you never know, you know?). |
1920 | |
2194 | |
1921 | As another example, the Perl Coro module uses these hooks to integrate |
2195 | As another example, the Perl Coro module uses these hooks to integrate |
1922 | coroutines into libev programs, by yielding to other active coroutines |
2196 | coroutines into libev programs, by yielding to other active coroutines |
1923 | during each prepare and only letting the process block if no coroutines |
2197 | during each prepare and only letting the process block if no coroutines |
1924 | are ready to run (it's actually more complicated: it only runs coroutines |
2198 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1927 | loop from blocking if lower-priority coroutines are active, thus mapping |
2201 | loop from blocking if lower-priority coroutines are active, thus mapping |
1928 | low-priority coroutines to idle/background tasks). |
2202 | low-priority coroutines to idle/background tasks). |
1929 | |
2203 | |
1930 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2204 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1931 | priority, to ensure that they are being run before any other watchers |
2205 | priority, to ensure that they are being run before any other watchers |
|
|
2206 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2207 | |
1932 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2208 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1933 | too) should not activate ("feed") events into libev. While libev fully |
2209 | activate ("feed") events into libev. While libev fully supports this, they |
1934 | supports this, they might get executed before other C<ev_check> watchers |
2210 | might get executed before other C<ev_check> watchers did their job. As |
1935 | did their job. As C<ev_check> watchers are often used to embed other |
2211 | C<ev_check> watchers are often used to embed other (non-libev) event |
1936 | (non-libev) event loops those other event loops might be in an unusable |
2212 | loops those other event loops might be in an unusable state until their |
1937 | state until their C<ev_check> watcher ran (always remind yourself to |
2213 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1938 | coexist peacefully with others). |
2214 | others). |
1939 | |
2215 | |
1940 | =head3 Watcher-Specific Functions and Data Members |
2216 | =head3 Watcher-Specific Functions and Data Members |
1941 | |
2217 | |
1942 | =over 4 |
2218 | =over 4 |
1943 | |
2219 | |
… | |
… | |
1945 | |
2221 | |
1946 | =item ev_check_init (ev_check *, callback) |
2222 | =item ev_check_init (ev_check *, callback) |
1947 | |
2223 | |
1948 | Initialises and configures the prepare or check watcher - they have no |
2224 | Initialises and configures the prepare or check watcher - they have no |
1949 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2225 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1950 | macros, but using them is utterly, utterly and completely pointless. |
2226 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2227 | pointless. |
1951 | |
2228 | |
1952 | =back |
2229 | =back |
1953 | |
2230 | |
1954 | =head3 Examples |
2231 | =head3 Examples |
1955 | |
2232 | |
… | |
… | |
1968 | |
2245 | |
1969 | static ev_io iow [nfd]; |
2246 | static ev_io iow [nfd]; |
1970 | static ev_timer tw; |
2247 | static ev_timer tw; |
1971 | |
2248 | |
1972 | static void |
2249 | static void |
1973 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2250 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1974 | { |
2251 | { |
1975 | } |
2252 | } |
1976 | |
2253 | |
1977 | // create io watchers for each fd and a timer before blocking |
2254 | // create io watchers for each fd and a timer before blocking |
1978 | static void |
2255 | static void |
1979 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2256 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1980 | { |
2257 | { |
1981 | int timeout = 3600000; |
2258 | int timeout = 3600000; |
1982 | struct pollfd fds [nfd]; |
2259 | struct pollfd fds [nfd]; |
1983 | // actual code will need to loop here and realloc etc. |
2260 | // actual code will need to loop here and realloc etc. |
1984 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2261 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
1999 | } |
2276 | } |
2000 | } |
2277 | } |
2001 | |
2278 | |
2002 | // stop all watchers after blocking |
2279 | // stop all watchers after blocking |
2003 | static void |
2280 | static void |
2004 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2281 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2005 | { |
2282 | { |
2006 | ev_timer_stop (loop, &tw); |
2283 | ev_timer_stop (loop, &tw); |
2007 | |
2284 | |
2008 | for (int i = 0; i < nfd; ++i) |
2285 | for (int i = 0; i < nfd; ++i) |
2009 | { |
2286 | { |
… | |
… | |
2048 | } |
2325 | } |
2049 | |
2326 | |
2050 | // do not ever call adns_afterpoll |
2327 | // do not ever call adns_afterpoll |
2051 | |
2328 | |
2052 | Method 4: Do not use a prepare or check watcher because the module you |
2329 | Method 4: Do not use a prepare or check watcher because the module you |
2053 | want to embed is too inflexible to support it. Instead, you can override |
2330 | want to embed is not flexible enough to support it. Instead, you can |
2054 | their poll function. The drawback with this solution is that the main |
2331 | override their poll function. The drawback with this solution is that the |
2055 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2332 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2056 | this. |
2333 | this approach, effectively embedding EV as a client into the horrible |
|
|
2334 | libglib event loop. |
2057 | |
2335 | |
2058 | static gint |
2336 | static gint |
2059 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2337 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2060 | { |
2338 | { |
2061 | int got_events = 0; |
2339 | int got_events = 0; |
… | |
… | |
2092 | prioritise I/O. |
2370 | prioritise I/O. |
2093 | |
2371 | |
2094 | As an example for a bug workaround, the kqueue backend might only support |
2372 | As an example for a bug workaround, the kqueue backend might only support |
2095 | sockets on some platform, so it is unusable as generic backend, but you |
2373 | sockets on some platform, so it is unusable as generic backend, but you |
2096 | still want to make use of it because you have many sockets and it scales |
2374 | still want to make use of it because you have many sockets and it scales |
2097 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2375 | so nicely. In this case, you would create a kqueue-based loop and embed |
2098 | into your default loop (which might use e.g. poll). Overall operation will |
2376 | it into your default loop (which might use e.g. poll). Overall operation |
2099 | be a bit slower because first libev has to poll and then call kevent, but |
2377 | will be a bit slower because first libev has to call C<poll> and then |
2100 | at least you can use both at what they are best. |
2378 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2379 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2101 | |
2380 | |
2102 | As for prioritising I/O: rarely you have the case where some fds have |
2381 | As for prioritising I/O: under rare circumstances you have the case where |
2103 | to be watched and handled very quickly (with low latency), and even |
2382 | some fds have to be watched and handled very quickly (with low latency), |
2104 | priorities and idle watchers might have too much overhead. In this case |
2383 | and even priorities and idle watchers might have too much overhead. In |
2105 | you would put all the high priority stuff in one loop and all the rest in |
2384 | this case you would put all the high priority stuff in one loop and all |
2106 | a second one, and embed the second one in the first. |
2385 | the rest in a second one, and embed the second one in the first. |
2107 | |
2386 | |
2108 | As long as the watcher is active, the callback will be invoked every time |
2387 | As long as the watcher is active, the callback will be invoked every time |
2109 | there might be events pending in the embedded loop. The callback must then |
2388 | there might be events pending in the embedded loop. The callback must then |
2110 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2389 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2111 | their callbacks (you could also start an idle watcher to give the embedded |
2390 | their callbacks (you could also start an idle watcher to give the embedded |
… | |
… | |
2119 | interested in that. |
2398 | interested in that. |
2120 | |
2399 | |
2121 | Also, there have not currently been made special provisions for forking: |
2400 | Also, there have not currently been made special provisions for forking: |
2122 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2401 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2123 | but you will also have to stop and restart any C<ev_embed> watchers |
2402 | but you will also have to stop and restart any C<ev_embed> watchers |
2124 | yourself. |
2403 | yourself - but you can use a fork watcher to handle this automatically, |
|
|
2404 | and future versions of libev might do just that. |
2125 | |
2405 | |
2126 | Unfortunately, not all backends are embeddable, only the ones returned by |
2406 | Unfortunately, not all backends are embeddable: only the ones returned by |
2127 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2407 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2128 | portable one. |
2408 | portable one. |
2129 | |
2409 | |
2130 | So when you want to use this feature you will always have to be prepared |
2410 | So when you want to use this feature you will always have to be prepared |
2131 | that you cannot get an embeddable loop. The recommended way to get around |
2411 | that you cannot get an embeddable loop. The recommended way to get around |
2132 | this is to have a separate variables for your embeddable loop, try to |
2412 | this is to have a separate variables for your embeddable loop, try to |
2133 | create it, and if that fails, use the normal loop for everything. |
2413 | create it, and if that fails, use the normal loop for everything. |
|
|
2414 | |
|
|
2415 | =head3 C<ev_embed> and fork |
|
|
2416 | |
|
|
2417 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2418 | automatically be applied to the embedded loop as well, so no special |
|
|
2419 | fork handling is required in that case. When the watcher is not running, |
|
|
2420 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2421 | as applicable. |
2134 | |
2422 | |
2135 | =head3 Watcher-Specific Functions and Data Members |
2423 | =head3 Watcher-Specific Functions and Data Members |
2136 | |
2424 | |
2137 | =over 4 |
2425 | =over 4 |
2138 | |
2426 | |
… | |
… | |
2166 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2454 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2167 | used). |
2455 | used). |
2168 | |
2456 | |
2169 | struct ev_loop *loop_hi = ev_default_init (0); |
2457 | struct ev_loop *loop_hi = ev_default_init (0); |
2170 | struct ev_loop *loop_lo = 0; |
2458 | struct ev_loop *loop_lo = 0; |
2171 | struct ev_embed embed; |
2459 | ev_embed embed; |
2172 | |
2460 | |
2173 | // see if there is a chance of getting one that works |
2461 | // see if there is a chance of getting one that works |
2174 | // (remember that a flags value of 0 means autodetection) |
2462 | // (remember that a flags value of 0 means autodetection) |
2175 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2463 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2176 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2464 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2190 | kqueue implementation). Store the kqueue/socket-only event loop in |
2478 | kqueue implementation). Store the kqueue/socket-only event loop in |
2191 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2479 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2192 | |
2480 | |
2193 | struct ev_loop *loop = ev_default_init (0); |
2481 | struct ev_loop *loop = ev_default_init (0); |
2194 | struct ev_loop *loop_socket = 0; |
2482 | struct ev_loop *loop_socket = 0; |
2195 | struct ev_embed embed; |
2483 | ev_embed embed; |
2196 | |
2484 | |
2197 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2485 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2198 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2486 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2199 | { |
2487 | { |
2200 | ev_embed_init (&embed, 0, loop_socket); |
2488 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2256 | is that the author does not know of a simple (or any) algorithm for a |
2544 | is that the author does not know of a simple (or any) algorithm for a |
2257 | multiple-writer-single-reader queue that works in all cases and doesn't |
2545 | multiple-writer-single-reader queue that works in all cases and doesn't |
2258 | need elaborate support such as pthreads. |
2546 | need elaborate support such as pthreads. |
2259 | |
2547 | |
2260 | That means that if you want to queue data, you have to provide your own |
2548 | That means that if you want to queue data, you have to provide your own |
2261 | queue. But at least I can tell you would implement locking around your |
2549 | queue. But at least I can tell you how to implement locking around your |
2262 | queue: |
2550 | queue: |
2263 | |
2551 | |
2264 | =over 4 |
2552 | =over 4 |
2265 | |
2553 | |
2266 | =item queueing from a signal handler context |
2554 | =item queueing from a signal handler context |
2267 | |
2555 | |
2268 | To implement race-free queueing, you simply add to the queue in the signal |
2556 | To implement race-free queueing, you simply add to the queue in the signal |
2269 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2557 | handler but you block the signal handler in the watcher callback. Here is |
2270 | some fictitious SIGUSR1 handler: |
2558 | an example that does that for some fictitious SIGUSR1 handler: |
2271 | |
2559 | |
2272 | static ev_async mysig; |
2560 | static ev_async mysig; |
2273 | |
2561 | |
2274 | static void |
2562 | static void |
2275 | sigusr1_handler (void) |
2563 | sigusr1_handler (void) |
… | |
… | |
2342 | |
2630 | |
2343 | =item ev_async_init (ev_async *, callback) |
2631 | =item ev_async_init (ev_async *, callback) |
2344 | |
2632 | |
2345 | Initialises and configures the async watcher - it has no parameters of any |
2633 | Initialises and configures the async watcher - it has no parameters of any |
2346 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2634 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2347 | believe me. |
2635 | trust me. |
2348 | |
2636 | |
2349 | =item ev_async_send (loop, ev_async *) |
2637 | =item ev_async_send (loop, ev_async *) |
2350 | |
2638 | |
2351 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2639 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2352 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2640 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2353 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
2641 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2354 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2642 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2355 | section below on what exactly this means). |
2643 | section below on what exactly this means). |
2356 | |
2644 | |
2357 | This call incurs the overhead of a system call only once per loop iteration, |
2645 | This call incurs the overhead of a system call only once per loop iteration, |
2358 | so while the overhead might be noticeable, it doesn't apply to repeated |
2646 | so while the overhead might be noticeable, it doesn't apply to repeated |
… | |
… | |
2382 | =over 4 |
2670 | =over 4 |
2383 | |
2671 | |
2384 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2672 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2385 | |
2673 | |
2386 | This function combines a simple timer and an I/O watcher, calls your |
2674 | This function combines a simple timer and an I/O watcher, calls your |
2387 | callback on whichever event happens first and automatically stop both |
2675 | callback on whichever event happens first and automatically stops both |
2388 | watchers. This is useful if you want to wait for a single event on an fd |
2676 | watchers. This is useful if you want to wait for a single event on an fd |
2389 | or timeout without having to allocate/configure/start/stop/free one or |
2677 | or timeout without having to allocate/configure/start/stop/free one or |
2390 | more watchers yourself. |
2678 | more watchers yourself. |
2391 | |
2679 | |
2392 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2680 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2393 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2681 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2394 | C<events> set will be created and started. |
2682 | the given C<fd> and C<events> set will be created and started. |
2395 | |
2683 | |
2396 | If C<timeout> is less than 0, then no timeout watcher will be |
2684 | If C<timeout> is less than 0, then no timeout watcher will be |
2397 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2685 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2398 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2686 | repeat = 0) will be started. C<0> is a valid timeout. |
2399 | dubious value. |
|
|
2400 | |
2687 | |
2401 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2688 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2402 | passed an C<revents> set like normal event callbacks (a combination of |
2689 | passed an C<revents> set like normal event callbacks (a combination of |
2403 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2690 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2404 | value passed to C<ev_once>: |
2691 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2692 | a timeout and an io event at the same time - you probably should give io |
|
|
2693 | events precedence. |
|
|
2694 | |
|
|
2695 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2405 | |
2696 | |
2406 | static void stdin_ready (int revents, void *arg) |
2697 | static void stdin_ready (int revents, void *arg) |
2407 | { |
2698 | { |
|
|
2699 | if (revents & EV_READ) |
|
|
2700 | /* stdin might have data for us, joy! */; |
2408 | if (revents & EV_TIMEOUT) |
2701 | else if (revents & EV_TIMEOUT) |
2409 | /* doh, nothing entered */; |
2702 | /* doh, nothing entered */; |
2410 | else if (revents & EV_READ) |
|
|
2411 | /* stdin might have data for us, joy! */; |
|
|
2412 | } |
2703 | } |
2413 | |
2704 | |
2414 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2705 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2415 | |
2706 | |
2416 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2707 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2417 | |
2708 | |
2418 | Feeds the given event set into the event loop, as if the specified event |
2709 | Feeds the given event set into the event loop, as if the specified event |
2419 | had happened for the specified watcher (which must be a pointer to an |
2710 | had happened for the specified watcher (which must be a pointer to an |
2420 | initialised but not necessarily started event watcher). |
2711 | initialised but not necessarily started event watcher). |
2421 | |
2712 | |
2422 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2713 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2423 | |
2714 | |
2424 | Feed an event on the given fd, as if a file descriptor backend detected |
2715 | Feed an event on the given fd, as if a file descriptor backend detected |
2425 | the given events it. |
2716 | the given events it. |
2426 | |
2717 | |
2427 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2718 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2428 | |
2719 | |
2429 | Feed an event as if the given signal occurred (C<loop> must be the default |
2720 | Feed an event as if the given signal occurred (C<loop> must be the default |
2430 | loop!). |
2721 | loop!). |
2431 | |
2722 | |
2432 | =back |
2723 | =back |
… | |
… | |
2564 | |
2855 | |
2565 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2856 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2566 | |
2857 | |
2567 | See the method-C<set> above for more details. |
2858 | See the method-C<set> above for more details. |
2568 | |
2859 | |
2569 | Example: |
2860 | Example: Use a plain function as callback. |
2570 | |
2861 | |
2571 | static void io_cb (ev::io &w, int revents) { } |
2862 | static void io_cb (ev::io &w, int revents) { } |
2572 | iow.set <io_cb> (); |
2863 | iow.set <io_cb> (); |
2573 | |
2864 | |
2574 | =item w->set (struct ev_loop *) |
2865 | =item w->set (struct ev_loop *) |
… | |
… | |
2612 | Example: Define a class with an IO and idle watcher, start one of them in |
2903 | Example: Define a class with an IO and idle watcher, start one of them in |
2613 | the constructor. |
2904 | the constructor. |
2614 | |
2905 | |
2615 | class myclass |
2906 | class myclass |
2616 | { |
2907 | { |
2617 | ev::io io; void io_cb (ev::io &w, int revents); |
2908 | ev::io io ; void io_cb (ev::io &w, int revents); |
2618 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
2909 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2619 | |
2910 | |
2620 | myclass (int fd) |
2911 | myclass (int fd) |
2621 | { |
2912 | { |
2622 | io .set <myclass, &myclass::io_cb > (this); |
2913 | io .set <myclass, &myclass::io_cb > (this); |
2623 | idle.set <myclass, &myclass::idle_cb> (this); |
2914 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2639 | =item Perl |
2930 | =item Perl |
2640 | |
2931 | |
2641 | The EV module implements the full libev API and is actually used to test |
2932 | The EV module implements the full libev API and is actually used to test |
2642 | libev. EV is developed together with libev. Apart from the EV core module, |
2933 | libev. EV is developed together with libev. Apart from the EV core module, |
2643 | there are additional modules that implement libev-compatible interfaces |
2934 | there are additional modules that implement libev-compatible interfaces |
2644 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
2935 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2645 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
2936 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
2937 | and C<EV::Glib>). |
2646 | |
2938 | |
2647 | It can be found and installed via CPAN, its homepage is at |
2939 | It can be found and installed via CPAN, its homepage is at |
2648 | L<http://software.schmorp.de/pkg/EV>. |
2940 | L<http://software.schmorp.de/pkg/EV>. |
2649 | |
2941 | |
2650 | =item Python |
2942 | =item Python |
… | |
… | |
2666 | =item D |
2958 | =item D |
2667 | |
2959 | |
2668 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2960 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2669 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2961 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2670 | |
2962 | |
|
|
2963 | =item Ocaml |
|
|
2964 | |
|
|
2965 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
2966 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
2967 | |
2671 | =back |
2968 | =back |
2672 | |
2969 | |
2673 | |
2970 | |
2674 | =head1 MACRO MAGIC |
2971 | =head1 MACRO MAGIC |
2675 | |
2972 | |
… | |
… | |
2829 | |
3126 | |
2830 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3127 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2831 | |
3128 | |
2832 | Libev can be configured via a variety of preprocessor symbols you have to |
3129 | Libev can be configured via a variety of preprocessor symbols you have to |
2833 | define before including any of its files. The default in the absence of |
3130 | define before including any of its files. The default in the absence of |
2834 | autoconf is noted for every option. |
3131 | autoconf is documented for every option. |
2835 | |
3132 | |
2836 | =over 4 |
3133 | =over 4 |
2837 | |
3134 | |
2838 | =item EV_STANDALONE |
3135 | =item EV_STANDALONE |
2839 | |
3136 | |
… | |
… | |
3009 | When doing priority-based operations, libev usually has to linearly search |
3306 | When doing priority-based operations, libev usually has to linearly search |
3010 | all the priorities, so having many of them (hundreds) uses a lot of space |
3307 | all the priorities, so having many of them (hundreds) uses a lot of space |
3011 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3308 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3012 | fine. |
3309 | fine. |
3013 | |
3310 | |
3014 | If your embedding application does not need any priorities, defining these both to |
3311 | If your embedding application does not need any priorities, defining these |
3015 | C<0> will save some memory and CPU. |
3312 | both to C<0> will save some memory and CPU. |
3016 | |
3313 | |
3017 | =item EV_PERIODIC_ENABLE |
3314 | =item EV_PERIODIC_ENABLE |
3018 | |
3315 | |
3019 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3316 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3020 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3317 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3027 | code. |
3324 | code. |
3028 | |
3325 | |
3029 | =item EV_EMBED_ENABLE |
3326 | =item EV_EMBED_ENABLE |
3030 | |
3327 | |
3031 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3328 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3032 | defined to be C<0>, then they are not. |
3329 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3330 | watcher types, which therefore must not be disabled. |
3033 | |
3331 | |
3034 | =item EV_STAT_ENABLE |
3332 | =item EV_STAT_ENABLE |
3035 | |
3333 | |
3036 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3334 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3037 | defined to be C<0>, then they are not. |
3335 | defined to be C<0>, then they are not. |
… | |
… | |
3069 | two). |
3367 | two). |
3070 | |
3368 | |
3071 | =item EV_USE_4HEAP |
3369 | =item EV_USE_4HEAP |
3072 | |
3370 | |
3073 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3371 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3074 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3372 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3075 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3373 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3076 | noticeably faster performance with many (thousands) of watchers. |
3374 | faster performance with many (thousands) of watchers. |
3077 | |
3375 | |
3078 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3376 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3079 | (disabled). |
3377 | (disabled). |
3080 | |
3378 | |
3081 | =item EV_HEAP_CACHE_AT |
3379 | =item EV_HEAP_CACHE_AT |
3082 | |
3380 | |
3083 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3381 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3084 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3382 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3085 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3383 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3086 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3384 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3087 | but avoids random read accesses on heap changes. This improves performance |
3385 | but avoids random read accesses on heap changes. This improves performance |
3088 | noticeably with with many (hundreds) of watchers. |
3386 | noticeably with many (hundreds) of watchers. |
3089 | |
3387 | |
3090 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3388 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3091 | (disabled). |
3389 | (disabled). |
3092 | |
3390 | |
3093 | =item EV_VERIFY |
3391 | =item EV_VERIFY |
… | |
… | |
3099 | called once per loop, which can slow down libev. If set to C<3>, then the |
3397 | called once per loop, which can slow down libev. If set to C<3>, then the |
3100 | verification code will be called very frequently, which will slow down |
3398 | verification code will be called very frequently, which will slow down |
3101 | libev considerably. |
3399 | libev considerably. |
3102 | |
3400 | |
3103 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3401 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3104 | C<0.> |
3402 | C<0>. |
3105 | |
3403 | |
3106 | =item EV_COMMON |
3404 | =item EV_COMMON |
3107 | |
3405 | |
3108 | By default, all watchers have a C<void *data> member. By redefining |
3406 | By default, all watchers have a C<void *data> member. By redefining |
3109 | this macro to a something else you can include more and other types of |
3407 | this macro to a something else you can include more and other types of |
… | |
… | |
3126 | and the way callbacks are invoked and set. Must expand to a struct member |
3424 | and the way callbacks are invoked and set. Must expand to a struct member |
3127 | definition and a statement, respectively. See the F<ev.h> header file for |
3425 | definition and a statement, respectively. See the F<ev.h> header file for |
3128 | their default definitions. One possible use for overriding these is to |
3426 | their default definitions. One possible use for overriding these is to |
3129 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3427 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3130 | method calls instead of plain function calls in C++. |
3428 | method calls instead of plain function calls in C++. |
|
|
3429 | |
|
|
3430 | =back |
3131 | |
3431 | |
3132 | =head2 EXPORTED API SYMBOLS |
3432 | =head2 EXPORTED API SYMBOLS |
3133 | |
3433 | |
3134 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3434 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3135 | exported symbols, you can use the provided F<Symbol.*> files which list |
3435 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3182 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3482 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3183 | |
3483 | |
3184 | #include "ev_cpp.h" |
3484 | #include "ev_cpp.h" |
3185 | #include "ev.c" |
3485 | #include "ev.c" |
3186 | |
3486 | |
|
|
3487 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3187 | |
3488 | |
3188 | =head1 THREADS AND COROUTINES |
3489 | =head2 THREADS AND COROUTINES |
3189 | |
3490 | |
3190 | =head2 THREADS |
3491 | =head3 THREADS |
3191 | |
3492 | |
3192 | Libev itself is completely thread-safe, but it uses no locking. This |
3493 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
3494 | documented otherwise, but libev implements no locking itself. This means |
3193 | means that you can use as many loops as you want in parallel, as long as |
3495 | that you can use as many loops as you want in parallel, as long as there |
3194 | only one thread ever calls into one libev function with the same loop |
3496 | are no concurrent calls into any libev function with the same loop |
3195 | parameter. |
3497 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
3498 | of course): libev guarantees that different event loops share no data |
|
|
3499 | structures that need any locking. |
3196 | |
3500 | |
3197 | Or put differently: calls with different loop parameters can be done in |
3501 | Or to put it differently: calls with different loop parameters can be done |
3198 | parallel from multiple threads, calls with the same loop parameter must be |
3502 | concurrently from multiple threads, calls with the same loop parameter |
3199 | done serially (but can be done from different threads, as long as only one |
3503 | must be done serially (but can be done from different threads, as long as |
3200 | thread ever is inside a call at any point in time, e.g. by using a mutex |
3504 | only one thread ever is inside a call at any point in time, e.g. by using |
3201 | per loop). |
3505 | a mutex per loop). |
|
|
3506 | |
|
|
3507 | Specifically to support threads (and signal handlers), libev implements |
|
|
3508 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
3509 | concurrency on the same event loop, namely waking it up "from the |
|
|
3510 | outside". |
3202 | |
3511 | |
3203 | If you want to know which design (one loop, locking, or multiple loops |
3512 | If you want to know which design (one loop, locking, or multiple loops |
3204 | without or something else still) is best for your problem, then I cannot |
3513 | without or something else still) is best for your problem, then I cannot |
3205 | help you. I can give some generic advice however: |
3514 | help you, but here is some generic advice: |
3206 | |
3515 | |
3207 | =over 4 |
3516 | =over 4 |
3208 | |
3517 | |
3209 | =item * most applications have a main thread: use the default libev loop |
3518 | =item * most applications have a main thread: use the default libev loop |
3210 | in that thread, or create a separate thread running only the default loop. |
3519 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3222 | |
3531 | |
3223 | Choosing a model is hard - look around, learn, know that usually you can do |
3532 | Choosing a model is hard - look around, learn, know that usually you can do |
3224 | better than you currently do :-) |
3533 | better than you currently do :-) |
3225 | |
3534 | |
3226 | =item * often you need to talk to some other thread which blocks in the |
3535 | =item * often you need to talk to some other thread which blocks in the |
|
|
3536 | event loop. |
|
|
3537 | |
3227 | event loop - C<ev_async> watchers can be used to wake them up from other |
3538 | C<ev_async> watchers can be used to wake them up from other threads safely |
3228 | threads safely (or from signal contexts...). |
3539 | (or from signal contexts...). |
|
|
3540 | |
|
|
3541 | An example use would be to communicate signals or other events that only |
|
|
3542 | work in the default loop by registering the signal watcher with the |
|
|
3543 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
3544 | watcher callback into the event loop interested in the signal. |
3229 | |
3545 | |
3230 | =back |
3546 | =back |
3231 | |
3547 | |
3232 | =head2 COROUTINES |
3548 | =head3 COROUTINES |
3233 | |
3549 | |
3234 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3550 | Libev is very accommodating to coroutines ("cooperative threads"): |
3235 | libev fully supports nesting calls to it's functions from different |
3551 | libev fully supports nesting calls to its functions from different |
3236 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3552 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3237 | different coroutines and switch freely between both coroutines running the |
3553 | different coroutines, and switch freely between both coroutines running the |
3238 | loop, as long as you don't confuse yourself). The only exception is that |
3554 | loop, as long as you don't confuse yourself). The only exception is that |
3239 | you must not do this from C<ev_periodic> reschedule callbacks. |
3555 | you must not do this from C<ev_periodic> reschedule callbacks. |
3240 | |
3556 | |
3241 | Care has been invested into making sure that libev does not keep local |
3557 | Care has been taken to ensure that libev does not keep local state inside |
3242 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
3558 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3243 | switches. |
3559 | they do not clal any callbacks. |
3244 | |
3560 | |
|
|
3561 | =head2 COMPILER WARNINGS |
3245 | |
3562 | |
3246 | =head1 COMPLEXITIES |
3563 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3564 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3565 | scared by this. |
3247 | |
3566 | |
3248 | In this section the complexities of (many of) the algorithms used inside |
3567 | However, these are unavoidable for many reasons. For one, each compiler |
3249 | libev will be explained. For complexity discussions about backends see the |
3568 | has different warnings, and each user has different tastes regarding |
3250 | documentation for C<ev_default_init>. |
3569 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3570 | targeting a specific compiler and compiler-version. |
3251 | |
3571 | |
3252 | All of the following are about amortised time: If an array needs to be |
3572 | Another reason is that some compiler warnings require elaborate |
3253 | extended, libev needs to realloc and move the whole array, but this |
3573 | workarounds, or other changes to the code that make it less clear and less |
3254 | happens asymptotically never with higher number of elements, so O(1) might |
3574 | maintainable. |
3255 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3256 | it is much faster and asymptotically approaches constant time. |
|
|
3257 | |
3575 | |
3258 | =over 4 |
3576 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3577 | wrong (because they don't actually warn about the condition their message |
|
|
3578 | seems to warn about). For example, certain older gcc versions had some |
|
|
3579 | warnings that resulted an extreme number of false positives. These have |
|
|
3580 | been fixed, but some people still insist on making code warn-free with |
|
|
3581 | such buggy versions. |
3259 | |
3582 | |
3260 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3583 | While libev is written to generate as few warnings as possible, |
|
|
3584 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3585 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3586 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3587 | warnings, not errors, or proof of bugs. |
3261 | |
3588 | |
3262 | This means that, when you have a watcher that triggers in one hour and |
|
|
3263 | there are 100 watchers that would trigger before that then inserting will |
|
|
3264 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3265 | |
3589 | |
3266 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3590 | =head2 VALGRIND |
3267 | |
3591 | |
3268 | That means that changing a timer costs less than removing/adding them |
3592 | Valgrind has a special section here because it is a popular tool that is |
3269 | as only the relative motion in the event queue has to be paid for. |
3593 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3270 | |
3594 | |
3271 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3595 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3596 | in libev, then check twice: If valgrind reports something like: |
3272 | |
3597 | |
3273 | These just add the watcher into an array or at the head of a list. |
3598 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3599 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3600 | ==2274== still reachable: 256 bytes in 1 blocks. |
3274 | |
3601 | |
3275 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3602 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3603 | is not a memleak - the memory is still being refernced, and didn't leak. |
3276 | |
3604 | |
3277 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3605 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3606 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3607 | although an acceptable workaround has been found here), or it might be |
|
|
3608 | confused. |
3278 | |
3609 | |
3279 | These watchers are stored in lists then need to be walked to find the |
3610 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3280 | correct watcher to remove. The lists are usually short (you don't usually |
3611 | make it into some kind of religion. |
3281 | have many watchers waiting for the same fd or signal). |
|
|
3282 | |
3612 | |
3283 | =item Finding the next timer in each loop iteration: O(1) |
3613 | If you are unsure about something, feel free to contact the mailing list |
|
|
3614 | with the full valgrind report and an explanation on why you think this |
|
|
3615 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3616 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3617 | of learning how to interpret valgrind properly. |
3284 | |
3618 | |
3285 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3619 | If you need, for some reason, empty reports from valgrind for your project |
3286 | fixed position in the storage array. |
3620 | I suggest using suppression lists. |
3287 | |
3621 | |
3288 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3289 | |
3622 | |
3290 | A change means an I/O watcher gets started or stopped, which requires |
3623 | =head1 PORTABILITY NOTES |
3291 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3292 | on backend and whether C<ev_io_set> was used). |
|
|
3293 | |
3624 | |
3294 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3295 | |
|
|
3296 | =item Priority handling: O(number_of_priorities) |
|
|
3297 | |
|
|
3298 | Priorities are implemented by allocating some space for each |
|
|
3299 | priority. When doing priority-based operations, libev usually has to |
|
|
3300 | linearly search all the priorities, but starting/stopping and activating |
|
|
3301 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3302 | |
|
|
3303 | =item Sending an ev_async: O(1) |
|
|
3304 | |
|
|
3305 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3306 | |
|
|
3307 | =item Processing signals: O(max_signal_number) |
|
|
3308 | |
|
|
3309 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3310 | calls in the current loop iteration. Checking for async and signal events |
|
|
3311 | involves iterating over all running async watchers or all signal numbers. |
|
|
3312 | |
|
|
3313 | =back |
|
|
3314 | |
|
|
3315 | |
|
|
3316 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3625 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3317 | |
3626 | |
3318 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3627 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3319 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3628 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3320 | model. Libev still offers limited functionality on this platform in |
3629 | model. Libev still offers limited functionality on this platform in |
3321 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3630 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3332 | |
3641 | |
3333 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3642 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3334 | accept large writes: instead of resulting in a partial write, windows will |
3643 | accept large writes: instead of resulting in a partial write, windows will |
3335 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3644 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3336 | so make sure you only write small amounts into your sockets (less than a |
3645 | so make sure you only write small amounts into your sockets (less than a |
3337 | megabyte seems safe, but thsi apparently depends on the amount of memory |
3646 | megabyte seems safe, but this apparently depends on the amount of memory |
3338 | available). |
3647 | available). |
3339 | |
3648 | |
3340 | Due to the many, low, and arbitrary limits on the win32 platform and |
3649 | Due to the many, low, and arbitrary limits on the win32 platform and |
3341 | the abysmal performance of winsockets, using a large number of sockets |
3650 | the abysmal performance of winsockets, using a large number of sockets |
3342 | is not recommended (and not reasonable). If your program needs to use |
3651 | is not recommended (and not reasonable). If your program needs to use |
… | |
… | |
3353 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3662 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3354 | |
3663 | |
3355 | #include "ev.h" |
3664 | #include "ev.h" |
3356 | |
3665 | |
3357 | And compile the following F<evwrap.c> file into your project (make sure |
3666 | And compile the following F<evwrap.c> file into your project (make sure |
3358 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
3667 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3359 | |
3668 | |
3360 | #include "evwrap.h" |
3669 | #include "evwrap.h" |
3361 | #include "ev.c" |
3670 | #include "ev.c" |
3362 | |
3671 | |
3363 | =over 4 |
3672 | =over 4 |
… | |
… | |
3408 | wrap all I/O functions and provide your own fd management, but the cost of |
3717 | wrap all I/O functions and provide your own fd management, but the cost of |
3409 | calling select (O(n²)) will likely make this unworkable. |
3718 | calling select (O(n²)) will likely make this unworkable. |
3410 | |
3719 | |
3411 | =back |
3720 | =back |
3412 | |
3721 | |
3413 | |
|
|
3414 | =head1 PORTABILITY REQUIREMENTS |
3722 | =head2 PORTABILITY REQUIREMENTS |
3415 | |
3723 | |
3416 | In addition to a working ISO-C implementation, libev relies on a few |
3724 | In addition to a working ISO-C implementation and of course the |
3417 | additional extensions: |
3725 | backend-specific APIs, libev relies on a few additional extensions: |
3418 | |
3726 | |
3419 | =over 4 |
3727 | =over 4 |
3420 | |
3728 | |
3421 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3729 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3422 | calling conventions regardless of C<ev_watcher_type *>. |
3730 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3428 | calls them using an C<ev_watcher *> internally. |
3736 | calls them using an C<ev_watcher *> internally. |
3429 | |
3737 | |
3430 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3738 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3431 | |
3739 | |
3432 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3740 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3433 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
3741 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3434 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3742 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3435 | believed to be sufficiently portable. |
3743 | believed to be sufficiently portable. |
3436 | |
3744 | |
3437 | =item C<sigprocmask> must work in a threaded environment |
3745 | =item C<sigprocmask> must work in a threaded environment |
3438 | |
3746 | |
… | |
… | |
3447 | except the initial one, and run the default loop in the initial thread as |
3755 | except the initial one, and run the default loop in the initial thread as |
3448 | well. |
3756 | well. |
3449 | |
3757 | |
3450 | =item C<long> must be large enough for common memory allocation sizes |
3758 | =item C<long> must be large enough for common memory allocation sizes |
3451 | |
3759 | |
3452 | To improve portability and simplify using libev, libev uses C<long> |
3760 | To improve portability and simplify its API, libev uses C<long> internally |
3453 | internally instead of C<size_t> when allocating its data structures. On |
3761 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3454 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3762 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3455 | is still at least 31 bits everywhere, which is enough for hundreds of |
3763 | least 31 bits everywhere, which is enough for hundreds of millions of |
3456 | millions of watchers. |
3764 | watchers. |
3457 | |
3765 | |
3458 | =item C<double> must hold a time value in seconds with enough accuracy |
3766 | =item C<double> must hold a time value in seconds with enough accuracy |
3459 | |
3767 | |
3460 | The type C<double> is used to represent timestamps. It is required to |
3768 | The type C<double> is used to represent timestamps. It is required to |
3461 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3769 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3465 | =back |
3773 | =back |
3466 | |
3774 | |
3467 | If you know of other additional requirements drop me a note. |
3775 | If you know of other additional requirements drop me a note. |
3468 | |
3776 | |
3469 | |
3777 | |
3470 | =head1 COMPILER WARNINGS |
3778 | =head1 ALGORITHMIC COMPLEXITIES |
3471 | |
3779 | |
3472 | Depending on your compiler and compiler settings, you might get no or a |
3780 | In this section the complexities of (many of) the algorithms used inside |
3473 | lot of warnings when compiling libev code. Some people are apparently |
3781 | libev will be documented. For complexity discussions about backends see |
3474 | scared by this. |
3782 | the documentation for C<ev_default_init>. |
3475 | |
3783 | |
3476 | However, these are unavoidable for many reasons. For one, each compiler |
3784 | All of the following are about amortised time: If an array needs to be |
3477 | has different warnings, and each user has different tastes regarding |
3785 | extended, libev needs to realloc and move the whole array, but this |
3478 | warning options. "Warn-free" code therefore cannot be a goal except when |
3786 | happens asymptotically rarer with higher number of elements, so O(1) might |
3479 | targeting a specific compiler and compiler-version. |
3787 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3788 | average it is much faster and asymptotically approaches constant time. |
3480 | |
3789 | |
3481 | Another reason is that some compiler warnings require elaborate |
3790 | =over 4 |
3482 | workarounds, or other changes to the code that make it less clear and less |
|
|
3483 | maintainable. |
|
|
3484 | |
3791 | |
3485 | And of course, some compiler warnings are just plain stupid, or simply |
3792 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3486 | wrong (because they don't actually warn about the condition their message |
|
|
3487 | seems to warn about). |
|
|
3488 | |
3793 | |
3489 | While libev is written to generate as few warnings as possible, |
3794 | This means that, when you have a watcher that triggers in one hour and |
3490 | "warn-free" code is not a goal, and it is recommended not to build libev |
3795 | there are 100 watchers that would trigger before that, then inserting will |
3491 | with any compiler warnings enabled unless you are prepared to cope with |
3796 | have to skip roughly seven (C<ld 100>) of these watchers. |
3492 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3493 | warnings, not errors, or proof of bugs. |
|
|
3494 | |
3797 | |
|
|
3798 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3495 | |
3799 | |
3496 | =head1 VALGRIND |
3800 | That means that changing a timer costs less than removing/adding them, |
|
|
3801 | as only the relative motion in the event queue has to be paid for. |
3497 | |
3802 | |
3498 | Valgrind has a special section here because it is a popular tool that is |
3803 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3499 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3500 | |
3804 | |
3501 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3805 | These just add the watcher into an array or at the head of a list. |
3502 | in libev, then check twice: If valgrind reports something like: |
|
|
3503 | |
3806 | |
3504 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3807 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3505 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3506 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3507 | |
3808 | |
3508 | Then there is no memory leak. Similarly, under some circumstances, |
3809 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3509 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3510 | might be confused (it is a very good tool, but only a tool). |
|
|
3511 | |
3810 | |
3512 | If you are unsure about something, feel free to contact the mailing list |
3811 | These watchers are stored in lists, so they need to be walked to find the |
3513 | with the full valgrind report and an explanation on why you think this is |
3812 | correct watcher to remove. The lists are usually short (you don't usually |
3514 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3813 | have many watchers waiting for the same fd or signal: one is typical, two |
3515 | no bug" answer and take the chance of learning how to interpret valgrind |
3814 | is rare). |
3516 | properly. |
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3517 | |
3815 | |
3518 | If you need, for some reason, empty reports from valgrind for your project |
3816 | =item Finding the next timer in each loop iteration: O(1) |
3519 | I suggest using suppression lists. |
3817 | |
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|
3818 | By virtue of using a binary or 4-heap, the next timer is always found at a |
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|
3819 | fixed position in the storage array. |
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3820 | |
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3821 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
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3822 | |
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|
3823 | A change means an I/O watcher gets started or stopped, which requires |
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|
3824 | libev to recalculate its status (and possibly tell the kernel, depending |
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3825 | on backend and whether C<ev_io_set> was used). |
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3826 | |
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3827 | =item Activating one watcher (putting it into the pending state): O(1) |
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3828 | |
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3829 | =item Priority handling: O(number_of_priorities) |
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3830 | |
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3831 | Priorities are implemented by allocating some space for each |
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3832 | priority. When doing priority-based operations, libev usually has to |
|
|
3833 | linearly search all the priorities, but starting/stopping and activating |
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3834 | watchers becomes O(1) with respect to priority handling. |
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3835 | |
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3836 | =item Sending an ev_async: O(1) |
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3837 | |
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3838 | =item Processing ev_async_send: O(number_of_async_watchers) |
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3839 | |
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3840 | =item Processing signals: O(max_signal_number) |
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3841 | |
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3842 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
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3843 | calls in the current loop iteration. Checking for async and signal events |
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3844 | involves iterating over all running async watchers or all signal numbers. |
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3845 | |
|
|
3846 | =back |
3520 | |
3847 | |
3521 | |
3848 | |
3522 | =head1 AUTHOR |
3849 | =head1 AUTHOR |
3523 | |
3850 | |
3524 | Marc Lehmann <libev@schmorp.de>. |
3851 | Marc Lehmann <libev@schmorp.de>. |