… | |
… | |
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 |
… | |
… | |
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 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
298 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
299 | function. |
296 | |
300 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
303 | as loops cannot be shared easily between threads anyway). |
300 | |
304 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
305 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
385 | |
382 | 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, |
383 | but it scales phenomenally better. While poll and select usually scale |
387 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
389 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
390 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
391 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
392 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
393 | dropping file descriptors, requiring a system call per change per file |
|
|
394 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
395 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
396 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
397 | take considerable time (one syscall per file descriptor) and is of course |
|
|
398 | hard to detect. |
|
|
399 | |
|
|
400 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
401 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
402 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
403 | even remove them from the set) than registered in the set (especially |
|
|
404 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
405 | employing an additional generation counter and comparing that against the |
|
|
406 | events to filter out spurious ones, recreating the set when required. |
389 | |
407 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
408 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
409 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
410 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
411 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
412 | file descriptors might not work very well if you register events for both |
395 | |
413 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
414 | |
400 | Best performance from this backend is achieved by not unregistering all |
415 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
416 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
417 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
418 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
419 | extra overhead. A fork can both result in spurious notifications as well |
|
|
420 | as in libev having to destroy and recreate the epoll object, which can |
|
|
421 | take considerable time and thus should be avoided. |
405 | |
422 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
423 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
424 | all kernel versions tested so far. |
408 | |
425 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
426 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
427 | C<EVBACKEND_POLL>. |
411 | |
428 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
429 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
430 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
431 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
432 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
433 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
434 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
435 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
436 | without API changes to existing programs. For this reason it's not being |
|
|
437 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
438 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
439 | system like NetBSD. |
420 | |
440 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
441 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
442 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
443 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
444 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
445 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
446 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
447 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
448 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
449 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
450 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
451 | cases |
431 | |
452 | |
432 | This backend usually performs well under most conditions. |
453 | This backend usually performs well under most conditions. |
433 | |
454 | |
434 | While nominally embeddable in other event loops, this doesn't work |
455 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
456 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
464 | might perform better. |
485 | might perform better. |
465 | |
486 | |
466 | On the positive side, with the exception of the spurious readiness |
487 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
488 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
489 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
490 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
491 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
492 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
493 | C<EVBACKEND_POLL>. |
473 | |
494 | |
474 | =item C<EVBACKEND_ALL> |
495 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
548 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
549 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
550 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
551 | for example). |
531 | |
552 | |
532 | Note that certain global state, such as signal state, will not be freed by |
553 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
554 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
555 | as signal and child watchers) would need to be stopped manually. |
535 | |
556 | |
536 | In general it is not advisable to call this function except in the |
557 | In general it is not advisable to call this function except in the |
537 | rare occasion where you really need to free e.g. the signal handling |
558 | rare occasion where you really need to free e.g. the signal handling |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
559 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
560 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
631 | the loop. |
652 | the loop. |
632 | |
653 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
654 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
655 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
656 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
657 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
658 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
659 | iteration of the loop. |
639 | |
660 | |
640 | This is useful if you are waiting for some external event in conjunction |
661 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
662 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
706 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
707 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
687 | |
708 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
709 | This "unloop state" will be cleared when entering C<ev_loop> again. |
689 | |
710 | |
|
|
711 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
712 | |
690 | =item ev_ref (loop) |
713 | =item ev_ref (loop) |
691 | |
714 | |
692 | =item ev_unref (loop) |
715 | =item ev_unref (loop) |
693 | |
716 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
717 | Ref/unref can be used to add or remove a reference count on the event |
… | |
… | |
708 | respectively). |
731 | respectively). |
709 | |
732 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
733 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
711 | running when nothing else is active. |
734 | running when nothing else is active. |
712 | |
735 | |
713 | struct ev_signal exitsig; |
736 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
737 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
738 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
739 | evf_unref (loop); |
717 | |
740 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
741 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
766 | they fire on, say, one-second boundaries only. |
789 | they fire on, say, one-second boundaries only. |
767 | |
790 | |
768 | =item ev_loop_verify (loop) |
791 | =item ev_loop_verify (loop) |
769 | |
792 | |
770 | This function only does something when C<EV_VERIFY> support has been |
793 | This function only does something when C<EV_VERIFY> support has been |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
794 | compiled in, which is the default for non-minimal builds. It tries to go |
772 | through all internal structures and checks them for validity. If anything |
795 | through all internal structures and checks them for validity. If anything |
773 | is found to be inconsistent, it will print an error message to standard |
796 | is found to be inconsistent, it will print an error message to standard |
774 | error and call C<abort ()>. |
797 | error and call C<abort ()>. |
775 | |
798 | |
776 | This can be used to catch bugs inside libev itself: under normal |
799 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
780 | =back |
803 | =back |
781 | |
804 | |
782 | |
805 | |
783 | =head1 ANATOMY OF A WATCHER |
806 | =head1 ANATOMY OF A WATCHER |
784 | |
807 | |
|
|
808 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
809 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
810 | watchers and C<ev_io_start> for I/O watchers. |
|
|
811 | |
785 | A watcher is a structure that you create and register to record your |
812 | A watcher is a structure that you create and register to record your |
786 | interest in some event. For instance, if you want to wait for STDIN to |
813 | interest in some event. For instance, if you want to wait for STDIN to |
787 | become readable, you would create an C<ev_io> watcher for that: |
814 | become readable, you would create an C<ev_io> watcher for that: |
788 | |
815 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
816 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
817 | { |
791 | ev_io_stop (w); |
818 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
819 | ev_unloop (loop, EVUNLOOP_ALL); |
793 | } |
820 | } |
794 | |
821 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
822 | struct ev_loop *loop = ev_default_loop (0); |
|
|
823 | |
796 | struct ev_io stdin_watcher; |
824 | ev_io stdin_watcher; |
|
|
825 | |
797 | ev_init (&stdin_watcher, my_cb); |
826 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
827 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
828 | ev_io_start (loop, &stdin_watcher); |
|
|
829 | |
800 | ev_loop (loop, 0); |
830 | ev_loop (loop, 0); |
801 | |
831 | |
802 | As you can see, you are responsible for allocating the memory for your |
832 | As you can see, you are responsible for allocating the memory for your |
803 | watcher structures (and it is usually a bad idea to do this on the stack, |
833 | watcher structures (and it is I<usually> a bad idea to do this on the |
804 | although this can sometimes be quite valid). |
834 | stack). |
|
|
835 | |
|
|
836 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
837 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
805 | |
838 | |
806 | Each watcher structure must be initialised by a call to C<ev_init |
839 | Each watcher structure must be initialised by a call to C<ev_init |
807 | (watcher *, callback)>, which expects a callback to be provided. This |
840 | (watcher *, callback)>, which expects a callback to be provided. This |
808 | callback gets invoked each time the event occurs (or, in the case of I/O |
841 | callback gets invoked each time the event occurs (or, in the case of I/O |
809 | watchers, each time the event loop detects that the file descriptor given |
842 | watchers, each time the event loop detects that the file descriptor given |
810 | is readable and/or writable). |
843 | is readable and/or writable). |
811 | |
844 | |
812 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
845 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
813 | with arguments specific to this watcher type. There is also a macro |
846 | macro to configure it, with arguments specific to the watcher type. There |
814 | to combine initialisation and setting in one call: C<< ev_<type>_init |
847 | is also a macro to combine initialisation and setting in one call: C<< |
815 | (watcher *, callback, ...) >>. |
848 | ev_TYPE_init (watcher *, callback, ...) >>. |
816 | |
849 | |
817 | To make the watcher actually watch out for events, you have to start it |
850 | To make the watcher actually watch out for events, you have to start it |
818 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
851 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
819 | *) >>), and you can stop watching for events at any time by calling the |
852 | *) >>), and you can stop watching for events at any time by calling the |
820 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
853 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
821 | |
854 | |
822 | As long as your watcher is active (has been started but not stopped) you |
855 | As long as your watcher is active (has been started but not stopped) you |
823 | must not touch the values stored in it. Most specifically you must never |
856 | must not touch the values stored in it. Most specifically you must never |
824 | reinitialise it or call its C<set> macro. |
857 | reinitialise it or call its C<ev_TYPE_set> macro. |
825 | |
858 | |
826 | Each and every callback receives the event loop pointer as first, the |
859 | Each and every callback receives the event loop pointer as first, the |
827 | registered watcher structure as second, and a bitset of received events as |
860 | registered watcher structure as second, and a bitset of received events as |
828 | third argument. |
861 | third argument. |
829 | |
862 | |
… | |
… | |
892 | =item C<EV_ERROR> |
925 | =item C<EV_ERROR> |
893 | |
926 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
927 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
928 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
929 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
930 | problem. Libev considers these application bugs. |
|
|
931 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
932 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
933 | watcher being stopped. Note that well-written programs should not receive |
|
|
934 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
935 | bug in your program. |
899 | |
936 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
937 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
938 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
939 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
940 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
906 | |
943 | |
907 | =back |
944 | =back |
908 | |
945 | |
909 | =head2 GENERIC WATCHER FUNCTIONS |
946 | =head2 GENERIC WATCHER FUNCTIONS |
910 | |
947 | |
911 | In the following description, C<TYPE> stands for the watcher type, |
|
|
912 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
913 | |
|
|
914 | =over 4 |
948 | =over 4 |
915 | |
949 | |
916 | =item C<ev_init> (ev_TYPE *watcher, callback) |
950 | =item C<ev_init> (ev_TYPE *watcher, callback) |
917 | |
951 | |
918 | This macro initialises the generic portion of a watcher. The contents |
952 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
923 | which rolls both calls into one. |
957 | which rolls both calls into one. |
924 | |
958 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
959 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
960 | (or never started) and there are no pending events outstanding. |
927 | |
961 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
962 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
963 | int revents)>. |
930 | |
964 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
965 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
966 | |
933 | ev_io w; |
967 | ev_io w; |
… | |
… | |
967 | |
1001 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
1002 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
1003 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1004 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
971 | |
1005 | |
972 | Stops the given watcher again (if active) and clears the pending |
1006 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1007 | the watcher was active or not). |
|
|
1008 | |
973 | status. It is possible that stopped watchers are pending (for example, |
1009 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
1010 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1011 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
1012 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
1013 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
1014 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
1015 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
1016 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
1017 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
1018 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1024 | The default priority used by watchers when no priority has been set is |
1060 | The default priority used by watchers when no priority has been set is |
1025 | always C<0>, which is supposed to not be too high and not be too low :). |
1061 | always C<0>, which is supposed to not be too high and not be too low :). |
1026 | |
1062 | |
1027 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1063 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1028 | fine, as long as you do not mind that the priority value you query might |
1064 | fine, as long as you do not mind that the priority value you query might |
1029 | or might not have been adjusted to be within valid range. |
1065 | or might not have been clamped to the valid range. |
1030 | |
1066 | |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1067 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1032 | |
1068 | |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1069 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1070 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1092 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1093 | data: |
1058 | |
1094 | |
1059 | struct my_io |
1095 | struct my_io |
1060 | { |
1096 | { |
1061 | struct ev_io io; |
1097 | ev_io io; |
1062 | int otherfd; |
1098 | int otherfd; |
1063 | void *somedata; |
1099 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1100 | struct whatever *mostinteresting; |
1065 | }; |
1101 | }; |
1066 | |
1102 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1105 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1106 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1107 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1108 | can cast it back to your own type: |
1073 | |
1109 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1110 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1111 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1112 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1113 | ... |
1078 | } |
1114 | } |
1079 | |
1115 | |
… | |
… | |
1097 | programmers): |
1133 | programmers): |
1098 | |
1134 | |
1099 | #include <stddef.h> |
1135 | #include <stddef.h> |
1100 | |
1136 | |
1101 | static void |
1137 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1138 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1139 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1140 | struct my_biggy big = (struct my_biggy * |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1141 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1142 | } |
1107 | |
1143 | |
1108 | static void |
1144 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1145 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1146 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1147 | struct my_biggy big = (struct my_biggy * |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1148 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1149 | } |
1114 | |
1150 | |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1285 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1286 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1287 | attempt to read a whole line in the callback. |
1252 | |
1288 | |
1253 | static void |
1289 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1290 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1291 | { |
1256 | ev_io_stop (loop, w); |
1292 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1293 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1294 | } |
1259 | |
1295 | |
1260 | ... |
1296 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1297 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1298 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1299 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1300 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1301 | ev_loop (loop, 0); |
1266 | |
1302 | |
1267 | |
1303 | |
… | |
… | |
1278 | |
1314 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1315 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1316 | passed, but if multiple timers become ready during the same loop iteration |
1281 | then order of execution is undefined. |
1317 | then order of execution is undefined. |
1282 | |
1318 | |
|
|
1319 | =head3 Be smart about timeouts |
|
|
1320 | |
|
|
1321 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1322 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1323 | you want to raise some error after a while. |
|
|
1324 | |
|
|
1325 | What follows are some ways to handle this problem, from obvious and |
|
|
1326 | inefficient to smart and efficient. |
|
|
1327 | |
|
|
1328 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1329 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1330 | data or other life sign was received). |
|
|
1331 | |
|
|
1332 | =over 4 |
|
|
1333 | |
|
|
1334 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1335 | |
|
|
1336 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1337 | start the watcher: |
|
|
1338 | |
|
|
1339 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1340 | ev_timer_start (loop, timer); |
|
|
1341 | |
|
|
1342 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1343 | and start it again: |
|
|
1344 | |
|
|
1345 | ev_timer_stop (loop, timer); |
|
|
1346 | ev_timer_set (timer, 60., 0.); |
|
|
1347 | ev_timer_start (loop, timer); |
|
|
1348 | |
|
|
1349 | This is relatively simple to implement, but means that each time there is |
|
|
1350 | some activity, libev will first have to remove the timer from its internal |
|
|
1351 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1352 | still not a constant-time operation. |
|
|
1353 | |
|
|
1354 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1355 | |
|
|
1356 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1357 | C<ev_timer_start>. |
|
|
1358 | |
|
|
1359 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1360 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1361 | successfully read or write some data. If you go into an idle state where |
|
|
1362 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1363 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1364 | |
|
|
1365 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1366 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1367 | member and C<ev_timer_again>. |
|
|
1368 | |
|
|
1369 | At start: |
|
|
1370 | |
|
|
1371 | ev_timer_init (timer, callback); |
|
|
1372 | timer->repeat = 60.; |
|
|
1373 | ev_timer_again (loop, timer); |
|
|
1374 | |
|
|
1375 | Each time there is some activity: |
|
|
1376 | |
|
|
1377 | ev_timer_again (loop, timer); |
|
|
1378 | |
|
|
1379 | It is even possible to change the time-out on the fly, regardless of |
|
|
1380 | whether the watcher is active or not: |
|
|
1381 | |
|
|
1382 | timer->repeat = 30.; |
|
|
1383 | ev_timer_again (loop, timer); |
|
|
1384 | |
|
|
1385 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1386 | you want to modify its timeout value, as libev does not have to completely |
|
|
1387 | remove and re-insert the timer from/into its internal data structure. |
|
|
1388 | |
|
|
1389 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1390 | |
|
|
1391 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1392 | |
|
|
1393 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1394 | relatively long compared to the intervals between other activity - in |
|
|
1395 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1396 | associated activity resets. |
|
|
1397 | |
|
|
1398 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1399 | but remember the time of last activity, and check for a real timeout only |
|
|
1400 | within the callback: |
|
|
1401 | |
|
|
1402 | ev_tstamp last_activity; // time of last activity |
|
|
1403 | |
|
|
1404 | static void |
|
|
1405 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1406 | { |
|
|
1407 | ev_tstamp now = ev_now (EV_A); |
|
|
1408 | ev_tstamp timeout = last_activity + 60.; |
|
|
1409 | |
|
|
1410 | // if last_activity + 60. is older than now, we did time out |
|
|
1411 | if (timeout < now) |
|
|
1412 | { |
|
|
1413 | // timeout occured, take action |
|
|
1414 | } |
|
|
1415 | else |
|
|
1416 | { |
|
|
1417 | // callback was invoked, but there was some activity, re-arm |
|
|
1418 | // the watcher to fire in last_activity + 60, which is |
|
|
1419 | // guaranteed to be in the future, so "again" is positive: |
|
|
1420 | w->again = timeout - now; |
|
|
1421 | ev_timer_again (EV_A_ w); |
|
|
1422 | } |
|
|
1423 | } |
|
|
1424 | |
|
|
1425 | To summarise the callback: first calculate the real timeout (defined |
|
|
1426 | as "60 seconds after the last activity"), then check if that time has |
|
|
1427 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1428 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1429 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1430 | a timeout then. |
|
|
1431 | |
|
|
1432 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1433 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1434 | |
|
|
1435 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1436 | minus half the average time between activity), but virtually no calls to |
|
|
1437 | libev to change the timeout. |
|
|
1438 | |
|
|
1439 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1440 | to the current time (meaning we just have some activity :), then call the |
|
|
1441 | callback, which will "do the right thing" and start the timer: |
|
|
1442 | |
|
|
1443 | ev_timer_init (timer, callback); |
|
|
1444 | last_activity = ev_now (loop); |
|
|
1445 | callback (loop, timer, EV_TIMEOUT); |
|
|
1446 | |
|
|
1447 | And when there is some activity, simply store the current time in |
|
|
1448 | C<last_activity>, no libev calls at all: |
|
|
1449 | |
|
|
1450 | last_actiivty = ev_now (loop); |
|
|
1451 | |
|
|
1452 | This technique is slightly more complex, but in most cases where the |
|
|
1453 | time-out is unlikely to be triggered, much more efficient. |
|
|
1454 | |
|
|
1455 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1456 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1457 | fix things for you. |
|
|
1458 | |
|
|
1459 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1460 | |
|
|
1461 | If there is not one request, but many thousands (millions...), all |
|
|
1462 | employing some kind of timeout with the same timeout value, then one can |
|
|
1463 | do even better: |
|
|
1464 | |
|
|
1465 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1466 | at the I<end> of the list. |
|
|
1467 | |
|
|
1468 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1469 | the list is expected to fire (for example, using the technique #3). |
|
|
1470 | |
|
|
1471 | When there is some activity, remove the timer from the list, recalculate |
|
|
1472 | the timeout, append it to the end of the list again, and make sure to |
|
|
1473 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1474 | |
|
|
1475 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1476 | starting, stopping and updating the timers, at the expense of a major |
|
|
1477 | complication, and having to use a constant timeout. The constant timeout |
|
|
1478 | ensures that the list stays sorted. |
|
|
1479 | |
|
|
1480 | =back |
|
|
1481 | |
|
|
1482 | So which method the best? |
|
|
1483 | |
|
|
1484 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1485 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1486 | better, and isn't very complicated either. In most case, choosing either |
|
|
1487 | one is fine, with #3 being better in typical situations. |
|
|
1488 | |
|
|
1489 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1490 | rather complicated, but extremely efficient, something that really pays |
|
|
1491 | off after the first million or so of active timers, i.e. it's usually |
|
|
1492 | overkill :) |
|
|
1493 | |
1283 | =head3 The special problem of time updates |
1494 | =head3 The special problem of time updates |
1284 | |
1495 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1496 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1497 | least two system calls): EV therefore updates its idea of the current |
1287 | time only before and after C<ev_loop> collects new events, which causes a |
1498 | time only before and after C<ev_loop> collects new events, which causes a |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
1541 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
1542 | |
1332 | If the timer is repeating, either start it if necessary (with the |
1543 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1544 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
1545 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
1546 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
1547 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
|
|
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
|
|
1348 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | ... |
|
|
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value. |
|
|
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1548 | |
1366 | =item ev_tstamp repeat [read-write] |
1549 | =item ev_tstamp repeat [read-write] |
1367 | |
1550 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1551 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1552 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
1557 | =head3 Examples |
1375 | |
1558 | |
1376 | Example: Create a timer that fires after 60 seconds. |
1559 | Example: Create a timer that fires after 60 seconds. |
1377 | |
1560 | |
1378 | static void |
1561 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1562 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
1563 | { |
1381 | .. one minute over, w is actually stopped right here |
1564 | .. one minute over, w is actually stopped right here |
1382 | } |
1565 | } |
1383 | |
1566 | |
1384 | struct ev_timer mytimer; |
1567 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1568 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
1569 | ev_timer_start (loop, &mytimer); |
1387 | |
1570 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
1571 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
1572 | inactivity. |
1390 | |
1573 | |
1391 | static void |
1574 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1575 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
1576 | { |
1394 | .. ten seconds without any activity |
1577 | .. ten seconds without any activity |
1395 | } |
1578 | } |
1396 | |
1579 | |
1397 | struct ev_timer mytimer; |
1580 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1581 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
1582 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
1583 | ev_loop (loop, 0); |
1401 | |
1584 | |
1402 | // and in some piece of code that gets executed on any "activity": |
1585 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1488 | |
1671 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1672 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1673 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
1674 | only event loop modification you are allowed to do). |
1492 | |
1675 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1676 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
1677 | *w, ev_tstamp now)>, e.g.: |
1495 | |
1678 | |
|
|
1679 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1680 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
1681 | { |
1498 | return now + 60.; |
1682 | return now + 60.; |
1499 | } |
1683 | } |
1500 | |
1684 | |
1501 | It must return the next time to trigger, based on the passed time value |
1685 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1538 | |
1722 | |
1539 | The current interval value. Can be modified any time, but changes only |
1723 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1724 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
1725 | called. |
1542 | |
1726 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1727 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
1728 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
1729 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
1730 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
1731 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
1732 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1737 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
1738 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
1739 | potentially a lot of jitter, but good long-term stability. |
1556 | |
1740 | |
1557 | static void |
1741 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1742 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1559 | { |
1743 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1744 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
1745 | } |
1562 | |
1746 | |
1563 | struct ev_periodic hourly_tick; |
1747 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1748 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
1749 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
1750 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
1751 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
1752 | |
1569 | #include <math.h> |
1753 | #include <math.h> |
1570 | |
1754 | |
1571 | static ev_tstamp |
1755 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1756 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
1757 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
1758 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
1759 | } |
1576 | |
1760 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1761 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
1762 | |
1579 | Example: Call a callback every hour, starting now: |
1763 | Example: Call a callback every hour, starting now: |
1580 | |
1764 | |
1581 | struct ev_periodic hourly_tick; |
1765 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
1766 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
1767 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
1768 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
1769 | |
1586 | |
1770 | |
… | |
… | |
1628 | =head3 Examples |
1812 | =head3 Examples |
1629 | |
1813 | |
1630 | Example: Try to exit cleanly on SIGINT. |
1814 | Example: Try to exit cleanly on SIGINT. |
1631 | |
1815 | |
1632 | static void |
1816 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1817 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
1818 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
1819 | ev_unloop (loop, EVUNLOOP_ALL); |
1636 | } |
1820 | } |
1637 | |
1821 | |
1638 | struct ev_signal signal_watcher; |
1822 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1823 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &signal_watcher); |
1824 | ev_signal_start (loop, &signal_watcher); |
1641 | |
1825 | |
1642 | |
1826 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
1827 | =head2 C<ev_child> - watch out for process status changes |
… | |
… | |
1718 | its completion. |
1902 | its completion. |
1719 | |
1903 | |
1720 | ev_child cw; |
1904 | ev_child cw; |
1721 | |
1905 | |
1722 | static void |
1906 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
1907 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
1908 | { |
1725 | ev_child_stop (EV_A_ w); |
1909 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1910 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
1911 | } |
1728 | |
1912 | |
… | |
… | |
1743 | |
1927 | |
1744 | |
1928 | |
1745 | =head2 C<ev_stat> - did the file attributes just change? |
1929 | =head2 C<ev_stat> - did the file attributes just change? |
1746 | |
1930 | |
1747 | This watches a file system path for attribute changes. That is, it calls |
1931 | This watches a file system path for attribute changes. That is, it calls |
1748 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1932 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1749 | compared to the last time, invoking the callback if it did. |
1933 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1934 | it did. |
1750 | |
1935 | |
1751 | The path does not need to exist: changing from "path exists" to "path does |
1936 | The path does not need to exist: changing from "path exists" to "path does |
1752 | not exist" is a status change like any other. The condition "path does |
1937 | not exist" is a status change like any other. The condition "path does |
1753 | not exist" is signified by the C<st_nlink> field being zero (which is |
1938 | not exist" is signified by the C<st_nlink> field being zero (which is |
1754 | otherwise always forced to be at least one) and all the other fields of |
1939 | otherwise always forced to be at least one) and all the other fields of |
1755 | the stat buffer having unspecified contents. |
1940 | the stat buffer having unspecified contents. |
1756 | |
1941 | |
1757 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1942 | The path I<must not> end in a slash or contain special components such as |
|
|
1943 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1758 | relative and your working directory changes, the behaviour is undefined. |
1944 | your working directory changes, then the behaviour is undefined. |
1759 | |
1945 | |
1760 | Since there is no standard kernel interface to do this, the portable |
1946 | Since there is no portable change notification interface available, the |
1761 | implementation simply calls C<stat (2)> regularly on the path to see if |
1947 | portable implementation simply calls C<stat(2)> regularly on the path |
1762 | it changed somehow. You can specify a recommended polling interval for |
1948 | to see if it changed somehow. You can specify a recommended polling |
1763 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1949 | interval for this case. If you specify a polling interval of C<0> (highly |
1764 | then a I<suitable, unspecified default> value will be used (which |
1950 | recommended!) then a I<suitable, unspecified default> value will be used |
1765 | you can expect to be around five seconds, although this might change |
1951 | (which you can expect to be around five seconds, although this might |
1766 | dynamically). Libev will also impose a minimum interval which is currently |
1952 | change dynamically). Libev will also impose a minimum interval which is |
1767 | around C<0.1>, but thats usually overkill. |
1953 | currently around C<0.1>, but that's usually overkill. |
1768 | |
1954 | |
1769 | This watcher type is not meant for massive numbers of stat watchers, |
1955 | This watcher type is not meant for massive numbers of stat watchers, |
1770 | as even with OS-supported change notifications, this can be |
1956 | as even with OS-supported change notifications, this can be |
1771 | resource-intensive. |
1957 | resource-intensive. |
1772 | |
1958 | |
… | |
… | |
1782 | support disabled by default, you get the 32 bit version of the stat |
1968 | support disabled by default, you get the 32 bit version of the stat |
1783 | structure. When using the library from programs that change the ABI to |
1969 | structure. When using the library from programs that change the ABI to |
1784 | use 64 bit file offsets the programs will fail. In that case you have to |
1970 | use 64 bit file offsets the programs will fail. In that case you have to |
1785 | compile libev with the same flags to get binary compatibility. This is |
1971 | compile libev with the same flags to get binary compatibility. This is |
1786 | obviously the case with any flags that change the ABI, but the problem is |
1972 | obviously the case with any flags that change the ABI, but the problem is |
1787 | most noticeably disabled with ev_stat and large file support. |
1973 | most noticeably displayed with ev_stat and large file support. |
1788 | |
1974 | |
1789 | The solution for this is to lobby your distribution maker to make large |
1975 | The solution for this is to lobby your distribution maker to make large |
1790 | file interfaces available by default (as e.g. FreeBSD does) and not |
1976 | file interfaces available by default (as e.g. FreeBSD does) and not |
1791 | optional. Libev cannot simply switch on large file support because it has |
1977 | optional. Libev cannot simply switch on large file support because it has |
1792 | to exchange stat structures with application programs compiled using the |
1978 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
1979 | default compilation environment. |
1794 | |
1980 | |
1795 | =head3 Inotify and Kqueue |
1981 | =head3 Inotify and Kqueue |
1796 | |
1982 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
1983 | When C<inotify (7)> support has been compiled into libev (generally |
|
|
1984 | only available with Linux 2.6.25 or above due to bugs in earlier |
1798 | available with Linux) and present at runtime, it will be used to speed up |
1985 | implementations) and present at runtime, it will be used to speed up |
1799 | change detection where possible. The inotify descriptor will be created lazily |
1986 | change detection where possible. The inotify descriptor will be created |
1800 | when the first C<ev_stat> watcher is being started. |
1987 | lazily when the first C<ev_stat> watcher is being started. |
1801 | |
1988 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1989 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
1990 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
1991 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
1992 | there are many cases where libev has to resort to regular C<stat> polling, |
… | |
… | |
1810 | descriptor open on the object at all times, and detecting renames, unlinks |
1997 | descriptor open on the object at all times, and detecting renames, unlinks |
1811 | etc. is difficult. |
1998 | etc. is difficult. |
1812 | |
1999 | |
1813 | =head3 The special problem of stat time resolution |
2000 | =head3 The special problem of stat time resolution |
1814 | |
2001 | |
1815 | The C<stat ()> system call only supports full-second resolution portably, and |
2002 | The C<stat ()> system call only supports full-second resolution portably, |
1816 | even on systems where the resolution is higher, most file systems still |
2003 | and even on systems where the resolution is higher, most file systems |
1817 | only support whole seconds. |
2004 | still only support whole seconds. |
1818 | |
2005 | |
1819 | That means that, if the time is the only thing that changes, you can |
2006 | That means that, if the time is the only thing that changes, you can |
1820 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2007 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1821 | calls your callback, which does something. When there is another update |
2008 | calls your callback, which does something. When there is another update |
1822 | within the same second, C<ev_stat> will be unable to detect unless the |
2009 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1979 | |
2166 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2167 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2168 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2169 | |
1983 | static void |
2170 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2171 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2172 | { |
1986 | free (w); |
2173 | free (w); |
1987 | // now do something you wanted to do when the program has |
2174 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2175 | // no longer anything immediate to do. |
1989 | } |
2176 | } |
1990 | |
2177 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2178 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2179 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2180 | ev_idle_start (loop, idle_cb); |
1994 | |
2181 | |
1995 | |
2182 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2183 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
… | |
… | |
2077 | |
2264 | |
2078 | static ev_io iow [nfd]; |
2265 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2266 | static ev_timer tw; |
2080 | |
2267 | |
2081 | static void |
2268 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2269 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2270 | { |
2084 | } |
2271 | } |
2085 | |
2272 | |
2086 | // create io watchers for each fd and a timer before blocking |
2273 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2274 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2275 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2276 | { |
2090 | int timeout = 3600000; |
2277 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2278 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2279 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2280 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2108 | } |
2295 | } |
2109 | } |
2296 | } |
2110 | |
2297 | |
2111 | // stop all watchers after blocking |
2298 | // stop all watchers after blocking |
2112 | static void |
2299 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2300 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2301 | { |
2115 | ev_timer_stop (loop, &tw); |
2302 | ev_timer_stop (loop, &tw); |
2116 | |
2303 | |
2117 | for (int i = 0; i < nfd; ++i) |
2304 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2305 | { |
… | |
… | |
2286 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2473 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2287 | used). |
2474 | used). |
2288 | |
2475 | |
2289 | struct ev_loop *loop_hi = ev_default_init (0); |
2476 | struct ev_loop *loop_hi = ev_default_init (0); |
2290 | struct ev_loop *loop_lo = 0; |
2477 | struct ev_loop *loop_lo = 0; |
2291 | struct ev_embed embed; |
2478 | ev_embed embed; |
2292 | |
2479 | |
2293 | // see if there is a chance of getting one that works |
2480 | // see if there is a chance of getting one that works |
2294 | // (remember that a flags value of 0 means autodetection) |
2481 | // (remember that a flags value of 0 means autodetection) |
2295 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2482 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2296 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2483 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2310 | kqueue implementation). Store the kqueue/socket-only event loop in |
2497 | kqueue implementation). Store the kqueue/socket-only event loop in |
2311 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2498 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2312 | |
2499 | |
2313 | struct ev_loop *loop = ev_default_init (0); |
2500 | struct ev_loop *loop = ev_default_init (0); |
2314 | struct ev_loop *loop_socket = 0; |
2501 | struct ev_loop *loop_socket = 0; |
2315 | struct ev_embed embed; |
2502 | ev_embed embed; |
2316 | |
2503 | |
2317 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2504 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2318 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2505 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2319 | { |
2506 | { |
2320 | ev_embed_init (&embed, 0, loop_socket); |
2507 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2384 | =over 4 |
2571 | =over 4 |
2385 | |
2572 | |
2386 | =item queueing from a signal handler context |
2573 | =item queueing from a signal handler context |
2387 | |
2574 | |
2388 | To implement race-free queueing, you simply add to the queue in the signal |
2575 | To implement race-free queueing, you simply add to the queue in the signal |
2389 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2576 | handler but you block the signal handler in the watcher callback. Here is |
2390 | some fictitious SIGUSR1 handler: |
2577 | an example that does that for some fictitious SIGUSR1 handler: |
2391 | |
2578 | |
2392 | static ev_async mysig; |
2579 | static ev_async mysig; |
2393 | |
2580 | |
2394 | static void |
2581 | static void |
2395 | sigusr1_handler (void) |
2582 | sigusr1_handler (void) |
… | |
… | |
2461 | =over 4 |
2648 | =over 4 |
2462 | |
2649 | |
2463 | =item ev_async_init (ev_async *, callback) |
2650 | =item ev_async_init (ev_async *, callback) |
2464 | |
2651 | |
2465 | Initialises and configures the async watcher - it has no parameters of any |
2652 | Initialises and configures the async watcher - it has no parameters of any |
2466 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2653 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2467 | trust me. |
2654 | trust me. |
2468 | |
2655 | |
2469 | =item ev_async_send (loop, ev_async *) |
2656 | =item ev_async_send (loop, ev_async *) |
2470 | |
2657 | |
2471 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2658 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
… | |
… | |
2502 | =over 4 |
2689 | =over 4 |
2503 | |
2690 | |
2504 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2691 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2505 | |
2692 | |
2506 | This function combines a simple timer and an I/O watcher, calls your |
2693 | This function combines a simple timer and an I/O watcher, calls your |
2507 | callback on whichever event happens first and automatically stop both |
2694 | callback on whichever event happens first and automatically stops both |
2508 | watchers. This is useful if you want to wait for a single event on an fd |
2695 | watchers. This is useful if you want to wait for a single event on an fd |
2509 | or timeout without having to allocate/configure/start/stop/free one or |
2696 | or timeout without having to allocate/configure/start/stop/free one or |
2510 | more watchers yourself. |
2697 | more watchers yourself. |
2511 | |
2698 | |
2512 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2699 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2513 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2700 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2514 | C<events> set will be created and started. |
2701 | the given C<fd> and C<events> set will be created and started. |
2515 | |
2702 | |
2516 | If C<timeout> is less than 0, then no timeout watcher will be |
2703 | If C<timeout> is less than 0, then no timeout watcher will be |
2517 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2704 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2518 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2705 | repeat = 0) will be started. C<0> is a valid timeout. |
2519 | dubious value. |
|
|
2520 | |
2706 | |
2521 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2707 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2522 | passed an C<revents> set like normal event callbacks (a combination of |
2708 | passed an C<revents> set like normal event callbacks (a combination of |
2523 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2709 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2524 | value passed to C<ev_once>: |
2710 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2711 | a timeout and an io event at the same time - you probably should give io |
|
|
2712 | events precedence. |
|
|
2713 | |
|
|
2714 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2525 | |
2715 | |
2526 | static void stdin_ready (int revents, void *arg) |
2716 | static void stdin_ready (int revents, void *arg) |
2527 | { |
2717 | { |
|
|
2718 | if (revents & EV_READ) |
|
|
2719 | /* stdin might have data for us, joy! */; |
2528 | if (revents & EV_TIMEOUT) |
2720 | else if (revents & EV_TIMEOUT) |
2529 | /* doh, nothing entered */; |
2721 | /* doh, nothing entered */; |
2530 | else if (revents & EV_READ) |
|
|
2531 | /* stdin might have data for us, joy! */; |
|
|
2532 | } |
2722 | } |
2533 | |
2723 | |
2534 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2724 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2535 | |
2725 | |
2536 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2726 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2537 | |
2727 | |
2538 | Feeds the given event set into the event loop, as if the specified event |
2728 | Feeds the given event set into the event loop, as if the specified event |
2539 | had happened for the specified watcher (which must be a pointer to an |
2729 | had happened for the specified watcher (which must be a pointer to an |
2540 | initialised but not necessarily started event watcher). |
2730 | initialised but not necessarily started event watcher). |
2541 | |
2731 | |
2542 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2732 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2543 | |
2733 | |
2544 | Feed an event on the given fd, as if a file descriptor backend detected |
2734 | Feed an event on the given fd, as if a file descriptor backend detected |
2545 | the given events it. |
2735 | the given events it. |
2546 | |
2736 | |
2547 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2737 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2548 | |
2738 | |
2549 | Feed an event as if the given signal occurred (C<loop> must be the default |
2739 | Feed an event as if the given signal occurred (C<loop> must be the default |
2550 | loop!). |
2740 | loop!). |
2551 | |
2741 | |
2552 | =back |
2742 | =back |
… | |
… | |
2787 | =item D |
2977 | =item D |
2788 | |
2978 | |
2789 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2979 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2790 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2980 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2791 | |
2981 | |
|
|
2982 | =item Ocaml |
|
|
2983 | |
|
|
2984 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
2985 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
2986 | |
2792 | =back |
2987 | =back |
2793 | |
2988 | |
2794 | |
2989 | |
2795 | =head1 MACRO MAGIC |
2990 | =head1 MACRO MAGIC |
2796 | |
2991 | |
… | |
… | |
2896 | |
3091 | |
2897 | #define EV_STANDALONE 1 |
3092 | #define EV_STANDALONE 1 |
2898 | #include "ev.h" |
3093 | #include "ev.h" |
2899 | |
3094 | |
2900 | Both header files and implementation files can be compiled with a C++ |
3095 | Both header files and implementation files can be compiled with a C++ |
2901 | compiler (at least, thats a stated goal, and breakage will be treated |
3096 | compiler (at least, that's a stated goal, and breakage will be treated |
2902 | as a bug). |
3097 | as a bug). |
2903 | |
3098 | |
2904 | You need the following files in your source tree, or in a directory |
3099 | You need the following files in your source tree, or in a directory |
2905 | in your include path (e.g. in libev/ when using -Ilibev): |
3100 | in your include path (e.g. in libev/ when using -Ilibev): |
2906 | |
3101 | |
… | |
… | |
3313 | =head2 THREADS AND COROUTINES |
3508 | =head2 THREADS AND COROUTINES |
3314 | |
3509 | |
3315 | =head3 THREADS |
3510 | =head3 THREADS |
3316 | |
3511 | |
3317 | All libev functions are reentrant and thread-safe unless explicitly |
3512 | All libev functions are reentrant and thread-safe unless explicitly |
3318 | documented otherwise, but it uses no locking itself. This means that you |
3513 | documented otherwise, but libev implements no locking itself. This means |
3319 | can use as many loops as you want in parallel, as long as there are no |
3514 | that you can use as many loops as you want in parallel, as long as there |
3320 | concurrent calls into any libev function with the same loop parameter |
3515 | are no concurrent calls into any libev function with the same loop |
3321 | (C<ev_default_*> calls have an implicit default loop parameter, of |
3516 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3322 | course): libev guarantees that different event loops share no data |
3517 | of course): libev guarantees that different event loops share no data |
3323 | structures that need any locking. |
3518 | structures that need any locking. |
3324 | |
3519 | |
3325 | Or to put it differently: calls with different loop parameters can be done |
3520 | Or to put it differently: calls with different loop parameters can be done |
3326 | concurrently from multiple threads, calls with the same loop parameter |
3521 | concurrently from multiple threads, calls with the same loop parameter |
3327 | must be done serially (but can be done from different threads, as long as |
3522 | must be done serially (but can be done from different threads, as long as |
… | |
… | |
3369 | |
3564 | |
3370 | =back |
3565 | =back |
3371 | |
3566 | |
3372 | =head3 COROUTINES |
3567 | =head3 COROUTINES |
3373 | |
3568 | |
3374 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3569 | Libev is very accommodating to coroutines ("cooperative threads"): |
3375 | libev fully supports nesting calls to it's functions from different |
3570 | libev fully supports nesting calls to its functions from different |
3376 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3571 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3377 | different coroutines and switch freely between both coroutines running the |
3572 | different coroutines, and switch freely between both coroutines running the |
3378 | loop, as long as you don't confuse yourself). The only exception is that |
3573 | loop, as long as you don't confuse yourself). The only exception is that |
3379 | you must not do this from C<ev_periodic> reschedule callbacks. |
3574 | you must not do this from C<ev_periodic> reschedule callbacks. |
3380 | |
3575 | |
3381 | Care has been taken to ensure that libev does not keep local state inside |
3576 | Care has been taken to ensure that libev does not keep local state inside |
3382 | C<ev_loop>, and other calls do not usually allow coroutine switches. |
3577 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3578 | they do not call any callbacks. |
3383 | |
3579 | |
3384 | =head2 COMPILER WARNINGS |
3580 | =head2 COMPILER WARNINGS |
3385 | |
3581 | |
3386 | Depending on your compiler and compiler settings, you might get no or a |
3582 | Depending on your compiler and compiler settings, you might get no or a |
3387 | lot of warnings when compiling libev code. Some people are apparently |
3583 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3408 | with any compiler warnings enabled unless you are prepared to cope with |
3604 | with any compiler warnings enabled unless you are prepared to cope with |
3409 | them (e.g. by ignoring them). Remember that warnings are just that: |
3605 | them (e.g. by ignoring them). Remember that warnings are just that: |
3410 | warnings, not errors, or proof of bugs. |
3606 | warnings, not errors, or proof of bugs. |
3411 | |
3607 | |
3412 | |
3608 | |
3413 | =head1 VALGRIND |
3609 | =head2 VALGRIND |
3414 | |
3610 | |
3415 | Valgrind has a special section here because it is a popular tool that is |
3611 | Valgrind has a special section here because it is a popular tool that is |
3416 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3612 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3417 | |
3613 | |
3418 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3614 | If you think you found a bug (memory leak, uninitialised data access etc.) |
… | |
… | |
3421 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3617 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3422 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3618 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3423 | ==2274== still reachable: 256 bytes in 1 blocks. |
3619 | ==2274== still reachable: 256 bytes in 1 blocks. |
3424 | |
3620 | |
3425 | Then there is no memory leak, just as memory accounted to global variables |
3621 | Then there is no memory leak, just as memory accounted to global variables |
3426 | is not a memleak - the memory is still being refernced, and didn't leak. |
3622 | is not a memleak - the memory is still being referenced, and didn't leak. |
3427 | |
3623 | |
3428 | Similarly, under some circumstances, valgrind might report kernel bugs |
3624 | Similarly, under some circumstances, valgrind might report kernel bugs |
3429 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3625 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3430 | although an acceptable workaround has been found here), or it might be |
3626 | although an acceptable workaround has been found here), or it might be |
3431 | confused. |
3627 | confused. |
… | |
… | |
3441 | |
3637 | |
3442 | If you need, for some reason, empty reports from valgrind for your project |
3638 | If you need, for some reason, empty reports from valgrind for your project |
3443 | I suggest using suppression lists. |
3639 | I suggest using suppression lists. |
3444 | |
3640 | |
3445 | |
3641 | |
3446 | |
|
|
3447 | =head1 COMPLEXITIES |
|
|
3448 | |
|
|
3449 | In this section the complexities of (many of) the algorithms used inside |
|
|
3450 | libev will be explained. For complexity discussions about backends see the |
|
|
3451 | documentation for C<ev_default_init>. |
|
|
3452 | |
|
|
3453 | All of the following are about amortised time: If an array needs to be |
|
|
3454 | extended, libev needs to realloc and move the whole array, but this |
|
|
3455 | happens asymptotically never with higher number of elements, so O(1) might |
|
|
3456 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3457 | it is much faster and asymptotically approaches constant time. |
|
|
3458 | |
|
|
3459 | =over 4 |
|
|
3460 | |
|
|
3461 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3462 | |
|
|
3463 | This means that, when you have a watcher that triggers in one hour and |
|
|
3464 | there are 100 watchers that would trigger before that then inserting will |
|
|
3465 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3466 | |
|
|
3467 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3468 | |
|
|
3469 | That means that changing a timer costs less than removing/adding them |
|
|
3470 | as only the relative motion in the event queue has to be paid for. |
|
|
3471 | |
|
|
3472 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3473 | |
|
|
3474 | These just add the watcher into an array or at the head of a list. |
|
|
3475 | |
|
|
3476 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3477 | |
|
|
3478 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3479 | |
|
|
3480 | These watchers are stored in lists then need to be walked to find the |
|
|
3481 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3482 | have many watchers waiting for the same fd or signal). |
|
|
3483 | |
|
|
3484 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3485 | |
|
|
3486 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3487 | fixed position in the storage array. |
|
|
3488 | |
|
|
3489 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3490 | |
|
|
3491 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3492 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3493 | on backend and whether C<ev_io_set> was used). |
|
|
3494 | |
|
|
3495 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3496 | |
|
|
3497 | =item Priority handling: O(number_of_priorities) |
|
|
3498 | |
|
|
3499 | Priorities are implemented by allocating some space for each |
|
|
3500 | priority. When doing priority-based operations, libev usually has to |
|
|
3501 | linearly search all the priorities, but starting/stopping and activating |
|
|
3502 | watchers becomes O(1) with respect to priority handling. |
|
|
3503 | |
|
|
3504 | =item Sending an ev_async: O(1) |
|
|
3505 | |
|
|
3506 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3507 | |
|
|
3508 | =item Processing signals: O(max_signal_number) |
|
|
3509 | |
|
|
3510 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3511 | calls in the current loop iteration. Checking for async and signal events |
|
|
3512 | involves iterating over all running async watchers or all signal numbers. |
|
|
3513 | |
|
|
3514 | =back |
|
|
3515 | |
|
|
3516 | |
|
|
3517 | =head1 PORTABILITY |
3642 | =head1 PORTABILITY NOTES |
3518 | |
3643 | |
3519 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3644 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3520 | |
3645 | |
3521 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3646 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3522 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3647 | requires, and its I/O model is fundamentally incompatible with the POSIX |
… | |
… | |
3667 | =back |
3792 | =back |
3668 | |
3793 | |
3669 | If you know of other additional requirements drop me a note. |
3794 | If you know of other additional requirements drop me a note. |
3670 | |
3795 | |
3671 | |
3796 | |
|
|
3797 | =head1 ALGORITHMIC COMPLEXITIES |
|
|
3798 | |
|
|
3799 | In this section the complexities of (many of) the algorithms used inside |
|
|
3800 | libev will be documented. For complexity discussions about backends see |
|
|
3801 | the documentation for C<ev_default_init>. |
|
|
3802 | |
|
|
3803 | All of the following are about amortised time: If an array needs to be |
|
|
3804 | extended, libev needs to realloc and move the whole array, but this |
|
|
3805 | happens asymptotically rarer with higher number of elements, so O(1) might |
|
|
3806 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3807 | average it is much faster and asymptotically approaches constant time. |
|
|
3808 | |
|
|
3809 | =over 4 |
|
|
3810 | |
|
|
3811 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
|
|
3812 | |
|
|
3813 | This means that, when you have a watcher that triggers in one hour and |
|
|
3814 | there are 100 watchers that would trigger before that, then inserting will |
|
|
3815 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3816 | |
|
|
3817 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
|
|
3818 | |
|
|
3819 | That means that changing a timer costs less than removing/adding them, |
|
|
3820 | as only the relative motion in the event queue has to be paid for. |
|
|
3821 | |
|
|
3822 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
|
|
3823 | |
|
|
3824 | These just add the watcher into an array or at the head of a list. |
|
|
3825 | |
|
|
3826 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
|
|
3827 | |
|
|
3828 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
|
|
3829 | |
|
|
3830 | These watchers are stored in lists, so they need to be walked to find the |
|
|
3831 | correct watcher to remove. The lists are usually short (you don't usually |
|
|
3832 | have many watchers waiting for the same fd or signal: one is typical, two |
|
|
3833 | is rare). |
|
|
3834 | |
|
|
3835 | =item Finding the next timer in each loop iteration: O(1) |
|
|
3836 | |
|
|
3837 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3838 | fixed position in the storage array. |
|
|
3839 | |
|
|
3840 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3841 | |
|
|
3842 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3843 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3844 | on backend and whether C<ev_io_set> was used). |
|
|
3845 | |
|
|
3846 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3847 | |
|
|
3848 | =item Priority handling: O(number_of_priorities) |
|
|
3849 | |
|
|
3850 | Priorities are implemented by allocating some space for each |
|
|
3851 | priority. When doing priority-based operations, libev usually has to |
|
|
3852 | linearly search all the priorities, but starting/stopping and activating |
|
|
3853 | watchers becomes O(1) with respect to priority handling. |
|
|
3854 | |
|
|
3855 | =item Sending an ev_async: O(1) |
|
|
3856 | |
|
|
3857 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3858 | |
|
|
3859 | =item Processing signals: O(max_signal_number) |
|
|
3860 | |
|
|
3861 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3862 | calls in the current loop iteration. Checking for async and signal events |
|
|
3863 | involves iterating over all running async watchers or all signal numbers. |
|
|
3864 | |
|
|
3865 | =back |
|
|
3866 | |
|
|
3867 | |
3672 | =head1 AUTHOR |
3868 | =head1 AUTHOR |
3673 | |
3869 | |
3674 | Marc Lehmann <libev@schmorp.de>. |
3870 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3675 | |
3871 | |