… | |
… | |
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 | |
… | |
… | |
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 syscalls are the most misdesigned of the more advanced event |
388 | support for dup. |
392 | mechanisms: problems include silently dropping fds, requiring a system |
|
|
393 | call per change per fd (and unnecessary guessing of parameters), problems |
|
|
394 | with dup and so on. The biggest issue is fork races, however - if a |
|
|
395 | program forks then I<both> parent and child process have to recreate the |
|
|
396 | epoll set, which can take considerable time (one syscall per fd) and is of |
|
|
397 | course hard to detect. |
|
|
398 | |
|
|
399 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
|
|
400 | of course doesn't, and epoll just loves to report events for totally |
|
|
401 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
402 | even remove them from the set) than registered in the set (especially |
|
|
403 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
404 | employing an additional generation counter and comparing that against the |
|
|
405 | events to filter out spurious ones. |
389 | |
406 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
407 | 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 |
408 | will result in some caching, there is still a system call per such incident |
392 | (because the fd could point to a different file description now), so its |
409 | (because the fd could point to a different file description now), so its |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
410 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
394 | very well if you register events for both fds. |
411 | very well if you register events for both fds. |
395 | |
412 | |
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 | |
|
|
400 | Best performance from this backend is achieved by not unregistering all |
413 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
414 | 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 |
415 | 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 |
416 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
417 | extra overhead. A fork can both result in spurious notifications as well |
|
|
418 | as in libev having to destroy and recreate the epoll object, which can |
|
|
419 | take considerable time and thus should be avoided. |
405 | |
420 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
421 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
422 | all kernel versions tested so far. |
408 | |
423 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
424 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
424 | |
439 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
440 | 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 |
441 | 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 |
442 | 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 |
443 | 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 |
444 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
445 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
446 | cases |
431 | |
447 | |
432 | This backend usually performs well under most conditions. |
448 | This backend usually performs well under most conditions. |
433 | |
449 | |
434 | While nominally embeddable in other event loops, this doesn't work |
450 | 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 |
451 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
464 | might perform better. |
480 | might perform better. |
465 | |
481 | |
466 | On the positive side, with the exception of the spurious readiness |
482 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
483 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
484 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
485 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
486 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
487 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
488 | C<EVBACKEND_POLL>. |
473 | |
489 | |
474 | =item C<EVBACKEND_ALL> |
490 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
543 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
544 | 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 |
545 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
546 | for example). |
531 | |
547 | |
532 | Note that certain global state, such as signal state, will not be freed by |
548 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
549 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
550 | as signal and child watchers) would need to be stopped manually. |
535 | |
551 | |
536 | In general it is not advisable to call this function except in the |
552 | 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 |
553 | 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 |
554 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
555 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
710 | respectively). |
726 | respectively). |
711 | |
727 | |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
728 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
713 | running when nothing else is active. |
729 | running when nothing else is active. |
714 | |
730 | |
715 | struct ev_signal exitsig; |
731 | ev_signal exitsig; |
716 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
732 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
717 | ev_signal_start (loop, &exitsig); |
733 | ev_signal_start (loop, &exitsig); |
718 | evf_unref (loop); |
734 | evf_unref (loop); |
719 | |
735 | |
720 | Example: For some weird reason, unregister the above signal handler again. |
736 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
768 | they fire on, say, one-second boundaries only. |
784 | they fire on, say, one-second boundaries only. |
769 | |
785 | |
770 | =item ev_loop_verify (loop) |
786 | =item ev_loop_verify (loop) |
771 | |
787 | |
772 | This function only does something when C<EV_VERIFY> support has been |
788 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
789 | compiled in, which is the default for non-minimal builds. It tries to go |
774 | through all internal structures and checks them for validity. If anything |
790 | through all internal structures and checks them for validity. If anything |
775 | is found to be inconsistent, it will print an error message to standard |
791 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
792 | error and call C<abort ()>. |
777 | |
793 | |
778 | This can be used to catch bugs inside libev itself: under normal |
794 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
782 | =back |
798 | =back |
783 | |
799 | |
784 | |
800 | |
785 | =head1 ANATOMY OF A WATCHER |
801 | =head1 ANATOMY OF A WATCHER |
786 | |
802 | |
|
|
803 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
804 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
805 | watchers and C<ev_io_start> for I/O watchers. |
|
|
806 | |
787 | A watcher is a structure that you create and register to record your |
807 | A watcher is a structure that you create and register to record your |
788 | interest in some event. For instance, if you want to wait for STDIN to |
808 | interest in some event. For instance, if you want to wait for STDIN to |
789 | become readable, you would create an C<ev_io> watcher for that: |
809 | become readable, you would create an C<ev_io> watcher for that: |
790 | |
810 | |
791 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
811 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
792 | { |
812 | { |
793 | ev_io_stop (w); |
813 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
814 | ev_unloop (loop, EVUNLOOP_ALL); |
795 | } |
815 | } |
796 | |
816 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
817 | struct ev_loop *loop = ev_default_loop (0); |
|
|
818 | |
798 | struct ev_io stdin_watcher; |
819 | ev_io stdin_watcher; |
|
|
820 | |
799 | ev_init (&stdin_watcher, my_cb); |
821 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
822 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
823 | ev_io_start (loop, &stdin_watcher); |
|
|
824 | |
802 | ev_loop (loop, 0); |
825 | ev_loop (loop, 0); |
803 | |
826 | |
804 | As you can see, you are responsible for allocating the memory for your |
827 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
828 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
829 | stack). |
|
|
830 | |
|
|
831 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
832 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
807 | |
833 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
834 | Each watcher structure must be initialised by a call to C<ev_init |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
835 | (watcher *, callback)>, which expects a callback to be provided. This |
810 | callback gets invoked each time the event occurs (or, in the case of I/O |
836 | callback gets invoked each time the event occurs (or, in the case of I/O |
811 | watchers, each time the event loop detects that the file descriptor given |
837 | watchers, each time the event loop detects that the file descriptor given |
812 | is readable and/or writable). |
838 | is readable and/or writable). |
813 | |
839 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
840 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
841 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
842 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
843 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
844 | |
819 | To make the watcher actually watch out for events, you have to start it |
845 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
846 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
847 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
848 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
849 | |
824 | As long as your watcher is active (has been started but not stopped) you |
850 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
851 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
852 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
853 | |
828 | Each and every callback receives the event loop pointer as first, the |
854 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
855 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
856 | third argument. |
831 | |
857 | |
… | |
… | |
894 | =item C<EV_ERROR> |
920 | =item C<EV_ERROR> |
895 | |
921 | |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
922 | An unspecified error has occurred, the watcher has been stopped. This might |
897 | happen because the watcher could not be properly started because libev |
923 | happen because the watcher could not be properly started because libev |
898 | ran out of memory, a file descriptor was found to be closed or any other |
924 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
925 | problem. Libev considers these application bugs. |
|
|
926 | |
899 | problem. You best act on it by reporting the problem and somehow coping |
927 | You best act on it by reporting the problem and somehow coping with the |
900 | with the watcher being stopped. |
928 | watcher being stopped. Note that well-written programs should not receive |
|
|
929 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
930 | bug in your program. |
901 | |
931 | |
902 | Libev will usually signal a few "dummy" events together with an error, for |
932 | Libev will usually signal a few "dummy" events together with an error, for |
903 | example it might indicate that a fd is readable or writable, and if your |
933 | example it might indicate that a fd is readable or writable, and if your |
904 | callbacks is well-written it can just attempt the operation and cope with |
934 | callbacks is well-written it can just attempt the operation and cope with |
905 | the error from read() or write(). This will not work in multi-threaded |
935 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
908 | |
938 | |
909 | =back |
939 | =back |
910 | |
940 | |
911 | =head2 GENERIC WATCHER FUNCTIONS |
941 | =head2 GENERIC WATCHER FUNCTIONS |
912 | |
942 | |
913 | In the following description, C<TYPE> stands for the watcher type, |
|
|
914 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
915 | |
|
|
916 | =over 4 |
943 | =over 4 |
917 | |
944 | |
918 | =item C<ev_init> (ev_TYPE *watcher, callback) |
945 | =item C<ev_init> (ev_TYPE *watcher, callback) |
919 | |
946 | |
920 | This macro initialises the generic portion of a watcher. The contents |
947 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
925 | which rolls both calls into one. |
952 | which rolls both calls into one. |
926 | |
953 | |
927 | You can reinitialise a watcher at any time as long as it has been stopped |
954 | You can reinitialise a watcher at any time as long as it has been stopped |
928 | (or never started) and there are no pending events outstanding. |
955 | (or never started) and there are no pending events outstanding. |
929 | |
956 | |
930 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
957 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
931 | int revents)>. |
958 | int revents)>. |
932 | |
959 | |
933 | Example: Initialise an C<ev_io> watcher in two steps. |
960 | Example: Initialise an C<ev_io> watcher in two steps. |
934 | |
961 | |
935 | ev_io w; |
962 | ev_io w; |
… | |
… | |
1028 | The default priority used by watchers when no priority has been set is |
1055 | The default priority used by watchers when no priority has been set is |
1029 | always C<0>, which is supposed to not be too high and not be too low :). |
1056 | always C<0>, which is supposed to not be too high and not be too low :). |
1030 | |
1057 | |
1031 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1058 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1032 | fine, as long as you do not mind that the priority value you query might |
1059 | fine, as long as you do not mind that the priority value you query might |
1033 | or might not have been adjusted to be within valid range. |
1060 | or might not have been clamped to the valid range. |
1034 | |
1061 | |
1035 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1062 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1036 | |
1063 | |
1037 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1064 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1038 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1065 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1060 | member, you can also "subclass" the watcher type and provide your own |
1087 | member, you can also "subclass" the watcher type and provide your own |
1061 | data: |
1088 | data: |
1062 | |
1089 | |
1063 | struct my_io |
1090 | struct my_io |
1064 | { |
1091 | { |
1065 | struct ev_io io; |
1092 | ev_io io; |
1066 | int otherfd; |
1093 | int otherfd; |
1067 | void *somedata; |
1094 | void *somedata; |
1068 | struct whatever *mostinteresting; |
1095 | struct whatever *mostinteresting; |
1069 | }; |
1096 | }; |
1070 | |
1097 | |
… | |
… | |
1073 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1100 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1074 | |
1101 | |
1075 | And since your callback will be called with a pointer to the watcher, you |
1102 | And since your callback will be called with a pointer to the watcher, you |
1076 | can cast it back to your own type: |
1103 | can cast it back to your own type: |
1077 | |
1104 | |
1078 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1105 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1079 | { |
1106 | { |
1080 | struct my_io *w = (struct my_io *)w_; |
1107 | struct my_io *w = (struct my_io *)w_; |
1081 | ... |
1108 | ... |
1082 | } |
1109 | } |
1083 | |
1110 | |
… | |
… | |
1101 | programmers): |
1128 | programmers): |
1102 | |
1129 | |
1103 | #include <stddef.h> |
1130 | #include <stddef.h> |
1104 | |
1131 | |
1105 | static void |
1132 | static void |
1106 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1133 | t1_cb (EV_P_ ev_timer *w, int revents) |
1107 | { |
1134 | { |
1108 | struct my_biggy big = (struct my_biggy * |
1135 | struct my_biggy big = (struct my_biggy * |
1109 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1136 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1110 | } |
1137 | } |
1111 | |
1138 | |
1112 | static void |
1139 | static void |
1113 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1140 | t2_cb (EV_P_ ev_timer *w, int revents) |
1114 | { |
1141 | { |
1115 | struct my_biggy big = (struct my_biggy * |
1142 | struct my_biggy big = (struct my_biggy * |
1116 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1143 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1117 | } |
1144 | } |
1118 | |
1145 | |
… | |
… | |
1253 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1280 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1254 | readable, but only once. Since it is likely line-buffered, you could |
1281 | readable, but only once. Since it is likely line-buffered, you could |
1255 | attempt to read a whole line in the callback. |
1282 | attempt to read a whole line in the callback. |
1256 | |
1283 | |
1257 | static void |
1284 | static void |
1258 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1285 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1259 | { |
1286 | { |
1260 | ev_io_stop (loop, w); |
1287 | ev_io_stop (loop, w); |
1261 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1288 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1262 | } |
1289 | } |
1263 | |
1290 | |
1264 | ... |
1291 | ... |
1265 | struct ev_loop *loop = ev_default_init (0); |
1292 | struct ev_loop *loop = ev_default_init (0); |
1266 | struct ev_io stdin_readable; |
1293 | ev_io stdin_readable; |
1267 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1294 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1268 | ev_io_start (loop, &stdin_readable); |
1295 | ev_io_start (loop, &stdin_readable); |
1269 | ev_loop (loop, 0); |
1296 | ev_loop (loop, 0); |
1270 | |
1297 | |
1271 | |
1298 | |
… | |
… | |
1282 | |
1309 | |
1283 | The callback is guaranteed to be invoked only I<after> its timeout has |
1310 | The callback is guaranteed to be invoked only I<after> its timeout has |
1284 | passed, but if multiple timers become ready during the same loop iteration |
1311 | passed, but if multiple timers become ready during the same loop iteration |
1285 | then order of execution is undefined. |
1312 | then order of execution is undefined. |
1286 | |
1313 | |
|
|
1314 | =head3 Be smart about timeouts |
|
|
1315 | |
|
|
1316 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1317 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1318 | you want to raise some error after a while. |
|
|
1319 | |
|
|
1320 | What follows are some ways to handle this problem, from obvious and |
|
|
1321 | inefficient to smart and efficient. |
|
|
1322 | |
|
|
1323 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1324 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1325 | data or other life sign was received). |
|
|
1326 | |
|
|
1327 | =over 4 |
|
|
1328 | |
|
|
1329 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1330 | |
|
|
1331 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1332 | start the watcher: |
|
|
1333 | |
|
|
1334 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1335 | ev_timer_start (loop, timer); |
|
|
1336 | |
|
|
1337 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1338 | and start it again: |
|
|
1339 | |
|
|
1340 | ev_timer_stop (loop, timer); |
|
|
1341 | ev_timer_set (timer, 60., 0.); |
|
|
1342 | ev_timer_start (loop, timer); |
|
|
1343 | |
|
|
1344 | This is relatively simple to implement, but means that each time there is |
|
|
1345 | some activity, libev will first have to remove the timer from its internal |
|
|
1346 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1347 | still not a constant-time operation. |
|
|
1348 | |
|
|
1349 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1350 | |
|
|
1351 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1352 | C<ev_timer_start>. |
|
|
1353 | |
|
|
1354 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1355 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1356 | successfully read or write some data. If you go into an idle state where |
|
|
1357 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1358 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1359 | |
|
|
1360 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1361 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1362 | member and C<ev_timer_again>. |
|
|
1363 | |
|
|
1364 | At start: |
|
|
1365 | |
|
|
1366 | ev_timer_init (timer, callback); |
|
|
1367 | timer->repeat = 60.; |
|
|
1368 | ev_timer_again (loop, timer); |
|
|
1369 | |
|
|
1370 | Each time there is some activity: |
|
|
1371 | |
|
|
1372 | ev_timer_again (loop, timer); |
|
|
1373 | |
|
|
1374 | It is even possible to change the time-out on the fly, regardless of |
|
|
1375 | whether the watcher is active or not: |
|
|
1376 | |
|
|
1377 | timer->repeat = 30.; |
|
|
1378 | ev_timer_again (loop, timer); |
|
|
1379 | |
|
|
1380 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1381 | you want to modify its timeout value, as libev does not have to completely |
|
|
1382 | remove and re-insert the timer from/into its internal data structure. |
|
|
1383 | |
|
|
1384 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1385 | |
|
|
1386 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1387 | |
|
|
1388 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1389 | relatively long compared to the intervals between other activity - in |
|
|
1390 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1391 | associated activity resets. |
|
|
1392 | |
|
|
1393 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1394 | but remember the time of last activity, and check for a real timeout only |
|
|
1395 | within the callback: |
|
|
1396 | |
|
|
1397 | ev_tstamp last_activity; // time of last activity |
|
|
1398 | |
|
|
1399 | static void |
|
|
1400 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1401 | { |
|
|
1402 | ev_tstamp now = ev_now (EV_A); |
|
|
1403 | ev_tstamp timeout = last_activity + 60.; |
|
|
1404 | |
|
|
1405 | // if last_activity + 60. is older than now, we did time out |
|
|
1406 | if (timeout < now) |
|
|
1407 | { |
|
|
1408 | // timeout occured, take action |
|
|
1409 | } |
|
|
1410 | else |
|
|
1411 | { |
|
|
1412 | // callback was invoked, but there was some activity, re-arm |
|
|
1413 | // the watcher to fire in last_activity + 60, which is |
|
|
1414 | // guaranteed to be in the future, so "again" is positive: |
|
|
1415 | w->again = timeout - now; |
|
|
1416 | ev_timer_again (EV_A_ w); |
|
|
1417 | } |
|
|
1418 | } |
|
|
1419 | |
|
|
1420 | To summarise the callback: first calculate the real timeout (defined |
|
|
1421 | as "60 seconds after the last activity"), then check if that time has |
|
|
1422 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1423 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1424 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1425 | a timeout then. |
|
|
1426 | |
|
|
1427 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1428 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1429 | |
|
|
1430 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1431 | minus half the average time between activity), but virtually no calls to |
|
|
1432 | libev to change the timeout. |
|
|
1433 | |
|
|
1434 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1435 | to the current time (meaning we just have some activity :), then call the |
|
|
1436 | callback, which will "do the right thing" and start the timer: |
|
|
1437 | |
|
|
1438 | ev_timer_init (timer, callback); |
|
|
1439 | last_activity = ev_now (loop); |
|
|
1440 | callback (loop, timer, EV_TIMEOUT); |
|
|
1441 | |
|
|
1442 | And when there is some activity, simply store the current time in |
|
|
1443 | C<last_activity>, no libev calls at all: |
|
|
1444 | |
|
|
1445 | last_actiivty = ev_now (loop); |
|
|
1446 | |
|
|
1447 | This technique is slightly more complex, but in most cases where the |
|
|
1448 | time-out is unlikely to be triggered, much more efficient. |
|
|
1449 | |
|
|
1450 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1451 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1452 | fix things for you. |
|
|
1453 | |
|
|
1454 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1455 | |
|
|
1456 | If there is not one request, but many thousands (millions...), all |
|
|
1457 | employing some kind of timeout with the same timeout value, then one can |
|
|
1458 | do even better: |
|
|
1459 | |
|
|
1460 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1461 | at the I<end> of the list. |
|
|
1462 | |
|
|
1463 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1464 | the list is expected to fire (for example, using the technique #3). |
|
|
1465 | |
|
|
1466 | When there is some activity, remove the timer from the list, recalculate |
|
|
1467 | the timeout, append it to the end of the list again, and make sure to |
|
|
1468 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1469 | |
|
|
1470 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1471 | starting, stopping and updating the timers, at the expense of a major |
|
|
1472 | complication, and having to use a constant timeout. The constant timeout |
|
|
1473 | ensures that the list stays sorted. |
|
|
1474 | |
|
|
1475 | =back |
|
|
1476 | |
|
|
1477 | So which method the best? |
|
|
1478 | |
|
|
1479 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1480 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1481 | better, and isn't very complicated either. In most case, choosing either |
|
|
1482 | one is fine, with #3 being better in typical situations. |
|
|
1483 | |
|
|
1484 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1485 | rather complicated, but extremely efficient, something that really pays |
|
|
1486 | off after the first million or so of active timers, i.e. it's usually |
|
|
1487 | overkill :) |
|
|
1488 | |
1287 | =head3 The special problem of time updates |
1489 | =head3 The special problem of time updates |
1288 | |
1490 | |
1289 | Establishing the current time is a costly operation (it usually takes at |
1491 | Establishing the current time is a costly operation (it usually takes at |
1290 | least two system calls): EV therefore updates its idea of the current |
1492 | least two system calls): EV therefore updates its idea of the current |
1291 | time only before and after C<ev_loop> collects new events, which causes a |
1493 | time only before and after C<ev_loop> collects new events, which causes a |
… | |
… | |
1334 | If the timer is started but non-repeating, stop it (as if it timed out). |
1536 | If the timer is started but non-repeating, stop it (as if it timed out). |
1335 | |
1537 | |
1336 | If the timer is repeating, either start it if necessary (with the |
1538 | If the timer is repeating, either start it if necessary (with the |
1337 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1539 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1338 | |
1540 | |
1339 | This sounds a bit complicated, but here is a useful and typical |
1541 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1340 | example: Imagine you have a TCP connection and you want a so-called idle |
1542 | usage example. |
1341 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1342 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1343 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1344 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1345 | you go into an idle state where you do not expect data to travel on the |
|
|
1346 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1347 | automatically restart it if need be. |
|
|
1348 | |
|
|
1349 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1350 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1351 | |
|
|
1352 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1353 | ev_timer_again (loop, timer); |
|
|
1354 | ... |
|
|
1355 | timer->again = 17.; |
|
|
1356 | ev_timer_again (loop, timer); |
|
|
1357 | ... |
|
|
1358 | timer->again = 10.; |
|
|
1359 | ev_timer_again (loop, timer); |
|
|
1360 | |
|
|
1361 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1362 | you want to modify its timeout value. |
|
|
1363 | |
|
|
1364 | Note, however, that it is often even more efficient to remember the |
|
|
1365 | time of the last activity and let the timer time-out naturally. In the |
|
|
1366 | callback, you then check whether the time-out is real, or, if there was |
|
|
1367 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1368 | timeout - ev_now ()" seconds. |
|
|
1369 | |
1543 | |
1370 | =item ev_tstamp repeat [read-write] |
1544 | =item ev_tstamp repeat [read-write] |
1371 | |
1545 | |
1372 | The current C<repeat> value. Will be used each time the watcher times out |
1546 | The current C<repeat> value. Will be used each time the watcher times out |
1373 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1547 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1378 | =head3 Examples |
1552 | =head3 Examples |
1379 | |
1553 | |
1380 | Example: Create a timer that fires after 60 seconds. |
1554 | Example: Create a timer that fires after 60 seconds. |
1381 | |
1555 | |
1382 | static void |
1556 | static void |
1383 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1557 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1384 | { |
1558 | { |
1385 | .. one minute over, w is actually stopped right here |
1559 | .. one minute over, w is actually stopped right here |
1386 | } |
1560 | } |
1387 | |
1561 | |
1388 | struct ev_timer mytimer; |
1562 | ev_timer mytimer; |
1389 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1563 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1390 | ev_timer_start (loop, &mytimer); |
1564 | ev_timer_start (loop, &mytimer); |
1391 | |
1565 | |
1392 | Example: Create a timeout timer that times out after 10 seconds of |
1566 | Example: Create a timeout timer that times out after 10 seconds of |
1393 | inactivity. |
1567 | inactivity. |
1394 | |
1568 | |
1395 | static void |
1569 | static void |
1396 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1570 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1397 | { |
1571 | { |
1398 | .. ten seconds without any activity |
1572 | .. ten seconds without any activity |
1399 | } |
1573 | } |
1400 | |
1574 | |
1401 | struct ev_timer mytimer; |
1575 | ev_timer mytimer; |
1402 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1576 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1403 | ev_timer_again (&mytimer); /* start timer */ |
1577 | ev_timer_again (&mytimer); /* start timer */ |
1404 | ev_loop (loop, 0); |
1578 | ev_loop (loop, 0); |
1405 | |
1579 | |
1406 | // and in some piece of code that gets executed on any "activity": |
1580 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1492 | |
1666 | |
1493 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1667 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1494 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1668 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1495 | only event loop modification you are allowed to do). |
1669 | only event loop modification you are allowed to do). |
1496 | |
1670 | |
1497 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1671 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1498 | *w, ev_tstamp now)>, e.g.: |
1672 | *w, ev_tstamp now)>, e.g.: |
1499 | |
1673 | |
|
|
1674 | static ev_tstamp |
1500 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1675 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1501 | { |
1676 | { |
1502 | return now + 60.; |
1677 | return now + 60.; |
1503 | } |
1678 | } |
1504 | |
1679 | |
1505 | It must return the next time to trigger, based on the passed time value |
1680 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1542 | |
1717 | |
1543 | The current interval value. Can be modified any time, but changes only |
1718 | The current interval value. Can be modified any time, but changes only |
1544 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1719 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1545 | called. |
1720 | called. |
1546 | |
1721 | |
1547 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1722 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1548 | |
1723 | |
1549 | The current reschedule callback, or C<0>, if this functionality is |
1724 | The current reschedule callback, or C<0>, if this functionality is |
1550 | switched off. Can be changed any time, but changes only take effect when |
1725 | switched off. Can be changed any time, but changes only take effect when |
1551 | the periodic timer fires or C<ev_periodic_again> is being called. |
1726 | the periodic timer fires or C<ev_periodic_again> is being called. |
1552 | |
1727 | |
… | |
… | |
1557 | Example: Call a callback every hour, or, more precisely, whenever the |
1732 | Example: Call a callback every hour, or, more precisely, whenever the |
1558 | system time is divisible by 3600. The callback invocation times have |
1733 | system time is divisible by 3600. The callback invocation times have |
1559 | potentially a lot of jitter, but good long-term stability. |
1734 | potentially a lot of jitter, but good long-term stability. |
1560 | |
1735 | |
1561 | static void |
1736 | static void |
1562 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1737 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1563 | { |
1738 | { |
1564 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1739 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1565 | } |
1740 | } |
1566 | |
1741 | |
1567 | struct ev_periodic hourly_tick; |
1742 | ev_periodic hourly_tick; |
1568 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1743 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1569 | ev_periodic_start (loop, &hourly_tick); |
1744 | ev_periodic_start (loop, &hourly_tick); |
1570 | |
1745 | |
1571 | Example: The same as above, but use a reschedule callback to do it: |
1746 | Example: The same as above, but use a reschedule callback to do it: |
1572 | |
1747 | |
1573 | #include <math.h> |
1748 | #include <math.h> |
1574 | |
1749 | |
1575 | static ev_tstamp |
1750 | static ev_tstamp |
1576 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1751 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1577 | { |
1752 | { |
1578 | return now + (3600. - fmod (now, 3600.)); |
1753 | return now + (3600. - fmod (now, 3600.)); |
1579 | } |
1754 | } |
1580 | |
1755 | |
1581 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1756 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1582 | |
1757 | |
1583 | Example: Call a callback every hour, starting now: |
1758 | Example: Call a callback every hour, starting now: |
1584 | |
1759 | |
1585 | struct ev_periodic hourly_tick; |
1760 | ev_periodic hourly_tick; |
1586 | ev_periodic_init (&hourly_tick, clock_cb, |
1761 | ev_periodic_init (&hourly_tick, clock_cb, |
1587 | fmod (ev_now (loop), 3600.), 3600., 0); |
1762 | fmod (ev_now (loop), 3600.), 3600., 0); |
1588 | ev_periodic_start (loop, &hourly_tick); |
1763 | ev_periodic_start (loop, &hourly_tick); |
1589 | |
1764 | |
1590 | |
1765 | |
… | |
… | |
1632 | =head3 Examples |
1807 | =head3 Examples |
1633 | |
1808 | |
1634 | Example: Try to exit cleanly on SIGINT. |
1809 | Example: Try to exit cleanly on SIGINT. |
1635 | |
1810 | |
1636 | static void |
1811 | static void |
1637 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1812 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1638 | { |
1813 | { |
1639 | ev_unloop (loop, EVUNLOOP_ALL); |
1814 | ev_unloop (loop, EVUNLOOP_ALL); |
1640 | } |
1815 | } |
1641 | |
1816 | |
1642 | struct ev_signal signal_watcher; |
1817 | ev_signal signal_watcher; |
1643 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1818 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1644 | ev_signal_start (loop, &signal_watcher); |
1819 | ev_signal_start (loop, &signal_watcher); |
1645 | |
1820 | |
1646 | |
1821 | |
1647 | =head2 C<ev_child> - watch out for process status changes |
1822 | =head2 C<ev_child> - watch out for process status changes |
… | |
… | |
1722 | its completion. |
1897 | its completion. |
1723 | |
1898 | |
1724 | ev_child cw; |
1899 | ev_child cw; |
1725 | |
1900 | |
1726 | static void |
1901 | static void |
1727 | child_cb (EV_P_ struct ev_child *w, int revents) |
1902 | child_cb (EV_P_ ev_child *w, int revents) |
1728 | { |
1903 | { |
1729 | ev_child_stop (EV_A_ w); |
1904 | ev_child_stop (EV_A_ w); |
1730 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1905 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1731 | } |
1906 | } |
1732 | |
1907 | |
… | |
… | |
1747 | |
1922 | |
1748 | |
1923 | |
1749 | =head2 C<ev_stat> - did the file attributes just change? |
1924 | =head2 C<ev_stat> - did the file attributes just change? |
1750 | |
1925 | |
1751 | This watches a file system path for attribute changes. That is, it calls |
1926 | This watches a file system path for attribute changes. That is, it calls |
1752 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1927 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1753 | compared to the last time, invoking the callback if it did. |
1928 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1929 | it did. |
1754 | |
1930 | |
1755 | The path does not need to exist: changing from "path exists" to "path does |
1931 | The path does not need to exist: changing from "path exists" to "path does |
1756 | not exist" is a status change like any other. The condition "path does |
1932 | not exist" is a status change like any other. The condition "path does |
1757 | not exist" is signified by the C<st_nlink> field being zero (which is |
1933 | not exist" is signified by the C<st_nlink> field being zero (which is |
1758 | otherwise always forced to be at least one) and all the other fields of |
1934 | otherwise always forced to be at least one) and all the other fields of |
1759 | the stat buffer having unspecified contents. |
1935 | the stat buffer having unspecified contents. |
1760 | |
1936 | |
1761 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1937 | The path I<must not> end in a slash or contain special components such as |
|
|
1938 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1762 | relative and your working directory changes, the behaviour is undefined. |
1939 | your working directory changes, then the behaviour is undefined. |
1763 | |
1940 | |
1764 | Since there is no standard kernel interface to do this, the portable |
1941 | Since there is no portable change notification interface available, the |
1765 | implementation simply calls C<stat (2)> regularly on the path to see if |
1942 | portable implementation simply calls C<stat(2)> regularly on the path |
1766 | it changed somehow. You can specify a recommended polling interval for |
1943 | to see if it changed somehow. You can specify a recommended polling |
1767 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1944 | interval for this case. If you specify a polling interval of C<0> (highly |
1768 | then a I<suitable, unspecified default> value will be used (which |
1945 | recommended!) then a I<suitable, unspecified default> value will be used |
1769 | you can expect to be around five seconds, although this might change |
1946 | (which you can expect to be around five seconds, although this might |
1770 | dynamically). Libev will also impose a minimum interval which is currently |
1947 | change dynamically). Libev will also impose a minimum interval which is |
1771 | around C<0.1>, but thats usually overkill. |
1948 | currently around C<0.1>, but thats usually overkill. |
1772 | |
1949 | |
1773 | This watcher type is not meant for massive numbers of stat watchers, |
1950 | This watcher type is not meant for massive numbers of stat watchers, |
1774 | as even with OS-supported change notifications, this can be |
1951 | as even with OS-supported change notifications, this can be |
1775 | resource-intensive. |
1952 | resource-intensive. |
1776 | |
1953 | |
… | |
… | |
1786 | support disabled by default, you get the 32 bit version of the stat |
1963 | support disabled by default, you get the 32 bit version of the stat |
1787 | structure. When using the library from programs that change the ABI to |
1964 | structure. When using the library from programs that change the ABI to |
1788 | use 64 bit file offsets the programs will fail. In that case you have to |
1965 | use 64 bit file offsets the programs will fail. In that case you have to |
1789 | compile libev with the same flags to get binary compatibility. This is |
1966 | compile libev with the same flags to get binary compatibility. This is |
1790 | obviously the case with any flags that change the ABI, but the problem is |
1967 | obviously the case with any flags that change the ABI, but the problem is |
1791 | most noticeably disabled with ev_stat and large file support. |
1968 | most noticeably displayed with ev_stat and large file support. |
1792 | |
1969 | |
1793 | The solution for this is to lobby your distribution maker to make large |
1970 | The solution for this is to lobby your distribution maker to make large |
1794 | file interfaces available by default (as e.g. FreeBSD does) and not |
1971 | file interfaces available by default (as e.g. FreeBSD does) and not |
1795 | optional. Libev cannot simply switch on large file support because it has |
1972 | optional. Libev cannot simply switch on large file support because it has |
1796 | to exchange stat structures with application programs compiled using the |
1973 | to exchange stat structures with application programs compiled using the |
… | |
… | |
1815 | descriptor open on the object at all times, and detecting renames, unlinks |
1992 | descriptor open on the object at all times, and detecting renames, unlinks |
1816 | etc. is difficult. |
1993 | etc. is difficult. |
1817 | |
1994 | |
1818 | =head3 The special problem of stat time resolution |
1995 | =head3 The special problem of stat time resolution |
1819 | |
1996 | |
1820 | The C<stat ()> system call only supports full-second resolution portably, and |
1997 | The C<stat ()> system call only supports full-second resolution portably, |
1821 | even on systems where the resolution is higher, most file systems still |
1998 | and even on systems where the resolution is higher, most file systems |
1822 | only support whole seconds. |
1999 | still only support whole seconds. |
1823 | |
2000 | |
1824 | That means that, if the time is the only thing that changes, you can |
2001 | That means that, if the time is the only thing that changes, you can |
1825 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2002 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1826 | calls your callback, which does something. When there is another update |
2003 | calls your callback, which does something. When there is another update |
1827 | within the same second, C<ev_stat> will be unable to detect unless the |
2004 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1984 | |
2161 | |
1985 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2162 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1986 | callback, free it. Also, use no error checking, as usual. |
2163 | callback, free it. Also, use no error checking, as usual. |
1987 | |
2164 | |
1988 | static void |
2165 | static void |
1989 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2166 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1990 | { |
2167 | { |
1991 | free (w); |
2168 | free (w); |
1992 | // now do something you wanted to do when the program has |
2169 | // now do something you wanted to do when the program has |
1993 | // no longer anything immediate to do. |
2170 | // no longer anything immediate to do. |
1994 | } |
2171 | } |
1995 | |
2172 | |
1996 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2173 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1997 | ev_idle_init (idle_watcher, idle_cb); |
2174 | ev_idle_init (idle_watcher, idle_cb); |
1998 | ev_idle_start (loop, idle_cb); |
2175 | ev_idle_start (loop, idle_cb); |
1999 | |
2176 | |
2000 | |
2177 | |
2001 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2178 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
… | |
… | |
2082 | |
2259 | |
2083 | static ev_io iow [nfd]; |
2260 | static ev_io iow [nfd]; |
2084 | static ev_timer tw; |
2261 | static ev_timer tw; |
2085 | |
2262 | |
2086 | static void |
2263 | static void |
2087 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2264 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2088 | { |
2265 | { |
2089 | } |
2266 | } |
2090 | |
2267 | |
2091 | // create io watchers for each fd and a timer before blocking |
2268 | // create io watchers for each fd and a timer before blocking |
2092 | static void |
2269 | static void |
2093 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2270 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2094 | { |
2271 | { |
2095 | int timeout = 3600000; |
2272 | int timeout = 3600000; |
2096 | struct pollfd fds [nfd]; |
2273 | struct pollfd fds [nfd]; |
2097 | // actual code will need to loop here and realloc etc. |
2274 | // actual code will need to loop here and realloc etc. |
2098 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2275 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2113 | } |
2290 | } |
2114 | } |
2291 | } |
2115 | |
2292 | |
2116 | // stop all watchers after blocking |
2293 | // stop all watchers after blocking |
2117 | static void |
2294 | static void |
2118 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2295 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2119 | { |
2296 | { |
2120 | ev_timer_stop (loop, &tw); |
2297 | ev_timer_stop (loop, &tw); |
2121 | |
2298 | |
2122 | for (int i = 0; i < nfd; ++i) |
2299 | for (int i = 0; i < nfd; ++i) |
2123 | { |
2300 | { |
… | |
… | |
2291 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2468 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2292 | used). |
2469 | used). |
2293 | |
2470 | |
2294 | struct ev_loop *loop_hi = ev_default_init (0); |
2471 | struct ev_loop *loop_hi = ev_default_init (0); |
2295 | struct ev_loop *loop_lo = 0; |
2472 | struct ev_loop *loop_lo = 0; |
2296 | struct ev_embed embed; |
2473 | ev_embed embed; |
2297 | |
2474 | |
2298 | // see if there is a chance of getting one that works |
2475 | // see if there is a chance of getting one that works |
2299 | // (remember that a flags value of 0 means autodetection) |
2476 | // (remember that a flags value of 0 means autodetection) |
2300 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2477 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2301 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2478 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2315 | kqueue implementation). Store the kqueue/socket-only event loop in |
2492 | kqueue implementation). Store the kqueue/socket-only event loop in |
2316 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2493 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2317 | |
2494 | |
2318 | struct ev_loop *loop = ev_default_init (0); |
2495 | struct ev_loop *loop = ev_default_init (0); |
2319 | struct ev_loop *loop_socket = 0; |
2496 | struct ev_loop *loop_socket = 0; |
2320 | struct ev_embed embed; |
2497 | ev_embed embed; |
2321 | |
2498 | |
2322 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2499 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2323 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2500 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2324 | { |
2501 | { |
2325 | ev_embed_init (&embed, 0, loop_socket); |
2502 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2539 | /* doh, nothing entered */; |
2716 | /* doh, nothing entered */; |
2540 | } |
2717 | } |
2541 | |
2718 | |
2542 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2719 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2543 | |
2720 | |
2544 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2721 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2545 | |
2722 | |
2546 | Feeds the given event set into the event loop, as if the specified event |
2723 | Feeds the given event set into the event loop, as if the specified event |
2547 | had happened for the specified watcher (which must be a pointer to an |
2724 | had happened for the specified watcher (which must be a pointer to an |
2548 | initialised but not necessarily started event watcher). |
2725 | initialised but not necessarily started event watcher). |
2549 | |
2726 | |
2550 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2727 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2551 | |
2728 | |
2552 | Feed an event on the given fd, as if a file descriptor backend detected |
2729 | Feed an event on the given fd, as if a file descriptor backend detected |
2553 | the given events it. |
2730 | the given events it. |
2554 | |
2731 | |
2555 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2732 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2556 | |
2733 | |
2557 | Feed an event as if the given signal occurred (C<loop> must be the default |
2734 | Feed an event as if the given signal occurred (C<loop> must be the default |
2558 | loop!). |
2735 | loop!). |
2559 | |
2736 | |
2560 | =back |
2737 | =back |
… | |
… | |
2794 | |
2971 | |
2795 | =item D |
2972 | =item D |
2796 | |
2973 | |
2797 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2974 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2798 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2975 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
2976 | |
|
|
2977 | =item Ocaml |
|
|
2978 | |
|
|
2979 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
2980 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2799 | |
2981 | |
2800 | =back |
2982 | =back |
2801 | |
2983 | |
2802 | |
2984 | |
2803 | =head1 MACRO MAGIC |
2985 | =head1 MACRO MAGIC |