… | |
… | |
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 |
… | |
… | |
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<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>). |
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|
284 | |
|
|
285 | The library knows two types of such loops, the I<default> loop, which |
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|
286 | supports signals and child events, and dynamically created loops which do |
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|
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 | |
… | |
… | |
768 | they fire on, say, one-second boundaries only. |
772 | they fire on, say, one-second boundaries only. |
769 | |
773 | |
770 | =item ev_loop_verify (loop) |
774 | =item ev_loop_verify (loop) |
771 | |
775 | |
772 | This function only does something when C<EV_VERIFY> support has been |
776 | This function only does something when C<EV_VERIFY> support has been |
773 | compiled in. which is the default for non-minimal builds. It tries to go |
777 | 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 |
778 | 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 |
779 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
780 | error and call C<abort ()>. |
777 | |
781 | |
778 | This can be used to catch bugs inside libev itself: under normal |
782 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
781 | |
785 | |
782 | =back |
786 | =back |
783 | |
787 | |
784 | |
788 | |
785 | =head1 ANATOMY OF A WATCHER |
789 | =head1 ANATOMY OF A WATCHER |
|
|
790 | |
|
|
791 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
792 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
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|
793 | watchers and C<ev_io_start> for I/O watchers. |
786 | |
794 | |
787 | A watcher is a structure that you create and register to record your |
795 | A watcher is a structure that you create and register to record your |
788 | interest in some event. For instance, if you want to wait for STDIN to |
796 | interest in some event. For instance, if you want to wait for STDIN to |
789 | become readable, you would create an C<ev_io> watcher for that: |
797 | become readable, you would create an C<ev_io> watcher for that: |
790 | |
798 | |
… | |
… | |
793 | ev_io_stop (w); |
801 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
802 | ev_unloop (loop, EVUNLOOP_ALL); |
795 | } |
803 | } |
796 | |
804 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
805 | struct ev_loop *loop = ev_default_loop (0); |
|
|
806 | |
798 | ev_io stdin_watcher; |
807 | ev_io stdin_watcher; |
|
|
808 | |
799 | ev_init (&stdin_watcher, my_cb); |
809 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
810 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
811 | ev_io_start (loop, &stdin_watcher); |
|
|
812 | |
802 | ev_loop (loop, 0); |
813 | ev_loop (loop, 0); |
803 | |
814 | |
804 | As you can see, you are responsible for allocating the memory for your |
815 | As you can see, you are responsible for allocating the memory for your |
805 | watcher structures (and it is usually a bad idea to do this on the stack, |
816 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
817 | stack). |
|
|
818 | |
|
|
819 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
820 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
807 | |
821 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
822 | Each watcher structure must be initialised by a call to C<ev_init |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
823 | (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 |
824 | 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 |
825 | watchers, each time the event loop detects that the file descriptor given |
812 | is readable and/or writable). |
826 | is readable and/or writable). |
813 | |
827 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
828 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
815 | with arguments specific to this watcher type. There is also a macro |
829 | macro to configure it, with arguments specific to the watcher type. There |
816 | to combine initialisation and setting in one call: C<< ev_<type>_init |
830 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
831 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
832 | |
819 | To make the watcher actually watch out for events, you have to start it |
833 | To make the watcher actually watch out for events, you have to start it |
820 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
834 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
821 | *) >>), and you can stop watching for events at any time by calling the |
835 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
836 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
837 | |
824 | As long as your watcher is active (has been started but not stopped) you |
838 | As long as your watcher is active (has been started but not stopped) you |
825 | must not touch the values stored in it. Most specifically you must never |
839 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
840 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
841 | |
828 | Each and every callback receives the event loop pointer as first, the |
842 | Each and every callback receives the event loop pointer as first, the |
829 | registered watcher structure as second, and a bitset of received events as |
843 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
844 | third argument. |
831 | |
845 | |
… | |
… | |
911 | thing, so beware. |
925 | thing, so beware. |
912 | |
926 | |
913 | =back |
927 | =back |
914 | |
928 | |
915 | =head2 GENERIC WATCHER FUNCTIONS |
929 | =head2 GENERIC WATCHER FUNCTIONS |
916 | |
|
|
917 | In the following description, C<TYPE> stands for the watcher type, |
|
|
918 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
919 | |
930 | |
920 | =over 4 |
931 | =over 4 |
921 | |
932 | |
922 | =item C<ev_init> (ev_TYPE *watcher, callback) |
933 | =item C<ev_init> (ev_TYPE *watcher, callback) |
923 | |
934 | |
… | |
… | |
1426 | |
1437 | |
1427 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1438 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1428 | callback :) - just change the timeout and invoke the callback, which will |
1439 | callback :) - just change the timeout and invoke the callback, which will |
1429 | fix things for you. |
1440 | fix things for you. |
1430 | |
1441 | |
1431 | =item 4. Whee, use a double-linked list for your timeouts. |
1442 | =item 4. Wee, just use a double-linked list for your timeouts. |
1432 | |
1443 | |
1433 | If there is not one request, but many thousands, all employing some kind |
1444 | If there is not one request, but many thousands (millions...), all |
1434 | of timeout with the same timeout value, then one can do even better: |
1445 | employing some kind of timeout with the same timeout value, then one can |
|
|
1446 | do even better: |
1435 | |
1447 | |
1436 | When starting the timeout, calculate the timeout value and put the timeout |
1448 | When starting the timeout, calculate the timeout value and put the timeout |
1437 | at the I<end> of the list. |
1449 | at the I<end> of the list. |
1438 | |
1450 | |
1439 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
1451 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
… | |
… | |
1448 | complication, and having to use a constant timeout. The constant timeout |
1460 | complication, and having to use a constant timeout. The constant timeout |
1449 | ensures that the list stays sorted. |
1461 | ensures that the list stays sorted. |
1450 | |
1462 | |
1451 | =back |
1463 | =back |
1452 | |
1464 | |
1453 | So what method is the best? |
1465 | So which method the best? |
1454 | |
1466 | |
1455 | The method #2 is a simple no-brain-required solution that is adequate in |
1467 | Method #2 is a simple no-brain-required solution that is adequate in most |
1456 | most situations. Method #3 requires a bit more thinking, but handles many |
1468 | situations. Method #3 requires a bit more thinking, but handles many cases |
1457 | cases better, and isn't very complicated either. In most case, choosing |
1469 | better, and isn't very complicated either. In most case, choosing either |
1458 | either one is fine. |
1470 | one is fine, with #3 being better in typical situations. |
1459 | |
1471 | |
1460 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1472 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1461 | rather complicated, but extremely efficient, something that really pays |
1473 | rather complicated, but extremely efficient, something that really pays |
1462 | off after the first or so million of active timers, i.e. it's usually |
1474 | off after the first million or so of active timers, i.e. it's usually |
1463 | overkill :) |
1475 | overkill :) |
1464 | |
1476 | |
1465 | =head3 The special problem of time updates |
1477 | =head3 The special problem of time updates |
1466 | |
1478 | |
1467 | Establishing the current time is a costly operation (it usually takes at |
1479 | Establishing the current time is a costly operation (it usually takes at |