… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
… | |
… | |
435 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
436 | |
442 | |
437 | =item C<EVFLAG_NOSIGMASK> |
443 | =item C<EVFLAG_NOSIGMASK> |
438 | |
444 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
445 | When this flag is specified, then libev will avoid to modify the signal |
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
446 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
447 | when you want to receive them. |
442 | |
448 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
449 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
450 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
446 | |
455 | |
447 | This flag's behaviour will become the default in future versions of libev. |
456 | This flag's behaviour will become the default in future versions of libev. |
448 | |
457 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
459 | |
… | |
… | |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
490 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
492 | kernels). |
484 | |
493 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
486 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
488 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
498 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
497 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
498 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
499 | and is of course hard to detect. |
508 | and is of course hard to detect. |
500 | |
509 | |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
503 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
504 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
506 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
507 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
508 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
509 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
510 | |
522 | |
511 | Epoll is truly the train wreck analog among event poll mechanisms, |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
512 | a frankenpoll, cobbled together in a hurry, no thought to design or |
524 | cobbled together in a hurry, no thought to design or interaction with |
513 | interaction with others. |
525 | others. Oh, the pain, will it ever stop... |
514 | |
526 | |
515 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
516 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
517 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
518 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
555 | |
567 | |
556 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
557 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
558 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
559 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
560 | two event changes per incident. Support for C<fork ()> is very bad (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
561 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
562 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
563 | |
575 | |
564 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
565 | |
577 | |
566 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
567 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
596 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
597 | hacks). |
609 | hacks). |
598 | |
610 | |
599 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
600 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
601 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
602 | occurred, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
603 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
604 | you absolutely have to know whether an event occurred or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
605 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
606 | |
618 | |
607 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
608 | |
620 | |
609 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
610 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
780 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
781 | |
793 | |
782 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
783 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
784 | |
796 | |
785 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
786 | |
798 | |
787 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
788 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
789 | handling events. It will ask the operating system for any new events, call |
801 | handling events. It will ask the operating system for any new events, call |
790 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
791 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
792 | |
804 | |
793 | If the flags argument is specified as C<0>, it will keep handling events |
805 | If the flags argument is specified as C<0>, it will keep handling events |
794 | until either no event watchers are active anymore or C<ev_break> was |
806 | until either no event watchers are active anymore or C<ev_break> was |
795 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
796 | |
812 | |
797 | Please note that an explicit C<ev_break> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
798 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
799 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
800 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
801 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
802 | beauty. |
818 | beauty. |
803 | |
819 | |
804 | This function is also I<mostly> exception-safe - you can break out of |
820 | This function is I<mostly> exception-safe - you can break out of a |
805 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
806 | exception and so on. This does not decrement the C<ev_depth> value, nor |
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
807 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
808 | |
824 | |
809 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
810 | those events and any already outstanding ones, but will not wait and |
826 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
822 | This is useful if you are waiting for some external event in conjunction |
838 | This is useful if you are waiting for some external event in conjunction |
823 | with something not expressible using other libev watchers (i.e. "roll your |
839 | with something not expressible using other libev watchers (i.e. "roll your |
824 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
840 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
825 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
826 | |
842 | |
827 | Here are the gory details of what C<ev_run> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
828 | |
846 | |
829 | - Increment loop depth. |
847 | - Increment loop depth. |
830 | - Reset the ev_break status. |
848 | - Reset the ev_break status. |
831 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
832 | LOOP: |
850 | LOOP: |
… | |
… | |
865 | anymore. |
883 | anymore. |
866 | |
884 | |
867 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
868 | ... as they still have work to do (even an idle watcher will do..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
869 | ev_run (my_loop, 0); |
887 | ev_run (my_loop, 0); |
870 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
871 | |
889 | |
872 | =item ev_break (loop, how) |
890 | =item ev_break (loop, how) |
873 | |
891 | |
874 | Can be used to make a call to C<ev_run> return early (but only after it |
892 | Can be used to make a call to C<ev_run> return early (but only after it |
875 | has processed all outstanding events). The C<how> argument must be either |
893 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
938 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
939 | |
957 | |
940 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
941 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
942 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
943 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
944 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
945 | sleep time ensures that libev will not poll for I/O events more often then |
963 | sleep time ensures that libev will not poll for I/O events more often then |
946 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
947 | |
966 | |
948 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
949 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
950 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
951 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
1005 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1006 | each call to a libev function. |
1025 | each call to a libev function. |
1007 | |
1026 | |
1008 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1009 | to wait for it to return. One way around this is to wake up the event |
1028 | to wait for it to return. One way around this is to wake up the event |
1010 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1011 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
1012 | |
1031 | |
1013 | When set, then C<release> will be called just before the thread is |
1032 | When set, then C<release> will be called just before the thread is |
1014 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
1015 | afterwards. |
1034 | afterwards. |
… | |
… | |
1371 | |
1390 | |
1372 | =over 4 |
1391 | =over 4 |
1373 | |
1392 | |
1374 | =item initialiased |
1393 | =item initialiased |
1375 | |
1394 | |
1376 | Before a watcher can be registered with the event looop it has to be |
1395 | Before a watcher can be registered with the event loop it has to be |
1377 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1396 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1378 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1379 | |
1398 | |
1380 | In this state it is simply some block of memory that is suitable for use |
1399 | In this state it is simply some block of memory that is suitable for |
1381 | in an event loop. It can be moved around, freed, reused etc. at will. |
1400 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1401 | will - as long as you either keep the memory contents intact, or call |
|
|
1402 | C<ev_TYPE_init> again. |
1382 | |
1403 | |
1383 | =item started/running/active |
1404 | =item started/running/active |
1384 | |
1405 | |
1385 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1406 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1386 | property of the event loop, and is actively waiting for events. While in |
1407 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1414 | latter will clear any pending state the watcher might be in, regardless |
1435 | latter will clear any pending state the watcher might be in, regardless |
1415 | of whether it was active or not, so stopping a watcher explicitly before |
1436 | of whether it was active or not, so stopping a watcher explicitly before |
1416 | freeing it is often a good idea. |
1437 | freeing it is often a good idea. |
1417 | |
1438 | |
1418 | While stopped (and not pending) the watcher is essentially in the |
1439 | While stopped (and not pending) the watcher is essentially in the |
1419 | initialised state, that is it can be reused, moved, modified in any way |
1440 | initialised state, that is, it can be reused, moved, modified in any way |
1420 | you wish. |
1441 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1442 | it again). |
1421 | |
1443 | |
1422 | =back |
1444 | =back |
1423 | |
1445 | |
1424 | =head2 WATCHER PRIORITY MODELS |
1446 | =head2 WATCHER PRIORITY MODELS |
1425 | |
1447 | |
… | |
… | |
1753 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1775 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1754 | monotonic clock option helps a lot here). |
1776 | monotonic clock option helps a lot here). |
1755 | |
1777 | |
1756 | The callback is guaranteed to be invoked only I<after> its timeout has |
1778 | The callback is guaranteed to be invoked only I<after> its timeout has |
1757 | passed (not I<at>, so on systems with very low-resolution clocks this |
1779 | passed (not I<at>, so on systems with very low-resolution clocks this |
1758 | might introduce a small delay). If multiple timers become ready during the |
1780 | might introduce a small delay, see "the special problem of being too |
|
|
1781 | early", below). If multiple timers become ready during the same loop |
1759 | same loop iteration then the ones with earlier time-out values are invoked |
1782 | iteration then the ones with earlier time-out values are invoked before |
1760 | before ones of the same priority with later time-out values (but this is |
1783 | ones of the same priority with later time-out values (but this is no |
1761 | no longer true when a callback calls C<ev_run> recursively). |
1784 | longer true when a callback calls C<ev_run> recursively). |
1762 | |
1785 | |
1763 | =head3 Be smart about timeouts |
1786 | =head3 Be smart about timeouts |
1764 | |
1787 | |
1765 | Many real-world problems involve some kind of timeout, usually for error |
1788 | Many real-world problems involve some kind of timeout, usually for error |
1766 | recovery. A typical example is an HTTP request - if the other side hangs, |
1789 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1841 | |
1864 | |
1842 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1865 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1843 | but remember the time of last activity, and check for a real timeout only |
1866 | but remember the time of last activity, and check for a real timeout only |
1844 | within the callback: |
1867 | within the callback: |
1845 | |
1868 | |
|
|
1869 | ev_tstamp timeout = 60.; |
1846 | ev_tstamp last_activity; // time of last activity |
1870 | ev_tstamp last_activity; // time of last activity |
|
|
1871 | ev_timer timer; |
1847 | |
1872 | |
1848 | static void |
1873 | static void |
1849 | callback (EV_P_ ev_timer *w, int revents) |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1850 | { |
1875 | { |
1851 | ev_tstamp now = ev_now (EV_A); |
1876 | // calculate when the timeout would happen |
1852 | ev_tstamp timeout = last_activity + 60.; |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1853 | |
1878 | |
1854 | // if last_activity + 60. is older than now, we did time out |
1879 | // if negative, it means we the timeout already occured |
1855 | if (timeout < now) |
1880 | if (after < 0.) |
1856 | { |
1881 | { |
1857 | // timeout occurred, take action |
1882 | // timeout occurred, take action |
1858 | } |
1883 | } |
1859 | else |
1884 | else |
1860 | { |
1885 | { |
1861 | // callback was invoked, but there was some activity, re-arm |
1886 | // callback was invoked, but there was some recent |
1862 | // the watcher to fire in last_activity + 60, which is |
1887 | // activity. simply restart the timer to time out |
1863 | // guaranteed to be in the future, so "again" is positive: |
1888 | // after "after" seconds, which is the earliest time |
1864 | w->repeat = timeout - now; |
1889 | // the timeout can occur. |
|
|
1890 | ev_timer_set (w, after, 0.); |
1865 | ev_timer_again (EV_A_ w); |
1891 | ev_timer_start (EV_A_ w); |
1866 | } |
1892 | } |
1867 | } |
1893 | } |
1868 | |
1894 | |
1869 | To summarise the callback: first calculate the real timeout (defined |
1895 | To summarise the callback: first calculate in how many seconds the |
1870 | as "60 seconds after the last activity"), then check if that time has |
1896 | timeout will occur (by calculating the absolute time when it would occur, |
1871 | been reached, which means something I<did>, in fact, time out. Otherwise |
1897 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1872 | the callback was invoked too early (C<timeout> is in the future), so |
1898 | (EV_A)> from that). |
1873 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1874 | a timeout then. |
|
|
1875 | |
1899 | |
1876 | Note how C<ev_timer_again> is used, taking advantage of the |
1900 | If this value is negative, then we are already past the timeout, i.e. we |
1877 | C<ev_timer_again> optimisation when the timer is already running. |
1901 | timed out, and need to do whatever is needed in this case. |
|
|
1902 | |
|
|
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1904 | and simply start the timer with this timeout value. |
|
|
1905 | |
|
|
1906 | In other words, each time the callback is invoked it will check whether |
|
|
1907 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1878 | |
1909 | |
1879 | This scheme causes more callback invocations (about one every 60 seconds |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1880 | minus half the average time between activity), but virtually no calls to |
1911 | minus half the average time between activity), but virtually no calls to |
1881 | libev to change the timeout. |
1912 | libev to change the timeout. |
1882 | |
1913 | |
1883 | To start the timer, simply initialise the watcher and set C<last_activity> |
1914 | To start the machinery, simply initialise the watcher and set |
1884 | to the current time (meaning we just have some activity :), then call the |
1915 | C<last_activity> to the current time (meaning there was some activity just |
1885 | callback, which will "do the right thing" and start the timer: |
1916 | now), then call the callback, which will "do the right thing" and start |
|
|
1917 | the timer: |
1886 | |
1918 | |
|
|
1919 | last_activity = ev_now (EV_A); |
1887 | ev_init (timer, callback); |
1920 | ev_init (&timer, callback); |
1888 | last_activity = ev_now (loop); |
1921 | callback (EV_A_ &timer, 0); |
1889 | callback (loop, timer, EV_TIMER); |
|
|
1890 | |
1922 | |
1891 | And when there is some activity, simply store the current time in |
1923 | When there is some activity, simply store the current time in |
1892 | C<last_activity>, no libev calls at all: |
1924 | C<last_activity>, no libev calls at all: |
1893 | |
1925 | |
|
|
1926 | if (activity detected) |
1894 | last_activity = ev_now (loop); |
1927 | last_activity = ev_now (EV_A); |
|
|
1928 | |
|
|
1929 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1930 | providing a new value, stopping the timer and calling the callback, which |
|
|
1931 | will agaion do the right thing (for example, time out immediately :). |
|
|
1932 | |
|
|
1933 | timeout = new_value; |
|
|
1934 | ev_timer_stop (EV_A_ &timer); |
|
|
1935 | callback (EV_A_ &timer, 0); |
1895 | |
1936 | |
1896 | This technique is slightly more complex, but in most cases where the |
1937 | This technique is slightly more complex, but in most cases where the |
1897 | time-out is unlikely to be triggered, much more efficient. |
1938 | time-out is unlikely to be triggered, much more efficient. |
1898 | |
|
|
1899 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1900 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1901 | fix things for you. |
|
|
1902 | |
1939 | |
1903 | =item 4. Wee, just use a double-linked list for your timeouts. |
1940 | =item 4. Wee, just use a double-linked list for your timeouts. |
1904 | |
1941 | |
1905 | If there is not one request, but many thousands (millions...), all |
1942 | If there is not one request, but many thousands (millions...), all |
1906 | employing some kind of timeout with the same timeout value, then one can |
1943 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1933 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1970 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1934 | rather complicated, but extremely efficient, something that really pays |
1971 | rather complicated, but extremely efficient, something that really pays |
1935 | off after the first million or so of active timers, i.e. it's usually |
1972 | off after the first million or so of active timers, i.e. it's usually |
1936 | overkill :) |
1973 | overkill :) |
1937 | |
1974 | |
|
|
1975 | =head3 The special problem of being too early |
|
|
1976 | |
|
|
1977 | If you ask a timer to call your callback after three seconds, then |
|
|
1978 | you expect it to be invoked after three seconds - but of course, this |
|
|
1979 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1980 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1981 | process with a STOP signal for a few hours for example. |
|
|
1982 | |
|
|
1983 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1984 | delay has occurred, but cannot guarantee this. |
|
|
1985 | |
|
|
1986 | A less obvious failure mode is calling your callback too early: many event |
|
|
1987 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1988 | this can cause your callback to be invoked much earlier than you would |
|
|
1989 | expect. |
|
|
1990 | |
|
|
1991 | To see why, imagine a system with a clock that only offers full second |
|
|
1992 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1993 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1994 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1995 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1996 | |
|
|
1997 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1998 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1999 | one-second delay was requested - this is being "too early", despite best |
|
|
2000 | intentions. |
|
|
2001 | |
|
|
2002 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2003 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2004 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2005 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2006 | |
|
|
2007 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2008 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2009 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2010 | late" side of things. |
|
|
2011 | |
1938 | =head3 The special problem of time updates |
2012 | =head3 The special problem of time updates |
1939 | |
2013 | |
1940 | Establishing the current time is a costly operation (it usually takes at |
2014 | Establishing the current time is a costly operation (it usually takes |
1941 | least two system calls): EV therefore updates its idea of the current |
2015 | at least one system call): EV therefore updates its idea of the current |
1942 | time only before and after C<ev_run> collects new events, which causes a |
2016 | time only before and after C<ev_run> collects new events, which causes a |
1943 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2017 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1944 | lots of events in one iteration. |
2018 | lots of events in one iteration. |
1945 | |
2019 | |
1946 | The relative timeouts are calculated relative to the C<ev_now ()> |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1952 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1953 | |
2027 | |
1954 | If the event loop is suspended for a long time, you can also force an |
2028 | If the event loop is suspended for a long time, you can also force an |
1955 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1956 | ()>. |
2030 | ()>. |
|
|
2031 | |
|
|
2032 | =head3 The special problem of unsynchronised clocks |
|
|
2033 | |
|
|
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2036 | jumps). |
|
|
2037 | |
|
|
2038 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2039 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2040 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2041 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2042 | than a directly following call to C<time>. |
|
|
2043 | |
|
|
2044 | The moral of this is to only compare libev-related timestamps with |
|
|
2045 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2046 | a second or so. |
|
|
2047 | |
|
|
2048 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2049 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2050 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2051 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2052 | |
|
|
2053 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2054 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2055 | I<measured according to the real time>, not the system clock. |
|
|
2056 | |
|
|
2057 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2058 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2059 | exactly the right behaviour. |
|
|
2060 | |
|
|
2061 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2062 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2063 | time, where your comparisons will always generate correct results. |
1957 | |
2064 | |
1958 | =head3 The special problems of suspended animation |
2065 | =head3 The special problems of suspended animation |
1959 | |
2066 | |
1960 | When you leave the server world it is quite customary to hit machines that |
2067 | When you leave the server world it is quite customary to hit machines that |
1961 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2068 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2005 | keep up with the timer (because it takes longer than those 10 seconds to |
2112 | keep up with the timer (because it takes longer than those 10 seconds to |
2006 | do stuff) the timer will not fire more than once per event loop iteration. |
2113 | do stuff) the timer will not fire more than once per event loop iteration. |
2007 | |
2114 | |
2008 | =item ev_timer_again (loop, ev_timer *) |
2115 | =item ev_timer_again (loop, ev_timer *) |
2009 | |
2116 | |
2010 | This will act as if the timer timed out and restart it again if it is |
2117 | This will act as if the timer timed out, and restarts it again if it is |
2011 | repeating. The exact semantics are: |
2118 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2119 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2012 | |
2120 | |
|
|
2121 | The exact semantics are as in the following rules, all of which will be |
|
|
2122 | applied to the watcher: |
|
|
2123 | |
|
|
2124 | =over 4 |
|
|
2125 | |
2013 | If the timer is pending, its pending status is cleared. |
2126 | =item If the timer is pending, the pending status is always cleared. |
2014 | |
2127 | |
2015 | If the timer is started but non-repeating, stop it (as if it timed out). |
2128 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2129 | out, without invoking it). |
2016 | |
2130 | |
2017 | If the timer is repeating, either start it if necessary (with the |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2018 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2132 | and start the timer, if necessary. |
|
|
2133 | |
|
|
2134 | =back |
2019 | |
2135 | |
2020 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2021 | usage example. |
2137 | usage example. |
2022 | |
2138 | |
2023 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
2145 | |
2261 | |
2146 | Another way to think about it (for the mathematically inclined) is that |
2262 | Another way to think about it (for the mathematically inclined) is that |
2147 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2263 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2148 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2264 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2149 | |
2265 | |
2150 | For numerical stability it is preferable that the C<offset> value is near |
2266 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2151 | C<ev_now ()> (the current time), but there is no range requirement for |
2267 | interval value should be higher than C<1/8192> (which is around 100 |
2152 | this value, and in fact is often specified as zero. |
2268 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2269 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2270 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2271 | C<0> and C<interval>, which is also the recommended range. |
2153 | |
2272 | |
2154 | Note also that there is an upper limit to how often a timer can fire (CPU |
2273 | Note also that there is an upper limit to how often a timer can fire (CPU |
2155 | speed for example), so if C<interval> is very small then timing stability |
2274 | speed for example), so if C<interval> is very small then timing stability |
2156 | will of course deteriorate. Libev itself tries to be exact to be about one |
2275 | will of course deteriorate. Libev itself tries to be exact to be about one |
2157 | millisecond (if the OS supports it and the machine is fast enough). |
2276 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2300 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2419 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2301 | |
2420 | |
2302 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2421 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2303 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2422 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2304 | stopping it again), that is, libev might or might not block the signal, |
2423 | stopping it again), that is, libev might or might not block the signal, |
2305 | and might or might not set or restore the installed signal handler. |
2424 | and might or might not set or restore the installed signal handler (but |
|
|
2425 | see C<EVFLAG_NOSIGMASK>). |
2306 | |
2426 | |
2307 | While this does not matter for the signal disposition (libev never |
2427 | While this does not matter for the signal disposition (libev never |
2308 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2428 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2309 | C<execve>), this matters for the signal mask: many programs do not expect |
2429 | C<execve>), this matters for the signal mask: many programs do not expect |
2310 | certain signals to be blocked. |
2430 | certain signals to be blocked. |
… | |
… | |
3181 | atexit (program_exits); |
3301 | atexit (program_exits); |
3182 | |
3302 | |
3183 | |
3303 | |
3184 | =head2 C<ev_async> - how to wake up an event loop |
3304 | =head2 C<ev_async> - how to wake up an event loop |
3185 | |
3305 | |
3186 | In general, you cannot use an C<ev_run> from multiple threads or other |
3306 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3187 | asynchronous sources such as signal handlers (as opposed to multiple event |
3307 | asynchronous sources such as signal handlers (as opposed to multiple event |
3188 | loops - those are of course safe to use in different threads). |
3308 | loops - those are of course safe to use in different threads). |
3189 | |
3309 | |
3190 | Sometimes, however, you need to wake up an event loop you do not control, |
3310 | Sometimes, however, you need to wake up an event loop you do not control, |
3191 | for example because it belongs to another thread. This is what C<ev_async> |
3311 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3198 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3199 | of "global async watchers" by using a watcher on an otherwise unused |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3200 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3201 | even without knowing which loop owns the signal. |
3321 | even without knowing which loop owns the signal. |
3202 | |
3322 | |
3203 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3204 | just the default loop. |
|
|
3205 | |
|
|
3206 | =head3 Queueing |
3323 | =head3 Queueing |
3207 | |
3324 | |
3208 | C<ev_async> does not support queueing of data in any way. The reason |
3325 | C<ev_async> does not support queueing of data in any way. The reason |
3209 | is that the author does not know of a simple (or any) algorithm for a |
3326 | is that the author does not know of a simple (or any) algorithm for a |
3210 | multiple-writer-single-reader queue that works in all cases and doesn't |
3327 | multiple-writer-single-reader queue that works in all cases and doesn't |
… | |
… | |
3301 | trust me. |
3418 | trust me. |
3302 | |
3419 | |
3303 | =item ev_async_send (loop, ev_async *) |
3420 | =item ev_async_send (loop, ev_async *) |
3304 | |
3421 | |
3305 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3422 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3306 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3423 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3424 | returns. |
|
|
3425 | |
3307 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3426 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3308 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3427 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3309 | section below on what exactly this means). |
3428 | embedding section below on what exactly this means). |
3310 | |
3429 | |
3311 | Note that, as with other watchers in libev, multiple events might get |
3430 | Note that, as with other watchers in libev, multiple events might get |
3312 | compressed into a single callback invocation (another way to look at this |
3431 | compressed into a single callback invocation (another way to look at |
3313 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3432 | this is that C<ev_async> watchers are level-triggered: they are set on |
3314 | reset when the event loop detects that). |
3433 | C<ev_async_send>, reset when the event loop detects that). |
3315 | |
3434 | |
3316 | This call incurs the overhead of a system call only once per event loop |
3435 | This call incurs the overhead of at most one extra system call per event |
3317 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3436 | loop iteration, if the event loop is blocked, and no syscall at all if |
3318 | repeated calls to C<ev_async_send> for the same event loop. |
3437 | the event loop (or your program) is processing events. That means that |
|
|
3438 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3439 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3440 | zero) under load. |
3319 | |
3441 | |
3320 | =item bool = ev_async_pending (ev_async *) |
3442 | =item bool = ev_async_pending (ev_async *) |
3321 | |
3443 | |
3322 | Returns a non-zero value when C<ev_async_send> has been called on the |
3444 | Returns a non-zero value when C<ev_async_send> has been called on the |
3323 | watcher but the event has not yet been processed (or even noted) by the |
3445 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3378 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3500 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3379 | |
3501 | |
3380 | =item ev_feed_fd_event (loop, int fd, int revents) |
3502 | =item ev_feed_fd_event (loop, int fd, int revents) |
3381 | |
3503 | |
3382 | Feed an event on the given fd, as if a file descriptor backend detected |
3504 | Feed an event on the given fd, as if a file descriptor backend detected |
3383 | the given events it. |
3505 | the given events. |
3384 | |
3506 | |
3385 | =item ev_feed_signal_event (loop, int signum) |
3507 | =item ev_feed_signal_event (loop, int signum) |
3386 | |
3508 | |
3387 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3509 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3388 | which is async-safe. |
3510 | which is async-safe. |
… | |
… | |
3462 | { |
3584 | { |
3463 | struct my_biggy big = (struct my_biggy *) |
3585 | struct my_biggy big = (struct my_biggy *) |
3464 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3586 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3465 | } |
3587 | } |
3466 | |
3588 | |
|
|
3589 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3590 | |
|
|
3591 | Often you have structures like this in event-based programs: |
|
|
3592 | |
|
|
3593 | callback () |
|
|
3594 | { |
|
|
3595 | free (request); |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | request = start_new_request (..., callback); |
|
|
3599 | |
|
|
3600 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3601 | used to cancel the operation, or do other things with it. |
|
|
3602 | |
|
|
3603 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3604 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3605 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3606 | operation and simply invoke the callback with the result. |
|
|
3607 | |
|
|
3608 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3609 | has returned, so C<request> is not set. |
|
|
3610 | |
|
|
3611 | Even if you pass the request by some safer means to the callback, you |
|
|
3612 | might want to do something to the request after starting it, such as |
|
|
3613 | canceling it, which probably isn't working so well when the callback has |
|
|
3614 | already been invoked. |
|
|
3615 | |
|
|
3616 | A common way around all these issues is to make sure that |
|
|
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3618 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3621 | and pushing it into the pending queue: |
|
|
3622 | |
|
|
3623 | ev_set_cb (watcher, callback); |
|
|
3624 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3625 | |
|
|
3626 | This way, C<start_new_request> can safely return before the callback is |
|
|
3627 | invoked, while not delaying callback invocation too much. |
|
|
3628 | |
3467 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3629 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3468 | |
3630 | |
3469 | Often (especially in GUI toolkits) there are places where you have |
3631 | Often (especially in GUI toolkits) there are places where you have |
3470 | I<modal> interaction, which is most easily implemented by recursively |
3632 | I<modal> interaction, which is most easily implemented by recursively |
3471 | invoking C<ev_run>. |
3633 | invoking C<ev_run>. |
… | |
… | |
3484 | int exit_main_loop = 0; |
3646 | int exit_main_loop = 0; |
3485 | |
3647 | |
3486 | while (!exit_main_loop) |
3648 | while (!exit_main_loop) |
3487 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3649 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3488 | |
3650 | |
3489 | // in a model watcher |
3651 | // in a modal watcher |
3490 | int exit_nested_loop = 0; |
3652 | int exit_nested_loop = 0; |
3491 | |
3653 | |
3492 | while (!exit_nested_loop) |
3654 | while (!exit_nested_loop) |
3493 | ev_run (EV_A_ EVRUN_ONCE); |
3655 | ev_run (EV_A_ EVRUN_ONCE); |
3494 | |
3656 | |
… | |
… | |
3504 | exit_main_loop = exit_nested_loop = 1; |
3666 | exit_main_loop = exit_nested_loop = 1; |
3505 | |
3667 | |
3506 | =head2 THREAD LOCKING EXAMPLE |
3668 | =head2 THREAD LOCKING EXAMPLE |
3507 | |
3669 | |
3508 | Here is a fictitious example of how to run an event loop in a different |
3670 | Here is a fictitious example of how to run an event loop in a different |
3509 | thread than where callbacks are being invoked and watchers are |
3671 | thread from where callbacks are being invoked and watchers are |
3510 | created/added/removed. |
3672 | created/added/removed. |
3511 | |
3673 | |
3512 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3674 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3513 | which uses exactly this technique (which is suited for many high-level |
3675 | which uses exactly this technique (which is suited for many high-level |
3514 | languages). |
3676 | languages). |
… | |
… | |
3540 | // now associate this with the loop |
3702 | // now associate this with the loop |
3541 | ev_set_userdata (EV_A_ u); |
3703 | ev_set_userdata (EV_A_ u); |
3542 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3704 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3543 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3705 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3544 | |
3706 | |
3545 | // then create the thread running ev_loop |
3707 | // then create the thread running ev_run |
3546 | pthread_create (&u->tid, 0, l_run, EV_A); |
3708 | pthread_create (&u->tid, 0, l_run, EV_A); |
3547 | } |
3709 | } |
3548 | |
3710 | |
3549 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3711 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3550 | solely to wake up the event loop so it takes notice of any new watchers |
3712 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
3674 | switch_to (libev_coro); |
3836 | switch_to (libev_coro); |
3675 | } |
3837 | } |
3676 | |
3838 | |
3677 | That basically suspends the coroutine inside C<wait_for_event> and |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
3678 | continues the libev coroutine, which, when appropriate, switches back to |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
3679 | this or any other coroutine. I am sure if you sue this your own :) |
3841 | this or any other coroutine. |
3680 | |
3842 | |
3681 | You can do similar tricks if you have, say, threads with an event queue - |
3843 | You can do similar tricks if you have, say, threads with an event queue - |
3682 | instead of storing a coroutine, you store the queue object and instead of |
3844 | instead of storing a coroutine, you store the queue object and instead of |
3683 | switching to a coroutine, you push the watcher onto the queue and notify |
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
3684 | any waiters. |
3846 | any waiters. |
… | |
… | |
3759 | with C<operator ()> can be used as callbacks. Other types should be easy |
3921 | with C<operator ()> can be used as callbacks. Other types should be easy |
3760 | to add as long as they only need one additional pointer for context. If |
3922 | to add as long as they only need one additional pointer for context. If |
3761 | you need support for other types of functors please contact the author |
3923 | you need support for other types of functors please contact the author |
3762 | (preferably after implementing it). |
3924 | (preferably after implementing it). |
3763 | |
3925 | |
|
|
3926 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3927 | conventions as your C compiler (for static member functions), or you have |
|
|
3928 | to embed libev and compile libev itself as C++. |
|
|
3929 | |
3764 | Here is a list of things available in the C<ev> namespace: |
3930 | Here is a list of things available in the C<ev> namespace: |
3765 | |
3931 | |
3766 | =over 4 |
3932 | =over 4 |
3767 | |
3933 | |
3768 | =item C<ev::READ>, C<ev::WRITE> etc. |
3934 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3777 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3943 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3778 | |
3944 | |
3779 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3945 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3780 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3946 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3781 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3947 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3782 | defines by many implementations. |
3948 | defined by many implementations. |
3783 | |
3949 | |
3784 | All of those classes have these methods: |
3950 | All of those classes have these methods: |
3785 | |
3951 | |
3786 | =over 4 |
3952 | =over 4 |
3787 | |
3953 | |
… | |
… | |
3920 | watchers in the constructor. |
4086 | watchers in the constructor. |
3921 | |
4087 | |
3922 | class myclass |
4088 | class myclass |
3923 | { |
4089 | { |
3924 | ev::io io ; void io_cb (ev::io &w, int revents); |
4090 | ev::io io ; void io_cb (ev::io &w, int revents); |
3925 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4091 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3926 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4092 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3927 | |
4093 | |
3928 | myclass (int fd) |
4094 | myclass (int fd) |
3929 | { |
4095 | { |
3930 | io .set <myclass, &myclass::io_cb > (this); |
4096 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3981 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4147 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3982 | |
4148 | |
3983 | =item D |
4149 | =item D |
3984 | |
4150 | |
3985 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4151 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3986 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4152 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3987 | |
4153 | |
3988 | =item Ocaml |
4154 | =item Ocaml |
3989 | |
4155 | |
3990 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4156 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3991 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4157 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4039 | suitable for use with C<EV_A>. |
4205 | suitable for use with C<EV_A>. |
4040 | |
4206 | |
4041 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4207 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4042 | |
4208 | |
4043 | Similar to the other two macros, this gives you the value of the default |
4209 | Similar to the other two macros, this gives you the value of the default |
4044 | loop, if multiple loops are supported ("ev loop default"). |
4210 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4211 | will be initialised if it isn't already initialised. |
|
|
4212 | |
|
|
4213 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4214 | to initialise the loop somewhere. |
4045 | |
4215 | |
4046 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4216 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4047 | |
4217 | |
4048 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4218 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4049 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4219 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4194 | supported). It will also not define any of the structs usually found in |
4364 | supported). It will also not define any of the structs usually found in |
4195 | F<event.h> that are not directly supported by the libev core alone. |
4365 | F<event.h> that are not directly supported by the libev core alone. |
4196 | |
4366 | |
4197 | In standalone mode, libev will still try to automatically deduce the |
4367 | In standalone mode, libev will still try to automatically deduce the |
4198 | configuration, but has to be more conservative. |
4368 | configuration, but has to be more conservative. |
|
|
4369 | |
|
|
4370 | =item EV_USE_FLOOR |
|
|
4371 | |
|
|
4372 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4373 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4374 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4375 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4376 | function is not available will fail, so the safe default is to not enable |
|
|
4377 | this. |
4199 | |
4378 | |
4200 | =item EV_USE_MONOTONIC |
4379 | =item EV_USE_MONOTONIC |
4201 | |
4380 | |
4202 | If defined to be C<1>, libev will try to detect the availability of the |
4381 | If defined to be C<1>, libev will try to detect the availability of the |
4203 | monotonic clock option at both compile time and runtime. Otherwise no |
4382 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
4333 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4512 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4334 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4513 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4335 | be detected at runtime. If undefined, it will be enabled if the headers |
4514 | be detected at runtime. If undefined, it will be enabled if the headers |
4336 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4515 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4337 | |
4516 | |
|
|
4517 | =item EV_NO_SMP |
|
|
4518 | |
|
|
4519 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4520 | between threads, that is, threads can be used, but threads never run on |
|
|
4521 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4522 | and makes libev faster. |
|
|
4523 | |
|
|
4524 | =item EV_NO_THREADS |
|
|
4525 | |
|
|
4526 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4527 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4528 | above. This reduces dependencies and makes libev faster. |
|
|
4529 | |
4338 | =item EV_ATOMIC_T |
4530 | =item EV_ATOMIC_T |
4339 | |
4531 | |
4340 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4532 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4341 | access is atomic with respect to other threads or signal contexts. No such |
4533 | access is atomic and serialised with respect to other threads or signal |
4342 | type is easily found in the C language, so you can provide your own type |
4534 | contexts. No such type is easily found in the C language, so you can |
4343 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4535 | provide your own type that you know is safe for your purposes. It is used |
4344 | as well as for signal and thread safety in C<ev_async> watchers. |
4536 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4537 | in C<ev_async> watchers. |
4345 | |
4538 | |
4346 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4539 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4347 | (from F<signal.h>), which is usually good enough on most platforms. |
4540 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4541 | although strictly speaking using a type that also implies a memory fence |
|
|
4542 | is required. |
4348 | |
4543 | |
4349 | =item EV_H (h) |
4544 | =item EV_H (h) |
4350 | |
4545 | |
4351 | The name of the F<ev.h> header file used to include it. The default if |
4546 | The name of the F<ev.h> header file used to include it. The default if |
4352 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4547 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4376 | will have the C<struct ev_loop *> as first argument, and you can create |
4571 | will have the C<struct ev_loop *> as first argument, and you can create |
4377 | additional independent event loops. Otherwise there will be no support |
4572 | additional independent event loops. Otherwise there will be no support |
4378 | for multiple event loops and there is no first event loop pointer |
4573 | for multiple event loops and there is no first event loop pointer |
4379 | argument. Instead, all functions act on the single default loop. |
4574 | argument. Instead, all functions act on the single default loop. |
4380 | |
4575 | |
|
|
4576 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4577 | default loop when multiplicity is switched off - you always have to |
|
|
4578 | initialise the loop manually in this case. |
|
|
4579 | |
4381 | =item EV_MINPRI |
4580 | =item EV_MINPRI |
4382 | |
4581 | |
4383 | =item EV_MAXPRI |
4582 | =item EV_MAXPRI |
4384 | |
4583 | |
4385 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4584 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4482 | |
4681 | |
4483 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4682 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4484 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4683 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4485 | your program might be left out as well - a binary starting a timer and an |
4684 | your program might be left out as well - a binary starting a timer and an |
4486 | I/O watcher then might come out at only 5Kb. |
4685 | I/O watcher then might come out at only 5Kb. |
|
|
4686 | |
|
|
4687 | =item EV_API_STATIC |
|
|
4688 | |
|
|
4689 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4690 | will have static linkage. This means that libev will not export any |
|
|
4691 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4692 | when you embed libev, only want to use libev functions in a single file, |
|
|
4693 | and do not want its identifiers to be visible. |
|
|
4694 | |
|
|
4695 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4696 | wants to use libev. |
|
|
4697 | |
|
|
4698 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4699 | doesn't support the required declaration syntax. |
4487 | |
4700 | |
4488 | =item EV_AVOID_STDIO |
4701 | =item EV_AVOID_STDIO |
4489 | |
4702 | |
4490 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4703 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4491 | functions (printf, scanf, perror etc.). This will increase the code size |
4704 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4871 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5084 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4872 | model. Libev still offers limited functionality on this platform in |
5085 | model. Libev still offers limited functionality on this platform in |
4873 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5086 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4874 | descriptors. This only applies when using Win32 natively, not when using |
5087 | descriptors. This only applies when using Win32 natively, not when using |
4875 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5088 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4876 | as every compielr comes with a slightly differently broken/incompatible |
5089 | as every compiler comes with a slightly differently broken/incompatible |
4877 | environment. |
5090 | environment. |
4878 | |
5091 | |
4879 | Lifting these limitations would basically require the full |
5092 | Lifting these limitations would basically require the full |
4880 | re-implementation of the I/O system. If you are into this kind of thing, |
5093 | re-implementation of the I/O system. If you are into this kind of thing, |
4881 | then note that glib does exactly that for you in a very portable way (note |
5094 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5014 | |
5227 | |
5015 | The type C<double> is used to represent timestamps. It is required to |
5228 | The type C<double> is used to represent timestamps. It is required to |
5016 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5229 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5017 | good enough for at least into the year 4000 with millisecond accuracy |
5230 | good enough for at least into the year 4000 with millisecond accuracy |
5018 | (the design goal for libev). This requirement is overfulfilled by |
5231 | (the design goal for libev). This requirement is overfulfilled by |
5019 | implementations using IEEE 754, which is basically all existing ones. With |
5232 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5233 | |
5020 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5234 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5235 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5236 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5237 | something like that, just kidding). |
5021 | |
5238 | |
5022 | =back |
5239 | =back |
5023 | |
5240 | |
5024 | If you know of other additional requirements drop me a note. |
5241 | If you know of other additional requirements drop me a note. |
5025 | |
5242 | |
… | |
… | |
5087 | =item Processing ev_async_send: O(number_of_async_watchers) |
5304 | =item Processing ev_async_send: O(number_of_async_watchers) |
5088 | |
5305 | |
5089 | =item Processing signals: O(max_signal_number) |
5306 | =item Processing signals: O(max_signal_number) |
5090 | |
5307 | |
5091 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5308 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5092 | calls in the current loop iteration. Checking for async and signal events |
5309 | calls in the current loop iteration and the loop is currently |
|
|
5310 | blocked. Checking for async and signal events involves iterating over all |
5093 | involves iterating over all running async watchers or all signal numbers. |
5311 | running async watchers or all signal numbers. |
5094 | |
5312 | |
5095 | =back |
5313 | =back |
5096 | |
5314 | |
5097 | |
5315 | |
5098 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5316 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5215 | The physical time that is observed. It is apparently strictly monotonic :) |
5433 | The physical time that is observed. It is apparently strictly monotonic :) |
5216 | |
5434 | |
5217 | =item wall-clock time |
5435 | =item wall-clock time |
5218 | |
5436 | |
5219 | The time and date as shown on clocks. Unlike real time, it can actually |
5437 | The time and date as shown on clocks. Unlike real time, it can actually |
5220 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5438 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5221 | clock. |
5439 | clock. |
5222 | |
5440 | |
5223 | =item watcher |
5441 | =item watcher |
5224 | |
5442 | |
5225 | A data structure that describes interest in certain events. Watchers need |
5443 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5228 | =back |
5446 | =back |
5229 | |
5447 | |
5230 | =head1 AUTHOR |
5448 | =head1 AUTHOR |
5231 | |
5449 | |
5232 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5450 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5233 | Magnusson and Emanuele Giaquinta. |
5451 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5234 | |
5452 | |