… | |
… | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
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 | #include <stdio.h> // for puts |
|
|
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
276 | |
278 | |
277 | =back |
279 | =back |
278 | |
280 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
281 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
282 | |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
283 | 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 |
284 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
285 | I<function>). |
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286 | |
|
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287 | The library knows two types of such loops, the I<default> loop, which |
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288 | supports signals and child events, and dynamically created loops which do |
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289 | not. |
284 | |
290 | |
285 | =over 4 |
291 | =over 4 |
286 | |
292 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
293 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
294 | |
… | |
… | |
294 | If you don't know what event loop to use, use the one returned from this |
300 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
301 | function. |
296 | |
302 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
303 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
304 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
305 | as loops cannot be shared easily between threads anyway). |
300 | |
306 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
307 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
308 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
309 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
310 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
387 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
388 | 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 |
389 | 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), |
390 | 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 |
391 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
392 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
393 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
394 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
395 | dropping file descriptors, requiring a system call per change per file |
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396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
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397 | so on. The biggest issue is fork races, however - if a program forks then |
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398 | I<both> parent and child process have to recreate the epoll set, which can |
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399 | take considerable time (one syscall per file descriptor) and is of course |
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|
400 | hard to detect. |
|
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401 | |
|
|
402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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|
403 | of course I<doesn't>, and epoll just loves to report events for totally |
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|
404 | I<different> file descriptors (even already closed ones, so one cannot |
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405 | even remove them from the set) than registered in the set (especially |
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406 | on SMP systems). Libev tries to counter these spurious notifications by |
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407 | employing an additional generation counter and comparing that against the |
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408 | events to filter out spurious ones, recreating the set when required. |
389 | |
409 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
410 | 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 |
411 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
412 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
414 | file descriptors might not work very well if you register events for both |
395 | |
415 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
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397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
416 | |
400 | Best performance from this backend is achieved by not unregistering all |
417 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
418 | 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 |
419 | 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 |
420 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
421 | extra overhead. A fork can both result in spurious notifications as well |
|
|
422 | as in libev having to destroy and recreate the epoll object, which can |
|
|
423 | take considerable time and thus should be avoided. |
|
|
424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
427 | the usage. So sad. |
405 | |
428 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
429 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
408 | |
431 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
432 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
433 | C<EVBACKEND_POLL>. |
411 | |
434 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
435 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
436 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
437 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
438 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
439 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
440 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
441 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
442 | without API changes to existing programs. For this reason it's not being |
|
|
443 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
444 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
445 | system like NetBSD. |
420 | |
446 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
447 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
448 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
449 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
450 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
451 | 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 |
452 | 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 |
453 | 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 |
454 | 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 |
455 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
456 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
457 | cases |
431 | |
458 | |
432 | This backend usually performs well under most conditions. |
459 | This backend usually performs well under most conditions. |
433 | |
460 | |
434 | While nominally embeddable in other event loops, this doesn't work |
461 | 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 |
462 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
463 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
464 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
465 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
466 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
467 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
468 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
469 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
470 | C<NOTE_EOF>. |
444 | |
471 | |
… | |
… | |
464 | might perform better. |
491 | might perform better. |
465 | |
492 | |
466 | On the positive side, with the exception of the spurious readiness |
493 | On the positive side, with the exception of the spurious readiness |
467 | notifications, this backend actually performed fully to specification |
494 | notifications, this backend actually performed fully to specification |
468 | in all tests and is fully embeddable, which is a rare feat among the |
495 | in all tests and is fully embeddable, which is a rare feat among the |
469 | OS-specific backends. |
496 | OS-specific backends (I vastly prefer correctness over speed hacks). |
470 | |
497 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
499 | C<EVBACKEND_POLL>. |
473 | |
500 | |
474 | =item C<EVBACKEND_ALL> |
501 | =item C<EVBACKEND_ALL> |
… | |
… | |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
554 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
555 | 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 |
556 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
557 | for example). |
531 | |
558 | |
532 | Note that certain global state, such as signal state, will not be freed by |
559 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
560 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
561 | as signal and child watchers) would need to be stopped manually. |
535 | |
562 | |
536 | In general it is not advisable to call this function except in the |
563 | 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 |
564 | 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 |
565 | pipe fds. If you need dynamically allocated loops it is better to use |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
566 | C<ev_loop_new> and C<ev_loop_destroy>). |
… | |
… | |
631 | the loop. |
658 | the loop. |
632 | |
659 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
660 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
661 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
662 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
663 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
664 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
665 | iteration of the loop. |
639 | |
666 | |
640 | This is useful if you are waiting for some external event in conjunction |
667 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
668 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
699 | |
726 | |
700 | If you have a watcher you never unregister that should not keep C<ev_loop> |
727 | If you have a watcher you never unregister that should not keep C<ev_loop> |
701 | from returning, call ev_unref() after starting, and ev_ref() before |
728 | from returning, call ev_unref() after starting, and ev_ref() before |
702 | stopping it. |
729 | stopping it. |
703 | |
730 | |
704 | As an example, libev itself uses this for its internal signal pipe: It is |
731 | As an example, libev itself uses this for its internal signal pipe: It |
705 | not visible to the libev user and should not keep C<ev_loop> from exiting |
732 | is not visible to the libev user and should not keep C<ev_loop> from |
706 | if no event watchers registered by it are active. It is also an excellent |
733 | exiting if no event watchers registered by it are active. It is also an |
707 | way to do this for generic recurring timers or from within third-party |
734 | excellent way to do this for generic recurring timers or from within |
708 | libraries. Just remember to I<unref after start> and I<ref before stop> |
735 | third-party libraries. Just remember to I<unref after start> and I<ref |
709 | (but only if the watcher wasn't active before, or was active before, |
736 | before stop> (but only if the watcher wasn't active before, or was active |
710 | respectively). |
737 | before, respectively. Note also that libev might stop watchers itself |
|
|
738 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
739 | in the callback). |
711 | |
740 | |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
741 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
713 | running when nothing else is active. |
742 | running when nothing else is active. |
714 | |
743 | |
715 | ev_signal exitsig; |
744 | ev_signal exitsig; |
… | |
… | |
768 | they fire on, say, one-second boundaries only. |
797 | they fire on, say, one-second boundaries only. |
769 | |
798 | |
770 | =item ev_loop_verify (loop) |
799 | =item ev_loop_verify (loop) |
771 | |
800 | |
772 | This function only does something when C<EV_VERIFY> support has been |
801 | 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 |
802 | 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 |
803 | 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 |
804 | is found to be inconsistent, it will print an error message to standard |
776 | error and call C<abort ()>. |
805 | error and call C<abort ()>. |
777 | |
806 | |
778 | This can be used to catch bugs inside libev itself: under normal |
807 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
781 | |
810 | |
782 | =back |
811 | =back |
783 | |
812 | |
784 | |
813 | |
785 | =head1 ANATOMY OF A WATCHER |
814 | =head1 ANATOMY OF A WATCHER |
|
|
815 | |
|
|
816 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
817 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
818 | watchers and C<ev_io_start> for I/O watchers. |
786 | |
819 | |
787 | A watcher is a structure that you create and register to record your |
820 | 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 |
821 | 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: |
822 | become readable, you would create an C<ev_io> watcher for that: |
790 | |
823 | |
… | |
… | |
793 | ev_io_stop (w); |
826 | ev_io_stop (w); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
827 | ev_unloop (loop, EVUNLOOP_ALL); |
795 | } |
828 | } |
796 | |
829 | |
797 | struct ev_loop *loop = ev_default_loop (0); |
830 | struct ev_loop *loop = ev_default_loop (0); |
|
|
831 | |
798 | ev_io stdin_watcher; |
832 | ev_io stdin_watcher; |
|
|
833 | |
799 | ev_init (&stdin_watcher, my_cb); |
834 | ev_init (&stdin_watcher, my_cb); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
835 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
801 | ev_io_start (loop, &stdin_watcher); |
836 | ev_io_start (loop, &stdin_watcher); |
|
|
837 | |
802 | ev_loop (loop, 0); |
838 | ev_loop (loop, 0); |
803 | |
839 | |
804 | As you can see, you are responsible for allocating the memory for your |
840 | 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, |
841 | watcher structures (and it is I<usually> a bad idea to do this on the |
806 | although this can sometimes be quite valid). |
842 | stack). |
|
|
843 | |
|
|
844 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
845 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
807 | |
846 | |
808 | Each watcher structure must be initialised by a call to C<ev_init |
847 | Each watcher structure must be initialised by a call to C<ev_init |
809 | (watcher *, callback)>, which expects a callback to be provided. This |
848 | (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 |
849 | 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 |
850 | watchers, each time the event loop detects that the file descriptor given |
812 | is readable and/or writable). |
851 | is readable and/or writable). |
813 | |
852 | |
814 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
853 | 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 |
854 | 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 |
855 | is also a macro to combine initialisation and setting in one call: C<< |
817 | (watcher *, callback, ...) >>. |
856 | ev_TYPE_init (watcher *, callback, ...) >>. |
818 | |
857 | |
819 | To make the watcher actually watch out for events, you have to start it |
858 | 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 |
859 | 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 |
860 | *) >>), and you can stop watching for events at any time by calling the |
822 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
861 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
823 | |
862 | |
824 | As long as your watcher is active (has been started but not stopped) you |
863 | 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 |
864 | must not touch the values stored in it. Most specifically you must never |
826 | reinitialise it or call its C<set> macro. |
865 | reinitialise it or call its C<ev_TYPE_set> macro. |
827 | |
866 | |
828 | Each and every callback receives the event loop pointer as first, the |
867 | 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 |
868 | registered watcher structure as second, and a bitset of received events as |
830 | third argument. |
869 | third argument. |
831 | |
870 | |
… | |
… | |
889 | |
928 | |
890 | =item C<EV_ASYNC> |
929 | =item C<EV_ASYNC> |
891 | |
930 | |
892 | The given async watcher has been asynchronously notified (see C<ev_async>). |
931 | The given async watcher has been asynchronously notified (see C<ev_async>). |
893 | |
932 | |
|
|
933 | =item C<EV_CUSTOM> |
|
|
934 | |
|
|
935 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
936 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
937 | |
894 | =item C<EV_ERROR> |
938 | =item C<EV_ERROR> |
895 | |
939 | |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
940 | An unspecified error has occurred, the watcher has been stopped. This might |
897 | happen because the watcher could not be properly started because libev |
941 | 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 |
942 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
912 | |
956 | |
913 | =back |
957 | =back |
914 | |
958 | |
915 | =head2 GENERIC WATCHER FUNCTIONS |
959 | =head2 GENERIC WATCHER FUNCTIONS |
916 | |
960 | |
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 | |
|
|
920 | =over 4 |
961 | =over 4 |
921 | |
962 | |
922 | =item C<ev_init> (ev_TYPE *watcher, callback) |
963 | =item C<ev_init> (ev_TYPE *watcher, callback) |
923 | |
964 | |
924 | This macro initialises the generic portion of a watcher. The contents |
965 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
1032 | The default priority used by watchers when no priority has been set is |
1073 | The default priority used by watchers when no priority has been set is |
1033 | always C<0>, which is supposed to not be too high and not be too low :). |
1074 | always C<0>, which is supposed to not be too high and not be too low :). |
1034 | |
1075 | |
1035 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1076 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1036 | fine, as long as you do not mind that the priority value you query might |
1077 | fine, as long as you do not mind that the priority value you query might |
1037 | or might not have been adjusted to be within valid range. |
1078 | or might not have been clamped to the valid range. |
1038 | |
1079 | |
1039 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1080 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1040 | |
1081 | |
1041 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1082 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1042 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1083 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1283 | year, it will still time out after (roughly) one hour. "Roughly" because |
1324 | year, it will still time out after (roughly) one hour. "Roughly" because |
1284 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1325 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1285 | monotonic clock option helps a lot here). |
1326 | monotonic clock option helps a lot here). |
1286 | |
1327 | |
1287 | The callback is guaranteed to be invoked only I<after> its timeout has |
1328 | The callback is guaranteed to be invoked only I<after> its timeout has |
1288 | passed, but if multiple timers become ready during the same loop iteration |
1329 | passed. If multiple timers become ready during the same loop iteration |
1289 | then order of execution is undefined. |
1330 | then the ones with earlier time-out values are invoked before ones with |
|
|
1331 | later time-out values (but this is no longer true when a callback calls |
|
|
1332 | C<ev_loop> recursively). |
1290 | |
1333 | |
1291 | =head3 Be smart about timeouts |
1334 | =head3 Be smart about timeouts |
1292 | |
1335 | |
1293 | Many real-world problems invole some kind of time-out, usually for error |
1336 | Many real-world problems involve some kind of timeout, usually for error |
1294 | recovery. A typical example is an HTTP request - if the other side hangs, |
1337 | recovery. A typical example is an HTTP request - if the other side hangs, |
1295 | you want to raise some error after a while. |
1338 | you want to raise some error after a while. |
1296 | |
1339 | |
1297 | Here are some ways on how to handle this problem, from simple and |
1340 | What follows are some ways to handle this problem, from obvious and |
1298 | inefficient to very efficient. |
1341 | inefficient to smart and efficient. |
1299 | |
1342 | |
1300 | In the following examples a 60 second activity timeout is assumed - a |
1343 | In the following, a 60 second activity timeout is assumed - a timeout that |
1301 | timeout that gets reset to 60 seconds each time some data ("a lifesign") |
1344 | gets reset to 60 seconds each time there is activity (e.g. each time some |
1302 | was received. |
1345 | data or other life sign was received). |
1303 | |
1346 | |
1304 | =over 4 |
1347 | =over 4 |
1305 | |
1348 | |
1306 | =item 1. Use a timer and stop, reinitialise, start it on activity. |
1349 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
1307 | |
1350 | |
1308 | This is the most obvious, but not the most simple way: In the beginning, |
1351 | This is the most obvious, but not the most simple way: In the beginning, |
1309 | start the watcher: |
1352 | start the watcher: |
1310 | |
1353 | |
1311 | ev_timer_init (timer, callback, 60., 0.); |
1354 | ev_timer_init (timer, callback, 60., 0.); |
1312 | ev_timer_start (loop, timer); |
1355 | ev_timer_start (loop, timer); |
1313 | |
1356 | |
1314 | Then, each time there is some activity, C<ev_timer_stop> the timer, |
1357 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
1315 | initialise it again, and start it: |
1358 | and start it again: |
1316 | |
1359 | |
1317 | ev_timer_stop (loop, timer); |
1360 | ev_timer_stop (loop, timer); |
1318 | ev_timer_set (timer, 60., 0.); |
1361 | ev_timer_set (timer, 60., 0.); |
1319 | ev_timer_start (loop, timer); |
1362 | ev_timer_start (loop, timer); |
1320 | |
1363 | |
1321 | This is relatively simple to implement, but means that each time there |
1364 | This is relatively simple to implement, but means that each time there is |
1322 | is some activity, libev will first have to remove the timer from it's |
1365 | some activity, libev will first have to remove the timer from its internal |
1323 | internal data strcuture and then add it again. |
1366 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1367 | still not a constant-time operation. |
1324 | |
1368 | |
1325 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
1369 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
1326 | |
1370 | |
1327 | This is the easiest way, and involves using C<ev_timer_again> instead of |
1371 | This is the easiest way, and involves using C<ev_timer_again> instead of |
1328 | C<ev_timer_start>. |
1372 | C<ev_timer_start>. |
1329 | |
1373 | |
1330 | For this, configure an C<ev_timer> with a C<repeat> value of C<60> and |
1374 | To implement this, configure an C<ev_timer> with a C<repeat> value |
1331 | then call C<ev_timer_again> at start and each time you successfully read |
1375 | of C<60> and then call C<ev_timer_again> at start and each time you |
1332 | or write some data. If you go into an idle state where you do not expect |
1376 | successfully read or write some data. If you go into an idle state where |
1333 | data to travel on the socket, you can C<ev_timer_stop> the timer, and |
1377 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
1334 | C<ev_timer_again> will automatically restart it if need be. |
1378 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
1335 | |
1379 | |
1336 | That means you can ignore the C<after> value and C<ev_timer_start> |
1380 | That means you can ignore both the C<ev_timer_start> function and the |
1337 | altogether and only ever use the C<repeat> value and C<ev_timer_again>. |
1381 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1382 | member and C<ev_timer_again>. |
1338 | |
1383 | |
1339 | At start: |
1384 | At start: |
1340 | |
1385 | |
1341 | ev_timer_init (timer, callback, 0., 60.); |
1386 | ev_timer_init (timer, callback); |
|
|
1387 | timer->repeat = 60.; |
1342 | ev_timer_again (loop, timer); |
1388 | ev_timer_again (loop, timer); |
1343 | |
1389 | |
1344 | Each time you receive some data: |
1390 | Each time there is some activity: |
1345 | |
1391 | |
1346 | ev_timer_again (loop, timer); |
1392 | ev_timer_again (loop, timer); |
1347 | |
1393 | |
1348 | It is even possible to change the time-out on the fly: |
1394 | It is even possible to change the time-out on the fly, regardless of |
|
|
1395 | whether the watcher is active or not: |
1349 | |
1396 | |
1350 | timer->repeat = 30.; |
1397 | timer->repeat = 30.; |
1351 | ev_timer_again (loop, timer); |
1398 | ev_timer_again (loop, timer); |
1352 | |
1399 | |
1353 | This is slightly more efficient then stopping/starting the timer each time |
1400 | This is slightly more efficient then stopping/starting the timer each time |
1354 | you want to modify its timeout value, as libev does not have to completely |
1401 | you want to modify its timeout value, as libev does not have to completely |
1355 | remove and re-insert the timer from/into it's internal data structure. |
1402 | remove and re-insert the timer from/into its internal data structure. |
|
|
1403 | |
|
|
1404 | It is, however, even simpler than the "obvious" way to do it. |
1356 | |
1405 | |
1357 | =item 3. Let the timer time out, but then re-arm it as required. |
1406 | =item 3. Let the timer time out, but then re-arm it as required. |
1358 | |
1407 | |
1359 | This method is more tricky, but usually most efficient: Most timeouts are |
1408 | This method is more tricky, but usually most efficient: Most timeouts are |
1360 | relatively long compared to the loop iteration time - in our example, |
1409 | relatively long compared to the intervals between other activity - in |
1361 | within 60 seconds, there are usually many I/O events with associated |
1410 | our example, within 60 seconds, there are usually many I/O events with |
1362 | activity resets. |
1411 | associated activity resets. |
1363 | |
1412 | |
1364 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1413 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1365 | but remember the time of last activity, and check for a real timeout only |
1414 | but remember the time of last activity, and check for a real timeout only |
1366 | within the callback: |
1415 | within the callback: |
1367 | |
1416 | |
1368 | ev_tstamp last_activity; // time of last activity |
1417 | ev_tstamp last_activity; // time of last activity |
1369 | |
1418 | |
1370 | static void |
1419 | static void |
1371 | callback (EV_P_ ev_timer *w, int revents) |
1420 | callback (EV_P_ ev_timer *w, int revents) |
1372 | { |
1421 | { |
1373 | ev_tstamp now = ev_now (EV_A); |
1422 | ev_tstamp now = ev_now (EV_A); |
1374 | ev_tstamp timeout = last_activity + 60.; |
1423 | ev_tstamp timeout = last_activity + 60.; |
1375 | |
1424 | |
1376 | // if last_activity is older than now - timeout, we did time out |
1425 | // if last_activity + 60. is older than now, we did time out |
1377 | if (timeout < now) |
1426 | if (timeout < now) |
1378 | { |
1427 | { |
1379 | // timeout occured, take action |
1428 | // timeout occured, take action |
1380 | } |
1429 | } |
1381 | else |
1430 | else |
1382 | { |
1431 | { |
1383 | // callback was invoked, but there was some activity, re-arm |
1432 | // callback was invoked, but there was some activity, re-arm |
1384 | // to fire in last_activity + 60. |
1433 | // the watcher to fire in last_activity + 60, which is |
|
|
1434 | // guaranteed to be in the future, so "again" is positive: |
1385 | w->again = timeout - now; |
1435 | w->repeat = timeout - now; |
1386 | ev_timer_again (EV_A_ w); |
1436 | ev_timer_again (EV_A_ w); |
1387 | } |
1437 | } |
1388 | } |
1438 | } |
1389 | |
1439 | |
1390 | To summarise the callback: first calculate the real time-out (defined as |
1440 | To summarise the callback: first calculate the real timeout (defined |
1391 | "60 seconds after the last activity"), then check if that time has been |
1441 | as "60 seconds after the last activity"), then check if that time has |
1392 | reached, which means there was a real timeout. Otherwise the callback was |
1442 | been reached, which means something I<did>, in fact, time out. Otherwise |
1393 | invoked too early (timeout is in the future), so re-schedule the timer to |
1443 | the callback was invoked too early (C<timeout> is in the future), so |
1394 | fire at that future time. |
1444 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1445 | a timeout then. |
1395 | |
1446 | |
1396 | Note how C<ev_timer_again> is used, taking advantage of the |
1447 | Note how C<ev_timer_again> is used, taking advantage of the |
1397 | C<ev_timer_again> optimisation when the timer is already running. |
1448 | C<ev_timer_again> optimisation when the timer is already running. |
1398 | |
1449 | |
1399 | This scheme causes more callback invocations (about one every 60 seconds), |
1450 | This scheme causes more callback invocations (about one every 60 seconds |
1400 | but virtually no calls to libev to change the timeout. |
1451 | minus half the average time between activity), but virtually no calls to |
|
|
1452 | libev to change the timeout. |
1401 | |
1453 | |
1402 | To start the timer, simply intiialise the watcher and C<last_activity>, |
1454 | To start the timer, simply initialise the watcher and set C<last_activity> |
1403 | then call the callback: |
1455 | to the current time (meaning we just have some activity :), then call the |
|
|
1456 | callback, which will "do the right thing" and start the timer: |
1404 | |
1457 | |
1405 | ev_timer_init (timer, callback); |
1458 | ev_timer_init (timer, callback); |
1406 | last_activity = ev_now (loop); |
1459 | last_activity = ev_now (loop); |
1407 | callback (loop, timer, EV_TIMEOUT); |
1460 | callback (loop, timer, EV_TIMEOUT); |
1408 | |
1461 | |
1409 | And when there is some activity, simply remember the time in |
1462 | And when there is some activity, simply store the current time in |
1410 | C<last_activity>: |
1463 | C<last_activity>, no libev calls at all: |
1411 | |
1464 | |
1412 | last_actiivty = ev_now (loop); |
1465 | last_actiivty = ev_now (loop); |
1413 | |
1466 | |
1414 | This technique is slightly more complex, but in most cases where the |
1467 | This technique is slightly more complex, but in most cases where the |
1415 | time-out is unlikely to be triggered, much more efficient. |
1468 | time-out is unlikely to be triggered, much more efficient. |
1416 | |
1469 | |
|
|
1470 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1471 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1472 | fix things for you. |
|
|
1473 | |
|
|
1474 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1475 | |
|
|
1476 | If there is not one request, but many thousands (millions...), all |
|
|
1477 | employing some kind of timeout with the same timeout value, then one can |
|
|
1478 | do even better: |
|
|
1479 | |
|
|
1480 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1481 | at the I<end> of the list. |
|
|
1482 | |
|
|
1483 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1484 | the list is expected to fire (for example, using the technique #3). |
|
|
1485 | |
|
|
1486 | When there is some activity, remove the timer from the list, recalculate |
|
|
1487 | the timeout, append it to the end of the list again, and make sure to |
|
|
1488 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1489 | |
|
|
1490 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1491 | starting, stopping and updating the timers, at the expense of a major |
|
|
1492 | complication, and having to use a constant timeout. The constant timeout |
|
|
1493 | ensures that the list stays sorted. |
|
|
1494 | |
1417 | =back |
1495 | =back |
|
|
1496 | |
|
|
1497 | So which method the best? |
|
|
1498 | |
|
|
1499 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1500 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1501 | better, and isn't very complicated either. In most case, choosing either |
|
|
1502 | one is fine, with #3 being better in typical situations. |
|
|
1503 | |
|
|
1504 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1505 | rather complicated, but extremely efficient, something that really pays |
|
|
1506 | off after the first million or so of active timers, i.e. it's usually |
|
|
1507 | overkill :) |
1418 | |
1508 | |
1419 | =head3 The special problem of time updates |
1509 | =head3 The special problem of time updates |
1420 | |
1510 | |
1421 | Establishing the current time is a costly operation (it usually takes at |
1511 | Establishing the current time is a costly operation (it usually takes at |
1422 | least two system calls): EV therefore updates its idea of the current |
1512 | least two system calls): EV therefore updates its idea of the current |
… | |
… | |
1515 | =head2 C<ev_periodic> - to cron or not to cron? |
1605 | =head2 C<ev_periodic> - to cron or not to cron? |
1516 | |
1606 | |
1517 | Periodic watchers are also timers of a kind, but they are very versatile |
1607 | Periodic watchers are also timers of a kind, but they are very versatile |
1518 | (and unfortunately a bit complex). |
1608 | (and unfortunately a bit complex). |
1519 | |
1609 | |
1520 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1610 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1521 | but on wall clock time (absolute time). You can tell a periodic watcher |
1611 | relative time, the physical time that passes) but on wall clock time |
1522 | to trigger after some specific point in time. For example, if you tell a |
1612 | (absolute time, the thing you can read on your calender or clock). The |
1523 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1613 | difference is that wall clock time can run faster or slower than real |
1524 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1614 | time, and time jumps are not uncommon (e.g. when you adjust your |
1525 | clock to January of the previous year, then it will take more than year |
1615 | wrist-watch). |
1526 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1527 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1528 | |
1616 | |
|
|
1617 | You can tell a periodic watcher to trigger after some specific point |
|
|
1618 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1619 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1620 | not a delay) and then reset your system clock to January of the previous |
|
|
1621 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1622 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1623 | it, as it uses a relative timeout). |
|
|
1624 | |
1529 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1625 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1530 | such as triggering an event on each "midnight, local time", or other |
1626 | timers, such as triggering an event on each "midnight, local time", or |
1531 | complicated rules. |
1627 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1628 | those cannot react to time jumps. |
1532 | |
1629 | |
1533 | As with timers, the callback is guaranteed to be invoked only when the |
1630 | As with timers, the callback is guaranteed to be invoked only when the |
1534 | time (C<at>) has passed, but if multiple periodic timers become ready |
1631 | point in time where it is supposed to trigger has passed. If multiple |
1535 | during the same loop iteration, then order of execution is undefined. |
1632 | timers become ready during the same loop iteration then the ones with |
|
|
1633 | earlier time-out values are invoked before ones with later time-out values |
|
|
1634 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1536 | |
1635 | |
1537 | =head3 Watcher-Specific Functions and Data Members |
1636 | =head3 Watcher-Specific Functions and Data Members |
1538 | |
1637 | |
1539 | =over 4 |
1638 | =over 4 |
1540 | |
1639 | |
1541 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1640 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1542 | |
1641 | |
1543 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1642 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1544 | |
1643 | |
1545 | Lots of arguments, lets sort it out... There are basically three modes of |
1644 | Lots of arguments, let's sort it out... There are basically three modes of |
1546 | operation, and we will explain them from simplest to most complex: |
1645 | operation, and we will explain them from simplest to most complex: |
1547 | |
1646 | |
1548 | =over 4 |
1647 | =over 4 |
1549 | |
1648 | |
1550 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1649 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1551 | |
1650 | |
1552 | In this configuration the watcher triggers an event after the wall clock |
1651 | In this configuration the watcher triggers an event after the wall clock |
1553 | time C<at> has passed. It will not repeat and will not adjust when a time |
1652 | time C<offset> has passed. It will not repeat and will not adjust when a |
1554 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1653 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1555 | only run when the system clock reaches or surpasses this time. |
1654 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1655 | this point in time. |
1556 | |
1656 | |
1557 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1657 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1558 | |
1658 | |
1559 | In this mode the watcher will always be scheduled to time out at the next |
1659 | In this mode the watcher will always be scheduled to time out at the next |
1560 | C<at + N * interval> time (for some integer N, which can also be negative) |
1660 | C<offset + N * interval> time (for some integer N, which can also be |
1561 | and then repeat, regardless of any time jumps. |
1661 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1662 | argument is merely an offset into the C<interval> periods. |
1562 | |
1663 | |
1563 | This can be used to create timers that do not drift with respect to the |
1664 | This can be used to create timers that do not drift with respect to the |
1564 | system clock, for example, here is a C<ev_periodic> that triggers each |
1665 | system clock, for example, here is an C<ev_periodic> that triggers each |
1565 | hour, on the hour: |
1666 | hour, on the hour (with respect to UTC): |
1566 | |
1667 | |
1567 | ev_periodic_set (&periodic, 0., 3600., 0); |
1668 | ev_periodic_set (&periodic, 0., 3600., 0); |
1568 | |
1669 | |
1569 | This doesn't mean there will always be 3600 seconds in between triggers, |
1670 | This doesn't mean there will always be 3600 seconds in between triggers, |
1570 | but only that the callback will be called when the system time shows a |
1671 | but only that the callback will be called when the system time shows a |
1571 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1672 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1572 | by 3600. |
1673 | by 3600. |
1573 | |
1674 | |
1574 | Another way to think about it (for the mathematically inclined) is that |
1675 | Another way to think about it (for the mathematically inclined) is that |
1575 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1676 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1576 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1677 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1577 | |
1678 | |
1578 | For numerical stability it is preferable that the C<at> value is near |
1679 | For numerical stability it is preferable that the C<offset> value is near |
1579 | C<ev_now ()> (the current time), but there is no range requirement for |
1680 | C<ev_now ()> (the current time), but there is no range requirement for |
1580 | this value, and in fact is often specified as zero. |
1681 | this value, and in fact is often specified as zero. |
1581 | |
1682 | |
1582 | Note also that there is an upper limit to how often a timer can fire (CPU |
1683 | Note also that there is an upper limit to how often a timer can fire (CPU |
1583 | speed for example), so if C<interval> is very small then timing stability |
1684 | speed for example), so if C<interval> is very small then timing stability |
1584 | will of course deteriorate. Libev itself tries to be exact to be about one |
1685 | will of course deteriorate. Libev itself tries to be exact to be about one |
1585 | millisecond (if the OS supports it and the machine is fast enough). |
1686 | millisecond (if the OS supports it and the machine is fast enough). |
1586 | |
1687 | |
1587 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1688 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1588 | |
1689 | |
1589 | In this mode the values for C<interval> and C<at> are both being |
1690 | In this mode the values for C<interval> and C<offset> are both being |
1590 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1691 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1591 | reschedule callback will be called with the watcher as first, and the |
1692 | reschedule callback will be called with the watcher as first, and the |
1592 | current time as second argument. |
1693 | current time as second argument. |
1593 | |
1694 | |
1594 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1695 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1595 | ever, or make ANY event loop modifications whatsoever>. |
1696 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1697 | allowed by documentation here>. |
1596 | |
1698 | |
1597 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1699 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1598 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1700 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1599 | only event loop modification you are allowed to do). |
1701 | only event loop modification you are allowed to do). |
1600 | |
1702 | |
… | |
… | |
1630 | a different time than the last time it was called (e.g. in a crond like |
1732 | a different time than the last time it was called (e.g. in a crond like |
1631 | program when the crontabs have changed). |
1733 | program when the crontabs have changed). |
1632 | |
1734 | |
1633 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1735 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1634 | |
1736 | |
1635 | When active, returns the absolute time that the watcher is supposed to |
1737 | When active, returns the absolute time that the watcher is supposed |
1636 | trigger next. |
1738 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1739 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1740 | rescheduling modes. |
1637 | |
1741 | |
1638 | =item ev_tstamp offset [read-write] |
1742 | =item ev_tstamp offset [read-write] |
1639 | |
1743 | |
1640 | When repeating, this contains the offset value, otherwise this is the |
1744 | When repeating, this contains the offset value, otherwise this is the |
1641 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1745 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1746 | although libev might modify this value for better numerical stability). |
1642 | |
1747 | |
1643 | Can be modified any time, but changes only take effect when the periodic |
1748 | Can be modified any time, but changes only take effect when the periodic |
1644 | timer fires or C<ev_periodic_again> is being called. |
1749 | timer fires or C<ev_periodic_again> is being called. |
1645 | |
1750 | |
1646 | =item ev_tstamp interval [read-write] |
1751 | =item ev_tstamp interval [read-write] |
… | |
… | |
1852 | |
1957 | |
1853 | |
1958 | |
1854 | =head2 C<ev_stat> - did the file attributes just change? |
1959 | =head2 C<ev_stat> - did the file attributes just change? |
1855 | |
1960 | |
1856 | This watches a file system path for attribute changes. That is, it calls |
1961 | This watches a file system path for attribute changes. That is, it calls |
1857 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1962 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1858 | compared to the last time, invoking the callback if it did. |
1963 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1964 | it did. |
1859 | |
1965 | |
1860 | The path does not need to exist: changing from "path exists" to "path does |
1966 | The path does not need to exist: changing from "path exists" to "path does |
1861 | not exist" is a status change like any other. The condition "path does |
1967 | not exist" is a status change like any other. The condition "path does not |
1862 | not exist" is signified by the C<st_nlink> field being zero (which is |
1968 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1863 | otherwise always forced to be at least one) and all the other fields of |
1969 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1864 | the stat buffer having unspecified contents. |
1970 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1971 | contents. |
1865 | |
1972 | |
1866 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1973 | The path I<must not> end in a slash or contain special components such as |
|
|
1974 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1867 | relative and your working directory changes, the behaviour is undefined. |
1975 | your working directory changes, then the behaviour is undefined. |
1868 | |
1976 | |
1869 | Since there is no standard kernel interface to do this, the portable |
1977 | Since there is no portable change notification interface available, the |
1870 | implementation simply calls C<stat (2)> regularly on the path to see if |
1978 | portable implementation simply calls C<stat(2)> regularly on the path |
1871 | it changed somehow. You can specify a recommended polling interval for |
1979 | to see if it changed somehow. You can specify a recommended polling |
1872 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1980 | interval for this case. If you specify a polling interval of C<0> (highly |
1873 | then a I<suitable, unspecified default> value will be used (which |
1981 | recommended!) then a I<suitable, unspecified default> value will be used |
1874 | you can expect to be around five seconds, although this might change |
1982 | (which you can expect to be around five seconds, although this might |
1875 | dynamically). Libev will also impose a minimum interval which is currently |
1983 | change dynamically). Libev will also impose a minimum interval which is |
1876 | around C<0.1>, but thats usually overkill. |
1984 | currently around C<0.1>, but that's usually overkill. |
1877 | |
1985 | |
1878 | This watcher type is not meant for massive numbers of stat watchers, |
1986 | This watcher type is not meant for massive numbers of stat watchers, |
1879 | as even with OS-supported change notifications, this can be |
1987 | as even with OS-supported change notifications, this can be |
1880 | resource-intensive. |
1988 | resource-intensive. |
1881 | |
1989 | |
1882 | At the time of this writing, the only OS-specific interface implemented |
1990 | At the time of this writing, the only OS-specific interface implemented |
1883 | is the Linux inotify interface (implementing kqueue support is left as |
1991 | is the Linux inotify interface (implementing kqueue support is left as an |
1884 | an exercise for the reader. Note, however, that the author sees no way |
1992 | exercise for the reader. Note, however, that the author sees no way of |
1885 | of implementing C<ev_stat> semantics with kqueue). |
1993 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1886 | |
1994 | |
1887 | =head3 ABI Issues (Largefile Support) |
1995 | =head3 ABI Issues (Largefile Support) |
1888 | |
1996 | |
1889 | Libev by default (unless the user overrides this) uses the default |
1997 | Libev by default (unless the user overrides this) uses the default |
1890 | compilation environment, which means that on systems with large file |
1998 | compilation environment, which means that on systems with large file |
1891 | support disabled by default, you get the 32 bit version of the stat |
1999 | support disabled by default, you get the 32 bit version of the stat |
1892 | structure. When using the library from programs that change the ABI to |
2000 | structure. When using the library from programs that change the ABI to |
1893 | use 64 bit file offsets the programs will fail. In that case you have to |
2001 | use 64 bit file offsets the programs will fail. In that case you have to |
1894 | compile libev with the same flags to get binary compatibility. This is |
2002 | compile libev with the same flags to get binary compatibility. This is |
1895 | obviously the case with any flags that change the ABI, but the problem is |
2003 | obviously the case with any flags that change the ABI, but the problem is |
1896 | most noticeably disabled with ev_stat and large file support. |
2004 | most noticeably displayed with ev_stat and large file support. |
1897 | |
2005 | |
1898 | The solution for this is to lobby your distribution maker to make large |
2006 | The solution for this is to lobby your distribution maker to make large |
1899 | file interfaces available by default (as e.g. FreeBSD does) and not |
2007 | file interfaces available by default (as e.g. FreeBSD does) and not |
1900 | optional. Libev cannot simply switch on large file support because it has |
2008 | optional. Libev cannot simply switch on large file support because it has |
1901 | to exchange stat structures with application programs compiled using the |
2009 | to exchange stat structures with application programs compiled using the |
1902 | default compilation environment. |
2010 | default compilation environment. |
1903 | |
2011 | |
1904 | =head3 Inotify and Kqueue |
2012 | =head3 Inotify and Kqueue |
1905 | |
2013 | |
1906 | When C<inotify (7)> support has been compiled into libev (generally |
2014 | When C<inotify (7)> support has been compiled into libev and present at |
1907 | only available with Linux 2.6.25 or above due to bugs in earlier |
2015 | runtime, it will be used to speed up change detection where possible. The |
1908 | implementations) and present at runtime, it will be used to speed up |
2016 | inotify descriptor will be created lazily when the first C<ev_stat> |
1909 | change detection where possible. The inotify descriptor will be created |
2017 | watcher is being started. |
1910 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1911 | |
2018 | |
1912 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2019 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1913 | except that changes might be detected earlier, and in some cases, to avoid |
2020 | except that changes might be detected earlier, and in some cases, to avoid |
1914 | making regular C<stat> calls. Even in the presence of inotify support |
2021 | making regular C<stat> calls. Even in the presence of inotify support |
1915 | there are many cases where libev has to resort to regular C<stat> polling, |
2022 | there are many cases where libev has to resort to regular C<stat> polling, |
1916 | but as long as the path exists, libev usually gets away without polling. |
2023 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2024 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2025 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2026 | xfs are fully working) libev usually gets away without polling. |
1917 | |
2027 | |
1918 | There is no support for kqueue, as apparently it cannot be used to |
2028 | There is no support for kqueue, as apparently it cannot be used to |
1919 | implement this functionality, due to the requirement of having a file |
2029 | implement this functionality, due to the requirement of having a file |
1920 | descriptor open on the object at all times, and detecting renames, unlinks |
2030 | descriptor open on the object at all times, and detecting renames, unlinks |
1921 | etc. is difficult. |
2031 | etc. is difficult. |
1922 | |
2032 | |
|
|
2033 | =head3 C<stat ()> is a synchronous operation |
|
|
2034 | |
|
|
2035 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2036 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2037 | ()>, which is a synchronous operation. |
|
|
2038 | |
|
|
2039 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2040 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2041 | as the path data is usually in memory already (except when starting the |
|
|
2042 | watcher). |
|
|
2043 | |
|
|
2044 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2045 | time due to network issues, and even under good conditions, a stat call |
|
|
2046 | often takes multiple milliseconds. |
|
|
2047 | |
|
|
2048 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2049 | paths, although this is fully supported by libev. |
|
|
2050 | |
1923 | =head3 The special problem of stat time resolution |
2051 | =head3 The special problem of stat time resolution |
1924 | |
2052 | |
1925 | The C<stat ()> system call only supports full-second resolution portably, and |
2053 | The C<stat ()> system call only supports full-second resolution portably, |
1926 | even on systems where the resolution is higher, most file systems still |
2054 | and even on systems where the resolution is higher, most file systems |
1927 | only support whole seconds. |
2055 | still only support whole seconds. |
1928 | |
2056 | |
1929 | That means that, if the time is the only thing that changes, you can |
2057 | That means that, if the time is the only thing that changes, you can |
1930 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2058 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1931 | calls your callback, which does something. When there is another update |
2059 | calls your callback, which does something. When there is another update |
1932 | within the same second, C<ev_stat> will be unable to detect unless the |
2060 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2075 | |
2203 | |
2076 | =head3 Watcher-Specific Functions and Data Members |
2204 | =head3 Watcher-Specific Functions and Data Members |
2077 | |
2205 | |
2078 | =over 4 |
2206 | =over 4 |
2079 | |
2207 | |
2080 | =item ev_idle_init (ev_signal *, callback) |
2208 | =item ev_idle_init (ev_idle *, callback) |
2081 | |
2209 | |
2082 | Initialises and configures the idle watcher - it has no parameters of any |
2210 | Initialises and configures the idle watcher - it has no parameters of any |
2083 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2211 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2084 | believe me. |
2212 | believe me. |
2085 | |
2213 | |
… | |
… | |
2324 | some fds have to be watched and handled very quickly (with low latency), |
2452 | some fds have to be watched and handled very quickly (with low latency), |
2325 | and even priorities and idle watchers might have too much overhead. In |
2453 | and even priorities and idle watchers might have too much overhead. In |
2326 | this case you would put all the high priority stuff in one loop and all |
2454 | this case you would put all the high priority stuff in one loop and all |
2327 | the rest in a second one, and embed the second one in the first. |
2455 | the rest in a second one, and embed the second one in the first. |
2328 | |
2456 | |
2329 | As long as the watcher is active, the callback will be invoked every time |
2457 | As long as the watcher is active, the callback will be invoked every |
2330 | there might be events pending in the embedded loop. The callback must then |
2458 | time there might be events pending in the embedded loop. The callback |
2331 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2459 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2332 | their callbacks (you could also start an idle watcher to give the embedded |
2460 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2333 | loop strictly lower priority for example). You can also set the callback |
2461 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2334 | to C<0>, in which case the embed watcher will automatically execute the |
2462 | to give the embedded loop strictly lower priority for example). |
2335 | embedded loop sweep. |
|
|
2336 | |
2463 | |
2337 | As long as the watcher is started it will automatically handle events. The |
2464 | You can also set the callback to C<0>, in which case the embed watcher |
2338 | callback will be invoked whenever some events have been handled. You can |
2465 | will automatically execute the embedded loop sweep whenever necessary. |
2339 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2340 | interested in that. |
|
|
2341 | |
2466 | |
2342 | Also, there have not currently been made special provisions for forking: |
2467 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2343 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2468 | is active, i.e., the embedded loop will automatically be forked when the |
2344 | but you will also have to stop and restart any C<ev_embed> watchers |
2469 | embedding loop forks. In other cases, the user is responsible for calling |
2345 | yourself - but you can use a fork watcher to handle this automatically, |
2470 | C<ev_loop_fork> on the embedded loop. |
2346 | and future versions of libev might do just that. |
|
|
2347 | |
2471 | |
2348 | Unfortunately, not all backends are embeddable: only the ones returned by |
2472 | Unfortunately, not all backends are embeddable: only the ones returned by |
2349 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2473 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2350 | portable one. |
2474 | portable one. |
2351 | |
2475 | |
… | |
… | |
2571 | =over 4 |
2695 | =over 4 |
2572 | |
2696 | |
2573 | =item ev_async_init (ev_async *, callback) |
2697 | =item ev_async_init (ev_async *, callback) |
2574 | |
2698 | |
2575 | Initialises and configures the async watcher - it has no parameters of any |
2699 | Initialises and configures the async watcher - it has no parameters of any |
2576 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2700 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2577 | trust me. |
2701 | trust me. |
2578 | |
2702 | |
2579 | =item ev_async_send (loop, ev_async *) |
2703 | =item ev_async_send (loop, ev_async *) |
2580 | |
2704 | |
2581 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2705 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2582 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2706 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2583 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2707 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2584 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2708 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2585 | section below on what exactly this means). |
2709 | section below on what exactly this means). |
2586 | |
2710 | |
|
|
2711 | Note that, as with other watchers in libev, multiple events might get |
|
|
2712 | compressed into a single callback invocation (another way to look at this |
|
|
2713 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2714 | reset when the event loop detects that). |
|
|
2715 | |
2587 | This call incurs the overhead of a system call only once per loop iteration, |
2716 | This call incurs the overhead of a system call only once per event loop |
2588 | so while the overhead might be noticeable, it doesn't apply to repeated |
2717 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2589 | calls to C<ev_async_send>. |
2718 | repeated calls to C<ev_async_send> for the same event loop. |
2590 | |
2719 | |
2591 | =item bool = ev_async_pending (ev_async *) |
2720 | =item bool = ev_async_pending (ev_async *) |
2592 | |
2721 | |
2593 | Returns a non-zero value when C<ev_async_send> has been called on the |
2722 | Returns a non-zero value when C<ev_async_send> has been called on the |
2594 | watcher but the event has not yet been processed (or even noted) by the |
2723 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2597 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2726 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2598 | the loop iterates next and checks for the watcher to have become active, |
2727 | the loop iterates next and checks for the watcher to have become active, |
2599 | it will reset the flag again. C<ev_async_pending> can be used to very |
2728 | it will reset the flag again. C<ev_async_pending> can be used to very |
2600 | quickly check whether invoking the loop might be a good idea. |
2729 | quickly check whether invoking the loop might be a good idea. |
2601 | |
2730 | |
2602 | Not that this does I<not> check whether the watcher itself is pending, only |
2731 | Not that this does I<not> check whether the watcher itself is pending, |
2603 | whether it has been requested to make this watcher pending. |
2732 | only whether it has been requested to make this watcher pending: there |
|
|
2733 | is a time window between the event loop checking and resetting the async |
|
|
2734 | notification, and the callback being invoked. |
2604 | |
2735 | |
2605 | =back |
2736 | =back |
2606 | |
2737 | |
2607 | |
2738 | |
2608 | =head1 OTHER FUNCTIONS |
2739 | =head1 OTHER FUNCTIONS |
… | |
… | |
2787 | |
2918 | |
2788 | myclass obj; |
2919 | myclass obj; |
2789 | ev::io iow; |
2920 | ev::io iow; |
2790 | iow.set <myclass, &myclass::io_cb> (&obj); |
2921 | iow.set <myclass, &myclass::io_cb> (&obj); |
2791 | |
2922 | |
|
|
2923 | =item w->set (object *) |
|
|
2924 | |
|
|
2925 | This is an B<experimental> feature that might go away in a future version. |
|
|
2926 | |
|
|
2927 | This is a variation of a method callback - leaving out the method to call |
|
|
2928 | will default the method to C<operator ()>, which makes it possible to use |
|
|
2929 | functor objects without having to manually specify the C<operator ()> all |
|
|
2930 | the time. Incidentally, you can then also leave out the template argument |
|
|
2931 | list. |
|
|
2932 | |
|
|
2933 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
2934 | int revents)>. |
|
|
2935 | |
|
|
2936 | See the method-C<set> above for more details. |
|
|
2937 | |
|
|
2938 | Example: use a functor object as callback. |
|
|
2939 | |
|
|
2940 | struct myfunctor |
|
|
2941 | { |
|
|
2942 | void operator() (ev::io &w, int revents) |
|
|
2943 | { |
|
|
2944 | ... |
|
|
2945 | } |
|
|
2946 | } |
|
|
2947 | |
|
|
2948 | myfunctor f; |
|
|
2949 | |
|
|
2950 | ev::io w; |
|
|
2951 | w.set (&f); |
|
|
2952 | |
2792 | =item w->set<function> (void *data = 0) |
2953 | =item w->set<function> (void *data = 0) |
2793 | |
2954 | |
2794 | Also sets a callback, but uses a static method or plain function as |
2955 | Also sets a callback, but uses a static method or plain function as |
2795 | callback. The optional C<data> argument will be stored in the watcher's |
2956 | callback. The optional C<data> argument will be stored in the watcher's |
2796 | C<data> member and is free for you to use. |
2957 | C<data> member and is free for you to use. |
… | |
… | |
2882 | L<http://software.schmorp.de/pkg/EV>. |
3043 | L<http://software.schmorp.de/pkg/EV>. |
2883 | |
3044 | |
2884 | =item Python |
3045 | =item Python |
2885 | |
3046 | |
2886 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3047 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2887 | seems to be quite complete and well-documented. Note, however, that the |
3048 | seems to be quite complete and well-documented. |
2888 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2889 | for everybody else, and therefore, should never be applied in an installed |
|
|
2890 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2891 | libev). |
|
|
2892 | |
3049 | |
2893 | =item Ruby |
3050 | =item Ruby |
2894 | |
3051 | |
2895 | Tony Arcieri has written a ruby extension that offers access to a subset |
3052 | Tony Arcieri has written a ruby extension that offers access to a subset |
2896 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3053 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2897 | more on top of it. It can be found via gem servers. Its homepage is at |
3054 | more on top of it. It can be found via gem servers. Its homepage is at |
2898 | L<http://rev.rubyforge.org/>. |
3055 | L<http://rev.rubyforge.org/>. |
2899 | |
3056 | |
|
|
3057 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3058 | makes rev work even on mingw. |
|
|
3059 | |
|
|
3060 | =item Haskell |
|
|
3061 | |
|
|
3062 | A haskell binding to libev is available at |
|
|
3063 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3064 | |
2900 | =item D |
3065 | =item D |
2901 | |
3066 | |
2902 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3067 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2903 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3068 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3069 | |
|
|
3070 | =item Ocaml |
|
|
3071 | |
|
|
3072 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3073 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
2904 | |
3074 | |
2905 | =back |
3075 | =back |
2906 | |
3076 | |
2907 | |
3077 | |
2908 | =head1 MACRO MAGIC |
3078 | =head1 MACRO MAGIC |
… | |
… | |
3009 | |
3179 | |
3010 | #define EV_STANDALONE 1 |
3180 | #define EV_STANDALONE 1 |
3011 | #include "ev.h" |
3181 | #include "ev.h" |
3012 | |
3182 | |
3013 | Both header files and implementation files can be compiled with a C++ |
3183 | Both header files and implementation files can be compiled with a C++ |
3014 | compiler (at least, thats a stated goal, and breakage will be treated |
3184 | compiler (at least, that's a stated goal, and breakage will be treated |
3015 | as a bug). |
3185 | as a bug). |
3016 | |
3186 | |
3017 | You need the following files in your source tree, or in a directory |
3187 | You need the following files in your source tree, or in a directory |
3018 | in your include path (e.g. in libev/ when using -Ilibev): |
3188 | in your include path (e.g. in libev/ when using -Ilibev): |
3019 | |
3189 | |
… | |
… | |
3075 | keeps libev from including F<config.h>, and it also defines dummy |
3245 | keeps libev from including F<config.h>, and it also defines dummy |
3076 | implementations for some libevent functions (such as logging, which is not |
3246 | implementations for some libevent functions (such as logging, which is not |
3077 | supported). It will also not define any of the structs usually found in |
3247 | supported). It will also not define any of the structs usually found in |
3078 | F<event.h> that are not directly supported by the libev core alone. |
3248 | F<event.h> that are not directly supported by the libev core alone. |
3079 | |
3249 | |
|
|
3250 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3251 | configuration, but has to be more conservative. |
|
|
3252 | |
3080 | =item EV_USE_MONOTONIC |
3253 | =item EV_USE_MONOTONIC |
3081 | |
3254 | |
3082 | If defined to be C<1>, libev will try to detect the availability of the |
3255 | If defined to be C<1>, libev will try to detect the availability of the |
3083 | monotonic clock option at both compile time and runtime. Otherwise no use |
3256 | monotonic clock option at both compile time and runtime. Otherwise no |
3084 | of the monotonic clock option will be attempted. If you enable this, you |
3257 | use of the monotonic clock option will be attempted. If you enable this, |
3085 | usually have to link against librt or something similar. Enabling it when |
3258 | you usually have to link against librt or something similar. Enabling it |
3086 | the functionality isn't available is safe, though, although you have |
3259 | when the functionality isn't available is safe, though, although you have |
3087 | to make sure you link against any libraries where the C<clock_gettime> |
3260 | to make sure you link against any libraries where the C<clock_gettime> |
3088 | function is hiding in (often F<-lrt>). |
3261 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3089 | |
3262 | |
3090 | =item EV_USE_REALTIME |
3263 | =item EV_USE_REALTIME |
3091 | |
3264 | |
3092 | If defined to be C<1>, libev will try to detect the availability of the |
3265 | If defined to be C<1>, libev will try to detect the availability of the |
3093 | real-time clock option at compile time (and assume its availability at |
3266 | real-time clock option at compile time (and assume its availability |
3094 | runtime if successful). Otherwise no use of the real-time clock option will |
3267 | at runtime if successful). Otherwise no use of the real-time clock |
3095 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3268 | option will be attempted. This effectively replaces C<gettimeofday> |
3096 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3269 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3097 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3270 | correctness. See the note about libraries in the description of |
|
|
3271 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3272 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3273 | |
|
|
3274 | =item EV_USE_CLOCK_SYSCALL |
|
|
3275 | |
|
|
3276 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3277 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3278 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3279 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3280 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3281 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3282 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3283 | higher, as it simplifies linking (no need for C<-lrt>). |
3098 | |
3284 | |
3099 | =item EV_USE_NANOSLEEP |
3285 | =item EV_USE_NANOSLEEP |
3100 | |
3286 | |
3101 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3287 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3102 | and will use it for delays. Otherwise it will use C<select ()>. |
3288 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3118 | |
3304 | |
3119 | =item EV_SELECT_USE_FD_SET |
3305 | =item EV_SELECT_USE_FD_SET |
3120 | |
3306 | |
3121 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3307 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3122 | structure. This is useful if libev doesn't compile due to a missing |
3308 | structure. This is useful if libev doesn't compile due to a missing |
3123 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3309 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3124 | exotic systems. This usually limits the range of file descriptors to some |
3310 | on exotic systems. This usually limits the range of file descriptors to |
3125 | low limit such as 1024 or might have other limitations (winsocket only |
3311 | some low limit such as 1024 or might have other limitations (winsocket |
3126 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3312 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3127 | influence the size of the C<fd_set> used. |
3313 | configures the maximum size of the C<fd_set>. |
3128 | |
3314 | |
3129 | =item EV_SELECT_IS_WINSOCKET |
3315 | =item EV_SELECT_IS_WINSOCKET |
3130 | |
3316 | |
3131 | When defined to C<1>, the select backend will assume that |
3317 | When defined to C<1>, the select backend will assume that |
3132 | select/socket/connect etc. don't understand file descriptors but |
3318 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3491 | loop, as long as you don't confuse yourself). The only exception is that |
3677 | loop, as long as you don't confuse yourself). The only exception is that |
3492 | you must not do this from C<ev_periodic> reschedule callbacks. |
3678 | you must not do this from C<ev_periodic> reschedule callbacks. |
3493 | |
3679 | |
3494 | Care has been taken to ensure that libev does not keep local state inside |
3680 | Care has been taken to ensure that libev does not keep local state inside |
3495 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3681 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3496 | they do not clal any callbacks. |
3682 | they do not call any callbacks. |
3497 | |
3683 | |
3498 | =head2 COMPILER WARNINGS |
3684 | =head2 COMPILER WARNINGS |
3499 | |
3685 | |
3500 | Depending on your compiler and compiler settings, you might get no or a |
3686 | Depending on your compiler and compiler settings, you might get no or a |
3501 | lot of warnings when compiling libev code. Some people are apparently |
3687 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3535 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3721 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3536 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3722 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3537 | ==2274== still reachable: 256 bytes in 1 blocks. |
3723 | ==2274== still reachable: 256 bytes in 1 blocks. |
3538 | |
3724 | |
3539 | Then there is no memory leak, just as memory accounted to global variables |
3725 | Then there is no memory leak, just as memory accounted to global variables |
3540 | is not a memleak - the memory is still being refernced, and didn't leak. |
3726 | is not a memleak - the memory is still being referenced, and didn't leak. |
3541 | |
3727 | |
3542 | Similarly, under some circumstances, valgrind might report kernel bugs |
3728 | Similarly, under some circumstances, valgrind might report kernel bugs |
3543 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3729 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3544 | although an acceptable workaround has been found here), or it might be |
3730 | although an acceptable workaround has been found here), or it might be |
3545 | confused. |
3731 | confused. |
… | |
… | |
3783 | =back |
3969 | =back |
3784 | |
3970 | |
3785 | |
3971 | |
3786 | =head1 AUTHOR |
3972 | =head1 AUTHOR |
3787 | |
3973 | |
3788 | Marc Lehmann <libev@schmorp.de>. |
3974 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3789 | |
3975 | |