… | |
… | |
75 | While this document tries to be as complete as possible in documenting |
75 | While this document tries to be as complete as possible in documenting |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
82 | |
82 | |
83 | =head1 ABOUT LIBEV |
83 | =head1 ABOUT LIBEV |
84 | |
84 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
… | |
… | |
124 | this argument. |
124 | this argument. |
125 | |
125 | |
126 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
127 | |
127 | |
128 | Libev represents time as a single floating point number, representing |
128 | Libev represents time as a single floating point number, representing |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practise |
130 | near the beginning of 1970, details are complicated, don't ask). This |
130 | somewhere near the beginning of 1970, details are complicated, don't |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
132 | aliases to the C<double> type in C. When you need to do any calculations |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
133 | on it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
|
|
134 | |
134 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
135 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
136 | |
137 | |
137 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
138 | |
139 | |
139 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
140 | and internal errors (bugs). |
141 | and internal errors (bugs). |
… | |
… | |
191 | as this indicates an incompatible change. Minor versions are usually |
192 | as this indicates an incompatible change. Minor versions are usually |
192 | compatible to older versions, so a larger minor version alone is usually |
193 | compatible to older versions, so a larger minor version alone is usually |
193 | not a problem. |
194 | not a problem. |
194 | |
195 | |
195 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | version. |
197 | version (note, however, that this will not detect ABI mismatches :). |
197 | |
198 | |
198 | assert (("libev version mismatch", |
199 | assert (("libev version mismatch", |
199 | ev_version_major () == EV_VERSION_MAJOR |
200 | ev_version_major () == EV_VERSION_MAJOR |
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | |
202 | |
… | |
… | |
345 | useful to try out specific backends to test their performance, or to work |
346 | useful to try out specific backends to test their performance, or to work |
346 | around bugs. |
347 | around bugs. |
347 | |
348 | |
348 | =item C<EVFLAG_FORKCHECK> |
349 | =item C<EVFLAG_FORKCHECK> |
349 | |
350 | |
350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
351 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
351 | a fork, you can also make libev check for a fork in each iteration by |
352 | make libev check for a fork in each iteration by enabling this flag. |
352 | enabling this flag. |
|
|
353 | |
353 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
355 | and thus this might slow down your event loop if you do a lot of loop |
355 | and thus this might slow down your event loop if you do a lot of loop |
356 | iterations and little real work, but is usually not noticeable (on my |
356 | iterations and little real work, but is usually not noticeable (on my |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
440 | I<different> file descriptors (even already closed ones, so one cannot |
440 | I<different> file descriptors (even already closed ones, so one cannot |
441 | even remove them from the set) than registered in the set (especially |
441 | even remove them from the set) than registered in the set (especially |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
443 | employing an additional generation counter and comparing that against the |
443 | employing an additional generation counter and comparing that against the |
444 | events to filter out spurious ones, recreating the set when required. |
444 | events to filter out spurious ones, recreating the set when required. Last |
|
|
445 | not least, it also refuses to work with some file descriptors which work |
|
|
446 | perfectly fine with C<select> (files, many character devices...). |
445 | |
447 | |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
447 | will result in some caching, there is still a system call per such |
449 | will result in some caching, there is still a system call per such |
448 | incident (because the same I<file descriptor> could point to a different |
450 | incident (because the same I<file descriptor> could point to a different |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
568 | |
570 | |
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
570 | |
572 | |
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
572 | always distinct from the default loop. Unlike the default loop, it cannot |
574 | always distinct from the default loop. |
573 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
574 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
575 | |
575 | |
576 | Note that this function I<is> thread-safe, and the recommended way to use |
576 | Note that this function I<is> thread-safe, and one common way to use |
577 | libev with threads is indeed to create one loop per thread, and using the |
577 | libev with threads is indeed to create one loop per thread, and using the |
578 | default loop in the "main" or "initial" thread. |
578 | default loop in the "main" or "initial" thread. |
579 | |
579 | |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
581 | |
… | |
… | |
583 | if (!epoller) |
583 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
585 | |
586 | =item ev_default_destroy () |
586 | =item ev_default_destroy () |
587 | |
587 | |
588 | Destroys the default loop again (frees all memory and kernel state |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
589 | etc.). None of the active event watchers will be stopped in the normal |
589 | of the active event watchers will be stopped in the normal sense, so |
590 | sense, so e.g. C<ev_is_active> might still return true. It is your |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
591 | responsibility to either stop all watchers cleanly yourself I<before> |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
592 | calling this function, or cope with the fact afterwards (which is usually |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
593 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
593 | can just ignore the watchers and/or C<free ()> them for example). |
594 | for example). |
|
|
595 | |
594 | |
596 | Note that certain global state, such as signal state (and installed signal |
595 | Note that certain global state, such as signal state (and installed signal |
597 | handlers), will not be freed by this function, and related watchers (such |
596 | handlers), will not be freed by this function, and related watchers (such |
598 | as signal and child watchers) would need to be stopped manually. |
597 | as signal and child watchers) would need to be stopped manually. |
599 | |
598 | |
… | |
… | |
614 | name, you can call it anytime, but it makes most sense after forking, in |
613 | name, you can call it anytime, but it makes most sense after forking, in |
615 | the child process (or both child and parent, but that again makes little |
614 | the child process (or both child and parent, but that again makes little |
616 | sense). You I<must> call it in the child before using any of the libev |
615 | sense). You I<must> call it in the child before using any of the libev |
617 | functions, and it will only take effect at the next C<ev_loop> iteration. |
616 | functions, and it will only take effect at the next C<ev_loop> iteration. |
618 | |
617 | |
|
|
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
621 | during fork. |
|
|
622 | |
619 | On the other hand, you only need to call this function in the child |
623 | On the other hand, you only need to call this function in the child |
620 | process if and only if you want to use the event library in the child. If |
624 | process if and only if you want to use the event loop in the child. If you |
621 | you just fork+exec, you don't have to call it at all. |
625 | just fork+exec or create a new loop in the child, you don't have to call |
|
|
626 | it at all. |
622 | |
627 | |
623 | The function itself is quite fast and it's usually not a problem to call |
628 | The function itself is quite fast and it's usually not a problem to call |
624 | it just in case after a fork. To make this easy, the function will fit in |
629 | it just in case after a fork. To make this easy, the function will fit in |
625 | quite nicely into a call to C<pthread_atfork>: |
630 | quite nicely into a call to C<pthread_atfork>: |
626 | |
631 | |
… | |
… | |
628 | |
633 | |
629 | =item ev_loop_fork (loop) |
634 | =item ev_loop_fork (loop) |
630 | |
635 | |
631 | Like C<ev_default_fork>, but acts on an event loop created by |
636 | Like C<ev_default_fork>, but acts on an event loop created by |
632 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
637 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
633 | after fork that you want to re-use in the child, and how you do this is |
638 | after fork that you want to re-use in the child, and how you keep track of |
634 | entirely your own problem. |
639 | them is entirely your own problem. |
635 | |
640 | |
636 | =item int ev_is_default_loop (loop) |
641 | =item int ev_is_default_loop (loop) |
637 | |
642 | |
638 | Returns true when the given loop is, in fact, the default loop, and false |
643 | Returns true when the given loop is, in fact, the default loop, and false |
639 | otherwise. |
644 | otherwise. |
640 | |
645 | |
641 | =item unsigned int ev_loop_count (loop) |
646 | =item unsigned int ev_iteration (loop) |
642 | |
647 | |
643 | Returns the count of loop iterations for the loop, which is identical to |
648 | Returns the current iteration count for the loop, which is identical to |
644 | the number of times libev did poll for new events. It starts at C<0> and |
649 | the number of times libev did poll for new events. It starts at C<0> and |
645 | happily wraps around with enough iterations. |
650 | happily wraps around with enough iterations. |
646 | |
651 | |
647 | This value can sometimes be useful as a generation counter of sorts (it |
652 | This value can sometimes be useful as a generation counter of sorts (it |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
653 | "ticks" the number of loop iterations), as it roughly corresponds with |
649 | C<ev_prepare> and C<ev_check> calls. |
654 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
655 | prepare and check phases. |
650 | |
656 | |
651 | =item unsigned int ev_loop_depth (loop) |
657 | =item unsigned int ev_depth (loop) |
652 | |
658 | |
653 | Returns the number of times C<ev_loop> was entered minus the number of |
659 | Returns the number of times C<ev_loop> was entered minus the number of |
654 | times C<ev_loop> was exited, in other words, the recursion depth. |
660 | times C<ev_loop> was exited, in other words, the recursion depth. |
655 | |
661 | |
656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
662 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
663 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
658 | in which case it is higher. |
664 | in which case it is higher. |
659 | |
665 | |
660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
666 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
661 | etc.), doesn't count as exit. |
667 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
668 | ungentleman behaviour unless it's really convenient. |
662 | |
669 | |
663 | =item unsigned int ev_backend (loop) |
670 | =item unsigned int ev_backend (loop) |
664 | |
671 | |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
672 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
666 | use. |
673 | use. |
… | |
… | |
700 | C<ev_resume> directly afterwards to resume timer processing. |
707 | C<ev_resume> directly afterwards to resume timer processing. |
701 | |
708 | |
702 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
709 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
703 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
710 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
704 | will be rescheduled (that is, they will lose any events that would have |
711 | will be rescheduled (that is, they will lose any events that would have |
705 | occured while suspended). |
712 | occurred while suspended). |
706 | |
713 | |
707 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
714 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
708 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
715 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
709 | without a previous call to C<ev_suspend>. |
716 | without a previous call to C<ev_suspend>. |
710 | |
717 | |
… | |
… | |
787 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
794 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
788 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
795 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
789 | |
796 | |
790 | This "unloop state" will be cleared when entering C<ev_loop> again. |
797 | This "unloop state" will be cleared when entering C<ev_loop> again. |
791 | |
798 | |
792 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
799 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
793 | |
800 | |
794 | =item ev_ref (loop) |
801 | =item ev_ref (loop) |
795 | |
802 | |
796 | =item ev_unref (loop) |
803 | =item ev_unref (loop) |
797 | |
804 | |
… | |
… | |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
874 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
868 | as this approaches the timing granularity of most systems. Note that if |
875 | as this approaches the timing granularity of most systems. Note that if |
869 | you do transactions with the outside world and you can't increase the |
876 | you do transactions with the outside world and you can't increase the |
870 | parallelity, then this setting will limit your transaction rate (if you |
877 | parallelity, then this setting will limit your transaction rate (if you |
871 | need to poll once per transaction and the I/O collect interval is 0.01, |
878 | need to poll once per transaction and the I/O collect interval is 0.01, |
872 | then you can't do more than 100 transations per second). |
879 | then you can't do more than 100 transactions per second). |
873 | |
880 | |
874 | Setting the I<timeout collect interval> can improve the opportunity for |
881 | Setting the I<timeout collect interval> can improve the opportunity for |
875 | saving power, as the program will "bundle" timer callback invocations that |
882 | saving power, as the program will "bundle" timer callback invocations that |
876 | are "near" in time together, by delaying some, thus reducing the number of |
883 | are "near" in time together, by delaying some, thus reducing the number of |
877 | times the process sleeps and wakes up again. Another useful technique to |
884 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
1032 | =item C<EV_WRITE> |
1039 | =item C<EV_WRITE> |
1033 | |
1040 | |
1034 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1041 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1035 | writable. |
1042 | writable. |
1036 | |
1043 | |
1037 | =item C<EV_TIMEOUT> |
1044 | =item C<EV_TIMER> |
1038 | |
1045 | |
1039 | The C<ev_timer> watcher has timed out. |
1046 | The C<ev_timer> watcher has timed out. |
1040 | |
1047 | |
1041 | =item C<EV_PERIODIC> |
1048 | =item C<EV_PERIODIC> |
1042 | |
1049 | |
… | |
… | |
1375 | |
1382 | |
1376 | For example, to emulate how many other event libraries handle priorities, |
1383 | For example, to emulate how many other event libraries handle priorities, |
1377 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1384 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1378 | the normal watcher callback, you just start the idle watcher. The real |
1385 | the normal watcher callback, you just start the idle watcher. The real |
1379 | processing is done in the idle watcher callback. This causes libev to |
1386 | processing is done in the idle watcher callback. This causes libev to |
1380 | continously poll and process kernel event data for the watcher, but when |
1387 | continuously poll and process kernel event data for the watcher, but when |
1381 | the lock-out case is known to be rare (which in turn is rare :), this is |
1388 | the lock-out case is known to be rare (which in turn is rare :), this is |
1382 | workable. |
1389 | workable. |
1383 | |
1390 | |
1384 | Usually, however, the lock-out model implemented that way will perform |
1391 | Usually, however, the lock-out model implemented that way will perform |
1385 | miserably under the type of load it was designed to handle. In that case, |
1392 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1399 | { |
1406 | { |
1400 | // stop the I/O watcher, we received the event, but |
1407 | // stop the I/O watcher, we received the event, but |
1401 | // are not yet ready to handle it. |
1408 | // are not yet ready to handle it. |
1402 | ev_io_stop (EV_A_ w); |
1409 | ev_io_stop (EV_A_ w); |
1403 | |
1410 | |
1404 | // start the idle watcher to ahndle the actual event. |
1411 | // start the idle watcher to handle the actual event. |
1405 | // it will not be executed as long as other watchers |
1412 | // it will not be executed as long as other watchers |
1406 | // with the default priority are receiving events. |
1413 | // with the default priority are receiving events. |
1407 | ev_idle_start (EV_A_ &idle); |
1414 | ev_idle_start (EV_A_ &idle); |
1408 | } |
1415 | } |
1409 | |
1416 | |
… | |
… | |
1463 | |
1470 | |
1464 | If you cannot use non-blocking mode, then force the use of a |
1471 | If you cannot use non-blocking mode, then force the use of a |
1465 | known-to-be-good backend (at the time of this writing, this includes only |
1472 | known-to-be-good backend (at the time of this writing, this includes only |
1466 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1473 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1467 | descriptors for which non-blocking operation makes no sense (such as |
1474 | descriptors for which non-blocking operation makes no sense (such as |
1468 | files) - libev doesn't guarentee any specific behaviour in that case. |
1475 | files) - libev doesn't guarantee any specific behaviour in that case. |
1469 | |
1476 | |
1470 | Another thing you have to watch out for is that it is quite easy to |
1477 | Another thing you have to watch out for is that it is quite easy to |
1471 | receive "spurious" readiness notifications, that is your callback might |
1478 | receive "spurious" readiness notifications, that is your callback might |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1479 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1473 | because there is no data. Not only are some backends known to create a |
1480 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1538 | |
1545 | |
1539 | So when you encounter spurious, unexplained daemon exits, make sure you |
1546 | So when you encounter spurious, unexplained daemon exits, make sure you |
1540 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1547 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1541 | somewhere, as that would have given you a big clue). |
1548 | somewhere, as that would have given you a big clue). |
1542 | |
1549 | |
|
|
1550 | =head3 The special problem of accept()ing when you can't |
|
|
1551 | |
|
|
1552 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1553 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1554 | connection from the pending queue in all error cases. |
|
|
1555 | |
|
|
1556 | For example, larger servers often run out of file descriptors (because |
|
|
1557 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1558 | rejecting the connection, leading to libev signalling readiness on |
|
|
1559 | the next iteration again (the connection still exists after all), and |
|
|
1560 | typically causing the program to loop at 100% CPU usage. |
|
|
1561 | |
|
|
1562 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1563 | operating systems, there is usually little the app can do to remedy the |
|
|
1564 | situation, and no known thread-safe method of removing the connection to |
|
|
1565 | cope with overload is known (to me). |
|
|
1566 | |
|
|
1567 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1568 | - when the program encounters an overload, it will just loop until the |
|
|
1569 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1570 | event-based way to handle this situation, so it's the best one can do. |
|
|
1571 | |
|
|
1572 | A better way to handle the situation is to log any errors other than |
|
|
1573 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1574 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1575 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1576 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1577 | usage. |
|
|
1578 | |
|
|
1579 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1580 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1581 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1582 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1583 | clients under typical overload conditions. |
|
|
1584 | |
|
|
1585 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1586 | is often done with C<malloc> failures, but this results in an easy |
|
|
1587 | opportunity for a DoS attack. |
1543 | |
1588 | |
1544 | =head3 Watcher-Specific Functions |
1589 | =head3 Watcher-Specific Functions |
1545 | |
1590 | |
1546 | =over 4 |
1591 | =over 4 |
1547 | |
1592 | |
… | |
… | |
1694 | ev_tstamp timeout = last_activity + 60.; |
1739 | ev_tstamp timeout = last_activity + 60.; |
1695 | |
1740 | |
1696 | // if last_activity + 60. is older than now, we did time out |
1741 | // if last_activity + 60. is older than now, we did time out |
1697 | if (timeout < now) |
1742 | if (timeout < now) |
1698 | { |
1743 | { |
1699 | // timeout occured, take action |
1744 | // timeout occurred, take action |
1700 | } |
1745 | } |
1701 | else |
1746 | else |
1702 | { |
1747 | { |
1703 | // callback was invoked, but there was some activity, re-arm |
1748 | // callback was invoked, but there was some activity, re-arm |
1704 | // the watcher to fire in last_activity + 60, which is |
1749 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1726 | to the current time (meaning we just have some activity :), then call the |
1771 | to the current time (meaning we just have some activity :), then call the |
1727 | callback, which will "do the right thing" and start the timer: |
1772 | callback, which will "do the right thing" and start the timer: |
1728 | |
1773 | |
1729 | ev_init (timer, callback); |
1774 | ev_init (timer, callback); |
1730 | last_activity = ev_now (loop); |
1775 | last_activity = ev_now (loop); |
1731 | callback (loop, timer, EV_TIMEOUT); |
1776 | callback (loop, timer, EV_TIMER); |
1732 | |
1777 | |
1733 | And when there is some activity, simply store the current time in |
1778 | And when there is some activity, simply store the current time in |
1734 | C<last_activity>, no libev calls at all: |
1779 | C<last_activity>, no libev calls at all: |
1735 | |
1780 | |
1736 | last_actiivty = ev_now (loop); |
1781 | last_activity = ev_now (loop); |
1737 | |
1782 | |
1738 | This technique is slightly more complex, but in most cases where the |
1783 | This technique is slightly more complex, but in most cases where the |
1739 | time-out is unlikely to be triggered, much more efficient. |
1784 | time-out is unlikely to be triggered, much more efficient. |
1740 | |
1785 | |
1741 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1786 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1867 | Returns the remaining time until a timer fires. If the timer is active, |
1912 | Returns the remaining time until a timer fires. If the timer is active, |
1868 | then this time is relative to the current event loop time, otherwise it's |
1913 | then this time is relative to the current event loop time, otherwise it's |
1869 | the timeout value currently configured. |
1914 | the timeout value currently configured. |
1870 | |
1915 | |
1871 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1916 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1872 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
1917 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1873 | will return C<4>. When the timer expires and is restarted, it will return |
1918 | will return C<4>. When the timer expires and is restarted, it will return |
1874 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1919 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1875 | too), and so on. |
1920 | too), and so on. |
1876 | |
1921 | |
1877 | =item ev_tstamp repeat [read-write] |
1922 | =item ev_tstamp repeat [read-write] |
… | |
… | |
2080 | Example: Call a callback every hour, or, more precisely, whenever the |
2125 | Example: Call a callback every hour, or, more precisely, whenever the |
2081 | system time is divisible by 3600. The callback invocation times have |
2126 | system time is divisible by 3600. The callback invocation times have |
2082 | potentially a lot of jitter, but good long-term stability. |
2127 | potentially a lot of jitter, but good long-term stability. |
2083 | |
2128 | |
2084 | static void |
2129 | static void |
2085 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2130 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2086 | { |
2131 | { |
2087 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2132 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2088 | } |
2133 | } |
2089 | |
2134 | |
2090 | ev_periodic hourly_tick; |
2135 | ev_periodic hourly_tick; |
… | |
… | |
2922 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2967 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2923 | handlers will be invoked, too, of course. |
2968 | handlers will be invoked, too, of course. |
2924 | |
2969 | |
2925 | =head3 The special problem of life after fork - how is it possible? |
2970 | =head3 The special problem of life after fork - how is it possible? |
2926 | |
2971 | |
2927 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
2972 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2928 | up/change the process environment, followed by a call to C<exec()>. This |
2973 | up/change the process environment, followed by a call to C<exec()>. This |
2929 | sequence should be handled by libev without any problems. |
2974 | sequence should be handled by libev without any problems. |
2930 | |
2975 | |
2931 | This changes when the application actually wants to do event handling |
2976 | This changes when the application actually wants to do event handling |
2932 | in the child, or both parent in child, in effect "continuing" after the |
2977 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2966 | believe me. |
3011 | believe me. |
2967 | |
3012 | |
2968 | =back |
3013 | =back |
2969 | |
3014 | |
2970 | |
3015 | |
2971 | =head2 C<ev_async> - how to wake up another event loop |
3016 | =head2 C<ev_async> - how to wake up an event loop |
2972 | |
3017 | |
2973 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3018 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2974 | asynchronous sources such as signal handlers (as opposed to multiple event |
3019 | asynchronous sources such as signal handlers (as opposed to multiple event |
2975 | loops - those are of course safe to use in different threads). |
3020 | loops - those are of course safe to use in different threads). |
2976 | |
3021 | |
2977 | Sometimes, however, you need to wake up another event loop you do not |
3022 | Sometimes, however, you need to wake up an event loop you do not control, |
2978 | control, for example because it belongs to another thread. This is what |
3023 | for example because it belongs to another thread. This is what C<ev_async> |
2979 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3024 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2980 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3025 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2981 | safe. |
|
|
2982 | |
3026 | |
2983 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3027 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2984 | too, are asynchronous in nature, and signals, too, will be compressed |
3028 | too, are asynchronous in nature, and signals, too, will be compressed |
2985 | (i.e. the number of callback invocations may be less than the number of |
3029 | (i.e. the number of callback invocations may be less than the number of |
2986 | C<ev_async_sent> calls). |
3030 | C<ev_async_sent> calls). |
… | |
… | |
3141 | |
3185 | |
3142 | If C<timeout> is less than 0, then no timeout watcher will be |
3186 | If C<timeout> is less than 0, then no timeout watcher will be |
3143 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3187 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3144 | repeat = 0) will be started. C<0> is a valid timeout. |
3188 | repeat = 0) will be started. C<0> is a valid timeout. |
3145 | |
3189 | |
3146 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3190 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3147 | passed an C<revents> set like normal event callbacks (a combination of |
3191 | passed an C<revents> set like normal event callbacks (a combination of |
3148 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3192 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3149 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3193 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3150 | a timeout and an io event at the same time - you probably should give io |
3194 | a timeout and an io event at the same time - you probably should give io |
3151 | events precedence. |
3195 | events precedence. |
3152 | |
3196 | |
3153 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3197 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3154 | |
3198 | |
3155 | static void stdin_ready (int revents, void *arg) |
3199 | static void stdin_ready (int revents, void *arg) |
3156 | { |
3200 | { |
3157 | if (revents & EV_READ) |
3201 | if (revents & EV_READ) |
3158 | /* stdin might have data for us, joy! */; |
3202 | /* stdin might have data for us, joy! */; |
3159 | else if (revents & EV_TIMEOUT) |
3203 | else if (revents & EV_TIMER) |
3160 | /* doh, nothing entered */; |
3204 | /* doh, nothing entered */; |
3161 | } |
3205 | } |
3162 | |
3206 | |
3163 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3207 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3164 | |
3208 | |
… | |
… | |
3298 | myclass obj; |
3342 | myclass obj; |
3299 | ev::io iow; |
3343 | ev::io iow; |
3300 | iow.set <myclass, &myclass::io_cb> (&obj); |
3344 | iow.set <myclass, &myclass::io_cb> (&obj); |
3301 | |
3345 | |
3302 | =item w->set (object *) |
3346 | =item w->set (object *) |
3303 | |
|
|
3304 | This is an B<experimental> feature that might go away in a future version. |
|
|
3305 | |
3347 | |
3306 | This is a variation of a method callback - leaving out the method to call |
3348 | This is a variation of a method callback - leaving out the method to call |
3307 | will default the method to C<operator ()>, which makes it possible to use |
3349 | will default the method to C<operator ()>, which makes it possible to use |
3308 | functor objects without having to manually specify the C<operator ()> all |
3350 | functor objects without having to manually specify the C<operator ()> all |
3309 | the time. Incidentally, you can then also leave out the template argument |
3351 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3451 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3493 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3452 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3494 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3453 | |
3495 | |
3454 | =item Lua |
3496 | =item Lua |
3455 | |
3497 | |
3456 | Brian Maher has written a partial interface to libev |
3498 | Brian Maher has written a partial interface to libev for lua (at the |
3457 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
3499 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3458 | L<http://github.com/brimworks/lua-ev>. |
3500 | L<http://github.com/brimworks/lua-ev>. |
3459 | |
3501 | |
3460 | =back |
3502 | =back |
3461 | |
3503 | |
3462 | |
3504 | |
… | |
… | |
3617 | libev.m4 |
3659 | libev.m4 |
3618 | |
3660 | |
3619 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3661 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3620 | |
3662 | |
3621 | Libev can be configured via a variety of preprocessor symbols you have to |
3663 | Libev can be configured via a variety of preprocessor symbols you have to |
3622 | define before including any of its files. The default in the absence of |
3664 | define before including (or compiling) any of its files. The default in |
3623 | autoconf is documented for every option. |
3665 | the absence of autoconf is documented for every option. |
|
|
3666 | |
|
|
3667 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3668 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3669 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3670 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3671 | users of libev and the libev code itself must be compiled with compatible |
|
|
3672 | settings. |
3624 | |
3673 | |
3625 | =over 4 |
3674 | =over 4 |
3626 | |
3675 | |
3627 | =item EV_STANDALONE |
3676 | =item EV_STANDALONE (h) |
3628 | |
3677 | |
3629 | Must always be C<1> if you do not use autoconf configuration, which |
3678 | Must always be C<1> if you do not use autoconf configuration, which |
3630 | keeps libev from including F<config.h>, and it also defines dummy |
3679 | keeps libev from including F<config.h>, and it also defines dummy |
3631 | implementations for some libevent functions (such as logging, which is not |
3680 | implementations for some libevent functions (such as logging, which is not |
3632 | supported). It will also not define any of the structs usually found in |
3681 | supported). It will also not define any of the structs usually found in |
… | |
… | |
3782 | as well as for signal and thread safety in C<ev_async> watchers. |
3831 | as well as for signal and thread safety in C<ev_async> watchers. |
3783 | |
3832 | |
3784 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3833 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3785 | (from F<signal.h>), which is usually good enough on most platforms. |
3834 | (from F<signal.h>), which is usually good enough on most platforms. |
3786 | |
3835 | |
3787 | =item EV_H |
3836 | =item EV_H (h) |
3788 | |
3837 | |
3789 | The name of the F<ev.h> header file used to include it. The default if |
3838 | The name of the F<ev.h> header file used to include it. The default if |
3790 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3839 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3791 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3840 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3792 | |
3841 | |
3793 | =item EV_CONFIG_H |
3842 | =item EV_CONFIG_H (h) |
3794 | |
3843 | |
3795 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3844 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3796 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3845 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3797 | C<EV_H>, above. |
3846 | C<EV_H>, above. |
3798 | |
3847 | |
3799 | =item EV_EVENT_H |
3848 | =item EV_EVENT_H (h) |
3800 | |
3849 | |
3801 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3850 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3802 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3851 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3803 | |
3852 | |
3804 | =item EV_PROTOTYPES |
3853 | =item EV_PROTOTYPES (h) |
3805 | |
3854 | |
3806 | If defined to be C<0>, then F<ev.h> will not define any function |
3855 | If defined to be C<0>, then F<ev.h> will not define any function |
3807 | prototypes, but still define all the structs and other symbols. This is |
3856 | prototypes, but still define all the structs and other symbols. This is |
3808 | occasionally useful if you want to provide your own wrapper functions |
3857 | occasionally useful if you want to provide your own wrapper functions |
3809 | around libev functions. |
3858 | around libev functions. |
… | |
… | |
3831 | fine. |
3880 | fine. |
3832 | |
3881 | |
3833 | If your embedding application does not need any priorities, defining these |
3882 | If your embedding application does not need any priorities, defining these |
3834 | both to C<0> will save some memory and CPU. |
3883 | both to C<0> will save some memory and CPU. |
3835 | |
3884 | |
3836 | =item EV_PERIODIC_ENABLE |
3885 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3886 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3887 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3837 | |
3888 | |
3838 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3889 | If undefined or defined to be C<1> (and the platform supports it), then |
3839 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3890 | the respective watcher type is supported. If defined to be C<0>, then it |
3840 | code. |
3891 | is not. Disabling watcher types mainly saves code size. |
3841 | |
3892 | |
3842 | =item EV_IDLE_ENABLE |
3893 | =item EV_FEATURES |
3843 | |
|
|
3844 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3845 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3846 | code. |
|
|
3847 | |
|
|
3848 | =item EV_EMBED_ENABLE |
|
|
3849 | |
|
|
3850 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3851 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3852 | watcher types, which therefore must not be disabled. |
|
|
3853 | |
|
|
3854 | =item EV_STAT_ENABLE |
|
|
3855 | |
|
|
3856 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3857 | defined to be C<0>, then they are not. |
|
|
3858 | |
|
|
3859 | =item EV_FORK_ENABLE |
|
|
3860 | |
|
|
3861 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3862 | defined to be C<0>, then they are not. |
|
|
3863 | |
|
|
3864 | =item EV_ASYNC_ENABLE |
|
|
3865 | |
|
|
3866 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3867 | defined to be C<0>, then they are not. |
|
|
3868 | |
|
|
3869 | =item EV_MINIMAL |
|
|
3870 | |
3894 | |
3871 | If you need to shave off some kilobytes of code at the expense of some |
3895 | If you need to shave off some kilobytes of code at the expense of some |
3872 | speed (but with the full API), define this symbol to C<1>. Currently this |
3896 | speed (but with the full API), you can define this symbol to request |
3873 | is used to override some inlining decisions, saves roughly 30% code size |
3897 | certain subsets of functionality. The default is to enable all features |
3874 | on amd64. It also selects a much smaller 2-heap for timer management over |
3898 | that can be enabled on the platform. |
3875 | the default 4-heap. |
|
|
3876 | |
3899 | |
3877 | You can save even more by disabling watcher types you do not need |
3900 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3878 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
3901 | with some broad features you want) and then selectively re-enable |
3879 | (C<-DNDEBUG>) will usually reduce code size a lot. |
3902 | additional parts you want, for example if you want everything minimal, |
|
|
3903 | but multiple event loop support, async and child watchers and the poll |
|
|
3904 | backend, use this: |
3880 | |
3905 | |
3881 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
3906 | #define EV_FEATURES 0 |
3882 | provide a bare-bones event library. See C<ev.h> for details on what parts |
3907 | #define EV_MULTIPLICITY 1 |
3883 | of the API are still available, and do not complain if this subset changes |
3908 | #define EV_USE_POLL 1 |
3884 | over time. |
3909 | #define EV_CHILD_ENABLE 1 |
|
|
3910 | #define EV_ASYNC_ENABLE 1 |
|
|
3911 | |
|
|
3912 | The actual value is a bitset, it can be a combination of the following |
|
|
3913 | values: |
|
|
3914 | |
|
|
3915 | =over 4 |
|
|
3916 | |
|
|
3917 | =item C<1> - faster/larger code |
|
|
3918 | |
|
|
3919 | Use larger code to speed up some operations. |
|
|
3920 | |
|
|
3921 | Currently this is used to override some inlining decisions (enlarging the |
|
|
3922 | code size by roughly 30% on amd64). |
|
|
3923 | |
|
|
3924 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3925 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3926 | assertions. |
|
|
3927 | |
|
|
3928 | =item C<2> - faster/larger data structures |
|
|
3929 | |
|
|
3930 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3931 | hash table sizes and so on. This will usually further increase code size |
|
|
3932 | and can additionally have an effect on the size of data structures at |
|
|
3933 | runtime. |
|
|
3934 | |
|
|
3935 | =item C<4> - full API configuration |
|
|
3936 | |
|
|
3937 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3938 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3939 | |
|
|
3940 | =item C<8> - full API |
|
|
3941 | |
|
|
3942 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3943 | details on which parts of the API are still available without this |
|
|
3944 | feature, and do not complain if this subset changes over time. |
|
|
3945 | |
|
|
3946 | =item C<16> - enable all optional watcher types |
|
|
3947 | |
|
|
3948 | Enables all optional watcher types. If you want to selectively enable |
|
|
3949 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3950 | embed, async, child...) you can enable them manually by defining |
|
|
3951 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3952 | |
|
|
3953 | =item C<32> - enable all backends |
|
|
3954 | |
|
|
3955 | This enables all backends - without this feature, you need to enable at |
|
|
3956 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3957 | |
|
|
3958 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3959 | |
|
|
3960 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3961 | default. |
|
|
3962 | |
|
|
3963 | =back |
|
|
3964 | |
|
|
3965 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3966 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3967 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3968 | watchers, timers and monotonic clock support. |
|
|
3969 | |
|
|
3970 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3971 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3972 | your program might be left out as well - a binary starting a timer and an |
|
|
3973 | I/O watcher then might come out at only 5Kb. |
|
|
3974 | |
|
|
3975 | =item EV_AVOID_STDIO |
|
|
3976 | |
|
|
3977 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3978 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
3979 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3980 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3981 | big. |
|
|
3982 | |
|
|
3983 | Note that error messages might become less precise when this option is |
|
|
3984 | enabled. |
3885 | |
3985 | |
3886 | =item EV_NSIG |
3986 | =item EV_NSIG |
3887 | |
3987 | |
3888 | The highest supported signal number, +1 (or, the number of |
3988 | The highest supported signal number, +1 (or, the number of |
3889 | signals): Normally, libev tries to deduce the maximum number of signals |
3989 | signals): Normally, libev tries to deduce the maximum number of signals |
3890 | automatically, but sometimes this fails, in which case it can be |
3990 | automatically, but sometimes this fails, in which case it can be |
3891 | specified. Also, using a lower number than detected (C<32> should be |
3991 | specified. Also, using a lower number than detected (C<32> should be |
3892 | good for about any system in existance) can save some memory, as libev |
3992 | good for about any system in existence) can save some memory, as libev |
3893 | statically allocates some 12-24 bytes per signal number. |
3993 | statically allocates some 12-24 bytes per signal number. |
3894 | |
3994 | |
3895 | =item EV_PID_HASHSIZE |
3995 | =item EV_PID_HASHSIZE |
3896 | |
3996 | |
3897 | C<ev_child> watchers use a small hash table to distribute workload by |
3997 | C<ev_child> watchers use a small hash table to distribute workload by |
3898 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3998 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3899 | than enough. If you need to manage thousands of children you might want to |
3999 | usually more than enough. If you need to manage thousands of children you |
3900 | increase this value (I<must> be a power of two). |
4000 | might want to increase this value (I<must> be a power of two). |
3901 | |
4001 | |
3902 | =item EV_INOTIFY_HASHSIZE |
4002 | =item EV_INOTIFY_HASHSIZE |
3903 | |
4003 | |
3904 | C<ev_stat> watchers use a small hash table to distribute workload by |
4004 | C<ev_stat> watchers use a small hash table to distribute workload by |
3905 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4005 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3906 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4006 | disabled), usually more than enough. If you need to manage thousands of |
3907 | watchers you might want to increase this value (I<must> be a power of |
4007 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3908 | two). |
4008 | power of two). |
3909 | |
4009 | |
3910 | =item EV_USE_4HEAP |
4010 | =item EV_USE_4HEAP |
3911 | |
4011 | |
3912 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4012 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3913 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4013 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3914 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4014 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3915 | faster performance with many (thousands) of watchers. |
4015 | faster performance with many (thousands) of watchers. |
3916 | |
4016 | |
3917 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4017 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3918 | (disabled). |
4018 | will be C<0>. |
3919 | |
4019 | |
3920 | =item EV_HEAP_CACHE_AT |
4020 | =item EV_HEAP_CACHE_AT |
3921 | |
4021 | |
3922 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4022 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3923 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4023 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3924 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4024 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3925 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4025 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3926 | but avoids random read accesses on heap changes. This improves performance |
4026 | but avoids random read accesses on heap changes. This improves performance |
3927 | noticeably with many (hundreds) of watchers. |
4027 | noticeably with many (hundreds) of watchers. |
3928 | |
4028 | |
3929 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4029 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3930 | (disabled). |
4030 | will be C<0>. |
3931 | |
4031 | |
3932 | =item EV_VERIFY |
4032 | =item EV_VERIFY |
3933 | |
4033 | |
3934 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4034 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3935 | be done: If set to C<0>, no internal verification code will be compiled |
4035 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3937 | called. If set to C<2>, then the internal verification code will be |
4037 | called. If set to C<2>, then the internal verification code will be |
3938 | called once per loop, which can slow down libev. If set to C<3>, then the |
4038 | called once per loop, which can slow down libev. If set to C<3>, then the |
3939 | verification code will be called very frequently, which will slow down |
4039 | verification code will be called very frequently, which will slow down |
3940 | libev considerably. |
4040 | libev considerably. |
3941 | |
4041 | |
3942 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3943 | C<0>. |
4043 | will be C<0>. |
3944 | |
4044 | |
3945 | =item EV_COMMON |
4045 | =item EV_COMMON |
3946 | |
4046 | |
3947 | By default, all watchers have a C<void *data> member. By redefining |
4047 | By default, all watchers have a C<void *data> member. By redefining |
3948 | this macro to a something else you can include more and other types of |
4048 | this macro to something else you can include more and other types of |
3949 | members. You have to define it each time you include one of the files, |
4049 | members. You have to define it each time you include one of the files, |
3950 | though, and it must be identical each time. |
4050 | though, and it must be identical each time. |
3951 | |
4051 | |
3952 | For example, the perl EV module uses something like this: |
4052 | For example, the perl EV module uses something like this: |
3953 | |
4053 | |
… | |
… | |
4006 | file. |
4106 | file. |
4007 | |
4107 | |
4008 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4108 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4009 | that everybody includes and which overrides some configure choices: |
4109 | that everybody includes and which overrides some configure choices: |
4010 | |
4110 | |
4011 | #define EV_MINIMAL 1 |
4111 | #define EV_FEATURES 8 |
4012 | #define EV_USE_POLL 0 |
4112 | #define EV_USE_SELECT 1 |
4013 | #define EV_MULTIPLICITY 0 |
|
|
4014 | #define EV_PERIODIC_ENABLE 0 |
4113 | #define EV_PREPARE_ENABLE 1 |
|
|
4114 | #define EV_IDLE_ENABLE 1 |
4015 | #define EV_STAT_ENABLE 0 |
4115 | #define EV_SIGNAL_ENABLE 1 |
4016 | #define EV_FORK_ENABLE 0 |
4116 | #define EV_CHILD_ENABLE 1 |
|
|
4117 | #define EV_USE_STDEXCEPT 0 |
4017 | #define EV_CONFIG_H <config.h> |
4118 | #define EV_CONFIG_H <config.h> |
4018 | #define EV_MINPRI 0 |
|
|
4019 | #define EV_MAXPRI 0 |
|
|
4020 | |
4119 | |
4021 | #include "ev++.h" |
4120 | #include "ev++.h" |
4022 | |
4121 | |
4023 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4122 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4024 | |
4123 | |
… | |
… | |
4253 | maintainable. |
4352 | maintainable. |
4254 | |
4353 | |
4255 | And of course, some compiler warnings are just plain stupid, or simply |
4354 | And of course, some compiler warnings are just plain stupid, or simply |
4256 | wrong (because they don't actually warn about the condition their message |
4355 | wrong (because they don't actually warn about the condition their message |
4257 | seems to warn about). For example, certain older gcc versions had some |
4356 | seems to warn about). For example, certain older gcc versions had some |
4258 | warnings that resulted an extreme number of false positives. These have |
4357 | warnings that resulted in an extreme number of false positives. These have |
4259 | been fixed, but some people still insist on making code warn-free with |
4358 | been fixed, but some people still insist on making code warn-free with |
4260 | such buggy versions. |
4359 | such buggy versions. |
4261 | |
4360 | |
4262 | While libev is written to generate as few warnings as possible, |
4361 | While libev is written to generate as few warnings as possible, |
4263 | "warn-free" code is not a goal, and it is recommended not to build libev |
4362 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
4299 | I suggest using suppression lists. |
4398 | I suggest using suppression lists. |
4300 | |
4399 | |
4301 | |
4400 | |
4302 | =head1 PORTABILITY NOTES |
4401 | =head1 PORTABILITY NOTES |
4303 | |
4402 | |
|
|
4403 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4404 | |
|
|
4405 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4406 | interfaces but I<disables> them by default. |
|
|
4407 | |
|
|
4408 | That means that libev compiled in the default environment doesn't support |
|
|
4409 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4410 | |
|
|
4411 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4412 | by enabling the large file API, which makes them incompatible with the |
|
|
4413 | standard libev compiled for their system. |
|
|
4414 | |
|
|
4415 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4416 | suddenly make it incompatible to the default compile time environment, |
|
|
4417 | i.e. all programs not using special compile switches. |
|
|
4418 | |
|
|
4419 | =head2 OS/X AND DARWIN BUGS |
|
|
4420 | |
|
|
4421 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4422 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4423 | OpenGL drivers. |
|
|
4424 | |
|
|
4425 | =head3 C<kqueue> is buggy |
|
|
4426 | |
|
|
4427 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4428 | only sockets, many support pipes. |
|
|
4429 | |
|
|
4430 | Libev tries to work around this by not using C<kqueue> by default on |
|
|
4431 | this rotten platform, but of course you can still ask for it when creating |
|
|
4432 | a loop. |
|
|
4433 | |
|
|
4434 | =head3 C<poll> is buggy |
|
|
4435 | |
|
|
4436 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4437 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4438 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4439 | |
|
|
4440 | Libev tries to work around this by not using C<poll> by default on |
|
|
4441 | this rotten platform, but of course you can still ask for it when creating |
|
|
4442 | a loop. |
|
|
4443 | |
|
|
4444 | =head3 C<select> is buggy |
|
|
4445 | |
|
|
4446 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4447 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4448 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4449 | you use more. |
|
|
4450 | |
|
|
4451 | There is an undocumented "workaround" for this - defining |
|
|
4452 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4453 | work on OS/X. |
|
|
4454 | |
|
|
4455 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4456 | |
|
|
4457 | =head3 C<errno> reentrancy |
|
|
4458 | |
|
|
4459 | The default compile environment on Solaris is unfortunately so |
|
|
4460 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4461 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
|
|
4462 | isn't defined by default. |
|
|
4463 | |
|
|
4464 | If you want to use libev in threaded environments you have to make sure |
|
|
4465 | it's compiled with C<_REENTRANT> defined. |
|
|
4466 | |
|
|
4467 | =head3 Event port backend |
|
|
4468 | |
|
|
4469 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
|
|
4470 | this mechanism is very buggy. If you run into high CPU usage, your program |
|
|
4471 | freezes or you get a large number of spurious wakeups, make sure you have |
|
|
4472 | all the relevant and latest kernel patches applied. No, I don't know which |
|
|
4473 | ones, but there are multiple ones. |
|
|
4474 | |
|
|
4475 | If you can't get it to work, you can try running the program by setting |
|
|
4476 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4477 | C<select> backends. |
|
|
4478 | |
|
|
4479 | =head2 AIX POLL BUG |
|
|
4480 | |
|
|
4481 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4482 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4483 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4484 | with large bitsets, and AIX is dead anyway. |
|
|
4485 | |
4304 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4486 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4487 | |
|
|
4488 | =head3 General issues |
4305 | |
4489 | |
4306 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4490 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4307 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4491 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4308 | model. Libev still offers limited functionality on this platform in |
4492 | model. Libev still offers limited functionality on this platform in |
4309 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4493 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4310 | descriptors. This only applies when using Win32 natively, not when using |
4494 | descriptors. This only applies when using Win32 natively, not when using |
4311 | e.g. cygwin. |
4495 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4496 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4497 | environment. |
4312 | |
4498 | |
4313 | Lifting these limitations would basically require the full |
4499 | Lifting these limitations would basically require the full |
4314 | re-implementation of the I/O system. If you are into these kinds of |
4500 | re-implementation of the I/O system. If you are into this kind of thing, |
4315 | things, then note that glib does exactly that for you in a very portable |
4501 | then note that glib does exactly that for you in a very portable way (note |
4316 | way (note also that glib is the slowest event library known to man). |
4502 | also that glib is the slowest event library known to man). |
4317 | |
4503 | |
4318 | There is no supported compilation method available on windows except |
4504 | There is no supported compilation method available on windows except |
4319 | embedding it into other applications. |
4505 | embedding it into other applications. |
4320 | |
4506 | |
4321 | Sensible signal handling is officially unsupported by Microsoft - libev |
4507 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4349 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4535 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4350 | |
4536 | |
4351 | #include "evwrap.h" |
4537 | #include "evwrap.h" |
4352 | #include "ev.c" |
4538 | #include "ev.c" |
4353 | |
4539 | |
4354 | =over 4 |
|
|
4355 | |
|
|
4356 | =item The winsocket select function |
4540 | =head3 The winsocket C<select> function |
4357 | |
4541 | |
4358 | The winsocket C<select> function doesn't follow POSIX in that it |
4542 | The winsocket C<select> function doesn't follow POSIX in that it |
4359 | requires socket I<handles> and not socket I<file descriptors> (it is |
4543 | requires socket I<handles> and not socket I<file descriptors> (it is |
4360 | also extremely buggy). This makes select very inefficient, and also |
4544 | also extremely buggy). This makes select very inefficient, and also |
4361 | requires a mapping from file descriptors to socket handles (the Microsoft |
4545 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4370 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4554 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4371 | |
4555 | |
4372 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4556 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4373 | complexity in the O(n²) range when using win32. |
4557 | complexity in the O(n²) range when using win32. |
4374 | |
4558 | |
4375 | =item Limited number of file descriptors |
4559 | =head3 Limited number of file descriptors |
4376 | |
4560 | |
4377 | Windows has numerous arbitrary (and low) limits on things. |
4561 | Windows has numerous arbitrary (and low) limits on things. |
4378 | |
4562 | |
4379 | Early versions of winsocket's select only supported waiting for a maximum |
4563 | Early versions of winsocket's select only supported waiting for a maximum |
4380 | of C<64> handles (probably owning to the fact that all windows kernels |
4564 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4395 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4579 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4396 | (depending on windows version and/or the phase of the moon). To get more, |
4580 | (depending on windows version and/or the phase of the moon). To get more, |
4397 | you need to wrap all I/O functions and provide your own fd management, but |
4581 | you need to wrap all I/O functions and provide your own fd management, but |
4398 | the cost of calling select (O(n²)) will likely make this unworkable. |
4582 | the cost of calling select (O(n²)) will likely make this unworkable. |
4399 | |
4583 | |
4400 | =back |
|
|
4401 | |
|
|
4402 | =head2 PORTABILITY REQUIREMENTS |
4584 | =head2 PORTABILITY REQUIREMENTS |
4403 | |
4585 | |
4404 | In addition to a working ISO-C implementation and of course the |
4586 | In addition to a working ISO-C implementation and of course the |
4405 | backend-specific APIs, libev relies on a few additional extensions: |
4587 | backend-specific APIs, libev relies on a few additional extensions: |
4406 | |
4588 | |
… | |
… | |
4526 | involves iterating over all running async watchers or all signal numbers. |
4708 | involves iterating over all running async watchers or all signal numbers. |
4527 | |
4709 | |
4528 | =back |
4710 | =back |
4529 | |
4711 | |
4530 | |
4712 | |
|
|
4713 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4714 | |
|
|
4715 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4716 | |
|
|
4717 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4718 | compatibility, so most programs should still compile. Those might be |
|
|
4719 | removed in later versions of libev, so better update early than late. |
|
|
4720 | |
|
|
4721 | =over 4 |
|
|
4722 | |
|
|
4723 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4724 | |
|
|
4725 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4726 | |
|
|
4727 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4728 | |
|
|
4729 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4730 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4731 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4732 | C<ev_fork> typedef. |
|
|
4733 | |
|
|
4734 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4735 | |
|
|
4736 | This is a simple rename - all other watcher types use their name |
|
|
4737 | as revents flag, and now C<ev_timer> does, too. |
|
|
4738 | |
|
|
4739 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4740 | and continue to be present for the foreseeable future, so this is mostly a |
|
|
4741 | documentation change. |
|
|
4742 | |
|
|
4743 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4744 | |
|
|
4745 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4746 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4747 | and work, but the library code will of course be larger. |
|
|
4748 | |
|
|
4749 | =back |
|
|
4750 | |
|
|
4751 | |
4531 | =head1 GLOSSARY |
4752 | =head1 GLOSSARY |
4532 | |
4753 | |
4533 | =over 4 |
4754 | =over 4 |
4534 | |
4755 | |
4535 | =item active |
4756 | =item active |
… | |
… | |
4556 | A change of state of some external event, such as data now being available |
4777 | A change of state of some external event, such as data now being available |
4557 | for reading on a file descriptor, time having passed or simply not having |
4778 | for reading on a file descriptor, time having passed or simply not having |
4558 | any other events happening anymore. |
4779 | any other events happening anymore. |
4559 | |
4780 | |
4560 | In libev, events are represented as single bits (such as C<EV_READ> or |
4781 | In libev, events are represented as single bits (such as C<EV_READ> or |
4561 | C<EV_TIMEOUT>). |
4782 | C<EV_TIMER>). |
4562 | |
4783 | |
4563 | =item event library |
4784 | =item event library |
4564 | |
4785 | |
4565 | A software package implementing an event model and loop. |
4786 | A software package implementing an event model and loop. |
4566 | |
4787 | |