… | |
… | |
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 |
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… | |
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. |
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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). |
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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 | |
… | |
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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. |
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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 |
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370 | When this flag is specified, then libev will not attempt to use the |
370 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
374 | |
375 | =item C<EVFLAG_NOSIGFD> |
375 | =item C<EVFLAG_SIGNALFD> |
376 | |
376 | |
377 | When this flag is specified, then libev will not attempt to use the |
377 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This is |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
379 | probably only useful to work around any bugs in libev. Consequently, this |
379 | delivers signals synchronously, which makes it both faster and might make |
380 | flag might go away once the signalfd functionality is considered stable, |
380 | it possible to get the queued signal data. It can also simplify signal |
381 | so it's useful mostly in environment variables and not in program code. |
381 | handling with threads, as long as you properly block signals in your |
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382 | threads that are not interested in handling them. |
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383 | |
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384 | Signalfd will not be used by default as this changes your signal mask, and |
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385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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386 | example) that can't properly initialise their signal masks. |
382 | |
387 | |
383 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
384 | |
389 | |
385 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
386 | libev tries to roll its own fd_set with no limits on the number of fds, |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
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562 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
563 | |
568 | |
564 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
565 | |
570 | |
566 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
567 | always distinct from the default loop. Unlike the default loop, it cannot |
572 | always distinct from the default loop. |
568 | handle signal and child watchers, and attempts to do so will be greeted by |
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569 | undefined behaviour (or a failed assertion if assertions are enabled). |
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570 | |
573 | |
571 | Note that this function I<is> thread-safe, and the recommended way to use |
574 | Note that this function I<is> thread-safe, and one common way to use |
572 | libev with threads is indeed to create one loop per thread, and using the |
575 | libev with threads is indeed to create one loop per thread, and using the |
573 | default loop in the "main" or "initial" thread. |
576 | default loop in the "main" or "initial" thread. |
574 | |
577 | |
575 | Example: Try to create a event loop that uses epoll and nothing else. |
578 | Example: Try to create a event loop that uses epoll and nothing else. |
576 | |
579 | |
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578 | if (!epoller) |
581 | if (!epoller) |
579 | fatal ("no epoll found here, maybe it hides under your chair"); |
582 | fatal ("no epoll found here, maybe it hides under your chair"); |
580 | |
583 | |
581 | =item ev_default_destroy () |
584 | =item ev_default_destroy () |
582 | |
585 | |
583 | Destroys the default loop again (frees all memory and kernel state |
586 | Destroys the default loop (frees all memory and kernel state etc.). None |
584 | etc.). None of the active event watchers will be stopped in the normal |
587 | of the active event watchers will be stopped in the normal sense, so |
585 | sense, so e.g. C<ev_is_active> might still return true. It is your |
588 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
586 | responsibility to either stop all watchers cleanly yourself I<before> |
589 | either stop all watchers cleanly yourself I<before> calling this function, |
587 | calling this function, or cope with the fact afterwards (which is usually |
590 | or cope with the fact afterwards (which is usually the easiest thing, you |
588 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
591 | can just ignore the watchers and/or C<free ()> them for example). |
589 | for example). |
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|
590 | |
592 | |
591 | Note that certain global state, such as signal state (and installed signal |
593 | Note that certain global state, such as signal state (and installed signal |
592 | handlers), will not be freed by this function, and related watchers (such |
594 | handlers), will not be freed by this function, and related watchers (such |
593 | as signal and child watchers) would need to be stopped manually. |
595 | as signal and child watchers) would need to be stopped manually. |
594 | |
596 | |
… | |
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609 | name, you can call it anytime, but it makes most sense after forking, in |
611 | name, you can call it anytime, but it makes most sense after forking, in |
610 | the child process (or both child and parent, but that again makes little |
612 | the child process (or both child and parent, but that again makes little |
611 | sense). You I<must> call it in the child before using any of the libev |
613 | sense). You I<must> call it in the child before using any of the libev |
612 | functions, and it will only take effect at the next C<ev_loop> iteration. |
614 | functions, and it will only take effect at the next C<ev_loop> iteration. |
613 | |
615 | |
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616 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
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617 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
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618 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
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619 | during fork. |
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620 | |
614 | On the other hand, you only need to call this function in the child |
621 | On the other hand, you only need to call this function in the child |
615 | process if and only if you want to use the event library in the child. If |
622 | process if and only if you want to use the event loop in the child. If you |
616 | you just fork+exec, you don't have to call it at all. |
623 | just fork+exec or create a new loop in the child, you don't have to call |
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624 | it at all. |
617 | |
625 | |
618 | The function itself is quite fast and it's usually not a problem to call |
626 | The function itself is quite fast and it's usually not a problem to call |
619 | it just in case after a fork. To make this easy, the function will fit in |
627 | it just in case after a fork. To make this easy, the function will fit in |
620 | quite nicely into a call to C<pthread_atfork>: |
628 | quite nicely into a call to C<pthread_atfork>: |
621 | |
629 | |
… | |
… | |
623 | |
631 | |
624 | =item ev_loop_fork (loop) |
632 | =item ev_loop_fork (loop) |
625 | |
633 | |
626 | Like C<ev_default_fork>, but acts on an event loop created by |
634 | Like C<ev_default_fork>, but acts on an event loop created by |
627 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
635 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
628 | after fork that you want to re-use in the child, and how you do this is |
636 | after fork that you want to re-use in the child, and how you keep track of |
629 | entirely your own problem. |
637 | them is entirely your own problem. |
630 | |
638 | |
631 | =item int ev_is_default_loop (loop) |
639 | =item int ev_is_default_loop (loop) |
632 | |
640 | |
633 | Returns true when the given loop is, in fact, the default loop, and false |
641 | Returns true when the given loop is, in fact, the default loop, and false |
634 | otherwise. |
642 | otherwise. |
635 | |
643 | |
636 | =item unsigned int ev_loop_count (loop) |
644 | =item unsigned int ev_iteration (loop) |
637 | |
645 | |
638 | Returns the count of loop iterations for the loop, which is identical to |
646 | Returns the current iteration count for the loop, which is identical to |
639 | the number of times libev did poll for new events. It starts at C<0> and |
647 | the number of times libev did poll for new events. It starts at C<0> and |
640 | happily wraps around with enough iterations. |
648 | happily wraps around with enough iterations. |
641 | |
649 | |
642 | This value can sometimes be useful as a generation counter of sorts (it |
650 | This value can sometimes be useful as a generation counter of sorts (it |
643 | "ticks" the number of loop iterations), as it roughly corresponds with |
651 | "ticks" the number of loop iterations), as it roughly corresponds with |
644 | C<ev_prepare> and C<ev_check> calls. |
652 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
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|
653 | prepare and check phases. |
645 | |
654 | |
646 | =item unsigned int ev_loop_depth (loop) |
655 | =item unsigned int ev_depth (loop) |
647 | |
656 | |
648 | Returns the number of times C<ev_loop> was entered minus the number of |
657 | Returns the number of times C<ev_loop> was entered minus the number of |
649 | times C<ev_loop> was exited, in other words, the recursion depth. |
658 | times C<ev_loop> was exited, in other words, the recursion depth. |
650 | |
659 | |
651 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
660 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
652 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
661 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
653 | in which case it is higher. |
662 | in which case it is higher. |
654 | |
663 | |
655 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
664 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
656 | etc.), doesn't count as exit. |
665 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
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|
666 | ungentleman behaviour unless it's really convenient. |
657 | |
667 | |
658 | =item unsigned int ev_backend (loop) |
668 | =item unsigned int ev_backend (loop) |
659 | |
669 | |
660 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
670 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
661 | use. |
671 | use. |
… | |
… | |
695 | C<ev_resume> directly afterwards to resume timer processing. |
705 | C<ev_resume> directly afterwards to resume timer processing. |
696 | |
706 | |
697 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
707 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
698 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
708 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
699 | will be rescheduled (that is, they will lose any events that would have |
709 | will be rescheduled (that is, they will lose any events that would have |
700 | occured while suspended). |
710 | occurred while suspended). |
701 | |
711 | |
702 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
712 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
703 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
713 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
704 | without a previous call to C<ev_suspend>. |
714 | without a previous call to C<ev_suspend>. |
705 | |
715 | |
… | |
… | |
782 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
783 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
784 | |
794 | |
785 | This "unloop state" will be cleared when entering C<ev_loop> again. |
795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
786 | |
796 | |
787 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
797 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
788 | |
798 | |
789 | =item ev_ref (loop) |
799 | =item ev_ref (loop) |
790 | |
800 | |
791 | =item ev_unref (loop) |
801 | =item ev_unref (loop) |
792 | |
802 | |
793 | Ref/unref can be used to add or remove a reference count on the event |
803 | Ref/unref can be used to add or remove a reference count on the event |
794 | loop: Every watcher keeps one reference, and as long as the reference |
804 | loop: Every watcher keeps one reference, and as long as the reference |
795 | count is nonzero, C<ev_loop> will not return on its own. |
805 | count is nonzero, C<ev_loop> will not return on its own. |
796 | |
806 | |
797 | If you have a watcher you never unregister that should not keep C<ev_loop> |
807 | This is useful when you have a watcher that you never intend to |
798 | from returning, call ev_unref() after starting, and ev_ref() before |
808 | unregister, but that nevertheless should not keep C<ev_loop> from |
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|
809 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
799 | stopping it. |
810 | before stopping it. |
800 | |
811 | |
801 | As an example, libev itself uses this for its internal signal pipe: It |
812 | As an example, libev itself uses this for its internal signal pipe: It |
802 | is not visible to the libev user and should not keep C<ev_loop> from |
813 | is not visible to the libev user and should not keep C<ev_loop> from |
803 | exiting if no event watchers registered by it are active. It is also an |
814 | exiting if no event watchers registered by it are active. It is also an |
804 | excellent way to do this for generic recurring timers or from within |
815 | excellent way to do this for generic recurring timers or from within |
… | |
… | |
861 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
872 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
862 | as this approaches the timing granularity of most systems. Note that if |
873 | as this approaches the timing granularity of most systems. Note that if |
863 | you do transactions with the outside world and you can't increase the |
874 | you do transactions with the outside world and you can't increase the |
864 | parallelity, then this setting will limit your transaction rate (if you |
875 | parallelity, then this setting will limit your transaction rate (if you |
865 | need to poll once per transaction and the I/O collect interval is 0.01, |
876 | need to poll once per transaction and the I/O collect interval is 0.01, |
866 | then you can't do more than 100 transations per second). |
877 | then you can't do more than 100 transactions per second). |
867 | |
878 | |
868 | Setting the I<timeout collect interval> can improve the opportunity for |
879 | Setting the I<timeout collect interval> can improve the opportunity for |
869 | saving power, as the program will "bundle" timer callback invocations that |
880 | saving power, as the program will "bundle" timer callback invocations that |
870 | are "near" in time together, by delaying some, thus reducing the number of |
881 | are "near" in time together, by delaying some, thus reducing the number of |
871 | times the process sleeps and wakes up again. Another useful technique to |
882 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
1026 | =item C<EV_WRITE> |
1037 | =item C<EV_WRITE> |
1027 | |
1038 | |
1028 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1039 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1029 | writable. |
1040 | writable. |
1030 | |
1041 | |
1031 | =item C<EV_TIMEOUT> |
1042 | =item C<EV_TIMER> |
1032 | |
1043 | |
1033 | The C<ev_timer> watcher has timed out. |
1044 | The C<ev_timer> watcher has timed out. |
1034 | |
1045 | |
1035 | =item C<EV_PERIODIC> |
1046 | =item C<EV_PERIODIC> |
1036 | |
1047 | |
… | |
… | |
1369 | |
1380 | |
1370 | For example, to emulate how many other event libraries handle priorities, |
1381 | For example, to emulate how many other event libraries handle priorities, |
1371 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1382 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1372 | the normal watcher callback, you just start the idle watcher. The real |
1383 | the normal watcher callback, you just start the idle watcher. The real |
1373 | processing is done in the idle watcher callback. This causes libev to |
1384 | processing is done in the idle watcher callback. This causes libev to |
1374 | continously poll and process kernel event data for the watcher, but when |
1385 | continuously poll and process kernel event data for the watcher, but when |
1375 | the lock-out case is known to be rare (which in turn is rare :), this is |
1386 | the lock-out case is known to be rare (which in turn is rare :), this is |
1376 | workable. |
1387 | workable. |
1377 | |
1388 | |
1378 | Usually, however, the lock-out model implemented that way will perform |
1389 | Usually, however, the lock-out model implemented that way will perform |
1379 | miserably under the type of load it was designed to handle. In that case, |
1390 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1393 | { |
1404 | { |
1394 | // stop the I/O watcher, we received the event, but |
1405 | // stop the I/O watcher, we received the event, but |
1395 | // are not yet ready to handle it. |
1406 | // are not yet ready to handle it. |
1396 | ev_io_stop (EV_A_ w); |
1407 | ev_io_stop (EV_A_ w); |
1397 | |
1408 | |
1398 | // start the idle watcher to ahndle the actual event. |
1409 | // start the idle watcher to handle the actual event. |
1399 | // it will not be executed as long as other watchers |
1410 | // it will not be executed as long as other watchers |
1400 | // with the default priority are receiving events. |
1411 | // with the default priority are receiving events. |
1401 | ev_idle_start (EV_A_ &idle); |
1412 | ev_idle_start (EV_A_ &idle); |
1402 | } |
1413 | } |
1403 | |
1414 | |
… | |
… | |
1457 | |
1468 | |
1458 | If you cannot use non-blocking mode, then force the use of a |
1469 | If you cannot use non-blocking mode, then force the use of a |
1459 | known-to-be-good backend (at the time of this writing, this includes only |
1470 | known-to-be-good backend (at the time of this writing, this includes only |
1460 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1461 | descriptors for which non-blocking operation makes no sense (such as |
1472 | descriptors for which non-blocking operation makes no sense (such as |
1462 | files) - libev doesn't guarentee any specific behaviour in that case. |
1473 | files) - libev doesn't guarantee any specific behaviour in that case. |
1463 | |
1474 | |
1464 | Another thing you have to watch out for is that it is quite easy to |
1475 | Another thing you have to watch out for is that it is quite easy to |
1465 | receive "spurious" readiness notifications, that is your callback might |
1476 | receive "spurious" readiness notifications, that is your callback might |
1466 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1467 | because there is no data. Not only are some backends known to create a |
1478 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1532 | |
1543 | |
1533 | So when you encounter spurious, unexplained daemon exits, make sure you |
1544 | So when you encounter spurious, unexplained daemon exits, make sure you |
1534 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1545 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1535 | somewhere, as that would have given you a big clue). |
1546 | somewhere, as that would have given you a big clue). |
1536 | |
1547 | |
|
|
1548 | =head3 The special problem of accept()ing when you can't |
|
|
1549 | |
|
|
1550 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1551 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1552 | connection from the pending queue in all error cases. |
|
|
1553 | |
|
|
1554 | For example, larger servers often run out of file descriptors (because |
|
|
1555 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1556 | rejecting the connection, leading to libev signalling readiness on |
|
|
1557 | the next iteration again (the connection still exists after all), and |
|
|
1558 | typically causing the program to loop at 100% CPU usage. |
|
|
1559 | |
|
|
1560 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1561 | operating systems, there is usually little the app can do to remedy the |
|
|
1562 | situation, and no known thread-safe method of removing the connection to |
|
|
1563 | cope with overload is known (to me). |
|
|
1564 | |
|
|
1565 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1566 | - when the program encounters an overload, it will just loop until the |
|
|
1567 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1568 | event-based way to handle this situation, so it's the best one can do. |
|
|
1569 | |
|
|
1570 | A better way to handle the situation is to log any errors other than |
|
|
1571 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1572 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1573 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1574 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1575 | usage. |
|
|
1576 | |
|
|
1577 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1578 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1579 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1580 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1581 | clients under typical overload conditions. |
|
|
1582 | |
|
|
1583 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1584 | is often done with C<malloc> failures, but this results in an easy |
|
|
1585 | opportunity for a DoS attack. |
1537 | |
1586 | |
1538 | =head3 Watcher-Specific Functions |
1587 | =head3 Watcher-Specific Functions |
1539 | |
1588 | |
1540 | =over 4 |
1589 | =over 4 |
1541 | |
1590 | |
… | |
… | |
1688 | ev_tstamp timeout = last_activity + 60.; |
1737 | ev_tstamp timeout = last_activity + 60.; |
1689 | |
1738 | |
1690 | // if last_activity + 60. is older than now, we did time out |
1739 | // if last_activity + 60. is older than now, we did time out |
1691 | if (timeout < now) |
1740 | if (timeout < now) |
1692 | { |
1741 | { |
1693 | // timeout occured, take action |
1742 | // timeout occurred, take action |
1694 | } |
1743 | } |
1695 | else |
1744 | else |
1696 | { |
1745 | { |
1697 | // callback was invoked, but there was some activity, re-arm |
1746 | // callback was invoked, but there was some activity, re-arm |
1698 | // the watcher to fire in last_activity + 60, which is |
1747 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1720 | to the current time (meaning we just have some activity :), then call the |
1769 | to the current time (meaning we just have some activity :), then call the |
1721 | callback, which will "do the right thing" and start the timer: |
1770 | callback, which will "do the right thing" and start the timer: |
1722 | |
1771 | |
1723 | ev_init (timer, callback); |
1772 | ev_init (timer, callback); |
1724 | last_activity = ev_now (loop); |
1773 | last_activity = ev_now (loop); |
1725 | callback (loop, timer, EV_TIMEOUT); |
1774 | callback (loop, timer, EV_TIMER); |
1726 | |
1775 | |
1727 | And when there is some activity, simply store the current time in |
1776 | And when there is some activity, simply store the current time in |
1728 | C<last_activity>, no libev calls at all: |
1777 | C<last_activity>, no libev calls at all: |
1729 | |
1778 | |
1730 | last_actiivty = ev_now (loop); |
1779 | last_activity = ev_now (loop); |
1731 | |
1780 | |
1732 | This technique is slightly more complex, but in most cases where the |
1781 | This technique is slightly more complex, but in most cases where the |
1733 | time-out is unlikely to be triggered, much more efficient. |
1782 | time-out is unlikely to be triggered, much more efficient. |
1734 | |
1783 | |
1735 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1784 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1861 | Returns the remaining time until a timer fires. If the timer is active, |
1910 | Returns the remaining time until a timer fires. If the timer is active, |
1862 | then this time is relative to the current event loop time, otherwise it's |
1911 | then this time is relative to the current event loop time, otherwise it's |
1863 | the timeout value currently configured. |
1912 | the timeout value currently configured. |
1864 | |
1913 | |
1865 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1914 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1866 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
1915 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1867 | will return C<4>. When the timer expires and is restarted, it will return |
1916 | will return C<4>. When the timer expires and is restarted, it will return |
1868 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1917 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1869 | too), and so on. |
1918 | too), and so on. |
1870 | |
1919 | |
1871 | =item ev_tstamp repeat [read-write] |
1920 | =item ev_tstamp repeat [read-write] |
… | |
… | |
2074 | Example: Call a callback every hour, or, more precisely, whenever the |
2123 | Example: Call a callback every hour, or, more precisely, whenever the |
2075 | system time is divisible by 3600. The callback invocation times have |
2124 | system time is divisible by 3600. The callback invocation times have |
2076 | potentially a lot of jitter, but good long-term stability. |
2125 | potentially a lot of jitter, but good long-term stability. |
2077 | |
2126 | |
2078 | static void |
2127 | static void |
2079 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2128 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2080 | { |
2129 | { |
2081 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2130 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2082 | } |
2131 | } |
2083 | |
2132 | |
2084 | ev_periodic hourly_tick; |
2133 | ev_periodic hourly_tick; |
… | |
… | |
2131 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2180 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2132 | not be unduly interrupted. If you have a problem with system calls getting |
2181 | not be unduly interrupted. If you have a problem with system calls getting |
2133 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2182 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2134 | and unblock them in an C<ev_prepare> watcher. |
2183 | and unblock them in an C<ev_prepare> watcher. |
2135 | |
2184 | |
2136 | =head3 The special problem of inheritance over execve |
2185 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2137 | |
2186 | |
2138 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2187 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2139 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2188 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2140 | stopping it again), that is, libev might or might not block the signal, |
2189 | stopping it again), that is, libev might or might not block the signal, |
2141 | and might or might not set or restore the installed signal handler. |
2190 | and might or might not set or restore the installed signal handler. |
… | |
… | |
2151 | |
2200 | |
2152 | The simplest way to ensure that the signal mask is reset in the child is |
2201 | The simplest way to ensure that the signal mask is reset in the child is |
2153 | to install a fork handler with C<pthread_atfork> that resets it. That will |
2202 | to install a fork handler with C<pthread_atfork> that resets it. That will |
2154 | catch fork calls done by libraries (such as the libc) as well. |
2203 | catch fork calls done by libraries (such as the libc) as well. |
2155 | |
2204 | |
2156 | In current versions of libev, you can also ensure that the signal mask is |
2205 | In current versions of libev, the signal will not be blocked indefinitely |
2157 | not blocking any signals (except temporarily, so thread users watch out) |
2206 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
2158 | by specifying the C<EVFLAG_NOSIGFD> when creating the event loop. This |
2207 | the window of opportunity for problems, it will not go away, as libev |
2159 | is not guaranteed for future versions, however. |
2208 | I<has> to modify the signal mask, at least temporarily. |
|
|
2209 | |
|
|
2210 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2211 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2212 | is not a libev-specific thing, this is true for most event libraries. |
2160 | |
2213 | |
2161 | =head3 Watcher-Specific Functions and Data Members |
2214 | =head3 Watcher-Specific Functions and Data Members |
2162 | |
2215 | |
2163 | =over 4 |
2216 | =over 4 |
2164 | |
2217 | |
… | |
… | |
2912 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2965 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2913 | handlers will be invoked, too, of course. |
2966 | handlers will be invoked, too, of course. |
2914 | |
2967 | |
2915 | =head3 The special problem of life after fork - how is it possible? |
2968 | =head3 The special problem of life after fork - how is it possible? |
2916 | |
2969 | |
2917 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
2970 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2918 | up/change the process environment, followed by a call to C<exec()>. This |
2971 | up/change the process environment, followed by a call to C<exec()>. This |
2919 | sequence should be handled by libev without any problems. |
2972 | sequence should be handled by libev without any problems. |
2920 | |
2973 | |
2921 | This changes when the application actually wants to do event handling |
2974 | This changes when the application actually wants to do event handling |
2922 | in the child, or both parent in child, in effect "continuing" after the |
2975 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2956 | believe me. |
3009 | believe me. |
2957 | |
3010 | |
2958 | =back |
3011 | =back |
2959 | |
3012 | |
2960 | |
3013 | |
2961 | =head2 C<ev_async> - how to wake up another event loop |
3014 | =head2 C<ev_async> - how to wake up an event loop |
2962 | |
3015 | |
2963 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3016 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2964 | asynchronous sources such as signal handlers (as opposed to multiple event |
3017 | asynchronous sources such as signal handlers (as opposed to multiple event |
2965 | loops - those are of course safe to use in different threads). |
3018 | loops - those are of course safe to use in different threads). |
2966 | |
3019 | |
2967 | Sometimes, however, you need to wake up another event loop you do not |
3020 | Sometimes, however, you need to wake up an event loop you do not control, |
2968 | control, for example because it belongs to another thread. This is what |
3021 | for example because it belongs to another thread. This is what C<ev_async> |
2969 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3022 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2970 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3023 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2971 | safe. |
|
|
2972 | |
3024 | |
2973 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3025 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2974 | too, are asynchronous in nature, and signals, too, will be compressed |
3026 | too, are asynchronous in nature, and signals, too, will be compressed |
2975 | (i.e. the number of callback invocations may be less than the number of |
3027 | (i.e. the number of callback invocations may be less than the number of |
2976 | C<ev_async_sent> calls). |
3028 | C<ev_async_sent> calls). |
… | |
… | |
3131 | |
3183 | |
3132 | If C<timeout> is less than 0, then no timeout watcher will be |
3184 | If C<timeout> is less than 0, then no timeout watcher will be |
3133 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3185 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3134 | repeat = 0) will be started. C<0> is a valid timeout. |
3186 | repeat = 0) will be started. C<0> is a valid timeout. |
3135 | |
3187 | |
3136 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3188 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3137 | passed an C<revents> set like normal event callbacks (a combination of |
3189 | passed an C<revents> set like normal event callbacks (a combination of |
3138 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3190 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3139 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3191 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3140 | a timeout and an io event at the same time - you probably should give io |
3192 | a timeout and an io event at the same time - you probably should give io |
3141 | events precedence. |
3193 | events precedence. |
3142 | |
3194 | |
3143 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3195 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3144 | |
3196 | |
3145 | static void stdin_ready (int revents, void *arg) |
3197 | static void stdin_ready (int revents, void *arg) |
3146 | { |
3198 | { |
3147 | if (revents & EV_READ) |
3199 | if (revents & EV_READ) |
3148 | /* stdin might have data for us, joy! */; |
3200 | /* stdin might have data for us, joy! */; |
3149 | else if (revents & EV_TIMEOUT) |
3201 | else if (revents & EV_TIMER) |
3150 | /* doh, nothing entered */; |
3202 | /* doh, nothing entered */; |
3151 | } |
3203 | } |
3152 | |
3204 | |
3153 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3205 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3154 | |
3206 | |
… | |
… | |
3288 | myclass obj; |
3340 | myclass obj; |
3289 | ev::io iow; |
3341 | ev::io iow; |
3290 | iow.set <myclass, &myclass::io_cb> (&obj); |
3342 | iow.set <myclass, &myclass::io_cb> (&obj); |
3291 | |
3343 | |
3292 | =item w->set (object *) |
3344 | =item w->set (object *) |
3293 | |
|
|
3294 | This is an B<experimental> feature that might go away in a future version. |
|
|
3295 | |
3345 | |
3296 | This is a variation of a method callback - leaving out the method to call |
3346 | This is a variation of a method callback - leaving out the method to call |
3297 | will default the method to C<operator ()>, which makes it possible to use |
3347 | will default the method to C<operator ()>, which makes it possible to use |
3298 | functor objects without having to manually specify the C<operator ()> all |
3348 | functor objects without having to manually specify the C<operator ()> all |
3299 | the time. Incidentally, you can then also leave out the template argument |
3349 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3441 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3491 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3442 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3492 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3443 | |
3493 | |
3444 | =item Lua |
3494 | =item Lua |
3445 | |
3495 | |
3446 | Brian Maher has written a partial interface to libev |
3496 | Brian Maher has written a partial interface to libev for lua (at the |
3447 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
3497 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3448 | L<http://github.com/brimworks/lua-ev>. |
3498 | L<http://github.com/brimworks/lua-ev>. |
3449 | |
3499 | |
3450 | =back |
3500 | =back |
3451 | |
3501 | |
3452 | |
3502 | |
… | |
… | |
3607 | libev.m4 |
3657 | libev.m4 |
3608 | |
3658 | |
3609 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3659 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3610 | |
3660 | |
3611 | Libev can be configured via a variety of preprocessor symbols you have to |
3661 | Libev can be configured via a variety of preprocessor symbols you have to |
3612 | define before including any of its files. The default in the absence of |
3662 | define before including (or compiling) any of its files. The default in |
3613 | autoconf is documented for every option. |
3663 | the absence of autoconf is documented for every option. |
|
|
3664 | |
|
|
3665 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3666 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3667 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3668 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3669 | users of libev and the libev code itself must be compiled with compatible |
|
|
3670 | settings. |
3614 | |
3671 | |
3615 | =over 4 |
3672 | =over 4 |
3616 | |
3673 | |
3617 | =item EV_STANDALONE |
3674 | =item EV_STANDALONE (h) |
3618 | |
3675 | |
3619 | Must always be C<1> if you do not use autoconf configuration, which |
3676 | Must always be C<1> if you do not use autoconf configuration, which |
3620 | keeps libev from including F<config.h>, and it also defines dummy |
3677 | keeps libev from including F<config.h>, and it also defines dummy |
3621 | implementations for some libevent functions (such as logging, which is not |
3678 | implementations for some libevent functions (such as logging, which is not |
3622 | supported). It will also not define any of the structs usually found in |
3679 | supported). It will also not define any of the structs usually found in |
… | |
… | |
3772 | as well as for signal and thread safety in C<ev_async> watchers. |
3829 | as well as for signal and thread safety in C<ev_async> watchers. |
3773 | |
3830 | |
3774 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3831 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3775 | (from F<signal.h>), which is usually good enough on most platforms. |
3832 | (from F<signal.h>), which is usually good enough on most platforms. |
3776 | |
3833 | |
3777 | =item EV_H |
3834 | =item EV_H (h) |
3778 | |
3835 | |
3779 | The name of the F<ev.h> header file used to include it. The default if |
3836 | The name of the F<ev.h> header file used to include it. The default if |
3780 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3837 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3781 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3838 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3782 | |
3839 | |
3783 | =item EV_CONFIG_H |
3840 | =item EV_CONFIG_H (h) |
3784 | |
3841 | |
3785 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3842 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3786 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3843 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3787 | C<EV_H>, above. |
3844 | C<EV_H>, above. |
3788 | |
3845 | |
3789 | =item EV_EVENT_H |
3846 | =item EV_EVENT_H (h) |
3790 | |
3847 | |
3791 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3848 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3792 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3849 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3793 | |
3850 | |
3794 | =item EV_PROTOTYPES |
3851 | =item EV_PROTOTYPES (h) |
3795 | |
3852 | |
3796 | If defined to be C<0>, then F<ev.h> will not define any function |
3853 | If defined to be C<0>, then F<ev.h> will not define any function |
3797 | prototypes, but still define all the structs and other symbols. This is |
3854 | prototypes, but still define all the structs and other symbols. This is |
3798 | occasionally useful if you want to provide your own wrapper functions |
3855 | occasionally useful if you want to provide your own wrapper functions |
3799 | around libev functions. |
3856 | around libev functions. |
… | |
… | |
3821 | fine. |
3878 | fine. |
3822 | |
3879 | |
3823 | If your embedding application does not need any priorities, defining these |
3880 | If your embedding application does not need any priorities, defining these |
3824 | both to C<0> will save some memory and CPU. |
3881 | both to C<0> will save some memory and CPU. |
3825 | |
3882 | |
3826 | =item EV_PERIODIC_ENABLE |
3883 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3884 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3885 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3827 | |
3886 | |
3828 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3887 | If undefined or defined to be C<1> (and the platform supports it), then |
3829 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3888 | the respective watcher type is supported. If defined to be C<0>, then it |
3830 | code. |
3889 | is not. Disabling watcher types mainly saves code size. |
3831 | |
3890 | |
3832 | =item EV_IDLE_ENABLE |
3891 | =item EV_FEATURES |
3833 | |
|
|
3834 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3835 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3836 | code. |
|
|
3837 | |
|
|
3838 | =item EV_EMBED_ENABLE |
|
|
3839 | |
|
|
3840 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3841 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3842 | watcher types, which therefore must not be disabled. |
|
|
3843 | |
|
|
3844 | =item EV_STAT_ENABLE |
|
|
3845 | |
|
|
3846 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3847 | defined to be C<0>, then they are not. |
|
|
3848 | |
|
|
3849 | =item EV_FORK_ENABLE |
|
|
3850 | |
|
|
3851 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3852 | defined to be C<0>, then they are not. |
|
|
3853 | |
|
|
3854 | =item EV_ASYNC_ENABLE |
|
|
3855 | |
|
|
3856 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3857 | defined to be C<0>, then they are not. |
|
|
3858 | |
|
|
3859 | =item EV_MINIMAL |
|
|
3860 | |
3892 | |
3861 | If you need to shave off some kilobytes of code at the expense of some |
3893 | If you need to shave off some kilobytes of code at the expense of some |
3862 | speed (but with the full API), define this symbol to C<1>. Currently this |
3894 | speed (but with the full API), you can define this symbol to request |
3863 | is used to override some inlining decisions, saves roughly 30% code size |
3895 | certain subsets of functionality. The default is to enable all features |
3864 | on amd64. It also selects a much smaller 2-heap for timer management over |
3896 | that can be enabled on the platform. |
3865 | the default 4-heap. |
|
|
3866 | |
3897 | |
3867 | You can save even more by disabling watcher types you do not need |
3898 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3868 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
3899 | with some broad features you want) and then selectively re-enable |
3869 | (C<-DNDEBUG>) will usually reduce code size a lot. |
3900 | additional parts you want, for example if you want everything minimal, |
|
|
3901 | but multiple event loop support, async and child watchers and the poll |
|
|
3902 | backend, use this: |
3870 | |
3903 | |
3871 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
3904 | #define EV_FEATURES 0 |
3872 | provide a bare-bones event library. See C<ev.h> for details on what parts |
3905 | #define EV_MULTIPLICITY 1 |
3873 | of the API are still available, and do not complain if this subset changes |
3906 | #define EV_USE_POLL 1 |
3874 | over time. |
3907 | #define EV_CHILD_ENABLE 1 |
|
|
3908 | #define EV_ASYNC_ENABLE 1 |
|
|
3909 | |
|
|
3910 | The actual value is a bitset, it can be a combination of the following |
|
|
3911 | values: |
|
|
3912 | |
|
|
3913 | =over 4 |
|
|
3914 | |
|
|
3915 | =item C<1> - faster/larger code |
|
|
3916 | |
|
|
3917 | Use larger code to speed up some operations. |
|
|
3918 | |
|
|
3919 | Currently this is used to override some inlining decisions (enlarging the |
|
|
3920 | code size by roughly 30% on amd64). |
|
|
3921 | |
|
|
3922 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3923 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3924 | assertions. |
|
|
3925 | |
|
|
3926 | =item C<2> - faster/larger data structures |
|
|
3927 | |
|
|
3928 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3929 | hash table sizes and so on. This will usually further increase code size |
|
|
3930 | and can additionally have an effect on the size of data structures at |
|
|
3931 | runtime. |
|
|
3932 | |
|
|
3933 | =item C<4> - full API configuration |
|
|
3934 | |
|
|
3935 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3936 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3937 | |
|
|
3938 | =item C<8> - full API |
|
|
3939 | |
|
|
3940 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3941 | details on which parts of the API are still available without this |
|
|
3942 | feature, and do not complain if this subset changes over time. |
|
|
3943 | |
|
|
3944 | =item C<16> - enable all optional watcher types |
|
|
3945 | |
|
|
3946 | Enables all optional watcher types. If you want to selectively enable |
|
|
3947 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3948 | embed, async, child...) you can enable them manually by defining |
|
|
3949 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3950 | |
|
|
3951 | =item C<32> - enable all backends |
|
|
3952 | |
|
|
3953 | This enables all backends - without this feature, you need to enable at |
|
|
3954 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3955 | |
|
|
3956 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3957 | |
|
|
3958 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3959 | default. |
|
|
3960 | |
|
|
3961 | =back |
|
|
3962 | |
|
|
3963 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3964 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3965 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3966 | watchers, timers and monotonic clock support. |
|
|
3967 | |
|
|
3968 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3969 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3970 | your program might be left out as well - a binary starting a timer and an |
|
|
3971 | I/O watcher then might come out at only 5Kb. |
|
|
3972 | |
|
|
3973 | =item EV_AVOID_STDIO |
|
|
3974 | |
|
|
3975 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3976 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
3977 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3978 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3979 | big. |
|
|
3980 | |
|
|
3981 | Note that error messages might become less precise when this option is |
|
|
3982 | enabled. |
3875 | |
3983 | |
3876 | =item EV_NSIG |
3984 | =item EV_NSIG |
3877 | |
3985 | |
3878 | The highest supported signal number, +1 (or, the number of |
3986 | The highest supported signal number, +1 (or, the number of |
3879 | signals): Normally, libev tries to deduce the maximum number of signals |
3987 | signals): Normally, libev tries to deduce the maximum number of signals |
3880 | automatically, but sometimes this fails, in which case it can be |
3988 | automatically, but sometimes this fails, in which case it can be |
3881 | specified. Also, using a lower number than detected (C<32> should be |
3989 | specified. Also, using a lower number than detected (C<32> should be |
3882 | good for about any system in existance) can save some memory, as libev |
3990 | good for about any system in existence) can save some memory, as libev |
3883 | statically allocates some 12-24 bytes per signal number. |
3991 | statically allocates some 12-24 bytes per signal number. |
3884 | |
3992 | |
3885 | =item EV_PID_HASHSIZE |
3993 | =item EV_PID_HASHSIZE |
3886 | |
3994 | |
3887 | C<ev_child> watchers use a small hash table to distribute workload by |
3995 | C<ev_child> watchers use a small hash table to distribute workload by |
3888 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3996 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3889 | than enough. If you need to manage thousands of children you might want to |
3997 | usually more than enough. If you need to manage thousands of children you |
3890 | increase this value (I<must> be a power of two). |
3998 | might want to increase this value (I<must> be a power of two). |
3891 | |
3999 | |
3892 | =item EV_INOTIFY_HASHSIZE |
4000 | =item EV_INOTIFY_HASHSIZE |
3893 | |
4001 | |
3894 | C<ev_stat> watchers use a small hash table to distribute workload by |
4002 | C<ev_stat> watchers use a small hash table to distribute workload by |
3895 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4003 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3896 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4004 | disabled), usually more than enough. If you need to manage thousands of |
3897 | watchers you might want to increase this value (I<must> be a power of |
4005 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3898 | two). |
4006 | power of two). |
3899 | |
4007 | |
3900 | =item EV_USE_4HEAP |
4008 | =item EV_USE_4HEAP |
3901 | |
4009 | |
3902 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4010 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3903 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4011 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3904 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4012 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3905 | faster performance with many (thousands) of watchers. |
4013 | faster performance with many (thousands) of watchers. |
3906 | |
4014 | |
3907 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4015 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3908 | (disabled). |
4016 | will be C<0>. |
3909 | |
4017 | |
3910 | =item EV_HEAP_CACHE_AT |
4018 | =item EV_HEAP_CACHE_AT |
3911 | |
4019 | |
3912 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4020 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3913 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4021 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3914 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4022 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3915 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4023 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3916 | but avoids random read accesses on heap changes. This improves performance |
4024 | but avoids random read accesses on heap changes. This improves performance |
3917 | noticeably with many (hundreds) of watchers. |
4025 | noticeably with many (hundreds) of watchers. |
3918 | |
4026 | |
3919 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4027 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3920 | (disabled). |
4028 | will be C<0>. |
3921 | |
4029 | |
3922 | =item EV_VERIFY |
4030 | =item EV_VERIFY |
3923 | |
4031 | |
3924 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4032 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3925 | be done: If set to C<0>, no internal verification code will be compiled |
4033 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3927 | called. If set to C<2>, then the internal verification code will be |
4035 | called. If set to C<2>, then the internal verification code will be |
3928 | called once per loop, which can slow down libev. If set to C<3>, then the |
4036 | called once per loop, which can slow down libev. If set to C<3>, then the |
3929 | verification code will be called very frequently, which will slow down |
4037 | verification code will be called very frequently, which will slow down |
3930 | libev considerably. |
4038 | libev considerably. |
3931 | |
4039 | |
3932 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4040 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3933 | C<0>. |
4041 | will be C<0>. |
3934 | |
4042 | |
3935 | =item EV_COMMON |
4043 | =item EV_COMMON |
3936 | |
4044 | |
3937 | By default, all watchers have a C<void *data> member. By redefining |
4045 | By default, all watchers have a C<void *data> member. By redefining |
3938 | this macro to a something else you can include more and other types of |
4046 | this macro to something else you can include more and other types of |
3939 | members. You have to define it each time you include one of the files, |
4047 | members. You have to define it each time you include one of the files, |
3940 | though, and it must be identical each time. |
4048 | though, and it must be identical each time. |
3941 | |
4049 | |
3942 | For example, the perl EV module uses something like this: |
4050 | For example, the perl EV module uses something like this: |
3943 | |
4051 | |
… | |
… | |
3996 | file. |
4104 | file. |
3997 | |
4105 | |
3998 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4106 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3999 | that everybody includes and which overrides some configure choices: |
4107 | that everybody includes and which overrides some configure choices: |
4000 | |
4108 | |
4001 | #define EV_MINIMAL 1 |
4109 | #define EV_FEATURES 8 |
4002 | #define EV_USE_POLL 0 |
4110 | #define EV_USE_SELECT 1 |
4003 | #define EV_MULTIPLICITY 0 |
|
|
4004 | #define EV_PERIODIC_ENABLE 0 |
4111 | #define EV_PREPARE_ENABLE 1 |
|
|
4112 | #define EV_IDLE_ENABLE 1 |
4005 | #define EV_STAT_ENABLE 0 |
4113 | #define EV_SIGNAL_ENABLE 1 |
4006 | #define EV_FORK_ENABLE 0 |
4114 | #define EV_CHILD_ENABLE 1 |
|
|
4115 | #define EV_USE_STDEXCEPT 0 |
4007 | #define EV_CONFIG_H <config.h> |
4116 | #define EV_CONFIG_H <config.h> |
4008 | #define EV_MINPRI 0 |
|
|
4009 | #define EV_MAXPRI 0 |
|
|
4010 | |
4117 | |
4011 | #include "ev++.h" |
4118 | #include "ev++.h" |
4012 | |
4119 | |
4013 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4120 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4014 | |
4121 | |
… | |
… | |
4243 | maintainable. |
4350 | maintainable. |
4244 | |
4351 | |
4245 | And of course, some compiler warnings are just plain stupid, or simply |
4352 | And of course, some compiler warnings are just plain stupid, or simply |
4246 | wrong (because they don't actually warn about the condition their message |
4353 | wrong (because they don't actually warn about the condition their message |
4247 | seems to warn about). For example, certain older gcc versions had some |
4354 | seems to warn about). For example, certain older gcc versions had some |
4248 | warnings that resulted an extreme number of false positives. These have |
4355 | warnings that resulted in an extreme number of false positives. These have |
4249 | been fixed, but some people still insist on making code warn-free with |
4356 | been fixed, but some people still insist on making code warn-free with |
4250 | such buggy versions. |
4357 | such buggy versions. |
4251 | |
4358 | |
4252 | While libev is written to generate as few warnings as possible, |
4359 | While libev is written to generate as few warnings as possible, |
4253 | "warn-free" code is not a goal, and it is recommended not to build libev |
4360 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
4288 | If you need, for some reason, empty reports from valgrind for your project |
4395 | If you need, for some reason, empty reports from valgrind for your project |
4289 | I suggest using suppression lists. |
4396 | I suggest using suppression lists. |
4290 | |
4397 | |
4291 | |
4398 | |
4292 | =head1 PORTABILITY NOTES |
4399 | =head1 PORTABILITY NOTES |
|
|
4400 | |
|
|
4401 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4402 | |
|
|
4403 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4404 | interfaces but disables them by default. |
|
|
4405 | |
|
|
4406 | That means that libev compiled in the default environment doesn't support |
|
|
4407 | files larger than 2GiB, which mainly affects C<ev_stat> watchers. |
|
|
4408 | |
|
|
4409 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4410 | by enabling the large file API, which makes them incompatible with the |
|
|
4411 | standard libev compiled for their system. |
|
|
4412 | |
|
|
4413 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4414 | suddenly make it incompatible to the default compile time environment, |
|
|
4415 | i.e. all programs not using special compile switches. |
|
|
4416 | |
|
|
4417 | =head2 OS/X AND DARWIN BUGS |
|
|
4418 | |
|
|
4419 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4420 | you touch is broken, whether it is locales, poll, kqueue or even their |
|
|
4421 | OpenGL drivers. |
|
|
4422 | |
|
|
4423 | =over 4 |
|
|
4424 | |
|
|
4425 | =item 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 | =item POLL IS BUGGY |
|
|
4431 | |
|
|
4432 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4433 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4434 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4435 | |
|
|
4436 | Libev tries to work around this by neither using C<kqueue> nor C<poll> by |
|
|
4437 | default on this rotten platform, but of course you cna still ask for them |
|
|
4438 | when creating a loop. |
|
|
4439 | |
|
|
4440 | =item SELECT IS BUGGY |
|
|
4441 | |
|
|
4442 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4443 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4444 | descriptors you can pass in to 1024 - your program suddenyl crashes when |
|
|
4445 | you use more. |
|
|
4446 | |
|
|
4447 | There is an undocumented "workaround" for this - defining |
|
|
4448 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4449 | work on OS/X. |
|
|
4450 | |
|
|
4451 | =back |
|
|
4452 | |
|
|
4453 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4454 | |
|
|
4455 | =over 4 |
|
|
4456 | |
|
|
4457 | =item 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 | =item 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 with |
|
|
4476 | C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends. |
|
|
4477 | |
|
|
4478 | =back |
|
|
4479 | |
|
|
4480 | =head2 AIX POLL BUG |
|
|
4481 | |
|
|
4482 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4483 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4484 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4485 | with large bitsets, and AIX is dead anyway. |
4293 | |
4486 | |
4294 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4487 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4295 | |
4488 | |
4296 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4489 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4297 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4490 | requires, and its I/O model is fundamentally incompatible with the POSIX |
… | |
… | |
4516 | involves iterating over all running async watchers or all signal numbers. |
4709 | involves iterating over all running async watchers or all signal numbers. |
4517 | |
4710 | |
4518 | =back |
4711 | =back |
4519 | |
4712 | |
4520 | |
4713 | |
|
|
4714 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4715 | |
|
|
4716 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4717 | |
|
|
4718 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4719 | compatibility, so most programs should still compile. Those might be |
|
|
4720 | removed in later versions of libev, so better update early than late. |
|
|
4721 | |
|
|
4722 | =over 4 |
|
|
4723 | |
|
|
4724 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4725 | |
|
|
4726 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4727 | |
|
|
4728 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4729 | |
|
|
4730 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4731 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4732 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4733 | C<ev_fork> typedef. |
|
|
4734 | |
|
|
4735 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4736 | |
|
|
4737 | This is a simple rename - all other watcher types use their name |
|
|
4738 | as revents flag, and now C<ev_timer> does, too. |
|
|
4739 | |
|
|
4740 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4741 | and continue to be present for the foreseeable future, so this is mostly a |
|
|
4742 | documentation change. |
|
|
4743 | |
|
|
4744 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4745 | |
|
|
4746 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4747 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4748 | and work, but the library code will of course be larger. |
|
|
4749 | |
|
|
4750 | =back |
|
|
4751 | |
|
|
4752 | |
4521 | =head1 GLOSSARY |
4753 | =head1 GLOSSARY |
4522 | |
4754 | |
4523 | =over 4 |
4755 | =over 4 |
4524 | |
4756 | |
4525 | =item active |
4757 | =item active |
… | |
… | |
4546 | A change of state of some external event, such as data now being available |
4778 | A change of state of some external event, such as data now being available |
4547 | for reading on a file descriptor, time having passed or simply not having |
4779 | for reading on a file descriptor, time having passed or simply not having |
4548 | any other events happening anymore. |
4780 | any other events happening anymore. |
4549 | |
4781 | |
4550 | In libev, events are represented as single bits (such as C<EV_READ> or |
4782 | In libev, events are represented as single bits (such as C<EV_READ> or |
4551 | C<EV_TIMEOUT>). |
4783 | C<EV_TIMER>). |
4552 | |
4784 | |
4553 | =item event library |
4785 | =item event library |
4554 | |
4786 | |
4555 | A software package implementing an event model and loop. |
4787 | A software package implementing an event model and loop. |
4556 | |
4788 | |