… | |
… | |
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 |
… | |
… | |
611 | 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 |
612 | 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 |
613 | 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 |
614 | 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. |
615 | |
615 | |
|
|
616 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
617 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
618 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
619 | during fork. |
|
|
620 | |
616 | 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 |
617 | 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 |
618 | 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 |
|
|
624 | it at all. |
619 | |
625 | |
620 | 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 |
621 | 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 |
622 | quite nicely into a call to C<pthread_atfork>: |
628 | quite nicely into a call to C<pthread_atfork>: |
623 | |
629 | |
… | |
… | |
625 | |
631 | |
626 | =item ev_loop_fork (loop) |
632 | =item ev_loop_fork (loop) |
627 | |
633 | |
628 | 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 |
629 | 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 |
630 | 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 |
631 | entirely your own problem. |
637 | them is entirely your own problem. |
632 | |
638 | |
633 | =item int ev_is_default_loop (loop) |
639 | =item int ev_is_default_loop (loop) |
634 | |
640 | |
635 | 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 |
636 | otherwise. |
642 | otherwise. |
637 | |
643 | |
638 | =item unsigned int ev_loop_count (loop) |
644 | =item unsigned int ev_iteration (loop) |
639 | |
645 | |
640 | 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 |
641 | 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 |
642 | happily wraps around with enough iterations. |
648 | happily wraps around with enough iterations. |
643 | |
649 | |
644 | 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 |
645 | "ticks" the number of loop iterations), as it roughly corresponds with |
651 | "ticks" the number of loop iterations), as it roughly corresponds with |
646 | C<ev_prepare> and C<ev_check> calls. |
652 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
653 | prepare and check phases. |
647 | |
654 | |
648 | =item unsigned int ev_loop_depth (loop) |
655 | =item unsigned int ev_depth (loop) |
649 | |
656 | |
650 | 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 |
651 | 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. |
652 | |
659 | |
653 | 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 |
654 | 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), |
655 | in which case it is higher. |
662 | in which case it is higher. |
656 | |
663 | |
657 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
664 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
658 | etc.), doesn't count as exit. |
665 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
666 | ungentleman behaviour unless it's really convenient. |
659 | |
667 | |
660 | =item unsigned int ev_backend (loop) |
668 | =item unsigned int ev_backend (loop) |
661 | |
669 | |
662 | 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 |
663 | use. |
671 | use. |
… | |
… | |
697 | C<ev_resume> directly afterwards to resume timer processing. |
705 | C<ev_resume> directly afterwards to resume timer processing. |
698 | |
706 | |
699 | 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 |
700 | 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 |
701 | 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 |
702 | occured while suspended). |
710 | occurred while suspended). |
703 | |
711 | |
704 | 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 |
705 | 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> |
706 | without a previous call to C<ev_suspend>. |
714 | without a previous call to C<ev_suspend>. |
707 | |
715 | |
… | |
… | |
784 | 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 |
785 | 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. |
786 | |
794 | |
787 | 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. |
788 | |
796 | |
789 | 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. |
790 | |
798 | |
791 | =item ev_ref (loop) |
799 | =item ev_ref (loop) |
792 | |
800 | |
793 | =item ev_unref (loop) |
801 | =item ev_unref (loop) |
794 | |
802 | |
… | |
… | |
864 | 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>, |
865 | 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 |
866 | 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 |
867 | parallelity, then this setting will limit your transaction rate (if you |
875 | parallelity, then this setting will limit your transaction rate (if you |
868 | 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, |
869 | then you can't do more than 100 transations per second). |
877 | then you can't do more than 100 transactions per second). |
870 | |
878 | |
871 | Setting the I<timeout collect interval> can improve the opportunity for |
879 | Setting the I<timeout collect interval> can improve the opportunity for |
872 | saving power, as the program will "bundle" timer callback invocations that |
880 | saving power, as the program will "bundle" timer callback invocations that |
873 | 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 |
874 | 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 |
… | |
… | |
1372 | |
1380 | |
1373 | For example, to emulate how many other event libraries handle priorities, |
1381 | For example, to emulate how many other event libraries handle priorities, |
1374 | 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 |
1375 | 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 |
1376 | 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 |
1377 | 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 |
1378 | 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 |
1379 | workable. |
1387 | workable. |
1380 | |
1388 | |
1381 | Usually, however, the lock-out model implemented that way will perform |
1389 | Usually, however, the lock-out model implemented that way will perform |
1382 | 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, |
… | |
… | |
1396 | { |
1404 | { |
1397 | // stop the I/O watcher, we received the event, but |
1405 | // stop the I/O watcher, we received the event, but |
1398 | // are not yet ready to handle it. |
1406 | // are not yet ready to handle it. |
1399 | ev_io_stop (EV_A_ w); |
1407 | ev_io_stop (EV_A_ w); |
1400 | |
1408 | |
1401 | // start the idle watcher to ahndle the actual event. |
1409 | // start the idle watcher to handle the actual event. |
1402 | // it will not be executed as long as other watchers |
1410 | // it will not be executed as long as other watchers |
1403 | // with the default priority are receiving events. |
1411 | // with the default priority are receiving events. |
1404 | ev_idle_start (EV_A_ &idle); |
1412 | ev_idle_start (EV_A_ &idle); |
1405 | } |
1413 | } |
1406 | |
1414 | |
… | |
… | |
1460 | |
1468 | |
1461 | 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 |
1462 | 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 |
1463 | 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 |
1464 | descriptors for which non-blocking operation makes no sense (such as |
1472 | descriptors for which non-blocking operation makes no sense (such as |
1465 | files) - libev doesn't guarentee any specific behaviour in that case. |
1473 | files) - libev doesn't guarantee any specific behaviour in that case. |
1466 | |
1474 | |
1467 | 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 |
1468 | receive "spurious" readiness notifications, that is your callback might |
1476 | receive "spurious" readiness notifications, that is your callback might |
1469 | 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 |
1470 | 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 |
… | |
… | |
1538 | somewhere, as that would have given you a big clue). |
1546 | somewhere, as that would have given you a big clue). |
1539 | |
1547 | |
1540 | =head3 The special problem of accept()ing when you can't |
1548 | =head3 The special problem of accept()ing when you can't |
1541 | |
1549 | |
1542 | Many implementations of the POSIX C<accept> function (for example, |
1550 | Many implementations of the POSIX C<accept> function (for example, |
1543 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
1551 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
1544 | connection from the pending queue in all error cases. |
1552 | connection from the pending queue in all error cases. |
1545 | |
1553 | |
1546 | For example, larger servers often run out of file descriptors (because |
1554 | For example, larger servers often run out of file descriptors (because |
1547 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1555 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1548 | rejecting the connection, leading to libev signalling readiness on |
1556 | rejecting the connection, leading to libev signalling readiness on |
… | |
… | |
1729 | ev_tstamp timeout = last_activity + 60.; |
1737 | ev_tstamp timeout = last_activity + 60.; |
1730 | |
1738 | |
1731 | // 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 |
1732 | if (timeout < now) |
1740 | if (timeout < now) |
1733 | { |
1741 | { |
1734 | // timeout occured, take action |
1742 | // timeout occurred, take action |
1735 | } |
1743 | } |
1736 | else |
1744 | else |
1737 | { |
1745 | { |
1738 | // callback was invoked, but there was some activity, re-arm |
1746 | // callback was invoked, but there was some activity, re-arm |
1739 | // the watcher to fire in last_activity + 60, which is |
1747 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1766 | callback (loop, timer, EV_TIMER); |
1774 | callback (loop, timer, EV_TIMER); |
1767 | |
1775 | |
1768 | 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 |
1769 | C<last_activity>, no libev calls at all: |
1777 | C<last_activity>, no libev calls at all: |
1770 | |
1778 | |
1771 | last_actiivty = ev_now (loop); |
1779 | last_activity = ev_now (loop); |
1772 | |
1780 | |
1773 | 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 |
1774 | time-out is unlikely to be triggered, much more efficient. |
1782 | time-out is unlikely to be triggered, much more efficient. |
1775 | |
1783 | |
1776 | 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 |
… | |
… | |
2115 | Example: Call a callback every hour, or, more precisely, whenever the |
2123 | Example: Call a callback every hour, or, more precisely, whenever the |
2116 | system time is divisible by 3600. The callback invocation times have |
2124 | system time is divisible by 3600. The callback invocation times have |
2117 | potentially a lot of jitter, but good long-term stability. |
2125 | potentially a lot of jitter, but good long-term stability. |
2118 | |
2126 | |
2119 | static void |
2127 | static void |
2120 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2128 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2121 | { |
2129 | { |
2122 | ... 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) |
2123 | } |
2131 | } |
2124 | |
2132 | |
2125 | ev_periodic hourly_tick; |
2133 | ev_periodic hourly_tick; |
… | |
… | |
2957 | 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 |
2958 | handlers will be invoked, too, of course. |
2966 | handlers will be invoked, too, of course. |
2959 | |
2967 | |
2960 | =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? |
2961 | |
2969 | |
2962 | 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 |
2963 | 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 |
2964 | sequence should be handled by libev without any problems. |
2972 | sequence should be handled by libev without any problems. |
2965 | |
2973 | |
2966 | This changes when the application actually wants to do event handling |
2974 | This changes when the application actually wants to do event handling |
2967 | 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 |
… | |
… | |
3001 | believe me. |
3009 | believe me. |
3002 | |
3010 | |
3003 | =back |
3011 | =back |
3004 | |
3012 | |
3005 | |
3013 | |
3006 | =head2 C<ev_async> - how to wake up another event loop |
3014 | =head2 C<ev_async> - how to wake up an event loop |
3007 | |
3015 | |
3008 | 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 |
3009 | asynchronous sources such as signal handlers (as opposed to multiple event |
3017 | asynchronous sources such as signal handlers (as opposed to multiple event |
3010 | loops - those are of course safe to use in different threads). |
3018 | loops - those are of course safe to use in different threads). |
3011 | |
3019 | |
3012 | 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, |
3013 | 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> |
3014 | 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 |
3015 | 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. |
3016 | safe. |
|
|
3017 | |
3024 | |
3018 | 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, |
3019 | too, are asynchronous in nature, and signals, too, will be compressed |
3026 | too, are asynchronous in nature, and signals, too, will be compressed |
3020 | (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 |
3021 | C<ev_async_sent> calls). |
3028 | C<ev_async_sent> calls). |
… | |
… | |
3333 | myclass obj; |
3340 | myclass obj; |
3334 | ev::io iow; |
3341 | ev::io iow; |
3335 | iow.set <myclass, &myclass::io_cb> (&obj); |
3342 | iow.set <myclass, &myclass::io_cb> (&obj); |
3336 | |
3343 | |
3337 | =item w->set (object *) |
3344 | =item w->set (object *) |
3338 | |
|
|
3339 | This is an B<experimental> feature that might go away in a future version. |
|
|
3340 | |
3345 | |
3341 | 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 |
3342 | 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 |
3343 | functor objects without having to manually specify the C<operator ()> all |
3348 | functor objects without having to manually specify the C<operator ()> all |
3344 | 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 |
… | |
… | |
3657 | define before including (or compiling) any of its files. The default in |
3662 | define before including (or compiling) any of its files. The default in |
3658 | the absence of autoconf is documented for every option. |
3663 | the absence of autoconf is documented for every option. |
3659 | |
3664 | |
3660 | Symbols marked with "(h)" do not change the ABI, and can have different |
3665 | Symbols marked with "(h)" do not change the ABI, and can have different |
3661 | values when compiling libev vs. including F<ev.h>, so it is permissible |
3666 | values when compiling libev vs. including F<ev.h>, so it is permissible |
3662 | to redefine them before including F<ev.h> without breakign compatibility |
3667 | to redefine them before including F<ev.h> without breaking compatibility |
3663 | to a compiled library. All other symbols change the ABI, which means all |
3668 | to a compiled library. All other symbols change the ABI, which means all |
3664 | users of libev and the libev code itself must be compiled with compatible |
3669 | users of libev and the libev code itself must be compiled with compatible |
3665 | settings. |
3670 | settings. |
3666 | |
3671 | |
3667 | =over 4 |
3672 | =over 4 |
… | |
… | |
3879 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
3884 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
3880 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3885 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3881 | |
3886 | |
3882 | If undefined or defined to be C<1> (and the platform supports it), then |
3887 | If undefined or defined to be C<1> (and the platform supports it), then |
3883 | the respective watcher type is supported. If defined to be C<0>, then it |
3888 | the respective watcher type is supported. If defined to be C<0>, then it |
3884 | is not. Disabling watcher types mainly saves codesize. |
3889 | is not. Disabling watcher types mainly saves code size. |
3885 | |
3890 | |
3886 | =item EV_FEATURES |
3891 | =item EV_FEATURES |
3887 | |
3892 | |
3888 | 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 |
3889 | speed (but with the full API), you can define this symbol to request |
3894 | speed (but with the full API), you can define this symbol to request |
… | |
… | |
3909 | |
3914 | |
3910 | =item C<1> - faster/larger code |
3915 | =item C<1> - faster/larger code |
3911 | |
3916 | |
3912 | Use larger code to speed up some operations. |
3917 | Use larger code to speed up some operations. |
3913 | |
3918 | |
3914 | Currently this is used to override some inlining decisions (enlarging the roughly |
3919 | Currently this is used to override some inlining decisions (enlarging the |
3915 | 30% code size on amd64. |
3920 | code size by roughly 30% on amd64). |
3916 | |
3921 | |
3917 | When optimising for size, use of compiler flags such as C<-Os> with |
3922 | When optimising for size, use of compiler flags such as C<-Os> with |
3918 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
3923 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
3919 | assertions. |
3924 | assertions. |
3920 | |
3925 | |
3921 | =item C<2> - faster/larger data structures |
3926 | =item C<2> - faster/larger data structures |
3922 | |
3927 | |
3923 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
3928 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
3924 | hash table sizes and so on. This will usually further increase codesize |
3929 | hash table sizes and so on. This will usually further increase code size |
3925 | and can additionally have an effect on the size of data structures at |
3930 | and can additionally have an effect on the size of data structures at |
3926 | runtime. |
3931 | runtime. |
3927 | |
3932 | |
3928 | =item C<4> - full API configuration |
3933 | =item C<4> - full API configuration |
3929 | |
3934 | |
… | |
… | |
3966 | I/O watcher then might come out at only 5Kb. |
3971 | I/O watcher then might come out at only 5Kb. |
3967 | |
3972 | |
3968 | =item EV_AVOID_STDIO |
3973 | =item EV_AVOID_STDIO |
3969 | |
3974 | |
3970 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
3975 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
3971 | functions (printf, scanf, perror etc.). This will increase the codesize |
3976 | functions (printf, scanf, perror etc.). This will increase the code size |
3972 | somewhat, but if your program doesn't otherwise depend on stdio and your |
3977 | somewhat, but if your program doesn't otherwise depend on stdio and your |
3973 | libc allows it, this avoids linking in the stdio library which is quite |
3978 | libc allows it, this avoids linking in the stdio library which is quite |
3974 | big. |
3979 | big. |
3975 | |
3980 | |
3976 | Note that error messages might become less precise when this option is |
3981 | Note that error messages might become less precise when this option is |
… | |
… | |
3980 | |
3985 | |
3981 | The highest supported signal number, +1 (or, the number of |
3986 | The highest supported signal number, +1 (or, the number of |
3982 | signals): Normally, libev tries to deduce the maximum number of signals |
3987 | signals): Normally, libev tries to deduce the maximum number of signals |
3983 | automatically, but sometimes this fails, in which case it can be |
3988 | automatically, but sometimes this fails, in which case it can be |
3984 | 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 |
3985 | 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 |
3986 | statically allocates some 12-24 bytes per signal number. |
3991 | statically allocates some 12-24 bytes per signal number. |
3987 | |
3992 | |
3988 | =item EV_PID_HASHSIZE |
3993 | =item EV_PID_HASHSIZE |
3989 | |
3994 | |
3990 | 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 |
… | |
… | |
4036 | will be C<0>. |
4041 | will be C<0>. |
4037 | |
4042 | |
4038 | =item EV_COMMON |
4043 | =item EV_COMMON |
4039 | |
4044 | |
4040 | 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 |
4041 | 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 |
4042 | 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, |
4043 | though, and it must be identical each time. |
4048 | though, and it must be identical each time. |
4044 | |
4049 | |
4045 | For example, the perl EV module uses something like this: |
4050 | For example, the perl EV module uses something like this: |
4046 | |
4051 | |
… | |
… | |
4345 | maintainable. |
4350 | maintainable. |
4346 | |
4351 | |
4347 | 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 |
4348 | 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 |
4349 | 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 |
4350 | warnings that resulted an extreme number of false positives. These have |
4355 | warnings that resulted in an extreme number of false positives. These have |
4351 | 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 |
4352 | such buggy versions. |
4357 | such buggy versions. |
4353 | |
4358 | |
4354 | While libev is written to generate as few warnings as possible, |
4359 | While libev is written to generate as few warnings as possible, |
4355 | "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 |
… | |
… | |
4391 | I suggest using suppression lists. |
4396 | I suggest using suppression lists. |
4392 | |
4397 | |
4393 | |
4398 | |
4394 | =head1 PORTABILITY NOTES |
4399 | =head1 PORTABILITY NOTES |
4395 | |
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 I<disables> them by default. |
|
|
4405 | |
|
|
4406 | That means that libev compiled in the default environment doesn't support |
|
|
4407 | files larger than 2GiB or so, 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 the |
|
|
4421 | OpenGL drivers. |
|
|
4422 | |
|
|
4423 | =head3 C<kqueue> is buggy |
|
|
4424 | |
|
|
4425 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4426 | only sockets, many support pipes. |
|
|
4427 | |
|
|
4428 | Libev tries to work around this by not using C<kqueue> by default on |
|
|
4429 | this rotten platform, but of course you can still ask for it when creating |
|
|
4430 | a loop. |
|
|
4431 | |
|
|
4432 | =head3 C<poll> is buggy |
|
|
4433 | |
|
|
4434 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4435 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4436 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4437 | |
|
|
4438 | Libev tries to work around this by not using C<poll> by default on |
|
|
4439 | this rotten platform, but of course you can still ask for it when creating |
|
|
4440 | a loop. |
|
|
4441 | |
|
|
4442 | =head3 C<select> is buggy |
|
|
4443 | |
|
|
4444 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4445 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4446 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4447 | you use more. |
|
|
4448 | |
|
|
4449 | There is an undocumented "workaround" for this - defining |
|
|
4450 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4451 | work on OS/X. |
|
|
4452 | |
|
|
4453 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4454 | |
|
|
4455 | =head3 C<errno> reentrancy |
|
|
4456 | |
|
|
4457 | The default compile environment on Solaris is unfortunately so |
|
|
4458 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4459 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
|
|
4460 | isn't defined by default. |
|
|
4461 | |
|
|
4462 | If you want to use libev in threaded environments you have to make sure |
|
|
4463 | it's compiled with C<_REENTRANT> defined. |
|
|
4464 | |
|
|
4465 | =head3 Event port backend |
|
|
4466 | |
|
|
4467 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
|
|
4468 | this mechanism is very buggy. If you run into high CPU usage, your program |
|
|
4469 | freezes or you get a large number of spurious wakeups, make sure you have |
|
|
4470 | all the relevant and latest kernel patches applied. No, I don't know which |
|
|
4471 | ones, but there are multiple ones. |
|
|
4472 | |
|
|
4473 | If you can't get it to work, you can try running the program by setting |
|
|
4474 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4475 | C<select> backends. |
|
|
4476 | |
|
|
4477 | =head2 AIX POLL BUG |
|
|
4478 | |
|
|
4479 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4480 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4481 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4482 | with large bitsets, and AIX is dead anyway. |
|
|
4483 | |
4396 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4484 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4485 | |
|
|
4486 | =head3 General issues |
4397 | |
4487 | |
4398 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4488 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4399 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4489 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4400 | model. Libev still offers limited functionality on this platform in |
4490 | model. Libev still offers limited functionality on this platform in |
4401 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4491 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4402 | descriptors. This only applies when using Win32 natively, not when using |
4492 | descriptors. This only applies when using Win32 natively, not when using |
4403 | e.g. cygwin. |
4493 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4494 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4495 | environment. |
4404 | |
4496 | |
4405 | Lifting these limitations would basically require the full |
4497 | Lifting these limitations would basically require the full |
4406 | re-implementation of the I/O system. If you are into these kinds of |
4498 | re-implementation of the I/O system. If you are into this kind of thing, |
4407 | things, then note that glib does exactly that for you in a very portable |
4499 | then note that glib does exactly that for you in a very portable way (note |
4408 | way (note also that glib is the slowest event library known to man). |
4500 | also that glib is the slowest event library known to man). |
4409 | |
4501 | |
4410 | There is no supported compilation method available on windows except |
4502 | There is no supported compilation method available on windows except |
4411 | embedding it into other applications. |
4503 | embedding it into other applications. |
4412 | |
4504 | |
4413 | Sensible signal handling is officially unsupported by Microsoft - libev |
4505 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4441 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4533 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4442 | |
4534 | |
4443 | #include "evwrap.h" |
4535 | #include "evwrap.h" |
4444 | #include "ev.c" |
4536 | #include "ev.c" |
4445 | |
4537 | |
4446 | =over 4 |
|
|
4447 | |
|
|
4448 | =item The winsocket select function |
4538 | =head3 The winsocket C<select> function |
4449 | |
4539 | |
4450 | The winsocket C<select> function doesn't follow POSIX in that it |
4540 | The winsocket C<select> function doesn't follow POSIX in that it |
4451 | requires socket I<handles> and not socket I<file descriptors> (it is |
4541 | requires socket I<handles> and not socket I<file descriptors> (it is |
4452 | also extremely buggy). This makes select very inefficient, and also |
4542 | also extremely buggy). This makes select very inefficient, and also |
4453 | requires a mapping from file descriptors to socket handles (the Microsoft |
4543 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4462 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4552 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4463 | |
4553 | |
4464 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4554 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4465 | complexity in the O(n²) range when using win32. |
4555 | complexity in the O(n²) range when using win32. |
4466 | |
4556 | |
4467 | =item Limited number of file descriptors |
4557 | =head3 Limited number of file descriptors |
4468 | |
4558 | |
4469 | Windows has numerous arbitrary (and low) limits on things. |
4559 | Windows has numerous arbitrary (and low) limits on things. |
4470 | |
4560 | |
4471 | Early versions of winsocket's select only supported waiting for a maximum |
4561 | Early versions of winsocket's select only supported waiting for a maximum |
4472 | of C<64> handles (probably owning to the fact that all windows kernels |
4562 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4487 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4577 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4488 | (depending on windows version and/or the phase of the moon). To get more, |
4578 | (depending on windows version and/or the phase of the moon). To get more, |
4489 | you need to wrap all I/O functions and provide your own fd management, but |
4579 | you need to wrap all I/O functions and provide your own fd management, but |
4490 | the cost of calling select (O(n²)) will likely make this unworkable. |
4580 | the cost of calling select (O(n²)) will likely make this unworkable. |
4491 | |
4581 | |
4492 | =back |
|
|
4493 | |
|
|
4494 | =head2 PORTABILITY REQUIREMENTS |
4582 | =head2 PORTABILITY REQUIREMENTS |
4495 | |
4583 | |
4496 | In addition to a working ISO-C implementation and of course the |
4584 | In addition to a working ISO-C implementation and of course the |
4497 | backend-specific APIs, libev relies on a few additional extensions: |
4585 | backend-specific APIs, libev relies on a few additional extensions: |
4498 | |
4586 | |
… | |
… | |
4618 | involves iterating over all running async watchers or all signal numbers. |
4706 | involves iterating over all running async watchers or all signal numbers. |
4619 | |
4707 | |
4620 | =back |
4708 | =back |
4621 | |
4709 | |
4622 | |
4710 | |
4623 | =head1 PORTING FROM 3.X TO 4.X |
4711 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4624 | |
4712 | |
4625 | The major version 4 introduced some minor incompatible changes to the API. |
4713 | The major version 4 introduced some minor incompatible changes to the API. |
4626 | |
4714 | |
|
|
4715 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4716 | compatibility, so most programs should still compile. Those might be |
|
|
4717 | removed in later versions of libev, so better update early than late. |
|
|
4718 | |
4627 | =over 4 |
4719 | =over 4 |
4628 | |
4720 | |
|
|
4721 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4722 | |
|
|
4723 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4724 | |
|
|
4725 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4726 | |
|
|
4727 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4728 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4729 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4730 | C<ev_fork> typedef. |
|
|
4731 | |
4629 | =item C<EV_TIMEOUT> replaced by C<EV_TIMER> in C<revents> |
4732 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
4630 | |
4733 | |
4631 | This is a simple rename - all other watcher types use their name |
4734 | This is a simple rename - all other watcher types use their name |
4632 | as revents flag, and now C<ev_timer> does, too. |
4735 | as revents flag, and now C<ev_timer> does, too. |
4633 | |
4736 | |
4634 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
4737 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
4635 | and continue to be present for the forseeable future, so this is mostly a |
4738 | and continue to be present for the foreseeable future, so this is mostly a |
4636 | documentation change. |
4739 | documentation change. |
4637 | |
4740 | |
4638 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4741 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4639 | |
4742 | |
4640 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4743 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |