… | |
… | |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
68 | |
70 | |
69 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
70 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
71 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
72 | |
84 | |
73 | 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 |
74 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
75 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
76 | |
88 | |
… | |
… | |
110 | name C<loop> (which is always of type C<ev_loop *>) will not have |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
111 | this argument. |
123 | this argument. |
112 | |
124 | |
113 | =head2 TIME REPRESENTATION |
125 | =head2 TIME REPRESENTATION |
114 | |
126 | |
115 | Libev represents time as a single floating point number, representing the |
127 | Libev represents time as a single floating point number, representing |
116 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
117 | the beginning of 1970, details are complicated, don't ask). This type is |
129 | near the beginning of 1970, details are complicated, don't ask). This |
118 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
130 | type is called C<ev_tstamp>, which is what you should use too. It usually |
119 | to the C<double> type in C, and when you need to do any calculations on |
131 | aliases to the C<double> type in C. When you need to do any calculations |
120 | it, you should treat it as some floating point value. Unlike the name |
132 | on it, you should treat it as some floating point value. Unlike the name |
121 | component C<stamp> might indicate, it is also used for time differences |
133 | component C<stamp> might indicate, it is also used for time differences |
122 | throughout libev. |
134 | throughout libev. |
123 | |
135 | |
124 | =head1 ERROR HANDLING |
136 | =head1 ERROR HANDLING |
125 | |
137 | |
… | |
… | |
609 | |
621 | |
610 | This value can sometimes be useful as a generation counter of sorts (it |
622 | This value can sometimes be useful as a generation counter of sorts (it |
611 | "ticks" the number of loop iterations), as it roughly corresponds with |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
612 | C<ev_prepare> and C<ev_check> calls. |
624 | C<ev_prepare> and C<ev_check> calls. |
613 | |
625 | |
|
|
626 | =item unsigned int ev_loop_depth (loop) |
|
|
627 | |
|
|
628 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
629 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
630 | |
|
|
631 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
632 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
633 | in which case it is higher. |
|
|
634 | |
|
|
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
636 | etc.), doesn't count as exit. |
|
|
637 | |
614 | =item unsigned int ev_backend (loop) |
638 | =item unsigned int ev_backend (loop) |
615 | |
639 | |
616 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
640 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
617 | use. |
641 | use. |
618 | |
642 | |
… | |
… | |
632 | |
656 | |
633 | This function is rarely useful, but when some event callback runs for a |
657 | This function is rarely useful, but when some event callback runs for a |
634 | very long time without entering the event loop, updating libev's idea of |
658 | very long time without entering the event loop, updating libev's idea of |
635 | the current time is a good idea. |
659 | the current time is a good idea. |
636 | |
660 | |
637 | See also "The special problem of time updates" in the C<ev_timer> section. |
661 | See also L<The special problem of time updates> in the C<ev_timer> section. |
638 | |
662 | |
639 | =item ev_suspend (loop) |
663 | =item ev_suspend (loop) |
640 | |
664 | |
641 | =item ev_resume (loop) |
665 | =item ev_resume (loop) |
642 | |
666 | |
… | |
… | |
799 | |
823 | |
800 | By setting a higher I<io collect interval> you allow libev to spend more |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
801 | time collecting I/O events, so you can handle more events per iteration, |
825 | time collecting I/O events, so you can handle more events per iteration, |
802 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
803 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
804 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
829 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
830 | once per this interval, on average. |
805 | |
831 | |
806 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
807 | to spend more time collecting timeouts, at the expense of increased |
833 | to spend more time collecting timeouts, at the expense of increased |
808 | latency/jitter/inexactness (the watcher callback will be called |
834 | latency/jitter/inexactness (the watcher callback will be called |
809 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
811 | |
837 | |
812 | Many (busy) programs can usually benefit by setting the I/O collect |
838 | Many (busy) programs can usually benefit by setting the I/O collect |
813 | interval to a value near C<0.1> or so, which is often enough for |
839 | interval to a value near C<0.1> or so, which is often enough for |
814 | interactive servers (of course not for games), likewise for timeouts. It |
840 | interactive servers (of course not for games), likewise for timeouts. It |
815 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
816 | as this approaches the timing granularity of most systems. |
842 | as this approaches the timing granularity of most systems. Note that if |
|
|
843 | you do transactions with the outside world and you can't increase the |
|
|
844 | parallelity, then this setting will limit your transaction rate (if you |
|
|
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
846 | then you can't do more than 100 transations per second). |
817 | |
847 | |
818 | Setting the I<timeout collect interval> can improve the opportunity for |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
819 | saving power, as the program will "bundle" timer callback invocations that |
849 | saving power, as the program will "bundle" timer callback invocations that |
820 | are "near" in time together, by delaying some, thus reducing the number of |
850 | are "near" in time together, by delaying some, thus reducing the number of |
821 | times the process sleeps and wakes up again. Another useful technique to |
851 | times the process sleeps and wakes up again. Another useful technique to |
822 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
852 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
823 | they fire on, say, one-second boundaries only. |
853 | they fire on, say, one-second boundaries only. |
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|
854 | |
|
|
855 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
856 | more often than 100 times per second: |
|
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857 | |
|
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858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
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859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
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860 | |
|
|
861 | =item ev_invoke_pending (loop) |
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|
862 | |
|
|
863 | This call will simply invoke all pending watchers while resetting their |
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864 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
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865 | but when overriding the invoke callback this call comes handy. |
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866 | |
|
|
867 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
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|
868 | |
|
|
869 | This overrides the invoke pending functionality of the loop: Instead of |
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870 | invoking all pending watchers when there are any, C<ev_loop> will call |
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871 | this callback instead. This is useful, for example, when you want to |
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872 | invoke the actual watchers inside another context (another thread etc.). |
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873 | |
|
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874 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
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875 | callback. |
|
|
876 | |
|
|
877 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
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878 | |
|
|
879 | Sometimes you want to share the same loop between multiple threads. This |
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880 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
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881 | each call to a libev function. |
|
|
882 | |
|
|
883 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
884 | wait for it to return. One way around this is to wake up the loop via |
|
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885 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
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886 | and I<acquire> callbacks on the loop. |
|
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887 | |
|
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888 | When set, then C<release> will be called just before the thread is |
|
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889 | suspended waiting for new events, and C<acquire> is called just |
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|
890 | afterwards. |
|
|
891 | |
|
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892 | Ideally, C<release> will just call your mutex_unlock function, and |
|
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893 | C<acquire> will just call the mutex_lock function again. |
|
|
894 | |
|
|
895 | =item ev_set_userdata (loop, void *data) |
|
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896 | |
|
|
897 | =item ev_userdata (loop) |
|
|
898 | |
|
|
899 | Set and retrieve a single C<void *> associated with a loop. When |
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900 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
901 | C<0.> |
|
|
902 | |
|
|
903 | These two functions can be used to associate arbitrary data with a loop, |
|
|
904 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
905 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
906 | any other purpose as well. |
824 | |
907 | |
825 | =item ev_loop_verify (loop) |
908 | =item ev_loop_verify (loop) |
826 | |
909 | |
827 | This function only does something when C<EV_VERIFY> support has been |
910 | This function only does something when C<EV_VERIFY> support has been |
828 | compiled in, which is the default for non-minimal builds. It tries to go |
911 | compiled in, which is the default for non-minimal builds. It tries to go |
… | |
… | |
1096 | or might not have been clamped to the valid range. |
1179 | or might not have been clamped to the valid range. |
1097 | |
1180 | |
1098 | The default priority used by watchers when no priority has been set is |
1181 | The default priority used by watchers when no priority has been set is |
1099 | always C<0>, which is supposed to not be too high and not be too low :). |
1182 | always C<0>, which is supposed to not be too high and not be too low :). |
1100 | |
1183 | |
1101 | See L<WATCHER PRIORITIES>, below, for a more thorough treatment of |
1184 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1102 | priorities. |
1185 | priorities. |
1103 | |
1186 | |
1104 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1187 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1105 | |
1188 | |
1106 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1189 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1172 | #include <stddef.h> |
1255 | #include <stddef.h> |
1173 | |
1256 | |
1174 | static void |
1257 | static void |
1175 | t1_cb (EV_P_ ev_timer *w, int revents) |
1258 | t1_cb (EV_P_ ev_timer *w, int revents) |
1176 | { |
1259 | { |
1177 | struct my_biggy big = (struct my_biggy * |
1260 | struct my_biggy big = (struct my_biggy *) |
1178 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1261 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1179 | } |
1262 | } |
1180 | |
1263 | |
1181 | static void |
1264 | static void |
1182 | t2_cb (EV_P_ ev_timer *w, int revents) |
1265 | t2_cb (EV_P_ ev_timer *w, int revents) |
1183 | { |
1266 | { |
1184 | struct my_biggy big = (struct my_biggy * |
1267 | struct my_biggy big = (struct my_biggy *) |
1185 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1268 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1186 | } |
1269 | } |
1187 | |
1270 | |
1188 | =head2 WATCHER PRIORITY MODELS |
1271 | =head2 WATCHER PRIORITY MODELS |
1189 | |
1272 | |
… | |
… | |
1265 | // with the default priority are receiving events. |
1348 | // with the default priority are receiving events. |
1266 | ev_idle_start (EV_A_ &idle); |
1349 | ev_idle_start (EV_A_ &idle); |
1267 | } |
1350 | } |
1268 | |
1351 | |
1269 | static void |
1352 | static void |
1270 | idle-cb (EV_P_ ev_idle *w, int revents) |
1353 | idle_cb (EV_P_ ev_idle *w, int revents) |
1271 | { |
1354 | { |
1272 | // actual processing |
1355 | // actual processing |
1273 | read (STDIN_FILENO, ...); |
1356 | read (STDIN_FILENO, ...); |
1274 | |
1357 | |
1275 | // have to start the I/O watcher again, as |
1358 | // have to start the I/O watcher again, as |
… | |
… | |
1320 | descriptors to non-blocking mode is also usually a good idea (but not |
1403 | descriptors to non-blocking mode is also usually a good idea (but not |
1321 | required if you know what you are doing). |
1404 | required if you know what you are doing). |
1322 | |
1405 | |
1323 | If you cannot use non-blocking mode, then force the use of a |
1406 | If you cannot use non-blocking mode, then force the use of a |
1324 | known-to-be-good backend (at the time of this writing, this includes only |
1407 | known-to-be-good backend (at the time of this writing, this includes only |
1325 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1408 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1409 | descriptors for which non-blocking operation makes no sense (such as |
|
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1410 | files) - libev doesn't guarentee any specific behaviour in that case. |
1326 | |
1411 | |
1327 | Another thing you have to watch out for is that it is quite easy to |
1412 | Another thing you have to watch out for is that it is quite easy to |
1328 | receive "spurious" readiness notifications, that is your callback might |
1413 | receive "spurious" readiness notifications, that is your callback might |
1329 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1414 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1330 | because there is no data. Not only are some backends known to create a |
1415 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1451 | year, it will still time out after (roughly) one hour. "Roughly" because |
1536 | year, it will still time out after (roughly) one hour. "Roughly" because |
1452 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1537 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1453 | monotonic clock option helps a lot here). |
1538 | monotonic clock option helps a lot here). |
1454 | |
1539 | |
1455 | The callback is guaranteed to be invoked only I<after> its timeout has |
1540 | The callback is guaranteed to be invoked only I<after> its timeout has |
1456 | passed. If multiple timers become ready during the same loop iteration |
1541 | passed (not I<at>, so on systems with very low-resolution clocks this |
1457 | then the ones with earlier time-out values are invoked before ones with |
1542 | might introduce a small delay). If multiple timers become ready during the |
1458 | later time-out values (but this is no longer true when a callback calls |
1543 | same loop iteration then the ones with earlier time-out values are invoked |
1459 | C<ev_loop> recursively). |
1544 | before ones of the same priority with later time-out values (but this is |
|
|
1545 | no longer true when a callback calls C<ev_loop> recursively). |
1460 | |
1546 | |
1461 | =head3 Be smart about timeouts |
1547 | =head3 Be smart about timeouts |
1462 | |
1548 | |
1463 | Many real-world problems involve some kind of timeout, usually for error |
1549 | Many real-world problems involve some kind of timeout, usually for error |
1464 | recovery. A typical example is an HTTP request - if the other side hangs, |
1550 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1508 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1594 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
1509 | member and C<ev_timer_again>. |
1595 | member and C<ev_timer_again>. |
1510 | |
1596 | |
1511 | At start: |
1597 | At start: |
1512 | |
1598 | |
1513 | ev_timer_init (timer, callback); |
1599 | ev_init (timer, callback); |
1514 | timer->repeat = 60.; |
1600 | timer->repeat = 60.; |
1515 | ev_timer_again (loop, timer); |
1601 | ev_timer_again (loop, timer); |
1516 | |
1602 | |
1517 | Each time there is some activity: |
1603 | Each time there is some activity: |
1518 | |
1604 | |
… | |
… | |
1580 | |
1666 | |
1581 | To start the timer, simply initialise the watcher and set C<last_activity> |
1667 | To start the timer, simply initialise the watcher and set C<last_activity> |
1582 | to the current time (meaning we just have some activity :), then call the |
1668 | to the current time (meaning we just have some activity :), then call the |
1583 | callback, which will "do the right thing" and start the timer: |
1669 | callback, which will "do the right thing" and start the timer: |
1584 | |
1670 | |
1585 | ev_timer_init (timer, callback); |
1671 | ev_init (timer, callback); |
1586 | last_activity = ev_now (loop); |
1672 | last_activity = ev_now (loop); |
1587 | callback (loop, timer, EV_TIMEOUT); |
1673 | callback (loop, timer, EV_TIMEOUT); |
1588 | |
1674 | |
1589 | And when there is some activity, simply store the current time in |
1675 | And when there is some activity, simply store the current time in |
1590 | C<last_activity>, no libev calls at all: |
1676 | C<last_activity>, no libev calls at all: |
… | |
… | |
1987 | some child status changes (most typically when a child of yours dies or |
2073 | some child status changes (most typically when a child of yours dies or |
1988 | exits). It is permissible to install a child watcher I<after> the child |
2074 | exits). It is permissible to install a child watcher I<after> the child |
1989 | has been forked (which implies it might have already exited), as long |
2075 | has been forked (which implies it might have already exited), as long |
1990 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2076 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1991 | forking and then immediately registering a watcher for the child is fine, |
2077 | forking and then immediately registering a watcher for the child is fine, |
1992 | but forking and registering a watcher a few event loop iterations later is |
2078 | but forking and registering a watcher a few event loop iterations later or |
1993 | not. |
2079 | in the next callback invocation is not. |
1994 | |
2080 | |
1995 | Only the default event loop is capable of handling signals, and therefore |
2081 | Only the default event loop is capable of handling signals, and therefore |
1996 | you can only register child watchers in the default event loop. |
2082 | you can only register child watchers in the default event loop. |
|
|
2083 | |
|
|
2084 | Due to some design glitches inside libev, child watchers will always be |
|
|
2085 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2086 | libev) |
1997 | |
2087 | |
1998 | =head3 Process Interaction |
2088 | =head3 Process Interaction |
1999 | |
2089 | |
2000 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2090 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2001 | initialised. This is necessary to guarantee proper behaviour even if |
2091 | initialised. This is necessary to guarantee proper behaviour even if |
… | |
… | |
2353 | // no longer anything immediate to do. |
2443 | // no longer anything immediate to do. |
2354 | } |
2444 | } |
2355 | |
2445 | |
2356 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2446 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2357 | ev_idle_init (idle_watcher, idle_cb); |
2447 | ev_idle_init (idle_watcher, idle_cb); |
2358 | ev_idle_start (loop, idle_cb); |
2448 | ev_idle_start (loop, idle_watcher); |
2359 | |
2449 | |
2360 | |
2450 | |
2361 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2451 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2362 | |
2452 | |
2363 | Prepare and check watchers are usually (but not always) used in pairs: |
2453 | Prepare and check watchers are usually (but not always) used in pairs: |
… | |
… | |
2456 | struct pollfd fds [nfd]; |
2546 | struct pollfd fds [nfd]; |
2457 | // actual code will need to loop here and realloc etc. |
2547 | // actual code will need to loop here and realloc etc. |
2458 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2548 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2459 | |
2549 | |
2460 | /* the callback is illegal, but won't be called as we stop during check */ |
2550 | /* the callback is illegal, but won't be called as we stop during check */ |
2461 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2551 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2462 | ev_timer_start (loop, &tw); |
2552 | ev_timer_start (loop, &tw); |
2463 | |
2553 | |
2464 | // create one ev_io per pollfd |
2554 | // create one ev_io per pollfd |
2465 | for (int i = 0; i < nfd; ++i) |
2555 | for (int i = 0; i < nfd; ++i) |
2466 | { |
2556 | { |
… | |
… | |
2696 | event loop blocks next and before C<ev_check> watchers are being called, |
2786 | event loop blocks next and before C<ev_check> watchers are being called, |
2697 | and only in the child after the fork. If whoever good citizen calling |
2787 | and only in the child after the fork. If whoever good citizen calling |
2698 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2788 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2699 | handlers will be invoked, too, of course. |
2789 | handlers will be invoked, too, of course. |
2700 | |
2790 | |
|
|
2791 | =head3 The special problem of life after fork - how is it possible? |
|
|
2792 | |
|
|
2793 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2794 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2795 | sequence should be handled by libev without any problems. |
|
|
2796 | |
|
|
2797 | This changes when the application actually wants to do event handling |
|
|
2798 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2799 | fork. |
|
|
2800 | |
|
|
2801 | The default mode of operation (for libev, with application help to detect |
|
|
2802 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2803 | when I<either> the parent I<or> the child process continues. |
|
|
2804 | |
|
|
2805 | When both processes want to continue using libev, then this is usually the |
|
|
2806 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2807 | supposed to continue with all watchers in place as before, while the other |
|
|
2808 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2809 | |
|
|
2810 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2811 | simply create a new event loop, which of course will be "empty", and |
|
|
2812 | use that for new watchers. This has the advantage of not touching more |
|
|
2813 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2814 | disadvantage of having to use multiple event loops (which do not support |
|
|
2815 | signal watchers). |
|
|
2816 | |
|
|
2817 | When this is not possible, or you want to use the default loop for |
|
|
2818 | other reasons, then in the process that wants to start "fresh", call |
|
|
2819 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2820 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2821 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2822 | also that in that case, you have to re-register any signal watchers. |
|
|
2823 | |
2701 | =head3 Watcher-Specific Functions and Data Members |
2824 | =head3 Watcher-Specific Functions and Data Members |
2702 | |
2825 | |
2703 | =over 4 |
2826 | =over 4 |
2704 | |
2827 | |
2705 | =item ev_fork_init (ev_signal *, callback) |
2828 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
3595 | defined to be C<0>, then they are not. |
3718 | defined to be C<0>, then they are not. |
3596 | |
3719 | |
3597 | =item EV_MINIMAL |
3720 | =item EV_MINIMAL |
3598 | |
3721 | |
3599 | If you need to shave off some kilobytes of code at the expense of some |
3722 | If you need to shave off some kilobytes of code at the expense of some |
3600 | speed, define this symbol to C<1>. Currently this is used to override some |
3723 | speed (but with the full API), define this symbol to C<1>. Currently this |
3601 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3724 | is used to override some inlining decisions, saves roughly 30% code size |
3602 | much smaller 2-heap for timer management over the default 4-heap. |
3725 | on amd64. It also selects a much smaller 2-heap for timer management over |
|
|
3726 | the default 4-heap. |
|
|
3727 | |
|
|
3728 | You can save even more by disabling watcher types you do not need |
|
|
3729 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
|
|
3730 | (C<-DNDEBUG>) will usually reduce code size a lot. |
|
|
3731 | |
|
|
3732 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
|
|
3733 | provide a bare-bones event library. See C<ev.h> for details on what parts |
|
|
3734 | of the API are still available, and do not complain if this subset changes |
|
|
3735 | over time. |
3603 | |
3736 | |
3604 | =item EV_PID_HASHSIZE |
3737 | =item EV_PID_HASHSIZE |
3605 | |
3738 | |
3606 | C<ev_child> watchers use a small hash table to distribute workload by |
3739 | C<ev_child> watchers use a small hash table to distribute workload by |
3607 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3740 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
3793 | default loop and triggering an C<ev_async> watcher from the default loop |
3926 | default loop and triggering an C<ev_async> watcher from the default loop |
3794 | watcher callback into the event loop interested in the signal. |
3927 | watcher callback into the event loop interested in the signal. |
3795 | |
3928 | |
3796 | =back |
3929 | =back |
3797 | |
3930 | |
|
|
3931 | =head4 THREAD LOCKING EXAMPLE |
|
|
3932 | |
3798 | =head3 COROUTINES |
3933 | =head3 COROUTINES |
3799 | |
3934 | |
3800 | Libev is very accommodating to coroutines ("cooperative threads"): |
3935 | Libev is very accommodating to coroutines ("cooperative threads"): |
3801 | libev fully supports nesting calls to its functions from different |
3936 | libev fully supports nesting calls to its functions from different |
3802 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3937 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
… | |
… | |
3887 | way (note also that glib is the slowest event library known to man). |
4022 | way (note also that glib is the slowest event library known to man). |
3888 | |
4023 | |
3889 | There is no supported compilation method available on windows except |
4024 | There is no supported compilation method available on windows except |
3890 | embedding it into other applications. |
4025 | embedding it into other applications. |
3891 | |
4026 | |
|
|
4027 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4028 | tries its best, but under most conditions, signals will simply not work. |
|
|
4029 | |
3892 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4030 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3893 | accept large writes: instead of resulting in a partial write, windows will |
4031 | accept large writes: instead of resulting in a partial write, windows will |
3894 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4032 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3895 | so make sure you only write small amounts into your sockets (less than a |
4033 | so make sure you only write small amounts into your sockets (less than a |
3896 | megabyte seems safe, but this apparently depends on the amount of memory |
4034 | megabyte seems safe, but this apparently depends on the amount of memory |
… | |
… | |
3900 | the abysmal performance of winsockets, using a large number of sockets |
4038 | the abysmal performance of winsockets, using a large number of sockets |
3901 | is not recommended (and not reasonable). If your program needs to use |
4039 | is not recommended (and not reasonable). If your program needs to use |
3902 | more than a hundred or so sockets, then likely it needs to use a totally |
4040 | more than a hundred or so sockets, then likely it needs to use a totally |
3903 | different implementation for windows, as libev offers the POSIX readiness |
4041 | different implementation for windows, as libev offers the POSIX readiness |
3904 | notification model, which cannot be implemented efficiently on windows |
4042 | notification model, which cannot be implemented efficiently on windows |
3905 | (Microsoft monopoly games). |
4043 | (due to Microsoft monopoly games). |
3906 | |
4044 | |
3907 | A typical way to use libev under windows is to embed it (see the embedding |
4045 | A typical way to use libev under windows is to embed it (see the embedding |
3908 | section for details) and use the following F<evwrap.h> header file instead |
4046 | section for details) and use the following F<evwrap.h> header file instead |
3909 | of F<ev.h>: |
4047 | of F<ev.h>: |
3910 | |
4048 | |
… | |
… | |
3946 | |
4084 | |
3947 | Early versions of winsocket's select only supported waiting for a maximum |
4085 | Early versions of winsocket's select only supported waiting for a maximum |
3948 | of C<64> handles (probably owning to the fact that all windows kernels |
4086 | of C<64> handles (probably owning to the fact that all windows kernels |
3949 | can only wait for C<64> things at the same time internally; Microsoft |
4087 | can only wait for C<64> things at the same time internally; Microsoft |
3950 | recommends spawning a chain of threads and wait for 63 handles and the |
4088 | recommends spawning a chain of threads and wait for 63 handles and the |
3951 | previous thread in each. Great). |
4089 | previous thread in each. Sounds great!). |
3952 | |
4090 | |
3953 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4091 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3954 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4092 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3955 | call (which might be in libev or elsewhere, for example, perl does its own |
4093 | call (which might be in libev or elsewhere, for example, perl and many |
3956 | select emulation on windows). |
4094 | other interpreters do their own select emulation on windows). |
3957 | |
4095 | |
3958 | Another limit is the number of file descriptors in the Microsoft runtime |
4096 | Another limit is the number of file descriptors in the Microsoft runtime |
3959 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4097 | libraries, which by default is C<64> (there must be a hidden I<64> |
3960 | or something like this inside Microsoft). You can increase this by calling |
4098 | fetish or something like this inside Microsoft). You can increase this |
3961 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4099 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3962 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4100 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3963 | libraries. |
|
|
3964 | |
|
|
3965 | This might get you to about C<512> or C<2048> sockets (depending on |
4101 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3966 | windows version and/or the phase of the moon). To get more, you need to |
4102 | (depending on windows version and/or the phase of the moon). To get more, |
3967 | wrap all I/O functions and provide your own fd management, but the cost of |
4103 | you need to wrap all I/O functions and provide your own fd management, but |
3968 | calling select (O(n²)) will likely make this unworkable. |
4104 | the cost of calling select (O(n²)) will likely make this unworkable. |
3969 | |
4105 | |
3970 | =back |
4106 | =back |
3971 | |
4107 | |
3972 | =head2 PORTABILITY REQUIREMENTS |
4108 | =head2 PORTABILITY REQUIREMENTS |
3973 | |
4109 | |
… | |
… | |
4016 | =item C<double> must hold a time value in seconds with enough accuracy |
4152 | =item C<double> must hold a time value in seconds with enough accuracy |
4017 | |
4153 | |
4018 | The type C<double> is used to represent timestamps. It is required to |
4154 | The type C<double> is used to represent timestamps. It is required to |
4019 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4155 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4020 | enough for at least into the year 4000. This requirement is fulfilled by |
4156 | enough for at least into the year 4000. This requirement is fulfilled by |
4021 | implementations implementing IEEE 754 (basically all existing ones). |
4157 | implementations implementing IEEE 754, which is basically all existing |
|
|
4158 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4159 | 2200. |
4022 | |
4160 | |
4023 | =back |
4161 | =back |
4024 | |
4162 | |
4025 | If you know of other additional requirements drop me a note. |
4163 | If you know of other additional requirements drop me a note. |
4026 | |
4164 | |