… | |
… | |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
|
|
11 | // a single header file is required |
11 | #include <ev.h> |
12 | #include <ev.h> |
12 | |
13 | |
|
|
14 | // every watcher type has its own typedef'd struct |
|
|
15 | // with the name ev_<type> |
13 | ev_io stdin_watcher; |
16 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
15 | |
18 | |
|
|
19 | // all watcher callbacks have a similar signature |
16 | /* called when data readable on stdin */ |
20 | // this callback is called when data is readable on stdin |
17 | static void |
21 | static void |
18 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
19 | { |
23 | { |
20 | /* puts ("stdin ready"); */ |
24 | puts ("stdin ready"); |
21 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
25 | // for one-shot events, one must manually stop the watcher |
22 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
26 | // with its corresponding stop function. |
|
|
27 | ev_io_stop (EV_A_ w); |
|
|
28 | |
|
|
29 | // this causes all nested ev_loop's to stop iterating |
|
|
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
31 | } |
24 | |
32 | |
|
|
33 | // another callback, this time for a time-out |
25 | static void |
34 | static void |
26 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
27 | { |
36 | { |
28 | /* puts ("timeout"); */ |
37 | puts ("timeout"); |
29 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
38 | // this causes the innermost ev_loop to stop iterating |
|
|
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
30 | } |
40 | } |
31 | |
41 | |
32 | int |
42 | int |
33 | main (void) |
43 | main (void) |
34 | { |
44 | { |
|
|
45 | // use the default event loop unless you have special needs |
35 | struct ev_loop *loop = ev_default_loop (0); |
46 | struct ev_loop *loop = ev_default_loop (0); |
36 | |
47 | |
37 | /* initialise an io watcher, then start it */ |
48 | // initialise an io watcher, then start it |
|
|
49 | // this one will watch for stdin to become readable |
38 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
39 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
40 | |
52 | |
|
|
53 | // initialise a timer watcher, then start it |
41 | /* simple non-repeating 5.5 second timeout */ |
54 | // simple non-repeating 5.5 second timeout |
42 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
43 | ev_timer_start (loop, &timeout_watcher); |
56 | ev_timer_start (loop, &timeout_watcher); |
44 | |
57 | |
45 | /* loop till timeout or data ready */ |
58 | // now wait for events to arrive |
46 | ev_loop (loop, 0); |
59 | ev_loop (loop, 0); |
47 | |
60 | |
|
|
61 | // unloop was called, so exit |
48 | return 0; |
62 | return 0; |
49 | } |
63 | } |
50 | |
64 | |
51 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
52 | |
66 | |
53 | The newest version of this document is also available as a html-formatted |
67 | The newest version of this document is also available as an html-formatted |
54 | web page you might find easier to navigate when reading it for the first |
68 | web page you might find easier to navigate when reading it for the first |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
56 | |
70 | |
57 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
58 | file descriptor being readable or a timeout occurring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
99 | for example). |
86 | |
100 | |
87 | =head2 CONVENTIONS |
101 | =head2 CONVENTIONS |
88 | |
102 | |
89 | Libev is very configurable. In this manual the default configuration will |
103 | Libev is very configurable. In this manual the default (and most common) |
90 | be described, which supports multiple event loops. For more info about |
104 | configuration will be described, which supports multiple event loops. For |
91 | various configuration options please have a look at B<EMBED> section in |
105 | more info about various configuration options please have a look at |
92 | this manual. If libev was configured without support for multiple event |
106 | B<EMBED> section in this manual. If libev was configured without support |
93 | loops, then all functions taking an initial argument of name C<loop> |
107 | for multiple event loops, then all functions taking an initial argument of |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
|
|
109 | this argument. |
95 | |
110 | |
96 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
97 | |
112 | |
98 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
… | |
… | |
297 | enabling this flag. |
312 | enabling this flag. |
298 | |
313 | |
299 | This works by calling C<getpid ()> on every iteration of the loop, |
314 | This works by calling C<getpid ()> on every iteration of the loop, |
300 | and thus this might slow down your event loop if you do a lot of loop |
315 | and thus this might slow down your event loop if you do a lot of loop |
301 | iterations and little real work, but is usually not noticeable (on my |
316 | iterations and little real work, but is usually not noticeable (on my |
302 | Linux system for example, C<getpid> is actually a simple 5-insn sequence |
317 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
303 | without a syscall and thus I<very> fast, but my Linux system also has |
318 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
304 | C<pthread_atfork> which is even faster). |
319 | C<pthread_atfork> which is even faster). |
305 | |
320 | |
306 | The big advantage of this flag is that you can forget about fork (and |
321 | The big advantage of this flag is that you can forget about fork (and |
307 | forget about forgetting to tell libev about forking) when you use this |
322 | forget about forgetting to tell libev about forking) when you use this |
308 | flag. |
323 | flag. |
… | |
… | |
505 | =item ev_loop_fork (loop) |
520 | =item ev_loop_fork (loop) |
506 | |
521 | |
507 | Like C<ev_default_fork>, but acts on an event loop created by |
522 | Like C<ev_default_fork>, but acts on an event loop created by |
508 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
523 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
509 | after fork, and how you do this is entirely your own problem. |
524 | after fork, and how you do this is entirely your own problem. |
|
|
525 | |
|
|
526 | =item int ev_is_default_loop (loop) |
|
|
527 | |
|
|
528 | Returns true when the given loop actually is the default loop, false otherwise. |
510 | |
529 | |
511 | =item unsigned int ev_loop_count (loop) |
530 | =item unsigned int ev_loop_count (loop) |
512 | |
531 | |
513 | Returns the count of loop iterations for the loop, which is identical to |
532 | Returns the count of loop iterations for the loop, which is identical to |
514 | the number of times libev did poll for new events. It starts at C<0> and |
533 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
774 | =item C<EV_FORK> |
793 | =item C<EV_FORK> |
775 | |
794 | |
776 | The event loop has been resumed in the child process after fork (see |
795 | The event loop has been resumed in the child process after fork (see |
777 | C<ev_fork>). |
796 | C<ev_fork>). |
778 | |
797 | |
|
|
798 | =item C<EV_ASYNC> |
|
|
799 | |
|
|
800 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
801 | |
779 | =item C<EV_ERROR> |
802 | =item C<EV_ERROR> |
780 | |
803 | |
781 | An unspecified error has occured, the watcher has been stopped. This might |
804 | An unspecified error has occured, the watcher has been stopped. This might |
782 | happen because the watcher could not be properly started because libev |
805 | happen because the watcher could not be properly started because libev |
783 | ran out of memory, a file descriptor was found to be closed or any other |
806 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1062 | To support fork in your programs, you either have to call |
1085 | To support fork in your programs, you either have to call |
1063 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1086 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1064 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1087 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1065 | C<EVBACKEND_POLL>. |
1088 | C<EVBACKEND_POLL>. |
1066 | |
1089 | |
|
|
1090 | =head3 The special problem of SIGPIPE |
|
|
1091 | |
|
|
1092 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1093 | when reading from a pipe whose other end has been closed, your program |
|
|
1094 | gets send a SIGPIPE, which, by default, aborts your program. For most |
|
|
1095 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1096 | undesirable. |
|
|
1097 | |
|
|
1098 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1099 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1100 | somewhere, as that would have given you a big clue). |
|
|
1101 | |
1067 | |
1102 | |
1068 | =head3 Watcher-Specific Functions |
1103 | =head3 Watcher-Specific Functions |
1069 | |
1104 | |
1070 | =over 4 |
1105 | =over 4 |
1071 | |
1106 | |
… | |
… | |
1148 | configure a timer to trigger every 10 seconds, then it will trigger at |
1183 | configure a timer to trigger every 10 seconds, then it will trigger at |
1149 | exactly 10 second intervals. If, however, your program cannot keep up with |
1184 | exactly 10 second intervals. If, however, your program cannot keep up with |
1150 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1185 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1151 | timer will not fire more than once per event loop iteration. |
1186 | timer will not fire more than once per event loop iteration. |
1152 | |
1187 | |
1153 | =item ev_timer_again (loop) |
1188 | =item ev_timer_again (loop, ev_timer *) |
1154 | |
1189 | |
1155 | This will act as if the timer timed out and restart it again if it is |
1190 | This will act as if the timer timed out and restart it again if it is |
1156 | repeating. The exact semantics are: |
1191 | repeating. The exact semantics are: |
1157 | |
1192 | |
1158 | If the timer is pending, its pending status is cleared. |
1193 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1267 | In this configuration the watcher triggers an event at the wallclock time |
1302 | In this configuration the watcher triggers an event at the wallclock time |
1268 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1303 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1269 | that is, if it is to be run at January 1st 2011 then it will run when the |
1304 | that is, if it is to be run at January 1st 2011 then it will run when the |
1270 | system time reaches or surpasses this time. |
1305 | system time reaches or surpasses this time. |
1271 | |
1306 | |
1272 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1307 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1273 | |
1308 | |
1274 | In this mode the watcher will always be scheduled to time out at the next |
1309 | In this mode the watcher will always be scheduled to time out at the next |
1275 | C<at + N * interval> time (for some integer N, which can also be negative) |
1310 | C<at + N * interval> time (for some integer N, which can also be negative) |
1276 | and then repeat, regardless of any time jumps. |
1311 | and then repeat, regardless of any time jumps. |
1277 | |
1312 | |
… | |
… | |
1411 | with the kernel (thus it coexists with your own signal handlers as long |
1446 | with the kernel (thus it coexists with your own signal handlers as long |
1412 | as you don't register any with libev). Similarly, when the last signal |
1447 | as you don't register any with libev). Similarly, when the last signal |
1413 | watcher for a signal is stopped libev will reset the signal handler to |
1448 | watcher for a signal is stopped libev will reset the signal handler to |
1414 | SIG_DFL (regardless of what it was set to before). |
1449 | SIG_DFL (regardless of what it was set to before). |
1415 | |
1450 | |
|
|
1451 | If possible and supported, libev will install its handlers with |
|
|
1452 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1453 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1454 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1455 | them in an C<ev_prepare> watcher. |
|
|
1456 | |
1416 | =head3 Watcher-Specific Functions and Data Members |
1457 | =head3 Watcher-Specific Functions and Data Members |
1417 | |
1458 | |
1418 | =over 4 |
1459 | =over 4 |
1419 | |
1460 | |
1420 | =item ev_signal_init (ev_signal *, callback, int signum) |
1461 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1428 | |
1469 | |
1429 | The signal the watcher watches out for. |
1470 | The signal the watcher watches out for. |
1430 | |
1471 | |
1431 | =back |
1472 | =back |
1432 | |
1473 | |
|
|
1474 | =head3 Examples |
|
|
1475 | |
|
|
1476 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1477 | |
|
|
1478 | static void |
|
|
1479 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1480 | { |
|
|
1481 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1482 | } |
|
|
1483 | |
|
|
1484 | struct ev_signal signal_watcher; |
|
|
1485 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1486 | ev_signal_start (loop, &sigint_cb); |
|
|
1487 | |
1433 | |
1488 | |
1434 | =head2 C<ev_child> - watch out for process status changes |
1489 | =head2 C<ev_child> - watch out for process status changes |
1435 | |
1490 | |
1436 | Child watchers trigger when your process receives a SIGCHLD in response to |
1491 | Child watchers trigger when your process receives a SIGCHLD in response to |
1437 | some child status changes (most typically when a child of yours dies). |
1492 | some child status changes (most typically when a child of yours dies). It |
|
|
1493 | is permissible to install a child watcher I<after> the child has been |
|
|
1494 | forked (which implies it might have already exited), as long as the event |
|
|
1495 | loop isn't entered (or is continued from a watcher). |
|
|
1496 | |
|
|
1497 | Only the default event loop is capable of handling signals, and therefore |
|
|
1498 | you can only rgeister child watchers in the default event loop. |
|
|
1499 | |
|
|
1500 | =head3 Process Interaction |
|
|
1501 | |
|
|
1502 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1503 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1504 | the first child watcher is started after the child exits. The occurance |
|
|
1505 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1506 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1507 | children, even ones not watched. |
|
|
1508 | |
|
|
1509 | =head3 Overriding the Built-In Processing |
|
|
1510 | |
|
|
1511 | Libev offers no special support for overriding the built-in child |
|
|
1512 | processing, but if your application collides with libev's default child |
|
|
1513 | handler, you can override it easily by installing your own handler for |
|
|
1514 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1515 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1516 | event-based approach to child reaping and thus use libev's support for |
|
|
1517 | that, so other libev users can use C<ev_child> watchers freely. |
1438 | |
1518 | |
1439 | =head3 Watcher-Specific Functions and Data Members |
1519 | =head3 Watcher-Specific Functions and Data Members |
1440 | |
1520 | |
1441 | =over 4 |
1521 | =over 4 |
1442 | |
1522 | |
… | |
… | |
1468 | |
1548 | |
1469 | =back |
1549 | =back |
1470 | |
1550 | |
1471 | =head3 Examples |
1551 | =head3 Examples |
1472 | |
1552 | |
1473 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1553 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1554 | its completion. |
|
|
1555 | |
|
|
1556 | ev_child cw; |
1474 | |
1557 | |
1475 | static void |
1558 | static void |
1476 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1559 | child_cb (EV_P_ struct ev_child *w, int revents) |
1477 | { |
1560 | { |
1478 | ev_unloop (loop, EVUNLOOP_ALL); |
1561 | ev_child_stop (EV_A_ w); |
|
|
1562 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1479 | } |
1563 | } |
1480 | |
1564 | |
1481 | struct ev_signal signal_watcher; |
1565 | pid_t pid = fork (); |
1482 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1566 | |
1483 | ev_signal_start (loop, &sigint_cb); |
1567 | if (pid < 0) |
|
|
1568 | // error |
|
|
1569 | else if (pid == 0) |
|
|
1570 | { |
|
|
1571 | // the forked child executes here |
|
|
1572 | exit (1); |
|
|
1573 | } |
|
|
1574 | else |
|
|
1575 | { |
|
|
1576 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1577 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1578 | } |
1484 | |
1579 | |
1485 | |
1580 | |
1486 | =head2 C<ev_stat> - did the file attributes just change? |
1581 | =head2 C<ev_stat> - did the file attributes just change? |
1487 | |
1582 | |
1488 | This watches a filesystem path for attribute changes. That is, it calls |
1583 | This watches a filesystem path for attribute changes. That is, it calls |
… | |
… | |
1517 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1612 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1518 | to fall back to regular polling again even with inotify, but changes are |
1613 | to fall back to regular polling again even with inotify, but changes are |
1519 | usually detected immediately, and if the file exists there will be no |
1614 | usually detected immediately, and if the file exists there will be no |
1520 | polling. |
1615 | polling. |
1521 | |
1616 | |
|
|
1617 | =head3 ABI Issues (Largefile Support) |
|
|
1618 | |
|
|
1619 | Libev by default (unless the user overrides this) uses the default |
|
|
1620 | compilation environment, which means that on systems with optionally |
|
|
1621 | disabled large file support, you get the 32 bit version of the stat |
|
|
1622 | structure. When using the library from programs that change the ABI to |
|
|
1623 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1624 | compile libev with the same flags to get binary compatibility. This is |
|
|
1625 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1626 | most noticably with ev_stat and largefile support. |
|
|
1627 | |
1522 | =head3 Inotify |
1628 | =head3 Inotify |
1523 | |
1629 | |
1524 | When C<inotify (7)> support has been compiled into libev (generally only |
1630 | When C<inotify (7)> support has been compiled into libev (generally only |
1525 | available on Linux) and present at runtime, it will be used to speed up |
1631 | available on Linux) and present at runtime, it will be used to speed up |
1526 | change detection where possible. The inotify descriptor will be created lazily |
1632 | change detection where possible. The inotify descriptor will be created lazily |
… | |
… | |
1568 | |
1674 | |
1569 | The callback will be receive C<EV_STAT> when a change was detected, |
1675 | The callback will be receive C<EV_STAT> when a change was detected, |
1570 | relative to the attributes at the time the watcher was started (or the |
1676 | relative to the attributes at the time the watcher was started (or the |
1571 | last change was detected). |
1677 | last change was detected). |
1572 | |
1678 | |
1573 | =item ev_stat_stat (ev_stat *) |
1679 | =item ev_stat_stat (loop, ev_stat *) |
1574 | |
1680 | |
1575 | Updates the stat buffer immediately with new values. If you change the |
1681 | Updates the stat buffer immediately with new values. If you change the |
1576 | watched path in your callback, you could call this fucntion to avoid |
1682 | watched path in your callback, you could call this fucntion to avoid |
1577 | detecting this change (while introducing a race condition). Can also be |
1683 | detecting this change (while introducing a race condition). Can also be |
1578 | useful simply to find out the new values. |
1684 | useful simply to find out the new values. |
… | |
… | |
2046 | believe me. |
2152 | believe me. |
2047 | |
2153 | |
2048 | =back |
2154 | =back |
2049 | |
2155 | |
2050 | |
2156 | |
|
|
2157 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2158 | |
|
|
2159 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2160 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2161 | loops - those are of course safe to use in different threads). |
|
|
2162 | |
|
|
2163 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2164 | control, for example because it belongs to another thread. This is what |
|
|
2165 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2166 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2167 | safe. |
|
|
2168 | |
|
|
2169 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2170 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2171 | (i.e. the number of callback invocations may be less than the number of |
|
|
2172 | C<ev_async_sent> calls). |
|
|
2173 | |
|
|
2174 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2175 | just the default loop. |
|
|
2176 | |
|
|
2177 | =head3 Queueing |
|
|
2178 | |
|
|
2179 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2180 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2181 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2182 | need elaborate support such as pthreads. |
|
|
2183 | |
|
|
2184 | That means that if you want to queue data, you have to provide your own |
|
|
2185 | queue. But at least I can tell you would implement locking around your |
|
|
2186 | queue: |
|
|
2187 | |
|
|
2188 | =over 4 |
|
|
2189 | |
|
|
2190 | =item queueing from a signal handler context |
|
|
2191 | |
|
|
2192 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2193 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2194 | some fictitiuous SIGUSR1 handler: |
|
|
2195 | |
|
|
2196 | static ev_async mysig; |
|
|
2197 | |
|
|
2198 | static void |
|
|
2199 | sigusr1_handler (void) |
|
|
2200 | { |
|
|
2201 | sometype data; |
|
|
2202 | |
|
|
2203 | // no locking etc. |
|
|
2204 | queue_put (data); |
|
|
2205 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2206 | } |
|
|
2207 | |
|
|
2208 | static void |
|
|
2209 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2210 | { |
|
|
2211 | sometype data; |
|
|
2212 | sigset_t block, prev; |
|
|
2213 | |
|
|
2214 | sigemptyset (&block); |
|
|
2215 | sigaddset (&block, SIGUSR1); |
|
|
2216 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2217 | |
|
|
2218 | while (queue_get (&data)) |
|
|
2219 | process (data); |
|
|
2220 | |
|
|
2221 | if (sigismember (&prev, SIGUSR1) |
|
|
2222 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2223 | } |
|
|
2224 | |
|
|
2225 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2226 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2227 | either...). |
|
|
2228 | |
|
|
2229 | =item queueing from a thread context |
|
|
2230 | |
|
|
2231 | The strategy for threads is different, as you cannot (easily) block |
|
|
2232 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2233 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2234 | |
|
|
2235 | static ev_async mysig; |
|
|
2236 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2237 | |
|
|
2238 | static void |
|
|
2239 | otherthread (void) |
|
|
2240 | { |
|
|
2241 | // only need to lock the actual queueing operation |
|
|
2242 | pthread_mutex_lock (&mymutex); |
|
|
2243 | queue_put (data); |
|
|
2244 | pthread_mutex_unlock (&mymutex); |
|
|
2245 | |
|
|
2246 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2247 | } |
|
|
2248 | |
|
|
2249 | static void |
|
|
2250 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2251 | { |
|
|
2252 | pthread_mutex_lock (&mymutex); |
|
|
2253 | |
|
|
2254 | while (queue_get (&data)) |
|
|
2255 | process (data); |
|
|
2256 | |
|
|
2257 | pthread_mutex_unlock (&mymutex); |
|
|
2258 | } |
|
|
2259 | |
|
|
2260 | =back |
|
|
2261 | |
|
|
2262 | |
|
|
2263 | =head3 Watcher-Specific Functions and Data Members |
|
|
2264 | |
|
|
2265 | =over 4 |
|
|
2266 | |
|
|
2267 | =item ev_async_init (ev_async *, callback) |
|
|
2268 | |
|
|
2269 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2270 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
|
|
2271 | believe me. |
|
|
2272 | |
|
|
2273 | =item ev_async_send (loop, ev_async *) |
|
|
2274 | |
|
|
2275 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2276 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2277 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
|
|
2278 | similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding |
|
|
2279 | section below on what exactly this means). |
|
|
2280 | |
|
|
2281 | This call incurs the overhead of a syscall only once per loop iteration, |
|
|
2282 | so while the overhead might be noticable, it doesn't apply to repeated |
|
|
2283 | calls to C<ev_async_send>. |
|
|
2284 | |
|
|
2285 | =back |
|
|
2286 | |
|
|
2287 | |
2051 | =head1 OTHER FUNCTIONS |
2288 | =head1 OTHER FUNCTIONS |
2052 | |
2289 | |
2053 | There are some other functions of possible interest. Described. Here. Now. |
2290 | There are some other functions of possible interest. Described. Here. Now. |
2054 | |
2291 | |
2055 | =over 4 |
2292 | =over 4 |
… | |
… | |
2293 | idle.set <myclass, &myclass::idle_cb> (this); |
2530 | idle.set <myclass, &myclass::idle_cb> (this); |
2294 | |
2531 | |
2295 | io.start (fd, ev::READ); |
2532 | io.start (fd, ev::READ); |
2296 | } |
2533 | } |
2297 | }; |
2534 | }; |
|
|
2535 | |
|
|
2536 | |
|
|
2537 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2538 | |
|
|
2539 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2540 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2541 | any interesting language binding in addition to the ones listed here, drop |
|
|
2542 | me a note. |
|
|
2543 | |
|
|
2544 | =over 4 |
|
|
2545 | |
|
|
2546 | =item Perl |
|
|
2547 | |
|
|
2548 | The EV module implements the full libev API and is actually used to test |
|
|
2549 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2550 | there are additional modules that implement libev-compatible interfaces |
|
|
2551 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2552 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2553 | |
|
|
2554 | It can be found and installed via CPAN, its homepage is found at |
|
|
2555 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2556 | |
|
|
2557 | =item Ruby |
|
|
2558 | |
|
|
2559 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2560 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2561 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2562 | L<http://rev.rubyforge.org/>. |
|
|
2563 | |
|
|
2564 | =item D |
|
|
2565 | |
|
|
2566 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2567 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2568 | |
|
|
2569 | =back |
2298 | |
2570 | |
2299 | |
2571 | |
2300 | =head1 MACRO MAGIC |
2572 | =head1 MACRO MAGIC |
2301 | |
2573 | |
2302 | Libev can be compiled with a variety of options, the most fundamantal |
2574 | Libev can be compiled with a variety of options, the most fundamantal |
… | |
… | |
2558 | |
2830 | |
2559 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2831 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2560 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2832 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2561 | be detected at runtime. |
2833 | be detected at runtime. |
2562 | |
2834 | |
|
|
2835 | =item EV_ATOMIC_T |
|
|
2836 | |
|
|
2837 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
2838 | access is atomic with respect to other threads or signal contexts. No such |
|
|
2839 | type is easily found in the C language, so you can provide your own type |
|
|
2840 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2841 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
2842 | |
|
|
2843 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
|
|
2844 | (from F<signal.h>), which is usually good enough on most platforms. |
|
|
2845 | |
2563 | =item EV_H |
2846 | =item EV_H |
2564 | |
2847 | |
2565 | The name of the F<ev.h> header file used to include it. The default if |
2848 | The name of the F<ev.h> header file used to include it. The default if |
2566 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2849 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2567 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2850 | used to virtually rename the F<ev.h> header file in case of conflicts. |
… | |
… | |
2632 | defined to be C<0>, then they are not. |
2915 | defined to be C<0>, then they are not. |
2633 | |
2916 | |
2634 | =item EV_FORK_ENABLE |
2917 | =item EV_FORK_ENABLE |
2635 | |
2918 | |
2636 | If undefined or defined to be C<1>, then fork watchers are supported. If |
2919 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2920 | defined to be C<0>, then they are not. |
|
|
2921 | |
|
|
2922 | =item EV_ASYNC_ENABLE |
|
|
2923 | |
|
|
2924 | If undefined or defined to be C<1>, then async watchers are supported. If |
2637 | defined to be C<0>, then they are not. |
2925 | defined to be C<0>, then they are not. |
2638 | |
2926 | |
2639 | =item EV_MINIMAL |
2927 | =item EV_MINIMAL |
2640 | |
2928 | |
2641 | If you need to shave off some kilobytes of code at the expense of some |
2929 | If you need to shave off some kilobytes of code at the expense of some |
… | |
… | |
2762 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3050 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2763 | |
3051 | |
2764 | That means that changing a timer costs less than removing/adding them |
3052 | That means that changing a timer costs less than removing/adding them |
2765 | as only the relative motion in the event queue has to be paid for. |
3053 | as only the relative motion in the event queue has to be paid for. |
2766 | |
3054 | |
2767 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3055 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2768 | |
3056 | |
2769 | These just add the watcher into an array or at the head of a list. |
3057 | These just add the watcher into an array or at the head of a list. |
2770 | |
3058 | |
2771 | =item Stopping check/prepare/idle watchers: O(1) |
3059 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2772 | |
3060 | |
2773 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3061 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2774 | |
3062 | |
2775 | These watchers are stored in lists then need to be walked to find the |
3063 | These watchers are stored in lists then need to be walked to find the |
2776 | correct watcher to remove. The lists are usually short (you don't usually |
3064 | correct watcher to remove. The lists are usually short (you don't usually |
… | |
… | |
2792 | =item Priority handling: O(number_of_priorities) |
3080 | =item Priority handling: O(number_of_priorities) |
2793 | |
3081 | |
2794 | Priorities are implemented by allocating some space for each |
3082 | Priorities are implemented by allocating some space for each |
2795 | priority. When doing priority-based operations, libev usually has to |
3083 | priority. When doing priority-based operations, libev usually has to |
2796 | linearly search all the priorities, but starting/stopping and activating |
3084 | linearly search all the priorities, but starting/stopping and activating |
2797 | watchers becomes O(1) w.r.t. prioritiy handling. |
3085 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3086 | |
|
|
3087 | =item Sending an ev_async: O(1) |
|
|
3088 | |
|
|
3089 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3090 | |
|
|
3091 | =item Processing signals: O(max_signal_number) |
|
|
3092 | |
|
|
3093 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3094 | calls in the current loop iteration. Checking for async and signal events |
|
|
3095 | involves iterating over all running async watchers or all signal numbers. |
2798 | |
3096 | |
2799 | =back |
3097 | =back |
2800 | |
3098 | |
2801 | |
3099 | |
2802 | =head1 Win32 platform limitations and workarounds |
3100 | =head1 Win32 platform limitations and workarounds |