… | |
… | |
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 |
… | |
… | |
260 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
275 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
261 | |
276 | |
262 | If you don't know what event loop to use, use the one returned from this |
277 | If you don't know what event loop to use, use the one returned from this |
263 | function. |
278 | function. |
264 | |
279 | |
|
|
280 | Note that this function is I<not> thread-safe, so if you want to use it |
|
|
281 | from multiple threads, you have to lock (note also that this is unlikely, |
|
|
282 | as loops cannot bes hared easily between threads anyway). |
|
|
283 | |
265 | The default loop is the only loop that can handle C<ev_signal> and |
284 | The default loop is the only loop that can handle C<ev_signal> and |
266 | C<ev_child> watchers, and to do this, it always registers a handler |
285 | C<ev_child> watchers, and to do this, it always registers a handler |
267 | for C<SIGCHLD>. If this is a problem for your app you can either |
286 | for C<SIGCHLD>. If this is a problem for your app you can either |
268 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
287 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
269 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
288 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
… | |
… | |
297 | enabling this flag. |
316 | enabling this flag. |
298 | |
317 | |
299 | This works by calling C<getpid ()> on every iteration of the loop, |
318 | 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 |
319 | 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 |
320 | 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 |
321 | 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 |
322 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
304 | C<pthread_atfork> which is even faster). |
323 | C<pthread_atfork> which is even faster). |
305 | |
324 | |
306 | The big advantage of this flag is that you can forget about fork (and |
325 | 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 |
326 | forget about forgetting to tell libev about forking) when you use this |
308 | flag. |
327 | flag. |
… | |
… | |
451 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
470 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
452 | always distinct from the default loop. Unlike the default loop, it cannot |
471 | always distinct from the default loop. Unlike the default loop, it cannot |
453 | handle signal and child watchers, and attempts to do so will be greeted by |
472 | handle signal and child watchers, and attempts to do so will be greeted by |
454 | undefined behaviour (or a failed assertion if assertions are enabled). |
473 | undefined behaviour (or a failed assertion if assertions are enabled). |
455 | |
474 | |
|
|
475 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
476 | libev with threads is indeed to create one loop per thread, and using the |
|
|
477 | default loop in the "main" or "initial" thread. |
|
|
478 | |
456 | Example: Try to create a event loop that uses epoll and nothing else. |
479 | Example: Try to create a event loop that uses epoll and nothing else. |
457 | |
480 | |
458 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
481 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
459 | if (!epoller) |
482 | if (!epoller) |
460 | fatal ("no epoll found here, maybe it hides under your chair"); |
483 | fatal ("no epoll found here, maybe it hides under your chair"); |
… | |
… | |
505 | =item ev_loop_fork (loop) |
528 | =item ev_loop_fork (loop) |
506 | |
529 | |
507 | Like C<ev_default_fork>, but acts on an event loop created by |
530 | 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 |
531 | 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. |
532 | after fork, and how you do this is entirely your own problem. |
|
|
533 | |
|
|
534 | =item int ev_is_default_loop (loop) |
|
|
535 | |
|
|
536 | Returns true when the given loop actually is the default loop, false otherwise. |
510 | |
537 | |
511 | =item unsigned int ev_loop_count (loop) |
538 | =item unsigned int ev_loop_count (loop) |
512 | |
539 | |
513 | Returns the count of loop iterations for the loop, which is identical to |
540 | 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 |
541 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
1066 | To support fork in your programs, you either have to call |
1093 | To support fork in your programs, you either have to call |
1067 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1094 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1068 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1095 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1069 | C<EVBACKEND_POLL>. |
1096 | C<EVBACKEND_POLL>. |
1070 | |
1097 | |
|
|
1098 | =head3 The special problem of SIGPIPE |
|
|
1099 | |
|
|
1100 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1101 | when reading from a pipe whose other end has been closed, your program |
|
|
1102 | gets send a SIGPIPE, which, by default, aborts your program. For most |
|
|
1103 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1104 | undesirable. |
|
|
1105 | |
|
|
1106 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1107 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1108 | somewhere, as that would have given you a big clue). |
|
|
1109 | |
1071 | |
1110 | |
1072 | =head3 Watcher-Specific Functions |
1111 | =head3 Watcher-Specific Functions |
1073 | |
1112 | |
1074 | =over 4 |
1113 | =over 4 |
1075 | |
1114 | |
… | |
… | |
1152 | configure a timer to trigger every 10 seconds, then it will trigger at |
1191 | configure a timer to trigger every 10 seconds, then it will trigger at |
1153 | exactly 10 second intervals. If, however, your program cannot keep up with |
1192 | exactly 10 second intervals. If, however, your program cannot keep up with |
1154 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1193 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1155 | timer will not fire more than once per event loop iteration. |
1194 | timer will not fire more than once per event loop iteration. |
1156 | |
1195 | |
1157 | =item ev_timer_again (loop) |
1196 | =item ev_timer_again (loop, ev_timer *) |
1158 | |
1197 | |
1159 | This will act as if the timer timed out and restart it again if it is |
1198 | This will act as if the timer timed out and restart it again if it is |
1160 | repeating. The exact semantics are: |
1199 | repeating. The exact semantics are: |
1161 | |
1200 | |
1162 | If the timer is pending, its pending status is cleared. |
1201 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1271 | In this configuration the watcher triggers an event at the wallclock time |
1310 | In this configuration the watcher triggers an event at the wallclock time |
1272 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1311 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1273 | that is, if it is to be run at January 1st 2011 then it will run when the |
1312 | that is, if it is to be run at January 1st 2011 then it will run when the |
1274 | system time reaches or surpasses this time. |
1313 | system time reaches or surpasses this time. |
1275 | |
1314 | |
1276 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1315 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1277 | |
1316 | |
1278 | In this mode the watcher will always be scheduled to time out at the next |
1317 | In this mode the watcher will always be scheduled to time out at the next |
1279 | C<at + N * interval> time (for some integer N, which can also be negative) |
1318 | C<at + N * interval> time (for some integer N, which can also be negative) |
1280 | and then repeat, regardless of any time jumps. |
1319 | and then repeat, regardless of any time jumps. |
1281 | |
1320 | |
… | |
… | |
1415 | with the kernel (thus it coexists with your own signal handlers as long |
1454 | with the kernel (thus it coexists with your own signal handlers as long |
1416 | as you don't register any with libev). Similarly, when the last signal |
1455 | as you don't register any with libev). Similarly, when the last signal |
1417 | watcher for a signal is stopped libev will reset the signal handler to |
1456 | watcher for a signal is stopped libev will reset the signal handler to |
1418 | SIG_DFL (regardless of what it was set to before). |
1457 | SIG_DFL (regardless of what it was set to before). |
1419 | |
1458 | |
|
|
1459 | If possible and supported, libev will install its handlers with |
|
|
1460 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1461 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1462 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1463 | them in an C<ev_prepare> watcher. |
|
|
1464 | |
1420 | =head3 Watcher-Specific Functions and Data Members |
1465 | =head3 Watcher-Specific Functions and Data Members |
1421 | |
1466 | |
1422 | =over 4 |
1467 | =over 4 |
1423 | |
1468 | |
1424 | =item ev_signal_init (ev_signal *, callback, int signum) |
1469 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1432 | |
1477 | |
1433 | The signal the watcher watches out for. |
1478 | The signal the watcher watches out for. |
1434 | |
1479 | |
1435 | =back |
1480 | =back |
1436 | |
1481 | |
|
|
1482 | =head3 Examples |
|
|
1483 | |
|
|
1484 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1485 | |
|
|
1486 | static void |
|
|
1487 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1488 | { |
|
|
1489 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1490 | } |
|
|
1491 | |
|
|
1492 | struct ev_signal signal_watcher; |
|
|
1493 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1494 | ev_signal_start (loop, &sigint_cb); |
|
|
1495 | |
1437 | |
1496 | |
1438 | =head2 C<ev_child> - watch out for process status changes |
1497 | =head2 C<ev_child> - watch out for process status changes |
1439 | |
1498 | |
1440 | Child watchers trigger when your process receives a SIGCHLD in response to |
1499 | Child watchers trigger when your process receives a SIGCHLD in response to |
1441 | some child status changes (most typically when a child of yours dies). |
1500 | some child status changes (most typically when a child of yours dies). It |
|
|
1501 | is permissible to install a child watcher I<after> the child has been |
|
|
1502 | forked (which implies it might have already exited), as long as the event |
|
|
1503 | loop isn't entered (or is continued from a watcher). |
|
|
1504 | |
|
|
1505 | Only the default event loop is capable of handling signals, and therefore |
|
|
1506 | you can only rgeister child watchers in the default event loop. |
|
|
1507 | |
|
|
1508 | =head3 Process Interaction |
|
|
1509 | |
|
|
1510 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1511 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1512 | the first child watcher is started after the child exits. The occurance |
|
|
1513 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1514 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1515 | children, even ones not watched. |
|
|
1516 | |
|
|
1517 | =head3 Overriding the Built-In Processing |
|
|
1518 | |
|
|
1519 | Libev offers no special support for overriding the built-in child |
|
|
1520 | processing, but if your application collides with libev's default child |
|
|
1521 | handler, you can override it easily by installing your own handler for |
|
|
1522 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1523 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1524 | event-based approach to child reaping and thus use libev's support for |
|
|
1525 | that, so other libev users can use C<ev_child> watchers freely. |
1442 | |
1526 | |
1443 | =head3 Watcher-Specific Functions and Data Members |
1527 | =head3 Watcher-Specific Functions and Data Members |
1444 | |
1528 | |
1445 | =over 4 |
1529 | =over 4 |
1446 | |
1530 | |
… | |
… | |
1472 | |
1556 | |
1473 | =back |
1557 | =back |
1474 | |
1558 | |
1475 | =head3 Examples |
1559 | =head3 Examples |
1476 | |
1560 | |
1477 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1561 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1562 | its completion. |
|
|
1563 | |
|
|
1564 | ev_child cw; |
1478 | |
1565 | |
1479 | static void |
1566 | static void |
1480 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1567 | child_cb (EV_P_ struct ev_child *w, int revents) |
1481 | { |
1568 | { |
1482 | ev_unloop (loop, EVUNLOOP_ALL); |
1569 | ev_child_stop (EV_A_ w); |
|
|
1570 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1483 | } |
1571 | } |
1484 | |
1572 | |
1485 | struct ev_signal signal_watcher; |
1573 | pid_t pid = fork (); |
1486 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1574 | |
1487 | ev_signal_start (loop, &sigint_cb); |
1575 | if (pid < 0) |
|
|
1576 | // error |
|
|
1577 | else if (pid == 0) |
|
|
1578 | { |
|
|
1579 | // the forked child executes here |
|
|
1580 | exit (1); |
|
|
1581 | } |
|
|
1582 | else |
|
|
1583 | { |
|
|
1584 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1585 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1586 | } |
1488 | |
1587 | |
1489 | |
1588 | |
1490 | =head2 C<ev_stat> - did the file attributes just change? |
1589 | =head2 C<ev_stat> - did the file attributes just change? |
1491 | |
1590 | |
1492 | This watches a filesystem path for attribute changes. That is, it calls |
1591 | This watches a filesystem path for attribute changes. That is, it calls |
… | |
… | |
1521 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1620 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1522 | to fall back to regular polling again even with inotify, but changes are |
1621 | to fall back to regular polling again even with inotify, but changes are |
1523 | usually detected immediately, and if the file exists there will be no |
1622 | usually detected immediately, and if the file exists there will be no |
1524 | polling. |
1623 | polling. |
1525 | |
1624 | |
|
|
1625 | =head3 ABI Issues (Largefile Support) |
|
|
1626 | |
|
|
1627 | Libev by default (unless the user overrides this) uses the default |
|
|
1628 | compilation environment, which means that on systems with optionally |
|
|
1629 | disabled large file support, you get the 32 bit version of the stat |
|
|
1630 | structure. When using the library from programs that change the ABI to |
|
|
1631 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1632 | compile libev with the same flags to get binary compatibility. This is |
|
|
1633 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1634 | most noticably with ev_stat and largefile support. |
|
|
1635 | |
1526 | =head3 Inotify |
1636 | =head3 Inotify |
1527 | |
1637 | |
1528 | When C<inotify (7)> support has been compiled into libev (generally only |
1638 | When C<inotify (7)> support has been compiled into libev (generally only |
1529 | available on Linux) and present at runtime, it will be used to speed up |
1639 | available on Linux) and present at runtime, it will be used to speed up |
1530 | change detection where possible. The inotify descriptor will be created lazily |
1640 | change detection where possible. The inotify descriptor will be created lazily |
… | |
… | |
1572 | |
1682 | |
1573 | The callback will be receive C<EV_STAT> when a change was detected, |
1683 | The callback will be receive C<EV_STAT> when a change was detected, |
1574 | relative to the attributes at the time the watcher was started (or the |
1684 | relative to the attributes at the time the watcher was started (or the |
1575 | last change was detected). |
1685 | last change was detected). |
1576 | |
1686 | |
1577 | =item ev_stat_stat (ev_stat *) |
1687 | =item ev_stat_stat (loop, ev_stat *) |
1578 | |
1688 | |
1579 | Updates the stat buffer immediately with new values. If you change the |
1689 | Updates the stat buffer immediately with new values. If you change the |
1580 | watched path in your callback, you could call this fucntion to avoid |
1690 | watched path in your callback, you could call this fucntion to avoid |
1581 | detecting this change (while introducing a race condition). Can also be |
1691 | detecting this change (while introducing a race condition). Can also be |
1582 | useful simply to find out the new values. |
1692 | useful simply to find out the new values. |
… | |
… | |
2078 | is that the author does not know of a simple (or any) algorithm for a |
2188 | is that the author does not know of a simple (or any) algorithm for a |
2079 | multiple-writer-single-reader queue that works in all cases and doesn't |
2189 | multiple-writer-single-reader queue that works in all cases and doesn't |
2080 | need elaborate support such as pthreads. |
2190 | need elaborate support such as pthreads. |
2081 | |
2191 | |
2082 | That means that if you want to queue data, you have to provide your own |
2192 | That means that if you want to queue data, you have to provide your own |
2083 | queue. And here is how you would implement locking: |
2193 | queue. But at least I can tell you would implement locking around your |
|
|
2194 | queue: |
2084 | |
2195 | |
2085 | =over 4 |
2196 | =over 4 |
2086 | |
2197 | |
2087 | =item queueing from a signal handler context |
2198 | =item queueing from a signal handler context |
2088 | |
2199 | |
… | |
… | |
2097 | { |
2208 | { |
2098 | sometype data; |
2209 | sometype data; |
2099 | |
2210 | |
2100 | // no locking etc. |
2211 | // no locking etc. |
2101 | queue_put (data); |
2212 | queue_put (data); |
2102 | ev_async_send (DEFAULT_ &mysig); |
2213 | ev_async_send (EV_DEFAULT_ &mysig); |
2103 | } |
2214 | } |
2104 | |
2215 | |
2105 | static void |
2216 | static void |
2106 | mysig_cb (EV_P_ ev_async *w, int revents) |
2217 | mysig_cb (EV_P_ ev_async *w, int revents) |
2107 | { |
2218 | { |
… | |
… | |
2125 | |
2236 | |
2126 | =item queueing from a thread context |
2237 | =item queueing from a thread context |
2127 | |
2238 | |
2128 | The strategy for threads is different, as you cannot (easily) block |
2239 | The strategy for threads is different, as you cannot (easily) block |
2129 | threads but you can easily preempt them, so to queue safely you need to |
2240 | threads but you can easily preempt them, so to queue safely you need to |
2130 | emply a traditional mutex lock, such as in this pthread example: |
2241 | employ a traditional mutex lock, such as in this pthread example: |
2131 | |
2242 | |
2132 | static ev_async mysig; |
2243 | static ev_async mysig; |
2133 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2244 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2134 | |
2245 | |
2135 | static void |
2246 | static void |
… | |
… | |
2138 | // only need to lock the actual queueing operation |
2249 | // only need to lock the actual queueing operation |
2139 | pthread_mutex_lock (&mymutex); |
2250 | pthread_mutex_lock (&mymutex); |
2140 | queue_put (data); |
2251 | queue_put (data); |
2141 | pthread_mutex_unlock (&mymutex); |
2252 | pthread_mutex_unlock (&mymutex); |
2142 | |
2253 | |
2143 | ev_async_send (DEFAULT_ &mysig); |
2254 | ev_async_send (EV_DEFAULT_ &mysig); |
2144 | } |
2255 | } |
2145 | |
2256 | |
2146 | static void |
2257 | static void |
2147 | mysig_cb (EV_P_ ev_async *w, int revents) |
2258 | mysig_cb (EV_P_ ev_async *w, int revents) |
2148 | { |
2259 | { |
… | |
… | |
2427 | idle.set <myclass, &myclass::idle_cb> (this); |
2538 | idle.set <myclass, &myclass::idle_cb> (this); |
2428 | |
2539 | |
2429 | io.start (fd, ev::READ); |
2540 | io.start (fd, ev::READ); |
2430 | } |
2541 | } |
2431 | }; |
2542 | }; |
|
|
2543 | |
|
|
2544 | |
|
|
2545 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2546 | |
|
|
2547 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2548 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2549 | any interesting language binding in addition to the ones listed here, drop |
|
|
2550 | me a note. |
|
|
2551 | |
|
|
2552 | =over 4 |
|
|
2553 | |
|
|
2554 | =item Perl |
|
|
2555 | |
|
|
2556 | The EV module implements the full libev API and is actually used to test |
|
|
2557 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2558 | there are additional modules that implement libev-compatible interfaces |
|
|
2559 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2560 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2561 | |
|
|
2562 | It can be found and installed via CPAN, its homepage is found at |
|
|
2563 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2564 | |
|
|
2565 | =item Ruby |
|
|
2566 | |
|
|
2567 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2568 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2569 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2570 | L<http://rev.rubyforge.org/>. |
|
|
2571 | |
|
|
2572 | =item D |
|
|
2573 | |
|
|
2574 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2575 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2576 | |
|
|
2577 | =back |
2432 | |
2578 | |
2433 | |
2579 | |
2434 | =head1 MACRO MAGIC |
2580 | =head1 MACRO MAGIC |
2435 | |
2581 | |
2436 | Libev can be compiled with a variety of options, the most fundamantal |
2582 | Libev can be compiled with a variety of options, the most fundamantal |
… | |
… | |
2697 | =item EV_ATOMIC_T |
2843 | =item EV_ATOMIC_T |
2698 | |
2844 | |
2699 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2845 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2700 | access is atomic with respect to other threads or signal contexts. No such |
2846 | access is atomic with respect to other threads or signal contexts. No such |
2701 | type is easily found in the C language, so you can provide your own type |
2847 | type is easily found in the C language, so you can provide your own type |
2702 | that you know is safe for your purposes. |
2848 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2849 | as well as for signal and thread safety in C<ev_async> watchers. |
2703 | |
2850 | |
2704 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2851 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2705 | (from F<signal.h>), which is usually good enough on most platforms. |
2852 | (from F<signal.h>), which is usually good enough on most platforms. |
2706 | |
2853 | |
2707 | =item EV_H |
2854 | =item EV_H |
… | |
… | |
2911 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3058 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2912 | |
3059 | |
2913 | That means that changing a timer costs less than removing/adding them |
3060 | That means that changing a timer costs less than removing/adding them |
2914 | as only the relative motion in the event queue has to be paid for. |
3061 | as only the relative motion in the event queue has to be paid for. |
2915 | |
3062 | |
2916 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3063 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2917 | |
3064 | |
2918 | These just add the watcher into an array or at the head of a list. |
3065 | These just add the watcher into an array or at the head of a list. |
2919 | |
3066 | |
2920 | =item Stopping check/prepare/idle watchers: O(1) |
3067 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2921 | |
3068 | |
2922 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3069 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2923 | |
3070 | |
2924 | These watchers are stored in lists then need to be walked to find the |
3071 | These watchers are stored in lists then need to be walked to find the |
2925 | correct watcher to remove. The lists are usually short (you don't usually |
3072 | correct watcher to remove. The lists are usually short (you don't usually |
… | |
… | |
2941 | =item Priority handling: O(number_of_priorities) |
3088 | =item Priority handling: O(number_of_priorities) |
2942 | |
3089 | |
2943 | Priorities are implemented by allocating some space for each |
3090 | Priorities are implemented by allocating some space for each |
2944 | priority. When doing priority-based operations, libev usually has to |
3091 | priority. When doing priority-based operations, libev usually has to |
2945 | linearly search all the priorities, but starting/stopping and activating |
3092 | linearly search all the priorities, but starting/stopping and activating |
2946 | watchers becomes O(1) w.r.t. prioritiy handling. |
3093 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3094 | |
|
|
3095 | =item Sending an ev_async: O(1) |
|
|
3096 | |
|
|
3097 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3098 | |
|
|
3099 | =item Processing signals: O(max_signal_number) |
|
|
3100 | |
|
|
3101 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3102 | calls in the current loop iteration. Checking for async and signal events |
|
|
3103 | involves iterating over all running async watchers or all signal numbers. |
2947 | |
3104 | |
2948 | =back |
3105 | =back |
2949 | |
3106 | |
2950 | |
3107 | |
2951 | =head1 Win32 platform limitations and workarounds |
3108 | =head1 Win32 platform limitations and workarounds |