… | |
… | |
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 |
… | |
… | |
241 | |
256 | |
242 | An event loop is described by a C<struct ev_loop *>. The library knows two |
257 | An event loop is described by a C<struct ev_loop *>. The library knows two |
243 | types of such loops, the I<default> loop, which supports signals and child |
258 | types of such loops, the I<default> loop, which supports signals and child |
244 | events, and dynamically created loops which do not. |
259 | events, and dynamically created loops which do not. |
245 | |
260 | |
246 | If you use threads, a common model is to run the default event loop |
|
|
247 | in your main thread (or in a separate thread) and for each thread you |
|
|
248 | create, you also create another event loop. Libev itself does no locking |
|
|
249 | whatsoever, so if you mix calls to the same event loop in different |
|
|
250 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
251 | done correctly, because it's hideous and inefficient). |
|
|
252 | |
|
|
253 | =over 4 |
261 | =over 4 |
254 | |
262 | |
255 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
263 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
256 | |
264 | |
257 | This will initialise the default event loop if it hasn't been initialised |
265 | This will initialise the default event loop if it hasn't been initialised |
… | |
… | |
259 | false. If it already was initialised it simply returns it (and ignores the |
267 | false. If it already was initialised it simply returns it (and ignores the |
260 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
268 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
261 | |
269 | |
262 | If you don't know what event loop to use, use the one returned from this |
270 | If you don't know what event loop to use, use the one returned from this |
263 | function. |
271 | function. |
|
|
272 | |
|
|
273 | Note that this function is I<not> thread-safe, so if you want to use it |
|
|
274 | from multiple threads, you have to lock (note also that this is unlikely, |
|
|
275 | as loops cannot bes hared easily between threads anyway). |
264 | |
276 | |
265 | The default loop is the only loop that can handle C<ev_signal> and |
277 | 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 |
278 | 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 |
279 | 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 |
280 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
297 | enabling this flag. |
309 | enabling this flag. |
298 | |
310 | |
299 | This works by calling C<getpid ()> on every iteration of the loop, |
311 | 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 |
312 | 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 |
313 | 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 |
314 | 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 |
315 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
304 | C<pthread_atfork> which is even faster). |
316 | C<pthread_atfork> which is even faster). |
305 | |
317 | |
306 | The big advantage of this flag is that you can forget about fork (and |
318 | 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 |
319 | forget about forgetting to tell libev about forking) when you use this |
308 | flag. |
320 | flag. |
… | |
… | |
339 | For few fds, this backend is a bit little slower than poll and select, |
351 | For few fds, this backend is a bit little slower than poll and select, |
340 | but it scales phenomenally better. While poll and select usually scale |
352 | but it scales phenomenally better. While poll and select usually scale |
341 | like O(total_fds) where n is the total number of fds (or the highest fd), |
353 | like O(total_fds) where n is the total number of fds (or the highest fd), |
342 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
354 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
343 | of shortcomings, such as silently dropping events in some hard-to-detect |
355 | of shortcomings, such as silently dropping events in some hard-to-detect |
344 | cases and rewiring a syscall per fd change, no fork support and bad |
356 | cases and requiring a syscall per fd change, no fork support and bad |
345 | support for dup. |
357 | support for dup. |
346 | |
358 | |
347 | While stopping, setting and starting an I/O watcher in the same iteration |
359 | While stopping, setting and starting an I/O watcher in the same iteration |
348 | will result in some caching, there is still a syscall per such incident |
360 | will result in some caching, there is still a syscall per such incident |
349 | (because the fd could point to a different file description now), so its |
361 | (because the fd could point to a different file description now), so its |
… | |
… | |
451 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
463 | 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 |
464 | 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 |
465 | 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). |
466 | undefined behaviour (or a failed assertion if assertions are enabled). |
455 | |
467 | |
|
|
468 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
469 | libev with threads is indeed to create one loop per thread, and using the |
|
|
470 | default loop in the "main" or "initial" thread. |
|
|
471 | |
456 | Example: Try to create a event loop that uses epoll and nothing else. |
472 | Example: Try to create a event loop that uses epoll and nothing else. |
457 | |
473 | |
458 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
474 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
459 | if (!epoller) |
475 | if (!epoller) |
460 | fatal ("no epoll found here, maybe it hides under your chair"); |
476 | fatal ("no epoll found here, maybe it hides under your chair"); |
… | |
… | |
505 | =item ev_loop_fork (loop) |
521 | =item ev_loop_fork (loop) |
506 | |
522 | |
507 | Like C<ev_default_fork>, but acts on an event loop created by |
523 | 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 |
524 | 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. |
525 | after fork, and how you do this is entirely your own problem. |
|
|
526 | |
|
|
527 | =item int ev_is_default_loop (loop) |
|
|
528 | |
|
|
529 | Returns true when the given loop actually is the default loop, false otherwise. |
510 | |
530 | |
511 | =item unsigned int ev_loop_count (loop) |
531 | =item unsigned int ev_loop_count (loop) |
512 | |
532 | |
513 | Returns the count of loop iterations for the loop, which is identical to |
533 | 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 |
534 | 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 |
1086 | 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, |
1087 | 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 |
1088 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1069 | C<EVBACKEND_POLL>. |
1089 | C<EVBACKEND_POLL>. |
1070 | |
1090 | |
|
|
1091 | =head3 The special problem of SIGPIPE |
|
|
1092 | |
|
|
1093 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1094 | when reading from a pipe whose other end has been closed, your program |
|
|
1095 | gets send a SIGPIPE, which, by default, aborts your program. For most |
|
|
1096 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1097 | undesirable. |
|
|
1098 | |
|
|
1099 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1100 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1101 | somewhere, as that would have given you a big clue). |
|
|
1102 | |
1071 | |
1103 | |
1072 | =head3 Watcher-Specific Functions |
1104 | =head3 Watcher-Specific Functions |
1073 | |
1105 | |
1074 | =over 4 |
1106 | =over 4 |
1075 | |
1107 | |
… | |
… | |
1152 | configure a timer to trigger every 10 seconds, then it will trigger at |
1184 | 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 |
1185 | 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 |
1186 | 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. |
1187 | timer will not fire more than once per event loop iteration. |
1156 | |
1188 | |
1157 | =item ev_timer_again (loop) |
1189 | =item ev_timer_again (loop, ev_timer *) |
1158 | |
1190 | |
1159 | This will act as if the timer timed out and restart it again if it is |
1191 | This will act as if the timer timed out and restart it again if it is |
1160 | repeating. The exact semantics are: |
1192 | repeating. The exact semantics are: |
1161 | |
1193 | |
1162 | If the timer is pending, its pending status is cleared. |
1194 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1271 | In this configuration the watcher triggers an event at the wallclock time |
1303 | 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, |
1304 | 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 |
1305 | 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. |
1306 | system time reaches or surpasses this time. |
1275 | |
1307 | |
1276 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1308 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1277 | |
1309 | |
1278 | In this mode the watcher will always be scheduled to time out at the next |
1310 | 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) |
1311 | C<at + N * interval> time (for some integer N, which can also be negative) |
1280 | and then repeat, regardless of any time jumps. |
1312 | and then repeat, regardless of any time jumps. |
1281 | |
1313 | |
… | |
… | |
1415 | with the kernel (thus it coexists with your own signal handlers as long |
1447 | 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 |
1448 | 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 |
1449 | watcher for a signal is stopped libev will reset the signal handler to |
1418 | SIG_DFL (regardless of what it was set to before). |
1450 | SIG_DFL (regardless of what it was set to before). |
1419 | |
1451 | |
|
|
1452 | If possible and supported, libev will install its handlers with |
|
|
1453 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1454 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1455 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1456 | them in an C<ev_prepare> watcher. |
|
|
1457 | |
1420 | =head3 Watcher-Specific Functions and Data Members |
1458 | =head3 Watcher-Specific Functions and Data Members |
1421 | |
1459 | |
1422 | =over 4 |
1460 | =over 4 |
1423 | |
1461 | |
1424 | =item ev_signal_init (ev_signal *, callback, int signum) |
1462 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1432 | |
1470 | |
1433 | The signal the watcher watches out for. |
1471 | The signal the watcher watches out for. |
1434 | |
1472 | |
1435 | =back |
1473 | =back |
1436 | |
1474 | |
|
|
1475 | =head3 Examples |
|
|
1476 | |
|
|
1477 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1478 | |
|
|
1479 | static void |
|
|
1480 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1481 | { |
|
|
1482 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1483 | } |
|
|
1484 | |
|
|
1485 | struct ev_signal signal_watcher; |
|
|
1486 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1487 | ev_signal_start (loop, &sigint_cb); |
|
|
1488 | |
1437 | |
1489 | |
1438 | =head2 C<ev_child> - watch out for process status changes |
1490 | =head2 C<ev_child> - watch out for process status changes |
1439 | |
1491 | |
1440 | Child watchers trigger when your process receives a SIGCHLD in response to |
1492 | 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). |
1493 | some child status changes (most typically when a child of yours dies). It |
|
|
1494 | is permissible to install a child watcher I<after> the child has been |
|
|
1495 | forked (which implies it might have already exited), as long as the event |
|
|
1496 | loop isn't entered (or is continued from a watcher). |
|
|
1497 | |
|
|
1498 | Only the default event loop is capable of handling signals, and therefore |
|
|
1499 | you can only rgeister child watchers in the default event loop. |
|
|
1500 | |
|
|
1501 | =head3 Process Interaction |
|
|
1502 | |
|
|
1503 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1504 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1505 | the first child watcher is started after the child exits. The occurance |
|
|
1506 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1507 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1508 | children, even ones not watched. |
|
|
1509 | |
|
|
1510 | =head3 Overriding the Built-In Processing |
|
|
1511 | |
|
|
1512 | Libev offers no special support for overriding the built-in child |
|
|
1513 | processing, but if your application collides with libev's default child |
|
|
1514 | handler, you can override it easily by installing your own handler for |
|
|
1515 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1516 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1517 | event-based approach to child reaping and thus use libev's support for |
|
|
1518 | that, so other libev users can use C<ev_child> watchers freely. |
1442 | |
1519 | |
1443 | =head3 Watcher-Specific Functions and Data Members |
1520 | =head3 Watcher-Specific Functions and Data Members |
1444 | |
1521 | |
1445 | =over 4 |
1522 | =over 4 |
1446 | |
1523 | |
… | |
… | |
1472 | |
1549 | |
1473 | =back |
1550 | =back |
1474 | |
1551 | |
1475 | =head3 Examples |
1552 | =head3 Examples |
1476 | |
1553 | |
1477 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1554 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1555 | its completion. |
|
|
1556 | |
|
|
1557 | ev_child cw; |
1478 | |
1558 | |
1479 | static void |
1559 | static void |
1480 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1560 | child_cb (EV_P_ struct ev_child *w, int revents) |
1481 | { |
1561 | { |
1482 | ev_unloop (loop, EVUNLOOP_ALL); |
1562 | ev_child_stop (EV_A_ w); |
|
|
1563 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1483 | } |
1564 | } |
1484 | |
1565 | |
1485 | struct ev_signal signal_watcher; |
1566 | pid_t pid = fork (); |
1486 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1567 | |
1487 | ev_signal_start (loop, &sigint_cb); |
1568 | if (pid < 0) |
|
|
1569 | // error |
|
|
1570 | else if (pid == 0) |
|
|
1571 | { |
|
|
1572 | // the forked child executes here |
|
|
1573 | exit (1); |
|
|
1574 | } |
|
|
1575 | else |
|
|
1576 | { |
|
|
1577 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1578 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1579 | } |
1488 | |
1580 | |
1489 | |
1581 | |
1490 | =head2 C<ev_stat> - did the file attributes just change? |
1582 | =head2 C<ev_stat> - did the file attributes just change? |
1491 | |
1583 | |
1492 | This watches a filesystem path for attribute changes. That is, it calls |
1584 | 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 |
1613 | 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 |
1614 | 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 |
1615 | usually detected immediately, and if the file exists there will be no |
1524 | polling. |
1616 | polling. |
1525 | |
1617 | |
|
|
1618 | =head3 ABI Issues (Largefile Support) |
|
|
1619 | |
|
|
1620 | Libev by default (unless the user overrides this) uses the default |
|
|
1621 | compilation environment, which means that on systems with optionally |
|
|
1622 | disabled large file support, you get the 32 bit version of the stat |
|
|
1623 | structure. When using the library from programs that change the ABI to |
|
|
1624 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1625 | compile libev with the same flags to get binary compatibility. This is |
|
|
1626 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1627 | most noticably with ev_stat and largefile support. |
|
|
1628 | |
1526 | =head3 Inotify |
1629 | =head3 Inotify |
1527 | |
1630 | |
1528 | When C<inotify (7)> support has been compiled into libev (generally only |
1631 | 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 |
1632 | 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 |
1633 | change detection where possible. The inotify descriptor will be created lazily |
… | |
… | |
1572 | |
1675 | |
1573 | The callback will be receive C<EV_STAT> when a change was detected, |
1676 | 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 |
1677 | relative to the attributes at the time the watcher was started (or the |
1575 | last change was detected). |
1678 | last change was detected). |
1576 | |
1679 | |
1577 | =item ev_stat_stat (ev_stat *) |
1680 | =item ev_stat_stat (loop, ev_stat *) |
1578 | |
1681 | |
1579 | Updates the stat buffer immediately with new values. If you change the |
1682 | 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 |
1683 | watched path in your callback, you could call this fucntion to avoid |
1581 | detecting this change (while introducing a race condition). Can also be |
1684 | detecting this change (while introducing a race condition). Can also be |
1582 | useful simply to find out the new values. |
1685 | useful simply to find out the new values. |
… | |
… | |
2078 | is that the author does not know of a simple (or any) algorithm for a |
2181 | 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 |
2182 | multiple-writer-single-reader queue that works in all cases and doesn't |
2080 | need elaborate support such as pthreads. |
2183 | need elaborate support such as pthreads. |
2081 | |
2184 | |
2082 | That means that if you want to queue data, you have to provide your own |
2185 | 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: |
2186 | queue. But at least I can tell you would implement locking around your |
|
|
2187 | queue: |
2084 | |
2188 | |
2085 | =over 4 |
2189 | =over 4 |
2086 | |
2190 | |
2087 | =item queueing from a signal handler context |
2191 | =item queueing from a signal handler context |
2088 | |
2192 | |
… | |
… | |
2097 | { |
2201 | { |
2098 | sometype data; |
2202 | sometype data; |
2099 | |
2203 | |
2100 | // no locking etc. |
2204 | // no locking etc. |
2101 | queue_put (data); |
2205 | queue_put (data); |
2102 | ev_async_send (DEFAULT_ &mysig); |
2206 | ev_async_send (EV_DEFAULT_ &mysig); |
2103 | } |
2207 | } |
2104 | |
2208 | |
2105 | static void |
2209 | static void |
2106 | mysig_cb (EV_P_ ev_async *w, int revents) |
2210 | mysig_cb (EV_P_ ev_async *w, int revents) |
2107 | { |
2211 | { |
… | |
… | |
2125 | |
2229 | |
2126 | =item queueing from a thread context |
2230 | =item queueing from a thread context |
2127 | |
2231 | |
2128 | The strategy for threads is different, as you cannot (easily) block |
2232 | 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 |
2233 | 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: |
2234 | employ a traditional mutex lock, such as in this pthread example: |
2131 | |
2235 | |
2132 | static ev_async mysig; |
2236 | static ev_async mysig; |
2133 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2237 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2134 | |
2238 | |
2135 | static void |
2239 | static void |
… | |
… | |
2138 | // only need to lock the actual queueing operation |
2242 | // only need to lock the actual queueing operation |
2139 | pthread_mutex_lock (&mymutex); |
2243 | pthread_mutex_lock (&mymutex); |
2140 | queue_put (data); |
2244 | queue_put (data); |
2141 | pthread_mutex_unlock (&mymutex); |
2245 | pthread_mutex_unlock (&mymutex); |
2142 | |
2246 | |
2143 | ev_async_send (DEFAULT_ &mysig); |
2247 | ev_async_send (EV_DEFAULT_ &mysig); |
2144 | } |
2248 | } |
2145 | |
2249 | |
2146 | static void |
2250 | static void |
2147 | mysig_cb (EV_P_ ev_async *w, int revents) |
2251 | mysig_cb (EV_P_ ev_async *w, int revents) |
2148 | { |
2252 | { |
… | |
… | |
2176 | section below on what exactly this means). |
2280 | section below on what exactly this means). |
2177 | |
2281 | |
2178 | This call incurs the overhead of a syscall only once per loop iteration, |
2282 | This call incurs the overhead of a syscall only once per loop iteration, |
2179 | so while the overhead might be noticable, it doesn't apply to repeated |
2283 | so while the overhead might be noticable, it doesn't apply to repeated |
2180 | calls to C<ev_async_send>. |
2284 | calls to C<ev_async_send>. |
|
|
2285 | |
|
|
2286 | =item bool = ev_async_pending (ev_async *) |
|
|
2287 | |
|
|
2288 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2289 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2290 | event loop. |
|
|
2291 | |
|
|
2292 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2293 | the loop iterates next and checks for the watcher to have become active, |
|
|
2294 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2295 | quickly check wether invoking the loop might be a good idea. |
|
|
2296 | |
|
|
2297 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2298 | wether it has been requested to make this watcher pending. |
2181 | |
2299 | |
2182 | =back |
2300 | =back |
2183 | |
2301 | |
2184 | |
2302 | |
2185 | =head1 OTHER FUNCTIONS |
2303 | =head1 OTHER FUNCTIONS |
… | |
… | |
2429 | io.start (fd, ev::READ); |
2547 | io.start (fd, ev::READ); |
2430 | } |
2548 | } |
2431 | }; |
2549 | }; |
2432 | |
2550 | |
2433 | |
2551 | |
|
|
2552 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2553 | |
|
|
2554 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2555 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2556 | any interesting language binding in addition to the ones listed here, drop |
|
|
2557 | me a note. |
|
|
2558 | |
|
|
2559 | =over 4 |
|
|
2560 | |
|
|
2561 | =item Perl |
|
|
2562 | |
|
|
2563 | The EV module implements the full libev API and is actually used to test |
|
|
2564 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2565 | there are additional modules that implement libev-compatible interfaces |
|
|
2566 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2567 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2568 | |
|
|
2569 | It can be found and installed via CPAN, its homepage is found at |
|
|
2570 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2571 | |
|
|
2572 | =item Ruby |
|
|
2573 | |
|
|
2574 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2575 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2576 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2577 | L<http://rev.rubyforge.org/>. |
|
|
2578 | |
|
|
2579 | =item D |
|
|
2580 | |
|
|
2581 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2582 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2583 | |
|
|
2584 | =back |
|
|
2585 | |
|
|
2586 | |
2434 | =head1 MACRO MAGIC |
2587 | =head1 MACRO MAGIC |
2435 | |
2588 | |
2436 | Libev can be compiled with a variety of options, the most fundamantal |
2589 | Libev can be compiled with a variety of options, the most fundamantal |
2437 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2590 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2438 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2591 | functions and callbacks have an initial C<struct ev_loop *> argument. |
… | |
… | |
2472 | |
2625 | |
2473 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2626 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2474 | |
2627 | |
2475 | Similar to the other two macros, this gives you the value of the default |
2628 | Similar to the other two macros, this gives you the value of the default |
2476 | loop, if multiple loops are supported ("ev loop default"). |
2629 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2630 | |
|
|
2631 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2632 | |
|
|
2633 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2634 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2635 | is undefined when the default loop has not been initialised by a previous |
|
|
2636 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2637 | |
|
|
2638 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2639 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2477 | |
2640 | |
2478 | =back |
2641 | =back |
2479 | |
2642 | |
2480 | Example: Declare and initialise a check watcher, utilising the above |
2643 | Example: Declare and initialise a check watcher, utilising the above |
2481 | macros so it will work regardless of whether multiple loops are supported |
2644 | macros so it will work regardless of whether multiple loops are supported |
… | |
… | |
2577 | |
2740 | |
2578 | libev.m4 |
2741 | libev.m4 |
2579 | |
2742 | |
2580 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2743 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2581 | |
2744 | |
2582 | Libev can be configured via a variety of preprocessor symbols you have to define |
2745 | Libev can be configured via a variety of preprocessor symbols you have to |
2583 | before including any of its files. The default is not to build for multiplicity |
2746 | define before including any of its files. The default in the absense of |
2584 | and only include the select backend. |
2747 | autoconf is noted for every option. |
2585 | |
2748 | |
2586 | =over 4 |
2749 | =over 4 |
2587 | |
2750 | |
2588 | =item EV_STANDALONE |
2751 | =item EV_STANDALONE |
2589 | |
2752 | |
… | |
… | |
2615 | =item EV_USE_NANOSLEEP |
2778 | =item EV_USE_NANOSLEEP |
2616 | |
2779 | |
2617 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2780 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2618 | and will use it for delays. Otherwise it will use C<select ()>. |
2781 | and will use it for delays. Otherwise it will use C<select ()>. |
2619 | |
2782 | |
|
|
2783 | =item EV_USE_EVENTFD |
|
|
2784 | |
|
|
2785 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2786 | available and will probe for kernel support at runtime. This will improve |
|
|
2787 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2788 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2789 | 2.7 or newer, otherwise disabled. |
|
|
2790 | |
2620 | =item EV_USE_SELECT |
2791 | =item EV_USE_SELECT |
2621 | |
2792 | |
2622 | If undefined or defined to be C<1>, libev will compile in support for the |
2793 | If undefined or defined to be C<1>, libev will compile in support for the |
2623 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2794 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2624 | other method takes over, select will be it. Otherwise the select backend |
2795 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2660 | |
2831 | |
2661 | =item EV_USE_EPOLL |
2832 | =item EV_USE_EPOLL |
2662 | |
2833 | |
2663 | If defined to be C<1>, libev will compile in support for the Linux |
2834 | If defined to be C<1>, libev will compile in support for the Linux |
2664 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2835 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2665 | otherwise another method will be used as fallback. This is the |
2836 | otherwise another method will be used as fallback. This is the preferred |
2666 | preferred backend for GNU/Linux systems. |
2837 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2838 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2667 | |
2839 | |
2668 | =item EV_USE_KQUEUE |
2840 | =item EV_USE_KQUEUE |
2669 | |
2841 | |
2670 | If defined to be C<1>, libev will compile in support for the BSD style |
2842 | If defined to be C<1>, libev will compile in support for the BSD style |
2671 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2843 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2690 | |
2862 | |
2691 | =item EV_USE_INOTIFY |
2863 | =item EV_USE_INOTIFY |
2692 | |
2864 | |
2693 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2865 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2694 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2866 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2695 | be detected at runtime. |
2867 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2868 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2696 | |
2869 | |
2697 | =item EV_ATOMIC_T |
2870 | =item EV_ATOMIC_T |
2698 | |
2871 | |
2699 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2872 | 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 type |
2873 | access is atomic with respect to other threads or signal contexts. No such |
2701 | is easily found using, so you cna provide your own type that you know is safe. |
2874 | type is easily found in the C language, so you can provide your own type |
|
|
2875 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2876 | as well as for signal and thread safety in C<ev_async> watchers. |
2702 | |
2877 | |
2703 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2878 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2704 | from F<signal.h>, which is usually good enough on most platforms. |
2879 | (from F<signal.h>), which is usually good enough on most platforms. |
2705 | |
2880 | |
2706 | =item EV_H |
2881 | =item EV_H |
2707 | |
2882 | |
2708 | The name of the F<ev.h> header file used to include it. The default if |
2883 | The name of the F<ev.h> header file used to include it. The default if |
2709 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2884 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
2885 | |
3060 | |
2886 | #include "ev_cpp.h" |
3061 | #include "ev_cpp.h" |
2887 | #include "ev.c" |
3062 | #include "ev.c" |
2888 | |
3063 | |
2889 | |
3064 | |
|
|
3065 | =head1 THREADS AND COROUTINES |
|
|
3066 | |
|
|
3067 | =head2 THREADS |
|
|
3068 | |
|
|
3069 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3070 | means that you can use as many loops as you want in parallel, as long as |
|
|
3071 | only one thread ever calls into one libev function with the same loop |
|
|
3072 | parameter. |
|
|
3073 | |
|
|
3074 | Or put differently: calls with different loop parameters can be done in |
|
|
3075 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3076 | done serially (but can be done from different threads, as long as only one |
|
|
3077 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3078 | per loop). |
|
|
3079 | |
|
|
3080 | If you want to know which design is best for your problem, then I cannot |
|
|
3081 | help you but by giving some generic advice: |
|
|
3082 | |
|
|
3083 | =over 4 |
|
|
3084 | |
|
|
3085 | =item * most applications have a main thread: use the default libev loop |
|
|
3086 | in that thread, or create a seperate thread running only the default loop. |
|
|
3087 | |
|
|
3088 | This helps integrating other libraries or software modules that use libev |
|
|
3089 | themselves and don't care/know about threading. |
|
|
3090 | |
|
|
3091 | =item * one loop per thread is usually a good model. |
|
|
3092 | |
|
|
3093 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3094 | exists, but it is always a good start. |
|
|
3095 | |
|
|
3096 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3097 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3098 | |
|
|
3099 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3100 | better than you currently do :-) |
|
|
3101 | |
|
|
3102 | =item * often you need to talk to some other thread which blocks in the |
|
|
3103 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3104 | threads safely (or from signal contexts...). |
|
|
3105 | |
|
|
3106 | =back |
|
|
3107 | |
|
|
3108 | =head2 COROUTINES |
|
|
3109 | |
|
|
3110 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3111 | libev fully supports nesting calls to it's functions from different |
|
|
3112 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3113 | different coroutines and switch freely between both coroutines running the |
|
|
3114 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3115 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3116 | |
|
|
3117 | Care has been invested into making sure that libev does not keep local |
|
|
3118 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3119 | switches. |
|
|
3120 | |
|
|
3121 | |
2890 | =head1 COMPLEXITIES |
3122 | =head1 COMPLEXITIES |
2891 | |
3123 | |
2892 | In this section the complexities of (many of) the algorithms used inside |
3124 | In this section the complexities of (many of) the algorithms used inside |
2893 | libev will be explained. For complexity discussions about backends see the |
3125 | libev will be explained. For complexity discussions about backends see the |
2894 | documentation for C<ev_default_init>. |
3126 | documentation for C<ev_default_init>. |
… | |
… | |
2910 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3142 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2911 | |
3143 | |
2912 | That means that changing a timer costs less than removing/adding them |
3144 | That means that changing a timer costs less than removing/adding them |
2913 | as only the relative motion in the event queue has to be paid for. |
3145 | as only the relative motion in the event queue has to be paid for. |
2914 | |
3146 | |
2915 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3147 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2916 | |
3148 | |
2917 | These just add the watcher into an array or at the head of a list. |
3149 | These just add the watcher into an array or at the head of a list. |
2918 | |
3150 | |
2919 | =item Stopping check/prepare/idle watchers: O(1) |
3151 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2920 | |
3152 | |
2921 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3153 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2922 | |
3154 | |
2923 | These watchers are stored in lists then need to be walked to find the |
3155 | These watchers are stored in lists then need to be walked to find the |
2924 | correct watcher to remove. The lists are usually short (you don't usually |
3156 | correct watcher to remove. The lists are usually short (you don't usually |
… | |
… | |
2940 | =item Priority handling: O(number_of_priorities) |
3172 | =item Priority handling: O(number_of_priorities) |
2941 | |
3173 | |
2942 | Priorities are implemented by allocating some space for each |
3174 | Priorities are implemented by allocating some space for each |
2943 | priority. When doing priority-based operations, libev usually has to |
3175 | priority. When doing priority-based operations, libev usually has to |
2944 | linearly search all the priorities, but starting/stopping and activating |
3176 | linearly search all the priorities, but starting/stopping and activating |
2945 | watchers becomes O(1) w.r.t. prioritiy handling. |
3177 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3178 | |
|
|
3179 | =item Sending an ev_async: O(1) |
|
|
3180 | |
|
|
3181 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3182 | |
|
|
3183 | =item Processing signals: O(max_signal_number) |
|
|
3184 | |
|
|
3185 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3186 | calls in the current loop iteration. Checking for async and signal events |
|
|
3187 | involves iterating over all running async watchers or all signal numbers. |
2946 | |
3188 | |
2947 | =back |
3189 | =back |
2948 | |
3190 | |
2949 | |
3191 | |
2950 | =head1 Win32 platform limitations and workarounds |
3192 | =head1 Win32 platform limitations and workarounds |