… | |
… | |
17 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
18 | |
18 | |
19 | // all watcher callbacks have a similar signature |
19 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
20 | // this callback is called when data is readable on stdin |
21 | static void |
21 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
23 | { |
24 | puts ("stdin ready"); |
24 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
25 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
26 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
27 | ev_io_stop (EV_A_ w); |
… | |
… | |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
31 | } |
32 | |
32 | |
33 | // another callback, this time for a time-out |
33 | // another callback, this time for a time-out |
34 | static void |
34 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
36 | { |
37 | puts ("timeout"); |
37 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
38 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
40 | } |
41 | |
41 | |
42 | int |
42 | int |
43 | main (void) |
43 | main (void) |
44 | { |
44 | { |
45 | // use the default event loop unless you have special needs |
45 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
46 | ev_loop *loop = ev_default_loop (0); |
47 | |
47 | |
48 | // 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 |
49 | // this one will watch for stdin to become readable |
50 | 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); |
51 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
103 | Libev is very configurable. In this manual the default (and most common) |
103 | Libev is very configurable. In this manual the default (and most common) |
104 | configuration will be described, which supports multiple event loops. For |
104 | configuration will be described, which supports multiple event loops. For |
105 | more info about various configuration options please have a look at |
105 | more info about various configuration options please have a look at |
106 | B<EMBED> section in this manual. If libev was configured without support |
106 | B<EMBED> section in this manual. If libev was configured without support |
107 | for multiple event loops, then all functions taking an initial argument of |
107 | for multiple event loops, then all functions taking an initial argument of |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
108 | name C<loop> (which is always of type C<ev_loop *>) will not have |
109 | this argument. |
109 | this argument. |
110 | |
110 | |
111 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
112 | |
112 | |
113 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
… | |
… | |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
215 | recommended ones. |
216 | |
216 | |
217 | See the description of C<ev_embed> watchers for more info. |
217 | See the description of C<ev_embed> watchers for more info. |
218 | |
218 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
220 | |
221 | Sets the allocation function to use (the prototype is similar - the |
221 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
223 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
250 | } |
251 | |
251 | |
252 | ... |
252 | ... |
253 | ev_set_allocator (persistent_realloc); |
253 | ev_set_allocator (persistent_realloc); |
254 | |
254 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
256 | |
257 | Set the callback function to call on a retryable system call error (such |
257 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
258 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
259 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
260 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
276 | |
276 | |
277 | =back |
277 | =back |
278 | |
278 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
280 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<ev_loop *>. The library knows two |
282 | types of such loops, the I<default> loop, which supports signals and child |
282 | types of such loops, the I<default> loop, which supports signals and child |
283 | events, and dynamically created loops which do not. |
283 | events, and dynamically created loops which do not. |
284 | |
284 | |
285 | =over 4 |
285 | =over 4 |
286 | |
286 | |
… | |
… | |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
687 | |
687 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
689 | |
689 | |
|
|
690 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
691 | |
690 | =item ev_ref (loop) |
692 | =item ev_ref (loop) |
691 | |
693 | |
692 | =item ev_unref (loop) |
694 | =item ev_unref (loop) |
693 | |
695 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
696 | Ref/unref can be used to add or remove a reference count on the event |
… | |
… | |
708 | respectively). |
710 | respectively). |
709 | |
711 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
712 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
711 | running when nothing else is active. |
713 | running when nothing else is active. |
712 | |
714 | |
713 | struct ev_signal exitsig; |
715 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
716 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
717 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
718 | evf_unref (loop); |
717 | |
719 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
720 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
784 | |
786 | |
785 | A watcher is a structure that you create and register to record your |
787 | A watcher is a structure that you create and register to record your |
786 | interest in some event. For instance, if you want to wait for STDIN to |
788 | interest in some event. For instance, if you want to wait for STDIN to |
787 | become readable, you would create an C<ev_io> watcher for that: |
789 | become readable, you would create an C<ev_io> watcher for that: |
788 | |
790 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
791 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
792 | { |
791 | ev_io_stop (w); |
793 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
794 | ev_unloop (loop, EVUNLOOP_ALL); |
793 | } |
795 | } |
794 | |
796 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
797 | struct ev_loop *loop = ev_default_loop (0); |
796 | struct ev_io stdin_watcher; |
798 | ev_io stdin_watcher; |
797 | ev_init (&stdin_watcher, my_cb); |
799 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
800 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
801 | ev_io_start (loop, &stdin_watcher); |
800 | ev_loop (loop, 0); |
802 | ev_loop (loop, 0); |
801 | |
803 | |
… | |
… | |
892 | =item C<EV_ERROR> |
894 | =item C<EV_ERROR> |
893 | |
895 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
896 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
897 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
898 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
899 | problem. Libev considers these application bugs. |
|
|
900 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
901 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
902 | watcher being stopped. Note that well-written programs should not receive |
|
|
903 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
904 | bug in your program. |
899 | |
905 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
906 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
907 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
908 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
909 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
923 | which rolls both calls into one. |
929 | which rolls both calls into one. |
924 | |
930 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
931 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
932 | (or never started) and there are no pending events outstanding. |
927 | |
933 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
934 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
935 | int revents)>. |
930 | |
936 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
937 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
938 | |
933 | ev_io w; |
939 | ev_io w; |
… | |
… | |
967 | |
973 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
974 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
975 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
976 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
971 | |
977 | |
972 | Stops the given watcher again (if active) and clears the pending |
978 | Stops the given watcher if active, and clears the pending status (whether |
|
|
979 | the watcher was active or not). |
|
|
980 | |
973 | status. It is possible that stopped watchers are pending (for example, |
981 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
982 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
983 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
984 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
985 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
986 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
987 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
988 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
989 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
990 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1064 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1065 | data: |
1058 | |
1066 | |
1059 | struct my_io |
1067 | struct my_io |
1060 | { |
1068 | { |
1061 | struct ev_io io; |
1069 | ev_io io; |
1062 | int otherfd; |
1070 | int otherfd; |
1063 | void *somedata; |
1071 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1072 | struct whatever *mostinteresting; |
1065 | }; |
1073 | }; |
1066 | |
1074 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1077 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1078 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1079 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1080 | can cast it back to your own type: |
1073 | |
1081 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1082 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1083 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1084 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1085 | ... |
1078 | } |
1086 | } |
1079 | |
1087 | |
… | |
… | |
1097 | programmers): |
1105 | programmers): |
1098 | |
1106 | |
1099 | #include <stddef.h> |
1107 | #include <stddef.h> |
1100 | |
1108 | |
1101 | static void |
1109 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1110 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1111 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1112 | struct my_biggy big = (struct my_biggy * |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1113 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1114 | } |
1107 | |
1115 | |
1108 | static void |
1116 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1117 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1118 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1119 | struct my_biggy big = (struct my_biggy * |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1120 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1121 | } |
1114 | |
1122 | |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1257 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1258 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1259 | attempt to read a whole line in the callback. |
1252 | |
1260 | |
1253 | static void |
1261 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1262 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1263 | { |
1256 | ev_io_stop (loop, w); |
1264 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1265 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1266 | } |
1259 | |
1267 | |
1260 | ... |
1268 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1269 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1270 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1271 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1272 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1273 | ev_loop (loop, 0); |
1266 | |
1274 | |
1267 | |
1275 | |
… | |
… | |
1278 | |
1286 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1287 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1288 | passed, but if multiple timers become ready during the same loop iteration |
1281 | then order of execution is undefined. |
1289 | then order of execution is undefined. |
1282 | |
1290 | |
|
|
1291 | =head3 Be smart about timeouts |
|
|
1292 | |
|
|
1293 | Many real-world problems invole some kind of time-out, usually for error |
|
|
1294 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1295 | you want to raise some error after a while. |
|
|
1296 | |
|
|
1297 | Here are some ways on how to handle this problem, from simple and |
|
|
1298 | inefficient to very efficient. |
|
|
1299 | |
|
|
1300 | In the following examples a 60 second activity timeout is assumed - a |
|
|
1301 | timeout that gets reset to 60 seconds each time some data ("a lifesign") |
|
|
1302 | was received. |
|
|
1303 | |
|
|
1304 | =over 4 |
|
|
1305 | |
|
|
1306 | =item 1. Use a timer and stop, reinitialise, start it on activity. |
|
|
1307 | |
|
|
1308 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1309 | start the watcher: |
|
|
1310 | |
|
|
1311 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1312 | ev_timer_start (loop, timer); |
|
|
1313 | |
|
|
1314 | Then, each time there is some activity, C<ev_timer_stop> the timer, |
|
|
1315 | initialise it again, and start it: |
|
|
1316 | |
|
|
1317 | ev_timer_stop (loop, timer); |
|
|
1318 | ev_timer_set (timer, 60., 0.); |
|
|
1319 | ev_timer_start (loop, timer); |
|
|
1320 | |
|
|
1321 | This is relatively simple to implement, but means that each time there |
|
|
1322 | is some activity, libev will first have to remove the timer from it's |
|
|
1323 | internal data strcuture and then add it again. |
|
|
1324 | |
|
|
1325 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1326 | |
|
|
1327 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1328 | C<ev_timer_start>. |
|
|
1329 | |
|
|
1330 | For this, configure an C<ev_timer> with a C<repeat> value of C<60> and |
|
|
1331 | then call C<ev_timer_again> at start and each time you successfully read |
|
|
1332 | or write some data. If you go into an idle state where you do not expect |
|
|
1333 | data to travel on the socket, you can C<ev_timer_stop> the timer, and |
|
|
1334 | C<ev_timer_again> will automatically restart it if need be. |
|
|
1335 | |
|
|
1336 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1337 | altogether and only ever use the C<repeat> value and C<ev_timer_again>. |
|
|
1338 | |
|
|
1339 | At start: |
|
|
1340 | |
|
|
1341 | ev_timer_init (timer, callback, 0., 60.); |
|
|
1342 | ev_timer_again (loop, timer); |
|
|
1343 | |
|
|
1344 | Each time you receive some data: |
|
|
1345 | |
|
|
1346 | ev_timer_again (loop, timer); |
|
|
1347 | |
|
|
1348 | It is even possible to change the time-out on the fly: |
|
|
1349 | |
|
|
1350 | timer->repeat = 30.; |
|
|
1351 | ev_timer_again (loop, timer); |
|
|
1352 | |
|
|
1353 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1354 | you want to modify its timeout value, as libev does not have to completely |
|
|
1355 | remove and re-insert the timer from/into it's internal data structure. |
|
|
1356 | |
|
|
1357 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1358 | |
|
|
1359 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1360 | relatively long compared to the loop iteration time - in our example, |
|
|
1361 | within 60 seconds, there are usually many I/O events with associated |
|
|
1362 | activity resets. |
|
|
1363 | |
|
|
1364 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1365 | but remember the time of last activity, and check for a real timeout only |
|
|
1366 | within the callback: |
|
|
1367 | |
|
|
1368 | ev_tstamp last_activity; // time of last activity |
|
|
1369 | |
|
|
1370 | static void |
|
|
1371 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1372 | { |
|
|
1373 | ev_tstamp now = ev_now (EV_A); |
|
|
1374 | ev_tstamp timeout = last_activity + 60.; |
|
|
1375 | |
|
|
1376 | // if last_activity is older than now - timeout, we did time out |
|
|
1377 | if (timeout < now) |
|
|
1378 | { |
|
|
1379 | // timeout occured, take action |
|
|
1380 | } |
|
|
1381 | else |
|
|
1382 | { |
|
|
1383 | // callback was invoked, but there was some activity, re-arm |
|
|
1384 | // to fire in last_activity + 60. |
|
|
1385 | w->again = timeout - now; |
|
|
1386 | ev_timer_again (EV_A_ w); |
|
|
1387 | } |
|
|
1388 | } |
|
|
1389 | |
|
|
1390 | To summarise the callback: first calculate the real time-out (defined as |
|
|
1391 | "60 seconds after the last activity"), then check if that time has been |
|
|
1392 | reached, which means there was a real timeout. Otherwise the callback was |
|
|
1393 | invoked too early (timeout is in the future), so re-schedule the timer to |
|
|
1394 | fire at that future time. |
|
|
1395 | |
|
|
1396 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1397 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1398 | |
|
|
1399 | This scheme causes more callback invocations (about one every 60 seconds), |
|
|
1400 | but virtually no calls to libev to change the timeout. |
|
|
1401 | |
|
|
1402 | To start the timer, simply intiialise the watcher and C<last_activity>, |
|
|
1403 | then call the callback: |
|
|
1404 | |
|
|
1405 | ev_timer_init (timer, callback); |
|
|
1406 | last_activity = ev_now (loop); |
|
|
1407 | callback (loop, timer, EV_TIMEOUT); |
|
|
1408 | |
|
|
1409 | And when there is some activity, simply remember the time in |
|
|
1410 | C<last_activity>: |
|
|
1411 | |
|
|
1412 | last_actiivty = ev_now (loop); |
|
|
1413 | |
|
|
1414 | This technique is slightly more complex, but in most cases where the |
|
|
1415 | time-out is unlikely to be triggered, much more efficient. |
|
|
1416 | |
|
|
1417 | =back |
|
|
1418 | |
1283 | =head3 The special problem of time updates |
1419 | =head3 The special problem of time updates |
1284 | |
1420 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1421 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1422 | least two system calls): EV therefore updates its idea of the current |
1287 | time only before and after C<ev_loop> collects new events, which causes a |
1423 | time only before and after C<ev_loop> collects new events, which causes a |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
1466 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
1467 | |
1332 | If the timer is repeating, either start it if necessary (with the |
1468 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1469 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
1470 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
1471 | This sounds a bit complicated, see "Be smart about timeouts", above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
1472 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
|
|
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
|
|
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
|
|
1348 | ev_timer_init (timer, callback, 0., 5.); |
|
|
1349 | ev_timer_again (loop, timer); |
|
|
1350 | ... |
|
|
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
|
|
1357 | This is more slightly efficient then stopping/starting the timer each time |
|
|
1358 | you want to modify its timeout value. |
|
|
1359 | |
|
|
1360 | Note, however, that it is often even more efficient to remember the |
|
|
1361 | time of the last activity and let the timer time-out naturally. In the |
|
|
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
1473 | |
1366 | =item ev_tstamp repeat [read-write] |
1474 | =item ev_tstamp repeat [read-write] |
1367 | |
1475 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
1476 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1477 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
1482 | =head3 Examples |
1375 | |
1483 | |
1376 | Example: Create a timer that fires after 60 seconds. |
1484 | Example: Create a timer that fires after 60 seconds. |
1377 | |
1485 | |
1378 | static void |
1486 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1487 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
1488 | { |
1381 | .. one minute over, w is actually stopped right here |
1489 | .. one minute over, w is actually stopped right here |
1382 | } |
1490 | } |
1383 | |
1491 | |
1384 | struct ev_timer mytimer; |
1492 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1493 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
1494 | ev_timer_start (loop, &mytimer); |
1387 | |
1495 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
1496 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
1497 | inactivity. |
1390 | |
1498 | |
1391 | static void |
1499 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1500 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
1501 | { |
1394 | .. ten seconds without any activity |
1502 | .. ten seconds without any activity |
1395 | } |
1503 | } |
1396 | |
1504 | |
1397 | struct ev_timer mytimer; |
1505 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1506 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
1507 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
1508 | ev_loop (loop, 0); |
1401 | |
1509 | |
1402 | // and in some piece of code that gets executed on any "activity": |
1510 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1488 | |
1596 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1597 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1598 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
1599 | only event loop modification you are allowed to do). |
1492 | |
1600 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1601 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
1602 | *w, ev_tstamp now)>, e.g.: |
1495 | |
1603 | |
|
|
1604 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1605 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
1606 | { |
1498 | return now + 60.; |
1607 | return now + 60.; |
1499 | } |
1608 | } |
1500 | |
1609 | |
1501 | It must return the next time to trigger, based on the passed time value |
1610 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1538 | |
1647 | |
1539 | The current interval value. Can be modified any time, but changes only |
1648 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1649 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
1650 | called. |
1542 | |
1651 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1652 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
1653 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
1654 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
1655 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
1656 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
1657 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
1662 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
1663 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
1664 | potentially a lot of jitter, but good long-term stability. |
1556 | |
1665 | |
1557 | static void |
1666 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1667 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1559 | { |
1668 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1669 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
1670 | } |
1562 | |
1671 | |
1563 | struct ev_periodic hourly_tick; |
1672 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1673 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
1674 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
1675 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
1676 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
1677 | |
1569 | #include <math.h> |
1678 | #include <math.h> |
1570 | |
1679 | |
1571 | static ev_tstamp |
1680 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1681 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
1682 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
1683 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
1684 | } |
1576 | |
1685 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1686 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
1687 | |
1579 | Example: Call a callback every hour, starting now: |
1688 | Example: Call a callback every hour, starting now: |
1580 | |
1689 | |
1581 | struct ev_periodic hourly_tick; |
1690 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
1691 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
1692 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
1693 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
1694 | |
1586 | |
1695 | |
… | |
… | |
1625 | |
1734 | |
1626 | =back |
1735 | =back |
1627 | |
1736 | |
1628 | =head3 Examples |
1737 | =head3 Examples |
1629 | |
1738 | |
1630 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1739 | Example: Try to exit cleanly on SIGINT. |
1631 | |
1740 | |
1632 | static void |
1741 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1742 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
1743 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
1744 | ev_unloop (loop, EVUNLOOP_ALL); |
1636 | } |
1745 | } |
1637 | |
1746 | |
1638 | struct ev_signal signal_watcher; |
1747 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1748 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &sigint_cb); |
1749 | ev_signal_start (loop, &signal_watcher); |
1641 | |
1750 | |
1642 | |
1751 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
1752 | =head2 C<ev_child> - watch out for process status changes |
1644 | |
1753 | |
1645 | Child watchers trigger when your process receives a SIGCHLD in response to |
1754 | Child watchers trigger when your process receives a SIGCHLD in response to |
… | |
… | |
1718 | its completion. |
1827 | its completion. |
1719 | |
1828 | |
1720 | ev_child cw; |
1829 | ev_child cw; |
1721 | |
1830 | |
1722 | static void |
1831 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
1832 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
1833 | { |
1725 | ev_child_stop (EV_A_ w); |
1834 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1835 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
1836 | } |
1728 | |
1837 | |
… | |
… | |
1792 | to exchange stat structures with application programs compiled using the |
1901 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
1902 | default compilation environment. |
1794 | |
1903 | |
1795 | =head3 Inotify and Kqueue |
1904 | =head3 Inotify and Kqueue |
1796 | |
1905 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
1906 | When C<inotify (7)> support has been compiled into libev (generally |
|
|
1907 | only available with Linux 2.6.25 or above due to bugs in earlier |
1798 | available with Linux) and present at runtime, it will be used to speed up |
1908 | implementations) and present at runtime, it will be used to speed up |
1799 | change detection where possible. The inotify descriptor will be created lazily |
1909 | change detection where possible. The inotify descriptor will be created |
1800 | when the first C<ev_stat> watcher is being started. |
1910 | lazily when the first C<ev_stat> watcher is being started. |
1801 | |
1911 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1912 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
1913 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
1914 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
1915 | there are many cases where libev has to resort to regular C<stat> polling, |
… | |
… | |
1979 | |
2089 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2090 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2091 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2092 | |
1983 | static void |
2093 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2094 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2095 | { |
1986 | free (w); |
2096 | free (w); |
1987 | // now do something you wanted to do when the program has |
2097 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2098 | // no longer anything immediate to do. |
1989 | } |
2099 | } |
1990 | |
2100 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2101 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2102 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2103 | ev_idle_start (loop, idle_cb); |
1994 | |
2104 | |
1995 | |
2105 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2106 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
… | |
… | |
2077 | |
2187 | |
2078 | static ev_io iow [nfd]; |
2188 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2189 | static ev_timer tw; |
2080 | |
2190 | |
2081 | static void |
2191 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2192 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2193 | { |
2084 | } |
2194 | } |
2085 | |
2195 | |
2086 | // create io watchers for each fd and a timer before blocking |
2196 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2197 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2198 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2199 | { |
2090 | int timeout = 3600000; |
2200 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2201 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2202 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2203 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
… | |
… | |
2108 | } |
2218 | } |
2109 | } |
2219 | } |
2110 | |
2220 | |
2111 | // stop all watchers after blocking |
2221 | // stop all watchers after blocking |
2112 | static void |
2222 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2223 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2224 | { |
2115 | ev_timer_stop (loop, &tw); |
2225 | ev_timer_stop (loop, &tw); |
2116 | |
2226 | |
2117 | for (int i = 0; i < nfd; ++i) |
2227 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2228 | { |
… | |
… | |
2233 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2343 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2234 | but you will also have to stop and restart any C<ev_embed> watchers |
2344 | but you will also have to stop and restart any C<ev_embed> watchers |
2235 | yourself - but you can use a fork watcher to handle this automatically, |
2345 | yourself - but you can use a fork watcher to handle this automatically, |
2236 | and future versions of libev might do just that. |
2346 | and future versions of libev might do just that. |
2237 | |
2347 | |
2238 | Unfortunately, not all backends are embeddable, only the ones returned by |
2348 | Unfortunately, not all backends are embeddable: only the ones returned by |
2239 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2349 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2240 | portable one. |
2350 | portable one. |
2241 | |
2351 | |
2242 | So when you want to use this feature you will always have to be prepared |
2352 | So when you want to use this feature you will always have to be prepared |
2243 | that you cannot get an embeddable loop. The recommended way to get around |
2353 | that you cannot get an embeddable loop. The recommended way to get around |
2244 | this is to have a separate variables for your embeddable loop, try to |
2354 | this is to have a separate variables for your embeddable loop, try to |
2245 | create it, and if that fails, use the normal loop for everything. |
2355 | create it, and if that fails, use the normal loop for everything. |
|
|
2356 | |
|
|
2357 | =head3 C<ev_embed> and fork |
|
|
2358 | |
|
|
2359 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2360 | automatically be applied to the embedded loop as well, so no special |
|
|
2361 | fork handling is required in that case. When the watcher is not running, |
|
|
2362 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2363 | as applicable. |
2246 | |
2364 | |
2247 | =head3 Watcher-Specific Functions and Data Members |
2365 | =head3 Watcher-Specific Functions and Data Members |
2248 | |
2366 | |
2249 | =over 4 |
2367 | =over 4 |
2250 | |
2368 | |
… | |
… | |
2278 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2396 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2279 | used). |
2397 | used). |
2280 | |
2398 | |
2281 | struct ev_loop *loop_hi = ev_default_init (0); |
2399 | struct ev_loop *loop_hi = ev_default_init (0); |
2282 | struct ev_loop *loop_lo = 0; |
2400 | struct ev_loop *loop_lo = 0; |
2283 | struct ev_embed embed; |
2401 | ev_embed embed; |
2284 | |
2402 | |
2285 | // see if there is a chance of getting one that works |
2403 | // see if there is a chance of getting one that works |
2286 | // (remember that a flags value of 0 means autodetection) |
2404 | // (remember that a flags value of 0 means autodetection) |
2287 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2405 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2288 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2406 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2302 | kqueue implementation). Store the kqueue/socket-only event loop in |
2420 | kqueue implementation). Store the kqueue/socket-only event loop in |
2303 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2421 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2304 | |
2422 | |
2305 | struct ev_loop *loop = ev_default_init (0); |
2423 | struct ev_loop *loop = ev_default_init (0); |
2306 | struct ev_loop *loop_socket = 0; |
2424 | struct ev_loop *loop_socket = 0; |
2307 | struct ev_embed embed; |
2425 | ev_embed embed; |
2308 | |
2426 | |
2309 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2427 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2310 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2428 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2311 | { |
2429 | { |
2312 | ev_embed_init (&embed, 0, loop_socket); |
2430 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2368 | is that the author does not know of a simple (or any) algorithm for a |
2486 | is that the author does not know of a simple (or any) algorithm for a |
2369 | multiple-writer-single-reader queue that works in all cases and doesn't |
2487 | multiple-writer-single-reader queue that works in all cases and doesn't |
2370 | need elaborate support such as pthreads. |
2488 | need elaborate support such as pthreads. |
2371 | |
2489 | |
2372 | That means that if you want to queue data, you have to provide your own |
2490 | That means that if you want to queue data, you have to provide your own |
2373 | queue. But at least I can tell you would implement locking around your |
2491 | queue. But at least I can tell you how to implement locking around your |
2374 | queue: |
2492 | queue: |
2375 | |
2493 | |
2376 | =over 4 |
2494 | =over 4 |
2377 | |
2495 | |
2378 | =item queueing from a signal handler context |
2496 | =item queueing from a signal handler context |
2379 | |
2497 | |
2380 | To implement race-free queueing, you simply add to the queue in the signal |
2498 | To implement race-free queueing, you simply add to the queue in the signal |
2381 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
2499 | handler but you block the signal handler in the watcher callback. Here is |
2382 | some fictitious SIGUSR1 handler: |
2500 | an example that does that for some fictitious SIGUSR1 handler: |
2383 | |
2501 | |
2384 | static ev_async mysig; |
2502 | static ev_async mysig; |
2385 | |
2503 | |
2386 | static void |
2504 | static void |
2387 | sigusr1_handler (void) |
2505 | sigusr1_handler (void) |
… | |
… | |
2454 | |
2572 | |
2455 | =item ev_async_init (ev_async *, callback) |
2573 | =item ev_async_init (ev_async *, callback) |
2456 | |
2574 | |
2457 | Initialises and configures the async watcher - it has no parameters of any |
2575 | Initialises and configures the async watcher - it has no parameters of any |
2458 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2576 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2459 | believe me. |
2577 | trust me. |
2460 | |
2578 | |
2461 | =item ev_async_send (loop, ev_async *) |
2579 | =item ev_async_send (loop, ev_async *) |
2462 | |
2580 | |
2463 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2581 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2464 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2582 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2465 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
2583 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2466 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2584 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2467 | section below on what exactly this means). |
2585 | section below on what exactly this means). |
2468 | |
2586 | |
2469 | This call incurs the overhead of a system call only once per loop iteration, |
2587 | This call incurs the overhead of a system call only once per loop iteration, |
2470 | so while the overhead might be noticeable, it doesn't apply to repeated |
2588 | so while the overhead might be noticeable, it doesn't apply to repeated |
… | |
… | |
2494 | =over 4 |
2612 | =over 4 |
2495 | |
2613 | |
2496 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2614 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2497 | |
2615 | |
2498 | This function combines a simple timer and an I/O watcher, calls your |
2616 | This function combines a simple timer and an I/O watcher, calls your |
2499 | callback on whichever event happens first and automatically stop both |
2617 | callback on whichever event happens first and automatically stops both |
2500 | watchers. This is useful if you want to wait for a single event on an fd |
2618 | watchers. This is useful if you want to wait for a single event on an fd |
2501 | or timeout without having to allocate/configure/start/stop/free one or |
2619 | or timeout without having to allocate/configure/start/stop/free one or |
2502 | more watchers yourself. |
2620 | more watchers yourself. |
2503 | |
2621 | |
2504 | If C<fd> is less than 0, then no I/O watcher will be started and events |
2622 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2505 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
2623 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2506 | C<events> set will be created and started. |
2624 | the given C<fd> and C<events> set will be created and started. |
2507 | |
2625 | |
2508 | If C<timeout> is less than 0, then no timeout watcher will be |
2626 | If C<timeout> is less than 0, then no timeout watcher will be |
2509 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2627 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2510 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
2628 | repeat = 0) will be started. C<0> is a valid timeout. |
2511 | dubious value. |
|
|
2512 | |
2629 | |
2513 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2630 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
2514 | passed an C<revents> set like normal event callbacks (a combination of |
2631 | passed an C<revents> set like normal event callbacks (a combination of |
2515 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2632 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
2516 | value passed to C<ev_once>: |
2633 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
2634 | a timeout and an io event at the same time - you probably should give io |
|
|
2635 | events precedence. |
|
|
2636 | |
|
|
2637 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2517 | |
2638 | |
2518 | static void stdin_ready (int revents, void *arg) |
2639 | static void stdin_ready (int revents, void *arg) |
2519 | { |
2640 | { |
|
|
2641 | if (revents & EV_READ) |
|
|
2642 | /* stdin might have data for us, joy! */; |
2520 | if (revents & EV_TIMEOUT) |
2643 | else if (revents & EV_TIMEOUT) |
2521 | /* doh, nothing entered */; |
2644 | /* doh, nothing entered */; |
2522 | else if (revents & EV_READ) |
|
|
2523 | /* stdin might have data for us, joy! */; |
|
|
2524 | } |
2645 | } |
2525 | |
2646 | |
2526 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2647 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2527 | |
2648 | |
2528 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
2649 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
2529 | |
2650 | |
2530 | Feeds the given event set into the event loop, as if the specified event |
2651 | Feeds the given event set into the event loop, as if the specified event |
2531 | had happened for the specified watcher (which must be a pointer to an |
2652 | had happened for the specified watcher (which must be a pointer to an |
2532 | initialised but not necessarily started event watcher). |
2653 | initialised but not necessarily started event watcher). |
2533 | |
2654 | |
2534 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
2655 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
2535 | |
2656 | |
2536 | Feed an event on the given fd, as if a file descriptor backend detected |
2657 | Feed an event on the given fd, as if a file descriptor backend detected |
2537 | the given events it. |
2658 | the given events it. |
2538 | |
2659 | |
2539 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
2660 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
2540 | |
2661 | |
2541 | Feed an event as if the given signal occurred (C<loop> must be the default |
2662 | Feed an event as if the given signal occurred (C<loop> must be the default |
2542 | loop!). |
2663 | loop!). |
2543 | |
2664 | |
2544 | =back |
2665 | =back |
… | |
… | |
2676 | |
2797 | |
2677 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2798 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2678 | |
2799 | |
2679 | See the method-C<set> above for more details. |
2800 | See the method-C<set> above for more details. |
2680 | |
2801 | |
2681 | Example: |
2802 | Example: Use a plain function as callback. |
2682 | |
2803 | |
2683 | static void io_cb (ev::io &w, int revents) { } |
2804 | static void io_cb (ev::io &w, int revents) { } |
2684 | iow.set <io_cb> (); |
2805 | iow.set <io_cb> (); |
2685 | |
2806 | |
2686 | =item w->set (struct ev_loop *) |
2807 | =item w->set (struct ev_loop *) |
… | |
… | |
2724 | Example: Define a class with an IO and idle watcher, start one of them in |
2845 | Example: Define a class with an IO and idle watcher, start one of them in |
2725 | the constructor. |
2846 | the constructor. |
2726 | |
2847 | |
2727 | class myclass |
2848 | class myclass |
2728 | { |
2849 | { |
2729 | ev::io io; void io_cb (ev::io &w, int revents); |
2850 | ev::io io ; void io_cb (ev::io &w, int revents); |
2730 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
2851 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2731 | |
2852 | |
2732 | myclass (int fd) |
2853 | myclass (int fd) |
2733 | { |
2854 | { |
2734 | io .set <myclass, &myclass::io_cb > (this); |
2855 | io .set <myclass, &myclass::io_cb > (this); |
2735 | idle.set <myclass, &myclass::idle_cb> (this); |
2856 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2751 | =item Perl |
2872 | =item Perl |
2752 | |
2873 | |
2753 | The EV module implements the full libev API and is actually used to test |
2874 | The EV module implements the full libev API and is actually used to test |
2754 | libev. EV is developed together with libev. Apart from the EV core module, |
2875 | libev. EV is developed together with libev. Apart from the EV core module, |
2755 | there are additional modules that implement libev-compatible interfaces |
2876 | there are additional modules that implement libev-compatible interfaces |
2756 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
2877 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2757 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
2878 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
2879 | and C<EV::Glib>). |
2758 | |
2880 | |
2759 | It can be found and installed via CPAN, its homepage is at |
2881 | It can be found and installed via CPAN, its homepage is at |
2760 | L<http://software.schmorp.de/pkg/EV>. |
2882 | L<http://software.schmorp.de/pkg/EV>. |
2761 | |
2883 | |
2762 | =item Python |
2884 | =item Python |
… | |
… | |
2941 | |
3063 | |
2942 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3064 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2943 | |
3065 | |
2944 | Libev can be configured via a variety of preprocessor symbols you have to |
3066 | Libev can be configured via a variety of preprocessor symbols you have to |
2945 | define before including any of its files. The default in the absence of |
3067 | define before including any of its files. The default in the absence of |
2946 | autoconf is noted for every option. |
3068 | autoconf is documented for every option. |
2947 | |
3069 | |
2948 | =over 4 |
3070 | =over 4 |
2949 | |
3071 | |
2950 | =item EV_STANDALONE |
3072 | =item EV_STANDALONE |
2951 | |
3073 | |
… | |
… | |
3121 | When doing priority-based operations, libev usually has to linearly search |
3243 | When doing priority-based operations, libev usually has to linearly search |
3122 | all the priorities, so having many of them (hundreds) uses a lot of space |
3244 | all the priorities, so having many of them (hundreds) uses a lot of space |
3123 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3245 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3124 | fine. |
3246 | fine. |
3125 | |
3247 | |
3126 | If your embedding application does not need any priorities, defining these both to |
3248 | If your embedding application does not need any priorities, defining these |
3127 | C<0> will save some memory and CPU. |
3249 | both to C<0> will save some memory and CPU. |
3128 | |
3250 | |
3129 | =item EV_PERIODIC_ENABLE |
3251 | =item EV_PERIODIC_ENABLE |
3130 | |
3252 | |
3131 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3253 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3132 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3254 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
… | |
… | |
3139 | code. |
3261 | code. |
3140 | |
3262 | |
3141 | =item EV_EMBED_ENABLE |
3263 | =item EV_EMBED_ENABLE |
3142 | |
3264 | |
3143 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3265 | If undefined or defined to be C<1>, then embed watchers are supported. If |
3144 | defined to be C<0>, then they are not. |
3266 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3267 | watcher types, which therefore must not be disabled. |
3145 | |
3268 | |
3146 | =item EV_STAT_ENABLE |
3269 | =item EV_STAT_ENABLE |
3147 | |
3270 | |
3148 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3271 | If undefined or defined to be C<1>, then stat watchers are supported. If |
3149 | defined to be C<0>, then they are not. |
3272 | defined to be C<0>, then they are not. |
… | |
… | |
3181 | two). |
3304 | two). |
3182 | |
3305 | |
3183 | =item EV_USE_4HEAP |
3306 | =item EV_USE_4HEAP |
3184 | |
3307 | |
3185 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3308 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3186 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
3309 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3187 | to C<1>. The 4-heap uses more complicated (longer) code but has |
3310 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3188 | noticeably faster performance with many (thousands) of watchers. |
3311 | faster performance with many (thousands) of watchers. |
3189 | |
3312 | |
3190 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3313 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3191 | (disabled). |
3314 | (disabled). |
3192 | |
3315 | |
3193 | =item EV_HEAP_CACHE_AT |
3316 | =item EV_HEAP_CACHE_AT |
3194 | |
3317 | |
3195 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3318 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3196 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
3319 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3197 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3320 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3198 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3321 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3199 | but avoids random read accesses on heap changes. This improves performance |
3322 | but avoids random read accesses on heap changes. This improves performance |
3200 | noticeably with with many (hundreds) of watchers. |
3323 | noticeably with many (hundreds) of watchers. |
3201 | |
3324 | |
3202 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3325 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
3203 | (disabled). |
3326 | (disabled). |
3204 | |
3327 | |
3205 | =item EV_VERIFY |
3328 | =item EV_VERIFY |
… | |
… | |
3211 | called once per loop, which can slow down libev. If set to C<3>, then the |
3334 | called once per loop, which can slow down libev. If set to C<3>, then the |
3212 | verification code will be called very frequently, which will slow down |
3335 | verification code will be called very frequently, which will slow down |
3213 | libev considerably. |
3336 | libev considerably. |
3214 | |
3337 | |
3215 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3338 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
3216 | C<0.> |
3339 | C<0>. |
3217 | |
3340 | |
3218 | =item EV_COMMON |
3341 | =item EV_COMMON |
3219 | |
3342 | |
3220 | By default, all watchers have a C<void *data> member. By redefining |
3343 | By default, all watchers have a C<void *data> member. By redefining |
3221 | this macro to a something else you can include more and other types of |
3344 | this macro to a something else you can include more and other types of |
… | |
… | |
3238 | and the way callbacks are invoked and set. Must expand to a struct member |
3361 | and the way callbacks are invoked and set. Must expand to a struct member |
3239 | definition and a statement, respectively. See the F<ev.h> header file for |
3362 | definition and a statement, respectively. See the F<ev.h> header file for |
3240 | their default definitions. One possible use for overriding these is to |
3363 | their default definitions. One possible use for overriding these is to |
3241 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3364 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3242 | method calls instead of plain function calls in C++. |
3365 | method calls instead of plain function calls in C++. |
|
|
3366 | |
|
|
3367 | =back |
3243 | |
3368 | |
3244 | =head2 EXPORTED API SYMBOLS |
3369 | =head2 EXPORTED API SYMBOLS |
3245 | |
3370 | |
3246 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3371 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3247 | exported symbols, you can use the provided F<Symbol.*> files which list |
3372 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3294 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3419 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3295 | |
3420 | |
3296 | #include "ev_cpp.h" |
3421 | #include "ev_cpp.h" |
3297 | #include "ev.c" |
3422 | #include "ev.c" |
3298 | |
3423 | |
|
|
3424 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3299 | |
3425 | |
3300 | =head1 THREADS AND COROUTINES |
3426 | =head2 THREADS AND COROUTINES |
3301 | |
3427 | |
3302 | =head2 THREADS |
3428 | =head3 THREADS |
3303 | |
3429 | |
3304 | Libev itself is thread-safe (unless the opposite is specifically |
3430 | All libev functions are reentrant and thread-safe unless explicitly |
3305 | documented for a function), but it uses no locking itself. This means that |
3431 | documented otherwise, but libev implements no locking itself. This means |
3306 | you can use as many loops as you want in parallel, as long as only one |
3432 | that you can use as many loops as you want in parallel, as long as there |
3307 | thread ever calls into one libev function with the same loop parameter: |
3433 | are no concurrent calls into any libev function with the same loop |
|
|
3434 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3308 | libev guarentees that different event loops share no data structures that |
3435 | of course): libev guarantees that different event loops share no data |
3309 | need locking. |
3436 | structures that need any locking. |
3310 | |
3437 | |
3311 | Or to put it differently: calls with different loop parameters can be done |
3438 | Or to put it differently: calls with different loop parameters can be done |
3312 | concurrently from multiple threads, calls with the same loop parameter |
3439 | concurrently from multiple threads, calls with the same loop parameter |
3313 | must be done serially (but can be done from different threads, as long as |
3440 | must be done serially (but can be done from different threads, as long as |
3314 | only one thread ever is inside a call at any point in time, e.g. by using |
3441 | only one thread ever is inside a call at any point in time, e.g. by using |
3315 | a mutex per loop). |
3442 | a mutex per loop). |
3316 | |
3443 | |
3317 | Specifically to support threads (and signal handlers), libev implements |
3444 | Specifically to support threads (and signal handlers), libev implements |
3318 | so-called C<ev_async> watchers, which allow some limited form of |
3445 | so-called C<ev_async> watchers, which allow some limited form of |
3319 | concurrency on the same event loop. |
3446 | concurrency on the same event loop, namely waking it up "from the |
|
|
3447 | outside". |
3320 | |
3448 | |
3321 | If you want to know which design (one loop, locking, or multiple loops |
3449 | If you want to know which design (one loop, locking, or multiple loops |
3322 | without or something else still) is best for your problem, then I cannot |
3450 | without or something else still) is best for your problem, then I cannot |
3323 | help you. I can give some generic advice however: |
3451 | help you, but here is some generic advice: |
3324 | |
3452 | |
3325 | =over 4 |
3453 | =over 4 |
3326 | |
3454 | |
3327 | =item * most applications have a main thread: use the default libev loop |
3455 | =item * most applications have a main thread: use the default libev loop |
3328 | in that thread, or create a separate thread running only the default loop. |
3456 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3352 | default loop and triggering an C<ev_async> watcher from the default loop |
3480 | default loop and triggering an C<ev_async> watcher from the default loop |
3353 | watcher callback into the event loop interested in the signal. |
3481 | watcher callback into the event loop interested in the signal. |
3354 | |
3482 | |
3355 | =back |
3483 | =back |
3356 | |
3484 | |
3357 | =head2 COROUTINES |
3485 | =head3 COROUTINES |
3358 | |
3486 | |
3359 | Libev is much more accommodating to coroutines ("cooperative threads"): |
3487 | Libev is very accommodating to coroutines ("cooperative threads"): |
3360 | libev fully supports nesting calls to it's functions from different |
3488 | libev fully supports nesting calls to its functions from different |
3361 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3489 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3362 | different coroutines and switch freely between both coroutines running the |
3490 | different coroutines, and switch freely between both coroutines running the |
3363 | loop, as long as you don't confuse yourself). The only exception is that |
3491 | loop, as long as you don't confuse yourself). The only exception is that |
3364 | you must not do this from C<ev_periodic> reschedule callbacks. |
3492 | you must not do this from C<ev_periodic> reschedule callbacks. |
3365 | |
3493 | |
3366 | Care has been taken to ensure that libev does not keep local state inside |
3494 | Care has been taken to ensure that libev does not keep local state inside |
3367 | C<ev_loop>, and other calls do not usually allow coroutine switches. |
3495 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
|
|
3496 | they do not clal any callbacks. |
3368 | |
3497 | |
|
|
3498 | =head2 COMPILER WARNINGS |
3369 | |
3499 | |
3370 | =head1 COMPLEXITIES |
3500 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3501 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3502 | scared by this. |
3371 | |
3503 | |
3372 | In this section the complexities of (many of) the algorithms used inside |
3504 | However, these are unavoidable for many reasons. For one, each compiler |
3373 | libev will be explained. For complexity discussions about backends see the |
3505 | has different warnings, and each user has different tastes regarding |
3374 | documentation for C<ev_default_init>. |
3506 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3507 | targeting a specific compiler and compiler-version. |
3375 | |
3508 | |
3376 | All of the following are about amortised time: If an array needs to be |
3509 | Another reason is that some compiler warnings require elaborate |
3377 | extended, libev needs to realloc and move the whole array, but this |
3510 | workarounds, or other changes to the code that make it less clear and less |
3378 | happens asymptotically never with higher number of elements, so O(1) might |
3511 | maintainable. |
3379 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3380 | it is much faster and asymptotically approaches constant time. |
|
|
3381 | |
3512 | |
3382 | =over 4 |
3513 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3514 | wrong (because they don't actually warn about the condition their message |
|
|
3515 | seems to warn about). For example, certain older gcc versions had some |
|
|
3516 | warnings that resulted an extreme number of false positives. These have |
|
|
3517 | been fixed, but some people still insist on making code warn-free with |
|
|
3518 | such buggy versions. |
3383 | |
3519 | |
3384 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3520 | While libev is written to generate as few warnings as possible, |
|
|
3521 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
3522 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3523 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3524 | warnings, not errors, or proof of bugs. |
3385 | |
3525 | |
3386 | This means that, when you have a watcher that triggers in one hour and |
|
|
3387 | there are 100 watchers that would trigger before that then inserting will |
|
|
3388 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3389 | |
3526 | |
3390 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3527 | =head2 VALGRIND |
3391 | |
3528 | |
3392 | That means that changing a timer costs less than removing/adding them |
3529 | Valgrind has a special section here because it is a popular tool that is |
3393 | as only the relative motion in the event queue has to be paid for. |
3530 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3394 | |
3531 | |
3395 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3532 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3533 | in libev, then check twice: If valgrind reports something like: |
3396 | |
3534 | |
3397 | These just add the watcher into an array or at the head of a list. |
3535 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3536 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3537 | ==2274== still reachable: 256 bytes in 1 blocks. |
3398 | |
3538 | |
3399 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3539 | Then there is no memory leak, just as memory accounted to global variables |
|
|
3540 | is not a memleak - the memory is still being refernced, and didn't leak. |
3400 | |
3541 | |
3401 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3542 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
3543 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
3544 | although an acceptable workaround has been found here), or it might be |
|
|
3545 | confused. |
3402 | |
3546 | |
3403 | These watchers are stored in lists then need to be walked to find the |
3547 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3404 | correct watcher to remove. The lists are usually short (you don't usually |
3548 | make it into some kind of religion. |
3405 | have many watchers waiting for the same fd or signal). |
|
|
3406 | |
3549 | |
3407 | =item Finding the next timer in each loop iteration: O(1) |
3550 | If you are unsure about something, feel free to contact the mailing list |
|
|
3551 | with the full valgrind report and an explanation on why you think this |
|
|
3552 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
3553 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
3554 | of learning how to interpret valgrind properly. |
3408 | |
3555 | |
3409 | By virtue of using a binary or 4-heap, the next timer is always found at a |
3556 | If you need, for some reason, empty reports from valgrind for your project |
3410 | fixed position in the storage array. |
3557 | I suggest using suppression lists. |
3411 | |
3558 | |
3412 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3413 | |
3559 | |
3414 | A change means an I/O watcher gets started or stopped, which requires |
3560 | =head1 PORTABILITY NOTES |
3415 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3416 | on backend and whether C<ev_io_set> was used). |
|
|
3417 | |
3561 | |
3418 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3419 | |
|
|
3420 | =item Priority handling: O(number_of_priorities) |
|
|
3421 | |
|
|
3422 | Priorities are implemented by allocating some space for each |
|
|
3423 | priority. When doing priority-based operations, libev usually has to |
|
|
3424 | linearly search all the priorities, but starting/stopping and activating |
|
|
3425 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3426 | |
|
|
3427 | =item Sending an ev_async: O(1) |
|
|
3428 | |
|
|
3429 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3430 | |
|
|
3431 | =item Processing signals: O(max_signal_number) |
|
|
3432 | |
|
|
3433 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3434 | calls in the current loop iteration. Checking for async and signal events |
|
|
3435 | involves iterating over all running async watchers or all signal numbers. |
|
|
3436 | |
|
|
3437 | =back |
|
|
3438 | |
|
|
3439 | |
|
|
3440 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3562 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3441 | |
3563 | |
3442 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3564 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3443 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3565 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3444 | model. Libev still offers limited functionality on this platform in |
3566 | model. Libev still offers limited functionality on this platform in |
3445 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3567 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3456 | |
3578 | |
3457 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3579 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3458 | accept large writes: instead of resulting in a partial write, windows will |
3580 | accept large writes: instead of resulting in a partial write, windows will |
3459 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3581 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3460 | so make sure you only write small amounts into your sockets (less than a |
3582 | so make sure you only write small amounts into your sockets (less than a |
3461 | megabyte seems safe, but thsi apparently depends on the amount of memory |
3583 | megabyte seems safe, but this apparently depends on the amount of memory |
3462 | available). |
3584 | available). |
3463 | |
3585 | |
3464 | Due to the many, low, and arbitrary limits on the win32 platform and |
3586 | Due to the many, low, and arbitrary limits on the win32 platform and |
3465 | the abysmal performance of winsockets, using a large number of sockets |
3587 | the abysmal performance of winsockets, using a large number of sockets |
3466 | is not recommended (and not reasonable). If your program needs to use |
3588 | is not recommended (and not reasonable). If your program needs to use |
… | |
… | |
3477 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3599 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3478 | |
3600 | |
3479 | #include "ev.h" |
3601 | #include "ev.h" |
3480 | |
3602 | |
3481 | And compile the following F<evwrap.c> file into your project (make sure |
3603 | And compile the following F<evwrap.c> file into your project (make sure |
3482 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
3604 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3483 | |
3605 | |
3484 | #include "evwrap.h" |
3606 | #include "evwrap.h" |
3485 | #include "ev.c" |
3607 | #include "ev.c" |
3486 | |
3608 | |
3487 | =over 4 |
3609 | =over 4 |
… | |
… | |
3532 | wrap all I/O functions and provide your own fd management, but the cost of |
3654 | wrap all I/O functions and provide your own fd management, but the cost of |
3533 | calling select (O(n²)) will likely make this unworkable. |
3655 | calling select (O(n²)) will likely make this unworkable. |
3534 | |
3656 | |
3535 | =back |
3657 | =back |
3536 | |
3658 | |
3537 | |
|
|
3538 | =head1 PORTABILITY REQUIREMENTS |
3659 | =head2 PORTABILITY REQUIREMENTS |
3539 | |
3660 | |
3540 | In addition to a working ISO-C implementation, libev relies on a few |
3661 | In addition to a working ISO-C implementation and of course the |
3541 | additional extensions: |
3662 | backend-specific APIs, libev relies on a few additional extensions: |
3542 | |
3663 | |
3543 | =over 4 |
3664 | =over 4 |
3544 | |
3665 | |
3545 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3666 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3546 | calling conventions regardless of C<ev_watcher_type *>. |
3667 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3552 | calls them using an C<ev_watcher *> internally. |
3673 | calls them using an C<ev_watcher *> internally. |
3553 | |
3674 | |
3554 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3675 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3555 | |
3676 | |
3556 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3677 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3557 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
3678 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3558 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3679 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3559 | believed to be sufficiently portable. |
3680 | believed to be sufficiently portable. |
3560 | |
3681 | |
3561 | =item C<sigprocmask> must work in a threaded environment |
3682 | =item C<sigprocmask> must work in a threaded environment |
3562 | |
3683 | |
… | |
… | |
3571 | except the initial one, and run the default loop in the initial thread as |
3692 | except the initial one, and run the default loop in the initial thread as |
3572 | well. |
3693 | well. |
3573 | |
3694 | |
3574 | =item C<long> must be large enough for common memory allocation sizes |
3695 | =item C<long> must be large enough for common memory allocation sizes |
3575 | |
3696 | |
3576 | To improve portability and simplify using libev, libev uses C<long> |
3697 | To improve portability and simplify its API, libev uses C<long> internally |
3577 | internally instead of C<size_t> when allocating its data structures. On |
3698 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3578 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
3699 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3579 | is still at least 31 bits everywhere, which is enough for hundreds of |
3700 | least 31 bits everywhere, which is enough for hundreds of millions of |
3580 | millions of watchers. |
3701 | watchers. |
3581 | |
3702 | |
3582 | =item C<double> must hold a time value in seconds with enough accuracy |
3703 | =item C<double> must hold a time value in seconds with enough accuracy |
3583 | |
3704 | |
3584 | The type C<double> is used to represent timestamps. It is required to |
3705 | The type C<double> is used to represent timestamps. It is required to |
3585 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3706 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
… | |
… | |
3589 | =back |
3710 | =back |
3590 | |
3711 | |
3591 | If you know of other additional requirements drop me a note. |
3712 | If you know of other additional requirements drop me a note. |
3592 | |
3713 | |
3593 | |
3714 | |
3594 | =head1 COMPILER WARNINGS |
3715 | =head1 ALGORITHMIC COMPLEXITIES |
3595 | |
3716 | |
3596 | Depending on your compiler and compiler settings, you might get no or a |
3717 | In this section the complexities of (many of) the algorithms used inside |
3597 | lot of warnings when compiling libev code. Some people are apparently |
3718 | libev will be documented. For complexity discussions about backends see |
3598 | scared by this. |
3719 | the documentation for C<ev_default_init>. |
3599 | |
3720 | |
3600 | However, these are unavoidable for many reasons. For one, each compiler |
3721 | All of the following are about amortised time: If an array needs to be |
3601 | has different warnings, and each user has different tastes regarding |
3722 | extended, libev needs to realloc and move the whole array, but this |
3602 | warning options. "Warn-free" code therefore cannot be a goal except when |
3723 | happens asymptotically rarer with higher number of elements, so O(1) might |
3603 | targeting a specific compiler and compiler-version. |
3724 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
3725 | average it is much faster and asymptotically approaches constant time. |
3604 | |
3726 | |
3605 | Another reason is that some compiler warnings require elaborate |
3727 | =over 4 |
3606 | workarounds, or other changes to the code that make it less clear and less |
|
|
3607 | maintainable. |
|
|
3608 | |
3728 | |
3609 | And of course, some compiler warnings are just plain stupid, or simply |
3729 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3610 | wrong (because they don't actually warn about the condition their message |
|
|
3611 | seems to warn about). |
|
|
3612 | |
3730 | |
3613 | While libev is written to generate as few warnings as possible, |
3731 | This means that, when you have a watcher that triggers in one hour and |
3614 | "warn-free" code is not a goal, and it is recommended not to build libev |
3732 | there are 100 watchers that would trigger before that, then inserting will |
3615 | with any compiler warnings enabled unless you are prepared to cope with |
3733 | have to skip roughly seven (C<ld 100>) of these watchers. |
3616 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3617 | warnings, not errors, or proof of bugs. |
|
|
3618 | |
3734 | |
|
|
3735 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3619 | |
3736 | |
3620 | =head1 VALGRIND |
3737 | That means that changing a timer costs less than removing/adding them, |
|
|
3738 | as only the relative motion in the event queue has to be paid for. |
3621 | |
3739 | |
3622 | Valgrind has a special section here because it is a popular tool that is |
3740 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3623 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3624 | |
3741 | |
3625 | If you think you found a bug (memory leak, uninitialised data access etc.) |
3742 | These just add the watcher into an array or at the head of a list. |
3626 | in libev, then check twice: If valgrind reports something like: |
|
|
3627 | |
3743 | |
3628 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3744 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3629 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3630 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3631 | |
3745 | |
3632 | Then there is no memory leak. Similarly, under some circumstances, |
3746 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3633 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3634 | might be confused (it is a very good tool, but only a tool). |
|
|
3635 | |
3747 | |
3636 | If you are unsure about something, feel free to contact the mailing list |
3748 | These watchers are stored in lists, so they need to be walked to find the |
3637 | with the full valgrind report and an explanation on why you think this is |
3749 | correct watcher to remove. The lists are usually short (you don't usually |
3638 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
3750 | have many watchers waiting for the same fd or signal: one is typical, two |
3639 | no bug" answer and take the chance of learning how to interpret valgrind |
3751 | is rare). |
3640 | properly. |
|
|
3641 | |
3752 | |
3642 | If you need, for some reason, empty reports from valgrind for your project |
3753 | =item Finding the next timer in each loop iteration: O(1) |
3643 | I suggest using suppression lists. |
3754 | |
|
|
3755 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
3756 | fixed position in the storage array. |
|
|
3757 | |
|
|
3758 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3759 | |
|
|
3760 | A change means an I/O watcher gets started or stopped, which requires |
|
|
3761 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3762 | on backend and whether C<ev_io_set> was used). |
|
|
3763 | |
|
|
3764 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3765 | |
|
|
3766 | =item Priority handling: O(number_of_priorities) |
|
|
3767 | |
|
|
3768 | Priorities are implemented by allocating some space for each |
|
|
3769 | priority. When doing priority-based operations, libev usually has to |
|
|
3770 | linearly search all the priorities, but starting/stopping and activating |
|
|
3771 | watchers becomes O(1) with respect to priority handling. |
|
|
3772 | |
|
|
3773 | =item Sending an ev_async: O(1) |
|
|
3774 | |
|
|
3775 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3776 | |
|
|
3777 | =item Processing signals: O(max_signal_number) |
|
|
3778 | |
|
|
3779 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3780 | calls in the current loop iteration. Checking for async and signal events |
|
|
3781 | involves iterating over all running async watchers or all signal numbers. |
|
|
3782 | |
|
|
3783 | =back |
3644 | |
3784 | |
3645 | |
3785 | |
3646 | =head1 AUTHOR |
3786 | =head1 AUTHOR |
3647 | |
3787 | |
3648 | Marc Lehmann <libev@schmorp.de>. |
3788 | Marc Lehmann <libev@schmorp.de>. |