… | |
… | |
265 | |
265 | |
266 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
268 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
269 | |
269 | |
|
|
270 | Example: The following is the C<realloc> function that libev itself uses |
|
|
271 | which should work with C<realloc> and C<free> functions of all kinds and |
|
|
272 | is probably a good basis for your own implementation. |
|
|
273 | |
|
|
274 | static void * |
|
|
275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
|
|
276 | { |
|
|
277 | if (size) |
|
|
278 | return realloc (ptr, size); |
|
|
279 | |
|
|
280 | free (ptr); |
|
|
281 | return 0; |
|
|
282 | } |
|
|
283 | |
270 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
271 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
272 | |
286 | |
273 | static void * |
287 | static void * |
274 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
275 | { |
289 | { |
|
|
290 | if (!size) |
|
|
291 | { |
|
|
292 | free (ptr); |
|
|
293 | return 0; |
|
|
294 | } |
|
|
295 | |
276 | for (;;) |
296 | for (;;) |
277 | { |
297 | { |
278 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
279 | |
299 | |
280 | if (newptr) |
300 | if (newptr) |
… | |
… | |
411 | make libev check for a fork in each iteration by enabling this flag. |
431 | make libev check for a fork in each iteration by enabling this flag. |
412 | |
432 | |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
414 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
415 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
418 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
|
|
439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
419 | |
440 | |
420 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
421 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
422 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
423 | |
444 | |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | environment variable. |
446 | environment variable. |
426 | |
447 | |
427 | =item C<EVFLAG_NOINOTIFY> |
448 | =item C<EVFLAG_NOINOTIFY> |
… | |
… | |
688 | to reinitialise the kernel state for backends that have one. Despite |
709 | to reinitialise the kernel state for backends that have one. Despite |
689 | the name, you can call it anytime you are allowed to start or stop |
710 | the name, you can call it anytime you are allowed to start or stop |
690 | watchers (except inside an C<ev_prepare> callback), but it makes most |
711 | watchers (except inside an C<ev_prepare> callback), but it makes most |
691 | sense after forking, in the child process. You I<must> call it (or use |
712 | sense after forking, in the child process. You I<must> call it (or use |
692 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
713 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
|
|
714 | |
|
|
715 | In addition, if you want to reuse a loop (via this function or |
|
|
716 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
693 | |
717 | |
694 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
718 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
695 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
719 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
696 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
720 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
697 | during fork. |
721 | during fork. |
… | |
… | |
2110 | |
2134 | |
2111 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2135 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2112 | |
2136 | |
2113 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2137 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2114 | |
2138 | |
2115 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2139 | Configure the timer to trigger after C<after> seconds (fractional and |
2116 | is C<0.>, then it will automatically be stopped once the timeout is |
2140 | negative values are supported). If C<repeat> is C<0.>, then it will |
2117 | reached. If it is positive, then the timer will automatically be |
2141 | automatically be stopped once the timeout is reached. If it is positive, |
2118 | configured to trigger again C<repeat> seconds later, again, and again, |
2142 | then the timer will automatically be configured to trigger again C<repeat> |
2119 | until stopped manually. |
2143 | seconds later, again, and again, until stopped manually. |
2120 | |
2144 | |
2121 | The timer itself will do a best-effort at avoiding drift, that is, if |
2145 | The timer itself will do a best-effort at avoiding drift, that is, if |
2122 | you configure a timer to trigger every 10 seconds, then it will normally |
2146 | you configure a timer to trigger every 10 seconds, then it will normally |
2123 | trigger at exactly 10 second intervals. If, however, your program cannot |
2147 | trigger at exactly 10 second intervals. If, however, your program cannot |
2124 | keep up with the timer (because it takes longer than those 10 seconds to |
2148 | keep up with the timer (because it takes longer than those 10 seconds to |
… | |
… | |
2206 | Periodic watchers are also timers of a kind, but they are very versatile |
2230 | Periodic watchers are also timers of a kind, but they are very versatile |
2207 | (and unfortunately a bit complex). |
2231 | (and unfortunately a bit complex). |
2208 | |
2232 | |
2209 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2233 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2210 | relative time, the physical time that passes) but on wall clock time |
2234 | relative time, the physical time that passes) but on wall clock time |
2211 | (absolute time, the thing you can read on your calender or clock). The |
2235 | (absolute time, the thing you can read on your calendar or clock). The |
2212 | difference is that wall clock time can run faster or slower than real |
2236 | difference is that wall clock time can run faster or slower than real |
2213 | time, and time jumps are not uncommon (e.g. when you adjust your |
2237 | time, and time jumps are not uncommon (e.g. when you adjust your |
2214 | wrist-watch). |
2238 | wrist-watch). |
2215 | |
2239 | |
2216 | You can tell a periodic watcher to trigger after some specific point |
2240 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2221 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2245 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2222 | it, as it uses a relative timeout). |
2246 | it, as it uses a relative timeout). |
2223 | |
2247 | |
2224 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2248 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2225 | timers, such as triggering an event on each "midnight, local time", or |
2249 | timers, such as triggering an event on each "midnight, local time", or |
2226 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2250 | other complicated rules. This cannot easily be done with C<ev_timer> |
2227 | those cannot react to time jumps. |
2251 | watchers, as those cannot react to time jumps. |
2228 | |
2252 | |
2229 | As with timers, the callback is guaranteed to be invoked only when the |
2253 | As with timers, the callback is guaranteed to be invoked only when the |
2230 | point in time where it is supposed to trigger has passed. If multiple |
2254 | point in time where it is supposed to trigger has passed. If multiple |
2231 | timers become ready during the same loop iteration then the ones with |
2255 | timers become ready during the same loop iteration then the ones with |
2232 | earlier time-out values are invoked before ones with later time-out values |
2256 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2318 | |
2342 | |
2319 | NOTE: I<< This callback must always return a time that is higher than or |
2343 | NOTE: I<< This callback must always return a time that is higher than or |
2320 | equal to the passed C<now> value >>. |
2344 | equal to the passed C<now> value >>. |
2321 | |
2345 | |
2322 | This can be used to create very complex timers, such as a timer that |
2346 | This can be used to create very complex timers, such as a timer that |
2323 | triggers on "next midnight, local time". To do this, you would calculate the |
2347 | triggers on "next midnight, local time". To do this, you would calculate |
2324 | next midnight after C<now> and return the timestamp value for this. How |
2348 | the next midnight after C<now> and return the timestamp value for |
2325 | you do this is, again, up to you (but it is not trivial, which is the main |
2349 | this. Here is a (completely untested, no error checking) example on how to |
2326 | reason I omitted it as an example). |
2350 | do this: |
|
|
2351 | |
|
|
2352 | #include <time.h> |
|
|
2353 | |
|
|
2354 | static ev_tstamp |
|
|
2355 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2356 | { |
|
|
2357 | time_t tnow = (time_t)now; |
|
|
2358 | struct tm tm; |
|
|
2359 | localtime_r (&tnow, &tm); |
|
|
2360 | |
|
|
2361 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2362 | ++tm.tm_mday; // midnight next day |
|
|
2363 | |
|
|
2364 | return mktime (&tm); |
|
|
2365 | } |
|
|
2366 | |
|
|
2367 | Note: this code might run into trouble on days that have more then two |
|
|
2368 | midnights (beginning and end). |
2327 | |
2369 | |
2328 | =back |
2370 | =back |
2329 | |
2371 | |
2330 | =item ev_periodic_again (loop, ev_periodic *) |
2372 | =item ev_periodic_again (loop, ev_periodic *) |
2331 | |
2373 | |
… | |
… | |
3514 | |
3556 | |
3515 | There are some other functions of possible interest. Described. Here. Now. |
3557 | There are some other functions of possible interest. Described. Here. Now. |
3516 | |
3558 | |
3517 | =over 4 |
3559 | =over 4 |
3518 | |
3560 | |
3519 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3561 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3520 | |
3562 | |
3521 | This function combines a simple timer and an I/O watcher, calls your |
3563 | This function combines a simple timer and an I/O watcher, calls your |
3522 | callback on whichever event happens first and automatically stops both |
3564 | callback on whichever event happens first and automatically stops both |
3523 | watchers. This is useful if you want to wait for a single event on an fd |
3565 | watchers. This is useful if you want to wait for a single event on an fd |
3524 | or timeout without having to allocate/configure/start/stop/free one or |
3566 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3956 | The normal C API should work fine when used from C++: both ev.h and the |
3998 | The normal C API should work fine when used from C++: both ev.h and the |
3957 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3999 | libev sources can be compiled as C++. Therefore, code that uses the C API |
3958 | will work fine. |
4000 | will work fine. |
3959 | |
4001 | |
3960 | Proper exception specifications might have to be added to callbacks passed |
4002 | Proper exception specifications might have to be added to callbacks passed |
3961 | to libev: exceptions may be thrown only from watcher callbacks, all |
4003 | to libev: exceptions may be thrown only from watcher callbacks, all other |
3962 | other callbacks (allocator, syserr, loop acquire/release and periodic |
4004 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
3963 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
4005 | callbacks) must not throw exceptions, and might need a C<noexcept> |
3964 | ()> specification. If you have code that needs to be compiled as both C |
4006 | specification. If you have code that needs to be compiled as both C and |
3965 | and C++ you can use the C<EV_THROW> macro for this: |
4007 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
3966 | |
4008 | |
3967 | static void |
4009 | static void |
3968 | fatal_error (const char *msg) EV_THROW |
4010 | fatal_error (const char *msg) EV_NOEXCEPT |
3969 | { |
4011 | { |
3970 | perror (msg); |
4012 | perror (msg); |
3971 | abort (); |
4013 | abort (); |
3972 | } |
4014 | } |
3973 | |
4015 | |
… | |
… | |
4383 | ev_vars.h |
4425 | ev_vars.h |
4384 | ev_wrap.h |
4426 | ev_wrap.h |
4385 | |
4427 | |
4386 | ev_win32.c required on win32 platforms only |
4428 | ev_win32.c required on win32 platforms only |
4387 | |
4429 | |
4388 | ev_select.c only when select backend is enabled (which is enabled by default) |
4430 | ev_select.c only when select backend is enabled |
4389 | ev_poll.c only when poll backend is enabled (disabled by default) |
4431 | ev_poll.c only when poll backend is enabled |
4390 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4432 | ev_epoll.c only when the epoll backend is enabled |
4391 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4433 | ev_kqueue.c only when the kqueue backend is enabled |
4392 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4434 | ev_port.c only when the solaris port backend is enabled |
4393 | |
4435 | |
4394 | F<ev.c> includes the backend files directly when enabled, so you only need |
4436 | F<ev.c> includes the backend files directly when enabled, so you only need |
4395 | to compile this single file. |
4437 | to compile this single file. |
4396 | |
4438 | |
4397 | =head3 LIBEVENT COMPATIBILITY API |
4439 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
5297 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5339 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5298 | assumes that the same (machine) code can be used to call any watcher |
5340 | assumes that the same (machine) code can be used to call any watcher |
5299 | callback: The watcher callbacks have different type signatures, but libev |
5341 | callback: The watcher callbacks have different type signatures, but libev |
5300 | calls them using an C<ev_watcher *> internally. |
5342 | calls them using an C<ev_watcher *> internally. |
5301 | |
5343 | |
|
|
5344 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5345 | |
|
|
5346 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5347 | relies on this setting pointers and integers to null. |
|
|
5348 | |
5302 | =item pointer accesses must be thread-atomic |
5349 | =item pointer accesses must be thread-atomic |
5303 | |
5350 | |
5304 | Accessing a pointer value must be atomic, it must both be readable and |
5351 | Accessing a pointer value must be atomic, it must both be readable and |
5305 | writable in one piece - this is the case on all current architectures. |
5352 | writable in one piece - this is the case on all current architectures. |
5306 | |
5353 | |