… | |
… | |
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) |
… | |
… | |
2225 | 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 |
2226 | it, as it uses a relative timeout). |
2246 | it, as it uses a relative timeout). |
2227 | |
2247 | |
2228 | 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 |
2229 | 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 |
2230 | 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> |
2231 | those cannot react to time jumps. |
2251 | watchers, as those cannot react to time jumps. |
2232 | |
2252 | |
2233 | 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 |
2234 | 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 |
2235 | 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 |
2236 | 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 |
… | |
… | |
2322 | |
2342 | |
2323 | 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 |
2324 | equal to the passed C<now> value >>. |
2344 | equal to the passed C<now> value >>. |
2325 | |
2345 | |
2326 | 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 |
2327 | 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 |
2328 | 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 |
2329 | 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 |
2330 | 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). |
2331 | |
2369 | |
2332 | =back |
2370 | =back |
2333 | |
2371 | |
2334 | =item ev_periodic_again (loop, ev_periodic *) |
2372 | =item ev_periodic_again (loop, ev_periodic *) |
2335 | |
2373 | |
… | |
… | |
3960 | 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 |
3961 | 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 |
3962 | will work fine. |
4000 | will work fine. |
3963 | |
4001 | |
3964 | Proper exception specifications might have to be added to callbacks passed |
4002 | Proper exception specifications might have to be added to callbacks passed |
3965 | to libev: exceptions may be thrown only from watcher callbacks, all |
4003 | to libev: exceptions may be thrown only from watcher callbacks, all other |
3966 | other callbacks (allocator, syserr, loop acquire/release and periodic |
4004 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
3967 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
4005 | callbacks) must not throw exceptions, and might need a C<noexcept> |
3968 | ()> 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 |
3969 | and C++ you can use the C<EV_THROW> macro for this: |
4007 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
3970 | |
4008 | |
3971 | static void |
4009 | static void |
3972 | fatal_error (const char *msg) EV_THROW |
4010 | fatal_error (const char *msg) EV_NOEXCEPT |
3973 | { |
4011 | { |
3974 | perror (msg); |
4012 | perror (msg); |
3975 | abort (); |
4013 | abort (); |
3976 | } |
4014 | } |
3977 | |
4015 | |