… | |
… | |
43 | |
43 | |
44 | int |
44 | int |
45 | main (void) |
45 | main (void) |
46 | { |
46 | { |
47 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
49 | |
50 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L</WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
166 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
167 | |
175 | |
168 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
170 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
171 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
172 | |
180 | |
173 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
174 | |
182 | |
175 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
176 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
177 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
178 | |
192 | |
179 | =item int ev_version_major () |
193 | =item int ev_version_major () |
180 | |
194 | |
181 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
182 | |
196 | |
… | |
… | |
233 | the current system, you would need to look at C<ev_embeddable_backends () |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
235 | |
249 | |
236 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
237 | |
251 | |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
239 | |
253 | |
240 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
241 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
242 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
243 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
269 | } |
283 | } |
270 | |
284 | |
271 | ... |
285 | ... |
272 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
273 | |
287 | |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
275 | |
289 | |
276 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
277 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
278 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
279 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
291 | } |
305 | } |
292 | |
306 | |
293 | ... |
307 | ... |
294 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
295 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
296 | =back |
323 | =back |
297 | |
324 | |
298 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
299 | |
326 | |
300 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
303 | |
330 | |
304 | The library knows two types of such loops, the I<default> loop, which |
331 | The library knows two types of such loops, the I<default> loop, which |
305 | supports signals and child events, and dynamically created event loops |
332 | supports child process events, and dynamically created event loops which |
306 | which do not. |
333 | do not. |
307 | |
334 | |
308 | =over 4 |
335 | =over 4 |
309 | |
336 | |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
311 | |
338 | |
312 | This will initialise the default event loop if it hasn't been initialised |
339 | This returns the "default" event loop object, which is what you should |
313 | yet and return it. If the default loop could not be initialised, returns |
340 | normally use when you just need "the event loop". Event loop objects and |
314 | false. If it already was initialised it simply returns it (and ignores the |
341 | the C<flags> parameter are described in more detail in the entry for |
315 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
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343 | |
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344 | If the default loop is already initialised then this function simply |
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345 | returns it (and ignores the flags. If that is troubling you, check |
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346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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347 | flags, which should almost always be C<0>, unless the caller is also the |
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348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
316 | |
349 | |
317 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
318 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
319 | |
352 | |
320 | Note that this function is I<not> thread-safe, so if you want to use it |
353 | Note that this function is I<not> thread-safe, so if you want to use it |
321 | from multiple threads, you have to lock (note also that this is unlikely, |
354 | from multiple threads, you have to employ some kind of mutex (note also |
322 | as loops cannot be shared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
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356 | threads anyway). |
323 | |
357 | |
324 | The default loop is the only loop that can handle C<ev_signal> and |
358 | The default loop is the only loop that can handle C<ev_child> watchers, |
325 | C<ev_child> watchers, and to do this, it always registers a handler |
359 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
326 | for C<SIGCHLD>. If this is a problem for your application you can either |
360 | a problem for your application you can either create a dynamic loop with |
327 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
361 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
328 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
329 | C<ev_default_init>. |
363 | |
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364 | Example: This is the most typical usage. |
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365 | |
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366 | if (!ev_default_loop (0)) |
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367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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368 | |
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369 | Example: Restrict libev to the select and poll backends, and do not allow |
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370 | environment settings to be taken into account: |
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371 | |
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372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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373 | |
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374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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375 | |
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376 | This will create and initialise a new event loop object. If the loop |
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377 | could not be initialised, returns false. |
|
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378 | |
|
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379 | This function is thread-safe, and one common way to use libev with |
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380 | threads is indeed to create one loop per thread, and using the default |
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381 | loop in the "main" or "initial" thread. |
330 | |
382 | |
331 | The flags argument can be used to specify special behaviour or specific |
383 | The flags argument can be used to specify special behaviour or specific |
332 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
333 | |
385 | |
334 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
344 | |
396 | |
345 | If this flag bit is or'ed into the flag value (or the program runs setuid |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
346 | or setgid) then libev will I<not> look at the environment variable |
398 | or setgid) then libev will I<not> look at the environment variable |
347 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
348 | override the flags completely if it is found in the environment. This is |
400 | override the flags completely if it is found in the environment. This is |
349 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, to work |
350 | around bugs. |
402 | around bugs, or to make libev threadsafe (accessing environment variables |
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403 | cannot be done in a threadsafe way, but usually it works if no other |
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404 | thread modifies them). |
351 | |
405 | |
352 | =item C<EVFLAG_FORKCHECK> |
406 | =item C<EVFLAG_FORKCHECK> |
353 | |
407 | |
354 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
408 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
355 | make libev check for a fork in each iteration by enabling this flag. |
409 | make libev check for a fork in each iteration by enabling this flag. |
… | |
… | |
369 | environment variable. |
423 | environment variable. |
370 | |
424 | |
371 | =item C<EVFLAG_NOINOTIFY> |
425 | =item C<EVFLAG_NOINOTIFY> |
372 | |
426 | |
373 | When this flag is specified, then libev will not attempt to use the |
427 | When this flag is specified, then libev will not attempt to use the |
374 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
428 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
375 | testing, this flag can be useful to conserve inotify file descriptors, as |
429 | testing, this flag can be useful to conserve inotify file descriptors, as |
376 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
430 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
377 | |
431 | |
378 | =item C<EVFLAG_SIGNALFD> |
432 | =item C<EVFLAG_SIGNALFD> |
379 | |
433 | |
380 | When this flag is specified, then libev will attempt to use the |
434 | When this flag is specified, then libev will attempt to use the |
381 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
435 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
382 | delivers signals synchronously, which makes it both faster and might make |
436 | delivers signals synchronously, which makes it both faster and might make |
383 | it possible to get the queued signal data. It can also simplify signal |
437 | it possible to get the queued signal data. It can also simplify signal |
384 | handling with threads, as long as you properly block signals in your |
438 | handling with threads, as long as you properly block signals in your |
385 | threads that are not interested in handling them. |
439 | threads that are not interested in handling them. |
386 | |
440 | |
387 | Signalfd will not be used by default as this changes your signal mask, and |
441 | Signalfd will not be used by default as this changes your signal mask, and |
388 | there are a lot of shoddy libraries and programs (glib's threadpool for |
442 | there are a lot of shoddy libraries and programs (glib's threadpool for |
389 | example) that can't properly initialise their signal masks. |
443 | example) that can't properly initialise their signal masks. |
|
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444 | |
|
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445 | =item C<EVFLAG_NOSIGMASK> |
|
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446 | |
|
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447 | When this flag is specified, then libev will avoid to modify the signal |
|
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448 | mask. Specifically, this means you have to make sure signals are unblocked |
|
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449 | when you want to receive them. |
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450 | |
|
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451 | This behaviour is useful when you want to do your own signal handling, or |
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452 | want to handle signals only in specific threads and want to avoid libev |
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453 | unblocking the signals. |
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454 | |
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455 | It's also required by POSIX in a threaded program, as libev calls |
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456 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
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457 | |
|
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458 | This flag's behaviour will become the default in future versions of libev. |
390 | |
459 | |
391 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
460 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
392 | |
461 | |
393 | This is your standard select(2) backend. Not I<completely> standard, as |
462 | This is your standard select(2) backend. Not I<completely> standard, as |
394 | libev tries to roll its own fd_set with no limits on the number of fds, |
463 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
422 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
491 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
423 | |
492 | |
424 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
493 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
425 | kernels). |
494 | kernels). |
426 | |
495 | |
427 | For few fds, this backend is a bit little slower than poll and select, |
496 | For few fds, this backend is a bit little slower than poll and select, but |
428 | but it scales phenomenally better. While poll and select usually scale |
497 | it scales phenomenally better. While poll and select usually scale like |
429 | like O(total_fds) where n is the total number of fds (or the highest fd), |
498 | O(total_fds) where total_fds is the total number of fds (or the highest |
430 | epoll scales either O(1) or O(active_fds). |
499 | fd), epoll scales either O(1) or O(active_fds). |
431 | |
500 | |
432 | The epoll mechanism deserves honorable mention as the most misdesigned |
501 | The epoll mechanism deserves honorable mention as the most misdesigned |
433 | of the more advanced event mechanisms: mere annoyances include silently |
502 | of the more advanced event mechanisms: mere annoyances include silently |
434 | dropping file descriptors, requiring a system call per change per file |
503 | dropping file descriptors, requiring a system call per change per file |
435 | descriptor (and unnecessary guessing of parameters), problems with dup and |
504 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
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505 | returning before the timeout value, resulting in additional iterations |
|
|
506 | (and only giving 5ms accuracy while select on the same platform gives |
436 | so on. The biggest issue is fork races, however - if a program forks then |
507 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
437 | I<both> parent and child process have to recreate the epoll set, which can |
508 | forks then I<both> parent and child process have to recreate the epoll |
438 | take considerable time (one syscall per file descriptor) and is of course |
509 | set, which can take considerable time (one syscall per file descriptor) |
439 | hard to detect. |
510 | and is of course hard to detect. |
440 | |
511 | |
441 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
512 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
442 | of course I<doesn't>, and epoll just loves to report events for totally |
513 | but of course I<doesn't>, and epoll just loves to report events for |
443 | I<different> file descriptors (even already closed ones, so one cannot |
514 | totally I<different> file descriptors (even already closed ones, so |
444 | even remove them from the set) than registered in the set (especially |
515 | one cannot even remove them from the set) than registered in the set |
445 | on SMP systems). Libev tries to counter these spurious notifications by |
516 | (especially on SMP systems). Libev tries to counter these spurious |
446 | employing an additional generation counter and comparing that against the |
517 | notifications by employing an additional generation counter and comparing |
447 | events to filter out spurious ones, recreating the set when required. Last |
518 | that against the events to filter out spurious ones, recreating the set |
|
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519 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
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520 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
521 | because epoll returns immediately despite a nonzero timeout. And last |
448 | not least, it also refuses to work with some file descriptors which work |
522 | not least, it also refuses to work with some file descriptors which work |
449 | perfectly fine with C<select> (files, many character devices...). |
523 | perfectly fine with C<select> (files, many character devices...). |
|
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524 | |
|
|
525 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
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526 | cobbled together in a hurry, no thought to design or interaction with |
|
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527 | others. Oh, the pain, will it ever stop... |
450 | |
528 | |
451 | While stopping, setting and starting an I/O watcher in the same iteration |
529 | While stopping, setting and starting an I/O watcher in the same iteration |
452 | will result in some caching, there is still a system call per such |
530 | will result in some caching, there is still a system call per such |
453 | incident (because the same I<file descriptor> could point to a different |
531 | incident (because the same I<file descriptor> could point to a different |
454 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
532 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
491 | |
569 | |
492 | It scales in the same way as the epoll backend, but the interface to the |
570 | It scales in the same way as the epoll backend, but the interface to the |
493 | kernel is more efficient (which says nothing about its actual speed, of |
571 | kernel is more efficient (which says nothing about its actual speed, of |
494 | course). While stopping, setting and starting an I/O watcher does never |
572 | course). While stopping, setting and starting an I/O watcher does never |
495 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
573 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
496 | two event changes per incident. Support for C<fork ()> is very bad (but |
574 | two event changes per incident. Support for C<fork ()> is very bad (you |
497 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
575 | might have to leak fd's on fork, but it's more sane than epoll) and it |
498 | cases |
576 | drops fds silently in similarly hard-to-detect cases. |
499 | |
577 | |
500 | This backend usually performs well under most conditions. |
578 | This backend usually performs well under most conditions. |
501 | |
579 | |
502 | While nominally embeddable in other event loops, this doesn't work |
580 | While nominally embeddable in other event loops, this doesn't work |
503 | everywhere, so you might need to test for this. And since it is broken |
581 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
520 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
598 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
521 | |
599 | |
522 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
600 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
523 | it's really slow, but it still scales very well (O(active_fds)). |
601 | it's really slow, but it still scales very well (O(active_fds)). |
524 | |
602 | |
525 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
526 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
527 | blocking when no data (or space) is available. |
|
|
528 | |
|
|
529 | While this backend scales well, it requires one system call per active |
603 | While this backend scales well, it requires one system call per active |
530 | file descriptor per loop iteration. For small and medium numbers of file |
604 | file descriptor per loop iteration. For small and medium numbers of file |
531 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
605 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
532 | might perform better. |
606 | might perform better. |
533 | |
607 | |
534 | On the positive side, with the exception of the spurious readiness |
608 | On the positive side, this backend actually performed fully to |
535 | notifications, this backend actually performed fully to specification |
|
|
536 | in all tests and is fully embeddable, which is a rare feat among the |
609 | specification in all tests and is fully embeddable, which is a rare feat |
537 | OS-specific backends (I vastly prefer correctness over speed hacks). |
610 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
611 | hacks). |
|
|
612 | |
|
|
613 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
614 | even sun itself gets it wrong in their code examples: The event polling |
|
|
615 | function sometimes returns events to the caller even though an error |
|
|
616 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
617 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
618 | absolutely have to know whether an event occurred or not because you have |
|
|
619 | to re-arm the watcher. |
|
|
620 | |
|
|
621 | Fortunately libev seems to be able to work around these idiocies. |
538 | |
622 | |
539 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
623 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
540 | C<EVBACKEND_POLL>. |
624 | C<EVBACKEND_POLL>. |
541 | |
625 | |
542 | =item C<EVBACKEND_ALL> |
626 | =item C<EVBACKEND_ALL> |
543 | |
627 | |
544 | Try all backends (even potentially broken ones that wouldn't be tried |
628 | Try all backends (even potentially broken ones that wouldn't be tried |
545 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
629 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
546 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
630 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
547 | |
631 | |
548 | It is definitely not recommended to use this flag. |
632 | It is definitely not recommended to use this flag, use whatever |
|
|
633 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
634 | at all. |
|
|
635 | |
|
|
636 | =item C<EVBACKEND_MASK> |
|
|
637 | |
|
|
638 | Not a backend at all, but a mask to select all backend bits from a |
|
|
639 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
640 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
549 | |
641 | |
550 | =back |
642 | =back |
551 | |
643 | |
552 | If one or more of the backend flags are or'ed into the flags value, |
644 | If one or more of the backend flags are or'ed into the flags value, |
553 | then only these backends will be tried (in the reverse order as listed |
645 | then only these backends will be tried (in the reverse order as listed |
554 | here). If none are specified, all backends in C<ev_recommended_backends |
646 | here). If none are specified, all backends in C<ev_recommended_backends |
555 | ()> will be tried. |
647 | ()> will be tried. |
556 | |
648 | |
557 | Example: This is the most typical usage. |
|
|
558 | |
|
|
559 | if (!ev_default_loop (0)) |
|
|
560 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
561 | |
|
|
562 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
563 | environment settings to be taken into account: |
|
|
564 | |
|
|
565 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
566 | |
|
|
567 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
568 | used if available (warning, breaks stuff, best use only with your own |
|
|
569 | private event loop and only if you know the OS supports your types of |
|
|
570 | fds): |
|
|
571 | |
|
|
572 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
573 | |
|
|
574 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
575 | |
|
|
576 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
577 | always distinct from the default loop. |
|
|
578 | |
|
|
579 | Note that this function I<is> thread-safe, and one common way to use |
|
|
580 | libev with threads is indeed to create one loop per thread, and using the |
|
|
581 | default loop in the "main" or "initial" thread. |
|
|
582 | |
|
|
583 | Example: Try to create a event loop that uses epoll and nothing else. |
649 | Example: Try to create a event loop that uses epoll and nothing else. |
584 | |
650 | |
585 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
651 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
586 | if (!epoller) |
652 | if (!epoller) |
587 | fatal ("no epoll found here, maybe it hides under your chair"); |
653 | fatal ("no epoll found here, maybe it hides under your chair"); |
588 | |
654 | |
|
|
655 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
656 | used if available. |
|
|
657 | |
|
|
658 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
659 | |
589 | =item ev_default_destroy () |
660 | =item ev_loop_destroy (loop) |
590 | |
661 | |
591 | Destroys the default loop (frees all memory and kernel state etc.). None |
662 | Destroys an event loop object (frees all memory and kernel state |
592 | of the active event watchers will be stopped in the normal sense, so |
663 | etc.). None of the active event watchers will be stopped in the normal |
593 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
664 | sense, so e.g. C<ev_is_active> might still return true. It is your |
594 | either stop all watchers cleanly yourself I<before> calling this function, |
665 | responsibility to either stop all watchers cleanly yourself I<before> |
595 | or cope with the fact afterwards (which is usually the easiest thing, you |
666 | calling this function, or cope with the fact afterwards (which is usually |
596 | can just ignore the watchers and/or C<free ()> them for example). |
667 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
668 | for example). |
597 | |
669 | |
598 | Note that certain global state, such as signal state (and installed signal |
670 | Note that certain global state, such as signal state (and installed signal |
599 | handlers), will not be freed by this function, and related watchers (such |
671 | handlers), will not be freed by this function, and related watchers (such |
600 | as signal and child watchers) would need to be stopped manually. |
672 | as signal and child watchers) would need to be stopped manually. |
601 | |
673 | |
602 | In general it is not advisable to call this function except in the |
674 | This function is normally used on loop objects allocated by |
603 | rare occasion where you really need to free e.g. the signal handling |
675 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
676 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
677 | |
|
|
678 | Note that it is not advisable to call this function on the default loop |
|
|
679 | except in the rare occasion where you really need to free its resources. |
604 | pipe fds. If you need dynamically allocated loops it is better to use |
680 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
605 | C<ev_loop_new> and C<ev_loop_destroy>. |
681 | and C<ev_loop_destroy>. |
606 | |
682 | |
607 | =item ev_loop_destroy (loop) |
683 | =item ev_loop_fork (loop) |
608 | |
684 | |
609 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
610 | earlier call to C<ev_loop_new>. |
|
|
611 | |
|
|
612 | =item ev_default_fork () |
|
|
613 | |
|
|
614 | This function sets a flag that causes subsequent C<ev_run> iterations |
685 | This function sets a flag that causes subsequent C<ev_run> iterations to |
615 | to reinitialise the kernel state for backends that have one. Despite the |
686 | reinitialise the kernel state for backends that have one. Despite the |
616 | name, you can call it anytime, but it makes most sense after forking, in |
687 | name, you can call it anytime, but it makes most sense after forking, in |
617 | the child process (or both child and parent, but that again makes little |
688 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
618 | sense). You I<must> call it in the child before using any of the libev |
689 | child before resuming or calling C<ev_run>. |
619 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
620 | |
690 | |
621 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
691 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
622 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
692 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
623 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
693 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
624 | during fork. |
694 | during fork. |
… | |
… | |
629 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
699 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
630 | difference, but libev will usually detect this case on its own and do a |
700 | difference, but libev will usually detect this case on its own and do a |
631 | costly reset of the backend). |
701 | costly reset of the backend). |
632 | |
702 | |
633 | The function itself is quite fast and it's usually not a problem to call |
703 | The function itself is quite fast and it's usually not a problem to call |
634 | it just in case after a fork. To make this easy, the function will fit in |
704 | it just in case after a fork. |
635 | quite nicely into a call to C<pthread_atfork>: |
|
|
636 | |
705 | |
|
|
706 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
707 | using pthreads. |
|
|
708 | |
|
|
709 | static void |
|
|
710 | post_fork_child (void) |
|
|
711 | { |
|
|
712 | ev_loop_fork (EV_DEFAULT); |
|
|
713 | } |
|
|
714 | |
|
|
715 | ... |
637 | pthread_atfork (0, 0, ev_default_fork); |
716 | pthread_atfork (0, 0, post_fork_child); |
638 | |
|
|
639 | =item ev_loop_fork (loop) |
|
|
640 | |
|
|
641 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
642 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
643 | after fork that you want to re-use in the child, and how you keep track of |
|
|
644 | them is entirely your own problem. |
|
|
645 | |
717 | |
646 | =item int ev_is_default_loop (loop) |
718 | =item int ev_is_default_loop (loop) |
647 | |
719 | |
648 | Returns true when the given loop is, in fact, the default loop, and false |
720 | Returns true when the given loop is, in fact, the default loop, and false |
649 | otherwise. |
721 | otherwise. |
… | |
… | |
660 | prepare and check phases. |
732 | prepare and check phases. |
661 | |
733 | |
662 | =item unsigned int ev_depth (loop) |
734 | =item unsigned int ev_depth (loop) |
663 | |
735 | |
664 | Returns the number of times C<ev_run> was entered minus the number of |
736 | Returns the number of times C<ev_run> was entered minus the number of |
665 | times C<ev_run> was exited, in other words, the recursion depth. |
737 | times C<ev_run> was exited normally, in other words, the recursion depth. |
666 | |
738 | |
667 | Outside C<ev_run>, this number is zero. In a callback, this number is |
739 | Outside C<ev_run>, this number is zero. In a callback, this number is |
668 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
740 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
669 | in which case it is higher. |
741 | in which case it is higher. |
670 | |
742 | |
671 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
743 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
672 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
744 | throwing an exception etc.), doesn't count as "exit" - consider this |
673 | ungentleman-like behaviour unless it's really convenient. |
745 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
746 | convenient, in which case it is fully supported. |
674 | |
747 | |
675 | =item unsigned int ev_backend (loop) |
748 | =item unsigned int ev_backend (loop) |
676 | |
749 | |
677 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
750 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
678 | use. |
751 | use. |
… | |
… | |
693 | |
766 | |
694 | This function is rarely useful, but when some event callback runs for a |
767 | This function is rarely useful, but when some event callback runs for a |
695 | very long time without entering the event loop, updating libev's idea of |
768 | very long time without entering the event loop, updating libev's idea of |
696 | the current time is a good idea. |
769 | the current time is a good idea. |
697 | |
770 | |
698 | See also L<The special problem of time updates> in the C<ev_timer> section. |
771 | See also L</The special problem of time updates> in the C<ev_timer> section. |
699 | |
772 | |
700 | =item ev_suspend (loop) |
773 | =item ev_suspend (loop) |
701 | |
774 | |
702 | =item ev_resume (loop) |
775 | =item ev_resume (loop) |
703 | |
776 | |
… | |
… | |
721 | without a previous call to C<ev_suspend>. |
794 | without a previous call to C<ev_suspend>. |
722 | |
795 | |
723 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
796 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
724 | event loop time (see C<ev_now_update>). |
797 | event loop time (see C<ev_now_update>). |
725 | |
798 | |
726 | =item ev_run (loop, int flags) |
799 | =item bool ev_run (loop, int flags) |
727 | |
800 | |
728 | Finally, this is it, the event handler. This function usually is called |
801 | Finally, this is it, the event handler. This function usually is called |
729 | after you have initialised all your watchers and you want to start |
802 | after you have initialised all your watchers and you want to start |
730 | handling events. It will ask the operating system for any new events, call |
803 | handling events. It will ask the operating system for any new events, call |
731 | the watcher callbacks, an then repeat the whole process indefinitely: This |
804 | the watcher callbacks, and then repeat the whole process indefinitely: This |
732 | is why event loops are called I<loops>. |
805 | is why event loops are called I<loops>. |
733 | |
806 | |
734 | If the flags argument is specified as C<0>, it will keep handling events |
807 | If the flags argument is specified as C<0>, it will keep handling events |
735 | until either no event watchers are active anymore or C<ev_break> was |
808 | until either no event watchers are active anymore or C<ev_break> was |
736 | called. |
809 | called. |
|
|
810 | |
|
|
811 | The return value is false if there are no more active watchers (which |
|
|
812 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
813 | (which usually means " you should call C<ev_run> again"). |
737 | |
814 | |
738 | Please note that an explicit C<ev_break> is usually better than |
815 | Please note that an explicit C<ev_break> is usually better than |
739 | relying on all watchers to be stopped when deciding when a program has |
816 | relying on all watchers to be stopped when deciding when a program has |
740 | finished (especially in interactive programs), but having a program |
817 | finished (especially in interactive programs), but having a program |
741 | that automatically loops as long as it has to and no longer by virtue |
818 | that automatically loops as long as it has to and no longer by virtue |
742 | of relying on its watchers stopping correctly, that is truly a thing of |
819 | of relying on its watchers stopping correctly, that is truly a thing of |
743 | beauty. |
820 | beauty. |
744 | |
821 | |
|
|
822 | This function is I<mostly> exception-safe - you can break out of a |
|
|
823 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
824 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
825 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
826 | |
745 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
827 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
746 | those events and any already outstanding ones, but will not wait and |
828 | those events and any already outstanding ones, but will not wait and |
747 | block your process in case there are no events and will return after one |
829 | block your process in case there are no events and will return after one |
748 | iteration of the loop. This is sometimes useful to poll and handle new |
830 | iteration of the loop. This is sometimes useful to poll and handle new |
749 | events while doing lengthy calculations, to keep the program responsive. |
831 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
758 | This is useful if you are waiting for some external event in conjunction |
840 | This is useful if you are waiting for some external event in conjunction |
759 | with something not expressible using other libev watchers (i.e. "roll your |
841 | with something not expressible using other libev watchers (i.e. "roll your |
760 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
842 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
761 | usually a better approach for this kind of thing. |
843 | usually a better approach for this kind of thing. |
762 | |
844 | |
763 | Here are the gory details of what C<ev_run> does: |
845 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
846 | understanding, not a guarantee that things will work exactly like this in |
|
|
847 | future versions): |
764 | |
848 | |
765 | - Increment loop depth. |
849 | - Increment loop depth. |
766 | - Reset the ev_break status. |
850 | - Reset the ev_break status. |
767 | - Before the first iteration, call any pending watchers. |
851 | - Before the first iteration, call any pending watchers. |
768 | LOOP: |
852 | LOOP: |
… | |
… | |
801 | anymore. |
885 | anymore. |
802 | |
886 | |
803 | ... queue jobs here, make sure they register event watchers as long |
887 | ... queue jobs here, make sure they register event watchers as long |
804 | ... as they still have work to do (even an idle watcher will do..) |
888 | ... as they still have work to do (even an idle watcher will do..) |
805 | ev_run (my_loop, 0); |
889 | ev_run (my_loop, 0); |
806 | ... jobs done or somebody called unloop. yeah! |
890 | ... jobs done or somebody called break. yeah! |
807 | |
891 | |
808 | =item ev_break (loop, how) |
892 | =item ev_break (loop, how) |
809 | |
893 | |
810 | Can be used to make a call to C<ev_run> return early (but only after it |
894 | Can be used to make a call to C<ev_run> return early (but only after it |
811 | has processed all outstanding events). The C<how> argument must be either |
895 | has processed all outstanding events). The C<how> argument must be either |
812 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
896 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
813 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
897 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
814 | |
898 | |
815 | This "unloop state" will be cleared when entering C<ev_run> again. |
899 | This "break state" will be cleared on the next call to C<ev_run>. |
816 | |
900 | |
817 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
901 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
902 | which case it will have no effect. |
818 | |
903 | |
819 | =item ev_ref (loop) |
904 | =item ev_ref (loop) |
820 | |
905 | |
821 | =item ev_unref (loop) |
906 | =item ev_unref (loop) |
822 | |
907 | |
… | |
… | |
843 | running when nothing else is active. |
928 | running when nothing else is active. |
844 | |
929 | |
845 | ev_signal exitsig; |
930 | ev_signal exitsig; |
846 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
931 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
847 | ev_signal_start (loop, &exitsig); |
932 | ev_signal_start (loop, &exitsig); |
848 | evf_unref (loop); |
933 | ev_unref (loop); |
849 | |
934 | |
850 | Example: For some weird reason, unregister the above signal handler again. |
935 | Example: For some weird reason, unregister the above signal handler again. |
851 | |
936 | |
852 | ev_ref (loop); |
937 | ev_ref (loop); |
853 | ev_signal_stop (loop, &exitsig); |
938 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
873 | overhead for the actual polling but can deliver many events at once. |
958 | overhead for the actual polling but can deliver many events at once. |
874 | |
959 | |
875 | By setting a higher I<io collect interval> you allow libev to spend more |
960 | By setting a higher I<io collect interval> you allow libev to spend more |
876 | time collecting I/O events, so you can handle more events per iteration, |
961 | time collecting I/O events, so you can handle more events per iteration, |
877 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
962 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
878 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
963 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
879 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
964 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
880 | sleep time ensures that libev will not poll for I/O events more often then |
965 | sleep time ensures that libev will not poll for I/O events more often then |
881 | once per this interval, on average. |
966 | once per this interval, on average (as long as the host time resolution is |
|
|
967 | good enough). |
882 | |
968 | |
883 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
969 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
884 | to spend more time collecting timeouts, at the expense of increased |
970 | to spend more time collecting timeouts, at the expense of increased |
885 | latency/jitter/inexactness (the watcher callback will be called |
971 | latency/jitter/inexactness (the watcher callback will be called |
886 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
972 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
932 | invoke the actual watchers inside another context (another thread etc.). |
1018 | invoke the actual watchers inside another context (another thread etc.). |
933 | |
1019 | |
934 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1020 | If you want to reset the callback, use C<ev_invoke_pending> as new |
935 | callback. |
1021 | callback. |
936 | |
1022 | |
937 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1023 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
938 | |
1024 | |
939 | Sometimes you want to share the same loop between multiple threads. This |
1025 | Sometimes you want to share the same loop between multiple threads. This |
940 | can be done relatively simply by putting mutex_lock/unlock calls around |
1026 | can be done relatively simply by putting mutex_lock/unlock calls around |
941 | each call to a libev function. |
1027 | each call to a libev function. |
942 | |
1028 | |
943 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1029 | However, C<ev_run> can run an indefinite time, so it is not feasible |
944 | to wait for it to return. One way around this is to wake up the event |
1030 | to wait for it to return. One way around this is to wake up the event |
945 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1031 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
946 | I<release> and I<acquire> callbacks on the loop. |
1032 | I<release> and I<acquire> callbacks on the loop. |
947 | |
1033 | |
948 | When set, then C<release> will be called just before the thread is |
1034 | When set, then C<release> will be called just before the thread is |
949 | suspended waiting for new events, and C<acquire> is called just |
1035 | suspended waiting for new events, and C<acquire> is called just |
950 | afterwards. |
1036 | afterwards. |
… | |
… | |
965 | See also the locking example in the C<THREADS> section later in this |
1051 | See also the locking example in the C<THREADS> section later in this |
966 | document. |
1052 | document. |
967 | |
1053 | |
968 | =item ev_set_userdata (loop, void *data) |
1054 | =item ev_set_userdata (loop, void *data) |
969 | |
1055 | |
970 | =item ev_userdata (loop) |
1056 | =item void *ev_userdata (loop) |
971 | |
1057 | |
972 | Set and retrieve a single C<void *> associated with a loop. When |
1058 | Set and retrieve a single C<void *> associated with a loop. When |
973 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1059 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
974 | C<0.> |
1060 | C<0>. |
975 | |
1061 | |
976 | These two functions can be used to associate arbitrary data with a loop, |
1062 | These two functions can be used to associate arbitrary data with a loop, |
977 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1063 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
978 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1064 | C<acquire> callbacks described above, but of course can be (ab-)used for |
979 | any other purpose as well. |
1065 | any other purpose as well. |
… | |
… | |
1090 | |
1176 | |
1091 | =item C<EV_PREPARE> |
1177 | =item C<EV_PREPARE> |
1092 | |
1178 | |
1093 | =item C<EV_CHECK> |
1179 | =item C<EV_CHECK> |
1094 | |
1180 | |
1095 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1181 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1096 | to gather new events, and all C<ev_check> watchers are invoked just after |
1182 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1097 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1183 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1184 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1185 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1186 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1187 | or lower priority within an event loop iteration. |
|
|
1188 | |
1098 | received events. Callbacks of both watcher types can start and stop as |
1189 | Callbacks of both watcher types can start and stop as many watchers as |
1099 | many watchers as they want, and all of them will be taken into account |
1190 | they want, and all of them will be taken into account (for example, a |
1100 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1191 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1101 | C<ev_run> from blocking). |
1192 | blocking). |
1102 | |
1193 | |
1103 | =item C<EV_EMBED> |
1194 | =item C<EV_EMBED> |
1104 | |
1195 | |
1105 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1196 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1106 | |
1197 | |
1107 | =item C<EV_FORK> |
1198 | =item C<EV_FORK> |
1108 | |
1199 | |
1109 | The event loop has been resumed in the child process after fork (see |
1200 | The event loop has been resumed in the child process after fork (see |
1110 | C<ev_fork>). |
1201 | C<ev_fork>). |
|
|
1202 | |
|
|
1203 | =item C<EV_CLEANUP> |
|
|
1204 | |
|
|
1205 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1111 | |
1206 | |
1112 | =item C<EV_ASYNC> |
1207 | =item C<EV_ASYNC> |
1113 | |
1208 | |
1114 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1209 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1115 | |
1210 | |
… | |
… | |
1137 | programs, though, as the fd could already be closed and reused for another |
1232 | programs, though, as the fd could already be closed and reused for another |
1138 | thing, so beware. |
1233 | thing, so beware. |
1139 | |
1234 | |
1140 | =back |
1235 | =back |
1141 | |
1236 | |
|
|
1237 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1238 | |
|
|
1239 | =over 4 |
|
|
1240 | |
|
|
1241 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1242 | |
|
|
1243 | This macro initialises the generic portion of a watcher. The contents |
|
|
1244 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1245 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1246 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1247 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1248 | which rolls both calls into one. |
|
|
1249 | |
|
|
1250 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1251 | (or never started) and there are no pending events outstanding. |
|
|
1252 | |
|
|
1253 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1254 | int revents)>. |
|
|
1255 | |
|
|
1256 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1257 | |
|
|
1258 | ev_io w; |
|
|
1259 | ev_init (&w, my_cb); |
|
|
1260 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1261 | |
|
|
1262 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1263 | |
|
|
1264 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1265 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1266 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1267 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1268 | difference to the C<ev_init> macro). |
|
|
1269 | |
|
|
1270 | Although some watcher types do not have type-specific arguments |
|
|
1271 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1272 | |
|
|
1273 | See C<ev_init>, above, for an example. |
|
|
1274 | |
|
|
1275 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1276 | |
|
|
1277 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1278 | calls into a single call. This is the most convenient method to initialise |
|
|
1279 | a watcher. The same limitations apply, of course. |
|
|
1280 | |
|
|
1281 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1282 | |
|
|
1283 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1284 | |
|
|
1285 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1286 | |
|
|
1287 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1288 | events. If the watcher is already active nothing will happen. |
|
|
1289 | |
|
|
1290 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1291 | whole section. |
|
|
1292 | |
|
|
1293 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1294 | |
|
|
1295 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1296 | |
|
|
1297 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1298 | the watcher was active or not). |
|
|
1299 | |
|
|
1300 | It is possible that stopped watchers are pending - for example, |
|
|
1301 | non-repeating timers are being stopped when they become pending - but |
|
|
1302 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1303 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1304 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1305 | |
|
|
1306 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1307 | |
|
|
1308 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1309 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1310 | it. |
|
|
1311 | |
|
|
1312 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1313 | |
|
|
1314 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1315 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1316 | is pending (but not active) you must not call an init function on it (but |
|
|
1317 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1318 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1319 | it). |
|
|
1320 | |
|
|
1321 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1322 | |
|
|
1323 | Returns the callback currently set on the watcher. |
|
|
1324 | |
|
|
1325 | =item ev_set_cb (ev_TYPE *watcher, callback) |
|
|
1326 | |
|
|
1327 | Change the callback. You can change the callback at virtually any time |
|
|
1328 | (modulo threads). |
|
|
1329 | |
|
|
1330 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1331 | |
|
|
1332 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1333 | |
|
|
1334 | Set and query the priority of the watcher. The priority is a small |
|
|
1335 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1336 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1337 | before watchers with lower priority, but priority will not keep watchers |
|
|
1338 | from being executed (except for C<ev_idle> watchers). |
|
|
1339 | |
|
|
1340 | If you need to suppress invocation when higher priority events are pending |
|
|
1341 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1342 | |
|
|
1343 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1344 | pending. |
|
|
1345 | |
|
|
1346 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1347 | fine, as long as you do not mind that the priority value you query might |
|
|
1348 | or might not have been clamped to the valid range. |
|
|
1349 | |
|
|
1350 | The default priority used by watchers when no priority has been set is |
|
|
1351 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1352 | |
|
|
1353 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1354 | priorities. |
|
|
1355 | |
|
|
1356 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1357 | |
|
|
1358 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1359 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1360 | can deal with that fact, as both are simply passed through to the |
|
|
1361 | callback. |
|
|
1362 | |
|
|
1363 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1364 | |
|
|
1365 | If the watcher is pending, this function clears its pending status and |
|
|
1366 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1367 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1368 | |
|
|
1369 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1370 | callback to be invoked, which can be accomplished with this function. |
|
|
1371 | |
|
|
1372 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1373 | |
|
|
1374 | Feeds the given event set into the event loop, as if the specified event |
|
|
1375 | had happened for the specified watcher (which must be a pointer to an |
|
|
1376 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1377 | not free the watcher as long as it has pending events. |
|
|
1378 | |
|
|
1379 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1380 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1381 | not started in the first place. |
|
|
1382 | |
|
|
1383 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1384 | functions that do not need a watcher. |
|
|
1385 | |
|
|
1386 | =back |
|
|
1387 | |
|
|
1388 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1389 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1390 | |
1142 | =head2 WATCHER STATES |
1391 | =head2 WATCHER STATES |
1143 | |
1392 | |
1144 | There are various watcher states mentioned throughout this manual - |
1393 | There are various watcher states mentioned throughout this manual - |
1145 | active, pending and so on. In this section these states and the rules to |
1394 | active, pending and so on. In this section these states and the rules to |
1146 | transition between them will be described in more detail - and while these |
1395 | transition between them will be described in more detail - and while these |
1147 | rules might look complicated, they usually do "the right thing". |
1396 | rules might look complicated, they usually do "the right thing". |
1148 | |
1397 | |
1149 | =over 4 |
1398 | =over 4 |
1150 | |
1399 | |
1151 | =item initialiased |
1400 | =item initialised |
1152 | |
1401 | |
1153 | Before a watcher can be registered with the event looop it has to be |
1402 | Before a watcher can be registered with the event loop it has to be |
1154 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1403 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1155 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1404 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1156 | |
1405 | |
1157 | In this state it is simply some block of memory that is suitable for use |
1406 | In this state it is simply some block of memory that is suitable for |
1158 | in an event loop. It can be moved around, freed, reused etc. at will. |
1407 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1408 | will - as long as you either keep the memory contents intact, or call |
|
|
1409 | C<ev_TYPE_init> again. |
1159 | |
1410 | |
1160 | =item started/running/active |
1411 | =item started/running/active |
1161 | |
1412 | |
1162 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1413 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1163 | property of the event loop, and is actively waiting for events. While in |
1414 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1191 | latter will clear any pending state the watcher might be in, regardless |
1442 | latter will clear any pending state the watcher might be in, regardless |
1192 | of whether it was active or not, so stopping a watcher explicitly before |
1443 | of whether it was active or not, so stopping a watcher explicitly before |
1193 | freeing it is often a good idea. |
1444 | freeing it is often a good idea. |
1194 | |
1445 | |
1195 | While stopped (and not pending) the watcher is essentially in the |
1446 | While stopped (and not pending) the watcher is essentially in the |
1196 | initialised state, that is it can be reused, moved, modified in any way |
1447 | initialised state, that is, it can be reused, moved, modified in any way |
1197 | you wish. |
1448 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1449 | it again). |
1198 | |
1450 | |
1199 | =back |
1451 | =back |
1200 | |
|
|
1201 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1202 | |
|
|
1203 | =over 4 |
|
|
1204 | |
|
|
1205 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1206 | |
|
|
1207 | This macro initialises the generic portion of a watcher. The contents |
|
|
1208 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1209 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1210 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1211 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1212 | which rolls both calls into one. |
|
|
1213 | |
|
|
1214 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1215 | (or never started) and there are no pending events outstanding. |
|
|
1216 | |
|
|
1217 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1218 | int revents)>. |
|
|
1219 | |
|
|
1220 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1221 | |
|
|
1222 | ev_io w; |
|
|
1223 | ev_init (&w, my_cb); |
|
|
1224 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1225 | |
|
|
1226 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1227 | |
|
|
1228 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1229 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1230 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1231 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1232 | difference to the C<ev_init> macro). |
|
|
1233 | |
|
|
1234 | Although some watcher types do not have type-specific arguments |
|
|
1235 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1236 | |
|
|
1237 | See C<ev_init>, above, for an example. |
|
|
1238 | |
|
|
1239 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1240 | |
|
|
1241 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1242 | calls into a single call. This is the most convenient method to initialise |
|
|
1243 | a watcher. The same limitations apply, of course. |
|
|
1244 | |
|
|
1245 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1246 | |
|
|
1247 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1248 | |
|
|
1249 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1250 | |
|
|
1251 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1252 | events. If the watcher is already active nothing will happen. |
|
|
1253 | |
|
|
1254 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1255 | whole section. |
|
|
1256 | |
|
|
1257 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1258 | |
|
|
1259 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1260 | |
|
|
1261 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1262 | the watcher was active or not). |
|
|
1263 | |
|
|
1264 | It is possible that stopped watchers are pending - for example, |
|
|
1265 | non-repeating timers are being stopped when they become pending - but |
|
|
1266 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1267 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1268 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1269 | |
|
|
1270 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1271 | |
|
|
1272 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1273 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1274 | it. |
|
|
1275 | |
|
|
1276 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1277 | |
|
|
1278 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1279 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1280 | is pending (but not active) you must not call an init function on it (but |
|
|
1281 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1282 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1283 | it). |
|
|
1284 | |
|
|
1285 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1286 | |
|
|
1287 | Returns the callback currently set on the watcher. |
|
|
1288 | |
|
|
1289 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1290 | |
|
|
1291 | Change the callback. You can change the callback at virtually any time |
|
|
1292 | (modulo threads). |
|
|
1293 | |
|
|
1294 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1295 | |
|
|
1296 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1297 | |
|
|
1298 | Set and query the priority of the watcher. The priority is a small |
|
|
1299 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1300 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1301 | before watchers with lower priority, but priority will not keep watchers |
|
|
1302 | from being executed (except for C<ev_idle> watchers). |
|
|
1303 | |
|
|
1304 | If you need to suppress invocation when higher priority events are pending |
|
|
1305 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1306 | |
|
|
1307 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1308 | pending. |
|
|
1309 | |
|
|
1310 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1311 | fine, as long as you do not mind that the priority value you query might |
|
|
1312 | or might not have been clamped to the valid range. |
|
|
1313 | |
|
|
1314 | The default priority used by watchers when no priority has been set is |
|
|
1315 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1316 | |
|
|
1317 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1318 | priorities. |
|
|
1319 | |
|
|
1320 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1321 | |
|
|
1322 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1323 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1324 | can deal with that fact, as both are simply passed through to the |
|
|
1325 | callback. |
|
|
1326 | |
|
|
1327 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1328 | |
|
|
1329 | If the watcher is pending, this function clears its pending status and |
|
|
1330 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1331 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1332 | |
|
|
1333 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1334 | callback to be invoked, which can be accomplished with this function. |
|
|
1335 | |
|
|
1336 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1337 | |
|
|
1338 | Feeds the given event set into the event loop, as if the specified event |
|
|
1339 | had happened for the specified watcher (which must be a pointer to an |
|
|
1340 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1341 | not free the watcher as long as it has pending events. |
|
|
1342 | |
|
|
1343 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1344 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1345 | not started in the first place. |
|
|
1346 | |
|
|
1347 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1348 | functions that do not need a watcher. |
|
|
1349 | |
|
|
1350 | =back |
|
|
1351 | |
|
|
1352 | |
|
|
1353 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1354 | |
|
|
1355 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1356 | and read at any time: libev will completely ignore it. This can be used |
|
|
1357 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1358 | don't want to allocate memory and store a pointer to it in that data |
|
|
1359 | member, you can also "subclass" the watcher type and provide your own |
|
|
1360 | data: |
|
|
1361 | |
|
|
1362 | struct my_io |
|
|
1363 | { |
|
|
1364 | ev_io io; |
|
|
1365 | int otherfd; |
|
|
1366 | void *somedata; |
|
|
1367 | struct whatever *mostinteresting; |
|
|
1368 | }; |
|
|
1369 | |
|
|
1370 | ... |
|
|
1371 | struct my_io w; |
|
|
1372 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1373 | |
|
|
1374 | And since your callback will be called with a pointer to the watcher, you |
|
|
1375 | can cast it back to your own type: |
|
|
1376 | |
|
|
1377 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1378 | { |
|
|
1379 | struct my_io *w = (struct my_io *)w_; |
|
|
1380 | ... |
|
|
1381 | } |
|
|
1382 | |
|
|
1383 | More interesting and less C-conformant ways of casting your callback type |
|
|
1384 | instead have been omitted. |
|
|
1385 | |
|
|
1386 | Another common scenario is to use some data structure with multiple |
|
|
1387 | embedded watchers: |
|
|
1388 | |
|
|
1389 | struct my_biggy |
|
|
1390 | { |
|
|
1391 | int some_data; |
|
|
1392 | ev_timer t1; |
|
|
1393 | ev_timer t2; |
|
|
1394 | } |
|
|
1395 | |
|
|
1396 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1397 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1398 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1399 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1400 | programmers): |
|
|
1401 | |
|
|
1402 | #include <stddef.h> |
|
|
1403 | |
|
|
1404 | static void |
|
|
1405 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1406 | { |
|
|
1407 | struct my_biggy big = (struct my_biggy *) |
|
|
1408 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1409 | } |
|
|
1410 | |
|
|
1411 | static void |
|
|
1412 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1413 | { |
|
|
1414 | struct my_biggy big = (struct my_biggy *) |
|
|
1415 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1416 | } |
|
|
1417 | |
1452 | |
1418 | =head2 WATCHER PRIORITY MODELS |
1453 | =head2 WATCHER PRIORITY MODELS |
1419 | |
1454 | |
1420 | Many event loops support I<watcher priorities>, which are usually small |
1455 | Many event loops support I<watcher priorities>, which are usually small |
1421 | integers that influence the ordering of event callback invocation |
1456 | integers that influence the ordering of event callback invocation |
… | |
… | |
1548 | In general you can register as many read and/or write event watchers per |
1583 | In general you can register as many read and/or write event watchers per |
1549 | fd as you want (as long as you don't confuse yourself). Setting all file |
1584 | fd as you want (as long as you don't confuse yourself). Setting all file |
1550 | descriptors to non-blocking mode is also usually a good idea (but not |
1585 | descriptors to non-blocking mode is also usually a good idea (but not |
1551 | required if you know what you are doing). |
1586 | required if you know what you are doing). |
1552 | |
1587 | |
1553 | If you cannot use non-blocking mode, then force the use of a |
|
|
1554 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1555 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1556 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1557 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1558 | |
|
|
1559 | Another thing you have to watch out for is that it is quite easy to |
1588 | Another thing you have to watch out for is that it is quite easy to |
1560 | receive "spurious" readiness notifications, that is your callback might |
1589 | receive "spurious" readiness notifications, that is, your callback might |
1561 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1590 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1562 | because there is no data. Not only are some backends known to create a |
1591 | because there is no data. It is very easy to get into this situation even |
1563 | lot of those (for example Solaris ports), it is very easy to get into |
1592 | with a relatively standard program structure. Thus it is best to always |
1564 | this situation even with a relatively standard program structure. Thus |
1593 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1565 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1566 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1594 | preferable to a program hanging until some data arrives. |
1567 | |
1595 | |
1568 | If you cannot run the fd in non-blocking mode (for example you should |
1596 | If you cannot run the fd in non-blocking mode (for example you should |
1569 | not play around with an Xlib connection), then you have to separately |
1597 | not play around with an Xlib connection), then you have to separately |
1570 | re-test whether a file descriptor is really ready with a known-to-be good |
1598 | re-test whether a file descriptor is really ready with a known-to-be good |
1571 | interface such as poll (fortunately in our Xlib example, Xlib already |
1599 | interface such as poll (fortunately in the case of Xlib, it already does |
1572 | does this on its own, so its quite safe to use). Some people additionally |
1600 | this on its own, so its quite safe to use). Some people additionally |
1573 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1601 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1574 | indefinitely. |
1602 | indefinitely. |
1575 | |
1603 | |
1576 | But really, best use non-blocking mode. |
1604 | But really, best use non-blocking mode. |
1577 | |
1605 | |
… | |
… | |
1605 | |
1633 | |
1606 | There is no workaround possible except not registering events |
1634 | There is no workaround possible except not registering events |
1607 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1635 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1608 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1609 | |
1637 | |
|
|
1638 | =head3 The special problem of files |
|
|
1639 | |
|
|
1640 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1641 | representing files, and expect it to become ready when their program |
|
|
1642 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1643 | |
|
|
1644 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1645 | notification as soon as the kernel knows whether and how much data is |
|
|
1646 | there, and in the case of open files, that's always the case, so you |
|
|
1647 | always get a readiness notification instantly, and your read (or possibly |
|
|
1648 | write) will still block on the disk I/O. |
|
|
1649 | |
|
|
1650 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1651 | devices and so on, there is another party (the sender) that delivers data |
|
|
1652 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1653 | will not send data on its own, simply because it doesn't know what you |
|
|
1654 | wish to read - you would first have to request some data. |
|
|
1655 | |
|
|
1656 | Since files are typically not-so-well supported by advanced notification |
|
|
1657 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1658 | to files, even though you should not use it. The reason for this is |
|
|
1659 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1660 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1661 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1662 | F</dev/urandom>), and even though the file might better be served with |
|
|
1663 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1664 | it "just works" instead of freezing. |
|
|
1665 | |
|
|
1666 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1667 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1668 | when you rarely read from a file instead of from a socket, and want to |
|
|
1669 | reuse the same code path. |
|
|
1670 | |
1610 | =head3 The special problem of fork |
1671 | =head3 The special problem of fork |
1611 | |
1672 | |
1612 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1673 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1613 | useless behaviour. Libev fully supports fork, but needs to be told about |
1674 | useless behaviour. Libev fully supports fork, but needs to be told about |
1614 | it in the child. |
1675 | it in the child if you want to continue to use it in the child. |
1615 | |
1676 | |
1616 | To support fork in your programs, you either have to call |
1677 | To support fork in your child processes, you have to call C<ev_loop_fork |
1617 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1678 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1618 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1679 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1619 | C<EVBACKEND_POLL>. |
|
|
1620 | |
1680 | |
1621 | =head3 The special problem of SIGPIPE |
1681 | =head3 The special problem of SIGPIPE |
1622 | |
1682 | |
1623 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1683 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1624 | when writing to a pipe whose other end has been closed, your program gets |
1684 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1722 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1782 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1723 | monotonic clock option helps a lot here). |
1783 | monotonic clock option helps a lot here). |
1724 | |
1784 | |
1725 | The callback is guaranteed to be invoked only I<after> its timeout has |
1785 | The callback is guaranteed to be invoked only I<after> its timeout has |
1726 | passed (not I<at>, so on systems with very low-resolution clocks this |
1786 | passed (not I<at>, so on systems with very low-resolution clocks this |
1727 | might introduce a small delay). If multiple timers become ready during the |
1787 | might introduce a small delay, see "the special problem of being too |
|
|
1788 | early", below). If multiple timers become ready during the same loop |
1728 | same loop iteration then the ones with earlier time-out values are invoked |
1789 | iteration then the ones with earlier time-out values are invoked before |
1729 | before ones of the same priority with later time-out values (but this is |
1790 | ones of the same priority with later time-out values (but this is no |
1730 | no longer true when a callback calls C<ev_run> recursively). |
1791 | longer true when a callback calls C<ev_run> recursively). |
1731 | |
1792 | |
1732 | =head3 Be smart about timeouts |
1793 | =head3 Be smart about timeouts |
1733 | |
1794 | |
1734 | Many real-world problems involve some kind of timeout, usually for error |
1795 | Many real-world problems involve some kind of timeout, usually for error |
1735 | recovery. A typical example is an HTTP request - if the other side hangs, |
1796 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1810 | |
1871 | |
1811 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1872 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1812 | but remember the time of last activity, and check for a real timeout only |
1873 | but remember the time of last activity, and check for a real timeout only |
1813 | within the callback: |
1874 | within the callback: |
1814 | |
1875 | |
|
|
1876 | ev_tstamp timeout = 60.; |
1815 | ev_tstamp last_activity; // time of last activity |
1877 | ev_tstamp last_activity; // time of last activity |
|
|
1878 | ev_timer timer; |
1816 | |
1879 | |
1817 | static void |
1880 | static void |
1818 | callback (EV_P_ ev_timer *w, int revents) |
1881 | callback (EV_P_ ev_timer *w, int revents) |
1819 | { |
1882 | { |
1820 | ev_tstamp now = ev_now (EV_A); |
1883 | // calculate when the timeout would happen |
1821 | ev_tstamp timeout = last_activity + 60.; |
1884 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1822 | |
1885 | |
1823 | // if last_activity + 60. is older than now, we did time out |
1886 | // if negative, it means we the timeout already occurred |
1824 | if (timeout < now) |
1887 | if (after < 0.) |
1825 | { |
1888 | { |
1826 | // timeout occurred, take action |
1889 | // timeout occurred, take action |
1827 | } |
1890 | } |
1828 | else |
1891 | else |
1829 | { |
1892 | { |
1830 | // callback was invoked, but there was some activity, re-arm |
1893 | // callback was invoked, but there was some recent |
1831 | // the watcher to fire in last_activity + 60, which is |
1894 | // activity. simply restart the timer to time out |
1832 | // guaranteed to be in the future, so "again" is positive: |
1895 | // after "after" seconds, which is the earliest time |
1833 | w->repeat = timeout - now; |
1896 | // the timeout can occur. |
|
|
1897 | ev_timer_set (w, after, 0.); |
1834 | ev_timer_again (EV_A_ w); |
1898 | ev_timer_start (EV_A_ w); |
1835 | } |
1899 | } |
1836 | } |
1900 | } |
1837 | |
1901 | |
1838 | To summarise the callback: first calculate the real timeout (defined |
1902 | To summarise the callback: first calculate in how many seconds the |
1839 | as "60 seconds after the last activity"), then check if that time has |
1903 | timeout will occur (by calculating the absolute time when it would occur, |
1840 | been reached, which means something I<did>, in fact, time out. Otherwise |
1904 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1841 | the callback was invoked too early (C<timeout> is in the future), so |
1905 | (EV_A)> from that). |
1842 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1843 | a timeout then. |
|
|
1844 | |
1906 | |
1845 | Note how C<ev_timer_again> is used, taking advantage of the |
1907 | If this value is negative, then we are already past the timeout, i.e. we |
1846 | C<ev_timer_again> optimisation when the timer is already running. |
1908 | timed out, and need to do whatever is needed in this case. |
|
|
1909 | |
|
|
1910 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1911 | and simply start the timer with this timeout value. |
|
|
1912 | |
|
|
1913 | In other words, each time the callback is invoked it will check whether |
|
|
1914 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1915 | again at the earliest time it could time out. Rinse. Repeat. |
1847 | |
1916 | |
1848 | This scheme causes more callback invocations (about one every 60 seconds |
1917 | This scheme causes more callback invocations (about one every 60 seconds |
1849 | minus half the average time between activity), but virtually no calls to |
1918 | minus half the average time between activity), but virtually no calls to |
1850 | libev to change the timeout. |
1919 | libev to change the timeout. |
1851 | |
1920 | |
1852 | To start the timer, simply initialise the watcher and set C<last_activity> |
1921 | To start the machinery, simply initialise the watcher and set |
1853 | to the current time (meaning we just have some activity :), then call the |
1922 | C<last_activity> to the current time (meaning there was some activity just |
1854 | callback, which will "do the right thing" and start the timer: |
1923 | now), then call the callback, which will "do the right thing" and start |
|
|
1924 | the timer: |
1855 | |
1925 | |
|
|
1926 | last_activity = ev_now (EV_A); |
1856 | ev_init (timer, callback); |
1927 | ev_init (&timer, callback); |
1857 | last_activity = ev_now (loop); |
1928 | callback (EV_A_ &timer, 0); |
1858 | callback (loop, timer, EV_TIMER); |
|
|
1859 | |
1929 | |
1860 | And when there is some activity, simply store the current time in |
1930 | When there is some activity, simply store the current time in |
1861 | C<last_activity>, no libev calls at all: |
1931 | C<last_activity>, no libev calls at all: |
1862 | |
1932 | |
|
|
1933 | if (activity detected) |
1863 | last_activity = ev_now (loop); |
1934 | last_activity = ev_now (EV_A); |
|
|
1935 | |
|
|
1936 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1937 | providing a new value, stopping the timer and calling the callback, which |
|
|
1938 | will again do the right thing (for example, time out immediately :). |
|
|
1939 | |
|
|
1940 | timeout = new_value; |
|
|
1941 | ev_timer_stop (EV_A_ &timer); |
|
|
1942 | callback (EV_A_ &timer, 0); |
1864 | |
1943 | |
1865 | This technique is slightly more complex, but in most cases where the |
1944 | This technique is slightly more complex, but in most cases where the |
1866 | time-out is unlikely to be triggered, much more efficient. |
1945 | time-out is unlikely to be triggered, much more efficient. |
1867 | |
|
|
1868 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1869 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1870 | fix things for you. |
|
|
1871 | |
1946 | |
1872 | =item 4. Wee, just use a double-linked list for your timeouts. |
1947 | =item 4. Wee, just use a double-linked list for your timeouts. |
1873 | |
1948 | |
1874 | If there is not one request, but many thousands (millions...), all |
1949 | If there is not one request, but many thousands (millions...), all |
1875 | employing some kind of timeout with the same timeout value, then one can |
1950 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1902 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1977 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1903 | rather complicated, but extremely efficient, something that really pays |
1978 | rather complicated, but extremely efficient, something that really pays |
1904 | off after the first million or so of active timers, i.e. it's usually |
1979 | off after the first million or so of active timers, i.e. it's usually |
1905 | overkill :) |
1980 | overkill :) |
1906 | |
1981 | |
|
|
1982 | =head3 The special problem of being too early |
|
|
1983 | |
|
|
1984 | If you ask a timer to call your callback after three seconds, then |
|
|
1985 | you expect it to be invoked after three seconds - but of course, this |
|
|
1986 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1987 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1988 | process with a STOP signal for a few hours for example. |
|
|
1989 | |
|
|
1990 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1991 | delay has occurred, but cannot guarantee this. |
|
|
1992 | |
|
|
1993 | A less obvious failure mode is calling your callback too early: many event |
|
|
1994 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1995 | this can cause your callback to be invoked much earlier than you would |
|
|
1996 | expect. |
|
|
1997 | |
|
|
1998 | To see why, imagine a system with a clock that only offers full second |
|
|
1999 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2000 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2001 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2002 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2003 | |
|
|
2004 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2005 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2006 | one-second delay was requested - this is being "too early", despite best |
|
|
2007 | intentions. |
|
|
2008 | |
|
|
2009 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2010 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2011 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2012 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2013 | |
|
|
2014 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2015 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2016 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2017 | late" side of things. |
|
|
2018 | |
1907 | =head3 The special problem of time updates |
2019 | =head3 The special problem of time updates |
1908 | |
2020 | |
1909 | Establishing the current time is a costly operation (it usually takes at |
2021 | Establishing the current time is a costly operation (it usually takes |
1910 | least two system calls): EV therefore updates its idea of the current |
2022 | at least one system call): EV therefore updates its idea of the current |
1911 | time only before and after C<ev_run> collects new events, which causes a |
2023 | time only before and after C<ev_run> collects new events, which causes a |
1912 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2024 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1913 | lots of events in one iteration. |
2025 | lots of events in one iteration. |
1914 | |
2026 | |
1915 | The relative timeouts are calculated relative to the C<ev_now ()> |
2027 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1921 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2033 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1922 | |
2034 | |
1923 | If the event loop is suspended for a long time, you can also force an |
2035 | If the event loop is suspended for a long time, you can also force an |
1924 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2036 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1925 | ()>. |
2037 | ()>. |
|
|
2038 | |
|
|
2039 | =head3 The special problem of unsynchronised clocks |
|
|
2040 | |
|
|
2041 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2042 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2043 | jumps). |
|
|
2044 | |
|
|
2045 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2046 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2047 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2048 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2049 | than a directly following call to C<time>. |
|
|
2050 | |
|
|
2051 | The moral of this is to only compare libev-related timestamps with |
|
|
2052 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2053 | a second or so. |
|
|
2054 | |
|
|
2055 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2056 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2057 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2058 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2059 | |
|
|
2060 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2061 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2062 | I<measured according to the real time>, not the system clock. |
|
|
2063 | |
|
|
2064 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2065 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2066 | exactly the right behaviour. |
|
|
2067 | |
|
|
2068 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2069 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2070 | time, where your comparisons will always generate correct results. |
1926 | |
2071 | |
1927 | =head3 The special problems of suspended animation |
2072 | =head3 The special problems of suspended animation |
1928 | |
2073 | |
1929 | When you leave the server world it is quite customary to hit machines that |
2074 | When you leave the server world it is quite customary to hit machines that |
1930 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2075 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1974 | keep up with the timer (because it takes longer than those 10 seconds to |
2119 | keep up with the timer (because it takes longer than those 10 seconds to |
1975 | do stuff) the timer will not fire more than once per event loop iteration. |
2120 | do stuff) the timer will not fire more than once per event loop iteration. |
1976 | |
2121 | |
1977 | =item ev_timer_again (loop, ev_timer *) |
2122 | =item ev_timer_again (loop, ev_timer *) |
1978 | |
2123 | |
1979 | This will act as if the timer timed out and restart it again if it is |
2124 | This will act as if the timer timed out, and restarts it again if it is |
1980 | repeating. The exact semantics are: |
2125 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2126 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1981 | |
2127 | |
|
|
2128 | The exact semantics are as in the following rules, all of which will be |
|
|
2129 | applied to the watcher: |
|
|
2130 | |
|
|
2131 | =over 4 |
|
|
2132 | |
1982 | If the timer is pending, its pending status is cleared. |
2133 | =item If the timer is pending, the pending status is always cleared. |
1983 | |
2134 | |
1984 | If the timer is started but non-repeating, stop it (as if it timed out). |
2135 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2136 | out, without invoking it). |
1985 | |
2137 | |
1986 | If the timer is repeating, either start it if necessary (with the |
2138 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1987 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2139 | and start the timer, if necessary. |
1988 | |
2140 | |
|
|
2141 | =back |
|
|
2142 | |
1989 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2143 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1990 | usage example. |
2144 | usage example. |
1991 | |
2145 | |
1992 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2146 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1993 | |
2147 | |
1994 | Returns the remaining time until a timer fires. If the timer is active, |
2148 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2114 | |
2268 | |
2115 | Another way to think about it (for the mathematically inclined) is that |
2269 | Another way to think about it (for the mathematically inclined) is that |
2116 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2270 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2117 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2271 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2118 | |
2272 | |
2119 | For numerical stability it is preferable that the C<offset> value is near |
2273 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2120 | C<ev_now ()> (the current time), but there is no range requirement for |
2274 | interval value should be higher than C<1/8192> (which is around 100 |
2121 | this value, and in fact is often specified as zero. |
2275 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2276 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2277 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2278 | C<0> and C<interval>, which is also the recommended range. |
2122 | |
2279 | |
2123 | Note also that there is an upper limit to how often a timer can fire (CPU |
2280 | Note also that there is an upper limit to how often a timer can fire (CPU |
2124 | speed for example), so if C<interval> is very small then timing stability |
2281 | speed for example), so if C<interval> is very small then timing stability |
2125 | will of course deteriorate. Libev itself tries to be exact to be about one |
2282 | will of course deteriorate. Libev itself tries to be exact to be about one |
2126 | millisecond (if the OS supports it and the machine is fast enough). |
2283 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2240 | |
2397 | |
2241 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2398 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2242 | |
2399 | |
2243 | Signal watchers will trigger an event when the process receives a specific |
2400 | Signal watchers will trigger an event when the process receives a specific |
2244 | signal one or more times. Even though signals are very asynchronous, libev |
2401 | signal one or more times. Even though signals are very asynchronous, libev |
2245 | will try it's best to deliver signals synchronously, i.e. as part of the |
2402 | will try its best to deliver signals synchronously, i.e. as part of the |
2246 | normal event processing, like any other event. |
2403 | normal event processing, like any other event. |
2247 | |
2404 | |
2248 | If you want signals to be delivered truly asynchronously, just use |
2405 | If you want signals to be delivered truly asynchronously, just use |
2249 | C<sigaction> as you would do without libev and forget about sharing |
2406 | C<sigaction> as you would do without libev and forget about sharing |
2250 | the signal. You can even use C<ev_async> from a signal handler to |
2407 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2269 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2426 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2270 | |
2427 | |
2271 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2428 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2272 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2429 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2273 | stopping it again), that is, libev might or might not block the signal, |
2430 | stopping it again), that is, libev might or might not block the signal, |
2274 | and might or might not set or restore the installed signal handler. |
2431 | and might or might not set or restore the installed signal handler (but |
|
|
2432 | see C<EVFLAG_NOSIGMASK>). |
2275 | |
2433 | |
2276 | While this does not matter for the signal disposition (libev never |
2434 | While this does not matter for the signal disposition (libev never |
2277 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2435 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2278 | C<execve>), this matters for the signal mask: many programs do not expect |
2436 | C<execve>), this matters for the signal mask: many programs do not expect |
2279 | certain signals to be blocked. |
2437 | certain signals to be blocked. |
… | |
… | |
2292 | I<has> to modify the signal mask, at least temporarily. |
2450 | I<has> to modify the signal mask, at least temporarily. |
2293 | |
2451 | |
2294 | So I can't stress this enough: I<If you do not reset your signal mask when |
2452 | So I can't stress this enough: I<If you do not reset your signal mask when |
2295 | you expect it to be empty, you have a race condition in your code>. This |
2453 | you expect it to be empty, you have a race condition in your code>. This |
2296 | is not a libev-specific thing, this is true for most event libraries. |
2454 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2455 | |
|
|
2456 | =head3 The special problem of threads signal handling |
|
|
2457 | |
|
|
2458 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2459 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2460 | threads in a process block signals, which is hard to achieve. |
|
|
2461 | |
|
|
2462 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2463 | for the same signals), you can tackle this problem by globally blocking |
|
|
2464 | all signals before creating any threads (or creating them with a fully set |
|
|
2465 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2466 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2467 | these signals. You can pass on any signals that libev might be interested |
|
|
2468 | in by calling C<ev_feed_signal>. |
2297 | |
2469 | |
2298 | =head3 Watcher-Specific Functions and Data Members |
2470 | =head3 Watcher-Specific Functions and Data Members |
2299 | |
2471 | |
2300 | =over 4 |
2472 | =over 4 |
2301 | |
2473 | |
… | |
… | |
2436 | |
2608 | |
2437 | =head2 C<ev_stat> - did the file attributes just change? |
2609 | =head2 C<ev_stat> - did the file attributes just change? |
2438 | |
2610 | |
2439 | This watches a file system path for attribute changes. That is, it calls |
2611 | This watches a file system path for attribute changes. That is, it calls |
2440 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2612 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2441 | and sees if it changed compared to the last time, invoking the callback if |
2613 | and sees if it changed compared to the last time, invoking the callback |
2442 | it did. |
2614 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2615 | happen after the watcher has been started will be reported. |
2443 | |
2616 | |
2444 | The path does not need to exist: changing from "path exists" to "path does |
2617 | The path does not need to exist: changing from "path exists" to "path does |
2445 | not exist" is a status change like any other. The condition "path does not |
2618 | not exist" is a status change like any other. The condition "path does not |
2446 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2619 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2447 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2620 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2677 | Apart from keeping your process non-blocking (which is a useful |
2850 | Apart from keeping your process non-blocking (which is a useful |
2678 | effect on its own sometimes), idle watchers are a good place to do |
2851 | effect on its own sometimes), idle watchers are a good place to do |
2679 | "pseudo-background processing", or delay processing stuff to after the |
2852 | "pseudo-background processing", or delay processing stuff to after the |
2680 | event loop has handled all outstanding events. |
2853 | event loop has handled all outstanding events. |
2681 | |
2854 | |
|
|
2855 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2856 | |
|
|
2857 | As long as there is at least one active idle watcher, libev will never |
|
|
2858 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2859 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2860 | lowest priority will do. |
|
|
2861 | |
|
|
2862 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2863 | to do something on each event loop iteration - for example to balance load |
|
|
2864 | between different connections. |
|
|
2865 | |
|
|
2866 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2867 | example. |
|
|
2868 | |
2682 | =head3 Watcher-Specific Functions and Data Members |
2869 | =head3 Watcher-Specific Functions and Data Members |
2683 | |
2870 | |
2684 | =over 4 |
2871 | =over 4 |
2685 | |
2872 | |
2686 | =item ev_idle_init (ev_idle *, callback) |
2873 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2697 | callback, free it. Also, use no error checking, as usual. |
2884 | callback, free it. Also, use no error checking, as usual. |
2698 | |
2885 | |
2699 | static void |
2886 | static void |
2700 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2887 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2701 | { |
2888 | { |
|
|
2889 | // stop the watcher |
|
|
2890 | ev_idle_stop (loop, w); |
|
|
2891 | |
|
|
2892 | // now we can free it |
2702 | free (w); |
2893 | free (w); |
|
|
2894 | |
2703 | // now do something you wanted to do when the program has |
2895 | // now do something you wanted to do when the program has |
2704 | // no longer anything immediate to do. |
2896 | // no longer anything immediate to do. |
2705 | } |
2897 | } |
2706 | |
2898 | |
2707 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2899 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2709 | ev_idle_start (loop, idle_watcher); |
2901 | ev_idle_start (loop, idle_watcher); |
2710 | |
2902 | |
2711 | |
2903 | |
2712 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2904 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2713 | |
2905 | |
2714 | Prepare and check watchers are usually (but not always) used in pairs: |
2906 | Prepare and check watchers are often (but not always) used in pairs: |
2715 | prepare watchers get invoked before the process blocks and check watchers |
2907 | prepare watchers get invoked before the process blocks and check watchers |
2716 | afterwards. |
2908 | afterwards. |
2717 | |
2909 | |
2718 | You I<must not> call C<ev_run> or similar functions that enter |
2910 | You I<must not> call C<ev_run> or similar functions that enter |
2719 | the current event loop from either C<ev_prepare> or C<ev_check> |
2911 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2747 | with priority higher than or equal to the event loop and one coroutine |
2939 | with priority higher than or equal to the event loop and one coroutine |
2748 | of lower priority, but only once, using idle watchers to keep the event |
2940 | of lower priority, but only once, using idle watchers to keep the event |
2749 | loop from blocking if lower-priority coroutines are active, thus mapping |
2941 | loop from blocking if lower-priority coroutines are active, thus mapping |
2750 | low-priority coroutines to idle/background tasks). |
2942 | low-priority coroutines to idle/background tasks). |
2751 | |
2943 | |
2752 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2944 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2753 | priority, to ensure that they are being run before any other watchers |
2945 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2754 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2946 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2947 | watchers). |
2755 | |
2948 | |
2756 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2949 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2757 | activate ("feed") events into libev. While libev fully supports this, they |
2950 | activate ("feed") events into libev. While libev fully supports this, they |
2758 | might get executed before other C<ev_check> watchers did their job. As |
2951 | might get executed before other C<ev_check> watchers did their job. As |
2759 | C<ev_check> watchers are often used to embed other (non-libev) event |
2952 | C<ev_check> watchers are often used to embed other (non-libev) event |
2760 | loops those other event loops might be in an unusable state until their |
2953 | loops those other event loops might be in an unusable state until their |
2761 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2954 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2762 | others). |
2955 | others). |
|
|
2956 | |
|
|
2957 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2958 | |
|
|
2959 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2960 | useful because they are called once per event loop iteration. For |
|
|
2961 | example, if you want to handle a large number of connections fairly, you |
|
|
2962 | normally only do a bit of work for each active connection, and if there |
|
|
2963 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2964 | connections have a chance of making progress. |
|
|
2965 | |
|
|
2966 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2967 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2968 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2969 | |
|
|
2970 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2971 | single global idle watcher that is active as long as you have one active |
|
|
2972 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2973 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2974 | invoked. Neither watcher alone can do that. |
2763 | |
2975 | |
2764 | =head3 Watcher-Specific Functions and Data Members |
2976 | =head3 Watcher-Specific Functions and Data Members |
2765 | |
2977 | |
2766 | =over 4 |
2978 | =over 4 |
2767 | |
2979 | |
… | |
… | |
2968 | |
3180 | |
2969 | =over 4 |
3181 | =over 4 |
2970 | |
3182 | |
2971 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3183 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2972 | |
3184 | |
2973 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3185 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2974 | |
3186 | |
2975 | Configures the watcher to embed the given loop, which must be |
3187 | Configures the watcher to embed the given loop, which must be |
2976 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3188 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2977 | invoked automatically, otherwise it is the responsibility of the callback |
3189 | invoked automatically, otherwise it is the responsibility of the callback |
2978 | to invoke it (it will continue to be called until the sweep has been done, |
3190 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3041 | |
3253 | |
3042 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3254 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3043 | |
3255 | |
3044 | Fork watchers are called when a C<fork ()> was detected (usually because |
3256 | Fork watchers are called when a C<fork ()> was detected (usually because |
3045 | whoever is a good citizen cared to tell libev about it by calling |
3257 | whoever is a good citizen cared to tell libev about it by calling |
3046 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3258 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3047 | event loop blocks next and before C<ev_check> watchers are being called, |
3259 | and before C<ev_check> watchers are being called, and only in the child |
3048 | and only in the child after the fork. If whoever good citizen calling |
3260 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3049 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3261 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3050 | handlers will be invoked, too, of course. |
3262 | of course. |
3051 | |
3263 | |
3052 | =head3 The special problem of life after fork - how is it possible? |
3264 | =head3 The special problem of life after fork - how is it possible? |
3053 | |
3265 | |
3054 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3266 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3055 | up/change the process environment, followed by a call to C<exec()>. This |
3267 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3075 | disadvantage of having to use multiple event loops (which do not support |
3287 | disadvantage of having to use multiple event loops (which do not support |
3076 | signal watchers). |
3288 | signal watchers). |
3077 | |
3289 | |
3078 | When this is not possible, or you want to use the default loop for |
3290 | When this is not possible, or you want to use the default loop for |
3079 | other reasons, then in the process that wants to start "fresh", call |
3291 | other reasons, then in the process that wants to start "fresh", call |
3080 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3292 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3081 | the default loop will "orphan" (not stop) all registered watchers, so you |
3293 | Destroying the default loop will "orphan" (not stop) all registered |
3082 | have to be careful not to execute code that modifies those watchers. Note |
3294 | watchers, so you have to be careful not to execute code that modifies |
3083 | also that in that case, you have to re-register any signal watchers. |
3295 | those watchers. Note also that in that case, you have to re-register any |
|
|
3296 | signal watchers. |
3084 | |
3297 | |
3085 | =head3 Watcher-Specific Functions and Data Members |
3298 | =head3 Watcher-Specific Functions and Data Members |
3086 | |
3299 | |
3087 | =over 4 |
3300 | =over 4 |
3088 | |
3301 | |
3089 | =item ev_fork_init (ev_signal *, callback) |
3302 | =item ev_fork_init (ev_fork *, callback) |
3090 | |
3303 | |
3091 | Initialises and configures the fork watcher - it has no parameters of any |
3304 | Initialises and configures the fork watcher - it has no parameters of any |
3092 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3305 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3093 | believe me. |
3306 | really. |
3094 | |
3307 | |
3095 | =back |
3308 | =back |
3096 | |
3309 | |
3097 | |
3310 | |
|
|
3311 | =head2 C<ev_cleanup> - even the best things end |
|
|
3312 | |
|
|
3313 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3314 | by a call to C<ev_loop_destroy>. |
|
|
3315 | |
|
|
3316 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3317 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3318 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3319 | loop when you want them to be invoked. |
|
|
3320 | |
|
|
3321 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3322 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3323 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3324 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3325 | |
|
|
3326 | =head3 Watcher-Specific Functions and Data Members |
|
|
3327 | |
|
|
3328 | =over 4 |
|
|
3329 | |
|
|
3330 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3331 | |
|
|
3332 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3333 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3334 | pointless, I assure you. |
|
|
3335 | |
|
|
3336 | =back |
|
|
3337 | |
|
|
3338 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3339 | cleanup functions are called. |
|
|
3340 | |
|
|
3341 | static void |
|
|
3342 | program_exits (void) |
|
|
3343 | { |
|
|
3344 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3345 | } |
|
|
3346 | |
|
|
3347 | ... |
|
|
3348 | atexit (program_exits); |
|
|
3349 | |
|
|
3350 | |
3098 | =head2 C<ev_async> - how to wake up an event loop |
3351 | =head2 C<ev_async> - how to wake up an event loop |
3099 | |
3352 | |
3100 | In general, you cannot use an C<ev_run> from multiple threads or other |
3353 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3101 | asynchronous sources such as signal handlers (as opposed to multiple event |
3354 | asynchronous sources such as signal handlers (as opposed to multiple event |
3102 | loops - those are of course safe to use in different threads). |
3355 | loops - those are of course safe to use in different threads). |
3103 | |
3356 | |
3104 | Sometimes, however, you need to wake up an event loop you do not control, |
3357 | Sometimes, however, you need to wake up an event loop you do not control, |
3105 | for example because it belongs to another thread. This is what C<ev_async> |
3358 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3107 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3360 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3108 | |
3361 | |
3109 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3362 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3110 | too, are asynchronous in nature, and signals, too, will be compressed |
3363 | too, are asynchronous in nature, and signals, too, will be compressed |
3111 | (i.e. the number of callback invocations may be less than the number of |
3364 | (i.e. the number of callback invocations may be less than the number of |
3112 | C<ev_async_sent> calls). |
3365 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3113 | |
3366 | of "global async watchers" by using a watcher on an otherwise unused |
3114 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3367 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3115 | just the default loop. |
3368 | even without knowing which loop owns the signal. |
3116 | |
3369 | |
3117 | =head3 Queueing |
3370 | =head3 Queueing |
3118 | |
3371 | |
3119 | C<ev_async> does not support queueing of data in any way. The reason |
3372 | C<ev_async> does not support queueing of data in any way. The reason |
3120 | is that the author does not know of a simple (or any) algorithm for a |
3373 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3212 | trust me. |
3465 | trust me. |
3213 | |
3466 | |
3214 | =item ev_async_send (loop, ev_async *) |
3467 | =item ev_async_send (loop, ev_async *) |
3215 | |
3468 | |
3216 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3469 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3217 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3470 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3471 | returns. |
|
|
3472 | |
3218 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3473 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3219 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3474 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3220 | section below on what exactly this means). |
3475 | embedding section below on what exactly this means). |
3221 | |
3476 | |
3222 | Note that, as with other watchers in libev, multiple events might get |
3477 | Note that, as with other watchers in libev, multiple events might get |
3223 | compressed into a single callback invocation (another way to look at this |
3478 | compressed into a single callback invocation (another way to look at |
3224 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3479 | this is that C<ev_async> watchers are level-triggered: they are set on |
3225 | reset when the event loop detects that). |
3480 | C<ev_async_send>, reset when the event loop detects that). |
3226 | |
3481 | |
3227 | This call incurs the overhead of a system call only once per event loop |
3482 | This call incurs the overhead of at most one extra system call per event |
3228 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3483 | loop iteration, if the event loop is blocked, and no syscall at all if |
3229 | repeated calls to C<ev_async_send> for the same event loop. |
3484 | the event loop (or your program) is processing events. That means that |
|
|
3485 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3486 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3487 | zero) under load. |
3230 | |
3488 | |
3231 | =item bool = ev_async_pending (ev_async *) |
3489 | =item bool = ev_async_pending (ev_async *) |
3232 | |
3490 | |
3233 | Returns a non-zero value when C<ev_async_send> has been called on the |
3491 | Returns a non-zero value when C<ev_async_send> has been called on the |
3234 | watcher but the event has not yet been processed (or even noted) by the |
3492 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3289 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3547 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3290 | |
3548 | |
3291 | =item ev_feed_fd_event (loop, int fd, int revents) |
3549 | =item ev_feed_fd_event (loop, int fd, int revents) |
3292 | |
3550 | |
3293 | Feed an event on the given fd, as if a file descriptor backend detected |
3551 | Feed an event on the given fd, as if a file descriptor backend detected |
3294 | the given events it. |
3552 | the given events. |
3295 | |
3553 | |
3296 | =item ev_feed_signal_event (loop, int signum) |
3554 | =item ev_feed_signal_event (loop, int signum) |
3297 | |
3555 | |
3298 | Feed an event as if the given signal occurred (C<loop> must be the default |
3556 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3299 | loop!). |
3557 | which is async-safe. |
3300 | |
3558 | |
3301 | =back |
3559 | =back |
|
|
3560 | |
|
|
3561 | |
|
|
3562 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3563 | |
|
|
3564 | This section explains some common idioms that are not immediately |
|
|
3565 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3566 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3567 | |
|
|
3568 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3569 | |
|
|
3570 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3571 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3572 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3573 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3574 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3575 | data: |
|
|
3576 | |
|
|
3577 | struct my_io |
|
|
3578 | { |
|
|
3579 | ev_io io; |
|
|
3580 | int otherfd; |
|
|
3581 | void *somedata; |
|
|
3582 | struct whatever *mostinteresting; |
|
|
3583 | }; |
|
|
3584 | |
|
|
3585 | ... |
|
|
3586 | struct my_io w; |
|
|
3587 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3588 | |
|
|
3589 | And since your callback will be called with a pointer to the watcher, you |
|
|
3590 | can cast it back to your own type: |
|
|
3591 | |
|
|
3592 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3593 | { |
|
|
3594 | struct my_io *w = (struct my_io *)w_; |
|
|
3595 | ... |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | More interesting and less C-conformant ways of casting your callback |
|
|
3599 | function type instead have been omitted. |
|
|
3600 | |
|
|
3601 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3602 | |
|
|
3603 | Another common scenario is to use some data structure with multiple |
|
|
3604 | embedded watchers, in effect creating your own watcher that combines |
|
|
3605 | multiple libev event sources into one "super-watcher": |
|
|
3606 | |
|
|
3607 | struct my_biggy |
|
|
3608 | { |
|
|
3609 | int some_data; |
|
|
3610 | ev_timer t1; |
|
|
3611 | ev_timer t2; |
|
|
3612 | } |
|
|
3613 | |
|
|
3614 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3615 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3616 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3617 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3618 | real programmers): |
|
|
3619 | |
|
|
3620 | #include <stddef.h> |
|
|
3621 | |
|
|
3622 | static void |
|
|
3623 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3624 | { |
|
|
3625 | struct my_biggy big = (struct my_biggy *) |
|
|
3626 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3627 | } |
|
|
3628 | |
|
|
3629 | static void |
|
|
3630 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3631 | { |
|
|
3632 | struct my_biggy big = (struct my_biggy *) |
|
|
3633 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3634 | } |
|
|
3635 | |
|
|
3636 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3637 | |
|
|
3638 | Often you have structures like this in event-based programs: |
|
|
3639 | |
|
|
3640 | callback () |
|
|
3641 | { |
|
|
3642 | free (request); |
|
|
3643 | } |
|
|
3644 | |
|
|
3645 | request = start_new_request (..., callback); |
|
|
3646 | |
|
|
3647 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3648 | used to cancel the operation, or do other things with it. |
|
|
3649 | |
|
|
3650 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3651 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3652 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3653 | operation and simply invoke the callback with the result. |
|
|
3654 | |
|
|
3655 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3656 | has returned, so C<request> is not set. |
|
|
3657 | |
|
|
3658 | Even if you pass the request by some safer means to the callback, you |
|
|
3659 | might want to do something to the request after starting it, such as |
|
|
3660 | canceling it, which probably isn't working so well when the callback has |
|
|
3661 | already been invoked. |
|
|
3662 | |
|
|
3663 | A common way around all these issues is to make sure that |
|
|
3664 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3665 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3666 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3667 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3668 | pushing it into the pending queue: |
|
|
3669 | |
|
|
3670 | ev_set_cb (watcher, callback); |
|
|
3671 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3672 | |
|
|
3673 | This way, C<start_new_request> can safely return before the callback is |
|
|
3674 | invoked, while not delaying callback invocation too much. |
|
|
3675 | |
|
|
3676 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3677 | |
|
|
3678 | Often (especially in GUI toolkits) there are places where you have |
|
|
3679 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3680 | invoking C<ev_run>. |
|
|
3681 | |
|
|
3682 | This brings the problem of exiting - a callback might want to finish the |
|
|
3683 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3684 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3685 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3686 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3687 | |
|
|
3688 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3689 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3690 | triggered, using C<EVRUN_ONCE>: |
|
|
3691 | |
|
|
3692 | // main loop |
|
|
3693 | int exit_main_loop = 0; |
|
|
3694 | |
|
|
3695 | while (!exit_main_loop) |
|
|
3696 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3697 | |
|
|
3698 | // in a modal watcher |
|
|
3699 | int exit_nested_loop = 0; |
|
|
3700 | |
|
|
3701 | while (!exit_nested_loop) |
|
|
3702 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3703 | |
|
|
3704 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3705 | |
|
|
3706 | // exit modal loop |
|
|
3707 | exit_nested_loop = 1; |
|
|
3708 | |
|
|
3709 | // exit main program, after modal loop is finished |
|
|
3710 | exit_main_loop = 1; |
|
|
3711 | |
|
|
3712 | // exit both |
|
|
3713 | exit_main_loop = exit_nested_loop = 1; |
|
|
3714 | |
|
|
3715 | =head2 THREAD LOCKING EXAMPLE |
|
|
3716 | |
|
|
3717 | Here is a fictitious example of how to run an event loop in a different |
|
|
3718 | thread from where callbacks are being invoked and watchers are |
|
|
3719 | created/added/removed. |
|
|
3720 | |
|
|
3721 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3722 | which uses exactly this technique (which is suited for many high-level |
|
|
3723 | languages). |
|
|
3724 | |
|
|
3725 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3726 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3727 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3728 | |
|
|
3729 | First, you need to associate some data with the event loop: |
|
|
3730 | |
|
|
3731 | typedef struct { |
|
|
3732 | mutex_t lock; /* global loop lock */ |
|
|
3733 | ev_async async_w; |
|
|
3734 | thread_t tid; |
|
|
3735 | cond_t invoke_cv; |
|
|
3736 | } userdata; |
|
|
3737 | |
|
|
3738 | void prepare_loop (EV_P) |
|
|
3739 | { |
|
|
3740 | // for simplicity, we use a static userdata struct. |
|
|
3741 | static userdata u; |
|
|
3742 | |
|
|
3743 | ev_async_init (&u->async_w, async_cb); |
|
|
3744 | ev_async_start (EV_A_ &u->async_w); |
|
|
3745 | |
|
|
3746 | pthread_mutex_init (&u->lock, 0); |
|
|
3747 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3748 | |
|
|
3749 | // now associate this with the loop |
|
|
3750 | ev_set_userdata (EV_A_ u); |
|
|
3751 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3752 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3753 | |
|
|
3754 | // then create the thread running ev_run |
|
|
3755 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3756 | } |
|
|
3757 | |
|
|
3758 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3759 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3760 | that might have been added: |
|
|
3761 | |
|
|
3762 | static void |
|
|
3763 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3764 | { |
|
|
3765 | // just used for the side effects |
|
|
3766 | } |
|
|
3767 | |
|
|
3768 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3769 | protecting the loop data, respectively. |
|
|
3770 | |
|
|
3771 | static void |
|
|
3772 | l_release (EV_P) |
|
|
3773 | { |
|
|
3774 | userdata *u = ev_userdata (EV_A); |
|
|
3775 | pthread_mutex_unlock (&u->lock); |
|
|
3776 | } |
|
|
3777 | |
|
|
3778 | static void |
|
|
3779 | l_acquire (EV_P) |
|
|
3780 | { |
|
|
3781 | userdata *u = ev_userdata (EV_A); |
|
|
3782 | pthread_mutex_lock (&u->lock); |
|
|
3783 | } |
|
|
3784 | |
|
|
3785 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3786 | into C<ev_run>: |
|
|
3787 | |
|
|
3788 | void * |
|
|
3789 | l_run (void *thr_arg) |
|
|
3790 | { |
|
|
3791 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3792 | |
|
|
3793 | l_acquire (EV_A); |
|
|
3794 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3795 | ev_run (EV_A_ 0); |
|
|
3796 | l_release (EV_A); |
|
|
3797 | |
|
|
3798 | return 0; |
|
|
3799 | } |
|
|
3800 | |
|
|
3801 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3802 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3803 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3804 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3805 | and b) skipping inter-thread-communication when there are no pending |
|
|
3806 | watchers is very beneficial): |
|
|
3807 | |
|
|
3808 | static void |
|
|
3809 | l_invoke (EV_P) |
|
|
3810 | { |
|
|
3811 | userdata *u = ev_userdata (EV_A); |
|
|
3812 | |
|
|
3813 | while (ev_pending_count (EV_A)) |
|
|
3814 | { |
|
|
3815 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3816 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3817 | } |
|
|
3818 | } |
|
|
3819 | |
|
|
3820 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3821 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3822 | thread to continue: |
|
|
3823 | |
|
|
3824 | static void |
|
|
3825 | real_invoke_pending (EV_P) |
|
|
3826 | { |
|
|
3827 | userdata *u = ev_userdata (EV_A); |
|
|
3828 | |
|
|
3829 | pthread_mutex_lock (&u->lock); |
|
|
3830 | ev_invoke_pending (EV_A); |
|
|
3831 | pthread_cond_signal (&u->invoke_cv); |
|
|
3832 | pthread_mutex_unlock (&u->lock); |
|
|
3833 | } |
|
|
3834 | |
|
|
3835 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3836 | event loop, you will now have to lock: |
|
|
3837 | |
|
|
3838 | ev_timer timeout_watcher; |
|
|
3839 | userdata *u = ev_userdata (EV_A); |
|
|
3840 | |
|
|
3841 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3842 | |
|
|
3843 | pthread_mutex_lock (&u->lock); |
|
|
3844 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3845 | ev_async_send (EV_A_ &u->async_w); |
|
|
3846 | pthread_mutex_unlock (&u->lock); |
|
|
3847 | |
|
|
3848 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3849 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3850 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3851 | watchers in the next event loop iteration. |
|
|
3852 | |
|
|
3853 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3854 | |
|
|
3855 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3856 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3857 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3858 | doesn't need callbacks anymore. |
|
|
3859 | |
|
|
3860 | Imagine you have coroutines that you can switch to using a function |
|
|
3861 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3862 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3863 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3864 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3865 | the differing C<;> conventions): |
|
|
3866 | |
|
|
3867 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3868 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3869 | |
|
|
3870 | That means instead of having a C callback function, you store the |
|
|
3871 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3872 | your callback, you instead have it switch to that coroutine. |
|
|
3873 | |
|
|
3874 | A coroutine might now wait for an event with a function called |
|
|
3875 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3876 | matter when, or whether the watcher is active or not when this function is |
|
|
3877 | called): |
|
|
3878 | |
|
|
3879 | void |
|
|
3880 | wait_for_event (ev_watcher *w) |
|
|
3881 | { |
|
|
3882 | ev_set_cb (w, current_coro); |
|
|
3883 | switch_to (libev_coro); |
|
|
3884 | } |
|
|
3885 | |
|
|
3886 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3887 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3888 | this or any other coroutine. |
|
|
3889 | |
|
|
3890 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3891 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3892 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3893 | any waiters. |
|
|
3894 | |
|
|
3895 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3896 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3897 | |
|
|
3898 | // my_ev.h |
|
|
3899 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3900 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3901 | #include "../libev/ev.h" |
|
|
3902 | |
|
|
3903 | // my_ev.c |
|
|
3904 | #define EV_H "my_ev.h" |
|
|
3905 | #include "../libev/ev.c" |
|
|
3906 | |
|
|
3907 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3908 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3909 | can even use F<ev.h> as header file name directly. |
3302 | |
3910 | |
3303 | |
3911 | |
3304 | =head1 LIBEVENT EMULATION |
3912 | =head1 LIBEVENT EMULATION |
3305 | |
3913 | |
3306 | Libev offers a compatibility emulation layer for libevent. It cannot |
3914 | Libev offers a compatibility emulation layer for libevent. It cannot |
3307 | emulate the internals of libevent, so here are some usage hints: |
3915 | emulate the internals of libevent, so here are some usage hints: |
3308 | |
3916 | |
3309 | =over 4 |
3917 | =over 4 |
|
|
3918 | |
|
|
3919 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3920 | |
|
|
3921 | This was the newest libevent version available when libev was implemented, |
|
|
3922 | and is still mostly unchanged in 2010. |
3310 | |
3923 | |
3311 | =item * Use it by including <event.h>, as usual. |
3924 | =item * Use it by including <event.h>, as usual. |
3312 | |
3925 | |
3313 | =item * The following members are fully supported: ev_base, ev_callback, |
3926 | =item * The following members are fully supported: ev_base, ev_callback, |
3314 | ev_arg, ev_fd, ev_res, ev_events. |
3927 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3320 | =item * Priorities are not currently supported. Initialising priorities |
3933 | =item * Priorities are not currently supported. Initialising priorities |
3321 | will fail and all watchers will have the same priority, even though there |
3934 | will fail and all watchers will have the same priority, even though there |
3322 | is an ev_pri field. |
3935 | is an ev_pri field. |
3323 | |
3936 | |
3324 | =item * In libevent, the last base created gets the signals, in libev, the |
3937 | =item * In libevent, the last base created gets the signals, in libev, the |
3325 | first base created (== the default loop) gets the signals. |
3938 | base that registered the signal gets the signals. |
3326 | |
3939 | |
3327 | =item * Other members are not supported. |
3940 | =item * Other members are not supported. |
3328 | |
3941 | |
3329 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3942 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3330 | to use the libev header file and library. |
3943 | to use the libev header file and library. |
3331 | |
3944 | |
3332 | =back |
3945 | =back |
3333 | |
3946 | |
3334 | =head1 C++ SUPPORT |
3947 | =head1 C++ SUPPORT |
|
|
3948 | |
|
|
3949 | =head2 C API |
|
|
3950 | |
|
|
3951 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3952 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3953 | will work fine. |
|
|
3954 | |
|
|
3955 | Proper exception specifications might have to be added to callbacks passed |
|
|
3956 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3957 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3958 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3959 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3960 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3961 | |
|
|
3962 | static void |
|
|
3963 | fatal_error (const char *msg) EV_THROW |
|
|
3964 | { |
|
|
3965 | perror (msg); |
|
|
3966 | abort (); |
|
|
3967 | } |
|
|
3968 | |
|
|
3969 | ... |
|
|
3970 | ev_set_syserr_cb (fatal_error); |
|
|
3971 | |
|
|
3972 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3973 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3974 | because it runs cleanup watchers). |
|
|
3975 | |
|
|
3976 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3977 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3978 | throwing exceptions through C libraries (most do). |
|
|
3979 | |
|
|
3980 | =head2 C++ API |
3335 | |
3981 | |
3336 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3982 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3337 | you to use some convenience methods to start/stop watchers and also change |
3983 | you to use some convenience methods to start/stop watchers and also change |
3338 | the callback model to a model using method callbacks on objects. |
3984 | the callback model to a model using method callbacks on objects. |
3339 | |
3985 | |
3340 | To use it, |
3986 | To use it, |
3341 | |
3987 | |
3342 | #include <ev++.h> |
3988 | #include <ev++.h> |
3343 | |
3989 | |
3344 | This automatically includes F<ev.h> and puts all of its definitions (many |
3990 | This automatically includes F<ev.h> and puts all of its definitions (many |
3345 | of them macros) into the global namespace. All C++ specific things are |
3991 | of them macros) into the global namespace. All C++ specific things are |
3346 | put into the C<ev> namespace. It should support all the same embedding |
3992 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3349 | Care has been taken to keep the overhead low. The only data member the C++ |
3995 | Care has been taken to keep the overhead low. The only data member the C++ |
3350 | classes add (compared to plain C-style watchers) is the event loop pointer |
3996 | classes add (compared to plain C-style watchers) is the event loop pointer |
3351 | that the watcher is associated with (or no additional members at all if |
3997 | that the watcher is associated with (or no additional members at all if |
3352 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3998 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3353 | |
3999 | |
3354 | Currently, functions, and static and non-static member functions can be |
4000 | Currently, functions, static and non-static member functions and classes |
3355 | used as callbacks. Other types should be easy to add as long as they only |
4001 | with C<operator ()> can be used as callbacks. Other types should be easy |
3356 | need one additional pointer for context. If you need support for other |
4002 | to add as long as they only need one additional pointer for context. If |
3357 | types of functors please contact the author (preferably after implementing |
4003 | you need support for other types of functors please contact the author |
3358 | it). |
4004 | (preferably after implementing it). |
|
|
4005 | |
|
|
4006 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4007 | conventions as your C compiler (for static member functions), or you have |
|
|
4008 | to embed libev and compile libev itself as C++. |
3359 | |
4009 | |
3360 | Here is a list of things available in the C<ev> namespace: |
4010 | Here is a list of things available in the C<ev> namespace: |
3361 | |
4011 | |
3362 | =over 4 |
4012 | =over 4 |
3363 | |
4013 | |
… | |
… | |
3373 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4023 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3374 | |
4024 | |
3375 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4025 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3376 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4026 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3377 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4027 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3378 | defines by many implementations. |
4028 | defined by many implementations. |
3379 | |
4029 | |
3380 | All of those classes have these methods: |
4030 | All of those classes have these methods: |
3381 | |
4031 | |
3382 | =over 4 |
4032 | =over 4 |
3383 | |
4033 | |
… | |
… | |
3473 | Associates a different C<struct ev_loop> with this watcher. You can only |
4123 | Associates a different C<struct ev_loop> with this watcher. You can only |
3474 | do this when the watcher is inactive (and not pending either). |
4124 | do this when the watcher is inactive (and not pending either). |
3475 | |
4125 | |
3476 | =item w->set ([arguments]) |
4126 | =item w->set ([arguments]) |
3477 | |
4127 | |
3478 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4128 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3479 | method or a suitable start method must be called at least once. Unlike the |
4129 | with the same arguments. Either this method or a suitable start method |
3480 | C counterpart, an active watcher gets automatically stopped and restarted |
4130 | must be called at least once. Unlike the C counterpart, an active watcher |
3481 | when reconfiguring it with this method. |
4131 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4132 | method. |
|
|
4133 | |
|
|
4134 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4135 | clashing with the C<set (loop)> method. |
3482 | |
4136 | |
3483 | =item w->start () |
4137 | =item w->start () |
3484 | |
4138 | |
3485 | Starts the watcher. Note that there is no C<loop> argument, as the |
4139 | Starts the watcher. Note that there is no C<loop> argument, as the |
3486 | constructor already stores the event loop. |
4140 | constructor already stores the event loop. |
… | |
… | |
3516 | watchers in the constructor. |
4170 | watchers in the constructor. |
3517 | |
4171 | |
3518 | class myclass |
4172 | class myclass |
3519 | { |
4173 | { |
3520 | ev::io io ; void io_cb (ev::io &w, int revents); |
4174 | ev::io io ; void io_cb (ev::io &w, int revents); |
3521 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4175 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3522 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4176 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3523 | |
4177 | |
3524 | myclass (int fd) |
4178 | myclass (int fd) |
3525 | { |
4179 | { |
3526 | io .set <myclass, &myclass::io_cb > (this); |
4180 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3577 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4231 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3578 | |
4232 | |
3579 | =item D |
4233 | =item D |
3580 | |
4234 | |
3581 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4235 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3582 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4236 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3583 | |
4237 | |
3584 | =item Ocaml |
4238 | =item Ocaml |
3585 | |
4239 | |
3586 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4240 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3587 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4241 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3590 | |
4244 | |
3591 | Brian Maher has written a partial interface to libev for lua (at the |
4245 | Brian Maher has written a partial interface to libev for lua (at the |
3592 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4246 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3593 | L<http://github.com/brimworks/lua-ev>. |
4247 | L<http://github.com/brimworks/lua-ev>. |
3594 | |
4248 | |
|
|
4249 | =item Javascript |
|
|
4250 | |
|
|
4251 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4252 | |
|
|
4253 | =item Others |
|
|
4254 | |
|
|
4255 | There are others, and I stopped counting. |
|
|
4256 | |
3595 | =back |
4257 | =back |
3596 | |
4258 | |
3597 | |
4259 | |
3598 | =head1 MACRO MAGIC |
4260 | =head1 MACRO MAGIC |
3599 | |
4261 | |
… | |
… | |
3635 | suitable for use with C<EV_A>. |
4297 | suitable for use with C<EV_A>. |
3636 | |
4298 | |
3637 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4299 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3638 | |
4300 | |
3639 | Similar to the other two macros, this gives you the value of the default |
4301 | Similar to the other two macros, this gives you the value of the default |
3640 | loop, if multiple loops are supported ("ev loop default"). |
4302 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4303 | will be initialised if it isn't already initialised. |
|
|
4304 | |
|
|
4305 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4306 | to initialise the loop somewhere. |
3641 | |
4307 | |
3642 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4308 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3643 | |
4309 | |
3644 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4310 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3645 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4311 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3790 | supported). It will also not define any of the structs usually found in |
4456 | supported). It will also not define any of the structs usually found in |
3791 | F<event.h> that are not directly supported by the libev core alone. |
4457 | F<event.h> that are not directly supported by the libev core alone. |
3792 | |
4458 | |
3793 | In standalone mode, libev will still try to automatically deduce the |
4459 | In standalone mode, libev will still try to automatically deduce the |
3794 | configuration, but has to be more conservative. |
4460 | configuration, but has to be more conservative. |
|
|
4461 | |
|
|
4462 | =item EV_USE_FLOOR |
|
|
4463 | |
|
|
4464 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4465 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4466 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4467 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4468 | function is not available will fail, so the safe default is to not enable |
|
|
4469 | this. |
3795 | |
4470 | |
3796 | =item EV_USE_MONOTONIC |
4471 | =item EV_USE_MONOTONIC |
3797 | |
4472 | |
3798 | If defined to be C<1>, libev will try to detect the availability of the |
4473 | If defined to be C<1>, libev will try to detect the availability of the |
3799 | monotonic clock option at both compile time and runtime. Otherwise no |
4474 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3884 | |
4559 | |
3885 | If programs implement their own fd to handle mapping on win32, then this |
4560 | If programs implement their own fd to handle mapping on win32, then this |
3886 | macro can be used to override the C<close> function, useful to unregister |
4561 | macro can be used to override the C<close> function, useful to unregister |
3887 | file descriptors again. Note that the replacement function has to close |
4562 | file descriptors again. Note that the replacement function has to close |
3888 | the underlying OS handle. |
4563 | the underlying OS handle. |
|
|
4564 | |
|
|
4565 | =item EV_USE_WSASOCKET |
|
|
4566 | |
|
|
4567 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4568 | communication socket, which works better in some environments. Otherwise, |
|
|
4569 | the normal C<socket> function will be used, which works better in other |
|
|
4570 | environments. |
3889 | |
4571 | |
3890 | =item EV_USE_POLL |
4572 | =item EV_USE_POLL |
3891 | |
4573 | |
3892 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4574 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3893 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4575 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3929 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4611 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3930 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4612 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3931 | be detected at runtime. If undefined, it will be enabled if the headers |
4613 | be detected at runtime. If undefined, it will be enabled if the headers |
3932 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4614 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3933 | |
4615 | |
|
|
4616 | =item EV_NO_SMP |
|
|
4617 | |
|
|
4618 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4619 | between threads, that is, threads can be used, but threads never run on |
|
|
4620 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4621 | and makes libev faster. |
|
|
4622 | |
|
|
4623 | =item EV_NO_THREADS |
|
|
4624 | |
|
|
4625 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4626 | different threads (that includes signal handlers), which is a stronger |
|
|
4627 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4628 | libev faster. |
|
|
4629 | |
3934 | =item EV_ATOMIC_T |
4630 | =item EV_ATOMIC_T |
3935 | |
4631 | |
3936 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4632 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3937 | access is atomic with respect to other threads or signal contexts. No such |
4633 | access is atomic with respect to other threads or signal contexts. No |
3938 | type is easily found in the C language, so you can provide your own type |
4634 | such type is easily found in the C language, so you can provide your own |
3939 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4635 | type that you know is safe for your purposes. It is used both for signal |
3940 | as well as for signal and thread safety in C<ev_async> watchers. |
4636 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4637 | watchers. |
3941 | |
4638 | |
3942 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4639 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3943 | (from F<signal.h>), which is usually good enough on most platforms. |
4640 | (from F<signal.h>), which is usually good enough on most platforms. |
3944 | |
4641 | |
3945 | =item EV_H (h) |
4642 | =item EV_H (h) |
… | |
… | |
3972 | will have the C<struct ev_loop *> as first argument, and you can create |
4669 | will have the C<struct ev_loop *> as first argument, and you can create |
3973 | additional independent event loops. Otherwise there will be no support |
4670 | additional independent event loops. Otherwise there will be no support |
3974 | for multiple event loops and there is no first event loop pointer |
4671 | for multiple event loops and there is no first event loop pointer |
3975 | argument. Instead, all functions act on the single default loop. |
4672 | argument. Instead, all functions act on the single default loop. |
3976 | |
4673 | |
|
|
4674 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4675 | default loop when multiplicity is switched off - you always have to |
|
|
4676 | initialise the loop manually in this case. |
|
|
4677 | |
3977 | =item EV_MINPRI |
4678 | =item EV_MINPRI |
3978 | |
4679 | |
3979 | =item EV_MAXPRI |
4680 | =item EV_MAXPRI |
3980 | |
4681 | |
3981 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4682 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4017 | #define EV_USE_POLL 1 |
4718 | #define EV_USE_POLL 1 |
4018 | #define EV_CHILD_ENABLE 1 |
4719 | #define EV_CHILD_ENABLE 1 |
4019 | #define EV_ASYNC_ENABLE 1 |
4720 | #define EV_ASYNC_ENABLE 1 |
4020 | |
4721 | |
4021 | The actual value is a bitset, it can be a combination of the following |
4722 | The actual value is a bitset, it can be a combination of the following |
4022 | values: |
4723 | values (by default, all of these are enabled): |
4023 | |
4724 | |
4024 | =over 4 |
4725 | =over 4 |
4025 | |
4726 | |
4026 | =item C<1> - faster/larger code |
4727 | =item C<1> - faster/larger code |
4027 | |
4728 | |
… | |
… | |
4031 | code size by roughly 30% on amd64). |
4732 | code size by roughly 30% on amd64). |
4032 | |
4733 | |
4033 | When optimising for size, use of compiler flags such as C<-Os> with |
4734 | When optimising for size, use of compiler flags such as C<-Os> with |
4034 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4735 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4035 | assertions. |
4736 | assertions. |
|
|
4737 | |
|
|
4738 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4739 | (e.g. gcc with C<-Os>). |
4036 | |
4740 | |
4037 | =item C<2> - faster/larger data structures |
4741 | =item C<2> - faster/larger data structures |
4038 | |
4742 | |
4039 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4743 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4040 | hash table sizes and so on. This will usually further increase code size |
4744 | hash table sizes and so on. This will usually further increase code size |
4041 | and can additionally have an effect on the size of data structures at |
4745 | and can additionally have an effect on the size of data structures at |
4042 | runtime. |
4746 | runtime. |
4043 | |
4747 | |
|
|
4748 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4749 | (e.g. gcc with C<-Os>). |
|
|
4750 | |
4044 | =item C<4> - full API configuration |
4751 | =item C<4> - full API configuration |
4045 | |
4752 | |
4046 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4753 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4047 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4754 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4048 | |
4755 | |
… | |
… | |
4078 | |
4785 | |
4079 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4786 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4080 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4787 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4081 | your program might be left out as well - a binary starting a timer and an |
4788 | your program might be left out as well - a binary starting a timer and an |
4082 | I/O watcher then might come out at only 5Kb. |
4789 | I/O watcher then might come out at only 5Kb. |
|
|
4790 | |
|
|
4791 | =item EV_API_STATIC |
|
|
4792 | |
|
|
4793 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4794 | will have static linkage. This means that libev will not export any |
|
|
4795 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4796 | when you embed libev, only want to use libev functions in a single file, |
|
|
4797 | and do not want its identifiers to be visible. |
|
|
4798 | |
|
|
4799 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4800 | wants to use libev. |
|
|
4801 | |
|
|
4802 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4803 | doesn't support the required declaration syntax. |
4083 | |
4804 | |
4084 | =item EV_AVOID_STDIO |
4805 | =item EV_AVOID_STDIO |
4085 | |
4806 | |
4086 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4807 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4087 | functions (printf, scanf, perror etc.). This will increase the code size |
4808 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4231 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4952 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4232 | |
4953 | |
4233 | #include "ev_cpp.h" |
4954 | #include "ev_cpp.h" |
4234 | #include "ev.c" |
4955 | #include "ev.c" |
4235 | |
4956 | |
4236 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4957 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4237 | |
4958 | |
4238 | =head2 THREADS AND COROUTINES |
4959 | =head2 THREADS AND COROUTINES |
4239 | |
4960 | |
4240 | =head3 THREADS |
4961 | =head3 THREADS |
4241 | |
4962 | |
… | |
… | |
4292 | default loop and triggering an C<ev_async> watcher from the default loop |
5013 | default loop and triggering an C<ev_async> watcher from the default loop |
4293 | watcher callback into the event loop interested in the signal. |
5014 | watcher callback into the event loop interested in the signal. |
4294 | |
5015 | |
4295 | =back |
5016 | =back |
4296 | |
5017 | |
4297 | =head4 THREAD LOCKING EXAMPLE |
5018 | See also L</THREAD LOCKING EXAMPLE>. |
4298 | |
|
|
4299 | Here is a fictitious example of how to run an event loop in a different |
|
|
4300 | thread than where callbacks are being invoked and watchers are |
|
|
4301 | created/added/removed. |
|
|
4302 | |
|
|
4303 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4304 | which uses exactly this technique (which is suited for many high-level |
|
|
4305 | languages). |
|
|
4306 | |
|
|
4307 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4308 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4309 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4310 | |
|
|
4311 | First, you need to associate some data with the event loop: |
|
|
4312 | |
|
|
4313 | typedef struct { |
|
|
4314 | mutex_t lock; /* global loop lock */ |
|
|
4315 | ev_async async_w; |
|
|
4316 | thread_t tid; |
|
|
4317 | cond_t invoke_cv; |
|
|
4318 | } userdata; |
|
|
4319 | |
|
|
4320 | void prepare_loop (EV_P) |
|
|
4321 | { |
|
|
4322 | // for simplicity, we use a static userdata struct. |
|
|
4323 | static userdata u; |
|
|
4324 | |
|
|
4325 | ev_async_init (&u->async_w, async_cb); |
|
|
4326 | ev_async_start (EV_A_ &u->async_w); |
|
|
4327 | |
|
|
4328 | pthread_mutex_init (&u->lock, 0); |
|
|
4329 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4330 | |
|
|
4331 | // now associate this with the loop |
|
|
4332 | ev_set_userdata (EV_A_ u); |
|
|
4333 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4334 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4335 | |
|
|
4336 | // then create the thread running ev_loop |
|
|
4337 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4338 | } |
|
|
4339 | |
|
|
4340 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4341 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4342 | that might have been added: |
|
|
4343 | |
|
|
4344 | static void |
|
|
4345 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4346 | { |
|
|
4347 | // just used for the side effects |
|
|
4348 | } |
|
|
4349 | |
|
|
4350 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4351 | protecting the loop data, respectively. |
|
|
4352 | |
|
|
4353 | static void |
|
|
4354 | l_release (EV_P) |
|
|
4355 | { |
|
|
4356 | userdata *u = ev_userdata (EV_A); |
|
|
4357 | pthread_mutex_unlock (&u->lock); |
|
|
4358 | } |
|
|
4359 | |
|
|
4360 | static void |
|
|
4361 | l_acquire (EV_P) |
|
|
4362 | { |
|
|
4363 | userdata *u = ev_userdata (EV_A); |
|
|
4364 | pthread_mutex_lock (&u->lock); |
|
|
4365 | } |
|
|
4366 | |
|
|
4367 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4368 | into C<ev_run>: |
|
|
4369 | |
|
|
4370 | void * |
|
|
4371 | l_run (void *thr_arg) |
|
|
4372 | { |
|
|
4373 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4374 | |
|
|
4375 | l_acquire (EV_A); |
|
|
4376 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4377 | ev_run (EV_A_ 0); |
|
|
4378 | l_release (EV_A); |
|
|
4379 | |
|
|
4380 | return 0; |
|
|
4381 | } |
|
|
4382 | |
|
|
4383 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4384 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4385 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4386 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4387 | and b) skipping inter-thread-communication when there are no pending |
|
|
4388 | watchers is very beneficial): |
|
|
4389 | |
|
|
4390 | static void |
|
|
4391 | l_invoke (EV_P) |
|
|
4392 | { |
|
|
4393 | userdata *u = ev_userdata (EV_A); |
|
|
4394 | |
|
|
4395 | while (ev_pending_count (EV_A)) |
|
|
4396 | { |
|
|
4397 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4398 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4399 | } |
|
|
4400 | } |
|
|
4401 | |
|
|
4402 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4403 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4404 | thread to continue: |
|
|
4405 | |
|
|
4406 | static void |
|
|
4407 | real_invoke_pending (EV_P) |
|
|
4408 | { |
|
|
4409 | userdata *u = ev_userdata (EV_A); |
|
|
4410 | |
|
|
4411 | pthread_mutex_lock (&u->lock); |
|
|
4412 | ev_invoke_pending (EV_A); |
|
|
4413 | pthread_cond_signal (&u->invoke_cv); |
|
|
4414 | pthread_mutex_unlock (&u->lock); |
|
|
4415 | } |
|
|
4416 | |
|
|
4417 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4418 | event loop, you will now have to lock: |
|
|
4419 | |
|
|
4420 | ev_timer timeout_watcher; |
|
|
4421 | userdata *u = ev_userdata (EV_A); |
|
|
4422 | |
|
|
4423 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4424 | |
|
|
4425 | pthread_mutex_lock (&u->lock); |
|
|
4426 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4427 | ev_async_send (EV_A_ &u->async_w); |
|
|
4428 | pthread_mutex_unlock (&u->lock); |
|
|
4429 | |
|
|
4430 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4431 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4432 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4433 | watchers in the next event loop iteration. |
|
|
4434 | |
5019 | |
4435 | =head3 COROUTINES |
5020 | =head3 COROUTINES |
4436 | |
5021 | |
4437 | Libev is very accommodating to coroutines ("cooperative threads"): |
5022 | Libev is very accommodating to coroutines ("cooperative threads"): |
4438 | libev fully supports nesting calls to its functions from different |
5023 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4603 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5188 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4604 | model. Libev still offers limited functionality on this platform in |
5189 | model. Libev still offers limited functionality on this platform in |
4605 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5190 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4606 | descriptors. This only applies when using Win32 natively, not when using |
5191 | descriptors. This only applies when using Win32 natively, not when using |
4607 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5192 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4608 | as every compielr comes with a slightly differently broken/incompatible |
5193 | as every compiler comes with a slightly differently broken/incompatible |
4609 | environment. |
5194 | environment. |
4610 | |
5195 | |
4611 | Lifting these limitations would basically require the full |
5196 | Lifting these limitations would basically require the full |
4612 | re-implementation of the I/O system. If you are into this kind of thing, |
5197 | re-implementation of the I/O system. If you are into this kind of thing, |
4613 | then note that glib does exactly that for you in a very portable way (note |
5198 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4707 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5292 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4708 | assumes that the same (machine) code can be used to call any watcher |
5293 | assumes that the same (machine) code can be used to call any watcher |
4709 | callback: The watcher callbacks have different type signatures, but libev |
5294 | callback: The watcher callbacks have different type signatures, but libev |
4710 | calls them using an C<ev_watcher *> internally. |
5295 | calls them using an C<ev_watcher *> internally. |
4711 | |
5296 | |
|
|
5297 | =item pointer accesses must be thread-atomic |
|
|
5298 | |
|
|
5299 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5300 | writable in one piece - this is the case on all current architectures. |
|
|
5301 | |
4712 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5302 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4713 | |
5303 | |
4714 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5304 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4715 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5305 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4716 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5306 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4724 | thread" or will block signals process-wide, both behaviours would |
5314 | thread" or will block signals process-wide, both behaviours would |
4725 | be compatible with libev. Interaction between C<sigprocmask> and |
5315 | be compatible with libev. Interaction between C<sigprocmask> and |
4726 | C<pthread_sigmask> could complicate things, however. |
5316 | C<pthread_sigmask> could complicate things, however. |
4727 | |
5317 | |
4728 | The most portable way to handle signals is to block signals in all threads |
5318 | The most portable way to handle signals is to block signals in all threads |
4729 | except the initial one, and run the default loop in the initial thread as |
5319 | except the initial one, and run the signal handling loop in the initial |
4730 | well. |
5320 | thread as well. |
4731 | |
5321 | |
4732 | =item C<long> must be large enough for common memory allocation sizes |
5322 | =item C<long> must be large enough for common memory allocation sizes |
4733 | |
5323 | |
4734 | To improve portability and simplify its API, libev uses C<long> internally |
5324 | To improve portability and simplify its API, libev uses C<long> internally |
4735 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5325 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4741 | |
5331 | |
4742 | The type C<double> is used to represent timestamps. It is required to |
5332 | The type C<double> is used to represent timestamps. It is required to |
4743 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5333 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4744 | good enough for at least into the year 4000 with millisecond accuracy |
5334 | good enough for at least into the year 4000 with millisecond accuracy |
4745 | (the design goal for libev). This requirement is overfulfilled by |
5335 | (the design goal for libev). This requirement is overfulfilled by |
4746 | implementations using IEEE 754, which is basically all existing ones. With |
5336 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5337 | |
4747 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5338 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5339 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5340 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5341 | something like that, just kidding). |
4748 | |
5342 | |
4749 | =back |
5343 | =back |
4750 | |
5344 | |
4751 | If you know of other additional requirements drop me a note. |
5345 | If you know of other additional requirements drop me a note. |
4752 | |
5346 | |
… | |
… | |
4814 | =item Processing ev_async_send: O(number_of_async_watchers) |
5408 | =item Processing ev_async_send: O(number_of_async_watchers) |
4815 | |
5409 | |
4816 | =item Processing signals: O(max_signal_number) |
5410 | =item Processing signals: O(max_signal_number) |
4817 | |
5411 | |
4818 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5412 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4819 | calls in the current loop iteration. Checking for async and signal events |
5413 | calls in the current loop iteration and the loop is currently |
|
|
5414 | blocked. Checking for async and signal events involves iterating over all |
4820 | involves iterating over all running async watchers or all signal numbers. |
5415 | running async watchers or all signal numbers. |
4821 | |
5416 | |
4822 | =back |
5417 | =back |
4823 | |
5418 | |
4824 | |
5419 | |
4825 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5420 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4826 | |
5421 | |
4827 | The major version 4 introduced some minor incompatible changes to the API. |
5422 | The major version 4 introduced some incompatible changes to the API. |
4828 | |
5423 | |
4829 | At the moment, the C<ev.h> header file tries to implement superficial |
5424 | At the moment, the C<ev.h> header file provides compatibility definitions |
4830 | compatibility, so most programs should still compile. Those might be |
5425 | for all changes, so most programs should still compile. The compatibility |
4831 | removed in later versions of libev, so better update early than late. |
5426 | layer might be removed in later versions of libev, so better update to the |
|
|
5427 | new API early than late. |
4832 | |
5428 | |
4833 | =over 4 |
5429 | =over 4 |
|
|
5430 | |
|
|
5431 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5432 | |
|
|
5433 | The backward compatibility mechanism can be controlled by |
|
|
5434 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5435 | section. |
|
|
5436 | |
|
|
5437 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5438 | |
|
|
5439 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5440 | |
|
|
5441 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5442 | ev_loop_fork (EV_DEFAULT); |
4834 | |
5443 | |
4835 | =item function/symbol renames |
5444 | =item function/symbol renames |
4836 | |
5445 | |
4837 | A number of functions and symbols have been renamed: |
5446 | A number of functions and symbols have been renamed: |
4838 | |
5447 | |
… | |
… | |
4857 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5466 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4858 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5467 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4859 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5468 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4860 | typedef. |
5469 | typedef. |
4861 | |
5470 | |
4862 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4863 | |
|
|
4864 | The backward compatibility mechanism can be controlled by |
|
|
4865 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4866 | section. |
|
|
4867 | |
|
|
4868 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5471 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4869 | |
5472 | |
4870 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5473 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4871 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5474 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4872 | and work, but the library code will of course be larger. |
5475 | and work, but the library code will of course be larger. |
… | |
… | |
4879 | =over 4 |
5482 | =over 4 |
4880 | |
5483 | |
4881 | =item active |
5484 | =item active |
4882 | |
5485 | |
4883 | A watcher is active as long as it has been started and not yet stopped. |
5486 | A watcher is active as long as it has been started and not yet stopped. |
4884 | See L<WATCHER STATES> for details. |
5487 | See L</WATCHER STATES> for details. |
4885 | |
5488 | |
4886 | =item application |
5489 | =item application |
4887 | |
5490 | |
4888 | In this document, an application is whatever is using libev. |
5491 | In this document, an application is whatever is using libev. |
4889 | |
5492 | |
… | |
… | |
4925 | watchers and events. |
5528 | watchers and events. |
4926 | |
5529 | |
4927 | =item pending |
5530 | =item pending |
4928 | |
5531 | |
4929 | A watcher is pending as soon as the corresponding event has been |
5532 | A watcher is pending as soon as the corresponding event has been |
4930 | detected. See L<WATCHER STATES> for details. |
5533 | detected. See L</WATCHER STATES> for details. |
4931 | |
5534 | |
4932 | =item real time |
5535 | =item real time |
4933 | |
5536 | |
4934 | The physical time that is observed. It is apparently strictly monotonic :) |
5537 | The physical time that is observed. It is apparently strictly monotonic :) |
4935 | |
5538 | |
4936 | =item wall-clock time |
5539 | =item wall-clock time |
4937 | |
5540 | |
4938 | The time and date as shown on clocks. Unlike real time, it can actually |
5541 | The time and date as shown on clocks. Unlike real time, it can actually |
4939 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5542 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4940 | clock. |
5543 | clock. |
4941 | |
5544 | |
4942 | =item watcher |
5545 | =item watcher |
4943 | |
5546 | |
4944 | A data structure that describes interest in certain events. Watchers need |
5547 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
4946 | |
5549 | |
4947 | =back |
5550 | =back |
4948 | |
5551 | |
4949 | =head1 AUTHOR |
5552 | =head1 AUTHOR |
4950 | |
5553 | |
4951 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5554 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5555 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4952 | |
5556 | |