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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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58 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
59 | |
61 | |
60 | // now wait for events to arrive |
62 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
63 | ev_run (loop, 0); |
62 | |
64 | |
63 | // unloop was called, so exit |
65 | // break was called, so exit |
64 | return 0; |
66 | return 0; |
65 | } |
67 | } |
66 | |
68 | |
67 | =head1 ABOUT THIS DOCUMENT |
69 | =head1 ABOUT THIS DOCUMENT |
68 | |
70 | |
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82 | |
84 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
85 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
86 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
87 | This manual tries to be very detailed, but unfortunately, this also makes |
86 | it very long. If you just want to know the basics of libev, I suggest |
88 | it very long. If you just want to know the basics of libev, I suggest |
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
91 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
92 | |
91 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
92 | |
94 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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103 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
104 | watcher. |
106 | watcher. |
105 | |
107 | |
106 | =head2 FEATURES |
108 | =head2 FEATURES |
107 | |
109 | |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
114 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
115 | change events (C<ev_child>), and event watchers dealing with the event |
117 | change events (C<ev_child>), and event watchers dealing with the event |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
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174 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
175 | |
177 | |
176 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
180 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
181 | C<ev_now_update> and C<ev_now>. |
180 | |
182 | |
181 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
182 | |
184 | |
183 | Sleep for the given interval: The current thread will be blocked until |
185 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
186 | until either it is interrupted or the given time interval has |
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187 | passed (approximately - it might return a bit earlier even if not |
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188 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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189 | |
185 | this is a sub-second-resolution C<sleep ()>. |
190 | Basically this is a sub-second-resolution C<sleep ()>. |
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191 | |
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192 | The range of the C<interval> is limited - libev only guarantees to work |
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193 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
194 | |
187 | =item int ev_version_major () |
195 | =item int ev_version_major () |
188 | |
196 | |
189 | =item int ev_version_minor () |
197 | =item int ev_version_minor () |
190 | |
198 | |
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241 | the current system, you would need to look at C<ev_embeddable_backends () |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
243 | |
251 | |
244 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
245 | |
253 | |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
247 | |
255 | |
248 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
250 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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257 | |
265 | |
258 | You could override this function in high-availability programs to, say, |
266 | You could override this function in high-availability programs to, say, |
259 | free some memory if it cannot allocate memory, to use a special allocator, |
267 | free some memory if it cannot allocate memory, to use a special allocator, |
260 | or even to sleep a while and retry until some memory is available. |
268 | or even to sleep a while and retry until some memory is available. |
261 | |
269 | |
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270 | Example: The following is the C<realloc> function that libev itself uses |
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271 | which should work with C<realloc> and C<free> functions of all kinds and |
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272 | is probably a good basis for your own implementation. |
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273 | |
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274 | static void * |
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275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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276 | { |
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277 | if (size) |
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278 | return realloc (ptr, size); |
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279 | |
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280 | free (ptr); |
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281 | return 0; |
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282 | } |
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283 | |
262 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
263 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
264 | |
286 | |
265 | static void * |
287 | static void * |
266 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
267 | { |
289 | { |
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290 | if (!size) |
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291 | { |
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292 | free (ptr); |
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293 | return 0; |
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294 | } |
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295 | |
268 | for (;;) |
296 | for (;;) |
269 | { |
297 | { |
270 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
271 | |
299 | |
272 | if (newptr) |
300 | if (newptr) |
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277 | } |
305 | } |
278 | |
306 | |
279 | ... |
307 | ... |
280 | ev_set_allocator (persistent_realloc); |
308 | ev_set_allocator (persistent_realloc); |
281 | |
309 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
310 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
283 | |
311 | |
284 | Set the callback function to call on a retryable system call error (such |
312 | Set the callback function to call on a retryable system call error (such |
285 | as failed select, poll, epoll_wait). The message is a printable string |
313 | as failed select, poll, epoll_wait). The message is a printable string |
286 | indicating the system call or subsystem causing the problem. If this |
314 | indicating the system call or subsystem causing the problem. If this |
287 | callback is set, then libev will expect it to remedy the situation, no |
315 | callback is set, then libev will expect it to remedy the situation, no |
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299 | } |
327 | } |
300 | |
328 | |
301 | ... |
329 | ... |
302 | ev_set_syserr_cb (fatal_error); |
330 | ev_set_syserr_cb (fatal_error); |
303 | |
331 | |
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332 | =item ev_feed_signal (int signum) |
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333 | |
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334 | This function can be used to "simulate" a signal receive. It is completely |
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335 | safe to call this function at any time, from any context, including signal |
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336 | handlers or random threads. |
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337 | |
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338 | Its main use is to customise signal handling in your process, especially |
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339 | in the presence of threads. For example, you could block signals |
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340 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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341 | creating any loops), and in one thread, use C<sigwait> or any other |
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342 | mechanism to wait for signals, then "deliver" them to libev by calling |
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343 | C<ev_feed_signal>. |
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344 | |
304 | =back |
345 | =back |
305 | |
346 | |
306 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
347 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
307 | |
348 | |
308 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
349 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
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377 | |
418 | |
378 | If this flag bit is or'ed into the flag value (or the program runs setuid |
419 | If this flag bit is or'ed into the flag value (or the program runs setuid |
379 | or setgid) then libev will I<not> look at the environment variable |
420 | or setgid) then libev will I<not> look at the environment variable |
380 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
421 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
381 | override the flags completely if it is found in the environment. This is |
422 | override the flags completely if it is found in the environment. This is |
382 | useful to try out specific backends to test their performance, or to work |
423 | useful to try out specific backends to test their performance, to work |
383 | around bugs. |
424 | around bugs, or to make libev threadsafe (accessing environment variables |
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425 | cannot be done in a threadsafe way, but usually it works if no other |
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426 | thread modifies them). |
384 | |
427 | |
385 | =item C<EVFLAG_FORKCHECK> |
428 | =item C<EVFLAG_FORKCHECK> |
386 | |
429 | |
387 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
430 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
388 | make libev check for a fork in each iteration by enabling this flag. |
431 | make libev check for a fork in each iteration by enabling this flag. |
389 | |
432 | |
390 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
391 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
392 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
393 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
394 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
395 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
396 | |
440 | |
397 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
398 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
399 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
400 | |
444 | |
401 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
402 | environment variable. |
446 | environment variable. |
403 | |
447 | |
404 | =item C<EVFLAG_NOINOTIFY> |
448 | =item C<EVFLAG_NOINOTIFY> |
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419 | |
463 | |
420 | Signalfd will not be used by default as this changes your signal mask, and |
464 | Signalfd will not be used by default as this changes your signal mask, and |
421 | there are a lot of shoddy libraries and programs (glib's threadpool for |
465 | there are a lot of shoddy libraries and programs (glib's threadpool for |
422 | example) that can't properly initialise their signal masks. |
466 | example) that can't properly initialise their signal masks. |
423 | |
467 | |
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468 | =item C<EVFLAG_NOSIGMASK> |
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469 | |
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470 | When this flag is specified, then libev will avoid to modify the signal |
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471 | mask. Specifically, this means you have to make sure signals are unblocked |
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472 | when you want to receive them. |
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473 | |
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474 | This behaviour is useful when you want to do your own signal handling, or |
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475 | want to handle signals only in specific threads and want to avoid libev |
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476 | unblocking the signals. |
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477 | |
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478 | It's also required by POSIX in a threaded program, as libev calls |
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479 | C<sigprocmask>, whose behaviour is officially unspecified. |
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480 | |
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481 | This flag's behaviour will become the default in future versions of libev. |
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482 | |
424 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
483 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
425 | |
484 | |
426 | This is your standard select(2) backend. Not I<completely> standard, as |
485 | This is your standard select(2) backend. Not I<completely> standard, as |
427 | libev tries to roll its own fd_set with no limits on the number of fds, |
486 | libev tries to roll its own fd_set with no limits on the number of fds, |
428 | but if that fails, expect a fairly low limit on the number of fds when |
487 | but if that fails, expect a fairly low limit on the number of fds when |
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452 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
453 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
454 | |
513 | |
455 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
456 | |
515 | |
457 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
516 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
458 | kernels). |
517 | kernels). |
459 | |
518 | |
460 | For few fds, this backend is a bit little slower than poll and select, |
519 | For few fds, this backend is a bit little slower than poll and select, but |
461 | but it scales phenomenally better. While poll and select usually scale |
520 | it scales phenomenally better. While poll and select usually scale like |
462 | like O(total_fds) where n is the total number of fds (or the highest fd), |
521 | O(total_fds) where total_fds is the total number of fds (or the highest |
463 | epoll scales either O(1) or O(active_fds). |
522 | fd), epoll scales either O(1) or O(active_fds). |
464 | |
523 | |
465 | The epoll mechanism deserves honorable mention as the most misdesigned |
524 | The epoll mechanism deserves honorable mention as the most misdesigned |
466 | of the more advanced event mechanisms: mere annoyances include silently |
525 | of the more advanced event mechanisms: mere annoyances include silently |
467 | dropping file descriptors, requiring a system call per change per file |
526 | dropping file descriptors, requiring a system call per change per file |
468 | descriptor (and unnecessary guessing of parameters), problems with dup, |
527 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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471 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
530 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
472 | forks then I<both> parent and child process have to recreate the epoll |
531 | forks then I<both> parent and child process have to recreate the epoll |
473 | set, which can take considerable time (one syscall per file descriptor) |
532 | set, which can take considerable time (one syscall per file descriptor) |
474 | and is of course hard to detect. |
533 | and is of course hard to detect. |
475 | |
534 | |
476 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
535 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
477 | of course I<doesn't>, and epoll just loves to report events for totally |
536 | but of course I<doesn't>, and epoll just loves to report events for |
478 | I<different> file descriptors (even already closed ones, so one cannot |
537 | totally I<different> file descriptors (even already closed ones, so |
479 | even remove them from the set) than registered in the set (especially |
538 | one cannot even remove them from the set) than registered in the set |
480 | on SMP systems). Libev tries to counter these spurious notifications by |
539 | (especially on SMP systems). Libev tries to counter these spurious |
481 | employing an additional generation counter and comparing that against the |
540 | notifications by employing an additional generation counter and comparing |
482 | events to filter out spurious ones, recreating the set when required. Last |
541 | that against the events to filter out spurious ones, recreating the set |
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542 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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543 | no way to know when and by how much, so sometimes you have to busy-wait |
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544 | because epoll returns immediately despite a nonzero timeout. And last |
483 | not least, it also refuses to work with some file descriptors which work |
545 | not least, it also refuses to work with some file descriptors which work |
484 | perfectly fine with C<select> (files, many character devices...). |
546 | perfectly fine with C<select> (files, many character devices...). |
485 | |
547 | |
486 | Epoll is truly the train wreck analog among event poll mechanisms. |
548 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
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549 | cobbled together in a hurry, no thought to design or interaction with |
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550 | others. Oh, the pain, will it ever stop... |
487 | |
551 | |
488 | While stopping, setting and starting an I/O watcher in the same iteration |
552 | While stopping, setting and starting an I/O watcher in the same iteration |
489 | will result in some caching, there is still a system call per such |
553 | will result in some caching, there is still a system call per such |
490 | incident (because the same I<file descriptor> could point to a different |
554 | incident (because the same I<file descriptor> could point to a different |
491 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
555 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
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503 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
504 | faster than epoll for maybe up to a hundred file descriptors, depending on |
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
505 | the usage. So sad. |
569 | the usage. So sad. |
506 | |
570 | |
507 | While nominally embeddable in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
508 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
509 | |
573 | |
510 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
511 | C<EVBACKEND_POLL>. |
575 | C<EVBACKEND_POLL>. |
512 | |
576 | |
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577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
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578 | |
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579 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
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580 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
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581 | only tries to use it in 4.19+). |
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582 | |
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583 | This is another Linux train wreck of an event interface. |
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584 | |
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585 | If this backend works for you (as of this writing, it was very |
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586 | experimental), it is the best event interface available on Linux and might |
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587 | be well worth enabling it - if it isn't available in your kernel this will |
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588 | be detected and this backend will be skipped. |
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589 | |
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590 | This backend can batch oneshot requests and supports a user-space ring |
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591 | buffer to receive events. It also doesn't suffer from most of the design |
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592 | problems of epoll (such as not being able to remove event sources from |
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593 | the epoll set), and generally sounds too good to be true. Because, this |
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594 | being the Linux kernel, of course it suffers from a whole new set of |
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595 | limitations, forcing you to fall back to epoll, inheriting all its design |
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596 | issues. |
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597 | |
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598 | For one, it is not easily embeddable (but probably could be done using |
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599 | an event fd at some extra overhead). It also is subject to a system wide |
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600 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
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601 | requests are left, this backend will be skipped during initialisation, and |
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602 | will switch to epoll when the loop is active. |
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603 | |
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604 | Most problematic in practice, however, is that not all file descriptors |
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605 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
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606 | files, F</dev/null> and many others are supported, but ttys do not work |
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607 | properly (a known bug that the kernel developers don't care about, see |
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608 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
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609 | (yet?) a generic event polling interface. |
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610 | |
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611 | Overall, it seems the Linux developers just don't want it to have a |
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612 | generic event handling mechanism other than C<select> or C<poll>. |
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613 | |
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614 | To work around all these problem, the current version of libev uses its |
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615 | epoll backend as a fallback for file descriptor types that do not work. Or |
|
|
616 | falls back completely to epoll if the kernel acts up. |
|
|
617 | |
|
|
618 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
619 | C<EVBACKEND_POLL>. |
|
|
620 | |
513 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
621 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
514 | |
622 | |
515 | Kqueue deserves special mention, as at the time of this writing, it |
623 | Kqueue deserves special mention, as at the time this backend was |
516 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
624 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
517 | with anything but sockets and pipes, except on Darwin, where of course |
625 | work reliably with anything but sockets and pipes, except on Darwin, |
518 | it's completely useless). Unlike epoll, however, whose brokenness |
626 | where of course it's completely useless). Unlike epoll, however, whose |
519 | is by design, these kqueue bugs can (and eventually will) be fixed |
627 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
520 | without API changes to existing programs. For this reason it's not being |
628 | fixed without API changes to existing programs. For this reason it's not |
521 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
629 | being "auto-detected" on all platforms unless you explicitly specify it |
522 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
630 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
523 | system like NetBSD. |
631 | known-to-be-good (-enough) system like NetBSD. |
524 | |
632 | |
525 | You still can embed kqueue into a normal poll or select backend and use it |
633 | You still can embed kqueue into a normal poll or select backend and use it |
526 | only for sockets (after having made sure that sockets work with kqueue on |
634 | only for sockets (after having made sure that sockets work with kqueue on |
527 | the target platform). See C<ev_embed> watchers for more info. |
635 | the target platform). See C<ev_embed> watchers for more info. |
528 | |
636 | |
529 | It scales in the same way as the epoll backend, but the interface to the |
637 | It scales in the same way as the epoll backend, but the interface to the |
530 | kernel is more efficient (which says nothing about its actual speed, of |
638 | kernel is more efficient (which says nothing about its actual speed, of |
531 | course). While stopping, setting and starting an I/O watcher does never |
639 | course). While stopping, setting and starting an I/O watcher does never |
532 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
640 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
533 | two event changes per incident. Support for C<fork ()> is very bad (but |
641 | two event changes per incident. Support for C<fork ()> is very bad (you |
534 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
642 | might have to leak fds on fork, but it's more sane than epoll) and it |
535 | cases |
643 | drops fds silently in similarly hard-to-detect cases. |
536 | |
644 | |
537 | This backend usually performs well under most conditions. |
645 | This backend usually performs well under most conditions. |
538 | |
646 | |
539 | While nominally embeddable in other event loops, this doesn't work |
647 | While nominally embeddable in other event loops, this doesn't work |
540 | everywhere, so you might need to test for this. And since it is broken |
648 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
557 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
665 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
558 | |
666 | |
559 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
667 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
560 | it's really slow, but it still scales very well (O(active_fds)). |
668 | it's really slow, but it still scales very well (O(active_fds)). |
561 | |
669 | |
562 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
563 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
564 | blocking when no data (or space) is available. |
|
|
565 | |
|
|
566 | While this backend scales well, it requires one system call per active |
670 | While this backend scales well, it requires one system call per active |
567 | file descriptor per loop iteration. For small and medium numbers of file |
671 | file descriptor per loop iteration. For small and medium numbers of file |
568 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
672 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
569 | might perform better. |
673 | might perform better. |
570 | |
674 | |
571 | On the positive side, with the exception of the spurious readiness |
675 | On the positive side, this backend actually performed fully to |
572 | notifications, this backend actually performed fully to specification |
|
|
573 | in all tests and is fully embeddable, which is a rare feat among the |
676 | specification in all tests and is fully embeddable, which is a rare feat |
574 | OS-specific backends (I vastly prefer correctness over speed hacks). |
677 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
678 | hacks). |
|
|
679 | |
|
|
680 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
681 | even sun itself gets it wrong in their code examples: The event polling |
|
|
682 | function sometimes returns events to the caller even though an error |
|
|
683 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
684 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
685 | absolutely have to know whether an event occurred or not because you have |
|
|
686 | to re-arm the watcher. |
|
|
687 | |
|
|
688 | Fortunately libev seems to be able to work around these idiocies. |
575 | |
689 | |
576 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
690 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
577 | C<EVBACKEND_POLL>. |
691 | C<EVBACKEND_POLL>. |
578 | |
692 | |
579 | =item C<EVBACKEND_ALL> |
693 | =item C<EVBACKEND_ALL> |
580 | |
694 | |
581 | Try all backends (even potentially broken ones that wouldn't be tried |
695 | Try all backends (even potentially broken ones that wouldn't be tried |
582 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
696 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
583 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
697 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
584 | |
698 | |
585 | It is definitely not recommended to use this flag. |
699 | It is definitely not recommended to use this flag, use whatever |
|
|
700 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
701 | at all. |
|
|
702 | |
|
|
703 | =item C<EVBACKEND_MASK> |
|
|
704 | |
|
|
705 | Not a backend at all, but a mask to select all backend bits from a |
|
|
706 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
707 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
586 | |
708 | |
587 | =back |
709 | =back |
588 | |
710 | |
589 | If one or more of the backend flags are or'ed into the flags value, |
711 | If one or more of the backend flags are or'ed into the flags value, |
590 | then only these backends will be tried (in the reverse order as listed |
712 | then only these backends will be tried (in the reverse order as listed |
… | |
… | |
599 | |
721 | |
600 | Example: Use whatever libev has to offer, but make sure that kqueue is |
722 | Example: Use whatever libev has to offer, but make sure that kqueue is |
601 | used if available. |
723 | used if available. |
602 | |
724 | |
603 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
725 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
726 | |
|
|
727 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
728 | linux aio backend if possible, but fall back to something else if that |
|
|
729 | isn't available. |
|
|
730 | |
|
|
731 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
604 | |
732 | |
605 | =item ev_loop_destroy (loop) |
733 | =item ev_loop_destroy (loop) |
606 | |
734 | |
607 | Destroys an event loop object (frees all memory and kernel state |
735 | Destroys an event loop object (frees all memory and kernel state |
608 | etc.). None of the active event watchers will be stopped in the normal |
736 | etc.). None of the active event watchers will be stopped in the normal |
… | |
… | |
625 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
753 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
626 | and C<ev_loop_destroy>. |
754 | and C<ev_loop_destroy>. |
627 | |
755 | |
628 | =item ev_loop_fork (loop) |
756 | =item ev_loop_fork (loop) |
629 | |
757 | |
630 | This function sets a flag that causes subsequent C<ev_run> iterations to |
758 | This function sets a flag that causes subsequent C<ev_run> iterations |
631 | reinitialise the kernel state for backends that have one. Despite the |
759 | to reinitialise the kernel state for backends that have one. Despite |
632 | name, you can call it anytime, but it makes most sense after forking, in |
760 | the name, you can call it anytime you are allowed to start or stop |
633 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
761 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
762 | sense after forking, in the child process. You I<must> call it (or use |
634 | child before resuming or calling C<ev_run>. |
763 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
635 | |
764 | |
|
|
765 | In addition, if you want to reuse a loop (via this function or |
|
|
766 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
767 | |
636 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
768 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
637 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
769 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
638 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
770 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
639 | during fork. |
771 | during fork. |
640 | |
772 | |
641 | On the other hand, you only need to call this function in the child |
773 | On the other hand, you only need to call this function in the child |
… | |
… | |
711 | |
843 | |
712 | This function is rarely useful, but when some event callback runs for a |
844 | This function is rarely useful, but when some event callback runs for a |
713 | very long time without entering the event loop, updating libev's idea of |
845 | very long time without entering the event loop, updating libev's idea of |
714 | the current time is a good idea. |
846 | the current time is a good idea. |
715 | |
847 | |
716 | See also L<The special problem of time updates> in the C<ev_timer> section. |
848 | See also L</The special problem of time updates> in the C<ev_timer> section. |
717 | |
849 | |
718 | =item ev_suspend (loop) |
850 | =item ev_suspend (loop) |
719 | |
851 | |
720 | =item ev_resume (loop) |
852 | =item ev_resume (loop) |
721 | |
853 | |
… | |
… | |
739 | without a previous call to C<ev_suspend>. |
871 | without a previous call to C<ev_suspend>. |
740 | |
872 | |
741 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
873 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
742 | event loop time (see C<ev_now_update>). |
874 | event loop time (see C<ev_now_update>). |
743 | |
875 | |
744 | =item ev_run (loop, int flags) |
876 | =item bool ev_run (loop, int flags) |
745 | |
877 | |
746 | Finally, this is it, the event handler. This function usually is called |
878 | Finally, this is it, the event handler. This function usually is called |
747 | after you have initialised all your watchers and you want to start |
879 | after you have initialised all your watchers and you want to start |
748 | handling events. It will ask the operating system for any new events, call |
880 | handling events. It will ask the operating system for any new events, call |
749 | the watcher callbacks, an then repeat the whole process indefinitely: This |
881 | the watcher callbacks, and then repeat the whole process indefinitely: This |
750 | is why event loops are called I<loops>. |
882 | is why event loops are called I<loops>. |
751 | |
883 | |
752 | If the flags argument is specified as C<0>, it will keep handling events |
884 | If the flags argument is specified as C<0>, it will keep handling events |
753 | until either no event watchers are active anymore or C<ev_break> was |
885 | until either no event watchers are active anymore or C<ev_break> was |
754 | called. |
886 | called. |
|
|
887 | |
|
|
888 | The return value is false if there are no more active watchers (which |
|
|
889 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
890 | (which usually means " you should call C<ev_run> again"). |
755 | |
891 | |
756 | Please note that an explicit C<ev_break> is usually better than |
892 | Please note that an explicit C<ev_break> is usually better than |
757 | relying on all watchers to be stopped when deciding when a program has |
893 | relying on all watchers to be stopped when deciding when a program has |
758 | finished (especially in interactive programs), but having a program |
894 | finished (especially in interactive programs), but having a program |
759 | that automatically loops as long as it has to and no longer by virtue |
895 | that automatically loops as long as it has to and no longer by virtue |
760 | of relying on its watchers stopping correctly, that is truly a thing of |
896 | of relying on its watchers stopping correctly, that is truly a thing of |
761 | beauty. |
897 | beauty. |
762 | |
898 | |
763 | This function is also I<mostly> exception-safe - you can break out of |
899 | This function is I<mostly> exception-safe - you can break out of a |
764 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
900 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
765 | exception and so on. This does not decrement the C<ev_depth> value, nor |
901 | exception and so on. This does not decrement the C<ev_depth> value, nor |
766 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
902 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
767 | |
903 | |
768 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
904 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
769 | those events and any already outstanding ones, but will not wait and |
905 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
781 | This is useful if you are waiting for some external event in conjunction |
917 | This is useful if you are waiting for some external event in conjunction |
782 | with something not expressible using other libev watchers (i.e. "roll your |
918 | with something not expressible using other libev watchers (i.e. "roll your |
783 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
919 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
784 | usually a better approach for this kind of thing. |
920 | usually a better approach for this kind of thing. |
785 | |
921 | |
786 | Here are the gory details of what C<ev_run> does: |
922 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
923 | understanding, not a guarantee that things will work exactly like this in |
|
|
924 | future versions): |
787 | |
925 | |
788 | - Increment loop depth. |
926 | - Increment loop depth. |
789 | - Reset the ev_break status. |
927 | - Reset the ev_break status. |
790 | - Before the first iteration, call any pending watchers. |
928 | - Before the first iteration, call any pending watchers. |
791 | LOOP: |
929 | LOOP: |
… | |
… | |
824 | anymore. |
962 | anymore. |
825 | |
963 | |
826 | ... queue jobs here, make sure they register event watchers as long |
964 | ... queue jobs here, make sure they register event watchers as long |
827 | ... as they still have work to do (even an idle watcher will do..) |
965 | ... as they still have work to do (even an idle watcher will do..) |
828 | ev_run (my_loop, 0); |
966 | ev_run (my_loop, 0); |
829 | ... jobs done or somebody called unloop. yeah! |
967 | ... jobs done or somebody called break. yeah! |
830 | |
968 | |
831 | =item ev_break (loop, how) |
969 | =item ev_break (loop, how) |
832 | |
970 | |
833 | Can be used to make a call to C<ev_run> return early (but only after it |
971 | Can be used to make a call to C<ev_run> return early (but only after it |
834 | has processed all outstanding events). The C<how> argument must be either |
972 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
867 | running when nothing else is active. |
1005 | running when nothing else is active. |
868 | |
1006 | |
869 | ev_signal exitsig; |
1007 | ev_signal exitsig; |
870 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
1008 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
871 | ev_signal_start (loop, &exitsig); |
1009 | ev_signal_start (loop, &exitsig); |
872 | evf_unref (loop); |
1010 | ev_unref (loop); |
873 | |
1011 | |
874 | Example: For some weird reason, unregister the above signal handler again. |
1012 | Example: For some weird reason, unregister the above signal handler again. |
875 | |
1013 | |
876 | ev_ref (loop); |
1014 | ev_ref (loop); |
877 | ev_signal_stop (loop, &exitsig); |
1015 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
897 | overhead for the actual polling but can deliver many events at once. |
1035 | overhead for the actual polling but can deliver many events at once. |
898 | |
1036 | |
899 | By setting a higher I<io collect interval> you allow libev to spend more |
1037 | By setting a higher I<io collect interval> you allow libev to spend more |
900 | time collecting I/O events, so you can handle more events per iteration, |
1038 | time collecting I/O events, so you can handle more events per iteration, |
901 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1039 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
902 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1040 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
903 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
1041 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
904 | sleep time ensures that libev will not poll for I/O events more often then |
1042 | sleep time ensures that libev will not poll for I/O events more often then |
905 | once per this interval, on average. |
1043 | once per this interval, on average (as long as the host time resolution is |
|
|
1044 | good enough). |
906 | |
1045 | |
907 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1046 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
908 | to spend more time collecting timeouts, at the expense of increased |
1047 | to spend more time collecting timeouts, at the expense of increased |
909 | latency/jitter/inexactness (the watcher callback will be called |
1048 | latency/jitter/inexactness (the watcher callback will be called |
910 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
1049 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
956 | invoke the actual watchers inside another context (another thread etc.). |
1095 | invoke the actual watchers inside another context (another thread etc.). |
957 | |
1096 | |
958 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1097 | If you want to reset the callback, use C<ev_invoke_pending> as new |
959 | callback. |
1098 | callback. |
960 | |
1099 | |
961 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1100 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
962 | |
1101 | |
963 | Sometimes you want to share the same loop between multiple threads. This |
1102 | Sometimes you want to share the same loop between multiple threads. This |
964 | can be done relatively simply by putting mutex_lock/unlock calls around |
1103 | can be done relatively simply by putting mutex_lock/unlock calls around |
965 | each call to a libev function. |
1104 | each call to a libev function. |
966 | |
1105 | |
967 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1106 | However, C<ev_run> can run an indefinite time, so it is not feasible |
968 | to wait for it to return. One way around this is to wake up the event |
1107 | to wait for it to return. One way around this is to wake up the event |
969 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1108 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
970 | I<release> and I<acquire> callbacks on the loop. |
1109 | I<release> and I<acquire> callbacks on the loop. |
971 | |
1110 | |
972 | When set, then C<release> will be called just before the thread is |
1111 | When set, then C<release> will be called just before the thread is |
973 | suspended waiting for new events, and C<acquire> is called just |
1112 | suspended waiting for new events, and C<acquire> is called just |
974 | afterwards. |
1113 | afterwards. |
… | |
… | |
1114 | |
1253 | |
1115 | =item C<EV_PREPARE> |
1254 | =item C<EV_PREPARE> |
1116 | |
1255 | |
1117 | =item C<EV_CHECK> |
1256 | =item C<EV_CHECK> |
1118 | |
1257 | |
1119 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1258 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1120 | to gather new events, and all C<ev_check> watchers are invoked just after |
1259 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1121 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1260 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1261 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1262 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1263 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1264 | or lower priority within an event loop iteration. |
|
|
1265 | |
1122 | received events. Callbacks of both watcher types can start and stop as |
1266 | Callbacks of both watcher types can start and stop as many watchers as |
1123 | many watchers as they want, and all of them will be taken into account |
1267 | they want, and all of them will be taken into account (for example, a |
1124 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1268 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1125 | C<ev_run> from blocking). |
1269 | blocking). |
1126 | |
1270 | |
1127 | =item C<EV_EMBED> |
1271 | =item C<EV_EMBED> |
1128 | |
1272 | |
1129 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1273 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1130 | |
1274 | |
… | |
… | |
1253 | |
1397 | |
1254 | =item callback ev_cb (ev_TYPE *watcher) |
1398 | =item callback ev_cb (ev_TYPE *watcher) |
1255 | |
1399 | |
1256 | Returns the callback currently set on the watcher. |
1400 | Returns the callback currently set on the watcher. |
1257 | |
1401 | |
1258 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1402 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1259 | |
1403 | |
1260 | Change the callback. You can change the callback at virtually any time |
1404 | Change the callback. You can change the callback at virtually any time |
1261 | (modulo threads). |
1405 | (modulo threads). |
1262 | |
1406 | |
1263 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1407 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1281 | or might not have been clamped to the valid range. |
1425 | or might not have been clamped to the valid range. |
1282 | |
1426 | |
1283 | The default priority used by watchers when no priority has been set is |
1427 | The default priority used by watchers when no priority has been set is |
1284 | always C<0>, which is supposed to not be too high and not be too low :). |
1428 | always C<0>, which is supposed to not be too high and not be too low :). |
1285 | |
1429 | |
1286 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1430 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1287 | priorities. |
1431 | priorities. |
1288 | |
1432 | |
1289 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1433 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1290 | |
1434 | |
1291 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1435 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1316 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1460 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1317 | functions that do not need a watcher. |
1461 | functions that do not need a watcher. |
1318 | |
1462 | |
1319 | =back |
1463 | =back |
1320 | |
1464 | |
1321 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1465 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1322 | |
1466 | OWN COMPOSITE WATCHERS> idioms. |
1323 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1324 | and read at any time: libev will completely ignore it. This can be used |
|
|
1325 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1326 | don't want to allocate memory and store a pointer to it in that data |
|
|
1327 | member, you can also "subclass" the watcher type and provide your own |
|
|
1328 | data: |
|
|
1329 | |
|
|
1330 | struct my_io |
|
|
1331 | { |
|
|
1332 | ev_io io; |
|
|
1333 | int otherfd; |
|
|
1334 | void *somedata; |
|
|
1335 | struct whatever *mostinteresting; |
|
|
1336 | }; |
|
|
1337 | |
|
|
1338 | ... |
|
|
1339 | struct my_io w; |
|
|
1340 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1341 | |
|
|
1342 | And since your callback will be called with a pointer to the watcher, you |
|
|
1343 | can cast it back to your own type: |
|
|
1344 | |
|
|
1345 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1346 | { |
|
|
1347 | struct my_io *w = (struct my_io *)w_; |
|
|
1348 | ... |
|
|
1349 | } |
|
|
1350 | |
|
|
1351 | More interesting and less C-conformant ways of casting your callback type |
|
|
1352 | instead have been omitted. |
|
|
1353 | |
|
|
1354 | Another common scenario is to use some data structure with multiple |
|
|
1355 | embedded watchers: |
|
|
1356 | |
|
|
1357 | struct my_biggy |
|
|
1358 | { |
|
|
1359 | int some_data; |
|
|
1360 | ev_timer t1; |
|
|
1361 | ev_timer t2; |
|
|
1362 | } |
|
|
1363 | |
|
|
1364 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1365 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1366 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1367 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1368 | programmers): |
|
|
1369 | |
|
|
1370 | #include <stddef.h> |
|
|
1371 | |
|
|
1372 | static void |
|
|
1373 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1374 | { |
|
|
1375 | struct my_biggy big = (struct my_biggy *) |
|
|
1376 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1377 | } |
|
|
1378 | |
|
|
1379 | static void |
|
|
1380 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1381 | { |
|
|
1382 | struct my_biggy big = (struct my_biggy *) |
|
|
1383 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1384 | } |
|
|
1385 | |
1467 | |
1386 | =head2 WATCHER STATES |
1468 | =head2 WATCHER STATES |
1387 | |
1469 | |
1388 | There are various watcher states mentioned throughout this manual - |
1470 | There are various watcher states mentioned throughout this manual - |
1389 | active, pending and so on. In this section these states and the rules to |
1471 | active, pending and so on. In this section these states and the rules to |
1390 | transition between them will be described in more detail - and while these |
1472 | transition between them will be described in more detail - and while these |
1391 | rules might look complicated, they usually do "the right thing". |
1473 | rules might look complicated, they usually do "the right thing". |
1392 | |
1474 | |
1393 | =over 4 |
1475 | =over 4 |
1394 | |
1476 | |
1395 | =item initialiased |
1477 | =item initialised |
1396 | |
1478 | |
1397 | Before a watcher can be registered with the event looop it has to be |
1479 | Before a watcher can be registered with the event loop it has to be |
1398 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1480 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1399 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1481 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1400 | |
1482 | |
1401 | In this state it is simply some block of memory that is suitable for use |
1483 | In this state it is simply some block of memory that is suitable for |
1402 | in an event loop. It can be moved around, freed, reused etc. at will. |
1484 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1485 | will - as long as you either keep the memory contents intact, or call |
|
|
1486 | C<ev_TYPE_init> again. |
1403 | |
1487 | |
1404 | =item started/running/active |
1488 | =item started/running/active |
1405 | |
1489 | |
1406 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1490 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1407 | property of the event loop, and is actively waiting for events. While in |
1491 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1435 | latter will clear any pending state the watcher might be in, regardless |
1519 | latter will clear any pending state the watcher might be in, regardless |
1436 | of whether it was active or not, so stopping a watcher explicitly before |
1520 | of whether it was active or not, so stopping a watcher explicitly before |
1437 | freeing it is often a good idea. |
1521 | freeing it is often a good idea. |
1438 | |
1522 | |
1439 | While stopped (and not pending) the watcher is essentially in the |
1523 | While stopped (and not pending) the watcher is essentially in the |
1440 | initialised state, that is it can be reused, moved, modified in any way |
1524 | initialised state, that is, it can be reused, moved, modified in any way |
1441 | you wish. |
1525 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1526 | it again). |
1442 | |
1527 | |
1443 | =back |
1528 | =back |
1444 | |
1529 | |
1445 | =head2 WATCHER PRIORITY MODELS |
1530 | =head2 WATCHER PRIORITY MODELS |
1446 | |
1531 | |
… | |
… | |
1575 | In general you can register as many read and/or write event watchers per |
1660 | In general you can register as many read and/or write event watchers per |
1576 | fd as you want (as long as you don't confuse yourself). Setting all file |
1661 | fd as you want (as long as you don't confuse yourself). Setting all file |
1577 | descriptors to non-blocking mode is also usually a good idea (but not |
1662 | descriptors to non-blocking mode is also usually a good idea (but not |
1578 | required if you know what you are doing). |
1663 | required if you know what you are doing). |
1579 | |
1664 | |
1580 | If you cannot use non-blocking mode, then force the use of a |
|
|
1581 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1582 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1583 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1584 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1585 | |
|
|
1586 | Another thing you have to watch out for is that it is quite easy to |
1665 | Another thing you have to watch out for is that it is quite easy to |
1587 | receive "spurious" readiness notifications, that is your callback might |
1666 | receive "spurious" readiness notifications, that is, your callback might |
1588 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1667 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1589 | because there is no data. Not only are some backends known to create a |
1668 | because there is no data. It is very easy to get into this situation even |
1590 | lot of those (for example Solaris ports), it is very easy to get into |
1669 | with a relatively standard program structure. Thus it is best to always |
1591 | this situation even with a relatively standard program structure. Thus |
1670 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1592 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1593 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1671 | preferable to a program hanging until some data arrives. |
1594 | |
1672 | |
1595 | If you cannot run the fd in non-blocking mode (for example you should |
1673 | If you cannot run the fd in non-blocking mode (for example you should |
1596 | not play around with an Xlib connection), then you have to separately |
1674 | not play around with an Xlib connection), then you have to separately |
1597 | re-test whether a file descriptor is really ready with a known-to-be good |
1675 | re-test whether a file descriptor is really ready with a known-to-be good |
1598 | interface such as poll (fortunately in our Xlib example, Xlib already |
1676 | interface such as poll (fortunately in the case of Xlib, it already does |
1599 | does this on its own, so its quite safe to use). Some people additionally |
1677 | this on its own, so its quite safe to use). Some people additionally |
1600 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1678 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1601 | indefinitely. |
1679 | indefinitely. |
1602 | |
1680 | |
1603 | But really, best use non-blocking mode. |
1681 | But really, best use non-blocking mode. |
1604 | |
1682 | |
1605 | =head3 The special problem of disappearing file descriptors |
1683 | =head3 The special problem of disappearing file descriptors |
1606 | |
1684 | |
1607 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1685 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1608 | descriptor (either due to calling C<close> explicitly or any other means, |
1686 | a file descriptor (either due to calling C<close> explicitly or any other |
1609 | such as C<dup2>). The reason is that you register interest in some file |
1687 | means, such as C<dup2>). The reason is that you register interest in some |
1610 | descriptor, but when it goes away, the operating system will silently drop |
1688 | file descriptor, but when it goes away, the operating system will silently |
1611 | this interest. If another file descriptor with the same number then is |
1689 | drop this interest. If another file descriptor with the same number then |
1612 | registered with libev, there is no efficient way to see that this is, in |
1690 | is registered with libev, there is no efficient way to see that this is, |
1613 | fact, a different file descriptor. |
1691 | in fact, a different file descriptor. |
1614 | |
1692 | |
1615 | To avoid having to explicitly tell libev about such cases, libev follows |
1693 | To avoid having to explicitly tell libev about such cases, libev follows |
1616 | the following policy: Each time C<ev_io_set> is being called, libev |
1694 | the following policy: Each time C<ev_io_set> is being called, libev |
1617 | will assume that this is potentially a new file descriptor, otherwise |
1695 | will assume that this is potentially a new file descriptor, otherwise |
1618 | it is assumed that the file descriptor stays the same. That means that |
1696 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1632 | |
1710 | |
1633 | There is no workaround possible except not registering events |
1711 | There is no workaround possible except not registering events |
1634 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1712 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1635 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1713 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | |
1714 | |
|
|
1715 | =head3 The special problem of files |
|
|
1716 | |
|
|
1717 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1718 | representing files, and expect it to become ready when their program |
|
|
1719 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1720 | |
|
|
1721 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1722 | notification as soon as the kernel knows whether and how much data is |
|
|
1723 | there, and in the case of open files, that's always the case, so you |
|
|
1724 | always get a readiness notification instantly, and your read (or possibly |
|
|
1725 | write) will still block on the disk I/O. |
|
|
1726 | |
|
|
1727 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1728 | devices and so on, there is another party (the sender) that delivers data |
|
|
1729 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1730 | will not send data on its own, simply because it doesn't know what you |
|
|
1731 | wish to read - you would first have to request some data. |
|
|
1732 | |
|
|
1733 | Since files are typically not-so-well supported by advanced notification |
|
|
1734 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1735 | to files, even though you should not use it. The reason for this is |
|
|
1736 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1737 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1738 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1739 | F</dev/urandom>), and even though the file might better be served with |
|
|
1740 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1741 | it "just works" instead of freezing. |
|
|
1742 | |
|
|
1743 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1744 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1745 | when you rarely read from a file instead of from a socket, and want to |
|
|
1746 | reuse the same code path. |
|
|
1747 | |
1637 | =head3 The special problem of fork |
1748 | =head3 The special problem of fork |
1638 | |
1749 | |
1639 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1750 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1640 | useless behaviour. Libev fully supports fork, but needs to be told about |
1751 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1641 | it in the child. |
1752 | to be told about it in the child if you want to continue to use it in the |
|
|
1753 | child. |
1642 | |
1754 | |
1643 | To support fork in your programs, you either have to call |
1755 | To support fork in your child processes, you have to call C<ev_loop_fork |
1644 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1756 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1645 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1757 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1646 | C<EVBACKEND_POLL>. |
|
|
1647 | |
1758 | |
1648 | =head3 The special problem of SIGPIPE |
1759 | =head3 The special problem of SIGPIPE |
1649 | |
1760 | |
1650 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1761 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1651 | when writing to a pipe whose other end has been closed, your program gets |
1762 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1749 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1860 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1750 | monotonic clock option helps a lot here). |
1861 | monotonic clock option helps a lot here). |
1751 | |
1862 | |
1752 | The callback is guaranteed to be invoked only I<after> its timeout has |
1863 | The callback is guaranteed to be invoked only I<after> its timeout has |
1753 | passed (not I<at>, so on systems with very low-resolution clocks this |
1864 | passed (not I<at>, so on systems with very low-resolution clocks this |
1754 | might introduce a small delay). If multiple timers become ready during the |
1865 | might introduce a small delay, see "the special problem of being too |
|
|
1866 | early", below). If multiple timers become ready during the same loop |
1755 | same loop iteration then the ones with earlier time-out values are invoked |
1867 | iteration then the ones with earlier time-out values are invoked before |
1756 | before ones of the same priority with later time-out values (but this is |
1868 | ones of the same priority with later time-out values (but this is no |
1757 | no longer true when a callback calls C<ev_run> recursively). |
1869 | longer true when a callback calls C<ev_run> recursively). |
1758 | |
1870 | |
1759 | =head3 Be smart about timeouts |
1871 | =head3 Be smart about timeouts |
1760 | |
1872 | |
1761 | Many real-world problems involve some kind of timeout, usually for error |
1873 | Many real-world problems involve some kind of timeout, usually for error |
1762 | recovery. A typical example is an HTTP request - if the other side hangs, |
1874 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1837 | |
1949 | |
1838 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1950 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1839 | but remember the time of last activity, and check for a real timeout only |
1951 | but remember the time of last activity, and check for a real timeout only |
1840 | within the callback: |
1952 | within the callback: |
1841 | |
1953 | |
|
|
1954 | ev_tstamp timeout = 60.; |
1842 | ev_tstamp last_activity; // time of last activity |
1955 | ev_tstamp last_activity; // time of last activity |
|
|
1956 | ev_timer timer; |
1843 | |
1957 | |
1844 | static void |
1958 | static void |
1845 | callback (EV_P_ ev_timer *w, int revents) |
1959 | callback (EV_P_ ev_timer *w, int revents) |
1846 | { |
1960 | { |
1847 | ev_tstamp now = ev_now (EV_A); |
1961 | // calculate when the timeout would happen |
1848 | ev_tstamp timeout = last_activity + 60.; |
1962 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1849 | |
1963 | |
1850 | // if last_activity + 60. is older than now, we did time out |
1964 | // if negative, it means we the timeout already occurred |
1851 | if (timeout < now) |
1965 | if (after < 0.) |
1852 | { |
1966 | { |
1853 | // timeout occurred, take action |
1967 | // timeout occurred, take action |
1854 | } |
1968 | } |
1855 | else |
1969 | else |
1856 | { |
1970 | { |
1857 | // callback was invoked, but there was some activity, re-arm |
1971 | // callback was invoked, but there was some recent |
1858 | // the watcher to fire in last_activity + 60, which is |
1972 | // activity. simply restart the timer to time out |
1859 | // guaranteed to be in the future, so "again" is positive: |
1973 | // after "after" seconds, which is the earliest time |
1860 | w->repeat = timeout - now; |
1974 | // the timeout can occur. |
|
|
1975 | ev_timer_set (w, after, 0.); |
1861 | ev_timer_again (EV_A_ w); |
1976 | ev_timer_start (EV_A_ w); |
1862 | } |
1977 | } |
1863 | } |
1978 | } |
1864 | |
1979 | |
1865 | To summarise the callback: first calculate the real timeout (defined |
1980 | To summarise the callback: first calculate in how many seconds the |
1866 | as "60 seconds after the last activity"), then check if that time has |
1981 | timeout will occur (by calculating the absolute time when it would occur, |
1867 | been reached, which means something I<did>, in fact, time out. Otherwise |
1982 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1868 | the callback was invoked too early (C<timeout> is in the future), so |
1983 | (EV_A)> from that). |
1869 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1870 | a timeout then. |
|
|
1871 | |
1984 | |
1872 | Note how C<ev_timer_again> is used, taking advantage of the |
1985 | If this value is negative, then we are already past the timeout, i.e. we |
1873 | C<ev_timer_again> optimisation when the timer is already running. |
1986 | timed out, and need to do whatever is needed in this case. |
|
|
1987 | |
|
|
1988 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1989 | and simply start the timer with this timeout value. |
|
|
1990 | |
|
|
1991 | In other words, each time the callback is invoked it will check whether |
|
|
1992 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1993 | again at the earliest time it could time out. Rinse. Repeat. |
1874 | |
1994 | |
1875 | This scheme causes more callback invocations (about one every 60 seconds |
1995 | This scheme causes more callback invocations (about one every 60 seconds |
1876 | minus half the average time between activity), but virtually no calls to |
1996 | minus half the average time between activity), but virtually no calls to |
1877 | libev to change the timeout. |
1997 | libev to change the timeout. |
1878 | |
1998 | |
1879 | To start the timer, simply initialise the watcher and set C<last_activity> |
1999 | To start the machinery, simply initialise the watcher and set |
1880 | to the current time (meaning we just have some activity :), then call the |
2000 | C<last_activity> to the current time (meaning there was some activity just |
1881 | callback, which will "do the right thing" and start the timer: |
2001 | now), then call the callback, which will "do the right thing" and start |
|
|
2002 | the timer: |
1882 | |
2003 | |
|
|
2004 | last_activity = ev_now (EV_A); |
1883 | ev_init (timer, callback); |
2005 | ev_init (&timer, callback); |
1884 | last_activity = ev_now (loop); |
2006 | callback (EV_A_ &timer, 0); |
1885 | callback (loop, timer, EV_TIMER); |
|
|
1886 | |
2007 | |
1887 | And when there is some activity, simply store the current time in |
2008 | When there is some activity, simply store the current time in |
1888 | C<last_activity>, no libev calls at all: |
2009 | C<last_activity>, no libev calls at all: |
1889 | |
2010 | |
|
|
2011 | if (activity detected) |
1890 | last_activity = ev_now (loop); |
2012 | last_activity = ev_now (EV_A); |
|
|
2013 | |
|
|
2014 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2015 | providing a new value, stopping the timer and calling the callback, which |
|
|
2016 | will again do the right thing (for example, time out immediately :). |
|
|
2017 | |
|
|
2018 | timeout = new_value; |
|
|
2019 | ev_timer_stop (EV_A_ &timer); |
|
|
2020 | callback (EV_A_ &timer, 0); |
1891 | |
2021 | |
1892 | This technique is slightly more complex, but in most cases where the |
2022 | This technique is slightly more complex, but in most cases where the |
1893 | time-out is unlikely to be triggered, much more efficient. |
2023 | time-out is unlikely to be triggered, much more efficient. |
1894 | |
|
|
1895 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1896 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1897 | fix things for you. |
|
|
1898 | |
2024 | |
1899 | =item 4. Wee, just use a double-linked list for your timeouts. |
2025 | =item 4. Wee, just use a double-linked list for your timeouts. |
1900 | |
2026 | |
1901 | If there is not one request, but many thousands (millions...), all |
2027 | If there is not one request, but many thousands (millions...), all |
1902 | employing some kind of timeout with the same timeout value, then one can |
2028 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1929 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2055 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1930 | rather complicated, but extremely efficient, something that really pays |
2056 | rather complicated, but extremely efficient, something that really pays |
1931 | off after the first million or so of active timers, i.e. it's usually |
2057 | off after the first million or so of active timers, i.e. it's usually |
1932 | overkill :) |
2058 | overkill :) |
1933 | |
2059 | |
|
|
2060 | =head3 The special problem of being too early |
|
|
2061 | |
|
|
2062 | If you ask a timer to call your callback after three seconds, then |
|
|
2063 | you expect it to be invoked after three seconds - but of course, this |
|
|
2064 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2065 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2066 | process with a STOP signal for a few hours for example. |
|
|
2067 | |
|
|
2068 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2069 | delay has occurred, but cannot guarantee this. |
|
|
2070 | |
|
|
2071 | A less obvious failure mode is calling your callback too early: many event |
|
|
2072 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2073 | this can cause your callback to be invoked much earlier than you would |
|
|
2074 | expect. |
|
|
2075 | |
|
|
2076 | To see why, imagine a system with a clock that only offers full second |
|
|
2077 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2078 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2079 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2080 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2081 | |
|
|
2082 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2083 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2084 | one-second delay was requested - this is being "too early", despite best |
|
|
2085 | intentions. |
|
|
2086 | |
|
|
2087 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2088 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2089 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2090 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2091 | |
|
|
2092 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2093 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2094 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2095 | late" side of things. |
|
|
2096 | |
1934 | =head3 The special problem of time updates |
2097 | =head3 The special problem of time updates |
1935 | |
2098 | |
1936 | Establishing the current time is a costly operation (it usually takes at |
2099 | Establishing the current time is a costly operation (it usually takes |
1937 | least two system calls): EV therefore updates its idea of the current |
2100 | at least one system call): EV therefore updates its idea of the current |
1938 | time only before and after C<ev_run> collects new events, which causes a |
2101 | time only before and after C<ev_run> collects new events, which causes a |
1939 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2102 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1940 | lots of events in one iteration. |
2103 | lots of events in one iteration. |
1941 | |
2104 | |
1942 | The relative timeouts are calculated relative to the C<ev_now ()> |
2105 | The relative timeouts are calculated relative to the C<ev_now ()> |
1943 | time. This is usually the right thing as this timestamp refers to the time |
2106 | time. This is usually the right thing as this timestamp refers to the time |
1944 | of the event triggering whatever timeout you are modifying/starting. If |
2107 | of the event triggering whatever timeout you are modifying/starting. If |
1945 | you suspect event processing to be delayed and you I<need> to base the |
2108 | you suspect event processing to be delayed and you I<need> to base the |
1946 | timeout on the current time, use something like this to adjust for this: |
2109 | timeout on the current time, use something like the following to adjust |
|
|
2110 | for it: |
1947 | |
2111 | |
1948 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2112 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1949 | |
2113 | |
1950 | If the event loop is suspended for a long time, you can also force an |
2114 | If the event loop is suspended for a long time, you can also force an |
1951 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2115 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1952 | ()>. |
2116 | ()>, although that will push the event time of all outstanding events |
|
|
2117 | further into the future. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of unsynchronised clocks |
|
|
2120 | |
|
|
2121 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2122 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2123 | jumps). |
|
|
2124 | |
|
|
2125 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2126 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2127 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2128 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2129 | than a directly following call to C<time>. |
|
|
2130 | |
|
|
2131 | The moral of this is to only compare libev-related timestamps with |
|
|
2132 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2133 | a second or so. |
|
|
2134 | |
|
|
2135 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2136 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2137 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2138 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2139 | |
|
|
2140 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2141 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2142 | I<measured according to the real time>, not the system clock. |
|
|
2143 | |
|
|
2144 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2145 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2146 | exactly the right behaviour. |
|
|
2147 | |
|
|
2148 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2149 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2150 | time, where your comparisons will always generate correct results. |
1953 | |
2151 | |
1954 | =head3 The special problems of suspended animation |
2152 | =head3 The special problems of suspended animation |
1955 | |
2153 | |
1956 | When you leave the server world it is quite customary to hit machines that |
2154 | When you leave the server world it is quite customary to hit machines that |
1957 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2155 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1987 | |
2185 | |
1988 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2186 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1989 | |
2187 | |
1990 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2188 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1991 | |
2189 | |
1992 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2190 | Configure the timer to trigger after C<after> seconds (fractional and |
1993 | is C<0.>, then it will automatically be stopped once the timeout is |
2191 | negative values are supported). If C<repeat> is C<0.>, then it will |
1994 | reached. If it is positive, then the timer will automatically be |
2192 | automatically be stopped once the timeout is reached. If it is positive, |
1995 | configured to trigger again C<repeat> seconds later, again, and again, |
2193 | then the timer will automatically be configured to trigger again C<repeat> |
1996 | until stopped manually. |
2194 | seconds later, again, and again, until stopped manually. |
1997 | |
2195 | |
1998 | The timer itself will do a best-effort at avoiding drift, that is, if |
2196 | The timer itself will do a best-effort at avoiding drift, that is, if |
1999 | you configure a timer to trigger every 10 seconds, then it will normally |
2197 | you configure a timer to trigger every 10 seconds, then it will normally |
2000 | trigger at exactly 10 second intervals. If, however, your program cannot |
2198 | trigger at exactly 10 second intervals. If, however, your program cannot |
2001 | keep up with the timer (because it takes longer than those 10 seconds to |
2199 | keep up with the timer (because it takes longer than those 10 seconds to |
2002 | do stuff) the timer will not fire more than once per event loop iteration. |
2200 | do stuff) the timer will not fire more than once per event loop iteration. |
2003 | |
2201 | |
2004 | =item ev_timer_again (loop, ev_timer *) |
2202 | =item ev_timer_again (loop, ev_timer *) |
2005 | |
2203 | |
2006 | This will act as if the timer timed out and restart it again if it is |
2204 | This will act as if the timer timed out, and restarts it again if it is |
2007 | repeating. The exact semantics are: |
2205 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2206 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2008 | |
2207 | |
|
|
2208 | The exact semantics are as in the following rules, all of which will be |
|
|
2209 | applied to the watcher: |
|
|
2210 | |
|
|
2211 | =over 4 |
|
|
2212 | |
2009 | If the timer is pending, its pending status is cleared. |
2213 | =item If the timer is pending, the pending status is always cleared. |
2010 | |
2214 | |
2011 | If the timer is started but non-repeating, stop it (as if it timed out). |
2215 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2216 | out, without invoking it). |
2012 | |
2217 | |
2013 | If the timer is repeating, either start it if necessary (with the |
2218 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2014 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2219 | and start the timer, if necessary. |
2015 | |
2220 | |
|
|
2221 | =back |
|
|
2222 | |
2016 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2223 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2017 | usage example. |
2224 | usage example. |
2018 | |
2225 | |
2019 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2226 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2020 | |
2227 | |
2021 | Returns the remaining time until a timer fires. If the timer is active, |
2228 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2074 | Periodic watchers are also timers of a kind, but they are very versatile |
2281 | Periodic watchers are also timers of a kind, but they are very versatile |
2075 | (and unfortunately a bit complex). |
2282 | (and unfortunately a bit complex). |
2076 | |
2283 | |
2077 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2284 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2078 | relative time, the physical time that passes) but on wall clock time |
2285 | relative time, the physical time that passes) but on wall clock time |
2079 | (absolute time, the thing you can read on your calender or clock). The |
2286 | (absolute time, the thing you can read on your calendar or clock). The |
2080 | difference is that wall clock time can run faster or slower than real |
2287 | difference is that wall clock time can run faster or slower than real |
2081 | time, and time jumps are not uncommon (e.g. when you adjust your |
2288 | time, and time jumps are not uncommon (e.g. when you adjust your |
2082 | wrist-watch). |
2289 | wrist-watch). |
2083 | |
2290 | |
2084 | You can tell a periodic watcher to trigger after some specific point |
2291 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2089 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2296 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2090 | it, as it uses a relative timeout). |
2297 | it, as it uses a relative timeout). |
2091 | |
2298 | |
2092 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2299 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2093 | timers, such as triggering an event on each "midnight, local time", or |
2300 | timers, such as triggering an event on each "midnight, local time", or |
2094 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2301 | other complicated rules. This cannot easily be done with C<ev_timer> |
2095 | those cannot react to time jumps. |
2302 | watchers, as those cannot react to time jumps. |
2096 | |
2303 | |
2097 | As with timers, the callback is guaranteed to be invoked only when the |
2304 | As with timers, the callback is guaranteed to be invoked only when the |
2098 | point in time where it is supposed to trigger has passed. If multiple |
2305 | point in time where it is supposed to trigger has passed. If multiple |
2099 | timers become ready during the same loop iteration then the ones with |
2306 | timers become ready during the same loop iteration then the ones with |
2100 | earlier time-out values are invoked before ones with later time-out values |
2307 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2141 | |
2348 | |
2142 | Another way to think about it (for the mathematically inclined) is that |
2349 | Another way to think about it (for the mathematically inclined) is that |
2143 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2350 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2144 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2351 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2145 | |
2352 | |
2146 | For numerical stability it is preferable that the C<offset> value is near |
2353 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2147 | C<ev_now ()> (the current time), but there is no range requirement for |
2354 | interval value should be higher than C<1/8192> (which is around 100 |
2148 | this value, and in fact is often specified as zero. |
2355 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2356 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2357 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2358 | C<0> and C<interval>, which is also the recommended range. |
2149 | |
2359 | |
2150 | Note also that there is an upper limit to how often a timer can fire (CPU |
2360 | Note also that there is an upper limit to how often a timer can fire (CPU |
2151 | speed for example), so if C<interval> is very small then timing stability |
2361 | speed for example), so if C<interval> is very small then timing stability |
2152 | will of course deteriorate. Libev itself tries to be exact to be about one |
2362 | will of course deteriorate. Libev itself tries to be exact to be about one |
2153 | millisecond (if the OS supports it and the machine is fast enough). |
2363 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2183 | |
2393 | |
2184 | NOTE: I<< This callback must always return a time that is higher than or |
2394 | NOTE: I<< This callback must always return a time that is higher than or |
2185 | equal to the passed C<now> value >>. |
2395 | equal to the passed C<now> value >>. |
2186 | |
2396 | |
2187 | This can be used to create very complex timers, such as a timer that |
2397 | This can be used to create very complex timers, such as a timer that |
2188 | triggers on "next midnight, local time". To do this, you would calculate the |
2398 | triggers on "next midnight, local time". To do this, you would calculate |
2189 | next midnight after C<now> and return the timestamp value for this. How |
2399 | the next midnight after C<now> and return the timestamp value for |
2190 | you do this is, again, up to you (but it is not trivial, which is the main |
2400 | this. Here is a (completely untested, no error checking) example on how to |
2191 | reason I omitted it as an example). |
2401 | do this: |
|
|
2402 | |
|
|
2403 | #include <time.h> |
|
|
2404 | |
|
|
2405 | static ev_tstamp |
|
|
2406 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2407 | { |
|
|
2408 | time_t tnow = (time_t)now; |
|
|
2409 | struct tm tm; |
|
|
2410 | localtime_r (&tnow, &tm); |
|
|
2411 | |
|
|
2412 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2413 | ++tm.tm_mday; // midnight next day |
|
|
2414 | |
|
|
2415 | return mktime (&tm); |
|
|
2416 | } |
|
|
2417 | |
|
|
2418 | Note: this code might run into trouble on days that have more then two |
|
|
2419 | midnights (beginning and end). |
2192 | |
2420 | |
2193 | =back |
2421 | =back |
2194 | |
2422 | |
2195 | =item ev_periodic_again (loop, ev_periodic *) |
2423 | =item ev_periodic_again (loop, ev_periodic *) |
2196 | |
2424 | |
… | |
… | |
2261 | |
2489 | |
2262 | ev_periodic hourly_tick; |
2490 | ev_periodic hourly_tick; |
2263 | ev_periodic_init (&hourly_tick, clock_cb, |
2491 | ev_periodic_init (&hourly_tick, clock_cb, |
2264 | fmod (ev_now (loop), 3600.), 3600., 0); |
2492 | fmod (ev_now (loop), 3600.), 3600., 0); |
2265 | ev_periodic_start (loop, &hourly_tick); |
2493 | ev_periodic_start (loop, &hourly_tick); |
2266 | |
2494 | |
2267 | |
2495 | |
2268 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2496 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2269 | |
2497 | |
2270 | Signal watchers will trigger an event when the process receives a specific |
2498 | Signal watchers will trigger an event when the process receives a specific |
2271 | signal one or more times. Even though signals are very asynchronous, libev |
2499 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2281 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2509 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2282 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2510 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2283 | C<SIGINT> in both the default loop and another loop at the same time. At |
2511 | C<SIGINT> in both the default loop and another loop at the same time. At |
2284 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2512 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2285 | |
2513 | |
2286 | When the first watcher gets started will libev actually register something |
2514 | Only after the first watcher for a signal is started will libev actually |
2287 | with the kernel (thus it coexists with your own signal handlers as long as |
2515 | register something with the kernel. It thus coexists with your own signal |
2288 | you don't register any with libev for the same signal). |
2516 | handlers as long as you don't register any with libev for the same signal. |
2289 | |
2517 | |
2290 | If possible and supported, libev will install its handlers with |
2518 | If possible and supported, libev will install its handlers with |
2291 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2519 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2292 | not be unduly interrupted. If you have a problem with system calls getting |
2520 | not be unduly interrupted. If you have a problem with system calls getting |
2293 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2521 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2296 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2524 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2297 | |
2525 | |
2298 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2526 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2299 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2527 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2300 | stopping it again), that is, libev might or might not block the signal, |
2528 | stopping it again), that is, libev might or might not block the signal, |
2301 | and might or might not set or restore the installed signal handler. |
2529 | and might or might not set or restore the installed signal handler (but |
|
|
2530 | see C<EVFLAG_NOSIGMASK>). |
2302 | |
2531 | |
2303 | While this does not matter for the signal disposition (libev never |
2532 | While this does not matter for the signal disposition (libev never |
2304 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2533 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2305 | C<execve>), this matters for the signal mask: many programs do not expect |
2534 | C<execve>), this matters for the signal mask: many programs do not expect |
2306 | certain signals to be blocked. |
2535 | certain signals to be blocked. |
… | |
… | |
2319 | I<has> to modify the signal mask, at least temporarily. |
2548 | I<has> to modify the signal mask, at least temporarily. |
2320 | |
2549 | |
2321 | So I can't stress this enough: I<If you do not reset your signal mask when |
2550 | So I can't stress this enough: I<If you do not reset your signal mask when |
2322 | you expect it to be empty, you have a race condition in your code>. This |
2551 | you expect it to be empty, you have a race condition in your code>. This |
2323 | is not a libev-specific thing, this is true for most event libraries. |
2552 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2553 | |
|
|
2554 | =head3 The special problem of threads signal handling |
|
|
2555 | |
|
|
2556 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2557 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2558 | threads in a process block signals, which is hard to achieve. |
|
|
2559 | |
|
|
2560 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2561 | for the same signals), you can tackle this problem by globally blocking |
|
|
2562 | all signals before creating any threads (or creating them with a fully set |
|
|
2563 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2564 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2565 | these signals. You can pass on any signals that libev might be interested |
|
|
2566 | in by calling C<ev_feed_signal>. |
2324 | |
2567 | |
2325 | =head3 Watcher-Specific Functions and Data Members |
2568 | =head3 Watcher-Specific Functions and Data Members |
2326 | |
2569 | |
2327 | =over 4 |
2570 | =over 4 |
2328 | |
2571 | |
… | |
… | |
2463 | |
2706 | |
2464 | =head2 C<ev_stat> - did the file attributes just change? |
2707 | =head2 C<ev_stat> - did the file attributes just change? |
2465 | |
2708 | |
2466 | This watches a file system path for attribute changes. That is, it calls |
2709 | This watches a file system path for attribute changes. That is, it calls |
2467 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2710 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2468 | and sees if it changed compared to the last time, invoking the callback if |
2711 | and sees if it changed compared to the last time, invoking the callback |
2469 | it did. |
2712 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2713 | happen after the watcher has been started will be reported. |
2470 | |
2714 | |
2471 | The path does not need to exist: changing from "path exists" to "path does |
2715 | The path does not need to exist: changing from "path exists" to "path does |
2472 | not exist" is a status change like any other. The condition "path does not |
2716 | not exist" is a status change like any other. The condition "path does not |
2473 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2717 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2474 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2718 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2704 | Apart from keeping your process non-blocking (which is a useful |
2948 | Apart from keeping your process non-blocking (which is a useful |
2705 | effect on its own sometimes), idle watchers are a good place to do |
2949 | effect on its own sometimes), idle watchers are a good place to do |
2706 | "pseudo-background processing", or delay processing stuff to after the |
2950 | "pseudo-background processing", or delay processing stuff to after the |
2707 | event loop has handled all outstanding events. |
2951 | event loop has handled all outstanding events. |
2708 | |
2952 | |
|
|
2953 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2954 | |
|
|
2955 | As long as there is at least one active idle watcher, libev will never |
|
|
2956 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2957 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2958 | lowest priority will do. |
|
|
2959 | |
|
|
2960 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2961 | to do something on each event loop iteration - for example to balance load |
|
|
2962 | between different connections. |
|
|
2963 | |
|
|
2964 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2965 | example. |
|
|
2966 | |
2709 | =head3 Watcher-Specific Functions and Data Members |
2967 | =head3 Watcher-Specific Functions and Data Members |
2710 | |
2968 | |
2711 | =over 4 |
2969 | =over 4 |
2712 | |
2970 | |
2713 | =item ev_idle_init (ev_idle *, callback) |
2971 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2724 | callback, free it. Also, use no error checking, as usual. |
2982 | callback, free it. Also, use no error checking, as usual. |
2725 | |
2983 | |
2726 | static void |
2984 | static void |
2727 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2985 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2728 | { |
2986 | { |
|
|
2987 | // stop the watcher |
|
|
2988 | ev_idle_stop (loop, w); |
|
|
2989 | |
|
|
2990 | // now we can free it |
2729 | free (w); |
2991 | free (w); |
|
|
2992 | |
2730 | // now do something you wanted to do when the program has |
2993 | // now do something you wanted to do when the program has |
2731 | // no longer anything immediate to do. |
2994 | // no longer anything immediate to do. |
2732 | } |
2995 | } |
2733 | |
2996 | |
2734 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2997 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2736 | ev_idle_start (loop, idle_watcher); |
2999 | ev_idle_start (loop, idle_watcher); |
2737 | |
3000 | |
2738 | |
3001 | |
2739 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3002 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2740 | |
3003 | |
2741 | Prepare and check watchers are usually (but not always) used in pairs: |
3004 | Prepare and check watchers are often (but not always) used in pairs: |
2742 | prepare watchers get invoked before the process blocks and check watchers |
3005 | prepare watchers get invoked before the process blocks and check watchers |
2743 | afterwards. |
3006 | afterwards. |
2744 | |
3007 | |
2745 | You I<must not> call C<ev_run> or similar functions that enter |
3008 | You I<must not> call C<ev_run> (or similar functions that enter the |
2746 | the current event loop from either C<ev_prepare> or C<ev_check> |
3009 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2747 | watchers. Other loops than the current one are fine, however. The |
3010 | C<ev_check> watchers. Other loops than the current one are fine, |
2748 | rationale behind this is that you do not need to check for recursion in |
3011 | however. The rationale behind this is that you do not need to check |
2749 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3012 | for recursion in those watchers, i.e. the sequence will always be |
2750 | C<ev_check> so if you have one watcher of each kind they will always be |
3013 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2751 | called in pairs bracketing the blocking call. |
3014 | kind they will always be called in pairs bracketing the blocking call. |
2752 | |
3015 | |
2753 | Their main purpose is to integrate other event mechanisms into libev and |
3016 | Their main purpose is to integrate other event mechanisms into libev and |
2754 | their use is somewhat advanced. They could be used, for example, to track |
3017 | their use is somewhat advanced. They could be used, for example, to track |
2755 | variable changes, implement your own watchers, integrate net-snmp or a |
3018 | variable changes, implement your own watchers, integrate net-snmp or a |
2756 | coroutine library and lots more. They are also occasionally useful if |
3019 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2774 | with priority higher than or equal to the event loop and one coroutine |
3037 | with priority higher than or equal to the event loop and one coroutine |
2775 | of lower priority, but only once, using idle watchers to keep the event |
3038 | of lower priority, but only once, using idle watchers to keep the event |
2776 | loop from blocking if lower-priority coroutines are active, thus mapping |
3039 | loop from blocking if lower-priority coroutines are active, thus mapping |
2777 | low-priority coroutines to idle/background tasks). |
3040 | low-priority coroutines to idle/background tasks). |
2778 | |
3041 | |
2779 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3042 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2780 | priority, to ensure that they are being run before any other watchers |
3043 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2781 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3044 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3045 | watchers). |
2782 | |
3046 | |
2783 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3047 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2784 | activate ("feed") events into libev. While libev fully supports this, they |
3048 | activate ("feed") events into libev. While libev fully supports this, they |
2785 | might get executed before other C<ev_check> watchers did their job. As |
3049 | might get executed before other C<ev_check> watchers did their job. As |
2786 | C<ev_check> watchers are often used to embed other (non-libev) event |
3050 | C<ev_check> watchers are often used to embed other (non-libev) event |
2787 | loops those other event loops might be in an unusable state until their |
3051 | loops those other event loops might be in an unusable state until their |
2788 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3052 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2789 | others). |
3053 | others). |
|
|
3054 | |
|
|
3055 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3056 | |
|
|
3057 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3058 | useful because they are called once per event loop iteration. For |
|
|
3059 | example, if you want to handle a large number of connections fairly, you |
|
|
3060 | normally only do a bit of work for each active connection, and if there |
|
|
3061 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3062 | connections have a chance of making progress. |
|
|
3063 | |
|
|
3064 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3065 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3066 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3067 | |
|
|
3068 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3069 | single global idle watcher that is active as long as you have one active |
|
|
3070 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3071 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3072 | invoked. Neither watcher alone can do that. |
2790 | |
3073 | |
2791 | =head3 Watcher-Specific Functions and Data Members |
3074 | =head3 Watcher-Specific Functions and Data Members |
2792 | |
3075 | |
2793 | =over 4 |
3076 | =over 4 |
2794 | |
3077 | |
… | |
… | |
2995 | |
3278 | |
2996 | =over 4 |
3279 | =over 4 |
2997 | |
3280 | |
2998 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3281 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2999 | |
3282 | |
3000 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3283 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3001 | |
3284 | |
3002 | Configures the watcher to embed the given loop, which must be |
3285 | Configures the watcher to embed the given loop, which must be |
3003 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3286 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3004 | invoked automatically, otherwise it is the responsibility of the callback |
3287 | invoked automatically, otherwise it is the responsibility of the callback |
3005 | to invoke it (it will continue to be called until the sweep has been done, |
3288 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3026 | used). |
3309 | used). |
3027 | |
3310 | |
3028 | struct ev_loop *loop_hi = ev_default_init (0); |
3311 | struct ev_loop *loop_hi = ev_default_init (0); |
3029 | struct ev_loop *loop_lo = 0; |
3312 | struct ev_loop *loop_lo = 0; |
3030 | ev_embed embed; |
3313 | ev_embed embed; |
3031 | |
3314 | |
3032 | // see if there is a chance of getting one that works |
3315 | // see if there is a chance of getting one that works |
3033 | // (remember that a flags value of 0 means autodetection) |
3316 | // (remember that a flags value of 0 means autodetection) |
3034 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3317 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3035 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3318 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3036 | : 0; |
3319 | : 0; |
… | |
… | |
3050 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3333 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3051 | |
3334 | |
3052 | struct ev_loop *loop = ev_default_init (0); |
3335 | struct ev_loop *loop = ev_default_init (0); |
3053 | struct ev_loop *loop_socket = 0; |
3336 | struct ev_loop *loop_socket = 0; |
3054 | ev_embed embed; |
3337 | ev_embed embed; |
3055 | |
3338 | |
3056 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3339 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3057 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3340 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3058 | { |
3341 | { |
3059 | ev_embed_init (&embed, 0, loop_socket); |
3342 | ev_embed_init (&embed, 0, loop_socket); |
3060 | ev_embed_start (loop, &embed); |
3343 | ev_embed_start (loop, &embed); |
… | |
… | |
3068 | |
3351 | |
3069 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3352 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3070 | |
3353 | |
3071 | Fork watchers are called when a C<fork ()> was detected (usually because |
3354 | Fork watchers are called when a C<fork ()> was detected (usually because |
3072 | whoever is a good citizen cared to tell libev about it by calling |
3355 | whoever is a good citizen cared to tell libev about it by calling |
3073 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3356 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3074 | event loop blocks next and before C<ev_check> watchers are being called, |
3357 | and before C<ev_check> watchers are being called, and only in the child |
3075 | and only in the child after the fork. If whoever good citizen calling |
3358 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3076 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3359 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3077 | handlers will be invoked, too, of course. |
3360 | of course. |
3078 | |
3361 | |
3079 | =head3 The special problem of life after fork - how is it possible? |
3362 | =head3 The special problem of life after fork - how is it possible? |
3080 | |
3363 | |
3081 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3364 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3082 | up/change the process environment, followed by a call to C<exec()>. This |
3365 | up/change the process environment, followed by a call to C<exec()>. This |
3083 | sequence should be handled by libev without any problems. |
3366 | sequence should be handled by libev without any problems. |
3084 | |
3367 | |
3085 | This changes when the application actually wants to do event handling |
3368 | This changes when the application actually wants to do event handling |
3086 | in the child, or both parent in child, in effect "continuing" after the |
3369 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3163 | atexit (program_exits); |
3446 | atexit (program_exits); |
3164 | |
3447 | |
3165 | |
3448 | |
3166 | =head2 C<ev_async> - how to wake up an event loop |
3449 | =head2 C<ev_async> - how to wake up an event loop |
3167 | |
3450 | |
3168 | In general, you cannot use an C<ev_run> from multiple threads or other |
3451 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3169 | asynchronous sources such as signal handlers (as opposed to multiple event |
3452 | asynchronous sources such as signal handlers (as opposed to multiple event |
3170 | loops - those are of course safe to use in different threads). |
3453 | loops - those are of course safe to use in different threads). |
3171 | |
3454 | |
3172 | Sometimes, however, you need to wake up an event loop you do not control, |
3455 | Sometimes, however, you need to wake up an event loop you do not control, |
3173 | for example because it belongs to another thread. This is what C<ev_async> |
3456 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3175 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3458 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3176 | |
3459 | |
3177 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3460 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3178 | too, are asynchronous in nature, and signals, too, will be compressed |
3461 | too, are asynchronous in nature, and signals, too, will be compressed |
3179 | (i.e. the number of callback invocations may be less than the number of |
3462 | (i.e. the number of callback invocations may be less than the number of |
3180 | C<ev_async_sent> calls). |
3463 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3181 | |
3464 | of "global async watchers" by using a watcher on an otherwise unused |
3182 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3465 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3183 | just the default loop. |
3466 | even without knowing which loop owns the signal. |
3184 | |
3467 | |
3185 | =head3 Queueing |
3468 | =head3 Queueing |
3186 | |
3469 | |
3187 | C<ev_async> does not support queueing of data in any way. The reason |
3470 | C<ev_async> does not support queueing of data in any way. The reason |
3188 | is that the author does not know of a simple (or any) algorithm for a |
3471 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3280 | trust me. |
3563 | trust me. |
3281 | |
3564 | |
3282 | =item ev_async_send (loop, ev_async *) |
3565 | =item ev_async_send (loop, ev_async *) |
3283 | |
3566 | |
3284 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3567 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3285 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3568 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3569 | returns. |
|
|
3570 | |
3286 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3571 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3287 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3572 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3288 | section below on what exactly this means). |
3573 | embedding section below on what exactly this means). |
3289 | |
3574 | |
3290 | Note that, as with other watchers in libev, multiple events might get |
3575 | Note that, as with other watchers in libev, multiple events might get |
3291 | compressed into a single callback invocation (another way to look at this |
3576 | compressed into a single callback invocation (another way to look at |
3292 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3577 | this is that C<ev_async> watchers are level-triggered: they are set on |
3293 | reset when the event loop detects that). |
3578 | C<ev_async_send>, reset when the event loop detects that). |
3294 | |
3579 | |
3295 | This call incurs the overhead of a system call only once per event loop |
3580 | This call incurs the overhead of at most one extra system call per event |
3296 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3581 | loop iteration, if the event loop is blocked, and no syscall at all if |
3297 | repeated calls to C<ev_async_send> for the same event loop. |
3582 | the event loop (or your program) is processing events. That means that |
|
|
3583 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3584 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3585 | zero) under load. |
3298 | |
3586 | |
3299 | =item bool = ev_async_pending (ev_async *) |
3587 | =item bool = ev_async_pending (ev_async *) |
3300 | |
3588 | |
3301 | Returns a non-zero value when C<ev_async_send> has been called on the |
3589 | Returns a non-zero value when C<ev_async_send> has been called on the |
3302 | watcher but the event has not yet been processed (or even noted) by the |
3590 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3319 | |
3607 | |
3320 | There are some other functions of possible interest. Described. Here. Now. |
3608 | There are some other functions of possible interest. Described. Here. Now. |
3321 | |
3609 | |
3322 | =over 4 |
3610 | =over 4 |
3323 | |
3611 | |
3324 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3612 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3325 | |
3613 | |
3326 | This function combines a simple timer and an I/O watcher, calls your |
3614 | This function combines a simple timer and an I/O watcher, calls your |
3327 | callback on whichever event happens first and automatically stops both |
3615 | callback on whichever event happens first and automatically stops both |
3328 | watchers. This is useful if you want to wait for a single event on an fd |
3616 | watchers. This is useful if you want to wait for a single event on an fd |
3329 | or timeout without having to allocate/configure/start/stop/free one or |
3617 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3357 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3645 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3358 | |
3646 | |
3359 | =item ev_feed_fd_event (loop, int fd, int revents) |
3647 | =item ev_feed_fd_event (loop, int fd, int revents) |
3360 | |
3648 | |
3361 | Feed an event on the given fd, as if a file descriptor backend detected |
3649 | Feed an event on the given fd, as if a file descriptor backend detected |
3362 | the given events it. |
3650 | the given events. |
3363 | |
3651 | |
3364 | =item ev_feed_signal_event (loop, int signum) |
3652 | =item ev_feed_signal_event (loop, int signum) |
3365 | |
3653 | |
3366 | Feed an event as if the given signal occurred (C<loop> must be the default |
3654 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3367 | loop!). |
3655 | which is async-safe. |
3368 | |
3656 | |
3369 | =back |
3657 | =back |
3370 | |
3658 | |
3371 | |
3659 | |
3372 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
3660 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
3373 | |
3661 | |
3374 | This section explains some common idioms that are not immediately |
3662 | This section explains some common idioms that are not immediately |
3375 | obvious. Note that examples are sprinkled over the whole manual, and this |
3663 | obvious. Note that examples are sprinkled over the whole manual, and this |
3376 | section only contains stuff that wouldn't fit anywhere else. |
3664 | section only contains stuff that wouldn't fit anywhere else. |
3377 | |
3665 | |
3378 | =over 4 |
3666 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
3379 | |
3667 | |
3380 | =item Model/nested event loop invocations and exit conditions. |
3668 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3669 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3670 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3671 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3672 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3673 | data: |
|
|
3674 | |
|
|
3675 | struct my_io |
|
|
3676 | { |
|
|
3677 | ev_io io; |
|
|
3678 | int otherfd; |
|
|
3679 | void *somedata; |
|
|
3680 | struct whatever *mostinteresting; |
|
|
3681 | }; |
|
|
3682 | |
|
|
3683 | ... |
|
|
3684 | struct my_io w; |
|
|
3685 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3686 | |
|
|
3687 | And since your callback will be called with a pointer to the watcher, you |
|
|
3688 | can cast it back to your own type: |
|
|
3689 | |
|
|
3690 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3691 | { |
|
|
3692 | struct my_io *w = (struct my_io *)w_; |
|
|
3693 | ... |
|
|
3694 | } |
|
|
3695 | |
|
|
3696 | More interesting and less C-conformant ways of casting your callback |
|
|
3697 | function type instead have been omitted. |
|
|
3698 | |
|
|
3699 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3700 | |
|
|
3701 | Another common scenario is to use some data structure with multiple |
|
|
3702 | embedded watchers, in effect creating your own watcher that combines |
|
|
3703 | multiple libev event sources into one "super-watcher": |
|
|
3704 | |
|
|
3705 | struct my_biggy |
|
|
3706 | { |
|
|
3707 | int some_data; |
|
|
3708 | ev_timer t1; |
|
|
3709 | ev_timer t2; |
|
|
3710 | } |
|
|
3711 | |
|
|
3712 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3713 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3714 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3715 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3716 | real programmers): |
|
|
3717 | |
|
|
3718 | #include <stddef.h> |
|
|
3719 | |
|
|
3720 | static void |
|
|
3721 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3722 | { |
|
|
3723 | struct my_biggy big = (struct my_biggy *) |
|
|
3724 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3725 | } |
|
|
3726 | |
|
|
3727 | static void |
|
|
3728 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3729 | { |
|
|
3730 | struct my_biggy big = (struct my_biggy *) |
|
|
3731 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3732 | } |
|
|
3733 | |
|
|
3734 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3735 | |
|
|
3736 | Often you have structures like this in event-based programs: |
|
|
3737 | |
|
|
3738 | callback () |
|
|
3739 | { |
|
|
3740 | free (request); |
|
|
3741 | } |
|
|
3742 | |
|
|
3743 | request = start_new_request (..., callback); |
|
|
3744 | |
|
|
3745 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3746 | used to cancel the operation, or do other things with it. |
|
|
3747 | |
|
|
3748 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3749 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3750 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3751 | operation and simply invoke the callback with the result. |
|
|
3752 | |
|
|
3753 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3754 | has returned, so C<request> is not set. |
|
|
3755 | |
|
|
3756 | Even if you pass the request by some safer means to the callback, you |
|
|
3757 | might want to do something to the request after starting it, such as |
|
|
3758 | canceling it, which probably isn't working so well when the callback has |
|
|
3759 | already been invoked. |
|
|
3760 | |
|
|
3761 | A common way around all these issues is to make sure that |
|
|
3762 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3763 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3764 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3765 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3766 | pushing it into the pending queue: |
|
|
3767 | |
|
|
3768 | ev_set_cb (watcher, callback); |
|
|
3769 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3770 | |
|
|
3771 | This way, C<start_new_request> can safely return before the callback is |
|
|
3772 | invoked, while not delaying callback invocation too much. |
|
|
3773 | |
|
|
3774 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3381 | |
3775 | |
3382 | Often (especially in GUI toolkits) there are places where you have |
3776 | Often (especially in GUI toolkits) there are places where you have |
3383 | I<modal> interaction, which is most easily implemented by recursively |
3777 | I<modal> interaction, which is most easily implemented by recursively |
3384 | invoking C<ev_run>. |
3778 | invoking C<ev_run>. |
3385 | |
3779 | |
3386 | This brings the problem of exiting - a callback might want to finish the |
3780 | This brings the problem of exiting - a callback might want to finish the |
3387 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3781 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3388 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3782 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3389 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3783 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3390 | other combination: In these cases, C<ev_break> will not work alone. |
3784 | other combination: In these cases, a simple C<ev_break> will not work. |
3391 | |
3785 | |
3392 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3786 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3393 | invocation, and use a loop around C<ev_run> until the condition is |
3787 | invocation, and use a loop around C<ev_run> until the condition is |
3394 | triggered, using C<EVRUN_ONCE>: |
3788 | triggered, using C<EVRUN_ONCE>: |
3395 | |
3789 | |
… | |
… | |
3397 | int exit_main_loop = 0; |
3791 | int exit_main_loop = 0; |
3398 | |
3792 | |
3399 | while (!exit_main_loop) |
3793 | while (!exit_main_loop) |
3400 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3794 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3401 | |
3795 | |
3402 | // in a model watcher |
3796 | // in a modal watcher |
3403 | int exit_nested_loop = 0; |
3797 | int exit_nested_loop = 0; |
3404 | |
3798 | |
3405 | while (!exit_nested_loop) |
3799 | while (!exit_nested_loop) |
3406 | ev_run (EV_A_ EVRUN_ONCE); |
3800 | ev_run (EV_A_ EVRUN_ONCE); |
3407 | |
3801 | |
… | |
… | |
3414 | exit_main_loop = 1; |
3808 | exit_main_loop = 1; |
3415 | |
3809 | |
3416 | // exit both |
3810 | // exit both |
3417 | exit_main_loop = exit_nested_loop = 1; |
3811 | exit_main_loop = exit_nested_loop = 1; |
3418 | |
3812 | |
3419 | =back |
3813 | =head2 THREAD LOCKING EXAMPLE |
|
|
3814 | |
|
|
3815 | Here is a fictitious example of how to run an event loop in a different |
|
|
3816 | thread from where callbacks are being invoked and watchers are |
|
|
3817 | created/added/removed. |
|
|
3818 | |
|
|
3819 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3820 | which uses exactly this technique (which is suited for many high-level |
|
|
3821 | languages). |
|
|
3822 | |
|
|
3823 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3824 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3825 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3826 | |
|
|
3827 | First, you need to associate some data with the event loop: |
|
|
3828 | |
|
|
3829 | typedef struct { |
|
|
3830 | mutex_t lock; /* global loop lock */ |
|
|
3831 | ev_async async_w; |
|
|
3832 | thread_t tid; |
|
|
3833 | cond_t invoke_cv; |
|
|
3834 | } userdata; |
|
|
3835 | |
|
|
3836 | void prepare_loop (EV_P) |
|
|
3837 | { |
|
|
3838 | // for simplicity, we use a static userdata struct. |
|
|
3839 | static userdata u; |
|
|
3840 | |
|
|
3841 | ev_async_init (&u->async_w, async_cb); |
|
|
3842 | ev_async_start (EV_A_ &u->async_w); |
|
|
3843 | |
|
|
3844 | pthread_mutex_init (&u->lock, 0); |
|
|
3845 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3846 | |
|
|
3847 | // now associate this with the loop |
|
|
3848 | ev_set_userdata (EV_A_ u); |
|
|
3849 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3850 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3851 | |
|
|
3852 | // then create the thread running ev_run |
|
|
3853 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3854 | } |
|
|
3855 | |
|
|
3856 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3857 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3858 | that might have been added: |
|
|
3859 | |
|
|
3860 | static void |
|
|
3861 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3862 | { |
|
|
3863 | // just used for the side effects |
|
|
3864 | } |
|
|
3865 | |
|
|
3866 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3867 | protecting the loop data, respectively. |
|
|
3868 | |
|
|
3869 | static void |
|
|
3870 | l_release (EV_P) |
|
|
3871 | { |
|
|
3872 | userdata *u = ev_userdata (EV_A); |
|
|
3873 | pthread_mutex_unlock (&u->lock); |
|
|
3874 | } |
|
|
3875 | |
|
|
3876 | static void |
|
|
3877 | l_acquire (EV_P) |
|
|
3878 | { |
|
|
3879 | userdata *u = ev_userdata (EV_A); |
|
|
3880 | pthread_mutex_lock (&u->lock); |
|
|
3881 | } |
|
|
3882 | |
|
|
3883 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3884 | into C<ev_run>: |
|
|
3885 | |
|
|
3886 | void * |
|
|
3887 | l_run (void *thr_arg) |
|
|
3888 | { |
|
|
3889 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3890 | |
|
|
3891 | l_acquire (EV_A); |
|
|
3892 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3893 | ev_run (EV_A_ 0); |
|
|
3894 | l_release (EV_A); |
|
|
3895 | |
|
|
3896 | return 0; |
|
|
3897 | } |
|
|
3898 | |
|
|
3899 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3900 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3901 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3902 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3903 | and b) skipping inter-thread-communication when there are no pending |
|
|
3904 | watchers is very beneficial): |
|
|
3905 | |
|
|
3906 | static void |
|
|
3907 | l_invoke (EV_P) |
|
|
3908 | { |
|
|
3909 | userdata *u = ev_userdata (EV_A); |
|
|
3910 | |
|
|
3911 | while (ev_pending_count (EV_A)) |
|
|
3912 | { |
|
|
3913 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3914 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3915 | } |
|
|
3916 | } |
|
|
3917 | |
|
|
3918 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3919 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3920 | thread to continue: |
|
|
3921 | |
|
|
3922 | static void |
|
|
3923 | real_invoke_pending (EV_P) |
|
|
3924 | { |
|
|
3925 | userdata *u = ev_userdata (EV_A); |
|
|
3926 | |
|
|
3927 | pthread_mutex_lock (&u->lock); |
|
|
3928 | ev_invoke_pending (EV_A); |
|
|
3929 | pthread_cond_signal (&u->invoke_cv); |
|
|
3930 | pthread_mutex_unlock (&u->lock); |
|
|
3931 | } |
|
|
3932 | |
|
|
3933 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3934 | event loop, you will now have to lock: |
|
|
3935 | |
|
|
3936 | ev_timer timeout_watcher; |
|
|
3937 | userdata *u = ev_userdata (EV_A); |
|
|
3938 | |
|
|
3939 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3940 | |
|
|
3941 | pthread_mutex_lock (&u->lock); |
|
|
3942 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3943 | ev_async_send (EV_A_ &u->async_w); |
|
|
3944 | pthread_mutex_unlock (&u->lock); |
|
|
3945 | |
|
|
3946 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3947 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3948 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3949 | watchers in the next event loop iteration. |
|
|
3950 | |
|
|
3951 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3952 | |
|
|
3953 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3954 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3955 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3956 | doesn't need callbacks anymore. |
|
|
3957 | |
|
|
3958 | Imagine you have coroutines that you can switch to using a function |
|
|
3959 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3960 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3961 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3962 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3963 | the differing C<;> conventions): |
|
|
3964 | |
|
|
3965 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3966 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3967 | |
|
|
3968 | That means instead of having a C callback function, you store the |
|
|
3969 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3970 | your callback, you instead have it switch to that coroutine. |
|
|
3971 | |
|
|
3972 | A coroutine might now wait for an event with a function called |
|
|
3973 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3974 | matter when, or whether the watcher is active or not when this function is |
|
|
3975 | called): |
|
|
3976 | |
|
|
3977 | void |
|
|
3978 | wait_for_event (ev_watcher *w) |
|
|
3979 | { |
|
|
3980 | ev_set_cb (w, current_coro); |
|
|
3981 | switch_to (libev_coro); |
|
|
3982 | } |
|
|
3983 | |
|
|
3984 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3985 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3986 | this or any other coroutine. |
|
|
3987 | |
|
|
3988 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3989 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3990 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3991 | any waiters. |
|
|
3992 | |
|
|
3993 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3994 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3995 | |
|
|
3996 | // my_ev.h |
|
|
3997 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3998 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3999 | #include "../libev/ev.h" |
|
|
4000 | |
|
|
4001 | // my_ev.c |
|
|
4002 | #define EV_H "my_ev.h" |
|
|
4003 | #include "../libev/ev.c" |
|
|
4004 | |
|
|
4005 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
4006 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
4007 | can even use F<ev.h> as header file name directly. |
3420 | |
4008 | |
3421 | |
4009 | |
3422 | =head1 LIBEVENT EMULATION |
4010 | =head1 LIBEVENT EMULATION |
3423 | |
4011 | |
3424 | Libev offers a compatibility emulation layer for libevent. It cannot |
4012 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
3454 | |
4042 | |
3455 | =back |
4043 | =back |
3456 | |
4044 | |
3457 | =head1 C++ SUPPORT |
4045 | =head1 C++ SUPPORT |
3458 | |
4046 | |
|
|
4047 | =head2 C API |
|
|
4048 | |
|
|
4049 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4050 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4051 | will work fine. |
|
|
4052 | |
|
|
4053 | Proper exception specifications might have to be added to callbacks passed |
|
|
4054 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4055 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4056 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4057 | specification. If you have code that needs to be compiled as both C and |
|
|
4058 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4059 | |
|
|
4060 | static void |
|
|
4061 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4062 | { |
|
|
4063 | perror (msg); |
|
|
4064 | abort (); |
|
|
4065 | } |
|
|
4066 | |
|
|
4067 | ... |
|
|
4068 | ev_set_syserr_cb (fatal_error); |
|
|
4069 | |
|
|
4070 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4071 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4072 | because it runs cleanup watchers). |
|
|
4073 | |
|
|
4074 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4075 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4076 | throwing exceptions through C libraries (most do). |
|
|
4077 | |
|
|
4078 | =head2 C++ API |
|
|
4079 | |
3459 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4080 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3460 | you to use some convenience methods to start/stop watchers and also change |
4081 | you to use some convenience methods to start/stop watchers and also change |
3461 | the callback model to a model using method callbacks on objects. |
4082 | the callback model to a model using method callbacks on objects. |
3462 | |
4083 | |
3463 | To use it, |
4084 | To use it, |
3464 | |
4085 | |
3465 | #include <ev++.h> |
4086 | #include <ev++.h> |
3466 | |
4087 | |
3467 | This automatically includes F<ev.h> and puts all of its definitions (many |
4088 | This automatically includes F<ev.h> and puts all of its definitions (many |
3468 | of them macros) into the global namespace. All C++ specific things are |
4089 | of them macros) into the global namespace. All C++ specific things are |
3469 | put into the C<ev> namespace. It should support all the same embedding |
4090 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3478 | with C<operator ()> can be used as callbacks. Other types should be easy |
4099 | with C<operator ()> can be used as callbacks. Other types should be easy |
3479 | to add as long as they only need one additional pointer for context. If |
4100 | to add as long as they only need one additional pointer for context. If |
3480 | you need support for other types of functors please contact the author |
4101 | you need support for other types of functors please contact the author |
3481 | (preferably after implementing it). |
4102 | (preferably after implementing it). |
3482 | |
4103 | |
|
|
4104 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4105 | conventions as your C compiler (for static member functions), or you have |
|
|
4106 | to embed libev and compile libev itself as C++. |
|
|
4107 | |
3483 | Here is a list of things available in the C<ev> namespace: |
4108 | Here is a list of things available in the C<ev> namespace: |
3484 | |
4109 | |
3485 | =over 4 |
4110 | =over 4 |
3486 | |
4111 | |
3487 | =item C<ev::READ>, C<ev::WRITE> etc. |
4112 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3496 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4121 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3497 | |
4122 | |
3498 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4123 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3499 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4124 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3500 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4125 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3501 | defines by many implementations. |
4126 | defined by many implementations. |
3502 | |
4127 | |
3503 | All of those classes have these methods: |
4128 | All of those classes have these methods: |
3504 | |
4129 | |
3505 | =over 4 |
4130 | =over 4 |
3506 | |
4131 | |
… | |
… | |
3568 | void operator() (ev::io &w, int revents) |
4193 | void operator() (ev::io &w, int revents) |
3569 | { |
4194 | { |
3570 | ... |
4195 | ... |
3571 | } |
4196 | } |
3572 | } |
4197 | } |
3573 | |
4198 | |
3574 | myfunctor f; |
4199 | myfunctor f; |
3575 | |
4200 | |
3576 | ev::io w; |
4201 | ev::io w; |
3577 | w.set (&f); |
4202 | w.set (&f); |
3578 | |
4203 | |
… | |
… | |
3596 | Associates a different C<struct ev_loop> with this watcher. You can only |
4221 | Associates a different C<struct ev_loop> with this watcher. You can only |
3597 | do this when the watcher is inactive (and not pending either). |
4222 | do this when the watcher is inactive (and not pending either). |
3598 | |
4223 | |
3599 | =item w->set ([arguments]) |
4224 | =item w->set ([arguments]) |
3600 | |
4225 | |
3601 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4226 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3602 | method or a suitable start method must be called at least once. Unlike the |
4227 | with the same arguments. Either this method or a suitable start method |
3603 | C counterpart, an active watcher gets automatically stopped and restarted |
4228 | must be called at least once. Unlike the C counterpart, an active watcher |
3604 | when reconfiguring it with this method. |
4229 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4230 | method. |
|
|
4231 | |
|
|
4232 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4233 | clashing with the C<set (loop)> method. |
3605 | |
4234 | |
3606 | =item w->start () |
4235 | =item w->start () |
3607 | |
4236 | |
3608 | Starts the watcher. Note that there is no C<loop> argument, as the |
4237 | Starts the watcher. Note that there is no C<loop> argument, as the |
3609 | constructor already stores the event loop. |
4238 | constructor already stores the event loop. |
… | |
… | |
3639 | watchers in the constructor. |
4268 | watchers in the constructor. |
3640 | |
4269 | |
3641 | class myclass |
4270 | class myclass |
3642 | { |
4271 | { |
3643 | ev::io io ; void io_cb (ev::io &w, int revents); |
4272 | ev::io io ; void io_cb (ev::io &w, int revents); |
3644 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4273 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3645 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4274 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3646 | |
4275 | |
3647 | myclass (int fd) |
4276 | myclass (int fd) |
3648 | { |
4277 | { |
3649 | io .set <myclass, &myclass::io_cb > (this); |
4278 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3700 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4329 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3701 | |
4330 | |
3702 | =item D |
4331 | =item D |
3703 | |
4332 | |
3704 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4333 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3705 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4334 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3706 | |
4335 | |
3707 | =item Ocaml |
4336 | =item Ocaml |
3708 | |
4337 | |
3709 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4338 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3710 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4339 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3713 | |
4342 | |
3714 | Brian Maher has written a partial interface to libev for lua (at the |
4343 | Brian Maher has written a partial interface to libev for lua (at the |
3715 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4344 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3716 | L<http://github.com/brimworks/lua-ev>. |
4345 | L<http://github.com/brimworks/lua-ev>. |
3717 | |
4346 | |
|
|
4347 | =item Javascript |
|
|
4348 | |
|
|
4349 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4350 | |
|
|
4351 | =item Others |
|
|
4352 | |
|
|
4353 | There are others, and I stopped counting. |
|
|
4354 | |
3718 | =back |
4355 | =back |
3719 | |
4356 | |
3720 | |
4357 | |
3721 | =head1 MACRO MAGIC |
4358 | =head1 MACRO MAGIC |
3722 | |
4359 | |
… | |
… | |
3758 | suitable for use with C<EV_A>. |
4395 | suitable for use with C<EV_A>. |
3759 | |
4396 | |
3760 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4397 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3761 | |
4398 | |
3762 | Similar to the other two macros, this gives you the value of the default |
4399 | Similar to the other two macros, this gives you the value of the default |
3763 | loop, if multiple loops are supported ("ev loop default"). |
4400 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4401 | will be initialised if it isn't already initialised. |
|
|
4402 | |
|
|
4403 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4404 | to initialise the loop somewhere. |
3764 | |
4405 | |
3765 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4406 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3766 | |
4407 | |
3767 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4408 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3768 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4409 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3835 | ev_vars.h |
4476 | ev_vars.h |
3836 | ev_wrap.h |
4477 | ev_wrap.h |
3837 | |
4478 | |
3838 | ev_win32.c required on win32 platforms only |
4479 | ev_win32.c required on win32 platforms only |
3839 | |
4480 | |
3840 | ev_select.c only when select backend is enabled (which is enabled by default) |
4481 | ev_select.c only when select backend is enabled |
3841 | ev_poll.c only when poll backend is enabled (disabled by default) |
4482 | ev_poll.c only when poll backend is enabled |
3842 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4483 | ev_epoll.c only when the epoll backend is enabled |
|
|
4484 | ev_linuxaio.c only when the linux aio backend is enabled |
3843 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4485 | ev_kqueue.c only when the kqueue backend is enabled |
3844 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4486 | ev_port.c only when the solaris port backend is enabled |
3845 | |
4487 | |
3846 | F<ev.c> includes the backend files directly when enabled, so you only need |
4488 | F<ev.c> includes the backend files directly when enabled, so you only need |
3847 | to compile this single file. |
4489 | to compile this single file. |
3848 | |
4490 | |
3849 | =head3 LIBEVENT COMPATIBILITY API |
4491 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
3913 | supported). It will also not define any of the structs usually found in |
4555 | supported). It will also not define any of the structs usually found in |
3914 | F<event.h> that are not directly supported by the libev core alone. |
4556 | F<event.h> that are not directly supported by the libev core alone. |
3915 | |
4557 | |
3916 | In standalone mode, libev will still try to automatically deduce the |
4558 | In standalone mode, libev will still try to automatically deduce the |
3917 | configuration, but has to be more conservative. |
4559 | configuration, but has to be more conservative. |
|
|
4560 | |
|
|
4561 | =item EV_USE_FLOOR |
|
|
4562 | |
|
|
4563 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4564 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4565 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4566 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4567 | function is not available will fail, so the safe default is to not enable |
|
|
4568 | this. |
3918 | |
4569 | |
3919 | =item EV_USE_MONOTONIC |
4570 | =item EV_USE_MONOTONIC |
3920 | |
4571 | |
3921 | If defined to be C<1>, libev will try to detect the availability of the |
4572 | If defined to be C<1>, libev will try to detect the availability of the |
3922 | monotonic clock option at both compile time and runtime. Otherwise no |
4573 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
4008 | If programs implement their own fd to handle mapping on win32, then this |
4659 | If programs implement their own fd to handle mapping on win32, then this |
4009 | macro can be used to override the C<close> function, useful to unregister |
4660 | macro can be used to override the C<close> function, useful to unregister |
4010 | file descriptors again. Note that the replacement function has to close |
4661 | file descriptors again. Note that the replacement function has to close |
4011 | the underlying OS handle. |
4662 | the underlying OS handle. |
4012 | |
4663 | |
|
|
4664 | =item EV_USE_WSASOCKET |
|
|
4665 | |
|
|
4666 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4667 | communication socket, which works better in some environments. Otherwise, |
|
|
4668 | the normal C<socket> function will be used, which works better in other |
|
|
4669 | environments. |
|
|
4670 | |
4013 | =item EV_USE_POLL |
4671 | =item EV_USE_POLL |
4014 | |
4672 | |
4015 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4673 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4016 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4674 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4017 | takes precedence over select. |
4675 | takes precedence over select. |
… | |
… | |
4021 | If defined to be C<1>, libev will compile in support for the Linux |
4679 | If defined to be C<1>, libev will compile in support for the Linux |
4022 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4680 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4023 | otherwise another method will be used as fallback. This is the preferred |
4681 | otherwise another method will be used as fallback. This is the preferred |
4024 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4682 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4025 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4683 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4684 | |
|
|
4685 | =item EV_USE_LINUXAIO |
|
|
4686 | |
|
|
4687 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4688 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4689 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4690 | disabled. |
4026 | |
4691 | |
4027 | =item EV_USE_KQUEUE |
4692 | =item EV_USE_KQUEUE |
4028 | |
4693 | |
4029 | If defined to be C<1>, libev will compile in support for the BSD style |
4694 | If defined to be C<1>, libev will compile in support for the BSD style |
4030 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4695 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4052 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4717 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4053 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4718 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4054 | be detected at runtime. If undefined, it will be enabled if the headers |
4719 | be detected at runtime. If undefined, it will be enabled if the headers |
4055 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4720 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4056 | |
4721 | |
|
|
4722 | =item EV_NO_SMP |
|
|
4723 | |
|
|
4724 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4725 | between threads, that is, threads can be used, but threads never run on |
|
|
4726 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4727 | and makes libev faster. |
|
|
4728 | |
|
|
4729 | =item EV_NO_THREADS |
|
|
4730 | |
|
|
4731 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4732 | different threads (that includes signal handlers), which is a stronger |
|
|
4733 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4734 | libev faster. |
|
|
4735 | |
4057 | =item EV_ATOMIC_T |
4736 | =item EV_ATOMIC_T |
4058 | |
4737 | |
4059 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4738 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4060 | access is atomic with respect to other threads or signal contexts. No such |
4739 | access is atomic with respect to other threads or signal contexts. No |
4061 | type is easily found in the C language, so you can provide your own type |
4740 | such type is easily found in the C language, so you can provide your own |
4062 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4741 | type that you know is safe for your purposes. It is used both for signal |
4063 | as well as for signal and thread safety in C<ev_async> watchers. |
4742 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4743 | watchers. |
4064 | |
4744 | |
4065 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4745 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4066 | (from F<signal.h>), which is usually good enough on most platforms. |
4746 | (from F<signal.h>), which is usually good enough on most platforms. |
4067 | |
4747 | |
4068 | =item EV_H (h) |
4748 | =item EV_H (h) |
… | |
… | |
4095 | will have the C<struct ev_loop *> as first argument, and you can create |
4775 | will have the C<struct ev_loop *> as first argument, and you can create |
4096 | additional independent event loops. Otherwise there will be no support |
4776 | additional independent event loops. Otherwise there will be no support |
4097 | for multiple event loops and there is no first event loop pointer |
4777 | for multiple event loops and there is no first event loop pointer |
4098 | argument. Instead, all functions act on the single default loop. |
4778 | argument. Instead, all functions act on the single default loop. |
4099 | |
4779 | |
|
|
4780 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4781 | default loop when multiplicity is switched off - you always have to |
|
|
4782 | initialise the loop manually in this case. |
|
|
4783 | |
4100 | =item EV_MINPRI |
4784 | =item EV_MINPRI |
4101 | |
4785 | |
4102 | =item EV_MAXPRI |
4786 | =item EV_MAXPRI |
4103 | |
4787 | |
4104 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4788 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4140 | #define EV_USE_POLL 1 |
4824 | #define EV_USE_POLL 1 |
4141 | #define EV_CHILD_ENABLE 1 |
4825 | #define EV_CHILD_ENABLE 1 |
4142 | #define EV_ASYNC_ENABLE 1 |
4826 | #define EV_ASYNC_ENABLE 1 |
4143 | |
4827 | |
4144 | The actual value is a bitset, it can be a combination of the following |
4828 | The actual value is a bitset, it can be a combination of the following |
4145 | values: |
4829 | values (by default, all of these are enabled): |
4146 | |
4830 | |
4147 | =over 4 |
4831 | =over 4 |
4148 | |
4832 | |
4149 | =item C<1> - faster/larger code |
4833 | =item C<1> - faster/larger code |
4150 | |
4834 | |
… | |
… | |
4154 | code size by roughly 30% on amd64). |
4838 | code size by roughly 30% on amd64). |
4155 | |
4839 | |
4156 | When optimising for size, use of compiler flags such as C<-Os> with |
4840 | When optimising for size, use of compiler flags such as C<-Os> with |
4157 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4841 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4158 | assertions. |
4842 | assertions. |
|
|
4843 | |
|
|
4844 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4845 | (e.g. gcc with C<-Os>). |
4159 | |
4846 | |
4160 | =item C<2> - faster/larger data structures |
4847 | =item C<2> - faster/larger data structures |
4161 | |
4848 | |
4162 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4849 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4163 | hash table sizes and so on. This will usually further increase code size |
4850 | hash table sizes and so on. This will usually further increase code size |
4164 | and can additionally have an effect on the size of data structures at |
4851 | and can additionally have an effect on the size of data structures at |
4165 | runtime. |
4852 | runtime. |
4166 | |
4853 | |
|
|
4854 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4855 | (e.g. gcc with C<-Os>). |
|
|
4856 | |
4167 | =item C<4> - full API configuration |
4857 | =item C<4> - full API configuration |
4168 | |
4858 | |
4169 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4859 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4170 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4860 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4171 | |
4861 | |
… | |
… | |
4201 | |
4891 | |
4202 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4892 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4203 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4893 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4204 | your program might be left out as well - a binary starting a timer and an |
4894 | your program might be left out as well - a binary starting a timer and an |
4205 | I/O watcher then might come out at only 5Kb. |
4895 | I/O watcher then might come out at only 5Kb. |
|
|
4896 | |
|
|
4897 | =item EV_API_STATIC |
|
|
4898 | |
|
|
4899 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4900 | will have static linkage. This means that libev will not export any |
|
|
4901 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4902 | when you embed libev, only want to use libev functions in a single file, |
|
|
4903 | and do not want its identifiers to be visible. |
|
|
4904 | |
|
|
4905 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4906 | wants to use libev. |
|
|
4907 | |
|
|
4908 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4909 | doesn't support the required declaration syntax. |
4206 | |
4910 | |
4207 | =item EV_AVOID_STDIO |
4911 | =item EV_AVOID_STDIO |
4208 | |
4912 | |
4209 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4913 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4210 | functions (printf, scanf, perror etc.). This will increase the code size |
4914 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4354 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
5058 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4355 | |
5059 | |
4356 | #include "ev_cpp.h" |
5060 | #include "ev_cpp.h" |
4357 | #include "ev.c" |
5061 | #include "ev.c" |
4358 | |
5062 | |
4359 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
5063 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4360 | |
5064 | |
4361 | =head2 THREADS AND COROUTINES |
5065 | =head2 THREADS AND COROUTINES |
4362 | |
5066 | |
4363 | =head3 THREADS |
5067 | =head3 THREADS |
4364 | |
5068 | |
… | |
… | |
4415 | default loop and triggering an C<ev_async> watcher from the default loop |
5119 | default loop and triggering an C<ev_async> watcher from the default loop |
4416 | watcher callback into the event loop interested in the signal. |
5120 | watcher callback into the event loop interested in the signal. |
4417 | |
5121 | |
4418 | =back |
5122 | =back |
4419 | |
5123 | |
4420 | =head4 THREAD LOCKING EXAMPLE |
5124 | See also L</THREAD LOCKING EXAMPLE>. |
4421 | |
|
|
4422 | Here is a fictitious example of how to run an event loop in a different |
|
|
4423 | thread than where callbacks are being invoked and watchers are |
|
|
4424 | created/added/removed. |
|
|
4425 | |
|
|
4426 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4427 | which uses exactly this technique (which is suited for many high-level |
|
|
4428 | languages). |
|
|
4429 | |
|
|
4430 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4431 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4432 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4433 | |
|
|
4434 | First, you need to associate some data with the event loop: |
|
|
4435 | |
|
|
4436 | typedef struct { |
|
|
4437 | mutex_t lock; /* global loop lock */ |
|
|
4438 | ev_async async_w; |
|
|
4439 | thread_t tid; |
|
|
4440 | cond_t invoke_cv; |
|
|
4441 | } userdata; |
|
|
4442 | |
|
|
4443 | void prepare_loop (EV_P) |
|
|
4444 | { |
|
|
4445 | // for simplicity, we use a static userdata struct. |
|
|
4446 | static userdata u; |
|
|
4447 | |
|
|
4448 | ev_async_init (&u->async_w, async_cb); |
|
|
4449 | ev_async_start (EV_A_ &u->async_w); |
|
|
4450 | |
|
|
4451 | pthread_mutex_init (&u->lock, 0); |
|
|
4452 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4453 | |
|
|
4454 | // now associate this with the loop |
|
|
4455 | ev_set_userdata (EV_A_ u); |
|
|
4456 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4457 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4458 | |
|
|
4459 | // then create the thread running ev_loop |
|
|
4460 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4461 | } |
|
|
4462 | |
|
|
4463 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4464 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4465 | that might have been added: |
|
|
4466 | |
|
|
4467 | static void |
|
|
4468 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4469 | { |
|
|
4470 | // just used for the side effects |
|
|
4471 | } |
|
|
4472 | |
|
|
4473 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4474 | protecting the loop data, respectively. |
|
|
4475 | |
|
|
4476 | static void |
|
|
4477 | l_release (EV_P) |
|
|
4478 | { |
|
|
4479 | userdata *u = ev_userdata (EV_A); |
|
|
4480 | pthread_mutex_unlock (&u->lock); |
|
|
4481 | } |
|
|
4482 | |
|
|
4483 | static void |
|
|
4484 | l_acquire (EV_P) |
|
|
4485 | { |
|
|
4486 | userdata *u = ev_userdata (EV_A); |
|
|
4487 | pthread_mutex_lock (&u->lock); |
|
|
4488 | } |
|
|
4489 | |
|
|
4490 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4491 | into C<ev_run>: |
|
|
4492 | |
|
|
4493 | void * |
|
|
4494 | l_run (void *thr_arg) |
|
|
4495 | { |
|
|
4496 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4497 | |
|
|
4498 | l_acquire (EV_A); |
|
|
4499 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4500 | ev_run (EV_A_ 0); |
|
|
4501 | l_release (EV_A); |
|
|
4502 | |
|
|
4503 | return 0; |
|
|
4504 | } |
|
|
4505 | |
|
|
4506 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4507 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4508 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4509 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4510 | and b) skipping inter-thread-communication when there are no pending |
|
|
4511 | watchers is very beneficial): |
|
|
4512 | |
|
|
4513 | static void |
|
|
4514 | l_invoke (EV_P) |
|
|
4515 | { |
|
|
4516 | userdata *u = ev_userdata (EV_A); |
|
|
4517 | |
|
|
4518 | while (ev_pending_count (EV_A)) |
|
|
4519 | { |
|
|
4520 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4521 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4522 | } |
|
|
4523 | } |
|
|
4524 | |
|
|
4525 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4526 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4527 | thread to continue: |
|
|
4528 | |
|
|
4529 | static void |
|
|
4530 | real_invoke_pending (EV_P) |
|
|
4531 | { |
|
|
4532 | userdata *u = ev_userdata (EV_A); |
|
|
4533 | |
|
|
4534 | pthread_mutex_lock (&u->lock); |
|
|
4535 | ev_invoke_pending (EV_A); |
|
|
4536 | pthread_cond_signal (&u->invoke_cv); |
|
|
4537 | pthread_mutex_unlock (&u->lock); |
|
|
4538 | } |
|
|
4539 | |
|
|
4540 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4541 | event loop, you will now have to lock: |
|
|
4542 | |
|
|
4543 | ev_timer timeout_watcher; |
|
|
4544 | userdata *u = ev_userdata (EV_A); |
|
|
4545 | |
|
|
4546 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4547 | |
|
|
4548 | pthread_mutex_lock (&u->lock); |
|
|
4549 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4550 | ev_async_send (EV_A_ &u->async_w); |
|
|
4551 | pthread_mutex_unlock (&u->lock); |
|
|
4552 | |
|
|
4553 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4554 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4555 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4556 | watchers in the next event loop iteration. |
|
|
4557 | |
5125 | |
4558 | =head3 COROUTINES |
5126 | =head3 COROUTINES |
4559 | |
5127 | |
4560 | Libev is very accommodating to coroutines ("cooperative threads"): |
5128 | Libev is very accommodating to coroutines ("cooperative threads"): |
4561 | libev fully supports nesting calls to its functions from different |
5129 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4726 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5294 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4727 | model. Libev still offers limited functionality on this platform in |
5295 | model. Libev still offers limited functionality on this platform in |
4728 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5296 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4729 | descriptors. This only applies when using Win32 natively, not when using |
5297 | descriptors. This only applies when using Win32 natively, not when using |
4730 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5298 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4731 | as every compielr comes with a slightly differently broken/incompatible |
5299 | as every compiler comes with a slightly differently broken/incompatible |
4732 | environment. |
5300 | environment. |
4733 | |
5301 | |
4734 | Lifting these limitations would basically require the full |
5302 | Lifting these limitations would basically require the full |
4735 | re-implementation of the I/O system. If you are into this kind of thing, |
5303 | re-implementation of the I/O system. If you are into this kind of thing, |
4736 | then note that glib does exactly that for you in a very portable way (note |
5304 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4830 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5398 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4831 | assumes that the same (machine) code can be used to call any watcher |
5399 | assumes that the same (machine) code can be used to call any watcher |
4832 | callback: The watcher callbacks have different type signatures, but libev |
5400 | callback: The watcher callbacks have different type signatures, but libev |
4833 | calls them using an C<ev_watcher *> internally. |
5401 | calls them using an C<ev_watcher *> internally. |
4834 | |
5402 | |
|
|
5403 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5404 | |
|
|
5405 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5406 | relies on this setting pointers and integers to null. |
|
|
5407 | |
4835 | =item pointer accesses must be thread-atomic |
5408 | =item pointer accesses must be thread-atomic |
4836 | |
5409 | |
4837 | Accessing a pointer value must be atomic, it must both be readable and |
5410 | Accessing a pointer value must be atomic, it must both be readable and |
4838 | writable in one piece - this is the case on all current architectures. |
5411 | writable in one piece - this is the case on all current architectures. |
4839 | |
5412 | |
… | |
… | |
4852 | thread" or will block signals process-wide, both behaviours would |
5425 | thread" or will block signals process-wide, both behaviours would |
4853 | be compatible with libev. Interaction between C<sigprocmask> and |
5426 | be compatible with libev. Interaction between C<sigprocmask> and |
4854 | C<pthread_sigmask> could complicate things, however. |
5427 | C<pthread_sigmask> could complicate things, however. |
4855 | |
5428 | |
4856 | The most portable way to handle signals is to block signals in all threads |
5429 | The most portable way to handle signals is to block signals in all threads |
4857 | except the initial one, and run the default loop in the initial thread as |
5430 | except the initial one, and run the signal handling loop in the initial |
4858 | well. |
5431 | thread as well. |
4859 | |
5432 | |
4860 | =item C<long> must be large enough for common memory allocation sizes |
5433 | =item C<long> must be large enough for common memory allocation sizes |
4861 | |
5434 | |
4862 | To improve portability and simplify its API, libev uses C<long> internally |
5435 | To improve portability and simplify its API, libev uses C<long> internally |
4863 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5436 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4869 | |
5442 | |
4870 | The type C<double> is used to represent timestamps. It is required to |
5443 | The type C<double> is used to represent timestamps. It is required to |
4871 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5444 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4872 | good enough for at least into the year 4000 with millisecond accuracy |
5445 | good enough for at least into the year 4000 with millisecond accuracy |
4873 | (the design goal for libev). This requirement is overfulfilled by |
5446 | (the design goal for libev). This requirement is overfulfilled by |
4874 | implementations using IEEE 754, which is basically all existing ones. With |
5447 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5448 | |
4875 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5449 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5450 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5451 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5452 | something like that, just kidding). |
4876 | |
5453 | |
4877 | =back |
5454 | =back |
4878 | |
5455 | |
4879 | If you know of other additional requirements drop me a note. |
5456 | If you know of other additional requirements drop me a note. |
4880 | |
5457 | |
… | |
… | |
4942 | =item Processing ev_async_send: O(number_of_async_watchers) |
5519 | =item Processing ev_async_send: O(number_of_async_watchers) |
4943 | |
5520 | |
4944 | =item Processing signals: O(max_signal_number) |
5521 | =item Processing signals: O(max_signal_number) |
4945 | |
5522 | |
4946 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5523 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4947 | calls in the current loop iteration. Checking for async and signal events |
5524 | calls in the current loop iteration and the loop is currently |
|
|
5525 | blocked. Checking for async and signal events involves iterating over all |
4948 | involves iterating over all running async watchers or all signal numbers. |
5526 | running async watchers or all signal numbers. |
4949 | |
5527 | |
4950 | =back |
5528 | =back |
4951 | |
5529 | |
4952 | |
5530 | |
4953 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5531 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
4962 | =over 4 |
5540 | =over 4 |
4963 | |
5541 | |
4964 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5542 | =item C<EV_COMPAT3> backwards compatibility mechanism |
4965 | |
5543 | |
4966 | The backward compatibility mechanism can be controlled by |
5544 | The backward compatibility mechanism can be controlled by |
4967 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5545 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
4968 | section. |
5546 | section. |
4969 | |
5547 | |
4970 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5548 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
4971 | |
5549 | |
4972 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5550 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5015 | =over 4 |
5593 | =over 4 |
5016 | |
5594 | |
5017 | =item active |
5595 | =item active |
5018 | |
5596 | |
5019 | A watcher is active as long as it has been started and not yet stopped. |
5597 | A watcher is active as long as it has been started and not yet stopped. |
5020 | See L<WATCHER STATES> for details. |
5598 | See L</WATCHER STATES> for details. |
5021 | |
5599 | |
5022 | =item application |
5600 | =item application |
5023 | |
5601 | |
5024 | In this document, an application is whatever is using libev. |
5602 | In this document, an application is whatever is using libev. |
5025 | |
5603 | |
… | |
… | |
5061 | watchers and events. |
5639 | watchers and events. |
5062 | |
5640 | |
5063 | =item pending |
5641 | =item pending |
5064 | |
5642 | |
5065 | A watcher is pending as soon as the corresponding event has been |
5643 | A watcher is pending as soon as the corresponding event has been |
5066 | detected. See L<WATCHER STATES> for details. |
5644 | detected. See L</WATCHER STATES> for details. |
5067 | |
5645 | |
5068 | =item real time |
5646 | =item real time |
5069 | |
5647 | |
5070 | The physical time that is observed. It is apparently strictly monotonic :) |
5648 | The physical time that is observed. It is apparently strictly monotonic :) |
5071 | |
5649 | |
5072 | =item wall-clock time |
5650 | =item wall-clock time |
5073 | |
5651 | |
5074 | The time and date as shown on clocks. Unlike real time, it can actually |
5652 | The time and date as shown on clocks. Unlike real time, it can actually |
5075 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5653 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5076 | clock. |
5654 | clock. |
5077 | |
5655 | |
5078 | =item watcher |
5656 | =item watcher |
5079 | |
5657 | |
5080 | A data structure that describes interest in certain events. Watchers need |
5658 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5083 | =back |
5661 | =back |
5084 | |
5662 | |
5085 | =head1 AUTHOR |
5663 | =head1 AUTHOR |
5086 | |
5664 | |
5087 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5665 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5088 | Magnusson and Emanuele Giaquinta. |
5666 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5089 | |
5667 | |