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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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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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277 | } |
285 | } |
278 | |
286 | |
279 | ... |
287 | ... |
280 | ev_set_allocator (persistent_realloc); |
288 | ev_set_allocator (persistent_realloc); |
281 | |
289 | |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
290 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
283 | |
291 | |
284 | Set the callback function to call on a retryable system call error (such |
292 | 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 |
293 | as failed select, poll, epoll_wait). The message is a printable string |
286 | indicating the system call or subsystem causing the problem. If this |
294 | 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 |
295 | callback is set, then libev will expect it to remedy the situation, no |
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305 | |
313 | |
306 | This function can be used to "simulate" a signal receive. It is completely |
314 | This function can be used to "simulate" a signal receive. It is completely |
307 | safe to call this function at any time, from any context, including signal |
315 | safe to call this function at any time, from any context, including signal |
308 | handlers or random threads. |
316 | handlers or random threads. |
309 | |
317 | |
310 | It's main use is to customise signal handling in your process, especially |
318 | Its main use is to customise signal handling in your process, especially |
311 | in the presence of threads. For example, you could block signals |
319 | in the presence of threads. For example, you could block signals |
312 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
320 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
313 | creating any loops), and in one thread, use C<sigwait> or any other |
321 | creating any loops), and in one thread, use C<sigwait> or any other |
314 | mechanism to wait for signals, then "deliver" them to libev by calling |
322 | mechanism to wait for signals, then "deliver" them to libev by calling |
315 | C<ev_feed_signal>. |
323 | C<ev_feed_signal>. |
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390 | |
398 | |
391 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
392 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
393 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
394 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
395 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
396 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
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405 | cannot be done in a threadsafe way, but usually it works if no other |
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406 | thread modifies them). |
397 | |
407 | |
398 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
399 | |
409 | |
400 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
401 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
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406 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
407 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
408 | C<pthread_atfork> which is even faster). |
418 | C<pthread_atfork> which is even faster). |
409 | |
419 | |
410 | The big advantage of this flag is that you can forget about fork (and |
420 | The big advantage of this flag is that you can forget about fork (and |
411 | forget about forgetting to tell libev about forking) when you use this |
421 | forget about forgetting to tell libev about forking, although you still |
412 | flag. |
422 | have to ignore C<SIGPIPE>) when you use this flag. |
413 | |
423 | |
414 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
424 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
415 | environment variable. |
425 | environment variable. |
416 | |
426 | |
417 | =item C<EVFLAG_NOINOTIFY> |
427 | =item C<EVFLAG_NOINOTIFY> |
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435 | example) that can't properly initialise their signal masks. |
445 | example) that can't properly initialise their signal masks. |
436 | |
446 | |
437 | =item C<EVFLAG_NOSIGMASK> |
447 | =item C<EVFLAG_NOSIGMASK> |
438 | |
448 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
449 | When this flag is specified, then libev will avoid to modify the signal |
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
450 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
451 | when you want to receive them. |
442 | |
452 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
453 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
454 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
455 | unblocking the signals. |
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456 | |
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457 | It's also required by POSIX in a threaded program, as libev calls |
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458 | C<sigprocmask>, whose behaviour is officially unspecified. |
446 | |
459 | |
447 | This flag's behaviour will become the default in future versions of libev. |
460 | This flag's behaviour will become the default in future versions of libev. |
448 | |
461 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
462 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
463 | |
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480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
493 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
494 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
495 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
496 | kernels). |
484 | |
497 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
498 | For few fds, this backend is a bit little slower than poll and select, but |
486 | but it scales phenomenally better. While poll and select usually scale |
499 | it scales phenomenally better. While poll and select usually scale like |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
500 | O(total_fds) where total_fds is the total number of fds (or the highest |
488 | epoll scales either O(1) or O(active_fds). |
501 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
502 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
503 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
504 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
505 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
506 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
509 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
497 | forks then I<both> parent and child process have to recreate the epoll |
510 | forks then I<both> parent and child process have to recreate the epoll |
498 | set, which can take considerable time (one syscall per file descriptor) |
511 | set, which can take considerable time (one syscall per file descriptor) |
499 | and is of course hard to detect. |
512 | and is of course hard to detect. |
500 | |
513 | |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
514 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
515 | but of course I<doesn't>, and epoll just loves to report events for |
503 | I<different> file descriptors (even already closed ones, so one cannot |
516 | totally I<different> file descriptors (even already closed ones, so |
504 | even remove them from the set) than registered in the set (especially |
517 | one cannot even remove them from the set) than registered in the set |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
518 | (especially on SMP systems). Libev tries to counter these spurious |
506 | employing an additional generation counter and comparing that against the |
519 | notifications by employing an additional generation counter and comparing |
507 | events to filter out spurious ones, recreating the set when required. Last |
520 | that against the events to filter out spurious ones, recreating the set |
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521 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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522 | no way to know when and by how much, so sometimes you have to busy-wait |
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523 | because epoll returns immediately despite a nonzero timeout. And last |
508 | not least, it also refuses to work with some file descriptors which work |
524 | not least, it also refuses to work with some file descriptors which work |
509 | perfectly fine with C<select> (files, many character devices...). |
525 | perfectly fine with C<select> (files, many character devices...). |
510 | |
526 | |
511 | Epoll is truly the train wreck analog among event poll mechanisms. |
527 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
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528 | cobbled together in a hurry, no thought to design or interaction with |
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529 | others. Oh, the pain, will it ever stop... |
512 | |
530 | |
513 | While stopping, setting and starting an I/O watcher in the same iteration |
531 | While stopping, setting and starting an I/O watcher in the same iteration |
514 | will result in some caching, there is still a system call per such |
532 | will result in some caching, there is still a system call per such |
515 | incident (because the same I<file descriptor> could point to a different |
533 | incident (because the same I<file descriptor> could point to a different |
516 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
534 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
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553 | |
571 | |
554 | It scales in the same way as the epoll backend, but the interface to the |
572 | It scales in the same way as the epoll backend, but the interface to the |
555 | kernel is more efficient (which says nothing about its actual speed, of |
573 | kernel is more efficient (which says nothing about its actual speed, of |
556 | course). While stopping, setting and starting an I/O watcher does never |
574 | course). While stopping, setting and starting an I/O watcher does never |
557 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
575 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
558 | two event changes per incident. Support for C<fork ()> is very bad (but |
576 | two event changes per incident. Support for C<fork ()> is very bad (you |
559 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
577 | might have to leak fd's on fork, but it's more sane than epoll) and it |
560 | cases |
578 | drops fds silently in similarly hard-to-detect cases. |
561 | |
579 | |
562 | This backend usually performs well under most conditions. |
580 | This backend usually performs well under most conditions. |
563 | |
581 | |
564 | While nominally embeddable in other event loops, this doesn't work |
582 | While nominally embeddable in other event loops, this doesn't work |
565 | everywhere, so you might need to test for this. And since it is broken |
583 | everywhere, so you might need to test for this. And since it is broken |
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582 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
600 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
583 | |
601 | |
584 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
602 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
585 | it's really slow, but it still scales very well (O(active_fds)). |
603 | it's really slow, but it still scales very well (O(active_fds)). |
586 | |
604 | |
587 | Please note that Solaris event ports can deliver a lot of spurious |
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588 | notifications, so you need to use non-blocking I/O or other means to avoid |
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589 | blocking when no data (or space) is available. |
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590 | |
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591 | While this backend scales well, it requires one system call per active |
605 | While this backend scales well, it requires one system call per active |
592 | file descriptor per loop iteration. For small and medium numbers of file |
606 | file descriptor per loop iteration. For small and medium numbers of file |
593 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
607 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
594 | might perform better. |
608 | might perform better. |
595 | |
609 | |
596 | On the positive side, with the exception of the spurious readiness |
610 | On the positive side, this backend actually performed fully to |
597 | notifications, this backend actually performed fully to specification |
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598 | in all tests and is fully embeddable, which is a rare feat among the |
611 | specification in all tests and is fully embeddable, which is a rare feat |
599 | OS-specific backends (I vastly prefer correctness over speed hacks). |
612 | among the OS-specific backends (I vastly prefer correctness over speed |
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613 | hacks). |
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614 | |
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615 | On the negative side, the interface is I<bizarre> - so bizarre that |
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616 | even sun itself gets it wrong in their code examples: The event polling |
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617 | function sometimes returns events to the caller even though an error |
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618 | occurred, but with no indication whether it has done so or not (yes, it's |
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619 | even documented that way) - deadly for edge-triggered interfaces where you |
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620 | absolutely have to know whether an event occurred or not because you have |
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621 | to re-arm the watcher. |
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622 | |
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623 | Fortunately libev seems to be able to work around these idiocies. |
600 | |
624 | |
601 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
625 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
602 | C<EVBACKEND_POLL>. |
626 | C<EVBACKEND_POLL>. |
603 | |
627 | |
604 | =item C<EVBACKEND_ALL> |
628 | =item C<EVBACKEND_ALL> |
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658 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
682 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
659 | and C<ev_loop_destroy>. |
683 | and C<ev_loop_destroy>. |
660 | |
684 | |
661 | =item ev_loop_fork (loop) |
685 | =item ev_loop_fork (loop) |
662 | |
686 | |
663 | This function sets a flag that causes subsequent C<ev_run> iterations to |
687 | This function sets a flag that causes subsequent C<ev_run> iterations |
664 | reinitialise the kernel state for backends that have one. Despite the |
688 | to reinitialise the kernel state for backends that have one. Despite |
665 | name, you can call it anytime, but it makes most sense after forking, in |
689 | the name, you can call it anytime you are allowed to start or stop |
666 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
690 | watchers (except inside an C<ev_prepare> callback), but it makes most |
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691 | sense after forking, in the child process. You I<must> call it (or use |
667 | child before resuming or calling C<ev_run>. |
692 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
668 | |
693 | |
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694 | In addition, if you want to reuse a loop (via this function or |
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695 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
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696 | |
669 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
697 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
670 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
698 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
671 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
699 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
672 | during fork. |
700 | during fork. |
673 | |
701 | |
674 | On the other hand, you only need to call this function in the child |
702 | On the other hand, you only need to call this function in the child |
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744 | |
772 | |
745 | This function is rarely useful, but when some event callback runs for a |
773 | This function is rarely useful, but when some event callback runs for a |
746 | very long time without entering the event loop, updating libev's idea of |
774 | very long time without entering the event loop, updating libev's idea of |
747 | the current time is a good idea. |
775 | the current time is a good idea. |
748 | |
776 | |
749 | See also L<The special problem of time updates> in the C<ev_timer> section. |
777 | See also L</The special problem of time updates> in the C<ev_timer> section. |
750 | |
778 | |
751 | =item ev_suspend (loop) |
779 | =item ev_suspend (loop) |
752 | |
780 | |
753 | =item ev_resume (loop) |
781 | =item ev_resume (loop) |
754 | |
782 | |
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772 | without a previous call to C<ev_suspend>. |
800 | without a previous call to C<ev_suspend>. |
773 | |
801 | |
774 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
802 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
775 | event loop time (see C<ev_now_update>). |
803 | event loop time (see C<ev_now_update>). |
776 | |
804 | |
777 | =item ev_run (loop, int flags) |
805 | =item bool ev_run (loop, int flags) |
778 | |
806 | |
779 | Finally, this is it, the event handler. This function usually is called |
807 | Finally, this is it, the event handler. This function usually is called |
780 | after you have initialised all your watchers and you want to start |
808 | after you have initialised all your watchers and you want to start |
781 | handling events. It will ask the operating system for any new events, call |
809 | handling events. It will ask the operating system for any new events, call |
782 | the watcher callbacks, an then repeat the whole process indefinitely: This |
810 | the watcher callbacks, and then repeat the whole process indefinitely: This |
783 | is why event loops are called I<loops>. |
811 | is why event loops are called I<loops>. |
784 | |
812 | |
785 | If the flags argument is specified as C<0>, it will keep handling events |
813 | If the flags argument is specified as C<0>, it will keep handling events |
786 | until either no event watchers are active anymore or C<ev_break> was |
814 | until either no event watchers are active anymore or C<ev_break> was |
787 | called. |
815 | called. |
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816 | |
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817 | The return value is false if there are no more active watchers (which |
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818 | usually means "all jobs done" or "deadlock"), and true in all other cases |
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819 | (which usually means " you should call C<ev_run> again"). |
788 | |
820 | |
789 | Please note that an explicit C<ev_break> is usually better than |
821 | Please note that an explicit C<ev_break> is usually better than |
790 | relying on all watchers to be stopped when deciding when a program has |
822 | relying on all watchers to be stopped when deciding when a program has |
791 | finished (especially in interactive programs), but having a program |
823 | finished (especially in interactive programs), but having a program |
792 | that automatically loops as long as it has to and no longer by virtue |
824 | that automatically loops as long as it has to and no longer by virtue |
793 | of relying on its watchers stopping correctly, that is truly a thing of |
825 | of relying on its watchers stopping correctly, that is truly a thing of |
794 | beauty. |
826 | beauty. |
795 | |
827 | |
796 | This function is also I<mostly> exception-safe - you can break out of |
828 | This function is I<mostly> exception-safe - you can break out of a |
797 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
829 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
798 | exception and so on. This does not decrement the C<ev_depth> value, nor |
830 | exception and so on. This does not decrement the C<ev_depth> value, nor |
799 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
831 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
800 | |
832 | |
801 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
833 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
802 | those events and any already outstanding ones, but will not wait and |
834 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
814 | This is useful if you are waiting for some external event in conjunction |
846 | This is useful if you are waiting for some external event in conjunction |
815 | with something not expressible using other libev watchers (i.e. "roll your |
847 | with something not expressible using other libev watchers (i.e. "roll your |
816 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
848 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
817 | usually a better approach for this kind of thing. |
849 | usually a better approach for this kind of thing. |
818 | |
850 | |
819 | Here are the gory details of what C<ev_run> does: |
851 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
852 | understanding, not a guarantee that things will work exactly like this in |
|
|
853 | future versions): |
820 | |
854 | |
821 | - Increment loop depth. |
855 | - Increment loop depth. |
822 | - Reset the ev_break status. |
856 | - Reset the ev_break status. |
823 | - Before the first iteration, call any pending watchers. |
857 | - Before the first iteration, call any pending watchers. |
824 | LOOP: |
858 | LOOP: |
… | |
… | |
857 | anymore. |
891 | anymore. |
858 | |
892 | |
859 | ... queue jobs here, make sure they register event watchers as long |
893 | ... queue jobs here, make sure they register event watchers as long |
860 | ... as they still have work to do (even an idle watcher will do..) |
894 | ... as they still have work to do (even an idle watcher will do..) |
861 | ev_run (my_loop, 0); |
895 | ev_run (my_loop, 0); |
862 | ... jobs done or somebody called unloop. yeah! |
896 | ... jobs done or somebody called break. yeah! |
863 | |
897 | |
864 | =item ev_break (loop, how) |
898 | =item ev_break (loop, how) |
865 | |
899 | |
866 | Can be used to make a call to C<ev_run> return early (but only after it |
900 | Can be used to make a call to C<ev_run> return early (but only after it |
867 | has processed all outstanding events). The C<how> argument must be either |
901 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
930 | overhead for the actual polling but can deliver many events at once. |
964 | overhead for the actual polling but can deliver many events at once. |
931 | |
965 | |
932 | By setting a higher I<io collect interval> you allow libev to spend more |
966 | By setting a higher I<io collect interval> you allow libev to spend more |
933 | time collecting I/O events, so you can handle more events per iteration, |
967 | time collecting I/O events, so you can handle more events per iteration, |
934 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
968 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
935 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
969 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
936 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
970 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
937 | sleep time ensures that libev will not poll for I/O events more often then |
971 | sleep time ensures that libev will not poll for I/O events more often then |
938 | once per this interval, on average. |
972 | once per this interval, on average (as long as the host time resolution is |
|
|
973 | good enough). |
939 | |
974 | |
940 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
975 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
941 | to spend more time collecting timeouts, at the expense of increased |
976 | to spend more time collecting timeouts, at the expense of increased |
942 | latency/jitter/inexactness (the watcher callback will be called |
977 | latency/jitter/inexactness (the watcher callback will be called |
943 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
978 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
989 | invoke the actual watchers inside another context (another thread etc.). |
1024 | invoke the actual watchers inside another context (another thread etc.). |
990 | |
1025 | |
991 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1026 | If you want to reset the callback, use C<ev_invoke_pending> as new |
992 | callback. |
1027 | callback. |
993 | |
1028 | |
994 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1029 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
995 | |
1030 | |
996 | Sometimes you want to share the same loop between multiple threads. This |
1031 | Sometimes you want to share the same loop between multiple threads. This |
997 | can be done relatively simply by putting mutex_lock/unlock calls around |
1032 | can be done relatively simply by putting mutex_lock/unlock calls around |
998 | each call to a libev function. |
1033 | each call to a libev function. |
999 | |
1034 | |
1000 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1035 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1001 | to wait for it to return. One way around this is to wake up the event |
1036 | to wait for it to return. One way around this is to wake up the event |
1002 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1037 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1003 | I<release> and I<acquire> callbacks on the loop. |
1038 | I<release> and I<acquire> callbacks on the loop. |
1004 | |
1039 | |
1005 | When set, then C<release> will be called just before the thread is |
1040 | When set, then C<release> will be called just before the thread is |
1006 | suspended waiting for new events, and C<acquire> is called just |
1041 | suspended waiting for new events, and C<acquire> is called just |
1007 | afterwards. |
1042 | afterwards. |
… | |
… | |
1147 | |
1182 | |
1148 | =item C<EV_PREPARE> |
1183 | =item C<EV_PREPARE> |
1149 | |
1184 | |
1150 | =item C<EV_CHECK> |
1185 | =item C<EV_CHECK> |
1151 | |
1186 | |
1152 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1187 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1153 | to gather new events, and all C<ev_check> watchers are invoked just after |
1188 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1154 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1189 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1190 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1191 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1192 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1193 | or lower priority within an event loop iteration. |
|
|
1194 | |
1155 | received events. Callbacks of both watcher types can start and stop as |
1195 | Callbacks of both watcher types can start and stop as many watchers as |
1156 | many watchers as they want, and all of them will be taken into account |
1196 | they want, and all of them will be taken into account (for example, a |
1157 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1197 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1158 | C<ev_run> from blocking). |
1198 | blocking). |
1159 | |
1199 | |
1160 | =item C<EV_EMBED> |
1200 | =item C<EV_EMBED> |
1161 | |
1201 | |
1162 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1202 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1163 | |
1203 | |
… | |
… | |
1286 | |
1326 | |
1287 | =item callback ev_cb (ev_TYPE *watcher) |
1327 | =item callback ev_cb (ev_TYPE *watcher) |
1288 | |
1328 | |
1289 | Returns the callback currently set on the watcher. |
1329 | Returns the callback currently set on the watcher. |
1290 | |
1330 | |
1291 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1331 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1292 | |
1332 | |
1293 | Change the callback. You can change the callback at virtually any time |
1333 | Change the callback. You can change the callback at virtually any time |
1294 | (modulo threads). |
1334 | (modulo threads). |
1295 | |
1335 | |
1296 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1336 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1314 | or might not have been clamped to the valid range. |
1354 | or might not have been clamped to the valid range. |
1315 | |
1355 | |
1316 | The default priority used by watchers when no priority has been set is |
1356 | The default priority used by watchers when no priority has been set is |
1317 | always C<0>, which is supposed to not be too high and not be too low :). |
1357 | always C<0>, which is supposed to not be too high and not be too low :). |
1318 | |
1358 | |
1319 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1359 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1320 | priorities. |
1360 | priorities. |
1321 | |
1361 | |
1322 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1362 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1323 | |
1363 | |
1324 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1364 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1349 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1389 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1350 | functions that do not need a watcher. |
1390 | functions that do not need a watcher. |
1351 | |
1391 | |
1352 | =back |
1392 | =back |
1353 | |
1393 | |
1354 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1394 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1355 | |
1395 | OWN COMPOSITE WATCHERS> idioms. |
1356 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1357 | and read at any time: libev will completely ignore it. This can be used |
|
|
1358 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1359 | don't want to allocate memory and store a pointer to it in that data |
|
|
1360 | member, you can also "subclass" the watcher type and provide your own |
|
|
1361 | data: |
|
|
1362 | |
|
|
1363 | struct my_io |
|
|
1364 | { |
|
|
1365 | ev_io io; |
|
|
1366 | int otherfd; |
|
|
1367 | void *somedata; |
|
|
1368 | struct whatever *mostinteresting; |
|
|
1369 | }; |
|
|
1370 | |
|
|
1371 | ... |
|
|
1372 | struct my_io w; |
|
|
1373 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1374 | |
|
|
1375 | And since your callback will be called with a pointer to the watcher, you |
|
|
1376 | can cast it back to your own type: |
|
|
1377 | |
|
|
1378 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1379 | { |
|
|
1380 | struct my_io *w = (struct my_io *)w_; |
|
|
1381 | ... |
|
|
1382 | } |
|
|
1383 | |
|
|
1384 | More interesting and less C-conformant ways of casting your callback type |
|
|
1385 | instead have been omitted. |
|
|
1386 | |
|
|
1387 | Another common scenario is to use some data structure with multiple |
|
|
1388 | embedded watchers: |
|
|
1389 | |
|
|
1390 | struct my_biggy |
|
|
1391 | { |
|
|
1392 | int some_data; |
|
|
1393 | ev_timer t1; |
|
|
1394 | ev_timer t2; |
|
|
1395 | } |
|
|
1396 | |
|
|
1397 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1398 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1399 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1400 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1401 | programmers): |
|
|
1402 | |
|
|
1403 | #include <stddef.h> |
|
|
1404 | |
|
|
1405 | static void |
|
|
1406 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1407 | { |
|
|
1408 | struct my_biggy big = (struct my_biggy *) |
|
|
1409 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1410 | } |
|
|
1411 | |
|
|
1412 | static void |
|
|
1413 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1414 | { |
|
|
1415 | struct my_biggy big = (struct my_biggy *) |
|
|
1416 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1417 | } |
|
|
1418 | |
1396 | |
1419 | =head2 WATCHER STATES |
1397 | =head2 WATCHER STATES |
1420 | |
1398 | |
1421 | There are various watcher states mentioned throughout this manual - |
1399 | There are various watcher states mentioned throughout this manual - |
1422 | active, pending and so on. In this section these states and the rules to |
1400 | active, pending and so on. In this section these states and the rules to |
1423 | transition between them will be described in more detail - and while these |
1401 | transition between them will be described in more detail - and while these |
1424 | rules might look complicated, they usually do "the right thing". |
1402 | rules might look complicated, they usually do "the right thing". |
1425 | |
1403 | |
1426 | =over 4 |
1404 | =over 4 |
1427 | |
1405 | |
1428 | =item initialiased |
1406 | =item initialised |
1429 | |
1407 | |
1430 | Before a watcher can be registered with the event looop it has to be |
1408 | Before a watcher can be registered with the event loop it has to be |
1431 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1409 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1432 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1410 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1433 | |
1411 | |
1434 | In this state it is simply some block of memory that is suitable for use |
1412 | In this state it is simply some block of memory that is suitable for |
1435 | in an event loop. It can be moved around, freed, reused etc. at will. |
1413 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1414 | will - as long as you either keep the memory contents intact, or call |
|
|
1415 | C<ev_TYPE_init> again. |
1436 | |
1416 | |
1437 | =item started/running/active |
1417 | =item started/running/active |
1438 | |
1418 | |
1439 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1419 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1440 | property of the event loop, and is actively waiting for events. While in |
1420 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1468 | latter will clear any pending state the watcher might be in, regardless |
1448 | latter will clear any pending state the watcher might be in, regardless |
1469 | of whether it was active or not, so stopping a watcher explicitly before |
1449 | of whether it was active or not, so stopping a watcher explicitly before |
1470 | freeing it is often a good idea. |
1450 | freeing it is often a good idea. |
1471 | |
1451 | |
1472 | While stopped (and not pending) the watcher is essentially in the |
1452 | While stopped (and not pending) the watcher is essentially in the |
1473 | initialised state, that is it can be reused, moved, modified in any way |
1453 | initialised state, that is, it can be reused, moved, modified in any way |
1474 | you wish. |
1454 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1455 | it again). |
1475 | |
1456 | |
1476 | =back |
1457 | =back |
1477 | |
1458 | |
1478 | =head2 WATCHER PRIORITY MODELS |
1459 | =head2 WATCHER PRIORITY MODELS |
1479 | |
1460 | |
… | |
… | |
1608 | In general you can register as many read and/or write event watchers per |
1589 | In general you can register as many read and/or write event watchers per |
1609 | fd as you want (as long as you don't confuse yourself). Setting all file |
1590 | fd as you want (as long as you don't confuse yourself). Setting all file |
1610 | descriptors to non-blocking mode is also usually a good idea (but not |
1591 | descriptors to non-blocking mode is also usually a good idea (but not |
1611 | required if you know what you are doing). |
1592 | required if you know what you are doing). |
1612 | |
1593 | |
1613 | If you cannot use non-blocking mode, then force the use of a |
|
|
1614 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1615 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1616 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1617 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1618 | |
|
|
1619 | Another thing you have to watch out for is that it is quite easy to |
1594 | Another thing you have to watch out for is that it is quite easy to |
1620 | receive "spurious" readiness notifications, that is your callback might |
1595 | receive "spurious" readiness notifications, that is, your callback might |
1621 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1596 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1622 | because there is no data. Not only are some backends known to create a |
1597 | because there is no data. It is very easy to get into this situation even |
1623 | lot of those (for example Solaris ports), it is very easy to get into |
1598 | with a relatively standard program structure. Thus it is best to always |
1624 | this situation even with a relatively standard program structure. Thus |
1599 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1625 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1626 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1600 | preferable to a program hanging until some data arrives. |
1627 | |
1601 | |
1628 | If you cannot run the fd in non-blocking mode (for example you should |
1602 | If you cannot run the fd in non-blocking mode (for example you should |
1629 | not play around with an Xlib connection), then you have to separately |
1603 | not play around with an Xlib connection), then you have to separately |
1630 | re-test whether a file descriptor is really ready with a known-to-be good |
1604 | re-test whether a file descriptor is really ready with a known-to-be good |
1631 | interface such as poll (fortunately in our Xlib example, Xlib already |
1605 | interface such as poll (fortunately in the case of Xlib, it already does |
1632 | does this on its own, so its quite safe to use). Some people additionally |
1606 | this on its own, so its quite safe to use). Some people additionally |
1633 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1607 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1634 | indefinitely. |
1608 | indefinitely. |
1635 | |
1609 | |
1636 | But really, best use non-blocking mode. |
1610 | But really, best use non-blocking mode. |
1637 | |
1611 | |
… | |
… | |
1665 | |
1639 | |
1666 | There is no workaround possible except not registering events |
1640 | There is no workaround possible except not registering events |
1667 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1641 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1642 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1669 | |
1643 | |
|
|
1644 | =head3 The special problem of files |
|
|
1645 | |
|
|
1646 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1647 | representing files, and expect it to become ready when their program |
|
|
1648 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1649 | |
|
|
1650 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1651 | notification as soon as the kernel knows whether and how much data is |
|
|
1652 | there, and in the case of open files, that's always the case, so you |
|
|
1653 | always get a readiness notification instantly, and your read (or possibly |
|
|
1654 | write) will still block on the disk I/O. |
|
|
1655 | |
|
|
1656 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1657 | devices and so on, there is another party (the sender) that delivers data |
|
|
1658 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1659 | will not send data on its own, simply because it doesn't know what you |
|
|
1660 | wish to read - you would first have to request some data. |
|
|
1661 | |
|
|
1662 | Since files are typically not-so-well supported by advanced notification |
|
|
1663 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1664 | to files, even though you should not use it. The reason for this is |
|
|
1665 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1666 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1667 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1668 | F</dev/urandom>), and even though the file might better be served with |
|
|
1669 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1670 | it "just works" instead of freezing. |
|
|
1671 | |
|
|
1672 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1673 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1674 | when you rarely read from a file instead of from a socket, and want to |
|
|
1675 | reuse the same code path. |
|
|
1676 | |
1670 | =head3 The special problem of fork |
1677 | =head3 The special problem of fork |
1671 | |
1678 | |
1672 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1679 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1673 | useless behaviour. Libev fully supports fork, but needs to be told about |
1680 | useless behaviour. Libev fully supports fork, but needs to be told about |
1674 | it in the child. |
1681 | it in the child if you want to continue to use it in the child. |
1675 | |
1682 | |
1676 | To support fork in your programs, you either have to call |
1683 | To support fork in your child processes, you have to call C<ev_loop_fork |
1677 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1684 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1678 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1685 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1679 | C<EVBACKEND_POLL>. |
|
|
1680 | |
1686 | |
1681 | =head3 The special problem of SIGPIPE |
1687 | =head3 The special problem of SIGPIPE |
1682 | |
1688 | |
1683 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1689 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1684 | when writing to a pipe whose other end has been closed, your program gets |
1690 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1782 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1788 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1783 | monotonic clock option helps a lot here). |
1789 | monotonic clock option helps a lot here). |
1784 | |
1790 | |
1785 | The callback is guaranteed to be invoked only I<after> its timeout has |
1791 | The callback is guaranteed to be invoked only I<after> its timeout has |
1786 | passed (not I<at>, so on systems with very low-resolution clocks this |
1792 | passed (not I<at>, so on systems with very low-resolution clocks this |
1787 | might introduce a small delay). If multiple timers become ready during the |
1793 | might introduce a small delay, see "the special problem of being too |
|
|
1794 | early", below). If multiple timers become ready during the same loop |
1788 | same loop iteration then the ones with earlier time-out values are invoked |
1795 | iteration then the ones with earlier time-out values are invoked before |
1789 | before ones of the same priority with later time-out values (but this is |
1796 | ones of the same priority with later time-out values (but this is no |
1790 | no longer true when a callback calls C<ev_run> recursively). |
1797 | longer true when a callback calls C<ev_run> recursively). |
1791 | |
1798 | |
1792 | =head3 Be smart about timeouts |
1799 | =head3 Be smart about timeouts |
1793 | |
1800 | |
1794 | Many real-world problems involve some kind of timeout, usually for error |
1801 | Many real-world problems involve some kind of timeout, usually for error |
1795 | recovery. A typical example is an HTTP request - if the other side hangs, |
1802 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1870 | |
1877 | |
1871 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1878 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1872 | but remember the time of last activity, and check for a real timeout only |
1879 | but remember the time of last activity, and check for a real timeout only |
1873 | within the callback: |
1880 | within the callback: |
1874 | |
1881 | |
|
|
1882 | ev_tstamp timeout = 60.; |
1875 | ev_tstamp last_activity; // time of last activity |
1883 | ev_tstamp last_activity; // time of last activity |
|
|
1884 | ev_timer timer; |
1876 | |
1885 | |
1877 | static void |
1886 | static void |
1878 | callback (EV_P_ ev_timer *w, int revents) |
1887 | callback (EV_P_ ev_timer *w, int revents) |
1879 | { |
1888 | { |
1880 | ev_tstamp now = ev_now (EV_A); |
1889 | // calculate when the timeout would happen |
1881 | ev_tstamp timeout = last_activity + 60.; |
1890 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1882 | |
1891 | |
1883 | // if last_activity + 60. is older than now, we did time out |
1892 | // if negative, it means we the timeout already occurred |
1884 | if (timeout < now) |
1893 | if (after < 0.) |
1885 | { |
1894 | { |
1886 | // timeout occurred, take action |
1895 | // timeout occurred, take action |
1887 | } |
1896 | } |
1888 | else |
1897 | else |
1889 | { |
1898 | { |
1890 | // callback was invoked, but there was some activity, re-arm |
1899 | // callback was invoked, but there was some recent |
1891 | // the watcher to fire in last_activity + 60, which is |
1900 | // activity. simply restart the timer to time out |
1892 | // guaranteed to be in the future, so "again" is positive: |
1901 | // after "after" seconds, which is the earliest time |
1893 | w->repeat = timeout - now; |
1902 | // the timeout can occur. |
|
|
1903 | ev_timer_set (w, after, 0.); |
1894 | ev_timer_again (EV_A_ w); |
1904 | ev_timer_start (EV_A_ w); |
1895 | } |
1905 | } |
1896 | } |
1906 | } |
1897 | |
1907 | |
1898 | To summarise the callback: first calculate the real timeout (defined |
1908 | To summarise the callback: first calculate in how many seconds the |
1899 | as "60 seconds after the last activity"), then check if that time has |
1909 | timeout will occur (by calculating the absolute time when it would occur, |
1900 | been reached, which means something I<did>, in fact, time out. Otherwise |
1910 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1901 | the callback was invoked too early (C<timeout> is in the future), so |
1911 | (EV_A)> from that). |
1902 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1903 | a timeout then. |
|
|
1904 | |
1912 | |
1905 | Note how C<ev_timer_again> is used, taking advantage of the |
1913 | If this value is negative, then we are already past the timeout, i.e. we |
1906 | C<ev_timer_again> optimisation when the timer is already running. |
1914 | timed out, and need to do whatever is needed in this case. |
|
|
1915 | |
|
|
1916 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1917 | and simply start the timer with this timeout value. |
|
|
1918 | |
|
|
1919 | In other words, each time the callback is invoked it will check whether |
|
|
1920 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1921 | again at the earliest time it could time out. Rinse. Repeat. |
1907 | |
1922 | |
1908 | This scheme causes more callback invocations (about one every 60 seconds |
1923 | This scheme causes more callback invocations (about one every 60 seconds |
1909 | minus half the average time between activity), but virtually no calls to |
1924 | minus half the average time between activity), but virtually no calls to |
1910 | libev to change the timeout. |
1925 | libev to change the timeout. |
1911 | |
1926 | |
1912 | To start the timer, simply initialise the watcher and set C<last_activity> |
1927 | To start the machinery, simply initialise the watcher and set |
1913 | to the current time (meaning we just have some activity :), then call the |
1928 | C<last_activity> to the current time (meaning there was some activity just |
1914 | callback, which will "do the right thing" and start the timer: |
1929 | now), then call the callback, which will "do the right thing" and start |
|
|
1930 | the timer: |
1915 | |
1931 | |
|
|
1932 | last_activity = ev_now (EV_A); |
1916 | ev_init (timer, callback); |
1933 | ev_init (&timer, callback); |
1917 | last_activity = ev_now (loop); |
1934 | callback (EV_A_ &timer, 0); |
1918 | callback (loop, timer, EV_TIMER); |
|
|
1919 | |
1935 | |
1920 | And when there is some activity, simply store the current time in |
1936 | When there is some activity, simply store the current time in |
1921 | C<last_activity>, no libev calls at all: |
1937 | C<last_activity>, no libev calls at all: |
1922 | |
1938 | |
|
|
1939 | if (activity detected) |
1923 | last_activity = ev_now (loop); |
1940 | last_activity = ev_now (EV_A); |
|
|
1941 | |
|
|
1942 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1943 | providing a new value, stopping the timer and calling the callback, which |
|
|
1944 | will again do the right thing (for example, time out immediately :). |
|
|
1945 | |
|
|
1946 | timeout = new_value; |
|
|
1947 | ev_timer_stop (EV_A_ &timer); |
|
|
1948 | callback (EV_A_ &timer, 0); |
1924 | |
1949 | |
1925 | This technique is slightly more complex, but in most cases where the |
1950 | This technique is slightly more complex, but in most cases where the |
1926 | time-out is unlikely to be triggered, much more efficient. |
1951 | time-out is unlikely to be triggered, much more efficient. |
1927 | |
|
|
1928 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1929 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1930 | fix things for you. |
|
|
1931 | |
1952 | |
1932 | =item 4. Wee, just use a double-linked list for your timeouts. |
1953 | =item 4. Wee, just use a double-linked list for your timeouts. |
1933 | |
1954 | |
1934 | If there is not one request, but many thousands (millions...), all |
1955 | If there is not one request, but many thousands (millions...), all |
1935 | employing some kind of timeout with the same timeout value, then one can |
1956 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1962 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1983 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1963 | rather complicated, but extremely efficient, something that really pays |
1984 | rather complicated, but extremely efficient, something that really pays |
1964 | off after the first million or so of active timers, i.e. it's usually |
1985 | off after the first million or so of active timers, i.e. it's usually |
1965 | overkill :) |
1986 | overkill :) |
1966 | |
1987 | |
|
|
1988 | =head3 The special problem of being too early |
|
|
1989 | |
|
|
1990 | If you ask a timer to call your callback after three seconds, then |
|
|
1991 | you expect it to be invoked after three seconds - but of course, this |
|
|
1992 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1993 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1994 | process with a STOP signal for a few hours for example. |
|
|
1995 | |
|
|
1996 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1997 | delay has occurred, but cannot guarantee this. |
|
|
1998 | |
|
|
1999 | A less obvious failure mode is calling your callback too early: many event |
|
|
2000 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2001 | this can cause your callback to be invoked much earlier than you would |
|
|
2002 | expect. |
|
|
2003 | |
|
|
2004 | To see why, imagine a system with a clock that only offers full second |
|
|
2005 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2006 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2007 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2008 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2009 | |
|
|
2010 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2011 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2012 | one-second delay was requested - this is being "too early", despite best |
|
|
2013 | intentions. |
|
|
2014 | |
|
|
2015 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2016 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2017 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2018 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2019 | |
|
|
2020 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2021 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2022 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2023 | late" side of things. |
|
|
2024 | |
1967 | =head3 The special problem of time updates |
2025 | =head3 The special problem of time updates |
1968 | |
2026 | |
1969 | Establishing the current time is a costly operation (it usually takes at |
2027 | Establishing the current time is a costly operation (it usually takes |
1970 | least two system calls): EV therefore updates its idea of the current |
2028 | at least one system call): EV therefore updates its idea of the current |
1971 | time only before and after C<ev_run> collects new events, which causes a |
2029 | time only before and after C<ev_run> collects new events, which causes a |
1972 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2030 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1973 | lots of events in one iteration. |
2031 | lots of events in one iteration. |
1974 | |
2032 | |
1975 | The relative timeouts are calculated relative to the C<ev_now ()> |
2033 | The relative timeouts are calculated relative to the C<ev_now ()> |
1976 | time. This is usually the right thing as this timestamp refers to the time |
2034 | time. This is usually the right thing as this timestamp refers to the time |
1977 | of the event triggering whatever timeout you are modifying/starting. If |
2035 | of the event triggering whatever timeout you are modifying/starting. If |
1978 | you suspect event processing to be delayed and you I<need> to base the |
2036 | you suspect event processing to be delayed and you I<need> to base the |
1979 | timeout on the current time, use something like this to adjust for this: |
2037 | timeout on the current time, use something like the following to adjust |
|
|
2038 | for it: |
1980 | |
2039 | |
1981 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2040 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1982 | |
2041 | |
1983 | If the event loop is suspended for a long time, you can also force an |
2042 | If the event loop is suspended for a long time, you can also force an |
1984 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2043 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1985 | ()>. |
2044 | ()>, although that will push the event time of all outstanding events |
|
|
2045 | further into the future. |
|
|
2046 | |
|
|
2047 | =head3 The special problem of unsynchronised clocks |
|
|
2048 | |
|
|
2049 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2050 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2051 | jumps). |
|
|
2052 | |
|
|
2053 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2054 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2055 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2056 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2057 | than a directly following call to C<time>. |
|
|
2058 | |
|
|
2059 | The moral of this is to only compare libev-related timestamps with |
|
|
2060 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2061 | a second or so. |
|
|
2062 | |
|
|
2063 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2064 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2065 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2066 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2067 | |
|
|
2068 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2069 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2070 | I<measured according to the real time>, not the system clock. |
|
|
2071 | |
|
|
2072 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2073 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2074 | exactly the right behaviour. |
|
|
2075 | |
|
|
2076 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2077 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2078 | time, where your comparisons will always generate correct results. |
1986 | |
2079 | |
1987 | =head3 The special problems of suspended animation |
2080 | =head3 The special problems of suspended animation |
1988 | |
2081 | |
1989 | When you leave the server world it is quite customary to hit machines that |
2082 | When you leave the server world it is quite customary to hit machines that |
1990 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2083 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2034 | keep up with the timer (because it takes longer than those 10 seconds to |
2127 | keep up with the timer (because it takes longer than those 10 seconds to |
2035 | do stuff) the timer will not fire more than once per event loop iteration. |
2128 | do stuff) the timer will not fire more than once per event loop iteration. |
2036 | |
2129 | |
2037 | =item ev_timer_again (loop, ev_timer *) |
2130 | =item ev_timer_again (loop, ev_timer *) |
2038 | |
2131 | |
2039 | This will act as if the timer timed out and restart it again if it is |
2132 | This will act as if the timer timed out, and restarts it again if it is |
2040 | repeating. The exact semantics are: |
2133 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2134 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2041 | |
2135 | |
|
|
2136 | The exact semantics are as in the following rules, all of which will be |
|
|
2137 | applied to the watcher: |
|
|
2138 | |
|
|
2139 | =over 4 |
|
|
2140 | |
2042 | If the timer is pending, its pending status is cleared. |
2141 | =item If the timer is pending, the pending status is always cleared. |
2043 | |
2142 | |
2044 | If the timer is started but non-repeating, stop it (as if it timed out). |
2143 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2144 | out, without invoking it). |
2045 | |
2145 | |
2046 | If the timer is repeating, either start it if necessary (with the |
2146 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2047 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2147 | and start the timer, if necessary. |
2048 | |
2148 | |
|
|
2149 | =back |
|
|
2150 | |
2049 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2151 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2050 | usage example. |
2152 | usage example. |
2051 | |
2153 | |
2052 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2154 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2053 | |
2155 | |
2054 | Returns the remaining time until a timer fires. If the timer is active, |
2156 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2107 | Periodic watchers are also timers of a kind, but they are very versatile |
2209 | Periodic watchers are also timers of a kind, but they are very versatile |
2108 | (and unfortunately a bit complex). |
2210 | (and unfortunately a bit complex). |
2109 | |
2211 | |
2110 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2212 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2111 | relative time, the physical time that passes) but on wall clock time |
2213 | relative time, the physical time that passes) but on wall clock time |
2112 | (absolute time, the thing you can read on your calender or clock). The |
2214 | (absolute time, the thing you can read on your calendar or clock). The |
2113 | difference is that wall clock time can run faster or slower than real |
2215 | difference is that wall clock time can run faster or slower than real |
2114 | time, and time jumps are not uncommon (e.g. when you adjust your |
2216 | time, and time jumps are not uncommon (e.g. when you adjust your |
2115 | wrist-watch). |
2217 | wrist-watch). |
2116 | |
2218 | |
2117 | You can tell a periodic watcher to trigger after some specific point |
2219 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2174 | |
2276 | |
2175 | Another way to think about it (for the mathematically inclined) is that |
2277 | Another way to think about it (for the mathematically inclined) is that |
2176 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2278 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2177 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2279 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2178 | |
2280 | |
2179 | For numerical stability it is preferable that the C<offset> value is near |
2281 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2180 | C<ev_now ()> (the current time), but there is no range requirement for |
2282 | interval value should be higher than C<1/8192> (which is around 100 |
2181 | this value, and in fact is often specified as zero. |
2283 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2284 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2285 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2286 | C<0> and C<interval>, which is also the recommended range. |
2182 | |
2287 | |
2183 | Note also that there is an upper limit to how often a timer can fire (CPU |
2288 | Note also that there is an upper limit to how often a timer can fire (CPU |
2184 | speed for example), so if C<interval> is very small then timing stability |
2289 | speed for example), so if C<interval> is very small then timing stability |
2185 | will of course deteriorate. Libev itself tries to be exact to be about one |
2290 | will of course deteriorate. Libev itself tries to be exact to be about one |
2186 | millisecond (if the OS supports it and the machine is fast enough). |
2291 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2294 | |
2399 | |
2295 | ev_periodic hourly_tick; |
2400 | ev_periodic hourly_tick; |
2296 | ev_periodic_init (&hourly_tick, clock_cb, |
2401 | ev_periodic_init (&hourly_tick, clock_cb, |
2297 | fmod (ev_now (loop), 3600.), 3600., 0); |
2402 | fmod (ev_now (loop), 3600.), 3600., 0); |
2298 | ev_periodic_start (loop, &hourly_tick); |
2403 | ev_periodic_start (loop, &hourly_tick); |
2299 | |
2404 | |
2300 | |
2405 | |
2301 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2406 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2302 | |
2407 | |
2303 | Signal watchers will trigger an event when the process receives a specific |
2408 | Signal watchers will trigger an event when the process receives a specific |
2304 | signal one or more times. Even though signals are very asynchronous, libev |
2409 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2314 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2419 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2315 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2420 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2316 | C<SIGINT> in both the default loop and another loop at the same time. At |
2421 | C<SIGINT> in both the default loop and another loop at the same time. At |
2317 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2422 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2318 | |
2423 | |
2319 | When the first watcher gets started will libev actually register something |
2424 | Only after the first watcher for a signal is started will libev actually |
2320 | with the kernel (thus it coexists with your own signal handlers as long as |
2425 | register something with the kernel. It thus coexists with your own signal |
2321 | you don't register any with libev for the same signal). |
2426 | handlers as long as you don't register any with libev for the same signal. |
2322 | |
2427 | |
2323 | If possible and supported, libev will install its handlers with |
2428 | If possible and supported, libev will install its handlers with |
2324 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2429 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2325 | not be unduly interrupted. If you have a problem with system calls getting |
2430 | not be unduly interrupted. If you have a problem with system calls getting |
2326 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2431 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2329 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2434 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2330 | |
2435 | |
2331 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2436 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2332 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2437 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2333 | stopping it again), that is, libev might or might not block the signal, |
2438 | stopping it again), that is, libev might or might not block the signal, |
2334 | and might or might not set or restore the installed signal handler. |
2439 | and might or might not set or restore the installed signal handler (but |
|
|
2440 | see C<EVFLAG_NOSIGMASK>). |
2335 | |
2441 | |
2336 | While this does not matter for the signal disposition (libev never |
2442 | While this does not matter for the signal disposition (libev never |
2337 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2443 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2338 | C<execve>), this matters for the signal mask: many programs do not expect |
2444 | C<execve>), this matters for the signal mask: many programs do not expect |
2339 | certain signals to be blocked. |
2445 | certain signals to be blocked. |
… | |
… | |
2510 | |
2616 | |
2511 | =head2 C<ev_stat> - did the file attributes just change? |
2617 | =head2 C<ev_stat> - did the file attributes just change? |
2512 | |
2618 | |
2513 | This watches a file system path for attribute changes. That is, it calls |
2619 | This watches a file system path for attribute changes. That is, it calls |
2514 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2620 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2515 | and sees if it changed compared to the last time, invoking the callback if |
2621 | and sees if it changed compared to the last time, invoking the callback |
2516 | it did. |
2622 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2623 | happen after the watcher has been started will be reported. |
2517 | |
2624 | |
2518 | The path does not need to exist: changing from "path exists" to "path does |
2625 | The path does not need to exist: changing from "path exists" to "path does |
2519 | not exist" is a status change like any other. The condition "path does not |
2626 | not exist" is a status change like any other. The condition "path does not |
2520 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2627 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2521 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2628 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2751 | Apart from keeping your process non-blocking (which is a useful |
2858 | Apart from keeping your process non-blocking (which is a useful |
2752 | effect on its own sometimes), idle watchers are a good place to do |
2859 | effect on its own sometimes), idle watchers are a good place to do |
2753 | "pseudo-background processing", or delay processing stuff to after the |
2860 | "pseudo-background processing", or delay processing stuff to after the |
2754 | event loop has handled all outstanding events. |
2861 | event loop has handled all outstanding events. |
2755 | |
2862 | |
|
|
2863 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2864 | |
|
|
2865 | As long as there is at least one active idle watcher, libev will never |
|
|
2866 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2867 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2868 | lowest priority will do. |
|
|
2869 | |
|
|
2870 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2871 | to do something on each event loop iteration - for example to balance load |
|
|
2872 | between different connections. |
|
|
2873 | |
|
|
2874 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2875 | example. |
|
|
2876 | |
2756 | =head3 Watcher-Specific Functions and Data Members |
2877 | =head3 Watcher-Specific Functions and Data Members |
2757 | |
2878 | |
2758 | =over 4 |
2879 | =over 4 |
2759 | |
2880 | |
2760 | =item ev_idle_init (ev_idle *, callback) |
2881 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2771 | callback, free it. Also, use no error checking, as usual. |
2892 | callback, free it. Also, use no error checking, as usual. |
2772 | |
2893 | |
2773 | static void |
2894 | static void |
2774 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2895 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2775 | { |
2896 | { |
|
|
2897 | // stop the watcher |
|
|
2898 | ev_idle_stop (loop, w); |
|
|
2899 | |
|
|
2900 | // now we can free it |
2776 | free (w); |
2901 | free (w); |
|
|
2902 | |
2777 | // now do something you wanted to do when the program has |
2903 | // now do something you wanted to do when the program has |
2778 | // no longer anything immediate to do. |
2904 | // no longer anything immediate to do. |
2779 | } |
2905 | } |
2780 | |
2906 | |
2781 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2907 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2783 | ev_idle_start (loop, idle_watcher); |
2909 | ev_idle_start (loop, idle_watcher); |
2784 | |
2910 | |
2785 | |
2911 | |
2786 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2912 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2787 | |
2913 | |
2788 | Prepare and check watchers are usually (but not always) used in pairs: |
2914 | Prepare and check watchers are often (but not always) used in pairs: |
2789 | prepare watchers get invoked before the process blocks and check watchers |
2915 | prepare watchers get invoked before the process blocks and check watchers |
2790 | afterwards. |
2916 | afterwards. |
2791 | |
2917 | |
2792 | You I<must not> call C<ev_run> or similar functions that enter |
2918 | You I<must not> call C<ev_run> (or similar functions that enter the |
2793 | the current event loop from either C<ev_prepare> or C<ev_check> |
2919 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2794 | watchers. Other loops than the current one are fine, however. The |
2920 | C<ev_check> watchers. Other loops than the current one are fine, |
2795 | rationale behind this is that you do not need to check for recursion in |
2921 | however. The rationale behind this is that you do not need to check |
2796 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2922 | for recursion in those watchers, i.e. the sequence will always be |
2797 | C<ev_check> so if you have one watcher of each kind they will always be |
2923 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2798 | called in pairs bracketing the blocking call. |
2924 | kind they will always be called in pairs bracketing the blocking call. |
2799 | |
2925 | |
2800 | Their main purpose is to integrate other event mechanisms into libev and |
2926 | Their main purpose is to integrate other event mechanisms into libev and |
2801 | their use is somewhat advanced. They could be used, for example, to track |
2927 | their use is somewhat advanced. They could be used, for example, to track |
2802 | variable changes, implement your own watchers, integrate net-snmp or a |
2928 | variable changes, implement your own watchers, integrate net-snmp or a |
2803 | coroutine library and lots more. They are also occasionally useful if |
2929 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2821 | with priority higher than or equal to the event loop and one coroutine |
2947 | with priority higher than or equal to the event loop and one coroutine |
2822 | of lower priority, but only once, using idle watchers to keep the event |
2948 | of lower priority, but only once, using idle watchers to keep the event |
2823 | loop from blocking if lower-priority coroutines are active, thus mapping |
2949 | loop from blocking if lower-priority coroutines are active, thus mapping |
2824 | low-priority coroutines to idle/background tasks). |
2950 | low-priority coroutines to idle/background tasks). |
2825 | |
2951 | |
2826 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2952 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2827 | priority, to ensure that they are being run before any other watchers |
2953 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2828 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2954 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2955 | watchers). |
2829 | |
2956 | |
2830 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2957 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2831 | activate ("feed") events into libev. While libev fully supports this, they |
2958 | activate ("feed") events into libev. While libev fully supports this, they |
2832 | might get executed before other C<ev_check> watchers did their job. As |
2959 | might get executed before other C<ev_check> watchers did their job. As |
2833 | C<ev_check> watchers are often used to embed other (non-libev) event |
2960 | C<ev_check> watchers are often used to embed other (non-libev) event |
2834 | loops those other event loops might be in an unusable state until their |
2961 | loops those other event loops might be in an unusable state until their |
2835 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2962 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2836 | others). |
2963 | others). |
|
|
2964 | |
|
|
2965 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2966 | |
|
|
2967 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2968 | useful because they are called once per event loop iteration. For |
|
|
2969 | example, if you want to handle a large number of connections fairly, you |
|
|
2970 | normally only do a bit of work for each active connection, and if there |
|
|
2971 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2972 | connections have a chance of making progress. |
|
|
2973 | |
|
|
2974 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2975 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2976 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2977 | |
|
|
2978 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2979 | single global idle watcher that is active as long as you have one active |
|
|
2980 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2981 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2982 | invoked. Neither watcher alone can do that. |
2837 | |
2983 | |
2838 | =head3 Watcher-Specific Functions and Data Members |
2984 | =head3 Watcher-Specific Functions and Data Members |
2839 | |
2985 | |
2840 | =over 4 |
2986 | =over 4 |
2841 | |
2987 | |
… | |
… | |
3042 | |
3188 | |
3043 | =over 4 |
3189 | =over 4 |
3044 | |
3190 | |
3045 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3191 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3046 | |
3192 | |
3047 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3193 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3048 | |
3194 | |
3049 | Configures the watcher to embed the given loop, which must be |
3195 | Configures the watcher to embed the given loop, which must be |
3050 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3196 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3051 | invoked automatically, otherwise it is the responsibility of the callback |
3197 | invoked automatically, otherwise it is the responsibility of the callback |
3052 | to invoke it (it will continue to be called until the sweep has been done, |
3198 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3073 | used). |
3219 | used). |
3074 | |
3220 | |
3075 | struct ev_loop *loop_hi = ev_default_init (0); |
3221 | struct ev_loop *loop_hi = ev_default_init (0); |
3076 | struct ev_loop *loop_lo = 0; |
3222 | struct ev_loop *loop_lo = 0; |
3077 | ev_embed embed; |
3223 | ev_embed embed; |
3078 | |
3224 | |
3079 | // see if there is a chance of getting one that works |
3225 | // see if there is a chance of getting one that works |
3080 | // (remember that a flags value of 0 means autodetection) |
3226 | // (remember that a flags value of 0 means autodetection) |
3081 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3227 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3082 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3228 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3083 | : 0; |
3229 | : 0; |
… | |
… | |
3097 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3243 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3098 | |
3244 | |
3099 | struct ev_loop *loop = ev_default_init (0); |
3245 | struct ev_loop *loop = ev_default_init (0); |
3100 | struct ev_loop *loop_socket = 0; |
3246 | struct ev_loop *loop_socket = 0; |
3101 | ev_embed embed; |
3247 | ev_embed embed; |
3102 | |
3248 | |
3103 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3249 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3104 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3250 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3105 | { |
3251 | { |
3106 | ev_embed_init (&embed, 0, loop_socket); |
3252 | ev_embed_init (&embed, 0, loop_socket); |
3107 | ev_embed_start (loop, &embed); |
3253 | ev_embed_start (loop, &embed); |
… | |
… | |
3115 | |
3261 | |
3116 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3262 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3117 | |
3263 | |
3118 | Fork watchers are called when a C<fork ()> was detected (usually because |
3264 | Fork watchers are called when a C<fork ()> was detected (usually because |
3119 | whoever is a good citizen cared to tell libev about it by calling |
3265 | whoever is a good citizen cared to tell libev about it by calling |
3120 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3266 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3121 | event loop blocks next and before C<ev_check> watchers are being called, |
3267 | and before C<ev_check> watchers are being called, and only in the child |
3122 | and only in the child after the fork. If whoever good citizen calling |
3268 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3123 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3269 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3124 | handlers will be invoked, too, of course. |
3270 | of course. |
3125 | |
3271 | |
3126 | =head3 The special problem of life after fork - how is it possible? |
3272 | =head3 The special problem of life after fork - how is it possible? |
3127 | |
3273 | |
3128 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3274 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3129 | up/change the process environment, followed by a call to C<exec()>. This |
3275 | up/change the process environment, followed by a call to C<exec()>. This |
3130 | sequence should be handled by libev without any problems. |
3276 | sequence should be handled by libev without any problems. |
3131 | |
3277 | |
3132 | This changes when the application actually wants to do event handling |
3278 | This changes when the application actually wants to do event handling |
3133 | in the child, or both parent in child, in effect "continuing" after the |
3279 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3210 | atexit (program_exits); |
3356 | atexit (program_exits); |
3211 | |
3357 | |
3212 | |
3358 | |
3213 | =head2 C<ev_async> - how to wake up an event loop |
3359 | =head2 C<ev_async> - how to wake up an event loop |
3214 | |
3360 | |
3215 | In general, you cannot use an C<ev_run> from multiple threads or other |
3361 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3216 | asynchronous sources such as signal handlers (as opposed to multiple event |
3362 | asynchronous sources such as signal handlers (as opposed to multiple event |
3217 | loops - those are of course safe to use in different threads). |
3363 | loops - those are of course safe to use in different threads). |
3218 | |
3364 | |
3219 | Sometimes, however, you need to wake up an event loop you do not control, |
3365 | Sometimes, however, you need to wake up an event loop you do not control, |
3220 | for example because it belongs to another thread. This is what C<ev_async> |
3366 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3222 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3368 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3223 | |
3369 | |
3224 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3370 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3225 | too, are asynchronous in nature, and signals, too, will be compressed |
3371 | too, are asynchronous in nature, and signals, too, will be compressed |
3226 | (i.e. the number of callback invocations may be less than the number of |
3372 | (i.e. the number of callback invocations may be less than the number of |
3227 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3373 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3228 | of "global async watchers" by using a watcher on an otherwise unused |
3374 | of "global async watchers" by using a watcher on an otherwise unused |
3229 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3375 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3230 | even without knowing which loop owns the signal. |
3376 | even without knowing which loop owns the signal. |
3231 | |
|
|
3232 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3233 | just the default loop. |
|
|
3234 | |
3377 | |
3235 | =head3 Queueing |
3378 | =head3 Queueing |
3236 | |
3379 | |
3237 | C<ev_async> does not support queueing of data in any way. The reason |
3380 | C<ev_async> does not support queueing of data in any way. The reason |
3238 | is that the author does not know of a simple (or any) algorithm for a |
3381 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3330 | trust me. |
3473 | trust me. |
3331 | |
3474 | |
3332 | =item ev_async_send (loop, ev_async *) |
3475 | =item ev_async_send (loop, ev_async *) |
3333 | |
3476 | |
3334 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3477 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3335 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3478 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3479 | returns. |
|
|
3480 | |
3336 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3481 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3337 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3482 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3338 | section below on what exactly this means). |
3483 | embedding section below on what exactly this means). |
3339 | |
3484 | |
3340 | Note that, as with other watchers in libev, multiple events might get |
3485 | Note that, as with other watchers in libev, multiple events might get |
3341 | compressed into a single callback invocation (another way to look at this |
3486 | compressed into a single callback invocation (another way to look at |
3342 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3487 | this is that C<ev_async> watchers are level-triggered: they are set on |
3343 | reset when the event loop detects that). |
3488 | C<ev_async_send>, reset when the event loop detects that). |
3344 | |
3489 | |
3345 | This call incurs the overhead of a system call only once per event loop |
3490 | This call incurs the overhead of at most one extra system call per event |
3346 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3491 | loop iteration, if the event loop is blocked, and no syscall at all if |
3347 | repeated calls to C<ev_async_send> for the same event loop. |
3492 | the event loop (or your program) is processing events. That means that |
|
|
3493 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3494 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3495 | zero) under load. |
3348 | |
3496 | |
3349 | =item bool = ev_async_pending (ev_async *) |
3497 | =item bool = ev_async_pending (ev_async *) |
3350 | |
3498 | |
3351 | Returns a non-zero value when C<ev_async_send> has been called on the |
3499 | Returns a non-zero value when C<ev_async_send> has been called on the |
3352 | watcher but the event has not yet been processed (or even noted) by the |
3500 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3407 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3555 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3408 | |
3556 | |
3409 | =item ev_feed_fd_event (loop, int fd, int revents) |
3557 | =item ev_feed_fd_event (loop, int fd, int revents) |
3410 | |
3558 | |
3411 | Feed an event on the given fd, as if a file descriptor backend detected |
3559 | Feed an event on the given fd, as if a file descriptor backend detected |
3412 | the given events it. |
3560 | the given events. |
3413 | |
3561 | |
3414 | =item ev_feed_signal_event (loop, int signum) |
3562 | =item ev_feed_signal_event (loop, int signum) |
3415 | |
3563 | |
3416 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3564 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3417 | which is async-safe. |
3565 | which is async-safe. |
… | |
… | |
3423 | |
3571 | |
3424 | This section explains some common idioms that are not immediately |
3572 | This section explains some common idioms that are not immediately |
3425 | obvious. Note that examples are sprinkled over the whole manual, and this |
3573 | obvious. Note that examples are sprinkled over the whole manual, and this |
3426 | section only contains stuff that wouldn't fit anywhere else. |
3574 | section only contains stuff that wouldn't fit anywhere else. |
3427 | |
3575 | |
3428 | =over 4 |
3576 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
3429 | |
3577 | |
3430 | =item Model/nested event loop invocations and exit conditions. |
3578 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3579 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3580 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3581 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3582 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3583 | data: |
|
|
3584 | |
|
|
3585 | struct my_io |
|
|
3586 | { |
|
|
3587 | ev_io io; |
|
|
3588 | int otherfd; |
|
|
3589 | void *somedata; |
|
|
3590 | struct whatever *mostinteresting; |
|
|
3591 | }; |
|
|
3592 | |
|
|
3593 | ... |
|
|
3594 | struct my_io w; |
|
|
3595 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3596 | |
|
|
3597 | And since your callback will be called with a pointer to the watcher, you |
|
|
3598 | can cast it back to your own type: |
|
|
3599 | |
|
|
3600 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3601 | { |
|
|
3602 | struct my_io *w = (struct my_io *)w_; |
|
|
3603 | ... |
|
|
3604 | } |
|
|
3605 | |
|
|
3606 | More interesting and less C-conformant ways of casting your callback |
|
|
3607 | function type instead have been omitted. |
|
|
3608 | |
|
|
3609 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3610 | |
|
|
3611 | Another common scenario is to use some data structure with multiple |
|
|
3612 | embedded watchers, in effect creating your own watcher that combines |
|
|
3613 | multiple libev event sources into one "super-watcher": |
|
|
3614 | |
|
|
3615 | struct my_biggy |
|
|
3616 | { |
|
|
3617 | int some_data; |
|
|
3618 | ev_timer t1; |
|
|
3619 | ev_timer t2; |
|
|
3620 | } |
|
|
3621 | |
|
|
3622 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3623 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3624 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3625 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3626 | real programmers): |
|
|
3627 | |
|
|
3628 | #include <stddef.h> |
|
|
3629 | |
|
|
3630 | static void |
|
|
3631 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3632 | { |
|
|
3633 | struct my_biggy big = (struct my_biggy *) |
|
|
3634 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3635 | } |
|
|
3636 | |
|
|
3637 | static void |
|
|
3638 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3639 | { |
|
|
3640 | struct my_biggy big = (struct my_biggy *) |
|
|
3641 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3642 | } |
|
|
3643 | |
|
|
3644 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3645 | |
|
|
3646 | Often you have structures like this in event-based programs: |
|
|
3647 | |
|
|
3648 | callback () |
|
|
3649 | { |
|
|
3650 | free (request); |
|
|
3651 | } |
|
|
3652 | |
|
|
3653 | request = start_new_request (..., callback); |
|
|
3654 | |
|
|
3655 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3656 | used to cancel the operation, or do other things with it. |
|
|
3657 | |
|
|
3658 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3659 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3660 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3661 | operation and simply invoke the callback with the result. |
|
|
3662 | |
|
|
3663 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3664 | has returned, so C<request> is not set. |
|
|
3665 | |
|
|
3666 | Even if you pass the request by some safer means to the callback, you |
|
|
3667 | might want to do something to the request after starting it, such as |
|
|
3668 | canceling it, which probably isn't working so well when the callback has |
|
|
3669 | already been invoked. |
|
|
3670 | |
|
|
3671 | A common way around all these issues is to make sure that |
|
|
3672 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3673 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3674 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3675 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3676 | pushing it into the pending queue: |
|
|
3677 | |
|
|
3678 | ev_set_cb (watcher, callback); |
|
|
3679 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3680 | |
|
|
3681 | This way, C<start_new_request> can safely return before the callback is |
|
|
3682 | invoked, while not delaying callback invocation too much. |
|
|
3683 | |
|
|
3684 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3431 | |
3685 | |
3432 | Often (especially in GUI toolkits) there are places where you have |
3686 | Often (especially in GUI toolkits) there are places where you have |
3433 | I<modal> interaction, which is most easily implemented by recursively |
3687 | I<modal> interaction, which is most easily implemented by recursively |
3434 | invoking C<ev_run>. |
3688 | invoking C<ev_run>. |
3435 | |
3689 | |
3436 | This brings the problem of exiting - a callback might want to finish the |
3690 | This brings the problem of exiting - a callback might want to finish the |
3437 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3691 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3438 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3692 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3439 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3693 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3440 | other combination: In these cases, C<ev_break> will not work alone. |
3694 | other combination: In these cases, a simple C<ev_break> will not work. |
3441 | |
3695 | |
3442 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3696 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3443 | invocation, and use a loop around C<ev_run> until the condition is |
3697 | invocation, and use a loop around C<ev_run> until the condition is |
3444 | triggered, using C<EVRUN_ONCE>: |
3698 | triggered, using C<EVRUN_ONCE>: |
3445 | |
3699 | |
… | |
… | |
3447 | int exit_main_loop = 0; |
3701 | int exit_main_loop = 0; |
3448 | |
3702 | |
3449 | while (!exit_main_loop) |
3703 | while (!exit_main_loop) |
3450 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3704 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3451 | |
3705 | |
3452 | // in a model watcher |
3706 | // in a modal watcher |
3453 | int exit_nested_loop = 0; |
3707 | int exit_nested_loop = 0; |
3454 | |
3708 | |
3455 | while (!exit_nested_loop) |
3709 | while (!exit_nested_loop) |
3456 | ev_run (EV_A_ EVRUN_ONCE); |
3710 | ev_run (EV_A_ EVRUN_ONCE); |
3457 | |
3711 | |
… | |
… | |
3464 | exit_main_loop = 1; |
3718 | exit_main_loop = 1; |
3465 | |
3719 | |
3466 | // exit both |
3720 | // exit both |
3467 | exit_main_loop = exit_nested_loop = 1; |
3721 | exit_main_loop = exit_nested_loop = 1; |
3468 | |
3722 | |
3469 | =back |
3723 | =head2 THREAD LOCKING EXAMPLE |
|
|
3724 | |
|
|
3725 | Here is a fictitious example of how to run an event loop in a different |
|
|
3726 | thread from where callbacks are being invoked and watchers are |
|
|
3727 | created/added/removed. |
|
|
3728 | |
|
|
3729 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3730 | which uses exactly this technique (which is suited for many high-level |
|
|
3731 | languages). |
|
|
3732 | |
|
|
3733 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3734 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3735 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3736 | |
|
|
3737 | First, you need to associate some data with the event loop: |
|
|
3738 | |
|
|
3739 | typedef struct { |
|
|
3740 | mutex_t lock; /* global loop lock */ |
|
|
3741 | ev_async async_w; |
|
|
3742 | thread_t tid; |
|
|
3743 | cond_t invoke_cv; |
|
|
3744 | } userdata; |
|
|
3745 | |
|
|
3746 | void prepare_loop (EV_P) |
|
|
3747 | { |
|
|
3748 | // for simplicity, we use a static userdata struct. |
|
|
3749 | static userdata u; |
|
|
3750 | |
|
|
3751 | ev_async_init (&u->async_w, async_cb); |
|
|
3752 | ev_async_start (EV_A_ &u->async_w); |
|
|
3753 | |
|
|
3754 | pthread_mutex_init (&u->lock, 0); |
|
|
3755 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3756 | |
|
|
3757 | // now associate this with the loop |
|
|
3758 | ev_set_userdata (EV_A_ u); |
|
|
3759 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3760 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3761 | |
|
|
3762 | // then create the thread running ev_run |
|
|
3763 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3764 | } |
|
|
3765 | |
|
|
3766 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3767 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3768 | that might have been added: |
|
|
3769 | |
|
|
3770 | static void |
|
|
3771 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3772 | { |
|
|
3773 | // just used for the side effects |
|
|
3774 | } |
|
|
3775 | |
|
|
3776 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3777 | protecting the loop data, respectively. |
|
|
3778 | |
|
|
3779 | static void |
|
|
3780 | l_release (EV_P) |
|
|
3781 | { |
|
|
3782 | userdata *u = ev_userdata (EV_A); |
|
|
3783 | pthread_mutex_unlock (&u->lock); |
|
|
3784 | } |
|
|
3785 | |
|
|
3786 | static void |
|
|
3787 | l_acquire (EV_P) |
|
|
3788 | { |
|
|
3789 | userdata *u = ev_userdata (EV_A); |
|
|
3790 | pthread_mutex_lock (&u->lock); |
|
|
3791 | } |
|
|
3792 | |
|
|
3793 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3794 | into C<ev_run>: |
|
|
3795 | |
|
|
3796 | void * |
|
|
3797 | l_run (void *thr_arg) |
|
|
3798 | { |
|
|
3799 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3800 | |
|
|
3801 | l_acquire (EV_A); |
|
|
3802 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3803 | ev_run (EV_A_ 0); |
|
|
3804 | l_release (EV_A); |
|
|
3805 | |
|
|
3806 | return 0; |
|
|
3807 | } |
|
|
3808 | |
|
|
3809 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3810 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3811 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3812 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3813 | and b) skipping inter-thread-communication when there are no pending |
|
|
3814 | watchers is very beneficial): |
|
|
3815 | |
|
|
3816 | static void |
|
|
3817 | l_invoke (EV_P) |
|
|
3818 | { |
|
|
3819 | userdata *u = ev_userdata (EV_A); |
|
|
3820 | |
|
|
3821 | while (ev_pending_count (EV_A)) |
|
|
3822 | { |
|
|
3823 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3824 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3825 | } |
|
|
3826 | } |
|
|
3827 | |
|
|
3828 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3829 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3830 | thread to continue: |
|
|
3831 | |
|
|
3832 | static void |
|
|
3833 | real_invoke_pending (EV_P) |
|
|
3834 | { |
|
|
3835 | userdata *u = ev_userdata (EV_A); |
|
|
3836 | |
|
|
3837 | pthread_mutex_lock (&u->lock); |
|
|
3838 | ev_invoke_pending (EV_A); |
|
|
3839 | pthread_cond_signal (&u->invoke_cv); |
|
|
3840 | pthread_mutex_unlock (&u->lock); |
|
|
3841 | } |
|
|
3842 | |
|
|
3843 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3844 | event loop, you will now have to lock: |
|
|
3845 | |
|
|
3846 | ev_timer timeout_watcher; |
|
|
3847 | userdata *u = ev_userdata (EV_A); |
|
|
3848 | |
|
|
3849 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3850 | |
|
|
3851 | pthread_mutex_lock (&u->lock); |
|
|
3852 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3853 | ev_async_send (EV_A_ &u->async_w); |
|
|
3854 | pthread_mutex_unlock (&u->lock); |
|
|
3855 | |
|
|
3856 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3857 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3858 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3859 | watchers in the next event loop iteration. |
|
|
3860 | |
|
|
3861 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3862 | |
|
|
3863 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3864 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3865 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3866 | doesn't need callbacks anymore. |
|
|
3867 | |
|
|
3868 | Imagine you have coroutines that you can switch to using a function |
|
|
3869 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3870 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3871 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3872 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3873 | the differing C<;> conventions): |
|
|
3874 | |
|
|
3875 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3876 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3877 | |
|
|
3878 | That means instead of having a C callback function, you store the |
|
|
3879 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3880 | your callback, you instead have it switch to that coroutine. |
|
|
3881 | |
|
|
3882 | A coroutine might now wait for an event with a function called |
|
|
3883 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3884 | matter when, or whether the watcher is active or not when this function is |
|
|
3885 | called): |
|
|
3886 | |
|
|
3887 | void |
|
|
3888 | wait_for_event (ev_watcher *w) |
|
|
3889 | { |
|
|
3890 | ev_set_cb (w, current_coro); |
|
|
3891 | switch_to (libev_coro); |
|
|
3892 | } |
|
|
3893 | |
|
|
3894 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3895 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3896 | this or any other coroutine. |
|
|
3897 | |
|
|
3898 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3899 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3900 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3901 | any waiters. |
|
|
3902 | |
|
|
3903 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3904 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3905 | |
|
|
3906 | // my_ev.h |
|
|
3907 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3908 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3909 | #include "../libev/ev.h" |
|
|
3910 | |
|
|
3911 | // my_ev.c |
|
|
3912 | #define EV_H "my_ev.h" |
|
|
3913 | #include "../libev/ev.c" |
|
|
3914 | |
|
|
3915 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3916 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3917 | can even use F<ev.h> as header file name directly. |
3470 | |
3918 | |
3471 | |
3919 | |
3472 | =head1 LIBEVENT EMULATION |
3920 | =head1 LIBEVENT EMULATION |
3473 | |
3921 | |
3474 | Libev offers a compatibility emulation layer for libevent. It cannot |
3922 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
3504 | |
3952 | |
3505 | =back |
3953 | =back |
3506 | |
3954 | |
3507 | =head1 C++ SUPPORT |
3955 | =head1 C++ SUPPORT |
3508 | |
3956 | |
|
|
3957 | =head2 C API |
|
|
3958 | |
|
|
3959 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3960 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3961 | will work fine. |
|
|
3962 | |
|
|
3963 | Proper exception specifications might have to be added to callbacks passed |
|
|
3964 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3965 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3966 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3967 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3968 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3969 | |
|
|
3970 | static void |
|
|
3971 | fatal_error (const char *msg) EV_THROW |
|
|
3972 | { |
|
|
3973 | perror (msg); |
|
|
3974 | abort (); |
|
|
3975 | } |
|
|
3976 | |
|
|
3977 | ... |
|
|
3978 | ev_set_syserr_cb (fatal_error); |
|
|
3979 | |
|
|
3980 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3981 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3982 | because it runs cleanup watchers). |
|
|
3983 | |
|
|
3984 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3985 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3986 | throwing exceptions through C libraries (most do). |
|
|
3987 | |
|
|
3988 | =head2 C++ API |
|
|
3989 | |
3509 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3990 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3510 | you to use some convenience methods to start/stop watchers and also change |
3991 | you to use some convenience methods to start/stop watchers and also change |
3511 | the callback model to a model using method callbacks on objects. |
3992 | the callback model to a model using method callbacks on objects. |
3512 | |
3993 | |
3513 | To use it, |
3994 | To use it, |
3514 | |
3995 | |
3515 | #include <ev++.h> |
3996 | #include <ev++.h> |
3516 | |
3997 | |
3517 | This automatically includes F<ev.h> and puts all of its definitions (many |
3998 | This automatically includes F<ev.h> and puts all of its definitions (many |
3518 | of them macros) into the global namespace. All C++ specific things are |
3999 | of them macros) into the global namespace. All C++ specific things are |
3519 | put into the C<ev> namespace. It should support all the same embedding |
4000 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3528 | with C<operator ()> can be used as callbacks. Other types should be easy |
4009 | with C<operator ()> can be used as callbacks. Other types should be easy |
3529 | to add as long as they only need one additional pointer for context. If |
4010 | to add as long as they only need one additional pointer for context. If |
3530 | you need support for other types of functors please contact the author |
4011 | you need support for other types of functors please contact the author |
3531 | (preferably after implementing it). |
4012 | (preferably after implementing it). |
3532 | |
4013 | |
|
|
4014 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4015 | conventions as your C compiler (for static member functions), or you have |
|
|
4016 | to embed libev and compile libev itself as C++. |
|
|
4017 | |
3533 | Here is a list of things available in the C<ev> namespace: |
4018 | Here is a list of things available in the C<ev> namespace: |
3534 | |
4019 | |
3535 | =over 4 |
4020 | =over 4 |
3536 | |
4021 | |
3537 | =item C<ev::READ>, C<ev::WRITE> etc. |
4022 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3546 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4031 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3547 | |
4032 | |
3548 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4033 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3549 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4034 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3550 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4035 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3551 | defines by many implementations. |
4036 | defined by many implementations. |
3552 | |
4037 | |
3553 | All of those classes have these methods: |
4038 | All of those classes have these methods: |
3554 | |
4039 | |
3555 | =over 4 |
4040 | =over 4 |
3556 | |
4041 | |
… | |
… | |
3618 | void operator() (ev::io &w, int revents) |
4103 | void operator() (ev::io &w, int revents) |
3619 | { |
4104 | { |
3620 | ... |
4105 | ... |
3621 | } |
4106 | } |
3622 | } |
4107 | } |
3623 | |
4108 | |
3624 | myfunctor f; |
4109 | myfunctor f; |
3625 | |
4110 | |
3626 | ev::io w; |
4111 | ev::io w; |
3627 | w.set (&f); |
4112 | w.set (&f); |
3628 | |
4113 | |
… | |
… | |
3646 | Associates a different C<struct ev_loop> with this watcher. You can only |
4131 | Associates a different C<struct ev_loop> with this watcher. You can only |
3647 | do this when the watcher is inactive (and not pending either). |
4132 | do this when the watcher is inactive (and not pending either). |
3648 | |
4133 | |
3649 | =item w->set ([arguments]) |
4134 | =item w->set ([arguments]) |
3650 | |
4135 | |
3651 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4136 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3652 | method or a suitable start method must be called at least once. Unlike the |
4137 | with the same arguments. Either this method or a suitable start method |
3653 | C counterpart, an active watcher gets automatically stopped and restarted |
4138 | must be called at least once. Unlike the C counterpart, an active watcher |
3654 | when reconfiguring it with this method. |
4139 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4140 | method. |
|
|
4141 | |
|
|
4142 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4143 | clashing with the C<set (loop)> method. |
3655 | |
4144 | |
3656 | =item w->start () |
4145 | =item w->start () |
3657 | |
4146 | |
3658 | Starts the watcher. Note that there is no C<loop> argument, as the |
4147 | Starts the watcher. Note that there is no C<loop> argument, as the |
3659 | constructor already stores the event loop. |
4148 | constructor already stores the event loop. |
… | |
… | |
3689 | watchers in the constructor. |
4178 | watchers in the constructor. |
3690 | |
4179 | |
3691 | class myclass |
4180 | class myclass |
3692 | { |
4181 | { |
3693 | ev::io io ; void io_cb (ev::io &w, int revents); |
4182 | ev::io io ; void io_cb (ev::io &w, int revents); |
3694 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4183 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3695 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4184 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3696 | |
4185 | |
3697 | myclass (int fd) |
4186 | myclass (int fd) |
3698 | { |
4187 | { |
3699 | io .set <myclass, &myclass::io_cb > (this); |
4188 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3750 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4239 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3751 | |
4240 | |
3752 | =item D |
4241 | =item D |
3753 | |
4242 | |
3754 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4243 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3755 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4244 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3756 | |
4245 | |
3757 | =item Ocaml |
4246 | =item Ocaml |
3758 | |
4247 | |
3759 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4248 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3760 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4249 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3763 | |
4252 | |
3764 | Brian Maher has written a partial interface to libev for lua (at the |
4253 | Brian Maher has written a partial interface to libev for lua (at the |
3765 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4254 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3766 | L<http://github.com/brimworks/lua-ev>. |
4255 | L<http://github.com/brimworks/lua-ev>. |
3767 | |
4256 | |
|
|
4257 | =item Javascript |
|
|
4258 | |
|
|
4259 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4260 | |
|
|
4261 | =item Others |
|
|
4262 | |
|
|
4263 | There are others, and I stopped counting. |
|
|
4264 | |
3768 | =back |
4265 | =back |
3769 | |
4266 | |
3770 | |
4267 | |
3771 | =head1 MACRO MAGIC |
4268 | =head1 MACRO MAGIC |
3772 | |
4269 | |
… | |
… | |
3808 | suitable for use with C<EV_A>. |
4305 | suitable for use with C<EV_A>. |
3809 | |
4306 | |
3810 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4307 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3811 | |
4308 | |
3812 | Similar to the other two macros, this gives you the value of the default |
4309 | Similar to the other two macros, this gives you the value of the default |
3813 | loop, if multiple loops are supported ("ev loop default"). |
4310 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4311 | will be initialised if it isn't already initialised. |
|
|
4312 | |
|
|
4313 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4314 | to initialise the loop somewhere. |
3814 | |
4315 | |
3815 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4316 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3816 | |
4317 | |
3817 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4318 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3818 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4319 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3963 | supported). It will also not define any of the structs usually found in |
4464 | supported). It will also not define any of the structs usually found in |
3964 | F<event.h> that are not directly supported by the libev core alone. |
4465 | F<event.h> that are not directly supported by the libev core alone. |
3965 | |
4466 | |
3966 | In standalone mode, libev will still try to automatically deduce the |
4467 | In standalone mode, libev will still try to automatically deduce the |
3967 | configuration, but has to be more conservative. |
4468 | configuration, but has to be more conservative. |
|
|
4469 | |
|
|
4470 | =item EV_USE_FLOOR |
|
|
4471 | |
|
|
4472 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4473 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4474 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4475 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4476 | function is not available will fail, so the safe default is to not enable |
|
|
4477 | this. |
3968 | |
4478 | |
3969 | =item EV_USE_MONOTONIC |
4479 | =item EV_USE_MONOTONIC |
3970 | |
4480 | |
3971 | If defined to be C<1>, libev will try to detect the availability of the |
4481 | If defined to be C<1>, libev will try to detect the availability of the |
3972 | monotonic clock option at both compile time and runtime. Otherwise no |
4482 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
4057 | |
4567 | |
4058 | If programs implement their own fd to handle mapping on win32, then this |
4568 | If programs implement their own fd to handle mapping on win32, then this |
4059 | macro can be used to override the C<close> function, useful to unregister |
4569 | macro can be used to override the C<close> function, useful to unregister |
4060 | file descriptors again. Note that the replacement function has to close |
4570 | file descriptors again. Note that the replacement function has to close |
4061 | the underlying OS handle. |
4571 | the underlying OS handle. |
|
|
4572 | |
|
|
4573 | =item EV_USE_WSASOCKET |
|
|
4574 | |
|
|
4575 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4576 | communication socket, which works better in some environments. Otherwise, |
|
|
4577 | the normal C<socket> function will be used, which works better in other |
|
|
4578 | environments. |
4062 | |
4579 | |
4063 | =item EV_USE_POLL |
4580 | =item EV_USE_POLL |
4064 | |
4581 | |
4065 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4582 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4066 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4583 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
4102 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4619 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4103 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4620 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4104 | be detected at runtime. If undefined, it will be enabled if the headers |
4621 | be detected at runtime. If undefined, it will be enabled if the headers |
4105 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4622 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4106 | |
4623 | |
|
|
4624 | =item EV_NO_SMP |
|
|
4625 | |
|
|
4626 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4627 | between threads, that is, threads can be used, but threads never run on |
|
|
4628 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4629 | and makes libev faster. |
|
|
4630 | |
|
|
4631 | =item EV_NO_THREADS |
|
|
4632 | |
|
|
4633 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4634 | different threads (that includes signal handlers), which is a stronger |
|
|
4635 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4636 | libev faster. |
|
|
4637 | |
4107 | =item EV_ATOMIC_T |
4638 | =item EV_ATOMIC_T |
4108 | |
4639 | |
4109 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4640 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4110 | access is atomic with respect to other threads or signal contexts. No such |
4641 | access is atomic with respect to other threads or signal contexts. No |
4111 | type is easily found in the C language, so you can provide your own type |
4642 | such type is easily found in the C language, so you can provide your own |
4112 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4643 | type that you know is safe for your purposes. It is used both for signal |
4113 | as well as for signal and thread safety in C<ev_async> watchers. |
4644 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4645 | watchers. |
4114 | |
4646 | |
4115 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4647 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4116 | (from F<signal.h>), which is usually good enough on most platforms. |
4648 | (from F<signal.h>), which is usually good enough on most platforms. |
4117 | |
4649 | |
4118 | =item EV_H (h) |
4650 | =item EV_H (h) |
… | |
… | |
4145 | will have the C<struct ev_loop *> as first argument, and you can create |
4677 | will have the C<struct ev_loop *> as first argument, and you can create |
4146 | additional independent event loops. Otherwise there will be no support |
4678 | additional independent event loops. Otherwise there will be no support |
4147 | for multiple event loops and there is no first event loop pointer |
4679 | for multiple event loops and there is no first event loop pointer |
4148 | argument. Instead, all functions act on the single default loop. |
4680 | argument. Instead, all functions act on the single default loop. |
4149 | |
4681 | |
|
|
4682 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4683 | default loop when multiplicity is switched off - you always have to |
|
|
4684 | initialise the loop manually in this case. |
|
|
4685 | |
4150 | =item EV_MINPRI |
4686 | =item EV_MINPRI |
4151 | |
4687 | |
4152 | =item EV_MAXPRI |
4688 | =item EV_MAXPRI |
4153 | |
4689 | |
4154 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4690 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4190 | #define EV_USE_POLL 1 |
4726 | #define EV_USE_POLL 1 |
4191 | #define EV_CHILD_ENABLE 1 |
4727 | #define EV_CHILD_ENABLE 1 |
4192 | #define EV_ASYNC_ENABLE 1 |
4728 | #define EV_ASYNC_ENABLE 1 |
4193 | |
4729 | |
4194 | The actual value is a bitset, it can be a combination of the following |
4730 | The actual value is a bitset, it can be a combination of the following |
4195 | values: |
4731 | values (by default, all of these are enabled): |
4196 | |
4732 | |
4197 | =over 4 |
4733 | =over 4 |
4198 | |
4734 | |
4199 | =item C<1> - faster/larger code |
4735 | =item C<1> - faster/larger code |
4200 | |
4736 | |
… | |
… | |
4204 | code size by roughly 30% on amd64). |
4740 | code size by roughly 30% on amd64). |
4205 | |
4741 | |
4206 | When optimising for size, use of compiler flags such as C<-Os> with |
4742 | When optimising for size, use of compiler flags such as C<-Os> with |
4207 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4743 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4208 | assertions. |
4744 | assertions. |
|
|
4745 | |
|
|
4746 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4747 | (e.g. gcc with C<-Os>). |
4209 | |
4748 | |
4210 | =item C<2> - faster/larger data structures |
4749 | =item C<2> - faster/larger data structures |
4211 | |
4750 | |
4212 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4751 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4213 | hash table sizes and so on. This will usually further increase code size |
4752 | hash table sizes and so on. This will usually further increase code size |
4214 | and can additionally have an effect on the size of data structures at |
4753 | and can additionally have an effect on the size of data structures at |
4215 | runtime. |
4754 | runtime. |
4216 | |
4755 | |
|
|
4756 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4757 | (e.g. gcc with C<-Os>). |
|
|
4758 | |
4217 | =item C<4> - full API configuration |
4759 | =item C<4> - full API configuration |
4218 | |
4760 | |
4219 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4761 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4220 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4762 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4221 | |
4763 | |
… | |
… | |
4251 | |
4793 | |
4252 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4794 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4253 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4795 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4254 | your program might be left out as well - a binary starting a timer and an |
4796 | your program might be left out as well - a binary starting a timer and an |
4255 | I/O watcher then might come out at only 5Kb. |
4797 | I/O watcher then might come out at only 5Kb. |
|
|
4798 | |
|
|
4799 | =item EV_API_STATIC |
|
|
4800 | |
|
|
4801 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4802 | will have static linkage. This means that libev will not export any |
|
|
4803 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4804 | when you embed libev, only want to use libev functions in a single file, |
|
|
4805 | and do not want its identifiers to be visible. |
|
|
4806 | |
|
|
4807 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4808 | wants to use libev. |
|
|
4809 | |
|
|
4810 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4811 | doesn't support the required declaration syntax. |
4256 | |
4812 | |
4257 | =item EV_AVOID_STDIO |
4813 | =item EV_AVOID_STDIO |
4258 | |
4814 | |
4259 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4815 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4260 | functions (printf, scanf, perror etc.). This will increase the code size |
4816 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4404 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4960 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4405 | |
4961 | |
4406 | #include "ev_cpp.h" |
4962 | #include "ev_cpp.h" |
4407 | #include "ev.c" |
4963 | #include "ev.c" |
4408 | |
4964 | |
4409 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4965 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4410 | |
4966 | |
4411 | =head2 THREADS AND COROUTINES |
4967 | =head2 THREADS AND COROUTINES |
4412 | |
4968 | |
4413 | =head3 THREADS |
4969 | =head3 THREADS |
4414 | |
4970 | |
… | |
… | |
4465 | default loop and triggering an C<ev_async> watcher from the default loop |
5021 | default loop and triggering an C<ev_async> watcher from the default loop |
4466 | watcher callback into the event loop interested in the signal. |
5022 | watcher callback into the event loop interested in the signal. |
4467 | |
5023 | |
4468 | =back |
5024 | =back |
4469 | |
5025 | |
4470 | =head4 THREAD LOCKING EXAMPLE |
5026 | See also L</THREAD LOCKING EXAMPLE>. |
4471 | |
|
|
4472 | Here is a fictitious example of how to run an event loop in a different |
|
|
4473 | thread than where callbacks are being invoked and watchers are |
|
|
4474 | created/added/removed. |
|
|
4475 | |
|
|
4476 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4477 | which uses exactly this technique (which is suited for many high-level |
|
|
4478 | languages). |
|
|
4479 | |
|
|
4480 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4481 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4482 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4483 | |
|
|
4484 | First, you need to associate some data with the event loop: |
|
|
4485 | |
|
|
4486 | typedef struct { |
|
|
4487 | mutex_t lock; /* global loop lock */ |
|
|
4488 | ev_async async_w; |
|
|
4489 | thread_t tid; |
|
|
4490 | cond_t invoke_cv; |
|
|
4491 | } userdata; |
|
|
4492 | |
|
|
4493 | void prepare_loop (EV_P) |
|
|
4494 | { |
|
|
4495 | // for simplicity, we use a static userdata struct. |
|
|
4496 | static userdata u; |
|
|
4497 | |
|
|
4498 | ev_async_init (&u->async_w, async_cb); |
|
|
4499 | ev_async_start (EV_A_ &u->async_w); |
|
|
4500 | |
|
|
4501 | pthread_mutex_init (&u->lock, 0); |
|
|
4502 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4503 | |
|
|
4504 | // now associate this with the loop |
|
|
4505 | ev_set_userdata (EV_A_ u); |
|
|
4506 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4507 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4508 | |
|
|
4509 | // then create the thread running ev_loop |
|
|
4510 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4511 | } |
|
|
4512 | |
|
|
4513 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4514 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4515 | that might have been added: |
|
|
4516 | |
|
|
4517 | static void |
|
|
4518 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4519 | { |
|
|
4520 | // just used for the side effects |
|
|
4521 | } |
|
|
4522 | |
|
|
4523 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4524 | protecting the loop data, respectively. |
|
|
4525 | |
|
|
4526 | static void |
|
|
4527 | l_release (EV_P) |
|
|
4528 | { |
|
|
4529 | userdata *u = ev_userdata (EV_A); |
|
|
4530 | pthread_mutex_unlock (&u->lock); |
|
|
4531 | } |
|
|
4532 | |
|
|
4533 | static void |
|
|
4534 | l_acquire (EV_P) |
|
|
4535 | { |
|
|
4536 | userdata *u = ev_userdata (EV_A); |
|
|
4537 | pthread_mutex_lock (&u->lock); |
|
|
4538 | } |
|
|
4539 | |
|
|
4540 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4541 | into C<ev_run>: |
|
|
4542 | |
|
|
4543 | void * |
|
|
4544 | l_run (void *thr_arg) |
|
|
4545 | { |
|
|
4546 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4547 | |
|
|
4548 | l_acquire (EV_A); |
|
|
4549 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4550 | ev_run (EV_A_ 0); |
|
|
4551 | l_release (EV_A); |
|
|
4552 | |
|
|
4553 | return 0; |
|
|
4554 | } |
|
|
4555 | |
|
|
4556 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4557 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4558 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4559 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4560 | and b) skipping inter-thread-communication when there are no pending |
|
|
4561 | watchers is very beneficial): |
|
|
4562 | |
|
|
4563 | static void |
|
|
4564 | l_invoke (EV_P) |
|
|
4565 | { |
|
|
4566 | userdata *u = ev_userdata (EV_A); |
|
|
4567 | |
|
|
4568 | while (ev_pending_count (EV_A)) |
|
|
4569 | { |
|
|
4570 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4571 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4572 | } |
|
|
4573 | } |
|
|
4574 | |
|
|
4575 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4576 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4577 | thread to continue: |
|
|
4578 | |
|
|
4579 | static void |
|
|
4580 | real_invoke_pending (EV_P) |
|
|
4581 | { |
|
|
4582 | userdata *u = ev_userdata (EV_A); |
|
|
4583 | |
|
|
4584 | pthread_mutex_lock (&u->lock); |
|
|
4585 | ev_invoke_pending (EV_A); |
|
|
4586 | pthread_cond_signal (&u->invoke_cv); |
|
|
4587 | pthread_mutex_unlock (&u->lock); |
|
|
4588 | } |
|
|
4589 | |
|
|
4590 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4591 | event loop, you will now have to lock: |
|
|
4592 | |
|
|
4593 | ev_timer timeout_watcher; |
|
|
4594 | userdata *u = ev_userdata (EV_A); |
|
|
4595 | |
|
|
4596 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4597 | |
|
|
4598 | pthread_mutex_lock (&u->lock); |
|
|
4599 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4600 | ev_async_send (EV_A_ &u->async_w); |
|
|
4601 | pthread_mutex_unlock (&u->lock); |
|
|
4602 | |
|
|
4603 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4604 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4605 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4606 | watchers in the next event loop iteration. |
|
|
4607 | |
5027 | |
4608 | =head3 COROUTINES |
5028 | =head3 COROUTINES |
4609 | |
5029 | |
4610 | Libev is very accommodating to coroutines ("cooperative threads"): |
5030 | Libev is very accommodating to coroutines ("cooperative threads"): |
4611 | libev fully supports nesting calls to its functions from different |
5031 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4776 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5196 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4777 | model. Libev still offers limited functionality on this platform in |
5197 | model. Libev still offers limited functionality on this platform in |
4778 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5198 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4779 | descriptors. This only applies when using Win32 natively, not when using |
5199 | descriptors. This only applies when using Win32 natively, not when using |
4780 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5200 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4781 | as every compielr comes with a slightly differently broken/incompatible |
5201 | as every compiler comes with a slightly differently broken/incompatible |
4782 | environment. |
5202 | environment. |
4783 | |
5203 | |
4784 | Lifting these limitations would basically require the full |
5204 | Lifting these limitations would basically require the full |
4785 | re-implementation of the I/O system. If you are into this kind of thing, |
5205 | re-implementation of the I/O system. If you are into this kind of thing, |
4786 | then note that glib does exactly that for you in a very portable way (note |
5206 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4880 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5300 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4881 | assumes that the same (machine) code can be used to call any watcher |
5301 | assumes that the same (machine) code can be used to call any watcher |
4882 | callback: The watcher callbacks have different type signatures, but libev |
5302 | callback: The watcher callbacks have different type signatures, but libev |
4883 | calls them using an C<ev_watcher *> internally. |
5303 | calls them using an C<ev_watcher *> internally. |
4884 | |
5304 | |
|
|
5305 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5306 | |
|
|
5307 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5308 | relies on this setting pointers and integers to null. |
|
|
5309 | |
4885 | =item pointer accesses must be thread-atomic |
5310 | =item pointer accesses must be thread-atomic |
4886 | |
5311 | |
4887 | Accessing a pointer value must be atomic, it must both be readable and |
5312 | Accessing a pointer value must be atomic, it must both be readable and |
4888 | writable in one piece - this is the case on all current architectures. |
5313 | writable in one piece - this is the case on all current architectures. |
4889 | |
5314 | |
… | |
… | |
4902 | thread" or will block signals process-wide, both behaviours would |
5327 | thread" or will block signals process-wide, both behaviours would |
4903 | be compatible with libev. Interaction between C<sigprocmask> and |
5328 | be compatible with libev. Interaction between C<sigprocmask> and |
4904 | C<pthread_sigmask> could complicate things, however. |
5329 | C<pthread_sigmask> could complicate things, however. |
4905 | |
5330 | |
4906 | The most portable way to handle signals is to block signals in all threads |
5331 | The most portable way to handle signals is to block signals in all threads |
4907 | except the initial one, and run the default loop in the initial thread as |
5332 | except the initial one, and run the signal handling loop in the initial |
4908 | well. |
5333 | thread as well. |
4909 | |
5334 | |
4910 | =item C<long> must be large enough for common memory allocation sizes |
5335 | =item C<long> must be large enough for common memory allocation sizes |
4911 | |
5336 | |
4912 | To improve portability and simplify its API, libev uses C<long> internally |
5337 | To improve portability and simplify its API, libev uses C<long> internally |
4913 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5338 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4919 | |
5344 | |
4920 | The type C<double> is used to represent timestamps. It is required to |
5345 | The type C<double> is used to represent timestamps. It is required to |
4921 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5346 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4922 | good enough for at least into the year 4000 with millisecond accuracy |
5347 | good enough for at least into the year 4000 with millisecond accuracy |
4923 | (the design goal for libev). This requirement is overfulfilled by |
5348 | (the design goal for libev). This requirement is overfulfilled by |
4924 | implementations using IEEE 754, which is basically all existing ones. With |
5349 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5350 | |
4925 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5351 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5352 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5353 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5354 | something like that, just kidding). |
4926 | |
5355 | |
4927 | =back |
5356 | =back |
4928 | |
5357 | |
4929 | If you know of other additional requirements drop me a note. |
5358 | If you know of other additional requirements drop me a note. |
4930 | |
5359 | |
… | |
… | |
4992 | =item Processing ev_async_send: O(number_of_async_watchers) |
5421 | =item Processing ev_async_send: O(number_of_async_watchers) |
4993 | |
5422 | |
4994 | =item Processing signals: O(max_signal_number) |
5423 | =item Processing signals: O(max_signal_number) |
4995 | |
5424 | |
4996 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5425 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4997 | calls in the current loop iteration. Checking for async and signal events |
5426 | calls in the current loop iteration and the loop is currently |
|
|
5427 | blocked. Checking for async and signal events involves iterating over all |
4998 | involves iterating over all running async watchers or all signal numbers. |
5428 | running async watchers or all signal numbers. |
4999 | |
5429 | |
5000 | =back |
5430 | =back |
5001 | |
5431 | |
5002 | |
5432 | |
5003 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5433 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5012 | =over 4 |
5442 | =over 4 |
5013 | |
5443 | |
5014 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5444 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5015 | |
5445 | |
5016 | The backward compatibility mechanism can be controlled by |
5446 | The backward compatibility mechanism can be controlled by |
5017 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5447 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5018 | section. |
5448 | section. |
5019 | |
5449 | |
5020 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5450 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5021 | |
5451 | |
5022 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5452 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5065 | =over 4 |
5495 | =over 4 |
5066 | |
5496 | |
5067 | =item active |
5497 | =item active |
5068 | |
5498 | |
5069 | A watcher is active as long as it has been started and not yet stopped. |
5499 | A watcher is active as long as it has been started and not yet stopped. |
5070 | See L<WATCHER STATES> for details. |
5500 | See L</WATCHER STATES> for details. |
5071 | |
5501 | |
5072 | =item application |
5502 | =item application |
5073 | |
5503 | |
5074 | In this document, an application is whatever is using libev. |
5504 | In this document, an application is whatever is using libev. |
5075 | |
5505 | |
… | |
… | |
5111 | watchers and events. |
5541 | watchers and events. |
5112 | |
5542 | |
5113 | =item pending |
5543 | =item pending |
5114 | |
5544 | |
5115 | A watcher is pending as soon as the corresponding event has been |
5545 | A watcher is pending as soon as the corresponding event has been |
5116 | detected. See L<WATCHER STATES> for details. |
5546 | detected. See L</WATCHER STATES> for details. |
5117 | |
5547 | |
5118 | =item real time |
5548 | =item real time |
5119 | |
5549 | |
5120 | The physical time that is observed. It is apparently strictly monotonic :) |
5550 | The physical time that is observed. It is apparently strictly monotonic :) |
5121 | |
5551 | |
5122 | =item wall-clock time |
5552 | =item wall-clock time |
5123 | |
5553 | |
5124 | The time and date as shown on clocks. Unlike real time, it can actually |
5554 | The time and date as shown on clocks. Unlike real time, it can actually |
5125 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5555 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5126 | clock. |
5556 | clock. |
5127 | |
5557 | |
5128 | =item watcher |
5558 | =item watcher |
5129 | |
5559 | |
5130 | A data structure that describes interest in certain events. Watchers need |
5560 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5133 | =back |
5563 | =back |
5134 | |
5564 | |
5135 | =head1 AUTHOR |
5565 | =head1 AUTHOR |
5136 | |
5566 | |
5137 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5567 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5138 | Magnusson and Emanuele Giaquinta. |
5568 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5139 | |
5569 | |