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3 | .\" Standard preamble: |
4 | .\" ======================================================================== |
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124 | .\" ======================================================================== |
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125 | .\" |
126 | .IX Title "LIBEV 3" |
126 | .IX Title "LIBEV 3" |
127 | .TH LIBEV 3 "2010-10-25" "libev-4.00" "libev - high performance full featured event loop" |
127 | .TH LIBEV 3 "2012-04-03" "libev-4.11" "libev - high performance full featured event loop" |
128 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
128 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
129 | .\" way too many mistakes in technical documents. |
129 | .\" way too many mistakes in technical documents. |
130 | .if n .ad l |
130 | .if n .ad l |
131 | .nh |
131 | .nh |
132 | .SH "NAME" |
132 | .SH "NAME" |
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189 | \& ev_timer_start (loop, &timeout_watcher); |
189 | \& ev_timer_start (loop, &timeout_watcher); |
190 | \& |
190 | \& |
191 | \& // now wait for events to arrive |
191 | \& // now wait for events to arrive |
192 | \& ev_run (loop, 0); |
192 | \& ev_run (loop, 0); |
193 | \& |
193 | \& |
194 | \& // unloop was called, so exit |
194 | \& // break was called, so exit |
195 | \& return 0; |
195 | \& return 0; |
196 | \& } |
196 | \& } |
197 | .Ve |
197 | .Ve |
198 | .SH "ABOUT THIS DOCUMENT" |
198 | .SH "ABOUT THIS DOCUMENT" |
199 | .IX Header "ABOUT THIS DOCUMENT" |
199 | .IX Header "ABOUT THIS DOCUMENT" |
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244 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
244 | loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and |
245 | \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even |
245 | \&\f(CW\*(C`ev_check\*(C'\fR watchers) as well as file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even |
246 | limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR). |
246 | limited support for fork events (\f(CW\*(C`ev_fork\*(C'\fR). |
247 | .PP |
247 | .PP |
248 | It also is quite fast (see this |
248 | It also is quite fast (see this |
249 | <benchmark> comparing it to libevent |
249 | benchmark <http://libev.schmorp.de/bench.html> comparing it to libevent |
250 | for example). |
250 | for example). |
251 | .SS "\s-1CONVENTIONS\s0" |
251 | .SS "\s-1CONVENTIONS\s0" |
252 | .IX Subsection "CONVENTIONS" |
252 | .IX Subsection "CONVENTIONS" |
253 | Libev is very configurable. In this manual the default (and most common) |
253 | Libev is very configurable. In this manual the default (and most common) |
254 | configuration will be described, which supports multiple event loops. For |
254 | configuration will be described, which supports multiple event loops. For |
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294 | .IP "ev_tstamp ev_time ()" 4 |
294 | .IP "ev_tstamp ev_time ()" 4 |
295 | .IX Item "ev_tstamp ev_time ()" |
295 | .IX Item "ev_tstamp ev_time ()" |
296 | Returns the current time as libev would use it. Please note that the |
296 | Returns the current time as libev would use it. Please note that the |
297 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
297 | \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
298 | you actually want to know. Also interesting is the combination of |
298 | you actually want to know. Also interesting is the combination of |
299 | \&\f(CW\*(C`ev_update_now\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR. |
299 | \&\f(CW\*(C`ev_now_update\*(C'\fR and \f(CW\*(C`ev_now\*(C'\fR. |
300 | .IP "ev_sleep (ev_tstamp interval)" 4 |
300 | .IP "ev_sleep (ev_tstamp interval)" 4 |
301 | .IX Item "ev_sleep (ev_tstamp interval)" |
301 | .IX Item "ev_sleep (ev_tstamp interval)" |
302 | Sleep for the given interval: The current thread will be blocked until |
302 | Sleep for the given interval: The current thread will be blocked |
303 | either it is interrupted or the given time interval has passed. Basically |
303 | until either it is interrupted or the given time interval has |
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304 | passed (approximately \- it might return a bit earlier even if not |
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305 | interrupted). Returns immediately if \f(CW\*(C`interval <= 0\*(C'\fR. |
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306 | .Sp |
304 | this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
307 | Basically this is a sub-second-resolution \f(CW\*(C`sleep ()\*(C'\fR. |
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308 | .Sp |
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309 | The range of the \f(CW\*(C`interval\*(C'\fR is limited \- libev only guarantees to work |
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310 | with sleep times of up to one day (\f(CW\*(C`interval <= 86400\*(C'\fR). |
305 | .IP "int ev_version_major ()" 4 |
311 | .IP "int ev_version_major ()" 4 |
306 | .IX Item "int ev_version_major ()" |
312 | .IX Item "int ev_version_major ()" |
307 | .PD 0 |
313 | .PD 0 |
308 | .IP "int ev_version_minor ()" 4 |
314 | .IP "int ev_version_minor ()" 4 |
309 | .IX Item "int ev_version_minor ()" |
315 | .IX Item "int ev_version_minor ()" |
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361 | current system. To find which embeddable backends might be supported on |
367 | current system. To find which embeddable backends might be supported on |
362 | the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends () |
368 | the current system, you would need to look at \f(CW\*(C`ev_embeddable_backends () |
363 | & ev_supported_backends ()\*(C'\fR, likewise for recommended ones. |
369 | & ev_supported_backends ()\*(C'\fR, likewise for recommended ones. |
364 | .Sp |
370 | .Sp |
365 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
371 | See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
366 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size)) [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
372 | .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 |
367 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT]" |
373 | .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" |
368 | Sets the allocation function to use (the prototype is similar \- the |
374 | Sets the allocation function to use (the prototype is similar \- the |
369 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
375 | semantics are identical to the \f(CW\*(C`realloc\*(C'\fR C89/SuS/POSIX function). It is |
370 | used to allocate and free memory (no surprises here). If it returns zero |
376 | used to allocate and free memory (no surprises here). If it returns zero |
371 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
377 | when memory needs to be allocated (\f(CW\*(C`size != 0\*(C'\fR), the library might abort |
372 | or take some potentially destructive action. |
378 | or take some potentially destructive action. |
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398 | \& } |
404 | \& } |
399 | \& |
405 | \& |
400 | \& ... |
406 | \& ... |
401 | \& ev_set_allocator (persistent_realloc); |
407 | \& ev_set_allocator (persistent_realloc); |
402 | .Ve |
408 | .Ve |
403 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg)); [\s-1NOT\s0 \s-1REENTRANT\s0]" 4 |
409 | .IP "ev_set_syserr_cb (void (*cb)(const char *msg))" 4 |
404 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT]" |
410 | .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg))" |
405 | Set the callback function to call on a retryable system call error (such |
411 | Set the callback function to call on a retryable system call error (such |
406 | as failed select, poll, epoll_wait). The message is a printable string |
412 | as failed select, poll, epoll_wait). The message is a printable string |
407 | indicating the system call or subsystem causing the problem. If this |
413 | indicating the system call or subsystem causing the problem. If this |
408 | callback is set, then libev will expect it to remedy the situation, no |
414 | callback is set, then libev will expect it to remedy the situation, no |
409 | matter what, when it returns. That is, libev will generally retry the |
415 | matter what, when it returns. That is, libev will generally retry the |
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421 | \& } |
427 | \& } |
422 | \& |
428 | \& |
423 | \& ... |
429 | \& ... |
424 | \& ev_set_syserr_cb (fatal_error); |
430 | \& ev_set_syserr_cb (fatal_error); |
425 | .Ve |
431 | .Ve |
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432 | .IP "ev_feed_signal (int signum)" 4 |
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433 | .IX Item "ev_feed_signal (int signum)" |
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434 | This function can be used to \*(L"simulate\*(R" a signal receive. It is completely |
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435 | safe to call this function at any time, from any context, including signal |
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436 | handlers or random threads. |
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437 | .Sp |
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438 | Its main use is to customise signal handling in your process, especially |
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439 | in the presence of threads. For example, you could block signals |
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440 | by default in all threads (and specifying \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when |
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441 | creating any loops), and in one thread, use \f(CW\*(C`sigwait\*(C'\fR or any other |
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442 | mechanism to wait for signals, then \*(L"deliver\*(R" them to libev by calling |
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443 | \&\f(CW\*(C`ev_feed_signal\*(C'\fR. |
426 | .SH "FUNCTIONS CONTROLLING EVENT LOOPS" |
444 | .SH "FUNCTIONS CONTROLLING EVENT LOOPS" |
427 | .IX Header "FUNCTIONS CONTROLLING EVENT LOOPS" |
445 | .IX Header "FUNCTIONS CONTROLLING EVENT LOOPS" |
428 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is |
446 | An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR (the \f(CW\*(C`struct\*(C'\fR is |
429 | \&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as |
447 | \&\fInot\fR optional in this case unless libev 3 compatibility is disabled, as |
430 | libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name). |
448 | libev 3 had an \f(CW\*(C`ev_loop\*(C'\fR function colliding with the struct name). |
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475 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
493 | .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
476 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
494 | .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
477 | This will create and initialise a new event loop object. If the loop |
495 | This will create and initialise a new event loop object. If the loop |
478 | could not be initialised, returns false. |
496 | could not be initialised, returns false. |
479 | .Sp |
497 | .Sp |
480 | Note that this function \fIis\fR thread-safe, and one common way to use |
498 | This function is thread-safe, and one common way to use libev with |
481 | libev with threads is indeed to create one loop per thread, and using the |
499 | threads is indeed to create one loop per thread, and using the default |
482 | default loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
500 | loop in the \*(L"main\*(R" or \*(L"initial\*(R" thread. |
483 | .Sp |
501 | .Sp |
484 | The flags argument can be used to specify special behaviour or specific |
502 | The flags argument can be used to specify special behaviour or specific |
485 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
503 | backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
486 | .Sp |
504 | .Sp |
487 | The following flags are supported: |
505 | The following flags are supported: |
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521 | environment variable. |
539 | environment variable. |
522 | .ie n .IP """EVFLAG_NOINOTIFY""" 4 |
540 | .ie n .IP """EVFLAG_NOINOTIFY""" 4 |
523 | .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 |
541 | .el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 |
524 | .IX Item "EVFLAG_NOINOTIFY" |
542 | .IX Item "EVFLAG_NOINOTIFY" |
525 | When this flag is specified, then libev will not attempt to use the |
543 | When this flag is specified, then libev will not attempt to use the |
526 | \&\fIinotify\fR \s-1API\s0 for it's \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and |
544 | \&\fIinotify\fR \s-1API\s0 for its \f(CW\*(C`ev_stat\*(C'\fR watchers. Apart from debugging and |
527 | testing, this flag can be useful to conserve inotify file descriptors, as |
545 | testing, this flag can be useful to conserve inotify file descriptors, as |
528 | otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle. |
546 | otherwise each loop using \f(CW\*(C`ev_stat\*(C'\fR watchers consumes one inotify handle. |
529 | .ie n .IP """EVFLAG_SIGNALFD""" 4 |
547 | .ie n .IP """EVFLAG_SIGNALFD""" 4 |
530 | .el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4 |
548 | .el .IP "\f(CWEVFLAG_SIGNALFD\fR" 4 |
531 | .IX Item "EVFLAG_SIGNALFD" |
549 | .IX Item "EVFLAG_SIGNALFD" |
532 | When this flag is specified, then libev will attempt to use the |
550 | When this flag is specified, then libev will attempt to use the |
533 | \&\fIsignalfd\fR \s-1API\s0 for it's \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0 |
551 | \&\fIsignalfd\fR \s-1API\s0 for its \f(CW\*(C`ev_signal\*(C'\fR (and \f(CW\*(C`ev_child\*(C'\fR) watchers. This \s-1API\s0 |
534 | delivers signals synchronously, which makes it both faster and might make |
552 | delivers signals synchronously, which makes it both faster and might make |
535 | it possible to get the queued signal data. It can also simplify signal |
553 | it possible to get the queued signal data. It can also simplify signal |
536 | handling with threads, as long as you properly block signals in your |
554 | handling with threads, as long as you properly block signals in your |
537 | threads that are not interested in handling them. |
555 | threads that are not interested in handling them. |
538 | .Sp |
556 | .Sp |
539 | Signalfd will not be used by default as this changes your signal mask, and |
557 | Signalfd will not be used by default as this changes your signal mask, and |
540 | there are a lot of shoddy libraries and programs (glib's threadpool for |
558 | there are a lot of shoddy libraries and programs (glib's threadpool for |
541 | example) that can't properly initialise their signal masks. |
559 | example) that can't properly initialise their signal masks. |
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560 | .ie n .IP """EVFLAG_NOSIGMASK""" 4 |
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561 | .el .IP "\f(CWEVFLAG_NOSIGMASK\fR" 4 |
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562 | .IX Item "EVFLAG_NOSIGMASK" |
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563 | When this flag is specified, then libev will avoid to modify the signal |
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564 | mask. Specifically, this means you have to make sure signals are unblocked |
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565 | when you want to receive them. |
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566 | .Sp |
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567 | This behaviour is useful when you want to do your own signal handling, or |
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568 | want to handle signals only in specific threads and want to avoid libev |
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569 | unblocking the signals. |
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570 | .Sp |
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571 | It's also required by \s-1POSIX\s0 in a threaded program, as libev calls |
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572 | \&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. |
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573 | .Sp |
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574 | This flag's behaviour will become the default in future versions of libev. |
542 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
575 | .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
543 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
576 | .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
544 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
577 | .IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
545 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
578 | This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
546 | libev tries to roll its own fd_set with no limits on the number of fds, |
579 | libev tries to roll its own fd_set with no limits on the number of fds, |
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574 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
607 | .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
575 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
608 | .IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
576 | Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
609 | Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 |
577 | kernels). |
610 | kernels). |
578 | .Sp |
611 | .Sp |
579 | For few fds, this backend is a bit little slower than poll and select, |
612 | For few fds, this backend is a bit little slower than poll and select, but |
580 | but it scales phenomenally better. While poll and select usually scale |
613 | it scales phenomenally better. While poll and select usually scale like |
581 | like O(total_fds) where n is the total number of fds (or the highest fd), |
614 | O(total_fds) where total_fds is the total number of fds (or the highest |
582 | epoll scales either O(1) or O(active_fds). |
615 | fd), epoll scales either O(1) or O(active_fds). |
583 | .Sp |
616 | .Sp |
584 | The epoll mechanism deserves honorable mention as the most misdesigned |
617 | The epoll mechanism deserves honorable mention as the most misdesigned |
585 | of the more advanced event mechanisms: mere annoyances include silently |
618 | of the more advanced event mechanisms: mere annoyances include silently |
586 | dropping file descriptors, requiring a system call per change per file |
619 | dropping file descriptors, requiring a system call per change per file |
587 | descriptor (and unnecessary guessing of parameters), problems with dup and |
620 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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621 | returning before the timeout value, resulting in additional iterations |
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622 | (and only giving 5ms accuracy while select on the same platform gives |
588 | so on. The biggest issue is fork races, however \- if a program forks then |
623 | 0.1ms) and so on. The biggest issue is fork races, however \- if a program |
589 | \&\fIboth\fR parent and child process have to recreate the epoll set, which can |
624 | forks then \fIboth\fR parent and child process have to recreate the epoll |
590 | take considerable time (one syscall per file descriptor) and is of course |
625 | set, which can take considerable time (one syscall per file descriptor) |
591 | hard to detect. |
626 | and is of course hard to detect. |
592 | .Sp |
627 | .Sp |
593 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, but |
628 | Epoll is also notoriously buggy \- embedding epoll fds \fIshould\fR work, |
594 | of course \fIdoesn't\fR, and epoll just loves to report events for totally |
629 | but of course \fIdoesn't\fR, and epoll just loves to report events for |
595 | \&\fIdifferent\fR file descriptors (even already closed ones, so one cannot |
630 | totally \fIdifferent\fR file descriptors (even already closed ones, so |
596 | even remove them from the set) than registered in the set (especially |
631 | one cannot even remove them from the set) than registered in the set |
597 | on \s-1SMP\s0 systems). Libev tries to counter these spurious notifications by |
632 | (especially on \s-1SMP\s0 systems). Libev tries to counter these spurious |
598 | employing an additional generation counter and comparing that against the |
633 | notifications by employing an additional generation counter and comparing |
599 | events to filter out spurious ones, recreating the set when required. Last |
634 | that against the events to filter out spurious ones, recreating the set |
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635 | when required. Epoll also erroneously rounds down timeouts, but gives you |
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636 | no way to know when and by how much, so sometimes you have to busy-wait |
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637 | because epoll returns immediately despite a nonzero timeout. And last |
600 | not least, it also refuses to work with some file descriptors which work |
638 | not least, it also refuses to work with some file descriptors which work |
601 | perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...). |
639 | perfectly fine with \f(CW\*(C`select\*(C'\fR (files, many character devices...). |
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640 | .Sp |
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641 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
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642 | cobbled together in a hurry, no thought to design or interaction with |
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643 | others. Oh, the pain, will it ever stop... |
602 | .Sp |
644 | .Sp |
603 | While stopping, setting and starting an I/O watcher in the same iteration |
645 | While stopping, setting and starting an I/O watcher in the same iteration |
604 | will result in some caching, there is still a system call per such |
646 | will result in some caching, there is still a system call per such |
605 | incident (because the same \fIfile descriptor\fR could point to a different |
647 | incident (because the same \fIfile descriptor\fR could point to a different |
606 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
648 | \&\fIfile description\fR now), so its best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed |
… | |
… | |
643 | .Sp |
685 | .Sp |
644 | It scales in the same way as the epoll backend, but the interface to the |
686 | It scales in the same way as the epoll backend, but the interface to the |
645 | kernel is more efficient (which says nothing about its actual speed, of |
687 | kernel is more efficient (which says nothing about its actual speed, of |
646 | course). While stopping, setting and starting an I/O watcher does never |
688 | course). While stopping, setting and starting an I/O watcher does never |
647 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
689 | cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to |
648 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (but |
690 | two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you |
649 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
691 | might have to leak fd's on fork, but it's more sane than epoll) and it |
650 | cases |
692 | drops fds silently in similarly hard-to-detect cases |
651 | .Sp |
693 | .Sp |
652 | This backend usually performs well under most conditions. |
694 | This backend usually performs well under most conditions. |
653 | .Sp |
695 | .Sp |
654 | While nominally embeddable in other event loops, this doesn't work |
696 | While nominally embeddable in other event loops, this doesn't work |
655 | everywhere, so you might need to test for this. And since it is broken |
697 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
672 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
714 | .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
673 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
715 | .IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
674 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
716 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
675 | it's really slow, but it still scales very well (O(active_fds)). |
717 | it's really slow, but it still scales very well (O(active_fds)). |
676 | .Sp |
718 | .Sp |
677 | Please note that Solaris event ports can deliver a lot of spurious |
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|
678 | notifications, so you need to use non-blocking I/O or other means to avoid |
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|
679 | blocking when no data (or space) is available. |
|
|
680 | .Sp |
|
|
681 | While this backend scales well, it requires one system call per active |
719 | While this backend scales well, it requires one system call per active |
682 | file descriptor per loop iteration. For small and medium numbers of file |
720 | file descriptor per loop iteration. For small and medium numbers of file |
683 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
721 | descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend |
684 | might perform better. |
722 | might perform better. |
685 | .Sp |
723 | .Sp |
686 | On the positive side, with the exception of the spurious readiness |
724 | On the positive side, this backend actually performed fully to |
687 | notifications, this backend actually performed fully to specification |
|
|
688 | in all tests and is fully embeddable, which is a rare feat among the |
725 | specification in all tests and is fully embeddable, which is a rare feat |
689 | OS-specific backends (I vastly prefer correctness over speed hacks). |
726 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
727 | hacks). |
|
|
728 | .Sp |
|
|
729 | On the negative side, the interface is \fIbizarre\fR \- so bizarre that |
|
|
730 | even sun itself gets it wrong in their code examples: The event polling |
|
|
731 | function sometimes returns events to the caller even though an error |
|
|
732 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
733 | even documented that way) \- deadly for edge-triggered interfaces where you |
|
|
734 | absolutely have to know whether an event occurred or not because you have |
|
|
735 | to re-arm the watcher. |
|
|
736 | .Sp |
|
|
737 | Fortunately libev seems to be able to work around these idiocies. |
690 | .Sp |
738 | .Sp |
691 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
739 | This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as |
692 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
740 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
693 | .ie n .IP """EVBACKEND_ALL""" 4 |
741 | .ie n .IP """EVBACKEND_ALL""" 4 |
694 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
742 | .el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
695 | .IX Item "EVBACKEND_ALL" |
743 | .IX Item "EVBACKEND_ALL" |
696 | Try all backends (even potentially broken ones that wouldn't be tried |
744 | Try all backends (even potentially broken ones that wouldn't be tried |
697 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
745 | with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
698 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
746 | \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
699 | .Sp |
747 | .Sp |
700 | It is definitely not recommended to use this flag. |
748 | It is definitely not recommended to use this flag, use whatever |
|
|
749 | \&\f(CW\*(C`ev_recommended_backends ()\*(C'\fR returns, or simply do not specify a backend |
|
|
750 | at all. |
|
|
751 | .ie n .IP """EVBACKEND_MASK""" 4 |
|
|
752 | .el .IP "\f(CWEVBACKEND_MASK\fR" 4 |
|
|
753 | .IX Item "EVBACKEND_MASK" |
|
|
754 | Not a backend at all, but a mask to select all backend bits from a |
|
|
755 | \&\f(CW\*(C`flags\*(C'\fR value, in case you want to mask out any backends from a flags |
|
|
756 | value (e.g. when modifying the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR environment variable). |
701 | .RE |
757 | .RE |
702 | .RS 4 |
758 | .RS 4 |
703 | .Sp |
759 | .Sp |
704 | If one or more of the backend flags are or'ed into the flags value, |
760 | If one or more of the backend flags are or'ed into the flags value, |
705 | then only these backends will be tried (in the reverse order as listed |
761 | then only these backends will be tried (in the reverse order as listed |
… | |
… | |
738 | This function is normally used on loop objects allocated by |
794 | This function is normally used on loop objects allocated by |
739 | \&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by |
795 | \&\f(CW\*(C`ev_loop_new\*(C'\fR, but it can also be used on the default loop returned by |
740 | \&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe. |
796 | \&\f(CW\*(C`ev_default_loop\*(C'\fR, in which case it is not thread-safe. |
741 | .Sp |
797 | .Sp |
742 | Note that it is not advisable to call this function on the default loop |
798 | Note that it is not advisable to call this function on the default loop |
743 | except in the rare occasion where you really need to free it's resources. |
799 | except in the rare occasion where you really need to free its resources. |
744 | If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR |
800 | If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR |
745 | and \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
801 | and \f(CW\*(C`ev_loop_destroy\*(C'\fR. |
746 | .IP "ev_loop_fork (loop)" 4 |
802 | .IP "ev_loop_fork (loop)" 4 |
747 | .IX Item "ev_loop_fork (loop)" |
803 | .IX Item "ev_loop_fork (loop)" |
748 | This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to |
804 | This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to |
… | |
… | |
794 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the |
850 | \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls \- and is incremented between the |
795 | prepare and check phases. |
851 | prepare and check phases. |
796 | .IP "unsigned int ev_depth (loop)" 4 |
852 | .IP "unsigned int ev_depth (loop)" 4 |
797 | .IX Item "unsigned int ev_depth (loop)" |
853 | .IX Item "unsigned int ev_depth (loop)" |
798 | Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of |
854 | Returns the number of times \f(CW\*(C`ev_run\*(C'\fR was entered minus the number of |
799 | times \f(CW\*(C`ev_run\*(C'\fR was exited, in other words, the recursion depth. |
855 | times \f(CW\*(C`ev_run\*(C'\fR was exited normally, in other words, the recursion depth. |
800 | .Sp |
856 | .Sp |
801 | Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is |
857 | Outside \f(CW\*(C`ev_run\*(C'\fR, this number is zero. In a callback, this number is |
802 | \&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread), |
858 | \&\f(CW1\fR, unless \f(CW\*(C`ev_run\*(C'\fR was invoked recursively (or from another thread), |
803 | in which case it is higher. |
859 | in which case it is higher. |
804 | .Sp |
860 | .Sp |
805 | Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread |
861 | Leaving \f(CW\*(C`ev_run\*(C'\fR abnormally (setjmp/longjmp, cancelling the thread, |
806 | etc.), doesn't count as \*(L"exit\*(R" \- consider this as a hint to avoid such |
862 | throwing an exception etc.), doesn't count as \*(L"exit\*(R" \- consider this |
807 | ungentleman-like behaviour unless it's really convenient. |
863 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
864 | convenient, in which case it is fully supported. |
808 | .IP "unsigned int ev_backend (loop)" 4 |
865 | .IP "unsigned int ev_backend (loop)" 4 |
809 | .IX Item "unsigned int ev_backend (loop)" |
866 | .IX Item "unsigned int ev_backend (loop)" |
810 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
867 | Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
811 | use. |
868 | use. |
812 | .IP "ev_tstamp ev_now (loop)" 4 |
869 | .IP "ev_tstamp ev_now (loop)" 4 |
… | |
… | |
852 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
909 | given loop other than \f(CW\*(C`ev_resume\*(C'\fR, and you \fBmust not\fR call \f(CW\*(C`ev_resume\*(C'\fR |
853 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
910 | without a previous call to \f(CW\*(C`ev_suspend\*(C'\fR. |
854 | .Sp |
911 | .Sp |
855 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
912 | Calling \f(CW\*(C`ev_suspend\*(C'\fR/\f(CW\*(C`ev_resume\*(C'\fR has the side effect of updating the |
856 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
913 | event loop time (see \f(CW\*(C`ev_now_update\*(C'\fR). |
857 | .IP "ev_run (loop, int flags)" 4 |
914 | .IP "bool ev_run (loop, int flags)" 4 |
858 | .IX Item "ev_run (loop, int flags)" |
915 | .IX Item "bool ev_run (loop, int flags)" |
859 | Finally, this is it, the event handler. This function usually is called |
916 | Finally, this is it, the event handler. This function usually is called |
860 | after you have initialised all your watchers and you want to start |
917 | after you have initialised all your watchers and you want to start |
861 | handling events. It will ask the operating system for any new events, call |
918 | handling events. It will ask the operating system for any new events, call |
862 | the watcher callbacks, an then repeat the whole process indefinitely: This |
919 | the watcher callbacks, and then repeat the whole process indefinitely: This |
863 | is why event loops are called \fIloops\fR. |
920 | is why event loops are called \fIloops\fR. |
864 | .Sp |
921 | .Sp |
865 | If the flags argument is specified as \f(CW0\fR, it will keep handling events |
922 | If the flags argument is specified as \f(CW0\fR, it will keep handling events |
866 | until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was |
923 | until either no event watchers are active anymore or \f(CW\*(C`ev_break\*(C'\fR was |
867 | called. |
924 | called. |
|
|
925 | .Sp |
|
|
926 | The return value is false if there are no more active watchers (which |
|
|
927 | usually means \*(L"all jobs done\*(R" or \*(L"deadlock\*(R"), and true in all other cases |
|
|
928 | (which usually means " you should call \f(CW\*(C`ev_run\*(C'\fR again"). |
868 | .Sp |
929 | .Sp |
869 | Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than |
930 | Please note that an explicit \f(CW\*(C`ev_break\*(C'\fR is usually better than |
870 | relying on all watchers to be stopped when deciding when a program has |
931 | relying on all watchers to be stopped when deciding when a program has |
871 | finished (especially in interactive programs), but having a program |
932 | finished (especially in interactive programs), but having a program |
872 | that automatically loops as long as it has to and no longer by virtue |
933 | that automatically loops as long as it has to and no longer by virtue |
873 | of relying on its watchers stopping correctly, that is truly a thing of |
934 | of relying on its watchers stopping correctly, that is truly a thing of |
874 | beauty. |
935 | beauty. |
875 | .Sp |
936 | .Sp |
|
|
937 | This function is \fImostly\fR exception-safe \- you can break out of a |
|
|
938 | \&\f(CW\*(C`ev_run\*(C'\fR call by calling \f(CW\*(C`longjmp\*(C'\fR in a callback, throwing a \*(C+ |
|
|
939 | exception and so on. This does not decrement the \f(CW\*(C`ev_depth\*(C'\fR value, nor |
|
|
940 | will it clear any outstanding \f(CW\*(C`EVBREAK_ONE\*(C'\fR breaks. |
|
|
941 | .Sp |
876 | A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle |
942 | A flags value of \f(CW\*(C`EVRUN_NOWAIT\*(C'\fR will look for new events, will handle |
877 | those events and any already outstanding ones, but will not wait and |
943 | those events and any already outstanding ones, but will not wait and |
878 | block your process in case there are no events and will return after one |
944 | block your process in case there are no events and will return after one |
879 | iteration of the loop. This is sometimes useful to poll and handle new |
945 | iteration of the loop. This is sometimes useful to poll and handle new |
880 | events while doing lengthy calculations, to keep the program responsive. |
946 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
889 | This is useful if you are waiting for some external event in conjunction |
955 | This is useful if you are waiting for some external event in conjunction |
890 | with something not expressible using other libev watchers (i.e. "roll your |
956 | with something not expressible using other libev watchers (i.e. "roll your |
891 | own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
957 | own \f(CW\*(C`ev_run\*(C'\fR"). However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
892 | usually a better approach for this kind of thing. |
958 | usually a better approach for this kind of thing. |
893 | .Sp |
959 | .Sp |
894 | Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does: |
960 | Here are the gory details of what \f(CW\*(C`ev_run\*(C'\fR does (this is for your |
|
|
961 | understanding, not a guarantee that things will work exactly like this in |
|
|
962 | future versions): |
895 | .Sp |
963 | .Sp |
896 | .Vb 10 |
964 | .Vb 10 |
897 | \& \- Increment loop depth. |
965 | \& \- Increment loop depth. |
898 | \& \- Reset the ev_break status. |
966 | \& \- Reset the ev_break status. |
899 | \& \- Before the first iteration, call any pending watchers. |
967 | \& \- Before the first iteration, call any pending watchers. |
… | |
… | |
935 | .Sp |
1003 | .Sp |
936 | .Vb 4 |
1004 | .Vb 4 |
937 | \& ... queue jobs here, make sure they register event watchers as long |
1005 | \& ... queue jobs here, make sure they register event watchers as long |
938 | \& ... as they still have work to do (even an idle watcher will do..) |
1006 | \& ... as they still have work to do (even an idle watcher will do..) |
939 | \& ev_run (my_loop, 0); |
1007 | \& ev_run (my_loop, 0); |
940 | \& ... jobs done or somebody called unloop. yeah! |
1008 | \& ... jobs done or somebody called break. yeah! |
941 | .Ve |
1009 | .Ve |
942 | .IP "ev_break (loop, how)" 4 |
1010 | .IP "ev_break (loop, how)" 4 |
943 | .IX Item "ev_break (loop, how)" |
1011 | .IX Item "ev_break (loop, how)" |
944 | Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it |
1012 | Can be used to make a call to \f(CW\*(C`ev_run\*(C'\fR return early (but only after it |
945 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
1013 | has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
946 | \&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or |
1014 | \&\f(CW\*(C`EVBREAK_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_run\*(C'\fR call return, or |
947 | \&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return. |
1015 | \&\f(CW\*(C`EVBREAK_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_run\*(C'\fR calls return. |
948 | .Sp |
1016 | .Sp |
949 | This \*(L"unloop state\*(R" will be cleared when entering \f(CW\*(C`ev_run\*(C'\fR again. |
1017 | This \*(L"break state\*(R" will be cleared on the next call to \f(CW\*(C`ev_run\*(C'\fR. |
950 | .Sp |
1018 | .Sp |
951 | It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls. ##TODO## |
1019 | It is safe to call \f(CW\*(C`ev_break\*(C'\fR from outside any \f(CW\*(C`ev_run\*(C'\fR calls, too, in |
|
|
1020 | which case it will have no effect. |
952 | .IP "ev_ref (loop)" 4 |
1021 | .IP "ev_ref (loop)" 4 |
953 | .IX Item "ev_ref (loop)" |
1022 | .IX Item "ev_ref (loop)" |
954 | .PD 0 |
1023 | .PD 0 |
955 | .IP "ev_unref (loop)" 4 |
1024 | .IP "ev_unref (loop)" 4 |
956 | .IX Item "ev_unref (loop)" |
1025 | .IX Item "ev_unref (loop)" |
… | |
… | |
979 | .Sp |
1048 | .Sp |
980 | .Vb 4 |
1049 | .Vb 4 |
981 | \& ev_signal exitsig; |
1050 | \& ev_signal exitsig; |
982 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
1051 | \& ev_signal_init (&exitsig, sig_cb, SIGINT); |
983 | \& ev_signal_start (loop, &exitsig); |
1052 | \& ev_signal_start (loop, &exitsig); |
984 | \& evf_unref (loop); |
1053 | \& ev_unref (loop); |
985 | .Ve |
1054 | .Ve |
986 | .Sp |
1055 | .Sp |
987 | Example: For some weird reason, unregister the above signal handler again. |
1056 | Example: For some weird reason, unregister the above signal handler again. |
988 | .Sp |
1057 | .Sp |
989 | .Vb 2 |
1058 | .Vb 2 |
… | |
… | |
1013 | overhead for the actual polling but can deliver many events at once. |
1082 | overhead for the actual polling but can deliver many events at once. |
1014 | .Sp |
1083 | .Sp |
1015 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
1084 | By setting a higher \fIio collect interval\fR you allow libev to spend more |
1016 | time collecting I/O events, so you can handle more events per iteration, |
1085 | time collecting I/O events, so you can handle more events per iteration, |
1017 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
1086 | at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and |
1018 | \&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will |
1087 | \&\f(CW\*(C`ev_timer\*(C'\fR) will not be affected. Setting this to a non-null value will |
1019 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
1088 | introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations. The |
1020 | sleep time ensures that libev will not poll for I/O events more often then |
1089 | sleep time ensures that libev will not poll for I/O events more often then |
1021 | once per this interval, on average. |
1090 | once per this interval, on average (as long as the host time resolution is |
|
|
1091 | good enough). |
1022 | .Sp |
1092 | .Sp |
1023 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
1093 | Likewise, by setting a higher \fItimeout collect interval\fR you allow libev |
1024 | to spend more time collecting timeouts, at the expense of increased |
1094 | to spend more time collecting timeouts, at the expense of increased |
1025 | latency/jitter/inexactness (the watcher callback will be called |
1095 | latency/jitter/inexactness (the watcher callback will be called |
1026 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
1096 | later). \f(CW\*(C`ev_io\*(C'\fR watchers will not be affected. Setting this to a non-null |
… | |
… | |
1078 | can be done relatively simply by putting mutex_lock/unlock calls around |
1148 | can be done relatively simply by putting mutex_lock/unlock calls around |
1079 | each call to a libev function. |
1149 | each call to a libev function. |
1080 | .Sp |
1150 | .Sp |
1081 | However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible |
1151 | However, \f(CW\*(C`ev_run\*(C'\fR can run an indefinite time, so it is not feasible |
1082 | to wait for it to return. One way around this is to wake up the event |
1152 | to wait for it to return. One way around this is to wake up the event |
1083 | loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`av_async_send\*(C'\fR, another way is to set these |
1153 | loop via \f(CW\*(C`ev_break\*(C'\fR and \f(CW\*(C`ev_async_send\*(C'\fR, another way is to set these |
1084 | \&\fIrelease\fR and \fIacquire\fR callbacks on the loop. |
1154 | \&\fIrelease\fR and \fIacquire\fR callbacks on the loop. |
1085 | .Sp |
1155 | .Sp |
1086 | When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
1156 | When set, then \f(CW\*(C`release\*(C'\fR will be called just before the thread is |
1087 | suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
1157 | suspended waiting for new events, and \f(CW\*(C`acquire\*(C'\fR is called just |
1088 | afterwards. |
1158 | afterwards. |
… | |
… | |
1103 | See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
1173 | See also the locking example in the \f(CW\*(C`THREADS\*(C'\fR section later in this |
1104 | document. |
1174 | document. |
1105 | .IP "ev_set_userdata (loop, void *data)" 4 |
1175 | .IP "ev_set_userdata (loop, void *data)" 4 |
1106 | .IX Item "ev_set_userdata (loop, void *data)" |
1176 | .IX Item "ev_set_userdata (loop, void *data)" |
1107 | .PD 0 |
1177 | .PD 0 |
1108 | .IP "ev_userdata (loop)" 4 |
1178 | .IP "void *ev_userdata (loop)" 4 |
1109 | .IX Item "ev_userdata (loop)" |
1179 | .IX Item "void *ev_userdata (loop)" |
1110 | .PD |
1180 | .PD |
1111 | Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
1181 | Set and retrieve a single \f(CW\*(C`void *\*(C'\fR associated with a loop. When |
1112 | \&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
1182 | \&\f(CW\*(C`ev_set_userdata\*(C'\fR has never been called, then \f(CW\*(C`ev_userdata\*(C'\fR returns |
1113 | \&\f(CW0.\fR |
1183 | \&\f(CW0\fR. |
1114 | .Sp |
1184 | .Sp |
1115 | These two functions can be used to associate arbitrary data with a loop, |
1185 | These two functions can be used to associate arbitrary data with a loop, |
1116 | and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
1186 | and are intended solely for the \f(CW\*(C`invoke_pending_cb\*(C'\fR, \f(CW\*(C`release\*(C'\fR and |
1117 | \&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
1187 | \&\f(CW\*(C`acquire\*(C'\fR callbacks described above, but of course can be (ab\-)used for |
1118 | any other purpose as well. |
1188 | any other purpose as well. |
… | |
… | |
1424 | \&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was |
1494 | \&\f(CW\*(C`ev_clear_pending\*(C'\fR will clear the pending event, even if the watcher was |
1425 | not started in the first place. |
1495 | not started in the first place. |
1426 | .Sp |
1496 | .Sp |
1427 | See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related |
1497 | See also \f(CW\*(C`ev_feed_fd_event\*(C'\fR and \f(CW\*(C`ev_feed_signal_event\*(C'\fR for related |
1428 | functions that do not need a watcher. |
1498 | functions that do not need a watcher. |
1429 | .SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
|
|
1430 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
|
|
1431 | Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
|
|
1432 | and read at any time: libev will completely ignore it. This can be used |
|
|
1433 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1434 | don't want to allocate memory and store a pointer to it in that data |
|
|
1435 | member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
|
|
1436 | data: |
|
|
1437 | .PP |
1499 | .PP |
1438 | .Vb 7 |
1500 | See also the \*(L"\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0\*(R" and \*(L"\s-1BUILDING\s0 \s-1YOUR\s0 |
1439 | \& struct my_io |
1501 | \&\s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0\*(R" idioms. |
1440 | \& { |
|
|
1441 | \& ev_io io; |
|
|
1442 | \& int otherfd; |
|
|
1443 | \& void *somedata; |
|
|
1444 | \& struct whatever *mostinteresting; |
|
|
1445 | \& }; |
|
|
1446 | \& |
|
|
1447 | \& ... |
|
|
1448 | \& struct my_io w; |
|
|
1449 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1450 | .Ve |
|
|
1451 | .PP |
|
|
1452 | And since your callback will be called with a pointer to the watcher, you |
|
|
1453 | can cast it back to your own type: |
|
|
1454 | .PP |
|
|
1455 | .Vb 5 |
|
|
1456 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1457 | \& { |
|
|
1458 | \& struct my_io *w = (struct my_io *)w_; |
|
|
1459 | \& ... |
|
|
1460 | \& } |
|
|
1461 | .Ve |
|
|
1462 | .PP |
|
|
1463 | More interesting and less C\-conformant ways of casting your callback type |
|
|
1464 | instead have been omitted. |
|
|
1465 | .PP |
|
|
1466 | Another common scenario is to use some data structure with multiple |
|
|
1467 | embedded watchers: |
|
|
1468 | .PP |
|
|
1469 | .Vb 6 |
|
|
1470 | \& struct my_biggy |
|
|
1471 | \& { |
|
|
1472 | \& int some_data; |
|
|
1473 | \& ev_timer t1; |
|
|
1474 | \& ev_timer t2; |
|
|
1475 | \& } |
|
|
1476 | .Ve |
|
|
1477 | .PP |
|
|
1478 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
1479 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct |
|
|
1480 | in the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies), or you need to use |
|
|
1481 | some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for real |
|
|
1482 | programmers): |
|
|
1483 | .PP |
|
|
1484 | .Vb 1 |
|
|
1485 | \& #include <stddef.h> |
|
|
1486 | \& |
|
|
1487 | \& static void |
|
|
1488 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1489 | \& { |
|
|
1490 | \& struct my_biggy big = (struct my_biggy *) |
|
|
1491 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
1492 | \& } |
|
|
1493 | \& |
|
|
1494 | \& static void |
|
|
1495 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1496 | \& { |
|
|
1497 | \& struct my_biggy big = (struct my_biggy *) |
|
|
1498 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
1499 | \& } |
|
|
1500 | .Ve |
|
|
1501 | .SS "\s-1WATCHER\s0 \s-1STATES\s0" |
1502 | .SS "\s-1WATCHER\s0 \s-1STATES\s0" |
1502 | .IX Subsection "WATCHER STATES" |
1503 | .IX Subsection "WATCHER STATES" |
1503 | There are various watcher states mentioned throughout this manual \- |
1504 | There are various watcher states mentioned throughout this manual \- |
1504 | active, pending and so on. In this section these states and the rules to |
1505 | active, pending and so on. In this section these states and the rules to |
1505 | transition between them will be described in more detail \- and while these |
1506 | transition between them will be described in more detail \- and while these |
1506 | rules might look complicated, they usually do \*(L"the right thing\*(R". |
1507 | rules might look complicated, they usually do \*(L"the right thing\*(R". |
1507 | .IP "initialiased" 4 |
1508 | .IP "initialiased" 4 |
1508 | .IX Item "initialiased" |
1509 | .IX Item "initialiased" |
1509 | Before a watcher can be registered with the event looop it has to be |
1510 | Before a watcher can be registered with the event loop it has to be |
1510 | initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to |
1511 | initialised. This can be done with a call to \f(CW\*(C`ev_TYPE_init\*(C'\fR, or calls to |
1511 | \&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function. |
1512 | \&\f(CW\*(C`ev_init\*(C'\fR followed by the watcher-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR function. |
1512 | .Sp |
1513 | .Sp |
1513 | In this state it is simply some block of memory that is suitable for use |
1514 | In this state it is simply some block of memory that is suitable for |
1514 | in an event loop. It can be moved around, freed, reused etc. at will. |
1515 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1516 | will \- as long as you either keep the memory contents intact, or call |
|
|
1517 | \&\f(CW\*(C`ev_TYPE_init\*(C'\fR again. |
1515 | .IP "started/running/active" 4 |
1518 | .IP "started/running/active" 4 |
1516 | .IX Item "started/running/active" |
1519 | .IX Item "started/running/active" |
1517 | Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes |
1520 | Once a watcher has been started with a call to \f(CW\*(C`ev_TYPE_start\*(C'\fR it becomes |
1518 | property of the event loop, and is actively waiting for events. While in |
1521 | property of the event loop, and is actively waiting for events. While in |
1519 | this state it cannot be accessed (except in a few documented ways), moved, |
1522 | this state it cannot be accessed (except in a few documented ways), moved, |
… | |
… | |
1544 | latter will clear any pending state the watcher might be in, regardless |
1547 | latter will clear any pending state the watcher might be in, regardless |
1545 | of whether it was active or not, so stopping a watcher explicitly before |
1548 | of whether it was active or not, so stopping a watcher explicitly before |
1546 | freeing it is often a good idea. |
1549 | freeing it is often a good idea. |
1547 | .Sp |
1550 | .Sp |
1548 | While stopped (and not pending) the watcher is essentially in the |
1551 | While stopped (and not pending) the watcher is essentially in the |
1549 | initialised state, that is it can be reused, moved, modified in any way |
1552 | initialised state, that is, it can be reused, moved, modified in any way |
1550 | you wish. |
1553 | you wish (but when you trash the memory block, you need to \f(CW\*(C`ev_TYPE_init\*(C'\fR |
|
|
1554 | it again). |
1551 | .SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
1555 | .SS "\s-1WATCHER\s0 \s-1PRIORITY\s0 \s-1MODELS\s0" |
1552 | .IX Subsection "WATCHER PRIORITY MODELS" |
1556 | .IX Subsection "WATCHER PRIORITY MODELS" |
1553 | Many event loops support \fIwatcher priorities\fR, which are usually small |
1557 | Many event loops support \fIwatcher priorities\fR, which are usually small |
1554 | integers that influence the ordering of event callback invocation |
1558 | integers that influence the ordering of event callback invocation |
1555 | between watchers in some way, all else being equal. |
1559 | between watchers in some way, all else being equal. |
… | |
… | |
1680 | In general you can register as many read and/or write event watchers per |
1684 | In general you can register as many read and/or write event watchers per |
1681 | fd as you want (as long as you don't confuse yourself). Setting all file |
1685 | fd as you want (as long as you don't confuse yourself). Setting all file |
1682 | descriptors to non-blocking mode is also usually a good idea (but not |
1686 | descriptors to non-blocking mode is also usually a good idea (but not |
1683 | required if you know what you are doing). |
1687 | required if you know what you are doing). |
1684 | .PP |
1688 | .PP |
1685 | If you cannot use non-blocking mode, then force the use of a |
|
|
1686 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1687 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR). The same applies to file |
|
|
1688 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1689 | files) \- libev doesn't guarantee any specific behaviour in that case. |
|
|
1690 | .PP |
|
|
1691 | Another thing you have to watch out for is that it is quite easy to |
1689 | Another thing you have to watch out for is that it is quite easy to |
1692 | receive \*(L"spurious\*(R" readiness notifications, that is your callback might |
1690 | receive \*(L"spurious\*(R" readiness notifications, that is, your callback might |
1693 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1691 | be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
1694 | because there is no data. Not only are some backends known to create a |
1692 | because there is no data. It is very easy to get into this situation even |
1695 | lot of those (for example Solaris ports), it is very easy to get into |
1693 | with a relatively standard program structure. Thus it is best to always |
1696 | this situation even with a relatively standard program structure. Thus |
1694 | use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning \f(CW\*(C`EAGAIN\*(C'\fR is far |
1697 | it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
|
|
1698 | \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
1695 | preferable to a program hanging until some data arrives. |
1699 | .PP |
1696 | .PP |
1700 | If you cannot run the fd in non-blocking mode (for example you should |
1697 | If you cannot run the fd in non-blocking mode (for example you should |
1701 | not play around with an Xlib connection), then you have to separately |
1698 | not play around with an Xlib connection), then you have to separately |
1702 | re-test whether a file descriptor is really ready with a known-to-be good |
1699 | re-test whether a file descriptor is really ready with a known-to-be good |
1703 | interface such as poll (fortunately in our Xlib example, Xlib already |
1700 | interface such as poll (fortunately in the case of Xlib, it already does |
1704 | does this on its own, so its quite safe to use). Some people additionally |
1701 | this on its own, so its quite safe to use). Some people additionally |
1705 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
1702 | use \f(CW\*(C`SIGALRM\*(C'\fR and an interval timer, just to be sure you won't block |
1706 | indefinitely. |
1703 | indefinitely. |
1707 | .PP |
1704 | .PP |
1708 | But really, best use non-blocking mode. |
1705 | But really, best use non-blocking mode. |
1709 | .PP |
1706 | .PP |
… | |
… | |
1739 | .PP |
1736 | .PP |
1740 | There is no workaround possible except not registering events |
1737 | There is no workaround possible except not registering events |
1741 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1738 | for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors, or to resort to |
1742 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1739 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1743 | .PP |
1740 | .PP |
|
|
1741 | \fIThe special problem of files\fR |
|
|
1742 | .IX Subsection "The special problem of files" |
|
|
1743 | .PP |
|
|
1744 | Many people try to use \f(CW\*(C`select\*(C'\fR (or libev) on file descriptors |
|
|
1745 | representing files, and expect it to become ready when their program |
|
|
1746 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1747 | .PP |
|
|
1748 | However, this cannot ever work in the \*(L"expected\*(R" way \- you get a readiness |
|
|
1749 | notification as soon as the kernel knows whether and how much data is |
|
|
1750 | there, and in the case of open files, that's always the case, so you |
|
|
1751 | always get a readiness notification instantly, and your read (or possibly |
|
|
1752 | write) will still block on the disk I/O. |
|
|
1753 | .PP |
|
|
1754 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1755 | devices and so on, there is another party (the sender) that delivers data |
|
|
1756 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1757 | will not send data on its own, simply because it doesn't know what you |
|
|
1758 | wish to read \- you would first have to request some data. |
|
|
1759 | .PP |
|
|
1760 | Since files are typically not-so-well supported by advanced notification |
|
|
1761 | mechanism, libev tries hard to emulate \s-1POSIX\s0 behaviour with respect |
|
|
1762 | to files, even though you should not use it. The reason for this is |
|
|
1763 | convenience: sometimes you want to watch \s-1STDIN\s0 or \s-1STDOUT\s0, which is |
|
|
1764 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1765 | (for example, \f(CW\*(C`epoll\*(C'\fR on Linux works with \fI/dev/random\fR but not with |
|
|
1766 | \&\fI/dev/urandom\fR), and even though the file might better be served with |
|
|
1767 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1768 | it \*(L"just works\*(R" instead of freezing. |
|
|
1769 | .PP |
|
|
1770 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1771 | libeio), but use them when it is convenient, e.g. for \s-1STDIN/STDOUT\s0, or |
|
|
1772 | when you rarely read from a file instead of from a socket, and want to |
|
|
1773 | reuse the same code path. |
|
|
1774 | .PP |
1744 | \fIThe special problem of fork\fR |
1775 | \fIThe special problem of fork\fR |
1745 | .IX Subsection "The special problem of fork" |
1776 | .IX Subsection "The special problem of fork" |
1746 | .PP |
1777 | .PP |
1747 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1778 | Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit |
1748 | useless behaviour. Libev fully supports fork, but needs to be told about |
1779 | useless behaviour. Libev fully supports fork, but needs to be told about |
1749 | it in the child. |
1780 | it in the child if you want to continue to use it in the child. |
1750 | .PP |
1781 | .PP |
1751 | To support fork in your programs, you either have to call |
1782 | To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork |
1752 | \&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child, |
1783 | ()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to |
1753 | enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or |
1784 | \&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
1754 | \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. |
|
|
1755 | .PP |
1785 | .PP |
1756 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1786 | \fIThe special problem of \s-1SIGPIPE\s0\fR |
1757 | .IX Subsection "The special problem of SIGPIPE" |
1787 | .IX Subsection "The special problem of SIGPIPE" |
1758 | .PP |
1788 | .PP |
1759 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
1789 | While not really specific to libev, it is easy to forget about \f(CW\*(C`SIGPIPE\*(C'\fR: |
… | |
… | |
1857 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1887 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1858 | monotonic clock option helps a lot here). |
1888 | monotonic clock option helps a lot here). |
1859 | .PP |
1889 | .PP |
1860 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1890 | The callback is guaranteed to be invoked only \fIafter\fR its timeout has |
1861 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
1891 | passed (not \fIat\fR, so on systems with very low-resolution clocks this |
1862 | might introduce a small delay). If multiple timers become ready during the |
1892 | might introduce a small delay, see \*(L"the special problem of being too |
|
|
1893 | early\*(R", below). If multiple timers become ready during the same loop |
1863 | same loop iteration then the ones with earlier time-out values are invoked |
1894 | iteration then the ones with earlier time-out values are invoked before |
1864 | before ones of the same priority with later time-out values (but this is |
1895 | ones of the same priority with later time-out values (but this is no |
1865 | no longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
1896 | longer true when a callback calls \f(CW\*(C`ev_run\*(C'\fR recursively). |
1866 | .PP |
1897 | .PP |
1867 | \fIBe smart about timeouts\fR |
1898 | \fIBe smart about timeouts\fR |
1868 | .IX Subsection "Be smart about timeouts" |
1899 | .IX Subsection "Be smart about timeouts" |
1869 | .PP |
1900 | .PP |
1870 | Many real-world problems involve some kind of timeout, usually for error |
1901 | Many real-world problems involve some kind of timeout, usually for error |
… | |
… | |
1952 | .Sp |
1983 | .Sp |
1953 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
1984 | In this case, it would be more efficient to leave the \f(CW\*(C`ev_timer\*(C'\fR alone, |
1954 | but remember the time of last activity, and check for a real timeout only |
1985 | but remember the time of last activity, and check for a real timeout only |
1955 | within the callback: |
1986 | within the callback: |
1956 | .Sp |
1987 | .Sp |
1957 | .Vb 1 |
1988 | .Vb 3 |
|
|
1989 | \& ev_tstamp timeout = 60.; |
1958 | \& ev_tstamp last_activity; // time of last activity |
1990 | \& ev_tstamp last_activity; // time of last activity |
|
|
1991 | \& ev_timer timer; |
1959 | \& |
1992 | \& |
1960 | \& static void |
1993 | \& static void |
1961 | \& callback (EV_P_ ev_timer *w, int revents) |
1994 | \& callback (EV_P_ ev_timer *w, int revents) |
1962 | \& { |
1995 | \& { |
1963 | \& ev_tstamp now = ev_now (EV_A); |
1996 | \& // calculate when the timeout would happen |
1964 | \& ev_tstamp timeout = last_activity + 60.; |
1997 | \& ev_tstamp after = last_activity \- ev_now (EV_A) + timeout; |
1965 | \& |
1998 | \& |
1966 | \& // if last_activity + 60. is older than now, we did time out |
1999 | \& // if negative, it means we the timeout already occured |
1967 | \& if (timeout < now) |
2000 | \& if (after < 0.) |
1968 | \& { |
2001 | \& { |
1969 | \& // timeout occurred, take action |
2002 | \& // timeout occurred, take action |
1970 | \& } |
2003 | \& } |
1971 | \& else |
2004 | \& else |
1972 | \& { |
2005 | \& { |
1973 | \& // callback was invoked, but there was some activity, re\-arm |
2006 | \& // callback was invoked, but there was some recent |
1974 | \& // the watcher to fire in last_activity + 60, which is |
2007 | \& // activity. simply restart the timer to time out |
1975 | \& // guaranteed to be in the future, so "again" is positive: |
2008 | \& // after "after" seconds, which is the earliest time |
1976 | \& w\->repeat = timeout \- now; |
2009 | \& // the timeout can occur. |
|
|
2010 | \& ev_timer_set (w, after, 0.); |
1977 | \& ev_timer_again (EV_A_ w); |
2011 | \& ev_timer_start (EV_A_ w); |
1978 | \& } |
2012 | \& } |
1979 | \& } |
2013 | \& } |
1980 | .Ve |
2014 | .Ve |
1981 | .Sp |
2015 | .Sp |
1982 | To summarise the callback: first calculate the real timeout (defined |
2016 | To summarise the callback: first calculate in how many seconds the |
1983 | as \*(L"60 seconds after the last activity\*(R"), then check if that time has |
2017 | timeout will occur (by calculating the absolute time when it would occur, |
1984 | been reached, which means something \fIdid\fR, in fact, time out. Otherwise |
2018 | \&\f(CW\*(C`last_activity + timeout\*(C'\fR, and subtracting the current time, \f(CW\*(C`ev_now |
1985 | the callback was invoked too early (\f(CW\*(C`timeout\*(C'\fR is in the future), so |
2019 | (EV_A)\*(C'\fR from that). |
1986 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1987 | a timeout then. |
|
|
1988 | .Sp |
2020 | .Sp |
1989 | Note how \f(CW\*(C`ev_timer_again\*(C'\fR is used, taking advantage of the |
2021 | If this value is negative, then we are already past the timeout, i.e. we |
1990 | \&\f(CW\*(C`ev_timer_again\*(C'\fR optimisation when the timer is already running. |
2022 | timed out, and need to do whatever is needed in this case. |
|
|
2023 | .Sp |
|
|
2024 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2025 | and simply start the timer with this timeout value. |
|
|
2026 | .Sp |
|
|
2027 | In other words, each time the callback is invoked it will check whether |
|
|
2028 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
2029 | again at the earliest time it could time out. Rinse. Repeat. |
1991 | .Sp |
2030 | .Sp |
1992 | This scheme causes more callback invocations (about one every 60 seconds |
2031 | This scheme causes more callback invocations (about one every 60 seconds |
1993 | minus half the average time between activity), but virtually no calls to |
2032 | minus half the average time between activity), but virtually no calls to |
1994 | libev to change the timeout. |
2033 | libev to change the timeout. |
1995 | .Sp |
2034 | .Sp |
1996 | To start the timer, simply initialise the watcher and set \f(CW\*(C`last_activity\*(C'\fR |
2035 | To start the machinery, simply initialise the watcher and set |
1997 | to the current time (meaning we just have some activity :), then call the |
2036 | \&\f(CW\*(C`last_activity\*(C'\fR to the current time (meaning there was some activity just |
1998 | callback, which will \*(L"do the right thing\*(R" and start the timer: |
2037 | now), then call the callback, which will \*(L"do the right thing\*(R" and start |
|
|
2038 | the timer: |
1999 | .Sp |
2039 | .Sp |
2000 | .Vb 3 |
2040 | .Vb 3 |
|
|
2041 | \& last_activity = ev_now (EV_A); |
2001 | \& ev_init (timer, callback); |
2042 | \& ev_init (&timer, callback); |
2002 | \& last_activity = ev_now (loop); |
2043 | \& callback (EV_A_ &timer, 0); |
2003 | \& callback (loop, timer, EV_TIMER); |
|
|
2004 | .Ve |
2044 | .Ve |
2005 | .Sp |
2045 | .Sp |
2006 | And when there is some activity, simply store the current time in |
2046 | When there is some activity, simply store the current time in |
2007 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
2047 | \&\f(CW\*(C`last_activity\*(C'\fR, no libev calls at all: |
2008 | .Sp |
2048 | .Sp |
2009 | .Vb 1 |
2049 | .Vb 2 |
|
|
2050 | \& if (activity detected) |
2010 | \& last_activity = ev_now (loop); |
2051 | \& last_activity = ev_now (EV_A); |
|
|
2052 | .Ve |
|
|
2053 | .Sp |
|
|
2054 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2055 | providing a new value, stopping the timer and calling the callback, which |
|
|
2056 | will agaion do the right thing (for example, time out immediately :). |
|
|
2057 | .Sp |
|
|
2058 | .Vb 3 |
|
|
2059 | \& timeout = new_value; |
|
|
2060 | \& ev_timer_stop (EV_A_ &timer); |
|
|
2061 | \& callback (EV_A_ &timer, 0); |
2011 | .Ve |
2062 | .Ve |
2012 | .Sp |
2063 | .Sp |
2013 | This technique is slightly more complex, but in most cases where the |
2064 | This technique is slightly more complex, but in most cases where the |
2014 | time-out is unlikely to be triggered, much more efficient. |
2065 | time-out is unlikely to be triggered, much more efficient. |
2015 | .Sp |
|
|
2016 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
2017 | callback :) \- just change the timeout and invoke the callback, which will |
|
|
2018 | fix things for you. |
|
|
2019 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
2066 | .IP "4. Wee, just use a double-linked list for your timeouts." 4 |
2020 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
2067 | .IX Item "4. Wee, just use a double-linked list for your timeouts." |
2021 | If there is not one request, but many thousands (millions...), all |
2068 | If there is not one request, but many thousands (millions...), all |
2022 | employing some kind of timeout with the same timeout value, then one can |
2069 | employing some kind of timeout with the same timeout value, then one can |
2023 | do even better: |
2070 | do even better: |
… | |
… | |
2047 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2094 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2048 | rather complicated, but extremely efficient, something that really pays |
2095 | rather complicated, but extremely efficient, something that really pays |
2049 | off after the first million or so of active timers, i.e. it's usually |
2096 | off after the first million or so of active timers, i.e. it's usually |
2050 | overkill :) |
2097 | overkill :) |
2051 | .PP |
2098 | .PP |
|
|
2099 | \fIThe special problem of being too early\fR |
|
|
2100 | .IX Subsection "The special problem of being too early" |
|
|
2101 | .PP |
|
|
2102 | If you ask a timer to call your callback after three seconds, then |
|
|
2103 | you expect it to be invoked after three seconds \- but of course, this |
|
|
2104 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2105 | guaranteed to any precision by libev \- imagine somebody suspending the |
|
|
2106 | process with a \s-1STOP\s0 signal for a few hours for example. |
|
|
2107 | .PP |
|
|
2108 | So, libev tries to invoke your callback as soon as possible \fIafter\fR the |
|
|
2109 | delay has occurred, but cannot guarantee this. |
|
|
2110 | .PP |
|
|
2111 | A less obvious failure mode is calling your callback too early: many event |
|
|
2112 | loops compare timestamps with a \*(L"elapsed delay >= requested delay\*(R", but |
|
|
2113 | this can cause your callback to be invoked much earlier than you would |
|
|
2114 | expect. |
|
|
2115 | .PP |
|
|
2116 | To see why, imagine a system with a clock that only offers full second |
|
|
2117 | resolution (think windows if you can't come up with a broken enough \s-1OS\s0 |
|
|
2118 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2119 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2120 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2121 | .PP |
|
|
2122 | If an event library looks at the timeout 0.1s later, it will see \*(L"501 >= |
|
|
2123 | 501\*(R" and invoke the callback 0.1s after it was started, even though a |
|
|
2124 | one-second delay was requested \- this is being \*(L"too early\*(R", despite best |
|
|
2125 | intentions. |
|
|
2126 | .PP |
|
|
2127 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2128 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2129 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2130 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2131 | .PP |
|
|
2132 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2133 | exactly when requested, it \fIcan\fR and \fIdoes\fR guarantee that the requested |
|
|
2134 | delay has actually elapsed, or in other words, it always errs on the \*(L"too |
|
|
2135 | late\*(R" side of things. |
|
|
2136 | .PP |
2052 | \fIThe special problem of time updates\fR |
2137 | \fIThe special problem of time updates\fR |
2053 | .IX Subsection "The special problem of time updates" |
2138 | .IX Subsection "The special problem of time updates" |
2054 | .PP |
2139 | .PP |
2055 | Establishing the current time is a costly operation (it usually takes at |
2140 | Establishing the current time is a costly operation (it usually takes |
2056 | least two system calls): \s-1EV\s0 therefore updates its idea of the current |
2141 | at least one system call): \s-1EV\s0 therefore updates its idea of the current |
2057 | time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a |
2142 | time only before and after \f(CW\*(C`ev_run\*(C'\fR collects new events, which causes a |
2058 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
2143 | growing difference between \f(CW\*(C`ev_now ()\*(C'\fR and \f(CW\*(C`ev_time ()\*(C'\fR when handling |
2059 | lots of events in one iteration. |
2144 | lots of events in one iteration. |
2060 | .PP |
2145 | .PP |
2061 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
2146 | The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
… | |
… | |
2069 | .Ve |
2154 | .Ve |
2070 | .PP |
2155 | .PP |
2071 | If the event loop is suspended for a long time, you can also force an |
2156 | If the event loop is suspended for a long time, you can also force an |
2072 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
2157 | update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update |
2073 | ()\*(C'\fR. |
2158 | ()\*(C'\fR. |
|
|
2159 | .PP |
|
|
2160 | \fIThe special problem of unsynchronised clocks\fR |
|
|
2161 | .IX Subsection "The special problem of unsynchronised clocks" |
|
|
2162 | .PP |
|
|
2163 | Modern systems have a variety of clocks \- libev itself uses the normal |
|
|
2164 | \&\*(L"wall clock\*(R" clock and, if available, the monotonic clock (to avoid time |
|
|
2165 | jumps). |
|
|
2166 | .PP |
|
|
2167 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2168 | on the system, so \f(CW\*(C`ev_time ()\*(C'\fR might return a considerably different time |
|
|
2169 | than \f(CW\*(C`gettimeofday ()\*(C'\fR or \f(CW\*(C`time ()\*(C'\fR. On a GNU/Linux system, for example, |
|
|
2170 | a call to \f(CW\*(C`gettimeofday\*(C'\fR might return a second count that is one higher |
|
|
2171 | than a directly following call to \f(CW\*(C`time\*(C'\fR. |
|
|
2172 | .PP |
|
|
2173 | The moral of this is to only compare libev-related timestamps with |
|
|
2174 | \&\f(CW\*(C`ev_time ()\*(C'\fR and \f(CW\*(C`ev_now ()\*(C'\fR, at least if you want better precision than |
|
|
2175 | a second or so. |
|
|
2176 | .PP |
|
|
2177 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2178 | the system monotonic clock and you compare timestamps from \f(CW\*(C`ev_time\*(C'\fR |
|
|
2179 | or \f(CW\*(C`ev_now\*(C'\fR from when you started your timer and when your callback is |
|
|
2180 | invoked, you will find that sometimes the callback is a bit \*(L"early\*(R". |
|
|
2181 | .PP |
|
|
2182 | This is because \f(CW\*(C`ev_timer\*(C'\fRs work in real time, not wall clock time, so |
|
|
2183 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2184 | \&\fImeasured according to the real time\fR, not the system clock. |
|
|
2185 | .PP |
|
|
2186 | If your timeouts are based on a physical timescale (e.g. \*(L"time out this |
|
|
2187 | connection after 100 seconds\*(R") then this shouldn't bother you as it is |
|
|
2188 | exactly the right behaviour. |
|
|
2189 | .PP |
|
|
2190 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2191 | you need to use \f(CW\*(C`ev_periodic\*(C'\fRs, as these are based on the wall clock |
|
|
2192 | time, where your comparisons will always generate correct results. |
2074 | .PP |
2193 | .PP |
2075 | \fIThe special problems of suspended animation\fR |
2194 | \fIThe special problems of suspended animation\fR |
2076 | .IX Subsection "The special problems of suspended animation" |
2195 | .IX Subsection "The special problems of suspended animation" |
2077 | .PP |
2196 | .PP |
2078 | When you leave the server world it is quite customary to hit machines that |
2197 | When you leave the server world it is quite customary to hit machines that |
… | |
… | |
2122 | trigger at exactly 10 second intervals. If, however, your program cannot |
2241 | trigger at exactly 10 second intervals. If, however, your program cannot |
2123 | keep up with the timer (because it takes longer than those 10 seconds to |
2242 | keep up with the timer (because it takes longer than those 10 seconds to |
2124 | do stuff) the timer will not fire more than once per event loop iteration. |
2243 | do stuff) the timer will not fire more than once per event loop iteration. |
2125 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
2244 | .IP "ev_timer_again (loop, ev_timer *)" 4 |
2126 | .IX Item "ev_timer_again (loop, ev_timer *)" |
2245 | .IX Item "ev_timer_again (loop, ev_timer *)" |
2127 | This will act as if the timer timed out and restart it again if it is |
2246 | This will act as if the timer timed out, and restarts it again if it is |
2128 | repeating. The exact semantics are: |
2247 | repeating. It basically works like calling \f(CW\*(C`ev_timer_stop\*(C'\fR, updating the |
|
|
2248 | timeout to the \f(CW\*(C`repeat\*(C'\fR value and calling \f(CW\*(C`ev_timer_start\*(C'\fR. |
2129 | .Sp |
2249 | .Sp |
|
|
2250 | The exact semantics are as in the following rules, all of which will be |
|
|
2251 | applied to the watcher: |
|
|
2252 | .RS 4 |
2130 | If the timer is pending, its pending status is cleared. |
2253 | .IP "If the timer is pending, the pending status is always cleared." 4 |
2131 | .Sp |
2254 | .IX Item "If the timer is pending, the pending status is always cleared." |
|
|
2255 | .PD 0 |
2132 | If the timer is started but non-repeating, stop it (as if it timed out). |
2256 | .IP "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." 4 |
2133 | .Sp |
2257 | .IX Item "If the timer is started but non-repeating, stop it (as if it timed out, without invoking it)." |
2134 | If the timer is repeating, either start it if necessary (with the |
2258 | .ie n .IP "If the timer is repeating, make the ""repeat"" value the new timeout and start the timer, if necessary." 4 |
2135 | \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value. |
2259 | .el .IP "If the timer is repeating, make the \f(CWrepeat\fR value the new timeout and start the timer, if necessary." 4 |
|
|
2260 | .IX Item "If the timer is repeating, make the repeat value the new timeout and start the timer, if necessary." |
|
|
2261 | .RE |
|
|
2262 | .RS 4 |
|
|
2263 | .PD |
2136 | .Sp |
2264 | .Sp |
2137 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
2265 | This sounds a bit complicated, see \*(L"Be smart about timeouts\*(R", above, for a |
2138 | usage example. |
2266 | usage example. |
|
|
2267 | .RE |
2139 | .IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4 |
2268 | .IP "ev_tstamp ev_timer_remaining (loop, ev_timer *)" 4 |
2140 | .IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)" |
2269 | .IX Item "ev_tstamp ev_timer_remaining (loop, ev_timer *)" |
2141 | Returns the remaining time until a timer fires. If the timer is active, |
2270 | Returns the remaining time until a timer fires. If the timer is active, |
2142 | then this time is relative to the current event loop time, otherwise it's |
2271 | then this time is relative to the current event loop time, otherwise it's |
2143 | the timeout value currently configured. |
2272 | the timeout value currently configured. |
… | |
… | |
2263 | .Sp |
2392 | .Sp |
2264 | Another way to think about it (for the mathematically inclined) is that |
2393 | Another way to think about it (for the mathematically inclined) is that |
2265 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2394 | \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
2266 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
2395 | time where \f(CW\*(C`time = offset (mod interval)\*(C'\fR, regardless of any time jumps. |
2267 | .Sp |
2396 | .Sp |
2268 | For numerical stability it is preferable that the \f(CW\*(C`offset\*(C'\fR value is near |
2397 | The \f(CW\*(C`interval\*(C'\fR \fI\s-1MUST\s0\fR be positive, and for numerical stability, the |
2269 | \&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for |
2398 | interval value should be higher than \f(CW\*(C`1/8192\*(C'\fR (which is around 100 |
2270 | this value, and in fact is often specified as zero. |
2399 | microseconds) and \f(CW\*(C`offset\*(C'\fR should be higher than \f(CW0\fR and should have |
|
|
2400 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2401 | ten). Typical values for offset are, in fact, \f(CW0\fR or something between |
|
|
2402 | \&\f(CW0\fR and \f(CW\*(C`interval\*(C'\fR, which is also the recommended range. |
2271 | .Sp |
2403 | .Sp |
2272 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
2404 | Note also that there is an upper limit to how often a timer can fire (\s-1CPU\s0 |
2273 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
2405 | speed for example), so if \f(CW\*(C`interval\*(C'\fR is very small then timing stability |
2274 | will of course deteriorate. Libev itself tries to be exact to be about one |
2406 | will of course deteriorate. Libev itself tries to be exact to be about one |
2275 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
2407 | millisecond (if the \s-1OS\s0 supports it and the machine is fast enough). |
… | |
… | |
2391 | .ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
2523 | .ie n .SS """ev_signal"" \- signal me when a signal gets signalled!" |
2392 | .el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2524 | .el .SS "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
2393 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2525 | .IX Subsection "ev_signal - signal me when a signal gets signalled!" |
2394 | Signal watchers will trigger an event when the process receives a specific |
2526 | Signal watchers will trigger an event when the process receives a specific |
2395 | signal one or more times. Even though signals are very asynchronous, libev |
2527 | signal one or more times. Even though signals are very asynchronous, libev |
2396 | will try it's best to deliver signals synchronously, i.e. as part of the |
2528 | will try its best to deliver signals synchronously, i.e. as part of the |
2397 | normal event processing, like any other event. |
2529 | normal event processing, like any other event. |
2398 | .PP |
2530 | .PP |
2399 | If you want signals to be delivered truly asynchronously, just use |
2531 | If you want signals to be delivered truly asynchronously, just use |
2400 | \&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing |
2532 | \&\f(CW\*(C`sigaction\*(C'\fR as you would do without libev and forget about sharing |
2401 | the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to |
2533 | the signal. You can even use \f(CW\*(C`ev_async\*(C'\fR from a signal handler to |
… | |
… | |
2421 | .IX Subsection "The special problem of inheritance over fork/execve/pthread_create" |
2553 | .IX Subsection "The special problem of inheritance over fork/execve/pthread_create" |
2422 | .PP |
2554 | .PP |
2423 | Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition |
2555 | Both the signal mask (\f(CW\*(C`sigprocmask\*(C'\fR) and the signal disposition |
2424 | (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after |
2556 | (\f(CW\*(C`sigaction\*(C'\fR) are unspecified after starting a signal watcher (and after |
2425 | stopping it again), that is, libev might or might not block the signal, |
2557 | stopping it again), that is, libev might or might not block the signal, |
2426 | and might or might not set or restore the installed signal handler. |
2558 | and might or might not set or restore the installed signal handler (but |
|
|
2559 | see \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR). |
2427 | .PP |
2560 | .PP |
2428 | While this does not matter for the signal disposition (libev never |
2561 | While this does not matter for the signal disposition (libev never |
2429 | sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on |
2562 | sets signals to \f(CW\*(C`SIG_IGN\*(C'\fR, so handlers will be reset to \f(CW\*(C`SIG_DFL\*(C'\fR on |
2430 | \&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect |
2563 | \&\f(CW\*(C`execve\*(C'\fR), this matters for the signal mask: many programs do not expect |
2431 | certain signals to be blocked. |
2564 | certain signals to be blocked. |
… | |
… | |
2444 | \&\fIhas\fR to modify the signal mask, at least temporarily. |
2577 | \&\fIhas\fR to modify the signal mask, at least temporarily. |
2445 | .PP |
2578 | .PP |
2446 | So I can't stress this enough: \fIIf you do not reset your signal mask when |
2579 | So I can't stress this enough: \fIIf you do not reset your signal mask when |
2447 | you expect it to be empty, you have a race condition in your code\fR. This |
2580 | you expect it to be empty, you have a race condition in your code\fR. This |
2448 | is not a libev-specific thing, this is true for most event libraries. |
2581 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2582 | .PP |
|
|
2583 | \fIThe special problem of threads signal handling\fR |
|
|
2584 | .IX Subsection "The special problem of threads signal handling" |
|
|
2585 | .PP |
|
|
2586 | \&\s-1POSIX\s0 threads has problematic signal handling semantics, specifically, |
|
|
2587 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2588 | threads in a process block signals, which is hard to achieve. |
|
|
2589 | .PP |
|
|
2590 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2591 | for the same signals), you can tackle this problem by globally blocking |
|
|
2592 | all signals before creating any threads (or creating them with a fully set |
|
|
2593 | sigprocmask) and also specifying the \f(CW\*(C`EVFLAG_NOSIGMASK\*(C'\fR when creating |
|
|
2594 | loops. Then designate one thread as \*(L"signal receiver thread\*(R" which handles |
|
|
2595 | these signals. You can pass on any signals that libev might be interested |
|
|
2596 | in by calling \f(CW\*(C`ev_feed_signal\*(C'\fR. |
2449 | .PP |
2597 | .PP |
2450 | \fIWatcher-Specific Functions and Data Members\fR |
2598 | \fIWatcher-Specific Functions and Data Members\fR |
2451 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2599 | .IX Subsection "Watcher-Specific Functions and Data Members" |
2452 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2600 | .IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
2453 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
2601 | .IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
… | |
… | |
3284 | \& atexit (program_exits); |
3432 | \& atexit (program_exits); |
3285 | .Ve |
3433 | .Ve |
3286 | .ie n .SS """ev_async"" \- how to wake up an event loop" |
3434 | .ie n .SS """ev_async"" \- how to wake up an event loop" |
3287 | .el .SS "\f(CWev_async\fP \- how to wake up an event loop" |
3435 | .el .SS "\f(CWev_async\fP \- how to wake up an event loop" |
3288 | .IX Subsection "ev_async - how to wake up an event loop" |
3436 | .IX Subsection "ev_async - how to wake up an event loop" |
3289 | In general, you cannot use an \f(CW\*(C`ev_run\*(C'\fR from multiple threads or other |
3437 | In general, you cannot use an \f(CW\*(C`ev_loop\*(C'\fR from multiple threads or other |
3290 | asynchronous sources such as signal handlers (as opposed to multiple event |
3438 | asynchronous sources such as signal handlers (as opposed to multiple event |
3291 | loops \- those are of course safe to use in different threads). |
3439 | loops \- those are of course safe to use in different threads). |
3292 | .PP |
3440 | .PP |
3293 | Sometimes, however, you need to wake up an event loop you do not control, |
3441 | Sometimes, however, you need to wake up an event loop you do not control, |
3294 | for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR |
3442 | for example because it belongs to another thread. This is what \f(CW\*(C`ev_async\*(C'\fR |
… | |
… | |
3296 | it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe. |
3444 | it by calling \f(CW\*(C`ev_async_send\*(C'\fR, which is thread\- and signal safe. |
3297 | .PP |
3445 | .PP |
3298 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
3446 | This functionality is very similar to \f(CW\*(C`ev_signal\*(C'\fR watchers, as signals, |
3299 | too, are asynchronous in nature, and signals, too, will be compressed |
3447 | too, are asynchronous in nature, and signals, too, will be compressed |
3300 | (i.e. the number of callback invocations may be less than the number of |
3448 | (i.e. the number of callback invocations may be less than the number of |
3301 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). |
3449 | \&\f(CW\*(C`ev_async_sent\*(C'\fR calls). In fact, you could use signal watchers as a kind |
3302 | .PP |
3450 | of \*(L"global async watchers\*(R" by using a watcher on an otherwise unused |
3303 | Unlike \f(CW\*(C`ev_signal\*(C'\fR watchers, \f(CW\*(C`ev_async\*(C'\fR works with any event loop, not |
3451 | signal, and \f(CW\*(C`ev_feed_signal\*(C'\fR to signal this watcher from another thread, |
3304 | just the default loop. |
3452 | even without knowing which loop owns the signal. |
3305 | .PP |
3453 | .PP |
3306 | \fIQueueing\fR |
3454 | \fIQueueing\fR |
3307 | .IX Subsection "Queueing" |
3455 | .IX Subsection "Queueing" |
3308 | .PP |
3456 | .PP |
3309 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
3457 | \&\f(CW\*(C`ev_async\*(C'\fR does not support queueing of data in any way. The reason |
… | |
… | |
3396 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
3544 | kind. There is a \f(CW\*(C`ev_async_set\*(C'\fR macro, but using it is utterly pointless, |
3397 | trust me. |
3545 | trust me. |
3398 | .IP "ev_async_send (loop, ev_async *)" 4 |
3546 | .IP "ev_async_send (loop, ev_async *)" 4 |
3399 | .IX Item "ev_async_send (loop, ev_async *)" |
3547 | .IX Item "ev_async_send (loop, ev_async *)" |
3400 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3548 | Sends/signals/activates the given \f(CW\*(C`ev_async\*(C'\fR watcher, that is, feeds |
3401 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop. Unlike |
3549 | an \f(CW\*(C`EV_ASYNC\*(C'\fR event on the watcher into the event loop, and instantly |
|
|
3550 | returns. |
|
|
3551 | .Sp |
3402 | \&\f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, signal or |
3552 | Unlike \f(CW\*(C`ev_feed_event\*(C'\fR, this call is safe to do from other threads, |
3403 | similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the embedding |
3553 | signal or similar contexts (see the discussion of \f(CW\*(C`EV_ATOMIC_T\*(C'\fR in the |
3404 | section below on what exactly this means). |
3554 | embedding section below on what exactly this means). |
3405 | .Sp |
3555 | .Sp |
3406 | Note that, as with other watchers in libev, multiple events might get |
3556 | Note that, as with other watchers in libev, multiple events might get |
3407 | compressed into a single callback invocation (another way to look at this |
3557 | compressed into a single callback invocation (another way to look at |
3408 | is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered, set on \f(CW\*(C`ev_async_send\*(C'\fR, |
3558 | this is that \f(CW\*(C`ev_async\*(C'\fR watchers are level-triggered: they are set on |
3409 | reset when the event loop detects that). |
3559 | \&\f(CW\*(C`ev_async_send\*(C'\fR, reset when the event loop detects that). |
3410 | .Sp |
3560 | .Sp |
3411 | This call incurs the overhead of a system call only once per event loop |
3561 | This call incurs the overhead of at most one extra system call per event |
3412 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3562 | loop iteration, if the event loop is blocked, and no syscall at all if |
3413 | repeated calls to \f(CW\*(C`ev_async_send\*(C'\fR for the same event loop. |
3563 | the event loop (or your program) is processing events. That means that |
|
|
3564 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3565 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3566 | zero) under load. |
3414 | .IP "bool = ev_async_pending (ev_async *)" 4 |
3567 | .IP "bool = ev_async_pending (ev_async *)" 4 |
3415 | .IX Item "bool = ev_async_pending (ev_async *)" |
3568 | .IX Item "bool = ev_async_pending (ev_async *)" |
3416 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3569 | Returns a non-zero value when \f(CW\*(C`ev_async_send\*(C'\fR has been called on the |
3417 | watcher but the event has not yet been processed (or even noted) by the |
3570 | watcher but the event has not yet been processed (or even noted) by the |
3418 | event loop. |
3571 | event loop. |
… | |
… | |
3466 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3619 | \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3467 | .Ve |
3620 | .Ve |
3468 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
3621 | .IP "ev_feed_fd_event (loop, int fd, int revents)" 4 |
3469 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
3622 | .IX Item "ev_feed_fd_event (loop, int fd, int revents)" |
3470 | Feed an event on the given fd, as if a file descriptor backend detected |
3623 | Feed an event on the given fd, as if a file descriptor backend detected |
3471 | the given events it. |
3624 | the given events. |
3472 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
3625 | .IP "ev_feed_signal_event (loop, int signum)" 4 |
3473 | .IX Item "ev_feed_signal_event (loop, int signum)" |
3626 | .IX Item "ev_feed_signal_event (loop, int signum)" |
3474 | Feed an event as if the given signal occurred (\f(CW\*(C`loop\*(C'\fR must be the default |
3627 | Feed an event as if the given signal occurred. See also \f(CW\*(C`ev_feed_signal\*(C'\fR, |
3475 | loop!). |
3628 | which is async-safe. |
|
|
3629 | .SH "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3630 | .IX Header "COMMON OR USEFUL IDIOMS (OR BOTH)" |
|
|
3631 | This section explains some common idioms that are not immediately |
|
|
3632 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3633 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3634 | .SS "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
|
|
3635 | .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
|
|
3636 | Each watcher has, by default, a \f(CW\*(C`void *data\*(C'\fR member that you can read |
|
|
3637 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3638 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3639 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3640 | data member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
|
|
3641 | data: |
|
|
3642 | .PP |
|
|
3643 | .Vb 7 |
|
|
3644 | \& struct my_io |
|
|
3645 | \& { |
|
|
3646 | \& ev_io io; |
|
|
3647 | \& int otherfd; |
|
|
3648 | \& void *somedata; |
|
|
3649 | \& struct whatever *mostinteresting; |
|
|
3650 | \& }; |
|
|
3651 | \& |
|
|
3652 | \& ... |
|
|
3653 | \& struct my_io w; |
|
|
3654 | \& ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3655 | .Ve |
|
|
3656 | .PP |
|
|
3657 | And since your callback will be called with a pointer to the watcher, you |
|
|
3658 | can cast it back to your own type: |
|
|
3659 | .PP |
|
|
3660 | .Vb 5 |
|
|
3661 | \& static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3662 | \& { |
|
|
3663 | \& struct my_io *w = (struct my_io *)w_; |
|
|
3664 | \& ... |
|
|
3665 | \& } |
|
|
3666 | .Ve |
|
|
3667 | .PP |
|
|
3668 | More interesting and less C\-conformant ways of casting your callback |
|
|
3669 | function type instead have been omitted. |
|
|
3670 | .SS "\s-1BUILDING\s0 \s-1YOUR\s0 \s-1OWN\s0 \s-1COMPOSITE\s0 \s-1WATCHERS\s0" |
|
|
3671 | .IX Subsection "BUILDING YOUR OWN COMPOSITE WATCHERS" |
|
|
3672 | Another common scenario is to use some data structure with multiple |
|
|
3673 | embedded watchers, in effect creating your own watcher that combines |
|
|
3674 | multiple libev event sources into one \*(L"super-watcher\*(R": |
|
|
3675 | .PP |
|
|
3676 | .Vb 6 |
|
|
3677 | \& struct my_biggy |
|
|
3678 | \& { |
|
|
3679 | \& int some_data; |
|
|
3680 | \& ev_timer t1; |
|
|
3681 | \& ev_timer t2; |
|
|
3682 | \& } |
|
|
3683 | .Ve |
|
|
3684 | .PP |
|
|
3685 | In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more |
|
|
3686 | complicated: Either you store the address of your \f(CW\*(C`my_biggy\*(C'\fR struct in |
|
|
3687 | the \f(CW\*(C`data\*(C'\fR member of the watcher (for woozies or \*(C+ coders), or you need |
|
|
3688 | to use some pointer arithmetic using \f(CW\*(C`offsetof\*(C'\fR inside your watchers (for |
|
|
3689 | real programmers): |
|
|
3690 | .PP |
|
|
3691 | .Vb 1 |
|
|
3692 | \& #include <stddef.h> |
|
|
3693 | \& |
|
|
3694 | \& static void |
|
|
3695 | \& t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3696 | \& { |
|
|
3697 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3698 | \& (((char *)w) \- offsetof (struct my_biggy, t1)); |
|
|
3699 | \& } |
|
|
3700 | \& |
|
|
3701 | \& static void |
|
|
3702 | \& t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3703 | \& { |
|
|
3704 | \& struct my_biggy big = (struct my_biggy *) |
|
|
3705 | \& (((char *)w) \- offsetof (struct my_biggy, t2)); |
|
|
3706 | \& } |
|
|
3707 | .Ve |
|
|
3708 | .SS "\s-1AVOIDING\s0 \s-1FINISHING\s0 \s-1BEFORE\s0 \s-1RETURNING\s0" |
|
|
3709 | .IX Subsection "AVOIDING FINISHING BEFORE RETURNING" |
|
|
3710 | Often you have structures like this in event-based programs: |
|
|
3711 | .PP |
|
|
3712 | .Vb 4 |
|
|
3713 | \& callback () |
|
|
3714 | \& { |
|
|
3715 | \& free (request); |
|
|
3716 | \& } |
|
|
3717 | \& |
|
|
3718 | \& request = start_new_request (..., callback); |
|
|
3719 | .Ve |
|
|
3720 | .PP |
|
|
3721 | The intent is to start some \*(L"lengthy\*(R" operation. The \f(CW\*(C`request\*(C'\fR could be |
|
|
3722 | used to cancel the operation, or do other things with it. |
|
|
3723 | .PP |
|
|
3724 | It's not uncommon to have code paths in \f(CW\*(C`start_new_request\*(C'\fR that |
|
|
3725 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3726 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3727 | operation and simply invoke the callback with the result. |
|
|
3728 | .PP |
|
|
3729 | The problem here is that this will happen \fIbefore\fR \f(CW\*(C`start_new_request\*(C'\fR |
|
|
3730 | has returned, so \f(CW\*(C`request\*(C'\fR is not set. |
|
|
3731 | .PP |
|
|
3732 | Even if you pass the request by some safer means to the callback, you |
|
|
3733 | might want to do something to the request after starting it, such as |
|
|
3734 | canceling it, which probably isn't working so well when the callback has |
|
|
3735 | already been invoked. |
|
|
3736 | .PP |
|
|
3737 | A common way around all these issues is to make sure that |
|
|
3738 | \&\f(CW\*(C`start_new_request\*(C'\fR \fIalways\fR returns before the callback is invoked. If |
|
|
3739 | \&\f(CW\*(C`start_new_request\*(C'\fR immediately knows the result, it can artificially |
|
|
3740 | delay invoking the callback by e.g. using a \f(CW\*(C`prepare\*(C'\fR or \f(CW\*(C`idle\*(C'\fR watcher |
|
|
3741 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3742 | and pushing it into the pending queue: |
|
|
3743 | .PP |
|
|
3744 | .Vb 2 |
|
|
3745 | \& ev_set_cb (watcher, callback); |
|
|
3746 | \& ev_feed_event (EV_A_ watcher, 0); |
|
|
3747 | .Ve |
|
|
3748 | .PP |
|
|
3749 | This way, \f(CW\*(C`start_new_request\*(C'\fR can safely return before the callback is |
|
|
3750 | invoked, while not delaying callback invocation too much. |
|
|
3751 | .SS "\s-1MODEL/NESTED\s0 \s-1EVENT\s0 \s-1LOOP\s0 \s-1INVOCATIONS\s0 \s-1AND\s0 \s-1EXIT\s0 \s-1CONDITIONS\s0" |
|
|
3752 | .IX Subsection "MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS" |
|
|
3753 | Often (especially in \s-1GUI\s0 toolkits) there are places where you have |
|
|
3754 | \&\fImodal\fR interaction, which is most easily implemented by recursively |
|
|
3755 | invoking \f(CW\*(C`ev_run\*(C'\fR. |
|
|
3756 | .PP |
|
|
3757 | This brings the problem of exiting \- a callback might want to finish the |
|
|
3758 | main \f(CW\*(C`ev_run\*(C'\fR call, but not the nested one (e.g. user clicked \*(L"Quit\*(R", but |
|
|
3759 | a modal \*(L"Are you sure?\*(R" dialog is still waiting), or just the nested one |
|
|
3760 | and not the main one (e.g. user clocked \*(L"Ok\*(R" in a modal dialog), or some |
|
|
3761 | other combination: In these cases, \f(CW\*(C`ev_break\*(C'\fR will not work alone. |
|
|
3762 | .PP |
|
|
3763 | The solution is to maintain \*(L"break this loop\*(R" variable for each \f(CW\*(C`ev_run\*(C'\fR |
|
|
3764 | invocation, and use a loop around \f(CW\*(C`ev_run\*(C'\fR until the condition is |
|
|
3765 | triggered, using \f(CW\*(C`EVRUN_ONCE\*(C'\fR: |
|
|
3766 | .PP |
|
|
3767 | .Vb 2 |
|
|
3768 | \& // main loop |
|
|
3769 | \& int exit_main_loop = 0; |
|
|
3770 | \& |
|
|
3771 | \& while (!exit_main_loop) |
|
|
3772 | \& ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3773 | \& |
|
|
3774 | \& // in a modal watcher |
|
|
3775 | \& int exit_nested_loop = 0; |
|
|
3776 | \& |
|
|
3777 | \& while (!exit_nested_loop) |
|
|
3778 | \& ev_run (EV_A_ EVRUN_ONCE); |
|
|
3779 | .Ve |
|
|
3780 | .PP |
|
|
3781 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3782 | .PP |
|
|
3783 | .Vb 2 |
|
|
3784 | \& // exit modal loop |
|
|
3785 | \& exit_nested_loop = 1; |
|
|
3786 | \& |
|
|
3787 | \& // exit main program, after modal loop is finished |
|
|
3788 | \& exit_main_loop = 1; |
|
|
3789 | \& |
|
|
3790 | \& // exit both |
|
|
3791 | \& exit_main_loop = exit_nested_loop = 1; |
|
|
3792 | .Ve |
|
|
3793 | .SS "\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0" |
|
|
3794 | .IX Subsection "THREAD LOCKING EXAMPLE" |
|
|
3795 | Here is a fictitious example of how to run an event loop in a different |
|
|
3796 | thread from where callbacks are being invoked and watchers are |
|
|
3797 | created/added/removed. |
|
|
3798 | .PP |
|
|
3799 | For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
|
|
3800 | which uses exactly this technique (which is suited for many high-level |
|
|
3801 | languages). |
|
|
3802 | .PP |
|
|
3803 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3804 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3805 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3806 | .PP |
|
|
3807 | First, you need to associate some data with the event loop: |
|
|
3808 | .PP |
|
|
3809 | .Vb 6 |
|
|
3810 | \& typedef struct { |
|
|
3811 | \& mutex_t lock; /* global loop lock */ |
|
|
3812 | \& ev_async async_w; |
|
|
3813 | \& thread_t tid; |
|
|
3814 | \& cond_t invoke_cv; |
|
|
3815 | \& } userdata; |
|
|
3816 | \& |
|
|
3817 | \& void prepare_loop (EV_P) |
|
|
3818 | \& { |
|
|
3819 | \& // for simplicity, we use a static userdata struct. |
|
|
3820 | \& static userdata u; |
|
|
3821 | \& |
|
|
3822 | \& ev_async_init (&u\->async_w, async_cb); |
|
|
3823 | \& ev_async_start (EV_A_ &u\->async_w); |
|
|
3824 | \& |
|
|
3825 | \& pthread_mutex_init (&u\->lock, 0); |
|
|
3826 | \& pthread_cond_init (&u\->invoke_cv, 0); |
|
|
3827 | \& |
|
|
3828 | \& // now associate this with the loop |
|
|
3829 | \& ev_set_userdata (EV_A_ u); |
|
|
3830 | \& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3831 | \& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3832 | \& |
|
|
3833 | \& // then create the thread running ev_run |
|
|
3834 | \& pthread_create (&u\->tid, 0, l_run, EV_A); |
|
|
3835 | \& } |
|
|
3836 | .Ve |
|
|
3837 | .PP |
|
|
3838 | The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
|
|
3839 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3840 | that might have been added: |
|
|
3841 | .PP |
|
|
3842 | .Vb 5 |
|
|
3843 | \& static void |
|
|
3844 | \& async_cb (EV_P_ ev_async *w, int revents) |
|
|
3845 | \& { |
|
|
3846 | \& // just used for the side effects |
|
|
3847 | \& } |
|
|
3848 | .Ve |
|
|
3849 | .PP |
|
|
3850 | The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
|
|
3851 | protecting the loop data, respectively. |
|
|
3852 | .PP |
|
|
3853 | .Vb 6 |
|
|
3854 | \& static void |
|
|
3855 | \& l_release (EV_P) |
|
|
3856 | \& { |
|
|
3857 | \& userdata *u = ev_userdata (EV_A); |
|
|
3858 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3859 | \& } |
|
|
3860 | \& |
|
|
3861 | \& static void |
|
|
3862 | \& l_acquire (EV_P) |
|
|
3863 | \& { |
|
|
3864 | \& userdata *u = ev_userdata (EV_A); |
|
|
3865 | \& pthread_mutex_lock (&u\->lock); |
|
|
3866 | \& } |
|
|
3867 | .Ve |
|
|
3868 | .PP |
|
|
3869 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3870 | into \f(CW\*(C`ev_run\*(C'\fR: |
|
|
3871 | .PP |
|
|
3872 | .Vb 4 |
|
|
3873 | \& void * |
|
|
3874 | \& l_run (void *thr_arg) |
|
|
3875 | \& { |
|
|
3876 | \& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3877 | \& |
|
|
3878 | \& l_acquire (EV_A); |
|
|
3879 | \& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3880 | \& ev_run (EV_A_ 0); |
|
|
3881 | \& l_release (EV_A); |
|
|
3882 | \& |
|
|
3883 | \& return 0; |
|
|
3884 | \& } |
|
|
3885 | .Ve |
|
|
3886 | .PP |
|
|
3887 | Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
|
|
3888 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3889 | writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
|
|
3890 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3891 | and b) skipping inter-thread-communication when there are no pending |
|
|
3892 | watchers is very beneficial): |
|
|
3893 | .PP |
|
|
3894 | .Vb 4 |
|
|
3895 | \& static void |
|
|
3896 | \& l_invoke (EV_P) |
|
|
3897 | \& { |
|
|
3898 | \& userdata *u = ev_userdata (EV_A); |
|
|
3899 | \& |
|
|
3900 | \& while (ev_pending_count (EV_A)) |
|
|
3901 | \& { |
|
|
3902 | \& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3903 | \& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
|
|
3904 | \& } |
|
|
3905 | \& } |
|
|
3906 | .Ve |
|
|
3907 | .PP |
|
|
3908 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3909 | will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
|
|
3910 | thread to continue: |
|
|
3911 | .PP |
|
|
3912 | .Vb 4 |
|
|
3913 | \& static void |
|
|
3914 | \& real_invoke_pending (EV_P) |
|
|
3915 | \& { |
|
|
3916 | \& userdata *u = ev_userdata (EV_A); |
|
|
3917 | \& |
|
|
3918 | \& pthread_mutex_lock (&u\->lock); |
|
|
3919 | \& ev_invoke_pending (EV_A); |
|
|
3920 | \& pthread_cond_signal (&u\->invoke_cv); |
|
|
3921 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3922 | \& } |
|
|
3923 | .Ve |
|
|
3924 | .PP |
|
|
3925 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3926 | event loop, you will now have to lock: |
|
|
3927 | .PP |
|
|
3928 | .Vb 2 |
|
|
3929 | \& ev_timer timeout_watcher; |
|
|
3930 | \& userdata *u = ev_userdata (EV_A); |
|
|
3931 | \& |
|
|
3932 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3933 | \& |
|
|
3934 | \& pthread_mutex_lock (&u\->lock); |
|
|
3935 | \& ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3936 | \& ev_async_send (EV_A_ &u\->async_w); |
|
|
3937 | \& pthread_mutex_unlock (&u\->lock); |
|
|
3938 | .Ve |
|
|
3939 | .PP |
|
|
3940 | Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
|
|
3941 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3942 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3943 | watchers in the next event loop iteration. |
|
|
3944 | .SS "\s-1THREADS\s0, \s-1COROUTINES\s0, \s-1CONTINUATIONS\s0, \s-1QUEUES\s0... \s-1INSTEAD\s0 \s-1OF\s0 \s-1CALLBACKS\s0" |
|
|
3945 | .IX Subsection "THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS" |
|
|
3946 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3947 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3948 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3949 | doesn't need callbacks anymore. |
|
|
3950 | .PP |
|
|
3951 | Imagine you have coroutines that you can switch to using a function |
|
|
3952 | \&\f(CW\*(C`switch_to (coro)\*(C'\fR, that libev runs in a coroutine called \f(CW\*(C`libev_coro\*(C'\fR |
|
|
3953 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3954 | global called \f(CW\*(C`current_coro\*(C'\fR. Then you can build your own \*(L"wait for libev |
|
|
3955 | event\*(R" primitive by changing \f(CW\*(C`EV_CB_DECLARE\*(C'\fR and \f(CW\*(C`EV_CB_INVOKE\*(C'\fR (note |
|
|
3956 | the differing \f(CW\*(C`;\*(C'\fR conventions): |
|
|
3957 | .PP |
|
|
3958 | .Vb 2 |
|
|
3959 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3960 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb) |
|
|
3961 | .Ve |
|
|
3962 | .PP |
|
|
3963 | That means instead of having a C callback function, you store the |
|
|
3964 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3965 | your callback, you instead have it switch to that coroutine. |
|
|
3966 | .PP |
|
|
3967 | A coroutine might now wait for an event with a function called |
|
|
3968 | \&\f(CW\*(C`wait_for_event\*(C'\fR. (the watcher needs to be started, as always, but it doesn't |
|
|
3969 | matter when, or whether the watcher is active or not when this function is |
|
|
3970 | called): |
|
|
3971 | .PP |
|
|
3972 | .Vb 6 |
|
|
3973 | \& void |
|
|
3974 | \& wait_for_event (ev_watcher *w) |
|
|
3975 | \& { |
|
|
3976 | \& ev_cb_set (w) = current_coro; |
|
|
3977 | \& switch_to (libev_coro); |
|
|
3978 | \& } |
|
|
3979 | .Ve |
|
|
3980 | .PP |
|
|
3981 | That basically suspends the coroutine inside \f(CW\*(C`wait_for_event\*(C'\fR and |
|
|
3982 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3983 | this or any other coroutine. |
|
|
3984 | .PP |
|
|
3985 | You can do similar tricks if you have, say, threads with an event queue \- |
|
|
3986 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3987 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3988 | any waiters. |
|
|
3989 | .PP |
|
|
3990 | To embed libev, see \s-1EMBEDDING\s0, but in short, it's easiest to create two |
|
|
3991 | files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files: |
|
|
3992 | .PP |
|
|
3993 | .Vb 4 |
|
|
3994 | \& // my_ev.h |
|
|
3995 | \& #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3996 | \& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb); |
|
|
3997 | \& #include "../libev/ev.h" |
|
|
3998 | \& |
|
|
3999 | \& // my_ev.c |
|
|
4000 | \& #define EV_H "my_ev.h" |
|
|
4001 | \& #include "../libev/ev.c" |
|
|
4002 | .Ve |
|
|
4003 | .PP |
|
|
4004 | And then use \fImy_ev.h\fR when you would normally use \fIev.h\fR, and compile |
|
|
4005 | \&\fImy_ev.c\fR into your project. When properly specifying include paths, you |
|
|
4006 | can even use \fIev.h\fR as header file name directly. |
3476 | .SH "LIBEVENT EMULATION" |
4007 | .SH "LIBEVENT EMULATION" |
3477 | .IX Header "LIBEVENT EMULATION" |
4008 | .IX Header "LIBEVENT EMULATION" |
3478 | Libev offers a compatibility emulation layer for libevent. It cannot |
4009 | Libev offers a compatibility emulation layer for libevent. It cannot |
3479 | emulate the internals of libevent, so here are some usage hints: |
4010 | emulate the internals of libevent, so here are some usage hints: |
|
|
4011 | .IP "\(bu" 4 |
|
|
4012 | Only the libevent\-1.4.1\-beta \s-1API\s0 is being emulated. |
|
|
4013 | .Sp |
|
|
4014 | This was the newest libevent version available when libev was implemented, |
|
|
4015 | and is still mostly unchanged in 2010. |
3480 | .IP "\(bu" 4 |
4016 | .IP "\(bu" 4 |
3481 | Use it by including <event.h>, as usual. |
4017 | Use it by including <event.h>, as usual. |
3482 | .IP "\(bu" 4 |
4018 | .IP "\(bu" 4 |
3483 | The following members are fully supported: ev_base, ev_callback, |
4019 | The following members are fully supported: ev_base, ev_callback, |
3484 | ev_arg, ev_fd, ev_res, ev_events. |
4020 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3490 | Priorities are not currently supported. Initialising priorities |
4026 | Priorities are not currently supported. Initialising priorities |
3491 | will fail and all watchers will have the same priority, even though there |
4027 | will fail and all watchers will have the same priority, even though there |
3492 | is an ev_pri field. |
4028 | is an ev_pri field. |
3493 | .IP "\(bu" 4 |
4029 | .IP "\(bu" 4 |
3494 | In libevent, the last base created gets the signals, in libev, the |
4030 | In libevent, the last base created gets the signals, in libev, the |
3495 | first base created (== the default loop) gets the signals. |
4031 | base that registered the signal gets the signals. |
3496 | .IP "\(bu" 4 |
4032 | .IP "\(bu" 4 |
3497 | Other members are not supported. |
4033 | Other members are not supported. |
3498 | .IP "\(bu" 4 |
4034 | .IP "\(bu" 4 |
3499 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
4035 | The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need |
3500 | to use the libev header file and library. |
4036 | to use the libev header file and library. |
… | |
… | |
3518 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
4054 | Care has been taken to keep the overhead low. The only data member the \*(C+ |
3519 | classes add (compared to plain C\-style watchers) is the event loop pointer |
4055 | classes add (compared to plain C\-style watchers) is the event loop pointer |
3520 | that the watcher is associated with (or no additional members at all if |
4056 | that the watcher is associated with (or no additional members at all if |
3521 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
4057 | you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev). |
3522 | .PP |
4058 | .PP |
3523 | Currently, functions, and static and non-static member functions can be |
4059 | Currently, functions, static and non-static member functions and classes |
3524 | used as callbacks. Other types should be easy to add as long as they only |
4060 | with \f(CW\*(C`operator ()\*(C'\fR can be used as callbacks. Other types should be easy |
3525 | need one additional pointer for context. If you need support for other |
4061 | to add as long as they only need one additional pointer for context. If |
3526 | types of functors please contact the author (preferably after implementing |
4062 | you need support for other types of functors please contact the author |
3527 | it). |
4063 | (preferably after implementing it). |
|
|
4064 | .PP |
|
|
4065 | For all this to work, your \*(C+ compiler either has to use the same calling |
|
|
4066 | conventions as your C compiler (for static member functions), or you have |
|
|
4067 | to embed libev and compile libev itself as \*(C+. |
3528 | .PP |
4068 | .PP |
3529 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
4069 | Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
3530 | .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
4070 | .ie n .IP """ev::READ"", ""ev::WRITE"" etc." 4 |
3531 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
4071 | .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
3532 | .IX Item "ev::READ, ev::WRITE etc." |
4072 | .IX Item "ev::READ, ev::WRITE etc." |
… | |
… | |
3540 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
4080 | .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
3541 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
4081 | .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
3542 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
4082 | For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
3543 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
4083 | the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
3544 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
4084 | which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
3545 | defines by many implementations. |
4085 | defined by many implementations. |
3546 | .Sp |
4086 | .Sp |
3547 | All of those classes have these methods: |
4087 | All of those classes have these methods: |
3548 | .RS 4 |
4088 | .RS 4 |
3549 | .IP "ev::TYPE::TYPE ()" 4 |
4089 | .IP "ev::TYPE::TYPE ()" 4 |
3550 | .IX Item "ev::TYPE::TYPE ()" |
4090 | .IX Item "ev::TYPE::TYPE ()" |
… | |
… | |
3681 | .PP |
4221 | .PP |
3682 | .Vb 5 |
4222 | .Vb 5 |
3683 | \& class myclass |
4223 | \& class myclass |
3684 | \& { |
4224 | \& { |
3685 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
4225 | \& ev::io io ; void io_cb (ev::io &w, int revents); |
3686 | \& ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4226 | \& ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3687 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4227 | \& ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3688 | \& |
4228 | \& |
3689 | \& myclass (int fd) |
4229 | \& myclass (int fd) |
3690 | \& { |
4230 | \& { |
3691 | \& io .set <myclass, &myclass::io_cb > (this); |
4231 | \& io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3730 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
4270 | Roger Pack reports that using the link order \f(CW\*(C`\-lws2_32 \-lmsvcrt\-ruby\-190\*(C'\fR |
3731 | makes rev work even on mingw. |
4271 | makes rev work even on mingw. |
3732 | .IP "Haskell" 4 |
4272 | .IP "Haskell" 4 |
3733 | .IX Item "Haskell" |
4273 | .IX Item "Haskell" |
3734 | A haskell binding to libev is available at |
4274 | A haskell binding to libev is available at |
3735 | <http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev>. |
4275 | http://hackage.haskell.org/cgi\-bin/hackage\-scripts/package/hlibev <http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3736 | .IP "D" 4 |
4276 | .IP "D" 4 |
3737 | .IX Item "D" |
4277 | .IX Item "D" |
3738 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
4278 | Leandro Lucarella has written a D language binding (\fIev.d\fR) for libev, to |
3739 | be found at <http://proj.llucax.com.ar/wiki/evd>. |
4279 | be found at <http://www.llucax.com.ar/proj/ev.d/index.html>. |
3740 | .IP "Ocaml" 4 |
4280 | .IP "Ocaml" 4 |
3741 | .IX Item "Ocaml" |
4281 | .IX Item "Ocaml" |
3742 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4282 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3743 | <http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/>. |
4283 | http://modeemi.cs.tut.fi/~flux/software/ocaml\-ev/ <http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3744 | .IP "Lua" 4 |
4284 | .IP "Lua" 4 |
3745 | .IX Item "Lua" |
4285 | .IX Item "Lua" |
3746 | Brian Maher has written a partial interface to libev for lua (at the |
4286 | Brian Maher has written a partial interface to libev for lua (at the |
3747 | time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at |
4287 | time of this writing, only \f(CW\*(C`ev_io\*(C'\fR and \f(CW\*(C`ev_timer\*(C'\fR), to be found at |
3748 | <http://github.com/brimworks/lua\-ev>. |
4288 | http://github.com/brimworks/lua\-ev <http://github.com/brimworks/lua-ev>. |
3749 | .SH "MACRO MAGIC" |
4289 | .SH "MACRO MAGIC" |
3750 | .IX Header "MACRO MAGIC" |
4290 | .IX Header "MACRO MAGIC" |
3751 | Libev can be compiled with a variety of options, the most fundamental |
4291 | Libev can be compiled with a variety of options, the most fundamental |
3752 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
4292 | of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) |
3753 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
4293 | functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
… | |
… | |
3788 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
4328 | suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
3789 | .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
4329 | .ie n .IP """EV_DEFAULT"", ""EV_DEFAULT_""" 4 |
3790 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
4330 | .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
3791 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
4331 | .IX Item "EV_DEFAULT, EV_DEFAULT_" |
3792 | Similar to the other two macros, this gives you the value of the default |
4332 | Similar to the other two macros, this gives you the value of the default |
3793 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
4333 | loop, if multiple loops are supported (\*(L"ev loop default\*(R"). The default loop |
|
|
4334 | will be initialised if it isn't already initialised. |
|
|
4335 | .Sp |
|
|
4336 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4337 | to initialise the loop somewhere. |
3794 | .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
4338 | .ie n .IP """EV_DEFAULT_UC"", ""EV_DEFAULT_UC_""" 4 |
3795 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
4339 | .el .IP "\f(CWEV_DEFAULT_UC\fR, \f(CWEV_DEFAULT_UC_\fR" 4 |
3796 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
4340 | .IX Item "EV_DEFAULT_UC, EV_DEFAULT_UC_" |
3797 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
4341 | Usage identical to \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR, but requires that the |
3798 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
4342 | default loop has been initialised (\f(CW\*(C`UC\*(C'\fR == unchecked). Their behaviour |
… | |
… | |
3953 | supported). It will also not define any of the structs usually found in |
4497 | supported). It will also not define any of the structs usually found in |
3954 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
4498 | \&\fIevent.h\fR that are not directly supported by the libev core alone. |
3955 | .Sp |
4499 | .Sp |
3956 | In standalone mode, libev will still try to automatically deduce the |
4500 | In standalone mode, libev will still try to automatically deduce the |
3957 | configuration, but has to be more conservative. |
4501 | configuration, but has to be more conservative. |
|
|
4502 | .IP "\s-1EV_USE_FLOOR\s0" 4 |
|
|
4503 | .IX Item "EV_USE_FLOOR" |
|
|
4504 | If defined to be \f(CW1\fR, libev will use the \f(CW\*(C`floor ()\*(C'\fR function for its |
|
|
4505 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4506 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4507 | link against libm or something equivalent. Enabling this when the \f(CW\*(C`floor\*(C'\fR |
|
|
4508 | function is not available will fail, so the safe default is to not enable |
|
|
4509 | this. |
3958 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
4510 | .IP "\s-1EV_USE_MONOTONIC\s0" 4 |
3959 | .IX Item "EV_USE_MONOTONIC" |
4511 | .IX Item "EV_USE_MONOTONIC" |
3960 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
4512 | If defined to be \f(CW1\fR, libev will try to detect the availability of the |
3961 | monotonic clock option at both compile time and runtime. Otherwise no |
4513 | monotonic clock option at both compile time and runtime. Otherwise no |
3962 | use of the monotonic clock option will be attempted. If you enable this, |
4514 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
4074 | .IX Item "EV_USE_INOTIFY" |
4626 | .IX Item "EV_USE_INOTIFY" |
4075 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
4627 | If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
4076 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
4628 | interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
4077 | be detected at runtime. If undefined, it will be enabled if the headers |
4629 | be detected at runtime. If undefined, it will be enabled if the headers |
4078 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4630 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4631 | .IP "\s-1EV_NO_SMP\s0" 4 |
|
|
4632 | .IX Item "EV_NO_SMP" |
|
|
4633 | If defined to be \f(CW1\fR, libev will assume that memory is always coherent |
|
|
4634 | between threads, that is, threads can be used, but threads never run on |
|
|
4635 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4636 | and makes libev faster. |
|
|
4637 | .IP "\s-1EV_NO_THREADS\s0" 4 |
|
|
4638 | .IX Item "EV_NO_THREADS" |
|
|
4639 | If defined to be \f(CW1\fR, libev will assume that it will never be called |
|
|
4640 | from different threads, which is a stronger assumption than \f(CW\*(C`EV_NO_SMP\*(C'\fR, |
|
|
4641 | above. This reduces dependencies and makes libev faster. |
4079 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
4642 | .IP "\s-1EV_ATOMIC_T\s0" 4 |
4080 | .IX Item "EV_ATOMIC_T" |
4643 | .IX Item "EV_ATOMIC_T" |
4081 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
4644 | Libev requires an integer type (suitable for storing \f(CW0\fR or \f(CW1\fR) whose |
4082 | access is atomic with respect to other threads or signal contexts. No such |
4645 | access is atomic and serialised with respect to other threads or signal |
4083 | type is easily found in the C language, so you can provide your own type |
4646 | contexts. No such type is easily found in the C language, so you can |
4084 | that you know is safe for your purposes. It is used both for signal handler \*(L"locking\*(R" |
4647 | provide your own type that you know is safe for your purposes. It is used |
4085 | as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR watchers. |
4648 | both for signal handler \*(L"locking\*(R" as well as for signal and thread safety |
|
|
4649 | in \f(CW\*(C`ev_async\*(C'\fR watchers. |
4086 | .Sp |
4650 | .Sp |
4087 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
4651 | In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR |
4088 | (from \fIsignal.h\fR), which is usually good enough on most platforms. |
4652 | (from \fIsignal.h\fR), which is usually good enough on most platforms, |
|
|
4653 | although strictly speaking using a type that also implies a memory fence |
|
|
4654 | is required. |
4089 | .IP "\s-1EV_H\s0 (h)" 4 |
4655 | .IP "\s-1EV_H\s0 (h)" 4 |
4090 | .IX Item "EV_H (h)" |
4656 | .IX Item "EV_H (h)" |
4091 | The name of the \fIev.h\fR header file used to include it. The default if |
4657 | The name of the \fIev.h\fR header file used to include it. The default if |
4092 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
4658 | undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be |
4093 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
4659 | used to virtually rename the \fIev.h\fR header file in case of conflicts. |
… | |
… | |
4111 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
4677 | If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
4112 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
4678 | will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
4113 | additional independent event loops. Otherwise there will be no support |
4679 | additional independent event loops. Otherwise there will be no support |
4114 | for multiple event loops and there is no first event loop pointer |
4680 | for multiple event loops and there is no first event loop pointer |
4115 | argument. Instead, all functions act on the single default loop. |
4681 | argument. Instead, all functions act on the single default loop. |
|
|
4682 | .Sp |
|
|
4683 | Note that \f(CW\*(C`EV_DEFAULT\*(C'\fR and \f(CW\*(C`EV_DEFAULT_\*(C'\fR will no longer provide a |
|
|
4684 | default loop when multiplicity is switched off \- you always have to |
|
|
4685 | initialise the loop manually in this case. |
4116 | .IP "\s-1EV_MINPRI\s0" 4 |
4686 | .IP "\s-1EV_MINPRI\s0" 4 |
4117 | .IX Item "EV_MINPRI" |
4687 | .IX Item "EV_MINPRI" |
4118 | .PD 0 |
4688 | .PD 0 |
4119 | .IP "\s-1EV_MAXPRI\s0" 4 |
4689 | .IP "\s-1EV_MAXPRI\s0" 4 |
4120 | .IX Item "EV_MAXPRI" |
4690 | .IX Item "EV_MAXPRI" |
… | |
… | |
4156 | \& #define EV_CHILD_ENABLE 1 |
4726 | \& #define EV_CHILD_ENABLE 1 |
4157 | \& #define EV_ASYNC_ENABLE 1 |
4727 | \& #define EV_ASYNC_ENABLE 1 |
4158 | .Ve |
4728 | .Ve |
4159 | .Sp |
4729 | .Sp |
4160 | 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 |
4161 | values: |
4731 | values (by default, all of these are enabled): |
4162 | .RS 4 |
4732 | .RS 4 |
4163 | .ie n .IP "1 \- faster/larger code" 4 |
4733 | .ie n .IP "1 \- faster/larger code" 4 |
4164 | .el .IP "\f(CW1\fR \- faster/larger code" 4 |
4734 | .el .IP "\f(CW1\fR \- faster/larger code" 4 |
4165 | .IX Item "1 - faster/larger code" |
4735 | .IX Item "1 - faster/larger code" |
4166 | Use larger code to speed up some operations. |
4736 | Use larger code to speed up some operations. |
… | |
… | |
4169 | code size by roughly 30% on amd64). |
4739 | code size by roughly 30% on amd64). |
4170 | .Sp |
4740 | .Sp |
4171 | When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with |
4741 | When optimising for size, use of compiler flags such as \f(CW\*(C`\-Os\*(C'\fR with |
4172 | gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of |
4742 | gcc is recommended, as well as \f(CW\*(C`\-DNDEBUG\*(C'\fR, as libev contains a number of |
4173 | assertions. |
4743 | assertions. |
|
|
4744 | .Sp |
|
|
4745 | The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler |
|
|
4746 | (e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR). |
4174 | .ie n .IP "2 \- faster/larger data structures" 4 |
4747 | .ie n .IP "2 \- faster/larger data structures" 4 |
4175 | .el .IP "\f(CW2\fR \- faster/larger data structures" 4 |
4748 | .el .IP "\f(CW2\fR \- faster/larger data structures" 4 |
4176 | .IX Item "2 - faster/larger data structures" |
4749 | .IX Item "2 - faster/larger data structures" |
4177 | Replaces the small 2\-heap for timer management by a faster 4\-heap, larger |
4750 | Replaces the small 2\-heap for timer management by a faster 4\-heap, larger |
4178 | hash table sizes and so on. This will usually further increase code size |
4751 | hash table sizes and so on. This will usually further increase code size |
4179 | and can additionally have an effect on the size of data structures at |
4752 | and can additionally have an effect on the size of data structures at |
4180 | runtime. |
4753 | runtime. |
|
|
4754 | .Sp |
|
|
4755 | The default is off when \f(CW\*(C`_\|_OPTIMIZE_SIZE_\|_\*(C'\fR is defined by your compiler |
|
|
4756 | (e.g. gcc with \f(CW\*(C`\-Os\*(C'\fR). |
4181 | .ie n .IP "4 \- full \s-1API\s0 configuration" 4 |
4757 | .ie n .IP "4 \- full \s-1API\s0 configuration" 4 |
4182 | .el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4 |
4758 | .el .IP "\f(CW4\fR \- full \s-1API\s0 configuration" 4 |
4183 | .IX Item "4 - full API configuration" |
4759 | .IX Item "4 - full API configuration" |
4184 | This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and |
4760 | This enables priorities (sets \f(CW\*(C`EV_MAXPRI\*(C'\fR=2 and \f(CW\*(C`EV_MINPRI\*(C'\fR=\-2), and |
4185 | enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1). |
4761 | enables multiplicity (\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR=1). |
… | |
… | |
4217 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4793 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4218 | when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by |
4794 | when you use \f(CW\*(C`\-Wl,\-\-gc\-sections \-ffunction\-sections\*(C'\fR) functions unused by |
4219 | your program might be left out as well \- a binary starting a timer and an |
4795 | your program might be left out as well \- a binary starting a timer and an |
4220 | I/O watcher then might come out at only 5Kb. |
4796 | I/O watcher then might come out at only 5Kb. |
4221 | .RE |
4797 | .RE |
|
|
4798 | .IP "\s-1EV_API_STATIC\s0" 4 |
|
|
4799 | .IX Item "EV_API_STATIC" |
|
|
4800 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4801 | will have static linkage. This means that libev will not export any |
|
|
4802 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4803 | when you embed libev, only want to use libev functions in a single file, |
|
|
4804 | and do not want its identifiers to be visible. |
|
|
4805 | .Sp |
|
|
4806 | To use this, define \f(CW\*(C`EV_API_STATIC\*(C'\fR and include \fIev.c\fR in the file that |
|
|
4807 | wants to use libev. |
|
|
4808 | .Sp |
|
|
4809 | This option only works when libev is compiled with a C compiler, as \*(C+ |
|
|
4810 | doesn't support the required declaration syntax. |
4222 | .IP "\s-1EV_AVOID_STDIO\s0" 4 |
4811 | .IP "\s-1EV_AVOID_STDIO\s0" 4 |
4223 | .IX Item "EV_AVOID_STDIO" |
4812 | .IX Item "EV_AVOID_STDIO" |
4224 | If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio |
4813 | If this is set to \f(CW1\fR at compiletime, then libev will avoid using stdio |
4225 | functions (printf, scanf, perror etc.). This will increase the code size |
4814 | functions (printf, scanf, perror etc.). This will increase the code size |
4226 | somewhat, but if your program doesn't otherwise depend on stdio and your |
4815 | somewhat, but if your program doesn't otherwise depend on stdio and your |
… | |
… | |
4370 | .PP |
4959 | .PP |
4371 | .Vb 2 |
4960 | .Vb 2 |
4372 | \& #include "ev_cpp.h" |
4961 | \& #include "ev_cpp.h" |
4373 | \& #include "ev.c" |
4962 | \& #include "ev.c" |
4374 | .Ve |
4963 | .Ve |
4375 | .SH "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
4964 | .SH "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
4376 | .IX Header "INTERACTION WITH OTHER PROGRAMS OR LIBRARIES" |
4965 | .IX Header "INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT" |
4377 | .SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
4966 | .SS "\s-1THREADS\s0 \s-1AND\s0 \s-1COROUTINES\s0" |
4378 | .IX Subsection "THREADS AND COROUTINES" |
4967 | .IX Subsection "THREADS AND COROUTINES" |
4379 | \fI\s-1THREADS\s0\fR |
4968 | \fI\s-1THREADS\s0\fR |
4380 | .IX Subsection "THREADS" |
4969 | .IX Subsection "THREADS" |
4381 | .PP |
4970 | .PP |
… | |
… | |
4428 | An example use would be to communicate signals or other events that only |
5017 | An example use would be to communicate signals or other events that only |
4429 | work in the default loop by registering the signal watcher with the |
5018 | work in the default loop by registering the signal watcher with the |
4430 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
5019 | default loop and triggering an \f(CW\*(C`ev_async\*(C'\fR watcher from the default loop |
4431 | watcher callback into the event loop interested in the signal. |
5020 | watcher callback into the event loop interested in the signal. |
4432 | .PP |
5021 | .PP |
4433 | \s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0 |
5022 | See also \*(L"\s-1THREAD\s0 \s-1LOCKING\s0 \s-1EXAMPLE\s0\*(R". |
4434 | .IX Subsection "THREAD LOCKING EXAMPLE" |
|
|
4435 | .PP |
|
|
4436 | Here is a fictitious example of how to run an event loop in a different |
|
|
4437 | thread than where callbacks are being invoked and watchers are |
|
|
4438 | created/added/removed. |
|
|
4439 | .PP |
|
|
4440 | For a real-world example, see the \f(CW\*(C`EV::Loop::Async\*(C'\fR perl module, |
|
|
4441 | which uses exactly this technique (which is suited for many high-level |
|
|
4442 | languages). |
|
|
4443 | .PP |
|
|
4444 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4445 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4446 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4447 | .PP |
|
|
4448 | First, you need to associate some data with the event loop: |
|
|
4449 | .PP |
|
|
4450 | .Vb 6 |
|
|
4451 | \& typedef struct { |
|
|
4452 | \& mutex_t lock; /* global loop lock */ |
|
|
4453 | \& ev_async async_w; |
|
|
4454 | \& thread_t tid; |
|
|
4455 | \& cond_t invoke_cv; |
|
|
4456 | \& } userdata; |
|
|
4457 | \& |
|
|
4458 | \& void prepare_loop (EV_P) |
|
|
4459 | \& { |
|
|
4460 | \& // for simplicity, we use a static userdata struct. |
|
|
4461 | \& static userdata u; |
|
|
4462 | \& |
|
|
4463 | \& ev_async_init (&u\->async_w, async_cb); |
|
|
4464 | \& ev_async_start (EV_A_ &u\->async_w); |
|
|
4465 | \& |
|
|
4466 | \& pthread_mutex_init (&u\->lock, 0); |
|
|
4467 | \& pthread_cond_init (&u\->invoke_cv, 0); |
|
|
4468 | \& |
|
|
4469 | \& // now associate this with the loop |
|
|
4470 | \& ev_set_userdata (EV_A_ u); |
|
|
4471 | \& ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4472 | \& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4473 | \& |
|
|
4474 | \& // then create the thread running ev_loop |
|
|
4475 | \& pthread_create (&u\->tid, 0, l_run, EV_A); |
|
|
4476 | \& } |
|
|
4477 | .Ve |
|
|
4478 | .PP |
|
|
4479 | The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used |
|
|
4480 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4481 | that might have been added: |
|
|
4482 | .PP |
|
|
4483 | .Vb 5 |
|
|
4484 | \& static void |
|
|
4485 | \& async_cb (EV_P_ ev_async *w, int revents) |
|
|
4486 | \& { |
|
|
4487 | \& // just used for the side effects |
|
|
4488 | \& } |
|
|
4489 | .Ve |
|
|
4490 | .PP |
|
|
4491 | The \f(CW\*(C`l_release\*(C'\fR and \f(CW\*(C`l_acquire\*(C'\fR callbacks simply unlock/lock the mutex |
|
|
4492 | protecting the loop data, respectively. |
|
|
4493 | .PP |
|
|
4494 | .Vb 6 |
|
|
4495 | \& static void |
|
|
4496 | \& l_release (EV_P) |
|
|
4497 | \& { |
|
|
4498 | \& userdata *u = ev_userdata (EV_A); |
|
|
4499 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4500 | \& } |
|
|
4501 | \& |
|
|
4502 | \& static void |
|
|
4503 | \& l_acquire (EV_P) |
|
|
4504 | \& { |
|
|
4505 | \& userdata *u = ev_userdata (EV_A); |
|
|
4506 | \& pthread_mutex_lock (&u\->lock); |
|
|
4507 | \& } |
|
|
4508 | .Ve |
|
|
4509 | .PP |
|
|
4510 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4511 | into \f(CW\*(C`ev_run\*(C'\fR: |
|
|
4512 | .PP |
|
|
4513 | .Vb 4 |
|
|
4514 | \& void * |
|
|
4515 | \& l_run (void *thr_arg) |
|
|
4516 | \& { |
|
|
4517 | \& struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4518 | \& |
|
|
4519 | \& l_acquire (EV_A); |
|
|
4520 | \& pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4521 | \& ev_run (EV_A_ 0); |
|
|
4522 | \& l_release (EV_A); |
|
|
4523 | \& |
|
|
4524 | \& return 0; |
|
|
4525 | \& } |
|
|
4526 | .Ve |
|
|
4527 | .PP |
|
|
4528 | Instead of invoking all pending watchers, the \f(CW\*(C`l_invoke\*(C'\fR callback will |
|
|
4529 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4530 | writes? \f(CW\*(C`Async::Interrupt\*(C'\fR?) and then waits until all pending watchers |
|
|
4531 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4532 | and b) skipping inter-thread-communication when there are no pending |
|
|
4533 | watchers is very beneficial): |
|
|
4534 | .PP |
|
|
4535 | .Vb 4 |
|
|
4536 | \& static void |
|
|
4537 | \& l_invoke (EV_P) |
|
|
4538 | \& { |
|
|
4539 | \& userdata *u = ev_userdata (EV_A); |
|
|
4540 | \& |
|
|
4541 | \& while (ev_pending_count (EV_A)) |
|
|
4542 | \& { |
|
|
4543 | \& wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4544 | \& pthread_cond_wait (&u\->invoke_cv, &u\->lock); |
|
|
4545 | \& } |
|
|
4546 | \& } |
|
|
4547 | .Ve |
|
|
4548 | .PP |
|
|
4549 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4550 | will grab the lock, call \f(CW\*(C`ev_invoke_pending\*(C'\fR and then signal the loop |
|
|
4551 | thread to continue: |
|
|
4552 | .PP |
|
|
4553 | .Vb 4 |
|
|
4554 | \& static void |
|
|
4555 | \& real_invoke_pending (EV_P) |
|
|
4556 | \& { |
|
|
4557 | \& userdata *u = ev_userdata (EV_A); |
|
|
4558 | \& |
|
|
4559 | \& pthread_mutex_lock (&u\->lock); |
|
|
4560 | \& ev_invoke_pending (EV_A); |
|
|
4561 | \& pthread_cond_signal (&u\->invoke_cv); |
|
|
4562 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4563 | \& } |
|
|
4564 | .Ve |
|
|
4565 | .PP |
|
|
4566 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4567 | event loop, you will now have to lock: |
|
|
4568 | .PP |
|
|
4569 | .Vb 2 |
|
|
4570 | \& ev_timer timeout_watcher; |
|
|
4571 | \& userdata *u = ev_userdata (EV_A); |
|
|
4572 | \& |
|
|
4573 | \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4574 | \& |
|
|
4575 | \& pthread_mutex_lock (&u\->lock); |
|
|
4576 | \& ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4577 | \& ev_async_send (EV_A_ &u\->async_w); |
|
|
4578 | \& pthread_mutex_unlock (&u\->lock); |
|
|
4579 | .Ve |
|
|
4580 | .PP |
|
|
4581 | Note that sending the \f(CW\*(C`ev_async\*(C'\fR watcher is required because otherwise |
|
|
4582 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4583 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4584 | watchers in the next event loop iteration. |
|
|
4585 | .PP |
5023 | .PP |
4586 | \fI\s-1COROUTINES\s0\fR |
5024 | \fI\s-1COROUTINES\s0\fR |
4587 | .IX Subsection "COROUTINES" |
5025 | .IX Subsection "COROUTINES" |
4588 | .PP |
5026 | .PP |
4589 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
5027 | Libev is very accommodating to coroutines (\*(L"cooperative threads\*(R"): |
… | |
… | |
4754 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
5192 | requires, and its I/O model is fundamentally incompatible with the \s-1POSIX\s0 |
4755 | model. Libev still offers limited functionality on this platform in |
5193 | model. Libev still offers limited functionality on this platform in |
4756 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
5194 | the form of the \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR backend, and only supports socket |
4757 | descriptors. This only applies when using Win32 natively, not when using |
5195 | descriptors. This only applies when using Win32 natively, not when using |
4758 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5196 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4759 | as every compielr comes with a slightly differently broken/incompatible |
5197 | as every compiler comes with a slightly differently broken/incompatible |
4760 | environment. |
5198 | environment. |
4761 | .PP |
5199 | .PP |
4762 | Lifting these limitations would basically require the full |
5200 | Lifting these limitations would basically require the full |
4763 | re-implementation of the I/O system. If you are into this kind of thing, |
5201 | re-implementation of the I/O system. If you are into this kind of thing, |
4764 | then note that glib does exactly that for you in a very portable way (note |
5202 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4900 | .IX Item "double must hold a time value in seconds with enough accuracy" |
5338 | .IX Item "double must hold a time value in seconds with enough accuracy" |
4901 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
5339 | The type \f(CW\*(C`double\*(C'\fR is used to represent timestamps. It is required to |
4902 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5340 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4903 | good enough for at least into the year 4000 with millisecond accuracy |
5341 | good enough for at least into the year 4000 with millisecond accuracy |
4904 | (the design goal for libev). This requirement is overfulfilled by |
5342 | (the design goal for libev). This requirement is overfulfilled by |
4905 | implementations using \s-1IEEE\s0 754, which is basically all existing ones. With |
5343 | implementations using \s-1IEEE\s0 754, which is basically all existing ones. |
|
|
5344 | .Sp |
4906 | \&\s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least 2200. |
5345 | With \s-1IEEE\s0 754 doubles, you get microsecond accuracy until at least the |
|
|
5346 | year 2255 (and millisecond accuracy till the year 287396 \- by then, libev |
|
|
5347 | is either obsolete or somebody patched it to use \f(CW\*(C`long double\*(C'\fR or |
|
|
5348 | something like that, just kidding). |
4907 | .PP |
5349 | .PP |
4908 | If you know of other additional requirements drop me a note. |
5350 | If you know of other additional requirements drop me a note. |
4909 | .SH "ALGORITHMIC COMPLEXITIES" |
5351 | .SH "ALGORITHMIC COMPLEXITIES" |
4910 | .IX Header "ALGORITHMIC COMPLEXITIES" |
5352 | .IX Header "ALGORITHMIC COMPLEXITIES" |
4911 | In this section the complexities of (many of) the algorithms used inside |
5353 | In this section the complexities of (many of) the algorithms used inside |
… | |
… | |
4965 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
5407 | .IX Item "Processing ev_async_send: O(number_of_async_watchers)" |
4966 | .IP "Processing signals: O(max_signal_number)" 4 |
5408 | .IP "Processing signals: O(max_signal_number)" 4 |
4967 | .IX Item "Processing signals: O(max_signal_number)" |
5409 | .IX Item "Processing signals: O(max_signal_number)" |
4968 | .PD |
5410 | .PD |
4969 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
5411 | Sending involves a system call \fIiff\fR there were no other \f(CW\*(C`ev_async_send\*(C'\fR |
4970 | calls in the current loop iteration. Checking for async and signal events |
5412 | calls in the current loop iteration and the loop is currently |
|
|
5413 | blocked. Checking for async and signal events involves iterating over all |
4971 | involves iterating over all running async watchers or all signal numbers. |
5414 | running async watchers or all signal numbers. |
4972 | .SH "PORTING FROM LIBEV 3.X TO 4.X" |
5415 | .SH "PORTING FROM LIBEV 3.X TO 4.X" |
4973 | .IX Header "PORTING FROM LIBEV 3.X TO 4.X" |
5416 | .IX Header "PORTING FROM LIBEV 3.X TO 4.X" |
4974 | The major version 4 introduced some incompatible changes to the \s-1API\s0. |
5417 | The major version 4 introduced some incompatible changes to the \s-1API\s0. |
4975 | .PP |
5418 | .PP |
4976 | At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions |
5419 | At the moment, the \f(CW\*(C`ev.h\*(C'\fR header file provides compatibility definitions |
… | |
… | |
5073 | .IX Item "real time" |
5516 | .IX Item "real time" |
5074 | The physical time that is observed. It is apparently strictly monotonic :) |
5517 | The physical time that is observed. It is apparently strictly monotonic :) |
5075 | .IP "wall-clock time" 4 |
5518 | .IP "wall-clock time" 4 |
5076 | .IX Item "wall-clock time" |
5519 | .IX Item "wall-clock time" |
5077 | The time and date as shown on clocks. Unlike real time, it can actually |
5520 | The time and date as shown on clocks. Unlike real time, it can actually |
5078 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5521 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5079 | clock. |
5522 | clock. |
5080 | .IP "watcher" 4 |
5523 | .IP "watcher" 4 |
5081 | .IX Item "watcher" |
5524 | .IX Item "watcher" |
5082 | A data structure that describes interest in certain events. Watchers need |
5525 | A data structure that describes interest in certain events. Watchers need |
5083 | to be started (attached to an event loop) before they can receive events. |
5526 | to be started (attached to an event loop) before they can receive events. |
5084 | .SH "AUTHOR" |
5527 | .SH "AUTHOR" |
5085 | .IX Header "AUTHOR" |
5528 | .IX Header "AUTHOR" |
5086 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5529 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5087 | Magnusson and Emanuele Giaquinta. |
5530 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |