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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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82 | |
84 | |
83 | =head1 WHAT TO READ WHEN IN A HURRY |
85 | =head1 WHAT TO READ WHEN IN A HURRY |
84 | |
86 | |
85 | This manual tries to be very detailed, but unfortunately, this also makes |
87 | This manual tries to be very detailed, but unfortunately, this also makes |
86 | it very long. If you just want to know the basics of libev, I suggest |
88 | it very long. If you just want to know the basics of libev, I suggest |
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
89 | C<ev_timer> sections in L<WATCHER TYPES>. |
91 | C<ev_timer> sections in L</WATCHER TYPES>. |
90 | |
92 | |
91 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
92 | |
94 | |
93 | Libev is an event loop: you register interest in certain events (such as a |
95 | Libev is an event loop: you register interest in certain events (such as a |
94 | file descriptor being readable or a timeout occurring), and it will manage |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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103 | details of the event, and then hand it over to libev by I<starting> the |
105 | details of the event, and then hand it over to libev by I<starting> the |
104 | watcher. |
106 | watcher. |
105 | |
107 | |
106 | =head2 FEATURES |
108 | =head2 FEATURES |
107 | |
109 | |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
110 | Libev supports C<select>, C<poll>, the Linux-specific aio and C<epoll> |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
111 | interfaces, the BSD-specific C<kqueue> and the Solaris-specific event port |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
112 | mechanisms for file descriptor events (C<ev_io>), the Linux C<inotify> |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
113 | interface (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
114 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
115 | timers (C<ev_timer>), absolute timers with customised rescheduling |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
116 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
115 | change events (C<ev_child>), and event watchers dealing with the event |
117 | change events (C<ev_child>), and event watchers dealing with the event |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
118 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
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157 | When libev detects a usage error such as a negative timer interval, then |
159 | When libev detects a usage error such as a negative timer interval, then |
158 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
160 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
159 | so C<NDEBUG> will disable this checking): these are programming errors in |
161 | so C<NDEBUG> will disable this checking): these are programming errors in |
160 | the libev caller and need to be fixed there. |
162 | the libev caller and need to be fixed there. |
161 | |
163 | |
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164 | Via the C<EV_FREQUENT> macro you can compile in and/or enable extensive |
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165 | consistency checking code inside libev that can be used to check for |
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166 | internal inconsistencies, suually caused by application bugs. |
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167 | |
162 | Libev also has a few internal error-checking C<assert>ions, and also has |
168 | Libev also has a few internal error-checking C<assert>ions. These do not |
163 | extensive consistency checking code. These do not trigger under normal |
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164 | circumstances, as they indicate either a bug in libev or worse. |
169 | trigger under normal circumstances, as they indicate either a bug in libev |
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170 | or worse. |
165 | |
171 | |
166 | |
172 | |
167 | =head1 GLOBAL FUNCTIONS |
173 | =head1 GLOBAL FUNCTIONS |
168 | |
174 | |
169 | These functions can be called anytime, even before initialising the |
175 | These functions can be called anytime, even before initialising the |
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174 | =item ev_tstamp ev_time () |
180 | =item ev_tstamp ev_time () |
175 | |
181 | |
176 | Returns the current time as libev would use it. Please note that the |
182 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
183 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
184 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
185 | C<ev_now_update> and C<ev_now>. |
180 | |
186 | |
181 | =item ev_sleep (ev_tstamp interval) |
187 | =item ev_sleep (ev_tstamp interval) |
182 | |
188 | |
183 | Sleep for the given interval: The current thread will be blocked |
189 | Sleep for the given interval: The current thread will be blocked |
184 | until either it is interrupted or the given time interval has |
190 | until either it is interrupted or the given time interval has |
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247 | the current system, you would need to look at C<ev_embeddable_backends () |
253 | the current system, you would need to look at C<ev_embeddable_backends () |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
254 | & ev_supported_backends ()>, likewise for recommended ones. |
249 | |
255 | |
250 | See the description of C<ev_embed> watchers for more info. |
256 | See the description of C<ev_embed> watchers for more info. |
251 | |
257 | |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
258 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
253 | |
259 | |
254 | Sets the allocation function to use (the prototype is similar - the |
260 | Sets the allocation function to use (the prototype is similar - the |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
261 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
256 | used to allocate and free memory (no surprises here). If it returns zero |
262 | used to allocate and free memory (no surprises here). If it returns zero |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
263 | when memory needs to be allocated (C<size != 0>), the library might abort |
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263 | |
269 | |
264 | You could override this function in high-availability programs to, say, |
270 | You could override this function in high-availability programs to, say, |
265 | free some memory if it cannot allocate memory, to use a special allocator, |
271 | free some memory if it cannot allocate memory, to use a special allocator, |
266 | or even to sleep a while and retry until some memory is available. |
272 | or even to sleep a while and retry until some memory is available. |
267 | |
273 | |
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274 | Example: The following is the C<realloc> function that libev itself uses |
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275 | which should work with C<realloc> and C<free> functions of all kinds and |
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276 | is probably a good basis for your own implementation. |
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277 | |
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278 | static void * |
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279 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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280 | { |
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281 | if (size) |
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282 | return realloc (ptr, size); |
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283 | |
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284 | free (ptr); |
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285 | return 0; |
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286 | } |
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287 | |
268 | Example: Replace the libev allocator with one that waits a bit and then |
288 | Example: Replace the libev allocator with one that waits a bit and then |
269 | retries (example requires a standards-compliant C<realloc>). |
289 | retries. |
270 | |
290 | |
271 | static void * |
291 | static void * |
272 | persistent_realloc (void *ptr, size_t size) |
292 | persistent_realloc (void *ptr, size_t size) |
273 | { |
293 | { |
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294 | if (!size) |
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295 | { |
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296 | free (ptr); |
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297 | return 0; |
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298 | } |
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299 | |
274 | for (;;) |
300 | for (;;) |
275 | { |
301 | { |
276 | void *newptr = realloc (ptr, size); |
302 | void *newptr = realloc (ptr, size); |
277 | |
303 | |
278 | if (newptr) |
304 | if (newptr) |
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283 | } |
309 | } |
284 | |
310 | |
285 | ... |
311 | ... |
286 | ev_set_allocator (persistent_realloc); |
312 | ev_set_allocator (persistent_realloc); |
287 | |
313 | |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
314 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
289 | |
315 | |
290 | Set the callback function to call on a retryable system call error (such |
316 | Set the callback function to call on a retryable system call error (such |
291 | as failed select, poll, epoll_wait). The message is a printable string |
317 | as failed select, poll, epoll_wait). The message is a printable string |
292 | indicating the system call or subsystem causing the problem. If this |
318 | indicating the system call or subsystem causing the problem. If this |
293 | callback is set, then libev will expect it to remedy the situation, no |
319 | callback is set, then libev will expect it to remedy the situation, no |
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396 | |
422 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
423 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
424 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
425 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
426 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
427 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
428 | around bugs, or to make libev threadsafe (accessing environment variables |
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429 | cannot be done in a threadsafe way, but usually it works if no other |
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430 | thread modifies them). |
403 | |
431 | |
404 | =item C<EVFLAG_FORKCHECK> |
432 | =item C<EVFLAG_FORKCHECK> |
405 | |
433 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
434 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
435 | make libev check for a fork in each iteration by enabling this flag. |
408 | |
436 | |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
437 | This works by calling C<getpid ()> on every iteration of the loop, |
410 | and thus this might slow down your event loop if you do a lot of loop |
438 | and thus this might slow down your event loop if you do a lot of loop |
411 | iterations and little real work, but is usually not noticeable (on my |
439 | iterations and little real work, but is usually not noticeable (on my |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
440 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
441 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
414 | C<pthread_atfork> which is even faster). |
442 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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443 | versions 2.25 apparently removed the C<getpid> optimisation again). |
415 | |
444 | |
416 | The big advantage of this flag is that you can forget about fork (and |
445 | The big advantage of this flag is that you can forget about fork (and |
417 | forget about forgetting to tell libev about forking) when you use this |
446 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
447 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
448 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
449 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
450 | environment variable. |
422 | |
451 | |
423 | =item C<EVFLAG_NOINOTIFY> |
452 | =item C<EVFLAG_NOINOTIFY> |
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441 | example) that can't properly initialise their signal masks. |
470 | example) that can't properly initialise their signal masks. |
442 | |
471 | |
443 | =item C<EVFLAG_NOSIGMASK> |
472 | =item C<EVFLAG_NOSIGMASK> |
444 | |
473 | |
445 | When this flag is specified, then libev will avoid to modify the signal |
474 | When this flag is specified, then libev will avoid to modify the signal |
446 | mask. Specifically, this means you ahve to make sure signals are unblocked |
475 | mask. Specifically, this means you have to make sure signals are unblocked |
447 | when you want to receive them. |
476 | when you want to receive them. |
448 | |
477 | |
449 | This behaviour is useful when you want to do your own signal handling, or |
478 | This behaviour is useful when you want to do your own signal handling, or |
450 | want to handle signals only in specific threads and want to avoid libev |
479 | want to handle signals only in specific threads and want to avoid libev |
451 | unblocking the signals. |
480 | unblocking the signals. |
452 | |
481 | |
453 | It's also required by POSIX in a threaded program, as libev calls |
482 | It's also required by POSIX in a threaded program, as libev calls |
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
483 | C<sigprocmask>, whose behaviour is officially unspecified. |
455 | |
484 | |
456 | This flag's behaviour will become the default in future versions of libev. |
485 | =item C<EVFLAG_NOTIMERFD> |
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486 | |
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487 | When this flag is specified, the libev will avoid using a C<timerfd> to |
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488 | detect time jumps. It will still be able to detect time jumps, but takes |
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489 | longer and has a lower accuracy in doing so, but saves a file descriptor |
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490 | per loop. |
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491 | |
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492 | The current implementation only tries to use a C<timerfd> when the first |
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493 | C<ev_periodic> watcher is started and falls back on other methods if it |
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494 | cannot be created, but this behaviour might change in the future. |
457 | |
495 | |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
496 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
459 | |
497 | |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
498 | This is your standard select(2) backend. Not I<completely> standard, as |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
499 | libev tries to roll its own fd_set with no limits on the number of fds, |
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486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
524 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
525 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
488 | |
526 | |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
527 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
490 | |
528 | |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
529 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
492 | kernels). |
530 | kernels). |
493 | |
531 | |
494 | For few fds, this backend is a bit little slower than poll and select, but |
532 | For few fds, this backend is a bit little slower than poll and select, but |
495 | it scales phenomenally better. While poll and select usually scale like |
533 | it scales phenomenally better. While poll and select usually scale like |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
534 | O(total_fds) where total_fds is the total number of fds (or the highest |
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512 | totally I<different> file descriptors (even already closed ones, so |
550 | totally I<different> file descriptors (even already closed ones, so |
513 | one cannot even remove them from the set) than registered in the set |
551 | one cannot even remove them from the set) than registered in the set |
514 | (especially on SMP systems). Libev tries to counter these spurious |
552 | (especially on SMP systems). Libev tries to counter these spurious |
515 | notifications by employing an additional generation counter and comparing |
553 | notifications by employing an additional generation counter and comparing |
516 | that against the events to filter out spurious ones, recreating the set |
554 | that against the events to filter out spurious ones, recreating the set |
517 | when required. Epoll also errornously rounds down timeouts, but gives you |
555 | when required. Epoll also erroneously rounds down timeouts, but gives you |
518 | no way to know when and by how much, so sometimes you have to busy-wait |
556 | no way to know when and by how much, so sometimes you have to busy-wait |
519 | because epoll returns immediately despite a nonzero timeout. And last |
557 | because epoll returns immediately despite a nonzero timeout. And last |
520 | not least, it also refuses to work with some file descriptors which work |
558 | not least, it also refuses to work with some file descriptors which work |
521 | perfectly fine with C<select> (files, many character devices...). |
559 | perfectly fine with C<select> (files, many character devices...). |
522 | |
560 | |
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542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
580 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
543 | faster than epoll for maybe up to a hundred file descriptors, depending on |
581 | faster than epoll for maybe up to a hundred file descriptors, depending on |
544 | the usage. So sad. |
582 | the usage. So sad. |
545 | |
583 | |
546 | While nominally embeddable in other event loops, this feature is broken in |
584 | While nominally embeddable in other event loops, this feature is broken in |
547 | all kernel versions tested so far. |
585 | a lot of kernel revisions, but probably(!) works in current versions. |
548 | |
586 | |
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
587 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
550 | C<EVBACKEND_POLL>. |
588 | C<EVBACKEND_POLL>. |
551 | |
589 | |
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590 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
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591 | |
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592 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
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593 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
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594 | only tries to use it in 4.19+). |
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595 | |
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596 | This is another Linux train wreck of an event interface. |
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597 | |
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598 | If this backend works for you (as of this writing, it was very |
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599 | experimental), it is the best event interface available on Linux and might |
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600 | be well worth enabling it - if it isn't available in your kernel this will |
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601 | be detected and this backend will be skipped. |
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602 | |
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603 | This backend can batch oneshot requests and supports a user-space ring |
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604 | buffer to receive events. It also doesn't suffer from most of the design |
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605 | problems of epoll (such as not being able to remove event sources from |
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606 | the epoll set), and generally sounds too good to be true. Because, this |
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607 | being the Linux kernel, of course it suffers from a whole new set of |
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608 | limitations, forcing you to fall back to epoll, inheriting all its design |
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609 | issues. |
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610 | |
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611 | For one, it is not easily embeddable (but probably could be done using |
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612 | an event fd at some extra overhead). It also is subject to a system wide |
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613 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
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614 | requests are left, this backend will be skipped during initialisation, and |
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615 | will switch to epoll when the loop is active. |
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616 | |
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617 | Most problematic in practice, however, is that not all file descriptors |
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618 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
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619 | files, F</dev/null> and many others are supported, but ttys do not work |
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620 | properly (a known bug that the kernel developers don't care about, see |
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621 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
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622 | (yet?) a generic event polling interface. |
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623 | |
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624 | Overall, it seems the Linux developers just don't want it to have a |
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625 | generic event handling mechanism other than C<select> or C<poll>. |
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626 | |
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627 | To work around all these problem, the current version of libev uses its |
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628 | epoll backend as a fallback for file descriptor types that do not work. Or |
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629 | falls back completely to epoll if the kernel acts up. |
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630 | |
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631 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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632 | C<EVBACKEND_POLL>. |
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633 | |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
634 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
553 | |
635 | |
554 | Kqueue deserves special mention, as at the time of this writing, it |
636 | Kqueue deserves special mention, as at the time this backend was |
555 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
637 | implemented, it was broken on all BSDs except NetBSD (usually it doesn't |
556 | with anything but sockets and pipes, except on Darwin, where of course |
638 | work reliably with anything but sockets and pipes, except on Darwin, |
557 | it's completely useless). Unlike epoll, however, whose brokenness |
639 | where of course it's completely useless). Unlike epoll, however, whose |
558 | is by design, these kqueue bugs can (and eventually will) be fixed |
640 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
559 | without API changes to existing programs. For this reason it's not being |
641 | fixed without API changes to existing programs. For this reason it's not |
560 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
642 | being "auto-detected" on all platforms unless you explicitly specify it |
561 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
643 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
562 | system like NetBSD. |
644 | known-to-be-good (-enough) system like NetBSD. |
563 | |
645 | |
564 | You still can embed kqueue into a normal poll or select backend and use it |
646 | You still can embed kqueue into a normal poll or select backend and use it |
565 | only for sockets (after having made sure that sockets work with kqueue on |
647 | only for sockets (after having made sure that sockets work with kqueue on |
566 | the target platform). See C<ev_embed> watchers for more info. |
648 | the target platform). See C<ev_embed> watchers for more info. |
567 | |
649 | |
568 | It scales in the same way as the epoll backend, but the interface to the |
650 | It scales in the same way as the epoll backend, but the interface to the |
569 | kernel is more efficient (which says nothing about its actual speed, of |
651 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
652 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
653 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (but |
654 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
655 | might have to leak fds on fork, but it's more sane than epoll) and it |
574 | cases |
656 | drops fds silently in similarly hard-to-detect cases. |
575 | |
657 | |
576 | This backend usually performs well under most conditions. |
658 | This backend usually performs well under most conditions. |
577 | |
659 | |
578 | While nominally embeddable in other event loops, this doesn't work |
660 | While nominally embeddable in other event loops, this doesn't work |
579 | everywhere, so you might need to test for this. And since it is broken |
661 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
690 | among the OS-specific backends (I vastly prefer correctness over speed |
609 | hacks). |
691 | hacks). |
610 | |
692 | |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
693 | On the negative side, the interface is I<bizarre> - so bizarre that |
612 | even sun itself gets it wrong in their code examples: The event polling |
694 | even sun itself gets it wrong in their code examples: The event polling |
613 | function sometimes returning events to the caller even though an error |
695 | function sometimes returns events to the caller even though an error |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
696 | occurred, but with no indication whether it has done so or not (yes, it's |
615 | even documented that way) - deadly for edge-triggered interfaces where |
697 | even documented that way) - deadly for edge-triggered interfaces where you |
616 | you absolutely have to know whether an event occurred or not because you |
698 | absolutely have to know whether an event occurred or not because you have |
617 | have to re-arm the watcher. |
699 | to re-arm the watcher. |
618 | |
700 | |
619 | Fortunately libev seems to be able to work around these idiocies. |
701 | Fortunately libev seems to be able to work around these idiocies. |
620 | |
702 | |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
703 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | C<EVBACKEND_POLL>. |
704 | C<EVBACKEND_POLL>. |
… | |
… | |
652 | |
734 | |
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
735 | Example: Use whatever libev has to offer, but make sure that kqueue is |
654 | used if available. |
736 | used if available. |
655 | |
737 | |
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
738 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
739 | |
|
|
740 | Example: Similarly, on linux, you mgiht want to take advantage of the |
|
|
741 | linux aio backend if possible, but fall back to something else if that |
|
|
742 | isn't available. |
|
|
743 | |
|
|
744 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
657 | |
745 | |
658 | =item ev_loop_destroy (loop) |
746 | =item ev_loop_destroy (loop) |
659 | |
747 | |
660 | Destroys an event loop object (frees all memory and kernel state |
748 | Destroys an event loop object (frees all memory and kernel state |
661 | etc.). None of the active event watchers will be stopped in the normal |
749 | etc.). None of the active event watchers will be stopped in the normal |
… | |
… | |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
766 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
767 | and C<ev_loop_destroy>. |
680 | |
768 | |
681 | =item ev_loop_fork (loop) |
769 | =item ev_loop_fork (loop) |
682 | |
770 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
771 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
772 | to reinitialise the kernel state for backends that have one. Despite |
685 | name, you can call it anytime, but it makes most sense after forking, in |
773 | the name, you can call it anytime you are allowed to start or stop |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
774 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
775 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
776 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
777 | |
|
|
778 | In addition, if you want to reuse a loop (via this function or |
|
|
779 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
780 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
781 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
782 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
783 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
784 | during fork. |
693 | |
785 | |
694 | On the other hand, you only need to call this function in the child |
786 | On the other hand, you only need to call this function in the child |
… | |
… | |
764 | |
856 | |
765 | This function is rarely useful, but when some event callback runs for a |
857 | This function is rarely useful, but when some event callback runs for a |
766 | very long time without entering the event loop, updating libev's idea of |
858 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
859 | the current time is a good idea. |
768 | |
860 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
861 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
862 | |
771 | =item ev_suspend (loop) |
863 | =item ev_suspend (loop) |
772 | |
864 | |
773 | =item ev_resume (loop) |
865 | =item ev_resume (loop) |
774 | |
866 | |
… | |
… | |
792 | without a previous call to C<ev_suspend>. |
884 | without a previous call to C<ev_suspend>. |
793 | |
885 | |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
886 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
795 | event loop time (see C<ev_now_update>). |
887 | event loop time (see C<ev_now_update>). |
796 | |
888 | |
797 | =item ev_run (loop, int flags) |
889 | =item bool ev_run (loop, int flags) |
798 | |
890 | |
799 | Finally, this is it, the event handler. This function usually is called |
891 | Finally, this is it, the event handler. This function usually is called |
800 | after you have initialised all your watchers and you want to start |
892 | after you have initialised all your watchers and you want to start |
801 | handling events. It will ask the operating system for any new events, call |
893 | handling events. It will ask the operating system for any new events, call |
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
894 | the watcher callbacks, and then repeat the whole process indefinitely: This |
803 | is why event loops are called I<loops>. |
895 | is why event loops are called I<loops>. |
804 | |
896 | |
805 | If the flags argument is specified as C<0>, it will keep handling events |
897 | If the flags argument is specified as C<0>, it will keep handling events |
806 | until either no event watchers are active anymore or C<ev_break> was |
898 | until either no event watchers are active anymore or C<ev_break> was |
807 | called. |
899 | called. |
|
|
900 | |
|
|
901 | The return value is false if there are no more active watchers (which |
|
|
902 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
903 | (which usually means " you should call C<ev_run> again"). |
808 | |
904 | |
809 | Please note that an explicit C<ev_break> is usually better than |
905 | Please note that an explicit C<ev_break> is usually better than |
810 | relying on all watchers to be stopped when deciding when a program has |
906 | relying on all watchers to be stopped when deciding when a program has |
811 | finished (especially in interactive programs), but having a program |
907 | finished (especially in interactive programs), but having a program |
812 | that automatically loops as long as it has to and no longer by virtue |
908 | that automatically loops as long as it has to and no longer by virtue |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
909 | of relying on its watchers stopping correctly, that is truly a thing of |
814 | beauty. |
910 | beauty. |
815 | |
911 | |
816 | This function is also I<mostly> exception-safe - you can break out of |
912 | This function is I<mostly> exception-safe - you can break out of a |
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
913 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
914 | exception and so on. This does not decrement the C<ev_depth> value, nor |
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
915 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
820 | |
916 | |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
917 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
822 | those events and any already outstanding ones, but will not wait and |
918 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
952 | overhead for the actual polling but can deliver many events at once. |
1048 | overhead for the actual polling but can deliver many events at once. |
953 | |
1049 | |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
1050 | By setting a higher I<io collect interval> you allow libev to spend more |
955 | time collecting I/O events, so you can handle more events per iteration, |
1051 | time collecting I/O events, so you can handle more events per iteration, |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1052 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
957 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
1053 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
1054 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
959 | sleep time ensures that libev will not poll for I/O events more often then |
1055 | sleep time ensures that libev will not poll for I/O events more often then |
960 | once per this interval, on average. |
1056 | once per this interval, on average (as long as the host time resolution is |
|
|
1057 | good enough). |
961 | |
1058 | |
962 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1059 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | to spend more time collecting timeouts, at the expense of increased |
1060 | to spend more time collecting timeouts, at the expense of increased |
964 | latency/jitter/inexactness (the watcher callback will be called |
1061 | latency/jitter/inexactness (the watcher callback will be called |
965 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
1062 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
1011 | invoke the actual watchers inside another context (another thread etc.). |
1108 | invoke the actual watchers inside another context (another thread etc.). |
1012 | |
1109 | |
1013 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1110 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1014 | callback. |
1111 | callback. |
1015 | |
1112 | |
1016 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1113 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1017 | |
1114 | |
1018 | Sometimes you want to share the same loop between multiple threads. This |
1115 | Sometimes you want to share the same loop between multiple threads. This |
1019 | can be done relatively simply by putting mutex_lock/unlock calls around |
1116 | can be done relatively simply by putting mutex_lock/unlock calls around |
1020 | each call to a libev function. |
1117 | each call to a libev function. |
1021 | |
1118 | |
1022 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1119 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1023 | to wait for it to return. One way around this is to wake up the event |
1120 | to wait for it to return. One way around this is to wake up the event |
1024 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1121 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1025 | I<release> and I<acquire> callbacks on the loop. |
1122 | I<release> and I<acquire> callbacks on the loop. |
1026 | |
1123 | |
1027 | When set, then C<release> will be called just before the thread is |
1124 | When set, then C<release> will be called just before the thread is |
1028 | suspended waiting for new events, and C<acquire> is called just |
1125 | suspended waiting for new events, and C<acquire> is called just |
1029 | afterwards. |
1126 | afterwards. |
… | |
… | |
1121 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
1218 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
1122 | *) >>), and you can stop watching for events at any time by calling the |
1219 | *) >>), and you can stop watching for events at any time by calling the |
1123 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
1220 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
1124 | |
1221 | |
1125 | As long as your watcher is active (has been started but not stopped) you |
1222 | As long as your watcher is active (has been started but not stopped) you |
1126 | must not touch the values stored in it. Most specifically you must never |
1223 | must not touch the values stored in it except when explicitly documented |
1127 | reinitialise it or call its C<ev_TYPE_set> macro. |
1224 | otherwise. Most specifically you must never reinitialise it or call its |
|
|
1225 | C<ev_TYPE_set> macro. |
1128 | |
1226 | |
1129 | Each and every callback receives the event loop pointer as first, the |
1227 | Each and every callback receives the event loop pointer as first, the |
1130 | registered watcher structure as second, and a bitset of received events as |
1228 | registered watcher structure as second, and a bitset of received events as |
1131 | third argument. |
1229 | third argument. |
1132 | |
1230 | |
… | |
… | |
1169 | |
1267 | |
1170 | =item C<EV_PREPARE> |
1268 | =item C<EV_PREPARE> |
1171 | |
1269 | |
1172 | =item C<EV_CHECK> |
1270 | =item C<EV_CHECK> |
1173 | |
1271 | |
1174 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1272 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1175 | to gather new events, and all C<ev_check> watchers are invoked just after |
1273 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1176 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1274 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1275 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1276 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1277 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1278 | or lower priority within an event loop iteration. |
|
|
1279 | |
1177 | received events. Callbacks of both watcher types can start and stop as |
1280 | Callbacks of both watcher types can start and stop as many watchers as |
1178 | many watchers as they want, and all of them will be taken into account |
1281 | they want, and all of them will be taken into account (for example, a |
1179 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1282 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1180 | C<ev_run> from blocking). |
1283 | blocking). |
1181 | |
1284 | |
1182 | =item C<EV_EMBED> |
1285 | =item C<EV_EMBED> |
1183 | |
1286 | |
1184 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1287 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1185 | |
1288 | |
… | |
… | |
1308 | |
1411 | |
1309 | =item callback ev_cb (ev_TYPE *watcher) |
1412 | =item callback ev_cb (ev_TYPE *watcher) |
1310 | |
1413 | |
1311 | Returns the callback currently set on the watcher. |
1414 | Returns the callback currently set on the watcher. |
1312 | |
1415 | |
1313 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1416 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1314 | |
1417 | |
1315 | Change the callback. You can change the callback at virtually any time |
1418 | Change the callback. You can change the callback at virtually any time |
1316 | (modulo threads). |
1419 | (modulo threads). |
1317 | |
1420 | |
1318 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1421 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1336 | or might not have been clamped to the valid range. |
1439 | or might not have been clamped to the valid range. |
1337 | |
1440 | |
1338 | The default priority used by watchers when no priority has been set is |
1441 | The default priority used by watchers when no priority has been set is |
1339 | always C<0>, which is supposed to not be too high and not be too low :). |
1442 | always C<0>, which is supposed to not be too high and not be too low :). |
1340 | |
1443 | |
1341 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1444 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1342 | priorities. |
1445 | priorities. |
1343 | |
1446 | |
1344 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1447 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1345 | |
1448 | |
1346 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1449 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1371 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1474 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1372 | functions that do not need a watcher. |
1475 | functions that do not need a watcher. |
1373 | |
1476 | |
1374 | =back |
1477 | =back |
1375 | |
1478 | |
1376 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1479 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1377 | OWN COMPOSITE WATCHERS> idioms. |
1480 | OWN COMPOSITE WATCHERS> idioms. |
1378 | |
1481 | |
1379 | =head2 WATCHER STATES |
1482 | =head2 WATCHER STATES |
1380 | |
1483 | |
1381 | There are various watcher states mentioned throughout this manual - |
1484 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1383 | transition between them will be described in more detail - and while these |
1486 | transition between them will be described in more detail - and while these |
1384 | rules might look complicated, they usually do "the right thing". |
1487 | rules might look complicated, they usually do "the right thing". |
1385 | |
1488 | |
1386 | =over 4 |
1489 | =over 4 |
1387 | |
1490 | |
1388 | =item initialiased |
1491 | =item initialised |
1389 | |
1492 | |
1390 | Before a watcher can be registered with the event looop it has to be |
1493 | Before a watcher can be registered with the event loop it has to be |
1391 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1494 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1495 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | |
1496 | |
1394 | In this state it is simply some block of memory that is suitable for |
1497 | In this state it is simply some block of memory that is suitable for |
1395 | use in an event loop. It can be moved around, freed, reused etc. at |
1498 | use in an event loop. It can be moved around, freed, reused etc. at |
… | |
… | |
1442 | |
1545 | |
1443 | Many event loops support I<watcher priorities>, which are usually small |
1546 | Many event loops support I<watcher priorities>, which are usually small |
1444 | integers that influence the ordering of event callback invocation |
1547 | integers that influence the ordering of event callback invocation |
1445 | between watchers in some way, all else being equal. |
1548 | between watchers in some way, all else being equal. |
1446 | |
1549 | |
1447 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
1550 | In libev, watcher priorities can be set using C<ev_set_priority>. See its |
1448 | description for the more technical details such as the actual priority |
1551 | description for the more technical details such as the actual priority |
1449 | range. |
1552 | range. |
1450 | |
1553 | |
1451 | There are two common ways how these these priorities are being interpreted |
1554 | There are two common ways how these these priorities are being interpreted |
1452 | by event loops: |
1555 | by event loops: |
… | |
… | |
1546 | |
1649 | |
1547 | This section describes each watcher in detail, but will not repeat |
1650 | This section describes each watcher in detail, but will not repeat |
1548 | information given in the last section. Any initialisation/set macros, |
1651 | information given in the last section. Any initialisation/set macros, |
1549 | functions and members specific to the watcher type are explained. |
1652 | functions and members specific to the watcher type are explained. |
1550 | |
1653 | |
1551 | Members are additionally marked with either I<[read-only]>, meaning that, |
1654 | Most members are additionally marked with either I<[read-only]>, meaning |
1552 | while the watcher is active, you can look at the member and expect some |
1655 | that, while the watcher is active, you can look at the member and expect |
1553 | sensible content, but you must not modify it (you can modify it while the |
1656 | some sensible content, but you must not modify it (you can modify it while |
1554 | watcher is stopped to your hearts content), or I<[read-write]>, which |
1657 | the watcher is stopped to your hearts content), or I<[read-write]>, which |
1555 | means you can expect it to have some sensible content while the watcher |
1658 | means you can expect it to have some sensible content while the watcher |
1556 | is active, but you can also modify it. Modifying it may not do something |
1659 | is active, but you can also modify it. Modifying it may not do something |
1557 | sensible or take immediate effect (or do anything at all), but libev will |
1660 | sensible or take immediate effect (or do anything at all), but libev will |
1558 | not crash or malfunction in any way. |
1661 | not crash or malfunction in any way. |
1559 | |
1662 | |
|
|
1663 | In any case, the documentation for each member will explain what the |
|
|
1664 | effects are, and if there are any additional access restrictions. |
1560 | |
1665 | |
1561 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1666 | =head2 C<ev_io> - is this file descriptor readable or writable? |
1562 | |
1667 | |
1563 | I/O watchers check whether a file descriptor is readable or writable |
1668 | I/O watchers check whether a file descriptor is readable or writable |
1564 | in each iteration of the event loop, or, more precisely, when reading |
1669 | in each iteration of the event loop, or, more precisely, when reading |
… | |
… | |
1591 | |
1696 | |
1592 | But really, best use non-blocking mode. |
1697 | But really, best use non-blocking mode. |
1593 | |
1698 | |
1594 | =head3 The special problem of disappearing file descriptors |
1699 | =head3 The special problem of disappearing file descriptors |
1595 | |
1700 | |
1596 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1701 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1597 | descriptor (either due to calling C<close> explicitly or any other means, |
1702 | a file descriptor (either due to calling C<close> explicitly or any other |
1598 | such as C<dup2>). The reason is that you register interest in some file |
1703 | means, such as C<dup2>). The reason is that you register interest in some |
1599 | descriptor, but when it goes away, the operating system will silently drop |
1704 | file descriptor, but when it goes away, the operating system will silently |
1600 | this interest. If another file descriptor with the same number then is |
1705 | drop this interest. If another file descriptor with the same number then |
1601 | registered with libev, there is no efficient way to see that this is, in |
1706 | is registered with libev, there is no efficient way to see that this is, |
1602 | fact, a different file descriptor. |
1707 | in fact, a different file descriptor. |
1603 | |
1708 | |
1604 | To avoid having to explicitly tell libev about such cases, libev follows |
1709 | To avoid having to explicitly tell libev about such cases, libev follows |
1605 | the following policy: Each time C<ev_io_set> is being called, libev |
1710 | the following policy: Each time C<ev_io_set> is being called, libev |
1606 | will assume that this is potentially a new file descriptor, otherwise |
1711 | will assume that this is potentially a new file descriptor, otherwise |
1607 | it is assumed that the file descriptor stays the same. That means that |
1712 | it is assumed that the file descriptor stays the same. That means that |
… | |
… | |
1656 | when you rarely read from a file instead of from a socket, and want to |
1761 | when you rarely read from a file instead of from a socket, and want to |
1657 | reuse the same code path. |
1762 | reuse the same code path. |
1658 | |
1763 | |
1659 | =head3 The special problem of fork |
1764 | =head3 The special problem of fork |
1660 | |
1765 | |
1661 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1766 | Some backends (epoll, kqueue, linuxaio, iouring) do not support C<fork ()> |
1662 | useless behaviour. Libev fully supports fork, but needs to be told about |
1767 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1663 | it in the child if you want to continue to use it in the child. |
1768 | to be told about it in the child if you want to continue to use it in the |
|
|
1769 | child. |
1664 | |
1770 | |
1665 | To support fork in your child processes, you have to call C<ev_loop_fork |
1771 | To support fork in your child processes, you have to call C<ev_loop_fork |
1666 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1772 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1667 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1773 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1668 | |
1774 | |
… | |
… | |
1726 | |
1832 | |
1727 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1833 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1728 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1834 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1729 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1835 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1730 | |
1836 | |
1731 | =item int fd [read-only] |
1837 | =item ev_io_modify (ev_io *, int events) |
1732 | |
1838 | |
1733 | The file descriptor being watched. |
1839 | Similar to C<ev_io_set>, but only changes the event mask. Using this might |
|
|
1840 | be faster with some backends, as libev can assume that the C<fd> still |
|
|
1841 | refers to the same underlying file description, something it cannot do |
|
|
1842 | when using C<ev_io_set>. |
1734 | |
1843 | |
|
|
1844 | =item int fd [no-modify] |
|
|
1845 | |
|
|
1846 | The file descriptor being watched. While it can be read at any time, you |
|
|
1847 | must not modify this member even when the watcher is stopped - always use |
|
|
1848 | C<ev_io_set> for that. |
|
|
1849 | |
1735 | =item int events [read-only] |
1850 | =item int events [no-modify] |
1736 | |
1851 | |
1737 | The events being watched. |
1852 | The set of events the fd is being watched for, among other flags. Remember |
|
|
1853 | that this is a bit set - to test for C<EV_READ>, use C<< w->events & |
|
|
1854 | EV_READ >>, and similarly for C<EV_WRITE>. |
|
|
1855 | |
|
|
1856 | As with C<fd>, you must not modify this member even when the watcher is |
|
|
1857 | stopped, always use C<ev_io_set> or C<ev_io_modify> for that. |
1738 | |
1858 | |
1739 | =back |
1859 | =back |
1740 | |
1860 | |
1741 | =head3 Examples |
1861 | =head3 Examples |
1742 | |
1862 | |
… | |
… | |
1770 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1890 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | monotonic clock option helps a lot here). |
1891 | monotonic clock option helps a lot here). |
1772 | |
1892 | |
1773 | The callback is guaranteed to be invoked only I<after> its timeout has |
1893 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | passed (not I<at>, so on systems with very low-resolution clocks this |
1894 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | might introduce a small delay). If multiple timers become ready during the |
1895 | might introduce a small delay, see "the special problem of being too |
|
|
1896 | early", below). If multiple timers become ready during the same loop |
1776 | same loop iteration then the ones with earlier time-out values are invoked |
1897 | iteration then the ones with earlier time-out values are invoked before |
1777 | before ones of the same priority with later time-out values (but this is |
1898 | ones of the same priority with later time-out values (but this is no |
1778 | no longer true when a callback calls C<ev_run> recursively). |
1899 | longer true when a callback calls C<ev_run> recursively). |
1779 | |
1900 | |
1780 | =head3 Be smart about timeouts |
1901 | =head3 Be smart about timeouts |
1781 | |
1902 | |
1782 | Many real-world problems involve some kind of timeout, usually for error |
1903 | Many real-world problems involve some kind of timeout, usually for error |
1783 | recovery. A typical example is an HTTP request - if the other side hangs, |
1904 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1858 | |
1979 | |
1859 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1980 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1860 | but remember the time of last activity, and check for a real timeout only |
1981 | but remember the time of last activity, and check for a real timeout only |
1861 | within the callback: |
1982 | within the callback: |
1862 | |
1983 | |
|
|
1984 | ev_tstamp timeout = 60.; |
1863 | ev_tstamp last_activity; // time of last activity |
1985 | ev_tstamp last_activity; // time of last activity |
|
|
1986 | ev_timer timer; |
1864 | |
1987 | |
1865 | static void |
1988 | static void |
1866 | callback (EV_P_ ev_timer *w, int revents) |
1989 | callback (EV_P_ ev_timer *w, int revents) |
1867 | { |
1990 | { |
1868 | ev_tstamp now = ev_now (EV_A); |
1991 | // calculate when the timeout would happen |
1869 | ev_tstamp timeout = last_activity + 60.; |
1992 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1870 | |
1993 | |
1871 | // if last_activity + 60. is older than now, we did time out |
1994 | // if negative, it means we the timeout already occurred |
1872 | if (timeout < now) |
1995 | if (after < 0.) |
1873 | { |
1996 | { |
1874 | // timeout occurred, take action |
1997 | // timeout occurred, take action |
1875 | } |
1998 | } |
1876 | else |
1999 | else |
1877 | { |
2000 | { |
1878 | // callback was invoked, but there was some activity, re-arm |
2001 | // callback was invoked, but there was some recent |
1879 | // the watcher to fire in last_activity + 60, which is |
2002 | // activity. simply restart the timer to time out |
1880 | // guaranteed to be in the future, so "again" is positive: |
2003 | // after "after" seconds, which is the earliest time |
1881 | w->repeat = timeout - now; |
2004 | // the timeout can occur. |
|
|
2005 | ev_timer_set (w, after, 0.); |
1882 | ev_timer_again (EV_A_ w); |
2006 | ev_timer_start (EV_A_ w); |
1883 | } |
2007 | } |
1884 | } |
2008 | } |
1885 | |
2009 | |
1886 | To summarise the callback: first calculate the real timeout (defined |
2010 | To summarise the callback: first calculate in how many seconds the |
1887 | as "60 seconds after the last activity"), then check if that time has |
2011 | timeout will occur (by calculating the absolute time when it would occur, |
1888 | been reached, which means something I<did>, in fact, time out. Otherwise |
2012 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1889 | the callback was invoked too early (C<timeout> is in the future), so |
2013 | (EV_A)> from that). |
1890 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1891 | a timeout then. |
|
|
1892 | |
2014 | |
1893 | Note how C<ev_timer_again> is used, taking advantage of the |
2015 | If this value is negative, then we are already past the timeout, i.e. we |
1894 | C<ev_timer_again> optimisation when the timer is already running. |
2016 | timed out, and need to do whatever is needed in this case. |
|
|
2017 | |
|
|
2018 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
2019 | and simply start the timer with this timeout value. |
|
|
2020 | |
|
|
2021 | In other words, each time the callback is invoked it will check whether |
|
|
2022 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
2023 | again at the earliest time it could time out. Rinse. Repeat. |
1895 | |
2024 | |
1896 | This scheme causes more callback invocations (about one every 60 seconds |
2025 | This scheme causes more callback invocations (about one every 60 seconds |
1897 | minus half the average time between activity), but virtually no calls to |
2026 | minus half the average time between activity), but virtually no calls to |
1898 | libev to change the timeout. |
2027 | libev to change the timeout. |
1899 | |
2028 | |
1900 | To start the timer, simply initialise the watcher and set C<last_activity> |
2029 | To start the machinery, simply initialise the watcher and set |
1901 | to the current time (meaning we just have some activity :), then call the |
2030 | C<last_activity> to the current time (meaning there was some activity just |
1902 | callback, which will "do the right thing" and start the timer: |
2031 | now), then call the callback, which will "do the right thing" and start |
|
|
2032 | the timer: |
1903 | |
2033 | |
|
|
2034 | last_activity = ev_now (EV_A); |
1904 | ev_init (timer, callback); |
2035 | ev_init (&timer, callback); |
1905 | last_activity = ev_now (loop); |
2036 | callback (EV_A_ &timer, 0); |
1906 | callback (loop, timer, EV_TIMER); |
|
|
1907 | |
2037 | |
1908 | And when there is some activity, simply store the current time in |
2038 | When there is some activity, simply store the current time in |
1909 | C<last_activity>, no libev calls at all: |
2039 | C<last_activity>, no libev calls at all: |
1910 | |
2040 | |
|
|
2041 | if (activity detected) |
1911 | last_activity = ev_now (loop); |
2042 | last_activity = ev_now (EV_A); |
|
|
2043 | |
|
|
2044 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2045 | providing a new value, stopping the timer and calling the callback, which |
|
|
2046 | will again do the right thing (for example, time out immediately :). |
|
|
2047 | |
|
|
2048 | timeout = new_value; |
|
|
2049 | ev_timer_stop (EV_A_ &timer); |
|
|
2050 | callback (EV_A_ &timer, 0); |
1912 | |
2051 | |
1913 | This technique is slightly more complex, but in most cases where the |
2052 | This technique is slightly more complex, but in most cases where the |
1914 | time-out is unlikely to be triggered, much more efficient. |
2053 | time-out is unlikely to be triggered, much more efficient. |
1915 | |
|
|
1916 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1917 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1918 | fix things for you. |
|
|
1919 | |
2054 | |
1920 | =item 4. Wee, just use a double-linked list for your timeouts. |
2055 | =item 4. Wee, just use a double-linked list for your timeouts. |
1921 | |
2056 | |
1922 | If there is not one request, but many thousands (millions...), all |
2057 | If there is not one request, but many thousands (millions...), all |
1923 | employing some kind of timeout with the same timeout value, then one can |
2058 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1950 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
2085 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1951 | rather complicated, but extremely efficient, something that really pays |
2086 | rather complicated, but extremely efficient, something that really pays |
1952 | off after the first million or so of active timers, i.e. it's usually |
2087 | off after the first million or so of active timers, i.e. it's usually |
1953 | overkill :) |
2088 | overkill :) |
1954 | |
2089 | |
|
|
2090 | =head3 The special problem of being too early |
|
|
2091 | |
|
|
2092 | If you ask a timer to call your callback after three seconds, then |
|
|
2093 | you expect it to be invoked after three seconds - but of course, this |
|
|
2094 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2095 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2096 | process with a STOP signal for a few hours for example. |
|
|
2097 | |
|
|
2098 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2099 | delay has occurred, but cannot guarantee this. |
|
|
2100 | |
|
|
2101 | A less obvious failure mode is calling your callback too early: many event |
|
|
2102 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2103 | this can cause your callback to be invoked much earlier than you would |
|
|
2104 | expect. |
|
|
2105 | |
|
|
2106 | To see why, imagine a system with a clock that only offers full second |
|
|
2107 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2108 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2109 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2110 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2111 | |
|
|
2112 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2113 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2114 | one-second delay was requested - this is being "too early", despite best |
|
|
2115 | intentions. |
|
|
2116 | |
|
|
2117 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2118 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2119 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2120 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2121 | |
|
|
2122 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2123 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2124 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2125 | late" side of things. |
|
|
2126 | |
1955 | =head3 The special problem of time updates |
2127 | =head3 The special problem of time updates |
1956 | |
2128 | |
1957 | Establishing the current time is a costly operation (it usually takes at |
2129 | Establishing the current time is a costly operation (it usually takes |
1958 | least two system calls): EV therefore updates its idea of the current |
2130 | at least one system call): EV therefore updates its idea of the current |
1959 | time only before and after C<ev_run> collects new events, which causes a |
2131 | time only before and after C<ev_run> collects new events, which causes a |
1960 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2132 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1961 | lots of events in one iteration. |
2133 | lots of events in one iteration. |
1962 | |
2134 | |
1963 | The relative timeouts are calculated relative to the C<ev_now ()> |
2135 | The relative timeouts are calculated relative to the C<ev_now ()> |
1964 | time. This is usually the right thing as this timestamp refers to the time |
2136 | time. This is usually the right thing as this timestamp refers to the time |
1965 | of the event triggering whatever timeout you are modifying/starting. If |
2137 | of the event triggering whatever timeout you are modifying/starting. If |
1966 | you suspect event processing to be delayed and you I<need> to base the |
2138 | you suspect event processing to be delayed and you I<need> to base the |
1967 | timeout on the current time, use something like this to adjust for this: |
2139 | timeout on the current time, use something like the following to adjust |
|
|
2140 | for it: |
1968 | |
2141 | |
1969 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2142 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1970 | |
2143 | |
1971 | If the event loop is suspended for a long time, you can also force an |
2144 | If the event loop is suspended for a long time, you can also force an |
1972 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2145 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1973 | ()>. |
2146 | ()>, although that will push the event time of all outstanding events |
|
|
2147 | further into the future. |
|
|
2148 | |
|
|
2149 | =head3 The special problem of unsynchronised clocks |
|
|
2150 | |
|
|
2151 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2152 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2153 | jumps). |
|
|
2154 | |
|
|
2155 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2156 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2157 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2158 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2159 | than a directly following call to C<time>. |
|
|
2160 | |
|
|
2161 | The moral of this is to only compare libev-related timestamps with |
|
|
2162 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2163 | a second or so. |
|
|
2164 | |
|
|
2165 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2166 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2167 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2168 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2169 | |
|
|
2170 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2171 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2172 | I<measured according to the real time>, not the system clock. |
|
|
2173 | |
|
|
2174 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2175 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2176 | exactly the right behaviour. |
|
|
2177 | |
|
|
2178 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2179 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2180 | time, where your comparisons will always generate correct results. |
1974 | |
2181 | |
1975 | =head3 The special problems of suspended animation |
2182 | =head3 The special problems of suspended animation |
1976 | |
2183 | |
1977 | When you leave the server world it is quite customary to hit machines that |
2184 | When you leave the server world it is quite customary to hit machines that |
1978 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2185 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2008 | |
2215 | |
2009 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2216 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2010 | |
2217 | |
2011 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2218 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2012 | |
2219 | |
2013 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2220 | Configure the timer to trigger after C<after> seconds (fractional and |
2014 | is C<0.>, then it will automatically be stopped once the timeout is |
2221 | negative values are supported). If C<repeat> is C<0.>, then it will |
2015 | reached. If it is positive, then the timer will automatically be |
2222 | automatically be stopped once the timeout is reached. If it is positive, |
2016 | configured to trigger again C<repeat> seconds later, again, and again, |
2223 | then the timer will automatically be configured to trigger again C<repeat> |
2017 | until stopped manually. |
2224 | seconds later, again, and again, until stopped manually. |
2018 | |
2225 | |
2019 | The timer itself will do a best-effort at avoiding drift, that is, if |
2226 | The timer itself will do a best-effort at avoiding drift, that is, if |
2020 | you configure a timer to trigger every 10 seconds, then it will normally |
2227 | you configure a timer to trigger every 10 seconds, then it will normally |
2021 | trigger at exactly 10 second intervals. If, however, your program cannot |
2228 | trigger at exactly 10 second intervals. If, however, your program cannot |
2022 | keep up with the timer (because it takes longer than those 10 seconds to |
2229 | keep up with the timer (because it takes longer than those 10 seconds to |
2023 | do stuff) the timer will not fire more than once per event loop iteration. |
2230 | do stuff) the timer will not fire more than once per event loop iteration. |
2024 | |
2231 | |
2025 | =item ev_timer_again (loop, ev_timer *) |
2232 | =item ev_timer_again (loop, ev_timer *) |
2026 | |
2233 | |
2027 | This will act as if the timer timed out and restart it again if it is |
2234 | This will act as if the timer timed out, and restarts it again if it is |
2028 | repeating. The exact semantics are: |
2235 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2236 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2029 | |
2237 | |
|
|
2238 | The exact semantics are as in the following rules, all of which will be |
|
|
2239 | applied to the watcher: |
|
|
2240 | |
|
|
2241 | =over 4 |
|
|
2242 | |
2030 | If the timer is pending, its pending status is cleared. |
2243 | =item If the timer is pending, the pending status is always cleared. |
2031 | |
2244 | |
2032 | If the timer is started but non-repeating, stop it (as if it timed out). |
2245 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2246 | out, without invoking it). |
2033 | |
2247 | |
2034 | If the timer is repeating, either start it if necessary (with the |
2248 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2035 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2249 | and start the timer, if necessary. |
2036 | |
2250 | |
|
|
2251 | =back |
|
|
2252 | |
2037 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2253 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2038 | usage example. |
2254 | usage example. |
2039 | |
2255 | |
2040 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2256 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2041 | |
2257 | |
2042 | Returns the remaining time until a timer fires. If the timer is active, |
2258 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2095 | Periodic watchers are also timers of a kind, but they are very versatile |
2311 | Periodic watchers are also timers of a kind, but they are very versatile |
2096 | (and unfortunately a bit complex). |
2312 | (and unfortunately a bit complex). |
2097 | |
2313 | |
2098 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2314 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2099 | relative time, the physical time that passes) but on wall clock time |
2315 | relative time, the physical time that passes) but on wall clock time |
2100 | (absolute time, the thing you can read on your calender or clock). The |
2316 | (absolute time, the thing you can read on your calendar or clock). The |
2101 | difference is that wall clock time can run faster or slower than real |
2317 | difference is that wall clock time can run faster or slower than real |
2102 | time, and time jumps are not uncommon (e.g. when you adjust your |
2318 | time, and time jumps are not uncommon (e.g. when you adjust your |
2103 | wrist-watch). |
2319 | wrist-watch). |
2104 | |
2320 | |
2105 | You can tell a periodic watcher to trigger after some specific point |
2321 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2110 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2326 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2111 | it, as it uses a relative timeout). |
2327 | it, as it uses a relative timeout). |
2112 | |
2328 | |
2113 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2329 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2114 | timers, such as triggering an event on each "midnight, local time", or |
2330 | timers, such as triggering an event on each "midnight, local time", or |
2115 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2331 | other complicated rules. This cannot easily be done with C<ev_timer> |
2116 | those cannot react to time jumps. |
2332 | watchers, as those cannot react to time jumps. |
2117 | |
2333 | |
2118 | As with timers, the callback is guaranteed to be invoked only when the |
2334 | As with timers, the callback is guaranteed to be invoked only when the |
2119 | point in time where it is supposed to trigger has passed. If multiple |
2335 | point in time where it is supposed to trigger has passed. If multiple |
2120 | timers become ready during the same loop iteration then the ones with |
2336 | timers become ready during the same loop iteration then the ones with |
2121 | earlier time-out values are invoked before ones with later time-out values |
2337 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2207 | |
2423 | |
2208 | NOTE: I<< This callback must always return a time that is higher than or |
2424 | NOTE: I<< This callback must always return a time that is higher than or |
2209 | equal to the passed C<now> value >>. |
2425 | equal to the passed C<now> value >>. |
2210 | |
2426 | |
2211 | This can be used to create very complex timers, such as a timer that |
2427 | This can be used to create very complex timers, such as a timer that |
2212 | triggers on "next midnight, local time". To do this, you would calculate the |
2428 | triggers on "next midnight, local time". To do this, you would calculate |
2213 | next midnight after C<now> and return the timestamp value for this. How |
2429 | the next midnight after C<now> and return the timestamp value for |
2214 | you do this is, again, up to you (but it is not trivial, which is the main |
2430 | this. Here is a (completely untested, no error checking) example on how to |
2215 | reason I omitted it as an example). |
2431 | do this: |
|
|
2432 | |
|
|
2433 | #include <time.h> |
|
|
2434 | |
|
|
2435 | static ev_tstamp |
|
|
2436 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2437 | { |
|
|
2438 | time_t tnow = (time_t)now; |
|
|
2439 | struct tm tm; |
|
|
2440 | localtime_r (&tnow, &tm); |
|
|
2441 | |
|
|
2442 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2443 | ++tm.tm_mday; // midnight next day |
|
|
2444 | |
|
|
2445 | return mktime (&tm); |
|
|
2446 | } |
|
|
2447 | |
|
|
2448 | Note: this code might run into trouble on days that have more then two |
|
|
2449 | midnights (beginning and end). |
2216 | |
2450 | |
2217 | =back |
2451 | =back |
2218 | |
2452 | |
2219 | =item ev_periodic_again (loop, ev_periodic *) |
2453 | =item ev_periodic_again (loop, ev_periodic *) |
2220 | |
2454 | |
… | |
… | |
2285 | |
2519 | |
2286 | ev_periodic hourly_tick; |
2520 | ev_periodic hourly_tick; |
2287 | ev_periodic_init (&hourly_tick, clock_cb, |
2521 | ev_periodic_init (&hourly_tick, clock_cb, |
2288 | fmod (ev_now (loop), 3600.), 3600., 0); |
2522 | fmod (ev_now (loop), 3600.), 3600., 0); |
2289 | ev_periodic_start (loop, &hourly_tick); |
2523 | ev_periodic_start (loop, &hourly_tick); |
2290 | |
2524 | |
2291 | |
2525 | |
2292 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2526 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2293 | |
2527 | |
2294 | Signal watchers will trigger an event when the process receives a specific |
2528 | Signal watchers will trigger an event when the process receives a specific |
2295 | signal one or more times. Even though signals are very asynchronous, libev |
2529 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2305 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2539 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2306 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2540 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2307 | C<SIGINT> in both the default loop and another loop at the same time. At |
2541 | C<SIGINT> in both the default loop and another loop at the same time. At |
2308 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2542 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2309 | |
2543 | |
2310 | When the first watcher gets started will libev actually register something |
2544 | Only after the first watcher for a signal is started will libev actually |
2311 | with the kernel (thus it coexists with your own signal handlers as long as |
2545 | register something with the kernel. It thus coexists with your own signal |
2312 | you don't register any with libev for the same signal). |
2546 | handlers as long as you don't register any with libev for the same signal. |
2313 | |
2547 | |
2314 | If possible and supported, libev will install its handlers with |
2548 | If possible and supported, libev will install its handlers with |
2315 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2549 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2316 | not be unduly interrupted. If you have a problem with system calls getting |
2550 | not be unduly interrupted. If you have a problem with system calls getting |
2317 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2551 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2502 | |
2736 | |
2503 | =head2 C<ev_stat> - did the file attributes just change? |
2737 | =head2 C<ev_stat> - did the file attributes just change? |
2504 | |
2738 | |
2505 | This watches a file system path for attribute changes. That is, it calls |
2739 | This watches a file system path for attribute changes. That is, it calls |
2506 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2740 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2507 | and sees if it changed compared to the last time, invoking the callback if |
2741 | and sees if it changed compared to the last time, invoking the callback |
2508 | it did. |
2742 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2743 | happen after the watcher has been started will be reported. |
2509 | |
2744 | |
2510 | The path does not need to exist: changing from "path exists" to "path does |
2745 | The path does not need to exist: changing from "path exists" to "path does |
2511 | not exist" is a status change like any other. The condition "path does not |
2746 | not exist" is a status change like any other. The condition "path does not |
2512 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2747 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2513 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2748 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2743 | Apart from keeping your process non-blocking (which is a useful |
2978 | Apart from keeping your process non-blocking (which is a useful |
2744 | effect on its own sometimes), idle watchers are a good place to do |
2979 | effect on its own sometimes), idle watchers are a good place to do |
2745 | "pseudo-background processing", or delay processing stuff to after the |
2980 | "pseudo-background processing", or delay processing stuff to after the |
2746 | event loop has handled all outstanding events. |
2981 | event loop has handled all outstanding events. |
2747 | |
2982 | |
|
|
2983 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2984 | |
|
|
2985 | As long as there is at least one active idle watcher, libev will never |
|
|
2986 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2987 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2988 | lowest priority will do. |
|
|
2989 | |
|
|
2990 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2991 | to do something on each event loop iteration - for example to balance load |
|
|
2992 | between different connections. |
|
|
2993 | |
|
|
2994 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2995 | example. |
|
|
2996 | |
2748 | =head3 Watcher-Specific Functions and Data Members |
2997 | =head3 Watcher-Specific Functions and Data Members |
2749 | |
2998 | |
2750 | =over 4 |
2999 | =over 4 |
2751 | |
3000 | |
2752 | =item ev_idle_init (ev_idle *, callback) |
3001 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2763 | callback, free it. Also, use no error checking, as usual. |
3012 | callback, free it. Also, use no error checking, as usual. |
2764 | |
3013 | |
2765 | static void |
3014 | static void |
2766 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
3015 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2767 | { |
3016 | { |
|
|
3017 | // stop the watcher |
|
|
3018 | ev_idle_stop (loop, w); |
|
|
3019 | |
|
|
3020 | // now we can free it |
2768 | free (w); |
3021 | free (w); |
|
|
3022 | |
2769 | // now do something you wanted to do when the program has |
3023 | // now do something you wanted to do when the program has |
2770 | // no longer anything immediate to do. |
3024 | // no longer anything immediate to do. |
2771 | } |
3025 | } |
2772 | |
3026 | |
2773 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
3027 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2775 | ev_idle_start (loop, idle_watcher); |
3029 | ev_idle_start (loop, idle_watcher); |
2776 | |
3030 | |
2777 | |
3031 | |
2778 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3032 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2779 | |
3033 | |
2780 | Prepare and check watchers are usually (but not always) used in pairs: |
3034 | Prepare and check watchers are often (but not always) used in pairs: |
2781 | prepare watchers get invoked before the process blocks and check watchers |
3035 | prepare watchers get invoked before the process blocks and check watchers |
2782 | afterwards. |
3036 | afterwards. |
2783 | |
3037 | |
2784 | You I<must not> call C<ev_run> or similar functions that enter |
3038 | You I<must not> call C<ev_run> (or similar functions that enter the |
2785 | the current event loop from either C<ev_prepare> or C<ev_check> |
3039 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2786 | watchers. Other loops than the current one are fine, however. The |
3040 | C<ev_check> watchers. Other loops than the current one are fine, |
2787 | rationale behind this is that you do not need to check for recursion in |
3041 | however. The rationale behind this is that you do not need to check |
2788 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
3042 | for recursion in those watchers, i.e. the sequence will always be |
2789 | C<ev_check> so if you have one watcher of each kind they will always be |
3043 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2790 | called in pairs bracketing the blocking call. |
3044 | kind they will always be called in pairs bracketing the blocking call. |
2791 | |
3045 | |
2792 | Their main purpose is to integrate other event mechanisms into libev and |
3046 | Their main purpose is to integrate other event mechanisms into libev and |
2793 | their use is somewhat advanced. They could be used, for example, to track |
3047 | their use is somewhat advanced. They could be used, for example, to track |
2794 | variable changes, implement your own watchers, integrate net-snmp or a |
3048 | variable changes, implement your own watchers, integrate net-snmp or a |
2795 | coroutine library and lots more. They are also occasionally useful if |
3049 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2813 | with priority higher than or equal to the event loop and one coroutine |
3067 | with priority higher than or equal to the event loop and one coroutine |
2814 | of lower priority, but only once, using idle watchers to keep the event |
3068 | of lower priority, but only once, using idle watchers to keep the event |
2815 | loop from blocking if lower-priority coroutines are active, thus mapping |
3069 | loop from blocking if lower-priority coroutines are active, thus mapping |
2816 | low-priority coroutines to idle/background tasks). |
3070 | low-priority coroutines to idle/background tasks). |
2817 | |
3071 | |
2818 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3072 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2819 | priority, to ensure that they are being run before any other watchers |
3073 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2820 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3074 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3075 | watchers). |
2821 | |
3076 | |
2822 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3077 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2823 | activate ("feed") events into libev. While libev fully supports this, they |
3078 | activate ("feed") events into libev. While libev fully supports this, they |
2824 | might get executed before other C<ev_check> watchers did their job. As |
3079 | might get executed before other C<ev_check> watchers did their job. As |
2825 | C<ev_check> watchers are often used to embed other (non-libev) event |
3080 | C<ev_check> watchers are often used to embed other (non-libev) event |
2826 | loops those other event loops might be in an unusable state until their |
3081 | loops those other event loops might be in an unusable state until their |
2827 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
3082 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2828 | others). |
3083 | others). |
|
|
3084 | |
|
|
3085 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3086 | |
|
|
3087 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3088 | useful because they are called once per event loop iteration. For |
|
|
3089 | example, if you want to handle a large number of connections fairly, you |
|
|
3090 | normally only do a bit of work for each active connection, and if there |
|
|
3091 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3092 | connections have a chance of making progress. |
|
|
3093 | |
|
|
3094 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3095 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3096 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3097 | |
|
|
3098 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3099 | single global idle watcher that is active as long as you have one active |
|
|
3100 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3101 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3102 | invoked. Neither watcher alone can do that. |
2829 | |
3103 | |
2830 | =head3 Watcher-Specific Functions and Data Members |
3104 | =head3 Watcher-Specific Functions and Data Members |
2831 | |
3105 | |
2832 | =over 4 |
3106 | =over 4 |
2833 | |
3107 | |
… | |
… | |
3034 | |
3308 | |
3035 | =over 4 |
3309 | =over 4 |
3036 | |
3310 | |
3037 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3311 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3038 | |
3312 | |
3039 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3313 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3040 | |
3314 | |
3041 | Configures the watcher to embed the given loop, which must be |
3315 | Configures the watcher to embed the given loop, which must be |
3042 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3316 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3043 | invoked automatically, otherwise it is the responsibility of the callback |
3317 | invoked automatically, otherwise it is the responsibility of the callback |
3044 | to invoke it (it will continue to be called until the sweep has been done, |
3318 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3065 | used). |
3339 | used). |
3066 | |
3340 | |
3067 | struct ev_loop *loop_hi = ev_default_init (0); |
3341 | struct ev_loop *loop_hi = ev_default_init (0); |
3068 | struct ev_loop *loop_lo = 0; |
3342 | struct ev_loop *loop_lo = 0; |
3069 | ev_embed embed; |
3343 | ev_embed embed; |
3070 | |
3344 | |
3071 | // see if there is a chance of getting one that works |
3345 | // see if there is a chance of getting one that works |
3072 | // (remember that a flags value of 0 means autodetection) |
3346 | // (remember that a flags value of 0 means autodetection) |
3073 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3347 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3074 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3348 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3075 | : 0; |
3349 | : 0; |
… | |
… | |
3089 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3363 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3090 | |
3364 | |
3091 | struct ev_loop *loop = ev_default_init (0); |
3365 | struct ev_loop *loop = ev_default_init (0); |
3092 | struct ev_loop *loop_socket = 0; |
3366 | struct ev_loop *loop_socket = 0; |
3093 | ev_embed embed; |
3367 | ev_embed embed; |
3094 | |
3368 | |
3095 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3369 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3096 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3370 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3097 | { |
3371 | { |
3098 | ev_embed_init (&embed, 0, loop_socket); |
3372 | ev_embed_init (&embed, 0, loop_socket); |
3099 | ev_embed_start (loop, &embed); |
3373 | ev_embed_start (loop, &embed); |
… | |
… | |
3107 | |
3381 | |
3108 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3382 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3109 | |
3383 | |
3110 | Fork watchers are called when a C<fork ()> was detected (usually because |
3384 | Fork watchers are called when a C<fork ()> was detected (usually because |
3111 | whoever is a good citizen cared to tell libev about it by calling |
3385 | whoever is a good citizen cared to tell libev about it by calling |
3112 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3386 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3113 | event loop blocks next and before C<ev_check> watchers are being called, |
3387 | and before C<ev_check> watchers are being called, and only in the child |
3114 | and only in the child after the fork. If whoever good citizen calling |
3388 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3115 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3389 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3116 | handlers will be invoked, too, of course. |
3390 | of course. |
3117 | |
3391 | |
3118 | =head3 The special problem of life after fork - how is it possible? |
3392 | =head3 The special problem of life after fork - how is it possible? |
3119 | |
3393 | |
3120 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3394 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3121 | up/change the process environment, followed by a call to C<exec()>. This |
3395 | up/change the process environment, followed by a call to C<exec()>. This |
3122 | sequence should be handled by libev without any problems. |
3396 | sequence should be handled by libev without any problems. |
3123 | |
3397 | |
3124 | This changes when the application actually wants to do event handling |
3398 | This changes when the application actually wants to do event handling |
3125 | in the child, or both parent in child, in effect "continuing" after the |
3399 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3214 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3488 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3215 | |
3489 | |
3216 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3490 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3217 | too, are asynchronous in nature, and signals, too, will be compressed |
3491 | too, are asynchronous in nature, and signals, too, will be compressed |
3218 | (i.e. the number of callback invocations may be less than the number of |
3492 | (i.e. the number of callback invocations may be less than the number of |
3219 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3493 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3220 | of "global async watchers" by using a watcher on an otherwise unused |
3494 | of "global async watchers" by using a watcher on an otherwise unused |
3221 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3495 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3222 | even without knowing which loop owns the signal. |
3496 | even without knowing which loop owns the signal. |
3223 | |
|
|
3224 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3225 | just the default loop. |
|
|
3226 | |
3497 | |
3227 | =head3 Queueing |
3498 | =head3 Queueing |
3228 | |
3499 | |
3229 | C<ev_async> does not support queueing of data in any way. The reason |
3500 | C<ev_async> does not support queueing of data in any way. The reason |
3230 | is that the author does not know of a simple (or any) algorithm for a |
3501 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3330 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3601 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3331 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3602 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3332 | embedding section below on what exactly this means). |
3603 | embedding section below on what exactly this means). |
3333 | |
3604 | |
3334 | Note that, as with other watchers in libev, multiple events might get |
3605 | Note that, as with other watchers in libev, multiple events might get |
3335 | compressed into a single callback invocation (another way to look at this |
3606 | compressed into a single callback invocation (another way to look at |
3336 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3607 | this is that C<ev_async> watchers are level-triggered: they are set on |
3337 | reset when the event loop detects that). |
3608 | C<ev_async_send>, reset when the event loop detects that). |
3338 | |
3609 | |
3339 | This call incurs the overhead of a system call only once per event loop |
3610 | This call incurs the overhead of at most one extra system call per event |
3340 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3611 | loop iteration, if the event loop is blocked, and no syscall at all if |
3341 | repeated calls to C<ev_async_send> for the same event loop. |
3612 | the event loop (or your program) is processing events. That means that |
|
|
3613 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3614 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3615 | zero) under load. |
3342 | |
3616 | |
3343 | =item bool = ev_async_pending (ev_async *) |
3617 | =item bool = ev_async_pending (ev_async *) |
3344 | |
3618 | |
3345 | Returns a non-zero value when C<ev_async_send> has been called on the |
3619 | Returns a non-zero value when C<ev_async_send> has been called on the |
3346 | watcher but the event has not yet been processed (or even noted) by the |
3620 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3363 | |
3637 | |
3364 | There are some other functions of possible interest. Described. Here. Now. |
3638 | There are some other functions of possible interest. Described. Here. Now. |
3365 | |
3639 | |
3366 | =over 4 |
3640 | =over 4 |
3367 | |
3641 | |
3368 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3642 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3369 | |
3643 | |
3370 | This function combines a simple timer and an I/O watcher, calls your |
3644 | This function combines a simple timer and an I/O watcher, calls your |
3371 | callback on whichever event happens first and automatically stops both |
3645 | callback on whichever event happens first and automatically stops both |
3372 | watchers. This is useful if you want to wait for a single event on an fd |
3646 | watchers. This is useful if you want to wait for a single event on an fd |
3373 | or timeout without having to allocate/configure/start/stop/free one or |
3647 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3401 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3675 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3402 | |
3676 | |
3403 | =item ev_feed_fd_event (loop, int fd, int revents) |
3677 | =item ev_feed_fd_event (loop, int fd, int revents) |
3404 | |
3678 | |
3405 | Feed an event on the given fd, as if a file descriptor backend detected |
3679 | Feed an event on the given fd, as if a file descriptor backend detected |
3406 | the given events it. |
3680 | the given events. |
3407 | |
3681 | |
3408 | =item ev_feed_signal_event (loop, int signum) |
3682 | =item ev_feed_signal_event (loop, int signum) |
3409 | |
3683 | |
3410 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3684 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3411 | which is async-safe. |
3685 | which is async-safe. |
… | |
… | |
3485 | { |
3759 | { |
3486 | struct my_biggy big = (struct my_biggy *) |
3760 | struct my_biggy big = (struct my_biggy *) |
3487 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3761 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3488 | } |
3762 | } |
3489 | |
3763 | |
|
|
3764 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3765 | |
|
|
3766 | Often you have structures like this in event-based programs: |
|
|
3767 | |
|
|
3768 | callback () |
|
|
3769 | { |
|
|
3770 | free (request); |
|
|
3771 | } |
|
|
3772 | |
|
|
3773 | request = start_new_request (..., callback); |
|
|
3774 | |
|
|
3775 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3776 | used to cancel the operation, or do other things with it. |
|
|
3777 | |
|
|
3778 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3779 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3780 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3781 | operation and simply invoke the callback with the result. |
|
|
3782 | |
|
|
3783 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3784 | has returned, so C<request> is not set. |
|
|
3785 | |
|
|
3786 | Even if you pass the request by some safer means to the callback, you |
|
|
3787 | might want to do something to the request after starting it, such as |
|
|
3788 | canceling it, which probably isn't working so well when the callback has |
|
|
3789 | already been invoked. |
|
|
3790 | |
|
|
3791 | A common way around all these issues is to make sure that |
|
|
3792 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3793 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3794 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3795 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3796 | pushing it into the pending queue: |
|
|
3797 | |
|
|
3798 | ev_set_cb (watcher, callback); |
|
|
3799 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3800 | |
|
|
3801 | This way, C<start_new_request> can safely return before the callback is |
|
|
3802 | invoked, while not delaying callback invocation too much. |
|
|
3803 | |
3490 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3804 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3491 | |
3805 | |
3492 | Often (especially in GUI toolkits) there are places where you have |
3806 | Often (especially in GUI toolkits) there are places where you have |
3493 | I<modal> interaction, which is most easily implemented by recursively |
3807 | I<modal> interaction, which is most easily implemented by recursively |
3494 | invoking C<ev_run>. |
3808 | invoking C<ev_run>. |
3495 | |
3809 | |
3496 | This brings the problem of exiting - a callback might want to finish the |
3810 | This brings the problem of exiting - a callback might want to finish the |
3497 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3811 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3498 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3812 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3499 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3813 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3500 | other combination: In these cases, C<ev_break> will not work alone. |
3814 | other combination: In these cases, a simple C<ev_break> will not work. |
3501 | |
3815 | |
3502 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3816 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3503 | invocation, and use a loop around C<ev_run> until the condition is |
3817 | invocation, and use a loop around C<ev_run> until the condition is |
3504 | triggered, using C<EVRUN_ONCE>: |
3818 | triggered, using C<EVRUN_ONCE>: |
3505 | |
3819 | |
… | |
… | |
3507 | int exit_main_loop = 0; |
3821 | int exit_main_loop = 0; |
3508 | |
3822 | |
3509 | while (!exit_main_loop) |
3823 | while (!exit_main_loop) |
3510 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3824 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3511 | |
3825 | |
3512 | // in a model watcher |
3826 | // in a modal watcher |
3513 | int exit_nested_loop = 0; |
3827 | int exit_nested_loop = 0; |
3514 | |
3828 | |
3515 | while (!exit_nested_loop) |
3829 | while (!exit_nested_loop) |
3516 | ev_run (EV_A_ EVRUN_ONCE); |
3830 | ev_run (EV_A_ EVRUN_ONCE); |
3517 | |
3831 | |
… | |
… | |
3691 | called): |
4005 | called): |
3692 | |
4006 | |
3693 | void |
4007 | void |
3694 | wait_for_event (ev_watcher *w) |
4008 | wait_for_event (ev_watcher *w) |
3695 | { |
4009 | { |
3696 | ev_cb_set (w) = current_coro; |
4010 | ev_set_cb (w, current_coro); |
3697 | switch_to (libev_coro); |
4011 | switch_to (libev_coro); |
3698 | } |
4012 | } |
3699 | |
4013 | |
3700 | That basically suspends the coroutine inside C<wait_for_event> and |
4014 | That basically suspends the coroutine inside C<wait_for_event> and |
3701 | continues the libev coroutine, which, when appropriate, switches back to |
4015 | continues the libev coroutine, which, when appropriate, switches back to |
3702 | this or any other coroutine. I am sure if you sue this your own :) |
4016 | this or any other coroutine. |
3703 | |
4017 | |
3704 | You can do similar tricks if you have, say, threads with an event queue - |
4018 | You can do similar tricks if you have, say, threads with an event queue - |
3705 | instead of storing a coroutine, you store the queue object and instead of |
4019 | instead of storing a coroutine, you store the queue object and instead of |
3706 | switching to a coroutine, you push the watcher onto the queue and notify |
4020 | switching to a coroutine, you push the watcher onto the queue and notify |
3707 | any waiters. |
4021 | any waiters. |
3708 | |
4022 | |
3709 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
4023 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
3710 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
4024 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3711 | |
4025 | |
3712 | // my_ev.h |
4026 | // my_ev.h |
3713 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
4027 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3714 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
4028 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3715 | #include "../libev/ev.h" |
4029 | #include "../libev/ev.h" |
3716 | |
4030 | |
3717 | // my_ev.c |
4031 | // my_ev.c |
3718 | #define EV_H "my_ev.h" |
4032 | #define EV_H "my_ev.h" |
3719 | #include "../libev/ev.c" |
4033 | #include "../libev/ev.c" |
… | |
… | |
3758 | |
4072 | |
3759 | =back |
4073 | =back |
3760 | |
4074 | |
3761 | =head1 C++ SUPPORT |
4075 | =head1 C++ SUPPORT |
3762 | |
4076 | |
|
|
4077 | =head2 C API |
|
|
4078 | |
|
|
4079 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4080 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4081 | will work fine. |
|
|
4082 | |
|
|
4083 | Proper exception specifications might have to be added to callbacks passed |
|
|
4084 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4085 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4086 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4087 | specification. If you have code that needs to be compiled as both C and |
|
|
4088 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4089 | |
|
|
4090 | static void |
|
|
4091 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4092 | { |
|
|
4093 | perror (msg); |
|
|
4094 | abort (); |
|
|
4095 | } |
|
|
4096 | |
|
|
4097 | ... |
|
|
4098 | ev_set_syserr_cb (fatal_error); |
|
|
4099 | |
|
|
4100 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4101 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4102 | because it runs cleanup watchers). |
|
|
4103 | |
|
|
4104 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4105 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4106 | throwing exceptions through C libraries (most do). |
|
|
4107 | |
|
|
4108 | =head2 C++ API |
|
|
4109 | |
3763 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4110 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3764 | you to use some convenience methods to start/stop watchers and also change |
4111 | you to use some convenience methods to start/stop watchers and also change |
3765 | the callback model to a model using method callbacks on objects. |
4112 | the callback model to a model using method callbacks on objects. |
3766 | |
4113 | |
3767 | To use it, |
4114 | To use it, |
3768 | |
4115 | |
3769 | #include <ev++.h> |
4116 | #include <ev++.h> |
3770 | |
4117 | |
3771 | This automatically includes F<ev.h> and puts all of its definitions (many |
4118 | This automatically includes F<ev.h> and puts all of its definitions (many |
3772 | of them macros) into the global namespace. All C++ specific things are |
4119 | of them macros) into the global namespace. All C++ specific things are |
3773 | put into the C<ev> namespace. It should support all the same embedding |
4120 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3782 | with C<operator ()> can be used as callbacks. Other types should be easy |
4129 | with C<operator ()> can be used as callbacks. Other types should be easy |
3783 | to add as long as they only need one additional pointer for context. If |
4130 | to add as long as they only need one additional pointer for context. If |
3784 | you need support for other types of functors please contact the author |
4131 | you need support for other types of functors please contact the author |
3785 | (preferably after implementing it). |
4132 | (preferably after implementing it). |
3786 | |
4133 | |
|
|
4134 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4135 | conventions as your C compiler (for static member functions), or you have |
|
|
4136 | to embed libev and compile libev itself as C++. |
|
|
4137 | |
3787 | Here is a list of things available in the C<ev> namespace: |
4138 | Here is a list of things available in the C<ev> namespace: |
3788 | |
4139 | |
3789 | =over 4 |
4140 | =over 4 |
3790 | |
4141 | |
3791 | =item C<ev::READ>, C<ev::WRITE> etc. |
4142 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3800 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4151 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3801 | |
4152 | |
3802 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4153 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3803 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4154 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3804 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4155 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3805 | defines by many implementations. |
4156 | defined by many implementations. |
3806 | |
4157 | |
3807 | All of those classes have these methods: |
4158 | All of those classes have these methods: |
3808 | |
4159 | |
3809 | =over 4 |
4160 | =over 4 |
3810 | |
4161 | |
… | |
… | |
3872 | void operator() (ev::io &w, int revents) |
4223 | void operator() (ev::io &w, int revents) |
3873 | { |
4224 | { |
3874 | ... |
4225 | ... |
3875 | } |
4226 | } |
3876 | } |
4227 | } |
3877 | |
4228 | |
3878 | myfunctor f; |
4229 | myfunctor f; |
3879 | |
4230 | |
3880 | ev::io w; |
4231 | ev::io w; |
3881 | w.set (&f); |
4232 | w.set (&f); |
3882 | |
4233 | |
… | |
… | |
3900 | Associates a different C<struct ev_loop> with this watcher. You can only |
4251 | Associates a different C<struct ev_loop> with this watcher. You can only |
3901 | do this when the watcher is inactive (and not pending either). |
4252 | do this when the watcher is inactive (and not pending either). |
3902 | |
4253 | |
3903 | =item w->set ([arguments]) |
4254 | =item w->set ([arguments]) |
3904 | |
4255 | |
3905 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4256 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3906 | method or a suitable start method must be called at least once. Unlike the |
4257 | with the same arguments. Either this method or a suitable start method |
3907 | C counterpart, an active watcher gets automatically stopped and restarted |
4258 | must be called at least once. Unlike the C counterpart, an active watcher |
3908 | when reconfiguring it with this method. |
4259 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4260 | method. |
|
|
4261 | |
|
|
4262 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4263 | clashing with the C<set (loop)> method. |
3909 | |
4264 | |
3910 | =item w->start () |
4265 | =item w->start () |
3911 | |
4266 | |
3912 | Starts the watcher. Note that there is no C<loop> argument, as the |
4267 | Starts the watcher. Note that there is no C<loop> argument, as the |
3913 | constructor already stores the event loop. |
4268 | constructor already stores the event loop. |
… | |
… | |
3943 | watchers in the constructor. |
4298 | watchers in the constructor. |
3944 | |
4299 | |
3945 | class myclass |
4300 | class myclass |
3946 | { |
4301 | { |
3947 | ev::io io ; void io_cb (ev::io &w, int revents); |
4302 | ev::io io ; void io_cb (ev::io &w, int revents); |
3948 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4303 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3949 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4304 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3950 | |
4305 | |
3951 | myclass (int fd) |
4306 | myclass (int fd) |
3952 | { |
4307 | { |
3953 | io .set <myclass, &myclass::io_cb > (this); |
4308 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
4004 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4359 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4005 | |
4360 | |
4006 | =item D |
4361 | =item D |
4007 | |
4362 | |
4008 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4363 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4009 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4364 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4010 | |
4365 | |
4011 | =item Ocaml |
4366 | =item Ocaml |
4012 | |
4367 | |
4013 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4368 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4014 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4369 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4017 | |
4372 | |
4018 | Brian Maher has written a partial interface to libev for lua (at the |
4373 | Brian Maher has written a partial interface to libev for lua (at the |
4019 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4374 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4020 | L<http://github.com/brimworks/lua-ev>. |
4375 | L<http://github.com/brimworks/lua-ev>. |
4021 | |
4376 | |
|
|
4377 | =item Javascript |
|
|
4378 | |
|
|
4379 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4380 | |
|
|
4381 | =item Others |
|
|
4382 | |
|
|
4383 | There are others, and I stopped counting. |
|
|
4384 | |
4022 | =back |
4385 | =back |
4023 | |
4386 | |
4024 | |
4387 | |
4025 | =head1 MACRO MAGIC |
4388 | =head1 MACRO MAGIC |
4026 | |
4389 | |
… | |
… | |
4062 | suitable for use with C<EV_A>. |
4425 | suitable for use with C<EV_A>. |
4063 | |
4426 | |
4064 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4427 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4065 | |
4428 | |
4066 | Similar to the other two macros, this gives you the value of the default |
4429 | Similar to the other two macros, this gives you the value of the default |
4067 | loop, if multiple loops are supported ("ev loop default"). |
4430 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4431 | will be initialised if it isn't already initialised. |
|
|
4432 | |
|
|
4433 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4434 | to initialise the loop somewhere. |
4068 | |
4435 | |
4069 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4436 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4070 | |
4437 | |
4071 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4438 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4072 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4439 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4139 | ev_vars.h |
4506 | ev_vars.h |
4140 | ev_wrap.h |
4507 | ev_wrap.h |
4141 | |
4508 | |
4142 | ev_win32.c required on win32 platforms only |
4509 | ev_win32.c required on win32 platforms only |
4143 | |
4510 | |
4144 | ev_select.c only when select backend is enabled (which is enabled by default) |
4511 | ev_select.c only when select backend is enabled |
4145 | ev_poll.c only when poll backend is enabled (disabled by default) |
4512 | ev_poll.c only when poll backend is enabled |
4146 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4513 | ev_epoll.c only when the epoll backend is enabled |
|
|
4514 | ev_linuxaio.c only when the linux aio backend is enabled |
|
|
4515 | ev_iouring.c only when the linux io_uring backend is enabled |
4147 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4516 | ev_kqueue.c only when the kqueue backend is enabled |
4148 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4517 | ev_port.c only when the solaris port backend is enabled |
4149 | |
4518 | |
4150 | F<ev.c> includes the backend files directly when enabled, so you only need |
4519 | F<ev.c> includes the backend files directly when enabled, so you only need |
4151 | to compile this single file. |
4520 | to compile this single file. |
4152 | |
4521 | |
4153 | =head3 LIBEVENT COMPATIBILITY API |
4522 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4272 | available and will probe for kernel support at runtime. This will improve |
4641 | available and will probe for kernel support at runtime. This will improve |
4273 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4642 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
4274 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4643 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
4275 | 2.7 or newer, otherwise disabled. |
4644 | 2.7 or newer, otherwise disabled. |
4276 | |
4645 | |
|
|
4646 | =item EV_USE_SIGNALFD |
|
|
4647 | |
|
|
4648 | If defined to be C<1>, then libev will assume that C<signalfd ()> is |
|
|
4649 | available and will probe for kernel support at runtime. This enables |
|
|
4650 | the use of EVFLAG_SIGNALFD for faster and simpler signal handling. If |
|
|
4651 | undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4652 | 2.7 or newer, otherwise disabled. |
|
|
4653 | |
|
|
4654 | =item EV_USE_TIMERFD |
|
|
4655 | |
|
|
4656 | If defined to be C<1>, then libev will assume that C<timerfd ()> is |
|
|
4657 | available and will probe for kernel support at runtime. This allows |
|
|
4658 | libev to detect time jumps accurately. If undefined, it will be enabled |
|
|
4659 | if the headers indicate GNU/Linux + Glibc 2.8 or newer and define |
|
|
4660 | C<TFD_TIMER_CANCEL_ON_SET>, otherwise disabled. |
|
|
4661 | |
|
|
4662 | =item EV_USE_EVENTFD |
|
|
4663 | |
|
|
4664 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
4665 | available and will probe for kernel support at runtime. This will improve |
|
|
4666 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
4667 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
4668 | 2.7 or newer, otherwise disabled. |
|
|
4669 | |
4277 | =item EV_USE_SELECT |
4670 | =item EV_USE_SELECT |
4278 | |
4671 | |
4279 | If undefined or defined to be C<1>, libev will compile in support for the |
4672 | If undefined or defined to be C<1>, libev will compile in support for the |
4280 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4673 | C<select>(2) backend. No attempt at auto-detection will be done: if no |
4281 | other method takes over, select will be it. Otherwise the select backend |
4674 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
4321 | If programs implement their own fd to handle mapping on win32, then this |
4714 | If programs implement their own fd to handle mapping on win32, then this |
4322 | macro can be used to override the C<close> function, useful to unregister |
4715 | macro can be used to override the C<close> function, useful to unregister |
4323 | file descriptors again. Note that the replacement function has to close |
4716 | file descriptors again. Note that the replacement function has to close |
4324 | the underlying OS handle. |
4717 | the underlying OS handle. |
4325 | |
4718 | |
|
|
4719 | =item EV_USE_WSASOCKET |
|
|
4720 | |
|
|
4721 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4722 | communication socket, which works better in some environments. Otherwise, |
|
|
4723 | the normal C<socket> function will be used, which works better in other |
|
|
4724 | environments. |
|
|
4725 | |
4326 | =item EV_USE_POLL |
4726 | =item EV_USE_POLL |
4327 | |
4727 | |
4328 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4728 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4329 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4729 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4330 | takes precedence over select. |
4730 | takes precedence over select. |
… | |
… | |
4334 | If defined to be C<1>, libev will compile in support for the Linux |
4734 | If defined to be C<1>, libev will compile in support for the Linux |
4335 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4735 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4336 | otherwise another method will be used as fallback. This is the preferred |
4736 | otherwise another method will be used as fallback. This is the preferred |
4337 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4737 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4338 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4738 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4739 | |
|
|
4740 | =item EV_USE_LINUXAIO |
|
|
4741 | |
|
|
4742 | If defined to be C<1>, libev will compile in support for the Linux aio |
|
|
4743 | backend (C<EV_USE_EPOLL> must also be enabled). If undefined, it will be |
|
|
4744 | enabled on linux, otherwise disabled. |
|
|
4745 | |
|
|
4746 | =item EV_USE_IOURING |
|
|
4747 | |
|
|
4748 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4749 | io_uring backend (C<EV_USE_EPOLL> must also be enabled). Due to it's |
|
|
4750 | current limitations it has to be requested explicitly. If undefined, it |
|
|
4751 | will be enabled on linux, otherwise disabled. |
4339 | |
4752 | |
4340 | =item EV_USE_KQUEUE |
4753 | =item EV_USE_KQUEUE |
4341 | |
4754 | |
4342 | If defined to be C<1>, libev will compile in support for the BSD style |
4755 | If defined to be C<1>, libev will compile in support for the BSD style |
4343 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4756 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4365 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4778 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4366 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4779 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4367 | be detected at runtime. If undefined, it will be enabled if the headers |
4780 | be detected at runtime. If undefined, it will be enabled if the headers |
4368 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4781 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4369 | |
4782 | |
|
|
4783 | =item EV_NO_SMP |
|
|
4784 | |
|
|
4785 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4786 | between threads, that is, threads can be used, but threads never run on |
|
|
4787 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4788 | and makes libev faster. |
|
|
4789 | |
|
|
4790 | =item EV_NO_THREADS |
|
|
4791 | |
|
|
4792 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4793 | different threads (that includes signal handlers), which is a stronger |
|
|
4794 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4795 | libev faster. |
|
|
4796 | |
4370 | =item EV_ATOMIC_T |
4797 | =item EV_ATOMIC_T |
4371 | |
4798 | |
4372 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4799 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4373 | access is atomic with respect to other threads or signal contexts. No such |
4800 | access is atomic with respect to other threads or signal contexts. No |
4374 | type is easily found in the C language, so you can provide your own type |
4801 | such type is easily found in the C language, so you can provide your own |
4375 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4802 | type that you know is safe for your purposes. It is used both for signal |
4376 | as well as for signal and thread safety in C<ev_async> watchers. |
4803 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4804 | watchers. |
4377 | |
4805 | |
4378 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4806 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4379 | (from F<signal.h>), which is usually good enough on most platforms. |
4807 | (from F<signal.h>), which is usually good enough on most platforms. |
4380 | |
4808 | |
4381 | =item EV_H (h) |
4809 | =item EV_H (h) |
… | |
… | |
4408 | will have the C<struct ev_loop *> as first argument, and you can create |
4836 | will have the C<struct ev_loop *> as first argument, and you can create |
4409 | additional independent event loops. Otherwise there will be no support |
4837 | additional independent event loops. Otherwise there will be no support |
4410 | for multiple event loops and there is no first event loop pointer |
4838 | for multiple event loops and there is no first event loop pointer |
4411 | argument. Instead, all functions act on the single default loop. |
4839 | argument. Instead, all functions act on the single default loop. |
4412 | |
4840 | |
|
|
4841 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4842 | default loop when multiplicity is switched off - you always have to |
|
|
4843 | initialise the loop manually in this case. |
|
|
4844 | |
4413 | =item EV_MINPRI |
4845 | =item EV_MINPRI |
4414 | |
4846 | |
4415 | =item EV_MAXPRI |
4847 | =item EV_MAXPRI |
4416 | |
4848 | |
4417 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4849 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4453 | #define EV_USE_POLL 1 |
4885 | #define EV_USE_POLL 1 |
4454 | #define EV_CHILD_ENABLE 1 |
4886 | #define EV_CHILD_ENABLE 1 |
4455 | #define EV_ASYNC_ENABLE 1 |
4887 | #define EV_ASYNC_ENABLE 1 |
4456 | |
4888 | |
4457 | The actual value is a bitset, it can be a combination of the following |
4889 | The actual value is a bitset, it can be a combination of the following |
4458 | values: |
4890 | values (by default, all of these are enabled): |
4459 | |
4891 | |
4460 | =over 4 |
4892 | =over 4 |
4461 | |
4893 | |
4462 | =item C<1> - faster/larger code |
4894 | =item C<1> - faster/larger code |
4463 | |
4895 | |
… | |
… | |
4467 | code size by roughly 30% on amd64). |
4899 | code size by roughly 30% on amd64). |
4468 | |
4900 | |
4469 | When optimising for size, use of compiler flags such as C<-Os> with |
4901 | When optimising for size, use of compiler flags such as C<-Os> with |
4470 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4902 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4471 | assertions. |
4903 | assertions. |
|
|
4904 | |
|
|
4905 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4906 | (e.g. gcc with C<-Os>). |
4472 | |
4907 | |
4473 | =item C<2> - faster/larger data structures |
4908 | =item C<2> - faster/larger data structures |
4474 | |
4909 | |
4475 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4910 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4476 | hash table sizes and so on. This will usually further increase code size |
4911 | hash table sizes and so on. This will usually further increase code size |
4477 | and can additionally have an effect on the size of data structures at |
4912 | and can additionally have an effect on the size of data structures at |
4478 | runtime. |
4913 | runtime. |
4479 | |
4914 | |
|
|
4915 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4916 | (e.g. gcc with C<-Os>). |
|
|
4917 | |
4480 | =item C<4> - full API configuration |
4918 | =item C<4> - full API configuration |
4481 | |
4919 | |
4482 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4920 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4483 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4921 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4484 | |
4922 | |
… | |
… | |
4514 | |
4952 | |
4515 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4953 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4516 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4954 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4517 | your program might be left out as well - a binary starting a timer and an |
4955 | your program might be left out as well - a binary starting a timer and an |
4518 | I/O watcher then might come out at only 5Kb. |
4956 | I/O watcher then might come out at only 5Kb. |
|
|
4957 | |
|
|
4958 | =item EV_API_STATIC |
|
|
4959 | |
|
|
4960 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4961 | will have static linkage. This means that libev will not export any |
|
|
4962 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4963 | when you embed libev, only want to use libev functions in a single file, |
|
|
4964 | and do not want its identifiers to be visible. |
|
|
4965 | |
|
|
4966 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4967 | wants to use libev. |
|
|
4968 | |
|
|
4969 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4970 | doesn't support the required declaration syntax. |
4519 | |
4971 | |
4520 | =item EV_AVOID_STDIO |
4972 | =item EV_AVOID_STDIO |
4521 | |
4973 | |
4522 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4974 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4523 | functions (printf, scanf, perror etc.). This will increase the code size |
4975 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4581 | in. If set to C<1>, then verification code will be compiled in, but not |
5033 | in. If set to C<1>, then verification code will be compiled in, but not |
4582 | called. If set to C<2>, then the internal verification code will be |
5034 | called. If set to C<2>, then the internal verification code will be |
4583 | called once per loop, which can slow down libev. If set to C<3>, then the |
5035 | called once per loop, which can slow down libev. If set to C<3>, then the |
4584 | verification code will be called very frequently, which will slow down |
5036 | verification code will be called very frequently, which will slow down |
4585 | libev considerably. |
5037 | libev considerably. |
|
|
5038 | |
|
|
5039 | Verification errors are reported via C's C<assert> mechanism, so if you |
|
|
5040 | disable that (e.g. by defining C<NDEBUG>) then no errors will be reported. |
4586 | |
5041 | |
4587 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
5042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4588 | will be C<0>. |
5043 | will be C<0>. |
4589 | |
5044 | |
4590 | =item EV_COMMON |
5045 | =item EV_COMMON |
… | |
… | |
4728 | default loop and triggering an C<ev_async> watcher from the default loop |
5183 | default loop and triggering an C<ev_async> watcher from the default loop |
4729 | watcher callback into the event loop interested in the signal. |
5184 | watcher callback into the event loop interested in the signal. |
4730 | |
5185 | |
4731 | =back |
5186 | =back |
4732 | |
5187 | |
4733 | See also L<THREAD LOCKING EXAMPLE>. |
5188 | See also L</THREAD LOCKING EXAMPLE>. |
4734 | |
5189 | |
4735 | =head3 COROUTINES |
5190 | =head3 COROUTINES |
4736 | |
5191 | |
4737 | Libev is very accommodating to coroutines ("cooperative threads"): |
5192 | Libev is very accommodating to coroutines ("cooperative threads"): |
4738 | libev fully supports nesting calls to its functions from different |
5193 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4903 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5358 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4904 | model. Libev still offers limited functionality on this platform in |
5359 | model. Libev still offers limited functionality on this platform in |
4905 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5360 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4906 | descriptors. This only applies when using Win32 natively, not when using |
5361 | descriptors. This only applies when using Win32 natively, not when using |
4907 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5362 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4908 | as every compielr comes with a slightly differently broken/incompatible |
5363 | as every compiler comes with a slightly differently broken/incompatible |
4909 | environment. |
5364 | environment. |
4910 | |
5365 | |
4911 | Lifting these limitations would basically require the full |
5366 | Lifting these limitations would basically require the full |
4912 | re-implementation of the I/O system. If you are into this kind of thing, |
5367 | re-implementation of the I/O system. If you are into this kind of thing, |
4913 | then note that glib does exactly that for you in a very portable way (note |
5368 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5007 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5462 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5008 | assumes that the same (machine) code can be used to call any watcher |
5463 | assumes that the same (machine) code can be used to call any watcher |
5009 | callback: The watcher callbacks have different type signatures, but libev |
5464 | callback: The watcher callbacks have different type signatures, but libev |
5010 | calls them using an C<ev_watcher *> internally. |
5465 | calls them using an C<ev_watcher *> internally. |
5011 | |
5466 | |
|
|
5467 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5468 | |
|
|
5469 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5470 | relies on this setting pointers and integers to null. |
|
|
5471 | |
5012 | =item pointer accesses must be thread-atomic |
5472 | =item pointer accesses must be thread-atomic |
5013 | |
5473 | |
5014 | Accessing a pointer value must be atomic, it must both be readable and |
5474 | Accessing a pointer value must be atomic, it must both be readable and |
5015 | writable in one piece - this is the case on all current architectures. |
5475 | writable in one piece - this is the case on all current architectures. |
5016 | |
5476 | |
… | |
… | |
5029 | thread" or will block signals process-wide, both behaviours would |
5489 | thread" or will block signals process-wide, both behaviours would |
5030 | be compatible with libev. Interaction between C<sigprocmask> and |
5490 | be compatible with libev. Interaction between C<sigprocmask> and |
5031 | C<pthread_sigmask> could complicate things, however. |
5491 | C<pthread_sigmask> could complicate things, however. |
5032 | |
5492 | |
5033 | The most portable way to handle signals is to block signals in all threads |
5493 | The most portable way to handle signals is to block signals in all threads |
5034 | except the initial one, and run the default loop in the initial thread as |
5494 | except the initial one, and run the signal handling loop in the initial |
5035 | well. |
5495 | thread as well. |
5036 | |
5496 | |
5037 | =item C<long> must be large enough for common memory allocation sizes |
5497 | =item C<long> must be large enough for common memory allocation sizes |
5038 | |
5498 | |
5039 | To improve portability and simplify its API, libev uses C<long> internally |
5499 | To improve portability and simplify its API, libev uses C<long> internally |
5040 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5500 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5046 | |
5506 | |
5047 | The type C<double> is used to represent timestamps. It is required to |
5507 | The type C<double> is used to represent timestamps. It is required to |
5048 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5508 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5049 | good enough for at least into the year 4000 with millisecond accuracy |
5509 | good enough for at least into the year 4000 with millisecond accuracy |
5050 | (the design goal for libev). This requirement is overfulfilled by |
5510 | (the design goal for libev). This requirement is overfulfilled by |
5051 | implementations using IEEE 754, which is basically all existing ones. With |
5511 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5512 | |
5052 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5513 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5514 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5515 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5516 | something like that, just kidding). |
5053 | |
5517 | |
5054 | =back |
5518 | =back |
5055 | |
5519 | |
5056 | If you know of other additional requirements drop me a note. |
5520 | If you know of other additional requirements drop me a note. |
5057 | |
5521 | |
… | |
… | |
5119 | =item Processing ev_async_send: O(number_of_async_watchers) |
5583 | =item Processing ev_async_send: O(number_of_async_watchers) |
5120 | |
5584 | |
5121 | =item Processing signals: O(max_signal_number) |
5585 | =item Processing signals: O(max_signal_number) |
5122 | |
5586 | |
5123 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5587 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5124 | calls in the current loop iteration. Checking for async and signal events |
5588 | calls in the current loop iteration and the loop is currently |
|
|
5589 | blocked. Checking for async and signal events involves iterating over all |
5125 | involves iterating over all running async watchers or all signal numbers. |
5590 | running async watchers or all signal numbers. |
5126 | |
5591 | |
5127 | =back |
5592 | =back |
5128 | |
5593 | |
5129 | |
5594 | |
5130 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5595 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5139 | =over 4 |
5604 | =over 4 |
5140 | |
5605 | |
5141 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5606 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5142 | |
5607 | |
5143 | The backward compatibility mechanism can be controlled by |
5608 | The backward compatibility mechanism can be controlled by |
5144 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5609 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5145 | section. |
5610 | section. |
5146 | |
5611 | |
5147 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5612 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5148 | |
5613 | |
5149 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5614 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5192 | =over 4 |
5657 | =over 4 |
5193 | |
5658 | |
5194 | =item active |
5659 | =item active |
5195 | |
5660 | |
5196 | A watcher is active as long as it has been started and not yet stopped. |
5661 | A watcher is active as long as it has been started and not yet stopped. |
5197 | See L<WATCHER STATES> for details. |
5662 | See L</WATCHER STATES> for details. |
5198 | |
5663 | |
5199 | =item application |
5664 | =item application |
5200 | |
5665 | |
5201 | In this document, an application is whatever is using libev. |
5666 | In this document, an application is whatever is using libev. |
5202 | |
5667 | |
… | |
… | |
5238 | watchers and events. |
5703 | watchers and events. |
5239 | |
5704 | |
5240 | =item pending |
5705 | =item pending |
5241 | |
5706 | |
5242 | A watcher is pending as soon as the corresponding event has been |
5707 | A watcher is pending as soon as the corresponding event has been |
5243 | detected. See L<WATCHER STATES> for details. |
5708 | detected. See L</WATCHER STATES> for details. |
5244 | |
5709 | |
5245 | =item real time |
5710 | =item real time |
5246 | |
5711 | |
5247 | The physical time that is observed. It is apparently strictly monotonic :) |
5712 | The physical time that is observed. It is apparently strictly monotonic :) |
5248 | |
5713 | |