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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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174 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
175 | |
177 | |
176 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
180 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
181 | C<ev_now_update> and C<ev_now>. |
180 | |
182 | |
181 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
182 | |
184 | |
183 | Sleep for the given interval: The current thread will be blocked |
185 | Sleep for the given interval: The current thread will be blocked |
184 | until either it is interrupted or the given time interval has |
186 | 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 () |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
249 | |
251 | |
250 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
251 | |
253 | |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
253 | |
255 | |
254 | Sets the allocation function to use (the prototype is similar - the |
256 | 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 |
257 | 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 |
258 | 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 |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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263 | |
265 | |
264 | You could override this function in high-availability programs to, say, |
266 | 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, |
267 | 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. |
268 | or even to sleep a while and retry until some memory is available. |
267 | |
269 | |
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270 | Example: The following is the C<realloc> function that libev itself uses |
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271 | which should work with C<realloc> and C<free> functions of all kinds and |
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272 | is probably a good basis for your own implementation. |
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273 | |
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274 | static void * |
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275 | ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT |
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276 | { |
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277 | if (size) |
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278 | return realloc (ptr, size); |
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279 | |
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280 | free (ptr); |
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281 | return 0; |
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282 | } |
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283 | |
268 | Example: Replace the libev allocator with one that waits a bit and then |
284 | Example: Replace the libev allocator with one that waits a bit and then |
269 | retries (example requires a standards-compliant C<realloc>). |
285 | retries. |
270 | |
286 | |
271 | static void * |
287 | static void * |
272 | persistent_realloc (void *ptr, size_t size) |
288 | persistent_realloc (void *ptr, size_t size) |
273 | { |
289 | { |
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290 | if (!size) |
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291 | { |
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292 | free (ptr); |
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293 | return 0; |
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294 | } |
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295 | |
274 | for (;;) |
296 | for (;;) |
275 | { |
297 | { |
276 | void *newptr = realloc (ptr, size); |
298 | void *newptr = realloc (ptr, size); |
277 | |
299 | |
278 | if (newptr) |
300 | if (newptr) |
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283 | } |
305 | } |
284 | |
306 | |
285 | ... |
307 | ... |
286 | ev_set_allocator (persistent_realloc); |
308 | ev_set_allocator (persistent_realloc); |
287 | |
309 | |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
310 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
289 | |
311 | |
290 | Set the callback function to call on a retryable system call error (such |
312 | Set the callback function to call on a retryable system call error (such |
291 | as failed select, poll, epoll_wait). The message is a printable string |
313 | as failed select, poll, epoll_wait). The message is a printable string |
292 | indicating the system call or subsystem causing the problem. If this |
314 | 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 |
315 | callback is set, then libev will expect it to remedy the situation, no |
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396 | |
418 | |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
419 | If this flag bit is or'ed into the flag value (or the program runs setuid |
398 | or setgid) then libev will I<not> look at the environment variable |
420 | or setgid) then libev will I<not> look at the environment variable |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
421 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
400 | override the flags completely if it is found in the environment. This is |
422 | override the flags completely if it is found in the environment. This is |
401 | useful to try out specific backends to test their performance, or to work |
423 | useful to try out specific backends to test their performance, to work |
402 | around bugs. |
424 | around bugs, or to make libev threadsafe (accessing environment variables |
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425 | cannot be done in a threadsafe way, but usually it works if no other |
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426 | thread modifies them). |
403 | |
427 | |
404 | =item C<EVFLAG_FORKCHECK> |
428 | =item C<EVFLAG_FORKCHECK> |
405 | |
429 | |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
430 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
407 | make libev check for a fork in each iteration by enabling this flag. |
431 | make libev check for a fork in each iteration by enabling this flag. |
408 | |
432 | |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
433 | This works by calling C<getpid ()> on every iteration of the loop, |
410 | and thus this might slow down your event loop if you do a lot of loop |
434 | and thus this might slow down your event loop if you do a lot of loop |
411 | iterations and little real work, but is usually not noticeable (on my |
435 | iterations and little real work, but is usually not noticeable (on my |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
436 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
413 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
437 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
414 | C<pthread_atfork> which is even faster). |
438 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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439 | versions 2.25 apparently removed the C<getpid> optimisation again). |
415 | |
440 | |
416 | The big advantage of this flag is that you can forget about fork (and |
441 | The big advantage of this flag is that you can forget about fork (and |
417 | forget about forgetting to tell libev about forking) when you use this |
442 | forget about forgetting to tell libev about forking, although you still |
418 | flag. |
443 | have to ignore C<SIGPIPE>) when you use this flag. |
419 | |
444 | |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
445 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
421 | environment variable. |
446 | environment variable. |
422 | |
447 | |
423 | =item C<EVFLAG_NOINOTIFY> |
448 | =item C<EVFLAG_NOINOTIFY> |
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441 | example) that can't properly initialise their signal masks. |
466 | example) that can't properly initialise their signal masks. |
442 | |
467 | |
443 | =item C<EVFLAG_NOSIGMASK> |
468 | =item C<EVFLAG_NOSIGMASK> |
444 | |
469 | |
445 | When this flag is specified, then libev will avoid to modify the signal |
470 | 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 |
471 | mask. Specifically, this means you have to make sure signals are unblocked |
447 | when you want to receive them. |
472 | when you want to receive them. |
448 | |
473 | |
449 | This behaviour is useful when you want to do your own signal handling, or |
474 | 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 |
475 | want to handle signals only in specific threads and want to avoid libev |
451 | unblocking the signals. |
476 | unblocking the signals. |
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486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
511 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
512 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
488 | |
513 | |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
514 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
490 | |
515 | |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
516 | Use the Linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
492 | kernels). |
517 | kernels). |
493 | |
518 | |
494 | For few fds, this backend is a bit little slower than poll and select, but |
519 | 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 |
520 | 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 |
521 | 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 |
537 | totally I<different> file descriptors (even already closed ones, so |
513 | one cannot even remove them from the set) than registered in the set |
538 | one cannot even remove them from the set) than registered in the set |
514 | (especially on SMP systems). Libev tries to counter these spurious |
539 | (especially on SMP systems). Libev tries to counter these spurious |
515 | notifications by employing an additional generation counter and comparing |
540 | notifications by employing an additional generation counter and comparing |
516 | that against the events to filter out spurious ones, recreating the set |
541 | that against the events to filter out spurious ones, recreating the set |
517 | when required. Epoll also errornously rounds down timeouts, but gives you |
542 | 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 |
543 | 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 |
544 | because epoll returns immediately despite a nonzero timeout. And last |
520 | not least, it also refuses to work with some file descriptors which work |
545 | not least, it also refuses to work with some file descriptors which work |
521 | perfectly fine with C<select> (files, many character devices...). |
546 | perfectly fine with C<select> (files, many character devices...). |
522 | |
547 | |
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542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
567 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
543 | faster than epoll for maybe up to a hundred file descriptors, depending on |
568 | faster than epoll for maybe up to a hundred file descriptors, depending on |
544 | the usage. So sad. |
569 | the usage. So sad. |
545 | |
570 | |
546 | While nominally embeddable in other event loops, this feature is broken in |
571 | While nominally embeddable in other event loops, this feature is broken in |
547 | all kernel versions tested so far. |
572 | a lot of kernel revisions, but probably(!) works in current versions. |
548 | |
573 | |
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
574 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
550 | C<EVBACKEND_POLL>. |
575 | C<EVBACKEND_POLL>. |
551 | |
576 | |
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577 | =item C<EVBACKEND_LINUXAIO> (value 64, Linux) |
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578 | |
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579 | Use the Linux-specific Linux AIO (I<not> C<< aio(7) >> but C<< |
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580 | io_submit(2) >>) event interface available in post-4.18 kernels (but libev |
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581 | only tries to use it in 4.19+). |
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582 | |
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583 | This is another Linux train wreck of an event interface. |
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584 | |
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585 | If this backend works for you (as of this writing, it was very |
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586 | experimental), it is the best event interface available on Linux and might |
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587 | be well worth enabling it - if it isn't available in your kernel this will |
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588 | be detected and this backend will be skipped. |
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589 | |
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590 | This backend can batch oneshot requests and supports a user-space ring |
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591 | buffer to receive events. It also doesn't suffer from most of the design |
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592 | problems of epoll (such as not being able to remove event sources from |
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593 | the epoll set), and generally sounds too good to be true. Because, this |
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594 | being the Linux kernel, of course it suffers from a whole new set of |
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595 | limitations, forcing you to fall back to epoll, inheriting all its design |
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596 | issues. |
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597 | |
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598 | For one, it is not easily embeddable (but probably could be done using |
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599 | an event fd at some extra overhead). It also is subject to a system wide |
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600 | limit that can be configured in F</proc/sys/fs/aio-max-nr>. If no AIO |
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601 | requests are left, this backend will be skipped during initialisation, and |
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602 | will switch to epoll when the loop is active. |
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603 | |
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604 | Most problematic in practice, however, is that not all file descriptors |
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605 | work with it. For example, in Linux 5.1, TCP sockets, pipes, event fds, |
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606 | files, F</dev/null> and many others are supported, but ttys do not work |
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607 | properly (a known bug that the kernel developers don't care about, see |
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608 | L<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not |
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609 | (yet?) a generic event polling interface. |
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610 | |
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611 | Overall, it seems the Linux developers just don't want it to have a |
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612 | generic event handling mechanism other than C<select> or C<poll>. |
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613 | |
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614 | To work around all these problem, the current version of libev uses its |
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615 | epoll backend as a fallback for file descriptor types that do not work. Or |
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616 | falls back completely to epoll if the kernel acts up. |
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617 | |
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618 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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619 | C<EVBACKEND_POLL>. |
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620 | |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
621 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
553 | |
622 | |
554 | Kqueue deserves special mention, as at the time of this writing, it |
623 | 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 |
624 | 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 |
625 | work reliably with anything but sockets and pipes, except on Darwin, |
557 | it's completely useless). Unlike epoll, however, whose brokenness |
626 | where of course it's completely useless). Unlike epoll, however, whose |
558 | is by design, these kqueue bugs can (and eventually will) be fixed |
627 | brokenness is by design, these kqueue bugs can be (and mostly have been) |
559 | without API changes to existing programs. For this reason it's not being |
628 | fixed without API changes to existing programs. For this reason it's not |
560 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
629 | being "auto-detected" on all platforms unless you explicitly specify it |
561 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
630 | in the flags (i.e. using C<EVBACKEND_KQUEUE>) or libev was compiled on a |
562 | system like NetBSD. |
631 | known-to-be-good (-enough) system like NetBSD. |
563 | |
632 | |
564 | You still can embed kqueue into a normal poll or select backend and use it |
633 | You still can embed kqueue into a normal poll or select backend and use it |
565 | only for sockets (after having made sure that sockets work with kqueue on |
634 | only for sockets (after having made sure that sockets work with kqueue on |
566 | the target platform). See C<ev_embed> watchers for more info. |
635 | the target platform). See C<ev_embed> watchers for more info. |
567 | |
636 | |
568 | It scales in the same way as the epoll backend, but the interface to the |
637 | It scales in the same way as the epoll backend, but the interface to the |
569 | kernel is more efficient (which says nothing about its actual speed, of |
638 | kernel is more efficient (which says nothing about its actual speed, of |
570 | course). While stopping, setting and starting an I/O watcher does never |
639 | course). While stopping, setting and starting an I/O watcher does never |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
640 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
572 | two event changes per incident. Support for C<fork ()> is very bad (but |
641 | two event changes per incident. Support for C<fork ()> is very bad (you |
573 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
642 | might have to leak fds on fork, but it's more sane than epoll) and it |
574 | cases |
643 | drops fds silently in similarly hard-to-detect cases. |
575 | |
644 | |
576 | This backend usually performs well under most conditions. |
645 | This backend usually performs well under most conditions. |
577 | |
646 | |
578 | While nominally embeddable in other event loops, this doesn't work |
647 | 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 |
648 | everywhere, so you might need to test for this. And since it is broken |
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608 | among the OS-specific backends (I vastly prefer correctness over speed |
677 | among the OS-specific backends (I vastly prefer correctness over speed |
609 | hacks). |
678 | hacks). |
610 | |
679 | |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
680 | 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 |
681 | 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 |
682 | 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 |
683 | 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 |
684 | 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 |
685 | absolutely have to know whether an event occurred or not because you have |
617 | have to re-arm the watcher. |
686 | to re-arm the watcher. |
618 | |
687 | |
619 | Fortunately libev seems to be able to work around these idiocies. |
688 | Fortunately libev seems to be able to work around these idiocies. |
620 | |
689 | |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
690 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
622 | C<EVBACKEND_POLL>. |
691 | C<EVBACKEND_POLL>. |
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652 | |
721 | |
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
722 | Example: Use whatever libev has to offer, but make sure that kqueue is |
654 | used if available. |
723 | used if available. |
655 | |
724 | |
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
725 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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726 | |
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727 | Example: Similarly, on linux, you mgiht want to take advantage of the |
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728 | linux aio backend if possible, but fall back to something else if that |
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729 | isn't available. |
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730 | |
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731 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO); |
657 | |
732 | |
658 | =item ev_loop_destroy (loop) |
733 | =item ev_loop_destroy (loop) |
659 | |
734 | |
660 | Destroys an event loop object (frees all memory and kernel state |
735 | 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 |
736 | 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> |
753 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
679 | and C<ev_loop_destroy>. |
754 | and C<ev_loop_destroy>. |
680 | |
755 | |
681 | =item ev_loop_fork (loop) |
756 | =item ev_loop_fork (loop) |
682 | |
757 | |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
758 | This function sets a flag that causes subsequent C<ev_run> iterations |
684 | reinitialise the kernel state for backends that have one. Despite the |
759 | 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 |
760 | 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 |
761 | watchers (except inside an C<ev_prepare> callback), but it makes most |
|
|
762 | sense after forking, in the child process. You I<must> call it (or use |
687 | child before resuming or calling C<ev_run>. |
763 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
688 | |
764 | |
|
|
765 | In addition, if you want to reuse a loop (via this function or |
|
|
766 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
767 | |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
768 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
769 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
770 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
692 | during fork. |
771 | during fork. |
693 | |
772 | |
694 | On the other hand, you only need to call this function in the child |
773 | On the other hand, you only need to call this function in the child |
… | |
… | |
764 | |
843 | |
765 | This function is rarely useful, but when some event callback runs for a |
844 | This function is rarely useful, but when some event callback runs for a |
766 | very long time without entering the event loop, updating libev's idea of |
845 | very long time without entering the event loop, updating libev's idea of |
767 | the current time is a good idea. |
846 | the current time is a good idea. |
768 | |
847 | |
769 | See also L<The special problem of time updates> in the C<ev_timer> section. |
848 | See also L</The special problem of time updates> in the C<ev_timer> section. |
770 | |
849 | |
771 | =item ev_suspend (loop) |
850 | =item ev_suspend (loop) |
772 | |
851 | |
773 | =item ev_resume (loop) |
852 | =item ev_resume (loop) |
774 | |
853 | |
… | |
… | |
792 | without a previous call to C<ev_suspend>. |
871 | without a previous call to C<ev_suspend>. |
793 | |
872 | |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
873 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
795 | event loop time (see C<ev_now_update>). |
874 | event loop time (see C<ev_now_update>). |
796 | |
875 | |
797 | =item ev_run (loop, int flags) |
876 | =item bool ev_run (loop, int flags) |
798 | |
877 | |
799 | Finally, this is it, the event handler. This function usually is called |
878 | Finally, this is it, the event handler. This function usually is called |
800 | after you have initialised all your watchers and you want to start |
879 | after you have initialised all your watchers and you want to start |
801 | handling events. It will ask the operating system for any new events, call |
880 | handling events. It will ask the operating system for any new events, call |
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
881 | the watcher callbacks, and then repeat the whole process indefinitely: This |
803 | is why event loops are called I<loops>. |
882 | is why event loops are called I<loops>. |
804 | |
883 | |
805 | If the flags argument is specified as C<0>, it will keep handling events |
884 | If the flags argument is specified as C<0>, it will keep handling events |
806 | until either no event watchers are active anymore or C<ev_break> was |
885 | until either no event watchers are active anymore or C<ev_break> was |
807 | called. |
886 | called. |
|
|
887 | |
|
|
888 | The return value is false if there are no more active watchers (which |
|
|
889 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
890 | (which usually means " you should call C<ev_run> again"). |
808 | |
891 | |
809 | Please note that an explicit C<ev_break> is usually better than |
892 | Please note that an explicit C<ev_break> is usually better than |
810 | relying on all watchers to be stopped when deciding when a program has |
893 | relying on all watchers to be stopped when deciding when a program has |
811 | finished (especially in interactive programs), but having a program |
894 | finished (especially in interactive programs), but having a program |
812 | that automatically loops as long as it has to and no longer by virtue |
895 | that automatically loops as long as it has to and no longer by virtue |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
896 | of relying on its watchers stopping correctly, that is truly a thing of |
814 | beauty. |
897 | beauty. |
815 | |
898 | |
816 | This function is also I<mostly> exception-safe - you can break out of |
899 | This function is I<mostly> exception-safe - you can break out of a |
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
900 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
901 | exception and so on. This does not decrement the C<ev_depth> value, nor |
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
902 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
820 | |
903 | |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
904 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
822 | those events and any already outstanding ones, but will not wait and |
905 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
955 | time collecting I/O events, so you can handle more events per iteration, |
1038 | time collecting I/O events, so you can handle more events per iteration, |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
1039 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
1040 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
1041 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
959 | sleep time ensures that libev will not poll for I/O events more often then |
1042 | sleep time ensures that libev will not poll for I/O events more often then |
960 | once per this interval, on average. |
1043 | once per this interval, on average (as long as the host time resolution is |
|
|
1044 | good enough). |
961 | |
1045 | |
962 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
1046 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | to spend more time collecting timeouts, at the expense of increased |
1047 | to spend more time collecting timeouts, at the expense of increased |
964 | latency/jitter/inexactness (the watcher callback will be called |
1048 | 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 |
1049 | 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.). |
1095 | invoke the actual watchers inside another context (another thread etc.). |
1012 | |
1096 | |
1013 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1097 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1014 | callback. |
1098 | callback. |
1015 | |
1099 | |
1016 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1100 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
1017 | |
1101 | |
1018 | Sometimes you want to share the same loop between multiple threads. This |
1102 | Sometimes you want to share the same loop between multiple threads. This |
1019 | can be done relatively simply by putting mutex_lock/unlock calls around |
1103 | can be done relatively simply by putting mutex_lock/unlock calls around |
1020 | each call to a libev function. |
1104 | each call to a libev function. |
1021 | |
1105 | |
1022 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1106 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1023 | to wait for it to return. One way around this is to wake up the event |
1107 | to wait for it to return. One way around this is to wake up the event |
1024 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1108 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1025 | I<release> and I<acquire> callbacks on the loop. |
1109 | I<release> and I<acquire> callbacks on the loop. |
1026 | |
1110 | |
1027 | When set, then C<release> will be called just before the thread is |
1111 | When set, then C<release> will be called just before the thread is |
1028 | suspended waiting for new events, and C<acquire> is called just |
1112 | suspended waiting for new events, and C<acquire> is called just |
1029 | afterwards. |
1113 | afterwards. |
… | |
… | |
1169 | |
1253 | |
1170 | =item C<EV_PREPARE> |
1254 | =item C<EV_PREPARE> |
1171 | |
1255 | |
1172 | =item C<EV_CHECK> |
1256 | =item C<EV_CHECK> |
1173 | |
1257 | |
1174 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1258 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1175 | to gather new events, and all C<ev_check> watchers are invoked just after |
1259 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1176 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1260 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1261 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1262 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1263 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1264 | or lower priority within an event loop iteration. |
|
|
1265 | |
1177 | received events. Callbacks of both watcher types can start and stop as |
1266 | Callbacks of both watcher types can start and stop as many watchers as |
1178 | many watchers as they want, and all of them will be taken into account |
1267 | they want, and all of them will be taken into account (for example, a |
1179 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1268 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1180 | C<ev_run> from blocking). |
1269 | blocking). |
1181 | |
1270 | |
1182 | =item C<EV_EMBED> |
1271 | =item C<EV_EMBED> |
1183 | |
1272 | |
1184 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1273 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1185 | |
1274 | |
… | |
… | |
1308 | |
1397 | |
1309 | =item callback ev_cb (ev_TYPE *watcher) |
1398 | =item callback ev_cb (ev_TYPE *watcher) |
1310 | |
1399 | |
1311 | Returns the callback currently set on the watcher. |
1400 | Returns the callback currently set on the watcher. |
1312 | |
1401 | |
1313 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1402 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1314 | |
1403 | |
1315 | Change the callback. You can change the callback at virtually any time |
1404 | Change the callback. You can change the callback at virtually any time |
1316 | (modulo threads). |
1405 | (modulo threads). |
1317 | |
1406 | |
1318 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1407 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1336 | or might not have been clamped to the valid range. |
1425 | or might not have been clamped to the valid range. |
1337 | |
1426 | |
1338 | The default priority used by watchers when no priority has been set is |
1427 | The default priority used by watchers when no priority has been set is |
1339 | always C<0>, which is supposed to not be too high and not be too low :). |
1428 | always C<0>, which is supposed to not be too high and not be too low :). |
1340 | |
1429 | |
1341 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1430 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1342 | priorities. |
1431 | priorities. |
1343 | |
1432 | |
1344 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1433 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1345 | |
1434 | |
1346 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1435 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1371 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1460 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1372 | functions that do not need a watcher. |
1461 | functions that do not need a watcher. |
1373 | |
1462 | |
1374 | =back |
1463 | =back |
1375 | |
1464 | |
1376 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1465 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
1377 | OWN COMPOSITE WATCHERS> idioms. |
1466 | OWN COMPOSITE WATCHERS> idioms. |
1378 | |
1467 | |
1379 | =head2 WATCHER STATES |
1468 | =head2 WATCHER STATES |
1380 | |
1469 | |
1381 | There are various watcher states mentioned throughout this manual - |
1470 | There are various watcher states mentioned throughout this manual - |
… | |
… | |
1383 | transition between them will be described in more detail - and while these |
1472 | transition between them will be described in more detail - and while these |
1384 | rules might look complicated, they usually do "the right thing". |
1473 | rules might look complicated, they usually do "the right thing". |
1385 | |
1474 | |
1386 | =over 4 |
1475 | =over 4 |
1387 | |
1476 | |
1388 | =item initialiased |
1477 | =item initialised |
1389 | |
1478 | |
1390 | Before a watcher can be registered with the event looop it has to be |
1479 | Before a watcher can be registered with the event loop it has to be |
1391 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1480 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1481 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | |
1482 | |
1394 | In this state it is simply some block of memory that is suitable for |
1483 | 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 |
1484 | use in an event loop. It can be moved around, freed, reused etc. at |
… | |
… | |
1591 | |
1680 | |
1592 | But really, best use non-blocking mode. |
1681 | But really, best use non-blocking mode. |
1593 | |
1682 | |
1594 | =head3 The special problem of disappearing file descriptors |
1683 | =head3 The special problem of disappearing file descriptors |
1595 | |
1684 | |
1596 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1685 | Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing |
1597 | descriptor (either due to calling C<close> explicitly or any other means, |
1686 | a file descriptor (either due to calling C<close> explicitly or any other |
1598 | such as C<dup2>). The reason is that you register interest in some file |
1687 | means, such as C<dup2>). The reason is that you register interest in some |
1599 | descriptor, but when it goes away, the operating system will silently drop |
1688 | file descriptor, but when it goes away, the operating system will silently |
1600 | this interest. If another file descriptor with the same number then is |
1689 | drop this interest. If another file descriptor with the same number then |
1601 | registered with libev, there is no efficient way to see that this is, in |
1690 | is registered with libev, there is no efficient way to see that this is, |
1602 | fact, a different file descriptor. |
1691 | in fact, a different file descriptor. |
1603 | |
1692 | |
1604 | To avoid having to explicitly tell libev about such cases, libev follows |
1693 | To avoid having to explicitly tell libev about such cases, libev follows |
1605 | the following policy: Each time C<ev_io_set> is being called, libev |
1694 | the following policy: Each time C<ev_io_set> is being called, libev |
1606 | will assume that this is potentially a new file descriptor, otherwise |
1695 | 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 |
1696 | 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 |
1745 | when you rarely read from a file instead of from a socket, and want to |
1657 | reuse the same code path. |
1746 | reuse the same code path. |
1658 | |
1747 | |
1659 | =head3 The special problem of fork |
1748 | =head3 The special problem of fork |
1660 | |
1749 | |
1661 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1750 | Some backends (epoll, kqueue, probably linuxaio) do not support C<fork ()> |
1662 | useless behaviour. Libev fully supports fork, but needs to be told about |
1751 | at all or exhibit useless behaviour. Libev fully supports fork, but needs |
1663 | it in the child if you want to continue to use it in the child. |
1752 | to be told about it in the child if you want to continue to use it in the |
|
|
1753 | child. |
1664 | |
1754 | |
1665 | To support fork in your child processes, you have to call C<ev_loop_fork |
1755 | 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 |
1756 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1667 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1757 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1668 | |
1758 | |
… | |
… | |
1770 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1860 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | monotonic clock option helps a lot here). |
1861 | monotonic clock option helps a lot here). |
1772 | |
1862 | |
1773 | The callback is guaranteed to be invoked only I<after> its timeout has |
1863 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | passed (not I<at>, so on systems with very low-resolution clocks this |
1864 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | might introduce a small delay). If multiple timers become ready during the |
1865 | might introduce a small delay, see "the special problem of being too |
|
|
1866 | early", below). If multiple timers become ready during the same loop |
1776 | same loop iteration then the ones with earlier time-out values are invoked |
1867 | iteration then the ones with earlier time-out values are invoked before |
1777 | before ones of the same priority with later time-out values (but this is |
1868 | ones of the same priority with later time-out values (but this is no |
1778 | no longer true when a callback calls C<ev_run> recursively). |
1869 | longer true when a callback calls C<ev_run> recursively). |
1779 | |
1870 | |
1780 | =head3 Be smart about timeouts |
1871 | =head3 Be smart about timeouts |
1781 | |
1872 | |
1782 | Many real-world problems involve some kind of timeout, usually for error |
1873 | Many real-world problems involve some kind of timeout, usually for error |
1783 | recovery. A typical example is an HTTP request - if the other side hangs, |
1874 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1858 | |
1949 | |
1859 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1950 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1860 | but remember the time of last activity, and check for a real timeout only |
1951 | but remember the time of last activity, and check for a real timeout only |
1861 | within the callback: |
1952 | within the callback: |
1862 | |
1953 | |
|
|
1954 | ev_tstamp timeout = 60.; |
1863 | ev_tstamp last_activity; // time of last activity |
1955 | ev_tstamp last_activity; // time of last activity |
|
|
1956 | ev_timer timer; |
1864 | |
1957 | |
1865 | static void |
1958 | static void |
1866 | callback (EV_P_ ev_timer *w, int revents) |
1959 | callback (EV_P_ ev_timer *w, int revents) |
1867 | { |
1960 | { |
1868 | ev_tstamp now = ev_now (EV_A); |
1961 | // calculate when the timeout would happen |
1869 | ev_tstamp timeout = last_activity + 60.; |
1962 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1870 | |
1963 | |
1871 | // if last_activity + 60. is older than now, we did time out |
1964 | // if negative, it means we the timeout already occurred |
1872 | if (timeout < now) |
1965 | if (after < 0.) |
1873 | { |
1966 | { |
1874 | // timeout occurred, take action |
1967 | // timeout occurred, take action |
1875 | } |
1968 | } |
1876 | else |
1969 | else |
1877 | { |
1970 | { |
1878 | // callback was invoked, but there was some activity, re-arm |
1971 | // callback was invoked, but there was some recent |
1879 | // the watcher to fire in last_activity + 60, which is |
1972 | // activity. simply restart the timer to time out |
1880 | // guaranteed to be in the future, so "again" is positive: |
1973 | // after "after" seconds, which is the earliest time |
1881 | w->repeat = timeout - now; |
1974 | // the timeout can occur. |
|
|
1975 | ev_timer_set (w, after, 0.); |
1882 | ev_timer_again (EV_A_ w); |
1976 | ev_timer_start (EV_A_ w); |
1883 | } |
1977 | } |
1884 | } |
1978 | } |
1885 | |
1979 | |
1886 | To summarise the callback: first calculate the real timeout (defined |
1980 | 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 |
1981 | 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 |
1982 | 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 |
1983 | (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 | |
1984 | |
1893 | Note how C<ev_timer_again> is used, taking advantage of the |
1985 | If this value is negative, then we are already past the timeout, i.e. we |
1894 | C<ev_timer_again> optimisation when the timer is already running. |
1986 | timed out, and need to do whatever is needed in this case. |
|
|
1987 | |
|
|
1988 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1989 | and simply start the timer with this timeout value. |
|
|
1990 | |
|
|
1991 | In other words, each time the callback is invoked it will check whether |
|
|
1992 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1993 | again at the earliest time it could time out. Rinse. Repeat. |
1895 | |
1994 | |
1896 | This scheme causes more callback invocations (about one every 60 seconds |
1995 | This scheme causes more callback invocations (about one every 60 seconds |
1897 | minus half the average time between activity), but virtually no calls to |
1996 | minus half the average time between activity), but virtually no calls to |
1898 | libev to change the timeout. |
1997 | libev to change the timeout. |
1899 | |
1998 | |
1900 | To start the timer, simply initialise the watcher and set C<last_activity> |
1999 | To start the machinery, simply initialise the watcher and set |
1901 | to the current time (meaning we just have some activity :), then call the |
2000 | C<last_activity> to the current time (meaning there was some activity just |
1902 | callback, which will "do the right thing" and start the timer: |
2001 | now), then call the callback, which will "do the right thing" and start |
|
|
2002 | the timer: |
1903 | |
2003 | |
|
|
2004 | last_activity = ev_now (EV_A); |
1904 | ev_init (timer, callback); |
2005 | ev_init (&timer, callback); |
1905 | last_activity = ev_now (loop); |
2006 | callback (EV_A_ &timer, 0); |
1906 | callback (loop, timer, EV_TIMER); |
|
|
1907 | |
2007 | |
1908 | And when there is some activity, simply store the current time in |
2008 | When there is some activity, simply store the current time in |
1909 | C<last_activity>, no libev calls at all: |
2009 | C<last_activity>, no libev calls at all: |
1910 | |
2010 | |
|
|
2011 | if (activity detected) |
1911 | last_activity = ev_now (loop); |
2012 | last_activity = ev_now (EV_A); |
|
|
2013 | |
|
|
2014 | When your timeout value changes, then the timeout can be changed by simply |
|
|
2015 | providing a new value, stopping the timer and calling the callback, which |
|
|
2016 | will again do the right thing (for example, time out immediately :). |
|
|
2017 | |
|
|
2018 | timeout = new_value; |
|
|
2019 | ev_timer_stop (EV_A_ &timer); |
|
|
2020 | callback (EV_A_ &timer, 0); |
1912 | |
2021 | |
1913 | This technique is slightly more complex, but in most cases where the |
2022 | This technique is slightly more complex, but in most cases where the |
1914 | time-out is unlikely to be triggered, much more efficient. |
2023 | 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 | |
2024 | |
1920 | =item 4. Wee, just use a double-linked list for your timeouts. |
2025 | =item 4. Wee, just use a double-linked list for your timeouts. |
1921 | |
2026 | |
1922 | If there is not one request, but many thousands (millions...), all |
2027 | 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 |
2028 | 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 |
2055 | 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 |
2056 | 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 |
2057 | off after the first million or so of active timers, i.e. it's usually |
1953 | overkill :) |
2058 | overkill :) |
1954 | |
2059 | |
|
|
2060 | =head3 The special problem of being too early |
|
|
2061 | |
|
|
2062 | If you ask a timer to call your callback after three seconds, then |
|
|
2063 | you expect it to be invoked after three seconds - but of course, this |
|
|
2064 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
2065 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
2066 | process with a STOP signal for a few hours for example. |
|
|
2067 | |
|
|
2068 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
2069 | delay has occurred, but cannot guarantee this. |
|
|
2070 | |
|
|
2071 | A less obvious failure mode is calling your callback too early: many event |
|
|
2072 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2073 | this can cause your callback to be invoked much earlier than you would |
|
|
2074 | expect. |
|
|
2075 | |
|
|
2076 | To see why, imagine a system with a clock that only offers full second |
|
|
2077 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2078 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2079 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2080 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2081 | |
|
|
2082 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2083 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2084 | one-second delay was requested - this is being "too early", despite best |
|
|
2085 | intentions. |
|
|
2086 | |
|
|
2087 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2088 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2089 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2090 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2091 | |
|
|
2092 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2093 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2094 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2095 | late" side of things. |
|
|
2096 | |
1955 | =head3 The special problem of time updates |
2097 | =head3 The special problem of time updates |
1956 | |
2098 | |
1957 | Establishing the current time is a costly operation (it usually takes at |
2099 | Establishing the current time is a costly operation (it usually takes |
1958 | least two system calls): EV therefore updates its idea of the current |
2100 | at least one system call): EV therefore updates its idea of the current |
1959 | time only before and after C<ev_run> collects new events, which causes a |
2101 | time only before and after C<ev_run> collects new events, which causes a |
1960 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2102 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1961 | lots of events in one iteration. |
2103 | lots of events in one iteration. |
1962 | |
2104 | |
1963 | The relative timeouts are calculated relative to the C<ev_now ()> |
2105 | 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 |
2106 | 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 |
2107 | 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 |
2108 | 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: |
2109 | timeout on the current time, use something like the following to adjust |
|
|
2110 | for it: |
1968 | |
2111 | |
1969 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2112 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1970 | |
2113 | |
1971 | If the event loop is suspended for a long time, you can also force an |
2114 | If the event loop is suspended for a long time, you can also force an |
1972 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2115 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1973 | ()>. |
2116 | ()>, although that will push the event time of all outstanding events |
|
|
2117 | further into the future. |
|
|
2118 | |
|
|
2119 | =head3 The special problem of unsynchronised clocks |
|
|
2120 | |
|
|
2121 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2122 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2123 | jumps). |
|
|
2124 | |
|
|
2125 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2126 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2127 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2128 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2129 | than a directly following call to C<time>. |
|
|
2130 | |
|
|
2131 | The moral of this is to only compare libev-related timestamps with |
|
|
2132 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2133 | a second or so. |
|
|
2134 | |
|
|
2135 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2136 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2137 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2138 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2139 | |
|
|
2140 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2141 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2142 | I<measured according to the real time>, not the system clock. |
|
|
2143 | |
|
|
2144 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2145 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2146 | exactly the right behaviour. |
|
|
2147 | |
|
|
2148 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2149 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2150 | time, where your comparisons will always generate correct results. |
1974 | |
2151 | |
1975 | =head3 The special problems of suspended animation |
2152 | =head3 The special problems of suspended animation |
1976 | |
2153 | |
1977 | When you leave the server world it is quite customary to hit machines that |
2154 | When you leave the server world it is quite customary to hit machines that |
1978 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2155 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2008 | |
2185 | |
2009 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2186 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2010 | |
2187 | |
2011 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2188 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2012 | |
2189 | |
2013 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2190 | 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 |
2191 | 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 |
2192 | automatically be stopped once the timeout is reached. If it is positive, |
2016 | configured to trigger again C<repeat> seconds later, again, and again, |
2193 | then the timer will automatically be configured to trigger again C<repeat> |
2017 | until stopped manually. |
2194 | seconds later, again, and again, until stopped manually. |
2018 | |
2195 | |
2019 | The timer itself will do a best-effort at avoiding drift, that is, if |
2196 | The timer itself will do a best-effort at avoiding drift, that is, if |
2020 | you configure a timer to trigger every 10 seconds, then it will normally |
2197 | you configure a timer to trigger every 10 seconds, then it will normally |
2021 | trigger at exactly 10 second intervals. If, however, your program cannot |
2198 | 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 |
2199 | 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. |
2200 | do stuff) the timer will not fire more than once per event loop iteration. |
2024 | |
2201 | |
2025 | =item ev_timer_again (loop, ev_timer *) |
2202 | =item ev_timer_again (loop, ev_timer *) |
2026 | |
2203 | |
2027 | This will act as if the timer timed out and restart it again if it is |
2204 | This will act as if the timer timed out, and restarts it again if it is |
2028 | repeating. The exact semantics are: |
2205 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2206 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2029 | |
2207 | |
|
|
2208 | The exact semantics are as in the following rules, all of which will be |
|
|
2209 | applied to the watcher: |
|
|
2210 | |
|
|
2211 | =over 4 |
|
|
2212 | |
2030 | If the timer is pending, its pending status is cleared. |
2213 | =item If the timer is pending, the pending status is always cleared. |
2031 | |
2214 | |
2032 | If the timer is started but non-repeating, stop it (as if it timed out). |
2215 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2216 | out, without invoking it). |
2033 | |
2217 | |
2034 | If the timer is repeating, either start it if necessary (with the |
2218 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2035 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2219 | and start the timer, if necessary. |
2036 | |
2220 | |
|
|
2221 | =back |
|
|
2222 | |
2037 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2223 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
2038 | usage example. |
2224 | usage example. |
2039 | |
2225 | |
2040 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2226 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2041 | |
2227 | |
2042 | Returns the remaining time until a timer fires. If the timer is active, |
2228 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2095 | Periodic watchers are also timers of a kind, but they are very versatile |
2281 | Periodic watchers are also timers of a kind, but they are very versatile |
2096 | (and unfortunately a bit complex). |
2282 | (and unfortunately a bit complex). |
2097 | |
2283 | |
2098 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2284 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2099 | relative time, the physical time that passes) but on wall clock time |
2285 | relative time, the physical time that passes) but on wall clock time |
2100 | (absolute time, the thing you can read on your calender or clock). The |
2286 | (absolute time, the thing you can read on your calendar or clock). The |
2101 | difference is that wall clock time can run faster or slower than real |
2287 | difference is that wall clock time can run faster or slower than real |
2102 | time, and time jumps are not uncommon (e.g. when you adjust your |
2288 | time, and time jumps are not uncommon (e.g. when you adjust your |
2103 | wrist-watch). |
2289 | wrist-watch). |
2104 | |
2290 | |
2105 | You can tell a periodic watcher to trigger after some specific point |
2291 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2110 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2296 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2111 | it, as it uses a relative timeout). |
2297 | it, as it uses a relative timeout). |
2112 | |
2298 | |
2113 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2299 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2114 | timers, such as triggering an event on each "midnight, local time", or |
2300 | timers, such as triggering an event on each "midnight, local time", or |
2115 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2301 | other complicated rules. This cannot easily be done with C<ev_timer> |
2116 | those cannot react to time jumps. |
2302 | watchers, as those cannot react to time jumps. |
2117 | |
2303 | |
2118 | As with timers, the callback is guaranteed to be invoked only when the |
2304 | As with timers, the callback is guaranteed to be invoked only when the |
2119 | point in time where it is supposed to trigger has passed. If multiple |
2305 | point in time where it is supposed to trigger has passed. If multiple |
2120 | timers become ready during the same loop iteration then the ones with |
2306 | timers become ready during the same loop iteration then the ones with |
2121 | earlier time-out values are invoked before ones with later time-out values |
2307 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2207 | |
2393 | |
2208 | NOTE: I<< This callback must always return a time that is higher than or |
2394 | NOTE: I<< This callback must always return a time that is higher than or |
2209 | equal to the passed C<now> value >>. |
2395 | equal to the passed C<now> value >>. |
2210 | |
2396 | |
2211 | This can be used to create very complex timers, such as a timer that |
2397 | This can be used to create very complex timers, such as a timer that |
2212 | triggers on "next midnight, local time". To do this, you would calculate the |
2398 | triggers on "next midnight, local time". To do this, you would calculate |
2213 | next midnight after C<now> and return the timestamp value for this. How |
2399 | the next midnight after C<now> and return the timestamp value for |
2214 | you do this is, again, up to you (but it is not trivial, which is the main |
2400 | this. Here is a (completely untested, no error checking) example on how to |
2215 | reason I omitted it as an example). |
2401 | do this: |
|
|
2402 | |
|
|
2403 | #include <time.h> |
|
|
2404 | |
|
|
2405 | static ev_tstamp |
|
|
2406 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2407 | { |
|
|
2408 | time_t tnow = (time_t)now; |
|
|
2409 | struct tm tm; |
|
|
2410 | localtime_r (&tnow, &tm); |
|
|
2411 | |
|
|
2412 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2413 | ++tm.tm_mday; // midnight next day |
|
|
2414 | |
|
|
2415 | return mktime (&tm); |
|
|
2416 | } |
|
|
2417 | |
|
|
2418 | Note: this code might run into trouble on days that have more then two |
|
|
2419 | midnights (beginning and end). |
2216 | |
2420 | |
2217 | =back |
2421 | =back |
2218 | |
2422 | |
2219 | =item ev_periodic_again (loop, ev_periodic *) |
2423 | =item ev_periodic_again (loop, ev_periodic *) |
2220 | |
2424 | |
… | |
… | |
2285 | |
2489 | |
2286 | ev_periodic hourly_tick; |
2490 | ev_periodic hourly_tick; |
2287 | ev_periodic_init (&hourly_tick, clock_cb, |
2491 | ev_periodic_init (&hourly_tick, clock_cb, |
2288 | fmod (ev_now (loop), 3600.), 3600., 0); |
2492 | fmod (ev_now (loop), 3600.), 3600., 0); |
2289 | ev_periodic_start (loop, &hourly_tick); |
2493 | ev_periodic_start (loop, &hourly_tick); |
2290 | |
2494 | |
2291 | |
2495 | |
2292 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2496 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2293 | |
2497 | |
2294 | Signal watchers will trigger an event when the process receives a specific |
2498 | Signal watchers will trigger an event when the process receives a specific |
2295 | signal one or more times. Even though signals are very asynchronous, libev |
2499 | signal one or more times. Even though signals are very asynchronous, libev |
… | |
… | |
2305 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2509 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2306 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2510 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2307 | C<SIGINT> in both the default loop and another loop at the same time. At |
2511 | C<SIGINT> in both the default loop and another loop at the same time. At |
2308 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2512 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2309 | |
2513 | |
2310 | When the first watcher gets started will libev actually register something |
2514 | Only after the first watcher for a signal is started will libev actually |
2311 | with the kernel (thus it coexists with your own signal handlers as long as |
2515 | register something with the kernel. It thus coexists with your own signal |
2312 | you don't register any with libev for the same signal). |
2516 | handlers as long as you don't register any with libev for the same signal. |
2313 | |
2517 | |
2314 | If possible and supported, libev will install its handlers with |
2518 | If possible and supported, libev will install its handlers with |
2315 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2519 | 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 |
2520 | 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 |
2521 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2502 | |
2706 | |
2503 | =head2 C<ev_stat> - did the file attributes just change? |
2707 | =head2 C<ev_stat> - did the file attributes just change? |
2504 | |
2708 | |
2505 | This watches a file system path for attribute changes. That is, it calls |
2709 | This watches a file system path for attribute changes. That is, it calls |
2506 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2710 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2507 | and sees if it changed compared to the last time, invoking the callback if |
2711 | and sees if it changed compared to the last time, invoking the callback |
2508 | it did. |
2712 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2713 | happen after the watcher has been started will be reported. |
2509 | |
2714 | |
2510 | The path does not need to exist: changing from "path exists" to "path does |
2715 | The path does not need to exist: changing from "path exists" to "path does |
2511 | not exist" is a status change like any other. The condition "path does not |
2716 | not exist" is a status change like any other. The condition "path does not |
2512 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2717 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2513 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2718 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2743 | Apart from keeping your process non-blocking (which is a useful |
2948 | 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 |
2949 | effect on its own sometimes), idle watchers are a good place to do |
2745 | "pseudo-background processing", or delay processing stuff to after the |
2950 | "pseudo-background processing", or delay processing stuff to after the |
2746 | event loop has handled all outstanding events. |
2951 | event loop has handled all outstanding events. |
2747 | |
2952 | |
|
|
2953 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2954 | |
|
|
2955 | As long as there is at least one active idle watcher, libev will never |
|
|
2956 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2957 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2958 | lowest priority will do. |
|
|
2959 | |
|
|
2960 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2961 | to do something on each event loop iteration - for example to balance load |
|
|
2962 | between different connections. |
|
|
2963 | |
|
|
2964 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2965 | example. |
|
|
2966 | |
2748 | =head3 Watcher-Specific Functions and Data Members |
2967 | =head3 Watcher-Specific Functions and Data Members |
2749 | |
2968 | |
2750 | =over 4 |
2969 | =over 4 |
2751 | |
2970 | |
2752 | =item ev_idle_init (ev_idle *, callback) |
2971 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2763 | callback, free it. Also, use no error checking, as usual. |
2982 | callback, free it. Also, use no error checking, as usual. |
2764 | |
2983 | |
2765 | static void |
2984 | static void |
2766 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2985 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2767 | { |
2986 | { |
|
|
2987 | // stop the watcher |
|
|
2988 | ev_idle_stop (loop, w); |
|
|
2989 | |
|
|
2990 | // now we can free it |
2768 | free (w); |
2991 | free (w); |
|
|
2992 | |
2769 | // now do something you wanted to do when the program has |
2993 | // now do something you wanted to do when the program has |
2770 | // no longer anything immediate to do. |
2994 | // no longer anything immediate to do. |
2771 | } |
2995 | } |
2772 | |
2996 | |
2773 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2997 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2775 | ev_idle_start (loop, idle_watcher); |
2999 | ev_idle_start (loop, idle_watcher); |
2776 | |
3000 | |
2777 | |
3001 | |
2778 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
3002 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2779 | |
3003 | |
2780 | Prepare and check watchers are usually (but not always) used in pairs: |
3004 | Prepare and check watchers are often (but not always) used in pairs: |
2781 | prepare watchers get invoked before the process blocks and check watchers |
3005 | prepare watchers get invoked before the process blocks and check watchers |
2782 | afterwards. |
3006 | afterwards. |
2783 | |
3007 | |
2784 | You I<must not> call C<ev_run> or similar functions that enter |
3008 | You I<must not> call C<ev_run> (or similar functions that enter the |
2785 | the current event loop from either C<ev_prepare> or C<ev_check> |
3009 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2786 | watchers. Other loops than the current one are fine, however. The |
3010 | 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 |
3011 | 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, |
3012 | 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 |
3013 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2790 | called in pairs bracketing the blocking call. |
3014 | kind they will always be called in pairs bracketing the blocking call. |
2791 | |
3015 | |
2792 | Their main purpose is to integrate other event mechanisms into libev and |
3016 | Their main purpose is to integrate other event mechanisms into libev and |
2793 | their use is somewhat advanced. They could be used, for example, to track |
3017 | their use is somewhat advanced. They could be used, for example, to track |
2794 | variable changes, implement your own watchers, integrate net-snmp or a |
3018 | variable changes, implement your own watchers, integrate net-snmp or a |
2795 | coroutine library and lots more. They are also occasionally useful if |
3019 | 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 |
3037 | 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 |
3038 | 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 |
3039 | loop from blocking if lower-priority coroutines are active, thus mapping |
2816 | low-priority coroutines to idle/background tasks). |
3040 | low-priority coroutines to idle/background tasks). |
2817 | |
3041 | |
2818 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
3042 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2819 | priority, to ensure that they are being run before any other watchers |
3043 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2820 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
3044 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
3045 | watchers). |
2821 | |
3046 | |
2822 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
3047 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2823 | activate ("feed") events into libev. While libev fully supports this, they |
3048 | 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 |
3049 | 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 |
3050 | 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 |
3051 | 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 |
3052 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2828 | others). |
3053 | others). |
|
|
3054 | |
|
|
3055 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
3056 | |
|
|
3057 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
3058 | useful because they are called once per event loop iteration. For |
|
|
3059 | example, if you want to handle a large number of connections fairly, you |
|
|
3060 | normally only do a bit of work for each active connection, and if there |
|
|
3061 | is more work to do, you wait for the next event loop iteration, so other |
|
|
3062 | connections have a chance of making progress. |
|
|
3063 | |
|
|
3064 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
3065 | next event loop iteration. However, that isn't as soon as possible - |
|
|
3066 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
3067 | |
|
|
3068 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
3069 | single global idle watcher that is active as long as you have one active |
|
|
3070 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3071 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3072 | invoked. Neither watcher alone can do that. |
2829 | |
3073 | |
2830 | =head3 Watcher-Specific Functions and Data Members |
3074 | =head3 Watcher-Specific Functions and Data Members |
2831 | |
3075 | |
2832 | =over 4 |
3076 | =over 4 |
2833 | |
3077 | |
… | |
… | |
3034 | |
3278 | |
3035 | =over 4 |
3279 | =over 4 |
3036 | |
3280 | |
3037 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3281 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3038 | |
3282 | |
3039 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3283 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
3040 | |
3284 | |
3041 | Configures the watcher to embed the given loop, which must be |
3285 | 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 |
3286 | 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 |
3287 | 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, |
3288 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
3065 | used). |
3309 | used). |
3066 | |
3310 | |
3067 | struct ev_loop *loop_hi = ev_default_init (0); |
3311 | struct ev_loop *loop_hi = ev_default_init (0); |
3068 | struct ev_loop *loop_lo = 0; |
3312 | struct ev_loop *loop_lo = 0; |
3069 | ev_embed embed; |
3313 | ev_embed embed; |
3070 | |
3314 | |
3071 | // see if there is a chance of getting one that works |
3315 | // see if there is a chance of getting one that works |
3072 | // (remember that a flags value of 0 means autodetection) |
3316 | // (remember that a flags value of 0 means autodetection) |
3073 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3317 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3074 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3318 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3075 | : 0; |
3319 | : 0; |
… | |
… | |
3089 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3333 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3090 | |
3334 | |
3091 | struct ev_loop *loop = ev_default_init (0); |
3335 | struct ev_loop *loop = ev_default_init (0); |
3092 | struct ev_loop *loop_socket = 0; |
3336 | struct ev_loop *loop_socket = 0; |
3093 | ev_embed embed; |
3337 | ev_embed embed; |
3094 | |
3338 | |
3095 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3339 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3096 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3340 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3097 | { |
3341 | { |
3098 | ev_embed_init (&embed, 0, loop_socket); |
3342 | ev_embed_init (&embed, 0, loop_socket); |
3099 | ev_embed_start (loop, &embed); |
3343 | ev_embed_start (loop, &embed); |
… | |
… | |
3107 | |
3351 | |
3108 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3352 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3109 | |
3353 | |
3110 | Fork watchers are called when a C<fork ()> was detected (usually because |
3354 | Fork watchers are called when a C<fork ()> was detected (usually because |
3111 | whoever is a good citizen cared to tell libev about it by calling |
3355 | whoever is a good citizen cared to tell libev about it by calling |
3112 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3356 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3113 | event loop blocks next and before C<ev_check> watchers are being called, |
3357 | and before C<ev_check> watchers are being called, and only in the child |
3114 | and only in the child after the fork. If whoever good citizen calling |
3358 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3115 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3359 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3116 | handlers will be invoked, too, of course. |
3360 | of course. |
3117 | |
3361 | |
3118 | =head3 The special problem of life after fork - how is it possible? |
3362 | =head3 The special problem of life after fork - how is it possible? |
3119 | |
3363 | |
3120 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3364 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3121 | up/change the process environment, followed by a call to C<exec()>. This |
3365 | up/change the process environment, followed by a call to C<exec()>. This |
3122 | sequence should be handled by libev without any problems. |
3366 | sequence should be handled by libev without any problems. |
3123 | |
3367 | |
3124 | This changes when the application actually wants to do event handling |
3368 | 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 |
3369 | 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. |
3458 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3215 | |
3459 | |
3216 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3460 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3217 | too, are asynchronous in nature, and signals, too, will be compressed |
3461 | 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 |
3462 | (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 |
3463 | 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 |
3464 | 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, |
3465 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3222 | even without knowing which loop owns the signal. |
3466 | 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 | |
3467 | |
3227 | =head3 Queueing |
3468 | =head3 Queueing |
3228 | |
3469 | |
3229 | C<ev_async> does not support queueing of data in any way. The reason |
3470 | C<ev_async> does not support queueing of data in any way. The reason |
3230 | is that the author does not know of a simple (or any) algorithm for a |
3471 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3330 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3571 | 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 |
3572 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3332 | embedding section below on what exactly this means). |
3573 | embedding section below on what exactly this means). |
3333 | |
3574 | |
3334 | Note that, as with other watchers in libev, multiple events might get |
3575 | Note that, as with other watchers in libev, multiple events might get |
3335 | compressed into a single callback invocation (another way to look at this |
3576 | 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>, |
3577 | this is that C<ev_async> watchers are level-triggered: they are set on |
3337 | reset when the event loop detects that). |
3578 | C<ev_async_send>, reset when the event loop detects that). |
3338 | |
3579 | |
3339 | This call incurs the overhead of a system call only once per event loop |
3580 | This call incurs the overhead of at most one extra system call per event |
3340 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3581 | loop iteration, if the event loop is blocked, and no syscall at all if |
3341 | repeated calls to C<ev_async_send> for the same event loop. |
3582 | the event loop (or your program) is processing events. That means that |
|
|
3583 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3584 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3585 | zero) under load. |
3342 | |
3586 | |
3343 | =item bool = ev_async_pending (ev_async *) |
3587 | =item bool = ev_async_pending (ev_async *) |
3344 | |
3588 | |
3345 | Returns a non-zero value when C<ev_async_send> has been called on the |
3589 | Returns a non-zero value when C<ev_async_send> has been called on the |
3346 | watcher but the event has not yet been processed (or even noted) by the |
3590 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3363 | |
3607 | |
3364 | There are some other functions of possible interest. Described. Here. Now. |
3608 | There are some other functions of possible interest. Described. Here. Now. |
3365 | |
3609 | |
3366 | =over 4 |
3610 | =over 4 |
3367 | |
3611 | |
3368 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3612 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3369 | |
3613 | |
3370 | This function combines a simple timer and an I/O watcher, calls your |
3614 | This function combines a simple timer and an I/O watcher, calls your |
3371 | callback on whichever event happens first and automatically stops both |
3615 | 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 |
3616 | 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 |
3617 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3401 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3645 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3402 | |
3646 | |
3403 | =item ev_feed_fd_event (loop, int fd, int revents) |
3647 | =item ev_feed_fd_event (loop, int fd, int revents) |
3404 | |
3648 | |
3405 | Feed an event on the given fd, as if a file descriptor backend detected |
3649 | Feed an event on the given fd, as if a file descriptor backend detected |
3406 | the given events it. |
3650 | the given events. |
3407 | |
3651 | |
3408 | =item ev_feed_signal_event (loop, int signum) |
3652 | =item ev_feed_signal_event (loop, int signum) |
3409 | |
3653 | |
3410 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3654 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3411 | which is async-safe. |
3655 | which is async-safe. |
… | |
… | |
3485 | { |
3729 | { |
3486 | struct my_biggy big = (struct my_biggy *) |
3730 | struct my_biggy big = (struct my_biggy *) |
3487 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3731 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3488 | } |
3732 | } |
3489 | |
3733 | |
|
|
3734 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3735 | |
|
|
3736 | Often you have structures like this in event-based programs: |
|
|
3737 | |
|
|
3738 | callback () |
|
|
3739 | { |
|
|
3740 | free (request); |
|
|
3741 | } |
|
|
3742 | |
|
|
3743 | request = start_new_request (..., callback); |
|
|
3744 | |
|
|
3745 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3746 | used to cancel the operation, or do other things with it. |
|
|
3747 | |
|
|
3748 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3749 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3750 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3751 | operation and simply invoke the callback with the result. |
|
|
3752 | |
|
|
3753 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3754 | has returned, so C<request> is not set. |
|
|
3755 | |
|
|
3756 | Even if you pass the request by some safer means to the callback, you |
|
|
3757 | might want to do something to the request after starting it, such as |
|
|
3758 | canceling it, which probably isn't working so well when the callback has |
|
|
3759 | already been invoked. |
|
|
3760 | |
|
|
3761 | A common way around all these issues is to make sure that |
|
|
3762 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3763 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3764 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3765 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3766 | pushing it into the pending queue: |
|
|
3767 | |
|
|
3768 | ev_set_cb (watcher, callback); |
|
|
3769 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3770 | |
|
|
3771 | This way, C<start_new_request> can safely return before the callback is |
|
|
3772 | invoked, while not delaying callback invocation too much. |
|
|
3773 | |
3490 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3774 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3491 | |
3775 | |
3492 | Often (especially in GUI toolkits) there are places where you have |
3776 | Often (especially in GUI toolkits) there are places where you have |
3493 | I<modal> interaction, which is most easily implemented by recursively |
3777 | I<modal> interaction, which is most easily implemented by recursively |
3494 | invoking C<ev_run>. |
3778 | invoking C<ev_run>. |
3495 | |
3779 | |
3496 | This brings the problem of exiting - a callback might want to finish the |
3780 | This brings the problem of exiting - a callback might want to finish the |
3497 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3781 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
3498 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3782 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
3499 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3783 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
3500 | other combination: In these cases, C<ev_break> will not work alone. |
3784 | other combination: In these cases, a simple C<ev_break> will not work. |
3501 | |
3785 | |
3502 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3786 | The solution is to maintain "break this loop" variable for each C<ev_run> |
3503 | invocation, and use a loop around C<ev_run> until the condition is |
3787 | invocation, and use a loop around C<ev_run> until the condition is |
3504 | triggered, using C<EVRUN_ONCE>: |
3788 | triggered, using C<EVRUN_ONCE>: |
3505 | |
3789 | |
… | |
… | |
3507 | int exit_main_loop = 0; |
3791 | int exit_main_loop = 0; |
3508 | |
3792 | |
3509 | while (!exit_main_loop) |
3793 | while (!exit_main_loop) |
3510 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3794 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3511 | |
3795 | |
3512 | // in a model watcher |
3796 | // in a modal watcher |
3513 | int exit_nested_loop = 0; |
3797 | int exit_nested_loop = 0; |
3514 | |
3798 | |
3515 | while (!exit_nested_loop) |
3799 | while (!exit_nested_loop) |
3516 | ev_run (EV_A_ EVRUN_ONCE); |
3800 | ev_run (EV_A_ EVRUN_ONCE); |
3517 | |
3801 | |
… | |
… | |
3691 | called): |
3975 | called): |
3692 | |
3976 | |
3693 | void |
3977 | void |
3694 | wait_for_event (ev_watcher *w) |
3978 | wait_for_event (ev_watcher *w) |
3695 | { |
3979 | { |
3696 | ev_cb_set (w) = current_coro; |
3980 | ev_set_cb (w, current_coro); |
3697 | switch_to (libev_coro); |
3981 | switch_to (libev_coro); |
3698 | } |
3982 | } |
3699 | |
3983 | |
3700 | That basically suspends the coroutine inside C<wait_for_event> and |
3984 | That basically suspends the coroutine inside C<wait_for_event> and |
3701 | continues the libev coroutine, which, when appropriate, switches back to |
3985 | 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 :) |
3986 | this or any other coroutine. |
3703 | |
3987 | |
3704 | You can do similar tricks if you have, say, threads with an event queue - |
3988 | 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 |
3989 | 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 |
3990 | switching to a coroutine, you push the watcher onto the queue and notify |
3707 | any waiters. |
3991 | any waiters. |
3708 | |
3992 | |
3709 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
3993 | 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: |
3994 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
3711 | |
3995 | |
3712 | // my_ev.h |
3996 | // my_ev.h |
3713 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3997 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
3714 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
3998 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
3715 | #include "../libev/ev.h" |
3999 | #include "../libev/ev.h" |
3716 | |
4000 | |
3717 | // my_ev.c |
4001 | // my_ev.c |
3718 | #define EV_H "my_ev.h" |
4002 | #define EV_H "my_ev.h" |
3719 | #include "../libev/ev.c" |
4003 | #include "../libev/ev.c" |
… | |
… | |
3758 | |
4042 | |
3759 | =back |
4043 | =back |
3760 | |
4044 | |
3761 | =head1 C++ SUPPORT |
4045 | =head1 C++ SUPPORT |
3762 | |
4046 | |
|
|
4047 | =head2 C API |
|
|
4048 | |
|
|
4049 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
4050 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
4051 | will work fine. |
|
|
4052 | |
|
|
4053 | Proper exception specifications might have to be added to callbacks passed |
|
|
4054 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
4055 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
4056 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
4057 | specification. If you have code that needs to be compiled as both C and |
|
|
4058 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
4059 | |
|
|
4060 | static void |
|
|
4061 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
4062 | { |
|
|
4063 | perror (msg); |
|
|
4064 | abort (); |
|
|
4065 | } |
|
|
4066 | |
|
|
4067 | ... |
|
|
4068 | ev_set_syserr_cb (fatal_error); |
|
|
4069 | |
|
|
4070 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4071 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4072 | because it runs cleanup watchers). |
|
|
4073 | |
|
|
4074 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4075 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4076 | throwing exceptions through C libraries (most do). |
|
|
4077 | |
|
|
4078 | =head2 C++ API |
|
|
4079 | |
3763 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4080 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3764 | you to use some convenience methods to start/stop watchers and also change |
4081 | you to use some convenience methods to start/stop watchers and also change |
3765 | the callback model to a model using method callbacks on objects. |
4082 | the callback model to a model using method callbacks on objects. |
3766 | |
4083 | |
3767 | To use it, |
4084 | To use it, |
3768 | |
4085 | |
3769 | #include <ev++.h> |
4086 | #include <ev++.h> |
3770 | |
4087 | |
3771 | This automatically includes F<ev.h> and puts all of its definitions (many |
4088 | This automatically includes F<ev.h> and puts all of its definitions (many |
3772 | of them macros) into the global namespace. All C++ specific things are |
4089 | of them macros) into the global namespace. All C++ specific things are |
3773 | put into the C<ev> namespace. It should support all the same embedding |
4090 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3782 | with C<operator ()> can be used as callbacks. Other types should be easy |
4099 | with C<operator ()> can be used as callbacks. Other types should be easy |
3783 | to add as long as they only need one additional pointer for context. If |
4100 | to add as long as they only need one additional pointer for context. If |
3784 | you need support for other types of functors please contact the author |
4101 | you need support for other types of functors please contact the author |
3785 | (preferably after implementing it). |
4102 | (preferably after implementing it). |
3786 | |
4103 | |
|
|
4104 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4105 | conventions as your C compiler (for static member functions), or you have |
|
|
4106 | to embed libev and compile libev itself as C++. |
|
|
4107 | |
3787 | Here is a list of things available in the C<ev> namespace: |
4108 | Here is a list of things available in the C<ev> namespace: |
3788 | |
4109 | |
3789 | =over 4 |
4110 | =over 4 |
3790 | |
4111 | |
3791 | =item C<ev::READ>, C<ev::WRITE> etc. |
4112 | =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. |
4121 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3801 | |
4122 | |
3802 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4123 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3803 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4124 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3804 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4125 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3805 | defines by many implementations. |
4126 | defined by many implementations. |
3806 | |
4127 | |
3807 | All of those classes have these methods: |
4128 | All of those classes have these methods: |
3808 | |
4129 | |
3809 | =over 4 |
4130 | =over 4 |
3810 | |
4131 | |
… | |
… | |
3872 | void operator() (ev::io &w, int revents) |
4193 | void operator() (ev::io &w, int revents) |
3873 | { |
4194 | { |
3874 | ... |
4195 | ... |
3875 | } |
4196 | } |
3876 | } |
4197 | } |
3877 | |
4198 | |
3878 | myfunctor f; |
4199 | myfunctor f; |
3879 | |
4200 | |
3880 | ev::io w; |
4201 | ev::io w; |
3881 | w.set (&f); |
4202 | w.set (&f); |
3882 | |
4203 | |
… | |
… | |
3900 | Associates a different C<struct ev_loop> with this watcher. You can only |
4221 | Associates a different C<struct ev_loop> with this watcher. You can only |
3901 | do this when the watcher is inactive (and not pending either). |
4222 | do this when the watcher is inactive (and not pending either). |
3902 | |
4223 | |
3903 | =item w->set ([arguments]) |
4224 | =item w->set ([arguments]) |
3904 | |
4225 | |
3905 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4226 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3906 | method or a suitable start method must be called at least once. Unlike the |
4227 | with the same arguments. Either this method or a suitable start method |
3907 | C counterpart, an active watcher gets automatically stopped and restarted |
4228 | must be called at least once. Unlike the C counterpart, an active watcher |
3908 | when reconfiguring it with this method. |
4229 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4230 | method. |
|
|
4231 | |
|
|
4232 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4233 | clashing with the C<set (loop)> method. |
3909 | |
4234 | |
3910 | =item w->start () |
4235 | =item w->start () |
3911 | |
4236 | |
3912 | Starts the watcher. Note that there is no C<loop> argument, as the |
4237 | Starts the watcher. Note that there is no C<loop> argument, as the |
3913 | constructor already stores the event loop. |
4238 | constructor already stores the event loop. |
… | |
… | |
3943 | watchers in the constructor. |
4268 | watchers in the constructor. |
3944 | |
4269 | |
3945 | class myclass |
4270 | class myclass |
3946 | { |
4271 | { |
3947 | ev::io io ; void io_cb (ev::io &w, int revents); |
4272 | ev::io io ; void io_cb (ev::io &w, int revents); |
3948 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4273 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3949 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4274 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3950 | |
4275 | |
3951 | myclass (int fd) |
4276 | myclass (int fd) |
3952 | { |
4277 | { |
3953 | io .set <myclass, &myclass::io_cb > (this); |
4278 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
4004 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4329 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4005 | |
4330 | |
4006 | =item D |
4331 | =item D |
4007 | |
4332 | |
4008 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4333 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4009 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4334 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4010 | |
4335 | |
4011 | =item Ocaml |
4336 | =item Ocaml |
4012 | |
4337 | |
4013 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4338 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4014 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4339 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4017 | |
4342 | |
4018 | Brian Maher has written a partial interface to libev for lua (at the |
4343 | Brian Maher has written a partial interface to libev for lua (at the |
4019 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4344 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4020 | L<http://github.com/brimworks/lua-ev>. |
4345 | L<http://github.com/brimworks/lua-ev>. |
4021 | |
4346 | |
|
|
4347 | =item Javascript |
|
|
4348 | |
|
|
4349 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4350 | |
|
|
4351 | =item Others |
|
|
4352 | |
|
|
4353 | There are others, and I stopped counting. |
|
|
4354 | |
4022 | =back |
4355 | =back |
4023 | |
4356 | |
4024 | |
4357 | |
4025 | =head1 MACRO MAGIC |
4358 | =head1 MACRO MAGIC |
4026 | |
4359 | |
… | |
… | |
4062 | suitable for use with C<EV_A>. |
4395 | suitable for use with C<EV_A>. |
4063 | |
4396 | |
4064 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4397 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4065 | |
4398 | |
4066 | Similar to the other two macros, this gives you the value of the default |
4399 | Similar to the other two macros, this gives you the value of the default |
4067 | loop, if multiple loops are supported ("ev loop default"). |
4400 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4401 | will be initialised if it isn't already initialised. |
|
|
4402 | |
|
|
4403 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4404 | to initialise the loop somewhere. |
4068 | |
4405 | |
4069 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4406 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4070 | |
4407 | |
4071 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4408 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4072 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4409 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4139 | ev_vars.h |
4476 | ev_vars.h |
4140 | ev_wrap.h |
4477 | ev_wrap.h |
4141 | |
4478 | |
4142 | ev_win32.c required on win32 platforms only |
4479 | ev_win32.c required on win32 platforms only |
4143 | |
4480 | |
4144 | ev_select.c only when select backend is enabled (which is enabled by default) |
4481 | ev_select.c only when select backend is enabled |
4145 | ev_poll.c only when poll backend is enabled (disabled by default) |
4482 | ev_poll.c only when poll backend is enabled |
4146 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4483 | ev_epoll.c only when the epoll backend is enabled |
|
|
4484 | ev_linuxaio.c only when the linux aio backend is enabled |
4147 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4485 | 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) |
4486 | ev_port.c only when the solaris port backend is enabled |
4149 | |
4487 | |
4150 | F<ev.c> includes the backend files directly when enabled, so you only need |
4488 | F<ev.c> includes the backend files directly when enabled, so you only need |
4151 | to compile this single file. |
4489 | to compile this single file. |
4152 | |
4490 | |
4153 | =head3 LIBEVENT COMPATIBILITY API |
4491 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
4321 | If programs implement their own fd to handle mapping on win32, then this |
4659 | If programs implement their own fd to handle mapping on win32, then this |
4322 | macro can be used to override the C<close> function, useful to unregister |
4660 | macro can be used to override the C<close> function, useful to unregister |
4323 | file descriptors again. Note that the replacement function has to close |
4661 | file descriptors again. Note that the replacement function has to close |
4324 | the underlying OS handle. |
4662 | the underlying OS handle. |
4325 | |
4663 | |
|
|
4664 | =item EV_USE_WSASOCKET |
|
|
4665 | |
|
|
4666 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4667 | communication socket, which works better in some environments. Otherwise, |
|
|
4668 | the normal C<socket> function will be used, which works better in other |
|
|
4669 | environments. |
|
|
4670 | |
4326 | =item EV_USE_POLL |
4671 | =item EV_USE_POLL |
4327 | |
4672 | |
4328 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4673 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4329 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4674 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4330 | takes precedence over select. |
4675 | takes precedence over select. |
… | |
… | |
4334 | If defined to be C<1>, libev will compile in support for the Linux |
4679 | If defined to be C<1>, libev will compile in support for the Linux |
4335 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4680 | C<epoll>(7) backend. Its availability will be detected at runtime, |
4336 | otherwise another method will be used as fallback. This is the preferred |
4681 | otherwise another method will be used as fallback. This is the preferred |
4337 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4682 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
4338 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4683 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
4684 | |
|
|
4685 | =item EV_USE_LINUXAIO |
|
|
4686 | |
|
|
4687 | If defined to be C<1>, libev will compile in support for the Linux |
|
|
4688 | aio backend. Due to it's currenbt limitations it has to be requested |
|
|
4689 | explicitly. If undefined, it will be enabled on linux, otherwise |
|
|
4690 | disabled. |
4339 | |
4691 | |
4340 | =item EV_USE_KQUEUE |
4692 | =item EV_USE_KQUEUE |
4341 | |
4693 | |
4342 | If defined to be C<1>, libev will compile in support for the BSD style |
4694 | If defined to be C<1>, libev will compile in support for the BSD style |
4343 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
4695 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
4365 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4717 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4366 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4718 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4367 | be detected at runtime. If undefined, it will be enabled if the headers |
4719 | be detected at runtime. If undefined, it will be enabled if the headers |
4368 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4720 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4369 | |
4721 | |
|
|
4722 | =item EV_NO_SMP |
|
|
4723 | |
|
|
4724 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4725 | between threads, that is, threads can be used, but threads never run on |
|
|
4726 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4727 | and makes libev faster. |
|
|
4728 | |
|
|
4729 | =item EV_NO_THREADS |
|
|
4730 | |
|
|
4731 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4732 | different threads (that includes signal handlers), which is a stronger |
|
|
4733 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4734 | libev faster. |
|
|
4735 | |
4370 | =item EV_ATOMIC_T |
4736 | =item EV_ATOMIC_T |
4371 | |
4737 | |
4372 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4738 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4373 | access is atomic with respect to other threads or signal contexts. No such |
4739 | access is atomic with respect to other threads or signal contexts. No |
4374 | type is easily found in the C language, so you can provide your own type |
4740 | such type is easily found in the C language, so you can provide your own |
4375 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4741 | type that you know is safe for your purposes. It is used both for signal |
4376 | as well as for signal and thread safety in C<ev_async> watchers. |
4742 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4743 | watchers. |
4377 | |
4744 | |
4378 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4745 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4379 | (from F<signal.h>), which is usually good enough on most platforms. |
4746 | (from F<signal.h>), which is usually good enough on most platforms. |
4380 | |
4747 | |
4381 | =item EV_H (h) |
4748 | =item EV_H (h) |
… | |
… | |
4408 | will have the C<struct ev_loop *> as first argument, and you can create |
4775 | will have the C<struct ev_loop *> as first argument, and you can create |
4409 | additional independent event loops. Otherwise there will be no support |
4776 | additional independent event loops. Otherwise there will be no support |
4410 | for multiple event loops and there is no first event loop pointer |
4777 | for multiple event loops and there is no first event loop pointer |
4411 | argument. Instead, all functions act on the single default loop. |
4778 | argument. Instead, all functions act on the single default loop. |
4412 | |
4779 | |
|
|
4780 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4781 | default loop when multiplicity is switched off - you always have to |
|
|
4782 | initialise the loop manually in this case. |
|
|
4783 | |
4413 | =item EV_MINPRI |
4784 | =item EV_MINPRI |
4414 | |
4785 | |
4415 | =item EV_MAXPRI |
4786 | =item EV_MAXPRI |
4416 | |
4787 | |
4417 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4788 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4453 | #define EV_USE_POLL 1 |
4824 | #define EV_USE_POLL 1 |
4454 | #define EV_CHILD_ENABLE 1 |
4825 | #define EV_CHILD_ENABLE 1 |
4455 | #define EV_ASYNC_ENABLE 1 |
4826 | #define EV_ASYNC_ENABLE 1 |
4456 | |
4827 | |
4457 | The actual value is a bitset, it can be a combination of the following |
4828 | The actual value is a bitset, it can be a combination of the following |
4458 | values: |
4829 | values (by default, all of these are enabled): |
4459 | |
4830 | |
4460 | =over 4 |
4831 | =over 4 |
4461 | |
4832 | |
4462 | =item C<1> - faster/larger code |
4833 | =item C<1> - faster/larger code |
4463 | |
4834 | |
… | |
… | |
4467 | code size by roughly 30% on amd64). |
4838 | code size by roughly 30% on amd64). |
4468 | |
4839 | |
4469 | When optimising for size, use of compiler flags such as C<-Os> with |
4840 | When optimising for size, use of compiler flags such as C<-Os> with |
4470 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4841 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4471 | assertions. |
4842 | assertions. |
|
|
4843 | |
|
|
4844 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4845 | (e.g. gcc with C<-Os>). |
4472 | |
4846 | |
4473 | =item C<2> - faster/larger data structures |
4847 | =item C<2> - faster/larger data structures |
4474 | |
4848 | |
4475 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4849 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4476 | hash table sizes and so on. This will usually further increase code size |
4850 | hash table sizes and so on. This will usually further increase code size |
4477 | and can additionally have an effect on the size of data structures at |
4851 | and can additionally have an effect on the size of data structures at |
4478 | runtime. |
4852 | runtime. |
4479 | |
4853 | |
|
|
4854 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4855 | (e.g. gcc with C<-Os>). |
|
|
4856 | |
4480 | =item C<4> - full API configuration |
4857 | =item C<4> - full API configuration |
4481 | |
4858 | |
4482 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4859 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4483 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4860 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4484 | |
4861 | |
… | |
… | |
4514 | |
4891 | |
4515 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4892 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4516 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4893 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4517 | your program might be left out as well - a binary starting a timer and an |
4894 | your program might be left out as well - a binary starting a timer and an |
4518 | I/O watcher then might come out at only 5Kb. |
4895 | I/O watcher then might come out at only 5Kb. |
|
|
4896 | |
|
|
4897 | =item EV_API_STATIC |
|
|
4898 | |
|
|
4899 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4900 | will have static linkage. This means that libev will not export any |
|
|
4901 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4902 | when you embed libev, only want to use libev functions in a single file, |
|
|
4903 | and do not want its identifiers to be visible. |
|
|
4904 | |
|
|
4905 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4906 | wants to use libev. |
|
|
4907 | |
|
|
4908 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4909 | doesn't support the required declaration syntax. |
4519 | |
4910 | |
4520 | =item EV_AVOID_STDIO |
4911 | =item EV_AVOID_STDIO |
4521 | |
4912 | |
4522 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4913 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4523 | functions (printf, scanf, perror etc.). This will increase the code size |
4914 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4728 | default loop and triggering an C<ev_async> watcher from the default loop |
5119 | default loop and triggering an C<ev_async> watcher from the default loop |
4729 | watcher callback into the event loop interested in the signal. |
5120 | watcher callback into the event loop interested in the signal. |
4730 | |
5121 | |
4731 | =back |
5122 | =back |
4732 | |
5123 | |
4733 | See also L<THREAD LOCKING EXAMPLE>. |
5124 | See also L</THREAD LOCKING EXAMPLE>. |
4734 | |
5125 | |
4735 | =head3 COROUTINES |
5126 | =head3 COROUTINES |
4736 | |
5127 | |
4737 | Libev is very accommodating to coroutines ("cooperative threads"): |
5128 | Libev is very accommodating to coroutines ("cooperative threads"): |
4738 | libev fully supports nesting calls to its functions from different |
5129 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4903 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5294 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4904 | model. Libev still offers limited functionality on this platform in |
5295 | model. Libev still offers limited functionality on this platform in |
4905 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5296 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4906 | descriptors. This only applies when using Win32 natively, not when using |
5297 | descriptors. This only applies when using Win32 natively, not when using |
4907 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5298 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4908 | as every compielr comes with a slightly differently broken/incompatible |
5299 | as every compiler comes with a slightly differently broken/incompatible |
4909 | environment. |
5300 | environment. |
4910 | |
5301 | |
4911 | Lifting these limitations would basically require the full |
5302 | Lifting these limitations would basically require the full |
4912 | re-implementation of the I/O system. If you are into this kind of thing, |
5303 | re-implementation of the I/O system. If you are into this kind of thing, |
4913 | then note that glib does exactly that for you in a very portable way (note |
5304 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5007 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5398 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5008 | assumes that the same (machine) code can be used to call any watcher |
5399 | assumes that the same (machine) code can be used to call any watcher |
5009 | callback: The watcher callbacks have different type signatures, but libev |
5400 | callback: The watcher callbacks have different type signatures, but libev |
5010 | calls them using an C<ev_watcher *> internally. |
5401 | calls them using an C<ev_watcher *> internally. |
5011 | |
5402 | |
|
|
5403 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5404 | |
|
|
5405 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5406 | relies on this setting pointers and integers to null. |
|
|
5407 | |
5012 | =item pointer accesses must be thread-atomic |
5408 | =item pointer accesses must be thread-atomic |
5013 | |
5409 | |
5014 | Accessing a pointer value must be atomic, it must both be readable and |
5410 | Accessing a pointer value must be atomic, it must both be readable and |
5015 | writable in one piece - this is the case on all current architectures. |
5411 | writable in one piece - this is the case on all current architectures. |
5016 | |
5412 | |
… | |
… | |
5029 | thread" or will block signals process-wide, both behaviours would |
5425 | thread" or will block signals process-wide, both behaviours would |
5030 | be compatible with libev. Interaction between C<sigprocmask> and |
5426 | be compatible with libev. Interaction between C<sigprocmask> and |
5031 | C<pthread_sigmask> could complicate things, however. |
5427 | C<pthread_sigmask> could complicate things, however. |
5032 | |
5428 | |
5033 | The most portable way to handle signals is to block signals in all threads |
5429 | The most portable way to handle signals is to block signals in all threads |
5034 | except the initial one, and run the default loop in the initial thread as |
5430 | except the initial one, and run the signal handling loop in the initial |
5035 | well. |
5431 | thread as well. |
5036 | |
5432 | |
5037 | =item C<long> must be large enough for common memory allocation sizes |
5433 | =item C<long> must be large enough for common memory allocation sizes |
5038 | |
5434 | |
5039 | To improve portability and simplify its API, libev uses C<long> internally |
5435 | To improve portability and simplify its API, libev uses C<long> internally |
5040 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5436 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
5046 | |
5442 | |
5047 | The type C<double> is used to represent timestamps. It is required to |
5443 | The type C<double> is used to represent timestamps. It is required to |
5048 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5444 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5049 | good enough for at least into the year 4000 with millisecond accuracy |
5445 | good enough for at least into the year 4000 with millisecond accuracy |
5050 | (the design goal for libev). This requirement is overfulfilled by |
5446 | (the design goal for libev). This requirement is overfulfilled by |
5051 | implementations using IEEE 754, which is basically all existing ones. With |
5447 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5448 | |
5052 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5449 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5450 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5451 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5452 | something like that, just kidding). |
5053 | |
5453 | |
5054 | =back |
5454 | =back |
5055 | |
5455 | |
5056 | If you know of other additional requirements drop me a note. |
5456 | If you know of other additional requirements drop me a note. |
5057 | |
5457 | |
… | |
… | |
5119 | =item Processing ev_async_send: O(number_of_async_watchers) |
5519 | =item Processing ev_async_send: O(number_of_async_watchers) |
5120 | |
5520 | |
5121 | =item Processing signals: O(max_signal_number) |
5521 | =item Processing signals: O(max_signal_number) |
5122 | |
5522 | |
5123 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5523 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5124 | calls in the current loop iteration. Checking for async and signal events |
5524 | calls in the current loop iteration and the loop is currently |
|
|
5525 | blocked. Checking for async and signal events involves iterating over all |
5125 | involves iterating over all running async watchers or all signal numbers. |
5526 | running async watchers or all signal numbers. |
5126 | |
5527 | |
5127 | =back |
5528 | =back |
5128 | |
5529 | |
5129 | |
5530 | |
5130 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5531 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5139 | =over 4 |
5540 | =over 4 |
5140 | |
5541 | |
5141 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5542 | =item C<EV_COMPAT3> backwards compatibility mechanism |
5142 | |
5543 | |
5143 | The backward compatibility mechanism can be controlled by |
5544 | The backward compatibility mechanism can be controlled by |
5144 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
5545 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
5145 | section. |
5546 | section. |
5146 | |
5547 | |
5147 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5548 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
5148 | |
5549 | |
5149 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
5550 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
… | |
… | |
5192 | =over 4 |
5593 | =over 4 |
5193 | |
5594 | |
5194 | =item active |
5595 | =item active |
5195 | |
5596 | |
5196 | A watcher is active as long as it has been started and not yet stopped. |
5597 | A watcher is active as long as it has been started and not yet stopped. |
5197 | See L<WATCHER STATES> for details. |
5598 | See L</WATCHER STATES> for details. |
5198 | |
5599 | |
5199 | =item application |
5600 | =item application |
5200 | |
5601 | |
5201 | In this document, an application is whatever is using libev. |
5602 | In this document, an application is whatever is using libev. |
5202 | |
5603 | |
… | |
… | |
5238 | watchers and events. |
5639 | watchers and events. |
5239 | |
5640 | |
5240 | =item pending |
5641 | =item pending |
5241 | |
5642 | |
5242 | A watcher is pending as soon as the corresponding event has been |
5643 | A watcher is pending as soon as the corresponding event has been |
5243 | detected. See L<WATCHER STATES> for details. |
5644 | detected. See L</WATCHER STATES> for details. |
5244 | |
5645 | |
5245 | =item real time |
5646 | =item real time |
5246 | |
5647 | |
5247 | The physical time that is observed. It is apparently strictly monotonic :) |
5648 | The physical time that is observed. It is apparently strictly monotonic :) |
5248 | |
5649 | |