… | |
… | |
43 | |
43 | |
44 | int |
44 | int |
45 | main (void) |
45 | main (void) |
46 | { |
46 | { |
47 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
49 | |
50 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
165 | |
173 | |
166 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
167 | |
175 | |
168 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
170 | you actually want to know. Also interetsing is the combination of |
178 | you actually want to know. Also interesting is the combination of |
171 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_update_now> and C<ev_now>. |
172 | |
180 | |
173 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
174 | |
182 | |
175 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked until |
… | |
… | |
193 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
194 | compatible to older versions, so a larger minor version alone is usually |
202 | compatible to older versions, so a larger minor version alone is usually |
195 | not a problem. |
203 | not a problem. |
196 | |
204 | |
197 | Example: Make sure we haven't accidentally been linked against the wrong |
205 | Example: Make sure we haven't accidentally been linked against the wrong |
198 | version (note, however, that this will not detect ABI mismatches :). |
206 | version (note, however, that this will not detect other ABI mismatches, |
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207 | such as LFS or reentrancy). |
199 | |
208 | |
200 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
201 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
202 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
203 | |
212 | |
… | |
… | |
225 | probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
226 | |
235 | |
227 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
228 | |
237 | |
229 | Returns the set of backends that are embeddable in other event loops. This |
238 | Returns the set of backends that are embeddable in other event loops. This |
230 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
231 | might be supported on the current system, you would need to look at |
240 | current system. To find which embeddable backends might be supported on |
232 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
233 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
234 | |
243 | |
235 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
236 | |
245 | |
237 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
238 | |
247 | |
239 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
240 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
241 | used to allocate and free memory (no surprises here). If it returns zero |
250 | used to allocate and free memory (no surprises here). If it returns zero |
242 | when memory needs to be allocated (C<size != 0>), the library might abort |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
268 | } |
277 | } |
269 | |
278 | |
270 | ... |
279 | ... |
271 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
272 | |
281 | |
273 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
274 | |
283 | |
275 | Set the callback function to call on a retryable system call error (such |
284 | Set the callback function to call on a retryable system call error (such |
276 | as failed select, poll, epoll_wait). The message is a printable string |
285 | as failed select, poll, epoll_wait). The message is a printable string |
277 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
278 | callback is set, then libev will expect it to remedy the situation, no |
287 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
290 | } |
299 | } |
291 | |
300 | |
292 | ... |
301 | ... |
293 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
294 | |
303 | |
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304 | =item ev_feed_signal (int signum) |
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305 | |
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306 | This function can be used to "simulate" a signal receive. It is completely |
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307 | safe to call this function at any time, from any context, including signal |
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308 | handlers or random threads. |
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309 | |
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310 | Its main use is to customise signal handling in your process, especially |
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311 | in the presence of threads. For example, you could block signals |
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312 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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313 | creating any loops), and in one thread, use C<sigwait> or any other |
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314 | mechanism to wait for signals, then "deliver" them to libev by calling |
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315 | C<ev_feed_signal>. |
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316 | |
295 | =back |
317 | =back |
296 | |
318 | |
297 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
319 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
298 | |
320 | |
299 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
321 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
300 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
322 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
301 | libev 3 had an C<ev_loop> function colliding with the struct name). |
323 | libev 3 had an C<ev_loop> function colliding with the struct name). |
302 | |
324 | |
303 | The library knows two types of such loops, the I<default> loop, which |
325 | The library knows two types of such loops, the I<default> loop, which |
304 | supports signals and child events, and dynamically created event loops |
326 | supports child process events, and dynamically created event loops which |
305 | which do not. |
327 | do not. |
306 | |
328 | |
307 | =over 4 |
329 | =over 4 |
308 | |
330 | |
309 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
331 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
310 | |
332 | |
311 | This will initialise the default event loop if it hasn't been initialised |
333 | This returns the "default" event loop object, which is what you should |
312 | yet and return it. If the default loop could not be initialised, returns |
334 | normally use when you just need "the event loop". Event loop objects and |
313 | false. If it already was initialised it simply returns it (and ignores the |
335 | the C<flags> parameter are described in more detail in the entry for |
314 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
336 | C<ev_loop_new>. |
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337 | |
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338 | If the default loop is already initialised then this function simply |
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339 | returns it (and ignores the flags. If that is troubling you, check |
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340 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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341 | flags, which should almost always be C<0>, unless the caller is also the |
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342 | one calling C<ev_run> or otherwise qualifies as "the main program". |
315 | |
343 | |
316 | If you don't know what event loop to use, use the one returned from this |
344 | If you don't know what event loop to use, use the one returned from this |
317 | function. |
345 | function (or via the C<EV_DEFAULT> macro). |
318 | |
346 | |
319 | Note that this function is I<not> thread-safe, so if you want to use it |
347 | Note that this function is I<not> thread-safe, so if you want to use it |
320 | from multiple threads, you have to lock (note also that this is unlikely, |
348 | from multiple threads, you have to employ some kind of mutex (note also |
321 | as loops cannot be shared easily between threads anyway). |
349 | that this case is unlikely, as loops cannot be shared easily between |
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350 | threads anyway). |
322 | |
351 | |
323 | The default loop is the only loop that can handle C<ev_signal> and |
352 | The default loop is the only loop that can handle C<ev_child> watchers, |
324 | C<ev_child> watchers, and to do this, it always registers a handler |
353 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
325 | for C<SIGCHLD>. If this is a problem for your application you can either |
354 | a problem for your application you can either create a dynamic loop with |
326 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
355 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
327 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
356 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
328 | C<ev_default_init>. |
357 | |
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358 | Example: This is the most typical usage. |
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359 | |
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360 | if (!ev_default_loop (0)) |
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361 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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362 | |
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363 | Example: Restrict libev to the select and poll backends, and do not allow |
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364 | environment settings to be taken into account: |
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365 | |
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366 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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367 | |
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368 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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369 | |
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370 | This will create and initialise a new event loop object. If the loop |
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371 | could not be initialised, returns false. |
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372 | |
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373 | This function is thread-safe, and one common way to use libev with |
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374 | threads is indeed to create one loop per thread, and using the default |
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375 | loop in the "main" or "initial" thread. |
329 | |
376 | |
330 | The flags argument can be used to specify special behaviour or specific |
377 | The flags argument can be used to specify special behaviour or specific |
331 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
378 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
332 | |
379 | |
333 | The following flags are supported: |
380 | The following flags are supported: |
… | |
… | |
368 | environment variable. |
415 | environment variable. |
369 | |
416 | |
370 | =item C<EVFLAG_NOINOTIFY> |
417 | =item C<EVFLAG_NOINOTIFY> |
371 | |
418 | |
372 | When this flag is specified, then libev will not attempt to use the |
419 | When this flag is specified, then libev will not attempt to use the |
373 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
420 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
374 | testing, this flag can be useful to conserve inotify file descriptors, as |
421 | testing, this flag can be useful to conserve inotify file descriptors, as |
375 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
422 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
376 | |
423 | |
377 | =item C<EVFLAG_SIGNALFD> |
424 | =item C<EVFLAG_SIGNALFD> |
378 | |
425 | |
379 | When this flag is specified, then libev will attempt to use the |
426 | When this flag is specified, then libev will attempt to use the |
380 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
427 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
381 | delivers signals synchronously, which makes it both faster and might make |
428 | delivers signals synchronously, which makes it both faster and might make |
382 | it possible to get the queued signal data. It can also simplify signal |
429 | it possible to get the queued signal data. It can also simplify signal |
383 | handling with threads, as long as you properly block signals in your |
430 | handling with threads, as long as you properly block signals in your |
384 | threads that are not interested in handling them. |
431 | threads that are not interested in handling them. |
385 | |
432 | |
386 | Signalfd will not be used by default as this changes your signal mask, and |
433 | Signalfd will not be used by default as this changes your signal mask, and |
387 | there are a lot of shoddy libraries and programs (glib's threadpool for |
434 | there are a lot of shoddy libraries and programs (glib's threadpool for |
388 | example) that can't properly initialise their signal masks. |
435 | example) that can't properly initialise their signal masks. |
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436 | |
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437 | =item C<EVFLAG_NOSIGMASK> |
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438 | |
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439 | When this flag is specified, then libev will avoid to modify the signal |
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440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
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441 | when you want to receive them. |
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442 | |
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443 | This behaviour is useful when you want to do your own signal handling, or |
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444 | want to handle signals only in specific threads and want to avoid libev |
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445 | unblocking the signals. |
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446 | |
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447 | It's also required by POSIX in a threaded program, as libev calls |
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448 | C<sigprocmask>, whose behaviour is officially unspecified. |
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449 | |
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450 | This flag's behaviour will become the default in future versions of libev. |
389 | |
451 | |
390 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
452 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
391 | |
453 | |
392 | This is your standard select(2) backend. Not I<completely> standard, as |
454 | This is your standard select(2) backend. Not I<completely> standard, as |
393 | libev tries to roll its own fd_set with no limits on the number of fds, |
455 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
429 | epoll scales either O(1) or O(active_fds). |
491 | epoll scales either O(1) or O(active_fds). |
430 | |
492 | |
431 | The epoll mechanism deserves honorable mention as the most misdesigned |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
432 | of the more advanced event mechanisms: mere annoyances include silently |
494 | of the more advanced event mechanisms: mere annoyances include silently |
433 | dropping file descriptors, requiring a system call per change per file |
495 | dropping file descriptors, requiring a system call per change per file |
434 | descriptor (and unnecessary guessing of parameters), problems with dup and |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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497 | returning before the timeout value, resulting in additional iterations |
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498 | (and only giving 5ms accuracy while select on the same platform gives |
435 | so on. The biggest issue is fork races, however - if a program forks then |
499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
436 | I<both> parent and child process have to recreate the epoll set, which can |
500 | forks then I<both> parent and child process have to recreate the epoll |
437 | take considerable time (one syscall per file descriptor) and is of course |
501 | set, which can take considerable time (one syscall per file descriptor) |
438 | hard to detect. |
502 | and is of course hard to detect. |
439 | |
503 | |
440 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
441 | of course I<doesn't>, and epoll just loves to report events for totally |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
442 | I<different> file descriptors (even already closed ones, so one cannot |
506 | I<different> file descriptors (even already closed ones, so one cannot |
443 | even remove them from the set) than registered in the set (especially |
507 | even remove them from the set) than registered in the set (especially |
… | |
… | |
445 | employing an additional generation counter and comparing that against the |
509 | employing an additional generation counter and comparing that against the |
446 | events to filter out spurious ones, recreating the set when required. Last |
510 | events to filter out spurious ones, recreating the set when required. Last |
447 | not least, it also refuses to work with some file descriptors which work |
511 | not least, it also refuses to work with some file descriptors which work |
448 | perfectly fine with C<select> (files, many character devices...). |
512 | perfectly fine with C<select> (files, many character devices...). |
449 | |
513 | |
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514 | Epoll is truly the train wreck analog among event poll mechanisms, |
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515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
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516 | interaction with others. |
|
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517 | |
450 | While stopping, setting and starting an I/O watcher in the same iteration |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
451 | will result in some caching, there is still a system call per such |
519 | will result in some caching, there is still a system call per such |
452 | incident (because the same I<file descriptor> could point to a different |
520 | incident (because the same I<file descriptor> could point to a different |
453 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
454 | file descriptors might not work very well if you register events for both |
522 | file descriptors might not work very well if you register events for both |
… | |
… | |
519 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
587 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
520 | |
588 | |
521 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
589 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
522 | it's really slow, but it still scales very well (O(active_fds)). |
590 | it's really slow, but it still scales very well (O(active_fds)). |
523 | |
591 | |
524 | Please note that Solaris event ports can deliver a lot of spurious |
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525 | notifications, so you need to use non-blocking I/O or other means to avoid |
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526 | blocking when no data (or space) is available. |
|
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527 | |
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528 | While this backend scales well, it requires one system call per active |
592 | While this backend scales well, it requires one system call per active |
529 | file descriptor per loop iteration. For small and medium numbers of file |
593 | file descriptor per loop iteration. For small and medium numbers of file |
530 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
594 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
531 | might perform better. |
595 | might perform better. |
532 | |
596 | |
533 | On the positive side, with the exception of the spurious readiness |
597 | On the positive side, this backend actually performed fully to |
534 | notifications, this backend actually performed fully to specification |
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535 | in all tests and is fully embeddable, which is a rare feat among the |
598 | specification in all tests and is fully embeddable, which is a rare feat |
536 | OS-specific backends (I vastly prefer correctness over speed hacks). |
599 | among the OS-specific backends (I vastly prefer correctness over speed |
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600 | hacks). |
|
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601 | |
|
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602 | On the negative side, the interface is I<bizarre> - so bizarre that |
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603 | even sun itself gets it wrong in their code examples: The event polling |
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604 | function sometimes returning events to the caller even though an error |
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605 | occurred, but with no indication whether it has done so or not (yes, it's |
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606 | even documented that way) - deadly for edge-triggered interfaces where |
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607 | you absolutely have to know whether an event occurred or not because you |
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608 | have to re-arm the watcher. |
|
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609 | |
|
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610 | Fortunately libev seems to be able to work around these idiocies. |
537 | |
611 | |
538 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
539 | C<EVBACKEND_POLL>. |
613 | C<EVBACKEND_POLL>. |
540 | |
614 | |
541 | =item C<EVBACKEND_ALL> |
615 | =item C<EVBACKEND_ALL> |
542 | |
616 | |
543 | Try all backends (even potentially broken ones that wouldn't be tried |
617 | Try all backends (even potentially broken ones that wouldn't be tried |
544 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
618 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
545 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
619 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
546 | |
620 | |
547 | It is definitely not recommended to use this flag. |
621 | It is definitely not recommended to use this flag, use whatever |
|
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622 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
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623 | at all. |
|
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624 | |
|
|
625 | =item C<EVBACKEND_MASK> |
|
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626 | |
|
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627 | Not a backend at all, but a mask to select all backend bits from a |
|
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628 | C<flags> value, in case you want to mask out any backends from a flags |
|
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629 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
548 | |
630 | |
549 | =back |
631 | =back |
550 | |
632 | |
551 | If one or more of the backend flags are or'ed into the flags value, |
633 | If one or more of the backend flags are or'ed into the flags value, |
552 | then only these backends will be tried (in the reverse order as listed |
634 | then only these backends will be tried (in the reverse order as listed |
553 | here). If none are specified, all backends in C<ev_recommended_backends |
635 | here). If none are specified, all backends in C<ev_recommended_backends |
554 | ()> will be tried. |
636 | ()> will be tried. |
555 | |
637 | |
556 | Example: This is the most typical usage. |
|
|
557 | |
|
|
558 | if (!ev_default_loop (0)) |
|
|
559 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
560 | |
|
|
561 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
562 | environment settings to be taken into account: |
|
|
563 | |
|
|
564 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
565 | |
|
|
566 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
567 | used if available (warning, breaks stuff, best use only with your own |
|
|
568 | private event loop and only if you know the OS supports your types of |
|
|
569 | fds): |
|
|
570 | |
|
|
571 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
572 | |
|
|
573 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
574 | |
|
|
575 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
576 | always distinct from the default loop. |
|
|
577 | |
|
|
578 | Note that this function I<is> thread-safe, and one common way to use |
|
|
579 | libev with threads is indeed to create one loop per thread, and using the |
|
|
580 | default loop in the "main" or "initial" thread. |
|
|
581 | |
|
|
582 | Example: Try to create a event loop that uses epoll and nothing else. |
638 | Example: Try to create a event loop that uses epoll and nothing else. |
583 | |
639 | |
584 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
640 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
585 | if (!epoller) |
641 | if (!epoller) |
586 | fatal ("no epoll found here, maybe it hides under your chair"); |
642 | fatal ("no epoll found here, maybe it hides under your chair"); |
587 | |
643 | |
|
|
644 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
645 | used if available. |
|
|
646 | |
|
|
647 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
648 | |
588 | =item ev_default_destroy () |
649 | =item ev_loop_destroy (loop) |
589 | |
650 | |
590 | Destroys the default loop (frees all memory and kernel state etc.). None |
651 | Destroys an event loop object (frees all memory and kernel state |
591 | of the active event watchers will be stopped in the normal sense, so |
652 | etc.). None of the active event watchers will be stopped in the normal |
592 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
653 | sense, so e.g. C<ev_is_active> might still return true. It is your |
593 | either stop all watchers cleanly yourself I<before> calling this function, |
654 | responsibility to either stop all watchers cleanly yourself I<before> |
594 | or cope with the fact afterwards (which is usually the easiest thing, you |
655 | calling this function, or cope with the fact afterwards (which is usually |
595 | can just ignore the watchers and/or C<free ()> them for example). |
656 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
657 | for example). |
596 | |
658 | |
597 | Note that certain global state, such as signal state (and installed signal |
659 | Note that certain global state, such as signal state (and installed signal |
598 | handlers), will not be freed by this function, and related watchers (such |
660 | handlers), will not be freed by this function, and related watchers (such |
599 | as signal and child watchers) would need to be stopped manually. |
661 | as signal and child watchers) would need to be stopped manually. |
600 | |
662 | |
601 | In general it is not advisable to call this function except in the |
663 | This function is normally used on loop objects allocated by |
602 | rare occasion where you really need to free e.g. the signal handling |
664 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
665 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
666 | |
|
|
667 | Note that it is not advisable to call this function on the default loop |
|
|
668 | except in the rare occasion where you really need to free its resources. |
603 | pipe fds. If you need dynamically allocated loops it is better to use |
669 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
604 | C<ev_loop_new> and C<ev_loop_destroy>. |
670 | and C<ev_loop_destroy>. |
605 | |
671 | |
606 | =item ev_loop_destroy (loop) |
672 | =item ev_loop_fork (loop) |
607 | |
673 | |
608 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
609 | earlier call to C<ev_loop_new>. |
|
|
610 | |
|
|
611 | =item ev_default_fork () |
|
|
612 | |
|
|
613 | This function sets a flag that causes subsequent C<ev_run> iterations |
674 | This function sets a flag that causes subsequent C<ev_run> iterations to |
614 | to reinitialise the kernel state for backends that have one. Despite the |
675 | reinitialise the kernel state for backends that have one. Despite the |
615 | name, you can call it anytime, but it makes most sense after forking, in |
676 | name, you can call it anytime, but it makes most sense after forking, in |
616 | the child process (or both child and parent, but that again makes little |
677 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
617 | sense). You I<must> call it in the child before using any of the libev |
678 | child before resuming or calling C<ev_run>. |
618 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
619 | |
679 | |
620 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
680 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
621 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
681 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
622 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
682 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
623 | during fork. |
683 | during fork. |
… | |
… | |
628 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
688 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
629 | difference, but libev will usually detect this case on its own and do a |
689 | difference, but libev will usually detect this case on its own and do a |
630 | costly reset of the backend). |
690 | costly reset of the backend). |
631 | |
691 | |
632 | The function itself is quite fast and it's usually not a problem to call |
692 | The function itself is quite fast and it's usually not a problem to call |
633 | it just in case after a fork. To make this easy, the function will fit in |
693 | it just in case after a fork. |
634 | quite nicely into a call to C<pthread_atfork>: |
|
|
635 | |
694 | |
|
|
695 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
696 | using pthreads. |
|
|
697 | |
|
|
698 | static void |
|
|
699 | post_fork_child (void) |
|
|
700 | { |
|
|
701 | ev_loop_fork (EV_DEFAULT); |
|
|
702 | } |
|
|
703 | |
|
|
704 | ... |
636 | pthread_atfork (0, 0, ev_default_fork); |
705 | pthread_atfork (0, 0, post_fork_child); |
637 | |
|
|
638 | =item ev_loop_fork (loop) |
|
|
639 | |
|
|
640 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
641 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
642 | after fork that you want to re-use in the child, and how you keep track of |
|
|
643 | them is entirely your own problem. |
|
|
644 | |
706 | |
645 | =item int ev_is_default_loop (loop) |
707 | =item int ev_is_default_loop (loop) |
646 | |
708 | |
647 | Returns true when the given loop is, in fact, the default loop, and false |
709 | Returns true when the given loop is, in fact, the default loop, and false |
648 | otherwise. |
710 | otherwise. |
… | |
… | |
659 | prepare and check phases. |
721 | prepare and check phases. |
660 | |
722 | |
661 | =item unsigned int ev_depth (loop) |
723 | =item unsigned int ev_depth (loop) |
662 | |
724 | |
663 | Returns the number of times C<ev_run> was entered minus the number of |
725 | Returns the number of times C<ev_run> was entered minus the number of |
664 | times C<ev_run> was exited, in other words, the recursion depth. |
726 | times C<ev_run> was exited normally, in other words, the recursion depth. |
665 | |
727 | |
666 | Outside C<ev_run>, this number is zero. In a callback, this number is |
728 | Outside C<ev_run>, this number is zero. In a callback, this number is |
667 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
729 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
668 | in which case it is higher. |
730 | in which case it is higher. |
669 | |
731 | |
670 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
732 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
671 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
733 | throwing an exception etc.), doesn't count as "exit" - consider this |
672 | ungentleman-like behaviour unless it's really convenient. |
734 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
735 | convenient, in which case it is fully supported. |
673 | |
736 | |
674 | =item unsigned int ev_backend (loop) |
737 | =item unsigned int ev_backend (loop) |
675 | |
738 | |
676 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
739 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
677 | use. |
740 | use. |
… | |
… | |
738 | relying on all watchers to be stopped when deciding when a program has |
801 | relying on all watchers to be stopped when deciding when a program has |
739 | finished (especially in interactive programs), but having a program |
802 | finished (especially in interactive programs), but having a program |
740 | that automatically loops as long as it has to and no longer by virtue |
803 | that automatically loops as long as it has to and no longer by virtue |
741 | of relying on its watchers stopping correctly, that is truly a thing of |
804 | of relying on its watchers stopping correctly, that is truly a thing of |
742 | beauty. |
805 | beauty. |
|
|
806 | |
|
|
807 | This function is also I<mostly> exception-safe - you can break out of |
|
|
808 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
809 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
810 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
743 | |
811 | |
744 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
812 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
745 | those events and any already outstanding ones, but will not wait and |
813 | those events and any already outstanding ones, but will not wait and |
746 | block your process in case there are no events and will return after one |
814 | block your process in case there are no events and will return after one |
747 | iteration of the loop. This is sometimes useful to poll and handle new |
815 | iteration of the loop. This is sometimes useful to poll and handle new |
… | |
… | |
800 | anymore. |
868 | anymore. |
801 | |
869 | |
802 | ... queue jobs here, make sure they register event watchers as long |
870 | ... queue jobs here, make sure they register event watchers as long |
803 | ... as they still have work to do (even an idle watcher will do..) |
871 | ... as they still have work to do (even an idle watcher will do..) |
804 | ev_run (my_loop, 0); |
872 | ev_run (my_loop, 0); |
805 | ... jobs done or somebody called unloop. yeah! |
873 | ... jobs done or somebody called break. yeah! |
806 | |
874 | |
807 | =item ev_break (loop, how) |
875 | =item ev_break (loop, how) |
808 | |
876 | |
809 | Can be used to make a call to C<ev_run> return early (but only after it |
877 | Can be used to make a call to C<ev_run> return early (but only after it |
810 | has processed all outstanding events). The C<how> argument must be either |
878 | has processed all outstanding events). The C<how> argument must be either |
811 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
879 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
812 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
880 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
813 | |
881 | |
814 | This "unloop state" will be cleared when entering C<ev_run> again. |
882 | This "break state" will be cleared on the next call to C<ev_run>. |
815 | |
883 | |
816 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
884 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
885 | which case it will have no effect. |
817 | |
886 | |
818 | =item ev_ref (loop) |
887 | =item ev_ref (loop) |
819 | |
888 | |
820 | =item ev_unref (loop) |
889 | =item ev_unref (loop) |
821 | |
890 | |
… | |
… | |
842 | running when nothing else is active. |
911 | running when nothing else is active. |
843 | |
912 | |
844 | ev_signal exitsig; |
913 | ev_signal exitsig; |
845 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
914 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
846 | ev_signal_start (loop, &exitsig); |
915 | ev_signal_start (loop, &exitsig); |
847 | evf_unref (loop); |
916 | ev_unref (loop); |
848 | |
917 | |
849 | Example: For some weird reason, unregister the above signal handler again. |
918 | Example: For some weird reason, unregister the above signal handler again. |
850 | |
919 | |
851 | ev_ref (loop); |
920 | ev_ref (loop); |
852 | ev_signal_stop (loop, &exitsig); |
921 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
964 | See also the locking example in the C<THREADS> section later in this |
1033 | See also the locking example in the C<THREADS> section later in this |
965 | document. |
1034 | document. |
966 | |
1035 | |
967 | =item ev_set_userdata (loop, void *data) |
1036 | =item ev_set_userdata (loop, void *data) |
968 | |
1037 | |
969 | =item ev_userdata (loop) |
1038 | =item void *ev_userdata (loop) |
970 | |
1039 | |
971 | Set and retrieve a single C<void *> associated with a loop. When |
1040 | Set and retrieve a single C<void *> associated with a loop. When |
972 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1041 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
973 | C<0.> |
1042 | C<0>. |
974 | |
1043 | |
975 | These two functions can be used to associate arbitrary data with a loop, |
1044 | These two functions can be used to associate arbitrary data with a loop, |
976 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1045 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
977 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1046 | C<acquire> callbacks described above, but of course can be (ab-)used for |
978 | any other purpose as well. |
1047 | any other purpose as well. |
… | |
… | |
1106 | =item C<EV_FORK> |
1175 | =item C<EV_FORK> |
1107 | |
1176 | |
1108 | The event loop has been resumed in the child process after fork (see |
1177 | The event loop has been resumed in the child process after fork (see |
1109 | C<ev_fork>). |
1178 | C<ev_fork>). |
1110 | |
1179 | |
|
|
1180 | =item C<EV_CLEANUP> |
|
|
1181 | |
|
|
1182 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1183 | |
1111 | =item C<EV_ASYNC> |
1184 | =item C<EV_ASYNC> |
1112 | |
1185 | |
1113 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1186 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1114 | |
1187 | |
1115 | =item C<EV_CUSTOM> |
1188 | =item C<EV_CUSTOM> |
… | |
… | |
1136 | programs, though, as the fd could already be closed and reused for another |
1209 | programs, though, as the fd could already be closed and reused for another |
1137 | thing, so beware. |
1210 | thing, so beware. |
1138 | |
1211 | |
1139 | =back |
1212 | =back |
1140 | |
1213 | |
|
|
1214 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1215 | |
|
|
1216 | =over 4 |
|
|
1217 | |
|
|
1218 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1219 | |
|
|
1220 | This macro initialises the generic portion of a watcher. The contents |
|
|
1221 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1222 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1223 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1224 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1225 | which rolls both calls into one. |
|
|
1226 | |
|
|
1227 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1228 | (or never started) and there are no pending events outstanding. |
|
|
1229 | |
|
|
1230 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1231 | int revents)>. |
|
|
1232 | |
|
|
1233 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1234 | |
|
|
1235 | ev_io w; |
|
|
1236 | ev_init (&w, my_cb); |
|
|
1237 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1238 | |
|
|
1239 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1240 | |
|
|
1241 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1242 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1243 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1244 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1245 | difference to the C<ev_init> macro). |
|
|
1246 | |
|
|
1247 | Although some watcher types do not have type-specific arguments |
|
|
1248 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1249 | |
|
|
1250 | See C<ev_init>, above, for an example. |
|
|
1251 | |
|
|
1252 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1253 | |
|
|
1254 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1255 | calls into a single call. This is the most convenient method to initialise |
|
|
1256 | a watcher. The same limitations apply, of course. |
|
|
1257 | |
|
|
1258 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1259 | |
|
|
1260 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1261 | |
|
|
1262 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1263 | |
|
|
1264 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1265 | events. If the watcher is already active nothing will happen. |
|
|
1266 | |
|
|
1267 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1268 | whole section. |
|
|
1269 | |
|
|
1270 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1271 | |
|
|
1272 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1273 | |
|
|
1274 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1275 | the watcher was active or not). |
|
|
1276 | |
|
|
1277 | It is possible that stopped watchers are pending - for example, |
|
|
1278 | non-repeating timers are being stopped when they become pending - but |
|
|
1279 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1280 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1281 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1282 | |
|
|
1283 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1284 | |
|
|
1285 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1286 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1287 | it. |
|
|
1288 | |
|
|
1289 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1290 | |
|
|
1291 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1292 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1293 | is pending (but not active) you must not call an init function on it (but |
|
|
1294 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1295 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1296 | it). |
|
|
1297 | |
|
|
1298 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1299 | |
|
|
1300 | Returns the callback currently set on the watcher. |
|
|
1301 | |
|
|
1302 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1303 | |
|
|
1304 | Change the callback. You can change the callback at virtually any time |
|
|
1305 | (modulo threads). |
|
|
1306 | |
|
|
1307 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1308 | |
|
|
1309 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1310 | |
|
|
1311 | Set and query the priority of the watcher. The priority is a small |
|
|
1312 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1313 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1314 | before watchers with lower priority, but priority will not keep watchers |
|
|
1315 | from being executed (except for C<ev_idle> watchers). |
|
|
1316 | |
|
|
1317 | If you need to suppress invocation when higher priority events are pending |
|
|
1318 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1319 | |
|
|
1320 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1321 | pending. |
|
|
1322 | |
|
|
1323 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1324 | fine, as long as you do not mind that the priority value you query might |
|
|
1325 | or might not have been clamped to the valid range. |
|
|
1326 | |
|
|
1327 | The default priority used by watchers when no priority has been set is |
|
|
1328 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1329 | |
|
|
1330 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1331 | priorities. |
|
|
1332 | |
|
|
1333 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1334 | |
|
|
1335 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1336 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1337 | can deal with that fact, as both are simply passed through to the |
|
|
1338 | callback. |
|
|
1339 | |
|
|
1340 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1341 | |
|
|
1342 | If the watcher is pending, this function clears its pending status and |
|
|
1343 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1344 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1345 | |
|
|
1346 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1347 | callback to be invoked, which can be accomplished with this function. |
|
|
1348 | |
|
|
1349 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1350 | |
|
|
1351 | Feeds the given event set into the event loop, as if the specified event |
|
|
1352 | had happened for the specified watcher (which must be a pointer to an |
|
|
1353 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1354 | not free the watcher as long as it has pending events. |
|
|
1355 | |
|
|
1356 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1357 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1358 | not started in the first place. |
|
|
1359 | |
|
|
1360 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1361 | functions that do not need a watcher. |
|
|
1362 | |
|
|
1363 | =back |
|
|
1364 | |
|
|
1365 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1366 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1367 | |
1141 | =head2 WATCHER STATES |
1368 | =head2 WATCHER STATES |
1142 | |
1369 | |
1143 | There are various watcher states mentioned throughout this manual - |
1370 | There are various watcher states mentioned throughout this manual - |
1144 | active, pending and so on. In this section these states and the rules to |
1371 | active, pending and so on. In this section these states and the rules to |
1145 | transition between them will be described in more detail - and while these |
1372 | transition between them will be described in more detail - and while these |
… | |
… | |
1151 | |
1378 | |
1152 | Before a watcher can be registered with the event looop it has to be |
1379 | Before a watcher can be registered with the event looop it has to be |
1153 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1380 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1154 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1381 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1155 | |
1382 | |
1156 | In this state it is simply some block of memory that is suitable for use |
1383 | In this state it is simply some block of memory that is suitable for |
1157 | in an event loop. It can be moved around, freed, reused etc. at will. |
1384 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1385 | will - as long as you either keep the memory contents intact, or call |
|
|
1386 | C<ev_TYPE_init> again. |
1158 | |
1387 | |
1159 | =item started/running/active |
1388 | =item started/running/active |
1160 | |
1389 | |
1161 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1390 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1162 | property of the event loop, and is actively waiting for events. While in |
1391 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1190 | latter will clear any pending state the watcher might be in, regardless |
1419 | latter will clear any pending state the watcher might be in, regardless |
1191 | of whether it was active or not, so stopping a watcher explicitly before |
1420 | of whether it was active or not, so stopping a watcher explicitly before |
1192 | freeing it is often a good idea. |
1421 | freeing it is often a good idea. |
1193 | |
1422 | |
1194 | While stopped (and not pending) the watcher is essentially in the |
1423 | While stopped (and not pending) the watcher is essentially in the |
1195 | initialised state, that is it can be reused, moved, modified in any way |
1424 | initialised state, that is, it can be reused, moved, modified in any way |
1196 | you wish. |
1425 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1426 | it again). |
1197 | |
1427 | |
1198 | =back |
1428 | =back |
1199 | |
|
|
1200 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1201 | |
|
|
1202 | =over 4 |
|
|
1203 | |
|
|
1204 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1205 | |
|
|
1206 | This macro initialises the generic portion of a watcher. The contents |
|
|
1207 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1208 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1209 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1210 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1211 | which rolls both calls into one. |
|
|
1212 | |
|
|
1213 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1214 | (or never started) and there are no pending events outstanding. |
|
|
1215 | |
|
|
1216 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1217 | int revents)>. |
|
|
1218 | |
|
|
1219 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1220 | |
|
|
1221 | ev_io w; |
|
|
1222 | ev_init (&w, my_cb); |
|
|
1223 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1224 | |
|
|
1225 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1226 | |
|
|
1227 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1228 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1229 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1230 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1231 | difference to the C<ev_init> macro). |
|
|
1232 | |
|
|
1233 | Although some watcher types do not have type-specific arguments |
|
|
1234 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1235 | |
|
|
1236 | See C<ev_init>, above, for an example. |
|
|
1237 | |
|
|
1238 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1239 | |
|
|
1240 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1241 | calls into a single call. This is the most convenient method to initialise |
|
|
1242 | a watcher. The same limitations apply, of course. |
|
|
1243 | |
|
|
1244 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1245 | |
|
|
1246 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1247 | |
|
|
1248 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1249 | |
|
|
1250 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1251 | events. If the watcher is already active nothing will happen. |
|
|
1252 | |
|
|
1253 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1254 | whole section. |
|
|
1255 | |
|
|
1256 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1257 | |
|
|
1258 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1259 | |
|
|
1260 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1261 | the watcher was active or not). |
|
|
1262 | |
|
|
1263 | It is possible that stopped watchers are pending - for example, |
|
|
1264 | non-repeating timers are being stopped when they become pending - but |
|
|
1265 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1266 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1267 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1268 | |
|
|
1269 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1270 | |
|
|
1271 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1272 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1273 | it. |
|
|
1274 | |
|
|
1275 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1276 | |
|
|
1277 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1278 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1279 | is pending (but not active) you must not call an init function on it (but |
|
|
1280 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1281 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1282 | it). |
|
|
1283 | |
|
|
1284 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1285 | |
|
|
1286 | Returns the callback currently set on the watcher. |
|
|
1287 | |
|
|
1288 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1289 | |
|
|
1290 | Change the callback. You can change the callback at virtually any time |
|
|
1291 | (modulo threads). |
|
|
1292 | |
|
|
1293 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1294 | |
|
|
1295 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1296 | |
|
|
1297 | Set and query the priority of the watcher. The priority is a small |
|
|
1298 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1299 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1300 | before watchers with lower priority, but priority will not keep watchers |
|
|
1301 | from being executed (except for C<ev_idle> watchers). |
|
|
1302 | |
|
|
1303 | If you need to suppress invocation when higher priority events are pending |
|
|
1304 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1305 | |
|
|
1306 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1307 | pending. |
|
|
1308 | |
|
|
1309 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1310 | fine, as long as you do not mind that the priority value you query might |
|
|
1311 | or might not have been clamped to the valid range. |
|
|
1312 | |
|
|
1313 | The default priority used by watchers when no priority has been set is |
|
|
1314 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1315 | |
|
|
1316 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1317 | priorities. |
|
|
1318 | |
|
|
1319 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1320 | |
|
|
1321 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1322 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1323 | can deal with that fact, as both are simply passed through to the |
|
|
1324 | callback. |
|
|
1325 | |
|
|
1326 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1327 | |
|
|
1328 | If the watcher is pending, this function clears its pending status and |
|
|
1329 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1330 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1331 | |
|
|
1332 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1333 | callback to be invoked, which can be accomplished with this function. |
|
|
1334 | |
|
|
1335 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1336 | |
|
|
1337 | Feeds the given event set into the event loop, as if the specified event |
|
|
1338 | had happened for the specified watcher (which must be a pointer to an |
|
|
1339 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1340 | not free the watcher as long as it has pending events. |
|
|
1341 | |
|
|
1342 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1343 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1344 | not started in the first place. |
|
|
1345 | |
|
|
1346 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1347 | functions that do not need a watcher. |
|
|
1348 | |
|
|
1349 | =back |
|
|
1350 | |
|
|
1351 | |
|
|
1352 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1353 | |
|
|
1354 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1355 | and read at any time: libev will completely ignore it. This can be used |
|
|
1356 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1357 | don't want to allocate memory and store a pointer to it in that data |
|
|
1358 | member, you can also "subclass" the watcher type and provide your own |
|
|
1359 | data: |
|
|
1360 | |
|
|
1361 | struct my_io |
|
|
1362 | { |
|
|
1363 | ev_io io; |
|
|
1364 | int otherfd; |
|
|
1365 | void *somedata; |
|
|
1366 | struct whatever *mostinteresting; |
|
|
1367 | }; |
|
|
1368 | |
|
|
1369 | ... |
|
|
1370 | struct my_io w; |
|
|
1371 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1372 | |
|
|
1373 | And since your callback will be called with a pointer to the watcher, you |
|
|
1374 | can cast it back to your own type: |
|
|
1375 | |
|
|
1376 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1377 | { |
|
|
1378 | struct my_io *w = (struct my_io *)w_; |
|
|
1379 | ... |
|
|
1380 | } |
|
|
1381 | |
|
|
1382 | More interesting and less C-conformant ways of casting your callback type |
|
|
1383 | instead have been omitted. |
|
|
1384 | |
|
|
1385 | Another common scenario is to use some data structure with multiple |
|
|
1386 | embedded watchers: |
|
|
1387 | |
|
|
1388 | struct my_biggy |
|
|
1389 | { |
|
|
1390 | int some_data; |
|
|
1391 | ev_timer t1; |
|
|
1392 | ev_timer t2; |
|
|
1393 | } |
|
|
1394 | |
|
|
1395 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1396 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1397 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1398 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1399 | programmers): |
|
|
1400 | |
|
|
1401 | #include <stddef.h> |
|
|
1402 | |
|
|
1403 | static void |
|
|
1404 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1405 | { |
|
|
1406 | struct my_biggy big = (struct my_biggy *) |
|
|
1407 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1408 | } |
|
|
1409 | |
|
|
1410 | static void |
|
|
1411 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1412 | { |
|
|
1413 | struct my_biggy big = (struct my_biggy *) |
|
|
1414 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1415 | } |
|
|
1416 | |
1429 | |
1417 | =head2 WATCHER PRIORITY MODELS |
1430 | =head2 WATCHER PRIORITY MODELS |
1418 | |
1431 | |
1419 | Many event loops support I<watcher priorities>, which are usually small |
1432 | Many event loops support I<watcher priorities>, which are usually small |
1420 | integers that influence the ordering of event callback invocation |
1433 | integers that influence the ordering of event callback invocation |
… | |
… | |
1547 | In general you can register as many read and/or write event watchers per |
1560 | In general you can register as many read and/or write event watchers per |
1548 | fd as you want (as long as you don't confuse yourself). Setting all file |
1561 | fd as you want (as long as you don't confuse yourself). Setting all file |
1549 | descriptors to non-blocking mode is also usually a good idea (but not |
1562 | descriptors to non-blocking mode is also usually a good idea (but not |
1550 | required if you know what you are doing). |
1563 | required if you know what you are doing). |
1551 | |
1564 | |
1552 | If you cannot use non-blocking mode, then force the use of a |
|
|
1553 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1554 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1555 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1556 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1557 | |
|
|
1558 | Another thing you have to watch out for is that it is quite easy to |
1565 | Another thing you have to watch out for is that it is quite easy to |
1559 | receive "spurious" readiness notifications, that is your callback might |
1566 | receive "spurious" readiness notifications, that is, your callback might |
1560 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1567 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1561 | because there is no data. Not only are some backends known to create a |
1568 | because there is no data. It is very easy to get into this situation even |
1562 | lot of those (for example Solaris ports), it is very easy to get into |
1569 | with a relatively standard program structure. Thus it is best to always |
1563 | this situation even with a relatively standard program structure. Thus |
1570 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1564 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1565 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1571 | preferable to a program hanging until some data arrives. |
1566 | |
1572 | |
1567 | If you cannot run the fd in non-blocking mode (for example you should |
1573 | If you cannot run the fd in non-blocking mode (for example you should |
1568 | not play around with an Xlib connection), then you have to separately |
1574 | not play around with an Xlib connection), then you have to separately |
1569 | re-test whether a file descriptor is really ready with a known-to-be good |
1575 | re-test whether a file descriptor is really ready with a known-to-be good |
1570 | interface such as poll (fortunately in our Xlib example, Xlib already |
1576 | interface such as poll (fortunately in the case of Xlib, it already does |
1571 | does this on its own, so its quite safe to use). Some people additionally |
1577 | this on its own, so its quite safe to use). Some people additionally |
1572 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1578 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1573 | indefinitely. |
1579 | indefinitely. |
1574 | |
1580 | |
1575 | But really, best use non-blocking mode. |
1581 | But really, best use non-blocking mode. |
1576 | |
1582 | |
… | |
… | |
1604 | |
1610 | |
1605 | There is no workaround possible except not registering events |
1611 | There is no workaround possible except not registering events |
1606 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1612 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1607 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1613 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1608 | |
1614 | |
|
|
1615 | =head3 The special problem of files |
|
|
1616 | |
|
|
1617 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1618 | representing files, and expect it to become ready when their program |
|
|
1619 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1620 | |
|
|
1621 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1622 | notification as soon as the kernel knows whether and how much data is |
|
|
1623 | there, and in the case of open files, that's always the case, so you |
|
|
1624 | always get a readiness notification instantly, and your read (or possibly |
|
|
1625 | write) will still block on the disk I/O. |
|
|
1626 | |
|
|
1627 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1628 | devices and so on, there is another party (the sender) that delivers data |
|
|
1629 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1630 | will not send data on its own, simply because it doesn't know what you |
|
|
1631 | wish to read - you would first have to request some data. |
|
|
1632 | |
|
|
1633 | Since files are typically not-so-well supported by advanced notification |
|
|
1634 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1635 | to files, even though you should not use it. The reason for this is |
|
|
1636 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1637 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1638 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1639 | F</dev/urandom>), and even though the file might better be served with |
|
|
1640 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1641 | it "just works" instead of freezing. |
|
|
1642 | |
|
|
1643 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1644 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1645 | when you rarely read from a file instead of from a socket, and want to |
|
|
1646 | reuse the same code path. |
|
|
1647 | |
1609 | =head3 The special problem of fork |
1648 | =head3 The special problem of fork |
1610 | |
1649 | |
1611 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1650 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1612 | useless behaviour. Libev fully supports fork, but needs to be told about |
1651 | useless behaviour. Libev fully supports fork, but needs to be told about |
1613 | it in the child. |
1652 | it in the child if you want to continue to use it in the child. |
1614 | |
1653 | |
1615 | To support fork in your programs, you either have to call |
1654 | To support fork in your child processes, you have to call C<ev_loop_fork |
1616 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1655 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1617 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1656 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1618 | C<EVBACKEND_POLL>. |
|
|
1619 | |
1657 | |
1620 | =head3 The special problem of SIGPIPE |
1658 | =head3 The special problem of SIGPIPE |
1621 | |
1659 | |
1622 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1660 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1623 | when writing to a pipe whose other end has been closed, your program gets |
1661 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
2239 | |
2277 | |
2240 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2278 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2241 | |
2279 | |
2242 | Signal watchers will trigger an event when the process receives a specific |
2280 | Signal watchers will trigger an event when the process receives a specific |
2243 | signal one or more times. Even though signals are very asynchronous, libev |
2281 | signal one or more times. Even though signals are very asynchronous, libev |
2244 | will try it's best to deliver signals synchronously, i.e. as part of the |
2282 | will try its best to deliver signals synchronously, i.e. as part of the |
2245 | normal event processing, like any other event. |
2283 | normal event processing, like any other event. |
2246 | |
2284 | |
2247 | If you want signals to be delivered truly asynchronously, just use |
2285 | If you want signals to be delivered truly asynchronously, just use |
2248 | C<sigaction> as you would do without libev and forget about sharing |
2286 | C<sigaction> as you would do without libev and forget about sharing |
2249 | the signal. You can even use C<ev_async> from a signal handler to |
2287 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2268 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2306 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2269 | |
2307 | |
2270 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2308 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2271 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2309 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2272 | stopping it again), that is, libev might or might not block the signal, |
2310 | stopping it again), that is, libev might or might not block the signal, |
2273 | and might or might not set or restore the installed signal handler. |
2311 | and might or might not set or restore the installed signal handler (but |
|
|
2312 | see C<EVFLAG_NOSIGMASK>). |
2274 | |
2313 | |
2275 | While this does not matter for the signal disposition (libev never |
2314 | While this does not matter for the signal disposition (libev never |
2276 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2315 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2277 | C<execve>), this matters for the signal mask: many programs do not expect |
2316 | C<execve>), this matters for the signal mask: many programs do not expect |
2278 | certain signals to be blocked. |
2317 | certain signals to be blocked. |
… | |
… | |
2291 | I<has> to modify the signal mask, at least temporarily. |
2330 | I<has> to modify the signal mask, at least temporarily. |
2292 | |
2331 | |
2293 | So I can't stress this enough: I<If you do not reset your signal mask when |
2332 | So I can't stress this enough: I<If you do not reset your signal mask when |
2294 | you expect it to be empty, you have a race condition in your code>. This |
2333 | you expect it to be empty, you have a race condition in your code>. This |
2295 | is not a libev-specific thing, this is true for most event libraries. |
2334 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2335 | |
|
|
2336 | =head3 The special problem of threads signal handling |
|
|
2337 | |
|
|
2338 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2339 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2340 | threads in a process block signals, which is hard to achieve. |
|
|
2341 | |
|
|
2342 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2343 | for the same signals), you can tackle this problem by globally blocking |
|
|
2344 | all signals before creating any threads (or creating them with a fully set |
|
|
2345 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2346 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2347 | these signals. You can pass on any signals that libev might be interested |
|
|
2348 | in by calling C<ev_feed_signal>. |
2296 | |
2349 | |
2297 | =head3 Watcher-Specific Functions and Data Members |
2350 | =head3 Watcher-Specific Functions and Data Members |
2298 | |
2351 | |
2299 | =over 4 |
2352 | =over 4 |
2300 | |
2353 | |
… | |
… | |
3074 | disadvantage of having to use multiple event loops (which do not support |
3127 | disadvantage of having to use multiple event loops (which do not support |
3075 | signal watchers). |
3128 | signal watchers). |
3076 | |
3129 | |
3077 | When this is not possible, or you want to use the default loop for |
3130 | When this is not possible, or you want to use the default loop for |
3078 | other reasons, then in the process that wants to start "fresh", call |
3131 | other reasons, then in the process that wants to start "fresh", call |
3079 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3132 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3080 | the default loop will "orphan" (not stop) all registered watchers, so you |
3133 | Destroying the default loop will "orphan" (not stop) all registered |
3081 | have to be careful not to execute code that modifies those watchers. Note |
3134 | watchers, so you have to be careful not to execute code that modifies |
3082 | also that in that case, you have to re-register any signal watchers. |
3135 | those watchers. Note also that in that case, you have to re-register any |
|
|
3136 | signal watchers. |
3083 | |
3137 | |
3084 | =head3 Watcher-Specific Functions and Data Members |
3138 | =head3 Watcher-Specific Functions and Data Members |
3085 | |
3139 | |
3086 | =over 4 |
3140 | =over 4 |
3087 | |
3141 | |
3088 | =item ev_fork_init (ev_signal *, callback) |
3142 | =item ev_fork_init (ev_fork *, callback) |
3089 | |
3143 | |
3090 | Initialises and configures the fork watcher - it has no parameters of any |
3144 | Initialises and configures the fork watcher - it has no parameters of any |
3091 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3145 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3092 | believe me. |
3146 | really. |
3093 | |
3147 | |
3094 | =back |
3148 | =back |
3095 | |
3149 | |
3096 | |
3150 | |
|
|
3151 | =head2 C<ev_cleanup> - even the best things end |
|
|
3152 | |
|
|
3153 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3154 | by a call to C<ev_loop_destroy>. |
|
|
3155 | |
|
|
3156 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3157 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3158 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3159 | loop when you want them to be invoked. |
|
|
3160 | |
|
|
3161 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3162 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3163 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3164 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3165 | |
|
|
3166 | =head3 Watcher-Specific Functions and Data Members |
|
|
3167 | |
|
|
3168 | =over 4 |
|
|
3169 | |
|
|
3170 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3171 | |
|
|
3172 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3173 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3174 | pointless, I assure you. |
|
|
3175 | |
|
|
3176 | =back |
|
|
3177 | |
|
|
3178 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3179 | cleanup functions are called. |
|
|
3180 | |
|
|
3181 | static void |
|
|
3182 | program_exits (void) |
|
|
3183 | { |
|
|
3184 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3185 | } |
|
|
3186 | |
|
|
3187 | ... |
|
|
3188 | atexit (program_exits); |
|
|
3189 | |
|
|
3190 | |
3097 | =head2 C<ev_async> - how to wake up an event loop |
3191 | =head2 C<ev_async> - how to wake up an event loop |
3098 | |
3192 | |
3099 | In general, you cannot use an C<ev_run> from multiple threads or other |
3193 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3100 | asynchronous sources such as signal handlers (as opposed to multiple event |
3194 | asynchronous sources such as signal handlers (as opposed to multiple event |
3101 | loops - those are of course safe to use in different threads). |
3195 | loops - those are of course safe to use in different threads). |
3102 | |
3196 | |
3103 | Sometimes, however, you need to wake up an event loop you do not control, |
3197 | Sometimes, however, you need to wake up an event loop you do not control, |
3104 | for example because it belongs to another thread. This is what C<ev_async> |
3198 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3106 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3200 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3107 | |
3201 | |
3108 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3202 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3109 | too, are asynchronous in nature, and signals, too, will be compressed |
3203 | too, are asynchronous in nature, and signals, too, will be compressed |
3110 | (i.e. the number of callback invocations may be less than the number of |
3204 | (i.e. the number of callback invocations may be less than the number of |
3111 | C<ev_async_sent> calls). |
3205 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
|
|
3206 | of "global async watchers" by using a watcher on an otherwise unused |
|
|
3207 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
|
|
3208 | even without knowing which loop owns the signal. |
3112 | |
3209 | |
3113 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3210 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3114 | just the default loop. |
3211 | just the default loop. |
3115 | |
3212 | |
3116 | =head3 Queueing |
3213 | =head3 Queueing |
… | |
… | |
3211 | trust me. |
3308 | trust me. |
3212 | |
3309 | |
3213 | =item ev_async_send (loop, ev_async *) |
3310 | =item ev_async_send (loop, ev_async *) |
3214 | |
3311 | |
3215 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3312 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3216 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3313 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3314 | returns. |
|
|
3315 | |
3217 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3316 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3218 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3317 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3219 | section below on what exactly this means). |
3318 | embedding section below on what exactly this means). |
3220 | |
3319 | |
3221 | Note that, as with other watchers in libev, multiple events might get |
3320 | Note that, as with other watchers in libev, multiple events might get |
3222 | compressed into a single callback invocation (another way to look at this |
3321 | compressed into a single callback invocation (another way to look at this |
3223 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3322 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3224 | reset when the event loop detects that). |
3323 | reset when the event loop detects that). |
… | |
… | |
3292 | Feed an event on the given fd, as if a file descriptor backend detected |
3391 | Feed an event on the given fd, as if a file descriptor backend detected |
3293 | the given events it. |
3392 | the given events it. |
3294 | |
3393 | |
3295 | =item ev_feed_signal_event (loop, int signum) |
3394 | =item ev_feed_signal_event (loop, int signum) |
3296 | |
3395 | |
3297 | Feed an event as if the given signal occurred (C<loop> must be the default |
3396 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3298 | loop!). |
3397 | which is async-safe. |
3299 | |
3398 | |
3300 | =back |
3399 | =back |
|
|
3400 | |
|
|
3401 | |
|
|
3402 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3403 | |
|
|
3404 | This section explains some common idioms that are not immediately |
|
|
3405 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3406 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3407 | |
|
|
3408 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3409 | |
|
|
3410 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3411 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3412 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3413 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3414 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3415 | data: |
|
|
3416 | |
|
|
3417 | struct my_io |
|
|
3418 | { |
|
|
3419 | ev_io io; |
|
|
3420 | int otherfd; |
|
|
3421 | void *somedata; |
|
|
3422 | struct whatever *mostinteresting; |
|
|
3423 | }; |
|
|
3424 | |
|
|
3425 | ... |
|
|
3426 | struct my_io w; |
|
|
3427 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3428 | |
|
|
3429 | And since your callback will be called with a pointer to the watcher, you |
|
|
3430 | can cast it back to your own type: |
|
|
3431 | |
|
|
3432 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3433 | { |
|
|
3434 | struct my_io *w = (struct my_io *)w_; |
|
|
3435 | ... |
|
|
3436 | } |
|
|
3437 | |
|
|
3438 | More interesting and less C-conformant ways of casting your callback |
|
|
3439 | function type instead have been omitted. |
|
|
3440 | |
|
|
3441 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3442 | |
|
|
3443 | Another common scenario is to use some data structure with multiple |
|
|
3444 | embedded watchers, in effect creating your own watcher that combines |
|
|
3445 | multiple libev event sources into one "super-watcher": |
|
|
3446 | |
|
|
3447 | struct my_biggy |
|
|
3448 | { |
|
|
3449 | int some_data; |
|
|
3450 | ev_timer t1; |
|
|
3451 | ev_timer t2; |
|
|
3452 | } |
|
|
3453 | |
|
|
3454 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3455 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3456 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3457 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3458 | real programmers): |
|
|
3459 | |
|
|
3460 | #include <stddef.h> |
|
|
3461 | |
|
|
3462 | static void |
|
|
3463 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3464 | { |
|
|
3465 | struct my_biggy big = (struct my_biggy *) |
|
|
3466 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3467 | } |
|
|
3468 | |
|
|
3469 | static void |
|
|
3470 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3471 | { |
|
|
3472 | struct my_biggy big = (struct my_biggy *) |
|
|
3473 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3474 | } |
|
|
3475 | |
|
|
3476 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3477 | |
|
|
3478 | Often (especially in GUI toolkits) there are places where you have |
|
|
3479 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3480 | invoking C<ev_run>. |
|
|
3481 | |
|
|
3482 | This brings the problem of exiting - a callback might want to finish the |
|
|
3483 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3484 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3485 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3486 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3487 | |
|
|
3488 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3489 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3490 | triggered, using C<EVRUN_ONCE>: |
|
|
3491 | |
|
|
3492 | // main loop |
|
|
3493 | int exit_main_loop = 0; |
|
|
3494 | |
|
|
3495 | while (!exit_main_loop) |
|
|
3496 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3497 | |
|
|
3498 | // in a model watcher |
|
|
3499 | int exit_nested_loop = 0; |
|
|
3500 | |
|
|
3501 | while (!exit_nested_loop) |
|
|
3502 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3503 | |
|
|
3504 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3505 | |
|
|
3506 | // exit modal loop |
|
|
3507 | exit_nested_loop = 1; |
|
|
3508 | |
|
|
3509 | // exit main program, after modal loop is finished |
|
|
3510 | exit_main_loop = 1; |
|
|
3511 | |
|
|
3512 | // exit both |
|
|
3513 | exit_main_loop = exit_nested_loop = 1; |
|
|
3514 | |
|
|
3515 | =head2 THREAD LOCKING EXAMPLE |
|
|
3516 | |
|
|
3517 | Here is a fictitious example of how to run an event loop in a different |
|
|
3518 | thread from where callbacks are being invoked and watchers are |
|
|
3519 | created/added/removed. |
|
|
3520 | |
|
|
3521 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3522 | which uses exactly this technique (which is suited for many high-level |
|
|
3523 | languages). |
|
|
3524 | |
|
|
3525 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3526 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3527 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3528 | |
|
|
3529 | First, you need to associate some data with the event loop: |
|
|
3530 | |
|
|
3531 | typedef struct { |
|
|
3532 | mutex_t lock; /* global loop lock */ |
|
|
3533 | ev_async async_w; |
|
|
3534 | thread_t tid; |
|
|
3535 | cond_t invoke_cv; |
|
|
3536 | } userdata; |
|
|
3537 | |
|
|
3538 | void prepare_loop (EV_P) |
|
|
3539 | { |
|
|
3540 | // for simplicity, we use a static userdata struct. |
|
|
3541 | static userdata u; |
|
|
3542 | |
|
|
3543 | ev_async_init (&u->async_w, async_cb); |
|
|
3544 | ev_async_start (EV_A_ &u->async_w); |
|
|
3545 | |
|
|
3546 | pthread_mutex_init (&u->lock, 0); |
|
|
3547 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3548 | |
|
|
3549 | // now associate this with the loop |
|
|
3550 | ev_set_userdata (EV_A_ u); |
|
|
3551 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3552 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3553 | |
|
|
3554 | // then create the thread running ev_run |
|
|
3555 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3556 | } |
|
|
3557 | |
|
|
3558 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3559 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3560 | that might have been added: |
|
|
3561 | |
|
|
3562 | static void |
|
|
3563 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3564 | { |
|
|
3565 | // just used for the side effects |
|
|
3566 | } |
|
|
3567 | |
|
|
3568 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3569 | protecting the loop data, respectively. |
|
|
3570 | |
|
|
3571 | static void |
|
|
3572 | l_release (EV_P) |
|
|
3573 | { |
|
|
3574 | userdata *u = ev_userdata (EV_A); |
|
|
3575 | pthread_mutex_unlock (&u->lock); |
|
|
3576 | } |
|
|
3577 | |
|
|
3578 | static void |
|
|
3579 | l_acquire (EV_P) |
|
|
3580 | { |
|
|
3581 | userdata *u = ev_userdata (EV_A); |
|
|
3582 | pthread_mutex_lock (&u->lock); |
|
|
3583 | } |
|
|
3584 | |
|
|
3585 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3586 | into C<ev_run>: |
|
|
3587 | |
|
|
3588 | void * |
|
|
3589 | l_run (void *thr_arg) |
|
|
3590 | { |
|
|
3591 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3592 | |
|
|
3593 | l_acquire (EV_A); |
|
|
3594 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3595 | ev_run (EV_A_ 0); |
|
|
3596 | l_release (EV_A); |
|
|
3597 | |
|
|
3598 | return 0; |
|
|
3599 | } |
|
|
3600 | |
|
|
3601 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3602 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3603 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3604 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3605 | and b) skipping inter-thread-communication when there are no pending |
|
|
3606 | watchers is very beneficial): |
|
|
3607 | |
|
|
3608 | static void |
|
|
3609 | l_invoke (EV_P) |
|
|
3610 | { |
|
|
3611 | userdata *u = ev_userdata (EV_A); |
|
|
3612 | |
|
|
3613 | while (ev_pending_count (EV_A)) |
|
|
3614 | { |
|
|
3615 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3616 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3617 | } |
|
|
3618 | } |
|
|
3619 | |
|
|
3620 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3621 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3622 | thread to continue: |
|
|
3623 | |
|
|
3624 | static void |
|
|
3625 | real_invoke_pending (EV_P) |
|
|
3626 | { |
|
|
3627 | userdata *u = ev_userdata (EV_A); |
|
|
3628 | |
|
|
3629 | pthread_mutex_lock (&u->lock); |
|
|
3630 | ev_invoke_pending (EV_A); |
|
|
3631 | pthread_cond_signal (&u->invoke_cv); |
|
|
3632 | pthread_mutex_unlock (&u->lock); |
|
|
3633 | } |
|
|
3634 | |
|
|
3635 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3636 | event loop, you will now have to lock: |
|
|
3637 | |
|
|
3638 | ev_timer timeout_watcher; |
|
|
3639 | userdata *u = ev_userdata (EV_A); |
|
|
3640 | |
|
|
3641 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3642 | |
|
|
3643 | pthread_mutex_lock (&u->lock); |
|
|
3644 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3645 | ev_async_send (EV_A_ &u->async_w); |
|
|
3646 | pthread_mutex_unlock (&u->lock); |
|
|
3647 | |
|
|
3648 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3649 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3650 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3651 | watchers in the next event loop iteration. |
|
|
3652 | |
|
|
3653 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3654 | |
|
|
3655 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3656 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3657 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3658 | doesn't need callbacks anymore. |
|
|
3659 | |
|
|
3660 | Imagine you have coroutines that you can switch to using a function |
|
|
3661 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3662 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3663 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3664 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3665 | the differing C<;> conventions): |
|
|
3666 | |
|
|
3667 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3668 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3669 | |
|
|
3670 | That means instead of having a C callback function, you store the |
|
|
3671 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3672 | your callback, you instead have it switch to that coroutine. |
|
|
3673 | |
|
|
3674 | A coroutine might now wait for an event with a function called |
|
|
3675 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3676 | matter when, or whether the watcher is active or not when this function is |
|
|
3677 | called): |
|
|
3678 | |
|
|
3679 | void |
|
|
3680 | wait_for_event (ev_watcher *w) |
|
|
3681 | { |
|
|
3682 | ev_cb_set (w) = current_coro; |
|
|
3683 | switch_to (libev_coro); |
|
|
3684 | } |
|
|
3685 | |
|
|
3686 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3687 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3688 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3689 | |
|
|
3690 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3691 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3692 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3693 | any waiters. |
|
|
3694 | |
|
|
3695 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3696 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3697 | |
|
|
3698 | // my_ev.h |
|
|
3699 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3700 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3701 | #include "../libev/ev.h" |
|
|
3702 | |
|
|
3703 | // my_ev.c |
|
|
3704 | #define EV_H "my_ev.h" |
|
|
3705 | #include "../libev/ev.c" |
|
|
3706 | |
|
|
3707 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3708 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3709 | can even use F<ev.h> as header file name directly. |
3301 | |
3710 | |
3302 | |
3711 | |
3303 | =head1 LIBEVENT EMULATION |
3712 | =head1 LIBEVENT EMULATION |
3304 | |
3713 | |
3305 | Libev offers a compatibility emulation layer for libevent. It cannot |
3714 | Libev offers a compatibility emulation layer for libevent. It cannot |
3306 | emulate the internals of libevent, so here are some usage hints: |
3715 | emulate the internals of libevent, so here are some usage hints: |
3307 | |
3716 | |
3308 | =over 4 |
3717 | =over 4 |
|
|
3718 | |
|
|
3719 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3720 | |
|
|
3721 | This was the newest libevent version available when libev was implemented, |
|
|
3722 | and is still mostly unchanged in 2010. |
3309 | |
3723 | |
3310 | =item * Use it by including <event.h>, as usual. |
3724 | =item * Use it by including <event.h>, as usual. |
3311 | |
3725 | |
3312 | =item * The following members are fully supported: ev_base, ev_callback, |
3726 | =item * The following members are fully supported: ev_base, ev_callback, |
3313 | ev_arg, ev_fd, ev_res, ev_events. |
3727 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3319 | =item * Priorities are not currently supported. Initialising priorities |
3733 | =item * Priorities are not currently supported. Initialising priorities |
3320 | will fail and all watchers will have the same priority, even though there |
3734 | will fail and all watchers will have the same priority, even though there |
3321 | is an ev_pri field. |
3735 | is an ev_pri field. |
3322 | |
3736 | |
3323 | =item * In libevent, the last base created gets the signals, in libev, the |
3737 | =item * In libevent, the last base created gets the signals, in libev, the |
3324 | first base created (== the default loop) gets the signals. |
3738 | base that registered the signal gets the signals. |
3325 | |
3739 | |
3326 | =item * Other members are not supported. |
3740 | =item * Other members are not supported. |
3327 | |
3741 | |
3328 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3742 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3329 | to use the libev header file and library. |
3743 | to use the libev header file and library. |
… | |
… | |
3348 | Care has been taken to keep the overhead low. The only data member the C++ |
3762 | Care has been taken to keep the overhead low. The only data member the C++ |
3349 | classes add (compared to plain C-style watchers) is the event loop pointer |
3763 | classes add (compared to plain C-style watchers) is the event loop pointer |
3350 | that the watcher is associated with (or no additional members at all if |
3764 | that the watcher is associated with (or no additional members at all if |
3351 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3765 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3352 | |
3766 | |
3353 | Currently, functions, and static and non-static member functions can be |
3767 | Currently, functions, static and non-static member functions and classes |
3354 | used as callbacks. Other types should be easy to add as long as they only |
3768 | with C<operator ()> can be used as callbacks. Other types should be easy |
3355 | need one additional pointer for context. If you need support for other |
3769 | to add as long as they only need one additional pointer for context. If |
3356 | types of functors please contact the author (preferably after implementing |
3770 | you need support for other types of functors please contact the author |
3357 | it). |
3771 | (preferably after implementing it). |
3358 | |
3772 | |
3359 | Here is a list of things available in the C<ev> namespace: |
3773 | Here is a list of things available in the C<ev> namespace: |
3360 | |
3774 | |
3361 | =over 4 |
3775 | =over 4 |
3362 | |
3776 | |
… | |
… | |
4230 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4644 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4231 | |
4645 | |
4232 | #include "ev_cpp.h" |
4646 | #include "ev_cpp.h" |
4233 | #include "ev.c" |
4647 | #include "ev.c" |
4234 | |
4648 | |
4235 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4649 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4236 | |
4650 | |
4237 | =head2 THREADS AND COROUTINES |
4651 | =head2 THREADS AND COROUTINES |
4238 | |
4652 | |
4239 | =head3 THREADS |
4653 | =head3 THREADS |
4240 | |
4654 | |
… | |
… | |
4291 | default loop and triggering an C<ev_async> watcher from the default loop |
4705 | default loop and triggering an C<ev_async> watcher from the default loop |
4292 | watcher callback into the event loop interested in the signal. |
4706 | watcher callback into the event loop interested in the signal. |
4293 | |
4707 | |
4294 | =back |
4708 | =back |
4295 | |
4709 | |
4296 | =head4 THREAD LOCKING EXAMPLE |
4710 | See also L<THREAD LOCKING EXAMPLE>. |
4297 | |
|
|
4298 | Here is a fictitious example of how to run an event loop in a different |
|
|
4299 | thread than where callbacks are being invoked and watchers are |
|
|
4300 | created/added/removed. |
|
|
4301 | |
|
|
4302 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4303 | which uses exactly this technique (which is suited for many high-level |
|
|
4304 | languages). |
|
|
4305 | |
|
|
4306 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4307 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4308 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4309 | |
|
|
4310 | First, you need to associate some data with the event loop: |
|
|
4311 | |
|
|
4312 | typedef struct { |
|
|
4313 | mutex_t lock; /* global loop lock */ |
|
|
4314 | ev_async async_w; |
|
|
4315 | thread_t tid; |
|
|
4316 | cond_t invoke_cv; |
|
|
4317 | } userdata; |
|
|
4318 | |
|
|
4319 | void prepare_loop (EV_P) |
|
|
4320 | { |
|
|
4321 | // for simplicity, we use a static userdata struct. |
|
|
4322 | static userdata u; |
|
|
4323 | |
|
|
4324 | ev_async_init (&u->async_w, async_cb); |
|
|
4325 | ev_async_start (EV_A_ &u->async_w); |
|
|
4326 | |
|
|
4327 | pthread_mutex_init (&u->lock, 0); |
|
|
4328 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4329 | |
|
|
4330 | // now associate this with the loop |
|
|
4331 | ev_set_userdata (EV_A_ u); |
|
|
4332 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4333 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4334 | |
|
|
4335 | // then create the thread running ev_loop |
|
|
4336 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4337 | } |
|
|
4338 | |
|
|
4339 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4340 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4341 | that might have been added: |
|
|
4342 | |
|
|
4343 | static void |
|
|
4344 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4345 | { |
|
|
4346 | // just used for the side effects |
|
|
4347 | } |
|
|
4348 | |
|
|
4349 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4350 | protecting the loop data, respectively. |
|
|
4351 | |
|
|
4352 | static void |
|
|
4353 | l_release (EV_P) |
|
|
4354 | { |
|
|
4355 | userdata *u = ev_userdata (EV_A); |
|
|
4356 | pthread_mutex_unlock (&u->lock); |
|
|
4357 | } |
|
|
4358 | |
|
|
4359 | static void |
|
|
4360 | l_acquire (EV_P) |
|
|
4361 | { |
|
|
4362 | userdata *u = ev_userdata (EV_A); |
|
|
4363 | pthread_mutex_lock (&u->lock); |
|
|
4364 | } |
|
|
4365 | |
|
|
4366 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4367 | into C<ev_run>: |
|
|
4368 | |
|
|
4369 | void * |
|
|
4370 | l_run (void *thr_arg) |
|
|
4371 | { |
|
|
4372 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4373 | |
|
|
4374 | l_acquire (EV_A); |
|
|
4375 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4376 | ev_run (EV_A_ 0); |
|
|
4377 | l_release (EV_A); |
|
|
4378 | |
|
|
4379 | return 0; |
|
|
4380 | } |
|
|
4381 | |
|
|
4382 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4383 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4384 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4385 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4386 | and b) skipping inter-thread-communication when there are no pending |
|
|
4387 | watchers is very beneficial): |
|
|
4388 | |
|
|
4389 | static void |
|
|
4390 | l_invoke (EV_P) |
|
|
4391 | { |
|
|
4392 | userdata *u = ev_userdata (EV_A); |
|
|
4393 | |
|
|
4394 | while (ev_pending_count (EV_A)) |
|
|
4395 | { |
|
|
4396 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4397 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4398 | } |
|
|
4399 | } |
|
|
4400 | |
|
|
4401 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4402 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4403 | thread to continue: |
|
|
4404 | |
|
|
4405 | static void |
|
|
4406 | real_invoke_pending (EV_P) |
|
|
4407 | { |
|
|
4408 | userdata *u = ev_userdata (EV_A); |
|
|
4409 | |
|
|
4410 | pthread_mutex_lock (&u->lock); |
|
|
4411 | ev_invoke_pending (EV_A); |
|
|
4412 | pthread_cond_signal (&u->invoke_cv); |
|
|
4413 | pthread_mutex_unlock (&u->lock); |
|
|
4414 | } |
|
|
4415 | |
|
|
4416 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4417 | event loop, you will now have to lock: |
|
|
4418 | |
|
|
4419 | ev_timer timeout_watcher; |
|
|
4420 | userdata *u = ev_userdata (EV_A); |
|
|
4421 | |
|
|
4422 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4423 | |
|
|
4424 | pthread_mutex_lock (&u->lock); |
|
|
4425 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4426 | ev_async_send (EV_A_ &u->async_w); |
|
|
4427 | pthread_mutex_unlock (&u->lock); |
|
|
4428 | |
|
|
4429 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4430 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4431 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4432 | watchers in the next event loop iteration. |
|
|
4433 | |
4711 | |
4434 | =head3 COROUTINES |
4712 | =head3 COROUTINES |
4435 | |
4713 | |
4436 | Libev is very accommodating to coroutines ("cooperative threads"): |
4714 | Libev is very accommodating to coroutines ("cooperative threads"): |
4437 | libev fully supports nesting calls to its functions from different |
4715 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4706 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4984 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4707 | assumes that the same (machine) code can be used to call any watcher |
4985 | assumes that the same (machine) code can be used to call any watcher |
4708 | callback: The watcher callbacks have different type signatures, but libev |
4986 | callback: The watcher callbacks have different type signatures, but libev |
4709 | calls them using an C<ev_watcher *> internally. |
4987 | calls them using an C<ev_watcher *> internally. |
4710 | |
4988 | |
|
|
4989 | =item pointer accesses must be thread-atomic |
|
|
4990 | |
|
|
4991 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4992 | writable in one piece - this is the case on all current architectures. |
|
|
4993 | |
4711 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4994 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4712 | |
4995 | |
4713 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4996 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4714 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4997 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4715 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4998 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4821 | =back |
5104 | =back |
4822 | |
5105 | |
4823 | |
5106 | |
4824 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5107 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4825 | |
5108 | |
4826 | The major version 4 introduced some minor incompatible changes to the API. |
5109 | The major version 4 introduced some incompatible changes to the API. |
4827 | |
5110 | |
4828 | At the moment, the C<ev.h> header file tries to implement superficial |
5111 | At the moment, the C<ev.h> header file provides compatibility definitions |
4829 | compatibility, so most programs should still compile. Those might be |
5112 | for all changes, so most programs should still compile. The compatibility |
4830 | removed in later versions of libev, so better update early than late. |
5113 | layer might be removed in later versions of libev, so better update to the |
|
|
5114 | new API early than late. |
4831 | |
5115 | |
4832 | =over 4 |
5116 | =over 4 |
|
|
5117 | |
|
|
5118 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5119 | |
|
|
5120 | The backward compatibility mechanism can be controlled by |
|
|
5121 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5122 | section. |
|
|
5123 | |
|
|
5124 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5125 | |
|
|
5126 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5127 | |
|
|
5128 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5129 | ev_loop_fork (EV_DEFAULT); |
4833 | |
5130 | |
4834 | =item function/symbol renames |
5131 | =item function/symbol renames |
4835 | |
5132 | |
4836 | A number of functions and symbols have been renamed: |
5133 | A number of functions and symbols have been renamed: |
4837 | |
5134 | |
… | |
… | |
4856 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5153 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4857 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5154 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4858 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5155 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4859 | typedef. |
5156 | typedef. |
4860 | |
5157 | |
4861 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4862 | |
|
|
4863 | The backward compatibility mechanism can be controlled by |
|
|
4864 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4865 | section. |
|
|
4866 | |
|
|
4867 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5158 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4868 | |
5159 | |
4869 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5160 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4870 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5161 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4871 | and work, but the library code will of course be larger. |
5162 | and work, but the library code will of course be larger. |
… | |
… | |
4933 | The physical time that is observed. It is apparently strictly monotonic :) |
5224 | The physical time that is observed. It is apparently strictly monotonic :) |
4934 | |
5225 | |
4935 | =item wall-clock time |
5226 | =item wall-clock time |
4936 | |
5227 | |
4937 | The time and date as shown on clocks. Unlike real time, it can actually |
5228 | The time and date as shown on clocks. Unlike real time, it can actually |
4938 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5229 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4939 | clock. |
5230 | clock. |
4940 | |
5231 | |
4941 | =item watcher |
5232 | =item watcher |
4942 | |
5233 | |
4943 | A data structure that describes interest in certain events. Watchers need |
5234 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
4945 | |
5236 | |
4946 | =back |
5237 | =back |
4947 | |
5238 | |
4948 | =head1 AUTHOR |
5239 | =head1 AUTHOR |
4949 | |
5240 | |
4950 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5241 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5242 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4951 | |
5243 | |