… | |
… | |
26 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
27 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
28 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
29 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
30 | |
30 | |
31 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
33 | } |
33 | } |
34 | |
34 | |
35 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
36 | static void |
36 | static void |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
38 | { |
38 | { |
39 | puts ("timeout"); |
39 | puts ("timeout"); |
40 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
42 | } |
42 | } |
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); |
… | |
… | |
56 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
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_loop (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // unloop was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
… | |
… | |
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 |
… | |
… | |
124 | this argument. |
132 | this argument. |
125 | |
133 | |
126 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
127 | |
135 | |
128 | Libev represents time as a single floating point number, representing |
136 | Libev represents time as a single floating point number, representing |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practise |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
130 | somewhere near the beginning of 1970, details are complicated, don't |
138 | somewhere near the beginning of 1970, details are complicated, don't |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
133 | any calculations on it, you should treat it as some floating point value. |
141 | any calculations on it, you should treat it as some floating point value. |
134 | |
142 | |
… | |
… | |
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. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_update_now> and C<ev_now>. |
171 | |
180 | |
172 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
173 | |
182 | |
174 | 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 |
175 | either it is interrupted or the given time interval has passed. Basically |
184 | either it is interrupted or the given time interval has passed. Basically |
… | |
… | |
192 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
193 | 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 |
194 | not a problem. |
203 | not a problem. |
195 | |
204 | |
196 | 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 |
197 | 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). |
198 | |
208 | |
199 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
200 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | |
212 | |
… | |
… | |
213 | assert (("sorry, no epoll, no sex", |
223 | assert (("sorry, no epoll, no sex", |
214 | ev_supported_backends () & EVBACKEND_EPOLL)); |
224 | ev_supported_backends () & EVBACKEND_EPOLL)); |
215 | |
225 | |
216 | =item unsigned int ev_recommended_backends () |
226 | =item unsigned int ev_recommended_backends () |
217 | |
227 | |
218 | Return the set of all backends compiled into this binary of libev and also |
228 | Return the set of all backends compiled into this binary of libev and |
219 | recommended for this platform. This set is often smaller than the one |
229 | also recommended for this platform, meaning it will work for most file |
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230 | descriptor types. This set is often smaller than the one returned by |
220 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
231 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
221 | most BSDs and will not be auto-detected unless you explicitly request it |
232 | and will not be auto-detected unless you explicitly request it (assuming |
222 | (assuming you know what you are doing). This is the set of backends that |
233 | you know what you are doing). This is the set of backends that libev will |
223 | libev will probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
224 | |
235 | |
225 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
226 | |
237 | |
227 | 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 |
228 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
229 | 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 |
230 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
231 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
232 | |
243 | |
233 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
234 | |
245 | |
235 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
236 | |
247 | |
237 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
238 | 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 |
239 | 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 |
240 | 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 |
… | |
… | |
266 | } |
277 | } |
267 | |
278 | |
268 | ... |
279 | ... |
269 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
270 | |
281 | |
271 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
272 | |
283 | |
273 | 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 |
274 | 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 |
275 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
276 | 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 |
… | |
… | |
288 | } |
299 | } |
289 | |
300 | |
290 | ... |
301 | ... |
291 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
292 | |
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 | |
293 | =back |
317 | =back |
294 | |
318 | |
295 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
319 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
296 | |
320 | |
297 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
321 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
298 | is I<not> optional in this case, as there is also an C<ev_loop> |
322 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
299 | I<function>). |
323 | libev 3 had an C<ev_loop> function colliding with the struct name). |
300 | |
324 | |
301 | 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 |
302 | supports signals and child events, and dynamically created loops which do |
326 | supports child process events, and dynamically created event loops which |
303 | not. |
327 | do not. |
304 | |
328 | |
305 | =over 4 |
329 | =over 4 |
306 | |
330 | |
307 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
331 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
308 | |
332 | |
309 | 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 |
310 | 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 |
311 | 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 |
312 | 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". |
313 | |
343 | |
314 | 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 |
315 | function. |
345 | function (or via the C<EV_DEFAULT> macro). |
316 | |
346 | |
317 | 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 |
318 | 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 |
319 | 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). |
320 | |
351 | |
321 | 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, |
322 | 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 |
323 | 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 |
324 | 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 |
325 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
356 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
326 | 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. |
327 | |
376 | |
328 | 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 |
329 | 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>). |
330 | |
379 | |
331 | The following flags are supported: |
380 | The following flags are supported: |
… | |
… | |
366 | environment variable. |
415 | environment variable. |
367 | |
416 | |
368 | =item C<EVFLAG_NOINOTIFY> |
417 | =item C<EVFLAG_NOINOTIFY> |
369 | |
418 | |
370 | 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 |
371 | 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 |
372 | 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 |
373 | 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. |
374 | |
423 | |
375 | =item C<EVFLAG_SIGNALFD> |
424 | =item C<EVFLAG_SIGNALFD> |
376 | |
425 | |
377 | 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 |
378 | 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 |
379 | delivers signals synchronously, which makes it both faster and might make |
428 | delivers signals synchronously, which makes it both faster and might make |
380 | 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 |
381 | 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 |
382 | threads that are not interested in handling them. |
431 | threads that are not interested in handling them. |
383 | |
432 | |
384 | 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 |
385 | 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 |
386 | 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 | This flag's behaviour will become the default in future versions of libev. |
387 | |
448 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
450 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
451 | This is your standard select(2) backend. Not I<completely> standard, as |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
452 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
427 | epoll scales either O(1) or O(active_fds). |
488 | epoll scales either O(1) or O(active_fds). |
428 | |
489 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
491 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
492 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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494 | returning before the timeout value, resulting in additional iterations |
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495 | (and only giving 5ms accuracy while select on the same platform gives |
433 | so on. The biggest issue is fork races, however - if a program forks then |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
434 | I<both> parent and child process have to recreate the epoll set, which can |
497 | forks then I<both> parent and child process have to recreate the epoll |
435 | take considerable time (one syscall per file descriptor) and is of course |
498 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
499 | and is of course hard to detect. |
437 | |
500 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
440 | I<different> file descriptors (even already closed ones, so one cannot |
503 | I<different> file descriptors (even already closed ones, so one cannot |
441 | even remove them from the set) than registered in the set (especially |
504 | even remove them from the set) than registered in the set (especially |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
443 | employing an additional generation counter and comparing that against the |
506 | employing an additional generation counter and comparing that against the |
444 | events to filter out spurious ones, recreating the set when required. |
507 | events to filter out spurious ones, recreating the set when required. Last |
|
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508 | not least, it also refuses to work with some file descriptors which work |
|
|
509 | perfectly fine with C<select> (files, many character devices...). |
|
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510 | |
|
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511 | Epoll is truly the train wreck analog among event poll mechanisms, |
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512 | a frankenpoll, cobbled together in a hurry, no thought to design or |
|
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513 | interaction with others. |
445 | |
514 | |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
515 | While stopping, setting and starting an I/O watcher in the same iteration |
447 | will result in some caching, there is still a system call per such |
516 | will result in some caching, there is still a system call per such |
448 | incident (because the same I<file descriptor> could point to a different |
517 | incident (because the same I<file descriptor> could point to a different |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
518 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
515 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
584 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
516 | |
585 | |
517 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
586 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
518 | it's really slow, but it still scales very well (O(active_fds)). |
587 | it's really slow, but it still scales very well (O(active_fds)). |
519 | |
588 | |
520 | Please note that Solaris event ports can deliver a lot of spurious |
|
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521 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
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522 | blocking when no data (or space) is available. |
|
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523 | |
|
|
524 | While this backend scales well, it requires one system call per active |
589 | While this backend scales well, it requires one system call per active |
525 | file descriptor per loop iteration. For small and medium numbers of file |
590 | file descriptor per loop iteration. For small and medium numbers of file |
526 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
591 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
527 | might perform better. |
592 | might perform better. |
528 | |
593 | |
529 | On the positive side, with the exception of the spurious readiness |
594 | On the positive side, this backend actually performed fully to |
530 | notifications, this backend actually performed fully to specification |
|
|
531 | in all tests and is fully embeddable, which is a rare feat among the |
595 | specification in all tests and is fully embeddable, which is a rare feat |
532 | OS-specific backends (I vastly prefer correctness over speed hacks). |
596 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
597 | hacks). |
|
|
598 | |
|
|
599 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
600 | even sun itself gets it wrong in their code examples: The event polling |
|
|
601 | function sometimes returning events to the caller even though an error |
|
|
602 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
603 | even documented that way) - deadly for edge-triggered interfaces where |
|
|
604 | you absolutely have to know whether an event occurred or not because you |
|
|
605 | have to re-arm the watcher. |
|
|
606 | |
|
|
607 | Fortunately libev seems to be able to work around these idiocies. |
533 | |
608 | |
534 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
609 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
535 | C<EVBACKEND_POLL>. |
610 | C<EVBACKEND_POLL>. |
536 | |
611 | |
537 | =item C<EVBACKEND_ALL> |
612 | =item C<EVBACKEND_ALL> |
538 | |
613 | |
539 | Try all backends (even potentially broken ones that wouldn't be tried |
614 | Try all backends (even potentially broken ones that wouldn't be tried |
540 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
615 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
541 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
616 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
542 | |
617 | |
543 | It is definitely not recommended to use this flag. |
618 | It is definitely not recommended to use this flag, use whatever |
|
|
619 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
620 | at all. |
|
|
621 | |
|
|
622 | =item C<EVBACKEND_MASK> |
|
|
623 | |
|
|
624 | Not a backend at all, but a mask to select all backend bits from a |
|
|
625 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
626 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
544 | |
627 | |
545 | =back |
628 | =back |
546 | |
629 | |
547 | If one or more of the backend flags are or'ed into the flags value, |
630 | If one or more of the backend flags are or'ed into the flags value, |
548 | then only these backends will be tried (in the reverse order as listed |
631 | then only these backends will be tried (in the reverse order as listed |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
632 | here). If none are specified, all backends in C<ev_recommended_backends |
550 | ()> will be tried. |
633 | ()> will be tried. |
551 | |
634 | |
552 | Example: This is the most typical usage. |
|
|
553 | |
|
|
554 | if (!ev_default_loop (0)) |
|
|
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
556 | |
|
|
557 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
558 | environment settings to be taken into account: |
|
|
559 | |
|
|
560 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
561 | |
|
|
562 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
563 | used if available (warning, breaks stuff, best use only with your own |
|
|
564 | private event loop and only if you know the OS supports your types of |
|
|
565 | fds): |
|
|
566 | |
|
|
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
568 | |
|
|
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
570 | |
|
|
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
572 | always distinct from the default loop. |
|
|
573 | |
|
|
574 | Note that this function I<is> thread-safe, and one common way to use |
|
|
575 | libev with threads is indeed to create one loop per thread, and using the |
|
|
576 | default loop in the "main" or "initial" thread. |
|
|
577 | |
|
|
578 | Example: Try to create a event loop that uses epoll and nothing else. |
635 | Example: Try to create a event loop that uses epoll and nothing else. |
579 | |
636 | |
580 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
637 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
581 | if (!epoller) |
638 | if (!epoller) |
582 | fatal ("no epoll found here, maybe it hides under your chair"); |
639 | fatal ("no epoll found here, maybe it hides under your chair"); |
583 | |
640 | |
|
|
641 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
642 | used if available. |
|
|
643 | |
|
|
644 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
645 | |
584 | =item ev_default_destroy () |
646 | =item ev_loop_destroy (loop) |
585 | |
647 | |
586 | Destroys the default loop (frees all memory and kernel state etc.). None |
648 | Destroys an event loop object (frees all memory and kernel state |
587 | of the active event watchers will be stopped in the normal sense, so |
649 | etc.). None of the active event watchers will be stopped in the normal |
588 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
650 | sense, so e.g. C<ev_is_active> might still return true. It is your |
589 | either stop all watchers cleanly yourself I<before> calling this function, |
651 | responsibility to either stop all watchers cleanly yourself I<before> |
590 | or cope with the fact afterwards (which is usually the easiest thing, you |
652 | calling this function, or cope with the fact afterwards (which is usually |
591 | can just ignore the watchers and/or C<free ()> them for example). |
653 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
654 | for example). |
592 | |
655 | |
593 | Note that certain global state, such as signal state (and installed signal |
656 | Note that certain global state, such as signal state (and installed signal |
594 | handlers), will not be freed by this function, and related watchers (such |
657 | handlers), will not be freed by this function, and related watchers (such |
595 | as signal and child watchers) would need to be stopped manually. |
658 | as signal and child watchers) would need to be stopped manually. |
596 | |
659 | |
597 | In general it is not advisable to call this function except in the |
660 | This function is normally used on loop objects allocated by |
598 | rare occasion where you really need to free e.g. the signal handling |
661 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
662 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
663 | |
|
|
664 | Note that it is not advisable to call this function on the default loop |
|
|
665 | except in the rare occasion where you really need to free its resources. |
599 | pipe fds. If you need dynamically allocated loops it is better to use |
666 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
600 | C<ev_loop_new> and C<ev_loop_destroy>. |
667 | and C<ev_loop_destroy>. |
601 | |
668 | |
602 | =item ev_loop_destroy (loop) |
669 | =item ev_loop_fork (loop) |
603 | |
670 | |
604 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
605 | earlier call to C<ev_loop_new>. |
|
|
606 | |
|
|
607 | =item ev_default_fork () |
|
|
608 | |
|
|
609 | This function sets a flag that causes subsequent C<ev_loop> iterations |
671 | This function sets a flag that causes subsequent C<ev_run> iterations to |
610 | to reinitialise the kernel state for backends that have one. Despite the |
672 | reinitialise the kernel state for backends that have one. Despite the |
611 | name, you can call it anytime, but it makes most sense after forking, in |
673 | name, you can call it anytime, but it makes most sense after forking, in |
612 | the child process (or both child and parent, but that again makes little |
674 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
613 | sense). You I<must> call it in the child before using any of the libev |
675 | child before resuming or calling C<ev_run>. |
614 | functions, and it will only take effect at the next C<ev_loop> iteration. |
|
|
615 | |
676 | |
616 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
677 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
617 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
678 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
618 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
679 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
619 | during fork. |
680 | during fork. |
620 | |
681 | |
621 | On the other hand, you only need to call this function in the child |
682 | On the other hand, you only need to call this function in the child |
622 | process if and only if you want to use the event loop in the child. If you |
683 | process if and only if you want to use the event loop in the child. If |
623 | just fork+exec or create a new loop in the child, you don't have to call |
684 | you just fork+exec or create a new loop in the child, you don't have to |
624 | it at all. |
685 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
686 | difference, but libev will usually detect this case on its own and do a |
|
|
687 | costly reset of the backend). |
625 | |
688 | |
626 | The function itself is quite fast and it's usually not a problem to call |
689 | The function itself is quite fast and it's usually not a problem to call |
627 | it just in case after a fork. To make this easy, the function will fit in |
690 | it just in case after a fork. |
628 | quite nicely into a call to C<pthread_atfork>: |
|
|
629 | |
691 | |
|
|
692 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
693 | using pthreads. |
|
|
694 | |
|
|
695 | static void |
|
|
696 | post_fork_child (void) |
|
|
697 | { |
|
|
698 | ev_loop_fork (EV_DEFAULT); |
|
|
699 | } |
|
|
700 | |
|
|
701 | ... |
630 | pthread_atfork (0, 0, ev_default_fork); |
702 | pthread_atfork (0, 0, post_fork_child); |
631 | |
|
|
632 | =item ev_loop_fork (loop) |
|
|
633 | |
|
|
634 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
635 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
636 | after fork that you want to re-use in the child, and how you keep track of |
|
|
637 | them is entirely your own problem. |
|
|
638 | |
703 | |
639 | =item int ev_is_default_loop (loop) |
704 | =item int ev_is_default_loop (loop) |
640 | |
705 | |
641 | Returns true when the given loop is, in fact, the default loop, and false |
706 | Returns true when the given loop is, in fact, the default loop, and false |
642 | otherwise. |
707 | otherwise. |
643 | |
708 | |
644 | =item unsigned int ev_iteration (loop) |
709 | =item unsigned int ev_iteration (loop) |
645 | |
710 | |
646 | Returns the current iteration count for the loop, which is identical to |
711 | Returns the current iteration count for the event loop, which is identical |
647 | the number of times libev did poll for new events. It starts at C<0> and |
712 | to the number of times libev did poll for new events. It starts at C<0> |
648 | happily wraps around with enough iterations. |
713 | and happily wraps around with enough iterations. |
649 | |
714 | |
650 | This value can sometimes be useful as a generation counter of sorts (it |
715 | This value can sometimes be useful as a generation counter of sorts (it |
651 | "ticks" the number of loop iterations), as it roughly corresponds with |
716 | "ticks" the number of loop iterations), as it roughly corresponds with |
652 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
717 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
653 | prepare and check phases. |
718 | prepare and check phases. |
654 | |
719 | |
655 | =item unsigned int ev_depth (loop) |
720 | =item unsigned int ev_depth (loop) |
656 | |
721 | |
657 | Returns the number of times C<ev_loop> was entered minus the number of |
722 | Returns the number of times C<ev_run> was entered minus the number of |
658 | times C<ev_loop> was exited, in other words, the recursion depth. |
723 | times C<ev_run> was exited normally, in other words, the recursion depth. |
659 | |
724 | |
660 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
725 | Outside C<ev_run>, this number is zero. In a callback, this number is |
661 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
726 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
662 | in which case it is higher. |
727 | in which case it is higher. |
663 | |
728 | |
664 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
729 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
665 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
730 | throwing an exception etc.), doesn't count as "exit" - consider this |
666 | ungentleman behaviour unless it's really convenient. |
731 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
732 | convenient, in which case it is fully supported. |
667 | |
733 | |
668 | =item unsigned int ev_backend (loop) |
734 | =item unsigned int ev_backend (loop) |
669 | |
735 | |
670 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
736 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
671 | use. |
737 | use. |
… | |
… | |
680 | |
746 | |
681 | =item ev_now_update (loop) |
747 | =item ev_now_update (loop) |
682 | |
748 | |
683 | Establishes the current time by querying the kernel, updating the time |
749 | Establishes the current time by querying the kernel, updating the time |
684 | returned by C<ev_now ()> in the progress. This is a costly operation and |
750 | returned by C<ev_now ()> in the progress. This is a costly operation and |
685 | is usually done automatically within C<ev_loop ()>. |
751 | is usually done automatically within C<ev_run ()>. |
686 | |
752 | |
687 | This function is rarely useful, but when some event callback runs for a |
753 | This function is rarely useful, but when some event callback runs for a |
688 | very long time without entering the event loop, updating libev's idea of |
754 | very long time without entering the event loop, updating libev's idea of |
689 | the current time is a good idea. |
755 | the current time is a good idea. |
690 | |
756 | |
… | |
… | |
692 | |
758 | |
693 | =item ev_suspend (loop) |
759 | =item ev_suspend (loop) |
694 | |
760 | |
695 | =item ev_resume (loop) |
761 | =item ev_resume (loop) |
696 | |
762 | |
697 | These two functions suspend and resume a loop, for use when the loop is |
763 | These two functions suspend and resume an event loop, for use when the |
698 | not used for a while and timeouts should not be processed. |
764 | loop is not used for a while and timeouts should not be processed. |
699 | |
765 | |
700 | A typical use case would be an interactive program such as a game: When |
766 | A typical use case would be an interactive program such as a game: When |
701 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
767 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
702 | would be best to handle timeouts as if no time had actually passed while |
768 | would be best to handle timeouts as if no time had actually passed while |
703 | the program was suspended. This can be achieved by calling C<ev_suspend> |
769 | the program was suspended. This can be achieved by calling C<ev_suspend> |
… | |
… | |
714 | without a previous call to C<ev_suspend>. |
780 | without a previous call to C<ev_suspend>. |
715 | |
781 | |
716 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
782 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
717 | event loop time (see C<ev_now_update>). |
783 | event loop time (see C<ev_now_update>). |
718 | |
784 | |
719 | =item ev_loop (loop, int flags) |
785 | =item ev_run (loop, int flags) |
720 | |
786 | |
721 | Finally, this is it, the event handler. This function usually is called |
787 | Finally, this is it, the event handler. This function usually is called |
722 | after you have initialised all your watchers and you want to start |
788 | after you have initialised all your watchers and you want to start |
723 | handling events. |
789 | handling events. It will ask the operating system for any new events, call |
|
|
790 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
791 | is why event loops are called I<loops>. |
724 | |
792 | |
725 | If the flags argument is specified as C<0>, it will not return until |
793 | If the flags argument is specified as C<0>, it will keep handling events |
726 | either no event watchers are active anymore or C<ev_unloop> was called. |
794 | until either no event watchers are active anymore or C<ev_break> was |
|
|
795 | called. |
727 | |
796 | |
728 | Please note that an explicit C<ev_unloop> is usually better than |
797 | Please note that an explicit C<ev_break> is usually better than |
729 | relying on all watchers to be stopped when deciding when a program has |
798 | relying on all watchers to be stopped when deciding when a program has |
730 | finished (especially in interactive programs), but having a program |
799 | finished (especially in interactive programs), but having a program |
731 | that automatically loops as long as it has to and no longer by virtue |
800 | that automatically loops as long as it has to and no longer by virtue |
732 | of relying on its watchers stopping correctly, that is truly a thing of |
801 | of relying on its watchers stopping correctly, that is truly a thing of |
733 | beauty. |
802 | beauty. |
734 | |
803 | |
|
|
804 | This function is also I<mostly> exception-safe - you can break out of |
|
|
805 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
806 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
807 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
808 | |
735 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
809 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
736 | those events and any already outstanding ones, but will not block your |
810 | those events and any already outstanding ones, but will not wait and |
737 | process in case there are no events and will return after one iteration of |
811 | block your process in case there are no events and will return after one |
738 | the loop. |
812 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
813 | events while doing lengthy calculations, to keep the program responsive. |
739 | |
814 | |
740 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
815 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
741 | necessary) and will handle those and any already outstanding ones. It |
816 | necessary) and will handle those and any already outstanding ones. It |
742 | will block your process until at least one new event arrives (which could |
817 | will block your process until at least one new event arrives (which could |
743 | be an event internal to libev itself, so there is no guarantee that a |
818 | be an event internal to libev itself, so there is no guarantee that a |
744 | user-registered callback will be called), and will return after one |
819 | user-registered callback will be called), and will return after one |
745 | iteration of the loop. |
820 | iteration of the loop. |
746 | |
821 | |
747 | This is useful if you are waiting for some external event in conjunction |
822 | This is useful if you are waiting for some external event in conjunction |
748 | with something not expressible using other libev watchers (i.e. "roll your |
823 | with something not expressible using other libev watchers (i.e. "roll your |
749 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
824 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
750 | usually a better approach for this kind of thing. |
825 | usually a better approach for this kind of thing. |
751 | |
826 | |
752 | Here are the gory details of what C<ev_loop> does: |
827 | Here are the gory details of what C<ev_run> does: |
753 | |
828 | |
|
|
829 | - Increment loop depth. |
|
|
830 | - Reset the ev_break status. |
754 | - Before the first iteration, call any pending watchers. |
831 | - Before the first iteration, call any pending watchers. |
|
|
832 | LOOP: |
755 | * If EVFLAG_FORKCHECK was used, check for a fork. |
833 | - If EVFLAG_FORKCHECK was used, check for a fork. |
756 | - If a fork was detected (by any means), queue and call all fork watchers. |
834 | - If a fork was detected (by any means), queue and call all fork watchers. |
757 | - Queue and call all prepare watchers. |
835 | - Queue and call all prepare watchers. |
|
|
836 | - If ev_break was called, goto FINISH. |
758 | - If we have been forked, detach and recreate the kernel state |
837 | - If we have been forked, detach and recreate the kernel state |
759 | as to not disturb the other process. |
838 | as to not disturb the other process. |
760 | - Update the kernel state with all outstanding changes. |
839 | - Update the kernel state with all outstanding changes. |
761 | - Update the "event loop time" (ev_now ()). |
840 | - Update the "event loop time" (ev_now ()). |
762 | - Calculate for how long to sleep or block, if at all |
841 | - Calculate for how long to sleep or block, if at all |
763 | (active idle watchers, EVLOOP_NONBLOCK or not having |
842 | (active idle watchers, EVRUN_NOWAIT or not having |
764 | any active watchers at all will result in not sleeping). |
843 | any active watchers at all will result in not sleeping). |
765 | - Sleep if the I/O and timer collect interval say so. |
844 | - Sleep if the I/O and timer collect interval say so. |
|
|
845 | - Increment loop iteration counter. |
766 | - Block the process, waiting for any events. |
846 | - Block the process, waiting for any events. |
767 | - Queue all outstanding I/O (fd) events. |
847 | - Queue all outstanding I/O (fd) events. |
768 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
848 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
769 | - Queue all expired timers. |
849 | - Queue all expired timers. |
770 | - Queue all expired periodics. |
850 | - Queue all expired periodics. |
771 | - Unless any events are pending now, queue all idle watchers. |
851 | - Queue all idle watchers with priority higher than that of pending events. |
772 | - Queue all check watchers. |
852 | - Queue all check watchers. |
773 | - Call all queued watchers in reverse order (i.e. check watchers first). |
853 | - Call all queued watchers in reverse order (i.e. check watchers first). |
774 | Signals and child watchers are implemented as I/O watchers, and will |
854 | Signals and child watchers are implemented as I/O watchers, and will |
775 | be handled here by queueing them when their watcher gets executed. |
855 | be handled here by queueing them when their watcher gets executed. |
776 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
856 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
777 | were used, or there are no active watchers, return, otherwise |
857 | were used, or there are no active watchers, goto FINISH, otherwise |
778 | continue with step *. |
858 | continue with step LOOP. |
|
|
859 | FINISH: |
|
|
860 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
861 | - Decrement the loop depth. |
|
|
862 | - Return. |
779 | |
863 | |
780 | Example: Queue some jobs and then loop until no events are outstanding |
864 | Example: Queue some jobs and then loop until no events are outstanding |
781 | anymore. |
865 | anymore. |
782 | |
866 | |
783 | ... queue jobs here, make sure they register event watchers as long |
867 | ... queue jobs here, make sure they register event watchers as long |
784 | ... as they still have work to do (even an idle watcher will do..) |
868 | ... as they still have work to do (even an idle watcher will do..) |
785 | ev_loop (my_loop, 0); |
869 | ev_run (my_loop, 0); |
786 | ... jobs done or somebody called unloop. yeah! |
870 | ... jobs done or somebody called unloop. yeah! |
787 | |
871 | |
788 | =item ev_unloop (loop, how) |
872 | =item ev_break (loop, how) |
789 | |
873 | |
790 | Can be used to make a call to C<ev_loop> return early (but only after it |
874 | Can be used to make a call to C<ev_run> return early (but only after it |
791 | has processed all outstanding events). The C<how> argument must be either |
875 | has processed all outstanding events). The C<how> argument must be either |
792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
876 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
877 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
794 | |
878 | |
795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
879 | This "break state" will be cleared on the next call to C<ev_run>. |
796 | |
880 | |
797 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
881 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
882 | which case it will have no effect. |
798 | |
883 | |
799 | =item ev_ref (loop) |
884 | =item ev_ref (loop) |
800 | |
885 | |
801 | =item ev_unref (loop) |
886 | =item ev_unref (loop) |
802 | |
887 | |
803 | Ref/unref can be used to add or remove a reference count on the event |
888 | Ref/unref can be used to add or remove a reference count on the event |
804 | loop: Every watcher keeps one reference, and as long as the reference |
889 | loop: Every watcher keeps one reference, and as long as the reference |
805 | count is nonzero, C<ev_loop> will not return on its own. |
890 | count is nonzero, C<ev_run> will not return on its own. |
806 | |
891 | |
807 | This is useful when you have a watcher that you never intend to |
892 | This is useful when you have a watcher that you never intend to |
808 | unregister, but that nevertheless should not keep C<ev_loop> from |
893 | unregister, but that nevertheless should not keep C<ev_run> from |
809 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
894 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
810 | before stopping it. |
895 | before stopping it. |
811 | |
896 | |
812 | As an example, libev itself uses this for its internal signal pipe: It |
897 | As an example, libev itself uses this for its internal signal pipe: It |
813 | is not visible to the libev user and should not keep C<ev_loop> from |
898 | is not visible to the libev user and should not keep C<ev_run> from |
814 | exiting if no event watchers registered by it are active. It is also an |
899 | exiting if no event watchers registered by it are active. It is also an |
815 | excellent way to do this for generic recurring timers or from within |
900 | excellent way to do this for generic recurring timers or from within |
816 | third-party libraries. Just remember to I<unref after start> and I<ref |
901 | third-party libraries. Just remember to I<unref after start> and I<ref |
817 | before stop> (but only if the watcher wasn't active before, or was active |
902 | before stop> (but only if the watcher wasn't active before, or was active |
818 | before, respectively. Note also that libev might stop watchers itself |
903 | before, respectively. Note also that libev might stop watchers itself |
819 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
904 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
820 | in the callback). |
905 | in the callback). |
821 | |
906 | |
822 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
907 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
823 | running when nothing else is active. |
908 | running when nothing else is active. |
824 | |
909 | |
825 | ev_signal exitsig; |
910 | ev_signal exitsig; |
826 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
911 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
827 | ev_signal_start (loop, &exitsig); |
912 | ev_signal_start (loop, &exitsig); |
828 | evf_unref (loop); |
913 | ev_unref (loop); |
829 | |
914 | |
830 | Example: For some weird reason, unregister the above signal handler again. |
915 | Example: For some weird reason, unregister the above signal handler again. |
831 | |
916 | |
832 | ev_ref (loop); |
917 | ev_ref (loop); |
833 | ev_signal_stop (loop, &exitsig); |
918 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
890 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
975 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
891 | |
976 | |
892 | =item ev_invoke_pending (loop) |
977 | =item ev_invoke_pending (loop) |
893 | |
978 | |
894 | This call will simply invoke all pending watchers while resetting their |
979 | This call will simply invoke all pending watchers while resetting their |
895 | pending state. Normally, C<ev_loop> does this automatically when required, |
980 | pending state. Normally, C<ev_run> does this automatically when required, |
896 | but when overriding the invoke callback this call comes handy. |
981 | but when overriding the invoke callback this call comes handy. This |
|
|
982 | function can be invoked from a watcher - this can be useful for example |
|
|
983 | when you want to do some lengthy calculation and want to pass further |
|
|
984 | event handling to another thread (you still have to make sure only one |
|
|
985 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
897 | |
986 | |
898 | =item int ev_pending_count (loop) |
987 | =item int ev_pending_count (loop) |
899 | |
988 | |
900 | Returns the number of pending watchers - zero indicates that no watchers |
989 | Returns the number of pending watchers - zero indicates that no watchers |
901 | are pending. |
990 | are pending. |
902 | |
991 | |
903 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
992 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
904 | |
993 | |
905 | This overrides the invoke pending functionality of the loop: Instead of |
994 | This overrides the invoke pending functionality of the loop: Instead of |
906 | invoking all pending watchers when there are any, C<ev_loop> will call |
995 | invoking all pending watchers when there are any, C<ev_run> will call |
907 | this callback instead. This is useful, for example, when you want to |
996 | this callback instead. This is useful, for example, when you want to |
908 | invoke the actual watchers inside another context (another thread etc.). |
997 | invoke the actual watchers inside another context (another thread etc.). |
909 | |
998 | |
910 | If you want to reset the callback, use C<ev_invoke_pending> as new |
999 | If you want to reset the callback, use C<ev_invoke_pending> as new |
911 | callback. |
1000 | callback. |
… | |
… | |
914 | |
1003 | |
915 | Sometimes you want to share the same loop between multiple threads. This |
1004 | Sometimes you want to share the same loop between multiple threads. This |
916 | can be done relatively simply by putting mutex_lock/unlock calls around |
1005 | can be done relatively simply by putting mutex_lock/unlock calls around |
917 | each call to a libev function. |
1006 | each call to a libev function. |
918 | |
1007 | |
919 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
1008 | However, C<ev_run> can run an indefinite time, so it is not feasible |
920 | wait for it to return. One way around this is to wake up the loop via |
1009 | to wait for it to return. One way around this is to wake up the event |
921 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
1010 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
922 | and I<acquire> callbacks on the loop. |
1011 | I<release> and I<acquire> callbacks on the loop. |
923 | |
1012 | |
924 | When set, then C<release> will be called just before the thread is |
1013 | When set, then C<release> will be called just before the thread is |
925 | suspended waiting for new events, and C<acquire> is called just |
1014 | suspended waiting for new events, and C<acquire> is called just |
926 | afterwards. |
1015 | afterwards. |
927 | |
1016 | |
… | |
… | |
930 | |
1019 | |
931 | While event loop modifications are allowed between invocations of |
1020 | While event loop modifications are allowed between invocations of |
932 | C<release> and C<acquire> (that's their only purpose after all), no |
1021 | C<release> and C<acquire> (that's their only purpose after all), no |
933 | modifications done will affect the event loop, i.e. adding watchers will |
1022 | modifications done will affect the event loop, i.e. adding watchers will |
934 | have no effect on the set of file descriptors being watched, or the time |
1023 | have no effect on the set of file descriptors being watched, or the time |
935 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
1024 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
936 | to take note of any changes you made. |
1025 | to take note of any changes you made. |
937 | |
1026 | |
938 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
1027 | In theory, threads executing C<ev_run> will be async-cancel safe between |
939 | invocations of C<release> and C<acquire>. |
1028 | invocations of C<release> and C<acquire>. |
940 | |
1029 | |
941 | See also the locking example in the C<THREADS> section later in this |
1030 | See also the locking example in the C<THREADS> section later in this |
942 | document. |
1031 | document. |
943 | |
1032 | |
944 | =item ev_set_userdata (loop, void *data) |
1033 | =item ev_set_userdata (loop, void *data) |
945 | |
1034 | |
946 | =item ev_userdata (loop) |
1035 | =item void *ev_userdata (loop) |
947 | |
1036 | |
948 | Set and retrieve a single C<void *> associated with a loop. When |
1037 | Set and retrieve a single C<void *> associated with a loop. When |
949 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1038 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
950 | C<0.> |
1039 | C<0>. |
951 | |
1040 | |
952 | These two functions can be used to associate arbitrary data with a loop, |
1041 | These two functions can be used to associate arbitrary data with a loop, |
953 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1042 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
954 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1043 | C<acquire> callbacks described above, but of course can be (ab-)used for |
955 | any other purpose as well. |
1044 | any other purpose as well. |
956 | |
1045 | |
957 | =item ev_loop_verify (loop) |
1046 | =item ev_verify (loop) |
958 | |
1047 | |
959 | This function only does something when C<EV_VERIFY> support has been |
1048 | This function only does something when C<EV_VERIFY> support has been |
960 | compiled in, which is the default for non-minimal builds. It tries to go |
1049 | compiled in, which is the default for non-minimal builds. It tries to go |
961 | through all internal structures and checks them for validity. If anything |
1050 | through all internal structures and checks them for validity. If anything |
962 | is found to be inconsistent, it will print an error message to standard |
1051 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
973 | |
1062 | |
974 | In the following description, uppercase C<TYPE> in names stands for the |
1063 | In the following description, uppercase C<TYPE> in names stands for the |
975 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1064 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
976 | watchers and C<ev_io_start> for I/O watchers. |
1065 | watchers and C<ev_io_start> for I/O watchers. |
977 | |
1066 | |
978 | A watcher is a structure that you create and register to record your |
1067 | A watcher is an opaque structure that you allocate and register to record |
979 | interest in some event. For instance, if you want to wait for STDIN to |
1068 | your interest in some event. To make a concrete example, imagine you want |
980 | become readable, you would create an C<ev_io> watcher for that: |
1069 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1070 | for that: |
981 | |
1071 | |
982 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1072 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
983 | { |
1073 | { |
984 | ev_io_stop (w); |
1074 | ev_io_stop (w); |
985 | ev_unloop (loop, EVUNLOOP_ALL); |
1075 | ev_break (loop, EVBREAK_ALL); |
986 | } |
1076 | } |
987 | |
1077 | |
988 | struct ev_loop *loop = ev_default_loop (0); |
1078 | struct ev_loop *loop = ev_default_loop (0); |
989 | |
1079 | |
990 | ev_io stdin_watcher; |
1080 | ev_io stdin_watcher; |
991 | |
1081 | |
992 | ev_init (&stdin_watcher, my_cb); |
1082 | ev_init (&stdin_watcher, my_cb); |
993 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1083 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
994 | ev_io_start (loop, &stdin_watcher); |
1084 | ev_io_start (loop, &stdin_watcher); |
995 | |
1085 | |
996 | ev_loop (loop, 0); |
1086 | ev_run (loop, 0); |
997 | |
1087 | |
998 | As you can see, you are responsible for allocating the memory for your |
1088 | As you can see, you are responsible for allocating the memory for your |
999 | watcher structures (and it is I<usually> a bad idea to do this on the |
1089 | watcher structures (and it is I<usually> a bad idea to do this on the |
1000 | stack). |
1090 | stack). |
1001 | |
1091 | |
1002 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1092 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1003 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1093 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1004 | |
1094 | |
1005 | Each watcher structure must be initialised by a call to C<ev_init |
1095 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
1006 | (watcher *, callback)>, which expects a callback to be provided. This |
1096 | *, callback)>, which expects a callback to be provided. This callback is |
1007 | callback gets invoked each time the event occurs (or, in the case of I/O |
1097 | invoked each time the event occurs (or, in the case of I/O watchers, each |
1008 | watchers, each time the event loop detects that the file descriptor given |
1098 | time the event loop detects that the file descriptor given is readable |
1009 | is readable and/or writable). |
1099 | and/or writable). |
1010 | |
1100 | |
1011 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1101 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1012 | macro to configure it, with arguments specific to the watcher type. There |
1102 | macro to configure it, with arguments specific to the watcher type. There |
1013 | is also a macro to combine initialisation and setting in one call: C<< |
1103 | is also a macro to combine initialisation and setting in one call: C<< |
1014 | ev_TYPE_init (watcher *, callback, ...) >>. |
1104 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
1065 | |
1155 | |
1066 | =item C<EV_PREPARE> |
1156 | =item C<EV_PREPARE> |
1067 | |
1157 | |
1068 | =item C<EV_CHECK> |
1158 | =item C<EV_CHECK> |
1069 | |
1159 | |
1070 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1160 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1071 | to gather new events, and all C<ev_check> watchers are invoked just after |
1161 | to gather new events, and all C<ev_check> watchers are invoked just after |
1072 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1162 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1073 | received events. Callbacks of both watcher types can start and stop as |
1163 | received events. Callbacks of both watcher types can start and stop as |
1074 | many watchers as they want, and all of them will be taken into account |
1164 | many watchers as they want, and all of them will be taken into account |
1075 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1165 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1076 | C<ev_loop> from blocking). |
1166 | C<ev_run> from blocking). |
1077 | |
1167 | |
1078 | =item C<EV_EMBED> |
1168 | =item C<EV_EMBED> |
1079 | |
1169 | |
1080 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1170 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1081 | |
1171 | |
1082 | =item C<EV_FORK> |
1172 | =item C<EV_FORK> |
1083 | |
1173 | |
1084 | The event loop has been resumed in the child process after fork (see |
1174 | The event loop has been resumed in the child process after fork (see |
1085 | C<ev_fork>). |
1175 | C<ev_fork>). |
|
|
1176 | |
|
|
1177 | =item C<EV_CLEANUP> |
|
|
1178 | |
|
|
1179 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1086 | |
1180 | |
1087 | =item C<EV_ASYNC> |
1181 | =item C<EV_ASYNC> |
1088 | |
1182 | |
1089 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1183 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1090 | |
1184 | |
… | |
… | |
1263 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1357 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1264 | functions that do not need a watcher. |
1358 | functions that do not need a watcher. |
1265 | |
1359 | |
1266 | =back |
1360 | =back |
1267 | |
1361 | |
|
|
1362 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1363 | OWN COMPOSITE WATCHERS> idioms. |
1268 | |
1364 | |
1269 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1365 | =head2 WATCHER STATES |
1270 | |
1366 | |
1271 | Each watcher has, by default, a member C<void *data> that you can change |
1367 | There are various watcher states mentioned throughout this manual - |
1272 | and read at any time: libev will completely ignore it. This can be used |
1368 | active, pending and so on. In this section these states and the rules to |
1273 | to associate arbitrary data with your watcher. If you need more data and |
1369 | transition between them will be described in more detail - and while these |
1274 | don't want to allocate memory and store a pointer to it in that data |
1370 | rules might look complicated, they usually do "the right thing". |
1275 | member, you can also "subclass" the watcher type and provide your own |
|
|
1276 | data: |
|
|
1277 | |
1371 | |
1278 | struct my_io |
1372 | =over 4 |
1279 | { |
|
|
1280 | ev_io io; |
|
|
1281 | int otherfd; |
|
|
1282 | void *somedata; |
|
|
1283 | struct whatever *mostinteresting; |
|
|
1284 | }; |
|
|
1285 | |
1373 | |
1286 | ... |
1374 | =item initialiased |
1287 | struct my_io w; |
|
|
1288 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1289 | |
1375 | |
1290 | And since your callback will be called with a pointer to the watcher, you |
1376 | Before a watcher can be registered with the event looop it has to be |
1291 | can cast it back to your own type: |
1377 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1378 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1292 | |
1379 | |
1293 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1380 | In this state it is simply some block of memory that is suitable for use |
1294 | { |
1381 | in an event loop. It can be moved around, freed, reused etc. at will. |
1295 | struct my_io *w = (struct my_io *)w_; |
|
|
1296 | ... |
|
|
1297 | } |
|
|
1298 | |
1382 | |
1299 | More interesting and less C-conformant ways of casting your callback type |
1383 | =item started/running/active |
1300 | instead have been omitted. |
|
|
1301 | |
1384 | |
1302 | Another common scenario is to use some data structure with multiple |
1385 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1303 | embedded watchers: |
1386 | property of the event loop, and is actively waiting for events. While in |
|
|
1387 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1388 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1389 | and call libev functions on it that are documented to work on active watchers. |
1304 | |
1390 | |
1305 | struct my_biggy |
1391 | =item pending |
1306 | { |
|
|
1307 | int some_data; |
|
|
1308 | ev_timer t1; |
|
|
1309 | ev_timer t2; |
|
|
1310 | } |
|
|
1311 | |
1392 | |
1312 | In this case getting the pointer to C<my_biggy> is a bit more |
1393 | If a watcher is active and libev determines that an event it is interested |
1313 | complicated: Either you store the address of your C<my_biggy> struct |
1394 | in has occurred (such as a timer expiring), it will become pending. It will |
1314 | in the C<data> member of the watcher (for woozies), or you need to use |
1395 | stay in this pending state until either it is stopped or its callback is |
1315 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1396 | about to be invoked, so it is not normally pending inside the watcher |
1316 | programmers): |
1397 | callback. |
1317 | |
1398 | |
1318 | #include <stddef.h> |
1399 | The watcher might or might not be active while it is pending (for example, |
|
|
1400 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1401 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1402 | but it is still property of the event loop at this time, so cannot be |
|
|
1403 | moved, freed or reused. And if it is active the rules described in the |
|
|
1404 | previous item still apply. |
1319 | |
1405 | |
1320 | static void |
1406 | It is also possible to feed an event on a watcher that is not active (e.g. |
1321 | t1_cb (EV_P_ ev_timer *w, int revents) |
1407 | via C<ev_feed_event>), in which case it becomes pending without being |
1322 | { |
1408 | active. |
1323 | struct my_biggy big = (struct my_biggy *) |
|
|
1324 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1325 | } |
|
|
1326 | |
1409 | |
1327 | static void |
1410 | =item stopped |
1328 | t2_cb (EV_P_ ev_timer *w, int revents) |
1411 | |
1329 | { |
1412 | A watcher can be stopped implicitly by libev (in which case it might still |
1330 | struct my_biggy big = (struct my_biggy *) |
1413 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1331 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1414 | latter will clear any pending state the watcher might be in, regardless |
1332 | } |
1415 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1416 | freeing it is often a good idea. |
|
|
1417 | |
|
|
1418 | While stopped (and not pending) the watcher is essentially in the |
|
|
1419 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1420 | you wish. |
|
|
1421 | |
|
|
1422 | =back |
1333 | |
1423 | |
1334 | =head2 WATCHER PRIORITY MODELS |
1424 | =head2 WATCHER PRIORITY MODELS |
1335 | |
1425 | |
1336 | Many event loops support I<watcher priorities>, which are usually small |
1426 | Many event loops support I<watcher priorities>, which are usually small |
1337 | integers that influence the ordering of event callback invocation |
1427 | integers that influence the ordering of event callback invocation |
… | |
… | |
1464 | In general you can register as many read and/or write event watchers per |
1554 | In general you can register as many read and/or write event watchers per |
1465 | fd as you want (as long as you don't confuse yourself). Setting all file |
1555 | fd as you want (as long as you don't confuse yourself). Setting all file |
1466 | descriptors to non-blocking mode is also usually a good idea (but not |
1556 | descriptors to non-blocking mode is also usually a good idea (but not |
1467 | required if you know what you are doing). |
1557 | required if you know what you are doing). |
1468 | |
1558 | |
1469 | If you cannot use non-blocking mode, then force the use of a |
|
|
1470 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1472 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1473 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1474 | |
|
|
1475 | Another thing you have to watch out for is that it is quite easy to |
1559 | Another thing you have to watch out for is that it is quite easy to |
1476 | receive "spurious" readiness notifications, that is your callback might |
1560 | receive "spurious" readiness notifications, that is, your callback might |
1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1561 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1478 | because there is no data. Not only are some backends known to create a |
1562 | because there is no data. It is very easy to get into this situation even |
1479 | lot of those (for example Solaris ports), it is very easy to get into |
1563 | with a relatively standard program structure. Thus it is best to always |
1480 | this situation even with a relatively standard program structure. Thus |
1564 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1481 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1482 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1565 | preferable to a program hanging until some data arrives. |
1483 | |
1566 | |
1484 | If you cannot run the fd in non-blocking mode (for example you should |
1567 | If you cannot run the fd in non-blocking mode (for example you should |
1485 | not play around with an Xlib connection), then you have to separately |
1568 | not play around with an Xlib connection), then you have to separately |
1486 | re-test whether a file descriptor is really ready with a known-to-be good |
1569 | re-test whether a file descriptor is really ready with a known-to-be good |
1487 | interface such as poll (fortunately in our Xlib example, Xlib already |
1570 | interface such as poll (fortunately in the case of Xlib, it already does |
1488 | does this on its own, so its quite safe to use). Some people additionally |
1571 | this on its own, so its quite safe to use). Some people additionally |
1489 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1572 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1490 | indefinitely. |
1573 | indefinitely. |
1491 | |
1574 | |
1492 | But really, best use non-blocking mode. |
1575 | But really, best use non-blocking mode. |
1493 | |
1576 | |
… | |
… | |
1521 | |
1604 | |
1522 | There is no workaround possible except not registering events |
1605 | There is no workaround possible except not registering events |
1523 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1606 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1524 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1607 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1525 | |
1608 | |
|
|
1609 | =head3 The special problem of files |
|
|
1610 | |
|
|
1611 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1612 | representing files, and expect it to become ready when their program |
|
|
1613 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1614 | |
|
|
1615 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1616 | notification as soon as the kernel knows whether and how much data is |
|
|
1617 | there, and in the case of open files, that's always the case, so you |
|
|
1618 | always get a readiness notification instantly, and your read (or possibly |
|
|
1619 | write) will still block on the disk I/O. |
|
|
1620 | |
|
|
1621 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1622 | devices and so on, there is another party (the sender) that delivers data |
|
|
1623 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1624 | will not send data on its own, simply because it doesn't know what you |
|
|
1625 | wish to read - you would first have to request some data. |
|
|
1626 | |
|
|
1627 | Since files are typically not-so-well supported by advanced notification |
|
|
1628 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1629 | to files, even though you should not use it. The reason for this is |
|
|
1630 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1631 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1632 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1633 | F</dev/urandom>), and even though the file might better be served with |
|
|
1634 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1635 | it "just works" instead of freezing. |
|
|
1636 | |
|
|
1637 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1638 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1639 | when you rarely read from a file instead of from a socket, and want to |
|
|
1640 | reuse the same code path. |
|
|
1641 | |
1526 | =head3 The special problem of fork |
1642 | =head3 The special problem of fork |
1527 | |
1643 | |
1528 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1644 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1529 | useless behaviour. Libev fully supports fork, but needs to be told about |
1645 | useless behaviour. Libev fully supports fork, but needs to be told about |
1530 | it in the child. |
1646 | it in the child if you want to continue to use it in the child. |
1531 | |
1647 | |
1532 | To support fork in your programs, you either have to call |
1648 | To support fork in your child processes, you have to call C<ev_loop_fork |
1533 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1649 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1534 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1650 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1535 | C<EVBACKEND_POLL>. |
|
|
1536 | |
1651 | |
1537 | =head3 The special problem of SIGPIPE |
1652 | =head3 The special problem of SIGPIPE |
1538 | |
1653 | |
1539 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1654 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1540 | when writing to a pipe whose other end has been closed, your program gets |
1655 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1622 | ... |
1737 | ... |
1623 | struct ev_loop *loop = ev_default_init (0); |
1738 | struct ev_loop *loop = ev_default_init (0); |
1624 | ev_io stdin_readable; |
1739 | ev_io stdin_readable; |
1625 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1740 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1626 | ev_io_start (loop, &stdin_readable); |
1741 | ev_io_start (loop, &stdin_readable); |
1627 | ev_loop (loop, 0); |
1742 | ev_run (loop, 0); |
1628 | |
1743 | |
1629 | |
1744 | |
1630 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1745 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1631 | |
1746 | |
1632 | Timer watchers are simple relative timers that generate an event after a |
1747 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1641 | The callback is guaranteed to be invoked only I<after> its timeout has |
1756 | The callback is guaranteed to be invoked only I<after> its timeout has |
1642 | passed (not I<at>, so on systems with very low-resolution clocks this |
1757 | passed (not I<at>, so on systems with very low-resolution clocks this |
1643 | might introduce a small delay). If multiple timers become ready during the |
1758 | might introduce a small delay). If multiple timers become ready during the |
1644 | same loop iteration then the ones with earlier time-out values are invoked |
1759 | same loop iteration then the ones with earlier time-out values are invoked |
1645 | before ones of the same priority with later time-out values (but this is |
1760 | before ones of the same priority with later time-out values (but this is |
1646 | no longer true when a callback calls C<ev_loop> recursively). |
1761 | no longer true when a callback calls C<ev_run> recursively). |
1647 | |
1762 | |
1648 | =head3 Be smart about timeouts |
1763 | =head3 Be smart about timeouts |
1649 | |
1764 | |
1650 | Many real-world problems involve some kind of timeout, usually for error |
1765 | Many real-world problems involve some kind of timeout, usually for error |
1651 | recovery. A typical example is an HTTP request - if the other side hangs, |
1766 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1822 | |
1937 | |
1823 | =head3 The special problem of time updates |
1938 | =head3 The special problem of time updates |
1824 | |
1939 | |
1825 | Establishing the current time is a costly operation (it usually takes at |
1940 | Establishing the current time is a costly operation (it usually takes at |
1826 | least two system calls): EV therefore updates its idea of the current |
1941 | least two system calls): EV therefore updates its idea of the current |
1827 | time only before and after C<ev_loop> collects new events, which causes a |
1942 | time only before and after C<ev_run> collects new events, which causes a |
1828 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1943 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1829 | lots of events in one iteration. |
1944 | lots of events in one iteration. |
1830 | |
1945 | |
1831 | The relative timeouts are calculated relative to the C<ev_now ()> |
1946 | The relative timeouts are calculated relative to the C<ev_now ()> |
1832 | time. This is usually the right thing as this timestamp refers to the time |
1947 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1949 | } |
2064 | } |
1950 | |
2065 | |
1951 | ev_timer mytimer; |
2066 | ev_timer mytimer; |
1952 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2067 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1953 | ev_timer_again (&mytimer); /* start timer */ |
2068 | ev_timer_again (&mytimer); /* start timer */ |
1954 | ev_loop (loop, 0); |
2069 | ev_run (loop, 0); |
1955 | |
2070 | |
1956 | // and in some piece of code that gets executed on any "activity": |
2071 | // and in some piece of code that gets executed on any "activity": |
1957 | // reset the timeout to start ticking again at 10 seconds |
2072 | // reset the timeout to start ticking again at 10 seconds |
1958 | ev_timer_again (&mytimer); |
2073 | ev_timer_again (&mytimer); |
1959 | |
2074 | |
… | |
… | |
1985 | |
2100 | |
1986 | As with timers, the callback is guaranteed to be invoked only when the |
2101 | As with timers, the callback is guaranteed to be invoked only when the |
1987 | point in time where it is supposed to trigger has passed. If multiple |
2102 | point in time where it is supposed to trigger has passed. If multiple |
1988 | timers become ready during the same loop iteration then the ones with |
2103 | timers become ready during the same loop iteration then the ones with |
1989 | earlier time-out values are invoked before ones with later time-out values |
2104 | earlier time-out values are invoked before ones with later time-out values |
1990 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
2105 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1991 | |
2106 | |
1992 | =head3 Watcher-Specific Functions and Data Members |
2107 | =head3 Watcher-Specific Functions and Data Members |
1993 | |
2108 | |
1994 | =over 4 |
2109 | =over 4 |
1995 | |
2110 | |
… | |
… | |
2156 | |
2271 | |
2157 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2272 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2158 | |
2273 | |
2159 | Signal watchers will trigger an event when the process receives a specific |
2274 | Signal watchers will trigger an event when the process receives a specific |
2160 | signal one or more times. Even though signals are very asynchronous, libev |
2275 | signal one or more times. Even though signals are very asynchronous, libev |
2161 | will try it's best to deliver signals synchronously, i.e. as part of the |
2276 | will try its best to deliver signals synchronously, i.e. as part of the |
2162 | normal event processing, like any other event. |
2277 | normal event processing, like any other event. |
2163 | |
2278 | |
2164 | If you want signals to be delivered truly asynchronously, just use |
2279 | If you want signals to be delivered truly asynchronously, just use |
2165 | C<sigaction> as you would do without libev and forget about sharing |
2280 | C<sigaction> as you would do without libev and forget about sharing |
2166 | the signal. You can even use C<ev_async> from a signal handler to |
2281 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2209 | |
2324 | |
2210 | So I can't stress this enough: I<If you do not reset your signal mask when |
2325 | So I can't stress this enough: I<If you do not reset your signal mask when |
2211 | you expect it to be empty, you have a race condition in your code>. This |
2326 | you expect it to be empty, you have a race condition in your code>. This |
2212 | is not a libev-specific thing, this is true for most event libraries. |
2327 | is not a libev-specific thing, this is true for most event libraries. |
2213 | |
2328 | |
|
|
2329 | =head3 The special problem of threads signal handling |
|
|
2330 | |
|
|
2331 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2332 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2333 | threads in a process block signals, which is hard to achieve. |
|
|
2334 | |
|
|
2335 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2336 | for the same signals), you can tackle this problem by globally blocking |
|
|
2337 | all signals before creating any threads (or creating them with a fully set |
|
|
2338 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2339 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2340 | these signals. You can pass on any signals that libev might be interested |
|
|
2341 | in by calling C<ev_feed_signal>. |
|
|
2342 | |
2214 | =head3 Watcher-Specific Functions and Data Members |
2343 | =head3 Watcher-Specific Functions and Data Members |
2215 | |
2344 | |
2216 | =over 4 |
2345 | =over 4 |
2217 | |
2346 | |
2218 | =item ev_signal_init (ev_signal *, callback, int signum) |
2347 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
2233 | Example: Try to exit cleanly on SIGINT. |
2362 | Example: Try to exit cleanly on SIGINT. |
2234 | |
2363 | |
2235 | static void |
2364 | static void |
2236 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2365 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2237 | { |
2366 | { |
2238 | ev_unloop (loop, EVUNLOOP_ALL); |
2367 | ev_break (loop, EVBREAK_ALL); |
2239 | } |
2368 | } |
2240 | |
2369 | |
2241 | ev_signal signal_watcher; |
2370 | ev_signal signal_watcher; |
2242 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2371 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2243 | ev_signal_start (loop, &signal_watcher); |
2372 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
2629 | |
2758 | |
2630 | Prepare and check watchers are usually (but not always) used in pairs: |
2759 | Prepare and check watchers are usually (but not always) used in pairs: |
2631 | prepare watchers get invoked before the process blocks and check watchers |
2760 | prepare watchers get invoked before the process blocks and check watchers |
2632 | afterwards. |
2761 | afterwards. |
2633 | |
2762 | |
2634 | You I<must not> call C<ev_loop> or similar functions that enter |
2763 | You I<must not> call C<ev_run> or similar functions that enter |
2635 | the current event loop from either C<ev_prepare> or C<ev_check> |
2764 | the current event loop from either C<ev_prepare> or C<ev_check> |
2636 | watchers. Other loops than the current one are fine, however. The |
2765 | watchers. Other loops than the current one are fine, however. The |
2637 | rationale behind this is that you do not need to check for recursion in |
2766 | rationale behind this is that you do not need to check for recursion in |
2638 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2767 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2639 | C<ev_check> so if you have one watcher of each kind they will always be |
2768 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2807 | |
2936 | |
2808 | if (timeout >= 0) |
2937 | if (timeout >= 0) |
2809 | // create/start timer |
2938 | // create/start timer |
2810 | |
2939 | |
2811 | // poll |
2940 | // poll |
2812 | ev_loop (EV_A_ 0); |
2941 | ev_run (EV_A_ 0); |
2813 | |
2942 | |
2814 | // stop timer again |
2943 | // stop timer again |
2815 | if (timeout >= 0) |
2944 | if (timeout >= 0) |
2816 | ev_timer_stop (EV_A_ &to); |
2945 | ev_timer_stop (EV_A_ &to); |
2817 | |
2946 | |
… | |
… | |
2895 | if you do not want that, you need to temporarily stop the embed watcher). |
3024 | if you do not want that, you need to temporarily stop the embed watcher). |
2896 | |
3025 | |
2897 | =item ev_embed_sweep (loop, ev_embed *) |
3026 | =item ev_embed_sweep (loop, ev_embed *) |
2898 | |
3027 | |
2899 | Make a single, non-blocking sweep over the embedded loop. This works |
3028 | Make a single, non-blocking sweep over the embedded loop. This works |
2900 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3029 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2901 | appropriate way for embedded loops. |
3030 | appropriate way for embedded loops. |
2902 | |
3031 | |
2903 | =item struct ev_loop *other [read-only] |
3032 | =item struct ev_loop *other [read-only] |
2904 | |
3033 | |
2905 | The embedded event loop. |
3034 | The embedded event loop. |
… | |
… | |
2991 | disadvantage of having to use multiple event loops (which do not support |
3120 | disadvantage of having to use multiple event loops (which do not support |
2992 | signal watchers). |
3121 | signal watchers). |
2993 | |
3122 | |
2994 | When this is not possible, or you want to use the default loop for |
3123 | When this is not possible, or you want to use the default loop for |
2995 | other reasons, then in the process that wants to start "fresh", call |
3124 | other reasons, then in the process that wants to start "fresh", call |
2996 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3125 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
2997 | the default loop will "orphan" (not stop) all registered watchers, so you |
3126 | Destroying the default loop will "orphan" (not stop) all registered |
2998 | have to be careful not to execute code that modifies those watchers. Note |
3127 | watchers, so you have to be careful not to execute code that modifies |
2999 | also that in that case, you have to re-register any signal watchers. |
3128 | those watchers. Note also that in that case, you have to re-register any |
|
|
3129 | signal watchers. |
3000 | |
3130 | |
3001 | =head3 Watcher-Specific Functions and Data Members |
3131 | =head3 Watcher-Specific Functions and Data Members |
3002 | |
3132 | |
3003 | =over 4 |
3133 | =over 4 |
3004 | |
3134 | |
3005 | =item ev_fork_init (ev_signal *, callback) |
3135 | =item ev_fork_init (ev_fork *, callback) |
3006 | |
3136 | |
3007 | Initialises and configures the fork watcher - it has no parameters of any |
3137 | Initialises and configures the fork watcher - it has no parameters of any |
3008 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3138 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3009 | believe me. |
3139 | really. |
3010 | |
3140 | |
3011 | =back |
3141 | =back |
3012 | |
3142 | |
3013 | |
3143 | |
|
|
3144 | =head2 C<ev_cleanup> - even the best things end |
|
|
3145 | |
|
|
3146 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3147 | by a call to C<ev_loop_destroy>. |
|
|
3148 | |
|
|
3149 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3150 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3151 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3152 | loop when you want them to be invoked. |
|
|
3153 | |
|
|
3154 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3155 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3156 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3157 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3158 | |
|
|
3159 | =head3 Watcher-Specific Functions and Data Members |
|
|
3160 | |
|
|
3161 | =over 4 |
|
|
3162 | |
|
|
3163 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3164 | |
|
|
3165 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3166 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3167 | pointless, I assure you. |
|
|
3168 | |
|
|
3169 | =back |
|
|
3170 | |
|
|
3171 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3172 | cleanup functions are called. |
|
|
3173 | |
|
|
3174 | static void |
|
|
3175 | program_exits (void) |
|
|
3176 | { |
|
|
3177 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3178 | } |
|
|
3179 | |
|
|
3180 | ... |
|
|
3181 | atexit (program_exits); |
|
|
3182 | |
|
|
3183 | |
3014 | =head2 C<ev_async> - how to wake up an event loop |
3184 | =head2 C<ev_async> - how to wake up an event loop |
3015 | |
3185 | |
3016 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3186 | In general, you cannot use an C<ev_run> from multiple threads or other |
3017 | asynchronous sources such as signal handlers (as opposed to multiple event |
3187 | asynchronous sources such as signal handlers (as opposed to multiple event |
3018 | loops - those are of course safe to use in different threads). |
3188 | loops - those are of course safe to use in different threads). |
3019 | |
3189 | |
3020 | Sometimes, however, you need to wake up an event loop you do not control, |
3190 | Sometimes, however, you need to wake up an event loop you do not control, |
3021 | for example because it belongs to another thread. This is what C<ev_async> |
3191 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3023 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3193 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3024 | |
3194 | |
3025 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3195 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3026 | too, are asynchronous in nature, and signals, too, will be compressed |
3196 | too, are asynchronous in nature, and signals, too, will be compressed |
3027 | (i.e. the number of callback invocations may be less than the number of |
3197 | (i.e. the number of callback invocations may be less than the number of |
3028 | C<ev_async_sent> calls). |
3198 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
|
|
3199 | of "global async watchers" by using a watcher on an otherwise unused |
|
|
3200 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
|
|
3201 | even without knowing which loop owns the signal. |
3029 | |
3202 | |
3030 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3203 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3031 | just the default loop. |
3204 | just the default loop. |
3032 | |
3205 | |
3033 | =head3 Queueing |
3206 | =head3 Queueing |
… | |
… | |
3209 | Feed an event on the given fd, as if a file descriptor backend detected |
3382 | Feed an event on the given fd, as if a file descriptor backend detected |
3210 | the given events it. |
3383 | the given events it. |
3211 | |
3384 | |
3212 | =item ev_feed_signal_event (loop, int signum) |
3385 | =item ev_feed_signal_event (loop, int signum) |
3213 | |
3386 | |
3214 | Feed an event as if the given signal occurred (C<loop> must be the default |
3387 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3215 | loop!). |
3388 | which is async-safe. |
3216 | |
3389 | |
3217 | =back |
3390 | =back |
|
|
3391 | |
|
|
3392 | |
|
|
3393 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3394 | |
|
|
3395 | This section explains some common idioms that are not immediately |
|
|
3396 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3397 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3398 | |
|
|
3399 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3400 | |
|
|
3401 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3402 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3403 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3404 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3405 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3406 | data: |
|
|
3407 | |
|
|
3408 | struct my_io |
|
|
3409 | { |
|
|
3410 | ev_io io; |
|
|
3411 | int otherfd; |
|
|
3412 | void *somedata; |
|
|
3413 | struct whatever *mostinteresting; |
|
|
3414 | }; |
|
|
3415 | |
|
|
3416 | ... |
|
|
3417 | struct my_io w; |
|
|
3418 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3419 | |
|
|
3420 | And since your callback will be called with a pointer to the watcher, you |
|
|
3421 | can cast it back to your own type: |
|
|
3422 | |
|
|
3423 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3424 | { |
|
|
3425 | struct my_io *w = (struct my_io *)w_; |
|
|
3426 | ... |
|
|
3427 | } |
|
|
3428 | |
|
|
3429 | More interesting and less C-conformant ways of casting your callback |
|
|
3430 | function type instead have been omitted. |
|
|
3431 | |
|
|
3432 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3433 | |
|
|
3434 | Another common scenario is to use some data structure with multiple |
|
|
3435 | embedded watchers, in effect creating your own watcher that combines |
|
|
3436 | multiple libev event sources into one "super-watcher": |
|
|
3437 | |
|
|
3438 | struct my_biggy |
|
|
3439 | { |
|
|
3440 | int some_data; |
|
|
3441 | ev_timer t1; |
|
|
3442 | ev_timer t2; |
|
|
3443 | } |
|
|
3444 | |
|
|
3445 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3446 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3447 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3448 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3449 | real programmers): |
|
|
3450 | |
|
|
3451 | #include <stddef.h> |
|
|
3452 | |
|
|
3453 | static void |
|
|
3454 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3455 | { |
|
|
3456 | struct my_biggy big = (struct my_biggy *) |
|
|
3457 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3458 | } |
|
|
3459 | |
|
|
3460 | static void |
|
|
3461 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3462 | { |
|
|
3463 | struct my_biggy big = (struct my_biggy *) |
|
|
3464 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3465 | } |
|
|
3466 | |
|
|
3467 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3468 | |
|
|
3469 | Often (especially in GUI toolkits) there are places where you have |
|
|
3470 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3471 | invoking C<ev_run>. |
|
|
3472 | |
|
|
3473 | This brings the problem of exiting - a callback might want to finish the |
|
|
3474 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3475 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3476 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3477 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3478 | |
|
|
3479 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3480 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3481 | triggered, using C<EVRUN_ONCE>: |
|
|
3482 | |
|
|
3483 | // main loop |
|
|
3484 | int exit_main_loop = 0; |
|
|
3485 | |
|
|
3486 | while (!exit_main_loop) |
|
|
3487 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3488 | |
|
|
3489 | // in a model watcher |
|
|
3490 | int exit_nested_loop = 0; |
|
|
3491 | |
|
|
3492 | while (!exit_nested_loop) |
|
|
3493 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3494 | |
|
|
3495 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3496 | |
|
|
3497 | // exit modal loop |
|
|
3498 | exit_nested_loop = 1; |
|
|
3499 | |
|
|
3500 | // exit main program, after modal loop is finished |
|
|
3501 | exit_main_loop = 1; |
|
|
3502 | |
|
|
3503 | // exit both |
|
|
3504 | exit_main_loop = exit_nested_loop = 1; |
|
|
3505 | |
|
|
3506 | =head2 THREAD LOCKING EXAMPLE |
|
|
3507 | |
|
|
3508 | Here is a fictitious example of how to run an event loop in a different |
|
|
3509 | thread than where callbacks are being invoked and watchers are |
|
|
3510 | created/added/removed. |
|
|
3511 | |
|
|
3512 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3513 | which uses exactly this technique (which is suited for many high-level |
|
|
3514 | languages). |
|
|
3515 | |
|
|
3516 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3517 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3518 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3519 | |
|
|
3520 | First, you need to associate some data with the event loop: |
|
|
3521 | |
|
|
3522 | typedef struct { |
|
|
3523 | mutex_t lock; /* global loop lock */ |
|
|
3524 | ev_async async_w; |
|
|
3525 | thread_t tid; |
|
|
3526 | cond_t invoke_cv; |
|
|
3527 | } userdata; |
|
|
3528 | |
|
|
3529 | void prepare_loop (EV_P) |
|
|
3530 | { |
|
|
3531 | // for simplicity, we use a static userdata struct. |
|
|
3532 | static userdata u; |
|
|
3533 | |
|
|
3534 | ev_async_init (&u->async_w, async_cb); |
|
|
3535 | ev_async_start (EV_A_ &u->async_w); |
|
|
3536 | |
|
|
3537 | pthread_mutex_init (&u->lock, 0); |
|
|
3538 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3539 | |
|
|
3540 | // now associate this with the loop |
|
|
3541 | ev_set_userdata (EV_A_ u); |
|
|
3542 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3543 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3544 | |
|
|
3545 | // then create the thread running ev_loop |
|
|
3546 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3547 | } |
|
|
3548 | |
|
|
3549 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3550 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3551 | that might have been added: |
|
|
3552 | |
|
|
3553 | static void |
|
|
3554 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3555 | { |
|
|
3556 | // just used for the side effects |
|
|
3557 | } |
|
|
3558 | |
|
|
3559 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3560 | protecting the loop data, respectively. |
|
|
3561 | |
|
|
3562 | static void |
|
|
3563 | l_release (EV_P) |
|
|
3564 | { |
|
|
3565 | userdata *u = ev_userdata (EV_A); |
|
|
3566 | pthread_mutex_unlock (&u->lock); |
|
|
3567 | } |
|
|
3568 | |
|
|
3569 | static void |
|
|
3570 | l_acquire (EV_P) |
|
|
3571 | { |
|
|
3572 | userdata *u = ev_userdata (EV_A); |
|
|
3573 | pthread_mutex_lock (&u->lock); |
|
|
3574 | } |
|
|
3575 | |
|
|
3576 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3577 | into C<ev_run>: |
|
|
3578 | |
|
|
3579 | void * |
|
|
3580 | l_run (void *thr_arg) |
|
|
3581 | { |
|
|
3582 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3583 | |
|
|
3584 | l_acquire (EV_A); |
|
|
3585 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3586 | ev_run (EV_A_ 0); |
|
|
3587 | l_release (EV_A); |
|
|
3588 | |
|
|
3589 | return 0; |
|
|
3590 | } |
|
|
3591 | |
|
|
3592 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3593 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3594 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3595 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3596 | and b) skipping inter-thread-communication when there are no pending |
|
|
3597 | watchers is very beneficial): |
|
|
3598 | |
|
|
3599 | static void |
|
|
3600 | l_invoke (EV_P) |
|
|
3601 | { |
|
|
3602 | userdata *u = ev_userdata (EV_A); |
|
|
3603 | |
|
|
3604 | while (ev_pending_count (EV_A)) |
|
|
3605 | { |
|
|
3606 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3607 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3608 | } |
|
|
3609 | } |
|
|
3610 | |
|
|
3611 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3612 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3613 | thread to continue: |
|
|
3614 | |
|
|
3615 | static void |
|
|
3616 | real_invoke_pending (EV_P) |
|
|
3617 | { |
|
|
3618 | userdata *u = ev_userdata (EV_A); |
|
|
3619 | |
|
|
3620 | pthread_mutex_lock (&u->lock); |
|
|
3621 | ev_invoke_pending (EV_A); |
|
|
3622 | pthread_cond_signal (&u->invoke_cv); |
|
|
3623 | pthread_mutex_unlock (&u->lock); |
|
|
3624 | } |
|
|
3625 | |
|
|
3626 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3627 | event loop, you will now have to lock: |
|
|
3628 | |
|
|
3629 | ev_timer timeout_watcher; |
|
|
3630 | userdata *u = ev_userdata (EV_A); |
|
|
3631 | |
|
|
3632 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3633 | |
|
|
3634 | pthread_mutex_lock (&u->lock); |
|
|
3635 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3636 | ev_async_send (EV_A_ &u->async_w); |
|
|
3637 | pthread_mutex_unlock (&u->lock); |
|
|
3638 | |
|
|
3639 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3640 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3641 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3642 | watchers in the next event loop iteration. |
|
|
3643 | |
|
|
3644 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3645 | |
|
|
3646 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3647 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3648 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3649 | doesn't need callbacks anymore. |
|
|
3650 | |
|
|
3651 | Imagine you have coroutines that you can switch to using a function |
|
|
3652 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3653 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3654 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3655 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3656 | the differing C<;> conventions): |
|
|
3657 | |
|
|
3658 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3659 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3660 | |
|
|
3661 | That means instead of having a C callback function, you store the |
|
|
3662 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3663 | your callback, you instead have it switch to that coroutine. |
|
|
3664 | |
|
|
3665 | A coroutine might now wait for an event with a function called |
|
|
3666 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3667 | matter when, or whether the watcher is active or not when this function is |
|
|
3668 | called): |
|
|
3669 | |
|
|
3670 | void |
|
|
3671 | wait_for_event (ev_watcher *w) |
|
|
3672 | { |
|
|
3673 | ev_cb_set (w) = current_coro; |
|
|
3674 | switch_to (libev_coro); |
|
|
3675 | } |
|
|
3676 | |
|
|
3677 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3678 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3679 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3680 | |
|
|
3681 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3682 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3683 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3684 | any waiters. |
|
|
3685 | |
|
|
3686 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3687 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3688 | |
|
|
3689 | // my_ev.h |
|
|
3690 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3691 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3692 | #include "../libev/ev.h" |
|
|
3693 | |
|
|
3694 | // my_ev.c |
|
|
3695 | #define EV_H "my_ev.h" |
|
|
3696 | #include "../libev/ev.c" |
|
|
3697 | |
|
|
3698 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3699 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3700 | can even use F<ev.h> as header file name directly. |
3218 | |
3701 | |
3219 | |
3702 | |
3220 | =head1 LIBEVENT EMULATION |
3703 | =head1 LIBEVENT EMULATION |
3221 | |
3704 | |
3222 | Libev offers a compatibility emulation layer for libevent. It cannot |
3705 | Libev offers a compatibility emulation layer for libevent. It cannot |
3223 | emulate the internals of libevent, so here are some usage hints: |
3706 | emulate the internals of libevent, so here are some usage hints: |
3224 | |
3707 | |
3225 | =over 4 |
3708 | =over 4 |
|
|
3709 | |
|
|
3710 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3711 | |
|
|
3712 | This was the newest libevent version available when libev was implemented, |
|
|
3713 | and is still mostly unchanged in 2010. |
3226 | |
3714 | |
3227 | =item * Use it by including <event.h>, as usual. |
3715 | =item * Use it by including <event.h>, as usual. |
3228 | |
3716 | |
3229 | =item * The following members are fully supported: ev_base, ev_callback, |
3717 | =item * The following members are fully supported: ev_base, ev_callback, |
3230 | ev_arg, ev_fd, ev_res, ev_events. |
3718 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3236 | =item * Priorities are not currently supported. Initialising priorities |
3724 | =item * Priorities are not currently supported. Initialising priorities |
3237 | will fail and all watchers will have the same priority, even though there |
3725 | will fail and all watchers will have the same priority, even though there |
3238 | is an ev_pri field. |
3726 | is an ev_pri field. |
3239 | |
3727 | |
3240 | =item * In libevent, the last base created gets the signals, in libev, the |
3728 | =item * In libevent, the last base created gets the signals, in libev, the |
3241 | first base created (== the default loop) gets the signals. |
3729 | base that registered the signal gets the signals. |
3242 | |
3730 | |
3243 | =item * Other members are not supported. |
3731 | =item * Other members are not supported. |
3244 | |
3732 | |
3245 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3733 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3246 | to use the libev header file and library. |
3734 | to use the libev header file and library. |
… | |
… | |
3265 | Care has been taken to keep the overhead low. The only data member the C++ |
3753 | Care has been taken to keep the overhead low. The only data member the C++ |
3266 | classes add (compared to plain C-style watchers) is the event loop pointer |
3754 | classes add (compared to plain C-style watchers) is the event loop pointer |
3267 | that the watcher is associated with (or no additional members at all if |
3755 | that the watcher is associated with (or no additional members at all if |
3268 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3756 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3269 | |
3757 | |
3270 | Currently, functions, and static and non-static member functions can be |
3758 | Currently, functions, static and non-static member functions and classes |
3271 | used as callbacks. Other types should be easy to add as long as they only |
3759 | with C<operator ()> can be used as callbacks. Other types should be easy |
3272 | need one additional pointer for context. If you need support for other |
3760 | to add as long as they only need one additional pointer for context. If |
3273 | types of functors please contact the author (preferably after implementing |
3761 | you need support for other types of functors please contact the author |
3274 | it). |
3762 | (preferably after implementing it). |
3275 | |
3763 | |
3276 | Here is a list of things available in the C<ev> namespace: |
3764 | Here is a list of things available in the C<ev> namespace: |
3277 | |
3765 | |
3278 | =over 4 |
3766 | =over 4 |
3279 | |
3767 | |
… | |
… | |
3389 | Associates a different C<struct ev_loop> with this watcher. You can only |
3877 | Associates a different C<struct ev_loop> with this watcher. You can only |
3390 | do this when the watcher is inactive (and not pending either). |
3878 | do this when the watcher is inactive (and not pending either). |
3391 | |
3879 | |
3392 | =item w->set ([arguments]) |
3880 | =item w->set ([arguments]) |
3393 | |
3881 | |
3394 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3882 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
3395 | called at least once. Unlike the C counterpart, an active watcher gets |
3883 | method or a suitable start method must be called at least once. Unlike the |
3396 | automatically stopped and restarted when reconfiguring it with this |
3884 | C counterpart, an active watcher gets automatically stopped and restarted |
3397 | method. |
3885 | when reconfiguring it with this method. |
3398 | |
3886 | |
3399 | =item w->start () |
3887 | =item w->start () |
3400 | |
3888 | |
3401 | Starts the watcher. Note that there is no C<loop> argument, as the |
3889 | Starts the watcher. Note that there is no C<loop> argument, as the |
3402 | constructor already stores the event loop. |
3890 | constructor already stores the event loop. |
3403 | |
3891 | |
|
|
3892 | =item w->start ([arguments]) |
|
|
3893 | |
|
|
3894 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3895 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3896 | the configure C<set> method of the watcher. |
|
|
3897 | |
3404 | =item w->stop () |
3898 | =item w->stop () |
3405 | |
3899 | |
3406 | Stops the watcher if it is active. Again, no C<loop> argument. |
3900 | Stops the watcher if it is active. Again, no C<loop> argument. |
3407 | |
3901 | |
3408 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3902 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3420 | |
3914 | |
3421 | =back |
3915 | =back |
3422 | |
3916 | |
3423 | =back |
3917 | =back |
3424 | |
3918 | |
3425 | Example: Define a class with an IO and idle watcher, start one of them in |
3919 | Example: Define a class with two I/O and idle watchers, start the I/O |
3426 | the constructor. |
3920 | watchers in the constructor. |
3427 | |
3921 | |
3428 | class myclass |
3922 | class myclass |
3429 | { |
3923 | { |
3430 | ev::io io ; void io_cb (ev::io &w, int revents); |
3924 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3925 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
3431 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3926 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3432 | |
3927 | |
3433 | myclass (int fd) |
3928 | myclass (int fd) |
3434 | { |
3929 | { |
3435 | io .set <myclass, &myclass::io_cb > (this); |
3930 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3931 | io2 .set <myclass, &myclass::io2_cb > (this); |
3436 | idle.set <myclass, &myclass::idle_cb> (this); |
3932 | idle.set <myclass, &myclass::idle_cb> (this); |
3437 | |
3933 | |
3438 | io.start (fd, ev::READ); |
3934 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3935 | io.start (); // start it whenever convenient |
|
|
3936 | |
|
|
3937 | io2.start (fd, ev::READ); // set + start in one call |
3439 | } |
3938 | } |
3440 | }; |
3939 | }; |
3441 | |
3940 | |
3442 | |
3941 | |
3443 | =head1 OTHER LANGUAGE BINDINGS |
3942 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3517 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4016 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3518 | C<EV_A_> is used when other arguments are following. Example: |
4017 | C<EV_A_> is used when other arguments are following. Example: |
3519 | |
4018 | |
3520 | ev_unref (EV_A); |
4019 | ev_unref (EV_A); |
3521 | ev_timer_add (EV_A_ watcher); |
4020 | ev_timer_add (EV_A_ watcher); |
3522 | ev_loop (EV_A_ 0); |
4021 | ev_run (EV_A_ 0); |
3523 | |
4022 | |
3524 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4023 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3525 | which is often provided by the following macro. |
4024 | which is often provided by the following macro. |
3526 | |
4025 | |
3527 | =item C<EV_P>, C<EV_P_> |
4026 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3567 | } |
4066 | } |
3568 | |
4067 | |
3569 | ev_check check; |
4068 | ev_check check; |
3570 | ev_check_init (&check, check_cb); |
4069 | ev_check_init (&check, check_cb); |
3571 | ev_check_start (EV_DEFAULT_ &check); |
4070 | ev_check_start (EV_DEFAULT_ &check); |
3572 | ev_loop (EV_DEFAULT_ 0); |
4071 | ev_run (EV_DEFAULT_ 0); |
3573 | |
4072 | |
3574 | =head1 EMBEDDING |
4073 | =head1 EMBEDDING |
3575 | |
4074 | |
3576 | Libev can (and often is) directly embedded into host |
4075 | Libev can (and often is) directly embedded into host |
3577 | applications. Examples of applications that embed it include the Deliantra |
4076 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3668 | to a compiled library. All other symbols change the ABI, which means all |
4167 | to a compiled library. All other symbols change the ABI, which means all |
3669 | users of libev and the libev code itself must be compiled with compatible |
4168 | users of libev and the libev code itself must be compiled with compatible |
3670 | settings. |
4169 | settings. |
3671 | |
4170 | |
3672 | =over 4 |
4171 | =over 4 |
|
|
4172 | |
|
|
4173 | =item EV_COMPAT3 (h) |
|
|
4174 | |
|
|
4175 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4176 | release of libev comes with wrappers for the functions and symbols that |
|
|
4177 | have been renamed between libev version 3 and 4. |
|
|
4178 | |
|
|
4179 | You can disable these wrappers (to test compatibility with future |
|
|
4180 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4181 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4182 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4183 | typedef in that case. |
|
|
4184 | |
|
|
4185 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4186 | and in some even more future version the compatibility code will be |
|
|
4187 | removed completely. |
3673 | |
4188 | |
3674 | =item EV_STANDALONE (h) |
4189 | =item EV_STANDALONE (h) |
3675 | |
4190 | |
3676 | Must always be C<1> if you do not use autoconf configuration, which |
4191 | Must always be C<1> if you do not use autoconf configuration, which |
3677 | keeps libev from including F<config.h>, and it also defines dummy |
4192 | keeps libev from including F<config.h>, and it also defines dummy |
… | |
… | |
4027 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4542 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4028 | will be C<0>. |
4543 | will be C<0>. |
4029 | |
4544 | |
4030 | =item EV_VERIFY |
4545 | =item EV_VERIFY |
4031 | |
4546 | |
4032 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4547 | Controls how much internal verification (see C<ev_verify ()>) will |
4033 | be done: If set to C<0>, no internal verification code will be compiled |
4548 | be done: If set to C<0>, no internal verification code will be compiled |
4034 | in. If set to C<1>, then verification code will be compiled in, but not |
4549 | in. If set to C<1>, then verification code will be compiled in, but not |
4035 | called. If set to C<2>, then the internal verification code will be |
4550 | called. If set to C<2>, then the internal verification code will be |
4036 | called once per loop, which can slow down libev. If set to C<3>, then the |
4551 | called once per loop, which can slow down libev. If set to C<3>, then the |
4037 | verification code will be called very frequently, which will slow down |
4552 | verification code will be called very frequently, which will slow down |
… | |
… | |
4120 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4635 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4121 | |
4636 | |
4122 | #include "ev_cpp.h" |
4637 | #include "ev_cpp.h" |
4123 | #include "ev.c" |
4638 | #include "ev.c" |
4124 | |
4639 | |
4125 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4640 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4126 | |
4641 | |
4127 | =head2 THREADS AND COROUTINES |
4642 | =head2 THREADS AND COROUTINES |
4128 | |
4643 | |
4129 | =head3 THREADS |
4644 | =head3 THREADS |
4130 | |
4645 | |
… | |
… | |
4181 | default loop and triggering an C<ev_async> watcher from the default loop |
4696 | default loop and triggering an C<ev_async> watcher from the default loop |
4182 | watcher callback into the event loop interested in the signal. |
4697 | watcher callback into the event loop interested in the signal. |
4183 | |
4698 | |
4184 | =back |
4699 | =back |
4185 | |
4700 | |
4186 | =head4 THREAD LOCKING EXAMPLE |
4701 | See also L<THREAD LOCKING EXAMPLE>. |
4187 | |
|
|
4188 | Here is a fictitious example of how to run an event loop in a different |
|
|
4189 | thread than where callbacks are being invoked and watchers are |
|
|
4190 | created/added/removed. |
|
|
4191 | |
|
|
4192 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4193 | which uses exactly this technique (which is suited for many high-level |
|
|
4194 | languages). |
|
|
4195 | |
|
|
4196 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4197 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4198 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4199 | |
|
|
4200 | First, you need to associate some data with the event loop: |
|
|
4201 | |
|
|
4202 | typedef struct { |
|
|
4203 | mutex_t lock; /* global loop lock */ |
|
|
4204 | ev_async async_w; |
|
|
4205 | thread_t tid; |
|
|
4206 | cond_t invoke_cv; |
|
|
4207 | } userdata; |
|
|
4208 | |
|
|
4209 | void prepare_loop (EV_P) |
|
|
4210 | { |
|
|
4211 | // for simplicity, we use a static userdata struct. |
|
|
4212 | static userdata u; |
|
|
4213 | |
|
|
4214 | ev_async_init (&u->async_w, async_cb); |
|
|
4215 | ev_async_start (EV_A_ &u->async_w); |
|
|
4216 | |
|
|
4217 | pthread_mutex_init (&u->lock, 0); |
|
|
4218 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4219 | |
|
|
4220 | // now associate this with the loop |
|
|
4221 | ev_set_userdata (EV_A_ u); |
|
|
4222 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4223 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4224 | |
|
|
4225 | // then create the thread running ev_loop |
|
|
4226 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4227 | } |
|
|
4228 | |
|
|
4229 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4230 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4231 | that might have been added: |
|
|
4232 | |
|
|
4233 | static void |
|
|
4234 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4235 | { |
|
|
4236 | // just used for the side effects |
|
|
4237 | } |
|
|
4238 | |
|
|
4239 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4240 | protecting the loop data, respectively. |
|
|
4241 | |
|
|
4242 | static void |
|
|
4243 | l_release (EV_P) |
|
|
4244 | { |
|
|
4245 | userdata *u = ev_userdata (EV_A); |
|
|
4246 | pthread_mutex_unlock (&u->lock); |
|
|
4247 | } |
|
|
4248 | |
|
|
4249 | static void |
|
|
4250 | l_acquire (EV_P) |
|
|
4251 | { |
|
|
4252 | userdata *u = ev_userdata (EV_A); |
|
|
4253 | pthread_mutex_lock (&u->lock); |
|
|
4254 | } |
|
|
4255 | |
|
|
4256 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4257 | into C<ev_loop>: |
|
|
4258 | |
|
|
4259 | void * |
|
|
4260 | l_run (void *thr_arg) |
|
|
4261 | { |
|
|
4262 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4263 | |
|
|
4264 | l_acquire (EV_A); |
|
|
4265 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4266 | ev_loop (EV_A_ 0); |
|
|
4267 | l_release (EV_A); |
|
|
4268 | |
|
|
4269 | return 0; |
|
|
4270 | } |
|
|
4271 | |
|
|
4272 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4273 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4274 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4275 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4276 | and b) skipping inter-thread-communication when there are no pending |
|
|
4277 | watchers is very beneficial): |
|
|
4278 | |
|
|
4279 | static void |
|
|
4280 | l_invoke (EV_P) |
|
|
4281 | { |
|
|
4282 | userdata *u = ev_userdata (EV_A); |
|
|
4283 | |
|
|
4284 | while (ev_pending_count (EV_A)) |
|
|
4285 | { |
|
|
4286 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4287 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4288 | } |
|
|
4289 | } |
|
|
4290 | |
|
|
4291 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4292 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4293 | thread to continue: |
|
|
4294 | |
|
|
4295 | static void |
|
|
4296 | real_invoke_pending (EV_P) |
|
|
4297 | { |
|
|
4298 | userdata *u = ev_userdata (EV_A); |
|
|
4299 | |
|
|
4300 | pthread_mutex_lock (&u->lock); |
|
|
4301 | ev_invoke_pending (EV_A); |
|
|
4302 | pthread_cond_signal (&u->invoke_cv); |
|
|
4303 | pthread_mutex_unlock (&u->lock); |
|
|
4304 | } |
|
|
4305 | |
|
|
4306 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4307 | event loop, you will now have to lock: |
|
|
4308 | |
|
|
4309 | ev_timer timeout_watcher; |
|
|
4310 | userdata *u = ev_userdata (EV_A); |
|
|
4311 | |
|
|
4312 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4313 | |
|
|
4314 | pthread_mutex_lock (&u->lock); |
|
|
4315 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4316 | ev_async_send (EV_A_ &u->async_w); |
|
|
4317 | pthread_mutex_unlock (&u->lock); |
|
|
4318 | |
|
|
4319 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4320 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4321 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4322 | watchers in the next event loop iteration. |
|
|
4323 | |
4702 | |
4324 | =head3 COROUTINES |
4703 | =head3 COROUTINES |
4325 | |
4704 | |
4326 | Libev is very accommodating to coroutines ("cooperative threads"): |
4705 | Libev is very accommodating to coroutines ("cooperative threads"): |
4327 | libev fully supports nesting calls to its functions from different |
4706 | libev fully supports nesting calls to its functions from different |
4328 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4707 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
4329 | different coroutines, and switch freely between both coroutines running |
4708 | different coroutines, and switch freely between both coroutines running |
4330 | the loop, as long as you don't confuse yourself). The only exception is |
4709 | the loop, as long as you don't confuse yourself). The only exception is |
4331 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4710 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4332 | |
4711 | |
4333 | Care has been taken to ensure that libev does not keep local state inside |
4712 | Care has been taken to ensure that libev does not keep local state inside |
4334 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4713 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
4335 | they do not call any callbacks. |
4714 | they do not call any callbacks. |
4336 | |
4715 | |
4337 | =head2 COMPILER WARNINGS |
4716 | =head2 COMPILER WARNINGS |
4338 | |
4717 | |
4339 | Depending on your compiler and compiler settings, you might get no or a |
4718 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
4399 | =head1 PORTABILITY NOTES |
4778 | =head1 PORTABILITY NOTES |
4400 | |
4779 | |
4401 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
4780 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
4402 | |
4781 | |
4403 | GNU/Linux is the only common platform that supports 64 bit file/large file |
4782 | GNU/Linux is the only common platform that supports 64 bit file/large file |
4404 | interfaces but disables them by default. |
4783 | interfaces but I<disables> them by default. |
4405 | |
4784 | |
4406 | That means that libev compiled in the default environment doesn't support |
4785 | That means that libev compiled in the default environment doesn't support |
4407 | files larger than 2GiB, which mainly affects C<ev_stat> watchers. |
4786 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
4408 | |
4787 | |
4409 | Unfortunately, many programs try to work around this GNU/Linux issue |
4788 | Unfortunately, many programs try to work around this GNU/Linux issue |
4410 | by enabling the large file API, which makes them incompatible with the |
4789 | by enabling the large file API, which makes them incompatible with the |
4411 | standard libev compiled for their system. |
4790 | standard libev compiled for their system. |
4412 | |
4791 | |
… | |
… | |
4415 | i.e. all programs not using special compile switches. |
4794 | i.e. all programs not using special compile switches. |
4416 | |
4795 | |
4417 | =head2 OS/X AND DARWIN BUGS |
4796 | =head2 OS/X AND DARWIN BUGS |
4418 | |
4797 | |
4419 | The whole thing is a bug if you ask me - basically any system interface |
4798 | The whole thing is a bug if you ask me - basically any system interface |
4420 | you touch is broken, whether it is locales, poll, kqueue or even their |
4799 | you touch is broken, whether it is locales, poll, kqueue or even the |
4421 | OpenGL drivers. |
4800 | OpenGL drivers. |
4422 | |
4801 | |
4423 | =over 4 |
4802 | =head3 C<kqueue> is buggy |
4424 | |
|
|
4425 | =item KQUEUE IS BUGGY |
|
|
4426 | |
4803 | |
4427 | The kqueue syscall is broken in all known versions - most versions support |
4804 | The kqueue syscall is broken in all known versions - most versions support |
4428 | only sockets, many support pipes. |
4805 | only sockets, many support pipes. |
4429 | |
4806 | |
4430 | =item POLL IS BUGGY |
4807 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4808 | rotten platform, but of course you can still ask for it when creating a |
|
|
4809 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4810 | probably going to work well. |
|
|
4811 | |
|
|
4812 | =head3 C<poll> is buggy |
4431 | |
4813 | |
4432 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
4814 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
4433 | implementation by something calling C<kqueue> internally around the 10.5.6 |
4815 | implementation by something calling C<kqueue> internally around the 10.5.6 |
4434 | release, so now C<kqueue> I<and> C<poll> are broken. |
4816 | release, so now C<kqueue> I<and> C<poll> are broken. |
4435 | |
4817 | |
4436 | Libev tries to work around this by neither using C<kqueue> nor C<poll> by |
4818 | Libev tries to work around this by not using C<poll> by default on |
4437 | default on this rotten platform, but of course you cna still ask for them |
4819 | this rotten platform, but of course you can still ask for it when creating |
4438 | when creating a loop. |
4820 | a loop. |
4439 | |
4821 | |
4440 | =item SELECT IS BUGGY |
4822 | =head3 C<select> is buggy |
4441 | |
4823 | |
4442 | All that's left is C<select>, and of course Apple found a way to fuck this |
4824 | All that's left is C<select>, and of course Apple found a way to fuck this |
4443 | one up as well: On OS/X, C<select> actively limits the number of file |
4825 | one up as well: On OS/X, C<select> actively limits the number of file |
4444 | descriptors you can pass in to 1024 - your program suddenyl crashes when |
4826 | descriptors you can pass in to 1024 - your program suddenly crashes when |
4445 | you use more. |
4827 | you use more. |
4446 | |
4828 | |
4447 | There is an undocumented "workaround" for this - defining |
4829 | There is an undocumented "workaround" for this - defining |
4448 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
4830 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
4449 | work on OS/X. |
4831 | work on OS/X. |
4450 | |
4832 | |
4451 | =back |
|
|
4452 | |
|
|
4453 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
4833 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
4454 | |
4834 | |
4455 | =over 4 |
|
|
4456 | |
|
|
4457 | =item C<errno> reentrancy |
4835 | =head3 C<errno> reentrancy |
4458 | |
4836 | |
4459 | The default compile environment on Solaris is unfortunately so |
4837 | The default compile environment on Solaris is unfortunately so |
4460 | thread-unsafe that you can't even use components/libraries compiled |
4838 | thread-unsafe that you can't even use components/libraries compiled |
4461 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
4839 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
4462 | isn't defined by default. |
4840 | defined by default. A valid, if stupid, implementation choice. |
4463 | |
4841 | |
4464 | If you want to use libev in threaded environments you have to make sure |
4842 | If you want to use libev in threaded environments you have to make sure |
4465 | it's compiled with C<_REENTRANT> defined. |
4843 | it's compiled with C<_REENTRANT> defined. |
4466 | |
4844 | |
4467 | =item Event Port Backend |
4845 | =head3 Event port backend |
4468 | |
4846 | |
4469 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
4847 | The scalable event interface for Solaris is called "event |
4470 | this mechanism is very buggy. If you run into high CPU usage, your program |
4848 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4849 | releases. If you run into high CPU usage, your program freezes or you get |
4471 | freezes or you get a large number of spurious wakeups, make sure you have |
4850 | a large number of spurious wakeups, make sure you have all the relevant |
4472 | all the relevant and latest kernel patches applied. No, I don't know which |
4851 | and latest kernel patches applied. No, I don't know which ones, but there |
4473 | ones, but there are multiple ones. |
4852 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4853 | great. |
4474 | |
4854 | |
4475 | If you can't get it to work, you can try running the program with |
4855 | If you can't get it to work, you can try running the program by setting |
4476 | C<LIBEV_FLAGS=3> to only allow C<poll> and C<select> backends. |
4856 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
4477 | |
4857 | C<select> backends. |
4478 | =back |
|
|
4479 | |
4858 | |
4480 | =head2 AIX POLL BUG |
4859 | =head2 AIX POLL BUG |
4481 | |
4860 | |
4482 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
4861 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
4483 | this by trying to avoid the poll backend altogether (i.e. it's not even |
4862 | this by trying to avoid the poll backend altogether (i.e. it's not even |
4484 | compiled in), which normally isn't a big problem as C<select> works fine |
4863 | compiled in), which normally isn't a big problem as C<select> works fine |
4485 | with large bitsets, and AIX is dead anyway. |
4864 | with large bitsets on AIX, and AIX is dead anyway. |
4486 | |
4865 | |
4487 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4866 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4867 | |
|
|
4868 | =head3 General issues |
4488 | |
4869 | |
4489 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4870 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4490 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4871 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4491 | model. Libev still offers limited functionality on this platform in |
4872 | model. Libev still offers limited functionality on this platform in |
4492 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4873 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4493 | descriptors. This only applies when using Win32 natively, not when using |
4874 | descriptors. This only applies when using Win32 natively, not when using |
4494 | e.g. cygwin. |
4875 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4876 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4877 | environment. |
4495 | |
4878 | |
4496 | Lifting these limitations would basically require the full |
4879 | Lifting these limitations would basically require the full |
4497 | re-implementation of the I/O system. If you are into these kinds of |
4880 | re-implementation of the I/O system. If you are into this kind of thing, |
4498 | things, then note that glib does exactly that for you in a very portable |
4881 | then note that glib does exactly that for you in a very portable way (note |
4499 | way (note also that glib is the slowest event library known to man). |
4882 | also that glib is the slowest event library known to man). |
4500 | |
4883 | |
4501 | There is no supported compilation method available on windows except |
4884 | There is no supported compilation method available on windows except |
4502 | embedding it into other applications. |
4885 | embedding it into other applications. |
4503 | |
4886 | |
4504 | Sensible signal handling is officially unsupported by Microsoft - libev |
4887 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4532 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4915 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4533 | |
4916 | |
4534 | #include "evwrap.h" |
4917 | #include "evwrap.h" |
4535 | #include "ev.c" |
4918 | #include "ev.c" |
4536 | |
4919 | |
4537 | =over 4 |
|
|
4538 | |
|
|
4539 | =item The winsocket select function |
4920 | =head3 The winsocket C<select> function |
4540 | |
4921 | |
4541 | The winsocket C<select> function doesn't follow POSIX in that it |
4922 | The winsocket C<select> function doesn't follow POSIX in that it |
4542 | requires socket I<handles> and not socket I<file descriptors> (it is |
4923 | requires socket I<handles> and not socket I<file descriptors> (it is |
4543 | also extremely buggy). This makes select very inefficient, and also |
4924 | also extremely buggy). This makes select very inefficient, and also |
4544 | requires a mapping from file descriptors to socket handles (the Microsoft |
4925 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4553 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4934 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4554 | |
4935 | |
4555 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4936 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4556 | complexity in the O(n²) range when using win32. |
4937 | complexity in the O(n²) range when using win32. |
4557 | |
4938 | |
4558 | =item Limited number of file descriptors |
4939 | =head3 Limited number of file descriptors |
4559 | |
4940 | |
4560 | Windows has numerous arbitrary (and low) limits on things. |
4941 | Windows has numerous arbitrary (and low) limits on things. |
4561 | |
4942 | |
4562 | Early versions of winsocket's select only supported waiting for a maximum |
4943 | Early versions of winsocket's select only supported waiting for a maximum |
4563 | of C<64> handles (probably owning to the fact that all windows kernels |
4944 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4578 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4959 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4579 | (depending on windows version and/or the phase of the moon). To get more, |
4960 | (depending on windows version and/or the phase of the moon). To get more, |
4580 | you need to wrap all I/O functions and provide your own fd management, but |
4961 | you need to wrap all I/O functions and provide your own fd management, but |
4581 | the cost of calling select (O(n²)) will likely make this unworkable. |
4962 | the cost of calling select (O(n²)) will likely make this unworkable. |
4582 | |
4963 | |
4583 | =back |
|
|
4584 | |
|
|
4585 | =head2 PORTABILITY REQUIREMENTS |
4964 | =head2 PORTABILITY REQUIREMENTS |
4586 | |
4965 | |
4587 | In addition to a working ISO-C implementation and of course the |
4966 | In addition to a working ISO-C implementation and of course the |
4588 | backend-specific APIs, libev relies on a few additional extensions: |
4967 | backend-specific APIs, libev relies on a few additional extensions: |
4589 | |
4968 | |
… | |
… | |
4595 | Libev assumes not only that all watcher pointers have the same internal |
4974 | Libev assumes not only that all watcher pointers have the same internal |
4596 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4975 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4597 | assumes that the same (machine) code can be used to call any watcher |
4976 | assumes that the same (machine) code can be used to call any watcher |
4598 | callback: The watcher callbacks have different type signatures, but libev |
4977 | callback: The watcher callbacks have different type signatures, but libev |
4599 | calls them using an C<ev_watcher *> internally. |
4978 | calls them using an C<ev_watcher *> internally. |
|
|
4979 | |
|
|
4980 | =item pointer accesses must be thread-atomic |
|
|
4981 | |
|
|
4982 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4983 | writable in one piece - this is the case on all current architectures. |
4600 | |
4984 | |
4601 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4985 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4602 | |
4986 | |
4603 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4987 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4604 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4988 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
4627 | watchers. |
5011 | watchers. |
4628 | |
5012 | |
4629 | =item C<double> must hold a time value in seconds with enough accuracy |
5013 | =item C<double> must hold a time value in seconds with enough accuracy |
4630 | |
5014 | |
4631 | The type C<double> is used to represent timestamps. It is required to |
5015 | The type C<double> is used to represent timestamps. It is required to |
4632 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5016 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4633 | enough for at least into the year 4000. This requirement is fulfilled by |
5017 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5018 | (the design goal for libev). This requirement is overfulfilled by |
4634 | implementations implementing IEEE 754, which is basically all existing |
5019 | implementations using IEEE 754, which is basically all existing ones. With |
4635 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
5020 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
4636 | 2200. |
|
|
4637 | |
5021 | |
4638 | =back |
5022 | =back |
4639 | |
5023 | |
4640 | If you know of other additional requirements drop me a note. |
5024 | If you know of other additional requirements drop me a note. |
4641 | |
5025 | |
… | |
… | |
4711 | =back |
5095 | =back |
4712 | |
5096 | |
4713 | |
5097 | |
4714 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5098 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4715 | |
5099 | |
4716 | The major version 4 introduced some minor incompatible changes to the API. |
5100 | The major version 4 introduced some incompatible changes to the API. |
4717 | |
5101 | |
4718 | At the moment, the C<ev.h> header file tries to implement superficial |
5102 | At the moment, the C<ev.h> header file provides compatibility definitions |
4719 | compatibility, so most programs should still compile. Those might be |
5103 | for all changes, so most programs should still compile. The compatibility |
4720 | removed in later versions of libev, so better update early than late. |
5104 | layer might be removed in later versions of libev, so better update to the |
|
|
5105 | new API early than late. |
4721 | |
5106 | |
4722 | =over 4 |
5107 | =over 4 |
4723 | |
5108 | |
4724 | =item C<ev_loop_count> renamed to C<ev_iteration> |
5109 | =item C<EV_COMPAT3> backwards compatibility mechanism |
4725 | |
5110 | |
4726 | =item C<ev_loop_depth> renamed to C<ev_depth> |
5111 | The backward compatibility mechanism can be controlled by |
|
|
5112 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5113 | section. |
4727 | |
5114 | |
4728 | =item C<ev_loop_verify> renamed to C<ev_verify> |
5115 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5116 | |
|
|
5117 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5118 | |
|
|
5119 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5120 | ev_loop_fork (EV_DEFAULT); |
|
|
5121 | |
|
|
5122 | =item function/symbol renames |
|
|
5123 | |
|
|
5124 | A number of functions and symbols have been renamed: |
|
|
5125 | |
|
|
5126 | ev_loop => ev_run |
|
|
5127 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5128 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5129 | |
|
|
5130 | ev_unloop => ev_break |
|
|
5131 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5132 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5133 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5134 | |
|
|
5135 | EV_TIMEOUT => EV_TIMER |
|
|
5136 | |
|
|
5137 | ev_loop_count => ev_iteration |
|
|
5138 | ev_loop_depth => ev_depth |
|
|
5139 | ev_loop_verify => ev_verify |
4729 | |
5140 | |
4730 | Most functions working on C<struct ev_loop> objects don't have an |
5141 | Most functions working on C<struct ev_loop> objects don't have an |
4731 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
5142 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5143 | associated constants have been renamed to not collide with the C<struct |
|
|
5144 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5145 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4732 | still called C<ev_loop_fork> because it would otherwise clash with the |
5146 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4733 | C<ev_fork> typedef. |
5147 | typedef. |
4734 | |
|
|
4735 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4736 | |
|
|
4737 | This is a simple rename - all other watcher types use their name |
|
|
4738 | as revents flag, and now C<ev_timer> does, too. |
|
|
4739 | |
|
|
4740 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4741 | and continue to be present for the foreseeable future, so this is mostly a |
|
|
4742 | documentation change. |
|
|
4743 | |
5148 | |
4744 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5149 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4745 | |
5150 | |
4746 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5151 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4747 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5152 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
… | |
… | |
4754 | |
5159 | |
4755 | =over 4 |
5160 | =over 4 |
4756 | |
5161 | |
4757 | =item active |
5162 | =item active |
4758 | |
5163 | |
4759 | A watcher is active as long as it has been started (has been attached to |
5164 | A watcher is active as long as it has been started and not yet stopped. |
4760 | an event loop) but not yet stopped (disassociated from the event loop). |
5165 | See L<WATCHER STATES> for details. |
4761 | |
5166 | |
4762 | =item application |
5167 | =item application |
4763 | |
5168 | |
4764 | In this document, an application is whatever is using libev. |
5169 | In this document, an application is whatever is using libev. |
|
|
5170 | |
|
|
5171 | =item backend |
|
|
5172 | |
|
|
5173 | The part of the code dealing with the operating system interfaces. |
4765 | |
5174 | |
4766 | =item callback |
5175 | =item callback |
4767 | |
5176 | |
4768 | The address of a function that is called when some event has been |
5177 | The address of a function that is called when some event has been |
4769 | detected. Callbacks are being passed the event loop, the watcher that |
5178 | detected. Callbacks are being passed the event loop, the watcher that |
4770 | received the event, and the actual event bitset. |
5179 | received the event, and the actual event bitset. |
4771 | |
5180 | |
4772 | =item callback invocation |
5181 | =item callback/watcher invocation |
4773 | |
5182 | |
4774 | The act of calling the callback associated with a watcher. |
5183 | The act of calling the callback associated with a watcher. |
4775 | |
5184 | |
4776 | =item event |
5185 | =item event |
4777 | |
5186 | |
… | |
… | |
4796 | The model used to describe how an event loop handles and processes |
5205 | The model used to describe how an event loop handles and processes |
4797 | watchers and events. |
5206 | watchers and events. |
4798 | |
5207 | |
4799 | =item pending |
5208 | =item pending |
4800 | |
5209 | |
4801 | A watcher is pending as soon as the corresponding event has been detected, |
5210 | A watcher is pending as soon as the corresponding event has been |
4802 | and stops being pending as soon as the watcher will be invoked or its |
5211 | detected. See L<WATCHER STATES> for details. |
4803 | pending status is explicitly cleared by the application. |
|
|
4804 | |
|
|
4805 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4806 | its pending status. |
|
|
4807 | |
5212 | |
4808 | =item real time |
5213 | =item real time |
4809 | |
5214 | |
4810 | The physical time that is observed. It is apparently strictly monotonic :) |
5215 | The physical time that is observed. It is apparently strictly monotonic :) |
4811 | |
5216 | |
… | |
… | |
4818 | =item watcher |
5223 | =item watcher |
4819 | |
5224 | |
4820 | A data structure that describes interest in certain events. Watchers need |
5225 | A data structure that describes interest in certain events. Watchers need |
4821 | to be started (attached to an event loop) before they can receive events. |
5226 | to be started (attached to an event loop) before they can receive events. |
4822 | |
5227 | |
4823 | =item watcher invocation |
|
|
4824 | |
|
|
4825 | The act of calling the callback associated with a watcher. |
|
|
4826 | |
|
|
4827 | =back |
5228 | =back |
4828 | |
5229 | |
4829 | =head1 AUTHOR |
5230 | =head1 AUTHOR |
4830 | |
5231 | |
4831 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5232 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5233 | Magnusson and Emanuele Giaquinta. |
4832 | |
5234 | |