… | |
… | |
43 | |
43 | |
44 | int |
44 | int |
45 | main (void) |
45 | main (void) |
46 | { |
46 | { |
47 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
49 | |
50 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
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 |
175 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
176 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
177 | |
192 | |
178 | =item int ev_version_major () |
193 | =item int ev_version_major () |
179 | |
194 | |
180 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
181 | |
196 | |
… | |
… | |
192 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
193 | compatible to older versions, so a larger minor version alone is usually |
208 | compatible to older versions, so a larger minor version alone is usually |
194 | not a problem. |
209 | not a problem. |
195 | |
210 | |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
211 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | version (note, however, that this will not detect ABI mismatches :). |
212 | version (note, however, that this will not detect other ABI mismatches, |
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213 | such as LFS or reentrancy). |
198 | |
214 | |
199 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
200 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | |
218 | |
… | |
… | |
213 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
214 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
215 | |
231 | |
216 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
217 | |
233 | |
218 | Return the set of all backends compiled into this binary of libev and also |
234 | 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 |
235 | also recommended for this platform, meaning it will work for most file |
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236 | 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 |
237 | 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 |
238 | 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 |
239 | 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. |
240 | probe for if you specify no backends explicitly. |
224 | |
241 | |
225 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
226 | |
243 | |
227 | Returns the set of backends that are embeddable in other event loops. This |
244 | Returns the set of backends that are embeddable in other event loops. This |
228 | is the theoretical, all-platform, value. To find which backends |
245 | 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 |
246 | current system. To find which embeddable backends might be supported on |
230 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
231 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
232 | |
249 | |
233 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
234 | |
251 | |
235 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
236 | |
253 | |
237 | Sets the allocation function to use (the prototype is similar - the |
254 | 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 |
255 | 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 |
256 | 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 |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
266 | } |
283 | } |
267 | |
284 | |
268 | ... |
285 | ... |
269 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
270 | |
287 | |
271 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
272 | |
289 | |
273 | Set the callback function to call on a retryable system call error (such |
290 | 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 |
291 | as failed select, poll, epoll_wait). The message is a printable string |
275 | indicating the system call or subsystem causing the problem. If this |
292 | 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 |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
288 | } |
305 | } |
289 | |
306 | |
290 | ... |
307 | ... |
291 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
292 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
293 | =back |
323 | =back |
294 | |
324 | |
295 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
296 | |
326 | |
297 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
298 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
299 | libev 3 had an C<ev_loop> function colliding with the struct name). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
300 | |
330 | |
301 | The library knows two types of such loops, the I<default> loop, which |
331 | The library knows two types of such loops, the I<default> loop, which |
302 | supports signals and child events, and dynamically created event loops |
332 | supports child process events, and dynamically created event loops which |
303 | which do not. |
333 | do not. |
304 | |
334 | |
305 | =over 4 |
335 | =over 4 |
306 | |
336 | |
307 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
308 | |
338 | |
309 | This will initialise the default event loop if it hasn't been initialised |
339 | 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 |
340 | 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 |
341 | 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). |
342 | C<ev_loop_new>. |
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343 | |
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344 | If the default loop is already initialised then this function simply |
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345 | returns it (and ignores the flags. If that is troubling you, check |
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346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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347 | flags, which should almost always be C<0>, unless the caller is also the |
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348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
313 | |
349 | |
314 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
315 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
316 | |
352 | |
317 | Note that this function is I<not> thread-safe, so if you want to use it |
353 | 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, |
354 | from multiple threads, you have to employ some kind of mutex (note also |
319 | as loops cannot be shared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
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356 | threads anyway). |
320 | |
357 | |
321 | The default loop is the only loop that can handle C<ev_signal> and |
358 | 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 |
359 | 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 |
360 | 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 |
361 | 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 |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
326 | C<ev_default_init>. |
363 | |
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364 | Example: This is the most typical usage. |
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365 | |
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366 | if (!ev_default_loop (0)) |
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367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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368 | |
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369 | Example: Restrict libev to the select and poll backends, and do not allow |
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370 | environment settings to be taken into account: |
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371 | |
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372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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373 | |
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374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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375 | |
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376 | This will create and initialise a new event loop object. If the loop |
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377 | could not be initialised, returns false. |
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378 | |
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379 | This function is thread-safe, and one common way to use libev with |
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380 | threads is indeed to create one loop per thread, and using the default |
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381 | loop in the "main" or "initial" thread. |
327 | |
382 | |
328 | The flags argument can be used to specify special behaviour or specific |
383 | 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>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
330 | |
385 | |
331 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
366 | environment variable. |
421 | environment variable. |
367 | |
422 | |
368 | =item C<EVFLAG_NOINOTIFY> |
423 | =item C<EVFLAG_NOINOTIFY> |
369 | |
424 | |
370 | When this flag is specified, then libev will not attempt to use the |
425 | 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 |
426 | 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 |
427 | 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. |
428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
429 | |
375 | =item C<EVFLAG_SIGNALFD> |
430 | =item C<EVFLAG_SIGNALFD> |
376 | |
431 | |
377 | When this flag is specified, then libev will attempt to use the |
432 | 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 |
433 | 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 |
434 | 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 |
435 | 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 |
436 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
437 | threads that are not interested in handling them. |
383 | |
438 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
439 | 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 |
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
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442 | |
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443 | =item C<EVFLAG_NOSIGMASK> |
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444 | |
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445 | When this flag is specified, then libev will avoid to modify the signal |
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446 | mask. Specifically, this means you have to make sure signals are unblocked |
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447 | when you want to receive them. |
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448 | |
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449 | This behaviour is useful when you want to do your own signal handling, or |
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450 | want to handle signals only in specific threads and want to avoid libev |
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451 | unblocking the signals. |
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452 | |
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453 | It's also required by POSIX in a threaded program, as libev calls |
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454 | C<sigprocmask>, whose behaviour is officially unspecified. |
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455 | |
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456 | This flag's behaviour will become the default in future versions of libev. |
387 | |
457 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
459 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | 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, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
420 | |
490 | |
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
422 | kernels). |
492 | kernels). |
423 | |
493 | |
424 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
425 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
427 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
428 | |
498 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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503 | returning before the timeout value, resulting in additional iterations |
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|
504 | (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 |
505 | 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 |
506 | 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 |
507 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
508 | and is of course hard to detect. |
437 | |
509 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
440 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
441 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
443 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
444 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
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517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
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518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
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519 | because epoll returns immediately despite a nonzero timeout. And last |
445 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
446 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
|
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522 | |
|
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523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
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524 | cobbled together in a hurry, no thought to design or interaction with |
|
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525 | others. Oh, the pain, will it ever stop... |
447 | |
526 | |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
449 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
450 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
517 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
518 | |
597 | |
519 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
520 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
521 | |
600 | |
522 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
523 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
524 | blocking when no data (or space) is available. |
|
|
525 | |
|
|
526 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
527 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
528 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
529 | might perform better. |
604 | might perform better. |
530 | |
605 | |
531 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
532 | notifications, this backend actually performed fully to specification |
|
|
533 | in all tests and is fully embeddable, which is a rare feat among the |
607 | specification in all tests and is fully embeddable, which is a rare feat |
534 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
535 | |
620 | |
536 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
537 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
538 | |
623 | |
539 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
540 | |
625 | |
541 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
542 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
543 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
544 | |
629 | |
545 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
546 | |
639 | |
547 | =back |
640 | =back |
548 | |
641 | |
549 | If one or more of the backend flags are or'ed into the flags value, |
642 | If one or more of the backend flags are or'ed into the flags value, |
550 | then only these backends will be tried (in the reverse order as listed |
643 | then only these backends will be tried (in the reverse order as listed |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
552 | ()> will be tried. |
645 | ()> will be tried. |
553 | |
646 | |
554 | Example: This is the most typical usage. |
|
|
555 | |
|
|
556 | if (!ev_default_loop (0)) |
|
|
557 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
558 | |
|
|
559 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
560 | environment settings to be taken into account: |
|
|
561 | |
|
|
562 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
563 | |
|
|
564 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
565 | used if available (warning, breaks stuff, best use only with your own |
|
|
566 | private event loop and only if you know the OS supports your types of |
|
|
567 | fds): |
|
|
568 | |
|
|
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
570 | |
|
|
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
572 | |
|
|
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
574 | always distinct from the default loop. |
|
|
575 | |
|
|
576 | Note that this function I<is> thread-safe, and one common way to use |
|
|
577 | libev with threads is indeed to create one loop per thread, and using the |
|
|
578 | default loop in the "main" or "initial" thread. |
|
|
579 | |
|
|
580 | Example: Try to create a event loop that uses epoll and nothing else. |
647 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
648 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
650 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
652 | |
|
|
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
654 | used if available. |
|
|
655 | |
|
|
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
657 | |
586 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
587 | |
659 | |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
660 | Destroys an event loop object (frees all memory and kernel state |
589 | of the active event watchers will be stopped in the normal sense, so |
661 | etc.). None of the active event watchers will be stopped in the normal |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
664 | calling this function, or cope with the fact afterwards (which is usually |
593 | can just ignore the watchers and/or C<free ()> them for example). |
665 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
666 | for example). |
594 | |
667 | |
595 | Note that certain global state, such as signal state (and installed signal |
668 | Note that certain global state, such as signal state (and installed signal |
596 | handlers), will not be freed by this function, and related watchers (such |
669 | handlers), will not be freed by this function, and related watchers (such |
597 | as signal and child watchers) would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
598 | |
671 | |
599 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
600 | rare occasion where you really need to free e.g. the signal handling |
673 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
674 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
675 | |
|
|
676 | Note that it is not advisable to call this function on the default loop |
|
|
677 | except in the rare occasion where you really need to free its resources. |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
679 | and C<ev_loop_destroy>. |
603 | |
680 | |
604 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
605 | |
682 | |
606 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
607 | earlier call to C<ev_loop_new>. |
|
|
608 | |
|
|
609 | =item ev_default_fork () |
|
|
610 | |
|
|
611 | This function sets a flag that causes subsequent C<ev_run> iterations |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
612 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
613 | name, you can call it anytime, but it makes most sense after forking, in |
685 | name, you can call it anytime, but it makes most sense after forking, in |
614 | the child process (or both child and parent, but that again makes little |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
615 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
616 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
617 | |
688 | |
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
621 | during fork. |
692 | during fork. |
… | |
… | |
626 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
697 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
627 | difference, but libev will usually detect this case on its own and do a |
698 | difference, but libev will usually detect this case on its own and do a |
628 | costly reset of the backend). |
699 | costly reset of the backend). |
629 | |
700 | |
630 | The function itself is quite fast and it's usually not a problem to call |
701 | The function itself is quite fast and it's usually not a problem to call |
631 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
632 | quite nicely into a call to C<pthread_atfork>: |
|
|
633 | |
703 | |
|
|
704 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
705 | using pthreads. |
|
|
706 | |
|
|
707 | static void |
|
|
708 | post_fork_child (void) |
|
|
709 | { |
|
|
710 | ev_loop_fork (EV_DEFAULT); |
|
|
711 | } |
|
|
712 | |
|
|
713 | ... |
634 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
635 | |
|
|
636 | =item ev_loop_fork (loop) |
|
|
637 | |
|
|
638 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
639 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
640 | after fork that you want to re-use in the child, and how you keep track of |
|
|
641 | them is entirely your own problem. |
|
|
642 | |
715 | |
643 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
644 | |
717 | |
645 | Returns true when the given loop is, in fact, the default loop, and false |
718 | Returns true when the given loop is, in fact, the default loop, and false |
646 | otherwise. |
719 | otherwise. |
… | |
… | |
657 | prepare and check phases. |
730 | prepare and check phases. |
658 | |
731 | |
659 | =item unsigned int ev_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
660 | |
733 | |
661 | Returns the number of times C<ev_run> was entered minus the number of |
734 | Returns the number of times C<ev_run> was entered minus the number of |
662 | times C<ev_run> was exited, in other words, the recursion depth. |
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
663 | |
736 | |
664 | Outside C<ev_run>, this number is zero. In a callback, this number is |
737 | Outside C<ev_run>, this number is zero. In a callback, this number is |
665 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
666 | in which case it is higher. |
739 | in which case it is higher. |
667 | |
740 | |
668 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
669 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
670 | ungentleman-like behaviour unless it's really convenient. |
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
671 | |
745 | |
672 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
673 | |
747 | |
674 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
675 | use. |
749 | use. |
… | |
… | |
737 | finished (especially in interactive programs), but having a program |
811 | finished (especially in interactive programs), but having a program |
738 | that automatically loops as long as it has to and no longer by virtue |
812 | that automatically loops as long as it has to and no longer by virtue |
739 | of relying on its watchers stopping correctly, that is truly a thing of |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
740 | beauty. |
814 | beauty. |
741 | |
815 | |
|
|
816 | This function is also I<mostly> exception-safe - you can break out of |
|
|
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
820 | |
742 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
743 | those events and any already outstanding ones, but will not wait and |
822 | those events and any already outstanding ones, but will not wait and |
744 | block your process in case there are no events and will return after one |
823 | block your process in case there are no events and will return after one |
745 | iteration of the loop. This is sometimes useful to poll and handle new |
824 | iteration of the loop. This is sometimes useful to poll and handle new |
746 | events while doing lengthy calculations, to keep the program responsive. |
825 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
755 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
756 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
757 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
758 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
759 | |
838 | |
760 | Here are the gory details of what C<ev_run> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
761 | |
842 | |
762 | - Increment loop depth. |
843 | - Increment loop depth. |
763 | - Reset the ev_break status. |
844 | - Reset the ev_break status. |
764 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
765 | LOOP: |
846 | LOOP: |
… | |
… | |
798 | anymore. |
879 | anymore. |
799 | |
880 | |
800 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
801 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
802 | ev_run (my_loop, 0); |
883 | ev_run (my_loop, 0); |
803 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
804 | |
885 | |
805 | =item ev_break (loop, how) |
886 | =item ev_break (loop, how) |
806 | |
887 | |
807 | Can be used to make a call to C<ev_run> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
808 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
809 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
890 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
810 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
891 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
811 | |
892 | |
812 | This "unloop state" will be cleared when entering C<ev_run> again. |
893 | This "break state" will be cleared on the next call to C<ev_run>. |
813 | |
894 | |
814 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
895 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
896 | which case it will have no effect. |
815 | |
897 | |
816 | =item ev_ref (loop) |
898 | =item ev_ref (loop) |
817 | |
899 | |
818 | =item ev_unref (loop) |
900 | =item ev_unref (loop) |
819 | |
901 | |
… | |
… | |
840 | running when nothing else is active. |
922 | running when nothing else is active. |
841 | |
923 | |
842 | ev_signal exitsig; |
924 | ev_signal exitsig; |
843 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
925 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
844 | ev_signal_start (loop, &exitsig); |
926 | ev_signal_start (loop, &exitsig); |
845 | evf_unref (loop); |
927 | ev_unref (loop); |
846 | |
928 | |
847 | Example: For some weird reason, unregister the above signal handler again. |
929 | Example: For some weird reason, unregister the above signal handler again. |
848 | |
930 | |
849 | ev_ref (loop); |
931 | ev_ref (loop); |
850 | ev_signal_stop (loop, &exitsig); |
932 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
870 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
871 | |
953 | |
872 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
873 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
874 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
875 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
876 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
877 | sleep time ensures that libev will not poll for I/O events more often then |
959 | sleep time ensures that libev will not poll for I/O events more often then |
878 | once per this interval, on average. |
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
879 | |
962 | |
880 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
881 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
882 | latency/jitter/inexactness (the watcher callback will be called |
965 | latency/jitter/inexactness (the watcher callback will be called |
883 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
962 | See also the locking example in the C<THREADS> section later in this |
1045 | See also the locking example in the C<THREADS> section later in this |
963 | document. |
1046 | document. |
964 | |
1047 | |
965 | =item ev_set_userdata (loop, void *data) |
1048 | =item ev_set_userdata (loop, void *data) |
966 | |
1049 | |
967 | =item ev_userdata (loop) |
1050 | =item void *ev_userdata (loop) |
968 | |
1051 | |
969 | Set and retrieve a single C<void *> associated with a loop. When |
1052 | Set and retrieve a single C<void *> associated with a loop. When |
970 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1053 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
971 | C<0.> |
1054 | C<0>. |
972 | |
1055 | |
973 | These two functions can be used to associate arbitrary data with a loop, |
1056 | These two functions can be used to associate arbitrary data with a loop, |
974 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1057 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
975 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1058 | C<acquire> callbacks described above, but of course can be (ab-)used for |
976 | any other purpose as well. |
1059 | any other purpose as well. |
… | |
… | |
1104 | =item C<EV_FORK> |
1187 | =item C<EV_FORK> |
1105 | |
1188 | |
1106 | The event loop has been resumed in the child process after fork (see |
1189 | The event loop has been resumed in the child process after fork (see |
1107 | C<ev_fork>). |
1190 | C<ev_fork>). |
1108 | |
1191 | |
|
|
1192 | =item C<EV_CLEANUP> |
|
|
1193 | |
|
|
1194 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1195 | |
1109 | =item C<EV_ASYNC> |
1196 | =item C<EV_ASYNC> |
1110 | |
1197 | |
1111 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1198 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1112 | |
1199 | |
1113 | =item C<EV_CUSTOM> |
1200 | =item C<EV_CUSTOM> |
… | |
… | |
1134 | programs, though, as the fd could already be closed and reused for another |
1221 | programs, though, as the fd could already be closed and reused for another |
1135 | thing, so beware. |
1222 | thing, so beware. |
1136 | |
1223 | |
1137 | =back |
1224 | =back |
1138 | |
1225 | |
|
|
1226 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1227 | |
|
|
1228 | =over 4 |
|
|
1229 | |
|
|
1230 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1231 | |
|
|
1232 | This macro initialises the generic portion of a watcher. The contents |
|
|
1233 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1234 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1235 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1236 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1237 | which rolls both calls into one. |
|
|
1238 | |
|
|
1239 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1240 | (or never started) and there are no pending events outstanding. |
|
|
1241 | |
|
|
1242 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1243 | int revents)>. |
|
|
1244 | |
|
|
1245 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1246 | |
|
|
1247 | ev_io w; |
|
|
1248 | ev_init (&w, my_cb); |
|
|
1249 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1250 | |
|
|
1251 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1252 | |
|
|
1253 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1254 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1255 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1256 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1257 | difference to the C<ev_init> macro). |
|
|
1258 | |
|
|
1259 | Although some watcher types do not have type-specific arguments |
|
|
1260 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1261 | |
|
|
1262 | See C<ev_init>, above, for an example. |
|
|
1263 | |
|
|
1264 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1265 | |
|
|
1266 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1267 | calls into a single call. This is the most convenient method to initialise |
|
|
1268 | a watcher. The same limitations apply, of course. |
|
|
1269 | |
|
|
1270 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1271 | |
|
|
1272 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1273 | |
|
|
1274 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1275 | |
|
|
1276 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1277 | events. If the watcher is already active nothing will happen. |
|
|
1278 | |
|
|
1279 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1280 | whole section. |
|
|
1281 | |
|
|
1282 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1283 | |
|
|
1284 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1285 | |
|
|
1286 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1287 | the watcher was active or not). |
|
|
1288 | |
|
|
1289 | It is possible that stopped watchers are pending - for example, |
|
|
1290 | non-repeating timers are being stopped when they become pending - but |
|
|
1291 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1292 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1293 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1294 | |
|
|
1295 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1296 | |
|
|
1297 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1298 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1299 | it. |
|
|
1300 | |
|
|
1301 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1302 | |
|
|
1303 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1304 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1305 | is pending (but not active) you must not call an init function on it (but |
|
|
1306 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1307 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1308 | it). |
|
|
1309 | |
|
|
1310 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1311 | |
|
|
1312 | Returns the callback currently set on the watcher. |
|
|
1313 | |
|
|
1314 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1315 | |
|
|
1316 | Change the callback. You can change the callback at virtually any time |
|
|
1317 | (modulo threads). |
|
|
1318 | |
|
|
1319 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1320 | |
|
|
1321 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1322 | |
|
|
1323 | Set and query the priority of the watcher. The priority is a small |
|
|
1324 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1325 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1326 | before watchers with lower priority, but priority will not keep watchers |
|
|
1327 | from being executed (except for C<ev_idle> watchers). |
|
|
1328 | |
|
|
1329 | If you need to suppress invocation when higher priority events are pending |
|
|
1330 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1331 | |
|
|
1332 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1333 | pending. |
|
|
1334 | |
|
|
1335 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1336 | fine, as long as you do not mind that the priority value you query might |
|
|
1337 | or might not have been clamped to the valid range. |
|
|
1338 | |
|
|
1339 | The default priority used by watchers when no priority has been set is |
|
|
1340 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1341 | |
|
|
1342 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1343 | priorities. |
|
|
1344 | |
|
|
1345 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1346 | |
|
|
1347 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1348 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1349 | can deal with that fact, as both are simply passed through to the |
|
|
1350 | callback. |
|
|
1351 | |
|
|
1352 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1353 | |
|
|
1354 | If the watcher is pending, this function clears its pending status and |
|
|
1355 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1356 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1357 | |
|
|
1358 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1359 | callback to be invoked, which can be accomplished with this function. |
|
|
1360 | |
|
|
1361 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1362 | |
|
|
1363 | Feeds the given event set into the event loop, as if the specified event |
|
|
1364 | had happened for the specified watcher (which must be a pointer to an |
|
|
1365 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1366 | not free the watcher as long as it has pending events. |
|
|
1367 | |
|
|
1368 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1369 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1370 | not started in the first place. |
|
|
1371 | |
|
|
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1373 | functions that do not need a watcher. |
|
|
1374 | |
|
|
1375 | =back |
|
|
1376 | |
|
|
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1378 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1379 | |
1139 | =head2 WATCHER STATES |
1380 | =head2 WATCHER STATES |
1140 | |
1381 | |
1141 | There are various watcher states mentioned throughout this manual - |
1382 | There are various watcher states mentioned throughout this manual - |
1142 | active, pending and so on. In this section these states and the rules to |
1383 | active, pending and so on. In this section these states and the rules to |
1143 | transition between them will be described in more detail - and while these |
1384 | transition between them will be described in more detail - and while these |
… | |
… | |
1145 | |
1386 | |
1146 | =over 4 |
1387 | =over 4 |
1147 | |
1388 | |
1148 | =item initialiased |
1389 | =item initialiased |
1149 | |
1390 | |
1150 | Before a watcher can be registered with the event looop it has to be |
1391 | Before a watcher can be registered with the event loop it has to be |
1151 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1152 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1153 | |
1394 | |
1154 | In this state it is simply some block of memory that is suitable for use |
1395 | In this state it is simply some block of memory that is suitable for |
1155 | in an event loop. It can be moved around, freed, reused etc. at will. |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1397 | will - as long as you either keep the memory contents intact, or call |
|
|
1398 | C<ev_TYPE_init> again. |
1156 | |
1399 | |
1157 | =item started/running/active |
1400 | =item started/running/active |
1158 | |
1401 | |
1159 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1160 | property of the event loop, and is actively waiting for events. While in |
1403 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1188 | latter will clear any pending state the watcher might be in, regardless |
1431 | latter will clear any pending state the watcher might be in, regardless |
1189 | of whether it was active or not, so stopping a watcher explicitly before |
1432 | of whether it was active or not, so stopping a watcher explicitly before |
1190 | freeing it is often a good idea. |
1433 | freeing it is often a good idea. |
1191 | |
1434 | |
1192 | While stopped (and not pending) the watcher is essentially in the |
1435 | While stopped (and not pending) the watcher is essentially in the |
1193 | initialised state, that is it can be reused, moved, modified in any way |
1436 | initialised state, that is, it can be reused, moved, modified in any way |
1194 | you wish. |
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
1195 | |
1439 | |
1196 | =back |
1440 | =back |
1197 | |
|
|
1198 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1199 | |
|
|
1200 | =over 4 |
|
|
1201 | |
|
|
1202 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1203 | |
|
|
1204 | This macro initialises the generic portion of a watcher. The contents |
|
|
1205 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1206 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1207 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1208 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1209 | which rolls both calls into one. |
|
|
1210 | |
|
|
1211 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1212 | (or never started) and there are no pending events outstanding. |
|
|
1213 | |
|
|
1214 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1215 | int revents)>. |
|
|
1216 | |
|
|
1217 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1218 | |
|
|
1219 | ev_io w; |
|
|
1220 | ev_init (&w, my_cb); |
|
|
1221 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1222 | |
|
|
1223 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1224 | |
|
|
1225 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1226 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1227 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1228 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1229 | difference to the C<ev_init> macro). |
|
|
1230 | |
|
|
1231 | Although some watcher types do not have type-specific arguments |
|
|
1232 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1233 | |
|
|
1234 | See C<ev_init>, above, for an example. |
|
|
1235 | |
|
|
1236 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1237 | |
|
|
1238 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1239 | calls into a single call. This is the most convenient method to initialise |
|
|
1240 | a watcher. The same limitations apply, of course. |
|
|
1241 | |
|
|
1242 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1243 | |
|
|
1244 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1245 | |
|
|
1246 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1247 | |
|
|
1248 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1249 | events. If the watcher is already active nothing will happen. |
|
|
1250 | |
|
|
1251 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1252 | whole section. |
|
|
1253 | |
|
|
1254 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1255 | |
|
|
1256 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1257 | |
|
|
1258 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1259 | the watcher was active or not). |
|
|
1260 | |
|
|
1261 | It is possible that stopped watchers are pending - for example, |
|
|
1262 | non-repeating timers are being stopped when they become pending - but |
|
|
1263 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1264 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1265 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1266 | |
|
|
1267 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1268 | |
|
|
1269 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1270 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1271 | it. |
|
|
1272 | |
|
|
1273 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1274 | |
|
|
1275 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1276 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1277 | is pending (but not active) you must not call an init function on it (but |
|
|
1278 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1279 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1280 | it). |
|
|
1281 | |
|
|
1282 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1283 | |
|
|
1284 | Returns the callback currently set on the watcher. |
|
|
1285 | |
|
|
1286 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1287 | |
|
|
1288 | Change the callback. You can change the callback at virtually any time |
|
|
1289 | (modulo threads). |
|
|
1290 | |
|
|
1291 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1292 | |
|
|
1293 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1294 | |
|
|
1295 | Set and query the priority of the watcher. The priority is a small |
|
|
1296 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1297 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1298 | before watchers with lower priority, but priority will not keep watchers |
|
|
1299 | from being executed (except for C<ev_idle> watchers). |
|
|
1300 | |
|
|
1301 | If you need to suppress invocation when higher priority events are pending |
|
|
1302 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1303 | |
|
|
1304 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1305 | pending. |
|
|
1306 | |
|
|
1307 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1308 | fine, as long as you do not mind that the priority value you query might |
|
|
1309 | or might not have been clamped to the valid range. |
|
|
1310 | |
|
|
1311 | The default priority used by watchers when no priority has been set is |
|
|
1312 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1313 | |
|
|
1314 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1315 | priorities. |
|
|
1316 | |
|
|
1317 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1318 | |
|
|
1319 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1320 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1321 | can deal with that fact, as both are simply passed through to the |
|
|
1322 | callback. |
|
|
1323 | |
|
|
1324 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1325 | |
|
|
1326 | If the watcher is pending, this function clears its pending status and |
|
|
1327 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1328 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1329 | |
|
|
1330 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1331 | callback to be invoked, which can be accomplished with this function. |
|
|
1332 | |
|
|
1333 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1334 | |
|
|
1335 | Feeds the given event set into the event loop, as if the specified event |
|
|
1336 | had happened for the specified watcher (which must be a pointer to an |
|
|
1337 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1338 | not free the watcher as long as it has pending events. |
|
|
1339 | |
|
|
1340 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1341 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1342 | not started in the first place. |
|
|
1343 | |
|
|
1344 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1345 | functions that do not need a watcher. |
|
|
1346 | |
|
|
1347 | =back |
|
|
1348 | |
|
|
1349 | |
|
|
1350 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1351 | |
|
|
1352 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1353 | and read at any time: libev will completely ignore it. This can be used |
|
|
1354 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1355 | don't want to allocate memory and store a pointer to it in that data |
|
|
1356 | member, you can also "subclass" the watcher type and provide your own |
|
|
1357 | data: |
|
|
1358 | |
|
|
1359 | struct my_io |
|
|
1360 | { |
|
|
1361 | ev_io io; |
|
|
1362 | int otherfd; |
|
|
1363 | void *somedata; |
|
|
1364 | struct whatever *mostinteresting; |
|
|
1365 | }; |
|
|
1366 | |
|
|
1367 | ... |
|
|
1368 | struct my_io w; |
|
|
1369 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1370 | |
|
|
1371 | And since your callback will be called with a pointer to the watcher, you |
|
|
1372 | can cast it back to your own type: |
|
|
1373 | |
|
|
1374 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1375 | { |
|
|
1376 | struct my_io *w = (struct my_io *)w_; |
|
|
1377 | ... |
|
|
1378 | } |
|
|
1379 | |
|
|
1380 | More interesting and less C-conformant ways of casting your callback type |
|
|
1381 | instead have been omitted. |
|
|
1382 | |
|
|
1383 | Another common scenario is to use some data structure with multiple |
|
|
1384 | embedded watchers: |
|
|
1385 | |
|
|
1386 | struct my_biggy |
|
|
1387 | { |
|
|
1388 | int some_data; |
|
|
1389 | ev_timer t1; |
|
|
1390 | ev_timer t2; |
|
|
1391 | } |
|
|
1392 | |
|
|
1393 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1394 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1395 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1396 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1397 | programmers): |
|
|
1398 | |
|
|
1399 | #include <stddef.h> |
|
|
1400 | |
|
|
1401 | static void |
|
|
1402 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1403 | { |
|
|
1404 | struct my_biggy big = (struct my_biggy *) |
|
|
1405 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1406 | } |
|
|
1407 | |
|
|
1408 | static void |
|
|
1409 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1410 | { |
|
|
1411 | struct my_biggy big = (struct my_biggy *) |
|
|
1412 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1413 | } |
|
|
1414 | |
1441 | |
1415 | =head2 WATCHER PRIORITY MODELS |
1442 | =head2 WATCHER PRIORITY MODELS |
1416 | |
1443 | |
1417 | Many event loops support I<watcher priorities>, which are usually small |
1444 | Many event loops support I<watcher priorities>, which are usually small |
1418 | integers that influence the ordering of event callback invocation |
1445 | integers that influence the ordering of event callback invocation |
… | |
… | |
1545 | In general you can register as many read and/or write event watchers per |
1572 | In general you can register as many read and/or write event watchers per |
1546 | fd as you want (as long as you don't confuse yourself). Setting all file |
1573 | fd as you want (as long as you don't confuse yourself). Setting all file |
1547 | descriptors to non-blocking mode is also usually a good idea (but not |
1574 | descriptors to non-blocking mode is also usually a good idea (but not |
1548 | required if you know what you are doing). |
1575 | required if you know what you are doing). |
1549 | |
1576 | |
1550 | If you cannot use non-blocking mode, then force the use of a |
|
|
1551 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1552 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1553 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1554 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1555 | |
|
|
1556 | Another thing you have to watch out for is that it is quite easy to |
1577 | Another thing you have to watch out for is that it is quite easy to |
1557 | receive "spurious" readiness notifications, that is your callback might |
1578 | receive "spurious" readiness notifications, that is, your callback might |
1558 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1559 | because there is no data. Not only are some backends known to create a |
1580 | because there is no data. It is very easy to get into this situation even |
1560 | lot of those (for example Solaris ports), it is very easy to get into |
1581 | with a relatively standard program structure. Thus it is best to always |
1561 | this situation even with a relatively standard program structure. Thus |
1582 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1562 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1563 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1583 | preferable to a program hanging until some data arrives. |
1564 | |
1584 | |
1565 | If you cannot run the fd in non-blocking mode (for example you should |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1566 | not play around with an Xlib connection), then you have to separately |
1586 | not play around with an Xlib connection), then you have to separately |
1567 | re-test whether a file descriptor is really ready with a known-to-be good |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1568 | interface such as poll (fortunately in our Xlib example, Xlib already |
1588 | interface such as poll (fortunately in the case of Xlib, it already does |
1569 | does this on its own, so its quite safe to use). Some people additionally |
1589 | this on its own, so its quite safe to use). Some people additionally |
1570 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1571 | indefinitely. |
1591 | indefinitely. |
1572 | |
1592 | |
1573 | But really, best use non-blocking mode. |
1593 | But really, best use non-blocking mode. |
1574 | |
1594 | |
… | |
… | |
1602 | |
1622 | |
1603 | There is no workaround possible except not registering events |
1623 | There is no workaround possible except not registering events |
1604 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1605 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1606 | |
1626 | |
|
|
1627 | =head3 The special problem of files |
|
|
1628 | |
|
|
1629 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1630 | representing files, and expect it to become ready when their program |
|
|
1631 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1632 | |
|
|
1633 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1634 | notification as soon as the kernel knows whether and how much data is |
|
|
1635 | there, and in the case of open files, that's always the case, so you |
|
|
1636 | always get a readiness notification instantly, and your read (or possibly |
|
|
1637 | write) will still block on the disk I/O. |
|
|
1638 | |
|
|
1639 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1640 | devices and so on, there is another party (the sender) that delivers data |
|
|
1641 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1642 | will not send data on its own, simply because it doesn't know what you |
|
|
1643 | wish to read - you would first have to request some data. |
|
|
1644 | |
|
|
1645 | Since files are typically not-so-well supported by advanced notification |
|
|
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1647 | to files, even though you should not use it. The reason for this is |
|
|
1648 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1649 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1650 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1651 | F</dev/urandom>), and even though the file might better be served with |
|
|
1652 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1653 | it "just works" instead of freezing. |
|
|
1654 | |
|
|
1655 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1656 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1657 | when you rarely read from a file instead of from a socket, and want to |
|
|
1658 | reuse the same code path. |
|
|
1659 | |
1607 | =head3 The special problem of fork |
1660 | =head3 The special problem of fork |
1608 | |
1661 | |
1609 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1662 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1610 | useless behaviour. Libev fully supports fork, but needs to be told about |
1663 | useless behaviour. Libev fully supports fork, but needs to be told about |
1611 | it in the child. |
1664 | it in the child if you want to continue to use it in the child. |
1612 | |
1665 | |
1613 | To support fork in your programs, you either have to call |
1666 | To support fork in your child processes, you have to call C<ev_loop_fork |
1614 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1667 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1615 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1616 | C<EVBACKEND_POLL>. |
|
|
1617 | |
1669 | |
1618 | =head3 The special problem of SIGPIPE |
1670 | =head3 The special problem of SIGPIPE |
1619 | |
1671 | |
1620 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1672 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1621 | when writing to a pipe whose other end has been closed, your program gets |
1673 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1971 | keep up with the timer (because it takes longer than those 10 seconds to |
2023 | keep up with the timer (because it takes longer than those 10 seconds to |
1972 | do stuff) the timer will not fire more than once per event loop iteration. |
2024 | do stuff) the timer will not fire more than once per event loop iteration. |
1973 | |
2025 | |
1974 | =item ev_timer_again (loop, ev_timer *) |
2026 | =item ev_timer_again (loop, ev_timer *) |
1975 | |
2027 | |
1976 | This will act as if the timer timed out and restart it again if it is |
2028 | This will act as if the timer timed out and restarts it again if it is |
1977 | repeating. The exact semantics are: |
2029 | repeating. The exact semantics are: |
1978 | |
2030 | |
1979 | If the timer is pending, its pending status is cleared. |
2031 | If the timer is pending, its pending status is cleared. |
1980 | |
2032 | |
1981 | If the timer is started but non-repeating, stop it (as if it timed out). |
2033 | If the timer is started but non-repeating, stop it (as if it timed out). |
… | |
… | |
2111 | |
2163 | |
2112 | Another way to think about it (for the mathematically inclined) is that |
2164 | Another way to think about it (for the mathematically inclined) is that |
2113 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2165 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2114 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2166 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2115 | |
2167 | |
2116 | For numerical stability it is preferable that the C<offset> value is near |
2168 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2117 | C<ev_now ()> (the current time), but there is no range requirement for |
2169 | interval value should be higher than C<1/8192> (which is around 100 |
2118 | this value, and in fact is often specified as zero. |
2170 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2171 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2172 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2173 | C<0> and C<interval>, which is also the recommended range. |
2119 | |
2174 | |
2120 | Note also that there is an upper limit to how often a timer can fire (CPU |
2175 | Note also that there is an upper limit to how often a timer can fire (CPU |
2121 | speed for example), so if C<interval> is very small then timing stability |
2176 | speed for example), so if C<interval> is very small then timing stability |
2122 | will of course deteriorate. Libev itself tries to be exact to be about one |
2177 | will of course deteriorate. Libev itself tries to be exact to be about one |
2123 | millisecond (if the OS supports it and the machine is fast enough). |
2178 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2237 | |
2292 | |
2238 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2293 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2239 | |
2294 | |
2240 | Signal watchers will trigger an event when the process receives a specific |
2295 | Signal watchers will trigger an event when the process receives a specific |
2241 | signal one or more times. Even though signals are very asynchronous, libev |
2296 | signal one or more times. Even though signals are very asynchronous, libev |
2242 | will try it's best to deliver signals synchronously, i.e. as part of the |
2297 | will try its best to deliver signals synchronously, i.e. as part of the |
2243 | normal event processing, like any other event. |
2298 | normal event processing, like any other event. |
2244 | |
2299 | |
2245 | If you want signals to be delivered truly asynchronously, just use |
2300 | If you want signals to be delivered truly asynchronously, just use |
2246 | C<sigaction> as you would do without libev and forget about sharing |
2301 | C<sigaction> as you would do without libev and forget about sharing |
2247 | the signal. You can even use C<ev_async> from a signal handler to |
2302 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2266 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2321 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2267 | |
2322 | |
2268 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2323 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2269 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2324 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2270 | stopping it again), that is, libev might or might not block the signal, |
2325 | stopping it again), that is, libev might or might not block the signal, |
2271 | and might or might not set or restore the installed signal handler. |
2326 | and might or might not set or restore the installed signal handler (but |
|
|
2327 | see C<EVFLAG_NOSIGMASK>). |
2272 | |
2328 | |
2273 | While this does not matter for the signal disposition (libev never |
2329 | While this does not matter for the signal disposition (libev never |
2274 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2330 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2275 | C<execve>), this matters for the signal mask: many programs do not expect |
2331 | C<execve>), this matters for the signal mask: many programs do not expect |
2276 | certain signals to be blocked. |
2332 | certain signals to be blocked. |
… | |
… | |
2289 | I<has> to modify the signal mask, at least temporarily. |
2345 | I<has> to modify the signal mask, at least temporarily. |
2290 | |
2346 | |
2291 | So I can't stress this enough: I<If you do not reset your signal mask when |
2347 | So I can't stress this enough: I<If you do not reset your signal mask when |
2292 | you expect it to be empty, you have a race condition in your code>. This |
2348 | you expect it to be empty, you have a race condition in your code>. This |
2293 | is not a libev-specific thing, this is true for most event libraries. |
2349 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2350 | |
|
|
2351 | =head3 The special problem of threads signal handling |
|
|
2352 | |
|
|
2353 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2354 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2355 | threads in a process block signals, which is hard to achieve. |
|
|
2356 | |
|
|
2357 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2358 | for the same signals), you can tackle this problem by globally blocking |
|
|
2359 | all signals before creating any threads (or creating them with a fully set |
|
|
2360 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2361 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2362 | these signals. You can pass on any signals that libev might be interested |
|
|
2363 | in by calling C<ev_feed_signal>. |
2294 | |
2364 | |
2295 | =head3 Watcher-Specific Functions and Data Members |
2365 | =head3 Watcher-Specific Functions and Data Members |
2296 | |
2366 | |
2297 | =over 4 |
2367 | =over 4 |
2298 | |
2368 | |
… | |
… | |
3072 | disadvantage of having to use multiple event loops (which do not support |
3142 | disadvantage of having to use multiple event loops (which do not support |
3073 | signal watchers). |
3143 | signal watchers). |
3074 | |
3144 | |
3075 | When this is not possible, or you want to use the default loop for |
3145 | When this is not possible, or you want to use the default loop for |
3076 | other reasons, then in the process that wants to start "fresh", call |
3146 | other reasons, then in the process that wants to start "fresh", call |
3077 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3147 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3078 | the default loop will "orphan" (not stop) all registered watchers, so you |
3148 | Destroying the default loop will "orphan" (not stop) all registered |
3079 | have to be careful not to execute code that modifies those watchers. Note |
3149 | watchers, so you have to be careful not to execute code that modifies |
3080 | also that in that case, you have to re-register any signal watchers. |
3150 | those watchers. Note also that in that case, you have to re-register any |
|
|
3151 | signal watchers. |
3081 | |
3152 | |
3082 | =head3 Watcher-Specific Functions and Data Members |
3153 | =head3 Watcher-Specific Functions and Data Members |
3083 | |
3154 | |
3084 | =over 4 |
3155 | =over 4 |
3085 | |
3156 | |
3086 | =item ev_fork_init (ev_signal *, callback) |
3157 | =item ev_fork_init (ev_fork *, callback) |
3087 | |
3158 | |
3088 | Initialises and configures the fork watcher - it has no parameters of any |
3159 | Initialises and configures the fork watcher - it has no parameters of any |
3089 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3160 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3090 | believe me. |
3161 | really. |
3091 | |
3162 | |
3092 | =back |
3163 | =back |
3093 | |
3164 | |
3094 | |
3165 | |
|
|
3166 | =head2 C<ev_cleanup> - even the best things end |
|
|
3167 | |
|
|
3168 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3169 | by a call to C<ev_loop_destroy>. |
|
|
3170 | |
|
|
3171 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3172 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3173 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3174 | loop when you want them to be invoked. |
|
|
3175 | |
|
|
3176 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3177 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3178 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3179 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3180 | |
|
|
3181 | =head3 Watcher-Specific Functions and Data Members |
|
|
3182 | |
|
|
3183 | =over 4 |
|
|
3184 | |
|
|
3185 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3186 | |
|
|
3187 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3188 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3189 | pointless, I assure you. |
|
|
3190 | |
|
|
3191 | =back |
|
|
3192 | |
|
|
3193 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3194 | cleanup functions are called. |
|
|
3195 | |
|
|
3196 | static void |
|
|
3197 | program_exits (void) |
|
|
3198 | { |
|
|
3199 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3200 | } |
|
|
3201 | |
|
|
3202 | ... |
|
|
3203 | atexit (program_exits); |
|
|
3204 | |
|
|
3205 | |
3095 | =head2 C<ev_async> - how to wake up an event loop |
3206 | =head2 C<ev_async> - how to wake up an event loop |
3096 | |
3207 | |
3097 | In general, you cannot use an C<ev_run> from multiple threads or other |
3208 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3098 | asynchronous sources such as signal handlers (as opposed to multiple event |
3209 | asynchronous sources such as signal handlers (as opposed to multiple event |
3099 | loops - those are of course safe to use in different threads). |
3210 | loops - those are of course safe to use in different threads). |
3100 | |
3211 | |
3101 | Sometimes, however, you need to wake up an event loop you do not control, |
3212 | Sometimes, however, you need to wake up an event loop you do not control, |
3102 | for example because it belongs to another thread. This is what C<ev_async> |
3213 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3104 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3215 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3105 | |
3216 | |
3106 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3217 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3107 | too, are asynchronous in nature, and signals, too, will be compressed |
3218 | too, are asynchronous in nature, and signals, too, will be compressed |
3108 | (i.e. the number of callback invocations may be less than the number of |
3219 | (i.e. the number of callback invocations may be less than the number of |
3109 | C<ev_async_sent> calls). |
3220 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3110 | |
3221 | of "global async watchers" by using a watcher on an otherwise unused |
3111 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3222 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3112 | just the default loop. |
3223 | even without knowing which loop owns the signal. |
3113 | |
3224 | |
3114 | =head3 Queueing |
3225 | =head3 Queueing |
3115 | |
3226 | |
3116 | C<ev_async> does not support queueing of data in any way. The reason |
3227 | C<ev_async> does not support queueing of data in any way. The reason |
3117 | is that the author does not know of a simple (or any) algorithm for a |
3228 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3209 | trust me. |
3320 | trust me. |
3210 | |
3321 | |
3211 | =item ev_async_send (loop, ev_async *) |
3322 | =item ev_async_send (loop, ev_async *) |
3212 | |
3323 | |
3213 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3324 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3214 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3325 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3326 | returns. |
|
|
3327 | |
3215 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3328 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3216 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3329 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3217 | section below on what exactly this means). |
3330 | embedding section below on what exactly this means). |
3218 | |
3331 | |
3219 | Note that, as with other watchers in libev, multiple events might get |
3332 | Note that, as with other watchers in libev, multiple events might get |
3220 | compressed into a single callback invocation (another way to look at this |
3333 | compressed into a single callback invocation (another way to look at |
3221 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3334 | this is that C<ev_async> watchers are level-triggered: they are set on |
3222 | reset when the event loop detects that). |
3335 | C<ev_async_send>, reset when the event loop detects that). |
3223 | |
3336 | |
3224 | This call incurs the overhead of a system call only once per event loop |
3337 | This call incurs the overhead of at most one extra system call per event |
3225 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3338 | loop iteration, if the event loop is blocked, and no syscall at all if |
3226 | repeated calls to C<ev_async_send> for the same event loop. |
3339 | the event loop (or your program) is processing events. That means that |
|
|
3340 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3341 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3342 | zero) under load. |
3227 | |
3343 | |
3228 | =item bool = ev_async_pending (ev_async *) |
3344 | =item bool = ev_async_pending (ev_async *) |
3229 | |
3345 | |
3230 | Returns a non-zero value when C<ev_async_send> has been called on the |
3346 | Returns a non-zero value when C<ev_async_send> has been called on the |
3231 | watcher but the event has not yet been processed (or even noted) by the |
3347 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3290 | Feed an event on the given fd, as if a file descriptor backend detected |
3406 | Feed an event on the given fd, as if a file descriptor backend detected |
3291 | the given events it. |
3407 | the given events it. |
3292 | |
3408 | |
3293 | =item ev_feed_signal_event (loop, int signum) |
3409 | =item ev_feed_signal_event (loop, int signum) |
3294 | |
3410 | |
3295 | Feed an event as if the given signal occurred (C<loop> must be the default |
3411 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3296 | loop!). |
3412 | which is async-safe. |
3297 | |
3413 | |
3298 | =back |
3414 | =back |
|
|
3415 | |
|
|
3416 | |
|
|
3417 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3418 | |
|
|
3419 | This section explains some common idioms that are not immediately |
|
|
3420 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3421 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3422 | |
|
|
3423 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3424 | |
|
|
3425 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3426 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3427 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3428 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3429 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3430 | data: |
|
|
3431 | |
|
|
3432 | struct my_io |
|
|
3433 | { |
|
|
3434 | ev_io io; |
|
|
3435 | int otherfd; |
|
|
3436 | void *somedata; |
|
|
3437 | struct whatever *mostinteresting; |
|
|
3438 | }; |
|
|
3439 | |
|
|
3440 | ... |
|
|
3441 | struct my_io w; |
|
|
3442 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3443 | |
|
|
3444 | And since your callback will be called with a pointer to the watcher, you |
|
|
3445 | can cast it back to your own type: |
|
|
3446 | |
|
|
3447 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3448 | { |
|
|
3449 | struct my_io *w = (struct my_io *)w_; |
|
|
3450 | ... |
|
|
3451 | } |
|
|
3452 | |
|
|
3453 | More interesting and less C-conformant ways of casting your callback |
|
|
3454 | function type instead have been omitted. |
|
|
3455 | |
|
|
3456 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3457 | |
|
|
3458 | Another common scenario is to use some data structure with multiple |
|
|
3459 | embedded watchers, in effect creating your own watcher that combines |
|
|
3460 | multiple libev event sources into one "super-watcher": |
|
|
3461 | |
|
|
3462 | struct my_biggy |
|
|
3463 | { |
|
|
3464 | int some_data; |
|
|
3465 | ev_timer t1; |
|
|
3466 | ev_timer t2; |
|
|
3467 | } |
|
|
3468 | |
|
|
3469 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3470 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3471 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3472 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3473 | real programmers): |
|
|
3474 | |
|
|
3475 | #include <stddef.h> |
|
|
3476 | |
|
|
3477 | static void |
|
|
3478 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3479 | { |
|
|
3480 | struct my_biggy big = (struct my_biggy *) |
|
|
3481 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3482 | } |
|
|
3483 | |
|
|
3484 | static void |
|
|
3485 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3486 | { |
|
|
3487 | struct my_biggy big = (struct my_biggy *) |
|
|
3488 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3489 | } |
|
|
3490 | |
|
|
3491 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3492 | |
|
|
3493 | Often (especially in GUI toolkits) there are places where you have |
|
|
3494 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3495 | invoking C<ev_run>. |
|
|
3496 | |
|
|
3497 | This brings the problem of exiting - a callback might want to finish the |
|
|
3498 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3499 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3500 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3501 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3502 | |
|
|
3503 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3504 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3505 | triggered, using C<EVRUN_ONCE>: |
|
|
3506 | |
|
|
3507 | // main loop |
|
|
3508 | int exit_main_loop = 0; |
|
|
3509 | |
|
|
3510 | while (!exit_main_loop) |
|
|
3511 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3512 | |
|
|
3513 | // in a model watcher |
|
|
3514 | int exit_nested_loop = 0; |
|
|
3515 | |
|
|
3516 | while (!exit_nested_loop) |
|
|
3517 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3518 | |
|
|
3519 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3520 | |
|
|
3521 | // exit modal loop |
|
|
3522 | exit_nested_loop = 1; |
|
|
3523 | |
|
|
3524 | // exit main program, after modal loop is finished |
|
|
3525 | exit_main_loop = 1; |
|
|
3526 | |
|
|
3527 | // exit both |
|
|
3528 | exit_main_loop = exit_nested_loop = 1; |
|
|
3529 | |
|
|
3530 | =head2 THREAD LOCKING EXAMPLE |
|
|
3531 | |
|
|
3532 | Here is a fictitious example of how to run an event loop in a different |
|
|
3533 | thread from where callbacks are being invoked and watchers are |
|
|
3534 | created/added/removed. |
|
|
3535 | |
|
|
3536 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3537 | which uses exactly this technique (which is suited for many high-level |
|
|
3538 | languages). |
|
|
3539 | |
|
|
3540 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3541 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3542 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3543 | |
|
|
3544 | First, you need to associate some data with the event loop: |
|
|
3545 | |
|
|
3546 | typedef struct { |
|
|
3547 | mutex_t lock; /* global loop lock */ |
|
|
3548 | ev_async async_w; |
|
|
3549 | thread_t tid; |
|
|
3550 | cond_t invoke_cv; |
|
|
3551 | } userdata; |
|
|
3552 | |
|
|
3553 | void prepare_loop (EV_P) |
|
|
3554 | { |
|
|
3555 | // for simplicity, we use a static userdata struct. |
|
|
3556 | static userdata u; |
|
|
3557 | |
|
|
3558 | ev_async_init (&u->async_w, async_cb); |
|
|
3559 | ev_async_start (EV_A_ &u->async_w); |
|
|
3560 | |
|
|
3561 | pthread_mutex_init (&u->lock, 0); |
|
|
3562 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3563 | |
|
|
3564 | // now associate this with the loop |
|
|
3565 | ev_set_userdata (EV_A_ u); |
|
|
3566 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3567 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3568 | |
|
|
3569 | // then create the thread running ev_run |
|
|
3570 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3571 | } |
|
|
3572 | |
|
|
3573 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3574 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3575 | that might have been added: |
|
|
3576 | |
|
|
3577 | static void |
|
|
3578 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3579 | { |
|
|
3580 | // just used for the side effects |
|
|
3581 | } |
|
|
3582 | |
|
|
3583 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3584 | protecting the loop data, respectively. |
|
|
3585 | |
|
|
3586 | static void |
|
|
3587 | l_release (EV_P) |
|
|
3588 | { |
|
|
3589 | userdata *u = ev_userdata (EV_A); |
|
|
3590 | pthread_mutex_unlock (&u->lock); |
|
|
3591 | } |
|
|
3592 | |
|
|
3593 | static void |
|
|
3594 | l_acquire (EV_P) |
|
|
3595 | { |
|
|
3596 | userdata *u = ev_userdata (EV_A); |
|
|
3597 | pthread_mutex_lock (&u->lock); |
|
|
3598 | } |
|
|
3599 | |
|
|
3600 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3601 | into C<ev_run>: |
|
|
3602 | |
|
|
3603 | void * |
|
|
3604 | l_run (void *thr_arg) |
|
|
3605 | { |
|
|
3606 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3607 | |
|
|
3608 | l_acquire (EV_A); |
|
|
3609 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3610 | ev_run (EV_A_ 0); |
|
|
3611 | l_release (EV_A); |
|
|
3612 | |
|
|
3613 | return 0; |
|
|
3614 | } |
|
|
3615 | |
|
|
3616 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3617 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3618 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3619 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3620 | and b) skipping inter-thread-communication when there are no pending |
|
|
3621 | watchers is very beneficial): |
|
|
3622 | |
|
|
3623 | static void |
|
|
3624 | l_invoke (EV_P) |
|
|
3625 | { |
|
|
3626 | userdata *u = ev_userdata (EV_A); |
|
|
3627 | |
|
|
3628 | while (ev_pending_count (EV_A)) |
|
|
3629 | { |
|
|
3630 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3631 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3632 | } |
|
|
3633 | } |
|
|
3634 | |
|
|
3635 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3636 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3637 | thread to continue: |
|
|
3638 | |
|
|
3639 | static void |
|
|
3640 | real_invoke_pending (EV_P) |
|
|
3641 | { |
|
|
3642 | userdata *u = ev_userdata (EV_A); |
|
|
3643 | |
|
|
3644 | pthread_mutex_lock (&u->lock); |
|
|
3645 | ev_invoke_pending (EV_A); |
|
|
3646 | pthread_cond_signal (&u->invoke_cv); |
|
|
3647 | pthread_mutex_unlock (&u->lock); |
|
|
3648 | } |
|
|
3649 | |
|
|
3650 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3651 | event loop, you will now have to lock: |
|
|
3652 | |
|
|
3653 | ev_timer timeout_watcher; |
|
|
3654 | userdata *u = ev_userdata (EV_A); |
|
|
3655 | |
|
|
3656 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3657 | |
|
|
3658 | pthread_mutex_lock (&u->lock); |
|
|
3659 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3660 | ev_async_send (EV_A_ &u->async_w); |
|
|
3661 | pthread_mutex_unlock (&u->lock); |
|
|
3662 | |
|
|
3663 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3664 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3665 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3666 | watchers in the next event loop iteration. |
|
|
3667 | |
|
|
3668 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3669 | |
|
|
3670 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3671 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3672 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3673 | doesn't need callbacks anymore. |
|
|
3674 | |
|
|
3675 | Imagine you have coroutines that you can switch to using a function |
|
|
3676 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3677 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3678 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3679 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3680 | the differing C<;> conventions): |
|
|
3681 | |
|
|
3682 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3683 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3684 | |
|
|
3685 | That means instead of having a C callback function, you store the |
|
|
3686 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3687 | your callback, you instead have it switch to that coroutine. |
|
|
3688 | |
|
|
3689 | A coroutine might now wait for an event with a function called |
|
|
3690 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3691 | matter when, or whether the watcher is active or not when this function is |
|
|
3692 | called): |
|
|
3693 | |
|
|
3694 | void |
|
|
3695 | wait_for_event (ev_watcher *w) |
|
|
3696 | { |
|
|
3697 | ev_cb_set (w) = current_coro; |
|
|
3698 | switch_to (libev_coro); |
|
|
3699 | } |
|
|
3700 | |
|
|
3701 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3702 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3703 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3704 | |
|
|
3705 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3706 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3707 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3708 | any waiters. |
|
|
3709 | |
|
|
3710 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3711 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3712 | |
|
|
3713 | // my_ev.h |
|
|
3714 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3715 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3716 | #include "../libev/ev.h" |
|
|
3717 | |
|
|
3718 | // my_ev.c |
|
|
3719 | #define EV_H "my_ev.h" |
|
|
3720 | #include "../libev/ev.c" |
|
|
3721 | |
|
|
3722 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3723 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3724 | can even use F<ev.h> as header file name directly. |
3299 | |
3725 | |
3300 | |
3726 | |
3301 | =head1 LIBEVENT EMULATION |
3727 | =head1 LIBEVENT EMULATION |
3302 | |
3728 | |
3303 | Libev offers a compatibility emulation layer for libevent. It cannot |
3729 | Libev offers a compatibility emulation layer for libevent. It cannot |
3304 | emulate the internals of libevent, so here are some usage hints: |
3730 | emulate the internals of libevent, so here are some usage hints: |
3305 | |
3731 | |
3306 | =over 4 |
3732 | =over 4 |
|
|
3733 | |
|
|
3734 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3735 | |
|
|
3736 | This was the newest libevent version available when libev was implemented, |
|
|
3737 | and is still mostly unchanged in 2010. |
3307 | |
3738 | |
3308 | =item * Use it by including <event.h>, as usual. |
3739 | =item * Use it by including <event.h>, as usual. |
3309 | |
3740 | |
3310 | =item * The following members are fully supported: ev_base, ev_callback, |
3741 | =item * The following members are fully supported: ev_base, ev_callback, |
3311 | ev_arg, ev_fd, ev_res, ev_events. |
3742 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3317 | =item * Priorities are not currently supported. Initialising priorities |
3748 | =item * Priorities are not currently supported. Initialising priorities |
3318 | will fail and all watchers will have the same priority, even though there |
3749 | will fail and all watchers will have the same priority, even though there |
3319 | is an ev_pri field. |
3750 | is an ev_pri field. |
3320 | |
3751 | |
3321 | =item * In libevent, the last base created gets the signals, in libev, the |
3752 | =item * In libevent, the last base created gets the signals, in libev, the |
3322 | first base created (== the default loop) gets the signals. |
3753 | base that registered the signal gets the signals. |
3323 | |
3754 | |
3324 | =item * Other members are not supported. |
3755 | =item * Other members are not supported. |
3325 | |
3756 | |
3326 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3757 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3327 | to use the libev header file and library. |
3758 | to use the libev header file and library. |
… | |
… | |
3346 | Care has been taken to keep the overhead low. The only data member the C++ |
3777 | Care has been taken to keep the overhead low. The only data member the C++ |
3347 | classes add (compared to plain C-style watchers) is the event loop pointer |
3778 | classes add (compared to plain C-style watchers) is the event loop pointer |
3348 | that the watcher is associated with (or no additional members at all if |
3779 | that the watcher is associated with (or no additional members at all if |
3349 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3780 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3350 | |
3781 | |
3351 | Currently, functions, and static and non-static member functions can be |
3782 | Currently, functions, static and non-static member functions and classes |
3352 | used as callbacks. Other types should be easy to add as long as they only |
3783 | with C<operator ()> can be used as callbacks. Other types should be easy |
3353 | need one additional pointer for context. If you need support for other |
3784 | to add as long as they only need one additional pointer for context. If |
3354 | types of functors please contact the author (preferably after implementing |
3785 | you need support for other types of functors please contact the author |
3355 | it). |
3786 | (preferably after implementing it). |
3356 | |
3787 | |
3357 | Here is a list of things available in the C<ev> namespace: |
3788 | Here is a list of things available in the C<ev> namespace: |
3358 | |
3789 | |
3359 | =over 4 |
3790 | =over 4 |
3360 | |
3791 | |
… | |
… | |
3788 | F<event.h> that are not directly supported by the libev core alone. |
4219 | F<event.h> that are not directly supported by the libev core alone. |
3789 | |
4220 | |
3790 | In standalone mode, libev will still try to automatically deduce the |
4221 | In standalone mode, libev will still try to automatically deduce the |
3791 | configuration, but has to be more conservative. |
4222 | configuration, but has to be more conservative. |
3792 | |
4223 | |
|
|
4224 | =item EV_USE_FLOOR |
|
|
4225 | |
|
|
4226 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4227 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4228 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4229 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4230 | function is not available will fail, so the safe default is to not enable |
|
|
4231 | this. |
|
|
4232 | |
3793 | =item EV_USE_MONOTONIC |
4233 | =item EV_USE_MONOTONIC |
3794 | |
4234 | |
3795 | If defined to be C<1>, libev will try to detect the availability of the |
4235 | If defined to be C<1>, libev will try to detect the availability of the |
3796 | monotonic clock option at both compile time and runtime. Otherwise no |
4236 | monotonic clock option at both compile time and runtime. Otherwise no |
3797 | use of the monotonic clock option will be attempted. If you enable this, |
4237 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
3929 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4369 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3930 | |
4370 | |
3931 | =item EV_ATOMIC_T |
4371 | =item EV_ATOMIC_T |
3932 | |
4372 | |
3933 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4373 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3934 | access is atomic with respect to other threads or signal contexts. No such |
4374 | access is atomic and serialised with respect to other threads or signal |
3935 | type is easily found in the C language, so you can provide your own type |
4375 | contexts. No such type is easily found in the C language, so you can |
3936 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4376 | provide your own type that you know is safe for your purposes. It is used |
3937 | as well as for signal and thread safety in C<ev_async> watchers. |
4377 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4378 | in C<ev_async> watchers. |
3938 | |
4379 | |
3939 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4380 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3940 | (from F<signal.h>), which is usually good enough on most platforms. |
4381 | (from F<signal.h>), which is usually good enough on most platforms. |
3941 | |
4382 | |
3942 | =item EV_H (h) |
4383 | =item EV_H (h) |
… | |
… | |
4228 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4669 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4229 | |
4670 | |
4230 | #include "ev_cpp.h" |
4671 | #include "ev_cpp.h" |
4231 | #include "ev.c" |
4672 | #include "ev.c" |
4232 | |
4673 | |
4233 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4674 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4234 | |
4675 | |
4235 | =head2 THREADS AND COROUTINES |
4676 | =head2 THREADS AND COROUTINES |
4236 | |
4677 | |
4237 | =head3 THREADS |
4678 | =head3 THREADS |
4238 | |
4679 | |
… | |
… | |
4289 | default loop and triggering an C<ev_async> watcher from the default loop |
4730 | default loop and triggering an C<ev_async> watcher from the default loop |
4290 | watcher callback into the event loop interested in the signal. |
4731 | watcher callback into the event loop interested in the signal. |
4291 | |
4732 | |
4292 | =back |
4733 | =back |
4293 | |
4734 | |
4294 | =head4 THREAD LOCKING EXAMPLE |
4735 | See also L<THREAD LOCKING EXAMPLE>. |
4295 | |
|
|
4296 | Here is a fictitious example of how to run an event loop in a different |
|
|
4297 | thread than where callbacks are being invoked and watchers are |
|
|
4298 | created/added/removed. |
|
|
4299 | |
|
|
4300 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4301 | which uses exactly this technique (which is suited for many high-level |
|
|
4302 | languages). |
|
|
4303 | |
|
|
4304 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4305 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4306 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4307 | |
|
|
4308 | First, you need to associate some data with the event loop: |
|
|
4309 | |
|
|
4310 | typedef struct { |
|
|
4311 | mutex_t lock; /* global loop lock */ |
|
|
4312 | ev_async async_w; |
|
|
4313 | thread_t tid; |
|
|
4314 | cond_t invoke_cv; |
|
|
4315 | } userdata; |
|
|
4316 | |
|
|
4317 | void prepare_loop (EV_P) |
|
|
4318 | { |
|
|
4319 | // for simplicity, we use a static userdata struct. |
|
|
4320 | static userdata u; |
|
|
4321 | |
|
|
4322 | ev_async_init (&u->async_w, async_cb); |
|
|
4323 | ev_async_start (EV_A_ &u->async_w); |
|
|
4324 | |
|
|
4325 | pthread_mutex_init (&u->lock, 0); |
|
|
4326 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4327 | |
|
|
4328 | // now associate this with the loop |
|
|
4329 | ev_set_userdata (EV_A_ u); |
|
|
4330 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4331 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4332 | |
|
|
4333 | // then create the thread running ev_loop |
|
|
4334 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4335 | } |
|
|
4336 | |
|
|
4337 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4338 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4339 | that might have been added: |
|
|
4340 | |
|
|
4341 | static void |
|
|
4342 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4343 | { |
|
|
4344 | // just used for the side effects |
|
|
4345 | } |
|
|
4346 | |
|
|
4347 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4348 | protecting the loop data, respectively. |
|
|
4349 | |
|
|
4350 | static void |
|
|
4351 | l_release (EV_P) |
|
|
4352 | { |
|
|
4353 | userdata *u = ev_userdata (EV_A); |
|
|
4354 | pthread_mutex_unlock (&u->lock); |
|
|
4355 | } |
|
|
4356 | |
|
|
4357 | static void |
|
|
4358 | l_acquire (EV_P) |
|
|
4359 | { |
|
|
4360 | userdata *u = ev_userdata (EV_A); |
|
|
4361 | pthread_mutex_lock (&u->lock); |
|
|
4362 | } |
|
|
4363 | |
|
|
4364 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4365 | into C<ev_run>: |
|
|
4366 | |
|
|
4367 | void * |
|
|
4368 | l_run (void *thr_arg) |
|
|
4369 | { |
|
|
4370 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4371 | |
|
|
4372 | l_acquire (EV_A); |
|
|
4373 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4374 | ev_run (EV_A_ 0); |
|
|
4375 | l_release (EV_A); |
|
|
4376 | |
|
|
4377 | return 0; |
|
|
4378 | } |
|
|
4379 | |
|
|
4380 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4381 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4382 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4383 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4384 | and b) skipping inter-thread-communication when there are no pending |
|
|
4385 | watchers is very beneficial): |
|
|
4386 | |
|
|
4387 | static void |
|
|
4388 | l_invoke (EV_P) |
|
|
4389 | { |
|
|
4390 | userdata *u = ev_userdata (EV_A); |
|
|
4391 | |
|
|
4392 | while (ev_pending_count (EV_A)) |
|
|
4393 | { |
|
|
4394 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4395 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4396 | } |
|
|
4397 | } |
|
|
4398 | |
|
|
4399 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4400 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4401 | thread to continue: |
|
|
4402 | |
|
|
4403 | static void |
|
|
4404 | real_invoke_pending (EV_P) |
|
|
4405 | { |
|
|
4406 | userdata *u = ev_userdata (EV_A); |
|
|
4407 | |
|
|
4408 | pthread_mutex_lock (&u->lock); |
|
|
4409 | ev_invoke_pending (EV_A); |
|
|
4410 | pthread_cond_signal (&u->invoke_cv); |
|
|
4411 | pthread_mutex_unlock (&u->lock); |
|
|
4412 | } |
|
|
4413 | |
|
|
4414 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4415 | event loop, you will now have to lock: |
|
|
4416 | |
|
|
4417 | ev_timer timeout_watcher; |
|
|
4418 | userdata *u = ev_userdata (EV_A); |
|
|
4419 | |
|
|
4420 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4421 | |
|
|
4422 | pthread_mutex_lock (&u->lock); |
|
|
4423 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4424 | ev_async_send (EV_A_ &u->async_w); |
|
|
4425 | pthread_mutex_unlock (&u->lock); |
|
|
4426 | |
|
|
4427 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4428 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4429 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4430 | watchers in the next event loop iteration. |
|
|
4431 | |
4736 | |
4432 | =head3 COROUTINES |
4737 | =head3 COROUTINES |
4433 | |
4738 | |
4434 | Libev is very accommodating to coroutines ("cooperative threads"): |
4739 | Libev is very accommodating to coroutines ("cooperative threads"): |
4435 | libev fully supports nesting calls to its functions from different |
4740 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4600 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4905 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4601 | model. Libev still offers limited functionality on this platform in |
4906 | model. Libev still offers limited functionality on this platform in |
4602 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4907 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4603 | descriptors. This only applies when using Win32 natively, not when using |
4908 | descriptors. This only applies when using Win32 natively, not when using |
4604 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4909 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4605 | as every compielr comes with a slightly differently broken/incompatible |
4910 | as every compiler comes with a slightly differently broken/incompatible |
4606 | environment. |
4911 | environment. |
4607 | |
4912 | |
4608 | Lifting these limitations would basically require the full |
4913 | Lifting these limitations would basically require the full |
4609 | re-implementation of the I/O system. If you are into this kind of thing, |
4914 | re-implementation of the I/O system. If you are into this kind of thing, |
4610 | then note that glib does exactly that for you in a very portable way (note |
4915 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4704 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5009 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4705 | assumes that the same (machine) code can be used to call any watcher |
5010 | assumes that the same (machine) code can be used to call any watcher |
4706 | callback: The watcher callbacks have different type signatures, but libev |
5011 | callback: The watcher callbacks have different type signatures, but libev |
4707 | calls them using an C<ev_watcher *> internally. |
5012 | calls them using an C<ev_watcher *> internally. |
4708 | |
5013 | |
|
|
5014 | =item pointer accesses must be thread-atomic |
|
|
5015 | |
|
|
5016 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5017 | writable in one piece - this is the case on all current architectures. |
|
|
5018 | |
4709 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5019 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4710 | |
5020 | |
4711 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5021 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4712 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5022 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4713 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5023 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4811 | =item Processing ev_async_send: O(number_of_async_watchers) |
5121 | =item Processing ev_async_send: O(number_of_async_watchers) |
4812 | |
5122 | |
4813 | =item Processing signals: O(max_signal_number) |
5123 | =item Processing signals: O(max_signal_number) |
4814 | |
5124 | |
4815 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5125 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4816 | calls in the current loop iteration. Checking for async and signal events |
5126 | calls in the current loop iteration and the loop is currently |
|
|
5127 | blocked. Checking for async and signal events involves iterating over all |
4817 | involves iterating over all running async watchers or all signal numbers. |
5128 | running async watchers or all signal numbers. |
4818 | |
5129 | |
4819 | =back |
5130 | =back |
4820 | |
5131 | |
4821 | |
5132 | |
4822 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5133 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4823 | |
5134 | |
4824 | The major version 4 introduced some minor incompatible changes to the API. |
5135 | The major version 4 introduced some incompatible changes to the API. |
4825 | |
5136 | |
4826 | At the moment, the C<ev.h> header file tries to implement superficial |
5137 | At the moment, the C<ev.h> header file provides compatibility definitions |
4827 | compatibility, so most programs should still compile. Those might be |
5138 | for all changes, so most programs should still compile. The compatibility |
4828 | removed in later versions of libev, so better update early than late. |
5139 | layer might be removed in later versions of libev, so better update to the |
|
|
5140 | new API early than late. |
4829 | |
5141 | |
4830 | =over 4 |
5142 | =over 4 |
|
|
5143 | |
|
|
5144 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5145 | |
|
|
5146 | The backward compatibility mechanism can be controlled by |
|
|
5147 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5148 | section. |
|
|
5149 | |
|
|
5150 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5151 | |
|
|
5152 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5153 | |
|
|
5154 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5155 | ev_loop_fork (EV_DEFAULT); |
4831 | |
5156 | |
4832 | =item function/symbol renames |
5157 | =item function/symbol renames |
4833 | |
5158 | |
4834 | A number of functions and symbols have been renamed: |
5159 | A number of functions and symbols have been renamed: |
4835 | |
5160 | |
… | |
… | |
4854 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5179 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4855 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5180 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4856 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5181 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4857 | typedef. |
5182 | typedef. |
4858 | |
5183 | |
4859 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4860 | |
|
|
4861 | The backward compatibility mechanism can be controlled by |
|
|
4862 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4863 | section. |
|
|
4864 | |
|
|
4865 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5184 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4866 | |
5185 | |
4867 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5186 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4868 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5187 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4869 | and work, but the library code will of course be larger. |
5188 | and work, but the library code will of course be larger. |
… | |
… | |
4931 | The physical time that is observed. It is apparently strictly monotonic :) |
5250 | The physical time that is observed. It is apparently strictly monotonic :) |
4932 | |
5251 | |
4933 | =item wall-clock time |
5252 | =item wall-clock time |
4934 | |
5253 | |
4935 | The time and date as shown on clocks. Unlike real time, it can actually |
5254 | The time and date as shown on clocks. Unlike real time, it can actually |
4936 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5255 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4937 | clock. |
5256 | clock. |
4938 | |
5257 | |
4939 | =item watcher |
5258 | =item watcher |
4940 | |
5259 | |
4941 | A data structure that describes interest in certain events. Watchers need |
5260 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
4943 | |
5262 | |
4944 | =back |
5263 | =back |
4945 | |
5264 | |
4946 | =head1 AUTHOR |
5265 | =head1 AUTHOR |
4947 | |
5266 | |
4948 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5267 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5268 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4949 | |
5269 | |