… | |
… | |
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_now_update> 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) throw ()) |
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) throw ()) |
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 case unless libev 3 compatibility is disabled, as libev |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
299 | 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: |
… | |
… | |
341 | |
396 | |
342 | If this flag bit is or'ed into the flag value (or the program runs setuid |
397 | If this flag bit is or'ed into the flag value (or the program runs setuid |
343 | or setgid) then libev will I<not> look at the environment variable |
398 | or setgid) then libev will I<not> look at the environment variable |
344 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
399 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
345 | override the flags completely if it is found in the environment. This is |
400 | override the flags completely if it is found in the environment. This is |
346 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, to work |
347 | around bugs. |
402 | around bugs, or to make libev threadsafe (accessing environment variables |
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403 | cannot be done in a threadsafe way, but usually it works if no other |
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404 | thread modifies them). |
348 | |
405 | |
349 | =item C<EVFLAG_FORKCHECK> |
406 | =item C<EVFLAG_FORKCHECK> |
350 | |
407 | |
351 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
408 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
352 | make libev check for a fork in each iteration by enabling this flag. |
409 | make libev check for a fork in each iteration by enabling this flag. |
… | |
… | |
366 | environment variable. |
423 | environment variable. |
367 | |
424 | |
368 | =item C<EVFLAG_NOINOTIFY> |
425 | =item C<EVFLAG_NOINOTIFY> |
369 | |
426 | |
370 | When this flag is specified, then libev will not attempt to use the |
427 | 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 |
428 | 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 |
429 | 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. |
430 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
431 | |
375 | =item C<EVFLAG_SIGNALFD> |
432 | =item C<EVFLAG_SIGNALFD> |
376 | |
433 | |
377 | When this flag is specified, then libev will attempt to use the |
434 | 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 |
435 | 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 |
436 | 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 |
437 | 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 |
438 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
439 | threads that are not interested in handling them. |
383 | |
440 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
441 | 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 |
442 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
443 | example) that can't properly initialise their signal masks. |
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444 | |
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445 | =item C<EVFLAG_NOSIGMASK> |
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446 | |
|
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447 | When this flag is specified, then libev will avoid to modify the signal |
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448 | mask. Specifically, this means you have to make sure signals are unblocked |
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449 | when you want to receive them. |
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450 | |
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451 | This behaviour is useful when you want to do your own signal handling, or |
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452 | want to handle signals only in specific threads and want to avoid libev |
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453 | unblocking the signals. |
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454 | |
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455 | It's also required by POSIX in a threaded program, as libev calls |
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456 | C<sigprocmask>, whose behaviour is officially unspecified. |
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457 | |
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458 | This flag's behaviour will become the default in future versions of libev. |
387 | |
459 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
460 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
461 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
462 | 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, |
463 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
491 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
420 | |
492 | |
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
493 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
422 | kernels). |
494 | kernels). |
423 | |
495 | |
424 | For few fds, this backend is a bit little slower than poll and select, |
496 | 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 |
497 | 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), |
498 | 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). |
499 | fd), epoll scales either O(1) or O(active_fds). |
428 | |
500 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
501 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
502 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
503 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
504 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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505 | returning before the timeout value, resulting in additional iterations |
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506 | (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 |
507 | 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 |
508 | 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 |
509 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
510 | and is of course hard to detect. |
437 | |
511 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
512 | 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 |
513 | 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 |
514 | totally I<different> file descriptors (even already closed ones, so |
441 | even remove them from the set) than registered in the set (especially |
515 | 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 |
516 | (especially on SMP systems). Libev tries to counter these spurious |
443 | employing an additional generation counter and comparing that against the |
517 | notifications by employing an additional generation counter and comparing |
444 | events to filter out spurious ones, recreating the set when required. Last |
518 | that against the events to filter out spurious ones, recreating the set |
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519 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
520 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
521 | because epoll returns immediately despite a nonzero timeout. And last |
445 | not least, it also refuses to work with some file descriptors which work |
522 | not least, it also refuses to work with some file descriptors which work |
446 | perfectly fine with C<select> (files, many character devices...). |
523 | perfectly fine with C<select> (files, many character devices...). |
|
|
524 | |
|
|
525 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
526 | cobbled together in a hurry, no thought to design or interaction with |
|
|
527 | others. Oh, the pain, will it ever stop... |
447 | |
528 | |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
529 | 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 |
530 | 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 |
531 | 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 |
532 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
488 | |
569 | |
489 | It scales in the same way as the epoll backend, but the interface to the |
570 | It scales in the same way as the epoll backend, but the interface to the |
490 | kernel is more efficient (which says nothing about its actual speed, of |
571 | kernel is more efficient (which says nothing about its actual speed, of |
491 | course). While stopping, setting and starting an I/O watcher does never |
572 | course). While stopping, setting and starting an I/O watcher does never |
492 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
573 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
493 | two event changes per incident. Support for C<fork ()> is very bad (but |
574 | two event changes per incident. Support for C<fork ()> is very bad (you |
494 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
575 | might have to leak fd's on fork, but it's more sane than epoll) and it |
495 | cases |
576 | drops fds silently in similarly hard-to-detect cases. |
496 | |
577 | |
497 | This backend usually performs well under most conditions. |
578 | This backend usually performs well under most conditions. |
498 | |
579 | |
499 | While nominally embeddable in other event loops, this doesn't work |
580 | While nominally embeddable in other event loops, this doesn't work |
500 | everywhere, so you might need to test for this. And since it is broken |
581 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
517 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
598 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
518 | |
599 | |
519 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
600 | 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)). |
601 | it's really slow, but it still scales very well (O(active_fds)). |
521 | |
602 | |
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 |
603 | 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 |
604 | file descriptor per loop iteration. For small and medium numbers of file |
528 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
605 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
529 | might perform better. |
606 | might perform better. |
530 | |
607 | |
531 | On the positive side, with the exception of the spurious readiness |
608 | 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 |
609 | specification in all tests and is fully embeddable, which is a rare feat |
534 | OS-specific backends (I vastly prefer correctness over speed hacks). |
610 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
611 | hacks). |
|
|
612 | |
|
|
613 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
614 | even sun itself gets it wrong in their code examples: The event polling |
|
|
615 | function sometimes returns events to the caller even though an error |
|
|
616 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
617 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
618 | absolutely have to know whether an event occurred or not because you have |
|
|
619 | to re-arm the watcher. |
|
|
620 | |
|
|
621 | Fortunately libev seems to be able to work around these idiocies. |
535 | |
622 | |
536 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
623 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
537 | C<EVBACKEND_POLL>. |
624 | C<EVBACKEND_POLL>. |
538 | |
625 | |
539 | =item C<EVBACKEND_ALL> |
626 | =item C<EVBACKEND_ALL> |
540 | |
627 | |
541 | Try all backends (even potentially broken ones that wouldn't be tried |
628 | 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 |
629 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
543 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
630 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
544 | |
631 | |
545 | It is definitely not recommended to use this flag. |
632 | It is definitely not recommended to use this flag, use whatever |
|
|
633 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
634 | at all. |
|
|
635 | |
|
|
636 | =item C<EVBACKEND_MASK> |
|
|
637 | |
|
|
638 | Not a backend at all, but a mask to select all backend bits from a |
|
|
639 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
640 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
546 | |
641 | |
547 | =back |
642 | =back |
548 | |
643 | |
549 | If one or more of the backend flags are or'ed into the flags value, |
644 | 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 |
645 | 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 |
646 | here). If none are specified, all backends in C<ev_recommended_backends |
552 | ()> will be tried. |
647 | ()> will be tried. |
553 | |
648 | |
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. |
649 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
650 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
651 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
652 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
653 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
654 | |
|
|
655 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
656 | used if available. |
|
|
657 | |
|
|
658 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
659 | |
586 | =item ev_default_destroy () |
660 | =item ev_loop_destroy (loop) |
587 | |
661 | |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
662 | 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 |
663 | 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 |
664 | 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, |
665 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
666 | 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). |
667 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
668 | for example). |
594 | |
669 | |
595 | Note that certain global state, such as signal state (and installed signal |
670 | 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 |
671 | handlers), will not be freed by this function, and related watchers (such |
597 | as signal and child watchers) would need to be stopped manually. |
672 | as signal and child watchers) would need to be stopped manually. |
598 | |
673 | |
599 | In general it is not advisable to call this function except in the |
674 | This function is normally used on loop objects allocated by |
600 | rare occasion where you really need to free e.g. the signal handling |
675 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
676 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
677 | |
|
|
678 | Note that it is not advisable to call this function on the default loop |
|
|
679 | 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 |
680 | 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>. |
681 | and C<ev_loop_destroy>. |
603 | |
682 | |
604 | =item ev_loop_destroy (loop) |
683 | =item ev_loop_fork (loop) |
605 | |
684 | |
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 |
685 | 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 |
686 | 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 |
687 | 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 |
688 | 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 |
689 | child before resuming or calling C<ev_run>. |
616 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
617 | |
690 | |
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
691 | 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 |
692 | 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 |
693 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
621 | during fork. |
694 | during fork. |
… | |
… | |
626 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
699 | 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 |
700 | difference, but libev will usually detect this case on its own and do a |
628 | costly reset of the backend). |
701 | costly reset of the backend). |
629 | |
702 | |
630 | The function itself is quite fast and it's usually not a problem to call |
703 | 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 |
704 | it just in case after a fork. |
632 | quite nicely into a call to C<pthread_atfork>: |
|
|
633 | |
705 | |
|
|
706 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
707 | using pthreads. |
|
|
708 | |
|
|
709 | static void |
|
|
710 | post_fork_child (void) |
|
|
711 | { |
|
|
712 | ev_loop_fork (EV_DEFAULT); |
|
|
713 | } |
|
|
714 | |
|
|
715 | ... |
634 | pthread_atfork (0, 0, ev_default_fork); |
716 | 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 | |
717 | |
643 | =item int ev_is_default_loop (loop) |
718 | =item int ev_is_default_loop (loop) |
644 | |
719 | |
645 | Returns true when the given loop is, in fact, the default loop, and false |
720 | Returns true when the given loop is, in fact, the default loop, and false |
646 | otherwise. |
721 | otherwise. |
… | |
… | |
657 | prepare and check phases. |
732 | prepare and check phases. |
658 | |
733 | |
659 | =item unsigned int ev_depth (loop) |
734 | =item unsigned int ev_depth (loop) |
660 | |
735 | |
661 | Returns the number of times C<ev_run> was entered minus the number of |
736 | 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. |
737 | times C<ev_run> was exited normally, in other words, the recursion depth. |
663 | |
738 | |
664 | Outside C<ev_run>, this number is zero. In a callback, this number is |
739 | 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), |
740 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
666 | in which case it is higher. |
741 | in which case it is higher. |
667 | |
742 | |
668 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
743 | 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 |
744 | throwing an exception etc.), doesn't count as "exit" - consider this |
670 | ungentleman-like behaviour unless it's really convenient. |
745 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
746 | convenient, in which case it is fully supported. |
671 | |
747 | |
672 | =item unsigned int ev_backend (loop) |
748 | =item unsigned int ev_backend (loop) |
673 | |
749 | |
674 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
750 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
675 | use. |
751 | use. |
… | |
… | |
690 | |
766 | |
691 | This function is rarely useful, but when some event callback runs for a |
767 | This function is rarely useful, but when some event callback runs for a |
692 | very long time without entering the event loop, updating libev's idea of |
768 | very long time without entering the event loop, updating libev's idea of |
693 | the current time is a good idea. |
769 | the current time is a good idea. |
694 | |
770 | |
695 | See also L<The special problem of time updates> in the C<ev_timer> section. |
771 | See also L</The special problem of time updates> in the C<ev_timer> section. |
696 | |
772 | |
697 | =item ev_suspend (loop) |
773 | =item ev_suspend (loop) |
698 | |
774 | |
699 | =item ev_resume (loop) |
775 | =item ev_resume (loop) |
700 | |
776 | |
… | |
… | |
718 | without a previous call to C<ev_suspend>. |
794 | without a previous call to C<ev_suspend>. |
719 | |
795 | |
720 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
796 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
721 | event loop time (see C<ev_now_update>). |
797 | event loop time (see C<ev_now_update>). |
722 | |
798 | |
723 | =item ev_run (loop, int flags) |
799 | =item bool ev_run (loop, int flags) |
724 | |
800 | |
725 | Finally, this is it, the event handler. This function usually is called |
801 | Finally, this is it, the event handler. This function usually is called |
726 | after you have initialised all your watchers and you want to start |
802 | after you have initialised all your watchers and you want to start |
727 | handling events. It will ask the operating system for any new events, call |
803 | handling events. It will ask the operating system for any new events, call |
728 | the watcher callbacks, an then repeat the whole process indefinitely: This |
804 | the watcher callbacks, and then repeat the whole process indefinitely: This |
729 | is why event loops are called I<loops>. |
805 | is why event loops are called I<loops>. |
730 | |
806 | |
731 | If the flags argument is specified as C<0>, it will keep handling events |
807 | If the flags argument is specified as C<0>, it will keep handling events |
732 | until either no event watchers are active anymore or C<ev_break> was |
808 | until either no event watchers are active anymore or C<ev_break> was |
733 | called. |
809 | called. |
|
|
810 | |
|
|
811 | The return value is false if there are no more active watchers (which |
|
|
812 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
813 | (which usually means " you should call C<ev_run> again"). |
734 | |
814 | |
735 | Please note that an explicit C<ev_break> is usually better than |
815 | Please note that an explicit C<ev_break> is usually better than |
736 | relying on all watchers to be stopped when deciding when a program has |
816 | relying on all watchers to be stopped when deciding when a program has |
737 | finished (especially in interactive programs), but having a program |
817 | finished (especially in interactive programs), but having a program |
738 | that automatically loops as long as it has to and no longer by virtue |
818 | 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 |
819 | of relying on its watchers stopping correctly, that is truly a thing of |
740 | beauty. |
820 | beauty. |
741 | |
821 | |
|
|
822 | This function is I<mostly> exception-safe - you can break out of a |
|
|
823 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
824 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
825 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
826 | |
742 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
827 | 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 |
828 | 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 |
829 | 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 |
830 | iteration of the loop. This is sometimes useful to poll and handle new |
746 | events while doing lengthy calculations, to keep the program responsive. |
831 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
755 | This is useful if you are waiting for some external event in conjunction |
840 | 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 |
841 | 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 |
842 | 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. |
843 | usually a better approach for this kind of thing. |
759 | |
844 | |
760 | Here are the gory details of what C<ev_run> does: |
845 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
846 | understanding, not a guarantee that things will work exactly like this in |
|
|
847 | future versions): |
761 | |
848 | |
762 | - Increment loop depth. |
849 | - Increment loop depth. |
763 | - Reset the ev_break status. |
850 | - Reset the ev_break status. |
764 | - Before the first iteration, call any pending watchers. |
851 | - Before the first iteration, call any pending watchers. |
765 | LOOP: |
852 | LOOP: |
… | |
… | |
798 | anymore. |
885 | anymore. |
799 | |
886 | |
800 | ... queue jobs here, make sure they register event watchers as long |
887 | ... 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..) |
888 | ... as they still have work to do (even an idle watcher will do..) |
802 | ev_run (my_loop, 0); |
889 | ev_run (my_loop, 0); |
803 | ... jobs done or somebody called unloop. yeah! |
890 | ... jobs done or somebody called break. yeah! |
804 | |
891 | |
805 | =item ev_break (loop, how) |
892 | =item ev_break (loop, how) |
806 | |
893 | |
807 | Can be used to make a call to C<ev_run> return early (but only after it |
894 | 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 |
895 | 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 |
896 | 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. |
897 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
811 | |
898 | |
812 | This "unloop state" will be cleared when entering C<ev_run> again. |
899 | This "break state" will be cleared on the next call to C<ev_run>. |
813 | |
900 | |
814 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
901 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
902 | which case it will have no effect. |
815 | |
903 | |
816 | =item ev_ref (loop) |
904 | =item ev_ref (loop) |
817 | |
905 | |
818 | =item ev_unref (loop) |
906 | =item ev_unref (loop) |
819 | |
907 | |
… | |
… | |
840 | running when nothing else is active. |
928 | running when nothing else is active. |
841 | |
929 | |
842 | ev_signal exitsig; |
930 | ev_signal exitsig; |
843 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
931 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
844 | ev_signal_start (loop, &exitsig); |
932 | ev_signal_start (loop, &exitsig); |
845 | evf_unref (loop); |
933 | ev_unref (loop); |
846 | |
934 | |
847 | Example: For some weird reason, unregister the above signal handler again. |
935 | Example: For some weird reason, unregister the above signal handler again. |
848 | |
936 | |
849 | ev_ref (loop); |
937 | ev_ref (loop); |
850 | ev_signal_stop (loop, &exitsig); |
938 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
870 | overhead for the actual polling but can deliver many events at once. |
958 | overhead for the actual polling but can deliver many events at once. |
871 | |
959 | |
872 | By setting a higher I<io collect interval> you allow libev to spend more |
960 | 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, |
961 | 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 |
962 | 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 |
963 | 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 |
964 | 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 |
965 | sleep time ensures that libev will not poll for I/O events more often then |
878 | once per this interval, on average. |
966 | once per this interval, on average (as long as the host time resolution is |
|
|
967 | good enough). |
879 | |
968 | |
880 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
969 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
881 | to spend more time collecting timeouts, at the expense of increased |
970 | to spend more time collecting timeouts, at the expense of increased |
882 | latency/jitter/inexactness (the watcher callback will be called |
971 | 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 |
972 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
908 | |
997 | |
909 | =item ev_invoke_pending (loop) |
998 | =item ev_invoke_pending (loop) |
910 | |
999 | |
911 | This call will simply invoke all pending watchers while resetting their |
1000 | This call will simply invoke all pending watchers while resetting their |
912 | pending state. Normally, C<ev_run> does this automatically when required, |
1001 | pending state. Normally, C<ev_run> does this automatically when required, |
913 | but when overriding the invoke callback this call comes handy. |
1002 | but when overriding the invoke callback this call comes handy. This |
|
|
1003 | function can be invoked from a watcher - this can be useful for example |
|
|
1004 | when you want to do some lengthy calculation and want to pass further |
|
|
1005 | event handling to another thread (you still have to make sure only one |
|
|
1006 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
914 | |
1007 | |
915 | =item int ev_pending_count (loop) |
1008 | =item int ev_pending_count (loop) |
916 | |
1009 | |
917 | Returns the number of pending watchers - zero indicates that no watchers |
1010 | Returns the number of pending watchers - zero indicates that no watchers |
918 | are pending. |
1011 | are pending. |
… | |
… | |
925 | invoke the actual watchers inside another context (another thread etc.). |
1018 | invoke the actual watchers inside another context (another thread etc.). |
926 | |
1019 | |
927 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1020 | If you want to reset the callback, use C<ev_invoke_pending> as new |
928 | callback. |
1021 | callback. |
929 | |
1022 | |
930 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1023 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
931 | |
1024 | |
932 | Sometimes you want to share the same loop between multiple threads. This |
1025 | Sometimes you want to share the same loop between multiple threads. This |
933 | can be done relatively simply by putting mutex_lock/unlock calls around |
1026 | can be done relatively simply by putting mutex_lock/unlock calls around |
934 | each call to a libev function. |
1027 | each call to a libev function. |
935 | |
1028 | |
936 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1029 | However, C<ev_run> can run an indefinite time, so it is not feasible |
937 | to wait for it to return. One way around this is to wake up the event |
1030 | to wait for it to return. One way around this is to wake up the event |
938 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1031 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
939 | I<release> and I<acquire> callbacks on the loop. |
1032 | I<release> and I<acquire> callbacks on the loop. |
940 | |
1033 | |
941 | When set, then C<release> will be called just before the thread is |
1034 | When set, then C<release> will be called just before the thread is |
942 | suspended waiting for new events, and C<acquire> is called just |
1035 | suspended waiting for new events, and C<acquire> is called just |
943 | afterwards. |
1036 | afterwards. |
… | |
… | |
958 | See also the locking example in the C<THREADS> section later in this |
1051 | See also the locking example in the C<THREADS> section later in this |
959 | document. |
1052 | document. |
960 | |
1053 | |
961 | =item ev_set_userdata (loop, void *data) |
1054 | =item ev_set_userdata (loop, void *data) |
962 | |
1055 | |
963 | =item ev_userdata (loop) |
1056 | =item void *ev_userdata (loop) |
964 | |
1057 | |
965 | Set and retrieve a single C<void *> associated with a loop. When |
1058 | Set and retrieve a single C<void *> associated with a loop. When |
966 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1059 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
967 | C<0.> |
1060 | C<0>. |
968 | |
1061 | |
969 | These two functions can be used to associate arbitrary data with a loop, |
1062 | These two functions can be used to associate arbitrary data with a loop, |
970 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1063 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
971 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1064 | C<acquire> callbacks described above, but of course can be (ab-)used for |
972 | any other purpose as well. |
1065 | any other purpose as well. |
… | |
… | |
990 | |
1083 | |
991 | In the following description, uppercase C<TYPE> in names stands for the |
1084 | In the following description, uppercase C<TYPE> in names stands for the |
992 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1085 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
993 | watchers and C<ev_io_start> for I/O watchers. |
1086 | watchers and C<ev_io_start> for I/O watchers. |
994 | |
1087 | |
995 | A watcher is a structure that you create and register to record your |
1088 | A watcher is an opaque structure that you allocate and register to record |
996 | interest in some event. For instance, if you want to wait for STDIN to |
1089 | your interest in some event. To make a concrete example, imagine you want |
997 | become readable, you would create an C<ev_io> watcher for that: |
1090 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1091 | for that: |
998 | |
1092 | |
999 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1093 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1000 | { |
1094 | { |
1001 | ev_io_stop (w); |
1095 | ev_io_stop (w); |
1002 | ev_break (loop, EVBREAK_ALL); |
1096 | ev_break (loop, EVBREAK_ALL); |
… | |
… | |
1017 | stack). |
1111 | stack). |
1018 | |
1112 | |
1019 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1113 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1020 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1114 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1021 | |
1115 | |
1022 | Each watcher structure must be initialised by a call to C<ev_init |
1116 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
1023 | (watcher *, callback)>, which expects a callback to be provided. This |
1117 | *, callback)>, which expects a callback to be provided. This callback is |
1024 | callback gets invoked each time the event occurs (or, in the case of I/O |
1118 | invoked each time the event occurs (or, in the case of I/O watchers, each |
1025 | watchers, each time the event loop detects that the file descriptor given |
1119 | time the event loop detects that the file descriptor given is readable |
1026 | is readable and/or writable). |
1120 | and/or writable). |
1027 | |
1121 | |
1028 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1122 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1029 | macro to configure it, with arguments specific to the watcher type. There |
1123 | macro to configure it, with arguments specific to the watcher type. There |
1030 | is also a macro to combine initialisation and setting in one call: C<< |
1124 | is also a macro to combine initialisation and setting in one call: C<< |
1031 | ev_TYPE_init (watcher *, callback, ...) >>. |
1125 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
1082 | |
1176 | |
1083 | =item C<EV_PREPARE> |
1177 | =item C<EV_PREPARE> |
1084 | |
1178 | |
1085 | =item C<EV_CHECK> |
1179 | =item C<EV_CHECK> |
1086 | |
1180 | |
1087 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1181 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1088 | to gather new events, and all C<ev_check> watchers are invoked just after |
1182 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1089 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1183 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1184 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1185 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1186 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1187 | or lower priority within an event loop iteration. |
|
|
1188 | |
1090 | received events. Callbacks of both watcher types can start and stop as |
1189 | Callbacks of both watcher types can start and stop as many watchers as |
1091 | many watchers as they want, and all of them will be taken into account |
1190 | they want, and all of them will be taken into account (for example, a |
1092 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1191 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1093 | C<ev_run> from blocking). |
1192 | blocking). |
1094 | |
1193 | |
1095 | =item C<EV_EMBED> |
1194 | =item C<EV_EMBED> |
1096 | |
1195 | |
1097 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1196 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1098 | |
1197 | |
1099 | =item C<EV_FORK> |
1198 | =item C<EV_FORK> |
1100 | |
1199 | |
1101 | The event loop has been resumed in the child process after fork (see |
1200 | The event loop has been resumed in the child process after fork (see |
1102 | C<ev_fork>). |
1201 | C<ev_fork>). |
|
|
1202 | |
|
|
1203 | =item C<EV_CLEANUP> |
|
|
1204 | |
|
|
1205 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1103 | |
1206 | |
1104 | =item C<EV_ASYNC> |
1207 | =item C<EV_ASYNC> |
1105 | |
1208 | |
1106 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1209 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1107 | |
1210 | |
… | |
… | |
1217 | |
1320 | |
1218 | =item callback ev_cb (ev_TYPE *watcher) |
1321 | =item callback ev_cb (ev_TYPE *watcher) |
1219 | |
1322 | |
1220 | Returns the callback currently set on the watcher. |
1323 | Returns the callback currently set on the watcher. |
1221 | |
1324 | |
1222 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1325 | =item ev_set_cb (ev_TYPE *watcher, callback) |
1223 | |
1326 | |
1224 | Change the callback. You can change the callback at virtually any time |
1327 | Change the callback. You can change the callback at virtually any time |
1225 | (modulo threads). |
1328 | (modulo threads). |
1226 | |
1329 | |
1227 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1330 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
… | |
… | |
1245 | or might not have been clamped to the valid range. |
1348 | or might not have been clamped to the valid range. |
1246 | |
1349 | |
1247 | The default priority used by watchers when no priority has been set is |
1350 | The default priority used by watchers when no priority has been set is |
1248 | always C<0>, which is supposed to not be too high and not be too low :). |
1351 | always C<0>, which is supposed to not be too high and not be too low :). |
1249 | |
1352 | |
1250 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1353 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1251 | priorities. |
1354 | priorities. |
1252 | |
1355 | |
1253 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1356 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1254 | |
1357 | |
1255 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1358 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
… | |
… | |
1280 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1383 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1281 | functions that do not need a watcher. |
1384 | functions that do not need a watcher. |
1282 | |
1385 | |
1283 | =back |
1386 | =back |
1284 | |
1387 | |
|
|
1388 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1389 | OWN COMPOSITE WATCHERS> idioms. |
1285 | |
1390 | |
1286 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1391 | =head2 WATCHER STATES |
1287 | |
1392 | |
1288 | Each watcher has, by default, a member C<void *data> that you can change |
1393 | There are various watcher states mentioned throughout this manual - |
1289 | and read at any time: libev will completely ignore it. This can be used |
1394 | active, pending and so on. In this section these states and the rules to |
1290 | to associate arbitrary data with your watcher. If you need more data and |
1395 | transition between them will be described in more detail - and while these |
1291 | don't want to allocate memory and store a pointer to it in that data |
1396 | rules might look complicated, they usually do "the right thing". |
1292 | member, you can also "subclass" the watcher type and provide your own |
|
|
1293 | data: |
|
|
1294 | |
1397 | |
1295 | struct my_io |
1398 | =over 4 |
1296 | { |
|
|
1297 | ev_io io; |
|
|
1298 | int otherfd; |
|
|
1299 | void *somedata; |
|
|
1300 | struct whatever *mostinteresting; |
|
|
1301 | }; |
|
|
1302 | |
1399 | |
1303 | ... |
1400 | =item initialised |
1304 | struct my_io w; |
|
|
1305 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1306 | |
1401 | |
1307 | And since your callback will be called with a pointer to the watcher, you |
1402 | Before a watcher can be registered with the event loop it has to be |
1308 | can cast it back to your own type: |
1403 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1404 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1309 | |
1405 | |
1310 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1406 | In this state it is simply some block of memory that is suitable for |
1311 | { |
1407 | use in an event loop. It can be moved around, freed, reused etc. at |
1312 | struct my_io *w = (struct my_io *)w_; |
1408 | will - as long as you either keep the memory contents intact, or call |
1313 | ... |
1409 | C<ev_TYPE_init> again. |
1314 | } |
|
|
1315 | |
1410 | |
1316 | More interesting and less C-conformant ways of casting your callback type |
1411 | =item started/running/active |
1317 | instead have been omitted. |
|
|
1318 | |
1412 | |
1319 | Another common scenario is to use some data structure with multiple |
1413 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1320 | embedded watchers: |
1414 | property of the event loop, and is actively waiting for events. While in |
|
|
1415 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1416 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1417 | and call libev functions on it that are documented to work on active watchers. |
1321 | |
1418 | |
1322 | struct my_biggy |
1419 | =item pending |
1323 | { |
|
|
1324 | int some_data; |
|
|
1325 | ev_timer t1; |
|
|
1326 | ev_timer t2; |
|
|
1327 | } |
|
|
1328 | |
1420 | |
1329 | In this case getting the pointer to C<my_biggy> is a bit more |
1421 | If a watcher is active and libev determines that an event it is interested |
1330 | complicated: Either you store the address of your C<my_biggy> struct |
1422 | in has occurred (such as a timer expiring), it will become pending. It will |
1331 | in the C<data> member of the watcher (for woozies), or you need to use |
1423 | stay in this pending state until either it is stopped or its callback is |
1332 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1424 | about to be invoked, so it is not normally pending inside the watcher |
1333 | programmers): |
1425 | callback. |
1334 | |
1426 | |
1335 | #include <stddef.h> |
1427 | The watcher might or might not be active while it is pending (for example, |
|
|
1428 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1429 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1430 | but it is still property of the event loop at this time, so cannot be |
|
|
1431 | moved, freed or reused. And if it is active the rules described in the |
|
|
1432 | previous item still apply. |
1336 | |
1433 | |
1337 | static void |
1434 | It is also possible to feed an event on a watcher that is not active (e.g. |
1338 | t1_cb (EV_P_ ev_timer *w, int revents) |
1435 | via C<ev_feed_event>), in which case it becomes pending without being |
1339 | { |
1436 | active. |
1340 | struct my_biggy big = (struct my_biggy *) |
|
|
1341 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1342 | } |
|
|
1343 | |
1437 | |
1344 | static void |
1438 | =item stopped |
1345 | t2_cb (EV_P_ ev_timer *w, int revents) |
1439 | |
1346 | { |
1440 | A watcher can be stopped implicitly by libev (in which case it might still |
1347 | struct my_biggy big = (struct my_biggy *) |
1441 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1348 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1442 | latter will clear any pending state the watcher might be in, regardless |
1349 | } |
1443 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1444 | freeing it is often a good idea. |
|
|
1445 | |
|
|
1446 | While stopped (and not pending) the watcher is essentially in the |
|
|
1447 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1448 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1449 | it again). |
|
|
1450 | |
|
|
1451 | =back |
1350 | |
1452 | |
1351 | =head2 WATCHER PRIORITY MODELS |
1453 | =head2 WATCHER PRIORITY MODELS |
1352 | |
1454 | |
1353 | Many event loops support I<watcher priorities>, which are usually small |
1455 | Many event loops support I<watcher priorities>, which are usually small |
1354 | integers that influence the ordering of event callback invocation |
1456 | integers that influence the ordering of event callback invocation |
… | |
… | |
1481 | In general you can register as many read and/or write event watchers per |
1583 | In general you can register as many read and/or write event watchers per |
1482 | fd as you want (as long as you don't confuse yourself). Setting all file |
1584 | fd as you want (as long as you don't confuse yourself). Setting all file |
1483 | descriptors to non-blocking mode is also usually a good idea (but not |
1585 | descriptors to non-blocking mode is also usually a good idea (but not |
1484 | required if you know what you are doing). |
1586 | required if you know what you are doing). |
1485 | |
1587 | |
1486 | If you cannot use non-blocking mode, then force the use of a |
|
|
1487 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1488 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1489 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1490 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1491 | |
|
|
1492 | Another thing you have to watch out for is that it is quite easy to |
1588 | Another thing you have to watch out for is that it is quite easy to |
1493 | receive "spurious" readiness notifications, that is your callback might |
1589 | receive "spurious" readiness notifications, that is, your callback might |
1494 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1590 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1495 | because there is no data. Not only are some backends known to create a |
1591 | because there is no data. It is very easy to get into this situation even |
1496 | lot of those (for example Solaris ports), it is very easy to get into |
1592 | with a relatively standard program structure. Thus it is best to always |
1497 | this situation even with a relatively standard program structure. Thus |
1593 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1498 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1499 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1594 | preferable to a program hanging until some data arrives. |
1500 | |
1595 | |
1501 | If you cannot run the fd in non-blocking mode (for example you should |
1596 | If you cannot run the fd in non-blocking mode (for example you should |
1502 | not play around with an Xlib connection), then you have to separately |
1597 | not play around with an Xlib connection), then you have to separately |
1503 | re-test whether a file descriptor is really ready with a known-to-be good |
1598 | re-test whether a file descriptor is really ready with a known-to-be good |
1504 | interface such as poll (fortunately in our Xlib example, Xlib already |
1599 | interface such as poll (fortunately in the case of Xlib, it already does |
1505 | does this on its own, so its quite safe to use). Some people additionally |
1600 | this on its own, so its quite safe to use). Some people additionally |
1506 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1601 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1507 | indefinitely. |
1602 | indefinitely. |
1508 | |
1603 | |
1509 | But really, best use non-blocking mode. |
1604 | But really, best use non-blocking mode. |
1510 | |
1605 | |
… | |
… | |
1538 | |
1633 | |
1539 | There is no workaround possible except not registering events |
1634 | There is no workaround possible except not registering events |
1540 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1635 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1541 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1636 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1542 | |
1637 | |
|
|
1638 | =head3 The special problem of files |
|
|
1639 | |
|
|
1640 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1641 | representing files, and expect it to become ready when their program |
|
|
1642 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1643 | |
|
|
1644 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1645 | notification as soon as the kernel knows whether and how much data is |
|
|
1646 | there, and in the case of open files, that's always the case, so you |
|
|
1647 | always get a readiness notification instantly, and your read (or possibly |
|
|
1648 | write) will still block on the disk I/O. |
|
|
1649 | |
|
|
1650 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1651 | devices and so on, there is another party (the sender) that delivers data |
|
|
1652 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1653 | will not send data on its own, simply because it doesn't know what you |
|
|
1654 | wish to read - you would first have to request some data. |
|
|
1655 | |
|
|
1656 | Since files are typically not-so-well supported by advanced notification |
|
|
1657 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1658 | to files, even though you should not use it. The reason for this is |
|
|
1659 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1660 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1661 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1662 | F</dev/urandom>), and even though the file might better be served with |
|
|
1663 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1664 | it "just works" instead of freezing. |
|
|
1665 | |
|
|
1666 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1667 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1668 | when you rarely read from a file instead of from a socket, and want to |
|
|
1669 | reuse the same code path. |
|
|
1670 | |
1543 | =head3 The special problem of fork |
1671 | =head3 The special problem of fork |
1544 | |
1672 | |
1545 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1673 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1546 | useless behaviour. Libev fully supports fork, but needs to be told about |
1674 | useless behaviour. Libev fully supports fork, but needs to be told about |
1547 | it in the child. |
1675 | it in the child if you want to continue to use it in the child. |
1548 | |
1676 | |
1549 | To support fork in your programs, you either have to call |
1677 | To support fork in your child processes, you have to call C<ev_loop_fork |
1550 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1678 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1551 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1679 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1552 | C<EVBACKEND_POLL>. |
|
|
1553 | |
1680 | |
1554 | =head3 The special problem of SIGPIPE |
1681 | =head3 The special problem of SIGPIPE |
1555 | |
1682 | |
1556 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1683 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1557 | when writing to a pipe whose other end has been closed, your program gets |
1684 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1655 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1782 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1656 | monotonic clock option helps a lot here). |
1783 | monotonic clock option helps a lot here). |
1657 | |
1784 | |
1658 | The callback is guaranteed to be invoked only I<after> its timeout has |
1785 | The callback is guaranteed to be invoked only I<after> its timeout has |
1659 | passed (not I<at>, so on systems with very low-resolution clocks this |
1786 | passed (not I<at>, so on systems with very low-resolution clocks this |
1660 | might introduce a small delay). If multiple timers become ready during the |
1787 | might introduce a small delay, see "the special problem of being too |
|
|
1788 | early", below). If multiple timers become ready during the same loop |
1661 | same loop iteration then the ones with earlier time-out values are invoked |
1789 | iteration then the ones with earlier time-out values are invoked before |
1662 | before ones of the same priority with later time-out values (but this is |
1790 | ones of the same priority with later time-out values (but this is no |
1663 | no longer true when a callback calls C<ev_run> recursively). |
1791 | longer true when a callback calls C<ev_run> recursively). |
1664 | |
1792 | |
1665 | =head3 Be smart about timeouts |
1793 | =head3 Be smart about timeouts |
1666 | |
1794 | |
1667 | Many real-world problems involve some kind of timeout, usually for error |
1795 | Many real-world problems involve some kind of timeout, usually for error |
1668 | recovery. A typical example is an HTTP request - if the other side hangs, |
1796 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1743 | |
1871 | |
1744 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1872 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1745 | but remember the time of last activity, and check for a real timeout only |
1873 | but remember the time of last activity, and check for a real timeout only |
1746 | within the callback: |
1874 | within the callback: |
1747 | |
1875 | |
|
|
1876 | ev_tstamp timeout = 60.; |
1748 | ev_tstamp last_activity; // time of last activity |
1877 | ev_tstamp last_activity; // time of last activity |
|
|
1878 | ev_timer timer; |
1749 | |
1879 | |
1750 | static void |
1880 | static void |
1751 | callback (EV_P_ ev_timer *w, int revents) |
1881 | callback (EV_P_ ev_timer *w, int revents) |
1752 | { |
1882 | { |
1753 | ev_tstamp now = ev_now (EV_A); |
1883 | // calculate when the timeout would happen |
1754 | ev_tstamp timeout = last_activity + 60.; |
1884 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1755 | |
1885 | |
1756 | // if last_activity + 60. is older than now, we did time out |
1886 | // if negative, it means we the timeout already occurred |
1757 | if (timeout < now) |
1887 | if (after < 0.) |
1758 | { |
1888 | { |
1759 | // timeout occurred, take action |
1889 | // timeout occurred, take action |
1760 | } |
1890 | } |
1761 | else |
1891 | else |
1762 | { |
1892 | { |
1763 | // callback was invoked, but there was some activity, re-arm |
1893 | // callback was invoked, but there was some recent |
1764 | // the watcher to fire in last_activity + 60, which is |
1894 | // activity. simply restart the timer to time out |
1765 | // guaranteed to be in the future, so "again" is positive: |
1895 | // after "after" seconds, which is the earliest time |
1766 | w->repeat = timeout - now; |
1896 | // the timeout can occur. |
|
|
1897 | ev_timer_set (w, after, 0.); |
1767 | ev_timer_again (EV_A_ w); |
1898 | ev_timer_start (EV_A_ w); |
1768 | } |
1899 | } |
1769 | } |
1900 | } |
1770 | |
1901 | |
1771 | To summarise the callback: first calculate the real timeout (defined |
1902 | To summarise the callback: first calculate in how many seconds the |
1772 | as "60 seconds after the last activity"), then check if that time has |
1903 | timeout will occur (by calculating the absolute time when it would occur, |
1773 | been reached, which means something I<did>, in fact, time out. Otherwise |
1904 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1774 | the callback was invoked too early (C<timeout> is in the future), so |
1905 | (EV_A)> from that). |
1775 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1776 | a timeout then. |
|
|
1777 | |
1906 | |
1778 | Note how C<ev_timer_again> is used, taking advantage of the |
1907 | If this value is negative, then we are already past the timeout, i.e. we |
1779 | C<ev_timer_again> optimisation when the timer is already running. |
1908 | timed out, and need to do whatever is needed in this case. |
|
|
1909 | |
|
|
1910 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1911 | and simply start the timer with this timeout value. |
|
|
1912 | |
|
|
1913 | In other words, each time the callback is invoked it will check whether |
|
|
1914 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1915 | again at the earliest time it could time out. Rinse. Repeat. |
1780 | |
1916 | |
1781 | This scheme causes more callback invocations (about one every 60 seconds |
1917 | This scheme causes more callback invocations (about one every 60 seconds |
1782 | minus half the average time between activity), but virtually no calls to |
1918 | minus half the average time between activity), but virtually no calls to |
1783 | libev to change the timeout. |
1919 | libev to change the timeout. |
1784 | |
1920 | |
1785 | To start the timer, simply initialise the watcher and set C<last_activity> |
1921 | To start the machinery, simply initialise the watcher and set |
1786 | to the current time (meaning we just have some activity :), then call the |
1922 | C<last_activity> to the current time (meaning there was some activity just |
1787 | callback, which will "do the right thing" and start the timer: |
1923 | now), then call the callback, which will "do the right thing" and start |
|
|
1924 | the timer: |
1788 | |
1925 | |
|
|
1926 | last_activity = ev_now (EV_A); |
1789 | ev_init (timer, callback); |
1927 | ev_init (&timer, callback); |
1790 | last_activity = ev_now (loop); |
1928 | callback (EV_A_ &timer, 0); |
1791 | callback (loop, timer, EV_TIMER); |
|
|
1792 | |
1929 | |
1793 | And when there is some activity, simply store the current time in |
1930 | When there is some activity, simply store the current time in |
1794 | C<last_activity>, no libev calls at all: |
1931 | C<last_activity>, no libev calls at all: |
1795 | |
1932 | |
|
|
1933 | if (activity detected) |
1796 | last_activity = ev_now (loop); |
1934 | last_activity = ev_now (EV_A); |
|
|
1935 | |
|
|
1936 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1937 | providing a new value, stopping the timer and calling the callback, which |
|
|
1938 | will again do the right thing (for example, time out immediately :). |
|
|
1939 | |
|
|
1940 | timeout = new_value; |
|
|
1941 | ev_timer_stop (EV_A_ &timer); |
|
|
1942 | callback (EV_A_ &timer, 0); |
1797 | |
1943 | |
1798 | This technique is slightly more complex, but in most cases where the |
1944 | This technique is slightly more complex, but in most cases where the |
1799 | time-out is unlikely to be triggered, much more efficient. |
1945 | time-out is unlikely to be triggered, much more efficient. |
1800 | |
|
|
1801 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1802 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1803 | fix things for you. |
|
|
1804 | |
1946 | |
1805 | =item 4. Wee, just use a double-linked list for your timeouts. |
1947 | =item 4. Wee, just use a double-linked list for your timeouts. |
1806 | |
1948 | |
1807 | If there is not one request, but many thousands (millions...), all |
1949 | If there is not one request, but many thousands (millions...), all |
1808 | employing some kind of timeout with the same timeout value, then one can |
1950 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1835 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1977 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1836 | rather complicated, but extremely efficient, something that really pays |
1978 | rather complicated, but extremely efficient, something that really pays |
1837 | off after the first million or so of active timers, i.e. it's usually |
1979 | off after the first million or so of active timers, i.e. it's usually |
1838 | overkill :) |
1980 | overkill :) |
1839 | |
1981 | |
|
|
1982 | =head3 The special problem of being too early |
|
|
1983 | |
|
|
1984 | If you ask a timer to call your callback after three seconds, then |
|
|
1985 | you expect it to be invoked after three seconds - but of course, this |
|
|
1986 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1987 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1988 | process with a STOP signal for a few hours for example. |
|
|
1989 | |
|
|
1990 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1991 | delay has occurred, but cannot guarantee this. |
|
|
1992 | |
|
|
1993 | A less obvious failure mode is calling your callback too early: many event |
|
|
1994 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1995 | this can cause your callback to be invoked much earlier than you would |
|
|
1996 | expect. |
|
|
1997 | |
|
|
1998 | To see why, imagine a system with a clock that only offers full second |
|
|
1999 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2000 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2001 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2002 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2003 | |
|
|
2004 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2005 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2006 | one-second delay was requested - this is being "too early", despite best |
|
|
2007 | intentions. |
|
|
2008 | |
|
|
2009 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2010 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2011 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2012 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2013 | |
|
|
2014 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2015 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2016 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2017 | late" side of things. |
|
|
2018 | |
1840 | =head3 The special problem of time updates |
2019 | =head3 The special problem of time updates |
1841 | |
2020 | |
1842 | Establishing the current time is a costly operation (it usually takes at |
2021 | Establishing the current time is a costly operation (it usually takes |
1843 | least two system calls): EV therefore updates its idea of the current |
2022 | at least one system call): EV therefore updates its idea of the current |
1844 | time only before and after C<ev_run> collects new events, which causes a |
2023 | time only before and after C<ev_run> collects new events, which causes a |
1845 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2024 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1846 | lots of events in one iteration. |
2025 | lots of events in one iteration. |
1847 | |
2026 | |
1848 | The relative timeouts are calculated relative to the C<ev_now ()> |
2027 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1854 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2033 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1855 | |
2034 | |
1856 | If the event loop is suspended for a long time, you can also force an |
2035 | If the event loop is suspended for a long time, you can also force an |
1857 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2036 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1858 | ()>. |
2037 | ()>. |
|
|
2038 | |
|
|
2039 | =head3 The special problem of unsynchronised clocks |
|
|
2040 | |
|
|
2041 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2042 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2043 | jumps). |
|
|
2044 | |
|
|
2045 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2046 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2047 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2048 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2049 | than a directly following call to C<time>. |
|
|
2050 | |
|
|
2051 | The moral of this is to only compare libev-related timestamps with |
|
|
2052 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2053 | a second or so. |
|
|
2054 | |
|
|
2055 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2056 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2057 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2058 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2059 | |
|
|
2060 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2061 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2062 | I<measured according to the real time>, not the system clock. |
|
|
2063 | |
|
|
2064 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2065 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2066 | exactly the right behaviour. |
|
|
2067 | |
|
|
2068 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2069 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2070 | time, where your comparisons will always generate correct results. |
1859 | |
2071 | |
1860 | =head3 The special problems of suspended animation |
2072 | =head3 The special problems of suspended animation |
1861 | |
2073 | |
1862 | When you leave the server world it is quite customary to hit machines that |
2074 | When you leave the server world it is quite customary to hit machines that |
1863 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2075 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1907 | keep up with the timer (because it takes longer than those 10 seconds to |
2119 | keep up with the timer (because it takes longer than those 10 seconds to |
1908 | do stuff) the timer will not fire more than once per event loop iteration. |
2120 | do stuff) the timer will not fire more than once per event loop iteration. |
1909 | |
2121 | |
1910 | =item ev_timer_again (loop, ev_timer *) |
2122 | =item ev_timer_again (loop, ev_timer *) |
1911 | |
2123 | |
1912 | This will act as if the timer timed out and restart it again if it is |
2124 | This will act as if the timer timed out, and restarts it again if it is |
1913 | repeating. The exact semantics are: |
2125 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2126 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1914 | |
2127 | |
|
|
2128 | The exact semantics are as in the following rules, all of which will be |
|
|
2129 | applied to the watcher: |
|
|
2130 | |
|
|
2131 | =over 4 |
|
|
2132 | |
1915 | If the timer is pending, its pending status is cleared. |
2133 | =item If the timer is pending, the pending status is always cleared. |
1916 | |
2134 | |
1917 | If the timer is started but non-repeating, stop it (as if it timed out). |
2135 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2136 | out, without invoking it). |
1918 | |
2137 | |
1919 | If the timer is repeating, either start it if necessary (with the |
2138 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1920 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2139 | and start the timer, if necessary. |
1921 | |
2140 | |
|
|
2141 | =back |
|
|
2142 | |
1922 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2143 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1923 | usage example. |
2144 | usage example. |
1924 | |
2145 | |
1925 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2146 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1926 | |
2147 | |
1927 | Returns the remaining time until a timer fires. If the timer is active, |
2148 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2047 | |
2268 | |
2048 | Another way to think about it (for the mathematically inclined) is that |
2269 | Another way to think about it (for the mathematically inclined) is that |
2049 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2270 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2050 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2271 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2051 | |
2272 | |
2052 | For numerical stability it is preferable that the C<offset> value is near |
2273 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2053 | C<ev_now ()> (the current time), but there is no range requirement for |
2274 | interval value should be higher than C<1/8192> (which is around 100 |
2054 | this value, and in fact is often specified as zero. |
2275 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2276 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2277 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2278 | C<0> and C<interval>, which is also the recommended range. |
2055 | |
2279 | |
2056 | Note also that there is an upper limit to how often a timer can fire (CPU |
2280 | Note also that there is an upper limit to how often a timer can fire (CPU |
2057 | speed for example), so if C<interval> is very small then timing stability |
2281 | speed for example), so if C<interval> is very small then timing stability |
2058 | will of course deteriorate. Libev itself tries to be exact to be about one |
2282 | will of course deteriorate. Libev itself tries to be exact to be about one |
2059 | millisecond (if the OS supports it and the machine is fast enough). |
2283 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2173 | |
2397 | |
2174 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2398 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2175 | |
2399 | |
2176 | Signal watchers will trigger an event when the process receives a specific |
2400 | Signal watchers will trigger an event when the process receives a specific |
2177 | signal one or more times. Even though signals are very asynchronous, libev |
2401 | signal one or more times. Even though signals are very asynchronous, libev |
2178 | will try it's best to deliver signals synchronously, i.e. as part of the |
2402 | will try its best to deliver signals synchronously, i.e. as part of the |
2179 | normal event processing, like any other event. |
2403 | normal event processing, like any other event. |
2180 | |
2404 | |
2181 | If you want signals to be delivered truly asynchronously, just use |
2405 | If you want signals to be delivered truly asynchronously, just use |
2182 | C<sigaction> as you would do without libev and forget about sharing |
2406 | C<sigaction> as you would do without libev and forget about sharing |
2183 | the signal. You can even use C<ev_async> from a signal handler to |
2407 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2202 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2426 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2203 | |
2427 | |
2204 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2428 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2205 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2429 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2206 | stopping it again), that is, libev might or might not block the signal, |
2430 | stopping it again), that is, libev might or might not block the signal, |
2207 | and might or might not set or restore the installed signal handler. |
2431 | and might or might not set or restore the installed signal handler (but |
|
|
2432 | see C<EVFLAG_NOSIGMASK>). |
2208 | |
2433 | |
2209 | While this does not matter for the signal disposition (libev never |
2434 | While this does not matter for the signal disposition (libev never |
2210 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2435 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2211 | C<execve>), this matters for the signal mask: many programs do not expect |
2436 | C<execve>), this matters for the signal mask: many programs do not expect |
2212 | certain signals to be blocked. |
2437 | certain signals to be blocked. |
… | |
… | |
2225 | I<has> to modify the signal mask, at least temporarily. |
2450 | I<has> to modify the signal mask, at least temporarily. |
2226 | |
2451 | |
2227 | So I can't stress this enough: I<If you do not reset your signal mask when |
2452 | So I can't stress this enough: I<If you do not reset your signal mask when |
2228 | you expect it to be empty, you have a race condition in your code>. This |
2453 | you expect it to be empty, you have a race condition in your code>. This |
2229 | is not a libev-specific thing, this is true for most event libraries. |
2454 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2455 | |
|
|
2456 | =head3 The special problem of threads signal handling |
|
|
2457 | |
|
|
2458 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2459 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2460 | threads in a process block signals, which is hard to achieve. |
|
|
2461 | |
|
|
2462 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2463 | for the same signals), you can tackle this problem by globally blocking |
|
|
2464 | all signals before creating any threads (or creating them with a fully set |
|
|
2465 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2466 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2467 | these signals. You can pass on any signals that libev might be interested |
|
|
2468 | in by calling C<ev_feed_signal>. |
2230 | |
2469 | |
2231 | =head3 Watcher-Specific Functions and Data Members |
2470 | =head3 Watcher-Specific Functions and Data Members |
2232 | |
2471 | |
2233 | =over 4 |
2472 | =over 4 |
2234 | |
2473 | |
… | |
… | |
2369 | |
2608 | |
2370 | =head2 C<ev_stat> - did the file attributes just change? |
2609 | =head2 C<ev_stat> - did the file attributes just change? |
2371 | |
2610 | |
2372 | This watches a file system path for attribute changes. That is, it calls |
2611 | This watches a file system path for attribute changes. That is, it calls |
2373 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2612 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2374 | and sees if it changed compared to the last time, invoking the callback if |
2613 | and sees if it changed compared to the last time, invoking the callback |
2375 | it did. |
2614 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2615 | happen after the watcher has been started will be reported. |
2376 | |
2616 | |
2377 | The path does not need to exist: changing from "path exists" to "path does |
2617 | The path does not need to exist: changing from "path exists" to "path does |
2378 | not exist" is a status change like any other. The condition "path does not |
2618 | not exist" is a status change like any other. The condition "path does not |
2379 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2619 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2380 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2620 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2610 | Apart from keeping your process non-blocking (which is a useful |
2850 | Apart from keeping your process non-blocking (which is a useful |
2611 | effect on its own sometimes), idle watchers are a good place to do |
2851 | effect on its own sometimes), idle watchers are a good place to do |
2612 | "pseudo-background processing", or delay processing stuff to after the |
2852 | "pseudo-background processing", or delay processing stuff to after the |
2613 | event loop has handled all outstanding events. |
2853 | event loop has handled all outstanding events. |
2614 | |
2854 | |
|
|
2855 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2856 | |
|
|
2857 | As long as there is at least one active idle watcher, libev will never |
|
|
2858 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2859 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2860 | lowest priority will do. |
|
|
2861 | |
|
|
2862 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2863 | to do something on each event loop iteration - for example to balance load |
|
|
2864 | between different connections. |
|
|
2865 | |
|
|
2866 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2867 | example. |
|
|
2868 | |
2615 | =head3 Watcher-Specific Functions and Data Members |
2869 | =head3 Watcher-Specific Functions and Data Members |
2616 | |
2870 | |
2617 | =over 4 |
2871 | =over 4 |
2618 | |
2872 | |
2619 | =item ev_idle_init (ev_idle *, callback) |
2873 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2630 | callback, free it. Also, use no error checking, as usual. |
2884 | callback, free it. Also, use no error checking, as usual. |
2631 | |
2885 | |
2632 | static void |
2886 | static void |
2633 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2887 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2634 | { |
2888 | { |
|
|
2889 | // stop the watcher |
|
|
2890 | ev_idle_stop (loop, w); |
|
|
2891 | |
|
|
2892 | // now we can free it |
2635 | free (w); |
2893 | free (w); |
|
|
2894 | |
2636 | // now do something you wanted to do when the program has |
2895 | // now do something you wanted to do when the program has |
2637 | // no longer anything immediate to do. |
2896 | // no longer anything immediate to do. |
2638 | } |
2897 | } |
2639 | |
2898 | |
2640 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2899 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2642 | ev_idle_start (loop, idle_watcher); |
2901 | ev_idle_start (loop, idle_watcher); |
2643 | |
2902 | |
2644 | |
2903 | |
2645 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2904 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2646 | |
2905 | |
2647 | Prepare and check watchers are usually (but not always) used in pairs: |
2906 | Prepare and check watchers are often (but not always) used in pairs: |
2648 | prepare watchers get invoked before the process blocks and check watchers |
2907 | prepare watchers get invoked before the process blocks and check watchers |
2649 | afterwards. |
2908 | afterwards. |
2650 | |
2909 | |
2651 | You I<must not> call C<ev_run> or similar functions that enter |
2910 | You I<must not> call C<ev_run> or similar functions that enter |
2652 | the current event loop from either C<ev_prepare> or C<ev_check> |
2911 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
2680 | with priority higher than or equal to the event loop and one coroutine |
2939 | with priority higher than or equal to the event loop and one coroutine |
2681 | of lower priority, but only once, using idle watchers to keep the event |
2940 | of lower priority, but only once, using idle watchers to keep the event |
2682 | loop from blocking if lower-priority coroutines are active, thus mapping |
2941 | loop from blocking if lower-priority coroutines are active, thus mapping |
2683 | low-priority coroutines to idle/background tasks). |
2942 | low-priority coroutines to idle/background tasks). |
2684 | |
2943 | |
2685 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2944 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2686 | priority, to ensure that they are being run before any other watchers |
2945 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2687 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2946 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2947 | watchers). |
2688 | |
2948 | |
2689 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2949 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2690 | activate ("feed") events into libev. While libev fully supports this, they |
2950 | activate ("feed") events into libev. While libev fully supports this, they |
2691 | might get executed before other C<ev_check> watchers did their job. As |
2951 | might get executed before other C<ev_check> watchers did their job. As |
2692 | C<ev_check> watchers are often used to embed other (non-libev) event |
2952 | C<ev_check> watchers are often used to embed other (non-libev) event |
2693 | loops those other event loops might be in an unusable state until their |
2953 | loops those other event loops might be in an unusable state until their |
2694 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2954 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2695 | others). |
2955 | others). |
|
|
2956 | |
|
|
2957 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2958 | |
|
|
2959 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2960 | useful because they are called once per event loop iteration. For |
|
|
2961 | example, if you want to handle a large number of connections fairly, you |
|
|
2962 | normally only do a bit of work for each active connection, and if there |
|
|
2963 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2964 | connections have a chance of making progress. |
|
|
2965 | |
|
|
2966 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2967 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2968 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2969 | |
|
|
2970 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2971 | single global idle watcher that is active as long as you have one active |
|
|
2972 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2973 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2974 | invoked. Neither watcher alone can do that. |
2696 | |
2975 | |
2697 | =head3 Watcher-Specific Functions and Data Members |
2976 | =head3 Watcher-Specific Functions and Data Members |
2698 | |
2977 | |
2699 | =over 4 |
2978 | =over 4 |
2700 | |
2979 | |
… | |
… | |
2901 | |
3180 | |
2902 | =over 4 |
3181 | =over 4 |
2903 | |
3182 | |
2904 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3183 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2905 | |
3184 | |
2906 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3185 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2907 | |
3186 | |
2908 | Configures the watcher to embed the given loop, which must be |
3187 | Configures the watcher to embed the given loop, which must be |
2909 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3188 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2910 | invoked automatically, otherwise it is the responsibility of the callback |
3189 | invoked automatically, otherwise it is the responsibility of the callback |
2911 | to invoke it (it will continue to be called until the sweep has been done, |
3190 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
2974 | |
3253 | |
2975 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3254 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
2976 | |
3255 | |
2977 | Fork watchers are called when a C<fork ()> was detected (usually because |
3256 | Fork watchers are called when a C<fork ()> was detected (usually because |
2978 | whoever is a good citizen cared to tell libev about it by calling |
3257 | whoever is a good citizen cared to tell libev about it by calling |
2979 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3258 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
2980 | event loop blocks next and before C<ev_check> watchers are being called, |
3259 | and before C<ev_check> watchers are being called, and only in the child |
2981 | and only in the child after the fork. If whoever good citizen calling |
3260 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
2982 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3261 | and calls it in the wrong process, the fork handlers will be invoked, too, |
2983 | handlers will be invoked, too, of course. |
3262 | of course. |
2984 | |
3263 | |
2985 | =head3 The special problem of life after fork - how is it possible? |
3264 | =head3 The special problem of life after fork - how is it possible? |
2986 | |
3265 | |
2987 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3266 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2988 | up/change the process environment, followed by a call to C<exec()>. This |
3267 | up/change the process environment, followed by a call to C<exec()>. This |
… | |
… | |
3008 | disadvantage of having to use multiple event loops (which do not support |
3287 | disadvantage of having to use multiple event loops (which do not support |
3009 | signal watchers). |
3288 | signal watchers). |
3010 | |
3289 | |
3011 | When this is not possible, or you want to use the default loop for |
3290 | When this is not possible, or you want to use the default loop for |
3012 | other reasons, then in the process that wants to start "fresh", call |
3291 | other reasons, then in the process that wants to start "fresh", call |
3013 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3292 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3014 | the default loop will "orphan" (not stop) all registered watchers, so you |
3293 | Destroying the default loop will "orphan" (not stop) all registered |
3015 | have to be careful not to execute code that modifies those watchers. Note |
3294 | watchers, so you have to be careful not to execute code that modifies |
3016 | also that in that case, you have to re-register any signal watchers. |
3295 | those watchers. Note also that in that case, you have to re-register any |
|
|
3296 | signal watchers. |
3017 | |
3297 | |
3018 | =head3 Watcher-Specific Functions and Data Members |
3298 | =head3 Watcher-Specific Functions and Data Members |
3019 | |
3299 | |
3020 | =over 4 |
3300 | =over 4 |
3021 | |
3301 | |
3022 | =item ev_fork_init (ev_signal *, callback) |
3302 | =item ev_fork_init (ev_fork *, callback) |
3023 | |
3303 | |
3024 | Initialises and configures the fork watcher - it has no parameters of any |
3304 | Initialises and configures the fork watcher - it has no parameters of any |
3025 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3305 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3026 | believe me. |
3306 | really. |
3027 | |
3307 | |
3028 | =back |
3308 | =back |
3029 | |
3309 | |
3030 | |
3310 | |
|
|
3311 | =head2 C<ev_cleanup> - even the best things end |
|
|
3312 | |
|
|
3313 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3314 | by a call to C<ev_loop_destroy>. |
|
|
3315 | |
|
|
3316 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3317 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3318 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3319 | loop when you want them to be invoked. |
|
|
3320 | |
|
|
3321 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3322 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3323 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3324 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3325 | |
|
|
3326 | =head3 Watcher-Specific Functions and Data Members |
|
|
3327 | |
|
|
3328 | =over 4 |
|
|
3329 | |
|
|
3330 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3331 | |
|
|
3332 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3333 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3334 | pointless, I assure you. |
|
|
3335 | |
|
|
3336 | =back |
|
|
3337 | |
|
|
3338 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3339 | cleanup functions are called. |
|
|
3340 | |
|
|
3341 | static void |
|
|
3342 | program_exits (void) |
|
|
3343 | { |
|
|
3344 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3345 | } |
|
|
3346 | |
|
|
3347 | ... |
|
|
3348 | atexit (program_exits); |
|
|
3349 | |
|
|
3350 | |
3031 | =head2 C<ev_async> - how to wake up an event loop |
3351 | =head2 C<ev_async> - how to wake up an event loop |
3032 | |
3352 | |
3033 | In general, you cannot use an C<ev_run> from multiple threads or other |
3353 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3034 | asynchronous sources such as signal handlers (as opposed to multiple event |
3354 | asynchronous sources such as signal handlers (as opposed to multiple event |
3035 | loops - those are of course safe to use in different threads). |
3355 | loops - those are of course safe to use in different threads). |
3036 | |
3356 | |
3037 | Sometimes, however, you need to wake up an event loop you do not control, |
3357 | Sometimes, however, you need to wake up an event loop you do not control, |
3038 | for example because it belongs to another thread. This is what C<ev_async> |
3358 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3040 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3360 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3041 | |
3361 | |
3042 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3362 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3043 | too, are asynchronous in nature, and signals, too, will be compressed |
3363 | too, are asynchronous in nature, and signals, too, will be compressed |
3044 | (i.e. the number of callback invocations may be less than the number of |
3364 | (i.e. the number of callback invocations may be less than the number of |
3045 | C<ev_async_sent> calls). |
3365 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3046 | |
3366 | of "global async watchers" by using a watcher on an otherwise unused |
3047 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3367 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3048 | just the default loop. |
3368 | even without knowing which loop owns the signal. |
3049 | |
3369 | |
3050 | =head3 Queueing |
3370 | =head3 Queueing |
3051 | |
3371 | |
3052 | C<ev_async> does not support queueing of data in any way. The reason |
3372 | C<ev_async> does not support queueing of data in any way. The reason |
3053 | is that the author does not know of a simple (or any) algorithm for a |
3373 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3145 | trust me. |
3465 | trust me. |
3146 | |
3466 | |
3147 | =item ev_async_send (loop, ev_async *) |
3467 | =item ev_async_send (loop, ev_async *) |
3148 | |
3468 | |
3149 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3469 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3150 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3470 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3471 | returns. |
|
|
3472 | |
3151 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3473 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3152 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3474 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3153 | section below on what exactly this means). |
3475 | embedding section below on what exactly this means). |
3154 | |
3476 | |
3155 | Note that, as with other watchers in libev, multiple events might get |
3477 | Note that, as with other watchers in libev, multiple events might get |
3156 | compressed into a single callback invocation (another way to look at this |
3478 | compressed into a single callback invocation (another way to look at |
3157 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3479 | this is that C<ev_async> watchers are level-triggered: they are set on |
3158 | reset when the event loop detects that). |
3480 | C<ev_async_send>, reset when the event loop detects that). |
3159 | |
3481 | |
3160 | This call incurs the overhead of a system call only once per event loop |
3482 | This call incurs the overhead of at most one extra system call per event |
3161 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3483 | loop iteration, if the event loop is blocked, and no syscall at all if |
3162 | repeated calls to C<ev_async_send> for the same event loop. |
3484 | the event loop (or your program) is processing events. That means that |
|
|
3485 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3486 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3487 | zero) under load. |
3163 | |
3488 | |
3164 | =item bool = ev_async_pending (ev_async *) |
3489 | =item bool = ev_async_pending (ev_async *) |
3165 | |
3490 | |
3166 | Returns a non-zero value when C<ev_async_send> has been called on the |
3491 | Returns a non-zero value when C<ev_async_send> has been called on the |
3167 | watcher but the event has not yet been processed (or even noted) by the |
3492 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3222 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3547 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3223 | |
3548 | |
3224 | =item ev_feed_fd_event (loop, int fd, int revents) |
3549 | =item ev_feed_fd_event (loop, int fd, int revents) |
3225 | |
3550 | |
3226 | Feed an event on the given fd, as if a file descriptor backend detected |
3551 | Feed an event on the given fd, as if a file descriptor backend detected |
3227 | the given events it. |
3552 | the given events. |
3228 | |
3553 | |
3229 | =item ev_feed_signal_event (loop, int signum) |
3554 | =item ev_feed_signal_event (loop, int signum) |
3230 | |
3555 | |
3231 | Feed an event as if the given signal occurred (C<loop> must be the default |
3556 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3232 | loop!). |
3557 | which is async-safe. |
3233 | |
3558 | |
3234 | =back |
3559 | =back |
|
|
3560 | |
|
|
3561 | |
|
|
3562 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3563 | |
|
|
3564 | This section explains some common idioms that are not immediately |
|
|
3565 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3566 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3567 | |
|
|
3568 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3569 | |
|
|
3570 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3571 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3572 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3573 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3574 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3575 | data: |
|
|
3576 | |
|
|
3577 | struct my_io |
|
|
3578 | { |
|
|
3579 | ev_io io; |
|
|
3580 | int otherfd; |
|
|
3581 | void *somedata; |
|
|
3582 | struct whatever *mostinteresting; |
|
|
3583 | }; |
|
|
3584 | |
|
|
3585 | ... |
|
|
3586 | struct my_io w; |
|
|
3587 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3588 | |
|
|
3589 | And since your callback will be called with a pointer to the watcher, you |
|
|
3590 | can cast it back to your own type: |
|
|
3591 | |
|
|
3592 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3593 | { |
|
|
3594 | struct my_io *w = (struct my_io *)w_; |
|
|
3595 | ... |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | More interesting and less C-conformant ways of casting your callback |
|
|
3599 | function type instead have been omitted. |
|
|
3600 | |
|
|
3601 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3602 | |
|
|
3603 | Another common scenario is to use some data structure with multiple |
|
|
3604 | embedded watchers, in effect creating your own watcher that combines |
|
|
3605 | multiple libev event sources into one "super-watcher": |
|
|
3606 | |
|
|
3607 | struct my_biggy |
|
|
3608 | { |
|
|
3609 | int some_data; |
|
|
3610 | ev_timer t1; |
|
|
3611 | ev_timer t2; |
|
|
3612 | } |
|
|
3613 | |
|
|
3614 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3615 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3616 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3617 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3618 | real programmers): |
|
|
3619 | |
|
|
3620 | #include <stddef.h> |
|
|
3621 | |
|
|
3622 | static void |
|
|
3623 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3624 | { |
|
|
3625 | struct my_biggy big = (struct my_biggy *) |
|
|
3626 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3627 | } |
|
|
3628 | |
|
|
3629 | static void |
|
|
3630 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3631 | { |
|
|
3632 | struct my_biggy big = (struct my_biggy *) |
|
|
3633 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3634 | } |
|
|
3635 | |
|
|
3636 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3637 | |
|
|
3638 | Often you have structures like this in event-based programs: |
|
|
3639 | |
|
|
3640 | callback () |
|
|
3641 | { |
|
|
3642 | free (request); |
|
|
3643 | } |
|
|
3644 | |
|
|
3645 | request = start_new_request (..., callback); |
|
|
3646 | |
|
|
3647 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3648 | used to cancel the operation, or do other things with it. |
|
|
3649 | |
|
|
3650 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3651 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3652 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3653 | operation and simply invoke the callback with the result. |
|
|
3654 | |
|
|
3655 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3656 | has returned, so C<request> is not set. |
|
|
3657 | |
|
|
3658 | Even if you pass the request by some safer means to the callback, you |
|
|
3659 | might want to do something to the request after starting it, such as |
|
|
3660 | canceling it, which probably isn't working so well when the callback has |
|
|
3661 | already been invoked. |
|
|
3662 | |
|
|
3663 | A common way around all these issues is to make sure that |
|
|
3664 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3665 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3666 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3667 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3668 | pushing it into the pending queue: |
|
|
3669 | |
|
|
3670 | ev_set_cb (watcher, callback); |
|
|
3671 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3672 | |
|
|
3673 | This way, C<start_new_request> can safely return before the callback is |
|
|
3674 | invoked, while not delaying callback invocation too much. |
|
|
3675 | |
|
|
3676 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3677 | |
|
|
3678 | Often (especially in GUI toolkits) there are places where you have |
|
|
3679 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3680 | invoking C<ev_run>. |
|
|
3681 | |
|
|
3682 | This brings the problem of exiting - a callback might want to finish the |
|
|
3683 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3684 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3685 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3686 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3687 | |
|
|
3688 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3689 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3690 | triggered, using C<EVRUN_ONCE>: |
|
|
3691 | |
|
|
3692 | // main loop |
|
|
3693 | int exit_main_loop = 0; |
|
|
3694 | |
|
|
3695 | while (!exit_main_loop) |
|
|
3696 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3697 | |
|
|
3698 | // in a modal watcher |
|
|
3699 | int exit_nested_loop = 0; |
|
|
3700 | |
|
|
3701 | while (!exit_nested_loop) |
|
|
3702 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3703 | |
|
|
3704 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3705 | |
|
|
3706 | // exit modal loop |
|
|
3707 | exit_nested_loop = 1; |
|
|
3708 | |
|
|
3709 | // exit main program, after modal loop is finished |
|
|
3710 | exit_main_loop = 1; |
|
|
3711 | |
|
|
3712 | // exit both |
|
|
3713 | exit_main_loop = exit_nested_loop = 1; |
|
|
3714 | |
|
|
3715 | =head2 THREAD LOCKING EXAMPLE |
|
|
3716 | |
|
|
3717 | Here is a fictitious example of how to run an event loop in a different |
|
|
3718 | thread from where callbacks are being invoked and watchers are |
|
|
3719 | created/added/removed. |
|
|
3720 | |
|
|
3721 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3722 | which uses exactly this technique (which is suited for many high-level |
|
|
3723 | languages). |
|
|
3724 | |
|
|
3725 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3726 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3727 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3728 | |
|
|
3729 | First, you need to associate some data with the event loop: |
|
|
3730 | |
|
|
3731 | typedef struct { |
|
|
3732 | mutex_t lock; /* global loop lock */ |
|
|
3733 | ev_async async_w; |
|
|
3734 | thread_t tid; |
|
|
3735 | cond_t invoke_cv; |
|
|
3736 | } userdata; |
|
|
3737 | |
|
|
3738 | void prepare_loop (EV_P) |
|
|
3739 | { |
|
|
3740 | // for simplicity, we use a static userdata struct. |
|
|
3741 | static userdata u; |
|
|
3742 | |
|
|
3743 | ev_async_init (&u->async_w, async_cb); |
|
|
3744 | ev_async_start (EV_A_ &u->async_w); |
|
|
3745 | |
|
|
3746 | pthread_mutex_init (&u->lock, 0); |
|
|
3747 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3748 | |
|
|
3749 | // now associate this with the loop |
|
|
3750 | ev_set_userdata (EV_A_ u); |
|
|
3751 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3752 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3753 | |
|
|
3754 | // then create the thread running ev_run |
|
|
3755 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3756 | } |
|
|
3757 | |
|
|
3758 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3759 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3760 | that might have been added: |
|
|
3761 | |
|
|
3762 | static void |
|
|
3763 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3764 | { |
|
|
3765 | // just used for the side effects |
|
|
3766 | } |
|
|
3767 | |
|
|
3768 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3769 | protecting the loop data, respectively. |
|
|
3770 | |
|
|
3771 | static void |
|
|
3772 | l_release (EV_P) |
|
|
3773 | { |
|
|
3774 | userdata *u = ev_userdata (EV_A); |
|
|
3775 | pthread_mutex_unlock (&u->lock); |
|
|
3776 | } |
|
|
3777 | |
|
|
3778 | static void |
|
|
3779 | l_acquire (EV_P) |
|
|
3780 | { |
|
|
3781 | userdata *u = ev_userdata (EV_A); |
|
|
3782 | pthread_mutex_lock (&u->lock); |
|
|
3783 | } |
|
|
3784 | |
|
|
3785 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3786 | into C<ev_run>: |
|
|
3787 | |
|
|
3788 | void * |
|
|
3789 | l_run (void *thr_arg) |
|
|
3790 | { |
|
|
3791 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3792 | |
|
|
3793 | l_acquire (EV_A); |
|
|
3794 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3795 | ev_run (EV_A_ 0); |
|
|
3796 | l_release (EV_A); |
|
|
3797 | |
|
|
3798 | return 0; |
|
|
3799 | } |
|
|
3800 | |
|
|
3801 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3802 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3803 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3804 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3805 | and b) skipping inter-thread-communication when there are no pending |
|
|
3806 | watchers is very beneficial): |
|
|
3807 | |
|
|
3808 | static void |
|
|
3809 | l_invoke (EV_P) |
|
|
3810 | { |
|
|
3811 | userdata *u = ev_userdata (EV_A); |
|
|
3812 | |
|
|
3813 | while (ev_pending_count (EV_A)) |
|
|
3814 | { |
|
|
3815 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3816 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3817 | } |
|
|
3818 | } |
|
|
3819 | |
|
|
3820 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3821 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3822 | thread to continue: |
|
|
3823 | |
|
|
3824 | static void |
|
|
3825 | real_invoke_pending (EV_P) |
|
|
3826 | { |
|
|
3827 | userdata *u = ev_userdata (EV_A); |
|
|
3828 | |
|
|
3829 | pthread_mutex_lock (&u->lock); |
|
|
3830 | ev_invoke_pending (EV_A); |
|
|
3831 | pthread_cond_signal (&u->invoke_cv); |
|
|
3832 | pthread_mutex_unlock (&u->lock); |
|
|
3833 | } |
|
|
3834 | |
|
|
3835 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3836 | event loop, you will now have to lock: |
|
|
3837 | |
|
|
3838 | ev_timer timeout_watcher; |
|
|
3839 | userdata *u = ev_userdata (EV_A); |
|
|
3840 | |
|
|
3841 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3842 | |
|
|
3843 | pthread_mutex_lock (&u->lock); |
|
|
3844 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3845 | ev_async_send (EV_A_ &u->async_w); |
|
|
3846 | pthread_mutex_unlock (&u->lock); |
|
|
3847 | |
|
|
3848 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3849 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3850 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3851 | watchers in the next event loop iteration. |
|
|
3852 | |
|
|
3853 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3854 | |
|
|
3855 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3856 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3857 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3858 | doesn't need callbacks anymore. |
|
|
3859 | |
|
|
3860 | Imagine you have coroutines that you can switch to using a function |
|
|
3861 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3862 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3863 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3864 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3865 | the differing C<;> conventions): |
|
|
3866 | |
|
|
3867 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3868 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3869 | |
|
|
3870 | That means instead of having a C callback function, you store the |
|
|
3871 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3872 | your callback, you instead have it switch to that coroutine. |
|
|
3873 | |
|
|
3874 | A coroutine might now wait for an event with a function called |
|
|
3875 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3876 | matter when, or whether the watcher is active or not when this function is |
|
|
3877 | called): |
|
|
3878 | |
|
|
3879 | void |
|
|
3880 | wait_for_event (ev_watcher *w) |
|
|
3881 | { |
|
|
3882 | ev_set_cb (w, current_coro); |
|
|
3883 | switch_to (libev_coro); |
|
|
3884 | } |
|
|
3885 | |
|
|
3886 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3887 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3888 | this or any other coroutine. |
|
|
3889 | |
|
|
3890 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3891 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3892 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3893 | any waiters. |
|
|
3894 | |
|
|
3895 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3896 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3897 | |
|
|
3898 | // my_ev.h |
|
|
3899 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3900 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3901 | #include "../libev/ev.h" |
|
|
3902 | |
|
|
3903 | // my_ev.c |
|
|
3904 | #define EV_H "my_ev.h" |
|
|
3905 | #include "../libev/ev.c" |
|
|
3906 | |
|
|
3907 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3908 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3909 | can even use F<ev.h> as header file name directly. |
3235 | |
3910 | |
3236 | |
3911 | |
3237 | =head1 LIBEVENT EMULATION |
3912 | =head1 LIBEVENT EMULATION |
3238 | |
3913 | |
3239 | Libev offers a compatibility emulation layer for libevent. It cannot |
3914 | Libev offers a compatibility emulation layer for libevent. It cannot |
3240 | emulate the internals of libevent, so here are some usage hints: |
3915 | emulate the internals of libevent, so here are some usage hints: |
3241 | |
3916 | |
3242 | =over 4 |
3917 | =over 4 |
|
|
3918 | |
|
|
3919 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3920 | |
|
|
3921 | This was the newest libevent version available when libev was implemented, |
|
|
3922 | and is still mostly unchanged in 2010. |
3243 | |
3923 | |
3244 | =item * Use it by including <event.h>, as usual. |
3924 | =item * Use it by including <event.h>, as usual. |
3245 | |
3925 | |
3246 | =item * The following members are fully supported: ev_base, ev_callback, |
3926 | =item * The following members are fully supported: ev_base, ev_callback, |
3247 | ev_arg, ev_fd, ev_res, ev_events. |
3927 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3253 | =item * Priorities are not currently supported. Initialising priorities |
3933 | =item * Priorities are not currently supported. Initialising priorities |
3254 | will fail and all watchers will have the same priority, even though there |
3934 | will fail and all watchers will have the same priority, even though there |
3255 | is an ev_pri field. |
3935 | is an ev_pri field. |
3256 | |
3936 | |
3257 | =item * In libevent, the last base created gets the signals, in libev, the |
3937 | =item * In libevent, the last base created gets the signals, in libev, the |
3258 | first base created (== the default loop) gets the signals. |
3938 | base that registered the signal gets the signals. |
3259 | |
3939 | |
3260 | =item * Other members are not supported. |
3940 | =item * Other members are not supported. |
3261 | |
3941 | |
3262 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3942 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3263 | to use the libev header file and library. |
3943 | to use the libev header file and library. |
3264 | |
3944 | |
3265 | =back |
3945 | =back |
3266 | |
3946 | |
3267 | =head1 C++ SUPPORT |
3947 | =head1 C++ SUPPORT |
|
|
3948 | |
|
|
3949 | =head2 C API |
|
|
3950 | |
|
|
3951 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3952 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3953 | will work fine. |
|
|
3954 | |
|
|
3955 | Proper exception specifications might have to be added to callbacks passed |
|
|
3956 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3957 | other callbacks (allocator, syserr, loop acquire/release and periodic |
|
|
3958 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3959 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3960 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3961 | |
|
|
3962 | static void |
|
|
3963 | fatal_error (const char *msg) EV_THROW |
|
|
3964 | { |
|
|
3965 | perror (msg); |
|
|
3966 | abort (); |
|
|
3967 | } |
|
|
3968 | |
|
|
3969 | ... |
|
|
3970 | ev_set_syserr_cb (fatal_error); |
|
|
3971 | |
|
|
3972 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3973 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3974 | because it runs cleanup watchers). |
|
|
3975 | |
|
|
3976 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3977 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3978 | throwing exceptions through C libraries (most do). |
|
|
3979 | |
|
|
3980 | =head2 C++ API |
3268 | |
3981 | |
3269 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3982 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3270 | you to use some convenience methods to start/stop watchers and also change |
3983 | you to use some convenience methods to start/stop watchers and also change |
3271 | the callback model to a model using method callbacks on objects. |
3984 | the callback model to a model using method callbacks on objects. |
3272 | |
3985 | |
… | |
… | |
3282 | Care has been taken to keep the overhead low. The only data member the C++ |
3995 | Care has been taken to keep the overhead low. The only data member the C++ |
3283 | classes add (compared to plain C-style watchers) is the event loop pointer |
3996 | classes add (compared to plain C-style watchers) is the event loop pointer |
3284 | that the watcher is associated with (or no additional members at all if |
3997 | that the watcher is associated with (or no additional members at all if |
3285 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3998 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3286 | |
3999 | |
3287 | Currently, functions, and static and non-static member functions can be |
4000 | Currently, functions, static and non-static member functions and classes |
3288 | used as callbacks. Other types should be easy to add as long as they only |
4001 | with C<operator ()> can be used as callbacks. Other types should be easy |
3289 | need one additional pointer for context. If you need support for other |
4002 | to add as long as they only need one additional pointer for context. If |
3290 | types of functors please contact the author (preferably after implementing |
4003 | you need support for other types of functors please contact the author |
3291 | it). |
4004 | (preferably after implementing it). |
|
|
4005 | |
|
|
4006 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4007 | conventions as your C compiler (for static member functions), or you have |
|
|
4008 | to embed libev and compile libev itself as C++. |
3292 | |
4009 | |
3293 | Here is a list of things available in the C<ev> namespace: |
4010 | Here is a list of things available in the C<ev> namespace: |
3294 | |
4011 | |
3295 | =over 4 |
4012 | =over 4 |
3296 | |
4013 | |
… | |
… | |
3306 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4023 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3307 | |
4024 | |
3308 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4025 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3309 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4026 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3310 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4027 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3311 | defines by many implementations. |
4028 | defined by many implementations. |
3312 | |
4029 | |
3313 | All of those classes have these methods: |
4030 | All of those classes have these methods: |
3314 | |
4031 | |
3315 | =over 4 |
4032 | =over 4 |
3316 | |
4033 | |
… | |
… | |
3406 | Associates a different C<struct ev_loop> with this watcher. You can only |
4123 | Associates a different C<struct ev_loop> with this watcher. You can only |
3407 | do this when the watcher is inactive (and not pending either). |
4124 | do this when the watcher is inactive (and not pending either). |
3408 | |
4125 | |
3409 | =item w->set ([arguments]) |
4126 | =item w->set ([arguments]) |
3410 | |
4127 | |
3411 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4128 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3412 | method or a suitable start method must be called at least once. Unlike the |
4129 | with the same arguments. Either this method or a suitable start method |
3413 | C counterpart, an active watcher gets automatically stopped and restarted |
4130 | must be called at least once. Unlike the C counterpart, an active watcher |
3414 | when reconfiguring it with this method. |
4131 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4132 | method. |
|
|
4133 | |
|
|
4134 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4135 | clashing with the C<set (loop)> method. |
3415 | |
4136 | |
3416 | =item w->start () |
4137 | =item w->start () |
3417 | |
4138 | |
3418 | Starts the watcher. Note that there is no C<loop> argument, as the |
4139 | Starts the watcher. Note that there is no C<loop> argument, as the |
3419 | constructor already stores the event loop. |
4140 | constructor already stores the event loop. |
… | |
… | |
3449 | watchers in the constructor. |
4170 | watchers in the constructor. |
3450 | |
4171 | |
3451 | class myclass |
4172 | class myclass |
3452 | { |
4173 | { |
3453 | ev::io io ; void io_cb (ev::io &w, int revents); |
4174 | ev::io io ; void io_cb (ev::io &w, int revents); |
3454 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4175 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3455 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4176 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3456 | |
4177 | |
3457 | myclass (int fd) |
4178 | myclass (int fd) |
3458 | { |
4179 | { |
3459 | io .set <myclass, &myclass::io_cb > (this); |
4180 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3510 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4231 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3511 | |
4232 | |
3512 | =item D |
4233 | =item D |
3513 | |
4234 | |
3514 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4235 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3515 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4236 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3516 | |
4237 | |
3517 | =item Ocaml |
4238 | =item Ocaml |
3518 | |
4239 | |
3519 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4240 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3520 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4241 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3523 | |
4244 | |
3524 | Brian Maher has written a partial interface to libev for lua (at the |
4245 | Brian Maher has written a partial interface to libev for lua (at the |
3525 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4246 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3526 | L<http://github.com/brimworks/lua-ev>. |
4247 | L<http://github.com/brimworks/lua-ev>. |
3527 | |
4248 | |
|
|
4249 | =item Javascript |
|
|
4250 | |
|
|
4251 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4252 | |
|
|
4253 | =item Others |
|
|
4254 | |
|
|
4255 | There are others, and I stopped counting. |
|
|
4256 | |
3528 | =back |
4257 | =back |
3529 | |
4258 | |
3530 | |
4259 | |
3531 | =head1 MACRO MAGIC |
4260 | =head1 MACRO MAGIC |
3532 | |
4261 | |
… | |
… | |
3568 | suitable for use with C<EV_A>. |
4297 | suitable for use with C<EV_A>. |
3569 | |
4298 | |
3570 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4299 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3571 | |
4300 | |
3572 | Similar to the other two macros, this gives you the value of the default |
4301 | Similar to the other two macros, this gives you the value of the default |
3573 | loop, if multiple loops are supported ("ev loop default"). |
4302 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4303 | will be initialised if it isn't already initialised. |
|
|
4304 | |
|
|
4305 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4306 | to initialise the loop somewhere. |
3574 | |
4307 | |
3575 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4308 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3576 | |
4309 | |
3577 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4310 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3578 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4311 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3723 | supported). It will also not define any of the structs usually found in |
4456 | supported). It will also not define any of the structs usually found in |
3724 | F<event.h> that are not directly supported by the libev core alone. |
4457 | F<event.h> that are not directly supported by the libev core alone. |
3725 | |
4458 | |
3726 | In standalone mode, libev will still try to automatically deduce the |
4459 | In standalone mode, libev will still try to automatically deduce the |
3727 | configuration, but has to be more conservative. |
4460 | configuration, but has to be more conservative. |
|
|
4461 | |
|
|
4462 | =item EV_USE_FLOOR |
|
|
4463 | |
|
|
4464 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4465 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4466 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4467 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4468 | function is not available will fail, so the safe default is to not enable |
|
|
4469 | this. |
3728 | |
4470 | |
3729 | =item EV_USE_MONOTONIC |
4471 | =item EV_USE_MONOTONIC |
3730 | |
4472 | |
3731 | If defined to be C<1>, libev will try to detect the availability of the |
4473 | If defined to be C<1>, libev will try to detect the availability of the |
3732 | monotonic clock option at both compile time and runtime. Otherwise no |
4474 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3817 | |
4559 | |
3818 | If programs implement their own fd to handle mapping on win32, then this |
4560 | If programs implement their own fd to handle mapping on win32, then this |
3819 | macro can be used to override the C<close> function, useful to unregister |
4561 | macro can be used to override the C<close> function, useful to unregister |
3820 | file descriptors again. Note that the replacement function has to close |
4562 | file descriptors again. Note that the replacement function has to close |
3821 | the underlying OS handle. |
4563 | the underlying OS handle. |
|
|
4564 | |
|
|
4565 | =item EV_USE_WSASOCKET |
|
|
4566 | |
|
|
4567 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4568 | communication socket, which works better in some environments. Otherwise, |
|
|
4569 | the normal C<socket> function will be used, which works better in other |
|
|
4570 | environments. |
3822 | |
4571 | |
3823 | =item EV_USE_POLL |
4572 | =item EV_USE_POLL |
3824 | |
4573 | |
3825 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4574 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3826 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4575 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3862 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4611 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3863 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4612 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3864 | be detected at runtime. If undefined, it will be enabled if the headers |
4613 | be detected at runtime. If undefined, it will be enabled if the headers |
3865 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4614 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3866 | |
4615 | |
|
|
4616 | =item EV_NO_SMP |
|
|
4617 | |
|
|
4618 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4619 | between threads, that is, threads can be used, but threads never run on |
|
|
4620 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4621 | and makes libev faster. |
|
|
4622 | |
|
|
4623 | =item EV_NO_THREADS |
|
|
4624 | |
|
|
4625 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4626 | different threads (that includes signal handlers), which is a stronger |
|
|
4627 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4628 | libev faster. |
|
|
4629 | |
3867 | =item EV_ATOMIC_T |
4630 | =item EV_ATOMIC_T |
3868 | |
4631 | |
3869 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4632 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3870 | access is atomic with respect to other threads or signal contexts. No such |
4633 | access is atomic with respect to other threads or signal contexts. No |
3871 | type is easily found in the C language, so you can provide your own type |
4634 | such type is easily found in the C language, so you can provide your own |
3872 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4635 | type that you know is safe for your purposes. It is used both for signal |
3873 | as well as for signal and thread safety in C<ev_async> watchers. |
4636 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4637 | watchers. |
3874 | |
4638 | |
3875 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4639 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3876 | (from F<signal.h>), which is usually good enough on most platforms. |
4640 | (from F<signal.h>), which is usually good enough on most platforms. |
3877 | |
4641 | |
3878 | =item EV_H (h) |
4642 | =item EV_H (h) |
… | |
… | |
3905 | will have the C<struct ev_loop *> as first argument, and you can create |
4669 | will have the C<struct ev_loop *> as first argument, and you can create |
3906 | additional independent event loops. Otherwise there will be no support |
4670 | additional independent event loops. Otherwise there will be no support |
3907 | for multiple event loops and there is no first event loop pointer |
4671 | for multiple event loops and there is no first event loop pointer |
3908 | argument. Instead, all functions act on the single default loop. |
4672 | argument. Instead, all functions act on the single default loop. |
3909 | |
4673 | |
|
|
4674 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4675 | default loop when multiplicity is switched off - you always have to |
|
|
4676 | initialise the loop manually in this case. |
|
|
4677 | |
3910 | =item EV_MINPRI |
4678 | =item EV_MINPRI |
3911 | |
4679 | |
3912 | =item EV_MAXPRI |
4680 | =item EV_MAXPRI |
3913 | |
4681 | |
3914 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4682 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3950 | #define EV_USE_POLL 1 |
4718 | #define EV_USE_POLL 1 |
3951 | #define EV_CHILD_ENABLE 1 |
4719 | #define EV_CHILD_ENABLE 1 |
3952 | #define EV_ASYNC_ENABLE 1 |
4720 | #define EV_ASYNC_ENABLE 1 |
3953 | |
4721 | |
3954 | The actual value is a bitset, it can be a combination of the following |
4722 | The actual value is a bitset, it can be a combination of the following |
3955 | values: |
4723 | values (by default, all of these are enabled): |
3956 | |
4724 | |
3957 | =over 4 |
4725 | =over 4 |
3958 | |
4726 | |
3959 | =item C<1> - faster/larger code |
4727 | =item C<1> - faster/larger code |
3960 | |
4728 | |
… | |
… | |
3964 | code size by roughly 30% on amd64). |
4732 | code size by roughly 30% on amd64). |
3965 | |
4733 | |
3966 | When optimising for size, use of compiler flags such as C<-Os> with |
4734 | When optimising for size, use of compiler flags such as C<-Os> with |
3967 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4735 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
3968 | assertions. |
4736 | assertions. |
|
|
4737 | |
|
|
4738 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4739 | (e.g. gcc with C<-Os>). |
3969 | |
4740 | |
3970 | =item C<2> - faster/larger data structures |
4741 | =item C<2> - faster/larger data structures |
3971 | |
4742 | |
3972 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4743 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
3973 | hash table sizes and so on. This will usually further increase code size |
4744 | hash table sizes and so on. This will usually further increase code size |
3974 | and can additionally have an effect on the size of data structures at |
4745 | and can additionally have an effect on the size of data structures at |
3975 | runtime. |
4746 | runtime. |
3976 | |
4747 | |
|
|
4748 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4749 | (e.g. gcc with C<-Os>). |
|
|
4750 | |
3977 | =item C<4> - full API configuration |
4751 | =item C<4> - full API configuration |
3978 | |
4752 | |
3979 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4753 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
3980 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4754 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
3981 | |
4755 | |
… | |
… | |
4011 | |
4785 | |
4012 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4786 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4013 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4787 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4014 | your program might be left out as well - a binary starting a timer and an |
4788 | your program might be left out as well - a binary starting a timer and an |
4015 | I/O watcher then might come out at only 5Kb. |
4789 | I/O watcher then might come out at only 5Kb. |
|
|
4790 | |
|
|
4791 | =item EV_API_STATIC |
|
|
4792 | |
|
|
4793 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4794 | will have static linkage. This means that libev will not export any |
|
|
4795 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4796 | when you embed libev, only want to use libev functions in a single file, |
|
|
4797 | and do not want its identifiers to be visible. |
|
|
4798 | |
|
|
4799 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4800 | wants to use libev. |
|
|
4801 | |
|
|
4802 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4803 | doesn't support the required declaration syntax. |
4016 | |
4804 | |
4017 | =item EV_AVOID_STDIO |
4805 | =item EV_AVOID_STDIO |
4018 | |
4806 | |
4019 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4807 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4020 | functions (printf, scanf, perror etc.). This will increase the code size |
4808 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4164 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4952 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4165 | |
4953 | |
4166 | #include "ev_cpp.h" |
4954 | #include "ev_cpp.h" |
4167 | #include "ev.c" |
4955 | #include "ev.c" |
4168 | |
4956 | |
4169 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4957 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4170 | |
4958 | |
4171 | =head2 THREADS AND COROUTINES |
4959 | =head2 THREADS AND COROUTINES |
4172 | |
4960 | |
4173 | =head3 THREADS |
4961 | =head3 THREADS |
4174 | |
4962 | |
… | |
… | |
4225 | default loop and triggering an C<ev_async> watcher from the default loop |
5013 | default loop and triggering an C<ev_async> watcher from the default loop |
4226 | watcher callback into the event loop interested in the signal. |
5014 | watcher callback into the event loop interested in the signal. |
4227 | |
5015 | |
4228 | =back |
5016 | =back |
4229 | |
5017 | |
4230 | =head4 THREAD LOCKING EXAMPLE |
5018 | See also L</THREAD LOCKING EXAMPLE>. |
4231 | |
|
|
4232 | Here is a fictitious example of how to run an event loop in a different |
|
|
4233 | thread than where callbacks are being invoked and watchers are |
|
|
4234 | created/added/removed. |
|
|
4235 | |
|
|
4236 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4237 | which uses exactly this technique (which is suited for many high-level |
|
|
4238 | languages). |
|
|
4239 | |
|
|
4240 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4241 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4242 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4243 | |
|
|
4244 | First, you need to associate some data with the event loop: |
|
|
4245 | |
|
|
4246 | typedef struct { |
|
|
4247 | mutex_t lock; /* global loop lock */ |
|
|
4248 | ev_async async_w; |
|
|
4249 | thread_t tid; |
|
|
4250 | cond_t invoke_cv; |
|
|
4251 | } userdata; |
|
|
4252 | |
|
|
4253 | void prepare_loop (EV_P) |
|
|
4254 | { |
|
|
4255 | // for simplicity, we use a static userdata struct. |
|
|
4256 | static userdata u; |
|
|
4257 | |
|
|
4258 | ev_async_init (&u->async_w, async_cb); |
|
|
4259 | ev_async_start (EV_A_ &u->async_w); |
|
|
4260 | |
|
|
4261 | pthread_mutex_init (&u->lock, 0); |
|
|
4262 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4263 | |
|
|
4264 | // now associate this with the loop |
|
|
4265 | ev_set_userdata (EV_A_ u); |
|
|
4266 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4267 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4268 | |
|
|
4269 | // then create the thread running ev_loop |
|
|
4270 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4271 | } |
|
|
4272 | |
|
|
4273 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4274 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4275 | that might have been added: |
|
|
4276 | |
|
|
4277 | static void |
|
|
4278 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4279 | { |
|
|
4280 | // just used for the side effects |
|
|
4281 | } |
|
|
4282 | |
|
|
4283 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4284 | protecting the loop data, respectively. |
|
|
4285 | |
|
|
4286 | static void |
|
|
4287 | l_release (EV_P) |
|
|
4288 | { |
|
|
4289 | userdata *u = ev_userdata (EV_A); |
|
|
4290 | pthread_mutex_unlock (&u->lock); |
|
|
4291 | } |
|
|
4292 | |
|
|
4293 | static void |
|
|
4294 | l_acquire (EV_P) |
|
|
4295 | { |
|
|
4296 | userdata *u = ev_userdata (EV_A); |
|
|
4297 | pthread_mutex_lock (&u->lock); |
|
|
4298 | } |
|
|
4299 | |
|
|
4300 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4301 | into C<ev_run>: |
|
|
4302 | |
|
|
4303 | void * |
|
|
4304 | l_run (void *thr_arg) |
|
|
4305 | { |
|
|
4306 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4307 | |
|
|
4308 | l_acquire (EV_A); |
|
|
4309 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4310 | ev_run (EV_A_ 0); |
|
|
4311 | l_release (EV_A); |
|
|
4312 | |
|
|
4313 | return 0; |
|
|
4314 | } |
|
|
4315 | |
|
|
4316 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4317 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4318 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4319 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4320 | and b) skipping inter-thread-communication when there are no pending |
|
|
4321 | watchers is very beneficial): |
|
|
4322 | |
|
|
4323 | static void |
|
|
4324 | l_invoke (EV_P) |
|
|
4325 | { |
|
|
4326 | userdata *u = ev_userdata (EV_A); |
|
|
4327 | |
|
|
4328 | while (ev_pending_count (EV_A)) |
|
|
4329 | { |
|
|
4330 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4331 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4332 | } |
|
|
4333 | } |
|
|
4334 | |
|
|
4335 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4336 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4337 | thread to continue: |
|
|
4338 | |
|
|
4339 | static void |
|
|
4340 | real_invoke_pending (EV_P) |
|
|
4341 | { |
|
|
4342 | userdata *u = ev_userdata (EV_A); |
|
|
4343 | |
|
|
4344 | pthread_mutex_lock (&u->lock); |
|
|
4345 | ev_invoke_pending (EV_A); |
|
|
4346 | pthread_cond_signal (&u->invoke_cv); |
|
|
4347 | pthread_mutex_unlock (&u->lock); |
|
|
4348 | } |
|
|
4349 | |
|
|
4350 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4351 | event loop, you will now have to lock: |
|
|
4352 | |
|
|
4353 | ev_timer timeout_watcher; |
|
|
4354 | userdata *u = ev_userdata (EV_A); |
|
|
4355 | |
|
|
4356 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4357 | |
|
|
4358 | pthread_mutex_lock (&u->lock); |
|
|
4359 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4360 | ev_async_send (EV_A_ &u->async_w); |
|
|
4361 | pthread_mutex_unlock (&u->lock); |
|
|
4362 | |
|
|
4363 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4364 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4365 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4366 | watchers in the next event loop iteration. |
|
|
4367 | |
5019 | |
4368 | =head3 COROUTINES |
5020 | =head3 COROUTINES |
4369 | |
5021 | |
4370 | Libev is very accommodating to coroutines ("cooperative threads"): |
5022 | Libev is very accommodating to coroutines ("cooperative threads"): |
4371 | libev fully supports nesting calls to its functions from different |
5023 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4467 | =head3 C<kqueue> is buggy |
5119 | =head3 C<kqueue> is buggy |
4468 | |
5120 | |
4469 | The kqueue syscall is broken in all known versions - most versions support |
5121 | The kqueue syscall is broken in all known versions - most versions support |
4470 | only sockets, many support pipes. |
5122 | only sockets, many support pipes. |
4471 | |
5123 | |
4472 | Libev tries to work around this by not using C<kqueue> by default on |
5124 | Libev tries to work around this by not using C<kqueue> by default on this |
4473 | this rotten platform, but of course you can still ask for it when creating |
5125 | rotten platform, but of course you can still ask for it when creating a |
4474 | a loop. |
5126 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5127 | probably going to work well. |
4475 | |
5128 | |
4476 | =head3 C<poll> is buggy |
5129 | =head3 C<poll> is buggy |
4477 | |
5130 | |
4478 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
5131 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
4479 | implementation by something calling C<kqueue> internally around the 10.5.6 |
5132 | implementation by something calling C<kqueue> internally around the 10.5.6 |
… | |
… | |
4498 | |
5151 | |
4499 | =head3 C<errno> reentrancy |
5152 | =head3 C<errno> reentrancy |
4500 | |
5153 | |
4501 | The default compile environment on Solaris is unfortunately so |
5154 | The default compile environment on Solaris is unfortunately so |
4502 | thread-unsafe that you can't even use components/libraries compiled |
5155 | thread-unsafe that you can't even use components/libraries compiled |
4503 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
5156 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
4504 | isn't defined by default. |
5157 | defined by default. A valid, if stupid, implementation choice. |
4505 | |
5158 | |
4506 | If you want to use libev in threaded environments you have to make sure |
5159 | If you want to use libev in threaded environments you have to make sure |
4507 | it's compiled with C<_REENTRANT> defined. |
5160 | it's compiled with C<_REENTRANT> defined. |
4508 | |
5161 | |
4509 | =head3 Event port backend |
5162 | =head3 Event port backend |
4510 | |
5163 | |
4511 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
5164 | The scalable event interface for Solaris is called "event |
4512 | this mechanism is very buggy. If you run into high CPU usage, your program |
5165 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5166 | releases. If you run into high CPU usage, your program freezes or you get |
4513 | freezes or you get a large number of spurious wakeups, make sure you have |
5167 | a large number of spurious wakeups, make sure you have all the relevant |
4514 | all the relevant and latest kernel patches applied. No, I don't know which |
5168 | and latest kernel patches applied. No, I don't know which ones, but there |
4515 | ones, but there are multiple ones. |
5169 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5170 | great. |
4516 | |
5171 | |
4517 | If you can't get it to work, you can try running the program by setting |
5172 | If you can't get it to work, you can try running the program by setting |
4518 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
5173 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
4519 | C<select> backends. |
5174 | C<select> backends. |
4520 | |
5175 | |
4521 | =head2 AIX POLL BUG |
5176 | =head2 AIX POLL BUG |
4522 | |
5177 | |
4523 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
5178 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
4524 | this by trying to avoid the poll backend altogether (i.e. it's not even |
5179 | this by trying to avoid the poll backend altogether (i.e. it's not even |
4525 | compiled in), which normally isn't a big problem as C<select> works fine |
5180 | compiled in), which normally isn't a big problem as C<select> works fine |
4526 | with large bitsets, and AIX is dead anyway. |
5181 | with large bitsets on AIX, and AIX is dead anyway. |
4527 | |
5182 | |
4528 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5183 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4529 | |
5184 | |
4530 | =head3 General issues |
5185 | =head3 General issues |
4531 | |
5186 | |
… | |
… | |
4533 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5188 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4534 | model. Libev still offers limited functionality on this platform in |
5189 | model. Libev still offers limited functionality on this platform in |
4535 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5190 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4536 | descriptors. This only applies when using Win32 natively, not when using |
5191 | descriptors. This only applies when using Win32 natively, not when using |
4537 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5192 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4538 | as every compielr comes with a slightly differently broken/incompatible |
5193 | as every compiler comes with a slightly differently broken/incompatible |
4539 | environment. |
5194 | environment. |
4540 | |
5195 | |
4541 | Lifting these limitations would basically require the full |
5196 | Lifting these limitations would basically require the full |
4542 | re-implementation of the I/O system. If you are into this kind of thing, |
5197 | re-implementation of the I/O system. If you are into this kind of thing, |
4543 | then note that glib does exactly that for you in a very portable way (note |
5198 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4637 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5292 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4638 | assumes that the same (machine) code can be used to call any watcher |
5293 | assumes that the same (machine) code can be used to call any watcher |
4639 | callback: The watcher callbacks have different type signatures, but libev |
5294 | callback: The watcher callbacks have different type signatures, but libev |
4640 | calls them using an C<ev_watcher *> internally. |
5295 | calls them using an C<ev_watcher *> internally. |
4641 | |
5296 | |
|
|
5297 | =item pointer accesses must be thread-atomic |
|
|
5298 | |
|
|
5299 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5300 | writable in one piece - this is the case on all current architectures. |
|
|
5301 | |
4642 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5302 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4643 | |
5303 | |
4644 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5304 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4645 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5305 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4646 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5306 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4654 | thread" or will block signals process-wide, both behaviours would |
5314 | thread" or will block signals process-wide, both behaviours would |
4655 | be compatible with libev. Interaction between C<sigprocmask> and |
5315 | be compatible with libev. Interaction between C<sigprocmask> and |
4656 | C<pthread_sigmask> could complicate things, however. |
5316 | C<pthread_sigmask> could complicate things, however. |
4657 | |
5317 | |
4658 | The most portable way to handle signals is to block signals in all threads |
5318 | The most portable way to handle signals is to block signals in all threads |
4659 | except the initial one, and run the default loop in the initial thread as |
5319 | except the initial one, and run the signal handling loop in the initial |
4660 | well. |
5320 | thread as well. |
4661 | |
5321 | |
4662 | =item C<long> must be large enough for common memory allocation sizes |
5322 | =item C<long> must be large enough for common memory allocation sizes |
4663 | |
5323 | |
4664 | To improve portability and simplify its API, libev uses C<long> internally |
5324 | To improve portability and simplify its API, libev uses C<long> internally |
4665 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5325 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4671 | |
5331 | |
4672 | The type C<double> is used to represent timestamps. It is required to |
5332 | The type C<double> is used to represent timestamps. It is required to |
4673 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5333 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4674 | good enough for at least into the year 4000 with millisecond accuracy |
5334 | good enough for at least into the year 4000 with millisecond accuracy |
4675 | (the design goal for libev). This requirement is overfulfilled by |
5335 | (the design goal for libev). This requirement is overfulfilled by |
4676 | implementations using IEEE 754, which is basically all existing ones. With |
5336 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5337 | |
4677 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5338 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5339 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5340 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5341 | something like that, just kidding). |
4678 | |
5342 | |
4679 | =back |
5343 | =back |
4680 | |
5344 | |
4681 | If you know of other additional requirements drop me a note. |
5345 | If you know of other additional requirements drop me a note. |
4682 | |
5346 | |
… | |
… | |
4744 | =item Processing ev_async_send: O(number_of_async_watchers) |
5408 | =item Processing ev_async_send: O(number_of_async_watchers) |
4745 | |
5409 | |
4746 | =item Processing signals: O(max_signal_number) |
5410 | =item Processing signals: O(max_signal_number) |
4747 | |
5411 | |
4748 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5412 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4749 | calls in the current loop iteration. Checking for async and signal events |
5413 | calls in the current loop iteration and the loop is currently |
|
|
5414 | blocked. Checking for async and signal events involves iterating over all |
4750 | involves iterating over all running async watchers or all signal numbers. |
5415 | running async watchers or all signal numbers. |
4751 | |
5416 | |
4752 | =back |
5417 | =back |
4753 | |
5418 | |
4754 | |
5419 | |
4755 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5420 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4756 | |
5421 | |
4757 | The major version 4 introduced some minor incompatible changes to the API. |
5422 | The major version 4 introduced some incompatible changes to the API. |
4758 | |
5423 | |
4759 | At the moment, the C<ev.h> header file tries to implement superficial |
5424 | At the moment, the C<ev.h> header file provides compatibility definitions |
4760 | compatibility, so most programs should still compile. Those might be |
5425 | for all changes, so most programs should still compile. The compatibility |
4761 | removed in later versions of libev, so better update early than late. |
5426 | layer might be removed in later versions of libev, so better update to the |
|
|
5427 | new API early than late. |
4762 | |
5428 | |
4763 | =over 4 |
5429 | =over 4 |
|
|
5430 | |
|
|
5431 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5432 | |
|
|
5433 | The backward compatibility mechanism can be controlled by |
|
|
5434 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
|
|
5435 | section. |
|
|
5436 | |
|
|
5437 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5438 | |
|
|
5439 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5440 | |
|
|
5441 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5442 | ev_loop_fork (EV_DEFAULT); |
4764 | |
5443 | |
4765 | =item function/symbol renames |
5444 | =item function/symbol renames |
4766 | |
5445 | |
4767 | A number of functions and symbols have been renamed: |
5446 | A number of functions and symbols have been renamed: |
4768 | |
5447 | |
… | |
… | |
4787 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5466 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4788 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5467 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4789 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5468 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4790 | typedef. |
5469 | typedef. |
4791 | |
5470 | |
4792 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4793 | |
|
|
4794 | The backward compatibility mechanism can be controlled by |
|
|
4795 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4796 | section. |
|
|
4797 | |
|
|
4798 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5471 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4799 | |
5472 | |
4800 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5473 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4801 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5474 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4802 | and work, but the library code will of course be larger. |
5475 | and work, but the library code will of course be larger. |
… | |
… | |
4808 | |
5481 | |
4809 | =over 4 |
5482 | =over 4 |
4810 | |
5483 | |
4811 | =item active |
5484 | =item active |
4812 | |
5485 | |
4813 | A watcher is active as long as it has been started (has been attached to |
5486 | A watcher is active as long as it has been started and not yet stopped. |
4814 | an event loop) but not yet stopped (disassociated from the event loop). |
5487 | See L</WATCHER STATES> for details. |
4815 | |
5488 | |
4816 | =item application |
5489 | =item application |
4817 | |
5490 | |
4818 | In this document, an application is whatever is using libev. |
5491 | In this document, an application is whatever is using libev. |
|
|
5492 | |
|
|
5493 | =item backend |
|
|
5494 | |
|
|
5495 | The part of the code dealing with the operating system interfaces. |
4819 | |
5496 | |
4820 | =item callback |
5497 | =item callback |
4821 | |
5498 | |
4822 | The address of a function that is called when some event has been |
5499 | The address of a function that is called when some event has been |
4823 | detected. Callbacks are being passed the event loop, the watcher that |
5500 | detected. Callbacks are being passed the event loop, the watcher that |
4824 | received the event, and the actual event bitset. |
5501 | received the event, and the actual event bitset. |
4825 | |
5502 | |
4826 | =item callback invocation |
5503 | =item callback/watcher invocation |
4827 | |
5504 | |
4828 | The act of calling the callback associated with a watcher. |
5505 | The act of calling the callback associated with a watcher. |
4829 | |
5506 | |
4830 | =item event |
5507 | =item event |
4831 | |
5508 | |
… | |
… | |
4850 | The model used to describe how an event loop handles and processes |
5527 | The model used to describe how an event loop handles and processes |
4851 | watchers and events. |
5528 | watchers and events. |
4852 | |
5529 | |
4853 | =item pending |
5530 | =item pending |
4854 | |
5531 | |
4855 | A watcher is pending as soon as the corresponding event has been detected, |
5532 | A watcher is pending as soon as the corresponding event has been |
4856 | and stops being pending as soon as the watcher will be invoked or its |
5533 | detected. See L</WATCHER STATES> for details. |
4857 | pending status is explicitly cleared by the application. |
|
|
4858 | |
|
|
4859 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4860 | its pending status. |
|
|
4861 | |
5534 | |
4862 | =item real time |
5535 | =item real time |
4863 | |
5536 | |
4864 | The physical time that is observed. It is apparently strictly monotonic :) |
5537 | The physical time that is observed. It is apparently strictly monotonic :) |
4865 | |
5538 | |
4866 | =item wall-clock time |
5539 | =item wall-clock time |
4867 | |
5540 | |
4868 | The time and date as shown on clocks. Unlike real time, it can actually |
5541 | The time and date as shown on clocks. Unlike real time, it can actually |
4869 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5542 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4870 | clock. |
5543 | clock. |
4871 | |
5544 | |
4872 | =item watcher |
5545 | =item watcher |
4873 | |
5546 | |
4874 | A data structure that describes interest in certain events. Watchers need |
5547 | A data structure that describes interest in certain events. Watchers need |
4875 | to be started (attached to an event loop) before they can receive events. |
5548 | to be started (attached to an event loop) before they can receive events. |
4876 | |
5549 | |
4877 | =item watcher invocation |
|
|
4878 | |
|
|
4879 | The act of calling the callback associated with a watcher. |
|
|
4880 | |
|
|
4881 | =back |
5550 | =back |
4882 | |
5551 | |
4883 | =head1 AUTHOR |
5552 | =head1 AUTHOR |
4884 | |
5553 | |
4885 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5554 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5555 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4886 | |
5556 | |