… | |
… | |
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); |
… | |
… | |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familiarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
165 | |
173 | |
166 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
167 | |
175 | |
168 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
170 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_update_now> and C<ev_now>. |
171 | |
180 | |
172 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
173 | |
182 | |
174 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked until |
175 | either it is interrupted or the given time interval has passed. Basically |
184 | either it is interrupted or the given time interval has passed. Basically |
… | |
… | |
192 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
193 | compatible to older versions, so a larger minor version alone is usually |
202 | compatible to older versions, so a larger minor version alone is usually |
194 | not a problem. |
203 | not a problem. |
195 | |
204 | |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
205 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | version (note, however, that this will not detect ABI mismatches :). |
206 | version (note, however, that this will not detect other ABI mismatches, |
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207 | such as LFS or reentrancy). |
198 | |
208 | |
199 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
200 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | |
212 | |
… | |
… | |
213 | assert (("sorry, no epoll, no sex", |
223 | assert (("sorry, no epoll, no sex", |
214 | ev_supported_backends () & EVBACKEND_EPOLL)); |
224 | ev_supported_backends () & EVBACKEND_EPOLL)); |
215 | |
225 | |
216 | =item unsigned int ev_recommended_backends () |
226 | =item unsigned int ev_recommended_backends () |
217 | |
227 | |
218 | Return the set of all backends compiled into this binary of libev and also |
228 | Return the set of all backends compiled into this binary of libev and |
219 | recommended for this platform. This set is often smaller than the one |
229 | also recommended for this platform, meaning it will work for most file |
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230 | descriptor types. This set is often smaller than the one returned by |
220 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
231 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
221 | most BSDs and will not be auto-detected unless you explicitly request it |
232 | and will not be auto-detected unless you explicitly request it (assuming |
222 | (assuming you know what you are doing). This is the set of backends that |
233 | you know what you are doing). This is the set of backends that libev will |
223 | libev will probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
224 | |
235 | |
225 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
226 | |
237 | |
227 | Returns the set of backends that are embeddable in other event loops. This |
238 | Returns the set of backends that are embeddable in other event loops. This |
228 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
229 | might be supported on the current system, you would need to look at |
240 | current system. To find which embeddable backends might be supported on |
230 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
231 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
232 | |
243 | |
233 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
234 | |
245 | |
235 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
236 | |
247 | |
237 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
238 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
249 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
239 | used to allocate and free memory (no surprises here). If it returns zero |
250 | used to allocate and free memory (no surprises here). If it returns zero |
240 | when memory needs to be allocated (C<size != 0>), the library might abort |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
266 | } |
277 | } |
267 | |
278 | |
268 | ... |
279 | ... |
269 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
270 | |
281 | |
271 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
272 | |
283 | |
273 | Set the callback function to call on a retryable system call error (such |
284 | Set the callback function to call on a retryable system call error (such |
274 | as failed select, poll, epoll_wait). The message is a printable string |
285 | as failed select, poll, epoll_wait). The message is a printable string |
275 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
276 | callback is set, then libev will expect it to remedy the situation, no |
287 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
288 | } |
299 | } |
289 | |
300 | |
290 | ... |
301 | ... |
291 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
292 | |
303 | |
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304 | =item ev_feed_signal (int signum) |
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305 | |
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306 | This function can be used to "simulate" a signal receive. It is completely |
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307 | safe to call this function at any time, from any context, including signal |
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308 | handlers or random threads. |
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309 | |
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310 | Its main use is to customise signal handling in your process, especially |
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311 | in the presence of threads. For example, you could block signals |
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312 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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313 | creating any loops), and in one thread, use C<sigwait> or any other |
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314 | mechanism to wait for signals, then "deliver" them to libev by calling |
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315 | C<ev_feed_signal>. |
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316 | |
293 | =back |
317 | =back |
294 | |
318 | |
295 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
319 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
296 | |
320 | |
297 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
321 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
298 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
322 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
299 | libev 3 had an C<ev_loop> function colliding with the struct name). |
323 | libev 3 had an C<ev_loop> function colliding with the struct name). |
300 | |
324 | |
301 | The library knows two types of such loops, the I<default> loop, which |
325 | The library knows two types of such loops, the I<default> loop, which |
302 | supports signals and child events, and dynamically created event loops |
326 | supports child process events, and dynamically created event loops which |
303 | which do not. |
327 | do not. |
304 | |
328 | |
305 | =over 4 |
329 | =over 4 |
306 | |
330 | |
307 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
331 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
308 | |
332 | |
309 | This will initialise the default event loop if it hasn't been initialised |
333 | This returns the "default" event loop object, which is what you should |
310 | yet and return it. If the default loop could not be initialised, returns |
334 | normally use when you just need "the event loop". Event loop objects and |
311 | false. If it already was initialised it simply returns it (and ignores the |
335 | the C<flags> parameter are described in more detail in the entry for |
312 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
336 | C<ev_loop_new>. |
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337 | |
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338 | If the default loop is already initialised then this function simply |
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339 | returns it (and ignores the flags. If that is troubling you, check |
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340 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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341 | flags, which should almost always be C<0>, unless the caller is also the |
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342 | one calling C<ev_run> or otherwise qualifies as "the main program". |
313 | |
343 | |
314 | If you don't know what event loop to use, use the one returned from this |
344 | If you don't know what event loop to use, use the one returned from this |
315 | function. |
345 | function (or via the C<EV_DEFAULT> macro). |
316 | |
346 | |
317 | Note that this function is I<not> thread-safe, so if you want to use it |
347 | Note that this function is I<not> thread-safe, so if you want to use it |
318 | from multiple threads, you have to lock (note also that this is unlikely, |
348 | from multiple threads, you have to employ some kind of mutex (note also |
319 | as loops cannot be shared easily between threads anyway). |
349 | that this case is unlikely, as loops cannot be shared easily between |
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350 | threads anyway). |
320 | |
351 | |
321 | The default loop is the only loop that can handle C<ev_signal> and |
352 | The default loop is the only loop that can handle C<ev_child> watchers, |
322 | C<ev_child> watchers, and to do this, it always registers a handler |
353 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
323 | for C<SIGCHLD>. If this is a problem for your application you can either |
354 | a problem for your application you can either create a dynamic loop with |
324 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
355 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
325 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
356 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
326 | C<ev_default_init>. |
357 | |
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358 | Example: This is the most typical usage. |
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359 | |
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360 | if (!ev_default_loop (0)) |
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361 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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362 | |
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363 | Example: Restrict libev to the select and poll backends, and do not allow |
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364 | environment settings to be taken into account: |
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365 | |
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366 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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367 | |
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368 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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369 | |
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370 | This will create and initialise a new event loop object. If the loop |
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371 | could not be initialised, returns false. |
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372 | |
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373 | This function is thread-safe, and one common way to use libev with |
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374 | threads is indeed to create one loop per thread, and using the default |
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375 | loop in the "main" or "initial" thread. |
327 | |
376 | |
328 | The flags argument can be used to specify special behaviour or specific |
377 | The flags argument can be used to specify special behaviour or specific |
329 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
378 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
330 | |
379 | |
331 | The following flags are supported: |
380 | The following flags are supported: |
… | |
… | |
366 | environment variable. |
415 | environment variable. |
367 | |
416 | |
368 | =item C<EVFLAG_NOINOTIFY> |
417 | =item C<EVFLAG_NOINOTIFY> |
369 | |
418 | |
370 | When this flag is specified, then libev will not attempt to use the |
419 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
420 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
421 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
422 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
423 | |
375 | =item C<EVFLAG_SIGNALFD> |
424 | =item C<EVFLAG_SIGNALFD> |
376 | |
425 | |
377 | When this flag is specified, then libev will attempt to use the |
426 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
427 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
379 | delivers signals synchronously, which makes it both faster and might make |
428 | delivers signals synchronously, which makes it both faster and might make |
380 | it possible to get the queued signal data. It can also simplify signal |
429 | it possible to get the queued signal data. It can also simplify signal |
381 | handling with threads, as long as you properly block signals in your |
430 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
431 | threads that are not interested in handling them. |
383 | |
432 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
433 | Signalfd will not be used by default as this changes your signal mask, and |
385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
434 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
435 | example) that can't properly initialise their signal masks. |
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436 | |
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437 | =item C<EVFLAG_NOSIGMASK> |
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438 | |
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439 | When this flag is specified, then libev will avoid to modify the signal |
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440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
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441 | when you want to receive them. |
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442 | |
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443 | This behaviour is useful when you want to do your own signal handling, or |
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444 | want to handle signals only in specific threads and want to avoid libev |
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445 | unblocking the signals. |
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446 | |
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447 | This flag's behaviour will become the default in future versions of libev. |
387 | |
448 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
450 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
451 | This is your standard select(2) backend. Not I<completely> standard, as |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
452 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
427 | epoll scales either O(1) or O(active_fds). |
488 | epoll scales either O(1) or O(active_fds). |
428 | |
489 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
491 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
492 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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494 | returning before the timeout value, resulting in additional iterations |
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495 | (and only giving 5ms accuracy while select on the same platform gives |
433 | so on. The biggest issue is fork races, however - if a program forks then |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
434 | I<both> parent and child process have to recreate the epoll set, which can |
497 | forks then I<both> parent and child process have to recreate the epoll |
435 | take considerable time (one syscall per file descriptor) and is of course |
498 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
499 | and is of course hard to detect. |
437 | |
500 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
440 | I<different> file descriptors (even already closed ones, so one cannot |
503 | I<different> file descriptors (even already closed ones, so one cannot |
441 | even remove them from the set) than registered in the set (especially |
504 | even remove them from the set) than registered in the set (especially |
… | |
… | |
443 | employing an additional generation counter and comparing that against the |
506 | employing an additional generation counter and comparing that against the |
444 | events to filter out spurious ones, recreating the set when required. Last |
507 | events to filter out spurious ones, recreating the set when required. Last |
445 | not least, it also refuses to work with some file descriptors which work |
508 | not least, it also refuses to work with some file descriptors which work |
446 | perfectly fine with C<select> (files, many character devices...). |
509 | perfectly fine with C<select> (files, many character devices...). |
447 | |
510 | |
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511 | Epoll is truly the train wreck analog among event poll mechanisms, |
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512 | a frankenpoll, cobbled together in a hurry, no thought to design or |
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513 | interaction with others. |
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514 | |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
515 | While stopping, setting and starting an I/O watcher in the same iteration |
449 | will result in some caching, there is still a system call per such |
516 | will result in some caching, there is still a system call per such |
450 | incident (because the same I<file descriptor> could point to a different |
517 | incident (because the same I<file descriptor> could point to a different |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
518 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
452 | file descriptors might not work very well if you register events for both |
519 | file descriptors might not work very well if you register events for both |
… | |
… | |
517 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
584 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
518 | |
585 | |
519 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
586 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
520 | it's really slow, but it still scales very well (O(active_fds)). |
587 | it's really slow, but it still scales very well (O(active_fds)). |
521 | |
588 | |
522 | Please note that Solaris event ports can deliver a lot of spurious |
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523 | notifications, so you need to use non-blocking I/O or other means to avoid |
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524 | blocking when no data (or space) is available. |
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525 | |
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526 | While this backend scales well, it requires one system call per active |
589 | While this backend scales well, it requires one system call per active |
527 | file descriptor per loop iteration. For small and medium numbers of file |
590 | file descriptor per loop iteration. For small and medium numbers of file |
528 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
591 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
529 | might perform better. |
592 | might perform better. |
530 | |
593 | |
531 | On the positive side, with the exception of the spurious readiness |
594 | On the positive side, this backend actually performed fully to |
532 | notifications, this backend actually performed fully to specification |
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533 | in all tests and is fully embeddable, which is a rare feat among the |
595 | specification in all tests and is fully embeddable, which is a rare feat |
534 | OS-specific backends (I vastly prefer correctness over speed hacks). |
596 | among the OS-specific backends (I vastly prefer correctness over speed |
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597 | hacks). |
|
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598 | |
|
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599 | On the negative side, the interface is I<bizarre> - so bizarre that |
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600 | even sun itself gets it wrong in their code examples: The event polling |
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601 | function sometimes returning events to the caller even though an error |
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602 | occurred, but with no indication whether it has done so or not (yes, it's |
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603 | even documented that way) - deadly for edge-triggered interfaces where |
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604 | you absolutely have to know whether an event occurred or not because you |
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605 | have to re-arm the watcher. |
|
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606 | |
|
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607 | Fortunately libev seems to be able to work around these idiocies. |
535 | |
608 | |
536 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
609 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
537 | C<EVBACKEND_POLL>. |
610 | C<EVBACKEND_POLL>. |
538 | |
611 | |
539 | =item C<EVBACKEND_ALL> |
612 | =item C<EVBACKEND_ALL> |
540 | |
613 | |
541 | Try all backends (even potentially broken ones that wouldn't be tried |
614 | Try all backends (even potentially broken ones that wouldn't be tried |
542 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
615 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
543 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
616 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
544 | |
617 | |
545 | It is definitely not recommended to use this flag. |
618 | It is definitely not recommended to use this flag, use whatever |
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619 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
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620 | at all. |
|
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621 | |
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622 | =item C<EVBACKEND_MASK> |
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623 | |
|
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624 | Not a backend at all, but a mask to select all backend bits from a |
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625 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
626 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
546 | |
627 | |
547 | =back |
628 | =back |
548 | |
629 | |
549 | If one or more of the backend flags are or'ed into the flags value, |
630 | If one or more of the backend flags are or'ed into the flags value, |
550 | then only these backends will be tried (in the reverse order as listed |
631 | then only these backends will be tried (in the reverse order as listed |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
632 | here). If none are specified, all backends in C<ev_recommended_backends |
552 | ()> will be tried. |
633 | ()> will be tried. |
553 | |
634 | |
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. |
635 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
636 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
637 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
638 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
639 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
640 | |
|
|
641 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
642 | used if available. |
|
|
643 | |
|
|
644 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
645 | |
586 | =item ev_default_destroy () |
646 | =item ev_loop_destroy (loop) |
587 | |
647 | |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
648 | 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 |
649 | 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 |
650 | 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, |
651 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
652 | calling this function, or cope with the fact afterwards (which is usually |
593 | can just ignore the watchers and/or C<free ()> them for example). |
653 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
654 | for example). |
594 | |
655 | |
595 | Note that certain global state, such as signal state (and installed signal |
656 | Note that certain global state, such as signal state (and installed signal |
596 | handlers), will not be freed by this function, and related watchers (such |
657 | handlers), will not be freed by this function, and related watchers (such |
597 | as signal and child watchers) would need to be stopped manually. |
658 | as signal and child watchers) would need to be stopped manually. |
598 | |
659 | |
599 | In general it is not advisable to call this function except in the |
660 | This function is normally used on loop objects allocated by |
600 | rare occasion where you really need to free e.g. the signal handling |
661 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
662 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
663 | |
|
|
664 | Note that it is not advisable to call this function on the default loop |
|
|
665 | except in the rare occasion where you really need to free its resources. |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
666 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
667 | and C<ev_loop_destroy>. |
603 | |
668 | |
604 | =item ev_loop_destroy (loop) |
669 | =item ev_loop_fork (loop) |
605 | |
670 | |
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 |
671 | 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 |
672 | 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 |
673 | 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 |
674 | 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 |
675 | child before resuming or calling C<ev_run>. |
616 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
617 | |
676 | |
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
677 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
678 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
679 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
621 | during fork. |
680 | during fork. |
… | |
… | |
626 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
685 | 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 |
686 | difference, but libev will usually detect this case on its own and do a |
628 | costly reset of the backend). |
687 | costly reset of the backend). |
629 | |
688 | |
630 | The function itself is quite fast and it's usually not a problem to call |
689 | The function itself is quite fast and it's usually not a problem to call |
631 | it just in case after a fork. To make this easy, the function will fit in |
690 | it just in case after a fork. |
632 | quite nicely into a call to C<pthread_atfork>: |
|
|
633 | |
691 | |
|
|
692 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
693 | using pthreads. |
|
|
694 | |
|
|
695 | static void |
|
|
696 | post_fork_child (void) |
|
|
697 | { |
|
|
698 | ev_loop_fork (EV_DEFAULT); |
|
|
699 | } |
|
|
700 | |
|
|
701 | ... |
634 | pthread_atfork (0, 0, ev_default_fork); |
702 | 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 | |
703 | |
643 | =item int ev_is_default_loop (loop) |
704 | =item int ev_is_default_loop (loop) |
644 | |
705 | |
645 | Returns true when the given loop is, in fact, the default loop, and false |
706 | Returns true when the given loop is, in fact, the default loop, and false |
646 | otherwise. |
707 | otherwise. |
… | |
… | |
657 | prepare and check phases. |
718 | prepare and check phases. |
658 | |
719 | |
659 | =item unsigned int ev_depth (loop) |
720 | =item unsigned int ev_depth (loop) |
660 | |
721 | |
661 | Returns the number of times C<ev_run> was entered minus the number of |
722 | 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. |
723 | times C<ev_run> was exited normally, in other words, the recursion depth. |
663 | |
724 | |
664 | Outside C<ev_run>, this number is zero. In a callback, this number is |
725 | Outside C<ev_run>, this number is zero. In a callback, this number is |
665 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
726 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
666 | in which case it is higher. |
727 | in which case it is higher. |
667 | |
728 | |
668 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
729 | 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 |
730 | throwing an exception etc.), doesn't count as "exit" - consider this |
670 | ungentleman-like behaviour unless it's really convenient. |
731 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
732 | convenient, in which case it is fully supported. |
671 | |
733 | |
672 | =item unsigned int ev_backend (loop) |
734 | =item unsigned int ev_backend (loop) |
673 | |
735 | |
674 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
736 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
675 | use. |
737 | use. |
… | |
… | |
736 | relying on all watchers to be stopped when deciding when a program has |
798 | relying on all watchers to be stopped when deciding when a program has |
737 | finished (especially in interactive programs), but having a program |
799 | finished (especially in interactive programs), but having a program |
738 | that automatically loops as long as it has to and no longer by virtue |
800 | that automatically loops as long as it has to and no longer by virtue |
739 | of relying on its watchers stopping correctly, that is truly a thing of |
801 | of relying on its watchers stopping correctly, that is truly a thing of |
740 | beauty. |
802 | beauty. |
|
|
803 | |
|
|
804 | This function is also I<mostly> exception-safe - you can break out of |
|
|
805 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
806 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
807 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
741 | |
808 | |
742 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
809 | 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 |
810 | 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 |
811 | 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 |
812 | iteration of the loop. This is sometimes useful to poll and handle new |
… | |
… | |
807 | Can be used to make a call to C<ev_run> return early (but only after it |
874 | 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 |
875 | 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 |
876 | 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. |
877 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
811 | |
878 | |
812 | This "unloop state" will be cleared when entering C<ev_run> again. |
879 | This "break state" will be cleared on the next call to C<ev_run>. |
813 | |
880 | |
814 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
881 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
882 | which case it will have no effect. |
815 | |
883 | |
816 | =item ev_ref (loop) |
884 | =item ev_ref (loop) |
817 | |
885 | |
818 | =item ev_unref (loop) |
886 | =item ev_unref (loop) |
819 | |
887 | |
… | |
… | |
840 | running when nothing else is active. |
908 | running when nothing else is active. |
841 | |
909 | |
842 | ev_signal exitsig; |
910 | ev_signal exitsig; |
843 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
911 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
844 | ev_signal_start (loop, &exitsig); |
912 | ev_signal_start (loop, &exitsig); |
845 | evf_unref (loop); |
913 | ev_unref (loop); |
846 | |
914 | |
847 | Example: For some weird reason, unregister the above signal handler again. |
915 | Example: For some weird reason, unregister the above signal handler again. |
848 | |
916 | |
849 | ev_ref (loop); |
917 | ev_ref (loop); |
850 | ev_signal_stop (loop, &exitsig); |
918 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
962 | See also the locking example in the C<THREADS> section later in this |
1030 | See also the locking example in the C<THREADS> section later in this |
963 | document. |
1031 | document. |
964 | |
1032 | |
965 | =item ev_set_userdata (loop, void *data) |
1033 | =item ev_set_userdata (loop, void *data) |
966 | |
1034 | |
967 | =item ev_userdata (loop) |
1035 | =item void *ev_userdata (loop) |
968 | |
1036 | |
969 | Set and retrieve a single C<void *> associated with a loop. When |
1037 | Set and retrieve a single C<void *> associated with a loop. When |
970 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1038 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
971 | C<0.> |
1039 | C<0>. |
972 | |
1040 | |
973 | These two functions can be used to associate arbitrary data with a loop, |
1041 | These two functions can be used to associate arbitrary data with a loop, |
974 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1042 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
975 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1043 | C<acquire> callbacks described above, but of course can be (ab-)used for |
976 | any other purpose as well. |
1044 | any other purpose as well. |
… | |
… | |
1104 | =item C<EV_FORK> |
1172 | =item C<EV_FORK> |
1105 | |
1173 | |
1106 | The event loop has been resumed in the child process after fork (see |
1174 | The event loop has been resumed in the child process after fork (see |
1107 | C<ev_fork>). |
1175 | C<ev_fork>). |
1108 | |
1176 | |
|
|
1177 | =item C<EV_CLEANUP> |
|
|
1178 | |
|
|
1179 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1180 | |
1109 | =item C<EV_ASYNC> |
1181 | =item C<EV_ASYNC> |
1110 | |
1182 | |
1111 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1183 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1112 | |
1184 | |
1113 | =item C<EV_CUSTOM> |
1185 | =item C<EV_CUSTOM> |
… | |
… | |
1134 | programs, though, as the fd could already be closed and reused for another |
1206 | programs, though, as the fd could already be closed and reused for another |
1135 | thing, so beware. |
1207 | thing, so beware. |
1136 | |
1208 | |
1137 | =back |
1209 | =back |
1138 | |
1210 | |
1139 | =head2 WATCHER STATES |
|
|
1140 | |
|
|
1141 | There are various watcher states mentioned throughout this manual - |
|
|
1142 | active, pending and so on. In this section these states and the rules to |
|
|
1143 | transition between them will be described in more detail - and while these |
|
|
1144 | rules might look complicated, they usually do "the right thing". |
|
|
1145 | |
|
|
1146 | =over 4 |
|
|
1147 | |
|
|
1148 | =item initialiased |
|
|
1149 | |
|
|
1150 | Before a watcher can be registered with the event looop it has to be |
|
|
1151 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1152 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1153 | |
|
|
1154 | In this state it is simply some block of memory that is suitable for use |
|
|
1155 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1156 | |
|
|
1157 | =item started/running/active |
|
|
1158 | |
|
|
1159 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1160 | property of the event loop, and is actively waiting for events. While in |
|
|
1161 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1162 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1163 | and call libev functions on it that are documented to work on active watchers. |
|
|
1164 | |
|
|
1165 | =item pending |
|
|
1166 | |
|
|
1167 | If a watcher is active and libev determines that an event it is interested |
|
|
1168 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1169 | stay in this pending state until either it is stopped or its callback is |
|
|
1170 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1171 | callback. |
|
|
1172 | |
|
|
1173 | The watcher might or might not be active while it is pending (for example, |
|
|
1174 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1175 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1176 | but it is still property of the event loop at this time, so cannot be |
|
|
1177 | moved, freed or reused. And if it is active the rules described in the |
|
|
1178 | previous item still apply. |
|
|
1179 | |
|
|
1180 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1181 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1182 | active. |
|
|
1183 | |
|
|
1184 | =item stopped |
|
|
1185 | |
|
|
1186 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1187 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1188 | latter will clear any pending state the watcher might be in, regardless |
|
|
1189 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1190 | freeing it is often a good idea. |
|
|
1191 | |
|
|
1192 | While stopped (and not pending) the watcher is essentially in the |
|
|
1193 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1194 | you wish. |
|
|
1195 | |
|
|
1196 | =back |
|
|
1197 | |
|
|
1198 | =head2 GENERIC WATCHER FUNCTIONS |
1211 | =head2 GENERIC WATCHER FUNCTIONS |
1199 | |
1212 | |
1200 | =over 4 |
1213 | =over 4 |
1201 | |
1214 | |
1202 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1215 | =item C<ev_init> (ev_TYPE *watcher, callback) |
… | |
… | |
1343 | |
1356 | |
1344 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1357 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1345 | functions that do not need a watcher. |
1358 | functions that do not need a watcher. |
1346 | |
1359 | |
1347 | =back |
1360 | =back |
1348 | |
|
|
1349 | |
1361 | |
1350 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1351 | |
1363 | |
1352 | Each watcher has, by default, a member C<void *data> that you can change |
1364 | Each watcher has, by default, a member C<void *data> that you can change |
1353 | and read at any time: libev will completely ignore it. This can be used |
1365 | and read at any time: libev will completely ignore it. This can be used |
… | |
… | |
1409 | t2_cb (EV_P_ ev_timer *w, int revents) |
1421 | t2_cb (EV_P_ ev_timer *w, int revents) |
1410 | { |
1422 | { |
1411 | struct my_biggy big = (struct my_biggy *) |
1423 | struct my_biggy big = (struct my_biggy *) |
1412 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1424 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1413 | } |
1425 | } |
|
|
1426 | |
|
|
1427 | =head2 WATCHER STATES |
|
|
1428 | |
|
|
1429 | There are various watcher states mentioned throughout this manual - |
|
|
1430 | active, pending and so on. In this section these states and the rules to |
|
|
1431 | transition between them will be described in more detail - and while these |
|
|
1432 | rules might look complicated, they usually do "the right thing". |
|
|
1433 | |
|
|
1434 | =over 4 |
|
|
1435 | |
|
|
1436 | =item initialiased |
|
|
1437 | |
|
|
1438 | Before a watcher can be registered with the event looop it has to be |
|
|
1439 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1440 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1441 | |
|
|
1442 | In this state it is simply some block of memory that is suitable for use |
|
|
1443 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1444 | |
|
|
1445 | =item started/running/active |
|
|
1446 | |
|
|
1447 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1448 | property of the event loop, and is actively waiting for events. While in |
|
|
1449 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1450 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1451 | and call libev functions on it that are documented to work on active watchers. |
|
|
1452 | |
|
|
1453 | =item pending |
|
|
1454 | |
|
|
1455 | If a watcher is active and libev determines that an event it is interested |
|
|
1456 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1457 | stay in this pending state until either it is stopped or its callback is |
|
|
1458 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1459 | callback. |
|
|
1460 | |
|
|
1461 | The watcher might or might not be active while it is pending (for example, |
|
|
1462 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1463 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1464 | but it is still property of the event loop at this time, so cannot be |
|
|
1465 | moved, freed or reused. And if it is active the rules described in the |
|
|
1466 | previous item still apply. |
|
|
1467 | |
|
|
1468 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1469 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1470 | active. |
|
|
1471 | |
|
|
1472 | =item stopped |
|
|
1473 | |
|
|
1474 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1475 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1476 | latter will clear any pending state the watcher might be in, regardless |
|
|
1477 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1478 | freeing it is often a good idea. |
|
|
1479 | |
|
|
1480 | While stopped (and not pending) the watcher is essentially in the |
|
|
1481 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1482 | you wish. |
|
|
1483 | |
|
|
1484 | =back |
1414 | |
1485 | |
1415 | =head2 WATCHER PRIORITY MODELS |
1486 | =head2 WATCHER PRIORITY MODELS |
1416 | |
1487 | |
1417 | Many event loops support I<watcher priorities>, which are usually small |
1488 | Many event loops support I<watcher priorities>, which are usually small |
1418 | integers that influence the ordering of event callback invocation |
1489 | integers that influence the ordering of event callback invocation |
… | |
… | |
1545 | In general you can register as many read and/or write event watchers per |
1616 | In general you can register as many read and/or write event watchers per |
1546 | fd as you want (as long as you don't confuse yourself). Setting all file |
1617 | fd as you want (as long as you don't confuse yourself). Setting all file |
1547 | descriptors to non-blocking mode is also usually a good idea (but not |
1618 | descriptors to non-blocking mode is also usually a good idea (but not |
1548 | required if you know what you are doing). |
1619 | required if you know what you are doing). |
1549 | |
1620 | |
1550 | If you cannot use non-blocking mode, then force the use of a |
|
|
1551 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1552 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1553 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1554 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1555 | |
|
|
1556 | Another thing you have to watch out for is that it is quite easy to |
1621 | Another thing you have to watch out for is that it is quite easy to |
1557 | receive "spurious" readiness notifications, that is your callback might |
1622 | receive "spurious" readiness notifications, that is, your callback might |
1558 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1623 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1559 | because there is no data. Not only are some backends known to create a |
1624 | because there is no data. It is very easy to get into this situation even |
1560 | lot of those (for example Solaris ports), it is very easy to get into |
1625 | with a relatively standard program structure. Thus it is best to always |
1561 | this situation even with a relatively standard program structure. Thus |
1626 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1562 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1563 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1627 | preferable to a program hanging until some data arrives. |
1564 | |
1628 | |
1565 | If you cannot run the fd in non-blocking mode (for example you should |
1629 | If you cannot run the fd in non-blocking mode (for example you should |
1566 | not play around with an Xlib connection), then you have to separately |
1630 | not play around with an Xlib connection), then you have to separately |
1567 | re-test whether a file descriptor is really ready with a known-to-be good |
1631 | re-test whether a file descriptor is really ready with a known-to-be good |
1568 | interface such as poll (fortunately in our Xlib example, Xlib already |
1632 | interface such as poll (fortunately in the case of Xlib, it already does |
1569 | does this on its own, so its quite safe to use). Some people additionally |
1633 | this on its own, so its quite safe to use). Some people additionally |
1570 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1634 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1571 | indefinitely. |
1635 | indefinitely. |
1572 | |
1636 | |
1573 | But really, best use non-blocking mode. |
1637 | But really, best use non-blocking mode. |
1574 | |
1638 | |
… | |
… | |
1602 | |
1666 | |
1603 | There is no workaround possible except not registering events |
1667 | There is no workaround possible except not registering events |
1604 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1668 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1605 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1669 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1606 | |
1670 | |
|
|
1671 | =head3 The special problem of files |
|
|
1672 | |
|
|
1673 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1674 | representing files, and expect it to become ready when their program |
|
|
1675 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1676 | |
|
|
1677 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1678 | notification as soon as the kernel knows whether and how much data is |
|
|
1679 | there, and in the case of open files, that's always the case, so you |
|
|
1680 | always get a readiness notification instantly, and your read (or possibly |
|
|
1681 | write) will still block on the disk I/O. |
|
|
1682 | |
|
|
1683 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1684 | devices and so on, there is another party (the sender) that delivers data |
|
|
1685 | on it's own, but in the case of files, there is no such thing: the disk |
|
|
1686 | will not send data on it's own, simply because it doesn't know what you |
|
|
1687 | wish to read - you would first have to request some data. |
|
|
1688 | |
|
|
1689 | Since files are typically not-so-well supported by advanced notification |
|
|
1690 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1691 | to files, even though you should not use it. The reason for this is |
|
|
1692 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1693 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1694 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1695 | F</dev/urandom>), and even though the file might better be served with |
|
|
1696 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1697 | it "just works" instead of freezing. |
|
|
1698 | |
|
|
1699 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1700 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1701 | when you rarely read from a file instead of from a socket, and want to |
|
|
1702 | reuse the same code path. |
|
|
1703 | |
1607 | =head3 The special problem of fork |
1704 | =head3 The special problem of fork |
1608 | |
1705 | |
1609 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1706 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1610 | useless behaviour. Libev fully supports fork, but needs to be told about |
1707 | useless behaviour. Libev fully supports fork, but needs to be told about |
1611 | it in the child. |
1708 | it in the child if you want to continue to use it in the child. |
1612 | |
1709 | |
1613 | To support fork in your programs, you either have to call |
1710 | To support fork in your child processes, you have to call C<ev_loop_fork |
1614 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1711 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1615 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1712 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1616 | C<EVBACKEND_POLL>. |
|
|
1617 | |
1713 | |
1618 | =head3 The special problem of SIGPIPE |
1714 | =head3 The special problem of SIGPIPE |
1619 | |
1715 | |
1620 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1716 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1621 | when writing to a pipe whose other end has been closed, your program gets |
1717 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
2237 | |
2333 | |
2238 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2334 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2239 | |
2335 | |
2240 | Signal watchers will trigger an event when the process receives a specific |
2336 | Signal watchers will trigger an event when the process receives a specific |
2241 | signal one or more times. Even though signals are very asynchronous, libev |
2337 | signal one or more times. Even though signals are very asynchronous, libev |
2242 | will try it's best to deliver signals synchronously, i.e. as part of the |
2338 | will try its best to deliver signals synchronously, i.e. as part of the |
2243 | normal event processing, like any other event. |
2339 | normal event processing, like any other event. |
2244 | |
2340 | |
2245 | If you want signals to be delivered truly asynchronously, just use |
2341 | If you want signals to be delivered truly asynchronously, just use |
2246 | C<sigaction> as you would do without libev and forget about sharing |
2342 | C<sigaction> as you would do without libev and forget about sharing |
2247 | the signal. You can even use C<ev_async> from a signal handler to |
2343 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2289 | I<has> to modify the signal mask, at least temporarily. |
2385 | I<has> to modify the signal mask, at least temporarily. |
2290 | |
2386 | |
2291 | So I can't stress this enough: I<If you do not reset your signal mask when |
2387 | So I can't stress this enough: I<If you do not reset your signal mask when |
2292 | you expect it to be empty, you have a race condition in your code>. This |
2388 | you expect it to be empty, you have a race condition in your code>. This |
2293 | is not a libev-specific thing, this is true for most event libraries. |
2389 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2390 | |
|
|
2391 | =head3 The special problem of threads signal handling |
|
|
2392 | |
|
|
2393 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2394 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2395 | threads in a process block signals, which is hard to achieve. |
|
|
2396 | |
|
|
2397 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2398 | for the same signals), you can tackle this problem by globally blocking |
|
|
2399 | all signals before creating any threads (or creating them with a fully set |
|
|
2400 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2401 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2402 | these signals. You can pass on any signals that libev might be interested |
|
|
2403 | in by calling C<ev_feed_signal>. |
2294 | |
2404 | |
2295 | =head3 Watcher-Specific Functions and Data Members |
2405 | =head3 Watcher-Specific Functions and Data Members |
2296 | |
2406 | |
2297 | =over 4 |
2407 | =over 4 |
2298 | |
2408 | |
… | |
… | |
3072 | disadvantage of having to use multiple event loops (which do not support |
3182 | disadvantage of having to use multiple event loops (which do not support |
3073 | signal watchers). |
3183 | signal watchers). |
3074 | |
3184 | |
3075 | When this is not possible, or you want to use the default loop for |
3185 | When this is not possible, or you want to use the default loop for |
3076 | other reasons, then in the process that wants to start "fresh", call |
3186 | other reasons, then in the process that wants to start "fresh", call |
3077 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3187 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3078 | the default loop will "orphan" (not stop) all registered watchers, so you |
3188 | Destroying the default loop will "orphan" (not stop) all registered |
3079 | have to be careful not to execute code that modifies those watchers. Note |
3189 | watchers, so you have to be careful not to execute code that modifies |
3080 | also that in that case, you have to re-register any signal watchers. |
3190 | those watchers. Note also that in that case, you have to re-register any |
|
|
3191 | signal watchers. |
3081 | |
3192 | |
3082 | =head3 Watcher-Specific Functions and Data Members |
3193 | =head3 Watcher-Specific Functions and Data Members |
3083 | |
3194 | |
3084 | =over 4 |
3195 | =over 4 |
3085 | |
3196 | |
3086 | =item ev_fork_init (ev_signal *, callback) |
3197 | =item ev_fork_init (ev_fork *, callback) |
3087 | |
3198 | |
3088 | Initialises and configures the fork watcher - it has no parameters of any |
3199 | Initialises and configures the fork watcher - it has no parameters of any |
3089 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3200 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3090 | believe me. |
3201 | really. |
3091 | |
3202 | |
3092 | =back |
3203 | =back |
|
|
3204 | |
|
|
3205 | |
|
|
3206 | =head2 C<ev_cleanup> - even the best things end |
|
|
3207 | |
|
|
3208 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3209 | by a call to C<ev_loop_destroy>. |
|
|
3210 | |
|
|
3211 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3212 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3213 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3214 | loop when you want them to be invoked. |
|
|
3215 | |
|
|
3216 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3217 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3218 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3219 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3220 | |
|
|
3221 | =head3 Watcher-Specific Functions and Data Members |
|
|
3222 | |
|
|
3223 | =over 4 |
|
|
3224 | |
|
|
3225 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3226 | |
|
|
3227 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3228 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3229 | pointless, I assure you. |
|
|
3230 | |
|
|
3231 | =back |
|
|
3232 | |
|
|
3233 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3234 | cleanup functions are called. |
|
|
3235 | |
|
|
3236 | static void |
|
|
3237 | program_exits (void) |
|
|
3238 | { |
|
|
3239 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3240 | } |
|
|
3241 | |
|
|
3242 | ... |
|
|
3243 | atexit (program_exits); |
3093 | |
3244 | |
3094 | |
3245 | |
3095 | =head2 C<ev_async> - how to wake up an event loop |
3246 | =head2 C<ev_async> - how to wake up an event loop |
3096 | |
3247 | |
3097 | In general, you cannot use an C<ev_run> from multiple threads or other |
3248 | In general, you cannot use an C<ev_run> from multiple threads or other |
… | |
… | |
3104 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3255 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3105 | |
3256 | |
3106 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3257 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3107 | too, are asynchronous in nature, and signals, too, will be compressed |
3258 | too, are asynchronous in nature, and signals, too, will be compressed |
3108 | (i.e. the number of callback invocations may be less than the number of |
3259 | (i.e. the number of callback invocations may be less than the number of |
3109 | C<ev_async_sent> calls). |
3260 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
|
|
3261 | of "global async watchers" by using a watcher on an otherwise unused |
|
|
3262 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
|
|
3263 | even without knowing which loop owns the signal. |
3110 | |
3264 | |
3111 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3265 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3112 | just the default loop. |
3266 | just the default loop. |
3113 | |
3267 | |
3114 | =head3 Queueing |
3268 | =head3 Queueing |
… | |
… | |
3290 | Feed an event on the given fd, as if a file descriptor backend detected |
3444 | Feed an event on the given fd, as if a file descriptor backend detected |
3291 | the given events it. |
3445 | the given events it. |
3292 | |
3446 | |
3293 | =item ev_feed_signal_event (loop, int signum) |
3447 | =item ev_feed_signal_event (loop, int signum) |
3294 | |
3448 | |
3295 | Feed an event as if the given signal occurred (C<loop> must be the default |
3449 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3296 | loop!). |
3450 | which is async-safe. |
|
|
3451 | |
|
|
3452 | =back |
|
|
3453 | |
|
|
3454 | |
|
|
3455 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3456 | |
|
|
3457 | This section explains some common idioms that are not immediately |
|
|
3458 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3459 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3460 | |
|
|
3461 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3462 | |
|
|
3463 | Often (especially in GUI toolkits) there are places where you have |
|
|
3464 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3465 | invoking C<ev_run>. |
|
|
3466 | |
|
|
3467 | This brings the problem of exiting - a callback might want to finish the |
|
|
3468 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3469 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3470 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3471 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3472 | |
|
|
3473 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3474 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3475 | triggered, using C<EVRUN_ONCE>: |
|
|
3476 | |
|
|
3477 | // main loop |
|
|
3478 | int exit_main_loop = 0; |
|
|
3479 | |
|
|
3480 | while (!exit_main_loop) |
|
|
3481 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3482 | |
|
|
3483 | // in a model watcher |
|
|
3484 | int exit_nested_loop = 0; |
|
|
3485 | |
|
|
3486 | while (!exit_nested_loop) |
|
|
3487 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3488 | |
|
|
3489 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3490 | |
|
|
3491 | // exit modal loop |
|
|
3492 | exit_nested_loop = 1; |
|
|
3493 | |
|
|
3494 | // exit main program, after modal loop is finished |
|
|
3495 | exit_main_loop = 1; |
|
|
3496 | |
|
|
3497 | // exit both |
|
|
3498 | exit_main_loop = exit_nested_loop = 1; |
|
|
3499 | |
|
|
3500 | =head2 THREAD LOCKING EXAMPLE |
|
|
3501 | |
|
|
3502 | Here is a fictitious example of how to run an event loop in a different |
|
|
3503 | thread than where callbacks are being invoked and watchers are |
|
|
3504 | created/added/removed. |
|
|
3505 | |
|
|
3506 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3507 | which uses exactly this technique (which is suited for many high-level |
|
|
3508 | languages). |
|
|
3509 | |
|
|
3510 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3511 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3512 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3513 | |
|
|
3514 | First, you need to associate some data with the event loop: |
|
|
3515 | |
|
|
3516 | typedef struct { |
|
|
3517 | mutex_t lock; /* global loop lock */ |
|
|
3518 | ev_async async_w; |
|
|
3519 | thread_t tid; |
|
|
3520 | cond_t invoke_cv; |
|
|
3521 | } userdata; |
|
|
3522 | |
|
|
3523 | void prepare_loop (EV_P) |
|
|
3524 | { |
|
|
3525 | // for simplicity, we use a static userdata struct. |
|
|
3526 | static userdata u; |
|
|
3527 | |
|
|
3528 | ev_async_init (&u->async_w, async_cb); |
|
|
3529 | ev_async_start (EV_A_ &u->async_w); |
|
|
3530 | |
|
|
3531 | pthread_mutex_init (&u->lock, 0); |
|
|
3532 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3533 | |
|
|
3534 | // now associate this with the loop |
|
|
3535 | ev_set_userdata (EV_A_ u); |
|
|
3536 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3537 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3538 | |
|
|
3539 | // then create the thread running ev_loop |
|
|
3540 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3541 | } |
|
|
3542 | |
|
|
3543 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3544 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3545 | that might have been added: |
|
|
3546 | |
|
|
3547 | static void |
|
|
3548 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3549 | { |
|
|
3550 | // just used for the side effects |
|
|
3551 | } |
|
|
3552 | |
|
|
3553 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3554 | protecting the loop data, respectively. |
|
|
3555 | |
|
|
3556 | static void |
|
|
3557 | l_release (EV_P) |
|
|
3558 | { |
|
|
3559 | userdata *u = ev_userdata (EV_A); |
|
|
3560 | pthread_mutex_unlock (&u->lock); |
|
|
3561 | } |
|
|
3562 | |
|
|
3563 | static void |
|
|
3564 | l_acquire (EV_P) |
|
|
3565 | { |
|
|
3566 | userdata *u = ev_userdata (EV_A); |
|
|
3567 | pthread_mutex_lock (&u->lock); |
|
|
3568 | } |
|
|
3569 | |
|
|
3570 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3571 | into C<ev_run>: |
|
|
3572 | |
|
|
3573 | void * |
|
|
3574 | l_run (void *thr_arg) |
|
|
3575 | { |
|
|
3576 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3577 | |
|
|
3578 | l_acquire (EV_A); |
|
|
3579 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3580 | ev_run (EV_A_ 0); |
|
|
3581 | l_release (EV_A); |
|
|
3582 | |
|
|
3583 | return 0; |
|
|
3584 | } |
|
|
3585 | |
|
|
3586 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3587 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3588 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3589 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3590 | and b) skipping inter-thread-communication when there are no pending |
|
|
3591 | watchers is very beneficial): |
|
|
3592 | |
|
|
3593 | static void |
|
|
3594 | l_invoke (EV_P) |
|
|
3595 | { |
|
|
3596 | userdata *u = ev_userdata (EV_A); |
|
|
3597 | |
|
|
3598 | while (ev_pending_count (EV_A)) |
|
|
3599 | { |
|
|
3600 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3601 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3602 | } |
|
|
3603 | } |
|
|
3604 | |
|
|
3605 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3606 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3607 | thread to continue: |
|
|
3608 | |
|
|
3609 | static void |
|
|
3610 | real_invoke_pending (EV_P) |
|
|
3611 | { |
|
|
3612 | userdata *u = ev_userdata (EV_A); |
|
|
3613 | |
|
|
3614 | pthread_mutex_lock (&u->lock); |
|
|
3615 | ev_invoke_pending (EV_A); |
|
|
3616 | pthread_cond_signal (&u->invoke_cv); |
|
|
3617 | pthread_mutex_unlock (&u->lock); |
|
|
3618 | } |
|
|
3619 | |
|
|
3620 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3621 | event loop, you will now have to lock: |
|
|
3622 | |
|
|
3623 | ev_timer timeout_watcher; |
|
|
3624 | userdata *u = ev_userdata (EV_A); |
|
|
3625 | |
|
|
3626 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3627 | |
|
|
3628 | pthread_mutex_lock (&u->lock); |
|
|
3629 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3630 | ev_async_send (EV_A_ &u->async_w); |
|
|
3631 | pthread_mutex_unlock (&u->lock); |
|
|
3632 | |
|
|
3633 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3634 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3635 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3636 | watchers in the next event loop iteration. |
3297 | |
3637 | |
3298 | =back |
3638 | =back |
3299 | |
3639 | |
3300 | |
3640 | |
3301 | =head1 LIBEVENT EMULATION |
3641 | =head1 LIBEVENT EMULATION |
3302 | |
3642 | |
3303 | Libev offers a compatibility emulation layer for libevent. It cannot |
3643 | Libev offers a compatibility emulation layer for libevent. It cannot |
3304 | emulate the internals of libevent, so here are some usage hints: |
3644 | emulate the internals of libevent, so here are some usage hints: |
3305 | |
3645 | |
3306 | =over 4 |
3646 | =over 4 |
|
|
3647 | |
|
|
3648 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3649 | |
|
|
3650 | This was the newest libevent version available when libev was implemented, |
|
|
3651 | and is still mostly unchanged in 2010. |
3307 | |
3652 | |
3308 | =item * Use it by including <event.h>, as usual. |
3653 | =item * Use it by including <event.h>, as usual. |
3309 | |
3654 | |
3310 | =item * The following members are fully supported: ev_base, ev_callback, |
3655 | =item * The following members are fully supported: ev_base, ev_callback, |
3311 | ev_arg, ev_fd, ev_res, ev_events. |
3656 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3317 | =item * Priorities are not currently supported. Initialising priorities |
3662 | =item * Priorities are not currently supported. Initialising priorities |
3318 | will fail and all watchers will have the same priority, even though there |
3663 | will fail and all watchers will have the same priority, even though there |
3319 | is an ev_pri field. |
3664 | is an ev_pri field. |
3320 | |
3665 | |
3321 | =item * In libevent, the last base created gets the signals, in libev, the |
3666 | =item * In libevent, the last base created gets the signals, in libev, the |
3322 | first base created (== the default loop) gets the signals. |
3667 | base that registered the signal gets the signals. |
3323 | |
3668 | |
3324 | =item * Other members are not supported. |
3669 | =item * Other members are not supported. |
3325 | |
3670 | |
3326 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3671 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3327 | to use the libev header file and library. |
3672 | to use the libev header file and library. |
… | |
… | |
3346 | Care has been taken to keep the overhead low. The only data member the C++ |
3691 | Care has been taken to keep the overhead low. The only data member the C++ |
3347 | classes add (compared to plain C-style watchers) is the event loop pointer |
3692 | classes add (compared to plain C-style watchers) is the event loop pointer |
3348 | that the watcher is associated with (or no additional members at all if |
3693 | that the watcher is associated with (or no additional members at all if |
3349 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3694 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3350 | |
3695 | |
3351 | Currently, functions, and static and non-static member functions can be |
3696 | Currently, functions, static and non-static member functions and classes |
3352 | used as callbacks. Other types should be easy to add as long as they only |
3697 | with C<operator ()> can be used as callbacks. Other types should be easy |
3353 | need one additional pointer for context. If you need support for other |
3698 | to add as long as they only need one additional pointer for context. If |
3354 | types of functors please contact the author (preferably after implementing |
3699 | you need support for other types of functors please contact the author |
3355 | it). |
3700 | (preferably after implementing it). |
3356 | |
3701 | |
3357 | Here is a list of things available in the C<ev> namespace: |
3702 | Here is a list of things available in the C<ev> namespace: |
3358 | |
3703 | |
3359 | =over 4 |
3704 | =over 4 |
3360 | |
3705 | |
… | |
… | |
4289 | default loop and triggering an C<ev_async> watcher from the default loop |
4634 | default loop and triggering an C<ev_async> watcher from the default loop |
4290 | watcher callback into the event loop interested in the signal. |
4635 | watcher callback into the event loop interested in the signal. |
4291 | |
4636 | |
4292 | =back |
4637 | =back |
4293 | |
4638 | |
4294 | =head4 THREAD LOCKING EXAMPLE |
4639 | See also L<THREAD LOCKING EXAMPLE>. |
4295 | |
|
|
4296 | Here is a fictitious example of how to run an event loop in a different |
|
|
4297 | thread than where callbacks are being invoked and watchers are |
|
|
4298 | created/added/removed. |
|
|
4299 | |
|
|
4300 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4301 | which uses exactly this technique (which is suited for many high-level |
|
|
4302 | languages). |
|
|
4303 | |
|
|
4304 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4305 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4306 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4307 | |
|
|
4308 | First, you need to associate some data with the event loop: |
|
|
4309 | |
|
|
4310 | typedef struct { |
|
|
4311 | mutex_t lock; /* global loop lock */ |
|
|
4312 | ev_async async_w; |
|
|
4313 | thread_t tid; |
|
|
4314 | cond_t invoke_cv; |
|
|
4315 | } userdata; |
|
|
4316 | |
|
|
4317 | void prepare_loop (EV_P) |
|
|
4318 | { |
|
|
4319 | // for simplicity, we use a static userdata struct. |
|
|
4320 | static userdata u; |
|
|
4321 | |
|
|
4322 | ev_async_init (&u->async_w, async_cb); |
|
|
4323 | ev_async_start (EV_A_ &u->async_w); |
|
|
4324 | |
|
|
4325 | pthread_mutex_init (&u->lock, 0); |
|
|
4326 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4327 | |
|
|
4328 | // now associate this with the loop |
|
|
4329 | ev_set_userdata (EV_A_ u); |
|
|
4330 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4331 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4332 | |
|
|
4333 | // then create the thread running ev_loop |
|
|
4334 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4335 | } |
|
|
4336 | |
|
|
4337 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4338 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4339 | that might have been added: |
|
|
4340 | |
|
|
4341 | static void |
|
|
4342 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4343 | { |
|
|
4344 | // just used for the side effects |
|
|
4345 | } |
|
|
4346 | |
|
|
4347 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4348 | protecting the loop data, respectively. |
|
|
4349 | |
|
|
4350 | static void |
|
|
4351 | l_release (EV_P) |
|
|
4352 | { |
|
|
4353 | userdata *u = ev_userdata (EV_A); |
|
|
4354 | pthread_mutex_unlock (&u->lock); |
|
|
4355 | } |
|
|
4356 | |
|
|
4357 | static void |
|
|
4358 | l_acquire (EV_P) |
|
|
4359 | { |
|
|
4360 | userdata *u = ev_userdata (EV_A); |
|
|
4361 | pthread_mutex_lock (&u->lock); |
|
|
4362 | } |
|
|
4363 | |
|
|
4364 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4365 | into C<ev_run>: |
|
|
4366 | |
|
|
4367 | void * |
|
|
4368 | l_run (void *thr_arg) |
|
|
4369 | { |
|
|
4370 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4371 | |
|
|
4372 | l_acquire (EV_A); |
|
|
4373 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4374 | ev_run (EV_A_ 0); |
|
|
4375 | l_release (EV_A); |
|
|
4376 | |
|
|
4377 | return 0; |
|
|
4378 | } |
|
|
4379 | |
|
|
4380 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4381 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4382 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4383 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4384 | and b) skipping inter-thread-communication when there are no pending |
|
|
4385 | watchers is very beneficial): |
|
|
4386 | |
|
|
4387 | static void |
|
|
4388 | l_invoke (EV_P) |
|
|
4389 | { |
|
|
4390 | userdata *u = ev_userdata (EV_A); |
|
|
4391 | |
|
|
4392 | while (ev_pending_count (EV_A)) |
|
|
4393 | { |
|
|
4394 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4395 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4396 | } |
|
|
4397 | } |
|
|
4398 | |
|
|
4399 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4400 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4401 | thread to continue: |
|
|
4402 | |
|
|
4403 | static void |
|
|
4404 | real_invoke_pending (EV_P) |
|
|
4405 | { |
|
|
4406 | userdata *u = ev_userdata (EV_A); |
|
|
4407 | |
|
|
4408 | pthread_mutex_lock (&u->lock); |
|
|
4409 | ev_invoke_pending (EV_A); |
|
|
4410 | pthread_cond_signal (&u->invoke_cv); |
|
|
4411 | pthread_mutex_unlock (&u->lock); |
|
|
4412 | } |
|
|
4413 | |
|
|
4414 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4415 | event loop, you will now have to lock: |
|
|
4416 | |
|
|
4417 | ev_timer timeout_watcher; |
|
|
4418 | userdata *u = ev_userdata (EV_A); |
|
|
4419 | |
|
|
4420 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4421 | |
|
|
4422 | pthread_mutex_lock (&u->lock); |
|
|
4423 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4424 | ev_async_send (EV_A_ &u->async_w); |
|
|
4425 | pthread_mutex_unlock (&u->lock); |
|
|
4426 | |
|
|
4427 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4428 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4429 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4430 | watchers in the next event loop iteration. |
|
|
4431 | |
4640 | |
4432 | =head3 COROUTINES |
4641 | =head3 COROUTINES |
4433 | |
4642 | |
4434 | Libev is very accommodating to coroutines ("cooperative threads"): |
4643 | Libev is very accommodating to coroutines ("cooperative threads"): |
4435 | libev fully supports nesting calls to its functions from different |
4644 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4704 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4913 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4705 | assumes that the same (machine) code can be used to call any watcher |
4914 | assumes that the same (machine) code can be used to call any watcher |
4706 | callback: The watcher callbacks have different type signatures, but libev |
4915 | callback: The watcher callbacks have different type signatures, but libev |
4707 | calls them using an C<ev_watcher *> internally. |
4916 | calls them using an C<ev_watcher *> internally. |
4708 | |
4917 | |
|
|
4918 | =item pointer accesses must be thread-atomic |
|
|
4919 | |
|
|
4920 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4921 | writable in one piece - this is the case on all current architectures. |
|
|
4922 | |
4709 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4923 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4710 | |
4924 | |
4711 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4925 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4712 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4926 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4713 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4927 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4819 | =back |
5033 | =back |
4820 | |
5034 | |
4821 | |
5035 | |
4822 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5036 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4823 | |
5037 | |
4824 | The major version 4 introduced some minor incompatible changes to the API. |
5038 | The major version 4 introduced some incompatible changes to the API. |
4825 | |
5039 | |
4826 | At the moment, the C<ev.h> header file tries to implement superficial |
5040 | At the moment, the C<ev.h> header file provides compatibility definitions |
4827 | compatibility, so most programs should still compile. Those might be |
5041 | for all changes, so most programs should still compile. The compatibility |
4828 | removed in later versions of libev, so better update early than late. |
5042 | layer might be removed in later versions of libev, so better update to the |
|
|
5043 | new API early than late. |
4829 | |
5044 | |
4830 | =over 4 |
5045 | =over 4 |
|
|
5046 | |
|
|
5047 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5048 | |
|
|
5049 | The backward compatibility mechanism can be controlled by |
|
|
5050 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5051 | section. |
|
|
5052 | |
|
|
5053 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5054 | |
|
|
5055 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5056 | |
|
|
5057 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5058 | ev_loop_fork (EV_DEFAULT); |
4831 | |
5059 | |
4832 | =item function/symbol renames |
5060 | =item function/symbol renames |
4833 | |
5061 | |
4834 | A number of functions and symbols have been renamed: |
5062 | A number of functions and symbols have been renamed: |
4835 | |
5063 | |
… | |
… | |
4854 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5082 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4855 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5083 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4856 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5084 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4857 | typedef. |
5085 | typedef. |
4858 | |
5086 | |
4859 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4860 | |
|
|
4861 | The backward compatibility mechanism can be controlled by |
|
|
4862 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4863 | section. |
|
|
4864 | |
|
|
4865 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5087 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4866 | |
5088 | |
4867 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5089 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4868 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5090 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4869 | and work, but the library code will of course be larger. |
5091 | and work, but the library code will of course be larger. |
… | |
… | |
4943 | |
5165 | |
4944 | =back |
5166 | =back |
4945 | |
5167 | |
4946 | =head1 AUTHOR |
5168 | =head1 AUTHOR |
4947 | |
5169 | |
4948 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5170 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5171 | Magnusson and Emanuele Giaquinta. |
4949 | |
5172 | |