… | |
… | |
26 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
27 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
28 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
29 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
30 | |
30 | |
31 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
33 | } |
33 | } |
34 | |
34 | |
35 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
36 | static void |
36 | static void |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
38 | { |
38 | { |
39 | puts ("timeout"); |
39 | puts ("timeout"); |
40 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
42 | } |
42 | } |
43 | |
43 | |
44 | int |
44 | int |
45 | main (void) |
45 | main (void) |
46 | { |
46 | { |
47 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
49 | |
50 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
56 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
75 | While this document tries to be as complete as possible in documenting |
75 | While this document tries to be as complete as possible in documenting |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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 | Familarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
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82 | |
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83 | =head1 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
82 | |
90 | |
83 | =head1 ABOUT LIBEV |
91 | =head1 ABOUT LIBEV |
84 | |
92 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
86 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
124 | this argument. |
132 | this argument. |
125 | |
133 | |
126 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
127 | |
135 | |
128 | Libev represents time as a single floating point number, representing |
136 | Libev represents time as a single floating point number, representing |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
130 | near the beginning of 1970, details are complicated, don't ask). This |
138 | somewhere near the beginning of 1970, details are complicated, don't |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
132 | aliases to the C<double> type in C. When you need to do any calculations |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
133 | on it, you should treat it as some floating point value. Unlike the name |
141 | any calculations on it, you should treat it as some floating point value. |
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142 | |
134 | component C<stamp> might indicate, it is also used for time differences |
143 | Unlike the name component C<stamp> might indicate, it is also used for |
135 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
136 | |
145 | |
137 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
138 | |
147 | |
139 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
140 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
164 | |
173 | |
165 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
166 | |
175 | |
167 | 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 |
168 | 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 |
169 | 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>. |
170 | |
180 | |
171 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
172 | |
182 | |
173 | 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 |
174 | 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 |
… | |
… | |
191 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
192 | 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 |
193 | not a problem. |
203 | not a problem. |
194 | |
204 | |
195 | 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 |
196 | version. |
206 | version (note, however, that this will not detect other ABI mismatches, |
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207 | such as LFS or reentrancy). |
197 | |
208 | |
198 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
199 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | |
212 | |
… | |
… | |
212 | assert (("sorry, no epoll, no sex", |
223 | assert (("sorry, no epoll, no sex", |
213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
224 | ev_supported_backends () & EVBACKEND_EPOLL)); |
214 | |
225 | |
215 | =item unsigned int ev_recommended_backends () |
226 | =item unsigned int ev_recommended_backends () |
216 | |
227 | |
217 | 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 |
218 | 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 |
219 | 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 |
220 | 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 |
221 | (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 |
222 | libev will probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
223 | |
235 | |
224 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
225 | |
237 | |
226 | 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 |
227 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
228 | 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 |
229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
230 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
231 | |
243 | |
232 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
233 | |
245 | |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
235 | |
247 | |
236 | Sets the allocation function to use (the prototype is similar - the |
248 | Sets the allocation function to use (the prototype is similar - the |
237 | 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 |
238 | 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 |
239 | 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 |
… | |
… | |
265 | } |
277 | } |
266 | |
278 | |
267 | ... |
279 | ... |
268 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
269 | |
281 | |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
271 | |
283 | |
272 | 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 |
273 | 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 |
274 | indicating the system call or subsystem causing the problem. If this |
286 | indicating the system call or subsystem causing the problem. If this |
275 | 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 |
… | |
… | |
287 | } |
299 | } |
288 | |
300 | |
289 | ... |
301 | ... |
290 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
291 | |
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 | |
292 | =back |
317 | =back |
293 | |
318 | |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
319 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
295 | |
320 | |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
321 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
297 | is I<not> optional in this case, as there is also an C<ev_loop> |
322 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
298 | I<function>). |
323 | libev 3 had an C<ev_loop> function colliding with the struct name). |
299 | |
324 | |
300 | 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 |
301 | supports signals and child events, and dynamically created loops which do |
326 | supports child process events, and dynamically created event loops which |
302 | not. |
327 | do not. |
303 | |
328 | |
304 | =over 4 |
329 | =over 4 |
305 | |
330 | |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
331 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
307 | |
332 | |
308 | 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 |
309 | 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 |
310 | 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 |
311 | 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". |
312 | |
343 | |
313 | 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 |
314 | function. |
345 | function (or via the C<EV_DEFAULT> macro). |
315 | |
346 | |
316 | 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 |
317 | 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 |
318 | 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). |
319 | |
351 | |
320 | 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, |
321 | 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 |
322 | 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 |
323 | 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 |
324 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
356 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
325 | 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. |
326 | |
376 | |
327 | 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 |
328 | 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>). |
329 | |
379 | |
330 | The following flags are supported: |
380 | The following flags are supported: |
… | |
… | |
345 | useful to try out specific backends to test their performance, or to work |
395 | useful to try out specific backends to test their performance, or to work |
346 | around bugs. |
396 | around bugs. |
347 | |
397 | |
348 | =item C<EVFLAG_FORKCHECK> |
398 | =item C<EVFLAG_FORKCHECK> |
349 | |
399 | |
350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
400 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
351 | a fork, you can also make libev check for a fork in each iteration by |
401 | make libev check for a fork in each iteration by enabling this flag. |
352 | enabling this flag. |
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353 | |
402 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
403 | This works by calling C<getpid ()> on every iteration of the loop, |
355 | and thus this might slow down your event loop if you do a lot of loop |
404 | and thus this might slow down your event loop if you do a lot of loop |
356 | iterations and little real work, but is usually not noticeable (on my |
405 | iterations and little real work, but is usually not noticeable (on my |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
406 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
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 is 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. |
429 | it possible to get the queued signal data. It can also simplify signal |
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430 | handling with threads, as long as you properly block signals in your |
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431 | threads that are not interested in handling them. |
381 | |
432 | |
382 | 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 |
383 | 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 |
384 | example) that can't properly initialise their signal masks. |
435 | example) that can't properly initialise their signal masks. |
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436 | |
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437 | =item C<EVFLAG_NOSIGMASK> |
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438 | |
|
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439 | When this flag is specified, then libev will avoid to modify the signal |
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440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
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441 | when you want to receive them. |
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442 | |
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443 | This behaviour is useful when you want to do your own signal handling, or |
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444 | want to handle signals only in specific threads and want to avoid libev |
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445 | unblocking the signals. |
|
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446 | |
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447 | It's also required by POSIX in a threaded program, as libev calls |
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448 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
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449 | |
|
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450 | This flag's behaviour will become the default in future versions of libev. |
385 | |
451 | |
386 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
452 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
387 | |
453 | |
388 | This is your standard select(2) backend. Not I<completely> standard, as |
454 | This is your standard select(2) backend. Not I<completely> standard, as |
389 | libev tries to roll its own fd_set with no limits on the number of fds, |
455 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
417 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
418 | |
484 | |
419 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
420 | kernels). |
486 | kernels). |
421 | |
487 | |
422 | For few fds, this backend is a bit little slower than poll and select, |
488 | For few fds, this backend is a bit little slower than poll and select, but |
423 | but it scales phenomenally better. While poll and select usually scale |
489 | it scales phenomenally better. While poll and select usually scale like |
424 | like O(total_fds) where n is the total number of fds (or the highest fd), |
490 | O(total_fds) where total_fds is the total number of fds (or the highest |
425 | epoll scales either O(1) or O(active_fds). |
491 | fd), epoll scales either O(1) or O(active_fds). |
426 | |
492 | |
427 | The epoll mechanism deserves honorable mention as the most misdesigned |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
428 | of the more advanced event mechanisms: mere annoyances include silently |
494 | of the more advanced event mechanisms: mere annoyances include silently |
429 | dropping file descriptors, requiring a system call per change per file |
495 | dropping file descriptors, requiring a system call per change per file |
430 | descriptor (and unnecessary guessing of parameters), problems with dup and |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
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497 | returning before the timeout value, resulting in additional iterations |
|
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498 | (and only giving 5ms accuracy while select on the same platform gives |
431 | so on. The biggest issue is fork races, however - if a program forks then |
499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
432 | I<both> parent and child process have to recreate the epoll set, which can |
500 | forks then I<both> parent and child process have to recreate the epoll |
433 | take considerable time (one syscall per file descriptor) and is of course |
501 | set, which can take considerable time (one syscall per file descriptor) |
434 | hard to detect. |
502 | and is of course hard to detect. |
435 | |
503 | |
436 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
437 | of course I<doesn't>, and epoll just loves to report events for totally |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
438 | I<different> file descriptors (even already closed ones, so one cannot |
506 | I<different> file descriptors (even already closed ones, so one cannot |
439 | even remove them from the set) than registered in the set (especially |
507 | even remove them from the set) than registered in the set (especially |
440 | on SMP systems). Libev tries to counter these spurious notifications by |
508 | on SMP systems). Libev tries to counter these spurious notifications by |
441 | employing an additional generation counter and comparing that against the |
509 | employing an additional generation counter and comparing that against the |
442 | events to filter out spurious ones, recreating the set when required. |
510 | events to filter out spurious ones, recreating the set when required. Last |
|
|
511 | not least, it also refuses to work with some file descriptors which work |
|
|
512 | perfectly fine with C<select> (files, many character devices...). |
|
|
513 | |
|
|
514 | Epoll is truly the train wreck analog among event poll mechanisms, |
|
|
515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
|
|
516 | interaction with others. |
443 | |
517 | |
444 | While stopping, setting and starting an I/O watcher in the same iteration |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
445 | will result in some caching, there is still a system call per such |
519 | will result in some caching, there is still a system call per such |
446 | incident (because the same I<file descriptor> could point to a different |
520 | incident (because the same I<file descriptor> could point to a different |
447 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
513 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
587 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
514 | |
588 | |
515 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
589 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
516 | it's really slow, but it still scales very well (O(active_fds)). |
590 | it's really slow, but it still scales very well (O(active_fds)). |
517 | |
591 | |
518 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
519 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
520 | blocking when no data (or space) is available. |
|
|
521 | |
|
|
522 | While this backend scales well, it requires one system call per active |
592 | While this backend scales well, it requires one system call per active |
523 | file descriptor per loop iteration. For small and medium numbers of file |
593 | file descriptor per loop iteration. For small and medium numbers of file |
524 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
594 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
525 | might perform better. |
595 | might perform better. |
526 | |
596 | |
527 | On the positive side, with the exception of the spurious readiness |
597 | On the positive side, this backend actually performed fully to |
528 | notifications, this backend actually performed fully to specification |
|
|
529 | in all tests and is fully embeddable, which is a rare feat among the |
598 | specification in all tests and is fully embeddable, which is a rare feat |
530 | OS-specific backends (I vastly prefer correctness over speed hacks). |
599 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
600 | hacks). |
|
|
601 | |
|
|
602 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
603 | even sun itself gets it wrong in their code examples: The event polling |
|
|
604 | function sometimes returning events to the caller even though an error |
|
|
605 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
606 | even documented that way) - deadly for edge-triggered interfaces where |
|
|
607 | you absolutely have to know whether an event occurred or not because you |
|
|
608 | have to re-arm the watcher. |
|
|
609 | |
|
|
610 | Fortunately libev seems to be able to work around these idiocies. |
531 | |
611 | |
532 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
533 | C<EVBACKEND_POLL>. |
613 | C<EVBACKEND_POLL>. |
534 | |
614 | |
535 | =item C<EVBACKEND_ALL> |
615 | =item C<EVBACKEND_ALL> |
536 | |
616 | |
537 | Try all backends (even potentially broken ones that wouldn't be tried |
617 | Try all backends (even potentially broken ones that wouldn't be tried |
538 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
618 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
539 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
619 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
540 | |
620 | |
541 | It is definitely not recommended to use this flag. |
621 | It is definitely not recommended to use this flag, use whatever |
|
|
622 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
623 | at all. |
|
|
624 | |
|
|
625 | =item C<EVBACKEND_MASK> |
|
|
626 | |
|
|
627 | Not a backend at all, but a mask to select all backend bits from a |
|
|
628 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
629 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
542 | |
630 | |
543 | =back |
631 | =back |
544 | |
632 | |
545 | If one or more of the backend flags are or'ed into the flags value, |
633 | If one or more of the backend flags are or'ed into the flags value, |
546 | then only these backends will be tried (in the reverse order as listed |
634 | then only these backends will be tried (in the reverse order as listed |
547 | here). If none are specified, all backends in C<ev_recommended_backends |
635 | here). If none are specified, all backends in C<ev_recommended_backends |
548 | ()> will be tried. |
636 | ()> will be tried. |
549 | |
637 | |
550 | Example: This is the most typical usage. |
|
|
551 | |
|
|
552 | if (!ev_default_loop (0)) |
|
|
553 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
554 | |
|
|
555 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
556 | environment settings to be taken into account: |
|
|
557 | |
|
|
558 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
559 | |
|
|
560 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
561 | used if available (warning, breaks stuff, best use only with your own |
|
|
562 | private event loop and only if you know the OS supports your types of |
|
|
563 | fds): |
|
|
564 | |
|
|
565 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
566 | |
|
|
567 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
568 | |
|
|
569 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
570 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
571 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
572 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
573 | |
|
|
574 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
575 | libev with threads is indeed to create one loop per thread, and using the |
|
|
576 | default loop in the "main" or "initial" thread. |
|
|
577 | |
|
|
578 | Example: Try to create a event loop that uses epoll and nothing else. |
638 | Example: Try to create a event loop that uses epoll and nothing else. |
579 | |
639 | |
580 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
640 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
581 | if (!epoller) |
641 | if (!epoller) |
582 | fatal ("no epoll found here, maybe it hides under your chair"); |
642 | fatal ("no epoll found here, maybe it hides under your chair"); |
583 | |
643 | |
|
|
644 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
645 | used if available. |
|
|
646 | |
|
|
647 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
648 | |
584 | =item ev_default_destroy () |
649 | =item ev_loop_destroy (loop) |
585 | |
650 | |
586 | Destroys the default loop again (frees all memory and kernel state |
651 | Destroys an event loop object (frees all memory and kernel state |
587 | etc.). None of the active event watchers will be stopped in the normal |
652 | etc.). None of the active event watchers will be stopped in the normal |
588 | sense, so e.g. C<ev_is_active> might still return true. It is your |
653 | sense, so e.g. C<ev_is_active> might still return true. It is your |
589 | responsibility to either stop all watchers cleanly yourself I<before> |
654 | responsibility to either stop all watchers cleanly yourself I<before> |
590 | calling this function, or cope with the fact afterwards (which is usually |
655 | calling this function, or cope with the fact afterwards (which is usually |
591 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
656 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
… | |
… | |
593 | |
658 | |
594 | Note that certain global state, such as signal state (and installed signal |
659 | Note that certain global state, such as signal state (and installed signal |
595 | handlers), will not be freed by this function, and related watchers (such |
660 | handlers), will not be freed by this function, and related watchers (such |
596 | as signal and child watchers) would need to be stopped manually. |
661 | as signal and child watchers) would need to be stopped manually. |
597 | |
662 | |
598 | In general it is not advisable to call this function except in the |
663 | This function is normally used on loop objects allocated by |
599 | rare occasion where you really need to free e.g. the signal handling |
664 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
665 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
666 | |
|
|
667 | Note that it is not advisable to call this function on the default loop |
|
|
668 | except in the rare occasion where you really need to free its resources. |
600 | pipe fds. If you need dynamically allocated loops it is better to use |
669 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
601 | C<ev_loop_new> and C<ev_loop_destroy>. |
670 | and C<ev_loop_destroy>. |
602 | |
671 | |
603 | =item ev_loop_destroy (loop) |
672 | =item ev_loop_fork (loop) |
604 | |
673 | |
605 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
606 | earlier call to C<ev_loop_new>. |
|
|
607 | |
|
|
608 | =item ev_default_fork () |
|
|
609 | |
|
|
610 | This function sets a flag that causes subsequent C<ev_loop> iterations |
674 | This function sets a flag that causes subsequent C<ev_run> iterations to |
611 | to reinitialise the kernel state for backends that have one. Despite the |
675 | reinitialise the kernel state for backends that have one. Despite the |
612 | name, you can call it anytime, but it makes most sense after forking, in |
676 | name, you can call it anytime, but it makes most sense after forking, in |
613 | the child process (or both child and parent, but that again makes little |
677 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
614 | sense). You I<must> call it in the child before using any of the libev |
678 | child before resuming or calling C<ev_run>. |
615 | functions, and it will only take effect at the next C<ev_loop> iteration. |
679 | |
|
|
680 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
681 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
682 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
683 | during fork. |
616 | |
684 | |
617 | On the other hand, you only need to call this function in the child |
685 | On the other hand, you only need to call this function in the child |
618 | process if and only if you want to use the event library in the child. If |
686 | process if and only if you want to use the event loop in the child. If |
619 | you just fork+exec, you don't have to call it at all. |
687 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
688 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
689 | difference, but libev will usually detect this case on its own and do a |
|
|
690 | costly reset of the backend). |
620 | |
691 | |
621 | The function itself is quite fast and it's usually not a problem to call |
692 | The function itself is quite fast and it's usually not a problem to call |
622 | it just in case after a fork. To make this easy, the function will fit in |
693 | it just in case after a fork. |
623 | quite nicely into a call to C<pthread_atfork>: |
|
|
624 | |
694 | |
|
|
695 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
696 | using pthreads. |
|
|
697 | |
|
|
698 | static void |
|
|
699 | post_fork_child (void) |
|
|
700 | { |
|
|
701 | ev_loop_fork (EV_DEFAULT); |
|
|
702 | } |
|
|
703 | |
|
|
704 | ... |
625 | pthread_atfork (0, 0, ev_default_fork); |
705 | pthread_atfork (0, 0, post_fork_child); |
626 | |
|
|
627 | =item ev_loop_fork (loop) |
|
|
628 | |
|
|
629 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
630 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
631 | after fork that you want to re-use in the child, and how you do this is |
|
|
632 | entirely your own problem. |
|
|
633 | |
706 | |
634 | =item int ev_is_default_loop (loop) |
707 | =item int ev_is_default_loop (loop) |
635 | |
708 | |
636 | Returns true when the given loop is, in fact, the default loop, and false |
709 | Returns true when the given loop is, in fact, the default loop, and false |
637 | otherwise. |
710 | otherwise. |
638 | |
711 | |
639 | =item unsigned int ev_loop_count (loop) |
712 | =item unsigned int ev_iteration (loop) |
640 | |
713 | |
641 | Returns the count of loop iterations for the loop, which is identical to |
714 | Returns the current iteration count for the event loop, which is identical |
642 | the number of times libev did poll for new events. It starts at C<0> and |
715 | to the number of times libev did poll for new events. It starts at C<0> |
643 | happily wraps around with enough iterations. |
716 | and happily wraps around with enough iterations. |
644 | |
717 | |
645 | This value can sometimes be useful as a generation counter of sorts (it |
718 | This value can sometimes be useful as a generation counter of sorts (it |
646 | "ticks" the number of loop iterations), as it roughly corresponds with |
719 | "ticks" the number of loop iterations), as it roughly corresponds with |
647 | C<ev_prepare> and C<ev_check> calls. |
720 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
721 | prepare and check phases. |
648 | |
722 | |
649 | =item unsigned int ev_loop_depth (loop) |
723 | =item unsigned int ev_depth (loop) |
650 | |
724 | |
651 | Returns the number of times C<ev_loop> was entered minus the number of |
725 | Returns the number of times C<ev_run> was entered minus the number of |
652 | times C<ev_loop> was exited, in other words, the recursion depth. |
726 | times C<ev_run> was exited normally, in other words, the recursion depth. |
653 | |
727 | |
654 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
728 | Outside C<ev_run>, this number is zero. In a callback, this number is |
655 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
729 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
656 | in which case it is higher. |
730 | in which case it is higher. |
657 | |
731 | |
658 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
732 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
659 | etc.), doesn't count as exit. |
733 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
734 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
735 | convenient, in which case it is fully supported. |
660 | |
736 | |
661 | =item unsigned int ev_backend (loop) |
737 | =item unsigned int ev_backend (loop) |
662 | |
738 | |
663 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
739 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
664 | use. |
740 | use. |
… | |
… | |
673 | |
749 | |
674 | =item ev_now_update (loop) |
750 | =item ev_now_update (loop) |
675 | |
751 | |
676 | Establishes the current time by querying the kernel, updating the time |
752 | Establishes the current time by querying the kernel, updating the time |
677 | returned by C<ev_now ()> in the progress. This is a costly operation and |
753 | returned by C<ev_now ()> in the progress. This is a costly operation and |
678 | is usually done automatically within C<ev_loop ()>. |
754 | is usually done automatically within C<ev_run ()>. |
679 | |
755 | |
680 | This function is rarely useful, but when some event callback runs for a |
756 | This function is rarely useful, but when some event callback runs for a |
681 | very long time without entering the event loop, updating libev's idea of |
757 | very long time without entering the event loop, updating libev's idea of |
682 | the current time is a good idea. |
758 | the current time is a good idea. |
683 | |
759 | |
… | |
… | |
685 | |
761 | |
686 | =item ev_suspend (loop) |
762 | =item ev_suspend (loop) |
687 | |
763 | |
688 | =item ev_resume (loop) |
764 | =item ev_resume (loop) |
689 | |
765 | |
690 | These two functions suspend and resume a loop, for use when the loop is |
766 | These two functions suspend and resume an event loop, for use when the |
691 | not used for a while and timeouts should not be processed. |
767 | loop is not used for a while and timeouts should not be processed. |
692 | |
768 | |
693 | A typical use case would be an interactive program such as a game: When |
769 | A typical use case would be an interactive program such as a game: When |
694 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
770 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
695 | would be best to handle timeouts as if no time had actually passed while |
771 | would be best to handle timeouts as if no time had actually passed while |
696 | the program was suspended. This can be achieved by calling C<ev_suspend> |
772 | the program was suspended. This can be achieved by calling C<ev_suspend> |
… | |
… | |
698 | C<ev_resume> directly afterwards to resume timer processing. |
774 | C<ev_resume> directly afterwards to resume timer processing. |
699 | |
775 | |
700 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
776 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
701 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
777 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
702 | will be rescheduled (that is, they will lose any events that would have |
778 | will be rescheduled (that is, they will lose any events that would have |
703 | occured while suspended). |
779 | occurred while suspended). |
704 | |
780 | |
705 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
781 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
706 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
782 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
707 | without a previous call to C<ev_suspend>. |
783 | without a previous call to C<ev_suspend>. |
708 | |
784 | |
709 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
785 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
710 | event loop time (see C<ev_now_update>). |
786 | event loop time (see C<ev_now_update>). |
711 | |
787 | |
712 | =item ev_loop (loop, int flags) |
788 | =item ev_run (loop, int flags) |
713 | |
789 | |
714 | Finally, this is it, the event handler. This function usually is called |
790 | Finally, this is it, the event handler. This function usually is called |
715 | after you have initialised all your watchers and you want to start |
791 | after you have initialised all your watchers and you want to start |
716 | handling events. |
792 | handling events. It will ask the operating system for any new events, call |
|
|
793 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
794 | is why event loops are called I<loops>. |
717 | |
795 | |
718 | If the flags argument is specified as C<0>, it will not return until |
796 | If the flags argument is specified as C<0>, it will keep handling events |
719 | either no event watchers are active anymore or C<ev_unloop> was called. |
797 | until either no event watchers are active anymore or C<ev_break> was |
|
|
798 | called. |
720 | |
799 | |
721 | Please note that an explicit C<ev_unloop> is usually better than |
800 | Please note that an explicit C<ev_break> is usually better than |
722 | relying on all watchers to be stopped when deciding when a program has |
801 | relying on all watchers to be stopped when deciding when a program has |
723 | finished (especially in interactive programs), but having a program |
802 | finished (especially in interactive programs), but having a program |
724 | that automatically loops as long as it has to and no longer by virtue |
803 | that automatically loops as long as it has to and no longer by virtue |
725 | of relying on its watchers stopping correctly, that is truly a thing of |
804 | of relying on its watchers stopping correctly, that is truly a thing of |
726 | beauty. |
805 | beauty. |
727 | |
806 | |
|
|
807 | This function is also I<mostly> exception-safe - you can break out of |
|
|
808 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
809 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
810 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
811 | |
728 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
812 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
729 | those events and any already outstanding ones, but will not block your |
813 | those events and any already outstanding ones, but will not wait and |
730 | process in case there are no events and will return after one iteration of |
814 | block your process in case there are no events and will return after one |
731 | the loop. |
815 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
816 | events while doing lengthy calculations, to keep the program responsive. |
732 | |
817 | |
733 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
818 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
734 | necessary) and will handle those and any already outstanding ones. It |
819 | necessary) and will handle those and any already outstanding ones. It |
735 | will block your process until at least one new event arrives (which could |
820 | will block your process until at least one new event arrives (which could |
736 | be an event internal to libev itself, so there is no guarantee that a |
821 | be an event internal to libev itself, so there is no guarantee that a |
737 | user-registered callback will be called), and will return after one |
822 | user-registered callback will be called), and will return after one |
738 | iteration of the loop. |
823 | iteration of the loop. |
739 | |
824 | |
740 | This is useful if you are waiting for some external event in conjunction |
825 | This is useful if you are waiting for some external event in conjunction |
741 | with something not expressible using other libev watchers (i.e. "roll your |
826 | with something not expressible using other libev watchers (i.e. "roll your |
742 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
827 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
743 | usually a better approach for this kind of thing. |
828 | usually a better approach for this kind of thing. |
744 | |
829 | |
745 | Here are the gory details of what C<ev_loop> does: |
830 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
831 | understanding, not a guarantee that things will work exactly like this in |
|
|
832 | future versions): |
746 | |
833 | |
|
|
834 | - Increment loop depth. |
|
|
835 | - Reset the ev_break status. |
747 | - Before the first iteration, call any pending watchers. |
836 | - Before the first iteration, call any pending watchers. |
|
|
837 | LOOP: |
748 | * If EVFLAG_FORKCHECK was used, check for a fork. |
838 | - If EVFLAG_FORKCHECK was used, check for a fork. |
749 | - If a fork was detected (by any means), queue and call all fork watchers. |
839 | - If a fork was detected (by any means), queue and call all fork watchers. |
750 | - Queue and call all prepare watchers. |
840 | - Queue and call all prepare watchers. |
|
|
841 | - If ev_break was called, goto FINISH. |
751 | - If we have been forked, detach and recreate the kernel state |
842 | - If we have been forked, detach and recreate the kernel state |
752 | as to not disturb the other process. |
843 | as to not disturb the other process. |
753 | - Update the kernel state with all outstanding changes. |
844 | - Update the kernel state with all outstanding changes. |
754 | - Update the "event loop time" (ev_now ()). |
845 | - Update the "event loop time" (ev_now ()). |
755 | - Calculate for how long to sleep or block, if at all |
846 | - Calculate for how long to sleep or block, if at all |
756 | (active idle watchers, EVLOOP_NONBLOCK or not having |
847 | (active idle watchers, EVRUN_NOWAIT or not having |
757 | any active watchers at all will result in not sleeping). |
848 | any active watchers at all will result in not sleeping). |
758 | - Sleep if the I/O and timer collect interval say so. |
849 | - Sleep if the I/O and timer collect interval say so. |
|
|
850 | - Increment loop iteration counter. |
759 | - Block the process, waiting for any events. |
851 | - Block the process, waiting for any events. |
760 | - Queue all outstanding I/O (fd) events. |
852 | - Queue all outstanding I/O (fd) events. |
761 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
853 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
762 | - Queue all expired timers. |
854 | - Queue all expired timers. |
763 | - Queue all expired periodics. |
855 | - Queue all expired periodics. |
764 | - Unless any events are pending now, queue all idle watchers. |
856 | - Queue all idle watchers with priority higher than that of pending events. |
765 | - Queue all check watchers. |
857 | - Queue all check watchers. |
766 | - Call all queued watchers in reverse order (i.e. check watchers first). |
858 | - Call all queued watchers in reverse order (i.e. check watchers first). |
767 | Signals and child watchers are implemented as I/O watchers, and will |
859 | Signals and child watchers are implemented as I/O watchers, and will |
768 | be handled here by queueing them when their watcher gets executed. |
860 | be handled here by queueing them when their watcher gets executed. |
769 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
861 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
770 | were used, or there are no active watchers, return, otherwise |
862 | were used, or there are no active watchers, goto FINISH, otherwise |
771 | continue with step *. |
863 | continue with step LOOP. |
|
|
864 | FINISH: |
|
|
865 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
866 | - Decrement the loop depth. |
|
|
867 | - Return. |
772 | |
868 | |
773 | Example: Queue some jobs and then loop until no events are outstanding |
869 | Example: Queue some jobs and then loop until no events are outstanding |
774 | anymore. |
870 | anymore. |
775 | |
871 | |
776 | ... queue jobs here, make sure they register event watchers as long |
872 | ... queue jobs here, make sure they register event watchers as long |
777 | ... as they still have work to do (even an idle watcher will do..) |
873 | ... as they still have work to do (even an idle watcher will do..) |
778 | ev_loop (my_loop, 0); |
874 | ev_run (my_loop, 0); |
779 | ... jobs done or somebody called unloop. yeah! |
875 | ... jobs done or somebody called break. yeah! |
780 | |
876 | |
781 | =item ev_unloop (loop, how) |
877 | =item ev_break (loop, how) |
782 | |
878 | |
783 | Can be used to make a call to C<ev_loop> return early (but only after it |
879 | Can be used to make a call to C<ev_run> return early (but only after it |
784 | has processed all outstanding events). The C<how> argument must be either |
880 | has processed all outstanding events). The C<how> argument must be either |
785 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
881 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
786 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
882 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
787 | |
883 | |
788 | This "unloop state" will be cleared when entering C<ev_loop> again. |
884 | This "break state" will be cleared on the next call to C<ev_run>. |
789 | |
885 | |
790 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
886 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
887 | which case it will have no effect. |
791 | |
888 | |
792 | =item ev_ref (loop) |
889 | =item ev_ref (loop) |
793 | |
890 | |
794 | =item ev_unref (loop) |
891 | =item ev_unref (loop) |
795 | |
892 | |
796 | Ref/unref can be used to add or remove a reference count on the event |
893 | Ref/unref can be used to add or remove a reference count on the event |
797 | loop: Every watcher keeps one reference, and as long as the reference |
894 | loop: Every watcher keeps one reference, and as long as the reference |
798 | count is nonzero, C<ev_loop> will not return on its own. |
895 | count is nonzero, C<ev_run> will not return on its own. |
799 | |
896 | |
800 | This is useful when you have a watcher that you never intend to |
897 | This is useful when you have a watcher that you never intend to |
801 | unregister, but that nevertheless should not keep C<ev_loop> from |
898 | unregister, but that nevertheless should not keep C<ev_run> from |
802 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
899 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
803 | before stopping it. |
900 | before stopping it. |
804 | |
901 | |
805 | As an example, libev itself uses this for its internal signal pipe: It |
902 | As an example, libev itself uses this for its internal signal pipe: It |
806 | is not visible to the libev user and should not keep C<ev_loop> from |
903 | is not visible to the libev user and should not keep C<ev_run> from |
807 | exiting if no event watchers registered by it are active. It is also an |
904 | exiting if no event watchers registered by it are active. It is also an |
808 | excellent way to do this for generic recurring timers or from within |
905 | excellent way to do this for generic recurring timers or from within |
809 | third-party libraries. Just remember to I<unref after start> and I<ref |
906 | third-party libraries. Just remember to I<unref after start> and I<ref |
810 | before stop> (but only if the watcher wasn't active before, or was active |
907 | before stop> (but only if the watcher wasn't active before, or was active |
811 | before, respectively. Note also that libev might stop watchers itself |
908 | before, respectively. Note also that libev might stop watchers itself |
812 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
909 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
813 | in the callback). |
910 | in the callback). |
814 | |
911 | |
815 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
912 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
816 | running when nothing else is active. |
913 | running when nothing else is active. |
817 | |
914 | |
818 | ev_signal exitsig; |
915 | ev_signal exitsig; |
819 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
916 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
820 | ev_signal_start (loop, &exitsig); |
917 | ev_signal_start (loop, &exitsig); |
821 | evf_unref (loop); |
918 | ev_unref (loop); |
822 | |
919 | |
823 | Example: For some weird reason, unregister the above signal handler again. |
920 | Example: For some weird reason, unregister the above signal handler again. |
824 | |
921 | |
825 | ev_ref (loop); |
922 | ev_ref (loop); |
826 | ev_signal_stop (loop, &exitsig); |
923 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
865 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
962 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
866 | as this approaches the timing granularity of most systems. Note that if |
963 | as this approaches the timing granularity of most systems. Note that if |
867 | you do transactions with the outside world and you can't increase the |
964 | you do transactions with the outside world and you can't increase the |
868 | parallelity, then this setting will limit your transaction rate (if you |
965 | parallelity, then this setting will limit your transaction rate (if you |
869 | need to poll once per transaction and the I/O collect interval is 0.01, |
966 | need to poll once per transaction and the I/O collect interval is 0.01, |
870 | then you can't do more than 100 transations per second). |
967 | then you can't do more than 100 transactions per second). |
871 | |
968 | |
872 | Setting the I<timeout collect interval> can improve the opportunity for |
969 | Setting the I<timeout collect interval> can improve the opportunity for |
873 | saving power, as the program will "bundle" timer callback invocations that |
970 | saving power, as the program will "bundle" timer callback invocations that |
874 | are "near" in time together, by delaying some, thus reducing the number of |
971 | are "near" in time together, by delaying some, thus reducing the number of |
875 | times the process sleeps and wakes up again. Another useful technique to |
972 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
883 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
980 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
884 | |
981 | |
885 | =item ev_invoke_pending (loop) |
982 | =item ev_invoke_pending (loop) |
886 | |
983 | |
887 | This call will simply invoke all pending watchers while resetting their |
984 | This call will simply invoke all pending watchers while resetting their |
888 | pending state. Normally, C<ev_loop> does this automatically when required, |
985 | pending state. Normally, C<ev_run> does this automatically when required, |
889 | but when overriding the invoke callback this call comes handy. |
986 | but when overriding the invoke callback this call comes handy. This |
|
|
987 | function can be invoked from a watcher - this can be useful for example |
|
|
988 | when you want to do some lengthy calculation and want to pass further |
|
|
989 | event handling to another thread (you still have to make sure only one |
|
|
990 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
890 | |
991 | |
891 | =item int ev_pending_count (loop) |
992 | =item int ev_pending_count (loop) |
892 | |
993 | |
893 | Returns the number of pending watchers - zero indicates that no watchers |
994 | Returns the number of pending watchers - zero indicates that no watchers |
894 | are pending. |
995 | are pending. |
895 | |
996 | |
896 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
997 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
897 | |
998 | |
898 | This overrides the invoke pending functionality of the loop: Instead of |
999 | This overrides the invoke pending functionality of the loop: Instead of |
899 | invoking all pending watchers when there are any, C<ev_loop> will call |
1000 | invoking all pending watchers when there are any, C<ev_run> will call |
900 | this callback instead. This is useful, for example, when you want to |
1001 | this callback instead. This is useful, for example, when you want to |
901 | invoke the actual watchers inside another context (another thread etc.). |
1002 | invoke the actual watchers inside another context (another thread etc.). |
902 | |
1003 | |
903 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1004 | If you want to reset the callback, use C<ev_invoke_pending> as new |
904 | callback. |
1005 | callback. |
… | |
… | |
907 | |
1008 | |
908 | Sometimes you want to share the same loop between multiple threads. This |
1009 | Sometimes you want to share the same loop between multiple threads. This |
909 | can be done relatively simply by putting mutex_lock/unlock calls around |
1010 | can be done relatively simply by putting mutex_lock/unlock calls around |
910 | each call to a libev function. |
1011 | each call to a libev function. |
911 | |
1012 | |
912 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
1013 | However, C<ev_run> can run an indefinite time, so it is not feasible |
913 | wait for it to return. One way around this is to wake up the loop via |
1014 | to wait for it to return. One way around this is to wake up the event |
914 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
1015 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
915 | and I<acquire> callbacks on the loop. |
1016 | I<release> and I<acquire> callbacks on the loop. |
916 | |
1017 | |
917 | When set, then C<release> will be called just before the thread is |
1018 | When set, then C<release> will be called just before the thread is |
918 | suspended waiting for new events, and C<acquire> is called just |
1019 | suspended waiting for new events, and C<acquire> is called just |
919 | afterwards. |
1020 | afterwards. |
920 | |
1021 | |
… | |
… | |
923 | |
1024 | |
924 | While event loop modifications are allowed between invocations of |
1025 | While event loop modifications are allowed between invocations of |
925 | C<release> and C<acquire> (that's their only purpose after all), no |
1026 | C<release> and C<acquire> (that's their only purpose after all), no |
926 | modifications done will affect the event loop, i.e. adding watchers will |
1027 | modifications done will affect the event loop, i.e. adding watchers will |
927 | have no effect on the set of file descriptors being watched, or the time |
1028 | have no effect on the set of file descriptors being watched, or the time |
928 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
1029 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
929 | to take note of any changes you made. |
1030 | to take note of any changes you made. |
930 | |
1031 | |
931 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
1032 | In theory, threads executing C<ev_run> will be async-cancel safe between |
932 | invocations of C<release> and C<acquire>. |
1033 | invocations of C<release> and C<acquire>. |
933 | |
1034 | |
934 | See also the locking example in the C<THREADS> section later in this |
1035 | See also the locking example in the C<THREADS> section later in this |
935 | document. |
1036 | document. |
936 | |
1037 | |
937 | =item ev_set_userdata (loop, void *data) |
1038 | =item ev_set_userdata (loop, void *data) |
938 | |
1039 | |
939 | =item ev_userdata (loop) |
1040 | =item void *ev_userdata (loop) |
940 | |
1041 | |
941 | Set and retrieve a single C<void *> associated with a loop. When |
1042 | Set and retrieve a single C<void *> associated with a loop. When |
942 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1043 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
943 | C<0.> |
1044 | C<0>. |
944 | |
1045 | |
945 | These two functions can be used to associate arbitrary data with a loop, |
1046 | These two functions can be used to associate arbitrary data with a loop, |
946 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1047 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
947 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1048 | C<acquire> callbacks described above, but of course can be (ab-)used for |
948 | any other purpose as well. |
1049 | any other purpose as well. |
949 | |
1050 | |
950 | =item ev_loop_verify (loop) |
1051 | =item ev_verify (loop) |
951 | |
1052 | |
952 | This function only does something when C<EV_VERIFY> support has been |
1053 | This function only does something when C<EV_VERIFY> support has been |
953 | compiled in, which is the default for non-minimal builds. It tries to go |
1054 | compiled in, which is the default for non-minimal builds. It tries to go |
954 | through all internal structures and checks them for validity. If anything |
1055 | through all internal structures and checks them for validity. If anything |
955 | is found to be inconsistent, it will print an error message to standard |
1056 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
966 | |
1067 | |
967 | In the following description, uppercase C<TYPE> in names stands for the |
1068 | In the following description, uppercase C<TYPE> in names stands for the |
968 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1069 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
969 | watchers and C<ev_io_start> for I/O watchers. |
1070 | watchers and C<ev_io_start> for I/O watchers. |
970 | |
1071 | |
971 | A watcher is a structure that you create and register to record your |
1072 | A watcher is an opaque structure that you allocate and register to record |
972 | interest in some event. For instance, if you want to wait for STDIN to |
1073 | your interest in some event. To make a concrete example, imagine you want |
973 | become readable, you would create an C<ev_io> watcher for that: |
1074 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1075 | for that: |
974 | |
1076 | |
975 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1077 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
976 | { |
1078 | { |
977 | ev_io_stop (w); |
1079 | ev_io_stop (w); |
978 | ev_unloop (loop, EVUNLOOP_ALL); |
1080 | ev_break (loop, EVBREAK_ALL); |
979 | } |
1081 | } |
980 | |
1082 | |
981 | struct ev_loop *loop = ev_default_loop (0); |
1083 | struct ev_loop *loop = ev_default_loop (0); |
982 | |
1084 | |
983 | ev_io stdin_watcher; |
1085 | ev_io stdin_watcher; |
984 | |
1086 | |
985 | ev_init (&stdin_watcher, my_cb); |
1087 | ev_init (&stdin_watcher, my_cb); |
986 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1088 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
987 | ev_io_start (loop, &stdin_watcher); |
1089 | ev_io_start (loop, &stdin_watcher); |
988 | |
1090 | |
989 | ev_loop (loop, 0); |
1091 | ev_run (loop, 0); |
990 | |
1092 | |
991 | As you can see, you are responsible for allocating the memory for your |
1093 | As you can see, you are responsible for allocating the memory for your |
992 | watcher structures (and it is I<usually> a bad idea to do this on the |
1094 | watcher structures (and it is I<usually> a bad idea to do this on the |
993 | stack). |
1095 | stack). |
994 | |
1096 | |
995 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1097 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
996 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1098 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
997 | |
1099 | |
998 | Each watcher structure must be initialised by a call to C<ev_init |
1100 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
999 | (watcher *, callback)>, which expects a callback to be provided. This |
1101 | *, callback)>, which expects a callback to be provided. This callback is |
1000 | callback gets invoked each time the event occurs (or, in the case of I/O |
1102 | invoked each time the event occurs (or, in the case of I/O watchers, each |
1001 | watchers, each time the event loop detects that the file descriptor given |
1103 | time the event loop detects that the file descriptor given is readable |
1002 | is readable and/or writable). |
1104 | and/or writable). |
1003 | |
1105 | |
1004 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1106 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1005 | macro to configure it, with arguments specific to the watcher type. There |
1107 | macro to configure it, with arguments specific to the watcher type. There |
1006 | is also a macro to combine initialisation and setting in one call: C<< |
1108 | is also a macro to combine initialisation and setting in one call: C<< |
1007 | ev_TYPE_init (watcher *, callback, ...) >>. |
1109 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
1030 | =item C<EV_WRITE> |
1132 | =item C<EV_WRITE> |
1031 | |
1133 | |
1032 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1134 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1033 | writable. |
1135 | writable. |
1034 | |
1136 | |
1035 | =item C<EV_TIMEOUT> |
1137 | =item C<EV_TIMER> |
1036 | |
1138 | |
1037 | The C<ev_timer> watcher has timed out. |
1139 | The C<ev_timer> watcher has timed out. |
1038 | |
1140 | |
1039 | =item C<EV_PERIODIC> |
1141 | =item C<EV_PERIODIC> |
1040 | |
1142 | |
… | |
… | |
1058 | |
1160 | |
1059 | =item C<EV_PREPARE> |
1161 | =item C<EV_PREPARE> |
1060 | |
1162 | |
1061 | =item C<EV_CHECK> |
1163 | =item C<EV_CHECK> |
1062 | |
1164 | |
1063 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1165 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1064 | to gather new events, and all C<ev_check> watchers are invoked just after |
1166 | to gather new events, and all C<ev_check> watchers are invoked just after |
1065 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1167 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1066 | received events. Callbacks of both watcher types can start and stop as |
1168 | received events. Callbacks of both watcher types can start and stop as |
1067 | many watchers as they want, and all of them will be taken into account |
1169 | many watchers as they want, and all of them will be taken into account |
1068 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1170 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1069 | C<ev_loop> from blocking). |
1171 | C<ev_run> from blocking). |
1070 | |
1172 | |
1071 | =item C<EV_EMBED> |
1173 | =item C<EV_EMBED> |
1072 | |
1174 | |
1073 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1175 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1074 | |
1176 | |
1075 | =item C<EV_FORK> |
1177 | =item C<EV_FORK> |
1076 | |
1178 | |
1077 | The event loop has been resumed in the child process after fork (see |
1179 | The event loop has been resumed in the child process after fork (see |
1078 | C<ev_fork>). |
1180 | C<ev_fork>). |
|
|
1181 | |
|
|
1182 | =item C<EV_CLEANUP> |
|
|
1183 | |
|
|
1184 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1079 | |
1185 | |
1080 | =item C<EV_ASYNC> |
1186 | =item C<EV_ASYNC> |
1081 | |
1187 | |
1082 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1188 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1083 | |
1189 | |
… | |
… | |
1256 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1362 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1257 | functions that do not need a watcher. |
1363 | functions that do not need a watcher. |
1258 | |
1364 | |
1259 | =back |
1365 | =back |
1260 | |
1366 | |
|
|
1367 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1368 | OWN COMPOSITE WATCHERS> idioms. |
1261 | |
1369 | |
1262 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1370 | =head2 WATCHER STATES |
1263 | |
1371 | |
1264 | Each watcher has, by default, a member C<void *data> that you can change |
1372 | There are various watcher states mentioned throughout this manual - |
1265 | and read at any time: libev will completely ignore it. This can be used |
1373 | active, pending and so on. In this section these states and the rules to |
1266 | to associate arbitrary data with your watcher. If you need more data and |
1374 | transition between them will be described in more detail - and while these |
1267 | don't want to allocate memory and store a pointer to it in that data |
1375 | rules might look complicated, they usually do "the right thing". |
1268 | member, you can also "subclass" the watcher type and provide your own |
|
|
1269 | data: |
|
|
1270 | |
1376 | |
1271 | struct my_io |
1377 | =over 4 |
1272 | { |
|
|
1273 | ev_io io; |
|
|
1274 | int otherfd; |
|
|
1275 | void *somedata; |
|
|
1276 | struct whatever *mostinteresting; |
|
|
1277 | }; |
|
|
1278 | |
1378 | |
1279 | ... |
1379 | =item initialiased |
1280 | struct my_io w; |
|
|
1281 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1282 | |
1380 | |
1283 | And since your callback will be called with a pointer to the watcher, you |
1381 | Before a watcher can be registered with the event looop it has to be |
1284 | can cast it back to your own type: |
1382 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1383 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1285 | |
1384 | |
1286 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1385 | In this state it is simply some block of memory that is suitable for |
1287 | { |
1386 | use in an event loop. It can be moved around, freed, reused etc. at |
1288 | struct my_io *w = (struct my_io *)w_; |
1387 | will - as long as you either keep the memory contents intact, or call |
1289 | ... |
1388 | C<ev_TYPE_init> again. |
1290 | } |
|
|
1291 | |
1389 | |
1292 | More interesting and less C-conformant ways of casting your callback type |
1390 | =item started/running/active |
1293 | instead have been omitted. |
|
|
1294 | |
1391 | |
1295 | Another common scenario is to use some data structure with multiple |
1392 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1296 | embedded watchers: |
1393 | property of the event loop, and is actively waiting for events. While in |
|
|
1394 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1395 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1396 | and call libev functions on it that are documented to work on active watchers. |
1297 | |
1397 | |
1298 | struct my_biggy |
1398 | =item pending |
1299 | { |
|
|
1300 | int some_data; |
|
|
1301 | ev_timer t1; |
|
|
1302 | ev_timer t2; |
|
|
1303 | } |
|
|
1304 | |
1399 | |
1305 | In this case getting the pointer to C<my_biggy> is a bit more |
1400 | If a watcher is active and libev determines that an event it is interested |
1306 | complicated: Either you store the address of your C<my_biggy> struct |
1401 | in has occurred (such as a timer expiring), it will become pending. It will |
1307 | in the C<data> member of the watcher (for woozies), or you need to use |
1402 | stay in this pending state until either it is stopped or its callback is |
1308 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1403 | about to be invoked, so it is not normally pending inside the watcher |
1309 | programmers): |
1404 | callback. |
1310 | |
1405 | |
1311 | #include <stddef.h> |
1406 | The watcher might or might not be active while it is pending (for example, |
|
|
1407 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1408 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1409 | but it is still property of the event loop at this time, so cannot be |
|
|
1410 | moved, freed or reused. And if it is active the rules described in the |
|
|
1411 | previous item still apply. |
1312 | |
1412 | |
1313 | static void |
1413 | It is also possible to feed an event on a watcher that is not active (e.g. |
1314 | t1_cb (EV_P_ ev_timer *w, int revents) |
1414 | via C<ev_feed_event>), in which case it becomes pending without being |
1315 | { |
1415 | active. |
1316 | struct my_biggy big = (struct my_biggy *) |
|
|
1317 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1318 | } |
|
|
1319 | |
1416 | |
1320 | static void |
1417 | =item stopped |
1321 | t2_cb (EV_P_ ev_timer *w, int revents) |
1418 | |
1322 | { |
1419 | A watcher can be stopped implicitly by libev (in which case it might still |
1323 | struct my_biggy big = (struct my_biggy *) |
1420 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1324 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1421 | latter will clear any pending state the watcher might be in, regardless |
1325 | } |
1422 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1423 | freeing it is often a good idea. |
|
|
1424 | |
|
|
1425 | While stopped (and not pending) the watcher is essentially in the |
|
|
1426 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1427 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1428 | it again). |
|
|
1429 | |
|
|
1430 | =back |
1326 | |
1431 | |
1327 | =head2 WATCHER PRIORITY MODELS |
1432 | =head2 WATCHER PRIORITY MODELS |
1328 | |
1433 | |
1329 | Many event loops support I<watcher priorities>, which are usually small |
1434 | Many event loops support I<watcher priorities>, which are usually small |
1330 | integers that influence the ordering of event callback invocation |
1435 | integers that influence the ordering of event callback invocation |
… | |
… | |
1373 | |
1478 | |
1374 | For example, to emulate how many other event libraries handle priorities, |
1479 | For example, to emulate how many other event libraries handle priorities, |
1375 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1480 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1376 | the normal watcher callback, you just start the idle watcher. The real |
1481 | the normal watcher callback, you just start the idle watcher. The real |
1377 | processing is done in the idle watcher callback. This causes libev to |
1482 | processing is done in the idle watcher callback. This causes libev to |
1378 | continously poll and process kernel event data for the watcher, but when |
1483 | continuously poll and process kernel event data for the watcher, but when |
1379 | the lock-out case is known to be rare (which in turn is rare :), this is |
1484 | the lock-out case is known to be rare (which in turn is rare :), this is |
1380 | workable. |
1485 | workable. |
1381 | |
1486 | |
1382 | Usually, however, the lock-out model implemented that way will perform |
1487 | Usually, however, the lock-out model implemented that way will perform |
1383 | miserably under the type of load it was designed to handle. In that case, |
1488 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1397 | { |
1502 | { |
1398 | // stop the I/O watcher, we received the event, but |
1503 | // stop the I/O watcher, we received the event, but |
1399 | // are not yet ready to handle it. |
1504 | // are not yet ready to handle it. |
1400 | ev_io_stop (EV_A_ w); |
1505 | ev_io_stop (EV_A_ w); |
1401 | |
1506 | |
1402 | // start the idle watcher to ahndle the actual event. |
1507 | // start the idle watcher to handle the actual event. |
1403 | // it will not be executed as long as other watchers |
1508 | // it will not be executed as long as other watchers |
1404 | // with the default priority are receiving events. |
1509 | // with the default priority are receiving events. |
1405 | ev_idle_start (EV_A_ &idle); |
1510 | ev_idle_start (EV_A_ &idle); |
1406 | } |
1511 | } |
1407 | |
1512 | |
… | |
… | |
1457 | In general you can register as many read and/or write event watchers per |
1562 | In general you can register as many read and/or write event watchers per |
1458 | fd as you want (as long as you don't confuse yourself). Setting all file |
1563 | fd as you want (as long as you don't confuse yourself). Setting all file |
1459 | descriptors to non-blocking mode is also usually a good idea (but not |
1564 | descriptors to non-blocking mode is also usually a good idea (but not |
1460 | required if you know what you are doing). |
1565 | required if you know what you are doing). |
1461 | |
1566 | |
1462 | If you cannot use non-blocking mode, then force the use of a |
|
|
1463 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1464 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1465 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1466 | files) - libev doesn't guarentee any specific behaviour in that case. |
|
|
1467 | |
|
|
1468 | Another thing you have to watch out for is that it is quite easy to |
1567 | Another thing you have to watch out for is that it is quite easy to |
1469 | receive "spurious" readiness notifications, that is your callback might |
1568 | receive "spurious" readiness notifications, that is, your callback might |
1470 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1569 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1471 | because there is no data. Not only are some backends known to create a |
1570 | because there is no data. It is very easy to get into this situation even |
1472 | lot of those (for example Solaris ports), it is very easy to get into |
1571 | with a relatively standard program structure. Thus it is best to always |
1473 | this situation even with a relatively standard program structure. Thus |
1572 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1474 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1475 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1573 | preferable to a program hanging until some data arrives. |
1476 | |
1574 | |
1477 | If you cannot run the fd in non-blocking mode (for example you should |
1575 | If you cannot run the fd in non-blocking mode (for example you should |
1478 | not play around with an Xlib connection), then you have to separately |
1576 | not play around with an Xlib connection), then you have to separately |
1479 | re-test whether a file descriptor is really ready with a known-to-be good |
1577 | re-test whether a file descriptor is really ready with a known-to-be good |
1480 | interface such as poll (fortunately in our Xlib example, Xlib already |
1578 | interface such as poll (fortunately in the case of Xlib, it already does |
1481 | does this on its own, so its quite safe to use). Some people additionally |
1579 | this on its own, so its quite safe to use). Some people additionally |
1482 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1580 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1483 | indefinitely. |
1581 | indefinitely. |
1484 | |
1582 | |
1485 | But really, best use non-blocking mode. |
1583 | But really, best use non-blocking mode. |
1486 | |
1584 | |
… | |
… | |
1514 | |
1612 | |
1515 | There is no workaround possible except not registering events |
1613 | There is no workaround possible except not registering events |
1516 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1614 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1517 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1615 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1518 | |
1616 | |
|
|
1617 | =head3 The special problem of files |
|
|
1618 | |
|
|
1619 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1620 | representing files, and expect it to become ready when their program |
|
|
1621 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1622 | |
|
|
1623 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1624 | notification as soon as the kernel knows whether and how much data is |
|
|
1625 | there, and in the case of open files, that's always the case, so you |
|
|
1626 | always get a readiness notification instantly, and your read (or possibly |
|
|
1627 | write) will still block on the disk I/O. |
|
|
1628 | |
|
|
1629 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1630 | devices and so on, there is another party (the sender) that delivers data |
|
|
1631 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1632 | will not send data on its own, simply because it doesn't know what you |
|
|
1633 | wish to read - you would first have to request some data. |
|
|
1634 | |
|
|
1635 | Since files are typically not-so-well supported by advanced notification |
|
|
1636 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1637 | to files, even though you should not use it. The reason for this is |
|
|
1638 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1639 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1640 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1641 | F</dev/urandom>), and even though the file might better be served with |
|
|
1642 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1643 | it "just works" instead of freezing. |
|
|
1644 | |
|
|
1645 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1646 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1647 | when you rarely read from a file instead of from a socket, and want to |
|
|
1648 | reuse the same code path. |
|
|
1649 | |
1519 | =head3 The special problem of fork |
1650 | =head3 The special problem of fork |
1520 | |
1651 | |
1521 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1652 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1522 | useless behaviour. Libev fully supports fork, but needs to be told about |
1653 | useless behaviour. Libev fully supports fork, but needs to be told about |
1523 | it in the child. |
1654 | it in the child if you want to continue to use it in the child. |
1524 | |
1655 | |
1525 | To support fork in your programs, you either have to call |
1656 | To support fork in your child processes, you have to call C<ev_loop_fork |
1526 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1657 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1527 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1658 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1528 | C<EVBACKEND_POLL>. |
|
|
1529 | |
1659 | |
1530 | =head3 The special problem of SIGPIPE |
1660 | =head3 The special problem of SIGPIPE |
1531 | |
1661 | |
1532 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1662 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1533 | when writing to a pipe whose other end has been closed, your program gets |
1663 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1536 | |
1666 | |
1537 | So when you encounter spurious, unexplained daemon exits, make sure you |
1667 | So when you encounter spurious, unexplained daemon exits, make sure you |
1538 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1668 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1539 | somewhere, as that would have given you a big clue). |
1669 | somewhere, as that would have given you a big clue). |
1540 | |
1670 | |
|
|
1671 | =head3 The special problem of accept()ing when you can't |
|
|
1672 | |
|
|
1673 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1674 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1675 | connection from the pending queue in all error cases. |
|
|
1676 | |
|
|
1677 | For example, larger servers often run out of file descriptors (because |
|
|
1678 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1679 | rejecting the connection, leading to libev signalling readiness on |
|
|
1680 | the next iteration again (the connection still exists after all), and |
|
|
1681 | typically causing the program to loop at 100% CPU usage. |
|
|
1682 | |
|
|
1683 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1684 | operating systems, there is usually little the app can do to remedy the |
|
|
1685 | situation, and no known thread-safe method of removing the connection to |
|
|
1686 | cope with overload is known (to me). |
|
|
1687 | |
|
|
1688 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1689 | - when the program encounters an overload, it will just loop until the |
|
|
1690 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1691 | event-based way to handle this situation, so it's the best one can do. |
|
|
1692 | |
|
|
1693 | A better way to handle the situation is to log any errors other than |
|
|
1694 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1695 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1696 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1697 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1698 | usage. |
|
|
1699 | |
|
|
1700 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1701 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1702 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1703 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1704 | clients under typical overload conditions. |
|
|
1705 | |
|
|
1706 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1707 | is often done with C<malloc> failures, but this results in an easy |
|
|
1708 | opportunity for a DoS attack. |
1541 | |
1709 | |
1542 | =head3 Watcher-Specific Functions |
1710 | =head3 Watcher-Specific Functions |
1543 | |
1711 | |
1544 | =over 4 |
1712 | =over 4 |
1545 | |
1713 | |
… | |
… | |
1577 | ... |
1745 | ... |
1578 | struct ev_loop *loop = ev_default_init (0); |
1746 | struct ev_loop *loop = ev_default_init (0); |
1579 | ev_io stdin_readable; |
1747 | ev_io stdin_readable; |
1580 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1748 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1581 | ev_io_start (loop, &stdin_readable); |
1749 | ev_io_start (loop, &stdin_readable); |
1582 | ev_loop (loop, 0); |
1750 | ev_run (loop, 0); |
1583 | |
1751 | |
1584 | |
1752 | |
1585 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1753 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1586 | |
1754 | |
1587 | Timer watchers are simple relative timers that generate an event after a |
1755 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1596 | The callback is guaranteed to be invoked only I<after> its timeout has |
1764 | The callback is guaranteed to be invoked only I<after> its timeout has |
1597 | passed (not I<at>, so on systems with very low-resolution clocks this |
1765 | passed (not I<at>, so on systems with very low-resolution clocks this |
1598 | might introduce a small delay). If multiple timers become ready during the |
1766 | might introduce a small delay). If multiple timers become ready during the |
1599 | same loop iteration then the ones with earlier time-out values are invoked |
1767 | same loop iteration then the ones with earlier time-out values are invoked |
1600 | before ones of the same priority with later time-out values (but this is |
1768 | before ones of the same priority with later time-out values (but this is |
1601 | no longer true when a callback calls C<ev_loop> recursively). |
1769 | no longer true when a callback calls C<ev_run> recursively). |
1602 | |
1770 | |
1603 | =head3 Be smart about timeouts |
1771 | =head3 Be smart about timeouts |
1604 | |
1772 | |
1605 | Many real-world problems involve some kind of timeout, usually for error |
1773 | Many real-world problems involve some kind of timeout, usually for error |
1606 | recovery. A typical example is an HTTP request - if the other side hangs, |
1774 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1692 | ev_tstamp timeout = last_activity + 60.; |
1860 | ev_tstamp timeout = last_activity + 60.; |
1693 | |
1861 | |
1694 | // if last_activity + 60. is older than now, we did time out |
1862 | // if last_activity + 60. is older than now, we did time out |
1695 | if (timeout < now) |
1863 | if (timeout < now) |
1696 | { |
1864 | { |
1697 | // timeout occured, take action |
1865 | // timeout occurred, take action |
1698 | } |
1866 | } |
1699 | else |
1867 | else |
1700 | { |
1868 | { |
1701 | // callback was invoked, but there was some activity, re-arm |
1869 | // callback was invoked, but there was some activity, re-arm |
1702 | // the watcher to fire in last_activity + 60, which is |
1870 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1724 | to the current time (meaning we just have some activity :), then call the |
1892 | to the current time (meaning we just have some activity :), then call the |
1725 | callback, which will "do the right thing" and start the timer: |
1893 | callback, which will "do the right thing" and start the timer: |
1726 | |
1894 | |
1727 | ev_init (timer, callback); |
1895 | ev_init (timer, callback); |
1728 | last_activity = ev_now (loop); |
1896 | last_activity = ev_now (loop); |
1729 | callback (loop, timer, EV_TIMEOUT); |
1897 | callback (loop, timer, EV_TIMER); |
1730 | |
1898 | |
1731 | And when there is some activity, simply store the current time in |
1899 | And when there is some activity, simply store the current time in |
1732 | C<last_activity>, no libev calls at all: |
1900 | C<last_activity>, no libev calls at all: |
1733 | |
1901 | |
1734 | last_actiivty = ev_now (loop); |
1902 | last_activity = ev_now (loop); |
1735 | |
1903 | |
1736 | This technique is slightly more complex, but in most cases where the |
1904 | This technique is slightly more complex, but in most cases where the |
1737 | time-out is unlikely to be triggered, much more efficient. |
1905 | time-out is unlikely to be triggered, much more efficient. |
1738 | |
1906 | |
1739 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1907 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
… | |
… | |
1777 | |
1945 | |
1778 | =head3 The special problem of time updates |
1946 | =head3 The special problem of time updates |
1779 | |
1947 | |
1780 | Establishing the current time is a costly operation (it usually takes at |
1948 | Establishing the current time is a costly operation (it usually takes at |
1781 | least two system calls): EV therefore updates its idea of the current |
1949 | least two system calls): EV therefore updates its idea of the current |
1782 | time only before and after C<ev_loop> collects new events, which causes a |
1950 | time only before and after C<ev_run> collects new events, which causes a |
1783 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1951 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1784 | lots of events in one iteration. |
1952 | lots of events in one iteration. |
1785 | |
1953 | |
1786 | The relative timeouts are calculated relative to the C<ev_now ()> |
1954 | The relative timeouts are calculated relative to the C<ev_now ()> |
1787 | time. This is usually the right thing as this timestamp refers to the time |
1955 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1865 | Returns the remaining time until a timer fires. If the timer is active, |
2033 | Returns the remaining time until a timer fires. If the timer is active, |
1866 | then this time is relative to the current event loop time, otherwise it's |
2034 | then this time is relative to the current event loop time, otherwise it's |
1867 | the timeout value currently configured. |
2035 | the timeout value currently configured. |
1868 | |
2036 | |
1869 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
2037 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1870 | C<5>. When the timer is started and one second passes, C<ev_timer_remain> |
2038 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1871 | will return C<4>. When the timer expires and is restarted, it will return |
2039 | will return C<4>. When the timer expires and is restarted, it will return |
1872 | roughly C<7> (likely slightly less as callback invocation takes some time, |
2040 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1873 | too), and so on. |
2041 | too), and so on. |
1874 | |
2042 | |
1875 | =item ev_tstamp repeat [read-write] |
2043 | =item ev_tstamp repeat [read-write] |
… | |
… | |
1904 | } |
2072 | } |
1905 | |
2073 | |
1906 | ev_timer mytimer; |
2074 | ev_timer mytimer; |
1907 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2075 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1908 | ev_timer_again (&mytimer); /* start timer */ |
2076 | ev_timer_again (&mytimer); /* start timer */ |
1909 | ev_loop (loop, 0); |
2077 | ev_run (loop, 0); |
1910 | |
2078 | |
1911 | // and in some piece of code that gets executed on any "activity": |
2079 | // and in some piece of code that gets executed on any "activity": |
1912 | // reset the timeout to start ticking again at 10 seconds |
2080 | // reset the timeout to start ticking again at 10 seconds |
1913 | ev_timer_again (&mytimer); |
2081 | ev_timer_again (&mytimer); |
1914 | |
2082 | |
… | |
… | |
1940 | |
2108 | |
1941 | As with timers, the callback is guaranteed to be invoked only when the |
2109 | As with timers, the callback is guaranteed to be invoked only when the |
1942 | point in time where it is supposed to trigger has passed. If multiple |
2110 | point in time where it is supposed to trigger has passed. If multiple |
1943 | timers become ready during the same loop iteration then the ones with |
2111 | timers become ready during the same loop iteration then the ones with |
1944 | earlier time-out values are invoked before ones with later time-out values |
2112 | earlier time-out values are invoked before ones with later time-out values |
1945 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
2113 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1946 | |
2114 | |
1947 | =head3 Watcher-Specific Functions and Data Members |
2115 | =head3 Watcher-Specific Functions and Data Members |
1948 | |
2116 | |
1949 | =over 4 |
2117 | =over 4 |
1950 | |
2118 | |
… | |
… | |
1985 | |
2153 | |
1986 | Another way to think about it (for the mathematically inclined) is that |
2154 | Another way to think about it (for the mathematically inclined) is that |
1987 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2155 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1988 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2156 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1989 | |
2157 | |
1990 | For numerical stability it is preferable that the C<offset> value is near |
2158 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1991 | C<ev_now ()> (the current time), but there is no range requirement for |
2159 | interval value should be higher than C<1/8192> (which is around 100 |
1992 | this value, and in fact is often specified as zero. |
2160 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2161 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2162 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2163 | C<0> and C<interval>, which is also the recommended range. |
1993 | |
2164 | |
1994 | Note also that there is an upper limit to how often a timer can fire (CPU |
2165 | Note also that there is an upper limit to how often a timer can fire (CPU |
1995 | speed for example), so if C<interval> is very small then timing stability |
2166 | speed for example), so if C<interval> is very small then timing stability |
1996 | will of course deteriorate. Libev itself tries to be exact to be about one |
2167 | will of course deteriorate. Libev itself tries to be exact to be about one |
1997 | millisecond (if the OS supports it and the machine is fast enough). |
2168 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2078 | Example: Call a callback every hour, or, more precisely, whenever the |
2249 | Example: Call a callback every hour, or, more precisely, whenever the |
2079 | system time is divisible by 3600. The callback invocation times have |
2250 | system time is divisible by 3600. The callback invocation times have |
2080 | potentially a lot of jitter, but good long-term stability. |
2251 | potentially a lot of jitter, but good long-term stability. |
2081 | |
2252 | |
2082 | static void |
2253 | static void |
2083 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2254 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2084 | { |
2255 | { |
2085 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2256 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2086 | } |
2257 | } |
2087 | |
2258 | |
2088 | ev_periodic hourly_tick; |
2259 | ev_periodic hourly_tick; |
… | |
… | |
2111 | |
2282 | |
2112 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2283 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2113 | |
2284 | |
2114 | Signal watchers will trigger an event when the process receives a specific |
2285 | Signal watchers will trigger an event when the process receives a specific |
2115 | signal one or more times. Even though signals are very asynchronous, libev |
2286 | signal one or more times. Even though signals are very asynchronous, libev |
2116 | will try it's best to deliver signals synchronously, i.e. as part of the |
2287 | will try its best to deliver signals synchronously, i.e. as part of the |
2117 | normal event processing, like any other event. |
2288 | normal event processing, like any other event. |
2118 | |
2289 | |
2119 | If you want signals to be delivered truly asynchronously, just use |
2290 | If you want signals to be delivered truly asynchronously, just use |
2120 | C<sigaction> as you would do without libev and forget about sharing |
2291 | C<sigaction> as you would do without libev and forget about sharing |
2121 | the signal. You can even use C<ev_async> from a signal handler to |
2292 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2140 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2311 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2141 | |
2312 | |
2142 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2313 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2143 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2314 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2144 | stopping it again), that is, libev might or might not block the signal, |
2315 | stopping it again), that is, libev might or might not block the signal, |
2145 | and might or might not set or restore the installed signal handler. |
2316 | and might or might not set or restore the installed signal handler (but |
|
|
2317 | see C<EVFLAG_NOSIGMASK>). |
2146 | |
2318 | |
2147 | While this does not matter for the signal disposition (libev never |
2319 | While this does not matter for the signal disposition (libev never |
2148 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2320 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2149 | C<execve>), this matters for the signal mask: many programs do not expect |
2321 | C<execve>), this matters for the signal mask: many programs do not expect |
2150 | certain signals to be blocked. |
2322 | certain signals to be blocked. |
… | |
… | |
2160 | In current versions of libev, the signal will not be blocked indefinitely |
2332 | In current versions of libev, the signal will not be blocked indefinitely |
2161 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
2333 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
2162 | the window of opportunity for problems, it will not go away, as libev |
2334 | the window of opportunity for problems, it will not go away, as libev |
2163 | I<has> to modify the signal mask, at least temporarily. |
2335 | I<has> to modify the signal mask, at least temporarily. |
2164 | |
2336 | |
2165 | So I can't stress this enough I<if you do not reset your signal mask |
2337 | So I can't stress this enough: I<If you do not reset your signal mask when |
2166 | when you expect it to be empty, you have a race condition in your |
2338 | you expect it to be empty, you have a race condition in your code>. This |
2167 | program>. This is not a libev-specific thing, this is true for most event |
2339 | is not a libev-specific thing, this is true for most event libraries. |
2168 | libraries. |
2340 | |
|
|
2341 | =head3 The special problem of threads signal handling |
|
|
2342 | |
|
|
2343 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2344 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2345 | threads in a process block signals, which is hard to achieve. |
|
|
2346 | |
|
|
2347 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2348 | for the same signals), you can tackle this problem by globally blocking |
|
|
2349 | all signals before creating any threads (or creating them with a fully set |
|
|
2350 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2351 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2352 | these signals. You can pass on any signals that libev might be interested |
|
|
2353 | in by calling C<ev_feed_signal>. |
2169 | |
2354 | |
2170 | =head3 Watcher-Specific Functions and Data Members |
2355 | =head3 Watcher-Specific Functions and Data Members |
2171 | |
2356 | |
2172 | =over 4 |
2357 | =over 4 |
2173 | |
2358 | |
… | |
… | |
2189 | Example: Try to exit cleanly on SIGINT. |
2374 | Example: Try to exit cleanly on SIGINT. |
2190 | |
2375 | |
2191 | static void |
2376 | static void |
2192 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2377 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2193 | { |
2378 | { |
2194 | ev_unloop (loop, EVUNLOOP_ALL); |
2379 | ev_break (loop, EVBREAK_ALL); |
2195 | } |
2380 | } |
2196 | |
2381 | |
2197 | ev_signal signal_watcher; |
2382 | ev_signal signal_watcher; |
2198 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2383 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2199 | ev_signal_start (loop, &signal_watcher); |
2384 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
2585 | |
2770 | |
2586 | Prepare and check watchers are usually (but not always) used in pairs: |
2771 | Prepare and check watchers are usually (but not always) used in pairs: |
2587 | prepare watchers get invoked before the process blocks and check watchers |
2772 | prepare watchers get invoked before the process blocks and check watchers |
2588 | afterwards. |
2773 | afterwards. |
2589 | |
2774 | |
2590 | You I<must not> call C<ev_loop> or similar functions that enter |
2775 | You I<must not> call C<ev_run> or similar functions that enter |
2591 | the current event loop from either C<ev_prepare> or C<ev_check> |
2776 | the current event loop from either C<ev_prepare> or C<ev_check> |
2592 | watchers. Other loops than the current one are fine, however. The |
2777 | watchers. Other loops than the current one are fine, however. The |
2593 | rationale behind this is that you do not need to check for recursion in |
2778 | rationale behind this is that you do not need to check for recursion in |
2594 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2779 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2595 | C<ev_check> so if you have one watcher of each kind they will always be |
2780 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2763 | |
2948 | |
2764 | if (timeout >= 0) |
2949 | if (timeout >= 0) |
2765 | // create/start timer |
2950 | // create/start timer |
2766 | |
2951 | |
2767 | // poll |
2952 | // poll |
2768 | ev_loop (EV_A_ 0); |
2953 | ev_run (EV_A_ 0); |
2769 | |
2954 | |
2770 | // stop timer again |
2955 | // stop timer again |
2771 | if (timeout >= 0) |
2956 | if (timeout >= 0) |
2772 | ev_timer_stop (EV_A_ &to); |
2957 | ev_timer_stop (EV_A_ &to); |
2773 | |
2958 | |
… | |
… | |
2851 | if you do not want that, you need to temporarily stop the embed watcher). |
3036 | if you do not want that, you need to temporarily stop the embed watcher). |
2852 | |
3037 | |
2853 | =item ev_embed_sweep (loop, ev_embed *) |
3038 | =item ev_embed_sweep (loop, ev_embed *) |
2854 | |
3039 | |
2855 | Make a single, non-blocking sweep over the embedded loop. This works |
3040 | Make a single, non-blocking sweep over the embedded loop. This works |
2856 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3041 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2857 | appropriate way for embedded loops. |
3042 | appropriate way for embedded loops. |
2858 | |
3043 | |
2859 | =item struct ev_loop *other [read-only] |
3044 | =item struct ev_loop *other [read-only] |
2860 | |
3045 | |
2861 | The embedded event loop. |
3046 | The embedded event loop. |
… | |
… | |
2921 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3106 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2922 | handlers will be invoked, too, of course. |
3107 | handlers will be invoked, too, of course. |
2923 | |
3108 | |
2924 | =head3 The special problem of life after fork - how is it possible? |
3109 | =head3 The special problem of life after fork - how is it possible? |
2925 | |
3110 | |
2926 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
3111 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2927 | up/change the process environment, followed by a call to C<exec()>. This |
3112 | up/change the process environment, followed by a call to C<exec()>. This |
2928 | sequence should be handled by libev without any problems. |
3113 | sequence should be handled by libev without any problems. |
2929 | |
3114 | |
2930 | This changes when the application actually wants to do event handling |
3115 | This changes when the application actually wants to do event handling |
2931 | in the child, or both parent in child, in effect "continuing" after the |
3116 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2947 | disadvantage of having to use multiple event loops (which do not support |
3132 | disadvantage of having to use multiple event loops (which do not support |
2948 | signal watchers). |
3133 | signal watchers). |
2949 | |
3134 | |
2950 | When this is not possible, or you want to use the default loop for |
3135 | When this is not possible, or you want to use the default loop for |
2951 | other reasons, then in the process that wants to start "fresh", call |
3136 | other reasons, then in the process that wants to start "fresh", call |
2952 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3137 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
2953 | the default loop will "orphan" (not stop) all registered watchers, so you |
3138 | Destroying the default loop will "orphan" (not stop) all registered |
2954 | have to be careful not to execute code that modifies those watchers. Note |
3139 | watchers, so you have to be careful not to execute code that modifies |
2955 | also that in that case, you have to re-register any signal watchers. |
3140 | those watchers. Note also that in that case, you have to re-register any |
|
|
3141 | signal watchers. |
2956 | |
3142 | |
2957 | =head3 Watcher-Specific Functions and Data Members |
3143 | =head3 Watcher-Specific Functions and Data Members |
2958 | |
3144 | |
2959 | =over 4 |
3145 | =over 4 |
2960 | |
3146 | |
2961 | =item ev_fork_init (ev_signal *, callback) |
3147 | =item ev_fork_init (ev_fork *, callback) |
2962 | |
3148 | |
2963 | Initialises and configures the fork watcher - it has no parameters of any |
3149 | Initialises and configures the fork watcher - it has no parameters of any |
2964 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3150 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2965 | believe me. |
3151 | really. |
2966 | |
3152 | |
2967 | =back |
3153 | =back |
2968 | |
3154 | |
2969 | |
3155 | |
|
|
3156 | =head2 C<ev_cleanup> - even the best things end |
|
|
3157 | |
|
|
3158 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3159 | by a call to C<ev_loop_destroy>. |
|
|
3160 | |
|
|
3161 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3162 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3163 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3164 | loop when you want them to be invoked. |
|
|
3165 | |
|
|
3166 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3167 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3168 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3169 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3170 | |
|
|
3171 | =head3 Watcher-Specific Functions and Data Members |
|
|
3172 | |
|
|
3173 | =over 4 |
|
|
3174 | |
|
|
3175 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3176 | |
|
|
3177 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3178 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3179 | pointless, I assure you. |
|
|
3180 | |
|
|
3181 | =back |
|
|
3182 | |
|
|
3183 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3184 | cleanup functions are called. |
|
|
3185 | |
|
|
3186 | static void |
|
|
3187 | program_exits (void) |
|
|
3188 | { |
|
|
3189 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3190 | } |
|
|
3191 | |
|
|
3192 | ... |
|
|
3193 | atexit (program_exits); |
|
|
3194 | |
|
|
3195 | |
2970 | =head2 C<ev_async> - how to wake up another event loop |
3196 | =head2 C<ev_async> - how to wake up an event loop |
2971 | |
3197 | |
2972 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3198 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2973 | asynchronous sources such as signal handlers (as opposed to multiple event |
3199 | asynchronous sources such as signal handlers (as opposed to multiple event |
2974 | loops - those are of course safe to use in different threads). |
3200 | loops - those are of course safe to use in different threads). |
2975 | |
3201 | |
2976 | Sometimes, however, you need to wake up another event loop you do not |
3202 | Sometimes, however, you need to wake up an event loop you do not control, |
2977 | control, for example because it belongs to another thread. This is what |
3203 | for example because it belongs to another thread. This is what C<ev_async> |
2978 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3204 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2979 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3205 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2980 | safe. |
|
|
2981 | |
3206 | |
2982 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3207 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2983 | too, are asynchronous in nature, and signals, too, will be compressed |
3208 | too, are asynchronous in nature, and signals, too, will be compressed |
2984 | (i.e. the number of callback invocations may be less than the number of |
3209 | (i.e. the number of callback invocations may be less than the number of |
2985 | C<ev_async_sent> calls). |
3210 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
|
|
3211 | of "global async watchers" by using a watcher on an otherwise unused |
|
|
3212 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
|
|
3213 | even without knowing which loop owns the signal. |
2986 | |
3214 | |
2987 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3215 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
2988 | just the default loop. |
3216 | just the default loop. |
2989 | |
3217 | |
2990 | =head3 Queueing |
3218 | =head3 Queueing |
… | |
… | |
3085 | trust me. |
3313 | trust me. |
3086 | |
3314 | |
3087 | =item ev_async_send (loop, ev_async *) |
3315 | =item ev_async_send (loop, ev_async *) |
3088 | |
3316 | |
3089 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3317 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3090 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3318 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3319 | returns. |
|
|
3320 | |
3091 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3321 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3092 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3322 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3093 | section below on what exactly this means). |
3323 | embedding section below on what exactly this means). |
3094 | |
3324 | |
3095 | Note that, as with other watchers in libev, multiple events might get |
3325 | Note that, as with other watchers in libev, multiple events might get |
3096 | compressed into a single callback invocation (another way to look at this |
3326 | compressed into a single callback invocation (another way to look at this |
3097 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3327 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3098 | reset when the event loop detects that). |
3328 | reset when the event loop detects that). |
… | |
… | |
3140 | |
3370 | |
3141 | If C<timeout> is less than 0, then no timeout watcher will be |
3371 | If C<timeout> is less than 0, then no timeout watcher will be |
3142 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3372 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3143 | repeat = 0) will be started. C<0> is a valid timeout. |
3373 | repeat = 0) will be started. C<0> is a valid timeout. |
3144 | |
3374 | |
3145 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3375 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3146 | passed an C<revents> set like normal event callbacks (a combination of |
3376 | passed an C<revents> set like normal event callbacks (a combination of |
3147 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3377 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3148 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3378 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3149 | a timeout and an io event at the same time - you probably should give io |
3379 | a timeout and an io event at the same time - you probably should give io |
3150 | events precedence. |
3380 | events precedence. |
3151 | |
3381 | |
3152 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3382 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3153 | |
3383 | |
3154 | static void stdin_ready (int revents, void *arg) |
3384 | static void stdin_ready (int revents, void *arg) |
3155 | { |
3385 | { |
3156 | if (revents & EV_READ) |
3386 | if (revents & EV_READ) |
3157 | /* stdin might have data for us, joy! */; |
3387 | /* stdin might have data for us, joy! */; |
3158 | else if (revents & EV_TIMEOUT) |
3388 | else if (revents & EV_TIMER) |
3159 | /* doh, nothing entered */; |
3389 | /* doh, nothing entered */; |
3160 | } |
3390 | } |
3161 | |
3391 | |
3162 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3392 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3163 | |
3393 | |
… | |
… | |
3166 | Feed an event on the given fd, as if a file descriptor backend detected |
3396 | Feed an event on the given fd, as if a file descriptor backend detected |
3167 | the given events it. |
3397 | the given events it. |
3168 | |
3398 | |
3169 | =item ev_feed_signal_event (loop, int signum) |
3399 | =item ev_feed_signal_event (loop, int signum) |
3170 | |
3400 | |
3171 | Feed an event as if the given signal occurred (C<loop> must be the default |
3401 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3172 | loop!). |
3402 | which is async-safe. |
3173 | |
3403 | |
3174 | =back |
3404 | =back |
|
|
3405 | |
|
|
3406 | |
|
|
3407 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3408 | |
|
|
3409 | This section explains some common idioms that are not immediately |
|
|
3410 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3411 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3412 | |
|
|
3413 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3414 | |
|
|
3415 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3416 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3417 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3418 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3419 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3420 | data: |
|
|
3421 | |
|
|
3422 | struct my_io |
|
|
3423 | { |
|
|
3424 | ev_io io; |
|
|
3425 | int otherfd; |
|
|
3426 | void *somedata; |
|
|
3427 | struct whatever *mostinteresting; |
|
|
3428 | }; |
|
|
3429 | |
|
|
3430 | ... |
|
|
3431 | struct my_io w; |
|
|
3432 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3433 | |
|
|
3434 | And since your callback will be called with a pointer to the watcher, you |
|
|
3435 | can cast it back to your own type: |
|
|
3436 | |
|
|
3437 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3438 | { |
|
|
3439 | struct my_io *w = (struct my_io *)w_; |
|
|
3440 | ... |
|
|
3441 | } |
|
|
3442 | |
|
|
3443 | More interesting and less C-conformant ways of casting your callback |
|
|
3444 | function type instead have been omitted. |
|
|
3445 | |
|
|
3446 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3447 | |
|
|
3448 | Another common scenario is to use some data structure with multiple |
|
|
3449 | embedded watchers, in effect creating your own watcher that combines |
|
|
3450 | multiple libev event sources into one "super-watcher": |
|
|
3451 | |
|
|
3452 | struct my_biggy |
|
|
3453 | { |
|
|
3454 | int some_data; |
|
|
3455 | ev_timer t1; |
|
|
3456 | ev_timer t2; |
|
|
3457 | } |
|
|
3458 | |
|
|
3459 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3460 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3461 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3462 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3463 | real programmers): |
|
|
3464 | |
|
|
3465 | #include <stddef.h> |
|
|
3466 | |
|
|
3467 | static void |
|
|
3468 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3469 | { |
|
|
3470 | struct my_biggy big = (struct my_biggy *) |
|
|
3471 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3472 | } |
|
|
3473 | |
|
|
3474 | static void |
|
|
3475 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3476 | { |
|
|
3477 | struct my_biggy big = (struct my_biggy *) |
|
|
3478 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3479 | } |
|
|
3480 | |
|
|
3481 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3482 | |
|
|
3483 | Often (especially in GUI toolkits) there are places where you have |
|
|
3484 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3485 | invoking C<ev_run>. |
|
|
3486 | |
|
|
3487 | This brings the problem of exiting - a callback might want to finish the |
|
|
3488 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3489 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3490 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3491 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3492 | |
|
|
3493 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3494 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3495 | triggered, using C<EVRUN_ONCE>: |
|
|
3496 | |
|
|
3497 | // main loop |
|
|
3498 | int exit_main_loop = 0; |
|
|
3499 | |
|
|
3500 | while (!exit_main_loop) |
|
|
3501 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3502 | |
|
|
3503 | // in a model watcher |
|
|
3504 | int exit_nested_loop = 0; |
|
|
3505 | |
|
|
3506 | while (!exit_nested_loop) |
|
|
3507 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3508 | |
|
|
3509 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3510 | |
|
|
3511 | // exit modal loop |
|
|
3512 | exit_nested_loop = 1; |
|
|
3513 | |
|
|
3514 | // exit main program, after modal loop is finished |
|
|
3515 | exit_main_loop = 1; |
|
|
3516 | |
|
|
3517 | // exit both |
|
|
3518 | exit_main_loop = exit_nested_loop = 1; |
|
|
3519 | |
|
|
3520 | =head2 THREAD LOCKING EXAMPLE |
|
|
3521 | |
|
|
3522 | Here is a fictitious example of how to run an event loop in a different |
|
|
3523 | thread from where callbacks are being invoked and watchers are |
|
|
3524 | created/added/removed. |
|
|
3525 | |
|
|
3526 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3527 | which uses exactly this technique (which is suited for many high-level |
|
|
3528 | languages). |
|
|
3529 | |
|
|
3530 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3531 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3532 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3533 | |
|
|
3534 | First, you need to associate some data with the event loop: |
|
|
3535 | |
|
|
3536 | typedef struct { |
|
|
3537 | mutex_t lock; /* global loop lock */ |
|
|
3538 | ev_async async_w; |
|
|
3539 | thread_t tid; |
|
|
3540 | cond_t invoke_cv; |
|
|
3541 | } userdata; |
|
|
3542 | |
|
|
3543 | void prepare_loop (EV_P) |
|
|
3544 | { |
|
|
3545 | // for simplicity, we use a static userdata struct. |
|
|
3546 | static userdata u; |
|
|
3547 | |
|
|
3548 | ev_async_init (&u->async_w, async_cb); |
|
|
3549 | ev_async_start (EV_A_ &u->async_w); |
|
|
3550 | |
|
|
3551 | pthread_mutex_init (&u->lock, 0); |
|
|
3552 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3553 | |
|
|
3554 | // now associate this with the loop |
|
|
3555 | ev_set_userdata (EV_A_ u); |
|
|
3556 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3557 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3558 | |
|
|
3559 | // then create the thread running ev_run |
|
|
3560 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3561 | } |
|
|
3562 | |
|
|
3563 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3564 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3565 | that might have been added: |
|
|
3566 | |
|
|
3567 | static void |
|
|
3568 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3569 | { |
|
|
3570 | // just used for the side effects |
|
|
3571 | } |
|
|
3572 | |
|
|
3573 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3574 | protecting the loop data, respectively. |
|
|
3575 | |
|
|
3576 | static void |
|
|
3577 | l_release (EV_P) |
|
|
3578 | { |
|
|
3579 | userdata *u = ev_userdata (EV_A); |
|
|
3580 | pthread_mutex_unlock (&u->lock); |
|
|
3581 | } |
|
|
3582 | |
|
|
3583 | static void |
|
|
3584 | l_acquire (EV_P) |
|
|
3585 | { |
|
|
3586 | userdata *u = ev_userdata (EV_A); |
|
|
3587 | pthread_mutex_lock (&u->lock); |
|
|
3588 | } |
|
|
3589 | |
|
|
3590 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3591 | into C<ev_run>: |
|
|
3592 | |
|
|
3593 | void * |
|
|
3594 | l_run (void *thr_arg) |
|
|
3595 | { |
|
|
3596 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3597 | |
|
|
3598 | l_acquire (EV_A); |
|
|
3599 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3600 | ev_run (EV_A_ 0); |
|
|
3601 | l_release (EV_A); |
|
|
3602 | |
|
|
3603 | return 0; |
|
|
3604 | } |
|
|
3605 | |
|
|
3606 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3607 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3608 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3609 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3610 | and b) skipping inter-thread-communication when there are no pending |
|
|
3611 | watchers is very beneficial): |
|
|
3612 | |
|
|
3613 | static void |
|
|
3614 | l_invoke (EV_P) |
|
|
3615 | { |
|
|
3616 | userdata *u = ev_userdata (EV_A); |
|
|
3617 | |
|
|
3618 | while (ev_pending_count (EV_A)) |
|
|
3619 | { |
|
|
3620 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3621 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3622 | } |
|
|
3623 | } |
|
|
3624 | |
|
|
3625 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3626 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3627 | thread to continue: |
|
|
3628 | |
|
|
3629 | static void |
|
|
3630 | real_invoke_pending (EV_P) |
|
|
3631 | { |
|
|
3632 | userdata *u = ev_userdata (EV_A); |
|
|
3633 | |
|
|
3634 | pthread_mutex_lock (&u->lock); |
|
|
3635 | ev_invoke_pending (EV_A); |
|
|
3636 | pthread_cond_signal (&u->invoke_cv); |
|
|
3637 | pthread_mutex_unlock (&u->lock); |
|
|
3638 | } |
|
|
3639 | |
|
|
3640 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3641 | event loop, you will now have to lock: |
|
|
3642 | |
|
|
3643 | ev_timer timeout_watcher; |
|
|
3644 | userdata *u = ev_userdata (EV_A); |
|
|
3645 | |
|
|
3646 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3647 | |
|
|
3648 | pthread_mutex_lock (&u->lock); |
|
|
3649 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3650 | ev_async_send (EV_A_ &u->async_w); |
|
|
3651 | pthread_mutex_unlock (&u->lock); |
|
|
3652 | |
|
|
3653 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3654 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3655 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3656 | watchers in the next event loop iteration. |
|
|
3657 | |
|
|
3658 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3659 | |
|
|
3660 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3661 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3662 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3663 | doesn't need callbacks anymore. |
|
|
3664 | |
|
|
3665 | Imagine you have coroutines that you can switch to using a function |
|
|
3666 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3667 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3668 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3669 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3670 | the differing C<;> conventions): |
|
|
3671 | |
|
|
3672 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3673 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3674 | |
|
|
3675 | That means instead of having a C callback function, you store the |
|
|
3676 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3677 | your callback, you instead have it switch to that coroutine. |
|
|
3678 | |
|
|
3679 | A coroutine might now wait for an event with a function called |
|
|
3680 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3681 | matter when, or whether the watcher is active or not when this function is |
|
|
3682 | called): |
|
|
3683 | |
|
|
3684 | void |
|
|
3685 | wait_for_event (ev_watcher *w) |
|
|
3686 | { |
|
|
3687 | ev_cb_set (w) = current_coro; |
|
|
3688 | switch_to (libev_coro); |
|
|
3689 | } |
|
|
3690 | |
|
|
3691 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3692 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3693 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3694 | |
|
|
3695 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3696 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3697 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3698 | any waiters. |
|
|
3699 | |
|
|
3700 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3701 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3702 | |
|
|
3703 | // my_ev.h |
|
|
3704 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3705 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3706 | #include "../libev/ev.h" |
|
|
3707 | |
|
|
3708 | // my_ev.c |
|
|
3709 | #define EV_H "my_ev.h" |
|
|
3710 | #include "../libev/ev.c" |
|
|
3711 | |
|
|
3712 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3713 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3714 | can even use F<ev.h> as header file name directly. |
3175 | |
3715 | |
3176 | |
3716 | |
3177 | =head1 LIBEVENT EMULATION |
3717 | =head1 LIBEVENT EMULATION |
3178 | |
3718 | |
3179 | Libev offers a compatibility emulation layer for libevent. It cannot |
3719 | Libev offers a compatibility emulation layer for libevent. It cannot |
3180 | emulate the internals of libevent, so here are some usage hints: |
3720 | emulate the internals of libevent, so here are some usage hints: |
3181 | |
3721 | |
3182 | =over 4 |
3722 | =over 4 |
|
|
3723 | |
|
|
3724 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3725 | |
|
|
3726 | This was the newest libevent version available when libev was implemented, |
|
|
3727 | and is still mostly unchanged in 2010. |
3183 | |
3728 | |
3184 | =item * Use it by including <event.h>, as usual. |
3729 | =item * Use it by including <event.h>, as usual. |
3185 | |
3730 | |
3186 | =item * The following members are fully supported: ev_base, ev_callback, |
3731 | =item * The following members are fully supported: ev_base, ev_callback, |
3187 | ev_arg, ev_fd, ev_res, ev_events. |
3732 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3193 | =item * Priorities are not currently supported. Initialising priorities |
3738 | =item * Priorities are not currently supported. Initialising priorities |
3194 | will fail and all watchers will have the same priority, even though there |
3739 | will fail and all watchers will have the same priority, even though there |
3195 | is an ev_pri field. |
3740 | is an ev_pri field. |
3196 | |
3741 | |
3197 | =item * In libevent, the last base created gets the signals, in libev, the |
3742 | =item * In libevent, the last base created gets the signals, in libev, the |
3198 | first base created (== the default loop) gets the signals. |
3743 | base that registered the signal gets the signals. |
3199 | |
3744 | |
3200 | =item * Other members are not supported. |
3745 | =item * Other members are not supported. |
3201 | |
3746 | |
3202 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3747 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3203 | to use the libev header file and library. |
3748 | to use the libev header file and library. |
… | |
… | |
3222 | Care has been taken to keep the overhead low. The only data member the C++ |
3767 | Care has been taken to keep the overhead low. The only data member the C++ |
3223 | classes add (compared to plain C-style watchers) is the event loop pointer |
3768 | classes add (compared to plain C-style watchers) is the event loop pointer |
3224 | that the watcher is associated with (or no additional members at all if |
3769 | that the watcher is associated with (or no additional members at all if |
3225 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3770 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3226 | |
3771 | |
3227 | Currently, functions, and static and non-static member functions can be |
3772 | Currently, functions, static and non-static member functions and classes |
3228 | used as callbacks. Other types should be easy to add as long as they only |
3773 | with C<operator ()> can be used as callbacks. Other types should be easy |
3229 | need one additional pointer for context. If you need support for other |
3774 | to add as long as they only need one additional pointer for context. If |
3230 | types of functors please contact the author (preferably after implementing |
3775 | you need support for other types of functors please contact the author |
3231 | it). |
3776 | (preferably after implementing it). |
3232 | |
3777 | |
3233 | Here is a list of things available in the C<ev> namespace: |
3778 | Here is a list of things available in the C<ev> namespace: |
3234 | |
3779 | |
3235 | =over 4 |
3780 | =over 4 |
3236 | |
3781 | |
… | |
… | |
3297 | myclass obj; |
3842 | myclass obj; |
3298 | ev::io iow; |
3843 | ev::io iow; |
3299 | iow.set <myclass, &myclass::io_cb> (&obj); |
3844 | iow.set <myclass, &myclass::io_cb> (&obj); |
3300 | |
3845 | |
3301 | =item w->set (object *) |
3846 | =item w->set (object *) |
3302 | |
|
|
3303 | This is an B<experimental> feature that might go away in a future version. |
|
|
3304 | |
3847 | |
3305 | This is a variation of a method callback - leaving out the method to call |
3848 | This is a variation of a method callback - leaving out the method to call |
3306 | will default the method to C<operator ()>, which makes it possible to use |
3849 | will default the method to C<operator ()>, which makes it possible to use |
3307 | functor objects without having to manually specify the C<operator ()> all |
3850 | functor objects without having to manually specify the C<operator ()> all |
3308 | the time. Incidentally, you can then also leave out the template argument |
3851 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3348 | Associates a different C<struct ev_loop> with this watcher. You can only |
3891 | Associates a different C<struct ev_loop> with this watcher. You can only |
3349 | do this when the watcher is inactive (and not pending either). |
3892 | do this when the watcher is inactive (and not pending either). |
3350 | |
3893 | |
3351 | =item w->set ([arguments]) |
3894 | =item w->set ([arguments]) |
3352 | |
3895 | |
3353 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3896 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
3354 | called at least once. Unlike the C counterpart, an active watcher gets |
3897 | method or a suitable start method must be called at least once. Unlike the |
3355 | automatically stopped and restarted when reconfiguring it with this |
3898 | C counterpart, an active watcher gets automatically stopped and restarted |
3356 | method. |
3899 | when reconfiguring it with this method. |
3357 | |
3900 | |
3358 | =item w->start () |
3901 | =item w->start () |
3359 | |
3902 | |
3360 | Starts the watcher. Note that there is no C<loop> argument, as the |
3903 | Starts the watcher. Note that there is no C<loop> argument, as the |
3361 | constructor already stores the event loop. |
3904 | constructor already stores the event loop. |
3362 | |
3905 | |
|
|
3906 | =item w->start ([arguments]) |
|
|
3907 | |
|
|
3908 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3909 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3910 | the configure C<set> method of the watcher. |
|
|
3911 | |
3363 | =item w->stop () |
3912 | =item w->stop () |
3364 | |
3913 | |
3365 | Stops the watcher if it is active. Again, no C<loop> argument. |
3914 | Stops the watcher if it is active. Again, no C<loop> argument. |
3366 | |
3915 | |
3367 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3916 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3379 | |
3928 | |
3380 | =back |
3929 | =back |
3381 | |
3930 | |
3382 | =back |
3931 | =back |
3383 | |
3932 | |
3384 | Example: Define a class with an IO and idle watcher, start one of them in |
3933 | Example: Define a class with two I/O and idle watchers, start the I/O |
3385 | the constructor. |
3934 | watchers in the constructor. |
3386 | |
3935 | |
3387 | class myclass |
3936 | class myclass |
3388 | { |
3937 | { |
3389 | ev::io io ; void io_cb (ev::io &w, int revents); |
3938 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3939 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
3390 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3940 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3391 | |
3941 | |
3392 | myclass (int fd) |
3942 | myclass (int fd) |
3393 | { |
3943 | { |
3394 | io .set <myclass, &myclass::io_cb > (this); |
3944 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3945 | io2 .set <myclass, &myclass::io2_cb > (this); |
3395 | idle.set <myclass, &myclass::idle_cb> (this); |
3946 | idle.set <myclass, &myclass::idle_cb> (this); |
3396 | |
3947 | |
3397 | io.start (fd, ev::READ); |
3948 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3949 | io.start (); // start it whenever convenient |
|
|
3950 | |
|
|
3951 | io2.start (fd, ev::READ); // set + start in one call |
3398 | } |
3952 | } |
3399 | }; |
3953 | }; |
3400 | |
3954 | |
3401 | |
3955 | |
3402 | =head1 OTHER LANGUAGE BINDINGS |
3956 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3450 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4004 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3451 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4005 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
3452 | |
4006 | |
3453 | =item Lua |
4007 | =item Lua |
3454 | |
4008 | |
3455 | Brian Maher has written a partial interface to libev |
4009 | Brian Maher has written a partial interface to libev for lua (at the |
3456 | for lua (only C<ev_io> and C<ev_timer>), to be found at |
4010 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3457 | L<http://github.com/brimworks/lua-ev>. |
4011 | L<http://github.com/brimworks/lua-ev>. |
3458 | |
4012 | |
3459 | =back |
4013 | =back |
3460 | |
4014 | |
3461 | |
4015 | |
… | |
… | |
3476 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4030 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3477 | C<EV_A_> is used when other arguments are following. Example: |
4031 | C<EV_A_> is used when other arguments are following. Example: |
3478 | |
4032 | |
3479 | ev_unref (EV_A); |
4033 | ev_unref (EV_A); |
3480 | ev_timer_add (EV_A_ watcher); |
4034 | ev_timer_add (EV_A_ watcher); |
3481 | ev_loop (EV_A_ 0); |
4035 | ev_run (EV_A_ 0); |
3482 | |
4036 | |
3483 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4037 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3484 | which is often provided by the following macro. |
4038 | which is often provided by the following macro. |
3485 | |
4039 | |
3486 | =item C<EV_P>, C<EV_P_> |
4040 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3526 | } |
4080 | } |
3527 | |
4081 | |
3528 | ev_check check; |
4082 | ev_check check; |
3529 | ev_check_init (&check, check_cb); |
4083 | ev_check_init (&check, check_cb); |
3530 | ev_check_start (EV_DEFAULT_ &check); |
4084 | ev_check_start (EV_DEFAULT_ &check); |
3531 | ev_loop (EV_DEFAULT_ 0); |
4085 | ev_run (EV_DEFAULT_ 0); |
3532 | |
4086 | |
3533 | =head1 EMBEDDING |
4087 | =head1 EMBEDDING |
3534 | |
4088 | |
3535 | Libev can (and often is) directly embedded into host |
4089 | Libev can (and often is) directly embedded into host |
3536 | applications. Examples of applications that embed it include the Deliantra |
4090 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3616 | libev.m4 |
4170 | libev.m4 |
3617 | |
4171 | |
3618 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4172 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3619 | |
4173 | |
3620 | Libev can be configured via a variety of preprocessor symbols you have to |
4174 | Libev can be configured via a variety of preprocessor symbols you have to |
3621 | define before including any of its files. The default in the absence of |
4175 | define before including (or compiling) any of its files. The default in |
3622 | autoconf is documented for every option. |
4176 | the absence of autoconf is documented for every option. |
|
|
4177 | |
|
|
4178 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4179 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4180 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4181 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4182 | users of libev and the libev code itself must be compiled with compatible |
|
|
4183 | settings. |
3623 | |
4184 | |
3624 | =over 4 |
4185 | =over 4 |
3625 | |
4186 | |
|
|
4187 | =item EV_COMPAT3 (h) |
|
|
4188 | |
|
|
4189 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4190 | release of libev comes with wrappers for the functions and symbols that |
|
|
4191 | have been renamed between libev version 3 and 4. |
|
|
4192 | |
|
|
4193 | You can disable these wrappers (to test compatibility with future |
|
|
4194 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4195 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4196 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4197 | typedef in that case. |
|
|
4198 | |
|
|
4199 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4200 | and in some even more future version the compatibility code will be |
|
|
4201 | removed completely. |
|
|
4202 | |
3626 | =item EV_STANDALONE |
4203 | =item EV_STANDALONE (h) |
3627 | |
4204 | |
3628 | Must always be C<1> if you do not use autoconf configuration, which |
4205 | Must always be C<1> if you do not use autoconf configuration, which |
3629 | keeps libev from including F<config.h>, and it also defines dummy |
4206 | keeps libev from including F<config.h>, and it also defines dummy |
3630 | implementations for some libevent functions (such as logging, which is not |
4207 | implementations for some libevent functions (such as logging, which is not |
3631 | supported). It will also not define any of the structs usually found in |
4208 | supported). It will also not define any of the structs usually found in |
3632 | F<event.h> that are not directly supported by the libev core alone. |
4209 | F<event.h> that are not directly supported by the libev core alone. |
3633 | |
4210 | |
3634 | In standalone mode, libev will still try to automatically deduce the |
4211 | In standalone mode, libev will still try to automatically deduce the |
3635 | configuration, but has to be more conservative. |
4212 | configuration, but has to be more conservative. |
|
|
4213 | |
|
|
4214 | =item EV_USE_FLOOR |
|
|
4215 | |
|
|
4216 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4217 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4218 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4219 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4220 | function is not available will fail, so the safe default is to not enable |
|
|
4221 | this. |
3636 | |
4222 | |
3637 | =item EV_USE_MONOTONIC |
4223 | =item EV_USE_MONOTONIC |
3638 | |
4224 | |
3639 | If defined to be C<1>, libev will try to detect the availability of the |
4225 | If defined to be C<1>, libev will try to detect the availability of the |
3640 | monotonic clock option at both compile time and runtime. Otherwise no |
4226 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3781 | as well as for signal and thread safety in C<ev_async> watchers. |
4367 | as well as for signal and thread safety in C<ev_async> watchers. |
3782 | |
4368 | |
3783 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4369 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3784 | (from F<signal.h>), which is usually good enough on most platforms. |
4370 | (from F<signal.h>), which is usually good enough on most platforms. |
3785 | |
4371 | |
3786 | =item EV_H |
4372 | =item EV_H (h) |
3787 | |
4373 | |
3788 | The name of the F<ev.h> header file used to include it. The default if |
4374 | The name of the F<ev.h> header file used to include it. The default if |
3789 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4375 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3790 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4376 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3791 | |
4377 | |
3792 | =item EV_CONFIG_H |
4378 | =item EV_CONFIG_H (h) |
3793 | |
4379 | |
3794 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4380 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3795 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4381 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3796 | C<EV_H>, above. |
4382 | C<EV_H>, above. |
3797 | |
4383 | |
3798 | =item EV_EVENT_H |
4384 | =item EV_EVENT_H (h) |
3799 | |
4385 | |
3800 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4386 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3801 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4387 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3802 | |
4388 | |
3803 | =item EV_PROTOTYPES |
4389 | =item EV_PROTOTYPES (h) |
3804 | |
4390 | |
3805 | If defined to be C<0>, then F<ev.h> will not define any function |
4391 | If defined to be C<0>, then F<ev.h> will not define any function |
3806 | prototypes, but still define all the structs and other symbols. This is |
4392 | prototypes, but still define all the structs and other symbols. This is |
3807 | occasionally useful if you want to provide your own wrapper functions |
4393 | occasionally useful if you want to provide your own wrapper functions |
3808 | around libev functions. |
4394 | around libev functions. |
… | |
… | |
3830 | fine. |
4416 | fine. |
3831 | |
4417 | |
3832 | If your embedding application does not need any priorities, defining these |
4418 | If your embedding application does not need any priorities, defining these |
3833 | both to C<0> will save some memory and CPU. |
4419 | both to C<0> will save some memory and CPU. |
3834 | |
4420 | |
3835 | =item EV_PERIODIC_ENABLE |
4421 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4422 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4423 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3836 | |
4424 | |
3837 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4425 | If undefined or defined to be C<1> (and the platform supports it), then |
3838 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4426 | the respective watcher type is supported. If defined to be C<0>, then it |
3839 | code. |
4427 | is not. Disabling watcher types mainly saves code size. |
3840 | |
4428 | |
3841 | =item EV_IDLE_ENABLE |
4429 | =item EV_FEATURES |
3842 | |
|
|
3843 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3844 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3845 | code. |
|
|
3846 | |
|
|
3847 | =item EV_EMBED_ENABLE |
|
|
3848 | |
|
|
3849 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3850 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3851 | watcher types, which therefore must not be disabled. |
|
|
3852 | |
|
|
3853 | =item EV_STAT_ENABLE |
|
|
3854 | |
|
|
3855 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3856 | defined to be C<0>, then they are not. |
|
|
3857 | |
|
|
3858 | =item EV_FORK_ENABLE |
|
|
3859 | |
|
|
3860 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3861 | defined to be C<0>, then they are not. |
|
|
3862 | |
|
|
3863 | =item EV_ASYNC_ENABLE |
|
|
3864 | |
|
|
3865 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3866 | defined to be C<0>, then they are not. |
|
|
3867 | |
|
|
3868 | =item EV_MINIMAL |
|
|
3869 | |
4430 | |
3870 | If you need to shave off some kilobytes of code at the expense of some |
4431 | If you need to shave off some kilobytes of code at the expense of some |
3871 | speed (but with the full API), define this symbol to C<1>. Currently this |
4432 | speed (but with the full API), you can define this symbol to request |
3872 | is used to override some inlining decisions, saves roughly 30% code size |
4433 | certain subsets of functionality. The default is to enable all features |
3873 | on amd64. It also selects a much smaller 2-heap for timer management over |
4434 | that can be enabled on the platform. |
3874 | the default 4-heap. |
|
|
3875 | |
4435 | |
3876 | You can save even more by disabling watcher types you do not need |
4436 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3877 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
4437 | with some broad features you want) and then selectively re-enable |
3878 | (C<-DNDEBUG>) will usually reduce code size a lot. |
4438 | additional parts you want, for example if you want everything minimal, |
|
|
4439 | but multiple event loop support, async and child watchers and the poll |
|
|
4440 | backend, use this: |
3879 | |
4441 | |
3880 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
4442 | #define EV_FEATURES 0 |
3881 | provide a bare-bones event library. See C<ev.h> for details on what parts |
4443 | #define EV_MULTIPLICITY 1 |
3882 | of the API are still available, and do not complain if this subset changes |
4444 | #define EV_USE_POLL 1 |
3883 | over time. |
4445 | #define EV_CHILD_ENABLE 1 |
|
|
4446 | #define EV_ASYNC_ENABLE 1 |
|
|
4447 | |
|
|
4448 | The actual value is a bitset, it can be a combination of the following |
|
|
4449 | values: |
|
|
4450 | |
|
|
4451 | =over 4 |
|
|
4452 | |
|
|
4453 | =item C<1> - faster/larger code |
|
|
4454 | |
|
|
4455 | Use larger code to speed up some operations. |
|
|
4456 | |
|
|
4457 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4458 | code size by roughly 30% on amd64). |
|
|
4459 | |
|
|
4460 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4461 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4462 | assertions. |
|
|
4463 | |
|
|
4464 | =item C<2> - faster/larger data structures |
|
|
4465 | |
|
|
4466 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4467 | hash table sizes and so on. This will usually further increase code size |
|
|
4468 | and can additionally have an effect on the size of data structures at |
|
|
4469 | runtime. |
|
|
4470 | |
|
|
4471 | =item C<4> - full API configuration |
|
|
4472 | |
|
|
4473 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4474 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4475 | |
|
|
4476 | =item C<8> - full API |
|
|
4477 | |
|
|
4478 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4479 | details on which parts of the API are still available without this |
|
|
4480 | feature, and do not complain if this subset changes over time. |
|
|
4481 | |
|
|
4482 | =item C<16> - enable all optional watcher types |
|
|
4483 | |
|
|
4484 | Enables all optional watcher types. If you want to selectively enable |
|
|
4485 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4486 | embed, async, child...) you can enable them manually by defining |
|
|
4487 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4488 | |
|
|
4489 | =item C<32> - enable all backends |
|
|
4490 | |
|
|
4491 | This enables all backends - without this feature, you need to enable at |
|
|
4492 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4493 | |
|
|
4494 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4495 | |
|
|
4496 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4497 | default. |
|
|
4498 | |
|
|
4499 | =back |
|
|
4500 | |
|
|
4501 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4502 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4503 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4504 | watchers, timers and monotonic clock support. |
|
|
4505 | |
|
|
4506 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4507 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4508 | your program might be left out as well - a binary starting a timer and an |
|
|
4509 | I/O watcher then might come out at only 5Kb. |
|
|
4510 | |
|
|
4511 | =item EV_AVOID_STDIO |
|
|
4512 | |
|
|
4513 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4514 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4515 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4516 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4517 | big. |
|
|
4518 | |
|
|
4519 | Note that error messages might become less precise when this option is |
|
|
4520 | enabled. |
3884 | |
4521 | |
3885 | =item EV_NSIG |
4522 | =item EV_NSIG |
3886 | |
4523 | |
3887 | The highest supported signal number, +1 (or, the number of |
4524 | The highest supported signal number, +1 (or, the number of |
3888 | signals): Normally, libev tries to deduce the maximum number of signals |
4525 | signals): Normally, libev tries to deduce the maximum number of signals |
3889 | automatically, but sometimes this fails, in which case it can be |
4526 | automatically, but sometimes this fails, in which case it can be |
3890 | specified. Also, using a lower number than detected (C<32> should be |
4527 | specified. Also, using a lower number than detected (C<32> should be |
3891 | good for about any system in existance) can save some memory, as libev |
4528 | good for about any system in existence) can save some memory, as libev |
3892 | statically allocates some 12-24 bytes per signal number. |
4529 | statically allocates some 12-24 bytes per signal number. |
3893 | |
4530 | |
3894 | =item EV_PID_HASHSIZE |
4531 | =item EV_PID_HASHSIZE |
3895 | |
4532 | |
3896 | C<ev_child> watchers use a small hash table to distribute workload by |
4533 | C<ev_child> watchers use a small hash table to distribute workload by |
3897 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4534 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3898 | than enough. If you need to manage thousands of children you might want to |
4535 | usually more than enough. If you need to manage thousands of children you |
3899 | increase this value (I<must> be a power of two). |
4536 | might want to increase this value (I<must> be a power of two). |
3900 | |
4537 | |
3901 | =item EV_INOTIFY_HASHSIZE |
4538 | =item EV_INOTIFY_HASHSIZE |
3902 | |
4539 | |
3903 | C<ev_stat> watchers use a small hash table to distribute workload by |
4540 | C<ev_stat> watchers use a small hash table to distribute workload by |
3904 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4541 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3905 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4542 | disabled), usually more than enough. If you need to manage thousands of |
3906 | watchers you might want to increase this value (I<must> be a power of |
4543 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3907 | two). |
4544 | power of two). |
3908 | |
4545 | |
3909 | =item EV_USE_4HEAP |
4546 | =item EV_USE_4HEAP |
3910 | |
4547 | |
3911 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4548 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3912 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4549 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3913 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4550 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3914 | faster performance with many (thousands) of watchers. |
4551 | faster performance with many (thousands) of watchers. |
3915 | |
4552 | |
3916 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4553 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3917 | (disabled). |
4554 | will be C<0>. |
3918 | |
4555 | |
3919 | =item EV_HEAP_CACHE_AT |
4556 | =item EV_HEAP_CACHE_AT |
3920 | |
4557 | |
3921 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4558 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3922 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4559 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3923 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4560 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3924 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4561 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3925 | but avoids random read accesses on heap changes. This improves performance |
4562 | but avoids random read accesses on heap changes. This improves performance |
3926 | noticeably with many (hundreds) of watchers. |
4563 | noticeably with many (hundreds) of watchers. |
3927 | |
4564 | |
3928 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4565 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3929 | (disabled). |
4566 | will be C<0>. |
3930 | |
4567 | |
3931 | =item EV_VERIFY |
4568 | =item EV_VERIFY |
3932 | |
4569 | |
3933 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4570 | Controls how much internal verification (see C<ev_verify ()>) will |
3934 | be done: If set to C<0>, no internal verification code will be compiled |
4571 | be done: If set to C<0>, no internal verification code will be compiled |
3935 | in. If set to C<1>, then verification code will be compiled in, but not |
4572 | in. If set to C<1>, then verification code will be compiled in, but not |
3936 | called. If set to C<2>, then the internal verification code will be |
4573 | called. If set to C<2>, then the internal verification code will be |
3937 | called once per loop, which can slow down libev. If set to C<3>, then the |
4574 | called once per loop, which can slow down libev. If set to C<3>, then the |
3938 | verification code will be called very frequently, which will slow down |
4575 | verification code will be called very frequently, which will slow down |
3939 | libev considerably. |
4576 | libev considerably. |
3940 | |
4577 | |
3941 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4578 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3942 | C<0>. |
4579 | will be C<0>. |
3943 | |
4580 | |
3944 | =item EV_COMMON |
4581 | =item EV_COMMON |
3945 | |
4582 | |
3946 | By default, all watchers have a C<void *data> member. By redefining |
4583 | By default, all watchers have a C<void *data> member. By redefining |
3947 | this macro to a something else you can include more and other types of |
4584 | this macro to something else you can include more and other types of |
3948 | members. You have to define it each time you include one of the files, |
4585 | members. You have to define it each time you include one of the files, |
3949 | though, and it must be identical each time. |
4586 | though, and it must be identical each time. |
3950 | |
4587 | |
3951 | For example, the perl EV module uses something like this: |
4588 | For example, the perl EV module uses something like this: |
3952 | |
4589 | |
… | |
… | |
4005 | file. |
4642 | file. |
4006 | |
4643 | |
4007 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4644 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4008 | that everybody includes and which overrides some configure choices: |
4645 | that everybody includes and which overrides some configure choices: |
4009 | |
4646 | |
4010 | #define EV_MINIMAL 1 |
4647 | #define EV_FEATURES 8 |
4011 | #define EV_USE_POLL 0 |
4648 | #define EV_USE_SELECT 1 |
4012 | #define EV_MULTIPLICITY 0 |
|
|
4013 | #define EV_PERIODIC_ENABLE 0 |
4649 | #define EV_PREPARE_ENABLE 1 |
|
|
4650 | #define EV_IDLE_ENABLE 1 |
4014 | #define EV_STAT_ENABLE 0 |
4651 | #define EV_SIGNAL_ENABLE 1 |
4015 | #define EV_FORK_ENABLE 0 |
4652 | #define EV_CHILD_ENABLE 1 |
|
|
4653 | #define EV_USE_STDEXCEPT 0 |
4016 | #define EV_CONFIG_H <config.h> |
4654 | #define EV_CONFIG_H <config.h> |
4017 | #define EV_MINPRI 0 |
|
|
4018 | #define EV_MAXPRI 0 |
|
|
4019 | |
4655 | |
4020 | #include "ev++.h" |
4656 | #include "ev++.h" |
4021 | |
4657 | |
4022 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4658 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4023 | |
4659 | |
4024 | #include "ev_cpp.h" |
4660 | #include "ev_cpp.h" |
4025 | #include "ev.c" |
4661 | #include "ev.c" |
4026 | |
4662 | |
4027 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4663 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4028 | |
4664 | |
4029 | =head2 THREADS AND COROUTINES |
4665 | =head2 THREADS AND COROUTINES |
4030 | |
4666 | |
4031 | =head3 THREADS |
4667 | =head3 THREADS |
4032 | |
4668 | |
… | |
… | |
4083 | default loop and triggering an C<ev_async> watcher from the default loop |
4719 | default loop and triggering an C<ev_async> watcher from the default loop |
4084 | watcher callback into the event loop interested in the signal. |
4720 | watcher callback into the event loop interested in the signal. |
4085 | |
4721 | |
4086 | =back |
4722 | =back |
4087 | |
4723 | |
4088 | =head4 THREAD LOCKING EXAMPLE |
4724 | See also L<THREAD LOCKING EXAMPLE>. |
4089 | |
|
|
4090 | Here is a fictitious example of how to run an event loop in a different |
|
|
4091 | thread than where callbacks are being invoked and watchers are |
|
|
4092 | created/added/removed. |
|
|
4093 | |
|
|
4094 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4095 | which uses exactly this technique (which is suited for many high-level |
|
|
4096 | languages). |
|
|
4097 | |
|
|
4098 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4099 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4100 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4101 | |
|
|
4102 | First, you need to associate some data with the event loop: |
|
|
4103 | |
|
|
4104 | typedef struct { |
|
|
4105 | mutex_t lock; /* global loop lock */ |
|
|
4106 | ev_async async_w; |
|
|
4107 | thread_t tid; |
|
|
4108 | cond_t invoke_cv; |
|
|
4109 | } userdata; |
|
|
4110 | |
|
|
4111 | void prepare_loop (EV_P) |
|
|
4112 | { |
|
|
4113 | // for simplicity, we use a static userdata struct. |
|
|
4114 | static userdata u; |
|
|
4115 | |
|
|
4116 | ev_async_init (&u->async_w, async_cb); |
|
|
4117 | ev_async_start (EV_A_ &u->async_w); |
|
|
4118 | |
|
|
4119 | pthread_mutex_init (&u->lock, 0); |
|
|
4120 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4121 | |
|
|
4122 | // now associate this with the loop |
|
|
4123 | ev_set_userdata (EV_A_ u); |
|
|
4124 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4125 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4126 | |
|
|
4127 | // then create the thread running ev_loop |
|
|
4128 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4129 | } |
|
|
4130 | |
|
|
4131 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4132 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4133 | that might have been added: |
|
|
4134 | |
|
|
4135 | static void |
|
|
4136 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4137 | { |
|
|
4138 | // just used for the side effects |
|
|
4139 | } |
|
|
4140 | |
|
|
4141 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4142 | protecting the loop data, respectively. |
|
|
4143 | |
|
|
4144 | static void |
|
|
4145 | l_release (EV_P) |
|
|
4146 | { |
|
|
4147 | userdata *u = ev_userdata (EV_A); |
|
|
4148 | pthread_mutex_unlock (&u->lock); |
|
|
4149 | } |
|
|
4150 | |
|
|
4151 | static void |
|
|
4152 | l_acquire (EV_P) |
|
|
4153 | { |
|
|
4154 | userdata *u = ev_userdata (EV_A); |
|
|
4155 | pthread_mutex_lock (&u->lock); |
|
|
4156 | } |
|
|
4157 | |
|
|
4158 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4159 | into C<ev_loop>: |
|
|
4160 | |
|
|
4161 | void * |
|
|
4162 | l_run (void *thr_arg) |
|
|
4163 | { |
|
|
4164 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4165 | |
|
|
4166 | l_acquire (EV_A); |
|
|
4167 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4168 | ev_loop (EV_A_ 0); |
|
|
4169 | l_release (EV_A); |
|
|
4170 | |
|
|
4171 | return 0; |
|
|
4172 | } |
|
|
4173 | |
|
|
4174 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4175 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4176 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4177 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4178 | and b) skipping inter-thread-communication when there are no pending |
|
|
4179 | watchers is very beneficial): |
|
|
4180 | |
|
|
4181 | static void |
|
|
4182 | l_invoke (EV_P) |
|
|
4183 | { |
|
|
4184 | userdata *u = ev_userdata (EV_A); |
|
|
4185 | |
|
|
4186 | while (ev_pending_count (EV_A)) |
|
|
4187 | { |
|
|
4188 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4189 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4190 | } |
|
|
4191 | } |
|
|
4192 | |
|
|
4193 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4194 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4195 | thread to continue: |
|
|
4196 | |
|
|
4197 | static void |
|
|
4198 | real_invoke_pending (EV_P) |
|
|
4199 | { |
|
|
4200 | userdata *u = ev_userdata (EV_A); |
|
|
4201 | |
|
|
4202 | pthread_mutex_lock (&u->lock); |
|
|
4203 | ev_invoke_pending (EV_A); |
|
|
4204 | pthread_cond_signal (&u->invoke_cv); |
|
|
4205 | pthread_mutex_unlock (&u->lock); |
|
|
4206 | } |
|
|
4207 | |
|
|
4208 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4209 | event loop, you will now have to lock: |
|
|
4210 | |
|
|
4211 | ev_timer timeout_watcher; |
|
|
4212 | userdata *u = ev_userdata (EV_A); |
|
|
4213 | |
|
|
4214 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4215 | |
|
|
4216 | pthread_mutex_lock (&u->lock); |
|
|
4217 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4218 | ev_async_send (EV_A_ &u->async_w); |
|
|
4219 | pthread_mutex_unlock (&u->lock); |
|
|
4220 | |
|
|
4221 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4222 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4223 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4224 | watchers in the next event loop iteration. |
|
|
4225 | |
4725 | |
4226 | =head3 COROUTINES |
4726 | =head3 COROUTINES |
4227 | |
4727 | |
4228 | Libev is very accommodating to coroutines ("cooperative threads"): |
4728 | Libev is very accommodating to coroutines ("cooperative threads"): |
4229 | libev fully supports nesting calls to its functions from different |
4729 | libev fully supports nesting calls to its functions from different |
4230 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4730 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
4231 | different coroutines, and switch freely between both coroutines running |
4731 | different coroutines, and switch freely between both coroutines running |
4232 | the loop, as long as you don't confuse yourself). The only exception is |
4732 | the loop, as long as you don't confuse yourself). The only exception is |
4233 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4733 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4234 | |
4734 | |
4235 | Care has been taken to ensure that libev does not keep local state inside |
4735 | Care has been taken to ensure that libev does not keep local state inside |
4236 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4736 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
4237 | they do not call any callbacks. |
4737 | they do not call any callbacks. |
4238 | |
4738 | |
4239 | =head2 COMPILER WARNINGS |
4739 | =head2 COMPILER WARNINGS |
4240 | |
4740 | |
4241 | Depending on your compiler and compiler settings, you might get no or a |
4741 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
4252 | maintainable. |
4752 | maintainable. |
4253 | |
4753 | |
4254 | And of course, some compiler warnings are just plain stupid, or simply |
4754 | And of course, some compiler warnings are just plain stupid, or simply |
4255 | wrong (because they don't actually warn about the condition their message |
4755 | wrong (because they don't actually warn about the condition their message |
4256 | seems to warn about). For example, certain older gcc versions had some |
4756 | seems to warn about). For example, certain older gcc versions had some |
4257 | warnings that resulted an extreme number of false positives. These have |
4757 | warnings that resulted in an extreme number of false positives. These have |
4258 | been fixed, but some people still insist on making code warn-free with |
4758 | been fixed, but some people still insist on making code warn-free with |
4259 | such buggy versions. |
4759 | such buggy versions. |
4260 | |
4760 | |
4261 | While libev is written to generate as few warnings as possible, |
4761 | While libev is written to generate as few warnings as possible, |
4262 | "warn-free" code is not a goal, and it is recommended not to build libev |
4762 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
4298 | I suggest using suppression lists. |
4798 | I suggest using suppression lists. |
4299 | |
4799 | |
4300 | |
4800 | |
4301 | =head1 PORTABILITY NOTES |
4801 | =head1 PORTABILITY NOTES |
4302 | |
4802 | |
|
|
4803 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4804 | |
|
|
4805 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4806 | interfaces but I<disables> them by default. |
|
|
4807 | |
|
|
4808 | That means that libev compiled in the default environment doesn't support |
|
|
4809 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4810 | |
|
|
4811 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4812 | by enabling the large file API, which makes them incompatible with the |
|
|
4813 | standard libev compiled for their system. |
|
|
4814 | |
|
|
4815 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4816 | suddenly make it incompatible to the default compile time environment, |
|
|
4817 | i.e. all programs not using special compile switches. |
|
|
4818 | |
|
|
4819 | =head2 OS/X AND DARWIN BUGS |
|
|
4820 | |
|
|
4821 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4822 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4823 | OpenGL drivers. |
|
|
4824 | |
|
|
4825 | =head3 C<kqueue> is buggy |
|
|
4826 | |
|
|
4827 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4828 | only sockets, many support pipes. |
|
|
4829 | |
|
|
4830 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4831 | rotten platform, but of course you can still ask for it when creating a |
|
|
4832 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4833 | probably going to work well. |
|
|
4834 | |
|
|
4835 | =head3 C<poll> is buggy |
|
|
4836 | |
|
|
4837 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4838 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4839 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4840 | |
|
|
4841 | Libev tries to work around this by not using C<poll> by default on |
|
|
4842 | this rotten platform, but of course you can still ask for it when creating |
|
|
4843 | a loop. |
|
|
4844 | |
|
|
4845 | =head3 C<select> is buggy |
|
|
4846 | |
|
|
4847 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4848 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4849 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4850 | you use more. |
|
|
4851 | |
|
|
4852 | There is an undocumented "workaround" for this - defining |
|
|
4853 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4854 | work on OS/X. |
|
|
4855 | |
|
|
4856 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4857 | |
|
|
4858 | =head3 C<errno> reentrancy |
|
|
4859 | |
|
|
4860 | The default compile environment on Solaris is unfortunately so |
|
|
4861 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4862 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4863 | defined by default. A valid, if stupid, implementation choice. |
|
|
4864 | |
|
|
4865 | If you want to use libev in threaded environments you have to make sure |
|
|
4866 | it's compiled with C<_REENTRANT> defined. |
|
|
4867 | |
|
|
4868 | =head3 Event port backend |
|
|
4869 | |
|
|
4870 | The scalable event interface for Solaris is called "event |
|
|
4871 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4872 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4873 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4874 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4875 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4876 | great. |
|
|
4877 | |
|
|
4878 | If you can't get it to work, you can try running the program by setting |
|
|
4879 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4880 | C<select> backends. |
|
|
4881 | |
|
|
4882 | =head2 AIX POLL BUG |
|
|
4883 | |
|
|
4884 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4885 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4886 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4887 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4888 | |
4303 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4889 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4890 | |
|
|
4891 | =head3 General issues |
4304 | |
4892 | |
4305 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4893 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4306 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4894 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4307 | model. Libev still offers limited functionality on this platform in |
4895 | model. Libev still offers limited functionality on this platform in |
4308 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4896 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4309 | descriptors. This only applies when using Win32 natively, not when using |
4897 | descriptors. This only applies when using Win32 natively, not when using |
4310 | e.g. cygwin. |
4898 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4899 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4900 | environment. |
4311 | |
4901 | |
4312 | Lifting these limitations would basically require the full |
4902 | Lifting these limitations would basically require the full |
4313 | re-implementation of the I/O system. If you are into these kinds of |
4903 | re-implementation of the I/O system. If you are into this kind of thing, |
4314 | things, then note that glib does exactly that for you in a very portable |
4904 | then note that glib does exactly that for you in a very portable way (note |
4315 | way (note also that glib is the slowest event library known to man). |
4905 | also that glib is the slowest event library known to man). |
4316 | |
4906 | |
4317 | There is no supported compilation method available on windows except |
4907 | There is no supported compilation method available on windows except |
4318 | embedding it into other applications. |
4908 | embedding it into other applications. |
4319 | |
4909 | |
4320 | Sensible signal handling is officially unsupported by Microsoft - libev |
4910 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4348 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4938 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4349 | |
4939 | |
4350 | #include "evwrap.h" |
4940 | #include "evwrap.h" |
4351 | #include "ev.c" |
4941 | #include "ev.c" |
4352 | |
4942 | |
4353 | =over 4 |
|
|
4354 | |
|
|
4355 | =item The winsocket select function |
4943 | =head3 The winsocket C<select> function |
4356 | |
4944 | |
4357 | The winsocket C<select> function doesn't follow POSIX in that it |
4945 | The winsocket C<select> function doesn't follow POSIX in that it |
4358 | requires socket I<handles> and not socket I<file descriptors> (it is |
4946 | requires socket I<handles> and not socket I<file descriptors> (it is |
4359 | also extremely buggy). This makes select very inefficient, and also |
4947 | also extremely buggy). This makes select very inefficient, and also |
4360 | requires a mapping from file descriptors to socket handles (the Microsoft |
4948 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4369 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4957 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4370 | |
4958 | |
4371 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4959 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4372 | complexity in the O(n²) range when using win32. |
4960 | complexity in the O(n²) range when using win32. |
4373 | |
4961 | |
4374 | =item Limited number of file descriptors |
4962 | =head3 Limited number of file descriptors |
4375 | |
4963 | |
4376 | Windows has numerous arbitrary (and low) limits on things. |
4964 | Windows has numerous arbitrary (and low) limits on things. |
4377 | |
4965 | |
4378 | Early versions of winsocket's select only supported waiting for a maximum |
4966 | Early versions of winsocket's select only supported waiting for a maximum |
4379 | of C<64> handles (probably owning to the fact that all windows kernels |
4967 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4394 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4982 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4395 | (depending on windows version and/or the phase of the moon). To get more, |
4983 | (depending on windows version and/or the phase of the moon). To get more, |
4396 | you need to wrap all I/O functions and provide your own fd management, but |
4984 | you need to wrap all I/O functions and provide your own fd management, but |
4397 | the cost of calling select (O(n²)) will likely make this unworkable. |
4985 | the cost of calling select (O(n²)) will likely make this unworkable. |
4398 | |
4986 | |
4399 | =back |
|
|
4400 | |
|
|
4401 | =head2 PORTABILITY REQUIREMENTS |
4987 | =head2 PORTABILITY REQUIREMENTS |
4402 | |
4988 | |
4403 | In addition to a working ISO-C implementation and of course the |
4989 | In addition to a working ISO-C implementation and of course the |
4404 | backend-specific APIs, libev relies on a few additional extensions: |
4990 | backend-specific APIs, libev relies on a few additional extensions: |
4405 | |
4991 | |
… | |
… | |
4411 | Libev assumes not only that all watcher pointers have the same internal |
4997 | Libev assumes not only that all watcher pointers have the same internal |
4412 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4998 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4413 | assumes that the same (machine) code can be used to call any watcher |
4999 | assumes that the same (machine) code can be used to call any watcher |
4414 | callback: The watcher callbacks have different type signatures, but libev |
5000 | callback: The watcher callbacks have different type signatures, but libev |
4415 | calls them using an C<ev_watcher *> internally. |
5001 | calls them using an C<ev_watcher *> internally. |
|
|
5002 | |
|
|
5003 | =item pointer accesses must be thread-atomic |
|
|
5004 | |
|
|
5005 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5006 | writable in one piece - this is the case on all current architectures. |
4416 | |
5007 | |
4417 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5008 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4418 | |
5009 | |
4419 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5010 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4420 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5011 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
4443 | watchers. |
5034 | watchers. |
4444 | |
5035 | |
4445 | =item C<double> must hold a time value in seconds with enough accuracy |
5036 | =item C<double> must hold a time value in seconds with enough accuracy |
4446 | |
5037 | |
4447 | The type C<double> is used to represent timestamps. It is required to |
5038 | The type C<double> is used to represent timestamps. It is required to |
4448 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5039 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4449 | enough for at least into the year 4000. This requirement is fulfilled by |
5040 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5041 | (the design goal for libev). This requirement is overfulfilled by |
4450 | implementations implementing IEEE 754, which is basically all existing |
5042 | implementations using IEEE 754, which is basically all existing ones. With |
4451 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
5043 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
4452 | 2200. |
|
|
4453 | |
5044 | |
4454 | =back |
5045 | =back |
4455 | |
5046 | |
4456 | If you know of other additional requirements drop me a note. |
5047 | If you know of other additional requirements drop me a note. |
4457 | |
5048 | |
… | |
… | |
4525 | involves iterating over all running async watchers or all signal numbers. |
5116 | involves iterating over all running async watchers or all signal numbers. |
4526 | |
5117 | |
4527 | =back |
5118 | =back |
4528 | |
5119 | |
4529 | |
5120 | |
|
|
5121 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5122 | |
|
|
5123 | The major version 4 introduced some incompatible changes to the API. |
|
|
5124 | |
|
|
5125 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5126 | for all changes, so most programs should still compile. The compatibility |
|
|
5127 | layer might be removed in later versions of libev, so better update to the |
|
|
5128 | new API early than late. |
|
|
5129 | |
|
|
5130 | =over 4 |
|
|
5131 | |
|
|
5132 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5133 | |
|
|
5134 | The backward compatibility mechanism can be controlled by |
|
|
5135 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5136 | section. |
|
|
5137 | |
|
|
5138 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5139 | |
|
|
5140 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5141 | |
|
|
5142 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5143 | ev_loop_fork (EV_DEFAULT); |
|
|
5144 | |
|
|
5145 | =item function/symbol renames |
|
|
5146 | |
|
|
5147 | A number of functions and symbols have been renamed: |
|
|
5148 | |
|
|
5149 | ev_loop => ev_run |
|
|
5150 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5151 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5152 | |
|
|
5153 | ev_unloop => ev_break |
|
|
5154 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5155 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5156 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5157 | |
|
|
5158 | EV_TIMEOUT => EV_TIMER |
|
|
5159 | |
|
|
5160 | ev_loop_count => ev_iteration |
|
|
5161 | ev_loop_depth => ev_depth |
|
|
5162 | ev_loop_verify => ev_verify |
|
|
5163 | |
|
|
5164 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5165 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5166 | associated constants have been renamed to not collide with the C<struct |
|
|
5167 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5168 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5169 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5170 | typedef. |
|
|
5171 | |
|
|
5172 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5173 | |
|
|
5174 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5175 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5176 | and work, but the library code will of course be larger. |
|
|
5177 | |
|
|
5178 | =back |
|
|
5179 | |
|
|
5180 | |
4530 | =head1 GLOSSARY |
5181 | =head1 GLOSSARY |
4531 | |
5182 | |
4532 | =over 4 |
5183 | =over 4 |
4533 | |
5184 | |
4534 | =item active |
5185 | =item active |
4535 | |
5186 | |
4536 | A watcher is active as long as it has been started (has been attached to |
5187 | A watcher is active as long as it has been started and not yet stopped. |
4537 | an event loop) but not yet stopped (disassociated from the event loop). |
5188 | See L<WATCHER STATES> for details. |
4538 | |
5189 | |
4539 | =item application |
5190 | =item application |
4540 | |
5191 | |
4541 | In this document, an application is whatever is using libev. |
5192 | In this document, an application is whatever is using libev. |
|
|
5193 | |
|
|
5194 | =item backend |
|
|
5195 | |
|
|
5196 | The part of the code dealing with the operating system interfaces. |
4542 | |
5197 | |
4543 | =item callback |
5198 | =item callback |
4544 | |
5199 | |
4545 | The address of a function that is called when some event has been |
5200 | The address of a function that is called when some event has been |
4546 | detected. Callbacks are being passed the event loop, the watcher that |
5201 | detected. Callbacks are being passed the event loop, the watcher that |
4547 | received the event, and the actual event bitset. |
5202 | received the event, and the actual event bitset. |
4548 | |
5203 | |
4549 | =item callback invocation |
5204 | =item callback/watcher invocation |
4550 | |
5205 | |
4551 | The act of calling the callback associated with a watcher. |
5206 | The act of calling the callback associated with a watcher. |
4552 | |
5207 | |
4553 | =item event |
5208 | =item event |
4554 | |
5209 | |
4555 | A change of state of some external event, such as data now being available |
5210 | A change of state of some external event, such as data now being available |
4556 | for reading on a file descriptor, time having passed or simply not having |
5211 | for reading on a file descriptor, time having passed or simply not having |
4557 | any other events happening anymore. |
5212 | any other events happening anymore. |
4558 | |
5213 | |
4559 | In libev, events are represented as single bits (such as C<EV_READ> or |
5214 | In libev, events are represented as single bits (such as C<EV_READ> or |
4560 | C<EV_TIMEOUT>). |
5215 | C<EV_TIMER>). |
4561 | |
5216 | |
4562 | =item event library |
5217 | =item event library |
4563 | |
5218 | |
4564 | A software package implementing an event model and loop. |
5219 | A software package implementing an event model and loop. |
4565 | |
5220 | |
… | |
… | |
4573 | The model used to describe how an event loop handles and processes |
5228 | The model used to describe how an event loop handles and processes |
4574 | watchers and events. |
5229 | watchers and events. |
4575 | |
5230 | |
4576 | =item pending |
5231 | =item pending |
4577 | |
5232 | |
4578 | A watcher is pending as soon as the corresponding event has been detected, |
5233 | A watcher is pending as soon as the corresponding event has been |
4579 | and stops being pending as soon as the watcher will be invoked or its |
5234 | detected. See L<WATCHER STATES> for details. |
4580 | pending status is explicitly cleared by the application. |
|
|
4581 | |
|
|
4582 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4583 | its pending status. |
|
|
4584 | |
5235 | |
4585 | =item real time |
5236 | =item real time |
4586 | |
5237 | |
4587 | The physical time that is observed. It is apparently strictly monotonic :) |
5238 | The physical time that is observed. It is apparently strictly monotonic :) |
4588 | |
5239 | |
4589 | =item wall-clock time |
5240 | =item wall-clock time |
4590 | |
5241 | |
4591 | The time and date as shown on clocks. Unlike real time, it can actually |
5242 | The time and date as shown on clocks. Unlike real time, it can actually |
4592 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5243 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4593 | clock. |
5244 | clock. |
4594 | |
5245 | |
4595 | =item watcher |
5246 | =item watcher |
4596 | |
5247 | |
4597 | A data structure that describes interest in certain events. Watchers need |
5248 | A data structure that describes interest in certain events. Watchers need |
4598 | to be started (attached to an event loop) before they can receive events. |
5249 | to be started (attached to an event loop) before they can receive events. |
4599 | |
5250 | |
4600 | =item watcher invocation |
|
|
4601 | |
|
|
4602 | The act of calling the callback associated with a watcher. |
|
|
4603 | |
|
|
4604 | =back |
5251 | =back |
4605 | |
5252 | |
4606 | =head1 AUTHOR |
5253 | =head1 AUTHOR |
4607 | |
5254 | |
4608 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5255 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5256 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4609 | |
5257 | |