… | |
… | |
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_now_update> 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 |
174 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
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185 | passed (approximately - it might return a bit earlier even if not |
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186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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187 | |
175 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
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189 | |
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190 | The range of the C<interval> is limited - libev only guarantees to work |
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191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
176 | |
192 | |
177 | =item int ev_version_major () |
193 | =item int ev_version_major () |
178 | |
194 | |
179 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
180 | |
196 | |
… | |
… | |
191 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
192 | compatible to older versions, so a larger minor version alone is usually |
208 | compatible to older versions, so a larger minor version alone is usually |
193 | not a problem. |
209 | not a problem. |
194 | |
210 | |
195 | Example: Make sure we haven't accidentally been linked against the wrong |
211 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | version. |
212 | version (note, however, that this will not detect other ABI mismatches, |
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213 | such as LFS or reentrancy). |
197 | |
214 | |
198 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
199 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
200 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | |
218 | |
… | |
… | |
212 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
213 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
214 | |
231 | |
215 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
216 | |
233 | |
217 | Return the set of all backends compiled into this binary of libev and also |
234 | Return the set of all backends compiled into this binary of libev and |
218 | recommended for this platform. This set is often smaller than the one |
235 | also recommended for this platform, meaning it will work for most file |
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236 | descriptor types. This set is often smaller than the one returned by |
219 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
237 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
220 | most BSDs and will not be auto-detected unless you explicitly request it |
238 | and will not be auto-detected unless you explicitly request it (assuming |
221 | (assuming you know what you are doing). This is the set of backends that |
239 | you know what you are doing). This is the set of backends that libev will |
222 | libev will probe for if you specify no backends explicitly. |
240 | probe for if you specify no backends explicitly. |
223 | |
241 | |
224 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
225 | |
243 | |
226 | Returns the set of backends that are embeddable in other event loops. This |
244 | Returns the set of backends that are embeddable in other event loops. This |
227 | is the theoretical, all-platform, value. To find which backends |
245 | 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 |
246 | current system. To find which embeddable backends might be supported on |
229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
230 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
231 | |
249 | |
232 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
233 | |
251 | |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
235 | |
253 | |
236 | Sets the allocation function to use (the prototype is similar - the |
254 | 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 |
255 | 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 |
256 | 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 |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
265 | } |
283 | } |
266 | |
284 | |
267 | ... |
285 | ... |
268 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
269 | |
287 | |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
271 | |
289 | |
272 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
273 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
274 | indicating the system call or subsystem causing the problem. If this |
292 | 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 |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
287 | } |
305 | } |
288 | |
306 | |
289 | ... |
307 | ... |
290 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
291 | |
309 | |
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310 | =item ev_feed_signal (int signum) |
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311 | |
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312 | This function can be used to "simulate" a signal receive. It is completely |
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313 | safe to call this function at any time, from any context, including signal |
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314 | handlers or random threads. |
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315 | |
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316 | Its main use is to customise signal handling in your process, especially |
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317 | in the presence of threads. For example, you could block signals |
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318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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319 | creating any loops), and in one thread, use C<sigwait> or any other |
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320 | mechanism to wait for signals, then "deliver" them to libev by calling |
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321 | C<ev_feed_signal>. |
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322 | |
292 | =back |
323 | =back |
293 | |
324 | |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
295 | |
326 | |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
327 | 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> |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
298 | I<function>). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
299 | |
330 | |
300 | The library knows two types of such loops, the I<default> loop, which |
331 | The library knows two types of such loops, the I<default> loop, which |
301 | supports signals and child events, and dynamically created loops which do |
332 | supports child process events, and dynamically created event loops which |
302 | not. |
333 | do not. |
303 | |
334 | |
304 | =over 4 |
335 | =over 4 |
305 | |
336 | |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
307 | |
338 | |
308 | This will initialise the default event loop if it hasn't been initialised |
339 | This returns the "default" event loop object, which is what you should |
309 | yet and return it. If the default loop could not be initialised, returns |
340 | normally use when you just need "the event loop". Event loop objects and |
310 | false. If it already was initialised it simply returns it (and ignores the |
341 | the C<flags> parameter are described in more detail in the entry for |
311 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
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343 | |
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344 | If the default loop is already initialised then this function simply |
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345 | returns it (and ignores the flags. If that is troubling you, check |
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346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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347 | flags, which should almost always be C<0>, unless the caller is also the |
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348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
312 | |
349 | |
313 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
314 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
315 | |
352 | |
316 | Note that this function is I<not> thread-safe, so if you want to use it |
353 | Note that this function is I<not> thread-safe, so if you want to use it |
317 | from multiple threads, you have to lock (note also that this is unlikely, |
354 | from multiple threads, you have to employ some kind of mutex (note also |
318 | as loops cannot be shared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
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356 | threads anyway). |
319 | |
357 | |
320 | The default loop is the only loop that can handle C<ev_signal> and |
358 | The default loop is the only loop that can handle C<ev_child> watchers, |
321 | C<ev_child> watchers, and to do this, it always registers a handler |
359 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
322 | for C<SIGCHLD>. If this is a problem for your application you can either |
360 | a problem for your application you can either create a dynamic loop with |
323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
361 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
324 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
325 | C<ev_default_init>. |
363 | |
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364 | Example: This is the most typical usage. |
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365 | |
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366 | if (!ev_default_loop (0)) |
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367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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368 | |
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369 | Example: Restrict libev to the select and poll backends, and do not allow |
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370 | environment settings to be taken into account: |
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371 | |
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372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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373 | |
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374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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375 | |
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376 | This will create and initialise a new event loop object. If the loop |
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377 | could not be initialised, returns false. |
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378 | |
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379 | This function is thread-safe, and one common way to use libev with |
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380 | threads is indeed to create one loop per thread, and using the default |
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381 | loop in the "main" or "initial" thread. |
326 | |
382 | |
327 | The flags argument can be used to specify special behaviour or specific |
383 | The flags argument can be used to specify special behaviour or specific |
328 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
329 | |
385 | |
330 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
345 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, or to work |
346 | around bugs. |
402 | around bugs. |
347 | |
403 | |
348 | =item C<EVFLAG_FORKCHECK> |
404 | =item C<EVFLAG_FORKCHECK> |
349 | |
405 | |
350 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
406 | 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 |
407 | make libev check for a fork in each iteration by enabling this flag. |
352 | enabling this flag. |
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353 | |
408 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
409 | 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 |
410 | 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 |
411 | 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 |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
366 | environment variable. |
421 | environment variable. |
367 | |
422 | |
368 | =item C<EVFLAG_NOINOTIFY> |
423 | =item C<EVFLAG_NOINOTIFY> |
369 | |
424 | |
370 | When this flag is specified, then libev will not attempt to use the |
425 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
426 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
427 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
429 | |
375 | =item C<EVFLAG_SIGNALFD> |
430 | =item C<EVFLAG_SIGNALFD> |
376 | |
431 | |
377 | When this flag is specified, then libev will attempt to use the |
432 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
433 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
379 | delivers signals synchronously, which makes it both faster and might make |
434 | delivers signals synchronously, which makes it both faster and might make |
380 | it possible to get the queued signal data. It can also simplify signal |
435 | it possible to get the queued signal data. It can also simplify signal |
381 | handling with threads, as long as you properly block signals in your |
436 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
437 | threads that are not interested in handling them. |
383 | |
438 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
439 | Signalfd will not be used by default as this changes your signal mask, and |
385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
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442 | |
|
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443 | =item C<EVFLAG_NOSIGMASK> |
|
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444 | |
|
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445 | When this flag is specified, then libev will avoid to modify the signal |
|
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446 | mask. Specifically, this means you have to make sure signals are unblocked |
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447 | when you want to receive them. |
|
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448 | |
|
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449 | This behaviour is useful when you want to do your own signal handling, or |
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450 | want to handle signals only in specific threads and want to avoid libev |
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451 | unblocking the signals. |
|
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452 | |
|
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453 | It's also required by POSIX in a threaded program, as libev calls |
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454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
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455 | |
|
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456 | This flag's behaviour will become the default in future versions of libev. |
387 | |
457 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
459 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
420 | |
490 | |
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
422 | kernels). |
492 | kernels). |
423 | |
493 | |
424 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
425 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
427 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
428 | |
498 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
433 | so on. The biggest issue is fork races, however - if a program forks then |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
434 | I<both> parent and child process have to recreate the epoll set, which can |
506 | forks then I<both> parent and child process have to recreate the epoll |
435 | take considerable time (one syscall per file descriptor) and is of course |
507 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
508 | and is of course hard to detect. |
437 | |
509 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
440 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
441 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
443 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
444 | events to filter out spurious ones, recreating the set when required. |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
520 | not least, it also refuses to work with some file descriptors which work |
|
|
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
522 | |
|
|
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
445 | |
526 | |
446 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
447 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
448 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
449 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
486 | |
567 | |
487 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
488 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
489 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
490 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
491 | two event changes per incident. Support for C<fork ()> is very bad (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
492 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
493 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
494 | |
575 | |
495 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
496 | |
577 | |
497 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
498 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
515 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
516 | |
597 | |
517 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
518 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
519 | |
600 | |
520 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
521 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
522 | blocking when no data (or space) is available. |
|
|
523 | |
|
|
524 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
525 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
526 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
527 | might perform better. |
604 | might perform better. |
528 | |
605 | |
529 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
530 | notifications, this backend actually performed fully to specification |
|
|
531 | in all tests and is fully embeddable, which is a rare feat among the |
607 | specification in all tests and is fully embeddable, which is a rare feat |
532 | OS-specific backends (I vastly prefer correctness over speed hacks). |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
533 | |
620 | |
534 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
535 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
536 | |
623 | |
537 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
538 | |
625 | |
539 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
540 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
541 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
542 | |
629 | |
543 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
544 | |
639 | |
545 | =back |
640 | =back |
546 | |
641 | |
547 | If one or more of the backend flags are or'ed into the flags value, |
642 | If one or more of the backend flags are or'ed into the flags value, |
548 | then only these backends will be tried (in the reverse order as listed |
643 | then only these backends will be tried (in the reverse order as listed |
549 | here). If none are specified, all backends in C<ev_recommended_backends |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
550 | ()> will be tried. |
645 | ()> will be tried. |
551 | |
646 | |
552 | Example: This is the most typical usage. |
|
|
553 | |
|
|
554 | if (!ev_default_loop (0)) |
|
|
555 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
556 | |
|
|
557 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
558 | environment settings to be taken into account: |
|
|
559 | |
|
|
560 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
561 | |
|
|
562 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
563 | used if available (warning, breaks stuff, best use only with your own |
|
|
564 | private event loop and only if you know the OS supports your types of |
|
|
565 | fds): |
|
|
566 | |
|
|
567 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
568 | |
|
|
569 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
570 | |
|
|
571 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
572 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
573 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
574 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
575 | |
|
|
576 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
577 | libev with threads is indeed to create one loop per thread, and using the |
|
|
578 | default loop in the "main" or "initial" thread. |
|
|
579 | |
|
|
580 | Example: Try to create a event loop that uses epoll and nothing else. |
647 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
648 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
650 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
652 | |
|
|
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
654 | used if available. |
|
|
655 | |
|
|
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
657 | |
586 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
587 | |
659 | |
588 | Destroys the default loop again (frees all memory and kernel state |
660 | Destroys an event loop object (frees all memory and kernel state |
589 | etc.). None of the active event watchers will be stopped in the normal |
661 | etc.). None of the active event watchers will be stopped in the normal |
590 | sense, so e.g. C<ev_is_active> might still return true. It is your |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
591 | responsibility to either stop all watchers cleanly yourself I<before> |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | calling this function, or cope with the fact afterwards (which is usually |
664 | calling this function, or cope with the fact afterwards (which is usually |
593 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
665 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
… | |
… | |
595 | |
667 | |
596 | Note that certain global state, such as signal state (and installed signal |
668 | Note that certain global state, such as signal state (and installed signal |
597 | handlers), will not be freed by this function, and related watchers (such |
669 | handlers), will not be freed by this function, and related watchers (such |
598 | as signal and child watchers) would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
599 | |
671 | |
600 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
601 | rare occasion where you really need to free e.g. the signal handling |
673 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
674 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
675 | |
|
|
676 | Note that it is not advisable to call this function on the default loop |
|
|
677 | except in the rare occasion where you really need to free its resources. |
602 | pipe fds. If you need dynamically allocated loops it is better to use |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
603 | C<ev_loop_new> and C<ev_loop_destroy>. |
679 | and C<ev_loop_destroy>. |
604 | |
680 | |
605 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
606 | |
682 | |
607 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
608 | earlier call to C<ev_loop_new>. |
|
|
609 | |
|
|
610 | =item ev_default_fork () |
|
|
611 | |
|
|
612 | This function sets a flag that causes subsequent C<ev_loop> iterations |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
613 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
614 | name, you can call it anytime, but it makes most sense after forking, in |
685 | name, you can call it anytime, but it makes most sense after forking, in |
615 | the child process (or both child and parent, but that again makes little |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
616 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
617 | functions, and it will only take effect at the next C<ev_loop> iteration. |
688 | |
|
|
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
692 | during fork. |
618 | |
693 | |
619 | On the other hand, you only need to call this function in the child |
694 | On the other hand, you only need to call this function in the child |
620 | process if and only if you want to use the event library in the child. If |
695 | process if and only if you want to use the event loop in the child. If |
621 | you just fork+exec, you don't have to call it at all. |
696 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
697 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
698 | difference, but libev will usually detect this case on its own and do a |
|
|
699 | costly reset of the backend). |
622 | |
700 | |
623 | The function itself is quite fast and it's usually not a problem to call |
701 | The function itself is quite fast and it's usually not a problem to call |
624 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
625 | quite nicely into a call to C<pthread_atfork>: |
|
|
626 | |
703 | |
|
|
704 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
705 | using pthreads. |
|
|
706 | |
|
|
707 | static void |
|
|
708 | post_fork_child (void) |
|
|
709 | { |
|
|
710 | ev_loop_fork (EV_DEFAULT); |
|
|
711 | } |
|
|
712 | |
|
|
713 | ... |
627 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
628 | |
|
|
629 | =item ev_loop_fork (loop) |
|
|
630 | |
|
|
631 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
632 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
633 | after fork that you want to re-use in the child, and how you do this is |
|
|
634 | entirely your own problem. |
|
|
635 | |
715 | |
636 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
637 | |
717 | |
638 | Returns true when the given loop is, in fact, the default loop, and false |
718 | Returns true when the given loop is, in fact, the default loop, and false |
639 | otherwise. |
719 | otherwise. |
640 | |
720 | |
641 | =item unsigned int ev_loop_count (loop) |
721 | =item unsigned int ev_iteration (loop) |
642 | |
722 | |
643 | Returns the count of loop iterations for the loop, which is identical to |
723 | Returns the current iteration count for the event loop, which is identical |
644 | the number of times libev did poll for new events. It starts at C<0> and |
724 | to the number of times libev did poll for new events. It starts at C<0> |
645 | happily wraps around with enough iterations. |
725 | and happily wraps around with enough iterations. |
646 | |
726 | |
647 | This value can sometimes be useful as a generation counter of sorts (it |
727 | This value can sometimes be useful as a generation counter of sorts (it |
648 | "ticks" the number of loop iterations), as it roughly corresponds with |
728 | "ticks" the number of loop iterations), as it roughly corresponds with |
649 | C<ev_prepare> and C<ev_check> calls. |
729 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
730 | prepare and check phases. |
650 | |
731 | |
651 | =item unsigned int ev_loop_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
652 | |
733 | |
653 | Returns the number of times C<ev_loop> was entered minus the number of |
734 | Returns the number of times C<ev_run> was entered minus the number of |
654 | times C<ev_loop> was exited, in other words, the recursion depth. |
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
655 | |
736 | |
656 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
737 | Outside C<ev_run>, this number is zero. In a callback, this number is |
657 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
658 | in which case it is higher. |
739 | in which case it is higher. |
659 | |
740 | |
660 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
661 | etc.), doesn't count as exit. |
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
662 | |
745 | |
663 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
664 | |
747 | |
665 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
666 | use. |
749 | use. |
… | |
… | |
675 | |
758 | |
676 | =item ev_now_update (loop) |
759 | =item ev_now_update (loop) |
677 | |
760 | |
678 | Establishes the current time by querying the kernel, updating the time |
761 | Establishes the current time by querying the kernel, updating the time |
679 | returned by C<ev_now ()> in the progress. This is a costly operation and |
762 | returned by C<ev_now ()> in the progress. This is a costly operation and |
680 | is usually done automatically within C<ev_loop ()>. |
763 | is usually done automatically within C<ev_run ()>. |
681 | |
764 | |
682 | This function is rarely useful, but when some event callback runs for a |
765 | This function is rarely useful, but when some event callback runs for a |
683 | very long time without entering the event loop, updating libev's idea of |
766 | very long time without entering the event loop, updating libev's idea of |
684 | the current time is a good idea. |
767 | the current time is a good idea. |
685 | |
768 | |
… | |
… | |
687 | |
770 | |
688 | =item ev_suspend (loop) |
771 | =item ev_suspend (loop) |
689 | |
772 | |
690 | =item ev_resume (loop) |
773 | =item ev_resume (loop) |
691 | |
774 | |
692 | These two functions suspend and resume a loop, for use when the loop is |
775 | These two functions suspend and resume an event loop, for use when the |
693 | not used for a while and timeouts should not be processed. |
776 | loop is not used for a while and timeouts should not be processed. |
694 | |
777 | |
695 | A typical use case would be an interactive program such as a game: When |
778 | A typical use case would be an interactive program such as a game: When |
696 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
779 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
697 | would be best to handle timeouts as if no time had actually passed while |
780 | would be best to handle timeouts as if no time had actually passed while |
698 | the program was suspended. This can be achieved by calling C<ev_suspend> |
781 | the program was suspended. This can be achieved by calling C<ev_suspend> |
… | |
… | |
700 | C<ev_resume> directly afterwards to resume timer processing. |
783 | C<ev_resume> directly afterwards to resume timer processing. |
701 | |
784 | |
702 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
785 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
703 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
786 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
704 | will be rescheduled (that is, they will lose any events that would have |
787 | will be rescheduled (that is, they will lose any events that would have |
705 | occured while suspended). |
788 | occurred while suspended). |
706 | |
789 | |
707 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
790 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
708 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
791 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
709 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
710 | |
793 | |
711 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
712 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
713 | |
796 | |
714 | =item ev_loop (loop, int flags) |
797 | =item ev_run (loop, int flags) |
715 | |
798 | |
716 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
717 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
718 | handling events. |
801 | handling events. It will ask the operating system for any new events, call |
|
|
802 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
803 | is why event loops are called I<loops>. |
719 | |
804 | |
720 | If the flags argument is specified as C<0>, it will not return until |
805 | If the flags argument is specified as C<0>, it will keep handling events |
721 | either no event watchers are active anymore or C<ev_unloop> was called. |
806 | until either no event watchers are active anymore or C<ev_break> was |
|
|
807 | called. |
722 | |
808 | |
723 | Please note that an explicit C<ev_unloop> is usually better than |
809 | Please note that an explicit C<ev_break> is usually better than |
724 | relying on all watchers to be stopped when deciding when a program has |
810 | relying on all watchers to be stopped when deciding when a program has |
725 | finished (especially in interactive programs), but having a program |
811 | finished (especially in interactive programs), but having a program |
726 | that automatically loops as long as it has to and no longer by virtue |
812 | that automatically loops as long as it has to and no longer by virtue |
727 | of relying on its watchers stopping correctly, that is truly a thing of |
813 | of relying on its watchers stopping correctly, that is truly a thing of |
728 | beauty. |
814 | beauty. |
729 | |
815 | |
|
|
816 | This function is also I<mostly> exception-safe - you can break out of |
|
|
817 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
818 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
819 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
820 | |
730 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
821 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
731 | those events and any already outstanding ones, but will not block your |
822 | those events and any already outstanding ones, but will not wait and |
732 | process in case there are no events and will return after one iteration of |
823 | block your process in case there are no events and will return after one |
733 | the loop. |
824 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
825 | events while doing lengthy calculations, to keep the program responsive. |
734 | |
826 | |
735 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
827 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
736 | necessary) and will handle those and any already outstanding ones. It |
828 | necessary) and will handle those and any already outstanding ones. It |
737 | will block your process until at least one new event arrives (which could |
829 | will block your process until at least one new event arrives (which could |
738 | be an event internal to libev itself, so there is no guarantee that a |
830 | be an event internal to libev itself, so there is no guarantee that a |
739 | user-registered callback will be called), and will return after one |
831 | user-registered callback will be called), and will return after one |
740 | iteration of the loop. |
832 | iteration of the loop. |
741 | |
833 | |
742 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
743 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
744 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
745 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
746 | |
838 | |
747 | Here are the gory details of what C<ev_loop> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
748 | |
842 | |
|
|
843 | - Increment loop depth. |
|
|
844 | - Reset the ev_break status. |
749 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
|
|
846 | LOOP: |
750 | * If EVFLAG_FORKCHECK was used, check for a fork. |
847 | - If EVFLAG_FORKCHECK was used, check for a fork. |
751 | - If a fork was detected (by any means), queue and call all fork watchers. |
848 | - If a fork was detected (by any means), queue and call all fork watchers. |
752 | - Queue and call all prepare watchers. |
849 | - Queue and call all prepare watchers. |
|
|
850 | - If ev_break was called, goto FINISH. |
753 | - If we have been forked, detach and recreate the kernel state |
851 | - If we have been forked, detach and recreate the kernel state |
754 | as to not disturb the other process. |
852 | as to not disturb the other process. |
755 | - Update the kernel state with all outstanding changes. |
853 | - Update the kernel state with all outstanding changes. |
756 | - Update the "event loop time" (ev_now ()). |
854 | - Update the "event loop time" (ev_now ()). |
757 | - Calculate for how long to sleep or block, if at all |
855 | - Calculate for how long to sleep or block, if at all |
758 | (active idle watchers, EVLOOP_NONBLOCK or not having |
856 | (active idle watchers, EVRUN_NOWAIT or not having |
759 | any active watchers at all will result in not sleeping). |
857 | any active watchers at all will result in not sleeping). |
760 | - Sleep if the I/O and timer collect interval say so. |
858 | - Sleep if the I/O and timer collect interval say so. |
|
|
859 | - Increment loop iteration counter. |
761 | - Block the process, waiting for any events. |
860 | - Block the process, waiting for any events. |
762 | - Queue all outstanding I/O (fd) events. |
861 | - Queue all outstanding I/O (fd) events. |
763 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
862 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
764 | - Queue all expired timers. |
863 | - Queue all expired timers. |
765 | - Queue all expired periodics. |
864 | - Queue all expired periodics. |
766 | - Unless any events are pending now, queue all idle watchers. |
865 | - Queue all idle watchers with priority higher than that of pending events. |
767 | - Queue all check watchers. |
866 | - Queue all check watchers. |
768 | - Call all queued watchers in reverse order (i.e. check watchers first). |
867 | - Call all queued watchers in reverse order (i.e. check watchers first). |
769 | Signals and child watchers are implemented as I/O watchers, and will |
868 | Signals and child watchers are implemented as I/O watchers, and will |
770 | be handled here by queueing them when their watcher gets executed. |
869 | be handled here by queueing them when their watcher gets executed. |
771 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
870 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
772 | were used, or there are no active watchers, return, otherwise |
871 | were used, or there are no active watchers, goto FINISH, otherwise |
773 | continue with step *. |
872 | continue with step LOOP. |
|
|
873 | FINISH: |
|
|
874 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
875 | - Decrement the loop depth. |
|
|
876 | - Return. |
774 | |
877 | |
775 | Example: Queue some jobs and then loop until no events are outstanding |
878 | Example: Queue some jobs and then loop until no events are outstanding |
776 | anymore. |
879 | anymore. |
777 | |
880 | |
778 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
779 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
780 | ev_loop (my_loop, 0); |
883 | ev_run (my_loop, 0); |
781 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
782 | |
885 | |
783 | =item ev_unloop (loop, how) |
886 | =item ev_break (loop, how) |
784 | |
887 | |
785 | Can be used to make a call to C<ev_loop> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
786 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
787 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
890 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
788 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
891 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
789 | |
892 | |
790 | This "unloop state" will be cleared when entering C<ev_loop> again. |
893 | This "break state" will be cleared on the next call to C<ev_run>. |
791 | |
894 | |
792 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
895 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
896 | which case it will have no effect. |
793 | |
897 | |
794 | =item ev_ref (loop) |
898 | =item ev_ref (loop) |
795 | |
899 | |
796 | =item ev_unref (loop) |
900 | =item ev_unref (loop) |
797 | |
901 | |
798 | Ref/unref can be used to add or remove a reference count on the event |
902 | Ref/unref can be used to add or remove a reference count on the event |
799 | loop: Every watcher keeps one reference, and as long as the reference |
903 | loop: Every watcher keeps one reference, and as long as the reference |
800 | count is nonzero, C<ev_loop> will not return on its own. |
904 | count is nonzero, C<ev_run> will not return on its own. |
801 | |
905 | |
802 | This is useful when you have a watcher that you never intend to |
906 | This is useful when you have a watcher that you never intend to |
803 | unregister, but that nevertheless should not keep C<ev_loop> from |
907 | unregister, but that nevertheless should not keep C<ev_run> from |
804 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
908 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
805 | before stopping it. |
909 | before stopping it. |
806 | |
910 | |
807 | As an example, libev itself uses this for its internal signal pipe: It |
911 | As an example, libev itself uses this for its internal signal pipe: It |
808 | is not visible to the libev user and should not keep C<ev_loop> from |
912 | is not visible to the libev user and should not keep C<ev_run> from |
809 | exiting if no event watchers registered by it are active. It is also an |
913 | exiting if no event watchers registered by it are active. It is also an |
810 | excellent way to do this for generic recurring timers or from within |
914 | excellent way to do this for generic recurring timers or from within |
811 | third-party libraries. Just remember to I<unref after start> and I<ref |
915 | third-party libraries. Just remember to I<unref after start> and I<ref |
812 | before stop> (but only if the watcher wasn't active before, or was active |
916 | before stop> (but only if the watcher wasn't active before, or was active |
813 | before, respectively. Note also that libev might stop watchers itself |
917 | before, respectively. Note also that libev might stop watchers itself |
814 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
918 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
815 | in the callback). |
919 | in the callback). |
816 | |
920 | |
817 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
921 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
818 | running when nothing else is active. |
922 | running when nothing else is active. |
819 | |
923 | |
820 | ev_signal exitsig; |
924 | ev_signal exitsig; |
821 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
925 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
822 | ev_signal_start (loop, &exitsig); |
926 | ev_signal_start (loop, &exitsig); |
823 | evf_unref (loop); |
927 | ev_unref (loop); |
824 | |
928 | |
825 | Example: For some weird reason, unregister the above signal handler again. |
929 | Example: For some weird reason, unregister the above signal handler again. |
826 | |
930 | |
827 | ev_ref (loop); |
931 | ev_ref (loop); |
828 | ev_signal_stop (loop, &exitsig); |
932 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
848 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
849 | |
953 | |
850 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
851 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
852 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
853 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
854 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
855 | sleep time ensures that libev will not poll for I/O events more often then |
959 | sleep time ensures that libev will not poll for I/O events more often then |
856 | once per this interval, on average. |
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
857 | |
962 | |
858 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
859 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
860 | latency/jitter/inexactness (the watcher callback will be called |
965 | latency/jitter/inexactness (the watcher callback will be called |
861 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
867 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
972 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
868 | as this approaches the timing granularity of most systems. Note that if |
973 | as this approaches the timing granularity of most systems. Note that if |
869 | you do transactions with the outside world and you can't increase the |
974 | you do transactions with the outside world and you can't increase the |
870 | parallelity, then this setting will limit your transaction rate (if you |
975 | parallelity, then this setting will limit your transaction rate (if you |
871 | need to poll once per transaction and the I/O collect interval is 0.01, |
976 | need to poll once per transaction and the I/O collect interval is 0.01, |
872 | then you can't do more than 100 transations per second). |
977 | then you can't do more than 100 transactions per second). |
873 | |
978 | |
874 | Setting the I<timeout collect interval> can improve the opportunity for |
979 | Setting the I<timeout collect interval> can improve the opportunity for |
875 | saving power, as the program will "bundle" timer callback invocations that |
980 | saving power, as the program will "bundle" timer callback invocations that |
876 | are "near" in time together, by delaying some, thus reducing the number of |
981 | are "near" in time together, by delaying some, thus reducing the number of |
877 | times the process sleeps and wakes up again. Another useful technique to |
982 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
885 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
990 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
886 | |
991 | |
887 | =item ev_invoke_pending (loop) |
992 | =item ev_invoke_pending (loop) |
888 | |
993 | |
889 | This call will simply invoke all pending watchers while resetting their |
994 | This call will simply invoke all pending watchers while resetting their |
890 | pending state. Normally, C<ev_loop> does this automatically when required, |
995 | pending state. Normally, C<ev_run> does this automatically when required, |
891 | but when overriding the invoke callback this call comes handy. |
996 | but when overriding the invoke callback this call comes handy. This |
|
|
997 | function can be invoked from a watcher - this can be useful for example |
|
|
998 | when you want to do some lengthy calculation and want to pass further |
|
|
999 | event handling to another thread (you still have to make sure only one |
|
|
1000 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
892 | |
1001 | |
893 | =item int ev_pending_count (loop) |
1002 | =item int ev_pending_count (loop) |
894 | |
1003 | |
895 | Returns the number of pending watchers - zero indicates that no watchers |
1004 | Returns the number of pending watchers - zero indicates that no watchers |
896 | are pending. |
1005 | are pending. |
897 | |
1006 | |
898 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
1007 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
899 | |
1008 | |
900 | This overrides the invoke pending functionality of the loop: Instead of |
1009 | This overrides the invoke pending functionality of the loop: Instead of |
901 | invoking all pending watchers when there are any, C<ev_loop> will call |
1010 | invoking all pending watchers when there are any, C<ev_run> will call |
902 | this callback instead. This is useful, for example, when you want to |
1011 | this callback instead. This is useful, for example, when you want to |
903 | invoke the actual watchers inside another context (another thread etc.). |
1012 | invoke the actual watchers inside another context (another thread etc.). |
904 | |
1013 | |
905 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1014 | If you want to reset the callback, use C<ev_invoke_pending> as new |
906 | callback. |
1015 | callback. |
… | |
… | |
909 | |
1018 | |
910 | Sometimes you want to share the same loop between multiple threads. This |
1019 | Sometimes you want to share the same loop between multiple threads. This |
911 | can be done relatively simply by putting mutex_lock/unlock calls around |
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
912 | each call to a libev function. |
1021 | each call to a libev function. |
913 | |
1022 | |
914 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
915 | wait for it to return. One way around this is to wake up the loop via |
1024 | to wait for it to return. One way around this is to wake up the event |
916 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
1025 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
917 | and I<acquire> callbacks on the loop. |
1026 | I<release> and I<acquire> callbacks on the loop. |
918 | |
1027 | |
919 | When set, then C<release> will be called just before the thread is |
1028 | When set, then C<release> will be called just before the thread is |
920 | suspended waiting for new events, and C<acquire> is called just |
1029 | suspended waiting for new events, and C<acquire> is called just |
921 | afterwards. |
1030 | afterwards. |
922 | |
1031 | |
… | |
… | |
925 | |
1034 | |
926 | While event loop modifications are allowed between invocations of |
1035 | While event loop modifications are allowed between invocations of |
927 | C<release> and C<acquire> (that's their only purpose after all), no |
1036 | C<release> and C<acquire> (that's their only purpose after all), no |
928 | modifications done will affect the event loop, i.e. adding watchers will |
1037 | modifications done will affect the event loop, i.e. adding watchers will |
929 | have no effect on the set of file descriptors being watched, or the time |
1038 | have no effect on the set of file descriptors being watched, or the time |
930 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
1039 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
931 | to take note of any changes you made. |
1040 | to take note of any changes you made. |
932 | |
1041 | |
933 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
1042 | In theory, threads executing C<ev_run> will be async-cancel safe between |
934 | invocations of C<release> and C<acquire>. |
1043 | invocations of C<release> and C<acquire>. |
935 | |
1044 | |
936 | See also the locking example in the C<THREADS> section later in this |
1045 | See also the locking example in the C<THREADS> section later in this |
937 | document. |
1046 | document. |
938 | |
1047 | |
939 | =item ev_set_userdata (loop, void *data) |
1048 | =item ev_set_userdata (loop, void *data) |
940 | |
1049 | |
941 | =item ev_userdata (loop) |
1050 | =item void *ev_userdata (loop) |
942 | |
1051 | |
943 | Set and retrieve a single C<void *> associated with a loop. When |
1052 | Set and retrieve a single C<void *> associated with a loop. When |
944 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1053 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
945 | C<0.> |
1054 | C<0>. |
946 | |
1055 | |
947 | These two functions can be used to associate arbitrary data with a loop, |
1056 | These two functions can be used to associate arbitrary data with a loop, |
948 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1057 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
949 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1058 | C<acquire> callbacks described above, but of course can be (ab-)used for |
950 | any other purpose as well. |
1059 | any other purpose as well. |
951 | |
1060 | |
952 | =item ev_loop_verify (loop) |
1061 | =item ev_verify (loop) |
953 | |
1062 | |
954 | This function only does something when C<EV_VERIFY> support has been |
1063 | This function only does something when C<EV_VERIFY> support has been |
955 | compiled in, which is the default for non-minimal builds. It tries to go |
1064 | compiled in, which is the default for non-minimal builds. It tries to go |
956 | through all internal structures and checks them for validity. If anything |
1065 | through all internal structures and checks them for validity. If anything |
957 | is found to be inconsistent, it will print an error message to standard |
1066 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
968 | |
1077 | |
969 | In the following description, uppercase C<TYPE> in names stands for the |
1078 | In the following description, uppercase C<TYPE> in names stands for the |
970 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1079 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
971 | watchers and C<ev_io_start> for I/O watchers. |
1080 | watchers and C<ev_io_start> for I/O watchers. |
972 | |
1081 | |
973 | A watcher is a structure that you create and register to record your |
1082 | A watcher is an opaque structure that you allocate and register to record |
974 | interest in some event. For instance, if you want to wait for STDIN to |
1083 | your interest in some event. To make a concrete example, imagine you want |
975 | become readable, you would create an C<ev_io> watcher for that: |
1084 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1085 | for that: |
976 | |
1086 | |
977 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1087 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
978 | { |
1088 | { |
979 | ev_io_stop (w); |
1089 | ev_io_stop (w); |
980 | ev_unloop (loop, EVUNLOOP_ALL); |
1090 | ev_break (loop, EVBREAK_ALL); |
981 | } |
1091 | } |
982 | |
1092 | |
983 | struct ev_loop *loop = ev_default_loop (0); |
1093 | struct ev_loop *loop = ev_default_loop (0); |
984 | |
1094 | |
985 | ev_io stdin_watcher; |
1095 | ev_io stdin_watcher; |
986 | |
1096 | |
987 | ev_init (&stdin_watcher, my_cb); |
1097 | ev_init (&stdin_watcher, my_cb); |
988 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1098 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
989 | ev_io_start (loop, &stdin_watcher); |
1099 | ev_io_start (loop, &stdin_watcher); |
990 | |
1100 | |
991 | ev_loop (loop, 0); |
1101 | ev_run (loop, 0); |
992 | |
1102 | |
993 | As you can see, you are responsible for allocating the memory for your |
1103 | As you can see, you are responsible for allocating the memory for your |
994 | watcher structures (and it is I<usually> a bad idea to do this on the |
1104 | watcher structures (and it is I<usually> a bad idea to do this on the |
995 | stack). |
1105 | stack). |
996 | |
1106 | |
997 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1107 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
998 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1108 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
999 | |
1109 | |
1000 | Each watcher structure must be initialised by a call to C<ev_init |
1110 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
1001 | (watcher *, callback)>, which expects a callback to be provided. This |
1111 | *, callback)>, which expects a callback to be provided. This callback is |
1002 | callback gets invoked each time the event occurs (or, in the case of I/O |
1112 | invoked each time the event occurs (or, in the case of I/O watchers, each |
1003 | watchers, each time the event loop detects that the file descriptor given |
1113 | time the event loop detects that the file descriptor given is readable |
1004 | is readable and/or writable). |
1114 | and/or writable). |
1005 | |
1115 | |
1006 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1116 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1007 | macro to configure it, with arguments specific to the watcher type. There |
1117 | macro to configure it, with arguments specific to the watcher type. There |
1008 | is also a macro to combine initialisation and setting in one call: C<< |
1118 | is also a macro to combine initialisation and setting in one call: C<< |
1009 | ev_TYPE_init (watcher *, callback, ...) >>. |
1119 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
1032 | =item C<EV_WRITE> |
1142 | =item C<EV_WRITE> |
1033 | |
1143 | |
1034 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1144 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1035 | writable. |
1145 | writable. |
1036 | |
1146 | |
1037 | =item C<EV_TIMEOUT> |
1147 | =item C<EV_TIMER> |
1038 | |
1148 | |
1039 | The C<ev_timer> watcher has timed out. |
1149 | The C<ev_timer> watcher has timed out. |
1040 | |
1150 | |
1041 | =item C<EV_PERIODIC> |
1151 | =item C<EV_PERIODIC> |
1042 | |
1152 | |
… | |
… | |
1060 | |
1170 | |
1061 | =item C<EV_PREPARE> |
1171 | =item C<EV_PREPARE> |
1062 | |
1172 | |
1063 | =item C<EV_CHECK> |
1173 | =item C<EV_CHECK> |
1064 | |
1174 | |
1065 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1175 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1066 | to gather new events, and all C<ev_check> watchers are invoked just after |
1176 | to gather new events, and all C<ev_check> watchers are invoked just after |
1067 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1177 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1068 | received events. Callbacks of both watcher types can start and stop as |
1178 | received events. Callbacks of both watcher types can start and stop as |
1069 | many watchers as they want, and all of them will be taken into account |
1179 | many watchers as they want, and all of them will be taken into account |
1070 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1180 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1071 | C<ev_loop> from blocking). |
1181 | C<ev_run> from blocking). |
1072 | |
1182 | |
1073 | =item C<EV_EMBED> |
1183 | =item C<EV_EMBED> |
1074 | |
1184 | |
1075 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1185 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1076 | |
1186 | |
1077 | =item C<EV_FORK> |
1187 | =item C<EV_FORK> |
1078 | |
1188 | |
1079 | The event loop has been resumed in the child process after fork (see |
1189 | The event loop has been resumed in the child process after fork (see |
1080 | C<ev_fork>). |
1190 | C<ev_fork>). |
|
|
1191 | |
|
|
1192 | =item C<EV_CLEANUP> |
|
|
1193 | |
|
|
1194 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1081 | |
1195 | |
1082 | =item C<EV_ASYNC> |
1196 | =item C<EV_ASYNC> |
1083 | |
1197 | |
1084 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1198 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1085 | |
1199 | |
… | |
… | |
1258 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1259 | functions that do not need a watcher. |
1373 | functions that do not need a watcher. |
1260 | |
1374 | |
1261 | =back |
1375 | =back |
1262 | |
1376 | |
|
|
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1378 | OWN COMPOSITE WATCHERS> idioms. |
1263 | |
1379 | |
1264 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1380 | =head2 WATCHER STATES |
1265 | |
1381 | |
1266 | Each watcher has, by default, a member C<void *data> that you can change |
1382 | There are various watcher states mentioned throughout this manual - |
1267 | and read at any time: libev will completely ignore it. This can be used |
1383 | active, pending and so on. In this section these states and the rules to |
1268 | to associate arbitrary data with your watcher. If you need more data and |
1384 | transition between them will be described in more detail - and while these |
1269 | don't want to allocate memory and store a pointer to it in that data |
1385 | rules might look complicated, they usually do "the right thing". |
1270 | member, you can also "subclass" the watcher type and provide your own |
|
|
1271 | data: |
|
|
1272 | |
1386 | |
1273 | struct my_io |
1387 | =over 4 |
1274 | { |
|
|
1275 | ev_io io; |
|
|
1276 | int otherfd; |
|
|
1277 | void *somedata; |
|
|
1278 | struct whatever *mostinteresting; |
|
|
1279 | }; |
|
|
1280 | |
1388 | |
1281 | ... |
1389 | =item initialiased |
1282 | struct my_io w; |
|
|
1283 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1284 | |
1390 | |
1285 | And since your callback will be called with a pointer to the watcher, you |
1391 | Before a watcher can be registered with the event loop it has to be |
1286 | can cast it back to your own type: |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1287 | |
1394 | |
1288 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1395 | In this state it is simply some block of memory that is suitable for |
1289 | { |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
1290 | struct my_io *w = (struct my_io *)w_; |
1397 | will - as long as you either keep the memory contents intact, or call |
1291 | ... |
1398 | C<ev_TYPE_init> again. |
1292 | } |
|
|
1293 | |
1399 | |
1294 | More interesting and less C-conformant ways of casting your callback type |
1400 | =item started/running/active |
1295 | instead have been omitted. |
|
|
1296 | |
1401 | |
1297 | Another common scenario is to use some data structure with multiple |
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1298 | embedded watchers: |
1403 | property of the event loop, and is actively waiting for events. While in |
|
|
1404 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1405 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1406 | and call libev functions on it that are documented to work on active watchers. |
1299 | |
1407 | |
1300 | struct my_biggy |
1408 | =item pending |
1301 | { |
|
|
1302 | int some_data; |
|
|
1303 | ev_timer t1; |
|
|
1304 | ev_timer t2; |
|
|
1305 | } |
|
|
1306 | |
1409 | |
1307 | In this case getting the pointer to C<my_biggy> is a bit more |
1410 | If a watcher is active and libev determines that an event it is interested |
1308 | complicated: Either you store the address of your C<my_biggy> struct |
1411 | in has occurred (such as a timer expiring), it will become pending. It will |
1309 | in the C<data> member of the watcher (for woozies), or you need to use |
1412 | stay in this pending state until either it is stopped or its callback is |
1310 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1413 | about to be invoked, so it is not normally pending inside the watcher |
1311 | programmers): |
1414 | callback. |
1312 | |
1415 | |
1313 | #include <stddef.h> |
1416 | The watcher might or might not be active while it is pending (for example, |
|
|
1417 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1418 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1419 | but it is still property of the event loop at this time, so cannot be |
|
|
1420 | moved, freed or reused. And if it is active the rules described in the |
|
|
1421 | previous item still apply. |
1314 | |
1422 | |
1315 | static void |
1423 | It is also possible to feed an event on a watcher that is not active (e.g. |
1316 | t1_cb (EV_P_ ev_timer *w, int revents) |
1424 | via C<ev_feed_event>), in which case it becomes pending without being |
1317 | { |
1425 | active. |
1318 | struct my_biggy big = (struct my_biggy *) |
|
|
1319 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1320 | } |
|
|
1321 | |
1426 | |
1322 | static void |
1427 | =item stopped |
1323 | t2_cb (EV_P_ ev_timer *w, int revents) |
1428 | |
1324 | { |
1429 | A watcher can be stopped implicitly by libev (in which case it might still |
1325 | struct my_biggy big = (struct my_biggy *) |
1430 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1326 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1431 | latter will clear any pending state the watcher might be in, regardless |
1327 | } |
1432 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1433 | freeing it is often a good idea. |
|
|
1434 | |
|
|
1435 | While stopped (and not pending) the watcher is essentially in the |
|
|
1436 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
|
|
1439 | |
|
|
1440 | =back |
1328 | |
1441 | |
1329 | =head2 WATCHER PRIORITY MODELS |
1442 | =head2 WATCHER PRIORITY MODELS |
1330 | |
1443 | |
1331 | Many event loops support I<watcher priorities>, which are usually small |
1444 | Many event loops support I<watcher priorities>, which are usually small |
1332 | integers that influence the ordering of event callback invocation |
1445 | integers that influence the ordering of event callback invocation |
… | |
… | |
1375 | |
1488 | |
1376 | For example, to emulate how many other event libraries handle priorities, |
1489 | For example, to emulate how many other event libraries handle priorities, |
1377 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1490 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1378 | the normal watcher callback, you just start the idle watcher. The real |
1491 | the normal watcher callback, you just start the idle watcher. The real |
1379 | processing is done in the idle watcher callback. This causes libev to |
1492 | processing is done in the idle watcher callback. This causes libev to |
1380 | continously poll and process kernel event data for the watcher, but when |
1493 | continuously poll and process kernel event data for the watcher, but when |
1381 | the lock-out case is known to be rare (which in turn is rare :), this is |
1494 | the lock-out case is known to be rare (which in turn is rare :), this is |
1382 | workable. |
1495 | workable. |
1383 | |
1496 | |
1384 | Usually, however, the lock-out model implemented that way will perform |
1497 | Usually, however, the lock-out model implemented that way will perform |
1385 | miserably under the type of load it was designed to handle. In that case, |
1498 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1399 | { |
1512 | { |
1400 | // stop the I/O watcher, we received the event, but |
1513 | // stop the I/O watcher, we received the event, but |
1401 | // are not yet ready to handle it. |
1514 | // are not yet ready to handle it. |
1402 | ev_io_stop (EV_A_ w); |
1515 | ev_io_stop (EV_A_ w); |
1403 | |
1516 | |
1404 | // start the idle watcher to ahndle the actual event. |
1517 | // start the idle watcher to handle the actual event. |
1405 | // it will not be executed as long as other watchers |
1518 | // it will not be executed as long as other watchers |
1406 | // with the default priority are receiving events. |
1519 | // with the default priority are receiving events. |
1407 | ev_idle_start (EV_A_ &idle); |
1520 | ev_idle_start (EV_A_ &idle); |
1408 | } |
1521 | } |
1409 | |
1522 | |
… | |
… | |
1459 | In general you can register as many read and/or write event watchers per |
1572 | In general you can register as many read and/or write event watchers per |
1460 | fd as you want (as long as you don't confuse yourself). Setting all file |
1573 | fd as you want (as long as you don't confuse yourself). Setting all file |
1461 | descriptors to non-blocking mode is also usually a good idea (but not |
1574 | descriptors to non-blocking mode is also usually a good idea (but not |
1462 | required if you know what you are doing). |
1575 | required if you know what you are doing). |
1463 | |
1576 | |
1464 | If you cannot use non-blocking mode, then force the use of a |
|
|
1465 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1466 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1467 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1468 | files) - libev doesn't guarentee any specific behaviour in that case. |
|
|
1469 | |
|
|
1470 | Another thing you have to watch out for is that it is quite easy to |
1577 | Another thing you have to watch out for is that it is quite easy to |
1471 | receive "spurious" readiness notifications, that is your callback might |
1578 | receive "spurious" readiness notifications, that is, your callback might |
1472 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1579 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1473 | because there is no data. Not only are some backends known to create a |
1580 | because there is no data. It is very easy to get into this situation even |
1474 | lot of those (for example Solaris ports), it is very easy to get into |
1581 | with a relatively standard program structure. Thus it is best to always |
1475 | this situation even with a relatively standard program structure. Thus |
1582 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1476 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1477 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1583 | preferable to a program hanging until some data arrives. |
1478 | |
1584 | |
1479 | If you cannot run the fd in non-blocking mode (for example you should |
1585 | If you cannot run the fd in non-blocking mode (for example you should |
1480 | not play around with an Xlib connection), then you have to separately |
1586 | not play around with an Xlib connection), then you have to separately |
1481 | re-test whether a file descriptor is really ready with a known-to-be good |
1587 | re-test whether a file descriptor is really ready with a known-to-be good |
1482 | interface such as poll (fortunately in our Xlib example, Xlib already |
1588 | interface such as poll (fortunately in the case of Xlib, it already does |
1483 | does this on its own, so its quite safe to use). Some people additionally |
1589 | this on its own, so its quite safe to use). Some people additionally |
1484 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1590 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1485 | indefinitely. |
1591 | indefinitely. |
1486 | |
1592 | |
1487 | But really, best use non-blocking mode. |
1593 | But really, best use non-blocking mode. |
1488 | |
1594 | |
… | |
… | |
1516 | |
1622 | |
1517 | There is no workaround possible except not registering events |
1623 | There is no workaround possible except not registering events |
1518 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1624 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1519 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1625 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1520 | |
1626 | |
|
|
1627 | =head3 The special problem of files |
|
|
1628 | |
|
|
1629 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1630 | representing files, and expect it to become ready when their program |
|
|
1631 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1632 | |
|
|
1633 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1634 | notification as soon as the kernel knows whether and how much data is |
|
|
1635 | there, and in the case of open files, that's always the case, so you |
|
|
1636 | always get a readiness notification instantly, and your read (or possibly |
|
|
1637 | write) will still block on the disk I/O. |
|
|
1638 | |
|
|
1639 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1640 | devices and so on, there is another party (the sender) that delivers data |
|
|
1641 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1642 | will not send data on its own, simply because it doesn't know what you |
|
|
1643 | wish to read - you would first have to request some data. |
|
|
1644 | |
|
|
1645 | Since files are typically not-so-well supported by advanced notification |
|
|
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1647 | to files, even though you should not use it. The reason for this is |
|
|
1648 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1649 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1650 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1651 | F</dev/urandom>), and even though the file might better be served with |
|
|
1652 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1653 | it "just works" instead of freezing. |
|
|
1654 | |
|
|
1655 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1656 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1657 | when you rarely read from a file instead of from a socket, and want to |
|
|
1658 | reuse the same code path. |
|
|
1659 | |
1521 | =head3 The special problem of fork |
1660 | =head3 The special problem of fork |
1522 | |
1661 | |
1523 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1662 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1524 | useless behaviour. Libev fully supports fork, but needs to be told about |
1663 | useless behaviour. Libev fully supports fork, but needs to be told about |
1525 | it in the child. |
1664 | it in the child if you want to continue to use it in the child. |
1526 | |
1665 | |
1527 | To support fork in your programs, you either have to call |
1666 | To support fork in your child processes, you have to call C<ev_loop_fork |
1528 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1667 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1529 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1668 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1530 | C<EVBACKEND_POLL>. |
|
|
1531 | |
1669 | |
1532 | =head3 The special problem of SIGPIPE |
1670 | =head3 The special problem of SIGPIPE |
1533 | |
1671 | |
1534 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1672 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1535 | when writing to a pipe whose other end has been closed, your program gets |
1673 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1541 | somewhere, as that would have given you a big clue). |
1679 | somewhere, as that would have given you a big clue). |
1542 | |
1680 | |
1543 | =head3 The special problem of accept()ing when you can't |
1681 | =head3 The special problem of accept()ing when you can't |
1544 | |
1682 | |
1545 | Many implementations of the POSIX C<accept> function (for example, |
1683 | Many implementations of the POSIX C<accept> function (for example, |
1546 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
1684 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
1547 | connection from the pending queue in all error cases. |
1685 | connection from the pending queue in all error cases. |
1548 | |
1686 | |
1549 | For example, larger servers often run out of file descriptors (because |
1687 | For example, larger servers often run out of file descriptors (because |
1550 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1688 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
1551 | rejecting the connection, leading to libev signalling readiness on |
1689 | rejecting the connection, leading to libev signalling readiness on |
… | |
… | |
1617 | ... |
1755 | ... |
1618 | struct ev_loop *loop = ev_default_init (0); |
1756 | struct ev_loop *loop = ev_default_init (0); |
1619 | ev_io stdin_readable; |
1757 | ev_io stdin_readable; |
1620 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1758 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1621 | ev_io_start (loop, &stdin_readable); |
1759 | ev_io_start (loop, &stdin_readable); |
1622 | ev_loop (loop, 0); |
1760 | ev_run (loop, 0); |
1623 | |
1761 | |
1624 | |
1762 | |
1625 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1763 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1626 | |
1764 | |
1627 | Timer watchers are simple relative timers that generate an event after a |
1765 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1633 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1634 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
1635 | |
1773 | |
1636 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1637 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1638 | might introduce a small delay). If multiple timers become ready during the |
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
1639 | same loop iteration then the ones with earlier time-out values are invoked |
1778 | iteration then the ones with earlier time-out values are invoked before |
1640 | before ones of the same priority with later time-out values (but this is |
1779 | ones of the same priority with later time-out values (but this is no |
1641 | no longer true when a callback calls C<ev_loop> recursively). |
1780 | longer true when a callback calls C<ev_run> recursively). |
1642 | |
1781 | |
1643 | =head3 Be smart about timeouts |
1782 | =head3 Be smart about timeouts |
1644 | |
1783 | |
1645 | Many real-world problems involve some kind of timeout, usually for error |
1784 | Many real-world problems involve some kind of timeout, usually for error |
1646 | recovery. A typical example is an HTTP request - if the other side hangs, |
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1721 | |
1860 | |
1722 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1861 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1723 | but remember the time of last activity, and check for a real timeout only |
1862 | but remember the time of last activity, and check for a real timeout only |
1724 | within the callback: |
1863 | within the callback: |
1725 | |
1864 | |
|
|
1865 | ev_tstamp timeout = 60.; |
1726 | ev_tstamp last_activity; // time of last activity |
1866 | ev_tstamp last_activity; // time of last activity |
|
|
1867 | ev_timer timer; |
1727 | |
1868 | |
1728 | static void |
1869 | static void |
1729 | callback (EV_P_ ev_timer *w, int revents) |
1870 | callback (EV_P_ ev_timer *w, int revents) |
1730 | { |
1871 | { |
1731 | ev_tstamp now = ev_now (EV_A); |
1872 | // calculate when the timeout would happen |
1732 | ev_tstamp timeout = last_activity + 60.; |
1873 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1733 | |
1874 | |
1734 | // if last_activity + 60. is older than now, we did time out |
1875 | // if negative, it means we the timeout already occured |
1735 | if (timeout < now) |
1876 | if (after < 0.) |
1736 | { |
1877 | { |
1737 | // timeout occured, take action |
1878 | // timeout occurred, take action |
1738 | } |
1879 | } |
1739 | else |
1880 | else |
1740 | { |
1881 | { |
1741 | // callback was invoked, but there was some activity, re-arm |
1882 | // callback was invoked, but there was some recent |
1742 | // the watcher to fire in last_activity + 60, which is |
1883 | // activity. simply restart the timer to time out |
1743 | // guaranteed to be in the future, so "again" is positive: |
1884 | // after "after" seconds, which is the earliest time |
1744 | w->repeat = timeout - now; |
1885 | // the timeout can occur. |
|
|
1886 | ev_timer_set (w, after, 0.); |
1745 | ev_timer_again (EV_A_ w); |
1887 | ev_timer_start (EV_A_ w); |
1746 | } |
1888 | } |
1747 | } |
1889 | } |
1748 | |
1890 | |
1749 | To summarise the callback: first calculate the real timeout (defined |
1891 | To summarise the callback: first calculate in how many seconds the |
1750 | as "60 seconds after the last activity"), then check if that time has |
1892 | timeout will occur (by calculating the absolute time when it would occur, |
1751 | been reached, which means something I<did>, in fact, time out. Otherwise |
1893 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1752 | the callback was invoked too early (C<timeout> is in the future), so |
1894 | (EV_A)> from that). |
1753 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1754 | a timeout then. |
|
|
1755 | |
1895 | |
1756 | Note how C<ev_timer_again> is used, taking advantage of the |
1896 | If this value is negative, then we are already past the timeout, i.e. we |
1757 | C<ev_timer_again> optimisation when the timer is already running. |
1897 | timed out, and need to do whatever is needed in this case. |
|
|
1898 | |
|
|
1899 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1900 | and simply start the timer with this timeout value. |
|
|
1901 | |
|
|
1902 | In other words, each time the callback is invoked it will check whether |
|
|
1903 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1904 | again at the earliest time it could time out. Rinse. Repeat. |
1758 | |
1905 | |
1759 | This scheme causes more callback invocations (about one every 60 seconds |
1906 | This scheme causes more callback invocations (about one every 60 seconds |
1760 | minus half the average time between activity), but virtually no calls to |
1907 | minus half the average time between activity), but virtually no calls to |
1761 | libev to change the timeout. |
1908 | libev to change the timeout. |
1762 | |
1909 | |
1763 | To start the timer, simply initialise the watcher and set C<last_activity> |
1910 | To start the machinery, simply initialise the watcher and set |
1764 | to the current time (meaning we just have some activity :), then call the |
1911 | C<last_activity> to the current time (meaning there was some activity just |
1765 | callback, which will "do the right thing" and start the timer: |
1912 | now), then call the callback, which will "do the right thing" and start |
|
|
1913 | the timer: |
1766 | |
1914 | |
|
|
1915 | last_activity = ev_now (EV_A); |
1767 | ev_init (timer, callback); |
1916 | ev_init (&timer, callback); |
1768 | last_activity = ev_now (loop); |
1917 | callback (EV_A_ &timer, 0); |
1769 | callback (loop, timer, EV_TIMEOUT); |
|
|
1770 | |
1918 | |
1771 | And when there is some activity, simply store the current time in |
1919 | When there is some activity, simply store the current time in |
1772 | C<last_activity>, no libev calls at all: |
1920 | C<last_activity>, no libev calls at all: |
1773 | |
1921 | |
|
|
1922 | if (activity detected) |
1774 | last_actiivty = ev_now (loop); |
1923 | last_activity = ev_now (EV_A); |
|
|
1924 | |
|
|
1925 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1926 | providing a new value, stopping the timer and calling the callback, which |
|
|
1927 | will agaion do the right thing (for example, time out immediately :). |
|
|
1928 | |
|
|
1929 | timeout = new_value; |
|
|
1930 | ev_timer_stop (EV_A_ &timer); |
|
|
1931 | callback (EV_A_ &timer, 0); |
1775 | |
1932 | |
1776 | This technique is slightly more complex, but in most cases where the |
1933 | This technique is slightly more complex, but in most cases where the |
1777 | time-out is unlikely to be triggered, much more efficient. |
1934 | time-out is unlikely to be triggered, much more efficient. |
1778 | |
|
|
1779 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1780 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1781 | fix things for you. |
|
|
1782 | |
1935 | |
1783 | =item 4. Wee, just use a double-linked list for your timeouts. |
1936 | =item 4. Wee, just use a double-linked list for your timeouts. |
1784 | |
1937 | |
1785 | If there is not one request, but many thousands (millions...), all |
1938 | If there is not one request, but many thousands (millions...), all |
1786 | employing some kind of timeout with the same timeout value, then one can |
1939 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1813 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1966 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1814 | rather complicated, but extremely efficient, something that really pays |
1967 | rather complicated, but extremely efficient, something that really pays |
1815 | off after the first million or so of active timers, i.e. it's usually |
1968 | off after the first million or so of active timers, i.e. it's usually |
1816 | overkill :) |
1969 | overkill :) |
1817 | |
1970 | |
|
|
1971 | =head3 The special problem of being too early |
|
|
1972 | |
|
|
1973 | If you ask a timer to call your callback after three seconds, then |
|
|
1974 | you expect it to be invoked after three seconds - but of course, this |
|
|
1975 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1976 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1977 | process with a STOP signal for a few hours for example. |
|
|
1978 | |
|
|
1979 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1980 | delay has occurred, but cannot guarantee this. |
|
|
1981 | |
|
|
1982 | A less obvious failure mode is calling your callback too early: many event |
|
|
1983 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1984 | this can cause your callback to be invoked much earlier than you would |
|
|
1985 | expect. |
|
|
1986 | |
|
|
1987 | To see why, imagine a system with a clock that only offers full second |
|
|
1988 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1989 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1990 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1991 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1992 | |
|
|
1993 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1994 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1995 | one-second delay was requested - this is being "too early", despite best |
|
|
1996 | intentions. |
|
|
1997 | |
|
|
1998 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1999 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2000 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2001 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2002 | |
|
|
2003 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2004 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2005 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2006 | late" side of things. |
|
|
2007 | |
1818 | =head3 The special problem of time updates |
2008 | =head3 The special problem of time updates |
1819 | |
2009 | |
1820 | Establishing the current time is a costly operation (it usually takes at |
2010 | Establishing the current time is a costly operation (it usually takes |
1821 | least two system calls): EV therefore updates its idea of the current |
2011 | at least one system call): EV therefore updates its idea of the current |
1822 | time only before and after C<ev_loop> collects new events, which causes a |
2012 | time only before and after C<ev_run> collects new events, which causes a |
1823 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2013 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1824 | lots of events in one iteration. |
2014 | lots of events in one iteration. |
1825 | |
2015 | |
1826 | The relative timeouts are calculated relative to the C<ev_now ()> |
2016 | The relative timeouts are calculated relative to the C<ev_now ()> |
1827 | time. This is usually the right thing as this timestamp refers to the time |
2017 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1832 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2022 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1833 | |
2023 | |
1834 | If the event loop is suspended for a long time, you can also force an |
2024 | If the event loop is suspended for a long time, you can also force an |
1835 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2025 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1836 | ()>. |
2026 | ()>. |
|
|
2027 | |
|
|
2028 | =head3 The special problem of unsynchronised clocks |
|
|
2029 | |
|
|
2030 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2031 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2032 | jumps). |
|
|
2033 | |
|
|
2034 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2035 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2036 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2037 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2038 | than a directly following call to C<time>. |
|
|
2039 | |
|
|
2040 | The moral of this is to only compare libev-related timestamps with |
|
|
2041 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2042 | a second or so. |
|
|
2043 | |
|
|
2044 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2045 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2046 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2047 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2048 | |
|
|
2049 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2050 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2051 | I<measured according to the real time>, not the system clock. |
|
|
2052 | |
|
|
2053 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2054 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2055 | exactly the right behaviour. |
|
|
2056 | |
|
|
2057 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2058 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2059 | time, where your comparisons will always generate correct results. |
1837 | |
2060 | |
1838 | =head3 The special problems of suspended animation |
2061 | =head3 The special problems of suspended animation |
1839 | |
2062 | |
1840 | When you leave the server world it is quite customary to hit machines that |
2063 | When you leave the server world it is quite customary to hit machines that |
1841 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2064 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1885 | keep up with the timer (because it takes longer than those 10 seconds to |
2108 | keep up with the timer (because it takes longer than those 10 seconds to |
1886 | do stuff) the timer will not fire more than once per event loop iteration. |
2109 | do stuff) the timer will not fire more than once per event loop iteration. |
1887 | |
2110 | |
1888 | =item ev_timer_again (loop, ev_timer *) |
2111 | =item ev_timer_again (loop, ev_timer *) |
1889 | |
2112 | |
1890 | This will act as if the timer timed out and restart it again if it is |
2113 | This will act as if the timer timed out, and restarts it again if it is |
1891 | repeating. The exact semantics are: |
2114 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2115 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1892 | |
2116 | |
|
|
2117 | The exact semantics are as in the following rules, all of which will be |
|
|
2118 | applied to the watcher: |
|
|
2119 | |
|
|
2120 | =over 4 |
|
|
2121 | |
1893 | If the timer is pending, its pending status is cleared. |
2122 | =item If the timer is pending, the pending status is always cleared. |
1894 | |
2123 | |
1895 | If the timer is started but non-repeating, stop it (as if it timed out). |
2124 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2125 | out, without invoking it). |
1896 | |
2126 | |
1897 | If the timer is repeating, either start it if necessary (with the |
2127 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1898 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2128 | and start the timer, if necessary. |
|
|
2129 | |
|
|
2130 | =back |
1899 | |
2131 | |
1900 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2132 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1901 | usage example. |
2133 | usage example. |
1902 | |
2134 | |
1903 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2135 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
1944 | } |
2176 | } |
1945 | |
2177 | |
1946 | ev_timer mytimer; |
2178 | ev_timer mytimer; |
1947 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2179 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1948 | ev_timer_again (&mytimer); /* start timer */ |
2180 | ev_timer_again (&mytimer); /* start timer */ |
1949 | ev_loop (loop, 0); |
2181 | ev_run (loop, 0); |
1950 | |
2182 | |
1951 | // and in some piece of code that gets executed on any "activity": |
2183 | // and in some piece of code that gets executed on any "activity": |
1952 | // reset the timeout to start ticking again at 10 seconds |
2184 | // reset the timeout to start ticking again at 10 seconds |
1953 | ev_timer_again (&mytimer); |
2185 | ev_timer_again (&mytimer); |
1954 | |
2186 | |
… | |
… | |
1980 | |
2212 | |
1981 | As with timers, the callback is guaranteed to be invoked only when the |
2213 | As with timers, the callback is guaranteed to be invoked only when the |
1982 | point in time where it is supposed to trigger has passed. If multiple |
2214 | point in time where it is supposed to trigger has passed. If multiple |
1983 | timers become ready during the same loop iteration then the ones with |
2215 | timers become ready during the same loop iteration then the ones with |
1984 | earlier time-out values are invoked before ones with later time-out values |
2216 | earlier time-out values are invoked before ones with later time-out values |
1985 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
2217 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1986 | |
2218 | |
1987 | =head3 Watcher-Specific Functions and Data Members |
2219 | =head3 Watcher-Specific Functions and Data Members |
1988 | |
2220 | |
1989 | =over 4 |
2221 | =over 4 |
1990 | |
2222 | |
… | |
… | |
2025 | |
2257 | |
2026 | Another way to think about it (for the mathematically inclined) is that |
2258 | Another way to think about it (for the mathematically inclined) is that |
2027 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2259 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2028 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2260 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2029 | |
2261 | |
2030 | For numerical stability it is preferable that the C<offset> value is near |
2262 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2031 | C<ev_now ()> (the current time), but there is no range requirement for |
2263 | interval value should be higher than C<1/8192> (which is around 100 |
2032 | this value, and in fact is often specified as zero. |
2264 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2265 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2266 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2267 | C<0> and C<interval>, which is also the recommended range. |
2033 | |
2268 | |
2034 | Note also that there is an upper limit to how often a timer can fire (CPU |
2269 | Note also that there is an upper limit to how often a timer can fire (CPU |
2035 | speed for example), so if C<interval> is very small then timing stability |
2270 | speed for example), so if C<interval> is very small then timing stability |
2036 | will of course deteriorate. Libev itself tries to be exact to be about one |
2271 | will of course deteriorate. Libev itself tries to be exact to be about one |
2037 | millisecond (if the OS supports it and the machine is fast enough). |
2272 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2118 | Example: Call a callback every hour, or, more precisely, whenever the |
2353 | Example: Call a callback every hour, or, more precisely, whenever the |
2119 | system time is divisible by 3600. The callback invocation times have |
2354 | system time is divisible by 3600. The callback invocation times have |
2120 | potentially a lot of jitter, but good long-term stability. |
2355 | potentially a lot of jitter, but good long-term stability. |
2121 | |
2356 | |
2122 | static void |
2357 | static void |
2123 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2358 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
2124 | { |
2359 | { |
2125 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2360 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2126 | } |
2361 | } |
2127 | |
2362 | |
2128 | ev_periodic hourly_tick; |
2363 | ev_periodic hourly_tick; |
… | |
… | |
2151 | |
2386 | |
2152 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2387 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2153 | |
2388 | |
2154 | Signal watchers will trigger an event when the process receives a specific |
2389 | Signal watchers will trigger an event when the process receives a specific |
2155 | signal one or more times. Even though signals are very asynchronous, libev |
2390 | signal one or more times. Even though signals are very asynchronous, libev |
2156 | will try it's best to deliver signals synchronously, i.e. as part of the |
2391 | will try its best to deliver signals synchronously, i.e. as part of the |
2157 | normal event processing, like any other event. |
2392 | normal event processing, like any other event. |
2158 | |
2393 | |
2159 | If you want signals to be delivered truly asynchronously, just use |
2394 | If you want signals to be delivered truly asynchronously, just use |
2160 | C<sigaction> as you would do without libev and forget about sharing |
2395 | C<sigaction> as you would do without libev and forget about sharing |
2161 | the signal. You can even use C<ev_async> from a signal handler to |
2396 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2180 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2415 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2181 | |
2416 | |
2182 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2417 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2183 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2418 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2184 | stopping it again), that is, libev might or might not block the signal, |
2419 | stopping it again), that is, libev might or might not block the signal, |
2185 | and might or might not set or restore the installed signal handler. |
2420 | and might or might not set or restore the installed signal handler (but |
|
|
2421 | see C<EVFLAG_NOSIGMASK>). |
2186 | |
2422 | |
2187 | While this does not matter for the signal disposition (libev never |
2423 | While this does not matter for the signal disposition (libev never |
2188 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2424 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2189 | C<execve>), this matters for the signal mask: many programs do not expect |
2425 | C<execve>), this matters for the signal mask: many programs do not expect |
2190 | certain signals to be blocked. |
2426 | certain signals to be blocked. |
… | |
… | |
2204 | |
2440 | |
2205 | So I can't stress this enough: I<If you do not reset your signal mask when |
2441 | So I can't stress this enough: I<If you do not reset your signal mask when |
2206 | you expect it to be empty, you have a race condition in your code>. This |
2442 | you expect it to be empty, you have a race condition in your code>. This |
2207 | is not a libev-specific thing, this is true for most event libraries. |
2443 | is not a libev-specific thing, this is true for most event libraries. |
2208 | |
2444 | |
|
|
2445 | =head3 The special problem of threads signal handling |
|
|
2446 | |
|
|
2447 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2448 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2449 | threads in a process block signals, which is hard to achieve. |
|
|
2450 | |
|
|
2451 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2452 | for the same signals), you can tackle this problem by globally blocking |
|
|
2453 | all signals before creating any threads (or creating them with a fully set |
|
|
2454 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2455 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2456 | these signals. You can pass on any signals that libev might be interested |
|
|
2457 | in by calling C<ev_feed_signal>. |
|
|
2458 | |
2209 | =head3 Watcher-Specific Functions and Data Members |
2459 | =head3 Watcher-Specific Functions and Data Members |
2210 | |
2460 | |
2211 | =over 4 |
2461 | =over 4 |
2212 | |
2462 | |
2213 | =item ev_signal_init (ev_signal *, callback, int signum) |
2463 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
2228 | Example: Try to exit cleanly on SIGINT. |
2478 | Example: Try to exit cleanly on SIGINT. |
2229 | |
2479 | |
2230 | static void |
2480 | static void |
2231 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2481 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2232 | { |
2482 | { |
2233 | ev_unloop (loop, EVUNLOOP_ALL); |
2483 | ev_break (loop, EVBREAK_ALL); |
2234 | } |
2484 | } |
2235 | |
2485 | |
2236 | ev_signal signal_watcher; |
2486 | ev_signal signal_watcher; |
2237 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2487 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2238 | ev_signal_start (loop, &signal_watcher); |
2488 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
2624 | |
2874 | |
2625 | Prepare and check watchers are usually (but not always) used in pairs: |
2875 | Prepare and check watchers are usually (but not always) used in pairs: |
2626 | prepare watchers get invoked before the process blocks and check watchers |
2876 | prepare watchers get invoked before the process blocks and check watchers |
2627 | afterwards. |
2877 | afterwards. |
2628 | |
2878 | |
2629 | You I<must not> call C<ev_loop> or similar functions that enter |
2879 | You I<must not> call C<ev_run> or similar functions that enter |
2630 | the current event loop from either C<ev_prepare> or C<ev_check> |
2880 | the current event loop from either C<ev_prepare> or C<ev_check> |
2631 | watchers. Other loops than the current one are fine, however. The |
2881 | watchers. Other loops than the current one are fine, however. The |
2632 | rationale behind this is that you do not need to check for recursion in |
2882 | rationale behind this is that you do not need to check for recursion in |
2633 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2883 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2634 | C<ev_check> so if you have one watcher of each kind they will always be |
2884 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2802 | |
3052 | |
2803 | if (timeout >= 0) |
3053 | if (timeout >= 0) |
2804 | // create/start timer |
3054 | // create/start timer |
2805 | |
3055 | |
2806 | // poll |
3056 | // poll |
2807 | ev_loop (EV_A_ 0); |
3057 | ev_run (EV_A_ 0); |
2808 | |
3058 | |
2809 | // stop timer again |
3059 | // stop timer again |
2810 | if (timeout >= 0) |
3060 | if (timeout >= 0) |
2811 | ev_timer_stop (EV_A_ &to); |
3061 | ev_timer_stop (EV_A_ &to); |
2812 | |
3062 | |
… | |
… | |
2890 | if you do not want that, you need to temporarily stop the embed watcher). |
3140 | if you do not want that, you need to temporarily stop the embed watcher). |
2891 | |
3141 | |
2892 | =item ev_embed_sweep (loop, ev_embed *) |
3142 | =item ev_embed_sweep (loop, ev_embed *) |
2893 | |
3143 | |
2894 | Make a single, non-blocking sweep over the embedded loop. This works |
3144 | Make a single, non-blocking sweep over the embedded loop. This works |
2895 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3145 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2896 | appropriate way for embedded loops. |
3146 | appropriate way for embedded loops. |
2897 | |
3147 | |
2898 | =item struct ev_loop *other [read-only] |
3148 | =item struct ev_loop *other [read-only] |
2899 | |
3149 | |
2900 | The embedded event loop. |
3150 | The embedded event loop. |
… | |
… | |
2960 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3210 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2961 | handlers will be invoked, too, of course. |
3211 | handlers will be invoked, too, of course. |
2962 | |
3212 | |
2963 | =head3 The special problem of life after fork - how is it possible? |
3213 | =head3 The special problem of life after fork - how is it possible? |
2964 | |
3214 | |
2965 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
3215 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2966 | up/change the process environment, followed by a call to C<exec()>. This |
3216 | up/change the process environment, followed by a call to C<exec()>. This |
2967 | sequence should be handled by libev without any problems. |
3217 | sequence should be handled by libev without any problems. |
2968 | |
3218 | |
2969 | This changes when the application actually wants to do event handling |
3219 | This changes when the application actually wants to do event handling |
2970 | in the child, or both parent in child, in effect "continuing" after the |
3220 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2986 | disadvantage of having to use multiple event loops (which do not support |
3236 | disadvantage of having to use multiple event loops (which do not support |
2987 | signal watchers). |
3237 | signal watchers). |
2988 | |
3238 | |
2989 | When this is not possible, or you want to use the default loop for |
3239 | When this is not possible, or you want to use the default loop for |
2990 | other reasons, then in the process that wants to start "fresh", call |
3240 | other reasons, then in the process that wants to start "fresh", call |
2991 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3241 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
2992 | the default loop will "orphan" (not stop) all registered watchers, so you |
3242 | Destroying the default loop will "orphan" (not stop) all registered |
2993 | have to be careful not to execute code that modifies those watchers. Note |
3243 | watchers, so you have to be careful not to execute code that modifies |
2994 | also that in that case, you have to re-register any signal watchers. |
3244 | those watchers. Note also that in that case, you have to re-register any |
|
|
3245 | signal watchers. |
2995 | |
3246 | |
2996 | =head3 Watcher-Specific Functions and Data Members |
3247 | =head3 Watcher-Specific Functions and Data Members |
2997 | |
3248 | |
2998 | =over 4 |
3249 | =over 4 |
2999 | |
3250 | |
3000 | =item ev_fork_init (ev_signal *, callback) |
3251 | =item ev_fork_init (ev_fork *, callback) |
3001 | |
3252 | |
3002 | Initialises and configures the fork watcher - it has no parameters of any |
3253 | Initialises and configures the fork watcher - it has no parameters of any |
3003 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3254 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3004 | believe me. |
3255 | really. |
3005 | |
3256 | |
3006 | =back |
3257 | =back |
3007 | |
3258 | |
3008 | |
3259 | |
|
|
3260 | =head2 C<ev_cleanup> - even the best things end |
|
|
3261 | |
|
|
3262 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3263 | by a call to C<ev_loop_destroy>. |
|
|
3264 | |
|
|
3265 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3266 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3267 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3268 | loop when you want them to be invoked. |
|
|
3269 | |
|
|
3270 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3271 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3272 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3273 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3274 | |
|
|
3275 | =head3 Watcher-Specific Functions and Data Members |
|
|
3276 | |
|
|
3277 | =over 4 |
|
|
3278 | |
|
|
3279 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3280 | |
|
|
3281 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3282 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3283 | pointless, I assure you. |
|
|
3284 | |
|
|
3285 | =back |
|
|
3286 | |
|
|
3287 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3288 | cleanup functions are called. |
|
|
3289 | |
|
|
3290 | static void |
|
|
3291 | program_exits (void) |
|
|
3292 | { |
|
|
3293 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3294 | } |
|
|
3295 | |
|
|
3296 | ... |
|
|
3297 | atexit (program_exits); |
|
|
3298 | |
|
|
3299 | |
3009 | =head2 C<ev_async> - how to wake up another event loop |
3300 | =head2 C<ev_async> - how to wake up an event loop |
3010 | |
3301 | |
3011 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3302 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3012 | asynchronous sources such as signal handlers (as opposed to multiple event |
3303 | asynchronous sources such as signal handlers (as opposed to multiple event |
3013 | loops - those are of course safe to use in different threads). |
3304 | loops - those are of course safe to use in different threads). |
3014 | |
3305 | |
3015 | Sometimes, however, you need to wake up another event loop you do not |
3306 | Sometimes, however, you need to wake up an event loop you do not control, |
3016 | control, for example because it belongs to another thread. This is what |
3307 | for example because it belongs to another thread. This is what C<ev_async> |
3017 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3308 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
3018 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3309 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3019 | safe. |
|
|
3020 | |
3310 | |
3021 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3311 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3022 | too, are asynchronous in nature, and signals, too, will be compressed |
3312 | too, are asynchronous in nature, and signals, too, will be compressed |
3023 | (i.e. the number of callback invocations may be less than the number of |
3313 | (i.e. the number of callback invocations may be less than the number of |
3024 | C<ev_async_sent> calls). |
3314 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3025 | |
3315 | of "global async watchers" by using a watcher on an otherwise unused |
3026 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3316 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3027 | just the default loop. |
3317 | even without knowing which loop owns the signal. |
3028 | |
3318 | |
3029 | =head3 Queueing |
3319 | =head3 Queueing |
3030 | |
3320 | |
3031 | C<ev_async> does not support queueing of data in any way. The reason |
3321 | C<ev_async> does not support queueing of data in any way. The reason |
3032 | is that the author does not know of a simple (or any) algorithm for a |
3322 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3124 | trust me. |
3414 | trust me. |
3125 | |
3415 | |
3126 | =item ev_async_send (loop, ev_async *) |
3416 | =item ev_async_send (loop, ev_async *) |
3127 | |
3417 | |
3128 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3418 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3129 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3419 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3420 | returns. |
|
|
3421 | |
3130 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3422 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3131 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3423 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3132 | section below on what exactly this means). |
3424 | embedding section below on what exactly this means). |
3133 | |
3425 | |
3134 | Note that, as with other watchers in libev, multiple events might get |
3426 | Note that, as with other watchers in libev, multiple events might get |
3135 | compressed into a single callback invocation (another way to look at this |
3427 | compressed into a single callback invocation (another way to look at |
3136 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3428 | this is that C<ev_async> watchers are level-triggered: they are set on |
3137 | reset when the event loop detects that). |
3429 | C<ev_async_send>, reset when the event loop detects that). |
3138 | |
3430 | |
3139 | This call incurs the overhead of a system call only once per event loop |
3431 | This call incurs the overhead of at most one extra system call per event |
3140 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3432 | loop iteration, if the event loop is blocked, and no syscall at all if |
3141 | repeated calls to C<ev_async_send> for the same event loop. |
3433 | the event loop (or your program) is processing events. That means that |
|
|
3434 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3435 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3436 | zero) under load. |
3142 | |
3437 | |
3143 | =item bool = ev_async_pending (ev_async *) |
3438 | =item bool = ev_async_pending (ev_async *) |
3144 | |
3439 | |
3145 | Returns a non-zero value when C<ev_async_send> has been called on the |
3440 | Returns a non-zero value when C<ev_async_send> has been called on the |
3146 | watcher but the event has not yet been processed (or even noted) by the |
3441 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3179 | |
3474 | |
3180 | If C<timeout> is less than 0, then no timeout watcher will be |
3475 | If C<timeout> is less than 0, then no timeout watcher will be |
3181 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3476 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3182 | repeat = 0) will be started. C<0> is a valid timeout. |
3477 | repeat = 0) will be started. C<0> is a valid timeout. |
3183 | |
3478 | |
3184 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3479 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
3185 | passed an C<revents> set like normal event callbacks (a combination of |
3480 | passed an C<revents> set like normal event callbacks (a combination of |
3186 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3481 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
3187 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3482 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3188 | a timeout and an io event at the same time - you probably should give io |
3483 | a timeout and an io event at the same time - you probably should give io |
3189 | events precedence. |
3484 | events precedence. |
3190 | |
3485 | |
3191 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3486 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3192 | |
3487 | |
3193 | static void stdin_ready (int revents, void *arg) |
3488 | static void stdin_ready (int revents, void *arg) |
3194 | { |
3489 | { |
3195 | if (revents & EV_READ) |
3490 | if (revents & EV_READ) |
3196 | /* stdin might have data for us, joy! */; |
3491 | /* stdin might have data for us, joy! */; |
3197 | else if (revents & EV_TIMEOUT) |
3492 | else if (revents & EV_TIMER) |
3198 | /* doh, nothing entered */; |
3493 | /* doh, nothing entered */; |
3199 | } |
3494 | } |
3200 | |
3495 | |
3201 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3496 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3202 | |
3497 | |
3203 | =item ev_feed_fd_event (loop, int fd, int revents) |
3498 | =item ev_feed_fd_event (loop, int fd, int revents) |
3204 | |
3499 | |
3205 | Feed an event on the given fd, as if a file descriptor backend detected |
3500 | Feed an event on the given fd, as if a file descriptor backend detected |
3206 | the given events it. |
3501 | the given events. |
3207 | |
3502 | |
3208 | =item ev_feed_signal_event (loop, int signum) |
3503 | =item ev_feed_signal_event (loop, int signum) |
3209 | |
3504 | |
3210 | Feed an event as if the given signal occurred (C<loop> must be the default |
3505 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3211 | loop!). |
3506 | which is async-safe. |
3212 | |
3507 | |
3213 | =back |
3508 | =back |
|
|
3509 | |
|
|
3510 | |
|
|
3511 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3512 | |
|
|
3513 | This section explains some common idioms that are not immediately |
|
|
3514 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3515 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3516 | |
|
|
3517 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3518 | |
|
|
3519 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3520 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3521 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3522 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3523 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3524 | data: |
|
|
3525 | |
|
|
3526 | struct my_io |
|
|
3527 | { |
|
|
3528 | ev_io io; |
|
|
3529 | int otherfd; |
|
|
3530 | void *somedata; |
|
|
3531 | struct whatever *mostinteresting; |
|
|
3532 | }; |
|
|
3533 | |
|
|
3534 | ... |
|
|
3535 | struct my_io w; |
|
|
3536 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3537 | |
|
|
3538 | And since your callback will be called with a pointer to the watcher, you |
|
|
3539 | can cast it back to your own type: |
|
|
3540 | |
|
|
3541 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3542 | { |
|
|
3543 | struct my_io *w = (struct my_io *)w_; |
|
|
3544 | ... |
|
|
3545 | } |
|
|
3546 | |
|
|
3547 | More interesting and less C-conformant ways of casting your callback |
|
|
3548 | function type instead have been omitted. |
|
|
3549 | |
|
|
3550 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3551 | |
|
|
3552 | Another common scenario is to use some data structure with multiple |
|
|
3553 | embedded watchers, in effect creating your own watcher that combines |
|
|
3554 | multiple libev event sources into one "super-watcher": |
|
|
3555 | |
|
|
3556 | struct my_biggy |
|
|
3557 | { |
|
|
3558 | int some_data; |
|
|
3559 | ev_timer t1; |
|
|
3560 | ev_timer t2; |
|
|
3561 | } |
|
|
3562 | |
|
|
3563 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3564 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3565 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3566 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3567 | real programmers): |
|
|
3568 | |
|
|
3569 | #include <stddef.h> |
|
|
3570 | |
|
|
3571 | static void |
|
|
3572 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3573 | { |
|
|
3574 | struct my_biggy big = (struct my_biggy *) |
|
|
3575 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3576 | } |
|
|
3577 | |
|
|
3578 | static void |
|
|
3579 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3580 | { |
|
|
3581 | struct my_biggy big = (struct my_biggy *) |
|
|
3582 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3583 | } |
|
|
3584 | |
|
|
3585 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3586 | |
|
|
3587 | Often you have structures like this in event-based programs: |
|
|
3588 | |
|
|
3589 | callback () |
|
|
3590 | { |
|
|
3591 | free (request); |
|
|
3592 | } |
|
|
3593 | |
|
|
3594 | request = start_new_request (..., callback); |
|
|
3595 | |
|
|
3596 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3597 | used to cancel the operation, or do other things with it. |
|
|
3598 | |
|
|
3599 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3600 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3601 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3602 | operation and simply invoke the callback with the result. |
|
|
3603 | |
|
|
3604 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3605 | has returned, so C<request> is not set. |
|
|
3606 | |
|
|
3607 | Even if you pass the request by some safer means to the callback, you |
|
|
3608 | might want to do something to the request after starting it, such as |
|
|
3609 | canceling it, which probably isn't working so well when the callback has |
|
|
3610 | already been invoked. |
|
|
3611 | |
|
|
3612 | A common way around all these issues is to make sure that |
|
|
3613 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3614 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3615 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3616 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3617 | and pushing it into the pending queue: |
|
|
3618 | |
|
|
3619 | ev_set_cb (watcher, callback); |
|
|
3620 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3621 | |
|
|
3622 | This way, C<start_new_request> can safely return before the callback is |
|
|
3623 | invoked, while not delaying callback invocation too much. |
|
|
3624 | |
|
|
3625 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3626 | |
|
|
3627 | Often (especially in GUI toolkits) there are places where you have |
|
|
3628 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3629 | invoking C<ev_run>. |
|
|
3630 | |
|
|
3631 | This brings the problem of exiting - a callback might want to finish the |
|
|
3632 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3633 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3634 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3635 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3636 | |
|
|
3637 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3638 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3639 | triggered, using C<EVRUN_ONCE>: |
|
|
3640 | |
|
|
3641 | // main loop |
|
|
3642 | int exit_main_loop = 0; |
|
|
3643 | |
|
|
3644 | while (!exit_main_loop) |
|
|
3645 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3646 | |
|
|
3647 | // in a modal watcher |
|
|
3648 | int exit_nested_loop = 0; |
|
|
3649 | |
|
|
3650 | while (!exit_nested_loop) |
|
|
3651 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3652 | |
|
|
3653 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3654 | |
|
|
3655 | // exit modal loop |
|
|
3656 | exit_nested_loop = 1; |
|
|
3657 | |
|
|
3658 | // exit main program, after modal loop is finished |
|
|
3659 | exit_main_loop = 1; |
|
|
3660 | |
|
|
3661 | // exit both |
|
|
3662 | exit_main_loop = exit_nested_loop = 1; |
|
|
3663 | |
|
|
3664 | =head2 THREAD LOCKING EXAMPLE |
|
|
3665 | |
|
|
3666 | Here is a fictitious example of how to run an event loop in a different |
|
|
3667 | thread from where callbacks are being invoked and watchers are |
|
|
3668 | created/added/removed. |
|
|
3669 | |
|
|
3670 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3671 | which uses exactly this technique (which is suited for many high-level |
|
|
3672 | languages). |
|
|
3673 | |
|
|
3674 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3675 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3676 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3677 | |
|
|
3678 | First, you need to associate some data with the event loop: |
|
|
3679 | |
|
|
3680 | typedef struct { |
|
|
3681 | mutex_t lock; /* global loop lock */ |
|
|
3682 | ev_async async_w; |
|
|
3683 | thread_t tid; |
|
|
3684 | cond_t invoke_cv; |
|
|
3685 | } userdata; |
|
|
3686 | |
|
|
3687 | void prepare_loop (EV_P) |
|
|
3688 | { |
|
|
3689 | // for simplicity, we use a static userdata struct. |
|
|
3690 | static userdata u; |
|
|
3691 | |
|
|
3692 | ev_async_init (&u->async_w, async_cb); |
|
|
3693 | ev_async_start (EV_A_ &u->async_w); |
|
|
3694 | |
|
|
3695 | pthread_mutex_init (&u->lock, 0); |
|
|
3696 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3697 | |
|
|
3698 | // now associate this with the loop |
|
|
3699 | ev_set_userdata (EV_A_ u); |
|
|
3700 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3701 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3702 | |
|
|
3703 | // then create the thread running ev_run |
|
|
3704 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3705 | } |
|
|
3706 | |
|
|
3707 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3708 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3709 | that might have been added: |
|
|
3710 | |
|
|
3711 | static void |
|
|
3712 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3713 | { |
|
|
3714 | // just used for the side effects |
|
|
3715 | } |
|
|
3716 | |
|
|
3717 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3718 | protecting the loop data, respectively. |
|
|
3719 | |
|
|
3720 | static void |
|
|
3721 | l_release (EV_P) |
|
|
3722 | { |
|
|
3723 | userdata *u = ev_userdata (EV_A); |
|
|
3724 | pthread_mutex_unlock (&u->lock); |
|
|
3725 | } |
|
|
3726 | |
|
|
3727 | static void |
|
|
3728 | l_acquire (EV_P) |
|
|
3729 | { |
|
|
3730 | userdata *u = ev_userdata (EV_A); |
|
|
3731 | pthread_mutex_lock (&u->lock); |
|
|
3732 | } |
|
|
3733 | |
|
|
3734 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3735 | into C<ev_run>: |
|
|
3736 | |
|
|
3737 | void * |
|
|
3738 | l_run (void *thr_arg) |
|
|
3739 | { |
|
|
3740 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3741 | |
|
|
3742 | l_acquire (EV_A); |
|
|
3743 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3744 | ev_run (EV_A_ 0); |
|
|
3745 | l_release (EV_A); |
|
|
3746 | |
|
|
3747 | return 0; |
|
|
3748 | } |
|
|
3749 | |
|
|
3750 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3751 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3752 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3753 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3754 | and b) skipping inter-thread-communication when there are no pending |
|
|
3755 | watchers is very beneficial): |
|
|
3756 | |
|
|
3757 | static void |
|
|
3758 | l_invoke (EV_P) |
|
|
3759 | { |
|
|
3760 | userdata *u = ev_userdata (EV_A); |
|
|
3761 | |
|
|
3762 | while (ev_pending_count (EV_A)) |
|
|
3763 | { |
|
|
3764 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3765 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3766 | } |
|
|
3767 | } |
|
|
3768 | |
|
|
3769 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3770 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3771 | thread to continue: |
|
|
3772 | |
|
|
3773 | static void |
|
|
3774 | real_invoke_pending (EV_P) |
|
|
3775 | { |
|
|
3776 | userdata *u = ev_userdata (EV_A); |
|
|
3777 | |
|
|
3778 | pthread_mutex_lock (&u->lock); |
|
|
3779 | ev_invoke_pending (EV_A); |
|
|
3780 | pthread_cond_signal (&u->invoke_cv); |
|
|
3781 | pthread_mutex_unlock (&u->lock); |
|
|
3782 | } |
|
|
3783 | |
|
|
3784 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3785 | event loop, you will now have to lock: |
|
|
3786 | |
|
|
3787 | ev_timer timeout_watcher; |
|
|
3788 | userdata *u = ev_userdata (EV_A); |
|
|
3789 | |
|
|
3790 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3791 | |
|
|
3792 | pthread_mutex_lock (&u->lock); |
|
|
3793 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3794 | ev_async_send (EV_A_ &u->async_w); |
|
|
3795 | pthread_mutex_unlock (&u->lock); |
|
|
3796 | |
|
|
3797 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3798 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3799 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3800 | watchers in the next event loop iteration. |
|
|
3801 | |
|
|
3802 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3803 | |
|
|
3804 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3805 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3806 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3807 | doesn't need callbacks anymore. |
|
|
3808 | |
|
|
3809 | Imagine you have coroutines that you can switch to using a function |
|
|
3810 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3811 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3812 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3813 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3814 | the differing C<;> conventions): |
|
|
3815 | |
|
|
3816 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3817 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3818 | |
|
|
3819 | That means instead of having a C callback function, you store the |
|
|
3820 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3821 | your callback, you instead have it switch to that coroutine. |
|
|
3822 | |
|
|
3823 | A coroutine might now wait for an event with a function called |
|
|
3824 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3825 | matter when, or whether the watcher is active or not when this function is |
|
|
3826 | called): |
|
|
3827 | |
|
|
3828 | void |
|
|
3829 | wait_for_event (ev_watcher *w) |
|
|
3830 | { |
|
|
3831 | ev_cb_set (w) = current_coro; |
|
|
3832 | switch_to (libev_coro); |
|
|
3833 | } |
|
|
3834 | |
|
|
3835 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3836 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3837 | this or any other coroutine. |
|
|
3838 | |
|
|
3839 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3840 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3841 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3842 | any waiters. |
|
|
3843 | |
|
|
3844 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3845 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3846 | |
|
|
3847 | // my_ev.h |
|
|
3848 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3849 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3850 | #include "../libev/ev.h" |
|
|
3851 | |
|
|
3852 | // my_ev.c |
|
|
3853 | #define EV_H "my_ev.h" |
|
|
3854 | #include "../libev/ev.c" |
|
|
3855 | |
|
|
3856 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3857 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3858 | can even use F<ev.h> as header file name directly. |
3214 | |
3859 | |
3215 | |
3860 | |
3216 | =head1 LIBEVENT EMULATION |
3861 | =head1 LIBEVENT EMULATION |
3217 | |
3862 | |
3218 | Libev offers a compatibility emulation layer for libevent. It cannot |
3863 | Libev offers a compatibility emulation layer for libevent. It cannot |
3219 | emulate the internals of libevent, so here are some usage hints: |
3864 | emulate the internals of libevent, so here are some usage hints: |
3220 | |
3865 | |
3221 | =over 4 |
3866 | =over 4 |
|
|
3867 | |
|
|
3868 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3869 | |
|
|
3870 | This was the newest libevent version available when libev was implemented, |
|
|
3871 | and is still mostly unchanged in 2010. |
3222 | |
3872 | |
3223 | =item * Use it by including <event.h>, as usual. |
3873 | =item * Use it by including <event.h>, as usual. |
3224 | |
3874 | |
3225 | =item * The following members are fully supported: ev_base, ev_callback, |
3875 | =item * The following members are fully supported: ev_base, ev_callback, |
3226 | ev_arg, ev_fd, ev_res, ev_events. |
3876 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3232 | =item * Priorities are not currently supported. Initialising priorities |
3882 | =item * Priorities are not currently supported. Initialising priorities |
3233 | will fail and all watchers will have the same priority, even though there |
3883 | will fail and all watchers will have the same priority, even though there |
3234 | is an ev_pri field. |
3884 | is an ev_pri field. |
3235 | |
3885 | |
3236 | =item * In libevent, the last base created gets the signals, in libev, the |
3886 | =item * In libevent, the last base created gets the signals, in libev, the |
3237 | first base created (== the default loop) gets the signals. |
3887 | base that registered the signal gets the signals. |
3238 | |
3888 | |
3239 | =item * Other members are not supported. |
3889 | =item * Other members are not supported. |
3240 | |
3890 | |
3241 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3891 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3242 | to use the libev header file and library. |
3892 | to use the libev header file and library. |
… | |
… | |
3261 | Care has been taken to keep the overhead low. The only data member the C++ |
3911 | Care has been taken to keep the overhead low. The only data member the C++ |
3262 | classes add (compared to plain C-style watchers) is the event loop pointer |
3912 | classes add (compared to plain C-style watchers) is the event loop pointer |
3263 | that the watcher is associated with (or no additional members at all if |
3913 | that the watcher is associated with (or no additional members at all if |
3264 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3914 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3265 | |
3915 | |
3266 | Currently, functions, and static and non-static member functions can be |
3916 | Currently, functions, static and non-static member functions and classes |
3267 | used as callbacks. Other types should be easy to add as long as they only |
3917 | with C<operator ()> can be used as callbacks. Other types should be easy |
3268 | need one additional pointer for context. If you need support for other |
3918 | to add as long as they only need one additional pointer for context. If |
3269 | types of functors please contact the author (preferably after implementing |
3919 | you need support for other types of functors please contact the author |
3270 | it). |
3920 | (preferably after implementing it). |
|
|
3921 | |
|
|
3922 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3923 | conventions as your C compiler (for static member functions), or you have |
|
|
3924 | to embed libev and compile libev itself as C++. |
3271 | |
3925 | |
3272 | Here is a list of things available in the C<ev> namespace: |
3926 | Here is a list of things available in the C<ev> namespace: |
3273 | |
3927 | |
3274 | =over 4 |
3928 | =over 4 |
3275 | |
3929 | |
… | |
… | |
3285 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3939 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3286 | |
3940 | |
3287 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3941 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3288 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3942 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3289 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3943 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3290 | defines by many implementations. |
3944 | defined by many implementations. |
3291 | |
3945 | |
3292 | All of those classes have these methods: |
3946 | All of those classes have these methods: |
3293 | |
3947 | |
3294 | =over 4 |
3948 | =over 4 |
3295 | |
3949 | |
… | |
… | |
3336 | myclass obj; |
3990 | myclass obj; |
3337 | ev::io iow; |
3991 | ev::io iow; |
3338 | iow.set <myclass, &myclass::io_cb> (&obj); |
3992 | iow.set <myclass, &myclass::io_cb> (&obj); |
3339 | |
3993 | |
3340 | =item w->set (object *) |
3994 | =item w->set (object *) |
3341 | |
|
|
3342 | This is an B<experimental> feature that might go away in a future version. |
|
|
3343 | |
3995 | |
3344 | This is a variation of a method callback - leaving out the method to call |
3996 | This is a variation of a method callback - leaving out the method to call |
3345 | will default the method to C<operator ()>, which makes it possible to use |
3997 | will default the method to C<operator ()>, which makes it possible to use |
3346 | functor objects without having to manually specify the C<operator ()> all |
3998 | functor objects without having to manually specify the C<operator ()> all |
3347 | the time. Incidentally, you can then also leave out the template argument |
3999 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3387 | Associates a different C<struct ev_loop> with this watcher. You can only |
4039 | Associates a different C<struct ev_loop> with this watcher. You can only |
3388 | do this when the watcher is inactive (and not pending either). |
4040 | do this when the watcher is inactive (and not pending either). |
3389 | |
4041 | |
3390 | =item w->set ([arguments]) |
4042 | =item w->set ([arguments]) |
3391 | |
4043 | |
3392 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
4044 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
3393 | called at least once. Unlike the C counterpart, an active watcher gets |
4045 | method or a suitable start method must be called at least once. Unlike the |
3394 | automatically stopped and restarted when reconfiguring it with this |
4046 | C counterpart, an active watcher gets automatically stopped and restarted |
3395 | method. |
4047 | when reconfiguring it with this method. |
3396 | |
4048 | |
3397 | =item w->start () |
4049 | =item w->start () |
3398 | |
4050 | |
3399 | Starts the watcher. Note that there is no C<loop> argument, as the |
4051 | Starts the watcher. Note that there is no C<loop> argument, as the |
3400 | constructor already stores the event loop. |
4052 | constructor already stores the event loop. |
3401 | |
4053 | |
|
|
4054 | =item w->start ([arguments]) |
|
|
4055 | |
|
|
4056 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4057 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4058 | the configure C<set> method of the watcher. |
|
|
4059 | |
3402 | =item w->stop () |
4060 | =item w->stop () |
3403 | |
4061 | |
3404 | Stops the watcher if it is active. Again, no C<loop> argument. |
4062 | Stops the watcher if it is active. Again, no C<loop> argument. |
3405 | |
4063 | |
3406 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4064 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3418 | |
4076 | |
3419 | =back |
4077 | =back |
3420 | |
4078 | |
3421 | =back |
4079 | =back |
3422 | |
4080 | |
3423 | Example: Define a class with an IO and idle watcher, start one of them in |
4081 | Example: Define a class with two I/O and idle watchers, start the I/O |
3424 | the constructor. |
4082 | watchers in the constructor. |
3425 | |
4083 | |
3426 | class myclass |
4084 | class myclass |
3427 | { |
4085 | { |
3428 | ev::io io ; void io_cb (ev::io &w, int revents); |
4086 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4087 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3429 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4088 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3430 | |
4089 | |
3431 | myclass (int fd) |
4090 | myclass (int fd) |
3432 | { |
4091 | { |
3433 | io .set <myclass, &myclass::io_cb > (this); |
4092 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4093 | io2 .set <myclass, &myclass::io2_cb > (this); |
3434 | idle.set <myclass, &myclass::idle_cb> (this); |
4094 | idle.set <myclass, &myclass::idle_cb> (this); |
3435 | |
4095 | |
3436 | io.start (fd, ev::READ); |
4096 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4097 | io.start (); // start it whenever convenient |
|
|
4098 | |
|
|
4099 | io2.start (fd, ev::READ); // set + start in one call |
3437 | } |
4100 | } |
3438 | }; |
4101 | }; |
3439 | |
4102 | |
3440 | |
4103 | |
3441 | =head1 OTHER LANGUAGE BINDINGS |
4104 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3480 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4143 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3481 | |
4144 | |
3482 | =item D |
4145 | =item D |
3483 | |
4146 | |
3484 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4147 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3485 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4148 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3486 | |
4149 | |
3487 | =item Ocaml |
4150 | =item Ocaml |
3488 | |
4151 | |
3489 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4152 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3490 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4153 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3515 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4178 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3516 | C<EV_A_> is used when other arguments are following. Example: |
4179 | C<EV_A_> is used when other arguments are following. Example: |
3517 | |
4180 | |
3518 | ev_unref (EV_A); |
4181 | ev_unref (EV_A); |
3519 | ev_timer_add (EV_A_ watcher); |
4182 | ev_timer_add (EV_A_ watcher); |
3520 | ev_loop (EV_A_ 0); |
4183 | ev_run (EV_A_ 0); |
3521 | |
4184 | |
3522 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4185 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3523 | which is often provided by the following macro. |
4186 | which is often provided by the following macro. |
3524 | |
4187 | |
3525 | =item C<EV_P>, C<EV_P_> |
4188 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3538 | suitable for use with C<EV_A>. |
4201 | suitable for use with C<EV_A>. |
3539 | |
4202 | |
3540 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4203 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3541 | |
4204 | |
3542 | Similar to the other two macros, this gives you the value of the default |
4205 | Similar to the other two macros, this gives you the value of the default |
3543 | loop, if multiple loops are supported ("ev loop default"). |
4206 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4207 | will be initialised if it isn't already initialised. |
|
|
4208 | |
|
|
4209 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4210 | to initialise the loop somewhere. |
3544 | |
4211 | |
3545 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4212 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3546 | |
4213 | |
3547 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4214 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3548 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4215 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3565 | } |
4232 | } |
3566 | |
4233 | |
3567 | ev_check check; |
4234 | ev_check check; |
3568 | ev_check_init (&check, check_cb); |
4235 | ev_check_init (&check, check_cb); |
3569 | ev_check_start (EV_DEFAULT_ &check); |
4236 | ev_check_start (EV_DEFAULT_ &check); |
3570 | ev_loop (EV_DEFAULT_ 0); |
4237 | ev_run (EV_DEFAULT_ 0); |
3571 | |
4238 | |
3572 | =head1 EMBEDDING |
4239 | =head1 EMBEDDING |
3573 | |
4240 | |
3574 | Libev can (and often is) directly embedded into host |
4241 | Libev can (and often is) directly embedded into host |
3575 | applications. Examples of applications that embed it include the Deliantra |
4242 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3660 | define before including (or compiling) any of its files. The default in |
4327 | define before including (or compiling) any of its files. The default in |
3661 | the absence of autoconf is documented for every option. |
4328 | the absence of autoconf is documented for every option. |
3662 | |
4329 | |
3663 | Symbols marked with "(h)" do not change the ABI, and can have different |
4330 | Symbols marked with "(h)" do not change the ABI, and can have different |
3664 | values when compiling libev vs. including F<ev.h>, so it is permissible |
4331 | values when compiling libev vs. including F<ev.h>, so it is permissible |
3665 | to redefine them before including F<ev.h> without breakign compatibility |
4332 | to redefine them before including F<ev.h> without breaking compatibility |
3666 | to a compiled library. All other symbols change the ABI, which means all |
4333 | to a compiled library. All other symbols change the ABI, which means all |
3667 | users of libev and the libev code itself must be compiled with compatible |
4334 | users of libev and the libev code itself must be compiled with compatible |
3668 | settings. |
4335 | settings. |
3669 | |
4336 | |
3670 | =over 4 |
4337 | =over 4 |
|
|
4338 | |
|
|
4339 | =item EV_COMPAT3 (h) |
|
|
4340 | |
|
|
4341 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4342 | release of libev comes with wrappers for the functions and symbols that |
|
|
4343 | have been renamed between libev version 3 and 4. |
|
|
4344 | |
|
|
4345 | You can disable these wrappers (to test compatibility with future |
|
|
4346 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4347 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4348 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4349 | typedef in that case. |
|
|
4350 | |
|
|
4351 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4352 | and in some even more future version the compatibility code will be |
|
|
4353 | removed completely. |
3671 | |
4354 | |
3672 | =item EV_STANDALONE (h) |
4355 | =item EV_STANDALONE (h) |
3673 | |
4356 | |
3674 | Must always be C<1> if you do not use autoconf configuration, which |
4357 | Must always be C<1> if you do not use autoconf configuration, which |
3675 | keeps libev from including F<config.h>, and it also defines dummy |
4358 | keeps libev from including F<config.h>, and it also defines dummy |
… | |
… | |
3677 | supported). It will also not define any of the structs usually found in |
4360 | supported). It will also not define any of the structs usually found in |
3678 | F<event.h> that are not directly supported by the libev core alone. |
4361 | F<event.h> that are not directly supported by the libev core alone. |
3679 | |
4362 | |
3680 | In standalone mode, libev will still try to automatically deduce the |
4363 | In standalone mode, libev will still try to automatically deduce the |
3681 | configuration, but has to be more conservative. |
4364 | configuration, but has to be more conservative. |
|
|
4365 | |
|
|
4366 | =item EV_USE_FLOOR |
|
|
4367 | |
|
|
4368 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4369 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4370 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4371 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4372 | function is not available will fail, so the safe default is to not enable |
|
|
4373 | this. |
3682 | |
4374 | |
3683 | =item EV_USE_MONOTONIC |
4375 | =item EV_USE_MONOTONIC |
3684 | |
4376 | |
3685 | If defined to be C<1>, libev will try to detect the availability of the |
4377 | If defined to be C<1>, libev will try to detect the availability of the |
3686 | monotonic clock option at both compile time and runtime. Otherwise no |
4378 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3816 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4508 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3817 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4509 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3818 | be detected at runtime. If undefined, it will be enabled if the headers |
4510 | be detected at runtime. If undefined, it will be enabled if the headers |
3819 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4511 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3820 | |
4512 | |
|
|
4513 | =item EV_NO_SMP |
|
|
4514 | |
|
|
4515 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4516 | between threads, that is, threads can be used, but threads never run on |
|
|
4517 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4518 | and makes libev faster. |
|
|
4519 | |
|
|
4520 | =item EV_NO_THREADS |
|
|
4521 | |
|
|
4522 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4523 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4524 | above. This reduces dependencies and makes libev faster. |
|
|
4525 | |
3821 | =item EV_ATOMIC_T |
4526 | =item EV_ATOMIC_T |
3822 | |
4527 | |
3823 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4528 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3824 | access is atomic with respect to other threads or signal contexts. No such |
4529 | access is atomic and serialised with respect to other threads or signal |
3825 | type is easily found in the C language, so you can provide your own type |
4530 | contexts. No such type is easily found in the C language, so you can |
3826 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4531 | provide your own type that you know is safe for your purposes. It is used |
3827 | as well as for signal and thread safety in C<ev_async> watchers. |
4532 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4533 | in C<ev_async> watchers. |
3828 | |
4534 | |
3829 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4535 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3830 | (from F<signal.h>), which is usually good enough on most platforms. |
4536 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4537 | although strictly speaking using a type that also implies a memory fence |
|
|
4538 | is required. |
3831 | |
4539 | |
3832 | =item EV_H (h) |
4540 | =item EV_H (h) |
3833 | |
4541 | |
3834 | The name of the F<ev.h> header file used to include it. The default if |
4542 | The name of the F<ev.h> header file used to include it. The default if |
3835 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4543 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
3859 | will have the C<struct ev_loop *> as first argument, and you can create |
4567 | will have the C<struct ev_loop *> as first argument, and you can create |
3860 | additional independent event loops. Otherwise there will be no support |
4568 | additional independent event loops. Otherwise there will be no support |
3861 | for multiple event loops and there is no first event loop pointer |
4569 | for multiple event loops and there is no first event loop pointer |
3862 | argument. Instead, all functions act on the single default loop. |
4570 | argument. Instead, all functions act on the single default loop. |
3863 | |
4571 | |
|
|
4572 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4573 | default loop when multiplicity is switched off - you always have to |
|
|
4574 | initialise the loop manually in this case. |
|
|
4575 | |
3864 | =item EV_MINPRI |
4576 | =item EV_MINPRI |
3865 | |
4577 | |
3866 | =item EV_MAXPRI |
4578 | =item EV_MAXPRI |
3867 | |
4579 | |
3868 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4580 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3882 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
4594 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
3883 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
4595 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3884 | |
4596 | |
3885 | If undefined or defined to be C<1> (and the platform supports it), then |
4597 | If undefined or defined to be C<1> (and the platform supports it), then |
3886 | the respective watcher type is supported. If defined to be C<0>, then it |
4598 | the respective watcher type is supported. If defined to be C<0>, then it |
3887 | is not. Disabling watcher types mainly saves codesize. |
4599 | is not. Disabling watcher types mainly saves code size. |
3888 | |
4600 | |
3889 | =item EV_FEATURES |
4601 | =item EV_FEATURES |
3890 | |
4602 | |
3891 | If you need to shave off some kilobytes of code at the expense of some |
4603 | If you need to shave off some kilobytes of code at the expense of some |
3892 | speed (but with the full API), you can define this symbol to request |
4604 | speed (but with the full API), you can define this symbol to request |
… | |
… | |
3912 | |
4624 | |
3913 | =item C<1> - faster/larger code |
4625 | =item C<1> - faster/larger code |
3914 | |
4626 | |
3915 | Use larger code to speed up some operations. |
4627 | Use larger code to speed up some operations. |
3916 | |
4628 | |
3917 | Currently this is used to override some inlining decisions (enlarging the roughly |
4629 | Currently this is used to override some inlining decisions (enlarging the |
3918 | 30% code size on amd64. |
4630 | code size by roughly 30% on amd64). |
3919 | |
4631 | |
3920 | When optimising for size, use of compiler flags such as C<-Os> with |
4632 | When optimising for size, use of compiler flags such as C<-Os> with |
3921 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4633 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
3922 | assertions. |
4634 | assertions. |
3923 | |
4635 | |
3924 | =item C<2> - faster/larger data structures |
4636 | =item C<2> - faster/larger data structures |
3925 | |
4637 | |
3926 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4638 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
3927 | hash table sizes and so on. This will usually further increase codesize |
4639 | hash table sizes and so on. This will usually further increase code size |
3928 | and can additionally have an effect on the size of data structures at |
4640 | and can additionally have an effect on the size of data structures at |
3929 | runtime. |
4641 | runtime. |
3930 | |
4642 | |
3931 | =item C<4> - full API configuration |
4643 | =item C<4> - full API configuration |
3932 | |
4644 | |
… | |
… | |
3966 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4678 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
3967 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4679 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
3968 | your program might be left out as well - a binary starting a timer and an |
4680 | your program might be left out as well - a binary starting a timer and an |
3969 | I/O watcher then might come out at only 5Kb. |
4681 | I/O watcher then might come out at only 5Kb. |
3970 | |
4682 | |
|
|
4683 | =item EV_API_STATIC |
|
|
4684 | |
|
|
4685 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4686 | will have static linkage. This means that libev will not export any |
|
|
4687 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4688 | when you embed libev, only want to use libev functions in a single file, |
|
|
4689 | and do not want its identifiers to be visible. |
|
|
4690 | |
|
|
4691 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4692 | wants to use libev. |
|
|
4693 | |
|
|
4694 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4695 | doesn't support the required declaration syntax. |
|
|
4696 | |
3971 | =item EV_AVOID_STDIO |
4697 | =item EV_AVOID_STDIO |
3972 | |
4698 | |
3973 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4699 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
3974 | functions (printf, scanf, perror etc.). This will increase the codesize |
4700 | functions (printf, scanf, perror etc.). This will increase the code size |
3975 | somewhat, but if your program doesn't otherwise depend on stdio and your |
4701 | somewhat, but if your program doesn't otherwise depend on stdio and your |
3976 | libc allows it, this avoids linking in the stdio library which is quite |
4702 | libc allows it, this avoids linking in the stdio library which is quite |
3977 | big. |
4703 | big. |
3978 | |
4704 | |
3979 | Note that error messages might become less precise when this option is |
4705 | Note that error messages might become less precise when this option is |
… | |
… | |
3983 | |
4709 | |
3984 | The highest supported signal number, +1 (or, the number of |
4710 | The highest supported signal number, +1 (or, the number of |
3985 | signals): Normally, libev tries to deduce the maximum number of signals |
4711 | signals): Normally, libev tries to deduce the maximum number of signals |
3986 | automatically, but sometimes this fails, in which case it can be |
4712 | automatically, but sometimes this fails, in which case it can be |
3987 | specified. Also, using a lower number than detected (C<32> should be |
4713 | specified. Also, using a lower number than detected (C<32> should be |
3988 | good for about any system in existance) can save some memory, as libev |
4714 | good for about any system in existence) can save some memory, as libev |
3989 | statically allocates some 12-24 bytes per signal number. |
4715 | statically allocates some 12-24 bytes per signal number. |
3990 | |
4716 | |
3991 | =item EV_PID_HASHSIZE |
4717 | =item EV_PID_HASHSIZE |
3992 | |
4718 | |
3993 | C<ev_child> watchers use a small hash table to distribute workload by |
4719 | C<ev_child> watchers use a small hash table to distribute workload by |
… | |
… | |
4025 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4751 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
4026 | will be C<0>. |
4752 | will be C<0>. |
4027 | |
4753 | |
4028 | =item EV_VERIFY |
4754 | =item EV_VERIFY |
4029 | |
4755 | |
4030 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4756 | Controls how much internal verification (see C<ev_verify ()>) will |
4031 | be done: If set to C<0>, no internal verification code will be compiled |
4757 | be done: If set to C<0>, no internal verification code will be compiled |
4032 | in. If set to C<1>, then verification code will be compiled in, but not |
4758 | in. If set to C<1>, then verification code will be compiled in, but not |
4033 | called. If set to C<2>, then the internal verification code will be |
4759 | called. If set to C<2>, then the internal verification code will be |
4034 | called once per loop, which can slow down libev. If set to C<3>, then the |
4760 | called once per loop, which can slow down libev. If set to C<3>, then the |
4035 | verification code will be called very frequently, which will slow down |
4761 | verification code will be called very frequently, which will slow down |
… | |
… | |
4039 | will be C<0>. |
4765 | will be C<0>. |
4040 | |
4766 | |
4041 | =item EV_COMMON |
4767 | =item EV_COMMON |
4042 | |
4768 | |
4043 | By default, all watchers have a C<void *data> member. By redefining |
4769 | By default, all watchers have a C<void *data> member. By redefining |
4044 | this macro to a something else you can include more and other types of |
4770 | this macro to something else you can include more and other types of |
4045 | members. You have to define it each time you include one of the files, |
4771 | members. You have to define it each time you include one of the files, |
4046 | though, and it must be identical each time. |
4772 | though, and it must be identical each time. |
4047 | |
4773 | |
4048 | For example, the perl EV module uses something like this: |
4774 | For example, the perl EV module uses something like this: |
4049 | |
4775 | |
… | |
… | |
4118 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4844 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4119 | |
4845 | |
4120 | #include "ev_cpp.h" |
4846 | #include "ev_cpp.h" |
4121 | #include "ev.c" |
4847 | #include "ev.c" |
4122 | |
4848 | |
4123 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4849 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4124 | |
4850 | |
4125 | =head2 THREADS AND COROUTINES |
4851 | =head2 THREADS AND COROUTINES |
4126 | |
4852 | |
4127 | =head3 THREADS |
4853 | =head3 THREADS |
4128 | |
4854 | |
… | |
… | |
4179 | default loop and triggering an C<ev_async> watcher from the default loop |
4905 | default loop and triggering an C<ev_async> watcher from the default loop |
4180 | watcher callback into the event loop interested in the signal. |
4906 | watcher callback into the event loop interested in the signal. |
4181 | |
4907 | |
4182 | =back |
4908 | =back |
4183 | |
4909 | |
4184 | =head4 THREAD LOCKING EXAMPLE |
4910 | See also L<THREAD LOCKING EXAMPLE>. |
4185 | |
|
|
4186 | Here is a fictitious example of how to run an event loop in a different |
|
|
4187 | thread than where callbacks are being invoked and watchers are |
|
|
4188 | created/added/removed. |
|
|
4189 | |
|
|
4190 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4191 | which uses exactly this technique (which is suited for many high-level |
|
|
4192 | languages). |
|
|
4193 | |
|
|
4194 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4195 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4196 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4197 | |
|
|
4198 | First, you need to associate some data with the event loop: |
|
|
4199 | |
|
|
4200 | typedef struct { |
|
|
4201 | mutex_t lock; /* global loop lock */ |
|
|
4202 | ev_async async_w; |
|
|
4203 | thread_t tid; |
|
|
4204 | cond_t invoke_cv; |
|
|
4205 | } userdata; |
|
|
4206 | |
|
|
4207 | void prepare_loop (EV_P) |
|
|
4208 | { |
|
|
4209 | // for simplicity, we use a static userdata struct. |
|
|
4210 | static userdata u; |
|
|
4211 | |
|
|
4212 | ev_async_init (&u->async_w, async_cb); |
|
|
4213 | ev_async_start (EV_A_ &u->async_w); |
|
|
4214 | |
|
|
4215 | pthread_mutex_init (&u->lock, 0); |
|
|
4216 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4217 | |
|
|
4218 | // now associate this with the loop |
|
|
4219 | ev_set_userdata (EV_A_ u); |
|
|
4220 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4221 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4222 | |
|
|
4223 | // then create the thread running ev_loop |
|
|
4224 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4225 | } |
|
|
4226 | |
|
|
4227 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4228 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4229 | that might have been added: |
|
|
4230 | |
|
|
4231 | static void |
|
|
4232 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4233 | { |
|
|
4234 | // just used for the side effects |
|
|
4235 | } |
|
|
4236 | |
|
|
4237 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4238 | protecting the loop data, respectively. |
|
|
4239 | |
|
|
4240 | static void |
|
|
4241 | l_release (EV_P) |
|
|
4242 | { |
|
|
4243 | userdata *u = ev_userdata (EV_A); |
|
|
4244 | pthread_mutex_unlock (&u->lock); |
|
|
4245 | } |
|
|
4246 | |
|
|
4247 | static void |
|
|
4248 | l_acquire (EV_P) |
|
|
4249 | { |
|
|
4250 | userdata *u = ev_userdata (EV_A); |
|
|
4251 | pthread_mutex_lock (&u->lock); |
|
|
4252 | } |
|
|
4253 | |
|
|
4254 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4255 | into C<ev_loop>: |
|
|
4256 | |
|
|
4257 | void * |
|
|
4258 | l_run (void *thr_arg) |
|
|
4259 | { |
|
|
4260 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4261 | |
|
|
4262 | l_acquire (EV_A); |
|
|
4263 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4264 | ev_loop (EV_A_ 0); |
|
|
4265 | l_release (EV_A); |
|
|
4266 | |
|
|
4267 | return 0; |
|
|
4268 | } |
|
|
4269 | |
|
|
4270 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4271 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4272 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4273 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4274 | and b) skipping inter-thread-communication when there are no pending |
|
|
4275 | watchers is very beneficial): |
|
|
4276 | |
|
|
4277 | static void |
|
|
4278 | l_invoke (EV_P) |
|
|
4279 | { |
|
|
4280 | userdata *u = ev_userdata (EV_A); |
|
|
4281 | |
|
|
4282 | while (ev_pending_count (EV_A)) |
|
|
4283 | { |
|
|
4284 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4285 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4286 | } |
|
|
4287 | } |
|
|
4288 | |
|
|
4289 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4290 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4291 | thread to continue: |
|
|
4292 | |
|
|
4293 | static void |
|
|
4294 | real_invoke_pending (EV_P) |
|
|
4295 | { |
|
|
4296 | userdata *u = ev_userdata (EV_A); |
|
|
4297 | |
|
|
4298 | pthread_mutex_lock (&u->lock); |
|
|
4299 | ev_invoke_pending (EV_A); |
|
|
4300 | pthread_cond_signal (&u->invoke_cv); |
|
|
4301 | pthread_mutex_unlock (&u->lock); |
|
|
4302 | } |
|
|
4303 | |
|
|
4304 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4305 | event loop, you will now have to lock: |
|
|
4306 | |
|
|
4307 | ev_timer timeout_watcher; |
|
|
4308 | userdata *u = ev_userdata (EV_A); |
|
|
4309 | |
|
|
4310 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4311 | |
|
|
4312 | pthread_mutex_lock (&u->lock); |
|
|
4313 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4314 | ev_async_send (EV_A_ &u->async_w); |
|
|
4315 | pthread_mutex_unlock (&u->lock); |
|
|
4316 | |
|
|
4317 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4318 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4319 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4320 | watchers in the next event loop iteration. |
|
|
4321 | |
4911 | |
4322 | =head3 COROUTINES |
4912 | =head3 COROUTINES |
4323 | |
4913 | |
4324 | Libev is very accommodating to coroutines ("cooperative threads"): |
4914 | Libev is very accommodating to coroutines ("cooperative threads"): |
4325 | libev fully supports nesting calls to its functions from different |
4915 | libev fully supports nesting calls to its functions from different |
4326 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4916 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
4327 | different coroutines, and switch freely between both coroutines running |
4917 | different coroutines, and switch freely between both coroutines running |
4328 | the loop, as long as you don't confuse yourself). The only exception is |
4918 | the loop, as long as you don't confuse yourself). The only exception is |
4329 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4919 | that you must not do this from C<ev_periodic> reschedule callbacks. |
4330 | |
4920 | |
4331 | Care has been taken to ensure that libev does not keep local state inside |
4921 | Care has been taken to ensure that libev does not keep local state inside |
4332 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4922 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
4333 | they do not call any callbacks. |
4923 | they do not call any callbacks. |
4334 | |
4924 | |
4335 | =head2 COMPILER WARNINGS |
4925 | =head2 COMPILER WARNINGS |
4336 | |
4926 | |
4337 | Depending on your compiler and compiler settings, you might get no or a |
4927 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
4348 | maintainable. |
4938 | maintainable. |
4349 | |
4939 | |
4350 | And of course, some compiler warnings are just plain stupid, or simply |
4940 | And of course, some compiler warnings are just plain stupid, or simply |
4351 | wrong (because they don't actually warn about the condition their message |
4941 | wrong (because they don't actually warn about the condition their message |
4352 | seems to warn about). For example, certain older gcc versions had some |
4942 | seems to warn about). For example, certain older gcc versions had some |
4353 | warnings that resulted an extreme number of false positives. These have |
4943 | warnings that resulted in an extreme number of false positives. These have |
4354 | been fixed, but some people still insist on making code warn-free with |
4944 | been fixed, but some people still insist on making code warn-free with |
4355 | such buggy versions. |
4945 | such buggy versions. |
4356 | |
4946 | |
4357 | While libev is written to generate as few warnings as possible, |
4947 | While libev is written to generate as few warnings as possible, |
4358 | "warn-free" code is not a goal, and it is recommended not to build libev |
4948 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
4394 | I suggest using suppression lists. |
4984 | I suggest using suppression lists. |
4395 | |
4985 | |
4396 | |
4986 | |
4397 | =head1 PORTABILITY NOTES |
4987 | =head1 PORTABILITY NOTES |
4398 | |
4988 | |
|
|
4989 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4990 | |
|
|
4991 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4992 | interfaces but I<disables> them by default. |
|
|
4993 | |
|
|
4994 | That means that libev compiled in the default environment doesn't support |
|
|
4995 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4996 | |
|
|
4997 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4998 | by enabling the large file API, which makes them incompatible with the |
|
|
4999 | standard libev compiled for their system. |
|
|
5000 | |
|
|
5001 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5002 | suddenly make it incompatible to the default compile time environment, |
|
|
5003 | i.e. all programs not using special compile switches. |
|
|
5004 | |
|
|
5005 | =head2 OS/X AND DARWIN BUGS |
|
|
5006 | |
|
|
5007 | The whole thing is a bug if you ask me - basically any system interface |
|
|
5008 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5009 | OpenGL drivers. |
|
|
5010 | |
|
|
5011 | =head3 C<kqueue> is buggy |
|
|
5012 | |
|
|
5013 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5014 | only sockets, many support pipes. |
|
|
5015 | |
|
|
5016 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5017 | rotten platform, but of course you can still ask for it when creating a |
|
|
5018 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5019 | probably going to work well. |
|
|
5020 | |
|
|
5021 | =head3 C<poll> is buggy |
|
|
5022 | |
|
|
5023 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5024 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5025 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5026 | |
|
|
5027 | Libev tries to work around this by not using C<poll> by default on |
|
|
5028 | this rotten platform, but of course you can still ask for it when creating |
|
|
5029 | a loop. |
|
|
5030 | |
|
|
5031 | =head3 C<select> is buggy |
|
|
5032 | |
|
|
5033 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5034 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5035 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5036 | you use more. |
|
|
5037 | |
|
|
5038 | There is an undocumented "workaround" for this - defining |
|
|
5039 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5040 | work on OS/X. |
|
|
5041 | |
|
|
5042 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5043 | |
|
|
5044 | =head3 C<errno> reentrancy |
|
|
5045 | |
|
|
5046 | The default compile environment on Solaris is unfortunately so |
|
|
5047 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5048 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5049 | defined by default. A valid, if stupid, implementation choice. |
|
|
5050 | |
|
|
5051 | If you want to use libev in threaded environments you have to make sure |
|
|
5052 | it's compiled with C<_REENTRANT> defined. |
|
|
5053 | |
|
|
5054 | =head3 Event port backend |
|
|
5055 | |
|
|
5056 | The scalable event interface for Solaris is called "event |
|
|
5057 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5058 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5059 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5060 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5061 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5062 | great. |
|
|
5063 | |
|
|
5064 | If you can't get it to work, you can try running the program by setting |
|
|
5065 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5066 | C<select> backends. |
|
|
5067 | |
|
|
5068 | =head2 AIX POLL BUG |
|
|
5069 | |
|
|
5070 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5071 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5072 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5073 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5074 | |
4399 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5075 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5076 | |
|
|
5077 | =head3 General issues |
4400 | |
5078 | |
4401 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5079 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4402 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5080 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4403 | model. Libev still offers limited functionality on this platform in |
5081 | model. Libev still offers limited functionality on this platform in |
4404 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5082 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4405 | descriptors. This only applies when using Win32 natively, not when using |
5083 | descriptors. This only applies when using Win32 natively, not when using |
4406 | e.g. cygwin. |
5084 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5085 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5086 | environment. |
4407 | |
5087 | |
4408 | Lifting these limitations would basically require the full |
5088 | Lifting these limitations would basically require the full |
4409 | re-implementation of the I/O system. If you are into these kinds of |
5089 | re-implementation of the I/O system. If you are into this kind of thing, |
4410 | things, then note that glib does exactly that for you in a very portable |
5090 | then note that glib does exactly that for you in a very portable way (note |
4411 | way (note also that glib is the slowest event library known to man). |
5091 | also that glib is the slowest event library known to man). |
4412 | |
5092 | |
4413 | There is no supported compilation method available on windows except |
5093 | There is no supported compilation method available on windows except |
4414 | embedding it into other applications. |
5094 | embedding it into other applications. |
4415 | |
5095 | |
4416 | Sensible signal handling is officially unsupported by Microsoft - libev |
5096 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4444 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
5124 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4445 | |
5125 | |
4446 | #include "evwrap.h" |
5126 | #include "evwrap.h" |
4447 | #include "ev.c" |
5127 | #include "ev.c" |
4448 | |
5128 | |
4449 | =over 4 |
|
|
4450 | |
|
|
4451 | =item The winsocket select function |
5129 | =head3 The winsocket C<select> function |
4452 | |
5130 | |
4453 | The winsocket C<select> function doesn't follow POSIX in that it |
5131 | The winsocket C<select> function doesn't follow POSIX in that it |
4454 | requires socket I<handles> and not socket I<file descriptors> (it is |
5132 | requires socket I<handles> and not socket I<file descriptors> (it is |
4455 | also extremely buggy). This makes select very inefficient, and also |
5133 | also extremely buggy). This makes select very inefficient, and also |
4456 | requires a mapping from file descriptors to socket handles (the Microsoft |
5134 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4465 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5143 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4466 | |
5144 | |
4467 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5145 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4468 | complexity in the O(n²) range when using win32. |
5146 | complexity in the O(n²) range when using win32. |
4469 | |
5147 | |
4470 | =item Limited number of file descriptors |
5148 | =head3 Limited number of file descriptors |
4471 | |
5149 | |
4472 | Windows has numerous arbitrary (and low) limits on things. |
5150 | Windows has numerous arbitrary (and low) limits on things. |
4473 | |
5151 | |
4474 | Early versions of winsocket's select only supported waiting for a maximum |
5152 | Early versions of winsocket's select only supported waiting for a maximum |
4475 | of C<64> handles (probably owning to the fact that all windows kernels |
5153 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4490 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
5168 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4491 | (depending on windows version and/or the phase of the moon). To get more, |
5169 | (depending on windows version and/or the phase of the moon). To get more, |
4492 | you need to wrap all I/O functions and provide your own fd management, but |
5170 | you need to wrap all I/O functions and provide your own fd management, but |
4493 | the cost of calling select (O(n²)) will likely make this unworkable. |
5171 | the cost of calling select (O(n²)) will likely make this unworkable. |
4494 | |
5172 | |
4495 | =back |
|
|
4496 | |
|
|
4497 | =head2 PORTABILITY REQUIREMENTS |
5173 | =head2 PORTABILITY REQUIREMENTS |
4498 | |
5174 | |
4499 | In addition to a working ISO-C implementation and of course the |
5175 | In addition to a working ISO-C implementation and of course the |
4500 | backend-specific APIs, libev relies on a few additional extensions: |
5176 | backend-specific APIs, libev relies on a few additional extensions: |
4501 | |
5177 | |
… | |
… | |
4507 | Libev assumes not only that all watcher pointers have the same internal |
5183 | Libev assumes not only that all watcher pointers have the same internal |
4508 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5184 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4509 | assumes that the same (machine) code can be used to call any watcher |
5185 | assumes that the same (machine) code can be used to call any watcher |
4510 | callback: The watcher callbacks have different type signatures, but libev |
5186 | callback: The watcher callbacks have different type signatures, but libev |
4511 | calls them using an C<ev_watcher *> internally. |
5187 | calls them using an C<ev_watcher *> internally. |
|
|
5188 | |
|
|
5189 | =item pointer accesses must be thread-atomic |
|
|
5190 | |
|
|
5191 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5192 | writable in one piece - this is the case on all current architectures. |
4512 | |
5193 | |
4513 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5194 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4514 | |
5195 | |
4515 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5196 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4516 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5197 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
4539 | watchers. |
5220 | watchers. |
4540 | |
5221 | |
4541 | =item C<double> must hold a time value in seconds with enough accuracy |
5222 | =item C<double> must hold a time value in seconds with enough accuracy |
4542 | |
5223 | |
4543 | The type C<double> is used to represent timestamps. It is required to |
5224 | The type C<double> is used to represent timestamps. It is required to |
4544 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5225 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4545 | enough for at least into the year 4000. This requirement is fulfilled by |
5226 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5227 | (the design goal for libev). This requirement is overfulfilled by |
4546 | implementations implementing IEEE 754, which is basically all existing |
5228 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5229 | |
4547 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
5230 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
4548 | 2200. |
5231 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5232 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5233 | something like that, just kidding). |
4549 | |
5234 | |
4550 | =back |
5235 | =back |
4551 | |
5236 | |
4552 | If you know of other additional requirements drop me a note. |
5237 | If you know of other additional requirements drop me a note. |
4553 | |
5238 | |
… | |
… | |
4615 | =item Processing ev_async_send: O(number_of_async_watchers) |
5300 | =item Processing ev_async_send: O(number_of_async_watchers) |
4616 | |
5301 | |
4617 | =item Processing signals: O(max_signal_number) |
5302 | =item Processing signals: O(max_signal_number) |
4618 | |
5303 | |
4619 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5304 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4620 | calls in the current loop iteration. Checking for async and signal events |
5305 | calls in the current loop iteration and the loop is currently |
|
|
5306 | blocked. Checking for async and signal events involves iterating over all |
4621 | involves iterating over all running async watchers or all signal numbers. |
5307 | running async watchers or all signal numbers. |
4622 | |
5308 | |
4623 | =back |
5309 | =back |
4624 | |
5310 | |
4625 | |
5311 | |
|
|
5312 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5313 | |
|
|
5314 | The major version 4 introduced some incompatible changes to the API. |
|
|
5315 | |
|
|
5316 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5317 | for all changes, so most programs should still compile. The compatibility |
|
|
5318 | layer might be removed in later versions of libev, so better update to the |
|
|
5319 | new API early than late. |
|
|
5320 | |
|
|
5321 | =over 4 |
|
|
5322 | |
|
|
5323 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5324 | |
|
|
5325 | The backward compatibility mechanism can be controlled by |
|
|
5326 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5327 | section. |
|
|
5328 | |
|
|
5329 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5330 | |
|
|
5331 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5332 | |
|
|
5333 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5334 | ev_loop_fork (EV_DEFAULT); |
|
|
5335 | |
|
|
5336 | =item function/symbol renames |
|
|
5337 | |
|
|
5338 | A number of functions and symbols have been renamed: |
|
|
5339 | |
|
|
5340 | ev_loop => ev_run |
|
|
5341 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5342 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5343 | |
|
|
5344 | ev_unloop => ev_break |
|
|
5345 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5346 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5347 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5348 | |
|
|
5349 | EV_TIMEOUT => EV_TIMER |
|
|
5350 | |
|
|
5351 | ev_loop_count => ev_iteration |
|
|
5352 | ev_loop_depth => ev_depth |
|
|
5353 | ev_loop_verify => ev_verify |
|
|
5354 | |
|
|
5355 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5356 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5357 | associated constants have been renamed to not collide with the C<struct |
|
|
5358 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5359 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5360 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5361 | typedef. |
|
|
5362 | |
|
|
5363 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5364 | |
|
|
5365 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5366 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5367 | and work, but the library code will of course be larger. |
|
|
5368 | |
|
|
5369 | =back |
|
|
5370 | |
|
|
5371 | |
4626 | =head1 GLOSSARY |
5372 | =head1 GLOSSARY |
4627 | |
5373 | |
4628 | =over 4 |
5374 | =over 4 |
4629 | |
5375 | |
4630 | =item active |
5376 | =item active |
4631 | |
5377 | |
4632 | A watcher is active as long as it has been started (has been attached to |
5378 | A watcher is active as long as it has been started and not yet stopped. |
4633 | an event loop) but not yet stopped (disassociated from the event loop). |
5379 | See L<WATCHER STATES> for details. |
4634 | |
5380 | |
4635 | =item application |
5381 | =item application |
4636 | |
5382 | |
4637 | In this document, an application is whatever is using libev. |
5383 | In this document, an application is whatever is using libev. |
|
|
5384 | |
|
|
5385 | =item backend |
|
|
5386 | |
|
|
5387 | The part of the code dealing with the operating system interfaces. |
4638 | |
5388 | |
4639 | =item callback |
5389 | =item callback |
4640 | |
5390 | |
4641 | The address of a function that is called when some event has been |
5391 | The address of a function that is called when some event has been |
4642 | detected. Callbacks are being passed the event loop, the watcher that |
5392 | detected. Callbacks are being passed the event loop, the watcher that |
4643 | received the event, and the actual event bitset. |
5393 | received the event, and the actual event bitset. |
4644 | |
5394 | |
4645 | =item callback invocation |
5395 | =item callback/watcher invocation |
4646 | |
5396 | |
4647 | The act of calling the callback associated with a watcher. |
5397 | The act of calling the callback associated with a watcher. |
4648 | |
5398 | |
4649 | =item event |
5399 | =item event |
4650 | |
5400 | |
4651 | A change of state of some external event, such as data now being available |
5401 | A change of state of some external event, such as data now being available |
4652 | for reading on a file descriptor, time having passed or simply not having |
5402 | for reading on a file descriptor, time having passed or simply not having |
4653 | any other events happening anymore. |
5403 | any other events happening anymore. |
4654 | |
5404 | |
4655 | In libev, events are represented as single bits (such as C<EV_READ> or |
5405 | In libev, events are represented as single bits (such as C<EV_READ> or |
4656 | C<EV_TIMEOUT>). |
5406 | C<EV_TIMER>). |
4657 | |
5407 | |
4658 | =item event library |
5408 | =item event library |
4659 | |
5409 | |
4660 | A software package implementing an event model and loop. |
5410 | A software package implementing an event model and loop. |
4661 | |
5411 | |
… | |
… | |
4669 | The model used to describe how an event loop handles and processes |
5419 | The model used to describe how an event loop handles and processes |
4670 | watchers and events. |
5420 | watchers and events. |
4671 | |
5421 | |
4672 | =item pending |
5422 | =item pending |
4673 | |
5423 | |
4674 | A watcher is pending as soon as the corresponding event has been detected, |
5424 | A watcher is pending as soon as the corresponding event has been |
4675 | and stops being pending as soon as the watcher will be invoked or its |
5425 | detected. See L<WATCHER STATES> for details. |
4676 | pending status is explicitly cleared by the application. |
|
|
4677 | |
|
|
4678 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4679 | its pending status. |
|
|
4680 | |
5426 | |
4681 | =item real time |
5427 | =item real time |
4682 | |
5428 | |
4683 | The physical time that is observed. It is apparently strictly monotonic :) |
5429 | The physical time that is observed. It is apparently strictly monotonic :) |
4684 | |
5430 | |
4685 | =item wall-clock time |
5431 | =item wall-clock time |
4686 | |
5432 | |
4687 | The time and date as shown on clocks. Unlike real time, it can actually |
5433 | The time and date as shown on clocks. Unlike real time, it can actually |
4688 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5434 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4689 | clock. |
5435 | clock. |
4690 | |
5436 | |
4691 | =item watcher |
5437 | =item watcher |
4692 | |
5438 | |
4693 | A data structure that describes interest in certain events. Watchers need |
5439 | A data structure that describes interest in certain events. Watchers need |
4694 | to be started (attached to an event loop) before they can receive events. |
5440 | to be started (attached to an event loop) before they can receive events. |
4695 | |
5441 | |
4696 | =item watcher invocation |
|
|
4697 | |
|
|
4698 | The act of calling the callback associated with a watcher. |
|
|
4699 | |
|
|
4700 | =back |
5442 | =back |
4701 | |
5443 | |
4702 | =head1 AUTHOR |
5444 | =head1 AUTHOR |
4703 | |
5445 | |
4704 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5446 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5447 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4705 | |
5448 | |