… | |
… | |
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. |
|
|
82 | |
|
|
83 | =head1 WHAT TO READ WHEN IN A HURRY |
|
|
84 | |
|
|
85 | This manual tries to be very detailed, but unfortunately, this also makes |
|
|
86 | it very long. If you just want to know the basics of libev, I suggest |
|
|
87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
|
|
88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
|
|
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 |
… | |
… | |
98 | =head2 FEATURES |
106 | =head2 FEATURES |
99 | |
107 | |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
103 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
104 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
105 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
106 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
107 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
115 | change events (C<ev_child>), and event watchers dealing with the event |
108 | file watchers (C<ev_stat>) and even limited support for fork events |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
109 | (C<ev_fork>). |
117 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
|
|
118 | limited support for fork events (C<ev_fork>). |
110 | |
119 | |
111 | It also is quite fast (see this |
120 | It also is quite fast (see this |
112 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
121 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | for example). |
122 | for example). |
114 | |
123 | |
… | |
… | |
117 | Libev is very configurable. In this manual the default (and most common) |
126 | Libev is very configurable. In this manual the default (and most common) |
118 | configuration will be described, which supports multiple event loops. For |
127 | configuration will be described, which supports multiple event loops. For |
119 | more info about various configuration options please have a look at |
128 | more info about various configuration options please have a look at |
120 | B<EMBED> section in this manual. If libev was configured without support |
129 | B<EMBED> section in this manual. If libev was configured without support |
121 | for multiple event loops, then all functions taking an initial argument of |
130 | for multiple event loops, then all functions taking an initial argument of |
122 | name C<loop> (which is always of type C<ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | this argument. |
132 | this argument. |
124 | |
133 | |
125 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
126 | |
135 | |
127 | Libev represents time as a single floating point number, representing |
136 | Libev represents time as a single floating point number, representing |
128 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
129 | near the beginning of 1970, details are complicated, don't ask). This |
138 | somewhere near the beginning of 1970, details are complicated, don't |
130 | 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 |
131 | 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 |
132 | 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. |
|
|
142 | |
133 | 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 |
134 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
135 | |
145 | |
136 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
137 | |
147 | |
138 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
139 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
163 | |
173 | |
164 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
165 | |
175 | |
166 | 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 |
167 | 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 |
168 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
|
|
179 | C<ev_now_update> and C<ev_now>. |
169 | |
180 | |
170 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
171 | |
182 | |
172 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
173 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
174 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
175 | |
192 | |
176 | =item int ev_version_major () |
193 | =item int ev_version_major () |
177 | |
194 | |
178 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
179 | |
196 | |
… | |
… | |
190 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
191 | 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 |
192 | not a problem. |
209 | not a problem. |
193 | |
210 | |
194 | 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 |
195 | version. |
212 | version (note, however, that this will not detect other ABI mismatches, |
|
|
213 | such as LFS or reentrancy). |
196 | |
214 | |
197 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
198 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
199 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
200 | |
218 | |
… | |
… | |
211 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
212 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
213 | |
231 | |
214 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
215 | |
233 | |
216 | 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 |
217 | 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 |
|
|
236 | descriptor types. This set is often smaller than the one returned by |
218 | 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 |
219 | 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 |
220 | (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 |
221 | libev will probe for if you specify no backends explicitly. |
240 | probe for if you specify no backends explicitly. |
222 | |
241 | |
223 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
224 | |
243 | |
225 | 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 |
226 | is the theoretical, all-platform, value. To find which backends |
245 | value is platform-specific but can include backends not available on the |
227 | 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 |
228 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
229 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
230 | |
249 | |
231 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
232 | |
251 | |
233 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
234 | |
253 | |
235 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
236 | 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 |
237 | 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 |
238 | 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 |
… | |
… | |
264 | } |
283 | } |
265 | |
284 | |
266 | ... |
285 | ... |
267 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
268 | |
287 | |
269 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
270 | |
289 | |
271 | 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 |
272 | 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 |
273 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
274 | 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 |
… | |
… | |
286 | } |
305 | } |
287 | |
306 | |
288 | ... |
307 | ... |
289 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
290 | |
309 | |
|
|
310 | =item ev_feed_signal (int signum) |
|
|
311 | |
|
|
312 | This function can be used to "simulate" a signal receive. It is completely |
|
|
313 | safe to call this function at any time, from any context, including signal |
|
|
314 | handlers or random threads. |
|
|
315 | |
|
|
316 | Its main use is to customise signal handling in your process, especially |
|
|
317 | in the presence of threads. For example, you could block signals |
|
|
318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
|
|
319 | creating any loops), and in one thread, use C<sigwait> or any other |
|
|
320 | mechanism to wait for signals, then "deliver" them to libev by calling |
|
|
321 | C<ev_feed_signal>. |
|
|
322 | |
291 | =back |
323 | =back |
292 | |
324 | |
293 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
294 | |
326 | |
295 | 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 |
296 | 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 |
297 | I<function>). |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
298 | |
330 | |
299 | 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 |
300 | supports signals and child events, and dynamically created loops which do |
332 | supports child process events, and dynamically created event loops which |
301 | not. |
333 | do not. |
302 | |
334 | |
303 | =over 4 |
335 | =over 4 |
304 | |
336 | |
305 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
306 | |
338 | |
307 | 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 |
308 | 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 |
309 | 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 |
310 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
|
|
343 | |
|
|
344 | If the default loop is already initialised then this function simply |
|
|
345 | returns it (and ignores the flags. If that is troubling you, check |
|
|
346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
|
|
347 | flags, which should almost always be C<0>, unless the caller is also the |
|
|
348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
311 | |
349 | |
312 | 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 |
313 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
314 | |
352 | |
315 | 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 |
316 | 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 |
317 | as loops cannot be shared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
|
|
356 | threads anyway). |
318 | |
357 | |
319 | 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, |
320 | 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 |
321 | 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 |
322 | 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 |
323 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
324 | C<ev_default_init>. |
363 | |
|
|
364 | Example: This is the most typical usage. |
|
|
365 | |
|
|
366 | if (!ev_default_loop (0)) |
|
|
367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
368 | |
|
|
369 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
370 | environment settings to be taken into account: |
|
|
371 | |
|
|
372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
373 | |
|
|
374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
375 | |
|
|
376 | This will create and initialise a new event loop object. If the loop |
|
|
377 | could not be initialised, returns false. |
|
|
378 | |
|
|
379 | This function is thread-safe, and one common way to use libev with |
|
|
380 | threads is indeed to create one loop per thread, and using the default |
|
|
381 | loop in the "main" or "initial" thread. |
325 | |
382 | |
326 | 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 |
327 | 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>). |
328 | |
385 | |
329 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
344 | 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 |
345 | around bugs. |
402 | around bugs. |
346 | |
403 | |
347 | =item C<EVFLAG_FORKCHECK> |
404 | =item C<EVFLAG_FORKCHECK> |
348 | |
405 | |
349 | 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 |
350 | 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. |
351 | enabling this flag. |
|
|
352 | |
408 | |
353 | 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, |
354 | 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 |
355 | 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 |
356 | 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 |
… | |
… | |
362 | flag. |
418 | flag. |
363 | |
419 | |
364 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | environment variable. |
421 | environment variable. |
366 | |
422 | |
|
|
423 | =item C<EVFLAG_NOINOTIFY> |
|
|
424 | |
|
|
425 | When this flag is specified, then libev will not attempt to use the |
|
|
426 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
|
|
427 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
429 | |
|
|
430 | =item C<EVFLAG_SIGNALFD> |
|
|
431 | |
|
|
432 | When this flag is specified, then libev will attempt to use the |
|
|
433 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
|
434 | delivers signals synchronously, which makes it both faster and might make |
|
|
435 | it possible to get the queued signal data. It can also simplify signal |
|
|
436 | handling with threads, as long as you properly block signals in your |
|
|
437 | threads that are not interested in handling them. |
|
|
438 | |
|
|
439 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
441 | example) that can't properly initialise their signal masks. |
|
|
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
|
444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
|
446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
447 | when you want to receive them. |
|
|
448 | |
|
|
449 | This behaviour is useful when you want to do your own signal handling, or |
|
|
450 | want to handle signals only in specific threads and want to avoid libev |
|
|
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
455 | |
|
|
456 | This flag's behaviour will become the default in future versions of libev. |
|
|
457 | |
367 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
368 | |
459 | |
369 | 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 |
370 | 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, |
371 | but if that fails, expect a fairly low limit on the number of fds when |
462 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
395 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
396 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
397 | |
488 | |
398 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
399 | |
490 | |
|
|
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
492 | kernels). |
|
|
493 | |
400 | 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 |
401 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
402 | 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 |
403 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
404 | |
498 | |
405 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
406 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
407 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
408 | 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 |
409 | 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 |
410 | 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 |
411 | take considerable time (one syscall per file descriptor) and is of course |
507 | set, which can take considerable time (one syscall per file descriptor) |
412 | hard to detect. |
508 | and is of course hard to detect. |
413 | |
509 | |
414 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
415 | 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 |
416 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
417 | 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 |
418 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
419 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
420 | 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... |
421 | |
526 | |
422 | 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 |
423 | 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 |
424 | 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 |
425 | 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 |
… | |
… | |
462 | |
567 | |
463 | 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 |
464 | 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 |
465 | 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 |
466 | 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 |
467 | 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 |
468 | 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 |
469 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
470 | |
575 | |
471 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
472 | |
577 | |
473 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
474 | 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 |
… | |
… | |
491 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
492 | |
597 | |
493 | 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, |
494 | 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)). |
495 | |
600 | |
496 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
497 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
498 | blocking when no data (or space) is available. |
|
|
499 | |
|
|
500 | 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 |
501 | 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 |
502 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
503 | might perform better. |
604 | might perform better. |
504 | |
605 | |
505 | On the positive side, with the exception of the spurious readiness |
606 | On the positive side, this backend actually performed fully to |
506 | notifications, this backend actually performed fully to specification |
|
|
507 | 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 |
508 | 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. |
509 | |
620 | |
510 | 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 |
511 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
512 | |
623 | |
513 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
514 | |
625 | |
515 | 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 |
516 | 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 |
517 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
518 | |
629 | |
519 | 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). |
520 | |
639 | |
521 | =back |
640 | =back |
522 | |
641 | |
523 | If one or more of these are or'ed into the flags value, then only these |
642 | If one or more of the backend flags are or'ed into the flags value, |
524 | backends will be tried (in the reverse order as listed here). If none are |
643 | then only these backends will be tried (in the reverse order as listed |
525 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
526 | |
645 | ()> will be tried. |
527 | Example: This is the most typical usage. |
|
|
528 | |
|
|
529 | if (!ev_default_loop (0)) |
|
|
530 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
531 | |
|
|
532 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
533 | environment settings to be taken into account: |
|
|
534 | |
|
|
535 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
536 | |
|
|
537 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
538 | used if available (warning, breaks stuff, best use only with your own |
|
|
539 | private event loop and only if you know the OS supports your types of |
|
|
540 | fds): |
|
|
541 | |
|
|
542 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
543 | |
|
|
544 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
545 | |
|
|
546 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
547 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
548 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
549 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
550 | |
|
|
551 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
552 | libev with threads is indeed to create one loop per thread, and using the |
|
|
553 | default loop in the "main" or "initial" thread. |
|
|
554 | |
646 | |
555 | 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. |
556 | |
648 | |
557 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
558 | if (!epoller) |
650 | if (!epoller) |
559 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
560 | |
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 | |
561 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
562 | |
659 | |
563 | Destroys the default loop again (frees all memory and kernel state |
660 | Destroys an event loop object (frees all memory and kernel state |
564 | 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 |
565 | 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 |
566 | responsibility to either stop all watchers cleanly yourself I<before> |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
567 | 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 |
568 | 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 |
… | |
… | |
570 | |
667 | |
571 | 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 |
572 | 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 |
573 | as signal and child watchers) would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
574 | |
671 | |
575 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
576 | 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. |
577 | 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> |
578 | C<ev_loop_new> and C<ev_loop_destroy>). |
679 | and C<ev_loop_destroy>. |
579 | |
680 | |
580 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
581 | |
682 | |
582 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
583 | earlier call to C<ev_loop_new>. |
|
|
584 | |
|
|
585 | =item ev_default_fork () |
|
|
586 | |
|
|
587 | 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 |
588 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
589 | 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 |
590 | 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 |
591 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
592 | 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. |
593 | |
693 | |
594 | 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 |
595 | 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 |
596 | 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). |
597 | |
700 | |
598 | 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 |
599 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
600 | quite nicely into a call to C<pthread_atfork>: |
|
|
601 | |
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 | ... |
602 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
603 | |
|
|
604 | =item ev_loop_fork (loop) |
|
|
605 | |
|
|
606 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
607 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
608 | after fork that you want to re-use in the child, and how you do this is |
|
|
609 | entirely your own problem. |
|
|
610 | |
715 | |
611 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
612 | |
717 | |
613 | 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 |
614 | otherwise. |
719 | otherwise. |
615 | |
720 | |
616 | =item unsigned int ev_loop_count (loop) |
721 | =item unsigned int ev_iteration (loop) |
617 | |
722 | |
618 | 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 |
619 | 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> |
620 | happily wraps around with enough iterations. |
725 | and happily wraps around with enough iterations. |
621 | |
726 | |
622 | 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 |
623 | "ticks" the number of loop iterations), as it roughly corresponds with |
728 | "ticks" the number of loop iterations), as it roughly corresponds with |
624 | 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. |
625 | |
731 | |
626 | =item unsigned int ev_loop_depth (loop) |
732 | =item unsigned int ev_depth (loop) |
627 | |
733 | |
628 | 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 |
629 | 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. |
630 | |
736 | |
631 | 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 |
632 | 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), |
633 | in which case it is higher. |
739 | in which case it is higher. |
634 | |
740 | |
635 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
636 | 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. |
637 | |
745 | |
638 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
639 | |
747 | |
640 | 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 |
641 | use. |
749 | use. |
… | |
… | |
650 | |
758 | |
651 | =item ev_now_update (loop) |
759 | =item ev_now_update (loop) |
652 | |
760 | |
653 | Establishes the current time by querying the kernel, updating the time |
761 | Establishes the current time by querying the kernel, updating the time |
654 | 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 |
655 | is usually done automatically within C<ev_loop ()>. |
763 | is usually done automatically within C<ev_run ()>. |
656 | |
764 | |
657 | 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 |
658 | 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 |
659 | the current time is a good idea. |
767 | the current time is a good idea. |
660 | |
768 | |
… | |
… | |
662 | |
770 | |
663 | =item ev_suspend (loop) |
771 | =item ev_suspend (loop) |
664 | |
772 | |
665 | =item ev_resume (loop) |
773 | =item ev_resume (loop) |
666 | |
774 | |
667 | 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 |
668 | 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. |
669 | |
777 | |
670 | 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 |
671 | 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 |
672 | 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 |
673 | 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> |
… | |
… | |
675 | C<ev_resume> directly afterwards to resume timer processing. |
783 | C<ev_resume> directly afterwards to resume timer processing. |
676 | |
784 | |
677 | 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 |
678 | 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 |
679 | 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 |
680 | occured while suspended). |
788 | occurred while suspended). |
681 | |
789 | |
682 | 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 |
683 | 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> |
684 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
685 | |
793 | |
686 | 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 |
687 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
688 | |
796 | |
689 | =item ev_loop (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
690 | |
798 | |
691 | 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 |
692 | after you initialised all your watchers and you want to start handling |
800 | after you have initialised all your watchers and you want to start |
693 | events. |
801 | handling events. It will ask the operating system for any new events, call |
|
|
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
803 | is why event loops are called I<loops>. |
694 | |
804 | |
695 | 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 |
696 | 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. |
697 | |
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
|
|
812 | |
698 | Please note that an explicit C<ev_unloop> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
699 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
700 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
701 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
702 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
703 | beauty. |
818 | beauty. |
704 | |
819 | |
|
|
820 | This function is I<mostly> exception-safe - you can break out of a |
|
|
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
824 | |
705 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
706 | those events and any already outstanding ones, but will not block your |
826 | those events and any already outstanding ones, but will not wait and |
707 | process in case there are no events and will return after one iteration of |
827 | block your process in case there are no events and will return after one |
708 | the loop. |
828 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
829 | events while doing lengthy calculations, to keep the program responsive. |
709 | |
830 | |
710 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
831 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
711 | necessary) and will handle those and any already outstanding ones. It |
832 | necessary) and will handle those and any already outstanding ones. It |
712 | will block your process until at least one new event arrives (which could |
833 | will block your process until at least one new event arrives (which could |
713 | be an event internal to libev itself, so there is no guarantee that a |
834 | be an event internal to libev itself, so there is no guarantee that a |
714 | user-registered callback will be called), and will return after one |
835 | user-registered callback will be called), and will return after one |
715 | iteration of the loop. |
836 | iteration of the loop. |
716 | |
837 | |
717 | This is useful if you are waiting for some external event in conjunction |
838 | This is useful if you are waiting for some external event in conjunction |
718 | with something not expressible using other libev watchers (i.e. "roll your |
839 | with something not expressible using other libev watchers (i.e. "roll your |
719 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
840 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
720 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
721 | |
842 | |
722 | Here are the gory details of what C<ev_loop> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
723 | |
846 | |
|
|
847 | - Increment loop depth. |
|
|
848 | - Reset the ev_break status. |
724 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
|
|
850 | LOOP: |
725 | * If EVFLAG_FORKCHECK was used, check for a fork. |
851 | - If EVFLAG_FORKCHECK was used, check for a fork. |
726 | - If a fork was detected (by any means), queue and call all fork watchers. |
852 | - If a fork was detected (by any means), queue and call all fork watchers. |
727 | - Queue and call all prepare watchers. |
853 | - Queue and call all prepare watchers. |
|
|
854 | - If ev_break was called, goto FINISH. |
728 | - If we have been forked, detach and recreate the kernel state |
855 | - If we have been forked, detach and recreate the kernel state |
729 | as to not disturb the other process. |
856 | as to not disturb the other process. |
730 | - Update the kernel state with all outstanding changes. |
857 | - Update the kernel state with all outstanding changes. |
731 | - Update the "event loop time" (ev_now ()). |
858 | - Update the "event loop time" (ev_now ()). |
732 | - Calculate for how long to sleep or block, if at all |
859 | - Calculate for how long to sleep or block, if at all |
733 | (active idle watchers, EVLOOP_NONBLOCK or not having |
860 | (active idle watchers, EVRUN_NOWAIT or not having |
734 | any active watchers at all will result in not sleeping). |
861 | any active watchers at all will result in not sleeping). |
735 | - Sleep if the I/O and timer collect interval say so. |
862 | - Sleep if the I/O and timer collect interval say so. |
|
|
863 | - Increment loop iteration counter. |
736 | - Block the process, waiting for any events. |
864 | - Block the process, waiting for any events. |
737 | - Queue all outstanding I/O (fd) events. |
865 | - Queue all outstanding I/O (fd) events. |
738 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
866 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
739 | - Queue all expired timers. |
867 | - Queue all expired timers. |
740 | - Queue all expired periodics. |
868 | - Queue all expired periodics. |
741 | - Unless any events are pending now, queue all idle watchers. |
869 | - Queue all idle watchers with priority higher than that of pending events. |
742 | - Queue all check watchers. |
870 | - Queue all check watchers. |
743 | - Call all queued watchers in reverse order (i.e. check watchers first). |
871 | - Call all queued watchers in reverse order (i.e. check watchers first). |
744 | Signals and child watchers are implemented as I/O watchers, and will |
872 | Signals and child watchers are implemented as I/O watchers, and will |
745 | be handled here by queueing them when their watcher gets executed. |
873 | be handled here by queueing them when their watcher gets executed. |
746 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
874 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
747 | were used, or there are no active watchers, return, otherwise |
875 | were used, or there are no active watchers, goto FINISH, otherwise |
748 | continue with step *. |
876 | continue with step LOOP. |
|
|
877 | FINISH: |
|
|
878 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
879 | - Decrement the loop depth. |
|
|
880 | - Return. |
749 | |
881 | |
750 | Example: Queue some jobs and then loop until no events are outstanding |
882 | Example: Queue some jobs and then loop until no events are outstanding |
751 | anymore. |
883 | anymore. |
752 | |
884 | |
753 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
754 | ... as they still have work to do (even an idle watcher will do..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
755 | ev_loop (my_loop, 0); |
887 | ev_run (my_loop, 0); |
756 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
757 | |
889 | |
758 | =item ev_unloop (loop, how) |
890 | =item ev_break (loop, how) |
759 | |
891 | |
760 | Can be used to make a call to C<ev_loop> return early (but only after it |
892 | Can be used to make a call to C<ev_run> return early (but only after it |
761 | has processed all outstanding events). The C<how> argument must be either |
893 | has processed all outstanding events). The C<how> argument must be either |
762 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
894 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
763 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
895 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
764 | |
896 | |
765 | This "unloop state" will be cleared when entering C<ev_loop> again. |
897 | This "break state" will be cleared on the next call to C<ev_run>. |
766 | |
898 | |
767 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
899 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
900 | which case it will have no effect. |
768 | |
901 | |
769 | =item ev_ref (loop) |
902 | =item ev_ref (loop) |
770 | |
903 | |
771 | =item ev_unref (loop) |
904 | =item ev_unref (loop) |
772 | |
905 | |
773 | Ref/unref can be used to add or remove a reference count on the event |
906 | Ref/unref can be used to add or remove a reference count on the event |
774 | loop: Every watcher keeps one reference, and as long as the reference |
907 | loop: Every watcher keeps one reference, and as long as the reference |
775 | count is nonzero, C<ev_loop> will not return on its own. |
908 | count is nonzero, C<ev_run> will not return on its own. |
776 | |
909 | |
777 | If you have a watcher you never unregister that should not keep C<ev_loop> |
910 | This is useful when you have a watcher that you never intend to |
778 | from returning, call ev_unref() after starting, and ev_ref() before |
911 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
912 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
779 | stopping it. |
913 | before stopping it. |
780 | |
914 | |
781 | As an example, libev itself uses this for its internal signal pipe: It |
915 | As an example, libev itself uses this for its internal signal pipe: It |
782 | is not visible to the libev user and should not keep C<ev_loop> from |
916 | is not visible to the libev user and should not keep C<ev_run> from |
783 | exiting if no event watchers registered by it are active. It is also an |
917 | exiting if no event watchers registered by it are active. It is also an |
784 | excellent way to do this for generic recurring timers or from within |
918 | excellent way to do this for generic recurring timers or from within |
785 | third-party libraries. Just remember to I<unref after start> and I<ref |
919 | third-party libraries. Just remember to I<unref after start> and I<ref |
786 | before stop> (but only if the watcher wasn't active before, or was active |
920 | before stop> (but only if the watcher wasn't active before, or was active |
787 | before, respectively. Note also that libev might stop watchers itself |
921 | before, respectively. Note also that libev might stop watchers itself |
788 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
922 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
789 | in the callback). |
923 | in the callback). |
790 | |
924 | |
791 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
925 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
792 | running when nothing else is active. |
926 | running when nothing else is active. |
793 | |
927 | |
794 | ev_signal exitsig; |
928 | ev_signal exitsig; |
795 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
929 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
796 | ev_signal_start (loop, &exitsig); |
930 | ev_signal_start (loop, &exitsig); |
797 | evf_unref (loop); |
931 | ev_unref (loop); |
798 | |
932 | |
799 | Example: For some weird reason, unregister the above signal handler again. |
933 | Example: For some weird reason, unregister the above signal handler again. |
800 | |
934 | |
801 | ev_ref (loop); |
935 | ev_ref (loop); |
802 | ev_signal_stop (loop, &exitsig); |
936 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
822 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
823 | |
957 | |
824 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
825 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
826 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
827 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
828 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
829 | sleep time ensures that libev will not poll for I/O events more often then |
963 | sleep time ensures that libev will not poll for I/O events more often then |
830 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
831 | |
966 | |
832 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
833 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
834 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
835 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
841 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
976 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
842 | as this approaches the timing granularity of most systems. Note that if |
977 | as this approaches the timing granularity of most systems. Note that if |
843 | you do transactions with the outside world and you can't increase the |
978 | you do transactions with the outside world and you can't increase the |
844 | parallelity, then this setting will limit your transaction rate (if you |
979 | parallelity, then this setting will limit your transaction rate (if you |
845 | need to poll once per transaction and the I/O collect interval is 0.01, |
980 | need to poll once per transaction and the I/O collect interval is 0.01, |
846 | then you can't do more than 100 transations per second). |
981 | then you can't do more than 100 transactions per second). |
847 | |
982 | |
848 | Setting the I<timeout collect interval> can improve the opportunity for |
983 | Setting the I<timeout collect interval> can improve the opportunity for |
849 | saving power, as the program will "bundle" timer callback invocations that |
984 | saving power, as the program will "bundle" timer callback invocations that |
850 | are "near" in time together, by delaying some, thus reducing the number of |
985 | are "near" in time together, by delaying some, thus reducing the number of |
851 | times the process sleeps and wakes up again. Another useful technique to |
986 | times the process sleeps and wakes up again. Another useful technique to |
… | |
… | |
856 | more often than 100 times per second: |
991 | more often than 100 times per second: |
857 | |
992 | |
858 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
993 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
859 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
994 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
860 | |
995 | |
|
|
996 | =item ev_invoke_pending (loop) |
|
|
997 | |
|
|
998 | This call will simply invoke all pending watchers while resetting their |
|
|
999 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
1000 | but when overriding the invoke callback this call comes handy. This |
|
|
1001 | function can be invoked from a watcher - this can be useful for example |
|
|
1002 | when you want to do some lengthy calculation and want to pass further |
|
|
1003 | event handling to another thread (you still have to make sure only one |
|
|
1004 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1005 | |
|
|
1006 | =item int ev_pending_count (loop) |
|
|
1007 | |
|
|
1008 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1009 | are pending. |
|
|
1010 | |
|
|
1011 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1012 | |
|
|
1013 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1014 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1015 | this callback instead. This is useful, for example, when you want to |
|
|
1016 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1017 | |
|
|
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1019 | callback. |
|
|
1020 | |
|
|
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
|
|
1022 | |
|
|
1023 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1025 | each call to a libev function. |
|
|
1026 | |
|
|
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1028 | to wait for it to return. One way around this is to wake up the event |
|
|
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
|
|
1030 | I<release> and I<acquire> callbacks on the loop. |
|
|
1031 | |
|
|
1032 | When set, then C<release> will be called just before the thread is |
|
|
1033 | suspended waiting for new events, and C<acquire> is called just |
|
|
1034 | afterwards. |
|
|
1035 | |
|
|
1036 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1037 | C<acquire> will just call the mutex_lock function again. |
|
|
1038 | |
|
|
1039 | While event loop modifications are allowed between invocations of |
|
|
1040 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1041 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1042 | have no effect on the set of file descriptors being watched, or the time |
|
|
1043 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1044 | to take note of any changes you made. |
|
|
1045 | |
|
|
1046 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1047 | invocations of C<release> and C<acquire>. |
|
|
1048 | |
|
|
1049 | See also the locking example in the C<THREADS> section later in this |
|
|
1050 | document. |
|
|
1051 | |
|
|
1052 | =item ev_set_userdata (loop, void *data) |
|
|
1053 | |
|
|
1054 | =item void *ev_userdata (loop) |
|
|
1055 | |
|
|
1056 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1057 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1058 | C<0>. |
|
|
1059 | |
|
|
1060 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1061 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1062 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1063 | any other purpose as well. |
|
|
1064 | |
861 | =item ev_loop_verify (loop) |
1065 | =item ev_verify (loop) |
862 | |
1066 | |
863 | This function only does something when C<EV_VERIFY> support has been |
1067 | This function only does something when C<EV_VERIFY> support has been |
864 | compiled in, which is the default for non-minimal builds. It tries to go |
1068 | compiled in, which is the default for non-minimal builds. It tries to go |
865 | through all internal structures and checks them for validity. If anything |
1069 | through all internal structures and checks them for validity. If anything |
866 | is found to be inconsistent, it will print an error message to standard |
1070 | is found to be inconsistent, it will print an error message to standard |
… | |
… | |
877 | |
1081 | |
878 | In the following description, uppercase C<TYPE> in names stands for the |
1082 | In the following description, uppercase C<TYPE> in names stands for the |
879 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
1083 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
880 | watchers and C<ev_io_start> for I/O watchers. |
1084 | watchers and C<ev_io_start> for I/O watchers. |
881 | |
1085 | |
882 | A watcher is a structure that you create and register to record your |
1086 | A watcher is an opaque structure that you allocate and register to record |
883 | interest in some event. For instance, if you want to wait for STDIN to |
1087 | your interest in some event. To make a concrete example, imagine you want |
884 | become readable, you would create an C<ev_io> watcher for that: |
1088 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1089 | for that: |
885 | |
1090 | |
886 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
1091 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
887 | { |
1092 | { |
888 | ev_io_stop (w); |
1093 | ev_io_stop (w); |
889 | ev_unloop (loop, EVUNLOOP_ALL); |
1094 | ev_break (loop, EVBREAK_ALL); |
890 | } |
1095 | } |
891 | |
1096 | |
892 | struct ev_loop *loop = ev_default_loop (0); |
1097 | struct ev_loop *loop = ev_default_loop (0); |
893 | |
1098 | |
894 | ev_io stdin_watcher; |
1099 | ev_io stdin_watcher; |
895 | |
1100 | |
896 | ev_init (&stdin_watcher, my_cb); |
1101 | ev_init (&stdin_watcher, my_cb); |
897 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1102 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
898 | ev_io_start (loop, &stdin_watcher); |
1103 | ev_io_start (loop, &stdin_watcher); |
899 | |
1104 | |
900 | ev_loop (loop, 0); |
1105 | ev_run (loop, 0); |
901 | |
1106 | |
902 | As you can see, you are responsible for allocating the memory for your |
1107 | As you can see, you are responsible for allocating the memory for your |
903 | watcher structures (and it is I<usually> a bad idea to do this on the |
1108 | watcher structures (and it is I<usually> a bad idea to do this on the |
904 | stack). |
1109 | stack). |
905 | |
1110 | |
906 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
1111 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
907 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
1112 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
908 | |
1113 | |
909 | Each watcher structure must be initialised by a call to C<ev_init |
1114 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
910 | (watcher *, callback)>, which expects a callback to be provided. This |
1115 | *, callback)>, which expects a callback to be provided. This callback is |
911 | callback gets invoked each time the event occurs (or, in the case of I/O |
1116 | invoked each time the event occurs (or, in the case of I/O watchers, each |
912 | watchers, each time the event loop detects that the file descriptor given |
1117 | time the event loop detects that the file descriptor given is readable |
913 | is readable and/or writable). |
1118 | and/or writable). |
914 | |
1119 | |
915 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
1120 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
916 | macro to configure it, with arguments specific to the watcher type. There |
1121 | macro to configure it, with arguments specific to the watcher type. There |
917 | is also a macro to combine initialisation and setting in one call: C<< |
1122 | is also a macro to combine initialisation and setting in one call: C<< |
918 | ev_TYPE_init (watcher *, callback, ...) >>. |
1123 | ev_TYPE_init (watcher *, callback, ...) >>. |
… | |
… | |
941 | =item C<EV_WRITE> |
1146 | =item C<EV_WRITE> |
942 | |
1147 | |
943 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1148 | The file descriptor in the C<ev_io> watcher has become readable and/or |
944 | writable. |
1149 | writable. |
945 | |
1150 | |
946 | =item C<EV_TIMEOUT> |
1151 | =item C<EV_TIMER> |
947 | |
1152 | |
948 | The C<ev_timer> watcher has timed out. |
1153 | The C<ev_timer> watcher has timed out. |
949 | |
1154 | |
950 | =item C<EV_PERIODIC> |
1155 | =item C<EV_PERIODIC> |
951 | |
1156 | |
… | |
… | |
969 | |
1174 | |
970 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
971 | |
1176 | |
972 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
973 | |
1178 | |
974 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
975 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
976 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
977 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
978 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
979 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
980 | C<ev_loop> from blocking). |
1190 | blocking). |
981 | |
1191 | |
982 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
983 | |
1193 | |
984 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
985 | |
1195 | |
986 | =item C<EV_FORK> |
1196 | =item C<EV_FORK> |
987 | |
1197 | |
988 | The event loop has been resumed in the child process after fork (see |
1198 | The event loop has been resumed in the child process after fork (see |
989 | C<ev_fork>). |
1199 | C<ev_fork>). |
|
|
1200 | |
|
|
1201 | =item C<EV_CLEANUP> |
|
|
1202 | |
|
|
1203 | The event loop is about to be destroyed (see C<ev_cleanup>). |
990 | |
1204 | |
991 | =item C<EV_ASYNC> |
1205 | =item C<EV_ASYNC> |
992 | |
1206 | |
993 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1207 | The given async watcher has been asynchronously notified (see C<ev_async>). |
994 | |
1208 | |
… | |
… | |
1041 | |
1255 | |
1042 | ev_io w; |
1256 | ev_io w; |
1043 | ev_init (&w, my_cb); |
1257 | ev_init (&w, my_cb); |
1044 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1258 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1045 | |
1259 | |
1046 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1260 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
1047 | |
1261 | |
1048 | This macro initialises the type-specific parts of a watcher. You need to |
1262 | This macro initialises the type-specific parts of a watcher. You need to |
1049 | call C<ev_init> at least once before you call this macro, but you can |
1263 | call C<ev_init> at least once before you call this macro, but you can |
1050 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1264 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1051 | macro on a watcher that is active (it can be pending, however, which is a |
1265 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
1064 | |
1278 | |
1065 | Example: Initialise and set an C<ev_io> watcher in one step. |
1279 | Example: Initialise and set an C<ev_io> watcher in one step. |
1066 | |
1280 | |
1067 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1281 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1068 | |
1282 | |
1069 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1283 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
1070 | |
1284 | |
1071 | Starts (activates) the given watcher. Only active watchers will receive |
1285 | Starts (activates) the given watcher. Only active watchers will receive |
1072 | events. If the watcher is already active nothing will happen. |
1286 | events. If the watcher is already active nothing will happen. |
1073 | |
1287 | |
1074 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1288 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1075 | whole section. |
1289 | whole section. |
1076 | |
1290 | |
1077 | ev_io_start (EV_DEFAULT_UC, &w); |
1291 | ev_io_start (EV_DEFAULT_UC, &w); |
1078 | |
1292 | |
1079 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1293 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
1080 | |
1294 | |
1081 | Stops the given watcher if active, and clears the pending status (whether |
1295 | Stops the given watcher if active, and clears the pending status (whether |
1082 | the watcher was active or not). |
1296 | the watcher was active or not). |
1083 | |
1297 | |
1084 | It is possible that stopped watchers are pending - for example, |
1298 | It is possible that stopped watchers are pending - for example, |
… | |
… | |
1109 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1323 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1110 | |
1324 | |
1111 | Change the callback. You can change the callback at virtually any time |
1325 | Change the callback. You can change the callback at virtually any time |
1112 | (modulo threads). |
1326 | (modulo threads). |
1113 | |
1327 | |
1114 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1328 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1115 | |
1329 | |
1116 | =item int ev_priority (ev_TYPE *watcher) |
1330 | =item int ev_priority (ev_TYPE *watcher) |
1117 | |
1331 | |
1118 | Set and query the priority of the watcher. The priority is a small |
1332 | Set and query the priority of the watcher. The priority is a small |
1119 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1333 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
… | |
… | |
1151 | watcher isn't pending it does nothing and returns C<0>. |
1365 | watcher isn't pending it does nothing and returns C<0>. |
1152 | |
1366 | |
1153 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1367 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1154 | callback to be invoked, which can be accomplished with this function. |
1368 | callback to be invoked, which can be accomplished with this function. |
1155 | |
1369 | |
|
|
1370 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1371 | |
|
|
1372 | Feeds the given event set into the event loop, as if the specified event |
|
|
1373 | had happened for the specified watcher (which must be a pointer to an |
|
|
1374 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1375 | not free the watcher as long as it has pending events. |
|
|
1376 | |
|
|
1377 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1378 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1379 | not started in the first place. |
|
|
1380 | |
|
|
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1382 | functions that do not need a watcher. |
|
|
1383 | |
1156 | =back |
1384 | =back |
1157 | |
1385 | |
|
|
1386 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
|
|
1387 | OWN COMPOSITE WATCHERS> idioms. |
1158 | |
1388 | |
1159 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1389 | =head2 WATCHER STATES |
1160 | |
1390 | |
1161 | Each watcher has, by default, a member C<void *data> that you can change |
1391 | There are various watcher states mentioned throughout this manual - |
1162 | and read at any time: libev will completely ignore it. This can be used |
1392 | active, pending and so on. In this section these states and the rules to |
1163 | to associate arbitrary data with your watcher. If you need more data and |
1393 | transition between them will be described in more detail - and while these |
1164 | don't want to allocate memory and store a pointer to it in that data |
1394 | rules might look complicated, they usually do "the right thing". |
1165 | member, you can also "subclass" the watcher type and provide your own |
|
|
1166 | data: |
|
|
1167 | |
1395 | |
1168 | struct my_io |
1396 | =over 4 |
1169 | { |
|
|
1170 | ev_io io; |
|
|
1171 | int otherfd; |
|
|
1172 | void *somedata; |
|
|
1173 | struct whatever *mostinteresting; |
|
|
1174 | }; |
|
|
1175 | |
1397 | |
1176 | ... |
1398 | =item initialiased |
1177 | struct my_io w; |
|
|
1178 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1179 | |
1399 | |
1180 | And since your callback will be called with a pointer to the watcher, you |
1400 | Before a watcher can be registered with the event loop it has to be |
1181 | can cast it back to your own type: |
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1182 | |
1403 | |
1183 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1404 | In this state it is simply some block of memory that is suitable for |
1184 | { |
1405 | use in an event loop. It can be moved around, freed, reused etc. at |
1185 | struct my_io *w = (struct my_io *)w_; |
1406 | will - as long as you either keep the memory contents intact, or call |
1186 | ... |
1407 | C<ev_TYPE_init> again. |
1187 | } |
|
|
1188 | |
1408 | |
1189 | More interesting and less C-conformant ways of casting your callback type |
1409 | =item started/running/active |
1190 | instead have been omitted. |
|
|
1191 | |
1410 | |
1192 | Another common scenario is to use some data structure with multiple |
1411 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1193 | embedded watchers: |
1412 | property of the event loop, and is actively waiting for events. While in |
|
|
1413 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1414 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1415 | and call libev functions on it that are documented to work on active watchers. |
1194 | |
1416 | |
1195 | struct my_biggy |
1417 | =item pending |
1196 | { |
|
|
1197 | int some_data; |
|
|
1198 | ev_timer t1; |
|
|
1199 | ev_timer t2; |
|
|
1200 | } |
|
|
1201 | |
1418 | |
1202 | In this case getting the pointer to C<my_biggy> is a bit more |
1419 | If a watcher is active and libev determines that an event it is interested |
1203 | complicated: Either you store the address of your C<my_biggy> struct |
1420 | in has occurred (such as a timer expiring), it will become pending. It will |
1204 | in the C<data> member of the watcher (for woozies), or you need to use |
1421 | stay in this pending state until either it is stopped or its callback is |
1205 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
1422 | about to be invoked, so it is not normally pending inside the watcher |
1206 | programmers): |
1423 | callback. |
1207 | |
1424 | |
1208 | #include <stddef.h> |
1425 | The watcher might or might not be active while it is pending (for example, |
|
|
1426 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1427 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1428 | but it is still property of the event loop at this time, so cannot be |
|
|
1429 | moved, freed or reused. And if it is active the rules described in the |
|
|
1430 | previous item still apply. |
1209 | |
1431 | |
1210 | static void |
1432 | It is also possible to feed an event on a watcher that is not active (e.g. |
1211 | t1_cb (EV_P_ ev_timer *w, int revents) |
1433 | via C<ev_feed_event>), in which case it becomes pending without being |
1212 | { |
1434 | active. |
1213 | struct my_biggy big = (struct my_biggy *) |
|
|
1214 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1215 | } |
|
|
1216 | |
1435 | |
1217 | static void |
1436 | =item stopped |
1218 | t2_cb (EV_P_ ev_timer *w, int revents) |
1437 | |
1219 | { |
1438 | A watcher can be stopped implicitly by libev (in which case it might still |
1220 | struct my_biggy big = (struct my_biggy *) |
1439 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
1221 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1440 | latter will clear any pending state the watcher might be in, regardless |
1222 | } |
1441 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1442 | freeing it is often a good idea. |
|
|
1443 | |
|
|
1444 | While stopped (and not pending) the watcher is essentially in the |
|
|
1445 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1446 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1447 | it again). |
|
|
1448 | |
|
|
1449 | =back |
1223 | |
1450 | |
1224 | =head2 WATCHER PRIORITY MODELS |
1451 | =head2 WATCHER PRIORITY MODELS |
1225 | |
1452 | |
1226 | Many event loops support I<watcher priorities>, which are usually small |
1453 | Many event loops support I<watcher priorities>, which are usually small |
1227 | integers that influence the ordering of event callback invocation |
1454 | integers that influence the ordering of event callback invocation |
… | |
… | |
1270 | |
1497 | |
1271 | For example, to emulate how many other event libraries handle priorities, |
1498 | For example, to emulate how many other event libraries handle priorities, |
1272 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1499 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1273 | the normal watcher callback, you just start the idle watcher. The real |
1500 | the normal watcher callback, you just start the idle watcher. The real |
1274 | processing is done in the idle watcher callback. This causes libev to |
1501 | processing is done in the idle watcher callback. This causes libev to |
1275 | continously poll and process kernel event data for the watcher, but when |
1502 | continuously poll and process kernel event data for the watcher, but when |
1276 | the lock-out case is known to be rare (which in turn is rare :), this is |
1503 | the lock-out case is known to be rare (which in turn is rare :), this is |
1277 | workable. |
1504 | workable. |
1278 | |
1505 | |
1279 | Usually, however, the lock-out model implemented that way will perform |
1506 | Usually, however, the lock-out model implemented that way will perform |
1280 | miserably under the type of load it was designed to handle. In that case, |
1507 | miserably under the type of load it was designed to handle. In that case, |
… | |
… | |
1294 | { |
1521 | { |
1295 | // stop the I/O watcher, we received the event, but |
1522 | // stop the I/O watcher, we received the event, but |
1296 | // are not yet ready to handle it. |
1523 | // are not yet ready to handle it. |
1297 | ev_io_stop (EV_A_ w); |
1524 | ev_io_stop (EV_A_ w); |
1298 | |
1525 | |
1299 | // start the idle watcher to ahndle the actual event. |
1526 | // start the idle watcher to handle the actual event. |
1300 | // it will not be executed as long as other watchers |
1527 | // it will not be executed as long as other watchers |
1301 | // with the default priority are receiving events. |
1528 | // with the default priority are receiving events. |
1302 | ev_idle_start (EV_A_ &idle); |
1529 | ev_idle_start (EV_A_ &idle); |
1303 | } |
1530 | } |
1304 | |
1531 | |
… | |
… | |
1354 | In general you can register as many read and/or write event watchers per |
1581 | In general you can register as many read and/or write event watchers per |
1355 | fd as you want (as long as you don't confuse yourself). Setting all file |
1582 | fd as you want (as long as you don't confuse yourself). Setting all file |
1356 | descriptors to non-blocking mode is also usually a good idea (but not |
1583 | descriptors to non-blocking mode is also usually a good idea (but not |
1357 | required if you know what you are doing). |
1584 | required if you know what you are doing). |
1358 | |
1585 | |
1359 | If you cannot use non-blocking mode, then force the use of a |
|
|
1360 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1361 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1362 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1363 | files) - libev doesn't guarentee any specific behaviour in that case. |
|
|
1364 | |
|
|
1365 | Another thing you have to watch out for is that it is quite easy to |
1586 | Another thing you have to watch out for is that it is quite easy to |
1366 | receive "spurious" readiness notifications, that is your callback might |
1587 | receive "spurious" readiness notifications, that is, your callback might |
1367 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1588 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1368 | because there is no data. Not only are some backends known to create a |
1589 | because there is no data. It is very easy to get into this situation even |
1369 | lot of those (for example Solaris ports), it is very easy to get into |
1590 | with a relatively standard program structure. Thus it is best to always |
1370 | this situation even with a relatively standard program structure. Thus |
1591 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1371 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1372 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1592 | preferable to a program hanging until some data arrives. |
1373 | |
1593 | |
1374 | If you cannot run the fd in non-blocking mode (for example you should |
1594 | If you cannot run the fd in non-blocking mode (for example you should |
1375 | not play around with an Xlib connection), then you have to separately |
1595 | not play around with an Xlib connection), then you have to separately |
1376 | re-test whether a file descriptor is really ready with a known-to-be good |
1596 | re-test whether a file descriptor is really ready with a known-to-be good |
1377 | interface such as poll (fortunately in our Xlib example, Xlib already |
1597 | interface such as poll (fortunately in the case of Xlib, it already does |
1378 | does this on its own, so its quite safe to use). Some people additionally |
1598 | this on its own, so its quite safe to use). Some people additionally |
1379 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1599 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1380 | indefinitely. |
1600 | indefinitely. |
1381 | |
1601 | |
1382 | But really, best use non-blocking mode. |
1602 | But really, best use non-blocking mode. |
1383 | |
1603 | |
… | |
… | |
1411 | |
1631 | |
1412 | There is no workaround possible except not registering events |
1632 | There is no workaround possible except not registering events |
1413 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1633 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1414 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1634 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1415 | |
1635 | |
|
|
1636 | =head3 The special problem of files |
|
|
1637 | |
|
|
1638 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1639 | representing files, and expect it to become ready when their program |
|
|
1640 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1641 | |
|
|
1642 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1643 | notification as soon as the kernel knows whether and how much data is |
|
|
1644 | there, and in the case of open files, that's always the case, so you |
|
|
1645 | always get a readiness notification instantly, and your read (or possibly |
|
|
1646 | write) will still block on the disk I/O. |
|
|
1647 | |
|
|
1648 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1649 | devices and so on, there is another party (the sender) that delivers data |
|
|
1650 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1651 | will not send data on its own, simply because it doesn't know what you |
|
|
1652 | wish to read - you would first have to request some data. |
|
|
1653 | |
|
|
1654 | Since files are typically not-so-well supported by advanced notification |
|
|
1655 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1656 | to files, even though you should not use it. The reason for this is |
|
|
1657 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1658 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1659 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1660 | F</dev/urandom>), and even though the file might better be served with |
|
|
1661 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1662 | it "just works" instead of freezing. |
|
|
1663 | |
|
|
1664 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1665 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1666 | when you rarely read from a file instead of from a socket, and want to |
|
|
1667 | reuse the same code path. |
|
|
1668 | |
1416 | =head3 The special problem of fork |
1669 | =head3 The special problem of fork |
1417 | |
1670 | |
1418 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1671 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1419 | useless behaviour. Libev fully supports fork, but needs to be told about |
1672 | useless behaviour. Libev fully supports fork, but needs to be told about |
1420 | it in the child. |
1673 | it in the child if you want to continue to use it in the child. |
1421 | |
1674 | |
1422 | To support fork in your programs, you either have to call |
1675 | To support fork in your child processes, you have to call C<ev_loop_fork |
1423 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1676 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1424 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1677 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1425 | C<EVBACKEND_POLL>. |
|
|
1426 | |
1678 | |
1427 | =head3 The special problem of SIGPIPE |
1679 | =head3 The special problem of SIGPIPE |
1428 | |
1680 | |
1429 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1681 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1430 | when writing to a pipe whose other end has been closed, your program gets |
1682 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1433 | |
1685 | |
1434 | So when you encounter spurious, unexplained daemon exits, make sure you |
1686 | So when you encounter spurious, unexplained daemon exits, make sure you |
1435 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1687 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1436 | somewhere, as that would have given you a big clue). |
1688 | somewhere, as that would have given you a big clue). |
1437 | |
1689 | |
|
|
1690 | =head3 The special problem of accept()ing when you can't |
|
|
1691 | |
|
|
1692 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1693 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1694 | connection from the pending queue in all error cases. |
|
|
1695 | |
|
|
1696 | For example, larger servers often run out of file descriptors (because |
|
|
1697 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1698 | rejecting the connection, leading to libev signalling readiness on |
|
|
1699 | the next iteration again (the connection still exists after all), and |
|
|
1700 | typically causing the program to loop at 100% CPU usage. |
|
|
1701 | |
|
|
1702 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1703 | operating systems, there is usually little the app can do to remedy the |
|
|
1704 | situation, and no known thread-safe method of removing the connection to |
|
|
1705 | cope with overload is known (to me). |
|
|
1706 | |
|
|
1707 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1708 | - when the program encounters an overload, it will just loop until the |
|
|
1709 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1710 | event-based way to handle this situation, so it's the best one can do. |
|
|
1711 | |
|
|
1712 | A better way to handle the situation is to log any errors other than |
|
|
1713 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1714 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1715 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1716 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1717 | usage. |
|
|
1718 | |
|
|
1719 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1720 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1721 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1722 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1723 | clients under typical overload conditions. |
|
|
1724 | |
|
|
1725 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1726 | is often done with C<malloc> failures, but this results in an easy |
|
|
1727 | opportunity for a DoS attack. |
1438 | |
1728 | |
1439 | =head3 Watcher-Specific Functions |
1729 | =head3 Watcher-Specific Functions |
1440 | |
1730 | |
1441 | =over 4 |
1731 | =over 4 |
1442 | |
1732 | |
… | |
… | |
1474 | ... |
1764 | ... |
1475 | struct ev_loop *loop = ev_default_init (0); |
1765 | struct ev_loop *loop = ev_default_init (0); |
1476 | ev_io stdin_readable; |
1766 | ev_io stdin_readable; |
1477 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1767 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1478 | ev_io_start (loop, &stdin_readable); |
1768 | ev_io_start (loop, &stdin_readable); |
1479 | ev_loop (loop, 0); |
1769 | ev_run (loop, 0); |
1480 | |
1770 | |
1481 | |
1771 | |
1482 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1772 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1483 | |
1773 | |
1484 | Timer watchers are simple relative timers that generate an event after a |
1774 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1490 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1780 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1491 | monotonic clock option helps a lot here). |
1781 | monotonic clock option helps a lot here). |
1492 | |
1782 | |
1493 | The callback is guaranteed to be invoked only I<after> its timeout has |
1783 | The callback is guaranteed to be invoked only I<after> its timeout has |
1494 | passed (not I<at>, so on systems with very low-resolution clocks this |
1784 | passed (not I<at>, so on systems with very low-resolution clocks this |
1495 | might introduce a small delay). If multiple timers become ready during the |
1785 | might introduce a small delay, see "the special problem of being too |
|
|
1786 | early", below). If multiple timers become ready during the same loop |
1496 | same loop iteration then the ones with earlier time-out values are invoked |
1787 | iteration then the ones with earlier time-out values are invoked before |
1497 | before ones of the same priority with later time-out values (but this is |
1788 | ones of the same priority with later time-out values (but this is no |
1498 | no longer true when a callback calls C<ev_loop> recursively). |
1789 | longer true when a callback calls C<ev_run> recursively). |
1499 | |
1790 | |
1500 | =head3 Be smart about timeouts |
1791 | =head3 Be smart about timeouts |
1501 | |
1792 | |
1502 | Many real-world problems involve some kind of timeout, usually for error |
1793 | Many real-world problems involve some kind of timeout, usually for error |
1503 | recovery. A typical example is an HTTP request - if the other side hangs, |
1794 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1578 | |
1869 | |
1579 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1870 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1580 | but remember the time of last activity, and check for a real timeout only |
1871 | but remember the time of last activity, and check for a real timeout only |
1581 | within the callback: |
1872 | within the callback: |
1582 | |
1873 | |
|
|
1874 | ev_tstamp timeout = 60.; |
1583 | ev_tstamp last_activity; // time of last activity |
1875 | ev_tstamp last_activity; // time of last activity |
|
|
1876 | ev_timer timer; |
1584 | |
1877 | |
1585 | static void |
1878 | static void |
1586 | callback (EV_P_ ev_timer *w, int revents) |
1879 | callback (EV_P_ ev_timer *w, int revents) |
1587 | { |
1880 | { |
1588 | ev_tstamp now = ev_now (EV_A); |
1881 | // calculate when the timeout would happen |
1589 | ev_tstamp timeout = last_activity + 60.; |
1882 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1590 | |
1883 | |
1591 | // if last_activity + 60. is older than now, we did time out |
1884 | // if negative, it means we the timeout already occurred |
1592 | if (timeout < now) |
1885 | if (after < 0.) |
1593 | { |
1886 | { |
1594 | // timeout occured, take action |
1887 | // timeout occurred, take action |
1595 | } |
1888 | } |
1596 | else |
1889 | else |
1597 | { |
1890 | { |
1598 | // callback was invoked, but there was some activity, re-arm |
1891 | // callback was invoked, but there was some recent |
1599 | // the watcher to fire in last_activity + 60, which is |
1892 | // activity. simply restart the timer to time out |
1600 | // guaranteed to be in the future, so "again" is positive: |
1893 | // after "after" seconds, which is the earliest time |
1601 | w->repeat = timeout - now; |
1894 | // the timeout can occur. |
|
|
1895 | ev_timer_set (w, after, 0.); |
1602 | ev_timer_again (EV_A_ w); |
1896 | ev_timer_start (EV_A_ w); |
1603 | } |
1897 | } |
1604 | } |
1898 | } |
1605 | |
1899 | |
1606 | To summarise the callback: first calculate the real timeout (defined |
1900 | To summarise the callback: first calculate in how many seconds the |
1607 | as "60 seconds after the last activity"), then check if that time has |
1901 | timeout will occur (by calculating the absolute time when it would occur, |
1608 | been reached, which means something I<did>, in fact, time out. Otherwise |
1902 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1609 | the callback was invoked too early (C<timeout> is in the future), so |
1903 | (EV_A)> from that). |
1610 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1611 | a timeout then. |
|
|
1612 | |
1904 | |
1613 | Note how C<ev_timer_again> is used, taking advantage of the |
1905 | If this value is negative, then we are already past the timeout, i.e. we |
1614 | C<ev_timer_again> optimisation when the timer is already running. |
1906 | timed out, and need to do whatever is needed in this case. |
|
|
1907 | |
|
|
1908 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1909 | and simply start the timer with this timeout value. |
|
|
1910 | |
|
|
1911 | In other words, each time the callback is invoked it will check whether |
|
|
1912 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1913 | again at the earliest time it could time out. Rinse. Repeat. |
1615 | |
1914 | |
1616 | This scheme causes more callback invocations (about one every 60 seconds |
1915 | This scheme causes more callback invocations (about one every 60 seconds |
1617 | minus half the average time between activity), but virtually no calls to |
1916 | minus half the average time between activity), but virtually no calls to |
1618 | libev to change the timeout. |
1917 | libev to change the timeout. |
1619 | |
1918 | |
1620 | To start the timer, simply initialise the watcher and set C<last_activity> |
1919 | To start the machinery, simply initialise the watcher and set |
1621 | to the current time (meaning we just have some activity :), then call the |
1920 | C<last_activity> to the current time (meaning there was some activity just |
1622 | callback, which will "do the right thing" and start the timer: |
1921 | now), then call the callback, which will "do the right thing" and start |
|
|
1922 | the timer: |
1623 | |
1923 | |
|
|
1924 | last_activity = ev_now (EV_A); |
1624 | ev_init (timer, callback); |
1925 | ev_init (&timer, callback); |
1625 | last_activity = ev_now (loop); |
1926 | callback (EV_A_ &timer, 0); |
1626 | callback (loop, timer, EV_TIMEOUT); |
|
|
1627 | |
1927 | |
1628 | And when there is some activity, simply store the current time in |
1928 | When there is some activity, simply store the current time in |
1629 | C<last_activity>, no libev calls at all: |
1929 | C<last_activity>, no libev calls at all: |
1630 | |
1930 | |
|
|
1931 | if (activity detected) |
1631 | last_actiivty = ev_now (loop); |
1932 | last_activity = ev_now (EV_A); |
|
|
1933 | |
|
|
1934 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1935 | providing a new value, stopping the timer and calling the callback, which |
|
|
1936 | will again do the right thing (for example, time out immediately :). |
|
|
1937 | |
|
|
1938 | timeout = new_value; |
|
|
1939 | ev_timer_stop (EV_A_ &timer); |
|
|
1940 | callback (EV_A_ &timer, 0); |
1632 | |
1941 | |
1633 | This technique is slightly more complex, but in most cases where the |
1942 | This technique is slightly more complex, but in most cases where the |
1634 | time-out is unlikely to be triggered, much more efficient. |
1943 | time-out is unlikely to be triggered, much more efficient. |
1635 | |
|
|
1636 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1637 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1638 | fix things for you. |
|
|
1639 | |
1944 | |
1640 | =item 4. Wee, just use a double-linked list for your timeouts. |
1945 | =item 4. Wee, just use a double-linked list for your timeouts. |
1641 | |
1946 | |
1642 | If there is not one request, but many thousands (millions...), all |
1947 | If there is not one request, but many thousands (millions...), all |
1643 | employing some kind of timeout with the same timeout value, then one can |
1948 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1670 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1975 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1671 | rather complicated, but extremely efficient, something that really pays |
1976 | rather complicated, but extremely efficient, something that really pays |
1672 | off after the first million or so of active timers, i.e. it's usually |
1977 | off after the first million or so of active timers, i.e. it's usually |
1673 | overkill :) |
1978 | overkill :) |
1674 | |
1979 | |
|
|
1980 | =head3 The special problem of being too early |
|
|
1981 | |
|
|
1982 | If you ask a timer to call your callback after three seconds, then |
|
|
1983 | you expect it to be invoked after three seconds - but of course, this |
|
|
1984 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1985 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1986 | process with a STOP signal for a few hours for example. |
|
|
1987 | |
|
|
1988 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1989 | delay has occurred, but cannot guarantee this. |
|
|
1990 | |
|
|
1991 | A less obvious failure mode is calling your callback too early: many event |
|
|
1992 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1993 | this can cause your callback to be invoked much earlier than you would |
|
|
1994 | expect. |
|
|
1995 | |
|
|
1996 | To see why, imagine a system with a clock that only offers full second |
|
|
1997 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1998 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1999 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2000 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2001 | |
|
|
2002 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2003 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2004 | one-second delay was requested - this is being "too early", despite best |
|
|
2005 | intentions. |
|
|
2006 | |
|
|
2007 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2008 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2009 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2010 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2011 | |
|
|
2012 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2013 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2014 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2015 | late" side of things. |
|
|
2016 | |
1675 | =head3 The special problem of time updates |
2017 | =head3 The special problem of time updates |
1676 | |
2018 | |
1677 | Establishing the current time is a costly operation (it usually takes at |
2019 | Establishing the current time is a costly operation (it usually takes |
1678 | least two system calls): EV therefore updates its idea of the current |
2020 | at least one system call): EV therefore updates its idea of the current |
1679 | time only before and after C<ev_loop> collects new events, which causes a |
2021 | time only before and after C<ev_run> collects new events, which causes a |
1680 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2022 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1681 | lots of events in one iteration. |
2023 | lots of events in one iteration. |
1682 | |
2024 | |
1683 | The relative timeouts are calculated relative to the C<ev_now ()> |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
1684 | time. This is usually the right thing as this timestamp refers to the time |
2026 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1690 | |
2032 | |
1691 | If the event loop is suspended for a long time, you can also force an |
2033 | If the event loop is suspended for a long time, you can also force an |
1692 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1693 | ()>. |
2035 | ()>. |
1694 | |
2036 | |
|
|
2037 | =head3 The special problem of unsynchronised clocks |
|
|
2038 | |
|
|
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2041 | jumps). |
|
|
2042 | |
|
|
2043 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2044 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2045 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2046 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2047 | than a directly following call to C<time>. |
|
|
2048 | |
|
|
2049 | The moral of this is to only compare libev-related timestamps with |
|
|
2050 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2051 | a second or so. |
|
|
2052 | |
|
|
2053 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2054 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2055 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2056 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2057 | |
|
|
2058 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2059 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2060 | I<measured according to the real time>, not the system clock. |
|
|
2061 | |
|
|
2062 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2063 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2064 | exactly the right behaviour. |
|
|
2065 | |
|
|
2066 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2067 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2068 | time, where your comparisons will always generate correct results. |
|
|
2069 | |
|
|
2070 | =head3 The special problems of suspended animation |
|
|
2071 | |
|
|
2072 | When you leave the server world it is quite customary to hit machines that |
|
|
2073 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2074 | |
|
|
2075 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2076 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2077 | to run until the system is suspended, but they will not advance while the |
|
|
2078 | system is suspended. That means, on resume, it will be as if the program |
|
|
2079 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2080 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2081 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2082 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2083 | be adjusted accordingly. |
|
|
2084 | |
|
|
2085 | I would not be surprised to see different behaviour in different between |
|
|
2086 | operating systems, OS versions or even different hardware. |
|
|
2087 | |
|
|
2088 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2089 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2090 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2091 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2092 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2093 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2094 | |
|
|
2095 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2096 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2097 | deterministic behaviour in this case (you can do nothing against |
|
|
2098 | C<SIGSTOP>). |
|
|
2099 | |
1695 | =head3 Watcher-Specific Functions and Data Members |
2100 | =head3 Watcher-Specific Functions and Data Members |
1696 | |
2101 | |
1697 | =over 4 |
2102 | =over 4 |
1698 | |
2103 | |
1699 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2104 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1712 | keep up with the timer (because it takes longer than those 10 seconds to |
2117 | keep up with the timer (because it takes longer than those 10 seconds to |
1713 | do stuff) the timer will not fire more than once per event loop iteration. |
2118 | do stuff) the timer will not fire more than once per event loop iteration. |
1714 | |
2119 | |
1715 | =item ev_timer_again (loop, ev_timer *) |
2120 | =item ev_timer_again (loop, ev_timer *) |
1716 | |
2121 | |
1717 | This will act as if the timer timed out and restart it again if it is |
2122 | This will act as if the timer timed out, and restarts it again if it is |
1718 | repeating. The exact semantics are: |
2123 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2124 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1719 | |
2125 | |
|
|
2126 | The exact semantics are as in the following rules, all of which will be |
|
|
2127 | applied to the watcher: |
|
|
2128 | |
|
|
2129 | =over 4 |
|
|
2130 | |
1720 | If the timer is pending, its pending status is cleared. |
2131 | =item If the timer is pending, the pending status is always cleared. |
1721 | |
2132 | |
1722 | If the timer is started but non-repeating, stop it (as if it timed out). |
2133 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2134 | out, without invoking it). |
1723 | |
2135 | |
1724 | If the timer is repeating, either start it if necessary (with the |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1725 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2137 | and start the timer, if necessary. |
|
|
2138 | |
|
|
2139 | =back |
1726 | |
2140 | |
1727 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2141 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1728 | usage example. |
2142 | usage example. |
|
|
2143 | |
|
|
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
|
|
2145 | |
|
|
2146 | Returns the remaining time until a timer fires. If the timer is active, |
|
|
2147 | then this time is relative to the current event loop time, otherwise it's |
|
|
2148 | the timeout value currently configured. |
|
|
2149 | |
|
|
2150 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2151 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2152 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2153 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2154 | too), and so on. |
1729 | |
2155 | |
1730 | =item ev_tstamp repeat [read-write] |
2156 | =item ev_tstamp repeat [read-write] |
1731 | |
2157 | |
1732 | The current C<repeat> value. Will be used each time the watcher times out |
2158 | The current C<repeat> value. Will be used each time the watcher times out |
1733 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2159 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1759 | } |
2185 | } |
1760 | |
2186 | |
1761 | ev_timer mytimer; |
2187 | ev_timer mytimer; |
1762 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2188 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1763 | ev_timer_again (&mytimer); /* start timer */ |
2189 | ev_timer_again (&mytimer); /* start timer */ |
1764 | ev_loop (loop, 0); |
2190 | ev_run (loop, 0); |
1765 | |
2191 | |
1766 | // and in some piece of code that gets executed on any "activity": |
2192 | // and in some piece of code that gets executed on any "activity": |
1767 | // reset the timeout to start ticking again at 10 seconds |
2193 | // reset the timeout to start ticking again at 10 seconds |
1768 | ev_timer_again (&mytimer); |
2194 | ev_timer_again (&mytimer); |
1769 | |
2195 | |
… | |
… | |
1795 | |
2221 | |
1796 | As with timers, the callback is guaranteed to be invoked only when the |
2222 | As with timers, the callback is guaranteed to be invoked only when the |
1797 | point in time where it is supposed to trigger has passed. If multiple |
2223 | point in time where it is supposed to trigger has passed. If multiple |
1798 | timers become ready during the same loop iteration then the ones with |
2224 | timers become ready during the same loop iteration then the ones with |
1799 | earlier time-out values are invoked before ones with later time-out values |
2225 | earlier time-out values are invoked before ones with later time-out values |
1800 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
2226 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1801 | |
2227 | |
1802 | =head3 Watcher-Specific Functions and Data Members |
2228 | =head3 Watcher-Specific Functions and Data Members |
1803 | |
2229 | |
1804 | =over 4 |
2230 | =over 4 |
1805 | |
2231 | |
… | |
… | |
1840 | |
2266 | |
1841 | Another way to think about it (for the mathematically inclined) is that |
2267 | Another way to think about it (for the mathematically inclined) is that |
1842 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2268 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1843 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2269 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1844 | |
2270 | |
1845 | For numerical stability it is preferable that the C<offset> value is near |
2271 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1846 | C<ev_now ()> (the current time), but there is no range requirement for |
2272 | interval value should be higher than C<1/8192> (which is around 100 |
1847 | this value, and in fact is often specified as zero. |
2273 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2274 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2275 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2276 | C<0> and C<interval>, which is also the recommended range. |
1848 | |
2277 | |
1849 | Note also that there is an upper limit to how often a timer can fire (CPU |
2278 | Note also that there is an upper limit to how often a timer can fire (CPU |
1850 | speed for example), so if C<interval> is very small then timing stability |
2279 | speed for example), so if C<interval> is very small then timing stability |
1851 | will of course deteriorate. Libev itself tries to be exact to be about one |
2280 | will of course deteriorate. Libev itself tries to be exact to be about one |
1852 | millisecond (if the OS supports it and the machine is fast enough). |
2281 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
1933 | Example: Call a callback every hour, or, more precisely, whenever the |
2362 | Example: Call a callback every hour, or, more precisely, whenever the |
1934 | system time is divisible by 3600. The callback invocation times have |
2363 | system time is divisible by 3600. The callback invocation times have |
1935 | potentially a lot of jitter, but good long-term stability. |
2364 | potentially a lot of jitter, but good long-term stability. |
1936 | |
2365 | |
1937 | static void |
2366 | static void |
1938 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
2367 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1939 | { |
2368 | { |
1940 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2369 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1941 | } |
2370 | } |
1942 | |
2371 | |
1943 | ev_periodic hourly_tick; |
2372 | ev_periodic hourly_tick; |
… | |
… | |
1966 | |
2395 | |
1967 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2396 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1968 | |
2397 | |
1969 | Signal watchers will trigger an event when the process receives a specific |
2398 | Signal watchers will trigger an event when the process receives a specific |
1970 | signal one or more times. Even though signals are very asynchronous, libev |
2399 | signal one or more times. Even though signals are very asynchronous, libev |
1971 | will try it's best to deliver signals synchronously, i.e. as part of the |
2400 | will try its best to deliver signals synchronously, i.e. as part of the |
1972 | normal event processing, like any other event. |
2401 | normal event processing, like any other event. |
1973 | |
2402 | |
1974 | If you want signals asynchronously, just use C<sigaction> as you would |
2403 | If you want signals to be delivered truly asynchronously, just use |
1975 | do without libev and forget about sharing the signal. You can even use |
2404 | C<sigaction> as you would do without libev and forget about sharing |
1976 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2405 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2406 | synchronously wake up an event loop. |
1977 | |
2407 | |
1978 | You can configure as many watchers as you like per signal. Only when the |
2408 | You can configure as many watchers as you like for the same signal, but |
|
|
2409 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2410 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2411 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2412 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2413 | |
1979 | first watcher gets started will libev actually register a signal handler |
2414 | When the first watcher gets started will libev actually register something |
1980 | with the kernel (thus it coexists with your own signal handlers as long as |
2415 | with the kernel (thus it coexists with your own signal handlers as long as |
1981 | you don't register any with libev for the same signal). Similarly, when |
2416 | you don't register any with libev for the same signal). |
1982 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1983 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1984 | |
2417 | |
1985 | If possible and supported, libev will install its handlers with |
2418 | If possible and supported, libev will install its handlers with |
1986 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2419 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1987 | interrupted. If you have a problem with system calls getting interrupted by |
2420 | not be unduly interrupted. If you have a problem with system calls getting |
1988 | signals you can block all signals in an C<ev_check> watcher and unblock |
2421 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1989 | them in an C<ev_prepare> watcher. |
2422 | and unblock them in an C<ev_prepare> watcher. |
|
|
2423 | |
|
|
2424 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2425 | |
|
|
2426 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2427 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2428 | stopping it again), that is, libev might or might not block the signal, |
|
|
2429 | and might or might not set or restore the installed signal handler (but |
|
|
2430 | see C<EVFLAG_NOSIGMASK>). |
|
|
2431 | |
|
|
2432 | While this does not matter for the signal disposition (libev never |
|
|
2433 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2434 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2435 | certain signals to be blocked. |
|
|
2436 | |
|
|
2437 | This means that before calling C<exec> (from the child) you should reset |
|
|
2438 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2439 | choice usually). |
|
|
2440 | |
|
|
2441 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2442 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2443 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2444 | |
|
|
2445 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2446 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2447 | the window of opportunity for problems, it will not go away, as libev |
|
|
2448 | I<has> to modify the signal mask, at least temporarily. |
|
|
2449 | |
|
|
2450 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2451 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2452 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2453 | |
|
|
2454 | =head3 The special problem of threads signal handling |
|
|
2455 | |
|
|
2456 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2457 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2458 | threads in a process block signals, which is hard to achieve. |
|
|
2459 | |
|
|
2460 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2461 | for the same signals), you can tackle this problem by globally blocking |
|
|
2462 | all signals before creating any threads (or creating them with a fully set |
|
|
2463 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2464 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2465 | these signals. You can pass on any signals that libev might be interested |
|
|
2466 | in by calling C<ev_feed_signal>. |
1990 | |
2467 | |
1991 | =head3 Watcher-Specific Functions and Data Members |
2468 | =head3 Watcher-Specific Functions and Data Members |
1992 | |
2469 | |
1993 | =over 4 |
2470 | =over 4 |
1994 | |
2471 | |
… | |
… | |
2010 | Example: Try to exit cleanly on SIGINT. |
2487 | Example: Try to exit cleanly on SIGINT. |
2011 | |
2488 | |
2012 | static void |
2489 | static void |
2013 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2490 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
2014 | { |
2491 | { |
2015 | ev_unloop (loop, EVUNLOOP_ALL); |
2492 | ev_break (loop, EVBREAK_ALL); |
2016 | } |
2493 | } |
2017 | |
2494 | |
2018 | ev_signal signal_watcher; |
2495 | ev_signal signal_watcher; |
2019 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2496 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2020 | ev_signal_start (loop, &signal_watcher); |
2497 | ev_signal_start (loop, &signal_watcher); |
… | |
… | |
2039 | libev) |
2516 | libev) |
2040 | |
2517 | |
2041 | =head3 Process Interaction |
2518 | =head3 Process Interaction |
2042 | |
2519 | |
2043 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2520 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2044 | initialised. This is necessary to guarantee proper behaviour even if |
2521 | initialised. This is necessary to guarantee proper behaviour even if the |
2045 | the first child watcher is started after the child exits. The occurrence |
2522 | first child watcher is started after the child exits. The occurrence |
2046 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2523 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2047 | synchronously as part of the event loop processing. Libev always reaps all |
2524 | synchronously as part of the event loop processing. Libev always reaps all |
2048 | children, even ones not watched. |
2525 | children, even ones not watched. |
2049 | |
2526 | |
2050 | =head3 Overriding the Built-In Processing |
2527 | =head3 Overriding the Built-In Processing |
… | |
… | |
2060 | =head3 Stopping the Child Watcher |
2537 | =head3 Stopping the Child Watcher |
2061 | |
2538 | |
2062 | Currently, the child watcher never gets stopped, even when the |
2539 | Currently, the child watcher never gets stopped, even when the |
2063 | child terminates, so normally one needs to stop the watcher in the |
2540 | child terminates, so normally one needs to stop the watcher in the |
2064 | callback. Future versions of libev might stop the watcher automatically |
2541 | callback. Future versions of libev might stop the watcher automatically |
2065 | when a child exit is detected. |
2542 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2543 | problem). |
2066 | |
2544 | |
2067 | =head3 Watcher-Specific Functions and Data Members |
2545 | =head3 Watcher-Specific Functions and Data Members |
2068 | |
2546 | |
2069 | =over 4 |
2547 | =over 4 |
2070 | |
2548 | |
… | |
… | |
2405 | |
2883 | |
2406 | Prepare and check watchers are usually (but not always) used in pairs: |
2884 | Prepare and check watchers are usually (but not always) used in pairs: |
2407 | prepare watchers get invoked before the process blocks and check watchers |
2885 | prepare watchers get invoked before the process blocks and check watchers |
2408 | afterwards. |
2886 | afterwards. |
2409 | |
2887 | |
2410 | You I<must not> call C<ev_loop> or similar functions that enter |
2888 | You I<must not> call C<ev_run> or similar functions that enter |
2411 | the current event loop from either C<ev_prepare> or C<ev_check> |
2889 | the current event loop from either C<ev_prepare> or C<ev_check> |
2412 | watchers. Other loops than the current one are fine, however. The |
2890 | watchers. Other loops than the current one are fine, however. The |
2413 | rationale behind this is that you do not need to check for recursion in |
2891 | rationale behind this is that you do not need to check for recursion in |
2414 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2892 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2415 | C<ev_check> so if you have one watcher of each kind they will always be |
2893 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2583 | |
3061 | |
2584 | if (timeout >= 0) |
3062 | if (timeout >= 0) |
2585 | // create/start timer |
3063 | // create/start timer |
2586 | |
3064 | |
2587 | // poll |
3065 | // poll |
2588 | ev_loop (EV_A_ 0); |
3066 | ev_run (EV_A_ 0); |
2589 | |
3067 | |
2590 | // stop timer again |
3068 | // stop timer again |
2591 | if (timeout >= 0) |
3069 | if (timeout >= 0) |
2592 | ev_timer_stop (EV_A_ &to); |
3070 | ev_timer_stop (EV_A_ &to); |
2593 | |
3071 | |
… | |
… | |
2671 | if you do not want that, you need to temporarily stop the embed watcher). |
3149 | if you do not want that, you need to temporarily stop the embed watcher). |
2672 | |
3150 | |
2673 | =item ev_embed_sweep (loop, ev_embed *) |
3151 | =item ev_embed_sweep (loop, ev_embed *) |
2674 | |
3152 | |
2675 | Make a single, non-blocking sweep over the embedded loop. This works |
3153 | Make a single, non-blocking sweep over the embedded loop. This works |
2676 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3154 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2677 | appropriate way for embedded loops. |
3155 | appropriate way for embedded loops. |
2678 | |
3156 | |
2679 | =item struct ev_loop *other [read-only] |
3157 | =item struct ev_loop *other [read-only] |
2680 | |
3158 | |
2681 | The embedded event loop. |
3159 | The embedded event loop. |
… | |
… | |
2741 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3219 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2742 | handlers will be invoked, too, of course. |
3220 | handlers will be invoked, too, of course. |
2743 | |
3221 | |
2744 | =head3 The special problem of life after fork - how is it possible? |
3222 | =head3 The special problem of life after fork - how is it possible? |
2745 | |
3223 | |
2746 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
3224 | Most uses of C<fork()> consist of forking, then some simple calls to set |
2747 | up/change the process environment, followed by a call to C<exec()>. This |
3225 | up/change the process environment, followed by a call to C<exec()>. This |
2748 | sequence should be handled by libev without any problems. |
3226 | sequence should be handled by libev without any problems. |
2749 | |
3227 | |
2750 | This changes when the application actually wants to do event handling |
3228 | This changes when the application actually wants to do event handling |
2751 | in the child, or both parent in child, in effect "continuing" after the |
3229 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
2767 | disadvantage of having to use multiple event loops (which do not support |
3245 | disadvantage of having to use multiple event loops (which do not support |
2768 | signal watchers). |
3246 | signal watchers). |
2769 | |
3247 | |
2770 | When this is not possible, or you want to use the default loop for |
3248 | When this is not possible, or you want to use the default loop for |
2771 | other reasons, then in the process that wants to start "fresh", call |
3249 | other reasons, then in the process that wants to start "fresh", call |
2772 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3250 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
2773 | the default loop will "orphan" (not stop) all registered watchers, so you |
3251 | Destroying the default loop will "orphan" (not stop) all registered |
2774 | have to be careful not to execute code that modifies those watchers. Note |
3252 | watchers, so you have to be careful not to execute code that modifies |
2775 | also that in that case, you have to re-register any signal watchers. |
3253 | those watchers. Note also that in that case, you have to re-register any |
|
|
3254 | signal watchers. |
2776 | |
3255 | |
2777 | =head3 Watcher-Specific Functions and Data Members |
3256 | =head3 Watcher-Specific Functions and Data Members |
2778 | |
3257 | |
2779 | =over 4 |
3258 | =over 4 |
2780 | |
3259 | |
2781 | =item ev_fork_init (ev_signal *, callback) |
3260 | =item ev_fork_init (ev_fork *, callback) |
2782 | |
3261 | |
2783 | Initialises and configures the fork watcher - it has no parameters of any |
3262 | Initialises and configures the fork watcher - it has no parameters of any |
2784 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3263 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2785 | believe me. |
3264 | really. |
2786 | |
3265 | |
2787 | =back |
3266 | =back |
2788 | |
3267 | |
2789 | |
3268 | |
|
|
3269 | =head2 C<ev_cleanup> - even the best things end |
|
|
3270 | |
|
|
3271 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3272 | by a call to C<ev_loop_destroy>. |
|
|
3273 | |
|
|
3274 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3275 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3276 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3277 | loop when you want them to be invoked. |
|
|
3278 | |
|
|
3279 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3280 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3281 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3282 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3283 | |
|
|
3284 | =head3 Watcher-Specific Functions and Data Members |
|
|
3285 | |
|
|
3286 | =over 4 |
|
|
3287 | |
|
|
3288 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3289 | |
|
|
3290 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3291 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3292 | pointless, I assure you. |
|
|
3293 | |
|
|
3294 | =back |
|
|
3295 | |
|
|
3296 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3297 | cleanup functions are called. |
|
|
3298 | |
|
|
3299 | static void |
|
|
3300 | program_exits (void) |
|
|
3301 | { |
|
|
3302 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3303 | } |
|
|
3304 | |
|
|
3305 | ... |
|
|
3306 | atexit (program_exits); |
|
|
3307 | |
|
|
3308 | |
2790 | =head2 C<ev_async> - how to wake up another event loop |
3309 | =head2 C<ev_async> - how to wake up an event loop |
2791 | |
3310 | |
2792 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3311 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2793 | asynchronous sources such as signal handlers (as opposed to multiple event |
3312 | asynchronous sources such as signal handlers (as opposed to multiple event |
2794 | loops - those are of course safe to use in different threads). |
3313 | loops - those are of course safe to use in different threads). |
2795 | |
3314 | |
2796 | Sometimes, however, you need to wake up another event loop you do not |
3315 | Sometimes, however, you need to wake up an event loop you do not control, |
2797 | control, for example because it belongs to another thread. This is what |
3316 | for example because it belongs to another thread. This is what C<ev_async> |
2798 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3317 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2799 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3318 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2800 | safe. |
|
|
2801 | |
3319 | |
2802 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3320 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2803 | too, are asynchronous in nature, and signals, too, will be compressed |
3321 | too, are asynchronous in nature, and signals, too, will be compressed |
2804 | (i.e. the number of callback invocations may be less than the number of |
3322 | (i.e. the number of callback invocations may be less than the number of |
2805 | C<ev_async_sent> calls). |
3323 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
2806 | |
3324 | of "global async watchers" by using a watcher on an otherwise unused |
2807 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3325 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2808 | just the default loop. |
3326 | even without knowing which loop owns the signal. |
2809 | |
3327 | |
2810 | =head3 Queueing |
3328 | =head3 Queueing |
2811 | |
3329 | |
2812 | C<ev_async> does not support queueing of data in any way. The reason |
3330 | C<ev_async> does not support queueing of data in any way. The reason |
2813 | is that the author does not know of a simple (or any) algorithm for a |
3331 | is that the author does not know of a simple (or any) algorithm for a |
2814 | multiple-writer-single-reader queue that works in all cases and doesn't |
3332 | multiple-writer-single-reader queue that works in all cases and doesn't |
2815 | need elaborate support such as pthreads. |
3333 | need elaborate support such as pthreads or unportable memory access |
|
|
3334 | semantics. |
2816 | |
3335 | |
2817 | That means that if you want to queue data, you have to provide your own |
3336 | That means that if you want to queue data, you have to provide your own |
2818 | queue. But at least I can tell you how to implement locking around your |
3337 | queue. But at least I can tell you how to implement locking around your |
2819 | queue: |
3338 | queue: |
2820 | |
3339 | |
… | |
… | |
2904 | trust me. |
3423 | trust me. |
2905 | |
3424 | |
2906 | =item ev_async_send (loop, ev_async *) |
3425 | =item ev_async_send (loop, ev_async *) |
2907 | |
3426 | |
2908 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3427 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2909 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3428 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3429 | returns. |
|
|
3430 | |
2910 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3431 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2911 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3432 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2912 | section below on what exactly this means). |
3433 | embedding section below on what exactly this means). |
2913 | |
3434 | |
2914 | Note that, as with other watchers in libev, multiple events might get |
3435 | Note that, as with other watchers in libev, multiple events might get |
2915 | compressed into a single callback invocation (another way to look at this |
3436 | compressed into a single callback invocation (another way to look at |
2916 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3437 | this is that C<ev_async> watchers are level-triggered: they are set on |
2917 | reset when the event loop detects that). |
3438 | C<ev_async_send>, reset when the event loop detects that). |
2918 | |
3439 | |
2919 | This call incurs the overhead of a system call only once per event loop |
3440 | This call incurs the overhead of at most one extra system call per event |
2920 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3441 | loop iteration, if the event loop is blocked, and no syscall at all if |
2921 | repeated calls to C<ev_async_send> for the same event loop. |
3442 | the event loop (or your program) is processing events. That means that |
|
|
3443 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3444 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3445 | zero) under load. |
2922 | |
3446 | |
2923 | =item bool = ev_async_pending (ev_async *) |
3447 | =item bool = ev_async_pending (ev_async *) |
2924 | |
3448 | |
2925 | Returns a non-zero value when C<ev_async_send> has been called on the |
3449 | Returns a non-zero value when C<ev_async_send> has been called on the |
2926 | watcher but the event has not yet been processed (or even noted) by the |
3450 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2959 | |
3483 | |
2960 | If C<timeout> is less than 0, then no timeout watcher will be |
3484 | If C<timeout> is less than 0, then no timeout watcher will be |
2961 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3485 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2962 | repeat = 0) will be started. C<0> is a valid timeout. |
3486 | repeat = 0) will be started. C<0> is a valid timeout. |
2963 | |
3487 | |
2964 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3488 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2965 | passed an C<revents> set like normal event callbacks (a combination of |
3489 | passed an C<revents> set like normal event callbacks (a combination of |
2966 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3490 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2967 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3491 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2968 | a timeout and an io event at the same time - you probably should give io |
3492 | a timeout and an io event at the same time - you probably should give io |
2969 | events precedence. |
3493 | events precedence. |
2970 | |
3494 | |
2971 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3495 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2972 | |
3496 | |
2973 | static void stdin_ready (int revents, void *arg) |
3497 | static void stdin_ready (int revents, void *arg) |
2974 | { |
3498 | { |
2975 | if (revents & EV_READ) |
3499 | if (revents & EV_READ) |
2976 | /* stdin might have data for us, joy! */; |
3500 | /* stdin might have data for us, joy! */; |
2977 | else if (revents & EV_TIMEOUT) |
3501 | else if (revents & EV_TIMER) |
2978 | /* doh, nothing entered */; |
3502 | /* doh, nothing entered */; |
2979 | } |
3503 | } |
2980 | |
3504 | |
2981 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3505 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2982 | |
3506 | |
2983 | =item ev_feed_event (struct ev_loop *, watcher *, int revents) |
|
|
2984 | |
|
|
2985 | Feeds the given event set into the event loop, as if the specified event |
|
|
2986 | had happened for the specified watcher (which must be a pointer to an |
|
|
2987 | initialised but not necessarily started event watcher). |
|
|
2988 | |
|
|
2989 | =item ev_feed_fd_event (struct ev_loop *, int fd, int revents) |
3507 | =item ev_feed_fd_event (loop, int fd, int revents) |
2990 | |
3508 | |
2991 | Feed an event on the given fd, as if a file descriptor backend detected |
3509 | Feed an event on the given fd, as if a file descriptor backend detected |
2992 | the given events it. |
3510 | the given events. |
2993 | |
3511 | |
2994 | =item ev_feed_signal_event (struct ev_loop *loop, int signum) |
3512 | =item ev_feed_signal_event (loop, int signum) |
2995 | |
3513 | |
2996 | Feed an event as if the given signal occurred (C<loop> must be the default |
3514 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
2997 | loop!). |
3515 | which is async-safe. |
2998 | |
3516 | |
2999 | =back |
3517 | =back |
|
|
3518 | |
|
|
3519 | |
|
|
3520 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3521 | |
|
|
3522 | This section explains some common idioms that are not immediately |
|
|
3523 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3524 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3525 | |
|
|
3526 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3527 | |
|
|
3528 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3529 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3530 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3531 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3532 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3533 | data: |
|
|
3534 | |
|
|
3535 | struct my_io |
|
|
3536 | { |
|
|
3537 | ev_io io; |
|
|
3538 | int otherfd; |
|
|
3539 | void *somedata; |
|
|
3540 | struct whatever *mostinteresting; |
|
|
3541 | }; |
|
|
3542 | |
|
|
3543 | ... |
|
|
3544 | struct my_io w; |
|
|
3545 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3546 | |
|
|
3547 | And since your callback will be called with a pointer to the watcher, you |
|
|
3548 | can cast it back to your own type: |
|
|
3549 | |
|
|
3550 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3551 | { |
|
|
3552 | struct my_io *w = (struct my_io *)w_; |
|
|
3553 | ... |
|
|
3554 | } |
|
|
3555 | |
|
|
3556 | More interesting and less C-conformant ways of casting your callback |
|
|
3557 | function type instead have been omitted. |
|
|
3558 | |
|
|
3559 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3560 | |
|
|
3561 | Another common scenario is to use some data structure with multiple |
|
|
3562 | embedded watchers, in effect creating your own watcher that combines |
|
|
3563 | multiple libev event sources into one "super-watcher": |
|
|
3564 | |
|
|
3565 | struct my_biggy |
|
|
3566 | { |
|
|
3567 | int some_data; |
|
|
3568 | ev_timer t1; |
|
|
3569 | ev_timer t2; |
|
|
3570 | } |
|
|
3571 | |
|
|
3572 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3573 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3574 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3575 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3576 | real programmers): |
|
|
3577 | |
|
|
3578 | #include <stddef.h> |
|
|
3579 | |
|
|
3580 | static void |
|
|
3581 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3582 | { |
|
|
3583 | struct my_biggy big = (struct my_biggy *) |
|
|
3584 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3585 | } |
|
|
3586 | |
|
|
3587 | static void |
|
|
3588 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3589 | { |
|
|
3590 | struct my_biggy big = (struct my_biggy *) |
|
|
3591 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3592 | } |
|
|
3593 | |
|
|
3594 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3595 | |
|
|
3596 | Often you have structures like this in event-based programs: |
|
|
3597 | |
|
|
3598 | callback () |
|
|
3599 | { |
|
|
3600 | free (request); |
|
|
3601 | } |
|
|
3602 | |
|
|
3603 | request = start_new_request (..., callback); |
|
|
3604 | |
|
|
3605 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3606 | used to cancel the operation, or do other things with it. |
|
|
3607 | |
|
|
3608 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3609 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3610 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3611 | operation and simply invoke the callback with the result. |
|
|
3612 | |
|
|
3613 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3614 | has returned, so C<request> is not set. |
|
|
3615 | |
|
|
3616 | Even if you pass the request by some safer means to the callback, you |
|
|
3617 | might want to do something to the request after starting it, such as |
|
|
3618 | canceling it, which probably isn't working so well when the callback has |
|
|
3619 | already been invoked. |
|
|
3620 | |
|
|
3621 | A common way around all these issues is to make sure that |
|
|
3622 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3623 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3624 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3625 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3626 | and pushing it into the pending queue: |
|
|
3627 | |
|
|
3628 | ev_set_cb (watcher, callback); |
|
|
3629 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3630 | |
|
|
3631 | This way, C<start_new_request> can safely return before the callback is |
|
|
3632 | invoked, while not delaying callback invocation too much. |
|
|
3633 | |
|
|
3634 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3635 | |
|
|
3636 | Often (especially in GUI toolkits) there are places where you have |
|
|
3637 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3638 | invoking C<ev_run>. |
|
|
3639 | |
|
|
3640 | This brings the problem of exiting - a callback might want to finish the |
|
|
3641 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3642 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3643 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3644 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3645 | |
|
|
3646 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3647 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3648 | triggered, using C<EVRUN_ONCE>: |
|
|
3649 | |
|
|
3650 | // main loop |
|
|
3651 | int exit_main_loop = 0; |
|
|
3652 | |
|
|
3653 | while (!exit_main_loop) |
|
|
3654 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3655 | |
|
|
3656 | // in a modal watcher |
|
|
3657 | int exit_nested_loop = 0; |
|
|
3658 | |
|
|
3659 | while (!exit_nested_loop) |
|
|
3660 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3661 | |
|
|
3662 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3663 | |
|
|
3664 | // exit modal loop |
|
|
3665 | exit_nested_loop = 1; |
|
|
3666 | |
|
|
3667 | // exit main program, after modal loop is finished |
|
|
3668 | exit_main_loop = 1; |
|
|
3669 | |
|
|
3670 | // exit both |
|
|
3671 | exit_main_loop = exit_nested_loop = 1; |
|
|
3672 | |
|
|
3673 | =head2 THREAD LOCKING EXAMPLE |
|
|
3674 | |
|
|
3675 | Here is a fictitious example of how to run an event loop in a different |
|
|
3676 | thread from where callbacks are being invoked and watchers are |
|
|
3677 | created/added/removed. |
|
|
3678 | |
|
|
3679 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3680 | which uses exactly this technique (which is suited for many high-level |
|
|
3681 | languages). |
|
|
3682 | |
|
|
3683 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3684 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3685 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3686 | |
|
|
3687 | First, you need to associate some data with the event loop: |
|
|
3688 | |
|
|
3689 | typedef struct { |
|
|
3690 | mutex_t lock; /* global loop lock */ |
|
|
3691 | ev_async async_w; |
|
|
3692 | thread_t tid; |
|
|
3693 | cond_t invoke_cv; |
|
|
3694 | } userdata; |
|
|
3695 | |
|
|
3696 | void prepare_loop (EV_P) |
|
|
3697 | { |
|
|
3698 | // for simplicity, we use a static userdata struct. |
|
|
3699 | static userdata u; |
|
|
3700 | |
|
|
3701 | ev_async_init (&u->async_w, async_cb); |
|
|
3702 | ev_async_start (EV_A_ &u->async_w); |
|
|
3703 | |
|
|
3704 | pthread_mutex_init (&u->lock, 0); |
|
|
3705 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3706 | |
|
|
3707 | // now associate this with the loop |
|
|
3708 | ev_set_userdata (EV_A_ u); |
|
|
3709 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3710 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3711 | |
|
|
3712 | // then create the thread running ev_run |
|
|
3713 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3714 | } |
|
|
3715 | |
|
|
3716 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3717 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3718 | that might have been added: |
|
|
3719 | |
|
|
3720 | static void |
|
|
3721 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3722 | { |
|
|
3723 | // just used for the side effects |
|
|
3724 | } |
|
|
3725 | |
|
|
3726 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3727 | protecting the loop data, respectively. |
|
|
3728 | |
|
|
3729 | static void |
|
|
3730 | l_release (EV_P) |
|
|
3731 | { |
|
|
3732 | userdata *u = ev_userdata (EV_A); |
|
|
3733 | pthread_mutex_unlock (&u->lock); |
|
|
3734 | } |
|
|
3735 | |
|
|
3736 | static void |
|
|
3737 | l_acquire (EV_P) |
|
|
3738 | { |
|
|
3739 | userdata *u = ev_userdata (EV_A); |
|
|
3740 | pthread_mutex_lock (&u->lock); |
|
|
3741 | } |
|
|
3742 | |
|
|
3743 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3744 | into C<ev_run>: |
|
|
3745 | |
|
|
3746 | void * |
|
|
3747 | l_run (void *thr_arg) |
|
|
3748 | { |
|
|
3749 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3750 | |
|
|
3751 | l_acquire (EV_A); |
|
|
3752 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3753 | ev_run (EV_A_ 0); |
|
|
3754 | l_release (EV_A); |
|
|
3755 | |
|
|
3756 | return 0; |
|
|
3757 | } |
|
|
3758 | |
|
|
3759 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3760 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3761 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3762 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3763 | and b) skipping inter-thread-communication when there are no pending |
|
|
3764 | watchers is very beneficial): |
|
|
3765 | |
|
|
3766 | static void |
|
|
3767 | l_invoke (EV_P) |
|
|
3768 | { |
|
|
3769 | userdata *u = ev_userdata (EV_A); |
|
|
3770 | |
|
|
3771 | while (ev_pending_count (EV_A)) |
|
|
3772 | { |
|
|
3773 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3774 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3775 | } |
|
|
3776 | } |
|
|
3777 | |
|
|
3778 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3779 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3780 | thread to continue: |
|
|
3781 | |
|
|
3782 | static void |
|
|
3783 | real_invoke_pending (EV_P) |
|
|
3784 | { |
|
|
3785 | userdata *u = ev_userdata (EV_A); |
|
|
3786 | |
|
|
3787 | pthread_mutex_lock (&u->lock); |
|
|
3788 | ev_invoke_pending (EV_A); |
|
|
3789 | pthread_cond_signal (&u->invoke_cv); |
|
|
3790 | pthread_mutex_unlock (&u->lock); |
|
|
3791 | } |
|
|
3792 | |
|
|
3793 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3794 | event loop, you will now have to lock: |
|
|
3795 | |
|
|
3796 | ev_timer timeout_watcher; |
|
|
3797 | userdata *u = ev_userdata (EV_A); |
|
|
3798 | |
|
|
3799 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3800 | |
|
|
3801 | pthread_mutex_lock (&u->lock); |
|
|
3802 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3803 | ev_async_send (EV_A_ &u->async_w); |
|
|
3804 | pthread_mutex_unlock (&u->lock); |
|
|
3805 | |
|
|
3806 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3807 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3808 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3809 | watchers in the next event loop iteration. |
|
|
3810 | |
|
|
3811 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3812 | |
|
|
3813 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3814 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3815 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3816 | doesn't need callbacks anymore. |
|
|
3817 | |
|
|
3818 | Imagine you have coroutines that you can switch to using a function |
|
|
3819 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3820 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3821 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3822 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3823 | the differing C<;> conventions): |
|
|
3824 | |
|
|
3825 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3826 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3827 | |
|
|
3828 | That means instead of having a C callback function, you store the |
|
|
3829 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3830 | your callback, you instead have it switch to that coroutine. |
|
|
3831 | |
|
|
3832 | A coroutine might now wait for an event with a function called |
|
|
3833 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3834 | matter when, or whether the watcher is active or not when this function is |
|
|
3835 | called): |
|
|
3836 | |
|
|
3837 | void |
|
|
3838 | wait_for_event (ev_watcher *w) |
|
|
3839 | { |
|
|
3840 | ev_cb_set (w) = current_coro; |
|
|
3841 | switch_to (libev_coro); |
|
|
3842 | } |
|
|
3843 | |
|
|
3844 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3845 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3846 | this or any other coroutine. |
|
|
3847 | |
|
|
3848 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3849 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3850 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3851 | any waiters. |
|
|
3852 | |
|
|
3853 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3854 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3855 | |
|
|
3856 | // my_ev.h |
|
|
3857 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3858 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3859 | #include "../libev/ev.h" |
|
|
3860 | |
|
|
3861 | // my_ev.c |
|
|
3862 | #define EV_H "my_ev.h" |
|
|
3863 | #include "../libev/ev.c" |
|
|
3864 | |
|
|
3865 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3866 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3867 | can even use F<ev.h> as header file name directly. |
3000 | |
3868 | |
3001 | |
3869 | |
3002 | =head1 LIBEVENT EMULATION |
3870 | =head1 LIBEVENT EMULATION |
3003 | |
3871 | |
3004 | Libev offers a compatibility emulation layer for libevent. It cannot |
3872 | Libev offers a compatibility emulation layer for libevent. It cannot |
3005 | emulate the internals of libevent, so here are some usage hints: |
3873 | emulate the internals of libevent, so here are some usage hints: |
3006 | |
3874 | |
3007 | =over 4 |
3875 | =over 4 |
|
|
3876 | |
|
|
3877 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3878 | |
|
|
3879 | This was the newest libevent version available when libev was implemented, |
|
|
3880 | and is still mostly unchanged in 2010. |
3008 | |
3881 | |
3009 | =item * Use it by including <event.h>, as usual. |
3882 | =item * Use it by including <event.h>, as usual. |
3010 | |
3883 | |
3011 | =item * The following members are fully supported: ev_base, ev_callback, |
3884 | =item * The following members are fully supported: ev_base, ev_callback, |
3012 | ev_arg, ev_fd, ev_res, ev_events. |
3885 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3018 | =item * Priorities are not currently supported. Initialising priorities |
3891 | =item * Priorities are not currently supported. Initialising priorities |
3019 | will fail and all watchers will have the same priority, even though there |
3892 | will fail and all watchers will have the same priority, even though there |
3020 | is an ev_pri field. |
3893 | is an ev_pri field. |
3021 | |
3894 | |
3022 | =item * In libevent, the last base created gets the signals, in libev, the |
3895 | =item * In libevent, the last base created gets the signals, in libev, the |
3023 | first base created (== the default loop) gets the signals. |
3896 | base that registered the signal gets the signals. |
3024 | |
3897 | |
3025 | =item * Other members are not supported. |
3898 | =item * Other members are not supported. |
3026 | |
3899 | |
3027 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3900 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3028 | to use the libev header file and library. |
3901 | to use the libev header file and library. |
3029 | |
3902 | |
3030 | =back |
3903 | =back |
3031 | |
3904 | |
3032 | =head1 C++ SUPPORT |
3905 | =head1 C++ SUPPORT |
|
|
3906 | |
|
|
3907 | =head2 C API |
|
|
3908 | |
|
|
3909 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3910 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3911 | will work fine. |
|
|
3912 | |
|
|
3913 | Proper exception specifications might have to be added to callbacks passed |
|
|
3914 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3915 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3916 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3917 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3918 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3919 | |
|
|
3920 | static void |
|
|
3921 | fatal_error (const char *msg) EV_THROW |
|
|
3922 | { |
|
|
3923 | perror (msg); |
|
|
3924 | abort (); |
|
|
3925 | } |
|
|
3926 | |
|
|
3927 | ... |
|
|
3928 | ev_set_syserr_cb (fatal_error); |
|
|
3929 | |
|
|
3930 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3931 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3932 | because it runs cleanup watchers). |
|
|
3933 | |
|
|
3934 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3935 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3936 | throwing exceptions through C libraries (most do). |
|
|
3937 | |
|
|
3938 | =head2 C++ API |
3033 | |
3939 | |
3034 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3940 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3035 | you to use some convenience methods to start/stop watchers and also change |
3941 | you to use some convenience methods to start/stop watchers and also change |
3036 | the callback model to a model using method callbacks on objects. |
3942 | the callback model to a model using method callbacks on objects. |
3037 | |
3943 | |
… | |
… | |
3047 | Care has been taken to keep the overhead low. The only data member the C++ |
3953 | Care has been taken to keep the overhead low. The only data member the C++ |
3048 | classes add (compared to plain C-style watchers) is the event loop pointer |
3954 | classes add (compared to plain C-style watchers) is the event loop pointer |
3049 | that the watcher is associated with (or no additional members at all if |
3955 | that the watcher is associated with (or no additional members at all if |
3050 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3956 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3051 | |
3957 | |
3052 | Currently, functions, and static and non-static member functions can be |
3958 | Currently, functions, static and non-static member functions and classes |
3053 | used as callbacks. Other types should be easy to add as long as they only |
3959 | with C<operator ()> can be used as callbacks. Other types should be easy |
3054 | need one additional pointer for context. If you need support for other |
3960 | to add as long as they only need one additional pointer for context. If |
3055 | types of functors please contact the author (preferably after implementing |
3961 | you need support for other types of functors please contact the author |
3056 | it). |
3962 | (preferably after implementing it). |
|
|
3963 | |
|
|
3964 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3965 | conventions as your C compiler (for static member functions), or you have |
|
|
3966 | to embed libev and compile libev itself as C++. |
3057 | |
3967 | |
3058 | Here is a list of things available in the C<ev> namespace: |
3968 | Here is a list of things available in the C<ev> namespace: |
3059 | |
3969 | |
3060 | =over 4 |
3970 | =over 4 |
3061 | |
3971 | |
… | |
… | |
3071 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3981 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3072 | |
3982 | |
3073 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3983 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3074 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3984 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3075 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3985 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3076 | defines by many implementations. |
3986 | defined by many implementations. |
3077 | |
3987 | |
3078 | All of those classes have these methods: |
3988 | All of those classes have these methods: |
3079 | |
3989 | |
3080 | =over 4 |
3990 | =over 4 |
3081 | |
3991 | |
3082 | =item ev::TYPE::TYPE () |
3992 | =item ev::TYPE::TYPE () |
3083 | |
3993 | |
3084 | =item ev::TYPE::TYPE (struct ev_loop *) |
3994 | =item ev::TYPE::TYPE (loop) |
3085 | |
3995 | |
3086 | =item ev::TYPE::~TYPE |
3996 | =item ev::TYPE::~TYPE |
3087 | |
3997 | |
3088 | The constructor (optionally) takes an event loop to associate the watcher |
3998 | The constructor (optionally) takes an event loop to associate the watcher |
3089 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3999 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
3122 | myclass obj; |
4032 | myclass obj; |
3123 | ev::io iow; |
4033 | ev::io iow; |
3124 | iow.set <myclass, &myclass::io_cb> (&obj); |
4034 | iow.set <myclass, &myclass::io_cb> (&obj); |
3125 | |
4035 | |
3126 | =item w->set (object *) |
4036 | =item w->set (object *) |
3127 | |
|
|
3128 | This is an B<experimental> feature that might go away in a future version. |
|
|
3129 | |
4037 | |
3130 | This is a variation of a method callback - leaving out the method to call |
4038 | This is a variation of a method callback - leaving out the method to call |
3131 | will default the method to C<operator ()>, which makes it possible to use |
4039 | will default the method to C<operator ()>, which makes it possible to use |
3132 | functor objects without having to manually specify the C<operator ()> all |
4040 | functor objects without having to manually specify the C<operator ()> all |
3133 | the time. Incidentally, you can then also leave out the template argument |
4041 | the time. Incidentally, you can then also leave out the template argument |
… | |
… | |
3166 | Example: Use a plain function as callback. |
4074 | Example: Use a plain function as callback. |
3167 | |
4075 | |
3168 | static void io_cb (ev::io &w, int revents) { } |
4076 | static void io_cb (ev::io &w, int revents) { } |
3169 | iow.set <io_cb> (); |
4077 | iow.set <io_cb> (); |
3170 | |
4078 | |
3171 | =item w->set (struct ev_loop *) |
4079 | =item w->set (loop) |
3172 | |
4080 | |
3173 | Associates a different C<struct ev_loop> with this watcher. You can only |
4081 | Associates a different C<struct ev_loop> with this watcher. You can only |
3174 | do this when the watcher is inactive (and not pending either). |
4082 | do this when the watcher is inactive (and not pending either). |
3175 | |
4083 | |
3176 | =item w->set ([arguments]) |
4084 | =item w->set ([arguments]) |
3177 | |
4085 | |
3178 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
4086 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
3179 | called at least once. Unlike the C counterpart, an active watcher gets |
4087 | method or a suitable start method must be called at least once. Unlike the |
3180 | automatically stopped and restarted when reconfiguring it with this |
4088 | C counterpart, an active watcher gets automatically stopped and restarted |
3181 | method. |
4089 | when reconfiguring it with this method. |
3182 | |
4090 | |
3183 | =item w->start () |
4091 | =item w->start () |
3184 | |
4092 | |
3185 | Starts the watcher. Note that there is no C<loop> argument, as the |
4093 | Starts the watcher. Note that there is no C<loop> argument, as the |
3186 | constructor already stores the event loop. |
4094 | constructor already stores the event loop. |
3187 | |
4095 | |
|
|
4096 | =item w->start ([arguments]) |
|
|
4097 | |
|
|
4098 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4099 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4100 | the configure C<set> method of the watcher. |
|
|
4101 | |
3188 | =item w->stop () |
4102 | =item w->stop () |
3189 | |
4103 | |
3190 | Stops the watcher if it is active. Again, no C<loop> argument. |
4104 | Stops the watcher if it is active. Again, no C<loop> argument. |
3191 | |
4105 | |
3192 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4106 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
3204 | |
4118 | |
3205 | =back |
4119 | =back |
3206 | |
4120 | |
3207 | =back |
4121 | =back |
3208 | |
4122 | |
3209 | Example: Define a class with an IO and idle watcher, start one of them in |
4123 | Example: Define a class with two I/O and idle watchers, start the I/O |
3210 | the constructor. |
4124 | watchers in the constructor. |
3211 | |
4125 | |
3212 | class myclass |
4126 | class myclass |
3213 | { |
4127 | { |
3214 | ev::io io ; void io_cb (ev::io &w, int revents); |
4128 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4129 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3215 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4130 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3216 | |
4131 | |
3217 | myclass (int fd) |
4132 | myclass (int fd) |
3218 | { |
4133 | { |
3219 | io .set <myclass, &myclass::io_cb > (this); |
4134 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4135 | io2 .set <myclass, &myclass::io2_cb > (this); |
3220 | idle.set <myclass, &myclass::idle_cb> (this); |
4136 | idle.set <myclass, &myclass::idle_cb> (this); |
3221 | |
4137 | |
3222 | io.start (fd, ev::READ); |
4138 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4139 | io.start (); // start it whenever convenient |
|
|
4140 | |
|
|
4141 | io2.start (fd, ev::READ); // set + start in one call |
3223 | } |
4142 | } |
3224 | }; |
4143 | }; |
3225 | |
4144 | |
3226 | |
4145 | |
3227 | =head1 OTHER LANGUAGE BINDINGS |
4146 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
3266 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4185 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3267 | |
4186 | |
3268 | =item D |
4187 | =item D |
3269 | |
4188 | |
3270 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4189 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3271 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4190 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3272 | |
4191 | |
3273 | =item Ocaml |
4192 | =item Ocaml |
3274 | |
4193 | |
3275 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4194 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3276 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4195 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4196 | |
|
|
4197 | =item Lua |
|
|
4198 | |
|
|
4199 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4200 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4201 | L<http://github.com/brimworks/lua-ev>. |
3277 | |
4202 | |
3278 | =back |
4203 | =back |
3279 | |
4204 | |
3280 | |
4205 | |
3281 | =head1 MACRO MAGIC |
4206 | =head1 MACRO MAGIC |
… | |
… | |
3295 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4220 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3296 | C<EV_A_> is used when other arguments are following. Example: |
4221 | C<EV_A_> is used when other arguments are following. Example: |
3297 | |
4222 | |
3298 | ev_unref (EV_A); |
4223 | ev_unref (EV_A); |
3299 | ev_timer_add (EV_A_ watcher); |
4224 | ev_timer_add (EV_A_ watcher); |
3300 | ev_loop (EV_A_ 0); |
4225 | ev_run (EV_A_ 0); |
3301 | |
4226 | |
3302 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4227 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3303 | which is often provided by the following macro. |
4228 | which is often provided by the following macro. |
3304 | |
4229 | |
3305 | =item C<EV_P>, C<EV_P_> |
4230 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
3318 | suitable for use with C<EV_A>. |
4243 | suitable for use with C<EV_A>. |
3319 | |
4244 | |
3320 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4245 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3321 | |
4246 | |
3322 | Similar to the other two macros, this gives you the value of the default |
4247 | Similar to the other two macros, this gives you the value of the default |
3323 | loop, if multiple loops are supported ("ev loop default"). |
4248 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4249 | will be initialised if it isn't already initialised. |
|
|
4250 | |
|
|
4251 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4252 | to initialise the loop somewhere. |
3324 | |
4253 | |
3325 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4254 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3326 | |
4255 | |
3327 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4256 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3328 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4257 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3345 | } |
4274 | } |
3346 | |
4275 | |
3347 | ev_check check; |
4276 | ev_check check; |
3348 | ev_check_init (&check, check_cb); |
4277 | ev_check_init (&check, check_cb); |
3349 | ev_check_start (EV_DEFAULT_ &check); |
4278 | ev_check_start (EV_DEFAULT_ &check); |
3350 | ev_loop (EV_DEFAULT_ 0); |
4279 | ev_run (EV_DEFAULT_ 0); |
3351 | |
4280 | |
3352 | =head1 EMBEDDING |
4281 | =head1 EMBEDDING |
3353 | |
4282 | |
3354 | Libev can (and often is) directly embedded into host |
4283 | Libev can (and often is) directly embedded into host |
3355 | applications. Examples of applications that embed it include the Deliantra |
4284 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
3435 | libev.m4 |
4364 | libev.m4 |
3436 | |
4365 | |
3437 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4366 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3438 | |
4367 | |
3439 | Libev can be configured via a variety of preprocessor symbols you have to |
4368 | Libev can be configured via a variety of preprocessor symbols you have to |
3440 | define before including any of its files. The default in the absence of |
4369 | define before including (or compiling) any of its files. The default in |
3441 | autoconf is documented for every option. |
4370 | the absence of autoconf is documented for every option. |
|
|
4371 | |
|
|
4372 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4373 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4374 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4375 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4376 | users of libev and the libev code itself must be compiled with compatible |
|
|
4377 | settings. |
3442 | |
4378 | |
3443 | =over 4 |
4379 | =over 4 |
3444 | |
4380 | |
|
|
4381 | =item EV_COMPAT3 (h) |
|
|
4382 | |
|
|
4383 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4384 | release of libev comes with wrappers for the functions and symbols that |
|
|
4385 | have been renamed between libev version 3 and 4. |
|
|
4386 | |
|
|
4387 | You can disable these wrappers (to test compatibility with future |
|
|
4388 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4389 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4390 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4391 | typedef in that case. |
|
|
4392 | |
|
|
4393 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4394 | and in some even more future version the compatibility code will be |
|
|
4395 | removed completely. |
|
|
4396 | |
3445 | =item EV_STANDALONE |
4397 | =item EV_STANDALONE (h) |
3446 | |
4398 | |
3447 | Must always be C<1> if you do not use autoconf configuration, which |
4399 | Must always be C<1> if you do not use autoconf configuration, which |
3448 | keeps libev from including F<config.h>, and it also defines dummy |
4400 | keeps libev from including F<config.h>, and it also defines dummy |
3449 | implementations for some libevent functions (such as logging, which is not |
4401 | implementations for some libevent functions (such as logging, which is not |
3450 | supported). It will also not define any of the structs usually found in |
4402 | supported). It will also not define any of the structs usually found in |
3451 | F<event.h> that are not directly supported by the libev core alone. |
4403 | F<event.h> that are not directly supported by the libev core alone. |
3452 | |
4404 | |
3453 | In stanbdalone mode, libev will still try to automatically deduce the |
4405 | In standalone mode, libev will still try to automatically deduce the |
3454 | configuration, but has to be more conservative. |
4406 | configuration, but has to be more conservative. |
|
|
4407 | |
|
|
4408 | =item EV_USE_FLOOR |
|
|
4409 | |
|
|
4410 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4411 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4412 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4413 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4414 | function is not available will fail, so the safe default is to not enable |
|
|
4415 | this. |
3455 | |
4416 | |
3456 | =item EV_USE_MONOTONIC |
4417 | =item EV_USE_MONOTONIC |
3457 | |
4418 | |
3458 | If defined to be C<1>, libev will try to detect the availability of the |
4419 | If defined to be C<1>, libev will try to detect the availability of the |
3459 | monotonic clock option at both compile time and runtime. Otherwise no |
4420 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3523 | be used is the winsock select). This means that it will call |
4484 | be used is the winsock select). This means that it will call |
3524 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4485 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3525 | it is assumed that all these functions actually work on fds, even |
4486 | it is assumed that all these functions actually work on fds, even |
3526 | on win32. Should not be defined on non-win32 platforms. |
4487 | on win32. Should not be defined on non-win32 platforms. |
3527 | |
4488 | |
3528 | =item EV_FD_TO_WIN32_HANDLE |
4489 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3529 | |
4490 | |
3530 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4491 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3531 | file descriptors to socket handles. When not defining this symbol (the |
4492 | file descriptors to socket handles. When not defining this symbol (the |
3532 | default), then libev will call C<_get_osfhandle>, which is usually |
4493 | default), then libev will call C<_get_osfhandle>, which is usually |
3533 | correct. In some cases, programs use their own file descriptor management, |
4494 | correct. In some cases, programs use their own file descriptor management, |
3534 | in which case they can provide this function to map fds to socket handles. |
4495 | in which case they can provide this function to map fds to socket handles. |
|
|
4496 | |
|
|
4497 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4498 | |
|
|
4499 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4500 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4501 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4502 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4503 | |
|
|
4504 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4505 | |
|
|
4506 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4507 | macro can be used to override the C<close> function, useful to unregister |
|
|
4508 | file descriptors again. Note that the replacement function has to close |
|
|
4509 | the underlying OS handle. |
3535 | |
4510 | |
3536 | =item EV_USE_POLL |
4511 | =item EV_USE_POLL |
3537 | |
4512 | |
3538 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4513 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3539 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4514 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3575 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4550 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3576 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4551 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3577 | be detected at runtime. If undefined, it will be enabled if the headers |
4552 | be detected at runtime. If undefined, it will be enabled if the headers |
3578 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4553 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3579 | |
4554 | |
|
|
4555 | =item EV_NO_SMP |
|
|
4556 | |
|
|
4557 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4558 | between threads, that is, threads can be used, but threads never run on |
|
|
4559 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4560 | and makes libev faster. |
|
|
4561 | |
|
|
4562 | =item EV_NO_THREADS |
|
|
4563 | |
|
|
4564 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4565 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4566 | above. This reduces dependencies and makes libev faster. |
|
|
4567 | |
3580 | =item EV_ATOMIC_T |
4568 | =item EV_ATOMIC_T |
3581 | |
4569 | |
3582 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4570 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3583 | access is atomic with respect to other threads or signal contexts. No such |
4571 | access is atomic and serialised with respect to other threads or signal |
3584 | type is easily found in the C language, so you can provide your own type |
4572 | contexts. No such type is easily found in the C language, so you can |
3585 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4573 | provide your own type that you know is safe for your purposes. It is used |
3586 | as well as for signal and thread safety in C<ev_async> watchers. |
4574 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4575 | in C<ev_async> watchers. |
3587 | |
4576 | |
3588 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4577 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3589 | (from F<signal.h>), which is usually good enough on most platforms. |
4578 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4579 | although strictly speaking using a type that also implies a memory fence |
|
|
4580 | is required. |
3590 | |
4581 | |
3591 | =item EV_H |
4582 | =item EV_H (h) |
3592 | |
4583 | |
3593 | The name of the F<ev.h> header file used to include it. The default if |
4584 | The name of the F<ev.h> header file used to include it. The default if |
3594 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4585 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3595 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4586 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3596 | |
4587 | |
3597 | =item EV_CONFIG_H |
4588 | =item EV_CONFIG_H (h) |
3598 | |
4589 | |
3599 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4590 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3600 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4591 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3601 | C<EV_H>, above. |
4592 | C<EV_H>, above. |
3602 | |
4593 | |
3603 | =item EV_EVENT_H |
4594 | =item EV_EVENT_H (h) |
3604 | |
4595 | |
3605 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4596 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3606 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4597 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3607 | |
4598 | |
3608 | =item EV_PROTOTYPES |
4599 | =item EV_PROTOTYPES (h) |
3609 | |
4600 | |
3610 | If defined to be C<0>, then F<ev.h> will not define any function |
4601 | If defined to be C<0>, then F<ev.h> will not define any function |
3611 | prototypes, but still define all the structs and other symbols. This is |
4602 | prototypes, but still define all the structs and other symbols. This is |
3612 | occasionally useful if you want to provide your own wrapper functions |
4603 | occasionally useful if you want to provide your own wrapper functions |
3613 | around libev functions. |
4604 | around libev functions. |
… | |
… | |
3618 | will have the C<struct ev_loop *> as first argument, and you can create |
4609 | will have the C<struct ev_loop *> as first argument, and you can create |
3619 | additional independent event loops. Otherwise there will be no support |
4610 | additional independent event loops. Otherwise there will be no support |
3620 | for multiple event loops and there is no first event loop pointer |
4611 | for multiple event loops and there is no first event loop pointer |
3621 | argument. Instead, all functions act on the single default loop. |
4612 | argument. Instead, all functions act on the single default loop. |
3622 | |
4613 | |
|
|
4614 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4615 | default loop when multiplicity is switched off - you always have to |
|
|
4616 | initialise the loop manually in this case. |
|
|
4617 | |
3623 | =item EV_MINPRI |
4618 | =item EV_MINPRI |
3624 | |
4619 | |
3625 | =item EV_MAXPRI |
4620 | =item EV_MAXPRI |
3626 | |
4621 | |
3627 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4622 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3635 | fine. |
4630 | fine. |
3636 | |
4631 | |
3637 | If your embedding application does not need any priorities, defining these |
4632 | If your embedding application does not need any priorities, defining these |
3638 | both to C<0> will save some memory and CPU. |
4633 | both to C<0> will save some memory and CPU. |
3639 | |
4634 | |
3640 | =item EV_PERIODIC_ENABLE |
4635 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4636 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4637 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3641 | |
4638 | |
3642 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4639 | If undefined or defined to be C<1> (and the platform supports it), then |
3643 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4640 | the respective watcher type is supported. If defined to be C<0>, then it |
3644 | code. |
4641 | is not. Disabling watcher types mainly saves code size. |
3645 | |
4642 | |
3646 | =item EV_IDLE_ENABLE |
4643 | =item EV_FEATURES |
3647 | |
|
|
3648 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3649 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3650 | code. |
|
|
3651 | |
|
|
3652 | =item EV_EMBED_ENABLE |
|
|
3653 | |
|
|
3654 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3655 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3656 | watcher types, which therefore must not be disabled. |
|
|
3657 | |
|
|
3658 | =item EV_STAT_ENABLE |
|
|
3659 | |
|
|
3660 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3661 | defined to be C<0>, then they are not. |
|
|
3662 | |
|
|
3663 | =item EV_FORK_ENABLE |
|
|
3664 | |
|
|
3665 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3666 | defined to be C<0>, then they are not. |
|
|
3667 | |
|
|
3668 | =item EV_ASYNC_ENABLE |
|
|
3669 | |
|
|
3670 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3671 | defined to be C<0>, then they are not. |
|
|
3672 | |
|
|
3673 | =item EV_MINIMAL |
|
|
3674 | |
4644 | |
3675 | If you need to shave off some kilobytes of code at the expense of some |
4645 | If you need to shave off some kilobytes of code at the expense of some |
3676 | speed (but with the full API), define this symbol to C<1>. Currently this |
4646 | speed (but with the full API), you can define this symbol to request |
3677 | is used to override some inlining decisions, saves roughly 30% code size |
4647 | certain subsets of functionality. The default is to enable all features |
3678 | on amd64. It also selects a much smaller 2-heap for timer management over |
4648 | that can be enabled on the platform. |
3679 | the default 4-heap. |
|
|
3680 | |
4649 | |
3681 | You can save even more by disabling watcher types you do not need |
4650 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
3682 | and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> |
4651 | with some broad features you want) and then selectively re-enable |
3683 | (C<-DNDEBUG>) will usually reduce code size a lot. |
4652 | additional parts you want, for example if you want everything minimal, |
|
|
4653 | but multiple event loop support, async and child watchers and the poll |
|
|
4654 | backend, use this: |
3684 | |
4655 | |
3685 | Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to |
4656 | #define EV_FEATURES 0 |
3686 | provide a bare-bones event library. See C<ev.h> for details on what parts |
4657 | #define EV_MULTIPLICITY 1 |
3687 | of the API are still available, and do not complain if this subset changes |
4658 | #define EV_USE_POLL 1 |
3688 | over time. |
4659 | #define EV_CHILD_ENABLE 1 |
|
|
4660 | #define EV_ASYNC_ENABLE 1 |
|
|
4661 | |
|
|
4662 | The actual value is a bitset, it can be a combination of the following |
|
|
4663 | values (by default, all of these are enabled): |
|
|
4664 | |
|
|
4665 | =over 4 |
|
|
4666 | |
|
|
4667 | =item C<1> - faster/larger code |
|
|
4668 | |
|
|
4669 | Use larger code to speed up some operations. |
|
|
4670 | |
|
|
4671 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4672 | code size by roughly 30% on amd64). |
|
|
4673 | |
|
|
4674 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4675 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4676 | assertions. |
|
|
4677 | |
|
|
4678 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4679 | (e.g. gcc with C<-Os>). |
|
|
4680 | |
|
|
4681 | =item C<2> - faster/larger data structures |
|
|
4682 | |
|
|
4683 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4684 | hash table sizes and so on. This will usually further increase code size |
|
|
4685 | and can additionally have an effect on the size of data structures at |
|
|
4686 | runtime. |
|
|
4687 | |
|
|
4688 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4689 | (e.g. gcc with C<-Os>). |
|
|
4690 | |
|
|
4691 | =item C<4> - full API configuration |
|
|
4692 | |
|
|
4693 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4694 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4695 | |
|
|
4696 | =item C<8> - full API |
|
|
4697 | |
|
|
4698 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4699 | details on which parts of the API are still available without this |
|
|
4700 | feature, and do not complain if this subset changes over time. |
|
|
4701 | |
|
|
4702 | =item C<16> - enable all optional watcher types |
|
|
4703 | |
|
|
4704 | Enables all optional watcher types. If you want to selectively enable |
|
|
4705 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4706 | embed, async, child...) you can enable them manually by defining |
|
|
4707 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4708 | |
|
|
4709 | =item C<32> - enable all backends |
|
|
4710 | |
|
|
4711 | This enables all backends - without this feature, you need to enable at |
|
|
4712 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4713 | |
|
|
4714 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4715 | |
|
|
4716 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4717 | default. |
|
|
4718 | |
|
|
4719 | =back |
|
|
4720 | |
|
|
4721 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4722 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4723 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4724 | watchers, timers and monotonic clock support. |
|
|
4725 | |
|
|
4726 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4727 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4728 | your program might be left out as well - a binary starting a timer and an |
|
|
4729 | I/O watcher then might come out at only 5Kb. |
|
|
4730 | |
|
|
4731 | =item EV_API_STATIC |
|
|
4732 | |
|
|
4733 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4734 | will have static linkage. This means that libev will not export any |
|
|
4735 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4736 | when you embed libev, only want to use libev functions in a single file, |
|
|
4737 | and do not want its identifiers to be visible. |
|
|
4738 | |
|
|
4739 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4740 | wants to use libev. |
|
|
4741 | |
|
|
4742 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4743 | doesn't support the required declaration syntax. |
|
|
4744 | |
|
|
4745 | =item EV_AVOID_STDIO |
|
|
4746 | |
|
|
4747 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4748 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4749 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4750 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4751 | big. |
|
|
4752 | |
|
|
4753 | Note that error messages might become less precise when this option is |
|
|
4754 | enabled. |
|
|
4755 | |
|
|
4756 | =item EV_NSIG |
|
|
4757 | |
|
|
4758 | The highest supported signal number, +1 (or, the number of |
|
|
4759 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4760 | automatically, but sometimes this fails, in which case it can be |
|
|
4761 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4762 | good for about any system in existence) can save some memory, as libev |
|
|
4763 | statically allocates some 12-24 bytes per signal number. |
3689 | |
4764 | |
3690 | =item EV_PID_HASHSIZE |
4765 | =item EV_PID_HASHSIZE |
3691 | |
4766 | |
3692 | C<ev_child> watchers use a small hash table to distribute workload by |
4767 | C<ev_child> watchers use a small hash table to distribute workload by |
3693 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4768 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3694 | than enough. If you need to manage thousands of children you might want to |
4769 | usually more than enough. If you need to manage thousands of children you |
3695 | increase this value (I<must> be a power of two). |
4770 | might want to increase this value (I<must> be a power of two). |
3696 | |
4771 | |
3697 | =item EV_INOTIFY_HASHSIZE |
4772 | =item EV_INOTIFY_HASHSIZE |
3698 | |
4773 | |
3699 | C<ev_stat> watchers use a small hash table to distribute workload by |
4774 | C<ev_stat> watchers use a small hash table to distribute workload by |
3700 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4775 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3701 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4776 | disabled), usually more than enough. If you need to manage thousands of |
3702 | watchers you might want to increase this value (I<must> be a power of |
4777 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3703 | two). |
4778 | power of two). |
3704 | |
4779 | |
3705 | =item EV_USE_4HEAP |
4780 | =item EV_USE_4HEAP |
3706 | |
4781 | |
3707 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4782 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3708 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4783 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3709 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4784 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3710 | faster performance with many (thousands) of watchers. |
4785 | faster performance with many (thousands) of watchers. |
3711 | |
4786 | |
3712 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4787 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3713 | (disabled). |
4788 | will be C<0>. |
3714 | |
4789 | |
3715 | =item EV_HEAP_CACHE_AT |
4790 | =item EV_HEAP_CACHE_AT |
3716 | |
4791 | |
3717 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4792 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3718 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4793 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3719 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4794 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3720 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4795 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3721 | but avoids random read accesses on heap changes. This improves performance |
4796 | but avoids random read accesses on heap changes. This improves performance |
3722 | noticeably with many (hundreds) of watchers. |
4797 | noticeably with many (hundreds) of watchers. |
3723 | |
4798 | |
3724 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4799 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3725 | (disabled). |
4800 | will be C<0>. |
3726 | |
4801 | |
3727 | =item EV_VERIFY |
4802 | =item EV_VERIFY |
3728 | |
4803 | |
3729 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4804 | Controls how much internal verification (see C<ev_verify ()>) will |
3730 | be done: If set to C<0>, no internal verification code will be compiled |
4805 | be done: If set to C<0>, no internal verification code will be compiled |
3731 | in. If set to C<1>, then verification code will be compiled in, but not |
4806 | in. If set to C<1>, then verification code will be compiled in, but not |
3732 | called. If set to C<2>, then the internal verification code will be |
4807 | called. If set to C<2>, then the internal verification code will be |
3733 | called once per loop, which can slow down libev. If set to C<3>, then the |
4808 | called once per loop, which can slow down libev. If set to C<3>, then the |
3734 | verification code will be called very frequently, which will slow down |
4809 | verification code will be called very frequently, which will slow down |
3735 | libev considerably. |
4810 | libev considerably. |
3736 | |
4811 | |
3737 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4812 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3738 | C<0>. |
4813 | will be C<0>. |
3739 | |
4814 | |
3740 | =item EV_COMMON |
4815 | =item EV_COMMON |
3741 | |
4816 | |
3742 | By default, all watchers have a C<void *data> member. By redefining |
4817 | By default, all watchers have a C<void *data> member. By redefining |
3743 | this macro to a something else you can include more and other types of |
4818 | this macro to something else you can include more and other types of |
3744 | members. You have to define it each time you include one of the files, |
4819 | members. You have to define it each time you include one of the files, |
3745 | though, and it must be identical each time. |
4820 | though, and it must be identical each time. |
3746 | |
4821 | |
3747 | For example, the perl EV module uses something like this: |
4822 | For example, the perl EV module uses something like this: |
3748 | |
4823 | |
… | |
… | |
3801 | file. |
4876 | file. |
3802 | |
4877 | |
3803 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4878 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3804 | that everybody includes and which overrides some configure choices: |
4879 | that everybody includes and which overrides some configure choices: |
3805 | |
4880 | |
3806 | #define EV_MINIMAL 1 |
4881 | #define EV_FEATURES 8 |
3807 | #define EV_USE_POLL 0 |
4882 | #define EV_USE_SELECT 1 |
3808 | #define EV_MULTIPLICITY 0 |
|
|
3809 | #define EV_PERIODIC_ENABLE 0 |
4883 | #define EV_PREPARE_ENABLE 1 |
|
|
4884 | #define EV_IDLE_ENABLE 1 |
3810 | #define EV_STAT_ENABLE 0 |
4885 | #define EV_SIGNAL_ENABLE 1 |
3811 | #define EV_FORK_ENABLE 0 |
4886 | #define EV_CHILD_ENABLE 1 |
|
|
4887 | #define EV_USE_STDEXCEPT 0 |
3812 | #define EV_CONFIG_H <config.h> |
4888 | #define EV_CONFIG_H <config.h> |
3813 | #define EV_MINPRI 0 |
|
|
3814 | #define EV_MAXPRI 0 |
|
|
3815 | |
4889 | |
3816 | #include "ev++.h" |
4890 | #include "ev++.h" |
3817 | |
4891 | |
3818 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4892 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3819 | |
4893 | |
3820 | #include "ev_cpp.h" |
4894 | #include "ev_cpp.h" |
3821 | #include "ev.c" |
4895 | #include "ev.c" |
3822 | |
4896 | |
3823 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4897 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3824 | |
4898 | |
3825 | =head2 THREADS AND COROUTINES |
4899 | =head2 THREADS AND COROUTINES |
3826 | |
4900 | |
3827 | =head3 THREADS |
4901 | =head3 THREADS |
3828 | |
4902 | |
… | |
… | |
3879 | default loop and triggering an C<ev_async> watcher from the default loop |
4953 | default loop and triggering an C<ev_async> watcher from the default loop |
3880 | watcher callback into the event loop interested in the signal. |
4954 | watcher callback into the event loop interested in the signal. |
3881 | |
4955 | |
3882 | =back |
4956 | =back |
3883 | |
4957 | |
|
|
4958 | See also L<THREAD LOCKING EXAMPLE>. |
|
|
4959 | |
3884 | =head3 COROUTINES |
4960 | =head3 COROUTINES |
3885 | |
4961 | |
3886 | Libev is very accommodating to coroutines ("cooperative threads"): |
4962 | Libev is very accommodating to coroutines ("cooperative threads"): |
3887 | libev fully supports nesting calls to its functions from different |
4963 | libev fully supports nesting calls to its functions from different |
3888 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4964 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3889 | different coroutines, and switch freely between both coroutines running the |
4965 | different coroutines, and switch freely between both coroutines running |
3890 | loop, as long as you don't confuse yourself). The only exception is that |
4966 | the loop, as long as you don't confuse yourself). The only exception is |
3891 | you must not do this from C<ev_periodic> reschedule callbacks. |
4967 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3892 | |
4968 | |
3893 | Care has been taken to ensure that libev does not keep local state inside |
4969 | Care has been taken to ensure that libev does not keep local state inside |
3894 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4970 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3895 | they do not call any callbacks. |
4971 | they do not call any callbacks. |
3896 | |
4972 | |
3897 | =head2 COMPILER WARNINGS |
4973 | =head2 COMPILER WARNINGS |
3898 | |
4974 | |
3899 | Depending on your compiler and compiler settings, you might get no or a |
4975 | Depending on your compiler and compiler settings, you might get no or a |
… | |
… | |
3910 | maintainable. |
4986 | maintainable. |
3911 | |
4987 | |
3912 | And of course, some compiler warnings are just plain stupid, or simply |
4988 | And of course, some compiler warnings are just plain stupid, or simply |
3913 | wrong (because they don't actually warn about the condition their message |
4989 | wrong (because they don't actually warn about the condition their message |
3914 | seems to warn about). For example, certain older gcc versions had some |
4990 | seems to warn about). For example, certain older gcc versions had some |
3915 | warnings that resulted an extreme number of false positives. These have |
4991 | warnings that resulted in an extreme number of false positives. These have |
3916 | been fixed, but some people still insist on making code warn-free with |
4992 | been fixed, but some people still insist on making code warn-free with |
3917 | such buggy versions. |
4993 | such buggy versions. |
3918 | |
4994 | |
3919 | While libev is written to generate as few warnings as possible, |
4995 | While libev is written to generate as few warnings as possible, |
3920 | "warn-free" code is not a goal, and it is recommended not to build libev |
4996 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3956 | I suggest using suppression lists. |
5032 | I suggest using suppression lists. |
3957 | |
5033 | |
3958 | |
5034 | |
3959 | =head1 PORTABILITY NOTES |
5035 | =head1 PORTABILITY NOTES |
3960 | |
5036 | |
|
|
5037 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
5038 | |
|
|
5039 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5040 | interfaces but I<disables> them by default. |
|
|
5041 | |
|
|
5042 | That means that libev compiled in the default environment doesn't support |
|
|
5043 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
5044 | |
|
|
5045 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5046 | by enabling the large file API, which makes them incompatible with the |
|
|
5047 | standard libev compiled for their system. |
|
|
5048 | |
|
|
5049 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5050 | suddenly make it incompatible to the default compile time environment, |
|
|
5051 | i.e. all programs not using special compile switches. |
|
|
5052 | |
|
|
5053 | =head2 OS/X AND DARWIN BUGS |
|
|
5054 | |
|
|
5055 | The whole thing is a bug if you ask me - basically any system interface |
|
|
5056 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
5057 | OpenGL drivers. |
|
|
5058 | |
|
|
5059 | =head3 C<kqueue> is buggy |
|
|
5060 | |
|
|
5061 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5062 | only sockets, many support pipes. |
|
|
5063 | |
|
|
5064 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5065 | rotten platform, but of course you can still ask for it when creating a |
|
|
5066 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5067 | probably going to work well. |
|
|
5068 | |
|
|
5069 | =head3 C<poll> is buggy |
|
|
5070 | |
|
|
5071 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5072 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5073 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5074 | |
|
|
5075 | Libev tries to work around this by not using C<poll> by default on |
|
|
5076 | this rotten platform, but of course you can still ask for it when creating |
|
|
5077 | a loop. |
|
|
5078 | |
|
|
5079 | =head3 C<select> is buggy |
|
|
5080 | |
|
|
5081 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5082 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5083 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5084 | you use more. |
|
|
5085 | |
|
|
5086 | There is an undocumented "workaround" for this - defining |
|
|
5087 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5088 | work on OS/X. |
|
|
5089 | |
|
|
5090 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5091 | |
|
|
5092 | =head3 C<errno> reentrancy |
|
|
5093 | |
|
|
5094 | The default compile environment on Solaris is unfortunately so |
|
|
5095 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5096 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5097 | defined by default. A valid, if stupid, implementation choice. |
|
|
5098 | |
|
|
5099 | If you want to use libev in threaded environments you have to make sure |
|
|
5100 | it's compiled with C<_REENTRANT> defined. |
|
|
5101 | |
|
|
5102 | =head3 Event port backend |
|
|
5103 | |
|
|
5104 | The scalable event interface for Solaris is called "event |
|
|
5105 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5106 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5107 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5108 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5109 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5110 | great. |
|
|
5111 | |
|
|
5112 | If you can't get it to work, you can try running the program by setting |
|
|
5113 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5114 | C<select> backends. |
|
|
5115 | |
|
|
5116 | =head2 AIX POLL BUG |
|
|
5117 | |
|
|
5118 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5119 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5120 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5121 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5122 | |
3961 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5123 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5124 | |
|
|
5125 | =head3 General issues |
3962 | |
5126 | |
3963 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5127 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3964 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5128 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3965 | model. Libev still offers limited functionality on this platform in |
5129 | model. Libev still offers limited functionality on this platform in |
3966 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5130 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3967 | descriptors. This only applies when using Win32 natively, not when using |
5131 | descriptors. This only applies when using Win32 natively, not when using |
3968 | e.g. cygwin. |
5132 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5133 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5134 | environment. |
3969 | |
5135 | |
3970 | Lifting these limitations would basically require the full |
5136 | Lifting these limitations would basically require the full |
3971 | re-implementation of the I/O system. If you are into these kinds of |
5137 | re-implementation of the I/O system. If you are into this kind of thing, |
3972 | things, then note that glib does exactly that for you in a very portable |
5138 | then note that glib does exactly that for you in a very portable way (note |
3973 | way (note also that glib is the slowest event library known to man). |
5139 | also that glib is the slowest event library known to man). |
3974 | |
5140 | |
3975 | There is no supported compilation method available on windows except |
5141 | There is no supported compilation method available on windows except |
3976 | embedding it into other applications. |
5142 | embedding it into other applications. |
3977 | |
5143 | |
3978 | Sensible signal handling is officially unsupported by Microsoft - libev |
5144 | Sensible signal handling is officially unsupported by Microsoft - libev |
… | |
… | |
4006 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
5172 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4007 | |
5173 | |
4008 | #include "evwrap.h" |
5174 | #include "evwrap.h" |
4009 | #include "ev.c" |
5175 | #include "ev.c" |
4010 | |
5176 | |
4011 | =over 4 |
|
|
4012 | |
|
|
4013 | =item The winsocket select function |
5177 | =head3 The winsocket C<select> function |
4014 | |
5178 | |
4015 | The winsocket C<select> function doesn't follow POSIX in that it |
5179 | The winsocket C<select> function doesn't follow POSIX in that it |
4016 | requires socket I<handles> and not socket I<file descriptors> (it is |
5180 | requires socket I<handles> and not socket I<file descriptors> (it is |
4017 | also extremely buggy). This makes select very inefficient, and also |
5181 | also extremely buggy). This makes select very inefficient, and also |
4018 | requires a mapping from file descriptors to socket handles (the Microsoft |
5182 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
4027 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5191 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4028 | |
5192 | |
4029 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5193 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4030 | complexity in the O(n²) range when using win32. |
5194 | complexity in the O(n²) range when using win32. |
4031 | |
5195 | |
4032 | =item Limited number of file descriptors |
5196 | =head3 Limited number of file descriptors |
4033 | |
5197 | |
4034 | Windows has numerous arbitrary (and low) limits on things. |
5198 | Windows has numerous arbitrary (and low) limits on things. |
4035 | |
5199 | |
4036 | Early versions of winsocket's select only supported waiting for a maximum |
5200 | Early versions of winsocket's select only supported waiting for a maximum |
4037 | of C<64> handles (probably owning to the fact that all windows kernels |
5201 | of C<64> handles (probably owning to the fact that all windows kernels |
… | |
… | |
4052 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
5216 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
4053 | (depending on windows version and/or the phase of the moon). To get more, |
5217 | (depending on windows version and/or the phase of the moon). To get more, |
4054 | you need to wrap all I/O functions and provide your own fd management, but |
5218 | you need to wrap all I/O functions and provide your own fd management, but |
4055 | the cost of calling select (O(n²)) will likely make this unworkable. |
5219 | the cost of calling select (O(n²)) will likely make this unworkable. |
4056 | |
5220 | |
4057 | =back |
|
|
4058 | |
|
|
4059 | =head2 PORTABILITY REQUIREMENTS |
5221 | =head2 PORTABILITY REQUIREMENTS |
4060 | |
5222 | |
4061 | In addition to a working ISO-C implementation and of course the |
5223 | In addition to a working ISO-C implementation and of course the |
4062 | backend-specific APIs, libev relies on a few additional extensions: |
5224 | backend-specific APIs, libev relies on a few additional extensions: |
4063 | |
5225 | |
… | |
… | |
4069 | Libev assumes not only that all watcher pointers have the same internal |
5231 | Libev assumes not only that all watcher pointers have the same internal |
4070 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5232 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4071 | assumes that the same (machine) code can be used to call any watcher |
5233 | assumes that the same (machine) code can be used to call any watcher |
4072 | callback: The watcher callbacks have different type signatures, but libev |
5234 | callback: The watcher callbacks have different type signatures, but libev |
4073 | calls them using an C<ev_watcher *> internally. |
5235 | calls them using an C<ev_watcher *> internally. |
|
|
5236 | |
|
|
5237 | =item pointer accesses must be thread-atomic |
|
|
5238 | |
|
|
5239 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5240 | writable in one piece - this is the case on all current architectures. |
4074 | |
5241 | |
4075 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5242 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4076 | |
5243 | |
4077 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5244 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4078 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5245 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
4101 | watchers. |
5268 | watchers. |
4102 | |
5269 | |
4103 | =item C<double> must hold a time value in seconds with enough accuracy |
5270 | =item C<double> must hold a time value in seconds with enough accuracy |
4104 | |
5271 | |
4105 | The type C<double> is used to represent timestamps. It is required to |
5272 | The type C<double> is used to represent timestamps. It is required to |
4106 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5273 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4107 | enough for at least into the year 4000. This requirement is fulfilled by |
5274 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5275 | (the design goal for libev). This requirement is overfulfilled by |
4108 | implementations implementing IEEE 754, which is basically all existing |
5276 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5277 | |
4109 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
5278 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
4110 | 2200. |
5279 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5280 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5281 | something like that, just kidding). |
4111 | |
5282 | |
4112 | =back |
5283 | =back |
4113 | |
5284 | |
4114 | If you know of other additional requirements drop me a note. |
5285 | If you know of other additional requirements drop me a note. |
4115 | |
5286 | |
… | |
… | |
4177 | =item Processing ev_async_send: O(number_of_async_watchers) |
5348 | =item Processing ev_async_send: O(number_of_async_watchers) |
4178 | |
5349 | |
4179 | =item Processing signals: O(max_signal_number) |
5350 | =item Processing signals: O(max_signal_number) |
4180 | |
5351 | |
4181 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5352 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4182 | calls in the current loop iteration. Checking for async and signal events |
5353 | calls in the current loop iteration and the loop is currently |
|
|
5354 | blocked. Checking for async and signal events involves iterating over all |
4183 | involves iterating over all running async watchers or all signal numbers. |
5355 | running async watchers or all signal numbers. |
4184 | |
5356 | |
4185 | =back |
5357 | =back |
4186 | |
5358 | |
4187 | |
5359 | |
|
|
5360 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5361 | |
|
|
5362 | The major version 4 introduced some incompatible changes to the API. |
|
|
5363 | |
|
|
5364 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5365 | for all changes, so most programs should still compile. The compatibility |
|
|
5366 | layer might be removed in later versions of libev, so better update to the |
|
|
5367 | new API early than late. |
|
|
5368 | |
|
|
5369 | =over 4 |
|
|
5370 | |
|
|
5371 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5372 | |
|
|
5373 | The backward compatibility mechanism can be controlled by |
|
|
5374 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5375 | section. |
|
|
5376 | |
|
|
5377 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5378 | |
|
|
5379 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5380 | |
|
|
5381 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5382 | ev_loop_fork (EV_DEFAULT); |
|
|
5383 | |
|
|
5384 | =item function/symbol renames |
|
|
5385 | |
|
|
5386 | A number of functions and symbols have been renamed: |
|
|
5387 | |
|
|
5388 | ev_loop => ev_run |
|
|
5389 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5390 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5391 | |
|
|
5392 | ev_unloop => ev_break |
|
|
5393 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5394 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5395 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5396 | |
|
|
5397 | EV_TIMEOUT => EV_TIMER |
|
|
5398 | |
|
|
5399 | ev_loop_count => ev_iteration |
|
|
5400 | ev_loop_depth => ev_depth |
|
|
5401 | ev_loop_verify => ev_verify |
|
|
5402 | |
|
|
5403 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5404 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5405 | associated constants have been renamed to not collide with the C<struct |
|
|
5406 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5407 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5408 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5409 | typedef. |
|
|
5410 | |
|
|
5411 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5412 | |
|
|
5413 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5414 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5415 | and work, but the library code will of course be larger. |
|
|
5416 | |
|
|
5417 | =back |
|
|
5418 | |
|
|
5419 | |
4188 | =head1 GLOSSARY |
5420 | =head1 GLOSSARY |
4189 | |
5421 | |
4190 | =over 4 |
5422 | =over 4 |
4191 | |
5423 | |
4192 | =item active |
5424 | =item active |
4193 | |
5425 | |
4194 | A watcher is active as long as it has been started (has been attached to |
5426 | A watcher is active as long as it has been started and not yet stopped. |
4195 | an event loop) but not yet stopped (disassociated from the event loop). |
5427 | See L<WATCHER STATES> for details. |
4196 | |
5428 | |
4197 | =item application |
5429 | =item application |
4198 | |
5430 | |
4199 | In this document, an application is whatever is using libev. |
5431 | In this document, an application is whatever is using libev. |
|
|
5432 | |
|
|
5433 | =item backend |
|
|
5434 | |
|
|
5435 | The part of the code dealing with the operating system interfaces. |
4200 | |
5436 | |
4201 | =item callback |
5437 | =item callback |
4202 | |
5438 | |
4203 | The address of a function that is called when some event has been |
5439 | The address of a function that is called when some event has been |
4204 | detected. Callbacks are being passed the event loop, the watcher that |
5440 | detected. Callbacks are being passed the event loop, the watcher that |
4205 | received the event, and the actual event bitset. |
5441 | received the event, and the actual event bitset. |
4206 | |
5442 | |
4207 | =item callback invocation |
5443 | =item callback/watcher invocation |
4208 | |
5444 | |
4209 | The act of calling the callback associated with a watcher. |
5445 | The act of calling the callback associated with a watcher. |
4210 | |
5446 | |
4211 | =item event |
5447 | =item event |
4212 | |
5448 | |
4213 | A change of state of some external event, such as data now being available |
5449 | A change of state of some external event, such as data now being available |
4214 | for reading on a file descriptor, time having passed or simply not having |
5450 | for reading on a file descriptor, time having passed or simply not having |
4215 | any other events happening anymore. |
5451 | any other events happening anymore. |
4216 | |
5452 | |
4217 | In libev, events are represented as single bits (such as C<EV_READ> or |
5453 | In libev, events are represented as single bits (such as C<EV_READ> or |
4218 | C<EV_TIMEOUT>). |
5454 | C<EV_TIMER>). |
4219 | |
5455 | |
4220 | =item event library |
5456 | =item event library |
4221 | |
5457 | |
4222 | A software package implementing an event model and loop. |
5458 | A software package implementing an event model and loop. |
4223 | |
5459 | |
… | |
… | |
4231 | The model used to describe how an event loop handles and processes |
5467 | The model used to describe how an event loop handles and processes |
4232 | watchers and events. |
5468 | watchers and events. |
4233 | |
5469 | |
4234 | =item pending |
5470 | =item pending |
4235 | |
5471 | |
4236 | A watcher is pending as soon as the corresponding event has been detected, |
5472 | A watcher is pending as soon as the corresponding event has been |
4237 | and stops being pending as soon as the watcher will be invoked or its |
5473 | detected. See L<WATCHER STATES> for details. |
4238 | pending status is explicitly cleared by the application. |
|
|
4239 | |
|
|
4240 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4241 | its pending status. |
|
|
4242 | |
5474 | |
4243 | =item real time |
5475 | =item real time |
4244 | |
5476 | |
4245 | The physical time that is observed. It is apparently strictly monotonic :) |
5477 | The physical time that is observed. It is apparently strictly monotonic :) |
4246 | |
5478 | |
4247 | =item wall-clock time |
5479 | =item wall-clock time |
4248 | |
5480 | |
4249 | The time and date as shown on clocks. Unlike real time, it can actually |
5481 | The time and date as shown on clocks. Unlike real time, it can actually |
4250 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5482 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4251 | clock. |
5483 | clock. |
4252 | |
5484 | |
4253 | =item watcher |
5485 | =item watcher |
4254 | |
5486 | |
4255 | A data structure that describes interest in certain events. Watchers need |
5487 | A data structure that describes interest in certain events. Watchers need |
4256 | to be started (attached to an event loop) before they can receive events. |
5488 | to be started (attached to an event loop) before they can receive events. |
4257 | |
5489 | |
4258 | =item watcher invocation |
|
|
4259 | |
|
|
4260 | The act of calling the callback associated with a watcher. |
|
|
4261 | |
|
|
4262 | =back |
5490 | =back |
4263 | |
5491 | |
4264 | =head1 AUTHOR |
5492 | =head1 AUTHOR |
4265 | |
5493 | |
4266 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5494 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5495 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4267 | |
5496 | |