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1 | =encoding utf-8 |
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2 | |
1 | =head1 NAME |
3 | =head1 NAME |
2 | |
4 | |
3 | libev - a high performance full-featured event loop written in C |
5 | libev - a high performance full-featured event loop written in C |
4 | |
6 | |
5 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
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43 | |
45 | |
44 | int |
46 | int |
45 | main (void) |
47 | main (void) |
46 | { |
48 | { |
47 | // use the default event loop unless you have special needs |
49 | // use the default event loop unless you have special needs |
48 | struct ev_loop *loop = ev_default_loop (0); |
50 | struct ev_loop *loop = EV_DEFAULT; |
49 | |
51 | |
50 | // initialise an io watcher, then start it |
52 | // initialise an io watcher, then start it |
51 | // this one will watch for stdin to become readable |
53 | // this one will watch for stdin to become readable |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
54 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
53 | ev_io_start (loop, &stdin_watcher); |
55 | ev_io_start (loop, &stdin_watcher); |
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58 | ev_timer_start (loop, &timeout_watcher); |
60 | ev_timer_start (loop, &timeout_watcher); |
59 | |
61 | |
60 | // now wait for events to arrive |
62 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
63 | ev_run (loop, 0); |
62 | |
64 | |
63 | // unloop was called, so exit |
65 | // break was called, so exit |
64 | return 0; |
66 | return 0; |
65 | } |
67 | } |
66 | |
68 | |
67 | =head1 ABOUT THIS DOCUMENT |
69 | =head1 ABOUT THIS DOCUMENT |
68 | |
70 | |
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77 | on event-based programming, nor will it introduce event-based programming |
79 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
80 | with libev. |
79 | |
81 | |
80 | Familiarity with event based programming techniques in general is assumed |
82 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
83 | throughout this document. |
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84 | |
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85 | =head1 WHAT TO READ WHEN IN A HURRY |
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86 | |
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87 | This manual tries to be very detailed, but unfortunately, this also makes |
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88 | it very long. If you just want to know the basics of libev, I suggest |
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89 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
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90 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
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91 | C<ev_timer> sections in L</WATCHER TYPES>. |
82 | |
92 | |
83 | =head1 ABOUT LIBEV |
93 | =head1 ABOUT LIBEV |
84 | |
94 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
95 | 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 |
96 | file descriptor being readable or a timeout occurring), and it will manage |
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124 | this argument. |
134 | this argument. |
125 | |
135 | |
126 | =head2 TIME REPRESENTATION |
136 | =head2 TIME REPRESENTATION |
127 | |
137 | |
128 | Libev represents time as a single floating point number, representing |
138 | Libev represents time as a single floating point number, representing |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practise |
139 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
130 | somewhere near the beginning of 1970, details are complicated, don't |
140 | somewhere near the beginning of 1970, details are complicated, don't |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
141 | ask). This type is called C<ev_tstamp>, which is what you should use |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
142 | too. It usually aliases to the C<double> type in C. When you need to do |
133 | any calculations on it, you should treat it as some floating point value. |
143 | any calculations on it, you should treat it as some floating point value. |
134 | |
144 | |
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165 | |
175 | |
166 | =item ev_tstamp ev_time () |
176 | =item ev_tstamp ev_time () |
167 | |
177 | |
168 | Returns the current time as libev would use it. Please note that the |
178 | Returns the current time as libev would use it. Please note that the |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
179 | C<ev_now> function is usually faster and also often returns the timestamp |
170 | you actually want to know. |
180 | you actually want to know. Also interesting is the combination of |
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181 | C<ev_now_update> and C<ev_now>. |
171 | |
182 | |
172 | =item ev_sleep (ev_tstamp interval) |
183 | =item ev_sleep (ev_tstamp interval) |
173 | |
184 | |
174 | Sleep for the given interval: The current thread will be blocked until |
185 | Sleep for the given interval: The current thread will be blocked |
175 | either it is interrupted or the given time interval has passed. Basically |
186 | until either it is interrupted or the given time interval has |
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187 | passed (approximately - it might return a bit earlier even if not |
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188 | interrupted). Returns immediately if C<< interval <= 0 >>. |
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189 | |
176 | this is a sub-second-resolution C<sleep ()>. |
190 | Basically this is a sub-second-resolution C<sleep ()>. |
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191 | |
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192 | The range of the C<interval> is limited - libev only guarantees to work |
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193 | with sleep times of up to one day (C<< interval <= 86400 >>). |
177 | |
194 | |
178 | =item int ev_version_major () |
195 | =item int ev_version_major () |
179 | |
196 | |
180 | =item int ev_version_minor () |
197 | =item int ev_version_minor () |
181 | |
198 | |
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192 | as this indicates an incompatible change. Minor versions are usually |
209 | as this indicates an incompatible change. Minor versions are usually |
193 | compatible to older versions, so a larger minor version alone is usually |
210 | compatible to older versions, so a larger minor version alone is usually |
194 | not a problem. |
211 | not a problem. |
195 | |
212 | |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
213 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | version (note, however, that this will not detect ABI mismatches :). |
214 | version (note, however, that this will not detect other ABI mismatches, |
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215 | such as LFS or reentrancy). |
198 | |
216 | |
199 | assert (("libev version mismatch", |
217 | assert (("libev version mismatch", |
200 | ev_version_major () == EV_VERSION_MAJOR |
218 | ev_version_major () == EV_VERSION_MAJOR |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
219 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | |
220 | |
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213 | assert (("sorry, no epoll, no sex", |
231 | assert (("sorry, no epoll, no sex", |
214 | ev_supported_backends () & EVBACKEND_EPOLL)); |
232 | ev_supported_backends () & EVBACKEND_EPOLL)); |
215 | |
233 | |
216 | =item unsigned int ev_recommended_backends () |
234 | =item unsigned int ev_recommended_backends () |
217 | |
235 | |
218 | Return the set of all backends compiled into this binary of libev and also |
236 | Return the set of all backends compiled into this binary of libev and |
219 | recommended for this platform. This set is often smaller than the one |
237 | also recommended for this platform, meaning it will work for most file |
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238 | descriptor types. This set is often smaller than the one returned by |
220 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
239 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
221 | most BSDs and will not be auto-detected unless you explicitly request it |
240 | and will not be auto-detected unless you explicitly request it (assuming |
222 | (assuming you know what you are doing). This is the set of backends that |
241 | you know what you are doing). This is the set of backends that libev will |
223 | libev will probe for if you specify no backends explicitly. |
242 | probe for if you specify no backends explicitly. |
224 | |
243 | |
225 | =item unsigned int ev_embeddable_backends () |
244 | =item unsigned int ev_embeddable_backends () |
226 | |
245 | |
227 | Returns the set of backends that are embeddable in other event loops. This |
246 | Returns the set of backends that are embeddable in other event loops. This |
228 | is the theoretical, all-platform, value. To find which backends |
247 | value is platform-specific but can include backends not available on the |
229 | might be supported on the current system, you would need to look at |
248 | current system. To find which embeddable backends might be supported on |
230 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
249 | the current system, you would need to look at C<ev_embeddable_backends () |
231 | recommended ones. |
250 | & ev_supported_backends ()>, likewise for recommended ones. |
232 | |
251 | |
233 | See the description of C<ev_embed> watchers for more info. |
252 | See the description of C<ev_embed> watchers for more info. |
234 | |
253 | |
235 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
254 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
236 | |
255 | |
237 | Sets the allocation function to use (the prototype is similar - the |
256 | Sets the allocation function to use (the prototype is similar - the |
238 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
257 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
239 | used to allocate and free memory (no surprises here). If it returns zero |
258 | used to allocate and free memory (no surprises here). If it returns zero |
240 | when memory needs to be allocated (C<size != 0>), the library might abort |
259 | when memory needs to be allocated (C<size != 0>), the library might abort |
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266 | } |
285 | } |
267 | |
286 | |
268 | ... |
287 | ... |
269 | ev_set_allocator (persistent_realloc); |
288 | ev_set_allocator (persistent_realloc); |
270 | |
289 | |
271 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
290 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
272 | |
291 | |
273 | Set the callback function to call on a retryable system call error (such |
292 | Set the callback function to call on a retryable system call error (such |
274 | as failed select, poll, epoll_wait). The message is a printable string |
293 | as failed select, poll, epoll_wait). The message is a printable string |
275 | indicating the system call or subsystem causing the problem. If this |
294 | indicating the system call or subsystem causing the problem. If this |
276 | callback is set, then libev will expect it to remedy the situation, no |
295 | callback is set, then libev will expect it to remedy the situation, no |
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288 | } |
307 | } |
289 | |
308 | |
290 | ... |
309 | ... |
291 | ev_set_syserr_cb (fatal_error); |
310 | ev_set_syserr_cb (fatal_error); |
292 | |
311 | |
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312 | =item ev_feed_signal (int signum) |
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313 | |
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314 | This function can be used to "simulate" a signal receive. It is completely |
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315 | safe to call this function at any time, from any context, including signal |
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316 | handlers or random threads. |
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317 | |
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318 | Its main use is to customise signal handling in your process, especially |
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319 | in the presence of threads. For example, you could block signals |
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320 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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321 | creating any loops), and in one thread, use C<sigwait> or any other |
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322 | mechanism to wait for signals, then "deliver" them to libev by calling |
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323 | C<ev_feed_signal>. |
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324 | |
293 | =back |
325 | =back |
294 | |
326 | |
295 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
327 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
296 | |
328 | |
297 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
329 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
298 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
330 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
299 | libev 3 had an C<ev_loop> function colliding with the struct name). |
331 | libev 3 had an C<ev_loop> function colliding with the struct name). |
300 | |
332 | |
301 | The library knows two types of such loops, the I<default> loop, which |
333 | The library knows two types of such loops, the I<default> loop, which |
302 | supports signals and child events, and dynamically created event loops |
334 | supports child process events, and dynamically created event loops which |
303 | which do not. |
335 | do not. |
304 | |
336 | |
305 | =over 4 |
337 | =over 4 |
306 | |
338 | |
307 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
339 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
308 | |
340 | |
309 | This will initialise the default event loop if it hasn't been initialised |
341 | This returns the "default" event loop object, which is what you should |
310 | yet and return it. If the default loop could not be initialised, returns |
342 | normally use when you just need "the event loop". Event loop objects and |
311 | false. If it already was initialised it simply returns it (and ignores the |
343 | the C<flags> parameter are described in more detail in the entry for |
312 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
344 | C<ev_loop_new>. |
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345 | |
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346 | If the default loop is already initialised then this function simply |
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347 | returns it (and ignores the flags. If that is troubling you, check |
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348 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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349 | flags, which should almost always be C<0>, unless the caller is also the |
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350 | one calling C<ev_run> or otherwise qualifies as "the main program". |
313 | |
351 | |
314 | If you don't know what event loop to use, use the one returned from this |
352 | If you don't know what event loop to use, use the one returned from this |
315 | function. |
353 | function (or via the C<EV_DEFAULT> macro). |
316 | |
354 | |
317 | Note that this function is I<not> thread-safe, so if you want to use it |
355 | Note that this function is I<not> thread-safe, so if you want to use it |
318 | from multiple threads, you have to lock (note also that this is unlikely, |
356 | from multiple threads, you have to employ some kind of mutex (note also |
319 | as loops cannot be shared easily between threads anyway). |
357 | that this case is unlikely, as loops cannot be shared easily between |
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358 | threads anyway). |
320 | |
359 | |
321 | The default loop is the only loop that can handle C<ev_signal> and |
360 | The default loop is the only loop that can handle C<ev_child> watchers, |
322 | C<ev_child> watchers, and to do this, it always registers a handler |
361 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
323 | for C<SIGCHLD>. If this is a problem for your application you can either |
362 | a problem for your application you can either create a dynamic loop with |
324 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
363 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
325 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
364 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
326 | C<ev_default_init>. |
365 | |
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366 | Example: This is the most typical usage. |
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367 | |
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368 | if (!ev_default_loop (0)) |
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369 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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370 | |
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371 | Example: Restrict libev to the select and poll backends, and do not allow |
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372 | environment settings to be taken into account: |
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373 | |
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374 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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375 | |
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376 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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377 | |
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378 | This will create and initialise a new event loop object. If the loop |
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379 | could not be initialised, returns false. |
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380 | |
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381 | This function is thread-safe, and one common way to use libev with |
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382 | threads is indeed to create one loop per thread, and using the default |
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383 | loop in the "main" or "initial" thread. |
327 | |
384 | |
328 | The flags argument can be used to specify special behaviour or specific |
385 | The flags argument can be used to specify special behaviour or specific |
329 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
386 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
330 | |
387 | |
331 | The following flags are supported: |
388 | The following flags are supported: |
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341 | |
398 | |
342 | If this flag bit is or'ed into the flag value (or the program runs setuid |
399 | If this flag bit is or'ed into the flag value (or the program runs setuid |
343 | or setgid) then libev will I<not> look at the environment variable |
400 | or setgid) then libev will I<not> look at the environment variable |
344 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
401 | C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will |
345 | override the flags completely if it is found in the environment. This is |
402 | override the flags completely if it is found in the environment. This is |
346 | useful to try out specific backends to test their performance, or to work |
403 | useful to try out specific backends to test their performance, to work |
347 | around bugs. |
404 | around bugs, or to make libev threadsafe (accessing environment variables |
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405 | cannot be done in a threadsafe way, but usually it works if no other |
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406 | thread modifies them). |
348 | |
407 | |
349 | =item C<EVFLAG_FORKCHECK> |
408 | =item C<EVFLAG_FORKCHECK> |
350 | |
409 | |
351 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
410 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
352 | make libev check for a fork in each iteration by enabling this flag. |
411 | make libev check for a fork in each iteration by enabling this flag. |
353 | |
412 | |
354 | This works by calling C<getpid ()> on every iteration of the loop, |
413 | This works by calling C<getpid ()> on every iteration of the loop, |
355 | and thus this might slow down your event loop if you do a lot of loop |
414 | and thus this might slow down your event loop if you do a lot of loop |
356 | iterations and little real work, but is usually not noticeable (on my |
415 | iterations and little real work, but is usually not noticeable (on my |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
416 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn |
358 | without a system call and thus I<very> fast, but my GNU/Linux system also has |
417 | sequence without a system call and thus I<very> fast, but my GNU/Linux |
359 | C<pthread_atfork> which is even faster). |
418 | system also has C<pthread_atfork> which is even faster). (Update: glibc |
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419 | versions 2.25 apparently removed the C<getpid> optimisation again). |
360 | |
420 | |
361 | The big advantage of this flag is that you can forget about fork (and |
421 | The big advantage of this flag is that you can forget about fork (and |
362 | forget about forgetting to tell libev about forking) when you use this |
422 | forget about forgetting to tell libev about forking, although you still |
363 | flag. |
423 | have to ignore C<SIGPIPE>) when you use this flag. |
364 | |
424 | |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
425 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
366 | environment variable. |
426 | environment variable. |
367 | |
427 | |
368 | =item C<EVFLAG_NOINOTIFY> |
428 | =item C<EVFLAG_NOINOTIFY> |
369 | |
429 | |
370 | When this flag is specified, then libev will not attempt to use the |
430 | When this flag is specified, then libev will not attempt to use the |
371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
431 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
372 | testing, this flag can be useful to conserve inotify file descriptors, as |
432 | testing, this flag can be useful to conserve inotify file descriptors, as |
373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
433 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
374 | |
434 | |
375 | =item C<EVFLAG_SIGNALFD> |
435 | =item C<EVFLAG_SIGNALFD> |
376 | |
436 | |
377 | When this flag is specified, then libev will attempt to use the |
437 | When this flag is specified, then libev will attempt to use the |
378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
438 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
379 | delivers signals synchronously, which makes it both faster and might make |
439 | delivers signals synchronously, which makes it both faster and might make |
380 | it possible to get the queued signal data. It can also simplify signal |
440 | it possible to get the queued signal data. It can also simplify signal |
381 | handling with threads, as long as you properly block signals in your |
441 | handling with threads, as long as you properly block signals in your |
382 | threads that are not interested in handling them. |
442 | threads that are not interested in handling them. |
383 | |
443 | |
384 | Signalfd will not be used by default as this changes your signal mask, and |
444 | Signalfd will not be used by default as this changes your signal mask, and |
385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
445 | there are a lot of shoddy libraries and programs (glib's threadpool for |
386 | example) that can't properly initialise their signal masks. |
446 | example) that can't properly initialise their signal masks. |
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447 | |
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448 | =item C<EVFLAG_NOSIGMASK> |
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449 | |
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450 | When this flag is specified, then libev will avoid to modify the signal |
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451 | mask. Specifically, this means you have to make sure signals are unblocked |
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452 | when you want to receive them. |
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453 | |
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454 | This behaviour is useful when you want to do your own signal handling, or |
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455 | want to handle signals only in specific threads and want to avoid libev |
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456 | unblocking the signals. |
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457 | |
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458 | It's also required by POSIX in a threaded program, as libev calls |
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459 | C<sigprocmask>, whose behaviour is officially unspecified. |
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460 | |
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461 | This flag's behaviour will become the default in future versions of libev. |
387 | |
462 | |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
463 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
389 | |
464 | |
390 | This is your standard select(2) backend. Not I<completely> standard, as |
465 | This is your standard select(2) backend. Not I<completely> standard, as |
391 | libev tries to roll its own fd_set with no limits on the number of fds, |
466 | libev tries to roll its own fd_set with no limits on the number of fds, |
… | |
… | |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
494 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
420 | |
495 | |
421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
496 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
422 | kernels). |
497 | kernels). |
423 | |
498 | |
424 | For few fds, this backend is a bit little slower than poll and select, |
499 | For few fds, this backend is a bit little slower than poll and select, but |
425 | but it scales phenomenally better. While poll and select usually scale |
500 | it scales phenomenally better. While poll and select usually scale like |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
501 | O(total_fds) where total_fds is the total number of fds (or the highest |
427 | epoll scales either O(1) or O(active_fds). |
502 | fd), epoll scales either O(1) or O(active_fds). |
428 | |
503 | |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
504 | The epoll mechanism deserves honorable mention as the most misdesigned |
430 | of the more advanced event mechanisms: mere annoyances include silently |
505 | of the more advanced event mechanisms: mere annoyances include silently |
431 | dropping file descriptors, requiring a system call per change per file |
506 | dropping file descriptors, requiring a system call per change per file |
432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
507 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
508 | returning before the timeout value, resulting in additional iterations |
|
|
509 | (and only giving 5ms accuracy while select on the same platform gives |
433 | so on. The biggest issue is fork races, however - if a program forks then |
510 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
434 | I<both> parent and child process have to recreate the epoll set, which can |
511 | forks then I<both> parent and child process have to recreate the epoll |
435 | take considerable time (one syscall per file descriptor) and is of course |
512 | set, which can take considerable time (one syscall per file descriptor) |
436 | hard to detect. |
513 | and is of course hard to detect. |
437 | |
514 | |
438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
515 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
439 | of course I<doesn't>, and epoll just loves to report events for totally |
516 | but of course I<doesn't>, and epoll just loves to report events for |
440 | I<different> file descriptors (even already closed ones, so one cannot |
517 | totally I<different> file descriptors (even already closed ones, so |
441 | even remove them from the set) than registered in the set (especially |
518 | one cannot even remove them from the set) than registered in the set |
442 | on SMP systems). Libev tries to counter these spurious notifications by |
519 | (especially on SMP systems). Libev tries to counter these spurious |
443 | employing an additional generation counter and comparing that against the |
520 | notifications by employing an additional generation counter and comparing |
444 | events to filter out spurious ones, recreating the set when required. Last |
521 | that against the events to filter out spurious ones, recreating the set |
|
|
522 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
523 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
524 | because epoll returns immediately despite a nonzero timeout. And last |
445 | not least, it also refuses to work with some file descriptors which work |
525 | not least, it also refuses to work with some file descriptors which work |
446 | perfectly fine with C<select> (files, many character devices...). |
526 | perfectly fine with C<select> (files, many character devices...). |
|
|
527 | |
|
|
528 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
529 | cobbled together in a hurry, no thought to design or interaction with |
|
|
530 | others. Oh, the pain, will it ever stop... |
447 | |
531 | |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
532 | While stopping, setting and starting an I/O watcher in the same iteration |
449 | will result in some caching, there is still a system call per such |
533 | will result in some caching, there is still a system call per such |
450 | incident (because the same I<file descriptor> could point to a different |
534 | incident (because the same I<file descriptor> could point to a different |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
535 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
488 | |
572 | |
489 | It scales in the same way as the epoll backend, but the interface to the |
573 | It scales in the same way as the epoll backend, but the interface to the |
490 | kernel is more efficient (which says nothing about its actual speed, of |
574 | kernel is more efficient (which says nothing about its actual speed, of |
491 | course). While stopping, setting and starting an I/O watcher does never |
575 | course). While stopping, setting and starting an I/O watcher does never |
492 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
576 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
493 | two event changes per incident. Support for C<fork ()> is very bad (but |
577 | two event changes per incident. Support for C<fork ()> is very bad (you |
494 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
578 | might have to leak fd's on fork, but it's more sane than epoll) and it |
495 | cases |
579 | drops fds silently in similarly hard-to-detect cases. |
496 | |
580 | |
497 | This backend usually performs well under most conditions. |
581 | This backend usually performs well under most conditions. |
498 | |
582 | |
499 | While nominally embeddable in other event loops, this doesn't work |
583 | While nominally embeddable in other event loops, this doesn't work |
500 | everywhere, so you might need to test for this. And since it is broken |
584 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
517 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
601 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
518 | |
602 | |
519 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
603 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
520 | it's really slow, but it still scales very well (O(active_fds)). |
604 | it's really slow, but it still scales very well (O(active_fds)). |
521 | |
605 | |
522 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
523 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
524 | blocking when no data (or space) is available. |
|
|
525 | |
|
|
526 | While this backend scales well, it requires one system call per active |
606 | While this backend scales well, it requires one system call per active |
527 | file descriptor per loop iteration. For small and medium numbers of file |
607 | file descriptor per loop iteration. For small and medium numbers of file |
528 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
608 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
529 | might perform better. |
609 | might perform better. |
530 | |
610 | |
531 | On the positive side, with the exception of the spurious readiness |
611 | On the positive side, this backend actually performed fully to |
532 | notifications, this backend actually performed fully to specification |
|
|
533 | in all tests and is fully embeddable, which is a rare feat among the |
612 | specification in all tests and is fully embeddable, which is a rare feat |
534 | OS-specific backends (I vastly prefer correctness over speed hacks). |
613 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
614 | hacks). |
|
|
615 | |
|
|
616 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
617 | even sun itself gets it wrong in their code examples: The event polling |
|
|
618 | function sometimes returns events to the caller even though an error |
|
|
619 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
620 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
621 | absolutely have to know whether an event occurred or not because you have |
|
|
622 | to re-arm the watcher. |
|
|
623 | |
|
|
624 | Fortunately libev seems to be able to work around these idiocies. |
535 | |
625 | |
536 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
626 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
537 | C<EVBACKEND_POLL>. |
627 | C<EVBACKEND_POLL>. |
538 | |
628 | |
539 | =item C<EVBACKEND_ALL> |
629 | =item C<EVBACKEND_ALL> |
540 | |
630 | |
541 | Try all backends (even potentially broken ones that wouldn't be tried |
631 | Try all backends (even potentially broken ones that wouldn't be tried |
542 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
632 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
543 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
633 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
544 | |
634 | |
545 | It is definitely not recommended to use this flag. |
635 | It is definitely not recommended to use this flag, use whatever |
|
|
636 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
637 | at all. |
|
|
638 | |
|
|
639 | =item C<EVBACKEND_MASK> |
|
|
640 | |
|
|
641 | Not a backend at all, but a mask to select all backend bits from a |
|
|
642 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
643 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
546 | |
644 | |
547 | =back |
645 | =back |
548 | |
646 | |
549 | If one or more of the backend flags are or'ed into the flags value, |
647 | If one or more of the backend flags are or'ed into the flags value, |
550 | then only these backends will be tried (in the reverse order as listed |
648 | then only these backends will be tried (in the reverse order as listed |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
649 | here). If none are specified, all backends in C<ev_recommended_backends |
552 | ()> will be tried. |
650 | ()> will be tried. |
553 | |
651 | |
554 | Example: This is the most typical usage. |
|
|
555 | |
|
|
556 | if (!ev_default_loop (0)) |
|
|
557 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
558 | |
|
|
559 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
560 | environment settings to be taken into account: |
|
|
561 | |
|
|
562 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
563 | |
|
|
564 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
565 | used if available (warning, breaks stuff, best use only with your own |
|
|
566 | private event loop and only if you know the OS supports your types of |
|
|
567 | fds): |
|
|
568 | |
|
|
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
570 | |
|
|
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
572 | |
|
|
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
574 | always distinct from the default loop. |
|
|
575 | |
|
|
576 | Note that this function I<is> thread-safe, and one common way to use |
|
|
577 | libev with threads is indeed to create one loop per thread, and using the |
|
|
578 | default loop in the "main" or "initial" thread. |
|
|
579 | |
|
|
580 | Example: Try to create a event loop that uses epoll and nothing else. |
652 | Example: Try to create a event loop that uses epoll and nothing else. |
581 | |
653 | |
582 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
654 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
583 | if (!epoller) |
655 | if (!epoller) |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
656 | fatal ("no epoll found here, maybe it hides under your chair"); |
585 | |
657 | |
|
|
658 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
659 | used if available. |
|
|
660 | |
|
|
661 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
662 | |
586 | =item ev_default_destroy () |
663 | =item ev_loop_destroy (loop) |
587 | |
664 | |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
665 | Destroys an event loop object (frees all memory and kernel state |
589 | of the active event watchers will be stopped in the normal sense, so |
666 | etc.). None of the active event watchers will be stopped in the normal |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
667 | sense, so e.g. C<ev_is_active> might still return true. It is your |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
668 | responsibility to either stop all watchers cleanly yourself I<before> |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
669 | calling this function, or cope with the fact afterwards (which is usually |
593 | can just ignore the watchers and/or C<free ()> them for example). |
670 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
|
|
671 | for example). |
594 | |
672 | |
595 | Note that certain global state, such as signal state (and installed signal |
673 | Note that certain global state, such as signal state (and installed signal |
596 | handlers), will not be freed by this function, and related watchers (such |
674 | handlers), will not be freed by this function, and related watchers (such |
597 | as signal and child watchers) would need to be stopped manually. |
675 | as signal and child watchers) would need to be stopped manually. |
598 | |
676 | |
599 | In general it is not advisable to call this function except in the |
677 | This function is normally used on loop objects allocated by |
600 | rare occasion where you really need to free e.g. the signal handling |
678 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
679 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
680 | |
|
|
681 | Note that it is not advisable to call this function on the default loop |
|
|
682 | except in the rare occasion where you really need to free its resources. |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
683 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
684 | and C<ev_loop_destroy>. |
603 | |
685 | |
604 | =item ev_loop_destroy (loop) |
686 | =item ev_loop_fork (loop) |
605 | |
|
|
606 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
607 | earlier call to C<ev_loop_new>. |
|
|
608 | |
|
|
609 | =item ev_default_fork () |
|
|
610 | |
687 | |
611 | This function sets a flag that causes subsequent C<ev_run> iterations |
688 | This function sets a flag that causes subsequent C<ev_run> iterations |
612 | to reinitialise the kernel state for backends that have one. Despite the |
689 | to reinitialise the kernel state for backends that have one. Despite |
613 | name, you can call it anytime, but it makes most sense after forking, in |
690 | the name, you can call it anytime you are allowed to start or stop |
614 | the child process (or both child and parent, but that again makes little |
691 | watchers (except inside an C<ev_prepare> callback), but it makes most |
615 | sense). You I<must> call it in the child before using any of the libev |
692 | sense after forking, in the child process. You I<must> call it (or use |
616 | functions, and it will only take effect at the next C<ev_run> iteration. |
693 | C<EVFLAG_FORKCHECK>) in the child before resuming or calling C<ev_run>. |
617 | |
694 | |
|
|
695 | In addition, if you want to reuse a loop (via this function or |
|
|
696 | C<EVFLAG_FORKCHECK>), you I<also> have to ignore C<SIGPIPE>. |
|
|
697 | |
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
698 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
699 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
700 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
621 | during fork. |
701 | during fork. |
622 | |
702 | |
623 | On the other hand, you only need to call this function in the child |
703 | On the other hand, you only need to call this function in the child |
… | |
… | |
626 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
706 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
627 | difference, but libev will usually detect this case on its own and do a |
707 | difference, but libev will usually detect this case on its own and do a |
628 | costly reset of the backend). |
708 | costly reset of the backend). |
629 | |
709 | |
630 | The function itself is quite fast and it's usually not a problem to call |
710 | The function itself is quite fast and it's usually not a problem to call |
631 | it just in case after a fork. To make this easy, the function will fit in |
711 | it just in case after a fork. |
632 | quite nicely into a call to C<pthread_atfork>: |
|
|
633 | |
712 | |
|
|
713 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
714 | using pthreads. |
|
|
715 | |
|
|
716 | static void |
|
|
717 | post_fork_child (void) |
|
|
718 | { |
|
|
719 | ev_loop_fork (EV_DEFAULT); |
|
|
720 | } |
|
|
721 | |
|
|
722 | ... |
634 | pthread_atfork (0, 0, ev_default_fork); |
723 | pthread_atfork (0, 0, post_fork_child); |
635 | |
|
|
636 | =item ev_loop_fork (loop) |
|
|
637 | |
|
|
638 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
639 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
640 | after fork that you want to re-use in the child, and how you keep track of |
|
|
641 | them is entirely your own problem. |
|
|
642 | |
724 | |
643 | =item int ev_is_default_loop (loop) |
725 | =item int ev_is_default_loop (loop) |
644 | |
726 | |
645 | Returns true when the given loop is, in fact, the default loop, and false |
727 | Returns true when the given loop is, in fact, the default loop, and false |
646 | otherwise. |
728 | otherwise. |
… | |
… | |
657 | prepare and check phases. |
739 | prepare and check phases. |
658 | |
740 | |
659 | =item unsigned int ev_depth (loop) |
741 | =item unsigned int ev_depth (loop) |
660 | |
742 | |
661 | Returns the number of times C<ev_run> was entered minus the number of |
743 | Returns the number of times C<ev_run> was entered minus the number of |
662 | times C<ev_run> was exited, in other words, the recursion depth. |
744 | times C<ev_run> was exited normally, in other words, the recursion depth. |
663 | |
745 | |
664 | Outside C<ev_run>, this number is zero. In a callback, this number is |
746 | Outside C<ev_run>, this number is zero. In a callback, this number is |
665 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
747 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
666 | in which case it is higher. |
748 | in which case it is higher. |
667 | |
749 | |
668 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
750 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
669 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
751 | throwing an exception etc.), doesn't count as "exit" - consider this |
670 | ungentleman-like behaviour unless it's really convenient. |
752 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
753 | convenient, in which case it is fully supported. |
671 | |
754 | |
672 | =item unsigned int ev_backend (loop) |
755 | =item unsigned int ev_backend (loop) |
673 | |
756 | |
674 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
757 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
675 | use. |
758 | use. |
… | |
… | |
690 | |
773 | |
691 | This function is rarely useful, but when some event callback runs for a |
774 | This function is rarely useful, but when some event callback runs for a |
692 | very long time without entering the event loop, updating libev's idea of |
775 | very long time without entering the event loop, updating libev's idea of |
693 | the current time is a good idea. |
776 | the current time is a good idea. |
694 | |
777 | |
695 | See also L<The special problem of time updates> in the C<ev_timer> section. |
778 | See also L</The special problem of time updates> in the C<ev_timer> section. |
696 | |
779 | |
697 | =item ev_suspend (loop) |
780 | =item ev_suspend (loop) |
698 | |
781 | |
699 | =item ev_resume (loop) |
782 | =item ev_resume (loop) |
700 | |
783 | |
… | |
… | |
718 | without a previous call to C<ev_suspend>. |
801 | without a previous call to C<ev_suspend>. |
719 | |
802 | |
720 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
803 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
721 | event loop time (see C<ev_now_update>). |
804 | event loop time (see C<ev_now_update>). |
722 | |
805 | |
723 | =item ev_run (loop, int flags) |
806 | =item bool ev_run (loop, int flags) |
724 | |
807 | |
725 | Finally, this is it, the event handler. This function usually is called |
808 | Finally, this is it, the event handler. This function usually is called |
726 | after you have initialised all your watchers and you want to start |
809 | after you have initialised all your watchers and you want to start |
727 | handling events. It will ask the operating system for any new events, call |
810 | handling events. It will ask the operating system for any new events, call |
728 | the watcher callbacks, an then repeat the whole process indefinitely: This |
811 | the watcher callbacks, and then repeat the whole process indefinitely: This |
729 | is why event loops are called I<loops>. |
812 | is why event loops are called I<loops>. |
730 | |
813 | |
731 | If the flags argument is specified as C<0>, it will keep handling events |
814 | If the flags argument is specified as C<0>, it will keep handling events |
732 | until either no event watchers are active anymore or C<ev_break> was |
815 | until either no event watchers are active anymore or C<ev_break> was |
733 | called. |
816 | called. |
|
|
817 | |
|
|
818 | The return value is false if there are no more active watchers (which |
|
|
819 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
820 | (which usually means " you should call C<ev_run> again"). |
734 | |
821 | |
735 | Please note that an explicit C<ev_break> is usually better than |
822 | Please note that an explicit C<ev_break> is usually better than |
736 | relying on all watchers to be stopped when deciding when a program has |
823 | relying on all watchers to be stopped when deciding when a program has |
737 | finished (especially in interactive programs), but having a program |
824 | finished (especially in interactive programs), but having a program |
738 | that automatically loops as long as it has to and no longer by virtue |
825 | that automatically loops as long as it has to and no longer by virtue |
739 | of relying on its watchers stopping correctly, that is truly a thing of |
826 | of relying on its watchers stopping correctly, that is truly a thing of |
740 | beauty. |
827 | beauty. |
741 | |
828 | |
|
|
829 | This function is I<mostly> exception-safe - you can break out of a |
|
|
830 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
831 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
832 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
833 | |
742 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
834 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
743 | those events and any already outstanding ones, but will not wait and |
835 | those events and any already outstanding ones, but will not wait and |
744 | block your process in case there are no events and will return after one |
836 | block your process in case there are no events and will return after one |
745 | iteration of the loop. This is sometimes useful to poll and handle new |
837 | iteration of the loop. This is sometimes useful to poll and handle new |
746 | events while doing lengthy calculations, to keep the program responsive. |
838 | events while doing lengthy calculations, to keep the program responsive. |
… | |
… | |
755 | This is useful if you are waiting for some external event in conjunction |
847 | This is useful if you are waiting for some external event in conjunction |
756 | with something not expressible using other libev watchers (i.e. "roll your |
848 | with something not expressible using other libev watchers (i.e. "roll your |
757 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
849 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
758 | usually a better approach for this kind of thing. |
850 | usually a better approach for this kind of thing. |
759 | |
851 | |
760 | Here are the gory details of what C<ev_run> does: |
852 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
853 | understanding, not a guarantee that things will work exactly like this in |
|
|
854 | future versions): |
761 | |
855 | |
762 | - Increment loop depth. |
856 | - Increment loop depth. |
763 | - Reset the ev_break status. |
857 | - Reset the ev_break status. |
764 | - Before the first iteration, call any pending watchers. |
858 | - Before the first iteration, call any pending watchers. |
765 | LOOP: |
859 | LOOP: |
… | |
… | |
798 | anymore. |
892 | anymore. |
799 | |
893 | |
800 | ... queue jobs here, make sure they register event watchers as long |
894 | ... queue jobs here, make sure they register event watchers as long |
801 | ... as they still have work to do (even an idle watcher will do..) |
895 | ... as they still have work to do (even an idle watcher will do..) |
802 | ev_run (my_loop, 0); |
896 | ev_run (my_loop, 0); |
803 | ... jobs done or somebody called unloop. yeah! |
897 | ... jobs done or somebody called break. yeah! |
804 | |
898 | |
805 | =item ev_break (loop, how) |
899 | =item ev_break (loop, how) |
806 | |
900 | |
807 | Can be used to make a call to C<ev_run> return early (but only after it |
901 | Can be used to make a call to C<ev_run> return early (but only after it |
808 | has processed all outstanding events). The C<how> argument must be either |
902 | has processed all outstanding events). The C<how> argument must be either |
809 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
903 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
810 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
904 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
811 | |
905 | |
812 | This "unloop state" will be cleared when entering C<ev_run> again. |
906 | This "break state" will be cleared on the next call to C<ev_run>. |
813 | |
907 | |
814 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
908 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
909 | which case it will have no effect. |
815 | |
910 | |
816 | =item ev_ref (loop) |
911 | =item ev_ref (loop) |
817 | |
912 | |
818 | =item ev_unref (loop) |
913 | =item ev_unref (loop) |
819 | |
914 | |
… | |
… | |
840 | running when nothing else is active. |
935 | running when nothing else is active. |
841 | |
936 | |
842 | ev_signal exitsig; |
937 | ev_signal exitsig; |
843 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
938 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
844 | ev_signal_start (loop, &exitsig); |
939 | ev_signal_start (loop, &exitsig); |
845 | evf_unref (loop); |
940 | ev_unref (loop); |
846 | |
941 | |
847 | Example: For some weird reason, unregister the above signal handler again. |
942 | Example: For some weird reason, unregister the above signal handler again. |
848 | |
943 | |
849 | ev_ref (loop); |
944 | ev_ref (loop); |
850 | ev_signal_stop (loop, &exitsig); |
945 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
870 | overhead for the actual polling but can deliver many events at once. |
965 | overhead for the actual polling but can deliver many events at once. |
871 | |
966 | |
872 | By setting a higher I<io collect interval> you allow libev to spend more |
967 | By setting a higher I<io collect interval> you allow libev to spend more |
873 | time collecting I/O events, so you can handle more events per iteration, |
968 | time collecting I/O events, so you can handle more events per iteration, |
874 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
969 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
875 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
970 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
876 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
971 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
877 | sleep time ensures that libev will not poll for I/O events more often then |
972 | sleep time ensures that libev will not poll for I/O events more often then |
878 | once per this interval, on average. |
973 | once per this interval, on average (as long as the host time resolution is |
|
|
974 | good enough). |
879 | |
975 | |
880 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
976 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
881 | to spend more time collecting timeouts, at the expense of increased |
977 | to spend more time collecting timeouts, at the expense of increased |
882 | latency/jitter/inexactness (the watcher callback will be called |
978 | latency/jitter/inexactness (the watcher callback will be called |
883 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
979 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
929 | invoke the actual watchers inside another context (another thread etc.). |
1025 | invoke the actual watchers inside another context (another thread etc.). |
930 | |
1026 | |
931 | If you want to reset the callback, use C<ev_invoke_pending> as new |
1027 | If you want to reset the callback, use C<ev_invoke_pending> as new |
932 | callback. |
1028 | callback. |
933 | |
1029 | |
934 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
1030 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
935 | |
1031 | |
936 | Sometimes you want to share the same loop between multiple threads. This |
1032 | Sometimes you want to share the same loop between multiple threads. This |
937 | can be done relatively simply by putting mutex_lock/unlock calls around |
1033 | can be done relatively simply by putting mutex_lock/unlock calls around |
938 | each call to a libev function. |
1034 | each call to a libev function. |
939 | |
1035 | |
940 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1036 | However, C<ev_run> can run an indefinite time, so it is not feasible |
941 | to wait for it to return. One way around this is to wake up the event |
1037 | to wait for it to return. One way around this is to wake up the event |
942 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1038 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
943 | I<release> and I<acquire> callbacks on the loop. |
1039 | I<release> and I<acquire> callbacks on the loop. |
944 | |
1040 | |
945 | When set, then C<release> will be called just before the thread is |
1041 | When set, then C<release> will be called just before the thread is |
946 | suspended waiting for new events, and C<acquire> is called just |
1042 | suspended waiting for new events, and C<acquire> is called just |
947 | afterwards. |
1043 | afterwards. |
… | |
… | |
962 | See also the locking example in the C<THREADS> section later in this |
1058 | See also the locking example in the C<THREADS> section later in this |
963 | document. |
1059 | document. |
964 | |
1060 | |
965 | =item ev_set_userdata (loop, void *data) |
1061 | =item ev_set_userdata (loop, void *data) |
966 | |
1062 | |
967 | =item ev_userdata (loop) |
1063 | =item void *ev_userdata (loop) |
968 | |
1064 | |
969 | Set and retrieve a single C<void *> associated with a loop. When |
1065 | Set and retrieve a single C<void *> associated with a loop. When |
970 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
1066 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
971 | C<0.> |
1067 | C<0>. |
972 | |
1068 | |
973 | These two functions can be used to associate arbitrary data with a loop, |
1069 | These two functions can be used to associate arbitrary data with a loop, |
974 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
1070 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
975 | C<acquire> callbacks described above, but of course can be (ab-)used for |
1071 | C<acquire> callbacks described above, but of course can be (ab-)used for |
976 | any other purpose as well. |
1072 | any other purpose as well. |
… | |
… | |
1087 | |
1183 | |
1088 | =item C<EV_PREPARE> |
1184 | =item C<EV_PREPARE> |
1089 | |
1185 | |
1090 | =item C<EV_CHECK> |
1186 | =item C<EV_CHECK> |
1091 | |
1187 | |
1092 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
1188 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
1093 | to gather new events, and all C<ev_check> watchers are invoked just after |
1189 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
1094 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
1190 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1191 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1192 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1193 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1194 | or lower priority within an event loop iteration. |
|
|
1195 | |
1095 | received events. Callbacks of both watcher types can start and stop as |
1196 | Callbacks of both watcher types can start and stop as many watchers as |
1096 | many watchers as they want, and all of them will be taken into account |
1197 | they want, and all of them will be taken into account (for example, a |
1097 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1198 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
1098 | C<ev_run> from blocking). |
1199 | blocking). |
1099 | |
1200 | |
1100 | =item C<EV_EMBED> |
1201 | =item C<EV_EMBED> |
1101 | |
1202 | |
1102 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1203 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1103 | |
1204 | |
1104 | =item C<EV_FORK> |
1205 | =item C<EV_FORK> |
1105 | |
1206 | |
1106 | The event loop has been resumed in the child process after fork (see |
1207 | The event loop has been resumed in the child process after fork (see |
1107 | C<ev_fork>). |
1208 | C<ev_fork>). |
|
|
1209 | |
|
|
1210 | =item C<EV_CLEANUP> |
|
|
1211 | |
|
|
1212 | The event loop is about to be destroyed (see C<ev_cleanup>). |
1108 | |
1213 | |
1109 | =item C<EV_ASYNC> |
1214 | =item C<EV_ASYNC> |
1110 | |
1215 | |
1111 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1216 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1112 | |
1217 | |
… | |
… | |
1134 | programs, though, as the fd could already be closed and reused for another |
1239 | programs, though, as the fd could already be closed and reused for another |
1135 | thing, so beware. |
1240 | thing, so beware. |
1136 | |
1241 | |
1137 | =back |
1242 | =back |
1138 | |
1243 | |
|
|
1244 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1245 | |
|
|
1246 | =over 4 |
|
|
1247 | |
|
|
1248 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1249 | |
|
|
1250 | This macro initialises the generic portion of a watcher. The contents |
|
|
1251 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1252 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1253 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1254 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1255 | which rolls both calls into one. |
|
|
1256 | |
|
|
1257 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1258 | (or never started) and there are no pending events outstanding. |
|
|
1259 | |
|
|
1260 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1261 | int revents)>. |
|
|
1262 | |
|
|
1263 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1264 | |
|
|
1265 | ev_io w; |
|
|
1266 | ev_init (&w, my_cb); |
|
|
1267 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1268 | |
|
|
1269 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1270 | |
|
|
1271 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1272 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1273 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1274 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1275 | difference to the C<ev_init> macro). |
|
|
1276 | |
|
|
1277 | Although some watcher types do not have type-specific arguments |
|
|
1278 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1279 | |
|
|
1280 | See C<ev_init>, above, for an example. |
|
|
1281 | |
|
|
1282 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1283 | |
|
|
1284 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1285 | calls into a single call. This is the most convenient method to initialise |
|
|
1286 | a watcher. The same limitations apply, of course. |
|
|
1287 | |
|
|
1288 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1289 | |
|
|
1290 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1291 | |
|
|
1292 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1293 | |
|
|
1294 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1295 | events. If the watcher is already active nothing will happen. |
|
|
1296 | |
|
|
1297 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1298 | whole section. |
|
|
1299 | |
|
|
1300 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1301 | |
|
|
1302 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1303 | |
|
|
1304 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1305 | the watcher was active or not). |
|
|
1306 | |
|
|
1307 | It is possible that stopped watchers are pending - for example, |
|
|
1308 | non-repeating timers are being stopped when they become pending - but |
|
|
1309 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1310 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1311 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1312 | |
|
|
1313 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1314 | |
|
|
1315 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1316 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1317 | it. |
|
|
1318 | |
|
|
1319 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1320 | |
|
|
1321 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1322 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1323 | is pending (but not active) you must not call an init function on it (but |
|
|
1324 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1325 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1326 | it). |
|
|
1327 | |
|
|
1328 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1329 | |
|
|
1330 | Returns the callback currently set on the watcher. |
|
|
1331 | |
|
|
1332 | =item ev_set_cb (ev_TYPE *watcher, callback) |
|
|
1333 | |
|
|
1334 | Change the callback. You can change the callback at virtually any time |
|
|
1335 | (modulo threads). |
|
|
1336 | |
|
|
1337 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1338 | |
|
|
1339 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1340 | |
|
|
1341 | Set and query the priority of the watcher. The priority is a small |
|
|
1342 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1343 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1344 | before watchers with lower priority, but priority will not keep watchers |
|
|
1345 | from being executed (except for C<ev_idle> watchers). |
|
|
1346 | |
|
|
1347 | If you need to suppress invocation when higher priority events are pending |
|
|
1348 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1349 | |
|
|
1350 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1351 | pending. |
|
|
1352 | |
|
|
1353 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1354 | fine, as long as you do not mind that the priority value you query might |
|
|
1355 | or might not have been clamped to the valid range. |
|
|
1356 | |
|
|
1357 | The default priority used by watchers when no priority has been set is |
|
|
1358 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1359 | |
|
|
1360 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1361 | priorities. |
|
|
1362 | |
|
|
1363 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1364 | |
|
|
1365 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1366 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1367 | can deal with that fact, as both are simply passed through to the |
|
|
1368 | callback. |
|
|
1369 | |
|
|
1370 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1371 | |
|
|
1372 | If the watcher is pending, this function clears its pending status and |
|
|
1373 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1374 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1375 | |
|
|
1376 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1377 | callback to be invoked, which can be accomplished with this function. |
|
|
1378 | |
|
|
1379 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1380 | |
|
|
1381 | Feeds the given event set into the event loop, as if the specified event |
|
|
1382 | had happened for the specified watcher (which must be a pointer to an |
|
|
1383 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1384 | not free the watcher as long as it has pending events. |
|
|
1385 | |
|
|
1386 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1387 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1388 | not started in the first place. |
|
|
1389 | |
|
|
1390 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1391 | functions that do not need a watcher. |
|
|
1392 | |
|
|
1393 | =back |
|
|
1394 | |
|
|
1395 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1396 | OWN COMPOSITE WATCHERS> idioms. |
|
|
1397 | |
1139 | =head2 WATCHER STATES |
1398 | =head2 WATCHER STATES |
1140 | |
1399 | |
1141 | There are various watcher states mentioned throughout this manual - |
1400 | There are various watcher states mentioned throughout this manual - |
1142 | active, pending and so on. In this section these states and the rules to |
1401 | active, pending and so on. In this section these states and the rules to |
1143 | transition between them will be described in more detail - and while these |
1402 | transition between them will be described in more detail - and while these |
1144 | rules might look complicated, they usually do "the right thing". |
1403 | rules might look complicated, they usually do "the right thing". |
1145 | |
1404 | |
1146 | =over 4 |
1405 | =over 4 |
1147 | |
1406 | |
1148 | =item initialiased |
1407 | =item initialised |
1149 | |
1408 | |
1150 | Before a watcher can be registered with the event looop it has to be |
1409 | Before a watcher can be registered with the event loop it has to be |
1151 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1410 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1152 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1411 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1153 | |
1412 | |
1154 | In this state it is simply some block of memory that is suitable for use |
1413 | In this state it is simply some block of memory that is suitable for |
1155 | in an event loop. It can be moved around, freed, reused etc. at will. |
1414 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1415 | will - as long as you either keep the memory contents intact, or call |
|
|
1416 | C<ev_TYPE_init> again. |
1156 | |
1417 | |
1157 | =item started/running/active |
1418 | =item started/running/active |
1158 | |
1419 | |
1159 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1420 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1160 | property of the event loop, and is actively waiting for events. While in |
1421 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1188 | latter will clear any pending state the watcher might be in, regardless |
1449 | latter will clear any pending state the watcher might be in, regardless |
1189 | of whether it was active or not, so stopping a watcher explicitly before |
1450 | of whether it was active or not, so stopping a watcher explicitly before |
1190 | freeing it is often a good idea. |
1451 | freeing it is often a good idea. |
1191 | |
1452 | |
1192 | While stopped (and not pending) the watcher is essentially in the |
1453 | While stopped (and not pending) the watcher is essentially in the |
1193 | initialised state, that is it can be reused, moved, modified in any way |
1454 | initialised state, that is, it can be reused, moved, modified in any way |
1194 | you wish. |
1455 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1456 | it again). |
1195 | |
1457 | |
1196 | =back |
1458 | =back |
1197 | |
|
|
1198 | =head2 GENERIC WATCHER FUNCTIONS |
|
|
1199 | |
|
|
1200 | =over 4 |
|
|
1201 | |
|
|
1202 | =item C<ev_init> (ev_TYPE *watcher, callback) |
|
|
1203 | |
|
|
1204 | This macro initialises the generic portion of a watcher. The contents |
|
|
1205 | of the watcher object can be arbitrary (so C<malloc> will do). Only |
|
|
1206 | the generic parts of the watcher are initialised, you I<need> to call |
|
|
1207 | the type-specific C<ev_TYPE_set> macro afterwards to initialise the |
|
|
1208 | type-specific parts. For each type there is also a C<ev_TYPE_init> macro |
|
|
1209 | which rolls both calls into one. |
|
|
1210 | |
|
|
1211 | You can reinitialise a watcher at any time as long as it has been stopped |
|
|
1212 | (or never started) and there are no pending events outstanding. |
|
|
1213 | |
|
|
1214 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
|
|
1215 | int revents)>. |
|
|
1216 | |
|
|
1217 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1218 | |
|
|
1219 | ev_io w; |
|
|
1220 | ev_init (&w, my_cb); |
|
|
1221 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1222 | |
|
|
1223 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
|
|
1224 | |
|
|
1225 | This macro initialises the type-specific parts of a watcher. You need to |
|
|
1226 | call C<ev_init> at least once before you call this macro, but you can |
|
|
1227 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
|
|
1228 | macro on a watcher that is active (it can be pending, however, which is a |
|
|
1229 | difference to the C<ev_init> macro). |
|
|
1230 | |
|
|
1231 | Although some watcher types do not have type-specific arguments |
|
|
1232 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
|
|
1233 | |
|
|
1234 | See C<ev_init>, above, for an example. |
|
|
1235 | |
|
|
1236 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
|
|
1237 | |
|
|
1238 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
|
|
1239 | calls into a single call. This is the most convenient method to initialise |
|
|
1240 | a watcher. The same limitations apply, of course. |
|
|
1241 | |
|
|
1242 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1243 | |
|
|
1244 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1245 | |
|
|
1246 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
|
|
1247 | |
|
|
1248 | Starts (activates) the given watcher. Only active watchers will receive |
|
|
1249 | events. If the watcher is already active nothing will happen. |
|
|
1250 | |
|
|
1251 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1252 | whole section. |
|
|
1253 | |
|
|
1254 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1255 | |
|
|
1256 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
|
|
1257 | |
|
|
1258 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1259 | the watcher was active or not). |
|
|
1260 | |
|
|
1261 | It is possible that stopped watchers are pending - for example, |
|
|
1262 | non-repeating timers are being stopped when they become pending - but |
|
|
1263 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
|
|
1264 | pending. If you want to free or reuse the memory used by the watcher it is |
|
|
1265 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
|
|
1266 | |
|
|
1267 | =item bool ev_is_active (ev_TYPE *watcher) |
|
|
1268 | |
|
|
1269 | Returns a true value iff the watcher is active (i.e. it has been started |
|
|
1270 | and not yet been stopped). As long as a watcher is active you must not modify |
|
|
1271 | it. |
|
|
1272 | |
|
|
1273 | =item bool ev_is_pending (ev_TYPE *watcher) |
|
|
1274 | |
|
|
1275 | Returns a true value iff the watcher is pending, (i.e. it has outstanding |
|
|
1276 | events but its callback has not yet been invoked). As long as a watcher |
|
|
1277 | is pending (but not active) you must not call an init function on it (but |
|
|
1278 | C<ev_TYPE_set> is safe), you must not change its priority, and you must |
|
|
1279 | make sure the watcher is available to libev (e.g. you cannot C<free ()> |
|
|
1280 | it). |
|
|
1281 | |
|
|
1282 | =item callback ev_cb (ev_TYPE *watcher) |
|
|
1283 | |
|
|
1284 | Returns the callback currently set on the watcher. |
|
|
1285 | |
|
|
1286 | =item ev_cb_set (ev_TYPE *watcher, callback) |
|
|
1287 | |
|
|
1288 | Change the callback. You can change the callback at virtually any time |
|
|
1289 | (modulo threads). |
|
|
1290 | |
|
|
1291 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
|
|
1292 | |
|
|
1293 | =item int ev_priority (ev_TYPE *watcher) |
|
|
1294 | |
|
|
1295 | Set and query the priority of the watcher. The priority is a small |
|
|
1296 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
|
|
1297 | (default: C<-2>). Pending watchers with higher priority will be invoked |
|
|
1298 | before watchers with lower priority, but priority will not keep watchers |
|
|
1299 | from being executed (except for C<ev_idle> watchers). |
|
|
1300 | |
|
|
1301 | If you need to suppress invocation when higher priority events are pending |
|
|
1302 | you need to look at C<ev_idle> watchers, which provide this functionality. |
|
|
1303 | |
|
|
1304 | You I<must not> change the priority of a watcher as long as it is active or |
|
|
1305 | pending. |
|
|
1306 | |
|
|
1307 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1308 | fine, as long as you do not mind that the priority value you query might |
|
|
1309 | or might not have been clamped to the valid range. |
|
|
1310 | |
|
|
1311 | The default priority used by watchers when no priority has been set is |
|
|
1312 | always C<0>, which is supposed to not be too high and not be too low :). |
|
|
1313 | |
|
|
1314 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
|
|
1315 | priorities. |
|
|
1316 | |
|
|
1317 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
|
|
1318 | |
|
|
1319 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
|
|
1320 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
|
|
1321 | can deal with that fact, as both are simply passed through to the |
|
|
1322 | callback. |
|
|
1323 | |
|
|
1324 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
|
|
1325 | |
|
|
1326 | If the watcher is pending, this function clears its pending status and |
|
|
1327 | returns its C<revents> bitset (as if its callback was invoked). If the |
|
|
1328 | watcher isn't pending it does nothing and returns C<0>. |
|
|
1329 | |
|
|
1330 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1331 | callback to be invoked, which can be accomplished with this function. |
|
|
1332 | |
|
|
1333 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1334 | |
|
|
1335 | Feeds the given event set into the event loop, as if the specified event |
|
|
1336 | had happened for the specified watcher (which must be a pointer to an |
|
|
1337 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1338 | not free the watcher as long as it has pending events. |
|
|
1339 | |
|
|
1340 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1341 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1342 | not started in the first place. |
|
|
1343 | |
|
|
1344 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1345 | functions that do not need a watcher. |
|
|
1346 | |
|
|
1347 | =back |
|
|
1348 | |
|
|
1349 | |
|
|
1350 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
1351 | |
|
|
1352 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1353 | and read at any time: libev will completely ignore it. This can be used |
|
|
1354 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1355 | don't want to allocate memory and store a pointer to it in that data |
|
|
1356 | member, you can also "subclass" the watcher type and provide your own |
|
|
1357 | data: |
|
|
1358 | |
|
|
1359 | struct my_io |
|
|
1360 | { |
|
|
1361 | ev_io io; |
|
|
1362 | int otherfd; |
|
|
1363 | void *somedata; |
|
|
1364 | struct whatever *mostinteresting; |
|
|
1365 | }; |
|
|
1366 | |
|
|
1367 | ... |
|
|
1368 | struct my_io w; |
|
|
1369 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1370 | |
|
|
1371 | And since your callback will be called with a pointer to the watcher, you |
|
|
1372 | can cast it back to your own type: |
|
|
1373 | |
|
|
1374 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1375 | { |
|
|
1376 | struct my_io *w = (struct my_io *)w_; |
|
|
1377 | ... |
|
|
1378 | } |
|
|
1379 | |
|
|
1380 | More interesting and less C-conformant ways of casting your callback type |
|
|
1381 | instead have been omitted. |
|
|
1382 | |
|
|
1383 | Another common scenario is to use some data structure with multiple |
|
|
1384 | embedded watchers: |
|
|
1385 | |
|
|
1386 | struct my_biggy |
|
|
1387 | { |
|
|
1388 | int some_data; |
|
|
1389 | ev_timer t1; |
|
|
1390 | ev_timer t2; |
|
|
1391 | } |
|
|
1392 | |
|
|
1393 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1394 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1395 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1396 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1397 | programmers): |
|
|
1398 | |
|
|
1399 | #include <stddef.h> |
|
|
1400 | |
|
|
1401 | static void |
|
|
1402 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1403 | { |
|
|
1404 | struct my_biggy big = (struct my_biggy *) |
|
|
1405 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1406 | } |
|
|
1407 | |
|
|
1408 | static void |
|
|
1409 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1410 | { |
|
|
1411 | struct my_biggy big = (struct my_biggy *) |
|
|
1412 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1413 | } |
|
|
1414 | |
1459 | |
1415 | =head2 WATCHER PRIORITY MODELS |
1460 | =head2 WATCHER PRIORITY MODELS |
1416 | |
1461 | |
1417 | Many event loops support I<watcher priorities>, which are usually small |
1462 | Many event loops support I<watcher priorities>, which are usually small |
1418 | integers that influence the ordering of event callback invocation |
1463 | integers that influence the ordering of event callback invocation |
… | |
… | |
1545 | In general you can register as many read and/or write event watchers per |
1590 | In general you can register as many read and/or write event watchers per |
1546 | fd as you want (as long as you don't confuse yourself). Setting all file |
1591 | fd as you want (as long as you don't confuse yourself). Setting all file |
1547 | descriptors to non-blocking mode is also usually a good idea (but not |
1592 | descriptors to non-blocking mode is also usually a good idea (but not |
1548 | required if you know what you are doing). |
1593 | required if you know what you are doing). |
1549 | |
1594 | |
1550 | If you cannot use non-blocking mode, then force the use of a |
|
|
1551 | known-to-be-good backend (at the time of this writing, this includes only |
|
|
1552 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1553 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1554 | files) - libev doesn't guarantee any specific behaviour in that case. |
|
|
1555 | |
|
|
1556 | Another thing you have to watch out for is that it is quite easy to |
1595 | Another thing you have to watch out for is that it is quite easy to |
1557 | receive "spurious" readiness notifications, that is your callback might |
1596 | receive "spurious" readiness notifications, that is, your callback might |
1558 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1597 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1559 | because there is no data. Not only are some backends known to create a |
1598 | because there is no data. It is very easy to get into this situation even |
1560 | lot of those (for example Solaris ports), it is very easy to get into |
1599 | with a relatively standard program structure. Thus it is best to always |
1561 | this situation even with a relatively standard program structure. Thus |
1600 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1562 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1563 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1601 | preferable to a program hanging until some data arrives. |
1564 | |
1602 | |
1565 | If you cannot run the fd in non-blocking mode (for example you should |
1603 | If you cannot run the fd in non-blocking mode (for example you should |
1566 | not play around with an Xlib connection), then you have to separately |
1604 | not play around with an Xlib connection), then you have to separately |
1567 | re-test whether a file descriptor is really ready with a known-to-be good |
1605 | re-test whether a file descriptor is really ready with a known-to-be good |
1568 | interface such as poll (fortunately in our Xlib example, Xlib already |
1606 | interface such as poll (fortunately in the case of Xlib, it already does |
1569 | does this on its own, so its quite safe to use). Some people additionally |
1607 | this on its own, so its quite safe to use). Some people additionally |
1570 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1608 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
1571 | indefinitely. |
1609 | indefinitely. |
1572 | |
1610 | |
1573 | But really, best use non-blocking mode. |
1611 | But really, best use non-blocking mode. |
1574 | |
1612 | |
… | |
… | |
1602 | |
1640 | |
1603 | There is no workaround possible except not registering events |
1641 | There is no workaround possible except not registering events |
1604 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1642 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1605 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1643 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1606 | |
1644 | |
|
|
1645 | =head3 The special problem of files |
|
|
1646 | |
|
|
1647 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1648 | representing files, and expect it to become ready when their program |
|
|
1649 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1650 | |
|
|
1651 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1652 | notification as soon as the kernel knows whether and how much data is |
|
|
1653 | there, and in the case of open files, that's always the case, so you |
|
|
1654 | always get a readiness notification instantly, and your read (or possibly |
|
|
1655 | write) will still block on the disk I/O. |
|
|
1656 | |
|
|
1657 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1658 | devices and so on, there is another party (the sender) that delivers data |
|
|
1659 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1660 | will not send data on its own, simply because it doesn't know what you |
|
|
1661 | wish to read - you would first have to request some data. |
|
|
1662 | |
|
|
1663 | Since files are typically not-so-well supported by advanced notification |
|
|
1664 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1665 | to files, even though you should not use it. The reason for this is |
|
|
1666 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1667 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1668 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1669 | F</dev/urandom>), and even though the file might better be served with |
|
|
1670 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1671 | it "just works" instead of freezing. |
|
|
1672 | |
|
|
1673 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1674 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1675 | when you rarely read from a file instead of from a socket, and want to |
|
|
1676 | reuse the same code path. |
|
|
1677 | |
1607 | =head3 The special problem of fork |
1678 | =head3 The special problem of fork |
1608 | |
1679 | |
1609 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1680 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1610 | useless behaviour. Libev fully supports fork, but needs to be told about |
1681 | useless behaviour. Libev fully supports fork, but needs to be told about |
1611 | it in the child. |
1682 | it in the child if you want to continue to use it in the child. |
1612 | |
1683 | |
1613 | To support fork in your programs, you either have to call |
1684 | To support fork in your child processes, you have to call C<ev_loop_fork |
1614 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1685 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1615 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1686 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1616 | C<EVBACKEND_POLL>. |
|
|
1617 | |
1687 | |
1618 | =head3 The special problem of SIGPIPE |
1688 | =head3 The special problem of SIGPIPE |
1619 | |
1689 | |
1620 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1690 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1621 | when writing to a pipe whose other end has been closed, your program gets |
1691 | when writing to a pipe whose other end has been closed, your program gets |
… | |
… | |
1719 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1789 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1720 | monotonic clock option helps a lot here). |
1790 | monotonic clock option helps a lot here). |
1721 | |
1791 | |
1722 | The callback is guaranteed to be invoked only I<after> its timeout has |
1792 | The callback is guaranteed to be invoked only I<after> its timeout has |
1723 | passed (not I<at>, so on systems with very low-resolution clocks this |
1793 | passed (not I<at>, so on systems with very low-resolution clocks this |
1724 | might introduce a small delay). If multiple timers become ready during the |
1794 | might introduce a small delay, see "the special problem of being too |
|
|
1795 | early", below). If multiple timers become ready during the same loop |
1725 | same loop iteration then the ones with earlier time-out values are invoked |
1796 | iteration then the ones with earlier time-out values are invoked before |
1726 | before ones of the same priority with later time-out values (but this is |
1797 | ones of the same priority with later time-out values (but this is no |
1727 | no longer true when a callback calls C<ev_run> recursively). |
1798 | longer true when a callback calls C<ev_run> recursively). |
1728 | |
1799 | |
1729 | =head3 Be smart about timeouts |
1800 | =head3 Be smart about timeouts |
1730 | |
1801 | |
1731 | Many real-world problems involve some kind of timeout, usually for error |
1802 | Many real-world problems involve some kind of timeout, usually for error |
1732 | recovery. A typical example is an HTTP request - if the other side hangs, |
1803 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1807 | |
1878 | |
1808 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1879 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1809 | but remember the time of last activity, and check for a real timeout only |
1880 | but remember the time of last activity, and check for a real timeout only |
1810 | within the callback: |
1881 | within the callback: |
1811 | |
1882 | |
|
|
1883 | ev_tstamp timeout = 60.; |
1812 | ev_tstamp last_activity; // time of last activity |
1884 | ev_tstamp last_activity; // time of last activity |
|
|
1885 | ev_timer timer; |
1813 | |
1886 | |
1814 | static void |
1887 | static void |
1815 | callback (EV_P_ ev_timer *w, int revents) |
1888 | callback (EV_P_ ev_timer *w, int revents) |
1816 | { |
1889 | { |
1817 | ev_tstamp now = ev_now (EV_A); |
1890 | // calculate when the timeout would happen |
1818 | ev_tstamp timeout = last_activity + 60.; |
1891 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1819 | |
1892 | |
1820 | // if last_activity + 60. is older than now, we did time out |
1893 | // if negative, it means we the timeout already occurred |
1821 | if (timeout < now) |
1894 | if (after < 0.) |
1822 | { |
1895 | { |
1823 | // timeout occurred, take action |
1896 | // timeout occurred, take action |
1824 | } |
1897 | } |
1825 | else |
1898 | else |
1826 | { |
1899 | { |
1827 | // callback was invoked, but there was some activity, re-arm |
1900 | // callback was invoked, but there was some recent |
1828 | // the watcher to fire in last_activity + 60, which is |
1901 | // activity. simply restart the timer to time out |
1829 | // guaranteed to be in the future, so "again" is positive: |
1902 | // after "after" seconds, which is the earliest time |
1830 | w->repeat = timeout - now; |
1903 | // the timeout can occur. |
|
|
1904 | ev_timer_set (w, after, 0.); |
1831 | ev_timer_again (EV_A_ w); |
1905 | ev_timer_start (EV_A_ w); |
1832 | } |
1906 | } |
1833 | } |
1907 | } |
1834 | |
1908 | |
1835 | To summarise the callback: first calculate the real timeout (defined |
1909 | To summarise the callback: first calculate in how many seconds the |
1836 | as "60 seconds after the last activity"), then check if that time has |
1910 | timeout will occur (by calculating the absolute time when it would occur, |
1837 | been reached, which means something I<did>, in fact, time out. Otherwise |
1911 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1838 | the callback was invoked too early (C<timeout> is in the future), so |
1912 | (EV_A)> from that). |
1839 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1840 | a timeout then. |
|
|
1841 | |
1913 | |
1842 | Note how C<ev_timer_again> is used, taking advantage of the |
1914 | If this value is negative, then we are already past the timeout, i.e. we |
1843 | C<ev_timer_again> optimisation when the timer is already running. |
1915 | timed out, and need to do whatever is needed in this case. |
|
|
1916 | |
|
|
1917 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1918 | and simply start the timer with this timeout value. |
|
|
1919 | |
|
|
1920 | In other words, each time the callback is invoked it will check whether |
|
|
1921 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1922 | again at the earliest time it could time out. Rinse. Repeat. |
1844 | |
1923 | |
1845 | This scheme causes more callback invocations (about one every 60 seconds |
1924 | This scheme causes more callback invocations (about one every 60 seconds |
1846 | minus half the average time between activity), but virtually no calls to |
1925 | minus half the average time between activity), but virtually no calls to |
1847 | libev to change the timeout. |
1926 | libev to change the timeout. |
1848 | |
1927 | |
1849 | To start the timer, simply initialise the watcher and set C<last_activity> |
1928 | To start the machinery, simply initialise the watcher and set |
1850 | to the current time (meaning we just have some activity :), then call the |
1929 | C<last_activity> to the current time (meaning there was some activity just |
1851 | callback, which will "do the right thing" and start the timer: |
1930 | now), then call the callback, which will "do the right thing" and start |
|
|
1931 | the timer: |
1852 | |
1932 | |
|
|
1933 | last_activity = ev_now (EV_A); |
1853 | ev_init (timer, callback); |
1934 | ev_init (&timer, callback); |
1854 | last_activity = ev_now (loop); |
1935 | callback (EV_A_ &timer, 0); |
1855 | callback (loop, timer, EV_TIMER); |
|
|
1856 | |
1936 | |
1857 | And when there is some activity, simply store the current time in |
1937 | When there is some activity, simply store the current time in |
1858 | C<last_activity>, no libev calls at all: |
1938 | C<last_activity>, no libev calls at all: |
1859 | |
1939 | |
|
|
1940 | if (activity detected) |
1860 | last_activity = ev_now (loop); |
1941 | last_activity = ev_now (EV_A); |
|
|
1942 | |
|
|
1943 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1944 | providing a new value, stopping the timer and calling the callback, which |
|
|
1945 | will again do the right thing (for example, time out immediately :). |
|
|
1946 | |
|
|
1947 | timeout = new_value; |
|
|
1948 | ev_timer_stop (EV_A_ &timer); |
|
|
1949 | callback (EV_A_ &timer, 0); |
1861 | |
1950 | |
1862 | This technique is slightly more complex, but in most cases where the |
1951 | This technique is slightly more complex, but in most cases where the |
1863 | time-out is unlikely to be triggered, much more efficient. |
1952 | time-out is unlikely to be triggered, much more efficient. |
1864 | |
|
|
1865 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1866 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1867 | fix things for you. |
|
|
1868 | |
1953 | |
1869 | =item 4. Wee, just use a double-linked list for your timeouts. |
1954 | =item 4. Wee, just use a double-linked list for your timeouts. |
1870 | |
1955 | |
1871 | If there is not one request, but many thousands (millions...), all |
1956 | If there is not one request, but many thousands (millions...), all |
1872 | employing some kind of timeout with the same timeout value, then one can |
1957 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1899 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1984 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1900 | rather complicated, but extremely efficient, something that really pays |
1985 | rather complicated, but extremely efficient, something that really pays |
1901 | off after the first million or so of active timers, i.e. it's usually |
1986 | off after the first million or so of active timers, i.e. it's usually |
1902 | overkill :) |
1987 | overkill :) |
1903 | |
1988 | |
|
|
1989 | =head3 The special problem of being too early |
|
|
1990 | |
|
|
1991 | If you ask a timer to call your callback after three seconds, then |
|
|
1992 | you expect it to be invoked after three seconds - but of course, this |
|
|
1993 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1994 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1995 | process with a STOP signal for a few hours for example. |
|
|
1996 | |
|
|
1997 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1998 | delay has occurred, but cannot guarantee this. |
|
|
1999 | |
|
|
2000 | A less obvious failure mode is calling your callback too early: many event |
|
|
2001 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
2002 | this can cause your callback to be invoked much earlier than you would |
|
|
2003 | expect. |
|
|
2004 | |
|
|
2005 | To see why, imagine a system with a clock that only offers full second |
|
|
2006 | resolution (think windows if you can't come up with a broken enough OS |
|
|
2007 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
2008 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2009 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2010 | |
|
|
2011 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2012 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2013 | one-second delay was requested - this is being "too early", despite best |
|
|
2014 | intentions. |
|
|
2015 | |
|
|
2016 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2017 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2018 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2019 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2020 | |
|
|
2021 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2022 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2023 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2024 | late" side of things. |
|
|
2025 | |
1904 | =head3 The special problem of time updates |
2026 | =head3 The special problem of time updates |
1905 | |
2027 | |
1906 | Establishing the current time is a costly operation (it usually takes at |
2028 | Establishing the current time is a costly operation (it usually takes |
1907 | least two system calls): EV therefore updates its idea of the current |
2029 | at least one system call): EV therefore updates its idea of the current |
1908 | time only before and after C<ev_run> collects new events, which causes a |
2030 | time only before and after C<ev_run> collects new events, which causes a |
1909 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2031 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1910 | lots of events in one iteration. |
2032 | lots of events in one iteration. |
1911 | |
2033 | |
1912 | The relative timeouts are calculated relative to the C<ev_now ()> |
2034 | The relative timeouts are calculated relative to the C<ev_now ()> |
1913 | time. This is usually the right thing as this timestamp refers to the time |
2035 | time. This is usually the right thing as this timestamp refers to the time |
1914 | of the event triggering whatever timeout you are modifying/starting. If |
2036 | of the event triggering whatever timeout you are modifying/starting. If |
1915 | you suspect event processing to be delayed and you I<need> to base the |
2037 | you suspect event processing to be delayed and you I<need> to base the |
1916 | timeout on the current time, use something like this to adjust for this: |
2038 | timeout on the current time, use something like the following to adjust |
|
|
2039 | for it: |
1917 | |
2040 | |
1918 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2041 | ev_timer_set (&timer, after + (ev_time () - ev_now ()), 0.); |
1919 | |
2042 | |
1920 | If the event loop is suspended for a long time, you can also force an |
2043 | If the event loop is suspended for a long time, you can also force an |
1921 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2044 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1922 | ()>. |
2045 | ()>, although that will push the event time of all outstanding events |
|
|
2046 | further into the future. |
|
|
2047 | |
|
|
2048 | =head3 The special problem of unsynchronised clocks |
|
|
2049 | |
|
|
2050 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2051 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2052 | jumps). |
|
|
2053 | |
|
|
2054 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2055 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2056 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2057 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2058 | than a directly following call to C<time>. |
|
|
2059 | |
|
|
2060 | The moral of this is to only compare libev-related timestamps with |
|
|
2061 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2062 | a second or so. |
|
|
2063 | |
|
|
2064 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2065 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2066 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2067 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2068 | |
|
|
2069 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2070 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2071 | I<measured according to the real time>, not the system clock. |
|
|
2072 | |
|
|
2073 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2074 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2075 | exactly the right behaviour. |
|
|
2076 | |
|
|
2077 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2078 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2079 | time, where your comparisons will always generate correct results. |
1923 | |
2080 | |
1924 | =head3 The special problems of suspended animation |
2081 | =head3 The special problems of suspended animation |
1925 | |
2082 | |
1926 | When you leave the server world it is quite customary to hit machines that |
2083 | When you leave the server world it is quite customary to hit machines that |
1927 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2084 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
1957 | |
2114 | |
1958 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2115 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1959 | |
2116 | |
1960 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
2117 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1961 | |
2118 | |
1962 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
2119 | Configure the timer to trigger after C<after> seconds (fractional and |
1963 | is C<0.>, then it will automatically be stopped once the timeout is |
2120 | negative values are supported). If C<repeat> is C<0.>, then it will |
1964 | reached. If it is positive, then the timer will automatically be |
2121 | automatically be stopped once the timeout is reached. If it is positive, |
1965 | configured to trigger again C<repeat> seconds later, again, and again, |
2122 | then the timer will automatically be configured to trigger again C<repeat> |
1966 | until stopped manually. |
2123 | seconds later, again, and again, until stopped manually. |
1967 | |
2124 | |
1968 | The timer itself will do a best-effort at avoiding drift, that is, if |
2125 | The timer itself will do a best-effort at avoiding drift, that is, if |
1969 | you configure a timer to trigger every 10 seconds, then it will normally |
2126 | you configure a timer to trigger every 10 seconds, then it will normally |
1970 | trigger at exactly 10 second intervals. If, however, your program cannot |
2127 | trigger at exactly 10 second intervals. If, however, your program cannot |
1971 | keep up with the timer (because it takes longer than those 10 seconds to |
2128 | keep up with the timer (because it takes longer than those 10 seconds to |
1972 | do stuff) the timer will not fire more than once per event loop iteration. |
2129 | do stuff) the timer will not fire more than once per event loop iteration. |
1973 | |
2130 | |
1974 | =item ev_timer_again (loop, ev_timer *) |
2131 | =item ev_timer_again (loop, ev_timer *) |
1975 | |
2132 | |
1976 | This will act as if the timer timed out and restart it again if it is |
2133 | This will act as if the timer timed out, and restarts it again if it is |
1977 | repeating. The exact semantics are: |
2134 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2135 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1978 | |
2136 | |
|
|
2137 | The exact semantics are as in the following rules, all of which will be |
|
|
2138 | applied to the watcher: |
|
|
2139 | |
|
|
2140 | =over 4 |
|
|
2141 | |
1979 | If the timer is pending, its pending status is cleared. |
2142 | =item If the timer is pending, the pending status is always cleared. |
1980 | |
2143 | |
1981 | If the timer is started but non-repeating, stop it (as if it timed out). |
2144 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2145 | out, without invoking it). |
1982 | |
2146 | |
1983 | If the timer is repeating, either start it if necessary (with the |
2147 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1984 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2148 | and start the timer, if necessary. |
1985 | |
2149 | |
|
|
2150 | =back |
|
|
2151 | |
1986 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2152 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1987 | usage example. |
2153 | usage example. |
1988 | |
2154 | |
1989 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2155 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1990 | |
2156 | |
1991 | Returns the remaining time until a timer fires. If the timer is active, |
2157 | Returns the remaining time until a timer fires. If the timer is active, |
… | |
… | |
2044 | Periodic watchers are also timers of a kind, but they are very versatile |
2210 | Periodic watchers are also timers of a kind, but they are very versatile |
2045 | (and unfortunately a bit complex). |
2211 | (and unfortunately a bit complex). |
2046 | |
2212 | |
2047 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2213 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
2048 | relative time, the physical time that passes) but on wall clock time |
2214 | relative time, the physical time that passes) but on wall clock time |
2049 | (absolute time, the thing you can read on your calender or clock). The |
2215 | (absolute time, the thing you can read on your calendar or clock). The |
2050 | difference is that wall clock time can run faster or slower than real |
2216 | difference is that wall clock time can run faster or slower than real |
2051 | time, and time jumps are not uncommon (e.g. when you adjust your |
2217 | time, and time jumps are not uncommon (e.g. when you adjust your |
2052 | wrist-watch). |
2218 | wrist-watch). |
2053 | |
2219 | |
2054 | You can tell a periodic watcher to trigger after some specific point |
2220 | You can tell a periodic watcher to trigger after some specific point |
… | |
… | |
2059 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2225 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
2060 | it, as it uses a relative timeout). |
2226 | it, as it uses a relative timeout). |
2061 | |
2227 | |
2062 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2228 | C<ev_periodic> watchers can also be used to implement vastly more complex |
2063 | timers, such as triggering an event on each "midnight, local time", or |
2229 | timers, such as triggering an event on each "midnight, local time", or |
2064 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
2230 | other complicated rules. This cannot easily be done with C<ev_timer> |
2065 | those cannot react to time jumps. |
2231 | watchers, as those cannot react to time jumps. |
2066 | |
2232 | |
2067 | As with timers, the callback is guaranteed to be invoked only when the |
2233 | As with timers, the callback is guaranteed to be invoked only when the |
2068 | point in time where it is supposed to trigger has passed. If multiple |
2234 | point in time where it is supposed to trigger has passed. If multiple |
2069 | timers become ready during the same loop iteration then the ones with |
2235 | timers become ready during the same loop iteration then the ones with |
2070 | earlier time-out values are invoked before ones with later time-out values |
2236 | earlier time-out values are invoked before ones with later time-out values |
… | |
… | |
2111 | |
2277 | |
2112 | Another way to think about it (for the mathematically inclined) is that |
2278 | Another way to think about it (for the mathematically inclined) is that |
2113 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2279 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2114 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2280 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2115 | |
2281 | |
2116 | For numerical stability it is preferable that the C<offset> value is near |
2282 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2117 | C<ev_now ()> (the current time), but there is no range requirement for |
2283 | interval value should be higher than C<1/8192> (which is around 100 |
2118 | this value, and in fact is often specified as zero. |
2284 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2285 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2286 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2287 | C<0> and C<interval>, which is also the recommended range. |
2119 | |
2288 | |
2120 | Note also that there is an upper limit to how often a timer can fire (CPU |
2289 | Note also that there is an upper limit to how often a timer can fire (CPU |
2121 | speed for example), so if C<interval> is very small then timing stability |
2290 | speed for example), so if C<interval> is very small then timing stability |
2122 | will of course deteriorate. Libev itself tries to be exact to be about one |
2291 | will of course deteriorate. Libev itself tries to be exact to be about one |
2123 | millisecond (if the OS supports it and the machine is fast enough). |
2292 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2153 | |
2322 | |
2154 | NOTE: I<< This callback must always return a time that is higher than or |
2323 | NOTE: I<< This callback must always return a time that is higher than or |
2155 | equal to the passed C<now> value >>. |
2324 | equal to the passed C<now> value >>. |
2156 | |
2325 | |
2157 | This can be used to create very complex timers, such as a timer that |
2326 | This can be used to create very complex timers, such as a timer that |
2158 | triggers on "next midnight, local time". To do this, you would calculate the |
2327 | triggers on "next midnight, local time". To do this, you would calculate |
2159 | next midnight after C<now> and return the timestamp value for this. How |
2328 | the next midnight after C<now> and return the timestamp value for |
2160 | you do this is, again, up to you (but it is not trivial, which is the main |
2329 | this. Here is a (completely untested, no error checking) example on how to |
2161 | reason I omitted it as an example). |
2330 | do this: |
|
|
2331 | |
|
|
2332 | #include <time.h> |
|
|
2333 | |
|
|
2334 | static ev_tstamp |
|
|
2335 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
|
|
2336 | { |
|
|
2337 | time_t tnow = (time_t)now; |
|
|
2338 | struct tm tm; |
|
|
2339 | localtime_r (&tnow, &tm); |
|
|
2340 | |
|
|
2341 | tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day |
|
|
2342 | ++tm.tm_mday; // midnight next day |
|
|
2343 | |
|
|
2344 | return mktime (&tm); |
|
|
2345 | } |
|
|
2346 | |
|
|
2347 | Note: this code might run into trouble on days that have more then two |
|
|
2348 | midnights (beginning and end). |
2162 | |
2349 | |
2163 | =back |
2350 | =back |
2164 | |
2351 | |
2165 | =item ev_periodic_again (loop, ev_periodic *) |
2352 | =item ev_periodic_again (loop, ev_periodic *) |
2166 | |
2353 | |
… | |
… | |
2231 | |
2418 | |
2232 | ev_periodic hourly_tick; |
2419 | ev_periodic hourly_tick; |
2233 | ev_periodic_init (&hourly_tick, clock_cb, |
2420 | ev_periodic_init (&hourly_tick, clock_cb, |
2234 | fmod (ev_now (loop), 3600.), 3600., 0); |
2421 | fmod (ev_now (loop), 3600.), 3600., 0); |
2235 | ev_periodic_start (loop, &hourly_tick); |
2422 | ev_periodic_start (loop, &hourly_tick); |
2236 | |
2423 | |
2237 | |
2424 | |
2238 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2425 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2239 | |
2426 | |
2240 | Signal watchers will trigger an event when the process receives a specific |
2427 | Signal watchers will trigger an event when the process receives a specific |
2241 | signal one or more times. Even though signals are very asynchronous, libev |
2428 | signal one or more times. Even though signals are very asynchronous, libev |
2242 | will try it's best to deliver signals synchronously, i.e. as part of the |
2429 | will try its best to deliver signals synchronously, i.e. as part of the |
2243 | normal event processing, like any other event. |
2430 | normal event processing, like any other event. |
2244 | |
2431 | |
2245 | If you want signals to be delivered truly asynchronously, just use |
2432 | If you want signals to be delivered truly asynchronously, just use |
2246 | C<sigaction> as you would do without libev and forget about sharing |
2433 | C<sigaction> as you would do without libev and forget about sharing |
2247 | the signal. You can even use C<ev_async> from a signal handler to |
2434 | the signal. You can even use C<ev_async> from a signal handler to |
… | |
… | |
2251 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2438 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
2252 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2439 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
2253 | C<SIGINT> in both the default loop and another loop at the same time. At |
2440 | C<SIGINT> in both the default loop and another loop at the same time. At |
2254 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2441 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
2255 | |
2442 | |
2256 | When the first watcher gets started will libev actually register something |
2443 | Only after the first watcher for a signal is started will libev actually |
2257 | with the kernel (thus it coexists with your own signal handlers as long as |
2444 | register something with the kernel. It thus coexists with your own signal |
2258 | you don't register any with libev for the same signal). |
2445 | handlers as long as you don't register any with libev for the same signal. |
2259 | |
2446 | |
2260 | If possible and supported, libev will install its handlers with |
2447 | If possible and supported, libev will install its handlers with |
2261 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2448 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
2262 | not be unduly interrupted. If you have a problem with system calls getting |
2449 | not be unduly interrupted. If you have a problem with system calls getting |
2263 | interrupted by signals you can block all signals in an C<ev_check> watcher |
2450 | interrupted by signals you can block all signals in an C<ev_check> watcher |
… | |
… | |
2266 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2453 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2267 | |
2454 | |
2268 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2455 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2269 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2456 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2270 | stopping it again), that is, libev might or might not block the signal, |
2457 | stopping it again), that is, libev might or might not block the signal, |
2271 | and might or might not set or restore the installed signal handler. |
2458 | and might or might not set or restore the installed signal handler (but |
|
|
2459 | see C<EVFLAG_NOSIGMASK>). |
2272 | |
2460 | |
2273 | While this does not matter for the signal disposition (libev never |
2461 | While this does not matter for the signal disposition (libev never |
2274 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2462 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2275 | C<execve>), this matters for the signal mask: many programs do not expect |
2463 | C<execve>), this matters for the signal mask: many programs do not expect |
2276 | certain signals to be blocked. |
2464 | certain signals to be blocked. |
… | |
… | |
2289 | I<has> to modify the signal mask, at least temporarily. |
2477 | I<has> to modify the signal mask, at least temporarily. |
2290 | |
2478 | |
2291 | So I can't stress this enough: I<If you do not reset your signal mask when |
2479 | So I can't stress this enough: I<If you do not reset your signal mask when |
2292 | you expect it to be empty, you have a race condition in your code>. This |
2480 | you expect it to be empty, you have a race condition in your code>. This |
2293 | is not a libev-specific thing, this is true for most event libraries. |
2481 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2482 | |
|
|
2483 | =head3 The special problem of threads signal handling |
|
|
2484 | |
|
|
2485 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2486 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2487 | threads in a process block signals, which is hard to achieve. |
|
|
2488 | |
|
|
2489 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2490 | for the same signals), you can tackle this problem by globally blocking |
|
|
2491 | all signals before creating any threads (or creating them with a fully set |
|
|
2492 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2493 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2494 | these signals. You can pass on any signals that libev might be interested |
|
|
2495 | in by calling C<ev_feed_signal>. |
2294 | |
2496 | |
2295 | =head3 Watcher-Specific Functions and Data Members |
2497 | =head3 Watcher-Specific Functions and Data Members |
2296 | |
2498 | |
2297 | =over 4 |
2499 | =over 4 |
2298 | |
2500 | |
… | |
… | |
2433 | |
2635 | |
2434 | =head2 C<ev_stat> - did the file attributes just change? |
2636 | =head2 C<ev_stat> - did the file attributes just change? |
2435 | |
2637 | |
2436 | This watches a file system path for attribute changes. That is, it calls |
2638 | This watches a file system path for attribute changes. That is, it calls |
2437 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2639 | C<stat> on that path in regular intervals (or when the OS says it changed) |
2438 | and sees if it changed compared to the last time, invoking the callback if |
2640 | and sees if it changed compared to the last time, invoking the callback |
2439 | it did. |
2641 | if it did. Starting the watcher C<stat>'s the file, so only changes that |
|
|
2642 | happen after the watcher has been started will be reported. |
2440 | |
2643 | |
2441 | The path does not need to exist: changing from "path exists" to "path does |
2644 | The path does not need to exist: changing from "path exists" to "path does |
2442 | not exist" is a status change like any other. The condition "path does not |
2645 | not exist" is a status change like any other. The condition "path does not |
2443 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2646 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
2444 | C<st_nlink> field being zero (which is otherwise always forced to be at |
2647 | C<st_nlink> field being zero (which is otherwise always forced to be at |
… | |
… | |
2674 | Apart from keeping your process non-blocking (which is a useful |
2877 | Apart from keeping your process non-blocking (which is a useful |
2675 | effect on its own sometimes), idle watchers are a good place to do |
2878 | effect on its own sometimes), idle watchers are a good place to do |
2676 | "pseudo-background processing", or delay processing stuff to after the |
2879 | "pseudo-background processing", or delay processing stuff to after the |
2677 | event loop has handled all outstanding events. |
2880 | event loop has handled all outstanding events. |
2678 | |
2881 | |
|
|
2882 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2883 | |
|
|
2884 | As long as there is at least one active idle watcher, libev will never |
|
|
2885 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2886 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2887 | lowest priority will do. |
|
|
2888 | |
|
|
2889 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2890 | to do something on each event loop iteration - for example to balance load |
|
|
2891 | between different connections. |
|
|
2892 | |
|
|
2893 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2894 | example. |
|
|
2895 | |
2679 | =head3 Watcher-Specific Functions and Data Members |
2896 | =head3 Watcher-Specific Functions and Data Members |
2680 | |
2897 | |
2681 | =over 4 |
2898 | =over 4 |
2682 | |
2899 | |
2683 | =item ev_idle_init (ev_idle *, callback) |
2900 | =item ev_idle_init (ev_idle *, callback) |
… | |
… | |
2694 | callback, free it. Also, use no error checking, as usual. |
2911 | callback, free it. Also, use no error checking, as usual. |
2695 | |
2912 | |
2696 | static void |
2913 | static void |
2697 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2914 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
2698 | { |
2915 | { |
|
|
2916 | // stop the watcher |
|
|
2917 | ev_idle_stop (loop, w); |
|
|
2918 | |
|
|
2919 | // now we can free it |
2699 | free (w); |
2920 | free (w); |
|
|
2921 | |
2700 | // now do something you wanted to do when the program has |
2922 | // now do something you wanted to do when the program has |
2701 | // no longer anything immediate to do. |
2923 | // no longer anything immediate to do. |
2702 | } |
2924 | } |
2703 | |
2925 | |
2704 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
2926 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
… | |
… | |
2706 | ev_idle_start (loop, idle_watcher); |
2928 | ev_idle_start (loop, idle_watcher); |
2707 | |
2929 | |
2708 | |
2930 | |
2709 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2931 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2710 | |
2932 | |
2711 | Prepare and check watchers are usually (but not always) used in pairs: |
2933 | Prepare and check watchers are often (but not always) used in pairs: |
2712 | prepare watchers get invoked before the process blocks and check watchers |
2934 | prepare watchers get invoked before the process blocks and check watchers |
2713 | afterwards. |
2935 | afterwards. |
2714 | |
2936 | |
2715 | You I<must not> call C<ev_run> or similar functions that enter |
2937 | You I<must not> call C<ev_run> (or similar functions that enter the |
2716 | the current event loop from either C<ev_prepare> or C<ev_check> |
2938 | current event loop) or C<ev_loop_fork> from either C<ev_prepare> or |
2717 | watchers. Other loops than the current one are fine, however. The |
2939 | C<ev_check> watchers. Other loops than the current one are fine, |
2718 | rationale behind this is that you do not need to check for recursion in |
2940 | however. The rationale behind this is that you do not need to check |
2719 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2941 | for recursion in those watchers, i.e. the sequence will always be |
2720 | C<ev_check> so if you have one watcher of each kind they will always be |
2942 | C<ev_prepare>, blocking, C<ev_check> so if you have one watcher of each |
2721 | called in pairs bracketing the blocking call. |
2943 | kind they will always be called in pairs bracketing the blocking call. |
2722 | |
2944 | |
2723 | Their main purpose is to integrate other event mechanisms into libev and |
2945 | Their main purpose is to integrate other event mechanisms into libev and |
2724 | their use is somewhat advanced. They could be used, for example, to track |
2946 | their use is somewhat advanced. They could be used, for example, to track |
2725 | variable changes, implement your own watchers, integrate net-snmp or a |
2947 | variable changes, implement your own watchers, integrate net-snmp or a |
2726 | coroutine library and lots more. They are also occasionally useful if |
2948 | coroutine library and lots more. They are also occasionally useful if |
… | |
… | |
2744 | with priority higher than or equal to the event loop and one coroutine |
2966 | with priority higher than or equal to the event loop and one coroutine |
2745 | of lower priority, but only once, using idle watchers to keep the event |
2967 | of lower priority, but only once, using idle watchers to keep the event |
2746 | loop from blocking if lower-priority coroutines are active, thus mapping |
2968 | loop from blocking if lower-priority coroutines are active, thus mapping |
2747 | low-priority coroutines to idle/background tasks). |
2969 | low-priority coroutines to idle/background tasks). |
2748 | |
2970 | |
2749 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2971 | When used for this purpose, it is recommended to give C<ev_check> watchers |
2750 | priority, to ensure that they are being run before any other watchers |
2972 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
2751 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
2973 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2974 | watchers). |
2752 | |
2975 | |
2753 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2976 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
2754 | activate ("feed") events into libev. While libev fully supports this, they |
2977 | activate ("feed") events into libev. While libev fully supports this, they |
2755 | might get executed before other C<ev_check> watchers did their job. As |
2978 | might get executed before other C<ev_check> watchers did their job. As |
2756 | C<ev_check> watchers are often used to embed other (non-libev) event |
2979 | C<ev_check> watchers are often used to embed other (non-libev) event |
2757 | loops those other event loops might be in an unusable state until their |
2980 | loops those other event loops might be in an unusable state until their |
2758 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2981 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
2759 | others). |
2982 | others). |
|
|
2983 | |
|
|
2984 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2985 | |
|
|
2986 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2987 | useful because they are called once per event loop iteration. For |
|
|
2988 | example, if you want to handle a large number of connections fairly, you |
|
|
2989 | normally only do a bit of work for each active connection, and if there |
|
|
2990 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2991 | connections have a chance of making progress. |
|
|
2992 | |
|
|
2993 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2994 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2995 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2996 | |
|
|
2997 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2998 | single global idle watcher that is active as long as you have one active |
|
|
2999 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
3000 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
3001 | invoked. Neither watcher alone can do that. |
2760 | |
3002 | |
2761 | =head3 Watcher-Specific Functions and Data Members |
3003 | =head3 Watcher-Specific Functions and Data Members |
2762 | |
3004 | |
2763 | =over 4 |
3005 | =over 4 |
2764 | |
3006 | |
… | |
… | |
2965 | |
3207 | |
2966 | =over 4 |
3208 | =over 4 |
2967 | |
3209 | |
2968 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
3210 | =item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) |
2969 | |
3211 | |
2970 | =item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) |
3212 | =item ev_embed_set (ev_embed *, struct ev_loop *embedded_loop) |
2971 | |
3213 | |
2972 | Configures the watcher to embed the given loop, which must be |
3214 | Configures the watcher to embed the given loop, which must be |
2973 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
3215 | embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be |
2974 | invoked automatically, otherwise it is the responsibility of the callback |
3216 | invoked automatically, otherwise it is the responsibility of the callback |
2975 | to invoke it (it will continue to be called until the sweep has been done, |
3217 | to invoke it (it will continue to be called until the sweep has been done, |
… | |
… | |
2996 | used). |
3238 | used). |
2997 | |
3239 | |
2998 | struct ev_loop *loop_hi = ev_default_init (0); |
3240 | struct ev_loop *loop_hi = ev_default_init (0); |
2999 | struct ev_loop *loop_lo = 0; |
3241 | struct ev_loop *loop_lo = 0; |
3000 | ev_embed embed; |
3242 | ev_embed embed; |
3001 | |
3243 | |
3002 | // see if there is a chance of getting one that works |
3244 | // see if there is a chance of getting one that works |
3003 | // (remember that a flags value of 0 means autodetection) |
3245 | // (remember that a flags value of 0 means autodetection) |
3004 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3246 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3005 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3247 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3006 | : 0; |
3248 | : 0; |
… | |
… | |
3020 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3262 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3021 | |
3263 | |
3022 | struct ev_loop *loop = ev_default_init (0); |
3264 | struct ev_loop *loop = ev_default_init (0); |
3023 | struct ev_loop *loop_socket = 0; |
3265 | struct ev_loop *loop_socket = 0; |
3024 | ev_embed embed; |
3266 | ev_embed embed; |
3025 | |
3267 | |
3026 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3268 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3027 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3269 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3028 | { |
3270 | { |
3029 | ev_embed_init (&embed, 0, loop_socket); |
3271 | ev_embed_init (&embed, 0, loop_socket); |
3030 | ev_embed_start (loop, &embed); |
3272 | ev_embed_start (loop, &embed); |
… | |
… | |
3038 | |
3280 | |
3039 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3281 | =head2 C<ev_fork> - the audacity to resume the event loop after a fork |
3040 | |
3282 | |
3041 | Fork watchers are called when a C<fork ()> was detected (usually because |
3283 | Fork watchers are called when a C<fork ()> was detected (usually because |
3042 | whoever is a good citizen cared to tell libev about it by calling |
3284 | whoever is a good citizen cared to tell libev about it by calling |
3043 | C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the |
3285 | C<ev_loop_fork>). The invocation is done before the event loop blocks next |
3044 | event loop blocks next and before C<ev_check> watchers are being called, |
3286 | and before C<ev_check> watchers are being called, and only in the child |
3045 | and only in the child after the fork. If whoever good citizen calling |
3287 | after the fork. If whoever good citizen calling C<ev_default_fork> cheats |
3046 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3288 | and calls it in the wrong process, the fork handlers will be invoked, too, |
3047 | handlers will be invoked, too, of course. |
3289 | of course. |
3048 | |
3290 | |
3049 | =head3 The special problem of life after fork - how is it possible? |
3291 | =head3 The special problem of life after fork - how is it possible? |
3050 | |
3292 | |
3051 | Most uses of C<fork()> consist of forking, then some simple calls to set |
3293 | Most uses of C<fork ()> consist of forking, then some simple calls to set |
3052 | up/change the process environment, followed by a call to C<exec()>. This |
3294 | up/change the process environment, followed by a call to C<exec()>. This |
3053 | sequence should be handled by libev without any problems. |
3295 | sequence should be handled by libev without any problems. |
3054 | |
3296 | |
3055 | This changes when the application actually wants to do event handling |
3297 | This changes when the application actually wants to do event handling |
3056 | in the child, or both parent in child, in effect "continuing" after the |
3298 | in the child, or both parent in child, in effect "continuing" after the |
… | |
… | |
3072 | disadvantage of having to use multiple event loops (which do not support |
3314 | disadvantage of having to use multiple event loops (which do not support |
3073 | signal watchers). |
3315 | signal watchers). |
3074 | |
3316 | |
3075 | When this is not possible, or you want to use the default loop for |
3317 | When this is not possible, or you want to use the default loop for |
3076 | other reasons, then in the process that wants to start "fresh", call |
3318 | other reasons, then in the process that wants to start "fresh", call |
3077 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
3319 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
3078 | the default loop will "orphan" (not stop) all registered watchers, so you |
3320 | Destroying the default loop will "orphan" (not stop) all registered |
3079 | have to be careful not to execute code that modifies those watchers. Note |
3321 | watchers, so you have to be careful not to execute code that modifies |
3080 | also that in that case, you have to re-register any signal watchers. |
3322 | those watchers. Note also that in that case, you have to re-register any |
|
|
3323 | signal watchers. |
3081 | |
3324 | |
3082 | =head3 Watcher-Specific Functions and Data Members |
3325 | =head3 Watcher-Specific Functions and Data Members |
3083 | |
3326 | |
3084 | =over 4 |
3327 | =over 4 |
3085 | |
3328 | |
3086 | =item ev_fork_init (ev_signal *, callback) |
3329 | =item ev_fork_init (ev_fork *, callback) |
3087 | |
3330 | |
3088 | Initialises and configures the fork watcher - it has no parameters of any |
3331 | Initialises and configures the fork watcher - it has no parameters of any |
3089 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3332 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3090 | believe me. |
3333 | really. |
3091 | |
3334 | |
3092 | =back |
3335 | =back |
3093 | |
3336 | |
3094 | |
3337 | |
|
|
3338 | =head2 C<ev_cleanup> - even the best things end |
|
|
3339 | |
|
|
3340 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3341 | by a call to C<ev_loop_destroy>. |
|
|
3342 | |
|
|
3343 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3344 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3345 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3346 | loop when you want them to be invoked. |
|
|
3347 | |
|
|
3348 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3349 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3350 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3351 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3352 | |
|
|
3353 | =head3 Watcher-Specific Functions and Data Members |
|
|
3354 | |
|
|
3355 | =over 4 |
|
|
3356 | |
|
|
3357 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3358 | |
|
|
3359 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3360 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3361 | pointless, I assure you. |
|
|
3362 | |
|
|
3363 | =back |
|
|
3364 | |
|
|
3365 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3366 | cleanup functions are called. |
|
|
3367 | |
|
|
3368 | static void |
|
|
3369 | program_exits (void) |
|
|
3370 | { |
|
|
3371 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3372 | } |
|
|
3373 | |
|
|
3374 | ... |
|
|
3375 | atexit (program_exits); |
|
|
3376 | |
|
|
3377 | |
3095 | =head2 C<ev_async> - how to wake up an event loop |
3378 | =head2 C<ev_async> - how to wake up an event loop |
3096 | |
3379 | |
3097 | In general, you cannot use an C<ev_run> from multiple threads or other |
3380 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3098 | asynchronous sources such as signal handlers (as opposed to multiple event |
3381 | asynchronous sources such as signal handlers (as opposed to multiple event |
3099 | loops - those are of course safe to use in different threads). |
3382 | loops - those are of course safe to use in different threads). |
3100 | |
3383 | |
3101 | Sometimes, however, you need to wake up an event loop you do not control, |
3384 | Sometimes, however, you need to wake up an event loop you do not control, |
3102 | for example because it belongs to another thread. This is what C<ev_async> |
3385 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3104 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3387 | it by calling C<ev_async_send>, which is thread- and signal safe. |
3105 | |
3388 | |
3106 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3389 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3107 | too, are asynchronous in nature, and signals, too, will be compressed |
3390 | too, are asynchronous in nature, and signals, too, will be compressed |
3108 | (i.e. the number of callback invocations may be less than the number of |
3391 | (i.e. the number of callback invocations may be less than the number of |
3109 | C<ev_async_sent> calls). |
3392 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
3110 | |
3393 | of "global async watchers" by using a watcher on an otherwise unused |
3111 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3394 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3112 | just the default loop. |
3395 | even without knowing which loop owns the signal. |
3113 | |
3396 | |
3114 | =head3 Queueing |
3397 | =head3 Queueing |
3115 | |
3398 | |
3116 | C<ev_async> does not support queueing of data in any way. The reason |
3399 | C<ev_async> does not support queueing of data in any way. The reason |
3117 | is that the author does not know of a simple (or any) algorithm for a |
3400 | is that the author does not know of a simple (or any) algorithm for a |
… | |
… | |
3209 | trust me. |
3492 | trust me. |
3210 | |
3493 | |
3211 | =item ev_async_send (loop, ev_async *) |
3494 | =item ev_async_send (loop, ev_async *) |
3212 | |
3495 | |
3213 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3496 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3214 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3497 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3498 | returns. |
|
|
3499 | |
3215 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3500 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3216 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3501 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3217 | section below on what exactly this means). |
3502 | embedding section below on what exactly this means). |
3218 | |
3503 | |
3219 | Note that, as with other watchers in libev, multiple events might get |
3504 | Note that, as with other watchers in libev, multiple events might get |
3220 | compressed into a single callback invocation (another way to look at this |
3505 | compressed into a single callback invocation (another way to look at |
3221 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3506 | this is that C<ev_async> watchers are level-triggered: they are set on |
3222 | reset when the event loop detects that). |
3507 | C<ev_async_send>, reset when the event loop detects that). |
3223 | |
3508 | |
3224 | This call incurs the overhead of a system call only once per event loop |
3509 | This call incurs the overhead of at most one extra system call per event |
3225 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3510 | loop iteration, if the event loop is blocked, and no syscall at all if |
3226 | repeated calls to C<ev_async_send> for the same event loop. |
3511 | the event loop (or your program) is processing events. That means that |
|
|
3512 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3513 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3514 | zero) under load. |
3227 | |
3515 | |
3228 | =item bool = ev_async_pending (ev_async *) |
3516 | =item bool = ev_async_pending (ev_async *) |
3229 | |
3517 | |
3230 | Returns a non-zero value when C<ev_async_send> has been called on the |
3518 | Returns a non-zero value when C<ev_async_send> has been called on the |
3231 | watcher but the event has not yet been processed (or even noted) by the |
3519 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3248 | |
3536 | |
3249 | There are some other functions of possible interest. Described. Here. Now. |
3537 | There are some other functions of possible interest. Described. Here. Now. |
3250 | |
3538 | |
3251 | =over 4 |
3539 | =over 4 |
3252 | |
3540 | |
3253 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3541 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg) |
3254 | |
3542 | |
3255 | This function combines a simple timer and an I/O watcher, calls your |
3543 | This function combines a simple timer and an I/O watcher, calls your |
3256 | callback on whichever event happens first and automatically stops both |
3544 | callback on whichever event happens first and automatically stops both |
3257 | watchers. This is useful if you want to wait for a single event on an fd |
3545 | watchers. This is useful if you want to wait for a single event on an fd |
3258 | or timeout without having to allocate/configure/start/stop/free one or |
3546 | or timeout without having to allocate/configure/start/stop/free one or |
… | |
… | |
3286 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3574 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3287 | |
3575 | |
3288 | =item ev_feed_fd_event (loop, int fd, int revents) |
3576 | =item ev_feed_fd_event (loop, int fd, int revents) |
3289 | |
3577 | |
3290 | Feed an event on the given fd, as if a file descriptor backend detected |
3578 | Feed an event on the given fd, as if a file descriptor backend detected |
3291 | the given events it. |
3579 | the given events. |
3292 | |
3580 | |
3293 | =item ev_feed_signal_event (loop, int signum) |
3581 | =item ev_feed_signal_event (loop, int signum) |
3294 | |
3582 | |
3295 | Feed an event as if the given signal occurred (C<loop> must be the default |
3583 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3296 | loop!). |
3584 | which is async-safe. |
3297 | |
3585 | |
3298 | =back |
3586 | =back |
|
|
3587 | |
|
|
3588 | |
|
|
3589 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3590 | |
|
|
3591 | This section explains some common idioms that are not immediately |
|
|
3592 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3593 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3594 | |
|
|
3595 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3596 | |
|
|
3597 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3598 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3599 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3600 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3601 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3602 | data: |
|
|
3603 | |
|
|
3604 | struct my_io |
|
|
3605 | { |
|
|
3606 | ev_io io; |
|
|
3607 | int otherfd; |
|
|
3608 | void *somedata; |
|
|
3609 | struct whatever *mostinteresting; |
|
|
3610 | }; |
|
|
3611 | |
|
|
3612 | ... |
|
|
3613 | struct my_io w; |
|
|
3614 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3615 | |
|
|
3616 | And since your callback will be called with a pointer to the watcher, you |
|
|
3617 | can cast it back to your own type: |
|
|
3618 | |
|
|
3619 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3620 | { |
|
|
3621 | struct my_io *w = (struct my_io *)w_; |
|
|
3622 | ... |
|
|
3623 | } |
|
|
3624 | |
|
|
3625 | More interesting and less C-conformant ways of casting your callback |
|
|
3626 | function type instead have been omitted. |
|
|
3627 | |
|
|
3628 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3629 | |
|
|
3630 | Another common scenario is to use some data structure with multiple |
|
|
3631 | embedded watchers, in effect creating your own watcher that combines |
|
|
3632 | multiple libev event sources into one "super-watcher": |
|
|
3633 | |
|
|
3634 | struct my_biggy |
|
|
3635 | { |
|
|
3636 | int some_data; |
|
|
3637 | ev_timer t1; |
|
|
3638 | ev_timer t2; |
|
|
3639 | } |
|
|
3640 | |
|
|
3641 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3642 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3643 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3644 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3645 | real programmers): |
|
|
3646 | |
|
|
3647 | #include <stddef.h> |
|
|
3648 | |
|
|
3649 | static void |
|
|
3650 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3651 | { |
|
|
3652 | struct my_biggy big = (struct my_biggy *) |
|
|
3653 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3654 | } |
|
|
3655 | |
|
|
3656 | static void |
|
|
3657 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3658 | { |
|
|
3659 | struct my_biggy big = (struct my_biggy *) |
|
|
3660 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3661 | } |
|
|
3662 | |
|
|
3663 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3664 | |
|
|
3665 | Often you have structures like this in event-based programs: |
|
|
3666 | |
|
|
3667 | callback () |
|
|
3668 | { |
|
|
3669 | free (request); |
|
|
3670 | } |
|
|
3671 | |
|
|
3672 | request = start_new_request (..., callback); |
|
|
3673 | |
|
|
3674 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3675 | used to cancel the operation, or do other things with it. |
|
|
3676 | |
|
|
3677 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3678 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3679 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3680 | operation and simply invoke the callback with the result. |
|
|
3681 | |
|
|
3682 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3683 | has returned, so C<request> is not set. |
|
|
3684 | |
|
|
3685 | Even if you pass the request by some safer means to the callback, you |
|
|
3686 | might want to do something to the request after starting it, such as |
|
|
3687 | canceling it, which probably isn't working so well when the callback has |
|
|
3688 | already been invoked. |
|
|
3689 | |
|
|
3690 | A common way around all these issues is to make sure that |
|
|
3691 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3692 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3693 | delay invoking the callback by using a C<prepare> or C<idle> watcher for |
|
|
3694 | example, or more sneakily, by reusing an existing (stopped) watcher and |
|
|
3695 | pushing it into the pending queue: |
|
|
3696 | |
|
|
3697 | ev_set_cb (watcher, callback); |
|
|
3698 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3699 | |
|
|
3700 | This way, C<start_new_request> can safely return before the callback is |
|
|
3701 | invoked, while not delaying callback invocation too much. |
|
|
3702 | |
|
|
3703 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3704 | |
|
|
3705 | Often (especially in GUI toolkits) there are places where you have |
|
|
3706 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3707 | invoking C<ev_run>. |
|
|
3708 | |
|
|
3709 | This brings the problem of exiting - a callback might want to finish the |
|
|
3710 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3711 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3712 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3713 | other combination: In these cases, a simple C<ev_break> will not work. |
|
|
3714 | |
|
|
3715 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3716 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3717 | triggered, using C<EVRUN_ONCE>: |
|
|
3718 | |
|
|
3719 | // main loop |
|
|
3720 | int exit_main_loop = 0; |
|
|
3721 | |
|
|
3722 | while (!exit_main_loop) |
|
|
3723 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3724 | |
|
|
3725 | // in a modal watcher |
|
|
3726 | int exit_nested_loop = 0; |
|
|
3727 | |
|
|
3728 | while (!exit_nested_loop) |
|
|
3729 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3730 | |
|
|
3731 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3732 | |
|
|
3733 | // exit modal loop |
|
|
3734 | exit_nested_loop = 1; |
|
|
3735 | |
|
|
3736 | // exit main program, after modal loop is finished |
|
|
3737 | exit_main_loop = 1; |
|
|
3738 | |
|
|
3739 | // exit both |
|
|
3740 | exit_main_loop = exit_nested_loop = 1; |
|
|
3741 | |
|
|
3742 | =head2 THREAD LOCKING EXAMPLE |
|
|
3743 | |
|
|
3744 | Here is a fictitious example of how to run an event loop in a different |
|
|
3745 | thread from where callbacks are being invoked and watchers are |
|
|
3746 | created/added/removed. |
|
|
3747 | |
|
|
3748 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3749 | which uses exactly this technique (which is suited for many high-level |
|
|
3750 | languages). |
|
|
3751 | |
|
|
3752 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3753 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3754 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3755 | |
|
|
3756 | First, you need to associate some data with the event loop: |
|
|
3757 | |
|
|
3758 | typedef struct { |
|
|
3759 | mutex_t lock; /* global loop lock */ |
|
|
3760 | ev_async async_w; |
|
|
3761 | thread_t tid; |
|
|
3762 | cond_t invoke_cv; |
|
|
3763 | } userdata; |
|
|
3764 | |
|
|
3765 | void prepare_loop (EV_P) |
|
|
3766 | { |
|
|
3767 | // for simplicity, we use a static userdata struct. |
|
|
3768 | static userdata u; |
|
|
3769 | |
|
|
3770 | ev_async_init (&u->async_w, async_cb); |
|
|
3771 | ev_async_start (EV_A_ &u->async_w); |
|
|
3772 | |
|
|
3773 | pthread_mutex_init (&u->lock, 0); |
|
|
3774 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3775 | |
|
|
3776 | // now associate this with the loop |
|
|
3777 | ev_set_userdata (EV_A_ u); |
|
|
3778 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3779 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3780 | |
|
|
3781 | // then create the thread running ev_run |
|
|
3782 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3783 | } |
|
|
3784 | |
|
|
3785 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3786 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3787 | that might have been added: |
|
|
3788 | |
|
|
3789 | static void |
|
|
3790 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3791 | { |
|
|
3792 | // just used for the side effects |
|
|
3793 | } |
|
|
3794 | |
|
|
3795 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3796 | protecting the loop data, respectively. |
|
|
3797 | |
|
|
3798 | static void |
|
|
3799 | l_release (EV_P) |
|
|
3800 | { |
|
|
3801 | userdata *u = ev_userdata (EV_A); |
|
|
3802 | pthread_mutex_unlock (&u->lock); |
|
|
3803 | } |
|
|
3804 | |
|
|
3805 | static void |
|
|
3806 | l_acquire (EV_P) |
|
|
3807 | { |
|
|
3808 | userdata *u = ev_userdata (EV_A); |
|
|
3809 | pthread_mutex_lock (&u->lock); |
|
|
3810 | } |
|
|
3811 | |
|
|
3812 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3813 | into C<ev_run>: |
|
|
3814 | |
|
|
3815 | void * |
|
|
3816 | l_run (void *thr_arg) |
|
|
3817 | { |
|
|
3818 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3819 | |
|
|
3820 | l_acquire (EV_A); |
|
|
3821 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3822 | ev_run (EV_A_ 0); |
|
|
3823 | l_release (EV_A); |
|
|
3824 | |
|
|
3825 | return 0; |
|
|
3826 | } |
|
|
3827 | |
|
|
3828 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3829 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3830 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3831 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3832 | and b) skipping inter-thread-communication when there are no pending |
|
|
3833 | watchers is very beneficial): |
|
|
3834 | |
|
|
3835 | static void |
|
|
3836 | l_invoke (EV_P) |
|
|
3837 | { |
|
|
3838 | userdata *u = ev_userdata (EV_A); |
|
|
3839 | |
|
|
3840 | while (ev_pending_count (EV_A)) |
|
|
3841 | { |
|
|
3842 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3843 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3844 | } |
|
|
3845 | } |
|
|
3846 | |
|
|
3847 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3848 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3849 | thread to continue: |
|
|
3850 | |
|
|
3851 | static void |
|
|
3852 | real_invoke_pending (EV_P) |
|
|
3853 | { |
|
|
3854 | userdata *u = ev_userdata (EV_A); |
|
|
3855 | |
|
|
3856 | pthread_mutex_lock (&u->lock); |
|
|
3857 | ev_invoke_pending (EV_A); |
|
|
3858 | pthread_cond_signal (&u->invoke_cv); |
|
|
3859 | pthread_mutex_unlock (&u->lock); |
|
|
3860 | } |
|
|
3861 | |
|
|
3862 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3863 | event loop, you will now have to lock: |
|
|
3864 | |
|
|
3865 | ev_timer timeout_watcher; |
|
|
3866 | userdata *u = ev_userdata (EV_A); |
|
|
3867 | |
|
|
3868 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3869 | |
|
|
3870 | pthread_mutex_lock (&u->lock); |
|
|
3871 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3872 | ev_async_send (EV_A_ &u->async_w); |
|
|
3873 | pthread_mutex_unlock (&u->lock); |
|
|
3874 | |
|
|
3875 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3876 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3877 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3878 | watchers in the next event loop iteration. |
|
|
3879 | |
|
|
3880 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3881 | |
|
|
3882 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3883 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3884 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3885 | doesn't need callbacks anymore. |
|
|
3886 | |
|
|
3887 | Imagine you have coroutines that you can switch to using a function |
|
|
3888 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3889 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3890 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3891 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3892 | the differing C<;> conventions): |
|
|
3893 | |
|
|
3894 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3895 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3896 | |
|
|
3897 | That means instead of having a C callback function, you store the |
|
|
3898 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3899 | your callback, you instead have it switch to that coroutine. |
|
|
3900 | |
|
|
3901 | A coroutine might now wait for an event with a function called |
|
|
3902 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3903 | matter when, or whether the watcher is active or not when this function is |
|
|
3904 | called): |
|
|
3905 | |
|
|
3906 | void |
|
|
3907 | wait_for_event (ev_watcher *w) |
|
|
3908 | { |
|
|
3909 | ev_set_cb (w, current_coro); |
|
|
3910 | switch_to (libev_coro); |
|
|
3911 | } |
|
|
3912 | |
|
|
3913 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3914 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3915 | this or any other coroutine. |
|
|
3916 | |
|
|
3917 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3918 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3919 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3920 | any waiters. |
|
|
3921 | |
|
|
3922 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3923 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3924 | |
|
|
3925 | // my_ev.h |
|
|
3926 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3927 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3928 | #include "../libev/ev.h" |
|
|
3929 | |
|
|
3930 | // my_ev.c |
|
|
3931 | #define EV_H "my_ev.h" |
|
|
3932 | #include "../libev/ev.c" |
|
|
3933 | |
|
|
3934 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3935 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3936 | can even use F<ev.h> as header file name directly. |
3299 | |
3937 | |
3300 | |
3938 | |
3301 | =head1 LIBEVENT EMULATION |
3939 | =head1 LIBEVENT EMULATION |
3302 | |
3940 | |
3303 | Libev offers a compatibility emulation layer for libevent. It cannot |
3941 | Libev offers a compatibility emulation layer for libevent. It cannot |
3304 | emulate the internals of libevent, so here are some usage hints: |
3942 | emulate the internals of libevent, so here are some usage hints: |
3305 | |
3943 | |
3306 | =over 4 |
3944 | =over 4 |
|
|
3945 | |
|
|
3946 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3947 | |
|
|
3948 | This was the newest libevent version available when libev was implemented, |
|
|
3949 | and is still mostly unchanged in 2010. |
3307 | |
3950 | |
3308 | =item * Use it by including <event.h>, as usual. |
3951 | =item * Use it by including <event.h>, as usual. |
3309 | |
3952 | |
3310 | =item * The following members are fully supported: ev_base, ev_callback, |
3953 | =item * The following members are fully supported: ev_base, ev_callback, |
3311 | ev_arg, ev_fd, ev_res, ev_events. |
3954 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
3317 | =item * Priorities are not currently supported. Initialising priorities |
3960 | =item * Priorities are not currently supported. Initialising priorities |
3318 | will fail and all watchers will have the same priority, even though there |
3961 | will fail and all watchers will have the same priority, even though there |
3319 | is an ev_pri field. |
3962 | is an ev_pri field. |
3320 | |
3963 | |
3321 | =item * In libevent, the last base created gets the signals, in libev, the |
3964 | =item * In libevent, the last base created gets the signals, in libev, the |
3322 | first base created (== the default loop) gets the signals. |
3965 | base that registered the signal gets the signals. |
3323 | |
3966 | |
3324 | =item * Other members are not supported. |
3967 | =item * Other members are not supported. |
3325 | |
3968 | |
3326 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3969 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3327 | to use the libev header file and library. |
3970 | to use the libev header file and library. |
3328 | |
3971 | |
3329 | =back |
3972 | =back |
3330 | |
3973 | |
3331 | =head1 C++ SUPPORT |
3974 | =head1 C++ SUPPORT |
|
|
3975 | |
|
|
3976 | =head2 C API |
|
|
3977 | |
|
|
3978 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3979 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3980 | will work fine. |
|
|
3981 | |
|
|
3982 | Proper exception specifications might have to be added to callbacks passed |
|
|
3983 | to libev: exceptions may be thrown only from watcher callbacks, all other |
|
|
3984 | callbacks (allocator, syserr, loop acquire/release and periodic reschedule |
|
|
3985 | callbacks) must not throw exceptions, and might need a C<noexcept> |
|
|
3986 | specification. If you have code that needs to be compiled as both C and |
|
|
3987 | C++ you can use the C<EV_NOEXCEPT> macro for this: |
|
|
3988 | |
|
|
3989 | static void |
|
|
3990 | fatal_error (const char *msg) EV_NOEXCEPT |
|
|
3991 | { |
|
|
3992 | perror (msg); |
|
|
3993 | abort (); |
|
|
3994 | } |
|
|
3995 | |
|
|
3996 | ... |
|
|
3997 | ev_set_syserr_cb (fatal_error); |
|
|
3998 | |
|
|
3999 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
4000 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
4001 | because it runs cleanup watchers). |
|
|
4002 | |
|
|
4003 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
4004 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
4005 | throwing exceptions through C libraries (most do). |
|
|
4006 | |
|
|
4007 | =head2 C++ API |
3332 | |
4008 | |
3333 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
4009 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3334 | you to use some convenience methods to start/stop watchers and also change |
4010 | you to use some convenience methods to start/stop watchers and also change |
3335 | the callback model to a model using method callbacks on objects. |
4011 | the callback model to a model using method callbacks on objects. |
3336 | |
4012 | |
3337 | To use it, |
4013 | To use it, |
3338 | |
4014 | |
3339 | #include <ev++.h> |
4015 | #include <ev++.h> |
3340 | |
4016 | |
3341 | This automatically includes F<ev.h> and puts all of its definitions (many |
4017 | This automatically includes F<ev.h> and puts all of its definitions (many |
3342 | of them macros) into the global namespace. All C++ specific things are |
4018 | of them macros) into the global namespace. All C++ specific things are |
3343 | put into the C<ev> namespace. It should support all the same embedding |
4019 | put into the C<ev> namespace. It should support all the same embedding |
… | |
… | |
3346 | Care has been taken to keep the overhead low. The only data member the C++ |
4022 | Care has been taken to keep the overhead low. The only data member the C++ |
3347 | classes add (compared to plain C-style watchers) is the event loop pointer |
4023 | classes add (compared to plain C-style watchers) is the event loop pointer |
3348 | that the watcher is associated with (or no additional members at all if |
4024 | that the watcher is associated with (or no additional members at all if |
3349 | you disable C<EV_MULTIPLICITY> when embedding libev). |
4025 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3350 | |
4026 | |
3351 | Currently, functions, and static and non-static member functions can be |
4027 | Currently, functions, static and non-static member functions and classes |
3352 | used as callbacks. Other types should be easy to add as long as they only |
4028 | with C<operator ()> can be used as callbacks. Other types should be easy |
3353 | need one additional pointer for context. If you need support for other |
4029 | to add as long as they only need one additional pointer for context. If |
3354 | types of functors please contact the author (preferably after implementing |
4030 | you need support for other types of functors please contact the author |
3355 | it). |
4031 | (preferably after implementing it). |
|
|
4032 | |
|
|
4033 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4034 | conventions as your C compiler (for static member functions), or you have |
|
|
4035 | to embed libev and compile libev itself as C++. |
3356 | |
4036 | |
3357 | Here is a list of things available in the C<ev> namespace: |
4037 | Here is a list of things available in the C<ev> namespace: |
3358 | |
4038 | |
3359 | =over 4 |
4039 | =over 4 |
3360 | |
4040 | |
… | |
… | |
3370 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4050 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3371 | |
4051 | |
3372 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4052 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3373 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4053 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3374 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4054 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3375 | defines by many implementations. |
4055 | defined by many implementations. |
3376 | |
4056 | |
3377 | All of those classes have these methods: |
4057 | All of those classes have these methods: |
3378 | |
4058 | |
3379 | =over 4 |
4059 | =over 4 |
3380 | |
4060 | |
… | |
… | |
3442 | void operator() (ev::io &w, int revents) |
4122 | void operator() (ev::io &w, int revents) |
3443 | { |
4123 | { |
3444 | ... |
4124 | ... |
3445 | } |
4125 | } |
3446 | } |
4126 | } |
3447 | |
4127 | |
3448 | myfunctor f; |
4128 | myfunctor f; |
3449 | |
4129 | |
3450 | ev::io w; |
4130 | ev::io w; |
3451 | w.set (&f); |
4131 | w.set (&f); |
3452 | |
4132 | |
… | |
… | |
3470 | Associates a different C<struct ev_loop> with this watcher. You can only |
4150 | Associates a different C<struct ev_loop> with this watcher. You can only |
3471 | do this when the watcher is inactive (and not pending either). |
4151 | do this when the watcher is inactive (and not pending either). |
3472 | |
4152 | |
3473 | =item w->set ([arguments]) |
4153 | =item w->set ([arguments]) |
3474 | |
4154 | |
3475 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
4155 | Basically the same as C<ev_TYPE_set> (except for C<ev::embed> watchers>), |
3476 | method or a suitable start method must be called at least once. Unlike the |
4156 | with the same arguments. Either this method or a suitable start method |
3477 | C counterpart, an active watcher gets automatically stopped and restarted |
4157 | must be called at least once. Unlike the C counterpart, an active watcher |
3478 | when reconfiguring it with this method. |
4158 | gets automatically stopped and restarted when reconfiguring it with this |
|
|
4159 | method. |
|
|
4160 | |
|
|
4161 | For C<ev::embed> watchers this method is called C<set_embed>, to avoid |
|
|
4162 | clashing with the C<set (loop)> method. |
3479 | |
4163 | |
3480 | =item w->start () |
4164 | =item w->start () |
3481 | |
4165 | |
3482 | Starts the watcher. Note that there is no C<loop> argument, as the |
4166 | Starts the watcher. Note that there is no C<loop> argument, as the |
3483 | constructor already stores the event loop. |
4167 | constructor already stores the event loop. |
… | |
… | |
3513 | watchers in the constructor. |
4197 | watchers in the constructor. |
3514 | |
4198 | |
3515 | class myclass |
4199 | class myclass |
3516 | { |
4200 | { |
3517 | ev::io io ; void io_cb (ev::io &w, int revents); |
4201 | ev::io io ; void io_cb (ev::io &w, int revents); |
3518 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4202 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3519 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4203 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3520 | |
4204 | |
3521 | myclass (int fd) |
4205 | myclass (int fd) |
3522 | { |
4206 | { |
3523 | io .set <myclass, &myclass::io_cb > (this); |
4207 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3574 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4258 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3575 | |
4259 | |
3576 | =item D |
4260 | =item D |
3577 | |
4261 | |
3578 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4262 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3579 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4263 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3580 | |
4264 | |
3581 | =item Ocaml |
4265 | =item Ocaml |
3582 | |
4266 | |
3583 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4267 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3584 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4268 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
3587 | |
4271 | |
3588 | Brian Maher has written a partial interface to libev for lua (at the |
4272 | Brian Maher has written a partial interface to libev for lua (at the |
3589 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
4273 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
3590 | L<http://github.com/brimworks/lua-ev>. |
4274 | L<http://github.com/brimworks/lua-ev>. |
3591 | |
4275 | |
|
|
4276 | =item Javascript |
|
|
4277 | |
|
|
4278 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4279 | |
|
|
4280 | =item Others |
|
|
4281 | |
|
|
4282 | There are others, and I stopped counting. |
|
|
4283 | |
3592 | =back |
4284 | =back |
3593 | |
4285 | |
3594 | |
4286 | |
3595 | =head1 MACRO MAGIC |
4287 | =head1 MACRO MAGIC |
3596 | |
4288 | |
… | |
… | |
3632 | suitable for use with C<EV_A>. |
4324 | suitable for use with C<EV_A>. |
3633 | |
4325 | |
3634 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4326 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
3635 | |
4327 | |
3636 | Similar to the other two macros, this gives you the value of the default |
4328 | Similar to the other two macros, this gives you the value of the default |
3637 | loop, if multiple loops are supported ("ev loop default"). |
4329 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4330 | will be initialised if it isn't already initialised. |
|
|
4331 | |
|
|
4332 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4333 | to initialise the loop somewhere. |
3638 | |
4334 | |
3639 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4335 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
3640 | |
4336 | |
3641 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4337 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
3642 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4338 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
3709 | ev_vars.h |
4405 | ev_vars.h |
3710 | ev_wrap.h |
4406 | ev_wrap.h |
3711 | |
4407 | |
3712 | ev_win32.c required on win32 platforms only |
4408 | ev_win32.c required on win32 platforms only |
3713 | |
4409 | |
3714 | ev_select.c only when select backend is enabled (which is enabled by default) |
4410 | ev_select.c only when select backend is enabled |
3715 | ev_poll.c only when poll backend is enabled (disabled by default) |
4411 | ev_poll.c only when poll backend is enabled |
3716 | ev_epoll.c only when the epoll backend is enabled (disabled by default) |
4412 | ev_epoll.c only when the epoll backend is enabled |
3717 | ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
4413 | ev_kqueue.c only when the kqueue backend is enabled |
3718 | ev_port.c only when the solaris port backend is enabled (disabled by default) |
4414 | ev_port.c only when the solaris port backend is enabled |
3719 | |
4415 | |
3720 | F<ev.c> includes the backend files directly when enabled, so you only need |
4416 | F<ev.c> includes the backend files directly when enabled, so you only need |
3721 | to compile this single file. |
4417 | to compile this single file. |
3722 | |
4418 | |
3723 | =head3 LIBEVENT COMPATIBILITY API |
4419 | =head3 LIBEVENT COMPATIBILITY API |
… | |
… | |
3787 | supported). It will also not define any of the structs usually found in |
4483 | supported). It will also not define any of the structs usually found in |
3788 | F<event.h> that are not directly supported by the libev core alone. |
4484 | F<event.h> that are not directly supported by the libev core alone. |
3789 | |
4485 | |
3790 | In standalone mode, libev will still try to automatically deduce the |
4486 | In standalone mode, libev will still try to automatically deduce the |
3791 | configuration, but has to be more conservative. |
4487 | configuration, but has to be more conservative. |
|
|
4488 | |
|
|
4489 | =item EV_USE_FLOOR |
|
|
4490 | |
|
|
4491 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4492 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4493 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4494 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4495 | function is not available will fail, so the safe default is to not enable |
|
|
4496 | this. |
3792 | |
4497 | |
3793 | =item EV_USE_MONOTONIC |
4498 | =item EV_USE_MONOTONIC |
3794 | |
4499 | |
3795 | If defined to be C<1>, libev will try to detect the availability of the |
4500 | If defined to be C<1>, libev will try to detect the availability of the |
3796 | monotonic clock option at both compile time and runtime. Otherwise no |
4501 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
3881 | |
4586 | |
3882 | If programs implement their own fd to handle mapping on win32, then this |
4587 | If programs implement their own fd to handle mapping on win32, then this |
3883 | macro can be used to override the C<close> function, useful to unregister |
4588 | macro can be used to override the C<close> function, useful to unregister |
3884 | file descriptors again. Note that the replacement function has to close |
4589 | file descriptors again. Note that the replacement function has to close |
3885 | the underlying OS handle. |
4590 | the underlying OS handle. |
|
|
4591 | |
|
|
4592 | =item EV_USE_WSASOCKET |
|
|
4593 | |
|
|
4594 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4595 | communication socket, which works better in some environments. Otherwise, |
|
|
4596 | the normal C<socket> function will be used, which works better in other |
|
|
4597 | environments. |
3886 | |
4598 | |
3887 | =item EV_USE_POLL |
4599 | =item EV_USE_POLL |
3888 | |
4600 | |
3889 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4601 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3890 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4602 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3926 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4638 | If defined to be C<1>, libev will compile in support for the Linux inotify |
3927 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4639 | interface to speed up C<ev_stat> watchers. Its actual availability will |
3928 | be detected at runtime. If undefined, it will be enabled if the headers |
4640 | be detected at runtime. If undefined, it will be enabled if the headers |
3929 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4641 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
3930 | |
4642 | |
|
|
4643 | =item EV_NO_SMP |
|
|
4644 | |
|
|
4645 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4646 | between threads, that is, threads can be used, but threads never run on |
|
|
4647 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4648 | and makes libev faster. |
|
|
4649 | |
|
|
4650 | =item EV_NO_THREADS |
|
|
4651 | |
|
|
4652 | If defined to be C<1>, libev will assume that it will never be called from |
|
|
4653 | different threads (that includes signal handlers), which is a stronger |
|
|
4654 | assumption than C<EV_NO_SMP>, above. This reduces dependencies and makes |
|
|
4655 | libev faster. |
|
|
4656 | |
3931 | =item EV_ATOMIC_T |
4657 | =item EV_ATOMIC_T |
3932 | |
4658 | |
3933 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4659 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
3934 | access is atomic with respect to other threads or signal contexts. No such |
4660 | access is atomic with respect to other threads or signal contexts. No |
3935 | type is easily found in the C language, so you can provide your own type |
4661 | such type is easily found in the C language, so you can provide your own |
3936 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4662 | type that you know is safe for your purposes. It is used both for signal |
3937 | as well as for signal and thread safety in C<ev_async> watchers. |
4663 | handler "locking" as well as for signal and thread safety in C<ev_async> |
|
|
4664 | watchers. |
3938 | |
4665 | |
3939 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4666 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3940 | (from F<signal.h>), which is usually good enough on most platforms. |
4667 | (from F<signal.h>), which is usually good enough on most platforms. |
3941 | |
4668 | |
3942 | =item EV_H (h) |
4669 | =item EV_H (h) |
… | |
… | |
3969 | will have the C<struct ev_loop *> as first argument, and you can create |
4696 | will have the C<struct ev_loop *> as first argument, and you can create |
3970 | additional independent event loops. Otherwise there will be no support |
4697 | additional independent event loops. Otherwise there will be no support |
3971 | for multiple event loops and there is no first event loop pointer |
4698 | for multiple event loops and there is no first event loop pointer |
3972 | argument. Instead, all functions act on the single default loop. |
4699 | argument. Instead, all functions act on the single default loop. |
3973 | |
4700 | |
|
|
4701 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4702 | default loop when multiplicity is switched off - you always have to |
|
|
4703 | initialise the loop manually in this case. |
|
|
4704 | |
3974 | =item EV_MINPRI |
4705 | =item EV_MINPRI |
3975 | |
4706 | |
3976 | =item EV_MAXPRI |
4707 | =item EV_MAXPRI |
3977 | |
4708 | |
3978 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4709 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4014 | #define EV_USE_POLL 1 |
4745 | #define EV_USE_POLL 1 |
4015 | #define EV_CHILD_ENABLE 1 |
4746 | #define EV_CHILD_ENABLE 1 |
4016 | #define EV_ASYNC_ENABLE 1 |
4747 | #define EV_ASYNC_ENABLE 1 |
4017 | |
4748 | |
4018 | The actual value is a bitset, it can be a combination of the following |
4749 | The actual value is a bitset, it can be a combination of the following |
4019 | values: |
4750 | values (by default, all of these are enabled): |
4020 | |
4751 | |
4021 | =over 4 |
4752 | =over 4 |
4022 | |
4753 | |
4023 | =item C<1> - faster/larger code |
4754 | =item C<1> - faster/larger code |
4024 | |
4755 | |
… | |
… | |
4028 | code size by roughly 30% on amd64). |
4759 | code size by roughly 30% on amd64). |
4029 | |
4760 | |
4030 | When optimising for size, use of compiler flags such as C<-Os> with |
4761 | When optimising for size, use of compiler flags such as C<-Os> with |
4031 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4762 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4032 | assertions. |
4763 | assertions. |
|
|
4764 | |
|
|
4765 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4766 | (e.g. gcc with C<-Os>). |
4033 | |
4767 | |
4034 | =item C<2> - faster/larger data structures |
4768 | =item C<2> - faster/larger data structures |
4035 | |
4769 | |
4036 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4770 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4037 | hash table sizes and so on. This will usually further increase code size |
4771 | hash table sizes and so on. This will usually further increase code size |
4038 | and can additionally have an effect on the size of data structures at |
4772 | and can additionally have an effect on the size of data structures at |
4039 | runtime. |
4773 | runtime. |
4040 | |
4774 | |
|
|
4775 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4776 | (e.g. gcc with C<-Os>). |
|
|
4777 | |
4041 | =item C<4> - full API configuration |
4778 | =item C<4> - full API configuration |
4042 | |
4779 | |
4043 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4780 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4044 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4781 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4045 | |
4782 | |
… | |
… | |
4075 | |
4812 | |
4076 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4813 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4077 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4814 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4078 | your program might be left out as well - a binary starting a timer and an |
4815 | your program might be left out as well - a binary starting a timer and an |
4079 | I/O watcher then might come out at only 5Kb. |
4816 | I/O watcher then might come out at only 5Kb. |
|
|
4817 | |
|
|
4818 | =item EV_API_STATIC |
|
|
4819 | |
|
|
4820 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4821 | will have static linkage. This means that libev will not export any |
|
|
4822 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4823 | when you embed libev, only want to use libev functions in a single file, |
|
|
4824 | and do not want its identifiers to be visible. |
|
|
4825 | |
|
|
4826 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4827 | wants to use libev. |
|
|
4828 | |
|
|
4829 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4830 | doesn't support the required declaration syntax. |
4080 | |
4831 | |
4081 | =item EV_AVOID_STDIO |
4832 | =item EV_AVOID_STDIO |
4082 | |
4833 | |
4083 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4834 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4084 | functions (printf, scanf, perror etc.). This will increase the code size |
4835 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4228 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4979 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4229 | |
4980 | |
4230 | #include "ev_cpp.h" |
4981 | #include "ev_cpp.h" |
4231 | #include "ev.c" |
4982 | #include "ev.c" |
4232 | |
4983 | |
4233 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4984 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4234 | |
4985 | |
4235 | =head2 THREADS AND COROUTINES |
4986 | =head2 THREADS AND COROUTINES |
4236 | |
4987 | |
4237 | =head3 THREADS |
4988 | =head3 THREADS |
4238 | |
4989 | |
… | |
… | |
4289 | default loop and triggering an C<ev_async> watcher from the default loop |
5040 | default loop and triggering an C<ev_async> watcher from the default loop |
4290 | watcher callback into the event loop interested in the signal. |
5041 | watcher callback into the event loop interested in the signal. |
4291 | |
5042 | |
4292 | =back |
5043 | =back |
4293 | |
5044 | |
4294 | =head4 THREAD LOCKING EXAMPLE |
5045 | See also L</THREAD LOCKING EXAMPLE>. |
4295 | |
|
|
4296 | Here is a fictitious example of how to run an event loop in a different |
|
|
4297 | thread than where callbacks are being invoked and watchers are |
|
|
4298 | created/added/removed. |
|
|
4299 | |
|
|
4300 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4301 | which uses exactly this technique (which is suited for many high-level |
|
|
4302 | languages). |
|
|
4303 | |
|
|
4304 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4305 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4306 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4307 | |
|
|
4308 | First, you need to associate some data with the event loop: |
|
|
4309 | |
|
|
4310 | typedef struct { |
|
|
4311 | mutex_t lock; /* global loop lock */ |
|
|
4312 | ev_async async_w; |
|
|
4313 | thread_t tid; |
|
|
4314 | cond_t invoke_cv; |
|
|
4315 | } userdata; |
|
|
4316 | |
|
|
4317 | void prepare_loop (EV_P) |
|
|
4318 | { |
|
|
4319 | // for simplicity, we use a static userdata struct. |
|
|
4320 | static userdata u; |
|
|
4321 | |
|
|
4322 | ev_async_init (&u->async_w, async_cb); |
|
|
4323 | ev_async_start (EV_A_ &u->async_w); |
|
|
4324 | |
|
|
4325 | pthread_mutex_init (&u->lock, 0); |
|
|
4326 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4327 | |
|
|
4328 | // now associate this with the loop |
|
|
4329 | ev_set_userdata (EV_A_ u); |
|
|
4330 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4331 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4332 | |
|
|
4333 | // then create the thread running ev_loop |
|
|
4334 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4335 | } |
|
|
4336 | |
|
|
4337 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4338 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4339 | that might have been added: |
|
|
4340 | |
|
|
4341 | static void |
|
|
4342 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4343 | { |
|
|
4344 | // just used for the side effects |
|
|
4345 | } |
|
|
4346 | |
|
|
4347 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4348 | protecting the loop data, respectively. |
|
|
4349 | |
|
|
4350 | static void |
|
|
4351 | l_release (EV_P) |
|
|
4352 | { |
|
|
4353 | userdata *u = ev_userdata (EV_A); |
|
|
4354 | pthread_mutex_unlock (&u->lock); |
|
|
4355 | } |
|
|
4356 | |
|
|
4357 | static void |
|
|
4358 | l_acquire (EV_P) |
|
|
4359 | { |
|
|
4360 | userdata *u = ev_userdata (EV_A); |
|
|
4361 | pthread_mutex_lock (&u->lock); |
|
|
4362 | } |
|
|
4363 | |
|
|
4364 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4365 | into C<ev_run>: |
|
|
4366 | |
|
|
4367 | void * |
|
|
4368 | l_run (void *thr_arg) |
|
|
4369 | { |
|
|
4370 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4371 | |
|
|
4372 | l_acquire (EV_A); |
|
|
4373 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4374 | ev_run (EV_A_ 0); |
|
|
4375 | l_release (EV_A); |
|
|
4376 | |
|
|
4377 | return 0; |
|
|
4378 | } |
|
|
4379 | |
|
|
4380 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4381 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4382 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4383 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4384 | and b) skipping inter-thread-communication when there are no pending |
|
|
4385 | watchers is very beneficial): |
|
|
4386 | |
|
|
4387 | static void |
|
|
4388 | l_invoke (EV_P) |
|
|
4389 | { |
|
|
4390 | userdata *u = ev_userdata (EV_A); |
|
|
4391 | |
|
|
4392 | while (ev_pending_count (EV_A)) |
|
|
4393 | { |
|
|
4394 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4395 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4396 | } |
|
|
4397 | } |
|
|
4398 | |
|
|
4399 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4400 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4401 | thread to continue: |
|
|
4402 | |
|
|
4403 | static void |
|
|
4404 | real_invoke_pending (EV_P) |
|
|
4405 | { |
|
|
4406 | userdata *u = ev_userdata (EV_A); |
|
|
4407 | |
|
|
4408 | pthread_mutex_lock (&u->lock); |
|
|
4409 | ev_invoke_pending (EV_A); |
|
|
4410 | pthread_cond_signal (&u->invoke_cv); |
|
|
4411 | pthread_mutex_unlock (&u->lock); |
|
|
4412 | } |
|
|
4413 | |
|
|
4414 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4415 | event loop, you will now have to lock: |
|
|
4416 | |
|
|
4417 | ev_timer timeout_watcher; |
|
|
4418 | userdata *u = ev_userdata (EV_A); |
|
|
4419 | |
|
|
4420 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4421 | |
|
|
4422 | pthread_mutex_lock (&u->lock); |
|
|
4423 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4424 | ev_async_send (EV_A_ &u->async_w); |
|
|
4425 | pthread_mutex_unlock (&u->lock); |
|
|
4426 | |
|
|
4427 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4428 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4429 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4430 | watchers in the next event loop iteration. |
|
|
4431 | |
5046 | |
4432 | =head3 COROUTINES |
5047 | =head3 COROUTINES |
4433 | |
5048 | |
4434 | Libev is very accommodating to coroutines ("cooperative threads"): |
5049 | Libev is very accommodating to coroutines ("cooperative threads"): |
4435 | libev fully supports nesting calls to its functions from different |
5050 | libev fully supports nesting calls to its functions from different |
… | |
… | |
4531 | =head3 C<kqueue> is buggy |
5146 | =head3 C<kqueue> is buggy |
4532 | |
5147 | |
4533 | The kqueue syscall is broken in all known versions - most versions support |
5148 | The kqueue syscall is broken in all known versions - most versions support |
4534 | only sockets, many support pipes. |
5149 | only sockets, many support pipes. |
4535 | |
5150 | |
4536 | Libev tries to work around this by not using C<kqueue> by default on |
5151 | Libev tries to work around this by not using C<kqueue> by default on this |
4537 | this rotten platform, but of course you can still ask for it when creating |
5152 | rotten platform, but of course you can still ask for it when creating a |
4538 | a loop. |
5153 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5154 | probably going to work well. |
4539 | |
5155 | |
4540 | =head3 C<poll> is buggy |
5156 | =head3 C<poll> is buggy |
4541 | |
5157 | |
4542 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
5158 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
4543 | implementation by something calling C<kqueue> internally around the 10.5.6 |
5159 | implementation by something calling C<kqueue> internally around the 10.5.6 |
… | |
… | |
4562 | |
5178 | |
4563 | =head3 C<errno> reentrancy |
5179 | =head3 C<errno> reentrancy |
4564 | |
5180 | |
4565 | The default compile environment on Solaris is unfortunately so |
5181 | The default compile environment on Solaris is unfortunately so |
4566 | thread-unsafe that you can't even use components/libraries compiled |
5182 | thread-unsafe that you can't even use components/libraries compiled |
4567 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
5183 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
4568 | isn't defined by default. |
5184 | defined by default. A valid, if stupid, implementation choice. |
4569 | |
5185 | |
4570 | If you want to use libev in threaded environments you have to make sure |
5186 | If you want to use libev in threaded environments you have to make sure |
4571 | it's compiled with C<_REENTRANT> defined. |
5187 | it's compiled with C<_REENTRANT> defined. |
4572 | |
5188 | |
4573 | =head3 Event port backend |
5189 | =head3 Event port backend |
4574 | |
5190 | |
4575 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
5191 | The scalable event interface for Solaris is called "event |
4576 | this mechanism is very buggy. If you run into high CPU usage, your program |
5192 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5193 | releases. If you run into high CPU usage, your program freezes or you get |
4577 | freezes or you get a large number of spurious wakeups, make sure you have |
5194 | a large number of spurious wakeups, make sure you have all the relevant |
4578 | all the relevant and latest kernel patches applied. No, I don't know which |
5195 | and latest kernel patches applied. No, I don't know which ones, but there |
4579 | ones, but there are multiple ones. |
5196 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5197 | great. |
4580 | |
5198 | |
4581 | If you can't get it to work, you can try running the program by setting |
5199 | If you can't get it to work, you can try running the program by setting |
4582 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
5200 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
4583 | C<select> backends. |
5201 | C<select> backends. |
4584 | |
5202 | |
4585 | =head2 AIX POLL BUG |
5203 | =head2 AIX POLL BUG |
4586 | |
5204 | |
4587 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
5205 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
4588 | this by trying to avoid the poll backend altogether (i.e. it's not even |
5206 | this by trying to avoid the poll backend altogether (i.e. it's not even |
4589 | compiled in), which normally isn't a big problem as C<select> works fine |
5207 | compiled in), which normally isn't a big problem as C<select> works fine |
4590 | with large bitsets, and AIX is dead anyway. |
5208 | with large bitsets on AIX, and AIX is dead anyway. |
4591 | |
5209 | |
4592 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5210 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4593 | |
5211 | |
4594 | =head3 General issues |
5212 | =head3 General issues |
4595 | |
5213 | |
… | |
… | |
4597 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5215 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4598 | model. Libev still offers limited functionality on this platform in |
5216 | model. Libev still offers limited functionality on this platform in |
4599 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5217 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4600 | descriptors. This only applies when using Win32 natively, not when using |
5218 | descriptors. This only applies when using Win32 natively, not when using |
4601 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5219 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4602 | as every compielr comes with a slightly differently broken/incompatible |
5220 | as every compiler comes with a slightly differently broken/incompatible |
4603 | environment. |
5221 | environment. |
4604 | |
5222 | |
4605 | Lifting these limitations would basically require the full |
5223 | Lifting these limitations would basically require the full |
4606 | re-implementation of the I/O system. If you are into this kind of thing, |
5224 | re-implementation of the I/O system. If you are into this kind of thing, |
4607 | then note that glib does exactly that for you in a very portable way (note |
5225 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
4701 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5319 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4702 | assumes that the same (machine) code can be used to call any watcher |
5320 | assumes that the same (machine) code can be used to call any watcher |
4703 | callback: The watcher callbacks have different type signatures, but libev |
5321 | callback: The watcher callbacks have different type signatures, but libev |
4704 | calls them using an C<ev_watcher *> internally. |
5322 | calls them using an C<ev_watcher *> internally. |
4705 | |
5323 | |
|
|
5324 | =item null pointers and integer zero are represented by 0 bytes |
|
|
5325 | |
|
|
5326 | Libev uses C<memset> to initialise structs and arrays to C<0> bytes, and |
|
|
5327 | relies on this setting pointers and integers to null. |
|
|
5328 | |
|
|
5329 | =item pointer accesses must be thread-atomic |
|
|
5330 | |
|
|
5331 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5332 | writable in one piece - this is the case on all current architectures. |
|
|
5333 | |
4706 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5334 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4707 | |
5335 | |
4708 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5336 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4709 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
5337 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4710 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5338 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
… | |
… | |
4718 | thread" or will block signals process-wide, both behaviours would |
5346 | thread" or will block signals process-wide, both behaviours would |
4719 | be compatible with libev. Interaction between C<sigprocmask> and |
5347 | be compatible with libev. Interaction between C<sigprocmask> and |
4720 | C<pthread_sigmask> could complicate things, however. |
5348 | C<pthread_sigmask> could complicate things, however. |
4721 | |
5349 | |
4722 | The most portable way to handle signals is to block signals in all threads |
5350 | The most portable way to handle signals is to block signals in all threads |
4723 | except the initial one, and run the default loop in the initial thread as |
5351 | except the initial one, and run the signal handling loop in the initial |
4724 | well. |
5352 | thread as well. |
4725 | |
5353 | |
4726 | =item C<long> must be large enough for common memory allocation sizes |
5354 | =item C<long> must be large enough for common memory allocation sizes |
4727 | |
5355 | |
4728 | To improve portability and simplify its API, libev uses C<long> internally |
5356 | To improve portability and simplify its API, libev uses C<long> internally |
4729 | instead of C<size_t> when allocating its data structures. On non-POSIX |
5357 | instead of C<size_t> when allocating its data structures. On non-POSIX |
… | |
… | |
4735 | |
5363 | |
4736 | The type C<double> is used to represent timestamps. It is required to |
5364 | The type C<double> is used to represent timestamps. It is required to |
4737 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5365 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
4738 | good enough for at least into the year 4000 with millisecond accuracy |
5366 | good enough for at least into the year 4000 with millisecond accuracy |
4739 | (the design goal for libev). This requirement is overfulfilled by |
5367 | (the design goal for libev). This requirement is overfulfilled by |
4740 | implementations using IEEE 754, which is basically all existing ones. With |
5368 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5369 | |
4741 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5370 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5371 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5372 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5373 | something like that, just kidding). |
4742 | |
5374 | |
4743 | =back |
5375 | =back |
4744 | |
5376 | |
4745 | If you know of other additional requirements drop me a note. |
5377 | If you know of other additional requirements drop me a note. |
4746 | |
5378 | |
… | |
… | |
4808 | =item Processing ev_async_send: O(number_of_async_watchers) |
5440 | =item Processing ev_async_send: O(number_of_async_watchers) |
4809 | |
5441 | |
4810 | =item Processing signals: O(max_signal_number) |
5442 | =item Processing signals: O(max_signal_number) |
4811 | |
5443 | |
4812 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5444 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4813 | calls in the current loop iteration. Checking for async and signal events |
5445 | calls in the current loop iteration and the loop is currently |
|
|
5446 | blocked. Checking for async and signal events involves iterating over all |
4814 | involves iterating over all running async watchers or all signal numbers. |
5447 | running async watchers or all signal numbers. |
4815 | |
5448 | |
4816 | =back |
5449 | =back |
4817 | |
5450 | |
4818 | |
5451 | |
4819 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5452 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
4820 | |
5453 | |
4821 | The major version 4 introduced some minor incompatible changes to the API. |
5454 | The major version 4 introduced some incompatible changes to the API. |
4822 | |
5455 | |
4823 | At the moment, the C<ev.h> header file tries to implement superficial |
5456 | At the moment, the C<ev.h> header file provides compatibility definitions |
4824 | compatibility, so most programs should still compile. Those might be |
5457 | for all changes, so most programs should still compile. The compatibility |
4825 | removed in later versions of libev, so better update early than late. |
5458 | layer might be removed in later versions of libev, so better update to the |
|
|
5459 | new API early than late. |
4826 | |
5460 | |
4827 | =over 4 |
5461 | =over 4 |
|
|
5462 | |
|
|
5463 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5464 | |
|
|
5465 | The backward compatibility mechanism can be controlled by |
|
|
5466 | C<EV_COMPAT3>. See L</"PREPROCESSOR SYMBOLS/MACROS"> in the L</EMBEDDING> |
|
|
5467 | section. |
|
|
5468 | |
|
|
5469 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5470 | |
|
|
5471 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5472 | |
|
|
5473 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5474 | ev_loop_fork (EV_DEFAULT); |
4828 | |
5475 | |
4829 | =item function/symbol renames |
5476 | =item function/symbol renames |
4830 | |
5477 | |
4831 | A number of functions and symbols have been renamed: |
5478 | A number of functions and symbols have been renamed: |
4832 | |
5479 | |
… | |
… | |
4851 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
5498 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
4852 | as all other watcher types. Note that C<ev_loop_fork> is still called |
5499 | as all other watcher types. Note that C<ev_loop_fork> is still called |
4853 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
5500 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
4854 | typedef. |
5501 | typedef. |
4855 | |
5502 | |
4856 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4857 | |
|
|
4858 | The backward compatibility mechanism can be controlled by |
|
|
4859 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4860 | section. |
|
|
4861 | |
|
|
4862 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
5503 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4863 | |
5504 | |
4864 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
5505 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4865 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
5506 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
4866 | and work, but the library code will of course be larger. |
5507 | and work, but the library code will of course be larger. |
… | |
… | |
4872 | |
5513 | |
4873 | =over 4 |
5514 | =over 4 |
4874 | |
5515 | |
4875 | =item active |
5516 | =item active |
4876 | |
5517 | |
4877 | A watcher is active as long as it has been started (has been attached to |
5518 | A watcher is active as long as it has been started and not yet stopped. |
4878 | an event loop) but not yet stopped (disassociated from the event loop). |
5519 | See L</WATCHER STATES> for details. |
4879 | |
5520 | |
4880 | =item application |
5521 | =item application |
4881 | |
5522 | |
4882 | In this document, an application is whatever is using libev. |
5523 | In this document, an application is whatever is using libev. |
|
|
5524 | |
|
|
5525 | =item backend |
|
|
5526 | |
|
|
5527 | The part of the code dealing with the operating system interfaces. |
4883 | |
5528 | |
4884 | =item callback |
5529 | =item callback |
4885 | |
5530 | |
4886 | The address of a function that is called when some event has been |
5531 | The address of a function that is called when some event has been |
4887 | detected. Callbacks are being passed the event loop, the watcher that |
5532 | detected. Callbacks are being passed the event loop, the watcher that |
4888 | received the event, and the actual event bitset. |
5533 | received the event, and the actual event bitset. |
4889 | |
5534 | |
4890 | =item callback invocation |
5535 | =item callback/watcher invocation |
4891 | |
5536 | |
4892 | The act of calling the callback associated with a watcher. |
5537 | The act of calling the callback associated with a watcher. |
4893 | |
5538 | |
4894 | =item event |
5539 | =item event |
4895 | |
5540 | |
… | |
… | |
4914 | The model used to describe how an event loop handles and processes |
5559 | The model used to describe how an event loop handles and processes |
4915 | watchers and events. |
5560 | watchers and events. |
4916 | |
5561 | |
4917 | =item pending |
5562 | =item pending |
4918 | |
5563 | |
4919 | A watcher is pending as soon as the corresponding event has been detected, |
5564 | A watcher is pending as soon as the corresponding event has been |
4920 | and stops being pending as soon as the watcher will be invoked or its |
5565 | detected. See L</WATCHER STATES> for details. |
4921 | pending status is explicitly cleared by the application. |
|
|
4922 | |
|
|
4923 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4924 | its pending status. |
|
|
4925 | |
5566 | |
4926 | =item real time |
5567 | =item real time |
4927 | |
5568 | |
4928 | The physical time that is observed. It is apparently strictly monotonic :) |
5569 | The physical time that is observed. It is apparently strictly monotonic :) |
4929 | |
5570 | |
4930 | =item wall-clock time |
5571 | =item wall-clock time |
4931 | |
5572 | |
4932 | The time and date as shown on clocks. Unlike real time, it can actually |
5573 | The time and date as shown on clocks. Unlike real time, it can actually |
4933 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5574 | be wrong and jump forwards and backwards, e.g. when you adjust your |
4934 | clock. |
5575 | clock. |
4935 | |
5576 | |
4936 | =item watcher |
5577 | =item watcher |
4937 | |
5578 | |
4938 | A data structure that describes interest in certain events. Watchers need |
5579 | A data structure that describes interest in certain events. Watchers need |
4939 | to be started (attached to an event loop) before they can receive events. |
5580 | to be started (attached to an event loop) before they can receive events. |
4940 | |
5581 | |
4941 | =item watcher invocation |
|
|
4942 | |
|
|
4943 | The act of calling the callback associated with a watcher. |
|
|
4944 | |
|
|
4945 | =back |
5582 | =back |
4946 | |
5583 | |
4947 | =head1 AUTHOR |
5584 | =head1 AUTHOR |
4948 | |
5585 | |
4949 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
5586 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5587 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
4950 | |
5588 | |