… | |
… | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
|
|
14 | #include <stdio.h> // for puts |
|
|
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // break was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
|
|
68 | |
|
|
69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
|
|
74 | |
|
|
75 | While this document tries to be as complete as possible in documenting |
|
|
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
|
|
77 | on event-based programming, nor will it introduce event-based programming |
|
|
78 | with libev. |
|
|
79 | |
|
|
80 | Familiarity with event based programming techniques in general is assumed |
|
|
81 | throughout this document. |
|
|
82 | |
|
|
83 | =head1 WHAT TO READ WHEN IN A HURRY |
|
|
84 | |
|
|
85 | This manual tries to be very detailed, but unfortunately, this also makes |
|
|
86 | it very long. If you just want to know the basics of libev, I suggest |
|
|
87 | reading L</ANATOMY OF A WATCHER>, then the L</EXAMPLE PROGRAM> above and |
|
|
88 | look up the missing functions in L</GLOBAL FUNCTIONS> and the C<ev_io> and |
|
|
89 | C<ev_timer> sections in L</WATCHER TYPES>. |
|
|
90 | |
|
|
91 | =head1 ABOUT LIBEV |
70 | |
92 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
95 | these event sources and provide your program with events. |
74 | |
96 | |
… | |
… | |
84 | =head2 FEATURES |
106 | =head2 FEATURES |
85 | |
107 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
115 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
117 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
|
|
118 | limited support for fork events (C<ev_fork>). |
96 | |
119 | |
97 | It also is quite fast (see this |
120 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
121 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
122 | for example). |
100 | |
123 | |
… | |
… | |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
132 | this argument. |
110 | |
133 | |
111 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
112 | |
135 | |
113 | Libev represents time as a single floating point number, representing the |
136 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
138 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
141 | any calculations on it, you should treat it as some floating point value. |
|
|
142 | |
119 | component C<stamp> might indicate, it is also used for time differences |
143 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
121 | |
145 | |
122 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
123 | |
147 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
149 | |
173 | |
150 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
151 | |
175 | |
152 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
|
|
179 | C<ev_now_update> and C<ev_now>. |
155 | |
180 | |
156 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
157 | |
182 | |
158 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
159 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
160 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
161 | |
192 | |
162 | =item int ev_version_major () |
193 | =item int ev_version_major () |
163 | |
194 | |
164 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
165 | |
196 | |
… | |
… | |
176 | as this indicates an incompatible change. Minor versions are usually |
207 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
208 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
209 | not a problem. |
179 | |
210 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
211 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
212 | version (note, however, that this will not detect other ABI mismatches, |
|
|
213 | such as LFS or reentrancy). |
182 | |
214 | |
183 | assert (("libev version mismatch", |
215 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
216 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
217 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
218 | |
… | |
… | |
197 | assert (("sorry, no epoll, no sex", |
229 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
230 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
231 | |
200 | =item unsigned int ev_recommended_backends () |
232 | =item unsigned int ev_recommended_backends () |
201 | |
233 | |
202 | Return the set of all backends compiled into this binary of libev and also |
234 | Return the set of all backends compiled into this binary of libev and |
203 | recommended for this platform. This set is often smaller than the one |
235 | also recommended for this platform, meaning it will work for most file |
|
|
236 | descriptor types. This set is often smaller than the one returned by |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
237 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
238 | and will not be auto-detected unless you explicitly request it (assuming |
206 | (assuming you know what you are doing). This is the set of backends that |
239 | you know what you are doing). This is the set of backends that libev will |
207 | libev will probe for if you specify no backends explicitly. |
240 | probe for if you specify no backends explicitly. |
208 | |
241 | |
209 | =item unsigned int ev_embeddable_backends () |
242 | =item unsigned int ev_embeddable_backends () |
210 | |
243 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
244 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
245 | value is platform-specific but can include backends not available on the |
213 | might be supported on the current system, you would need to look at |
246 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
247 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
248 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
249 | |
217 | See the description of C<ev_embed> watchers for more info. |
250 | See the description of C<ev_embed> watchers for more info. |
218 | |
251 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
252 | =item ev_set_allocator (void *(*cb)(void *ptr, long size) throw ()) |
220 | |
253 | |
221 | Sets the allocation function to use (the prototype is similar - the |
254 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
255 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
256 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
257 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
283 | } |
251 | |
284 | |
252 | ... |
285 | ... |
253 | ev_set_allocator (persistent_realloc); |
286 | ev_set_allocator (persistent_realloc); |
254 | |
287 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
288 | =item ev_set_syserr_cb (void (*cb)(const char *msg) throw ()) |
256 | |
289 | |
257 | Set the callback function to call on a retryable system call error (such |
290 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
291 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
292 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
293 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
272 | } |
305 | } |
273 | |
306 | |
274 | ... |
307 | ... |
275 | ev_set_syserr_cb (fatal_error); |
308 | ev_set_syserr_cb (fatal_error); |
276 | |
309 | |
|
|
310 | =item ev_feed_signal (int signum) |
|
|
311 | |
|
|
312 | This function can be used to "simulate" a signal receive. It is completely |
|
|
313 | safe to call this function at any time, from any context, including signal |
|
|
314 | handlers or random threads. |
|
|
315 | |
|
|
316 | Its main use is to customise signal handling in your process, especially |
|
|
317 | in the presence of threads. For example, you could block signals |
|
|
318 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
|
|
319 | creating any loops), and in one thread, use C<sigwait> or any other |
|
|
320 | mechanism to wait for signals, then "deliver" them to libev by calling |
|
|
321 | C<ev_feed_signal>. |
|
|
322 | |
277 | =back |
323 | =back |
278 | |
324 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
325 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
326 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
327 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
282 | types of such loops, the I<default> loop, which supports signals and child |
328 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
329 | libev 3 had an C<ev_loop> function colliding with the struct name). |
|
|
330 | |
|
|
331 | The library knows two types of such loops, the I<default> loop, which |
|
|
332 | supports child process events, and dynamically created event loops which |
|
|
333 | do not. |
284 | |
334 | |
285 | =over 4 |
335 | =over 4 |
286 | |
336 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
337 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
338 | |
289 | This will initialise the default event loop if it hasn't been initialised |
339 | This returns the "default" event loop object, which is what you should |
290 | yet and return it. If the default loop could not be initialised, returns |
340 | normally use when you just need "the event loop". Event loop objects and |
291 | false. If it already was initialised it simply returns it (and ignores the |
341 | the C<flags> parameter are described in more detail in the entry for |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
342 | C<ev_loop_new>. |
|
|
343 | |
|
|
344 | If the default loop is already initialised then this function simply |
|
|
345 | returns it (and ignores the flags. If that is troubling you, check |
|
|
346 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
|
|
347 | flags, which should almost always be C<0>, unless the caller is also the |
|
|
348 | one calling C<ev_run> or otherwise qualifies as "the main program". |
293 | |
349 | |
294 | If you don't know what event loop to use, use the one returned from this |
350 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
351 | function (or via the C<EV_DEFAULT> macro). |
296 | |
352 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
353 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
354 | from multiple threads, you have to employ some kind of mutex (note also |
299 | as loops cannot bes hared easily between threads anyway). |
355 | that this case is unlikely, as loops cannot be shared easily between |
|
|
356 | threads anyway). |
300 | |
357 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
358 | The default loop is the only loop that can handle C<ev_child> watchers, |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
359 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
360 | a problem for your application you can either create a dynamic loop with |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
361 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
362 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
306 | C<ev_default_init>. |
363 | |
|
|
364 | Example: This is the most typical usage. |
|
|
365 | |
|
|
366 | if (!ev_default_loop (0)) |
|
|
367 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
368 | |
|
|
369 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
370 | environment settings to be taken into account: |
|
|
371 | |
|
|
372 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
373 | |
|
|
374 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
375 | |
|
|
376 | This will create and initialise a new event loop object. If the loop |
|
|
377 | could not be initialised, returns false. |
|
|
378 | |
|
|
379 | This function is thread-safe, and one common way to use libev with |
|
|
380 | threads is indeed to create one loop per thread, and using the default |
|
|
381 | loop in the "main" or "initial" thread. |
307 | |
382 | |
308 | The flags argument can be used to specify special behaviour or specific |
383 | The flags argument can be used to specify special behaviour or specific |
309 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
384 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
310 | |
385 | |
311 | The following flags are supported: |
386 | The following flags are supported: |
… | |
… | |
326 | useful to try out specific backends to test their performance, or to work |
401 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
402 | around bugs. |
328 | |
403 | |
329 | =item C<EVFLAG_FORKCHECK> |
404 | =item C<EVFLAG_FORKCHECK> |
330 | |
405 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
406 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
332 | a fork, you can also make libev check for a fork in each iteration by |
407 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
|
|
334 | |
408 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
409 | This works by calling C<getpid ()> on every iteration of the loop, |
336 | and thus this might slow down your event loop if you do a lot of loop |
410 | and thus this might slow down your event loop if you do a lot of loop |
337 | iterations and little real work, but is usually not noticeable (on my |
411 | iterations and little real work, but is usually not noticeable (on my |
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
412 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
344 | flag. |
418 | flag. |
345 | |
419 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
420 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
421 | environment variable. |
348 | |
422 | |
|
|
423 | =item C<EVFLAG_NOINOTIFY> |
|
|
424 | |
|
|
425 | When this flag is specified, then libev will not attempt to use the |
|
|
426 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
|
|
427 | testing, this flag can be useful to conserve inotify file descriptors, as |
|
|
428 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
|
|
429 | |
|
|
430 | =item C<EVFLAG_SIGNALFD> |
|
|
431 | |
|
|
432 | When this flag is specified, then libev will attempt to use the |
|
|
433 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
|
|
434 | delivers signals synchronously, which makes it both faster and might make |
|
|
435 | it possible to get the queued signal data. It can also simplify signal |
|
|
436 | handling with threads, as long as you properly block signals in your |
|
|
437 | threads that are not interested in handling them. |
|
|
438 | |
|
|
439 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
440 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
441 | example) that can't properly initialise their signal masks. |
|
|
442 | |
|
|
443 | =item C<EVFLAG_NOSIGMASK> |
|
|
444 | |
|
|
445 | When this flag is specified, then libev will avoid to modify the signal |
|
|
446 | mask. Specifically, this means you have to make sure signals are unblocked |
|
|
447 | when you want to receive them. |
|
|
448 | |
|
|
449 | This behaviour is useful when you want to do your own signal handling, or |
|
|
450 | want to handle signals only in specific threads and want to avoid libev |
|
|
451 | unblocking the signals. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
455 | |
|
|
456 | This flag's behaviour will become the default in future versions of libev. |
|
|
457 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
459 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
352 | libev tries to roll its own fd_set with no limits on the number of fds, |
461 | libev tries to roll its own fd_set with no limits on the number of fds, |
353 | but if that fails, expect a fairly low limit on the number of fds when |
462 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
468 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
469 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
470 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
471 | readiness notifications you get per iteration. |
363 | |
472 | |
|
|
473 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
474 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
475 | C<exceptfds> set on that platform). |
|
|
476 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
477 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
478 | |
366 | And this is your standard poll(2) backend. It's more complicated |
479 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
480 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
481 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
482 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
483 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
484 | performance tips. |
372 | |
485 | |
|
|
486 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
487 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
488 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
374 | |
490 | |
|
|
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
492 | kernels). |
|
|
493 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
376 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
497 | fd), epoll scales either O(1) or O(active_fds). |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
498 | |
380 | cases and requiring a system call per fd change, no fork support and bad |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
381 | support for dup. |
500 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
501 | dropping file descriptors, requiring a system call per change per file |
|
|
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
503 | returning before the timeout value, resulting in additional iterations |
|
|
504 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
|
|
506 | forks then I<both> parent and child process have to recreate the epoll |
|
|
507 | set, which can take considerable time (one syscall per file descriptor) |
|
|
508 | and is of course hard to detect. |
|
|
509 | |
|
|
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
|
|
511 | but of course I<doesn't>, and epoll just loves to report events for |
|
|
512 | totally I<different> file descriptors (even already closed ones, so |
|
|
513 | one cannot even remove them from the set) than registered in the set |
|
|
514 | (especially on SMP systems). Libev tries to counter these spurious |
|
|
515 | notifications by employing an additional generation counter and comparing |
|
|
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
|
|
520 | not least, it also refuses to work with some file descriptors which work |
|
|
521 | perfectly fine with C<select> (files, many character devices...). |
|
|
522 | |
|
|
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
|
|
524 | cobbled together in a hurry, no thought to design or interaction with |
|
|
525 | others. Oh, the pain, will it ever stop... |
382 | |
526 | |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
384 | will result in some caching, there is still a system call per such incident |
528 | will result in some caching, there is still a system call per such |
385 | (because the fd could point to a different file description now), so its |
529 | incident (because the same I<file descriptor> could point to a different |
386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
387 | very well if you register events for both fds. |
531 | file descriptors might not work very well if you register events for both |
388 | |
532 | file descriptors. |
389 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
391 | (or space) is available. |
|
|
392 | |
533 | |
393 | Best performance from this backend is achieved by not unregistering all |
534 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
535 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
536 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
537 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
538 | extra overhead. A fork can both result in spurious notifications as well |
|
|
539 | as in libev having to destroy and recreate the epoll object, which can |
|
|
540 | take considerable time and thus should be avoided. |
|
|
541 | |
|
|
542 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
543 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
544 | the usage. So sad. |
396 | |
545 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
546 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
547 | all kernel versions tested so far. |
|
|
548 | |
|
|
549 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
550 | C<EVBACKEND_POLL>. |
399 | |
551 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
552 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
553 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
554 | Kqueue deserves special mention, as at the time of this writing, it |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
555 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
404 | with anything but sockets and pipes, except on Darwin, where of course |
556 | with anything but sockets and pipes, except on Darwin, where of course |
405 | it's completely useless). For this reason it's not being "auto-detected" |
557 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
558 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
559 | without API changes to existing programs. For this reason it's not being |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
560 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
561 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
408 | system like NetBSD. |
562 | system like NetBSD. |
409 | |
563 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
564 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
565 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
413 | |
567 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
|
|
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
419 | drops fds silently in similarly hard-to-detect cases. |
574 | drops fds silently in similarly hard-to-detect cases |
420 | |
575 | |
421 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
422 | |
577 | |
423 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
580 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
581 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
582 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
428 | sockets. |
583 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
584 | |
|
|
585 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
586 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
587 | C<NOTE_EOF>. |
429 | |
588 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
589 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
590 | |
432 | This is not implemented yet (and might never be, unless you send me an |
591 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
592 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
437 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
596 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
438 | |
597 | |
439 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
598 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
440 | it's really slow, but it still scales very well (O(active_fds)). |
599 | it's really slow, but it still scales very well (O(active_fds)). |
441 | |
600 | |
442 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
443 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
444 | blocking when no data (or space) is available. |
|
|
445 | |
|
|
446 | While this backend scales well, it requires one system call per active |
601 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
602 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
603 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
604 | might perform better. |
450 | |
605 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
606 | On the positive side, this backend actually performed fully to |
452 | backend actually performed to specification in all tests and is fully |
607 | specification in all tests and is fully embeddable, which is a rare feat |
453 | embeddable, which is a rare feat among the OS-specific backends. |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
609 | hacks). |
|
|
610 | |
|
|
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
612 | even sun itself gets it wrong in their code examples: The event polling |
|
|
613 | function sometimes returns events to the caller even though an error |
|
|
614 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
615 | even documented that way) - deadly for edge-triggered interfaces where you |
|
|
616 | absolutely have to know whether an event occurred or not because you have |
|
|
617 | to re-arm the watcher. |
|
|
618 | |
|
|
619 | Fortunately libev seems to be able to work around these idiocies. |
|
|
620 | |
|
|
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
622 | C<EVBACKEND_POLL>. |
454 | |
623 | |
455 | =item C<EVBACKEND_ALL> |
624 | =item C<EVBACKEND_ALL> |
456 | |
625 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
626 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
627 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
459 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
628 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
460 | |
629 | |
461 | It is definitely not recommended to use this flag. |
630 | It is definitely not recommended to use this flag, use whatever |
|
|
631 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
632 | at all. |
|
|
633 | |
|
|
634 | =item C<EVBACKEND_MASK> |
|
|
635 | |
|
|
636 | Not a backend at all, but a mask to select all backend bits from a |
|
|
637 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
638 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
462 | |
639 | |
463 | =back |
640 | =back |
464 | |
641 | |
465 | If one or more of these are or'ed into the flags value, then only these |
642 | If one or more of the backend flags are or'ed into the flags value, |
466 | backends will be tried (in the reverse order as listed here). If none are |
643 | then only these backends will be tried (in the reverse order as listed |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
644 | here). If none are specified, all backends in C<ev_recommended_backends |
468 | |
645 | ()> will be tried. |
469 | The most typical usage is like this: |
|
|
470 | |
|
|
471 | if (!ev_default_loop (0)) |
|
|
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
473 | |
|
|
474 | Restrict libev to the select and poll backends, and do not allow |
|
|
475 | environment settings to be taken into account: |
|
|
476 | |
|
|
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
478 | |
|
|
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
480 | available (warning, breaks stuff, best use only with your own private |
|
|
481 | event loop and only if you know the OS supports your types of fds): |
|
|
482 | |
|
|
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
484 | |
|
|
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
486 | |
|
|
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
488 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
489 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
491 | |
|
|
492 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
493 | libev with threads is indeed to create one loop per thread, and using the |
|
|
494 | default loop in the "main" or "initial" thread. |
|
|
495 | |
646 | |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
647 | Example: Try to create a event loop that uses epoll and nothing else. |
497 | |
648 | |
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
649 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
499 | if (!epoller) |
650 | if (!epoller) |
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
651 | fatal ("no epoll found here, maybe it hides under your chair"); |
501 | |
652 | |
|
|
653 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
654 | used if available. |
|
|
655 | |
|
|
656 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
657 | |
502 | =item ev_default_destroy () |
658 | =item ev_loop_destroy (loop) |
503 | |
659 | |
504 | Destroys the default loop again (frees all memory and kernel state |
660 | Destroys an event loop object (frees all memory and kernel state |
505 | etc.). None of the active event watchers will be stopped in the normal |
661 | etc.). None of the active event watchers will be stopped in the normal |
506 | sense, so e.g. C<ev_is_active> might still return true. It is your |
662 | sense, so e.g. C<ev_is_active> might still return true. It is your |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
663 | responsibility to either stop all watchers cleanly yourself I<before> |
508 | calling this function, or cope with the fact afterwards (which is usually |
664 | calling this function, or cope with the fact afterwards (which is usually |
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
665 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
510 | for example). |
666 | for example). |
511 | |
667 | |
512 | Note that certain global state, such as signal state, will not be freed by |
668 | Note that certain global state, such as signal state (and installed signal |
513 | this function, and related watchers (such as signal and child watchers) |
669 | handlers), will not be freed by this function, and related watchers (such |
514 | would need to be stopped manually. |
670 | as signal and child watchers) would need to be stopped manually. |
515 | |
671 | |
516 | In general it is not advisable to call this function except in the |
672 | This function is normally used on loop objects allocated by |
517 | rare occasion where you really need to free e.g. the signal handling |
673 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
674 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
675 | |
|
|
676 | Note that it is not advisable to call this function on the default loop |
|
|
677 | except in the rare occasion where you really need to free its resources. |
518 | pipe fds. If you need dynamically allocated loops it is better to use |
678 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
679 | and C<ev_loop_destroy>. |
520 | |
680 | |
521 | =item ev_loop_destroy (loop) |
681 | =item ev_loop_fork (loop) |
522 | |
682 | |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
524 | earlier call to C<ev_loop_new>. |
|
|
525 | |
|
|
526 | =item ev_default_fork () |
|
|
527 | |
|
|
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
683 | This function sets a flag that causes subsequent C<ev_run> iterations to |
529 | to reinitialise the kernel state for backends that have one. Despite the |
684 | reinitialise the kernel state for backends that have one. Despite the |
530 | name, you can call it anytime, but it makes most sense after forking, in |
685 | name, you can call it anytime, but it makes most sense after forking, in |
531 | the child process (or both child and parent, but that again makes little |
686 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
532 | sense). You I<must> call it in the child before using any of the libev |
687 | child before resuming or calling C<ev_run>. |
533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
688 | |
|
|
689 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
690 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
691 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
692 | during fork. |
534 | |
693 | |
535 | On the other hand, you only need to call this function in the child |
694 | On the other hand, you only need to call this function in the child |
536 | process if and only if you want to use the event library in the child. If |
695 | process if and only if you want to use the event loop in the child. If |
537 | you just fork+exec, you don't have to call it at all. |
696 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
697 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
698 | difference, but libev will usually detect this case on its own and do a |
|
|
699 | costly reset of the backend). |
538 | |
700 | |
539 | The function itself is quite fast and it's usually not a problem to call |
701 | The function itself is quite fast and it's usually not a problem to call |
540 | it just in case after a fork. To make this easy, the function will fit in |
702 | it just in case after a fork. |
541 | quite nicely into a call to C<pthread_atfork>: |
|
|
542 | |
703 | |
|
|
704 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
705 | using pthreads. |
|
|
706 | |
|
|
707 | static void |
|
|
708 | post_fork_child (void) |
|
|
709 | { |
|
|
710 | ev_loop_fork (EV_DEFAULT); |
|
|
711 | } |
|
|
712 | |
|
|
713 | ... |
543 | pthread_atfork (0, 0, ev_default_fork); |
714 | pthread_atfork (0, 0, post_fork_child); |
544 | |
|
|
545 | =item ev_loop_fork (loop) |
|
|
546 | |
|
|
547 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
549 | after fork, and how you do this is entirely your own problem. |
|
|
550 | |
715 | |
551 | =item int ev_is_default_loop (loop) |
716 | =item int ev_is_default_loop (loop) |
552 | |
717 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
718 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
719 | otherwise. |
554 | |
720 | |
555 | =item unsigned int ev_loop_count (loop) |
721 | =item unsigned int ev_iteration (loop) |
556 | |
722 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
723 | Returns the current iteration count for the event loop, which is identical |
558 | the number of times libev did poll for new events. It starts at C<0> and |
724 | to the number of times libev did poll for new events. It starts at C<0> |
559 | happily wraps around with enough iterations. |
725 | and happily wraps around with enough iterations. |
560 | |
726 | |
561 | This value can sometimes be useful as a generation counter of sorts (it |
727 | This value can sometimes be useful as a generation counter of sorts (it |
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
728 | "ticks" the number of loop iterations), as it roughly corresponds with |
563 | C<ev_prepare> and C<ev_check> calls. |
729 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
730 | prepare and check phases. |
|
|
731 | |
|
|
732 | =item unsigned int ev_depth (loop) |
|
|
733 | |
|
|
734 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
735 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
736 | |
|
|
737 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
738 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
739 | in which case it is higher. |
|
|
740 | |
|
|
741 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
742 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
743 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
744 | convenient, in which case it is fully supported. |
564 | |
745 | |
565 | =item unsigned int ev_backend (loop) |
746 | =item unsigned int ev_backend (loop) |
566 | |
747 | |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
748 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
568 | use. |
749 | use. |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
754 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
755 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
756 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
757 | event occurring (or more correctly, libev finding out about it). |
577 | |
758 | |
|
|
759 | =item ev_now_update (loop) |
|
|
760 | |
|
|
761 | Establishes the current time by querying the kernel, updating the time |
|
|
762 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
763 | is usually done automatically within C<ev_run ()>. |
|
|
764 | |
|
|
765 | This function is rarely useful, but when some event callback runs for a |
|
|
766 | very long time without entering the event loop, updating libev's idea of |
|
|
767 | the current time is a good idea. |
|
|
768 | |
|
|
769 | See also L</The special problem of time updates> in the C<ev_timer> section. |
|
|
770 | |
|
|
771 | =item ev_suspend (loop) |
|
|
772 | |
|
|
773 | =item ev_resume (loop) |
|
|
774 | |
|
|
775 | These two functions suspend and resume an event loop, for use when the |
|
|
776 | loop is not used for a while and timeouts should not be processed. |
|
|
777 | |
|
|
778 | A typical use case would be an interactive program such as a game: When |
|
|
779 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
780 | would be best to handle timeouts as if no time had actually passed while |
|
|
781 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
782 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
783 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
784 | |
|
|
785 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
786 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
787 | will be rescheduled (that is, they will lose any events that would have |
|
|
788 | occurred while suspended). |
|
|
789 | |
|
|
790 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
791 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
792 | without a previous call to C<ev_suspend>. |
|
|
793 | |
|
|
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
795 | event loop time (see C<ev_now_update>). |
|
|
796 | |
578 | =item ev_loop (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
579 | |
798 | |
580 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
581 | after you initialised all your watchers and you want to start handling |
800 | after you have initialised all your watchers and you want to start |
582 | events. |
801 | handling events. It will ask the operating system for any new events, call |
|
|
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
|
|
803 | is why event loops are called I<loops>. |
583 | |
804 | |
584 | If the flags argument is specified as C<0>, it will not return until |
805 | If the flags argument is specified as C<0>, it will keep handling events |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
806 | until either no event watchers are active anymore or C<ev_break> was |
|
|
807 | called. |
586 | |
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
|
|
812 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
815 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
816 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
818 | beauty. |
592 | |
819 | |
|
|
820 | This function is I<mostly> exception-safe - you can break out of a |
|
|
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
824 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
826 | those events and any already outstanding ones, but will not wait and |
595 | case there are no events and will return after one iteration of the loop. |
827 | block your process in case there are no events and will return after one |
|
|
828 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
829 | events while doing lengthy calculations, to keep the program responsive. |
596 | |
830 | |
597 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
831 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
598 | necessary) and will handle those and any outstanding ones. It will block |
832 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
833 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
834 | be an event internal to libev itself, so there is no guarantee that a |
601 | external event in conjunction with something not expressible using other |
835 | user-registered callback will be called), and will return after one |
|
|
836 | iteration of the loop. |
|
|
837 | |
|
|
838 | This is useful if you are waiting for some external event in conjunction |
|
|
839 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
840 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
841 | usually a better approach for this kind of thing. |
604 | |
842 | |
605 | Here are the gory details of what C<ev_loop> does: |
843 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
844 | understanding, not a guarantee that things will work exactly like this in |
|
|
845 | future versions): |
606 | |
846 | |
|
|
847 | - Increment loop depth. |
|
|
848 | - Reset the ev_break status. |
607 | - Before the first iteration, call any pending watchers. |
849 | - Before the first iteration, call any pending watchers. |
|
|
850 | LOOP: |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
851 | - If EVFLAG_FORKCHECK was used, check for a fork. |
609 | - If a fork was detected (by any means), queue and call all fork watchers. |
852 | - If a fork was detected (by any means), queue and call all fork watchers. |
610 | - Queue and call all prepare watchers. |
853 | - Queue and call all prepare watchers. |
|
|
854 | - If ev_break was called, goto FINISH. |
611 | - If we have been forked, detach and recreate the kernel state |
855 | - If we have been forked, detach and recreate the kernel state |
612 | as to not disturb the other process. |
856 | as to not disturb the other process. |
613 | - Update the kernel state with all outstanding changes. |
857 | - Update the kernel state with all outstanding changes. |
614 | - Update the "event loop time" (ev_now ()). |
858 | - Update the "event loop time" (ev_now ()). |
615 | - Calculate for how long to sleep or block, if at all |
859 | - Calculate for how long to sleep or block, if at all |
616 | (active idle watchers, EVLOOP_NONBLOCK or not having |
860 | (active idle watchers, EVRUN_NOWAIT or not having |
617 | any active watchers at all will result in not sleeping). |
861 | any active watchers at all will result in not sleeping). |
618 | - Sleep if the I/O and timer collect interval say so. |
862 | - Sleep if the I/O and timer collect interval say so. |
|
|
863 | - Increment loop iteration counter. |
619 | - Block the process, waiting for any events. |
864 | - Block the process, waiting for any events. |
620 | - Queue all outstanding I/O (fd) events. |
865 | - Queue all outstanding I/O (fd) events. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
866 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
622 | - Queue all outstanding timers. |
867 | - Queue all expired timers. |
623 | - Queue all outstanding periodics. |
868 | - Queue all expired periodics. |
624 | - Unless any events are pending now, queue all idle watchers. |
869 | - Queue all idle watchers with priority higher than that of pending events. |
625 | - Queue all check watchers. |
870 | - Queue all check watchers. |
626 | - Call all queued watchers in reverse order (i.e. check watchers first). |
871 | - Call all queued watchers in reverse order (i.e. check watchers first). |
627 | Signals and child watchers are implemented as I/O watchers, and will |
872 | Signals and child watchers are implemented as I/O watchers, and will |
628 | be handled here by queueing them when their watcher gets executed. |
873 | be handled here by queueing them when their watcher gets executed. |
629 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
874 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
630 | were used, or there are no active watchers, return, otherwise |
875 | were used, or there are no active watchers, goto FINISH, otherwise |
631 | continue with step *. |
876 | continue with step LOOP. |
|
|
877 | FINISH: |
|
|
878 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
879 | - Decrement the loop depth. |
|
|
880 | - Return. |
632 | |
881 | |
633 | Example: Queue some jobs and then loop until no events are outstanding |
882 | Example: Queue some jobs and then loop until no events are outstanding |
634 | anymore. |
883 | anymore. |
635 | |
884 | |
636 | ... queue jobs here, make sure they register event watchers as long |
885 | ... queue jobs here, make sure they register event watchers as long |
637 | ... as they still have work to do (even an idle watcher will do..) |
886 | ... as they still have work to do (even an idle watcher will do..) |
638 | ev_loop (my_loop, 0); |
887 | ev_run (my_loop, 0); |
639 | ... jobs done or somebody called unloop. yeah! |
888 | ... jobs done or somebody called break. yeah! |
640 | |
889 | |
641 | =item ev_unloop (loop, how) |
890 | =item ev_break (loop, how) |
642 | |
891 | |
643 | Can be used to make a call to C<ev_loop> return early (but only after it |
892 | Can be used to make a call to C<ev_run> return early (but only after it |
644 | has processed all outstanding events). The C<how> argument must be either |
893 | has processed all outstanding events). The C<how> argument must be either |
645 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
894 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
646 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
895 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
647 | |
896 | |
648 | This "unloop state" will be cleared when entering C<ev_loop> again. |
897 | This "break state" will be cleared on the next call to C<ev_run>. |
|
|
898 | |
|
|
899 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
900 | which case it will have no effect. |
649 | |
901 | |
650 | =item ev_ref (loop) |
902 | =item ev_ref (loop) |
651 | |
903 | |
652 | =item ev_unref (loop) |
904 | =item ev_unref (loop) |
653 | |
905 | |
654 | Ref/unref can be used to add or remove a reference count on the event |
906 | Ref/unref can be used to add or remove a reference count on the event |
655 | loop: Every watcher keeps one reference, and as long as the reference |
907 | loop: Every watcher keeps one reference, and as long as the reference |
656 | count is nonzero, C<ev_loop> will not return on its own. If you have |
908 | count is nonzero, C<ev_run> will not return on its own. |
657 | a watcher you never unregister that should not keep C<ev_loop> from |
909 | |
658 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
910 | This is useful when you have a watcher that you never intend to |
|
|
911 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
912 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
913 | before stopping it. |
|
|
914 | |
659 | example, libev itself uses this for its internal signal pipe: It is not |
915 | As an example, libev itself uses this for its internal signal pipe: It |
660 | visible to the libev user and should not keep C<ev_loop> from exiting if |
916 | is not visible to the libev user and should not keep C<ev_run> from |
661 | no event watchers registered by it are active. It is also an excellent |
917 | exiting if no event watchers registered by it are active. It is also an |
662 | way to do this for generic recurring timers or from within third-party |
918 | excellent way to do this for generic recurring timers or from within |
663 | libraries. Just remember to I<unref after start> and I<ref before stop> |
919 | third-party libraries. Just remember to I<unref after start> and I<ref |
664 | (but only if the watcher wasn't active before, or was active before, |
920 | before stop> (but only if the watcher wasn't active before, or was active |
665 | respectively). |
921 | before, respectively. Note also that libev might stop watchers itself |
|
|
922 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
923 | in the callback). |
666 | |
924 | |
667 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
925 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
668 | running when nothing else is active. |
926 | running when nothing else is active. |
669 | |
927 | |
670 | struct ev_signal exitsig; |
928 | ev_signal exitsig; |
671 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
929 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
672 | ev_signal_start (loop, &exitsig); |
930 | ev_signal_start (loop, &exitsig); |
673 | evf_unref (loop); |
931 | ev_unref (loop); |
674 | |
932 | |
675 | Example: For some weird reason, unregister the above signal handler again. |
933 | Example: For some weird reason, unregister the above signal handler again. |
676 | |
934 | |
677 | ev_ref (loop); |
935 | ev_ref (loop); |
678 | ev_signal_stop (loop, &exitsig); |
936 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
689 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
947 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
948 | allows libev to delay invocation of I/O and timer/periodic callbacks |
691 | to increase efficiency of loop iterations (or to increase power-saving |
949 | to increase efficiency of loop iterations (or to increase power-saving |
692 | opportunities). |
950 | opportunities). |
693 | |
951 | |
694 | The background is that sometimes your program runs just fast enough to |
952 | The idea is that sometimes your program runs just fast enough to handle |
695 | handle one (or very few) event(s) per loop iteration. While this makes |
953 | one (or very few) event(s) per loop iteration. While this makes the |
696 | the program responsive, it also wastes a lot of CPU time to poll for new |
954 | program responsive, it also wastes a lot of CPU time to poll for new |
697 | events, especially with backends like C<select ()> which have a high |
955 | events, especially with backends like C<select ()> which have a high |
698 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
699 | |
957 | |
700 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
701 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
702 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
703 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
704 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
963 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
705 | |
966 | |
706 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
707 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
708 | latency (the watcher callback will be called later). C<ev_io> watchers |
969 | latency/jitter/inexactness (the watcher callback will be called |
709 | will not be affected. Setting this to a non-null value will not introduce |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
710 | any overhead in libev. |
971 | value will not introduce any overhead in libev. |
711 | |
972 | |
712 | Many (busy) programs can usually benefit by setting the I/O collect |
973 | Many (busy) programs can usually benefit by setting the I/O collect |
713 | interval to a value near C<0.1> or so, which is often enough for |
974 | interval to a value near C<0.1> or so, which is often enough for |
714 | interactive servers (of course not for games), likewise for timeouts. It |
975 | interactive servers (of course not for games), likewise for timeouts. It |
715 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
976 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
716 | as this approaches the timing granularity of most systems. |
977 | as this approaches the timing granularity of most systems. Note that if |
|
|
978 | you do transactions with the outside world and you can't increase the |
|
|
979 | parallelity, then this setting will limit your transaction rate (if you |
|
|
980 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
981 | then you can't do more than 100 transactions per second). |
717 | |
982 | |
718 | Setting the I<timeout collect interval> can improve the opportunity for |
983 | Setting the I<timeout collect interval> can improve the opportunity for |
719 | saving power, as the program will "bundle" timer callback invocations that |
984 | saving power, as the program will "bundle" timer callback invocations that |
720 | are "near" in time together, by delaying some, thus reducing the number of |
985 | are "near" in time together, by delaying some, thus reducing the number of |
721 | times the process sleeps and wakes up again. Another useful technique to |
986 | times the process sleeps and wakes up again. Another useful technique to |
722 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
987 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
723 | they fire on, say, one-second boundaries only. |
988 | they fire on, say, one-second boundaries only. |
724 | |
989 | |
|
|
990 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
991 | more often than 100 times per second: |
|
|
992 | |
|
|
993 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
994 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
995 | |
|
|
996 | =item ev_invoke_pending (loop) |
|
|
997 | |
|
|
998 | This call will simply invoke all pending watchers while resetting their |
|
|
999 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
1000 | but when overriding the invoke callback this call comes handy. This |
|
|
1001 | function can be invoked from a watcher - this can be useful for example |
|
|
1002 | when you want to do some lengthy calculation and want to pass further |
|
|
1003 | event handling to another thread (you still have to make sure only one |
|
|
1004 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
1005 | |
|
|
1006 | =item int ev_pending_count (loop) |
|
|
1007 | |
|
|
1008 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
1009 | are pending. |
|
|
1010 | |
|
|
1011 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
1012 | |
|
|
1013 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
1014 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
1015 | this callback instead. This is useful, for example, when you want to |
|
|
1016 | invoke the actual watchers inside another context (another thread etc.). |
|
|
1017 | |
|
|
1018 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
1019 | callback. |
|
|
1020 | |
|
|
1021 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P) throw (), void (*acquire)(EV_P) throw ()) |
|
|
1022 | |
|
|
1023 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1025 | each call to a libev function. |
|
|
1026 | |
|
|
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1028 | to wait for it to return. One way around this is to wake up the event |
|
|
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
|
|
1030 | I<release> and I<acquire> callbacks on the loop. |
|
|
1031 | |
|
|
1032 | When set, then C<release> will be called just before the thread is |
|
|
1033 | suspended waiting for new events, and C<acquire> is called just |
|
|
1034 | afterwards. |
|
|
1035 | |
|
|
1036 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1037 | C<acquire> will just call the mutex_lock function again. |
|
|
1038 | |
|
|
1039 | While event loop modifications are allowed between invocations of |
|
|
1040 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1041 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1042 | have no effect on the set of file descriptors being watched, or the time |
|
|
1043 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1044 | to take note of any changes you made. |
|
|
1045 | |
|
|
1046 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1047 | invocations of C<release> and C<acquire>. |
|
|
1048 | |
|
|
1049 | See also the locking example in the C<THREADS> section later in this |
|
|
1050 | document. |
|
|
1051 | |
|
|
1052 | =item ev_set_userdata (loop, void *data) |
|
|
1053 | |
|
|
1054 | =item void *ev_userdata (loop) |
|
|
1055 | |
|
|
1056 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1057 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1058 | C<0>. |
|
|
1059 | |
|
|
1060 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1061 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1062 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1063 | any other purpose as well. |
|
|
1064 | |
725 | =item ev_loop_verify (loop) |
1065 | =item ev_verify (loop) |
726 | |
1066 | |
727 | This function only does something when C<EV_VERIFY> support has been |
1067 | This function only does something when C<EV_VERIFY> support has been |
728 | compiled in. It tries to go through all internal structures and checks |
1068 | compiled in, which is the default for non-minimal builds. It tries to go |
729 | them for validity. If anything is found to be inconsistent, it will print |
1069 | through all internal structures and checks them for validity. If anything |
730 | an error message to standard error and call C<abort ()>. |
1070 | is found to be inconsistent, it will print an error message to standard |
|
|
1071 | error and call C<abort ()>. |
731 | |
1072 | |
732 | This can be used to catch bugs inside libev itself: under normal |
1073 | This can be used to catch bugs inside libev itself: under normal |
733 | circumstances, this function will never abort as of course libev keeps its |
1074 | circumstances, this function will never abort as of course libev keeps its |
734 | data structures consistent. |
1075 | data structures consistent. |
735 | |
1076 | |
736 | =back |
1077 | =back |
737 | |
1078 | |
738 | |
1079 | |
739 | =head1 ANATOMY OF A WATCHER |
1080 | =head1 ANATOMY OF A WATCHER |
740 | |
1081 | |
|
|
1082 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1083 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1084 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1085 | |
741 | A watcher is a structure that you create and register to record your |
1086 | A watcher is an opaque structure that you allocate and register to record |
742 | interest in some event. For instance, if you want to wait for STDIN to |
1087 | your interest in some event. To make a concrete example, imagine you want |
743 | become readable, you would create an C<ev_io> watcher for that: |
1088 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1089 | for that: |
744 | |
1090 | |
745 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1091 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
746 | { |
1092 | { |
747 | ev_io_stop (w); |
1093 | ev_io_stop (w); |
748 | ev_unloop (loop, EVUNLOOP_ALL); |
1094 | ev_break (loop, EVBREAK_ALL); |
749 | } |
1095 | } |
750 | |
1096 | |
751 | struct ev_loop *loop = ev_default_loop (0); |
1097 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1098 | |
752 | struct ev_io stdin_watcher; |
1099 | ev_io stdin_watcher; |
|
|
1100 | |
753 | ev_init (&stdin_watcher, my_cb); |
1101 | ev_init (&stdin_watcher, my_cb); |
754 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1102 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
755 | ev_io_start (loop, &stdin_watcher); |
1103 | ev_io_start (loop, &stdin_watcher); |
|
|
1104 | |
756 | ev_loop (loop, 0); |
1105 | ev_run (loop, 0); |
757 | |
1106 | |
758 | As you can see, you are responsible for allocating the memory for your |
1107 | As you can see, you are responsible for allocating the memory for your |
759 | watcher structures (and it is usually a bad idea to do this on the stack, |
1108 | watcher structures (and it is I<usually> a bad idea to do this on the |
760 | although this can sometimes be quite valid). |
1109 | stack). |
761 | |
1110 | |
|
|
1111 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1112 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1113 | |
762 | Each watcher structure must be initialised by a call to C<ev_init |
1114 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
763 | (watcher *, callback)>, which expects a callback to be provided. This |
1115 | *, callback)>, which expects a callback to be provided. This callback is |
764 | callback gets invoked each time the event occurs (or, in the case of I/O |
1116 | invoked each time the event occurs (or, in the case of I/O watchers, each |
765 | watchers, each time the event loop detects that the file descriptor given |
1117 | time the event loop detects that the file descriptor given is readable |
766 | is readable and/or writable). |
1118 | and/or writable). |
767 | |
1119 | |
768 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1120 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
769 | with arguments specific to this watcher type. There is also a macro |
1121 | macro to configure it, with arguments specific to the watcher type. There |
770 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1122 | is also a macro to combine initialisation and setting in one call: C<< |
771 | (watcher *, callback, ...) >>. |
1123 | ev_TYPE_init (watcher *, callback, ...) >>. |
772 | |
1124 | |
773 | To make the watcher actually watch out for events, you have to start it |
1125 | To make the watcher actually watch out for events, you have to start it |
774 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1126 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
775 | *) >>), and you can stop watching for events at any time by calling the |
1127 | *) >>), and you can stop watching for events at any time by calling the |
776 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1128 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
777 | |
1129 | |
778 | As long as your watcher is active (has been started but not stopped) you |
1130 | As long as your watcher is active (has been started but not stopped) you |
779 | must not touch the values stored in it. Most specifically you must never |
1131 | must not touch the values stored in it. Most specifically you must never |
780 | reinitialise it or call its C<set> macro. |
1132 | reinitialise it or call its C<ev_TYPE_set> macro. |
781 | |
1133 | |
782 | Each and every callback receives the event loop pointer as first, the |
1134 | Each and every callback receives the event loop pointer as first, the |
783 | registered watcher structure as second, and a bitset of received events as |
1135 | registered watcher structure as second, and a bitset of received events as |
784 | third argument. |
1136 | third argument. |
785 | |
1137 | |
… | |
… | |
794 | =item C<EV_WRITE> |
1146 | =item C<EV_WRITE> |
795 | |
1147 | |
796 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1148 | The file descriptor in the C<ev_io> watcher has become readable and/or |
797 | writable. |
1149 | writable. |
798 | |
1150 | |
799 | =item C<EV_TIMEOUT> |
1151 | =item C<EV_TIMER> |
800 | |
1152 | |
801 | The C<ev_timer> watcher has timed out. |
1153 | The C<ev_timer> watcher has timed out. |
802 | |
1154 | |
803 | =item C<EV_PERIODIC> |
1155 | =item C<EV_PERIODIC> |
804 | |
1156 | |
… | |
… | |
822 | |
1174 | |
823 | =item C<EV_PREPARE> |
1175 | =item C<EV_PREPARE> |
824 | |
1176 | |
825 | =item C<EV_CHECK> |
1177 | =item C<EV_CHECK> |
826 | |
1178 | |
827 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1179 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts to |
828 | to gather new events, and all C<ev_check> watchers are invoked just after |
1180 | gather new events, and all C<ev_check> watchers are queued (not invoked) |
829 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1181 | just after C<ev_run> has gathered them, but before it queues any callbacks |
|
|
1182 | for any received events. That means C<ev_prepare> watchers are the last |
|
|
1183 | watchers invoked before the event loop sleeps or polls for new events, and |
|
|
1184 | C<ev_check> watchers will be invoked before any other watchers of the same |
|
|
1185 | or lower priority within an event loop iteration. |
|
|
1186 | |
830 | received events. Callbacks of both watcher types can start and stop as |
1187 | Callbacks of both watcher types can start and stop as many watchers as |
831 | many watchers as they want, and all of them will be taken into account |
1188 | they want, and all of them will be taken into account (for example, a |
832 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1189 | C<ev_prepare> watcher might start an idle watcher to keep C<ev_run> from |
833 | C<ev_loop> from blocking). |
1190 | blocking). |
834 | |
1191 | |
835 | =item C<EV_EMBED> |
1192 | =item C<EV_EMBED> |
836 | |
1193 | |
837 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1194 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
838 | |
1195 | |
839 | =item C<EV_FORK> |
1196 | =item C<EV_FORK> |
840 | |
1197 | |
841 | The event loop has been resumed in the child process after fork (see |
1198 | The event loop has been resumed in the child process after fork (see |
842 | C<ev_fork>). |
1199 | C<ev_fork>). |
843 | |
1200 | |
|
|
1201 | =item C<EV_CLEANUP> |
|
|
1202 | |
|
|
1203 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1204 | |
844 | =item C<EV_ASYNC> |
1205 | =item C<EV_ASYNC> |
845 | |
1206 | |
846 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1207 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1208 | |
|
|
1209 | =item C<EV_CUSTOM> |
|
|
1210 | |
|
|
1211 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1212 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
847 | |
1213 | |
848 | =item C<EV_ERROR> |
1214 | =item C<EV_ERROR> |
849 | |
1215 | |
850 | An unspecified error has occurred, the watcher has been stopped. This might |
1216 | An unspecified error has occurred, the watcher has been stopped. This might |
851 | happen because the watcher could not be properly started because libev |
1217 | happen because the watcher could not be properly started because libev |
852 | ran out of memory, a file descriptor was found to be closed or any other |
1218 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1219 | problem. Libev considers these application bugs. |
|
|
1220 | |
853 | problem. You best act on it by reporting the problem and somehow coping |
1221 | You best act on it by reporting the problem and somehow coping with the |
854 | with the watcher being stopped. |
1222 | watcher being stopped. Note that well-written programs should not receive |
|
|
1223 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1224 | bug in your program. |
855 | |
1225 | |
856 | Libev will usually signal a few "dummy" events together with an error, |
1226 | Libev will usually signal a few "dummy" events together with an error, for |
857 | for example it might indicate that a fd is readable or writable, and if |
1227 | example it might indicate that a fd is readable or writable, and if your |
858 | your callbacks is well-written it can just attempt the operation and cope |
1228 | callbacks is well-written it can just attempt the operation and cope with |
859 | with the error from read() or write(). This will not work in multi-threaded |
1229 | the error from read() or write(). This will not work in multi-threaded |
860 | programs, though, so beware. |
1230 | programs, though, as the fd could already be closed and reused for another |
|
|
1231 | thing, so beware. |
861 | |
1232 | |
862 | =back |
1233 | =back |
863 | |
1234 | |
864 | =head2 GENERIC WATCHER FUNCTIONS |
1235 | =head2 GENERIC WATCHER FUNCTIONS |
865 | |
|
|
866 | In the following description, C<TYPE> stands for the watcher type, |
|
|
867 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
868 | |
1236 | |
869 | =over 4 |
1237 | =over 4 |
870 | |
1238 | |
871 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1239 | =item C<ev_init> (ev_TYPE *watcher, callback) |
872 | |
1240 | |
… | |
… | |
878 | which rolls both calls into one. |
1246 | which rolls both calls into one. |
879 | |
1247 | |
880 | You can reinitialise a watcher at any time as long as it has been stopped |
1248 | You can reinitialise a watcher at any time as long as it has been stopped |
881 | (or never started) and there are no pending events outstanding. |
1249 | (or never started) and there are no pending events outstanding. |
882 | |
1250 | |
883 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1251 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
884 | int revents)>. |
1252 | int revents)>. |
885 | |
1253 | |
|
|
1254 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1255 | |
|
|
1256 | ev_io w; |
|
|
1257 | ev_init (&w, my_cb); |
|
|
1258 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1259 | |
886 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1260 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
887 | |
1261 | |
888 | This macro initialises the type-specific parts of a watcher. You need to |
1262 | This macro initialises the type-specific parts of a watcher. You need to |
889 | call C<ev_init> at least once before you call this macro, but you can |
1263 | call C<ev_init> at least once before you call this macro, but you can |
890 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1264 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
891 | macro on a watcher that is active (it can be pending, however, which is a |
1265 | macro on a watcher that is active (it can be pending, however, which is a |
892 | difference to the C<ev_init> macro). |
1266 | difference to the C<ev_init> macro). |
893 | |
1267 | |
894 | Although some watcher types do not have type-specific arguments |
1268 | Although some watcher types do not have type-specific arguments |
895 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1269 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
896 | |
1270 | |
|
|
1271 | See C<ev_init>, above, for an example. |
|
|
1272 | |
897 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1273 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
898 | |
1274 | |
899 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1275 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
900 | calls into a single call. This is the most convenient method to initialise |
1276 | calls into a single call. This is the most convenient method to initialise |
901 | a watcher. The same limitations apply, of course. |
1277 | a watcher. The same limitations apply, of course. |
902 | |
1278 | |
|
|
1279 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1280 | |
|
|
1281 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1282 | |
903 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1283 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
904 | |
1284 | |
905 | Starts (activates) the given watcher. Only active watchers will receive |
1285 | Starts (activates) the given watcher. Only active watchers will receive |
906 | events. If the watcher is already active nothing will happen. |
1286 | events. If the watcher is already active nothing will happen. |
907 | |
1287 | |
|
|
1288 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1289 | whole section. |
|
|
1290 | |
|
|
1291 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1292 | |
908 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1293 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
909 | |
1294 | |
910 | Stops the given watcher again (if active) and clears the pending |
1295 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1296 | the watcher was active or not). |
|
|
1297 | |
911 | status. It is possible that stopped watchers are pending (for example, |
1298 | It is possible that stopped watchers are pending - for example, |
912 | non-repeating timers are being stopped when they become pending), but |
1299 | non-repeating timers are being stopped when they become pending - but |
913 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1300 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
914 | you want to free or reuse the memory used by the watcher it is therefore a |
1301 | pending. If you want to free or reuse the memory used by the watcher it is |
915 | good idea to always call its C<ev_TYPE_stop> function. |
1302 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
916 | |
1303 | |
917 | =item bool ev_is_active (ev_TYPE *watcher) |
1304 | =item bool ev_is_active (ev_TYPE *watcher) |
918 | |
1305 | |
919 | Returns a true value iff the watcher is active (i.e. it has been started |
1306 | Returns a true value iff the watcher is active (i.e. it has been started |
920 | and not yet been stopped). As long as a watcher is active you must not modify |
1307 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
931 | |
1318 | |
932 | =item callback ev_cb (ev_TYPE *watcher) |
1319 | =item callback ev_cb (ev_TYPE *watcher) |
933 | |
1320 | |
934 | Returns the callback currently set on the watcher. |
1321 | Returns the callback currently set on the watcher. |
935 | |
1322 | |
936 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1323 | =item ev_set_cb (ev_TYPE *watcher, callback) |
937 | |
1324 | |
938 | Change the callback. You can change the callback at virtually any time |
1325 | Change the callback. You can change the callback at virtually any time |
939 | (modulo threads). |
1326 | (modulo threads). |
940 | |
1327 | |
941 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1328 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
942 | |
1329 | |
943 | =item int ev_priority (ev_TYPE *watcher) |
1330 | =item int ev_priority (ev_TYPE *watcher) |
944 | |
1331 | |
945 | Set and query the priority of the watcher. The priority is a small |
1332 | Set and query the priority of the watcher. The priority is a small |
946 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1333 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
947 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1334 | (default: C<-2>). Pending watchers with higher priority will be invoked |
948 | before watchers with lower priority, but priority will not keep watchers |
1335 | before watchers with lower priority, but priority will not keep watchers |
949 | from being executed (except for C<ev_idle> watchers). |
1336 | from being executed (except for C<ev_idle> watchers). |
950 | |
1337 | |
951 | This means that priorities are I<only> used for ordering callback |
|
|
952 | invocation after new events have been received. This is useful, for |
|
|
953 | example, to reduce latency after idling, or more often, to bind two |
|
|
954 | watchers on the same event and make sure one is called first. |
|
|
955 | |
|
|
956 | If you need to suppress invocation when higher priority events are pending |
1338 | If you need to suppress invocation when higher priority events are pending |
957 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1339 | you need to look at C<ev_idle> watchers, which provide this functionality. |
958 | |
1340 | |
959 | You I<must not> change the priority of a watcher as long as it is active or |
1341 | You I<must not> change the priority of a watcher as long as it is active or |
960 | pending. |
1342 | pending. |
961 | |
1343 | |
|
|
1344 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1345 | fine, as long as you do not mind that the priority value you query might |
|
|
1346 | or might not have been clamped to the valid range. |
|
|
1347 | |
962 | The default priority used by watchers when no priority has been set is |
1348 | The default priority used by watchers when no priority has been set is |
963 | always C<0>, which is supposed to not be too high and not be too low :). |
1349 | always C<0>, which is supposed to not be too high and not be too low :). |
964 | |
1350 | |
965 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1351 | See L</WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
966 | fine, as long as you do not mind that the priority value you query might |
1352 | priorities. |
967 | or might not have been adjusted to be within valid range. |
|
|
968 | |
1353 | |
969 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1354 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
970 | |
1355 | |
971 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1356 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
972 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1357 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
973 | can deal with that fact. |
1358 | can deal with that fact, as both are simply passed through to the |
|
|
1359 | callback. |
974 | |
1360 | |
975 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1361 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
976 | |
1362 | |
977 | If the watcher is pending, this function returns clears its pending status |
1363 | If the watcher is pending, this function clears its pending status and |
978 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1364 | returns its C<revents> bitset (as if its callback was invoked). If the |
979 | watcher isn't pending it does nothing and returns C<0>. |
1365 | watcher isn't pending it does nothing and returns C<0>. |
980 | |
1366 | |
|
|
1367 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1368 | callback to be invoked, which can be accomplished with this function. |
|
|
1369 | |
|
|
1370 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1371 | |
|
|
1372 | Feeds the given event set into the event loop, as if the specified event |
|
|
1373 | had happened for the specified watcher (which must be a pointer to an |
|
|
1374 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1375 | not free the watcher as long as it has pending events. |
|
|
1376 | |
|
|
1377 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1378 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1379 | not started in the first place. |
|
|
1380 | |
|
|
1381 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1382 | functions that do not need a watcher. |
|
|
1383 | |
981 | =back |
1384 | =back |
982 | |
1385 | |
|
|
1386 | See also the L</ASSOCIATING CUSTOM DATA WITH A WATCHER> and L</BUILDING YOUR |
|
|
1387 | OWN COMPOSITE WATCHERS> idioms. |
983 | |
1388 | |
984 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1389 | =head2 WATCHER STATES |
985 | |
1390 | |
986 | Each watcher has, by default, a member C<void *data> that you can change |
1391 | There are various watcher states mentioned throughout this manual - |
987 | and read at any time, libev will completely ignore it. This can be used |
1392 | active, pending and so on. In this section these states and the rules to |
988 | to associate arbitrary data with your watcher. If you need more data and |
1393 | transition between them will be described in more detail - and while these |
989 | don't want to allocate memory and store a pointer to it in that data |
1394 | rules might look complicated, they usually do "the right thing". |
990 | member, you can also "subclass" the watcher type and provide your own |
|
|
991 | data: |
|
|
992 | |
1395 | |
993 | struct my_io |
1396 | =over 4 |
|
|
1397 | |
|
|
1398 | =item initialiased |
|
|
1399 | |
|
|
1400 | Before a watcher can be registered with the event loop it has to be |
|
|
1401 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1402 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1403 | |
|
|
1404 | In this state it is simply some block of memory that is suitable for |
|
|
1405 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1406 | will - as long as you either keep the memory contents intact, or call |
|
|
1407 | C<ev_TYPE_init> again. |
|
|
1408 | |
|
|
1409 | =item started/running/active |
|
|
1410 | |
|
|
1411 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1412 | property of the event loop, and is actively waiting for events. While in |
|
|
1413 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1414 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1415 | and call libev functions on it that are documented to work on active watchers. |
|
|
1416 | |
|
|
1417 | =item pending |
|
|
1418 | |
|
|
1419 | If a watcher is active and libev determines that an event it is interested |
|
|
1420 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1421 | stay in this pending state until either it is stopped or its callback is |
|
|
1422 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1423 | callback. |
|
|
1424 | |
|
|
1425 | The watcher might or might not be active while it is pending (for example, |
|
|
1426 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1427 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1428 | but it is still property of the event loop at this time, so cannot be |
|
|
1429 | moved, freed or reused. And if it is active the rules described in the |
|
|
1430 | previous item still apply. |
|
|
1431 | |
|
|
1432 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1433 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1434 | active. |
|
|
1435 | |
|
|
1436 | =item stopped |
|
|
1437 | |
|
|
1438 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1439 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1440 | latter will clear any pending state the watcher might be in, regardless |
|
|
1441 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1442 | freeing it is often a good idea. |
|
|
1443 | |
|
|
1444 | While stopped (and not pending) the watcher is essentially in the |
|
|
1445 | initialised state, that is, it can be reused, moved, modified in any way |
|
|
1446 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1447 | it again). |
|
|
1448 | |
|
|
1449 | =back |
|
|
1450 | |
|
|
1451 | =head2 WATCHER PRIORITY MODELS |
|
|
1452 | |
|
|
1453 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1454 | integers that influence the ordering of event callback invocation |
|
|
1455 | between watchers in some way, all else being equal. |
|
|
1456 | |
|
|
1457 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1458 | description for the more technical details such as the actual priority |
|
|
1459 | range. |
|
|
1460 | |
|
|
1461 | There are two common ways how these these priorities are being interpreted |
|
|
1462 | by event loops: |
|
|
1463 | |
|
|
1464 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1465 | of lower priority watchers, which means as long as higher priority |
|
|
1466 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1467 | |
|
|
1468 | The less common only-for-ordering model uses priorities solely to order |
|
|
1469 | callback invocation within a single event loop iteration: Higher priority |
|
|
1470 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1471 | before polling for new events. |
|
|
1472 | |
|
|
1473 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1474 | except for idle watchers (which use the lock-out model). |
|
|
1475 | |
|
|
1476 | The rationale behind this is that implementing the lock-out model for |
|
|
1477 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1478 | libraries will just poll for the same events again and again as long as |
|
|
1479 | their callbacks have not been executed, which is very inefficient in the |
|
|
1480 | common case of one high-priority watcher locking out a mass of lower |
|
|
1481 | priority ones. |
|
|
1482 | |
|
|
1483 | Static (ordering) priorities are most useful when you have two or more |
|
|
1484 | watchers handling the same resource: a typical usage example is having an |
|
|
1485 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1486 | timeouts. Under load, data might be received while the program handles |
|
|
1487 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1488 | handler will be executed before checking for data. In that case, giving |
|
|
1489 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1490 | handled first even under adverse conditions (which is usually, but not |
|
|
1491 | always, what you want). |
|
|
1492 | |
|
|
1493 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1494 | will only be executed when no same or higher priority watchers have |
|
|
1495 | received events, they can be used to implement the "lock-out" model when |
|
|
1496 | required. |
|
|
1497 | |
|
|
1498 | For example, to emulate how many other event libraries handle priorities, |
|
|
1499 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1500 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1501 | processing is done in the idle watcher callback. This causes libev to |
|
|
1502 | continuously poll and process kernel event data for the watcher, but when |
|
|
1503 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1504 | workable. |
|
|
1505 | |
|
|
1506 | Usually, however, the lock-out model implemented that way will perform |
|
|
1507 | miserably under the type of load it was designed to handle. In that case, |
|
|
1508 | it might be preferable to stop the real watcher before starting the |
|
|
1509 | idle watcher, so the kernel will not have to process the event in case |
|
|
1510 | the actual processing will be delayed for considerable time. |
|
|
1511 | |
|
|
1512 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1513 | priority than the default, and which should only process data when no |
|
|
1514 | other events are pending: |
|
|
1515 | |
|
|
1516 | ev_idle idle; // actual processing watcher |
|
|
1517 | ev_io io; // actual event watcher |
|
|
1518 | |
|
|
1519 | static void |
|
|
1520 | io_cb (EV_P_ ev_io *w, int revents) |
994 | { |
1521 | { |
995 | struct ev_io io; |
1522 | // stop the I/O watcher, we received the event, but |
996 | int otherfd; |
1523 | // are not yet ready to handle it. |
997 | void *somedata; |
1524 | ev_io_stop (EV_A_ w); |
998 | struct whatever *mostinteresting; |
1525 | |
|
|
1526 | // start the idle watcher to handle the actual event. |
|
|
1527 | // it will not be executed as long as other watchers |
|
|
1528 | // with the default priority are receiving events. |
|
|
1529 | ev_idle_start (EV_A_ &idle); |
999 | } |
1530 | } |
1000 | |
1531 | |
1001 | And since your callback will be called with a pointer to the watcher, you |
1532 | static void |
1002 | can cast it back to your own type: |
1533 | idle_cb (EV_P_ ev_idle *w, int revents) |
1003 | |
|
|
1004 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
|
|
1005 | { |
1534 | { |
1006 | struct my_io *w = (struct my_io *)w_; |
1535 | // actual processing |
1007 | ... |
1536 | read (STDIN_FILENO, ...); |
|
|
1537 | |
|
|
1538 | // have to start the I/O watcher again, as |
|
|
1539 | // we have handled the event |
|
|
1540 | ev_io_start (EV_P_ &io); |
1008 | } |
1541 | } |
1009 | |
1542 | |
1010 | More interesting and less C-conformant ways of casting your callback type |
1543 | // initialisation |
1011 | instead have been omitted. |
1544 | ev_idle_init (&idle, idle_cb); |
|
|
1545 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1546 | ev_io_start (EV_DEFAULT_ &io); |
1012 | |
1547 | |
1013 | Another common scenario is having some data structure with multiple |
1548 | In the "real" world, it might also be beneficial to start a timer, so that |
1014 | watchers: |
1549 | low-priority connections can not be locked out forever under load. This |
1015 | |
1550 | enables your program to keep a lower latency for important connections |
1016 | struct my_biggy |
1551 | during short periods of high load, while not completely locking out less |
1017 | { |
1552 | important ones. |
1018 | int some_data; |
|
|
1019 | ev_timer t1; |
|
|
1020 | ev_timer t2; |
|
|
1021 | } |
|
|
1022 | |
|
|
1023 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
|
|
1024 | you need to use C<offsetof>: |
|
|
1025 | |
|
|
1026 | #include <stddef.h> |
|
|
1027 | |
|
|
1028 | static void |
|
|
1029 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1030 | { |
|
|
1031 | struct my_biggy big = (struct my_biggy * |
|
|
1032 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1033 | } |
|
|
1034 | |
|
|
1035 | static void |
|
|
1036 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
|
|
1037 | { |
|
|
1038 | struct my_biggy big = (struct my_biggy * |
|
|
1039 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1040 | } |
|
|
1041 | |
1553 | |
1042 | |
1554 | |
1043 | =head1 WATCHER TYPES |
1555 | =head1 WATCHER TYPES |
1044 | |
1556 | |
1045 | This section describes each watcher in detail, but will not repeat |
1557 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1069 | In general you can register as many read and/or write event watchers per |
1581 | In general you can register as many read and/or write event watchers per |
1070 | fd as you want (as long as you don't confuse yourself). Setting all file |
1582 | fd as you want (as long as you don't confuse yourself). Setting all file |
1071 | descriptors to non-blocking mode is also usually a good idea (but not |
1583 | descriptors to non-blocking mode is also usually a good idea (but not |
1072 | required if you know what you are doing). |
1584 | required if you know what you are doing). |
1073 | |
1585 | |
1074 | If you must do this, then force the use of a known-to-be-good backend |
|
|
1075 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
|
|
1076 | C<EVBACKEND_POLL>). |
|
|
1077 | |
|
|
1078 | Another thing you have to watch out for is that it is quite easy to |
1586 | Another thing you have to watch out for is that it is quite easy to |
1079 | receive "spurious" readiness notifications, that is your callback might |
1587 | receive "spurious" readiness notifications, that is, your callback might |
1080 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1588 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1081 | because there is no data. Not only are some backends known to create a |
1589 | because there is no data. It is very easy to get into this situation even |
1082 | lot of those (for example Solaris ports), it is very easy to get into |
1590 | with a relatively standard program structure. Thus it is best to always |
1083 | this situation even with a relatively standard program structure. Thus |
1591 | use non-blocking I/O: An extra C<read>(2) returning C<EAGAIN> is far |
1084 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
|
|
1085 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1592 | preferable to a program hanging until some data arrives. |
1086 | |
1593 | |
1087 | If you cannot run the fd in non-blocking mode (for example you should not |
1594 | If you cannot run the fd in non-blocking mode (for example you should |
1088 | play around with an Xlib connection), then you have to separately re-test |
1595 | not play around with an Xlib connection), then you have to separately |
1089 | whether a file descriptor is really ready with a known-to-be good interface |
1596 | re-test whether a file descriptor is really ready with a known-to-be good |
1090 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1597 | interface such as poll (fortunately in the case of Xlib, it already does |
1091 | its own, so its quite safe to use). |
1598 | this on its own, so its quite safe to use). Some people additionally |
|
|
1599 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1600 | indefinitely. |
|
|
1601 | |
|
|
1602 | But really, best use non-blocking mode. |
1092 | |
1603 | |
1093 | =head3 The special problem of disappearing file descriptors |
1604 | =head3 The special problem of disappearing file descriptors |
1094 | |
1605 | |
1095 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1606 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1096 | descriptor (either by calling C<close> explicitly or by any other means, |
1607 | descriptor (either due to calling C<close> explicitly or any other means, |
1097 | such as C<dup>). The reason is that you register interest in some file |
1608 | such as C<dup2>). The reason is that you register interest in some file |
1098 | descriptor, but when it goes away, the operating system will silently drop |
1609 | descriptor, but when it goes away, the operating system will silently drop |
1099 | this interest. If another file descriptor with the same number then is |
1610 | this interest. If another file descriptor with the same number then is |
1100 | registered with libev, there is no efficient way to see that this is, in |
1611 | registered with libev, there is no efficient way to see that this is, in |
1101 | fact, a different file descriptor. |
1612 | fact, a different file descriptor. |
1102 | |
1613 | |
… | |
… | |
1120 | |
1631 | |
1121 | There is no workaround possible except not registering events |
1632 | There is no workaround possible except not registering events |
1122 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1633 | for potentially C<dup ()>'ed file descriptors, or to resort to |
1123 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1634 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1124 | |
1635 | |
|
|
1636 | =head3 The special problem of files |
|
|
1637 | |
|
|
1638 | Many people try to use C<select> (or libev) on file descriptors |
|
|
1639 | representing files, and expect it to become ready when their program |
|
|
1640 | doesn't block on disk accesses (which can take a long time on their own). |
|
|
1641 | |
|
|
1642 | However, this cannot ever work in the "expected" way - you get a readiness |
|
|
1643 | notification as soon as the kernel knows whether and how much data is |
|
|
1644 | there, and in the case of open files, that's always the case, so you |
|
|
1645 | always get a readiness notification instantly, and your read (or possibly |
|
|
1646 | write) will still block on the disk I/O. |
|
|
1647 | |
|
|
1648 | Another way to view it is that in the case of sockets, pipes, character |
|
|
1649 | devices and so on, there is another party (the sender) that delivers data |
|
|
1650 | on its own, but in the case of files, there is no such thing: the disk |
|
|
1651 | will not send data on its own, simply because it doesn't know what you |
|
|
1652 | wish to read - you would first have to request some data. |
|
|
1653 | |
|
|
1654 | Since files are typically not-so-well supported by advanced notification |
|
|
1655 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
|
|
1656 | to files, even though you should not use it. The reason for this is |
|
|
1657 | convenience: sometimes you want to watch STDIN or STDOUT, which is |
|
|
1658 | usually a tty, often a pipe, but also sometimes files or special devices |
|
|
1659 | (for example, C<epoll> on Linux works with F</dev/random> but not with |
|
|
1660 | F</dev/urandom>), and even though the file might better be served with |
|
|
1661 | asynchronous I/O instead of with non-blocking I/O, it is still useful when |
|
|
1662 | it "just works" instead of freezing. |
|
|
1663 | |
|
|
1664 | So avoid file descriptors pointing to files when you know it (e.g. use |
|
|
1665 | libeio), but use them when it is convenient, e.g. for STDIN/STDOUT, or |
|
|
1666 | when you rarely read from a file instead of from a socket, and want to |
|
|
1667 | reuse the same code path. |
|
|
1668 | |
1125 | =head3 The special problem of fork |
1669 | =head3 The special problem of fork |
1126 | |
1670 | |
1127 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1671 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
1128 | useless behaviour. Libev fully supports fork, but needs to be told about |
1672 | useless behaviour. Libev fully supports fork, but needs to be told about |
1129 | it in the child. |
1673 | it in the child if you want to continue to use it in the child. |
1130 | |
1674 | |
1131 | To support fork in your programs, you either have to call |
1675 | To support fork in your child processes, you have to call C<ev_loop_fork |
1132 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1676 | ()> after a fork in the child, enable C<EVFLAG_FORKCHECK>, or resort to |
1133 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1677 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
1134 | C<EVBACKEND_POLL>. |
|
|
1135 | |
1678 | |
1136 | =head3 The special problem of SIGPIPE |
1679 | =head3 The special problem of SIGPIPE |
1137 | |
1680 | |
1138 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1681 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1139 | when reading from a pipe whose other end has been closed, your program |
1682 | when writing to a pipe whose other end has been closed, your program gets |
1140 | gets send a SIGPIPE, which, by default, aborts your program. For most |
1683 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1141 | programs this is sensible behaviour, for daemons, this is usually |
1684 | this is sensible behaviour, for daemons, this is usually undesirable. |
1142 | undesirable. |
|
|
1143 | |
1685 | |
1144 | So when you encounter spurious, unexplained daemon exits, make sure you |
1686 | So when you encounter spurious, unexplained daemon exits, make sure you |
1145 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1687 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1146 | somewhere, as that would have given you a big clue). |
1688 | somewhere, as that would have given you a big clue). |
1147 | |
1689 | |
|
|
1690 | =head3 The special problem of accept()ing when you can't |
|
|
1691 | |
|
|
1692 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1693 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1694 | connection from the pending queue in all error cases. |
|
|
1695 | |
|
|
1696 | For example, larger servers often run out of file descriptors (because |
|
|
1697 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1698 | rejecting the connection, leading to libev signalling readiness on |
|
|
1699 | the next iteration again (the connection still exists after all), and |
|
|
1700 | typically causing the program to loop at 100% CPU usage. |
|
|
1701 | |
|
|
1702 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1703 | operating systems, there is usually little the app can do to remedy the |
|
|
1704 | situation, and no known thread-safe method of removing the connection to |
|
|
1705 | cope with overload is known (to me). |
|
|
1706 | |
|
|
1707 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1708 | - when the program encounters an overload, it will just loop until the |
|
|
1709 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1710 | event-based way to handle this situation, so it's the best one can do. |
|
|
1711 | |
|
|
1712 | A better way to handle the situation is to log any errors other than |
|
|
1713 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1714 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1715 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1716 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1717 | usage. |
|
|
1718 | |
|
|
1719 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1720 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1721 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1722 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1723 | clients under typical overload conditions. |
|
|
1724 | |
|
|
1725 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1726 | is often done with C<malloc> failures, but this results in an easy |
|
|
1727 | opportunity for a DoS attack. |
1148 | |
1728 | |
1149 | =head3 Watcher-Specific Functions |
1729 | =head3 Watcher-Specific Functions |
1150 | |
1730 | |
1151 | =over 4 |
1731 | =over 4 |
1152 | |
1732 | |
1153 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1733 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1154 | |
1734 | |
1155 | =item ev_io_set (ev_io *, int fd, int events) |
1735 | =item ev_io_set (ev_io *, int fd, int events) |
1156 | |
1736 | |
1157 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1737 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1158 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1738 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1159 | C<EV_READ | EV_WRITE> to receive the given events. |
1739 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1160 | |
1740 | |
1161 | =item int fd [read-only] |
1741 | =item int fd [read-only] |
1162 | |
1742 | |
1163 | The file descriptor being watched. |
1743 | The file descriptor being watched. |
1164 | |
1744 | |
… | |
… | |
1173 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1753 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1174 | readable, but only once. Since it is likely line-buffered, you could |
1754 | readable, but only once. Since it is likely line-buffered, you could |
1175 | attempt to read a whole line in the callback. |
1755 | attempt to read a whole line in the callback. |
1176 | |
1756 | |
1177 | static void |
1757 | static void |
1178 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1758 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1179 | { |
1759 | { |
1180 | ev_io_stop (loop, w); |
1760 | ev_io_stop (loop, w); |
1181 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1761 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1182 | } |
1762 | } |
1183 | |
1763 | |
1184 | ... |
1764 | ... |
1185 | struct ev_loop *loop = ev_default_init (0); |
1765 | struct ev_loop *loop = ev_default_init (0); |
1186 | struct ev_io stdin_readable; |
1766 | ev_io stdin_readable; |
1187 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1767 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1188 | ev_io_start (loop, &stdin_readable); |
1768 | ev_io_start (loop, &stdin_readable); |
1189 | ev_loop (loop, 0); |
1769 | ev_run (loop, 0); |
1190 | |
1770 | |
1191 | |
1771 | |
1192 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1772 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1193 | |
1773 | |
1194 | Timer watchers are simple relative timers that generate an event after a |
1774 | Timer watchers are simple relative timers that generate an event after a |
1195 | given time, and optionally repeating in regular intervals after that. |
1775 | given time, and optionally repeating in regular intervals after that. |
1196 | |
1776 | |
1197 | The timers are based on real time, that is, if you register an event that |
1777 | The timers are based on real time, that is, if you register an event that |
1198 | times out after an hour and you reset your system clock to January last |
1778 | times out after an hour and you reset your system clock to January last |
1199 | year, it will still time out after (roughly) and hour. "Roughly" because |
1779 | year, it will still time out after (roughly) one hour. "Roughly" because |
1200 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1780 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1201 | monotonic clock option helps a lot here). |
1781 | monotonic clock option helps a lot here). |
|
|
1782 | |
|
|
1783 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1784 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1785 | might introduce a small delay, see "the special problem of being too |
|
|
1786 | early", below). If multiple timers become ready during the same loop |
|
|
1787 | iteration then the ones with earlier time-out values are invoked before |
|
|
1788 | ones of the same priority with later time-out values (but this is no |
|
|
1789 | longer true when a callback calls C<ev_run> recursively). |
|
|
1790 | |
|
|
1791 | =head3 Be smart about timeouts |
|
|
1792 | |
|
|
1793 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1794 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1795 | you want to raise some error after a while. |
|
|
1796 | |
|
|
1797 | What follows are some ways to handle this problem, from obvious and |
|
|
1798 | inefficient to smart and efficient. |
|
|
1799 | |
|
|
1800 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1801 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1802 | data or other life sign was received). |
|
|
1803 | |
|
|
1804 | =over 4 |
|
|
1805 | |
|
|
1806 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1807 | |
|
|
1808 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1809 | start the watcher: |
|
|
1810 | |
|
|
1811 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1812 | ev_timer_start (loop, timer); |
|
|
1813 | |
|
|
1814 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1815 | and start it again: |
|
|
1816 | |
|
|
1817 | ev_timer_stop (loop, timer); |
|
|
1818 | ev_timer_set (timer, 60., 0.); |
|
|
1819 | ev_timer_start (loop, timer); |
|
|
1820 | |
|
|
1821 | This is relatively simple to implement, but means that each time there is |
|
|
1822 | some activity, libev will first have to remove the timer from its internal |
|
|
1823 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1824 | still not a constant-time operation. |
|
|
1825 | |
|
|
1826 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1827 | |
|
|
1828 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1829 | C<ev_timer_start>. |
|
|
1830 | |
|
|
1831 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1832 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1833 | successfully read or write some data. If you go into an idle state where |
|
|
1834 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1835 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1836 | |
|
|
1837 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1838 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1839 | member and C<ev_timer_again>. |
|
|
1840 | |
|
|
1841 | At start: |
|
|
1842 | |
|
|
1843 | ev_init (timer, callback); |
|
|
1844 | timer->repeat = 60.; |
|
|
1845 | ev_timer_again (loop, timer); |
|
|
1846 | |
|
|
1847 | Each time there is some activity: |
|
|
1848 | |
|
|
1849 | ev_timer_again (loop, timer); |
|
|
1850 | |
|
|
1851 | It is even possible to change the time-out on the fly, regardless of |
|
|
1852 | whether the watcher is active or not: |
|
|
1853 | |
|
|
1854 | timer->repeat = 30.; |
|
|
1855 | ev_timer_again (loop, timer); |
|
|
1856 | |
|
|
1857 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1858 | you want to modify its timeout value, as libev does not have to completely |
|
|
1859 | remove and re-insert the timer from/into its internal data structure. |
|
|
1860 | |
|
|
1861 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1862 | |
|
|
1863 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1864 | |
|
|
1865 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1866 | relatively long compared to the intervals between other activity - in |
|
|
1867 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1868 | associated activity resets. |
|
|
1869 | |
|
|
1870 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1871 | but remember the time of last activity, and check for a real timeout only |
|
|
1872 | within the callback: |
|
|
1873 | |
|
|
1874 | ev_tstamp timeout = 60.; |
|
|
1875 | ev_tstamp last_activity; // time of last activity |
|
|
1876 | ev_timer timer; |
|
|
1877 | |
|
|
1878 | static void |
|
|
1879 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1880 | { |
|
|
1881 | // calculate when the timeout would happen |
|
|
1882 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
|
|
1883 | |
|
|
1884 | // if negative, it means we the timeout already occurred |
|
|
1885 | if (after < 0.) |
|
|
1886 | { |
|
|
1887 | // timeout occurred, take action |
|
|
1888 | } |
|
|
1889 | else |
|
|
1890 | { |
|
|
1891 | // callback was invoked, but there was some recent |
|
|
1892 | // activity. simply restart the timer to time out |
|
|
1893 | // after "after" seconds, which is the earliest time |
|
|
1894 | // the timeout can occur. |
|
|
1895 | ev_timer_set (w, after, 0.); |
|
|
1896 | ev_timer_start (EV_A_ w); |
|
|
1897 | } |
|
|
1898 | } |
|
|
1899 | |
|
|
1900 | To summarise the callback: first calculate in how many seconds the |
|
|
1901 | timeout will occur (by calculating the absolute time when it would occur, |
|
|
1902 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
|
|
1903 | (EV_A)> from that). |
|
|
1904 | |
|
|
1905 | If this value is negative, then we are already past the timeout, i.e. we |
|
|
1906 | timed out, and need to do whatever is needed in this case. |
|
|
1907 | |
|
|
1908 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1909 | and simply start the timer with this timeout value. |
|
|
1910 | |
|
|
1911 | In other words, each time the callback is invoked it will check whether |
|
|
1912 | the timeout occurred. If not, it will simply reschedule itself to check |
|
|
1913 | again at the earliest time it could time out. Rinse. Repeat. |
|
|
1914 | |
|
|
1915 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1916 | minus half the average time between activity), but virtually no calls to |
|
|
1917 | libev to change the timeout. |
|
|
1918 | |
|
|
1919 | To start the machinery, simply initialise the watcher and set |
|
|
1920 | C<last_activity> to the current time (meaning there was some activity just |
|
|
1921 | now), then call the callback, which will "do the right thing" and start |
|
|
1922 | the timer: |
|
|
1923 | |
|
|
1924 | last_activity = ev_now (EV_A); |
|
|
1925 | ev_init (&timer, callback); |
|
|
1926 | callback (EV_A_ &timer, 0); |
|
|
1927 | |
|
|
1928 | When there is some activity, simply store the current time in |
|
|
1929 | C<last_activity>, no libev calls at all: |
|
|
1930 | |
|
|
1931 | if (activity detected) |
|
|
1932 | last_activity = ev_now (EV_A); |
|
|
1933 | |
|
|
1934 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1935 | providing a new value, stopping the timer and calling the callback, which |
|
|
1936 | will again do the right thing (for example, time out immediately :). |
|
|
1937 | |
|
|
1938 | timeout = new_value; |
|
|
1939 | ev_timer_stop (EV_A_ &timer); |
|
|
1940 | callback (EV_A_ &timer, 0); |
|
|
1941 | |
|
|
1942 | This technique is slightly more complex, but in most cases where the |
|
|
1943 | time-out is unlikely to be triggered, much more efficient. |
|
|
1944 | |
|
|
1945 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1946 | |
|
|
1947 | If there is not one request, but many thousands (millions...), all |
|
|
1948 | employing some kind of timeout with the same timeout value, then one can |
|
|
1949 | do even better: |
|
|
1950 | |
|
|
1951 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1952 | at the I<end> of the list. |
|
|
1953 | |
|
|
1954 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1955 | the list is expected to fire (for example, using the technique #3). |
|
|
1956 | |
|
|
1957 | When there is some activity, remove the timer from the list, recalculate |
|
|
1958 | the timeout, append it to the end of the list again, and make sure to |
|
|
1959 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1960 | |
|
|
1961 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1962 | starting, stopping and updating the timers, at the expense of a major |
|
|
1963 | complication, and having to use a constant timeout. The constant timeout |
|
|
1964 | ensures that the list stays sorted. |
|
|
1965 | |
|
|
1966 | =back |
|
|
1967 | |
|
|
1968 | So which method the best? |
|
|
1969 | |
|
|
1970 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1971 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1972 | better, and isn't very complicated either. In most case, choosing either |
|
|
1973 | one is fine, with #3 being better in typical situations. |
|
|
1974 | |
|
|
1975 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1976 | rather complicated, but extremely efficient, something that really pays |
|
|
1977 | off after the first million or so of active timers, i.e. it's usually |
|
|
1978 | overkill :) |
|
|
1979 | |
|
|
1980 | =head3 The special problem of being too early |
|
|
1981 | |
|
|
1982 | If you ask a timer to call your callback after three seconds, then |
|
|
1983 | you expect it to be invoked after three seconds - but of course, this |
|
|
1984 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1985 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1986 | process with a STOP signal for a few hours for example. |
|
|
1987 | |
|
|
1988 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1989 | delay has occurred, but cannot guarantee this. |
|
|
1990 | |
|
|
1991 | A less obvious failure mode is calling your callback too early: many event |
|
|
1992 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1993 | this can cause your callback to be invoked much earlier than you would |
|
|
1994 | expect. |
|
|
1995 | |
|
|
1996 | To see why, imagine a system with a clock that only offers full second |
|
|
1997 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1998 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1999 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
2000 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
2001 | |
|
|
2002 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
2003 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
2004 | one-second delay was requested - this is being "too early", despite best |
|
|
2005 | intentions. |
|
|
2006 | |
|
|
2007 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2008 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2009 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2010 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2011 | |
|
|
2012 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2013 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2014 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2015 | late" side of things. |
|
|
2016 | |
|
|
2017 | =head3 The special problem of time updates |
|
|
2018 | |
|
|
2019 | Establishing the current time is a costly operation (it usually takes |
|
|
2020 | at least one system call): EV therefore updates its idea of the current |
|
|
2021 | time only before and after C<ev_run> collects new events, which causes a |
|
|
2022 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
2023 | lots of events in one iteration. |
1202 | |
2024 | |
1203 | The relative timeouts are calculated relative to the C<ev_now ()> |
2025 | The relative timeouts are calculated relative to the C<ev_now ()> |
1204 | time. This is usually the right thing as this timestamp refers to the time |
2026 | time. This is usually the right thing as this timestamp refers to the time |
1205 | of the event triggering whatever timeout you are modifying/starting. If |
2027 | of the event triggering whatever timeout you are modifying/starting. If |
1206 | you suspect event processing to be delayed and you I<need> to base the timeout |
2028 | you suspect event processing to be delayed and you I<need> to base the |
1207 | on the current time, use something like this to adjust for this: |
2029 | timeout on the current time, use something like this to adjust for this: |
1208 | |
2030 | |
1209 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2031 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1210 | |
2032 | |
1211 | The callback is guaranteed to be invoked only after its timeout has passed, |
2033 | If the event loop is suspended for a long time, you can also force an |
1212 | but if multiple timers become ready during the same loop iteration then |
2034 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1213 | order of execution is undefined. |
2035 | ()>. |
|
|
2036 | |
|
|
2037 | =head3 The special problem of unsynchronised clocks |
|
|
2038 | |
|
|
2039 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2040 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2041 | jumps). |
|
|
2042 | |
|
|
2043 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2044 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2045 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2046 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2047 | than a directly following call to C<time>. |
|
|
2048 | |
|
|
2049 | The moral of this is to only compare libev-related timestamps with |
|
|
2050 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2051 | a second or so. |
|
|
2052 | |
|
|
2053 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2054 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2055 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2056 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2057 | |
|
|
2058 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2059 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2060 | I<measured according to the real time>, not the system clock. |
|
|
2061 | |
|
|
2062 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2063 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2064 | exactly the right behaviour. |
|
|
2065 | |
|
|
2066 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2067 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2068 | time, where your comparisons will always generate correct results. |
|
|
2069 | |
|
|
2070 | =head3 The special problems of suspended animation |
|
|
2071 | |
|
|
2072 | When you leave the server world it is quite customary to hit machines that |
|
|
2073 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
2074 | |
|
|
2075 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
2076 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2077 | to run until the system is suspended, but they will not advance while the |
|
|
2078 | system is suspended. That means, on resume, it will be as if the program |
|
|
2079 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2080 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2081 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2082 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2083 | be adjusted accordingly. |
|
|
2084 | |
|
|
2085 | I would not be surprised to see different behaviour in different between |
|
|
2086 | operating systems, OS versions or even different hardware. |
|
|
2087 | |
|
|
2088 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2089 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2090 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2091 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2092 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2093 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2094 | |
|
|
2095 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2096 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2097 | deterministic behaviour in this case (you can do nothing against |
|
|
2098 | C<SIGSTOP>). |
1214 | |
2099 | |
1215 | =head3 Watcher-Specific Functions and Data Members |
2100 | =head3 Watcher-Specific Functions and Data Members |
1216 | |
2101 | |
1217 | =over 4 |
2102 | =over 4 |
1218 | |
2103 | |
… | |
… | |
1232 | keep up with the timer (because it takes longer than those 10 seconds to |
2117 | keep up with the timer (because it takes longer than those 10 seconds to |
1233 | do stuff) the timer will not fire more than once per event loop iteration. |
2118 | do stuff) the timer will not fire more than once per event loop iteration. |
1234 | |
2119 | |
1235 | =item ev_timer_again (loop, ev_timer *) |
2120 | =item ev_timer_again (loop, ev_timer *) |
1236 | |
2121 | |
1237 | This will act as if the timer timed out and restart it again if it is |
2122 | This will act as if the timer timed out, and restarts it again if it is |
1238 | repeating. The exact semantics are: |
2123 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2124 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
1239 | |
2125 | |
|
|
2126 | The exact semantics are as in the following rules, all of which will be |
|
|
2127 | applied to the watcher: |
|
|
2128 | |
|
|
2129 | =over 4 |
|
|
2130 | |
1240 | If the timer is pending, its pending status is cleared. |
2131 | =item If the timer is pending, the pending status is always cleared. |
1241 | |
2132 | |
1242 | If the timer is started but non-repeating, stop it (as if it timed out). |
2133 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2134 | out, without invoking it). |
1243 | |
2135 | |
1244 | If the timer is repeating, either start it if necessary (with the |
2136 | =item If the timer is repeating, make the C<repeat> value the new timeout |
1245 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2137 | and start the timer, if necessary. |
1246 | |
2138 | |
1247 | This sounds a bit complicated, but here is a useful and typical |
2139 | =back |
1248 | example: Imagine you have a TCP connection and you want a so-called idle |
|
|
1249 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1250 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1251 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1252 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1253 | you go into an idle state where you do not expect data to travel on the |
|
|
1254 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1255 | automatically restart it if need be. |
|
|
1256 | |
2140 | |
1257 | That means you can ignore the C<after> value and C<ev_timer_start> |
2141 | This sounds a bit complicated, see L</Be smart about timeouts>, above, for a |
1258 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
2142 | usage example. |
1259 | |
2143 | |
1260 | ev_timer_init (timer, callback, 0., 5.); |
2144 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1261 | ev_timer_again (loop, timer); |
|
|
1262 | ... |
|
|
1263 | timer->again = 17.; |
|
|
1264 | ev_timer_again (loop, timer); |
|
|
1265 | ... |
|
|
1266 | timer->again = 10.; |
|
|
1267 | ev_timer_again (loop, timer); |
|
|
1268 | |
2145 | |
1269 | This is more slightly efficient then stopping/starting the timer each time |
2146 | Returns the remaining time until a timer fires. If the timer is active, |
1270 | you want to modify its timeout value. |
2147 | then this time is relative to the current event loop time, otherwise it's |
|
|
2148 | the timeout value currently configured. |
|
|
2149 | |
|
|
2150 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
|
|
2151 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2152 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2153 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2154 | too), and so on. |
1271 | |
2155 | |
1272 | =item ev_tstamp repeat [read-write] |
2156 | =item ev_tstamp repeat [read-write] |
1273 | |
2157 | |
1274 | The current C<repeat> value. Will be used each time the watcher times out |
2158 | The current C<repeat> value. Will be used each time the watcher times out |
1275 | or C<ev_timer_again> is called and determines the next timeout (if any), |
2159 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1276 | which is also when any modifications are taken into account. |
2160 | which is also when any modifications are taken into account. |
1277 | |
2161 | |
1278 | =back |
2162 | =back |
1279 | |
2163 | |
1280 | =head3 Examples |
2164 | =head3 Examples |
1281 | |
2165 | |
1282 | Example: Create a timer that fires after 60 seconds. |
2166 | Example: Create a timer that fires after 60 seconds. |
1283 | |
2167 | |
1284 | static void |
2168 | static void |
1285 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2169 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1286 | { |
2170 | { |
1287 | .. one minute over, w is actually stopped right here |
2171 | .. one minute over, w is actually stopped right here |
1288 | } |
2172 | } |
1289 | |
2173 | |
1290 | struct ev_timer mytimer; |
2174 | ev_timer mytimer; |
1291 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2175 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1292 | ev_timer_start (loop, &mytimer); |
2176 | ev_timer_start (loop, &mytimer); |
1293 | |
2177 | |
1294 | Example: Create a timeout timer that times out after 10 seconds of |
2178 | Example: Create a timeout timer that times out after 10 seconds of |
1295 | inactivity. |
2179 | inactivity. |
1296 | |
2180 | |
1297 | static void |
2181 | static void |
1298 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2182 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1299 | { |
2183 | { |
1300 | .. ten seconds without any activity |
2184 | .. ten seconds without any activity |
1301 | } |
2185 | } |
1302 | |
2186 | |
1303 | struct ev_timer mytimer; |
2187 | ev_timer mytimer; |
1304 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2188 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1305 | ev_timer_again (&mytimer); /* start timer */ |
2189 | ev_timer_again (&mytimer); /* start timer */ |
1306 | ev_loop (loop, 0); |
2190 | ev_run (loop, 0); |
1307 | |
2191 | |
1308 | // and in some piece of code that gets executed on any "activity": |
2192 | // and in some piece of code that gets executed on any "activity": |
1309 | // reset the timeout to start ticking again at 10 seconds |
2193 | // reset the timeout to start ticking again at 10 seconds |
1310 | ev_timer_again (&mytimer); |
2194 | ev_timer_again (&mytimer); |
1311 | |
2195 | |
… | |
… | |
1313 | =head2 C<ev_periodic> - to cron or not to cron? |
2197 | =head2 C<ev_periodic> - to cron or not to cron? |
1314 | |
2198 | |
1315 | Periodic watchers are also timers of a kind, but they are very versatile |
2199 | Periodic watchers are also timers of a kind, but they are very versatile |
1316 | (and unfortunately a bit complex). |
2200 | (and unfortunately a bit complex). |
1317 | |
2201 | |
1318 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2202 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1319 | but on wall clock time (absolute time). You can tell a periodic watcher |
2203 | relative time, the physical time that passes) but on wall clock time |
1320 | to trigger after some specific point in time. For example, if you tell a |
2204 | (absolute time, the thing you can read on your calender or clock). The |
1321 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2205 | difference is that wall clock time can run faster or slower than real |
1322 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2206 | time, and time jumps are not uncommon (e.g. when you adjust your |
1323 | clock to January of the previous year, then it will take more than year |
2207 | wrist-watch). |
1324 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1325 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1326 | |
2208 | |
|
|
2209 | You can tell a periodic watcher to trigger after some specific point |
|
|
2210 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2211 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2212 | not a delay) and then reset your system clock to January of the previous |
|
|
2213 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2214 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2215 | it, as it uses a relative timeout). |
|
|
2216 | |
1327 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2217 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1328 | such as triggering an event on each "midnight, local time", or other |
2218 | timers, such as triggering an event on each "midnight, local time", or |
1329 | complicated, rules. |
2219 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2220 | those cannot react to time jumps. |
1330 | |
2221 | |
1331 | As with timers, the callback is guaranteed to be invoked only when the |
2222 | As with timers, the callback is guaranteed to be invoked only when the |
1332 | time (C<at>) has passed, but if multiple periodic timers become ready |
2223 | point in time where it is supposed to trigger has passed. If multiple |
1333 | during the same loop iteration then order of execution is undefined. |
2224 | timers become ready during the same loop iteration then the ones with |
|
|
2225 | earlier time-out values are invoked before ones with later time-out values |
|
|
2226 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1334 | |
2227 | |
1335 | =head3 Watcher-Specific Functions and Data Members |
2228 | =head3 Watcher-Specific Functions and Data Members |
1336 | |
2229 | |
1337 | =over 4 |
2230 | =over 4 |
1338 | |
2231 | |
1339 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2232 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1340 | |
2233 | |
1341 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2234 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1342 | |
2235 | |
1343 | Lots of arguments, lets sort it out... There are basically three modes of |
2236 | Lots of arguments, let's sort it out... There are basically three modes of |
1344 | operation, and we will explain them from simplest to complex: |
2237 | operation, and we will explain them from simplest to most complex: |
1345 | |
2238 | |
1346 | =over 4 |
2239 | =over 4 |
1347 | |
2240 | |
1348 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2241 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1349 | |
2242 | |
1350 | In this configuration the watcher triggers an event after the wall clock |
2243 | In this configuration the watcher triggers an event after the wall clock |
1351 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2244 | time C<offset> has passed. It will not repeat and will not adjust when a |
1352 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2245 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1353 | run when the system time reaches or surpasses this time. |
2246 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2247 | this point in time. |
1354 | |
2248 | |
1355 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2249 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1356 | |
2250 | |
1357 | In this mode the watcher will always be scheduled to time out at the next |
2251 | In this mode the watcher will always be scheduled to time out at the next |
1358 | C<at + N * interval> time (for some integer N, which can also be negative) |
2252 | C<offset + N * interval> time (for some integer N, which can also be |
1359 | and then repeat, regardless of any time jumps. |
2253 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2254 | argument is merely an offset into the C<interval> periods. |
1360 | |
2255 | |
1361 | This can be used to create timers that do not drift with respect to system |
2256 | This can be used to create timers that do not drift with respect to the |
1362 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2257 | system clock, for example, here is an C<ev_periodic> that triggers each |
1363 | the hour: |
2258 | hour, on the hour (with respect to UTC): |
1364 | |
2259 | |
1365 | ev_periodic_set (&periodic, 0., 3600., 0); |
2260 | ev_periodic_set (&periodic, 0., 3600., 0); |
1366 | |
2261 | |
1367 | This doesn't mean there will always be 3600 seconds in between triggers, |
2262 | This doesn't mean there will always be 3600 seconds in between triggers, |
1368 | but only that the callback will be called when the system time shows a |
2263 | but only that the callback will be called when the system time shows a |
1369 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2264 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1370 | by 3600. |
2265 | by 3600. |
1371 | |
2266 | |
1372 | Another way to think about it (for the mathematically inclined) is that |
2267 | Another way to think about it (for the mathematically inclined) is that |
1373 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2268 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1374 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2269 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1375 | |
2270 | |
1376 | For numerical stability it is preferable that the C<at> value is near |
2271 | The C<interval> I<MUST> be positive, and for numerical stability, the |
1377 | C<ev_now ()> (the current time), but there is no range requirement for |
2272 | interval value should be higher than C<1/8192> (which is around 100 |
1378 | this value, and in fact is often specified as zero. |
2273 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2274 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2275 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2276 | C<0> and C<interval>, which is also the recommended range. |
1379 | |
2277 | |
1380 | Note also that there is an upper limit to how often a timer can fire (CPU |
2278 | Note also that there is an upper limit to how often a timer can fire (CPU |
1381 | speed for example), so if C<interval> is very small then timing stability |
2279 | speed for example), so if C<interval> is very small then timing stability |
1382 | will of course deteriorate. Libev itself tries to be exact to be about one |
2280 | will of course deteriorate. Libev itself tries to be exact to be about one |
1383 | millisecond (if the OS supports it and the machine is fast enough). |
2281 | millisecond (if the OS supports it and the machine is fast enough). |
1384 | |
2282 | |
1385 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2283 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1386 | |
2284 | |
1387 | In this mode the values for C<interval> and C<at> are both being |
2285 | In this mode the values for C<interval> and C<offset> are both being |
1388 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2286 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1389 | reschedule callback will be called with the watcher as first, and the |
2287 | reschedule callback will be called with the watcher as first, and the |
1390 | current time as second argument. |
2288 | current time as second argument. |
1391 | |
2289 | |
1392 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2290 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1393 | ever, or make ANY event loop modifications whatsoever>. |
2291 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2292 | allowed by documentation here>. |
1394 | |
2293 | |
1395 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2294 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1396 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2295 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1397 | only event loop modification you are allowed to do). |
2296 | only event loop modification you are allowed to do). |
1398 | |
2297 | |
1399 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2298 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1400 | *w, ev_tstamp now)>, e.g.: |
2299 | *w, ev_tstamp now)>, e.g.: |
1401 | |
2300 | |
|
|
2301 | static ev_tstamp |
1402 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2302 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1403 | { |
2303 | { |
1404 | return now + 60.; |
2304 | return now + 60.; |
1405 | } |
2305 | } |
1406 | |
2306 | |
1407 | It must return the next time to trigger, based on the passed time value |
2307 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1427 | a different time than the last time it was called (e.g. in a crond like |
2327 | a different time than the last time it was called (e.g. in a crond like |
1428 | program when the crontabs have changed). |
2328 | program when the crontabs have changed). |
1429 | |
2329 | |
1430 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2330 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1431 | |
2331 | |
1432 | When active, returns the absolute time that the watcher is supposed to |
2332 | When active, returns the absolute time that the watcher is supposed |
1433 | trigger next. |
2333 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2334 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2335 | rescheduling modes. |
1434 | |
2336 | |
1435 | =item ev_tstamp offset [read-write] |
2337 | =item ev_tstamp offset [read-write] |
1436 | |
2338 | |
1437 | When repeating, this contains the offset value, otherwise this is the |
2339 | When repeating, this contains the offset value, otherwise this is the |
1438 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2340 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2341 | although libev might modify this value for better numerical stability). |
1439 | |
2342 | |
1440 | Can be modified any time, but changes only take effect when the periodic |
2343 | Can be modified any time, but changes only take effect when the periodic |
1441 | timer fires or C<ev_periodic_again> is being called. |
2344 | timer fires or C<ev_periodic_again> is being called. |
1442 | |
2345 | |
1443 | =item ev_tstamp interval [read-write] |
2346 | =item ev_tstamp interval [read-write] |
1444 | |
2347 | |
1445 | The current interval value. Can be modified any time, but changes only |
2348 | The current interval value. Can be modified any time, but changes only |
1446 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2349 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1447 | called. |
2350 | called. |
1448 | |
2351 | |
1449 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2352 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1450 | |
2353 | |
1451 | The current reschedule callback, or C<0>, if this functionality is |
2354 | The current reschedule callback, or C<0>, if this functionality is |
1452 | switched off. Can be changed any time, but changes only take effect when |
2355 | switched off. Can be changed any time, but changes only take effect when |
1453 | the periodic timer fires or C<ev_periodic_again> is being called. |
2356 | the periodic timer fires or C<ev_periodic_again> is being called. |
1454 | |
2357 | |
1455 | =back |
2358 | =back |
1456 | |
2359 | |
1457 | =head3 Examples |
2360 | =head3 Examples |
1458 | |
2361 | |
1459 | Example: Call a callback every hour, or, more precisely, whenever the |
2362 | Example: Call a callback every hour, or, more precisely, whenever the |
1460 | system clock is divisible by 3600. The callback invocation times have |
2363 | system time is divisible by 3600. The callback invocation times have |
1461 | potentially a lot of jitter, but good long-term stability. |
2364 | potentially a lot of jitter, but good long-term stability. |
1462 | |
2365 | |
1463 | static void |
2366 | static void |
1464 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2367 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1465 | { |
2368 | { |
1466 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2369 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1467 | } |
2370 | } |
1468 | |
2371 | |
1469 | struct ev_periodic hourly_tick; |
2372 | ev_periodic hourly_tick; |
1470 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2373 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1471 | ev_periodic_start (loop, &hourly_tick); |
2374 | ev_periodic_start (loop, &hourly_tick); |
1472 | |
2375 | |
1473 | Example: The same as above, but use a reschedule callback to do it: |
2376 | Example: The same as above, but use a reschedule callback to do it: |
1474 | |
2377 | |
1475 | #include <math.h> |
2378 | #include <math.h> |
1476 | |
2379 | |
1477 | static ev_tstamp |
2380 | static ev_tstamp |
1478 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2381 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1479 | { |
2382 | { |
1480 | return fmod (now, 3600.) + 3600.; |
2383 | return now + (3600. - fmod (now, 3600.)); |
1481 | } |
2384 | } |
1482 | |
2385 | |
1483 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2386 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1484 | |
2387 | |
1485 | Example: Call a callback every hour, starting now: |
2388 | Example: Call a callback every hour, starting now: |
1486 | |
2389 | |
1487 | struct ev_periodic hourly_tick; |
2390 | ev_periodic hourly_tick; |
1488 | ev_periodic_init (&hourly_tick, clock_cb, |
2391 | ev_periodic_init (&hourly_tick, clock_cb, |
1489 | fmod (ev_now (loop), 3600.), 3600., 0); |
2392 | fmod (ev_now (loop), 3600.), 3600., 0); |
1490 | ev_periodic_start (loop, &hourly_tick); |
2393 | ev_periodic_start (loop, &hourly_tick); |
1491 | |
2394 | |
1492 | |
2395 | |
1493 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2396 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1494 | |
2397 | |
1495 | Signal watchers will trigger an event when the process receives a specific |
2398 | Signal watchers will trigger an event when the process receives a specific |
1496 | signal one or more times. Even though signals are very asynchronous, libev |
2399 | signal one or more times. Even though signals are very asynchronous, libev |
1497 | will try it's best to deliver signals synchronously, i.e. as part of the |
2400 | will try its best to deliver signals synchronously, i.e. as part of the |
1498 | normal event processing, like any other event. |
2401 | normal event processing, like any other event. |
1499 | |
2402 | |
|
|
2403 | If you want signals to be delivered truly asynchronously, just use |
|
|
2404 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2405 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2406 | synchronously wake up an event loop. |
|
|
2407 | |
1500 | You can configure as many watchers as you like per signal. Only when the |
2408 | You can configure as many watchers as you like for the same signal, but |
|
|
2409 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2410 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2411 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2412 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2413 | |
1501 | first watcher gets started will libev actually register a signal watcher |
2414 | When the first watcher gets started will libev actually register something |
1502 | with the kernel (thus it coexists with your own signal handlers as long |
2415 | with the kernel (thus it coexists with your own signal handlers as long as |
1503 | as you don't register any with libev). Similarly, when the last signal |
2416 | you don't register any with libev for the same signal). |
1504 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1505 | SIG_DFL (regardless of what it was set to before). |
|
|
1506 | |
2417 | |
1507 | If possible and supported, libev will install its handlers with |
2418 | If possible and supported, libev will install its handlers with |
1508 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2419 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1509 | interrupted. If you have a problem with system calls getting interrupted by |
2420 | not be unduly interrupted. If you have a problem with system calls getting |
1510 | signals you can block all signals in an C<ev_check> watcher and unblock |
2421 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1511 | them in an C<ev_prepare> watcher. |
2422 | and unblock them in an C<ev_prepare> watcher. |
|
|
2423 | |
|
|
2424 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2425 | |
|
|
2426 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2427 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2428 | stopping it again), that is, libev might or might not block the signal, |
|
|
2429 | and might or might not set or restore the installed signal handler (but |
|
|
2430 | see C<EVFLAG_NOSIGMASK>). |
|
|
2431 | |
|
|
2432 | While this does not matter for the signal disposition (libev never |
|
|
2433 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2434 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2435 | certain signals to be blocked. |
|
|
2436 | |
|
|
2437 | This means that before calling C<exec> (from the child) you should reset |
|
|
2438 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2439 | choice usually). |
|
|
2440 | |
|
|
2441 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2442 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2443 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2444 | |
|
|
2445 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2446 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2447 | the window of opportunity for problems, it will not go away, as libev |
|
|
2448 | I<has> to modify the signal mask, at least temporarily. |
|
|
2449 | |
|
|
2450 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2451 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2452 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2453 | |
|
|
2454 | =head3 The special problem of threads signal handling |
|
|
2455 | |
|
|
2456 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2457 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2458 | threads in a process block signals, which is hard to achieve. |
|
|
2459 | |
|
|
2460 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2461 | for the same signals), you can tackle this problem by globally blocking |
|
|
2462 | all signals before creating any threads (or creating them with a fully set |
|
|
2463 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2464 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2465 | these signals. You can pass on any signals that libev might be interested |
|
|
2466 | in by calling C<ev_feed_signal>. |
1512 | |
2467 | |
1513 | =head3 Watcher-Specific Functions and Data Members |
2468 | =head3 Watcher-Specific Functions and Data Members |
1514 | |
2469 | |
1515 | =over 4 |
2470 | =over 4 |
1516 | |
2471 | |
… | |
… | |
1527 | |
2482 | |
1528 | =back |
2483 | =back |
1529 | |
2484 | |
1530 | =head3 Examples |
2485 | =head3 Examples |
1531 | |
2486 | |
1532 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2487 | Example: Try to exit cleanly on SIGINT. |
1533 | |
2488 | |
1534 | static void |
2489 | static void |
1535 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2490 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1536 | { |
2491 | { |
1537 | ev_unloop (loop, EVUNLOOP_ALL); |
2492 | ev_break (loop, EVBREAK_ALL); |
1538 | } |
2493 | } |
1539 | |
2494 | |
1540 | struct ev_signal signal_watcher; |
2495 | ev_signal signal_watcher; |
1541 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2496 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1542 | ev_signal_start (loop, &sigint_cb); |
2497 | ev_signal_start (loop, &signal_watcher); |
1543 | |
2498 | |
1544 | |
2499 | |
1545 | =head2 C<ev_child> - watch out for process status changes |
2500 | =head2 C<ev_child> - watch out for process status changes |
1546 | |
2501 | |
1547 | Child watchers trigger when your process receives a SIGCHLD in response to |
2502 | Child watchers trigger when your process receives a SIGCHLD in response to |
1548 | some child status changes (most typically when a child of yours dies). It |
2503 | some child status changes (most typically when a child of yours dies or |
1549 | is permissible to install a child watcher I<after> the child has been |
2504 | exits). It is permissible to install a child watcher I<after> the child |
1550 | forked (which implies it might have already exited), as long as the event |
2505 | has been forked (which implies it might have already exited), as long |
1551 | loop isn't entered (or is continued from a watcher). |
2506 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2507 | forking and then immediately registering a watcher for the child is fine, |
|
|
2508 | but forking and registering a watcher a few event loop iterations later or |
|
|
2509 | in the next callback invocation is not. |
1552 | |
2510 | |
1553 | Only the default event loop is capable of handling signals, and therefore |
2511 | Only the default event loop is capable of handling signals, and therefore |
1554 | you can only register child watchers in the default event loop. |
2512 | you can only register child watchers in the default event loop. |
1555 | |
2513 | |
|
|
2514 | Due to some design glitches inside libev, child watchers will always be |
|
|
2515 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2516 | libev) |
|
|
2517 | |
1556 | =head3 Process Interaction |
2518 | =head3 Process Interaction |
1557 | |
2519 | |
1558 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2520 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1559 | initialised. This is necessary to guarantee proper behaviour even if |
2521 | initialised. This is necessary to guarantee proper behaviour even if the |
1560 | the first child watcher is started after the child exits. The occurrence |
2522 | first child watcher is started after the child exits. The occurrence |
1561 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2523 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1562 | synchronously as part of the event loop processing. Libev always reaps all |
2524 | synchronously as part of the event loop processing. Libev always reaps all |
1563 | children, even ones not watched. |
2525 | children, even ones not watched. |
1564 | |
2526 | |
1565 | =head3 Overriding the Built-In Processing |
2527 | =head3 Overriding the Built-In Processing |
… | |
… | |
1575 | =head3 Stopping the Child Watcher |
2537 | =head3 Stopping the Child Watcher |
1576 | |
2538 | |
1577 | Currently, the child watcher never gets stopped, even when the |
2539 | Currently, the child watcher never gets stopped, even when the |
1578 | child terminates, so normally one needs to stop the watcher in the |
2540 | child terminates, so normally one needs to stop the watcher in the |
1579 | callback. Future versions of libev might stop the watcher automatically |
2541 | callback. Future versions of libev might stop the watcher automatically |
1580 | when a child exit is detected. |
2542 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2543 | problem). |
1581 | |
2544 | |
1582 | =head3 Watcher-Specific Functions and Data Members |
2545 | =head3 Watcher-Specific Functions and Data Members |
1583 | |
2546 | |
1584 | =over 4 |
2547 | =over 4 |
1585 | |
2548 | |
… | |
… | |
1617 | its completion. |
2580 | its completion. |
1618 | |
2581 | |
1619 | ev_child cw; |
2582 | ev_child cw; |
1620 | |
2583 | |
1621 | static void |
2584 | static void |
1622 | child_cb (EV_P_ struct ev_child *w, int revents) |
2585 | child_cb (EV_P_ ev_child *w, int revents) |
1623 | { |
2586 | { |
1624 | ev_child_stop (EV_A_ w); |
2587 | ev_child_stop (EV_A_ w); |
1625 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2588 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1626 | } |
2589 | } |
1627 | |
2590 | |
… | |
… | |
1642 | |
2605 | |
1643 | |
2606 | |
1644 | =head2 C<ev_stat> - did the file attributes just change? |
2607 | =head2 C<ev_stat> - did the file attributes just change? |
1645 | |
2608 | |
1646 | This watches a file system path for attribute changes. That is, it calls |
2609 | This watches a file system path for attribute changes. That is, it calls |
1647 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2610 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1648 | compared to the last time, invoking the callback if it did. |
2611 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2612 | it did. |
1649 | |
2613 | |
1650 | The path does not need to exist: changing from "path exists" to "path does |
2614 | The path does not need to exist: changing from "path exists" to "path does |
1651 | not exist" is a status change like any other. The condition "path does |
2615 | not exist" is a status change like any other. The condition "path does not |
1652 | not exist" is signified by the C<st_nlink> field being zero (which is |
2616 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1653 | otherwise always forced to be at least one) and all the other fields of |
2617 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1654 | the stat buffer having unspecified contents. |
2618 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2619 | contents. |
1655 | |
2620 | |
1656 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2621 | The path I<must not> end in a slash or contain special components such as |
|
|
2622 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1657 | relative and your working directory changes, the behaviour is undefined. |
2623 | your working directory changes, then the behaviour is undefined. |
1658 | |
2624 | |
1659 | Since there is no standard to do this, the portable implementation simply |
2625 | Since there is no portable change notification interface available, the |
1660 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2626 | portable implementation simply calls C<stat(2)> regularly on the path |
1661 | can specify a recommended polling interval for this case. If you specify |
2627 | to see if it changed somehow. You can specify a recommended polling |
1662 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2628 | interval for this case. If you specify a polling interval of C<0> (highly |
1663 | unspecified default> value will be used (which you can expect to be around |
2629 | recommended!) then a I<suitable, unspecified default> value will be used |
1664 | five seconds, although this might change dynamically). Libev will also |
2630 | (which you can expect to be around five seconds, although this might |
1665 | impose a minimum interval which is currently around C<0.1>, but thats |
2631 | change dynamically). Libev will also impose a minimum interval which is |
1666 | usually overkill. |
2632 | currently around C<0.1>, but that's usually overkill. |
1667 | |
2633 | |
1668 | This watcher type is not meant for massive numbers of stat watchers, |
2634 | This watcher type is not meant for massive numbers of stat watchers, |
1669 | as even with OS-supported change notifications, this can be |
2635 | as even with OS-supported change notifications, this can be |
1670 | resource-intensive. |
2636 | resource-intensive. |
1671 | |
2637 | |
1672 | At the time of this writing, only the Linux inotify interface is |
2638 | At the time of this writing, the only OS-specific interface implemented |
1673 | implemented (implementing kqueue support is left as an exercise for the |
2639 | is the Linux inotify interface (implementing kqueue support is left as an |
1674 | reader, note, however, that the author sees no way of implementing ev_stat |
2640 | exercise for the reader. Note, however, that the author sees no way of |
1675 | semantics with kqueue). Inotify will be used to give hints only and should |
2641 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1676 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1677 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1678 | but changes are usually detected immediately, and if the file exists there |
|
|
1679 | will be no polling. |
|
|
1680 | |
2642 | |
1681 | =head3 ABI Issues (Largefile Support) |
2643 | =head3 ABI Issues (Largefile Support) |
1682 | |
2644 | |
1683 | Libev by default (unless the user overrides this) uses the default |
2645 | Libev by default (unless the user overrides this) uses the default |
1684 | compilation environment, which means that on systems with large file |
2646 | compilation environment, which means that on systems with large file |
1685 | support disabled by default, you get the 32 bit version of the stat |
2647 | support disabled by default, you get the 32 bit version of the stat |
1686 | structure. When using the library from programs that change the ABI to |
2648 | structure. When using the library from programs that change the ABI to |
1687 | use 64 bit file offsets the programs will fail. In that case you have to |
2649 | use 64 bit file offsets the programs will fail. In that case you have to |
1688 | compile libev with the same flags to get binary compatibility. This is |
2650 | compile libev with the same flags to get binary compatibility. This is |
1689 | obviously the case with any flags that change the ABI, but the problem is |
2651 | obviously the case with any flags that change the ABI, but the problem is |
1690 | most noticeably disabled with ev_stat and large file support. |
2652 | most noticeably displayed with ev_stat and large file support. |
1691 | |
2653 | |
1692 | The solution for this is to lobby your distribution maker to make large |
2654 | The solution for this is to lobby your distribution maker to make large |
1693 | file interfaces available by default (as e.g. FreeBSD does) and not |
2655 | file interfaces available by default (as e.g. FreeBSD does) and not |
1694 | optional. Libev cannot simply switch on large file support because it has |
2656 | optional. Libev cannot simply switch on large file support because it has |
1695 | to exchange stat structures with application programs compiled using the |
2657 | to exchange stat structures with application programs compiled using the |
1696 | default compilation environment. |
2658 | default compilation environment. |
1697 | |
2659 | |
1698 | =head3 Inotify |
2660 | =head3 Inotify and Kqueue |
1699 | |
2661 | |
1700 | When C<inotify (7)> support has been compiled into libev (generally only |
2662 | When C<inotify (7)> support has been compiled into libev and present at |
1701 | available on Linux) and present at runtime, it will be used to speed up |
2663 | runtime, it will be used to speed up change detection where possible. The |
1702 | change detection where possible. The inotify descriptor will be created lazily |
2664 | inotify descriptor will be created lazily when the first C<ev_stat> |
1703 | when the first C<ev_stat> watcher is being started. |
2665 | watcher is being started. |
1704 | |
2666 | |
1705 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2667 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1706 | except that changes might be detected earlier, and in some cases, to avoid |
2668 | except that changes might be detected earlier, and in some cases, to avoid |
1707 | making regular C<stat> calls. Even in the presence of inotify support |
2669 | making regular C<stat> calls. Even in the presence of inotify support |
1708 | there are many cases where libev has to resort to regular C<stat> polling. |
2670 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2671 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2672 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2673 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2674 | xfs are fully working) libev usually gets away without polling. |
1709 | |
2675 | |
1710 | (There is no support for kqueue, as apparently it cannot be used to |
2676 | There is no support for kqueue, as apparently it cannot be used to |
1711 | implement this functionality, due to the requirement of having a file |
2677 | implement this functionality, due to the requirement of having a file |
1712 | descriptor open on the object at all times). |
2678 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2679 | etc. is difficult. |
|
|
2680 | |
|
|
2681 | =head3 C<stat ()> is a synchronous operation |
|
|
2682 | |
|
|
2683 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2684 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2685 | ()>, which is a synchronous operation. |
|
|
2686 | |
|
|
2687 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2688 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2689 | as the path data is usually in memory already (except when starting the |
|
|
2690 | watcher). |
|
|
2691 | |
|
|
2692 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2693 | time due to network issues, and even under good conditions, a stat call |
|
|
2694 | often takes multiple milliseconds. |
|
|
2695 | |
|
|
2696 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2697 | paths, although this is fully supported by libev. |
1713 | |
2698 | |
1714 | =head3 The special problem of stat time resolution |
2699 | =head3 The special problem of stat time resolution |
1715 | |
2700 | |
1716 | The C<stat ()> system call only supports full-second resolution portably, and |
2701 | The C<stat ()> system call only supports full-second resolution portably, |
1717 | even on systems where the resolution is higher, many file systems still |
2702 | and even on systems where the resolution is higher, most file systems |
1718 | only support whole seconds. |
2703 | still only support whole seconds. |
1719 | |
2704 | |
1720 | That means that, if the time is the only thing that changes, you can |
2705 | That means that, if the time is the only thing that changes, you can |
1721 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2706 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1722 | calls your callback, which does something. When there is another update |
2707 | calls your callback, which does something. When there is another update |
1723 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2708 | within the same second, C<ev_stat> will be unable to detect unless the |
1724 | data does not change. |
2709 | stat data does change in other ways (e.g. file size). |
1725 | |
2710 | |
1726 | The solution to this is to delay acting on a change for slightly more |
2711 | The solution to this is to delay acting on a change for slightly more |
1727 | than a second (or till slightly after the next full second boundary), using |
2712 | than a second (or till slightly after the next full second boundary), using |
1728 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2713 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1729 | ev_timer_again (loop, w)>). |
2714 | ev_timer_again (loop, w)>). |
… | |
… | |
1749 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2734 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1750 | be detected and should normally be specified as C<0> to let libev choose |
2735 | be detected and should normally be specified as C<0> to let libev choose |
1751 | a suitable value. The memory pointed to by C<path> must point to the same |
2736 | a suitable value. The memory pointed to by C<path> must point to the same |
1752 | path for as long as the watcher is active. |
2737 | path for as long as the watcher is active. |
1753 | |
2738 | |
1754 | The callback will receive C<EV_STAT> when a change was detected, relative |
2739 | The callback will receive an C<EV_STAT> event when a change was detected, |
1755 | to the attributes at the time the watcher was started (or the last change |
2740 | relative to the attributes at the time the watcher was started (or the |
1756 | was detected). |
2741 | last change was detected). |
1757 | |
2742 | |
1758 | =item ev_stat_stat (loop, ev_stat *) |
2743 | =item ev_stat_stat (loop, ev_stat *) |
1759 | |
2744 | |
1760 | Updates the stat buffer immediately with new values. If you change the |
2745 | Updates the stat buffer immediately with new values. If you change the |
1761 | watched path in your callback, you could call this function to avoid |
2746 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1844 | |
2829 | |
1845 | |
2830 | |
1846 | =head2 C<ev_idle> - when you've got nothing better to do... |
2831 | =head2 C<ev_idle> - when you've got nothing better to do... |
1847 | |
2832 | |
1848 | Idle watchers trigger events when no other events of the same or higher |
2833 | Idle watchers trigger events when no other events of the same or higher |
1849 | priority are pending (prepare, check and other idle watchers do not |
2834 | priority are pending (prepare, check and other idle watchers do not count |
1850 | count). |
2835 | as receiving "events"). |
1851 | |
2836 | |
1852 | That is, as long as your process is busy handling sockets or timeouts |
2837 | That is, as long as your process is busy handling sockets or timeouts |
1853 | (or even signals, imagine) of the same or higher priority it will not be |
2838 | (or even signals, imagine) of the same or higher priority it will not be |
1854 | triggered. But when your process is idle (or only lower-priority watchers |
2839 | triggered. But when your process is idle (or only lower-priority watchers |
1855 | are pending), the idle watchers are being called once per event loop |
2840 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1862 | Apart from keeping your process non-blocking (which is a useful |
2847 | Apart from keeping your process non-blocking (which is a useful |
1863 | effect on its own sometimes), idle watchers are a good place to do |
2848 | effect on its own sometimes), idle watchers are a good place to do |
1864 | "pseudo-background processing", or delay processing stuff to after the |
2849 | "pseudo-background processing", or delay processing stuff to after the |
1865 | event loop has handled all outstanding events. |
2850 | event loop has handled all outstanding events. |
1866 | |
2851 | |
|
|
2852 | =head3 Abusing an C<ev_idle> watcher for its side-effect |
|
|
2853 | |
|
|
2854 | As long as there is at least one active idle watcher, libev will never |
|
|
2855 | sleep unnecessarily. Or in other words, it will loop as fast as possible. |
|
|
2856 | For this to work, the idle watcher doesn't need to be invoked at all - the |
|
|
2857 | lowest priority will do. |
|
|
2858 | |
|
|
2859 | This mode of operation can be useful together with an C<ev_check> watcher, |
|
|
2860 | to do something on each event loop iteration - for example to balance load |
|
|
2861 | between different connections. |
|
|
2862 | |
|
|
2863 | See L</Abusing an ev_check watcher for its side-effect> for a longer |
|
|
2864 | example. |
|
|
2865 | |
1867 | =head3 Watcher-Specific Functions and Data Members |
2866 | =head3 Watcher-Specific Functions and Data Members |
1868 | |
2867 | |
1869 | =over 4 |
2868 | =over 4 |
1870 | |
2869 | |
1871 | =item ev_idle_init (ev_signal *, callback) |
2870 | =item ev_idle_init (ev_idle *, callback) |
1872 | |
2871 | |
1873 | Initialises and configures the idle watcher - it has no parameters of any |
2872 | Initialises and configures the idle watcher - it has no parameters of any |
1874 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2873 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1875 | believe me. |
2874 | believe me. |
1876 | |
2875 | |
… | |
… | |
1880 | |
2879 | |
1881 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2880 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1882 | callback, free it. Also, use no error checking, as usual. |
2881 | callback, free it. Also, use no error checking, as usual. |
1883 | |
2882 | |
1884 | static void |
2883 | static void |
1885 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2884 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1886 | { |
2885 | { |
|
|
2886 | // stop the watcher |
|
|
2887 | ev_idle_stop (loop, w); |
|
|
2888 | |
|
|
2889 | // now we can free it |
1887 | free (w); |
2890 | free (w); |
|
|
2891 | |
1888 | // now do something you wanted to do when the program has |
2892 | // now do something you wanted to do when the program has |
1889 | // no longer anything immediate to do. |
2893 | // no longer anything immediate to do. |
1890 | } |
2894 | } |
1891 | |
2895 | |
1892 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2896 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1893 | ev_idle_init (idle_watcher, idle_cb); |
2897 | ev_idle_init (idle_watcher, idle_cb); |
1894 | ev_idle_start (loop, idle_cb); |
2898 | ev_idle_start (loop, idle_watcher); |
1895 | |
2899 | |
1896 | |
2900 | |
1897 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2901 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1898 | |
2902 | |
1899 | Prepare and check watchers are usually (but not always) used in tandem: |
2903 | Prepare and check watchers are often (but not always) used in pairs: |
1900 | prepare watchers get invoked before the process blocks and check watchers |
2904 | prepare watchers get invoked before the process blocks and check watchers |
1901 | afterwards. |
2905 | afterwards. |
1902 | |
2906 | |
1903 | You I<must not> call C<ev_loop> or similar functions that enter |
2907 | You I<must not> call C<ev_run> or similar functions that enter |
1904 | the current event loop from either C<ev_prepare> or C<ev_check> |
2908 | the current event loop from either C<ev_prepare> or C<ev_check> |
1905 | watchers. Other loops than the current one are fine, however. The |
2909 | watchers. Other loops than the current one are fine, however. The |
1906 | rationale behind this is that you do not need to check for recursion in |
2910 | rationale behind this is that you do not need to check for recursion in |
1907 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2911 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1908 | C<ev_check> so if you have one watcher of each kind they will always be |
2912 | C<ev_check> so if you have one watcher of each kind they will always be |
1909 | called in pairs bracketing the blocking call. |
2913 | called in pairs bracketing the blocking call. |
1910 | |
2914 | |
1911 | Their main purpose is to integrate other event mechanisms into libev and |
2915 | Their main purpose is to integrate other event mechanisms into libev and |
1912 | their use is somewhat advanced. This could be used, for example, to track |
2916 | their use is somewhat advanced. They could be used, for example, to track |
1913 | variable changes, implement your own watchers, integrate net-snmp or a |
2917 | variable changes, implement your own watchers, integrate net-snmp or a |
1914 | coroutine library and lots more. They are also occasionally useful if |
2918 | coroutine library and lots more. They are also occasionally useful if |
1915 | you cache some data and want to flush it before blocking (for example, |
2919 | you cache some data and want to flush it before blocking (for example, |
1916 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2920 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1917 | watcher). |
2921 | watcher). |
1918 | |
2922 | |
1919 | This is done by examining in each prepare call which file descriptors need |
2923 | This is done by examining in each prepare call which file descriptors |
1920 | to be watched by the other library, registering C<ev_io> watchers for |
2924 | need to be watched by the other library, registering C<ev_io> watchers |
1921 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2925 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1922 | provide just this functionality). Then, in the check watcher you check for |
2926 | libraries provide exactly this functionality). Then, in the check watcher, |
1923 | any events that occurred (by checking the pending status of all watchers |
2927 | you check for any events that occurred (by checking the pending status |
1924 | and stopping them) and call back into the library. The I/O and timer |
2928 | of all watchers and stopping them) and call back into the library. The |
1925 | callbacks will never actually be called (but must be valid nevertheless, |
2929 | I/O and timer callbacks will never actually be called (but must be valid |
1926 | because you never know, you know?). |
2930 | nevertheless, because you never know, you know?). |
1927 | |
2931 | |
1928 | As another example, the Perl Coro module uses these hooks to integrate |
2932 | As another example, the Perl Coro module uses these hooks to integrate |
1929 | coroutines into libev programs, by yielding to other active coroutines |
2933 | coroutines into libev programs, by yielding to other active coroutines |
1930 | during each prepare and only letting the process block if no coroutines |
2934 | during each prepare and only letting the process block if no coroutines |
1931 | are ready to run (it's actually more complicated: it only runs coroutines |
2935 | are ready to run (it's actually more complicated: it only runs coroutines |
1932 | with priority higher than or equal to the event loop and one coroutine |
2936 | with priority higher than or equal to the event loop and one coroutine |
1933 | of lower priority, but only once, using idle watchers to keep the event |
2937 | of lower priority, but only once, using idle watchers to keep the event |
1934 | loop from blocking if lower-priority coroutines are active, thus mapping |
2938 | loop from blocking if lower-priority coroutines are active, thus mapping |
1935 | low-priority coroutines to idle/background tasks). |
2939 | low-priority coroutines to idle/background tasks). |
1936 | |
2940 | |
1937 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2941 | When used for this purpose, it is recommended to give C<ev_check> watchers |
1938 | priority, to ensure that they are being run before any other watchers |
2942 | highest (C<EV_MAXPRI>) priority, to ensure that they are being run before |
|
|
2943 | any other watchers after the poll (this doesn't matter for C<ev_prepare> |
|
|
2944 | watchers). |
|
|
2945 | |
1939 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2946 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1940 | too) should not activate ("feed") events into libev. While libev fully |
2947 | activate ("feed") events into libev. While libev fully supports this, they |
1941 | supports this, they might get executed before other C<ev_check> watchers |
2948 | might get executed before other C<ev_check> watchers did their job. As |
1942 | did their job. As C<ev_check> watchers are often used to embed other |
2949 | C<ev_check> watchers are often used to embed other (non-libev) event |
1943 | (non-libev) event loops those other event loops might be in an unusable |
2950 | loops those other event loops might be in an unusable state until their |
1944 | state until their C<ev_check> watcher ran (always remind yourself to |
2951 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1945 | coexist peacefully with others). |
2952 | others). |
|
|
2953 | |
|
|
2954 | =head3 Abusing an C<ev_check> watcher for its side-effect |
|
|
2955 | |
|
|
2956 | C<ev_check> (and less often also C<ev_prepare>) watchers can also be |
|
|
2957 | useful because they are called once per event loop iteration. For |
|
|
2958 | example, if you want to handle a large number of connections fairly, you |
|
|
2959 | normally only do a bit of work for each active connection, and if there |
|
|
2960 | is more work to do, you wait for the next event loop iteration, so other |
|
|
2961 | connections have a chance of making progress. |
|
|
2962 | |
|
|
2963 | Using an C<ev_check> watcher is almost enough: it will be called on the |
|
|
2964 | next event loop iteration. However, that isn't as soon as possible - |
|
|
2965 | without external events, your C<ev_check> watcher will not be invoked. |
|
|
2966 | |
|
|
2967 | |
|
|
2968 | This is where C<ev_idle> watchers come in handy - all you need is a |
|
|
2969 | single global idle watcher that is active as long as you have one active |
|
|
2970 | C<ev_check> watcher. The C<ev_idle> watcher makes sure the event loop |
|
|
2971 | will not sleep, and the C<ev_check> watcher makes sure a callback gets |
|
|
2972 | invoked. Neither watcher alone can do that. |
1946 | |
2973 | |
1947 | =head3 Watcher-Specific Functions and Data Members |
2974 | =head3 Watcher-Specific Functions and Data Members |
1948 | |
2975 | |
1949 | =over 4 |
2976 | =over 4 |
1950 | |
2977 | |
… | |
… | |
1952 | |
2979 | |
1953 | =item ev_check_init (ev_check *, callback) |
2980 | =item ev_check_init (ev_check *, callback) |
1954 | |
2981 | |
1955 | Initialises and configures the prepare or check watcher - they have no |
2982 | Initialises and configures the prepare or check watcher - they have no |
1956 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2983 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1957 | macros, but using them is utterly, utterly and completely pointless. |
2984 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2985 | pointless. |
1958 | |
2986 | |
1959 | =back |
2987 | =back |
1960 | |
2988 | |
1961 | =head3 Examples |
2989 | =head3 Examples |
1962 | |
2990 | |
… | |
… | |
1975 | |
3003 | |
1976 | static ev_io iow [nfd]; |
3004 | static ev_io iow [nfd]; |
1977 | static ev_timer tw; |
3005 | static ev_timer tw; |
1978 | |
3006 | |
1979 | static void |
3007 | static void |
1980 | io_cb (ev_loop *loop, ev_io *w, int revents) |
3008 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1981 | { |
3009 | { |
1982 | } |
3010 | } |
1983 | |
3011 | |
1984 | // create io watchers for each fd and a timer before blocking |
3012 | // create io watchers for each fd and a timer before blocking |
1985 | static void |
3013 | static void |
1986 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
3014 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1987 | { |
3015 | { |
1988 | int timeout = 3600000; |
3016 | int timeout = 3600000; |
1989 | struct pollfd fds [nfd]; |
3017 | struct pollfd fds [nfd]; |
1990 | // actual code will need to loop here and realloc etc. |
3018 | // actual code will need to loop here and realloc etc. |
1991 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
3019 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1992 | |
3020 | |
1993 | /* the callback is illegal, but won't be called as we stop during check */ |
3021 | /* the callback is illegal, but won't be called as we stop during check */ |
1994 | ev_timer_init (&tw, 0, timeout * 1e-3); |
3022 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1995 | ev_timer_start (loop, &tw); |
3023 | ev_timer_start (loop, &tw); |
1996 | |
3024 | |
1997 | // create one ev_io per pollfd |
3025 | // create one ev_io per pollfd |
1998 | for (int i = 0; i < nfd; ++i) |
3026 | for (int i = 0; i < nfd; ++i) |
1999 | { |
3027 | { |
… | |
… | |
2006 | } |
3034 | } |
2007 | } |
3035 | } |
2008 | |
3036 | |
2009 | // stop all watchers after blocking |
3037 | // stop all watchers after blocking |
2010 | static void |
3038 | static void |
2011 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
3039 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2012 | { |
3040 | { |
2013 | ev_timer_stop (loop, &tw); |
3041 | ev_timer_stop (loop, &tw); |
2014 | |
3042 | |
2015 | for (int i = 0; i < nfd; ++i) |
3043 | for (int i = 0; i < nfd; ++i) |
2016 | { |
3044 | { |
… | |
… | |
2055 | } |
3083 | } |
2056 | |
3084 | |
2057 | // do not ever call adns_afterpoll |
3085 | // do not ever call adns_afterpoll |
2058 | |
3086 | |
2059 | Method 4: Do not use a prepare or check watcher because the module you |
3087 | Method 4: Do not use a prepare or check watcher because the module you |
2060 | want to embed is too inflexible to support it. Instead, you can override |
3088 | want to embed is not flexible enough to support it. Instead, you can |
2061 | their poll function. The drawback with this solution is that the main |
3089 | override their poll function. The drawback with this solution is that the |
2062 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
3090 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2063 | this. |
3091 | this approach, effectively embedding EV as a client into the horrible |
|
|
3092 | libglib event loop. |
2064 | |
3093 | |
2065 | static gint |
3094 | static gint |
2066 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
3095 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2067 | { |
3096 | { |
2068 | int got_events = 0; |
3097 | int got_events = 0; |
… | |
… | |
2072 | |
3101 | |
2073 | if (timeout >= 0) |
3102 | if (timeout >= 0) |
2074 | // create/start timer |
3103 | // create/start timer |
2075 | |
3104 | |
2076 | // poll |
3105 | // poll |
2077 | ev_loop (EV_A_ 0); |
3106 | ev_run (EV_A_ 0); |
2078 | |
3107 | |
2079 | // stop timer again |
3108 | // stop timer again |
2080 | if (timeout >= 0) |
3109 | if (timeout >= 0) |
2081 | ev_timer_stop (EV_A_ &to); |
3110 | ev_timer_stop (EV_A_ &to); |
2082 | |
3111 | |
… | |
… | |
2099 | prioritise I/O. |
3128 | prioritise I/O. |
2100 | |
3129 | |
2101 | As an example for a bug workaround, the kqueue backend might only support |
3130 | As an example for a bug workaround, the kqueue backend might only support |
2102 | sockets on some platform, so it is unusable as generic backend, but you |
3131 | sockets on some platform, so it is unusable as generic backend, but you |
2103 | still want to make use of it because you have many sockets and it scales |
3132 | still want to make use of it because you have many sockets and it scales |
2104 | so nicely. In this case, you would create a kqueue-based loop and embed it |
3133 | so nicely. In this case, you would create a kqueue-based loop and embed |
2105 | into your default loop (which might use e.g. poll). Overall operation will |
3134 | it into your default loop (which might use e.g. poll). Overall operation |
2106 | be a bit slower because first libev has to poll and then call kevent, but |
3135 | will be a bit slower because first libev has to call C<poll> and then |
2107 | at least you can use both at what they are best. |
3136 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
3137 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2108 | |
3138 | |
2109 | As for prioritising I/O: rarely you have the case where some fds have |
3139 | As for prioritising I/O: under rare circumstances you have the case where |
2110 | to be watched and handled very quickly (with low latency), and even |
3140 | some fds have to be watched and handled very quickly (with low latency), |
2111 | priorities and idle watchers might have too much overhead. In this case |
3141 | and even priorities and idle watchers might have too much overhead. In |
2112 | you would put all the high priority stuff in one loop and all the rest in |
3142 | this case you would put all the high priority stuff in one loop and all |
2113 | a second one, and embed the second one in the first. |
3143 | the rest in a second one, and embed the second one in the first. |
2114 | |
3144 | |
2115 | As long as the watcher is active, the callback will be invoked every time |
3145 | As long as the watcher is active, the callback will be invoked every |
2116 | there might be events pending in the embedded loop. The callback must then |
3146 | time there might be events pending in the embedded loop. The callback |
2117 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
3147 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2118 | their callbacks (you could also start an idle watcher to give the embedded |
3148 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2119 | loop strictly lower priority for example). You can also set the callback |
3149 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2120 | to C<0>, in which case the embed watcher will automatically execute the |
3150 | to give the embedded loop strictly lower priority for example). |
2121 | embedded loop sweep. |
|
|
2122 | |
3151 | |
2123 | As long as the watcher is started it will automatically handle events. The |
3152 | You can also set the callback to C<0>, in which case the embed watcher |
2124 | callback will be invoked whenever some events have been handled. You can |
3153 | will automatically execute the embedded loop sweep whenever necessary. |
2125 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2126 | interested in that. |
|
|
2127 | |
3154 | |
2128 | Also, there have not currently been made special provisions for forking: |
3155 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2129 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
3156 | is active, i.e., the embedded loop will automatically be forked when the |
2130 | but you will also have to stop and restart any C<ev_embed> watchers |
3157 | embedding loop forks. In other cases, the user is responsible for calling |
2131 | yourself. |
3158 | C<ev_loop_fork> on the embedded loop. |
2132 | |
3159 | |
2133 | Unfortunately, not all backends are embeddable, only the ones returned by |
3160 | Unfortunately, not all backends are embeddable: only the ones returned by |
2134 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
3161 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2135 | portable one. |
3162 | portable one. |
2136 | |
3163 | |
2137 | So when you want to use this feature you will always have to be prepared |
3164 | So when you want to use this feature you will always have to be prepared |
2138 | that you cannot get an embeddable loop. The recommended way to get around |
3165 | that you cannot get an embeddable loop. The recommended way to get around |
2139 | this is to have a separate variables for your embeddable loop, try to |
3166 | this is to have a separate variables for your embeddable loop, try to |
2140 | create it, and if that fails, use the normal loop for everything. |
3167 | create it, and if that fails, use the normal loop for everything. |
|
|
3168 | |
|
|
3169 | =head3 C<ev_embed> and fork |
|
|
3170 | |
|
|
3171 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
3172 | automatically be applied to the embedded loop as well, so no special |
|
|
3173 | fork handling is required in that case. When the watcher is not running, |
|
|
3174 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
3175 | as applicable. |
2141 | |
3176 | |
2142 | =head3 Watcher-Specific Functions and Data Members |
3177 | =head3 Watcher-Specific Functions and Data Members |
2143 | |
3178 | |
2144 | =over 4 |
3179 | =over 4 |
2145 | |
3180 | |
… | |
… | |
2154 | if you do not want that, you need to temporarily stop the embed watcher). |
3189 | if you do not want that, you need to temporarily stop the embed watcher). |
2155 | |
3190 | |
2156 | =item ev_embed_sweep (loop, ev_embed *) |
3191 | =item ev_embed_sweep (loop, ev_embed *) |
2157 | |
3192 | |
2158 | Make a single, non-blocking sweep over the embedded loop. This works |
3193 | Make a single, non-blocking sweep over the embedded loop. This works |
2159 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3194 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2160 | appropriate way for embedded loops. |
3195 | appropriate way for embedded loops. |
2161 | |
3196 | |
2162 | =item struct ev_loop *other [read-only] |
3197 | =item struct ev_loop *other [read-only] |
2163 | |
3198 | |
2164 | The embedded event loop. |
3199 | The embedded event loop. |
… | |
… | |
2173 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
3208 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2174 | used). |
3209 | used). |
2175 | |
3210 | |
2176 | struct ev_loop *loop_hi = ev_default_init (0); |
3211 | struct ev_loop *loop_hi = ev_default_init (0); |
2177 | struct ev_loop *loop_lo = 0; |
3212 | struct ev_loop *loop_lo = 0; |
2178 | struct ev_embed embed; |
3213 | ev_embed embed; |
2179 | |
3214 | |
2180 | // see if there is a chance of getting one that works |
3215 | // see if there is a chance of getting one that works |
2181 | // (remember that a flags value of 0 means autodetection) |
3216 | // (remember that a flags value of 0 means autodetection) |
2182 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3217 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2183 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3218 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2197 | kqueue implementation). Store the kqueue/socket-only event loop in |
3232 | kqueue implementation). Store the kqueue/socket-only event loop in |
2198 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3233 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2199 | |
3234 | |
2200 | struct ev_loop *loop = ev_default_init (0); |
3235 | struct ev_loop *loop = ev_default_init (0); |
2201 | struct ev_loop *loop_socket = 0; |
3236 | struct ev_loop *loop_socket = 0; |
2202 | struct ev_embed embed; |
3237 | ev_embed embed; |
2203 | |
3238 | |
2204 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3239 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2205 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3240 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2206 | { |
3241 | { |
2207 | ev_embed_init (&embed, 0, loop_socket); |
3242 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2222 | event loop blocks next and before C<ev_check> watchers are being called, |
3257 | event loop blocks next and before C<ev_check> watchers are being called, |
2223 | and only in the child after the fork. If whoever good citizen calling |
3258 | and only in the child after the fork. If whoever good citizen calling |
2224 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3259 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2225 | handlers will be invoked, too, of course. |
3260 | handlers will be invoked, too, of course. |
2226 | |
3261 | |
|
|
3262 | =head3 The special problem of life after fork - how is it possible? |
|
|
3263 | |
|
|
3264 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3265 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3266 | sequence should be handled by libev without any problems. |
|
|
3267 | |
|
|
3268 | This changes when the application actually wants to do event handling |
|
|
3269 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3270 | fork. |
|
|
3271 | |
|
|
3272 | The default mode of operation (for libev, with application help to detect |
|
|
3273 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3274 | when I<either> the parent I<or> the child process continues. |
|
|
3275 | |
|
|
3276 | When both processes want to continue using libev, then this is usually the |
|
|
3277 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3278 | supposed to continue with all watchers in place as before, while the other |
|
|
3279 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3280 | |
|
|
3281 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3282 | simply create a new event loop, which of course will be "empty", and |
|
|
3283 | use that for new watchers. This has the advantage of not touching more |
|
|
3284 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3285 | disadvantage of having to use multiple event loops (which do not support |
|
|
3286 | signal watchers). |
|
|
3287 | |
|
|
3288 | When this is not possible, or you want to use the default loop for |
|
|
3289 | other reasons, then in the process that wants to start "fresh", call |
|
|
3290 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3291 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3292 | watchers, so you have to be careful not to execute code that modifies |
|
|
3293 | those watchers. Note also that in that case, you have to re-register any |
|
|
3294 | signal watchers. |
|
|
3295 | |
2227 | =head3 Watcher-Specific Functions and Data Members |
3296 | =head3 Watcher-Specific Functions and Data Members |
2228 | |
3297 | |
2229 | =over 4 |
3298 | =over 4 |
2230 | |
3299 | |
2231 | =item ev_fork_init (ev_signal *, callback) |
3300 | =item ev_fork_init (ev_fork *, callback) |
2232 | |
3301 | |
2233 | Initialises and configures the fork watcher - it has no parameters of any |
3302 | Initialises and configures the fork watcher - it has no parameters of any |
2234 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3303 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2235 | believe me. |
3304 | really. |
2236 | |
3305 | |
2237 | =back |
3306 | =back |
2238 | |
3307 | |
2239 | |
3308 | |
|
|
3309 | =head2 C<ev_cleanup> - even the best things end |
|
|
3310 | |
|
|
3311 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3312 | by a call to C<ev_loop_destroy>. |
|
|
3313 | |
|
|
3314 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3315 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3316 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3317 | loop when you want them to be invoked. |
|
|
3318 | |
|
|
3319 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3320 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3321 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3322 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3323 | |
|
|
3324 | =head3 Watcher-Specific Functions and Data Members |
|
|
3325 | |
|
|
3326 | =over 4 |
|
|
3327 | |
|
|
3328 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3329 | |
|
|
3330 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3331 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3332 | pointless, I assure you. |
|
|
3333 | |
|
|
3334 | =back |
|
|
3335 | |
|
|
3336 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3337 | cleanup functions are called. |
|
|
3338 | |
|
|
3339 | static void |
|
|
3340 | program_exits (void) |
|
|
3341 | { |
|
|
3342 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3343 | } |
|
|
3344 | |
|
|
3345 | ... |
|
|
3346 | atexit (program_exits); |
|
|
3347 | |
|
|
3348 | |
2240 | =head2 C<ev_async> - how to wake up another event loop |
3349 | =head2 C<ev_async> - how to wake up an event loop |
2241 | |
3350 | |
2242 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3351 | In general, you cannot use an C<ev_loop> from multiple threads or other |
2243 | asynchronous sources such as signal handlers (as opposed to multiple event |
3352 | asynchronous sources such as signal handlers (as opposed to multiple event |
2244 | loops - those are of course safe to use in different threads). |
3353 | loops - those are of course safe to use in different threads). |
2245 | |
3354 | |
2246 | Sometimes, however, you need to wake up another event loop you do not |
3355 | Sometimes, however, you need to wake up an event loop you do not control, |
2247 | control, for example because it belongs to another thread. This is what |
3356 | for example because it belongs to another thread. This is what C<ev_async> |
2248 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3357 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2249 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3358 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2250 | safe. |
|
|
2251 | |
3359 | |
2252 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3360 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2253 | too, are asynchronous in nature, and signals, too, will be compressed |
3361 | too, are asynchronous in nature, and signals, too, will be compressed |
2254 | (i.e. the number of callback invocations may be less than the number of |
3362 | (i.e. the number of callback invocations may be less than the number of |
2255 | C<ev_async_sent> calls). |
3363 | C<ev_async_send> calls). In fact, you could use signal watchers as a kind |
2256 | |
3364 | of "global async watchers" by using a watcher on an otherwise unused |
2257 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3365 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
2258 | just the default loop. |
3366 | even without knowing which loop owns the signal. |
2259 | |
3367 | |
2260 | =head3 Queueing |
3368 | =head3 Queueing |
2261 | |
3369 | |
2262 | C<ev_async> does not support queueing of data in any way. The reason |
3370 | C<ev_async> does not support queueing of data in any way. The reason |
2263 | is that the author does not know of a simple (or any) algorithm for a |
3371 | is that the author does not know of a simple (or any) algorithm for a |
2264 | multiple-writer-single-reader queue that works in all cases and doesn't |
3372 | multiple-writer-single-reader queue that works in all cases and doesn't |
2265 | need elaborate support such as pthreads. |
3373 | need elaborate support such as pthreads or unportable memory access |
|
|
3374 | semantics. |
2266 | |
3375 | |
2267 | That means that if you want to queue data, you have to provide your own |
3376 | That means that if you want to queue data, you have to provide your own |
2268 | queue. But at least I can tell you would implement locking around your |
3377 | queue. But at least I can tell you how to implement locking around your |
2269 | queue: |
3378 | queue: |
2270 | |
3379 | |
2271 | =over 4 |
3380 | =over 4 |
2272 | |
3381 | |
2273 | =item queueing from a signal handler context |
3382 | =item queueing from a signal handler context |
2274 | |
3383 | |
2275 | To implement race-free queueing, you simply add to the queue in the signal |
3384 | To implement race-free queueing, you simply add to the queue in the signal |
2276 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3385 | handler but you block the signal handler in the watcher callback. Here is |
2277 | some fictitious SIGUSR1 handler: |
3386 | an example that does that for some fictitious SIGUSR1 handler: |
2278 | |
3387 | |
2279 | static ev_async mysig; |
3388 | static ev_async mysig; |
2280 | |
3389 | |
2281 | static void |
3390 | static void |
2282 | sigusr1_handler (void) |
3391 | sigusr1_handler (void) |
… | |
… | |
2348 | =over 4 |
3457 | =over 4 |
2349 | |
3458 | |
2350 | =item ev_async_init (ev_async *, callback) |
3459 | =item ev_async_init (ev_async *, callback) |
2351 | |
3460 | |
2352 | Initialises and configures the async watcher - it has no parameters of any |
3461 | Initialises and configures the async watcher - it has no parameters of any |
2353 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3462 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2354 | believe me. |
3463 | trust me. |
2355 | |
3464 | |
2356 | =item ev_async_send (loop, ev_async *) |
3465 | =item ev_async_send (loop, ev_async *) |
2357 | |
3466 | |
2358 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3467 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2359 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3468 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3469 | returns. |
|
|
3470 | |
2360 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3471 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
2361 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3472 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
2362 | section below on what exactly this means). |
3473 | embedding section below on what exactly this means). |
2363 | |
3474 | |
2364 | This call incurs the overhead of a system call only once per loop iteration, |
3475 | Note that, as with other watchers in libev, multiple events might get |
2365 | so while the overhead might be noticeable, it doesn't apply to repeated |
3476 | compressed into a single callback invocation (another way to look at |
2366 | calls to C<ev_async_send>. |
3477 | this is that C<ev_async> watchers are level-triggered: they are set on |
|
|
3478 | C<ev_async_send>, reset when the event loop detects that). |
|
|
3479 | |
|
|
3480 | This call incurs the overhead of at most one extra system call per event |
|
|
3481 | loop iteration, if the event loop is blocked, and no syscall at all if |
|
|
3482 | the event loop (or your program) is processing events. That means that |
|
|
3483 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3484 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3485 | zero) under load. |
2367 | |
3486 | |
2368 | =item bool = ev_async_pending (ev_async *) |
3487 | =item bool = ev_async_pending (ev_async *) |
2369 | |
3488 | |
2370 | Returns a non-zero value when C<ev_async_send> has been called on the |
3489 | Returns a non-zero value when C<ev_async_send> has been called on the |
2371 | watcher but the event has not yet been processed (or even noted) by the |
3490 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2374 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3493 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2375 | the loop iterates next and checks for the watcher to have become active, |
3494 | the loop iterates next and checks for the watcher to have become active, |
2376 | it will reset the flag again. C<ev_async_pending> can be used to very |
3495 | it will reset the flag again. C<ev_async_pending> can be used to very |
2377 | quickly check whether invoking the loop might be a good idea. |
3496 | quickly check whether invoking the loop might be a good idea. |
2378 | |
3497 | |
2379 | Not that this does I<not> check whether the watcher itself is pending, only |
3498 | Not that this does I<not> check whether the watcher itself is pending, |
2380 | whether it has been requested to make this watcher pending. |
3499 | only whether it has been requested to make this watcher pending: there |
|
|
3500 | is a time window between the event loop checking and resetting the async |
|
|
3501 | notification, and the callback being invoked. |
2381 | |
3502 | |
2382 | =back |
3503 | =back |
2383 | |
3504 | |
2384 | |
3505 | |
2385 | =head1 OTHER FUNCTIONS |
3506 | =head1 OTHER FUNCTIONS |
… | |
… | |
2389 | =over 4 |
3510 | =over 4 |
2390 | |
3511 | |
2391 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3512 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2392 | |
3513 | |
2393 | This function combines a simple timer and an I/O watcher, calls your |
3514 | This function combines a simple timer and an I/O watcher, calls your |
2394 | callback on whichever event happens first and automatically stop both |
3515 | callback on whichever event happens first and automatically stops both |
2395 | watchers. This is useful if you want to wait for a single event on an fd |
3516 | watchers. This is useful if you want to wait for a single event on an fd |
2396 | or timeout without having to allocate/configure/start/stop/free one or |
3517 | or timeout without having to allocate/configure/start/stop/free one or |
2397 | more watchers yourself. |
3518 | more watchers yourself. |
2398 | |
3519 | |
2399 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3520 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2400 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3521 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2401 | C<events> set will be created and started. |
3522 | the given C<fd> and C<events> set will be created and started. |
2402 | |
3523 | |
2403 | If C<timeout> is less than 0, then no timeout watcher will be |
3524 | If C<timeout> is less than 0, then no timeout watcher will be |
2404 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3525 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2405 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3526 | repeat = 0) will be started. C<0> is a valid timeout. |
2406 | dubious value. |
|
|
2407 | |
3527 | |
2408 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3528 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2409 | passed an C<revents> set like normal event callbacks (a combination of |
3529 | passed an C<revents> set like normal event callbacks (a combination of |
2410 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3530 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2411 | value passed to C<ev_once>: |
3531 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3532 | a timeout and an io event at the same time - you probably should give io |
|
|
3533 | events precedence. |
|
|
3534 | |
|
|
3535 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2412 | |
3536 | |
2413 | static void stdin_ready (int revents, void *arg) |
3537 | static void stdin_ready (int revents, void *arg) |
2414 | { |
3538 | { |
|
|
3539 | if (revents & EV_READ) |
|
|
3540 | /* stdin might have data for us, joy! */; |
2415 | if (revents & EV_TIMEOUT) |
3541 | else if (revents & EV_TIMER) |
2416 | /* doh, nothing entered */; |
3542 | /* doh, nothing entered */; |
2417 | else if (revents & EV_READ) |
|
|
2418 | /* stdin might have data for us, joy! */; |
|
|
2419 | } |
3543 | } |
2420 | |
3544 | |
2421 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3545 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2422 | |
3546 | |
2423 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2424 | |
|
|
2425 | Feeds the given event set into the event loop, as if the specified event |
|
|
2426 | had happened for the specified watcher (which must be a pointer to an |
|
|
2427 | initialised but not necessarily started event watcher). |
|
|
2428 | |
|
|
2429 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3547 | =item ev_feed_fd_event (loop, int fd, int revents) |
2430 | |
3548 | |
2431 | Feed an event on the given fd, as if a file descriptor backend detected |
3549 | Feed an event on the given fd, as if a file descriptor backend detected |
2432 | the given events it. |
3550 | the given events. |
2433 | |
3551 | |
2434 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3552 | =item ev_feed_signal_event (loop, int signum) |
2435 | |
3553 | |
2436 | Feed an event as if the given signal occurred (C<loop> must be the default |
3554 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
2437 | loop!). |
3555 | which is async-safe. |
2438 | |
3556 | |
2439 | =back |
3557 | =back |
|
|
3558 | |
|
|
3559 | |
|
|
3560 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3561 | |
|
|
3562 | This section explains some common idioms that are not immediately |
|
|
3563 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3564 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3565 | |
|
|
3566 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3567 | |
|
|
3568 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3569 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3570 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3571 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3572 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3573 | data: |
|
|
3574 | |
|
|
3575 | struct my_io |
|
|
3576 | { |
|
|
3577 | ev_io io; |
|
|
3578 | int otherfd; |
|
|
3579 | void *somedata; |
|
|
3580 | struct whatever *mostinteresting; |
|
|
3581 | }; |
|
|
3582 | |
|
|
3583 | ... |
|
|
3584 | struct my_io w; |
|
|
3585 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3586 | |
|
|
3587 | And since your callback will be called with a pointer to the watcher, you |
|
|
3588 | can cast it back to your own type: |
|
|
3589 | |
|
|
3590 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3591 | { |
|
|
3592 | struct my_io *w = (struct my_io *)w_; |
|
|
3593 | ... |
|
|
3594 | } |
|
|
3595 | |
|
|
3596 | More interesting and less C-conformant ways of casting your callback |
|
|
3597 | function type instead have been omitted. |
|
|
3598 | |
|
|
3599 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3600 | |
|
|
3601 | Another common scenario is to use some data structure with multiple |
|
|
3602 | embedded watchers, in effect creating your own watcher that combines |
|
|
3603 | multiple libev event sources into one "super-watcher": |
|
|
3604 | |
|
|
3605 | struct my_biggy |
|
|
3606 | { |
|
|
3607 | int some_data; |
|
|
3608 | ev_timer t1; |
|
|
3609 | ev_timer t2; |
|
|
3610 | } |
|
|
3611 | |
|
|
3612 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3613 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3614 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3615 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3616 | real programmers): |
|
|
3617 | |
|
|
3618 | #include <stddef.h> |
|
|
3619 | |
|
|
3620 | static void |
|
|
3621 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3622 | { |
|
|
3623 | struct my_biggy big = (struct my_biggy *) |
|
|
3624 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3625 | } |
|
|
3626 | |
|
|
3627 | static void |
|
|
3628 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3629 | { |
|
|
3630 | struct my_biggy big = (struct my_biggy *) |
|
|
3631 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3632 | } |
|
|
3633 | |
|
|
3634 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3635 | |
|
|
3636 | Often you have structures like this in event-based programs: |
|
|
3637 | |
|
|
3638 | callback () |
|
|
3639 | { |
|
|
3640 | free (request); |
|
|
3641 | } |
|
|
3642 | |
|
|
3643 | request = start_new_request (..., callback); |
|
|
3644 | |
|
|
3645 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3646 | used to cancel the operation, or do other things with it. |
|
|
3647 | |
|
|
3648 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3649 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3650 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3651 | operation and simply invoke the callback with the result. |
|
|
3652 | |
|
|
3653 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3654 | has returned, so C<request> is not set. |
|
|
3655 | |
|
|
3656 | Even if you pass the request by some safer means to the callback, you |
|
|
3657 | might want to do something to the request after starting it, such as |
|
|
3658 | canceling it, which probably isn't working so well when the callback has |
|
|
3659 | already been invoked. |
|
|
3660 | |
|
|
3661 | A common way around all these issues is to make sure that |
|
|
3662 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3663 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3664 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3665 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3666 | and pushing it into the pending queue: |
|
|
3667 | |
|
|
3668 | ev_set_cb (watcher, callback); |
|
|
3669 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3670 | |
|
|
3671 | This way, C<start_new_request> can safely return before the callback is |
|
|
3672 | invoked, while not delaying callback invocation too much. |
|
|
3673 | |
|
|
3674 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
|
|
3675 | |
|
|
3676 | Often (especially in GUI toolkits) there are places where you have |
|
|
3677 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3678 | invoking C<ev_run>. |
|
|
3679 | |
|
|
3680 | This brings the problem of exiting - a callback might want to finish the |
|
|
3681 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3682 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3683 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3684 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3685 | |
|
|
3686 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3687 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3688 | triggered, using C<EVRUN_ONCE>: |
|
|
3689 | |
|
|
3690 | // main loop |
|
|
3691 | int exit_main_loop = 0; |
|
|
3692 | |
|
|
3693 | while (!exit_main_loop) |
|
|
3694 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3695 | |
|
|
3696 | // in a modal watcher |
|
|
3697 | int exit_nested_loop = 0; |
|
|
3698 | |
|
|
3699 | while (!exit_nested_loop) |
|
|
3700 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3701 | |
|
|
3702 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3703 | |
|
|
3704 | // exit modal loop |
|
|
3705 | exit_nested_loop = 1; |
|
|
3706 | |
|
|
3707 | // exit main program, after modal loop is finished |
|
|
3708 | exit_main_loop = 1; |
|
|
3709 | |
|
|
3710 | // exit both |
|
|
3711 | exit_main_loop = exit_nested_loop = 1; |
|
|
3712 | |
|
|
3713 | =head2 THREAD LOCKING EXAMPLE |
|
|
3714 | |
|
|
3715 | Here is a fictitious example of how to run an event loop in a different |
|
|
3716 | thread from where callbacks are being invoked and watchers are |
|
|
3717 | created/added/removed. |
|
|
3718 | |
|
|
3719 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
3720 | which uses exactly this technique (which is suited for many high-level |
|
|
3721 | languages). |
|
|
3722 | |
|
|
3723 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
3724 | variable to wait for callback invocations, an async watcher to notify the |
|
|
3725 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
3726 | |
|
|
3727 | First, you need to associate some data with the event loop: |
|
|
3728 | |
|
|
3729 | typedef struct { |
|
|
3730 | mutex_t lock; /* global loop lock */ |
|
|
3731 | ev_async async_w; |
|
|
3732 | thread_t tid; |
|
|
3733 | cond_t invoke_cv; |
|
|
3734 | } userdata; |
|
|
3735 | |
|
|
3736 | void prepare_loop (EV_P) |
|
|
3737 | { |
|
|
3738 | // for simplicity, we use a static userdata struct. |
|
|
3739 | static userdata u; |
|
|
3740 | |
|
|
3741 | ev_async_init (&u->async_w, async_cb); |
|
|
3742 | ev_async_start (EV_A_ &u->async_w); |
|
|
3743 | |
|
|
3744 | pthread_mutex_init (&u->lock, 0); |
|
|
3745 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
3746 | |
|
|
3747 | // now associate this with the loop |
|
|
3748 | ev_set_userdata (EV_A_ u); |
|
|
3749 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
3750 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
3751 | |
|
|
3752 | // then create the thread running ev_run |
|
|
3753 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
3754 | } |
|
|
3755 | |
|
|
3756 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
3757 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
3758 | that might have been added: |
|
|
3759 | |
|
|
3760 | static void |
|
|
3761 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
3762 | { |
|
|
3763 | // just used for the side effects |
|
|
3764 | } |
|
|
3765 | |
|
|
3766 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
3767 | protecting the loop data, respectively. |
|
|
3768 | |
|
|
3769 | static void |
|
|
3770 | l_release (EV_P) |
|
|
3771 | { |
|
|
3772 | userdata *u = ev_userdata (EV_A); |
|
|
3773 | pthread_mutex_unlock (&u->lock); |
|
|
3774 | } |
|
|
3775 | |
|
|
3776 | static void |
|
|
3777 | l_acquire (EV_P) |
|
|
3778 | { |
|
|
3779 | userdata *u = ev_userdata (EV_A); |
|
|
3780 | pthread_mutex_lock (&u->lock); |
|
|
3781 | } |
|
|
3782 | |
|
|
3783 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
3784 | into C<ev_run>: |
|
|
3785 | |
|
|
3786 | void * |
|
|
3787 | l_run (void *thr_arg) |
|
|
3788 | { |
|
|
3789 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
3790 | |
|
|
3791 | l_acquire (EV_A); |
|
|
3792 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
3793 | ev_run (EV_A_ 0); |
|
|
3794 | l_release (EV_A); |
|
|
3795 | |
|
|
3796 | return 0; |
|
|
3797 | } |
|
|
3798 | |
|
|
3799 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
3800 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
3801 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
3802 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
3803 | and b) skipping inter-thread-communication when there are no pending |
|
|
3804 | watchers is very beneficial): |
|
|
3805 | |
|
|
3806 | static void |
|
|
3807 | l_invoke (EV_P) |
|
|
3808 | { |
|
|
3809 | userdata *u = ev_userdata (EV_A); |
|
|
3810 | |
|
|
3811 | while (ev_pending_count (EV_A)) |
|
|
3812 | { |
|
|
3813 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
3814 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
3815 | } |
|
|
3816 | } |
|
|
3817 | |
|
|
3818 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
3819 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
3820 | thread to continue: |
|
|
3821 | |
|
|
3822 | static void |
|
|
3823 | real_invoke_pending (EV_P) |
|
|
3824 | { |
|
|
3825 | userdata *u = ev_userdata (EV_A); |
|
|
3826 | |
|
|
3827 | pthread_mutex_lock (&u->lock); |
|
|
3828 | ev_invoke_pending (EV_A); |
|
|
3829 | pthread_cond_signal (&u->invoke_cv); |
|
|
3830 | pthread_mutex_unlock (&u->lock); |
|
|
3831 | } |
|
|
3832 | |
|
|
3833 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
3834 | event loop, you will now have to lock: |
|
|
3835 | |
|
|
3836 | ev_timer timeout_watcher; |
|
|
3837 | userdata *u = ev_userdata (EV_A); |
|
|
3838 | |
|
|
3839 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
3840 | |
|
|
3841 | pthread_mutex_lock (&u->lock); |
|
|
3842 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
3843 | ev_async_send (EV_A_ &u->async_w); |
|
|
3844 | pthread_mutex_unlock (&u->lock); |
|
|
3845 | |
|
|
3846 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
3847 | an event loop currently blocking in the kernel will have no knowledge |
|
|
3848 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
3849 | watchers in the next event loop iteration. |
|
|
3850 | |
|
|
3851 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3852 | |
|
|
3853 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3854 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3855 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3856 | doesn't need callbacks anymore. |
|
|
3857 | |
|
|
3858 | Imagine you have coroutines that you can switch to using a function |
|
|
3859 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3860 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3861 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3862 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3863 | the differing C<;> conventions): |
|
|
3864 | |
|
|
3865 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3866 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3867 | |
|
|
3868 | That means instead of having a C callback function, you store the |
|
|
3869 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3870 | your callback, you instead have it switch to that coroutine. |
|
|
3871 | |
|
|
3872 | A coroutine might now wait for an event with a function called |
|
|
3873 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3874 | matter when, or whether the watcher is active or not when this function is |
|
|
3875 | called): |
|
|
3876 | |
|
|
3877 | void |
|
|
3878 | wait_for_event (ev_watcher *w) |
|
|
3879 | { |
|
|
3880 | ev_set_cb (w, current_coro); |
|
|
3881 | switch_to (libev_coro); |
|
|
3882 | } |
|
|
3883 | |
|
|
3884 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3885 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3886 | this or any other coroutine. |
|
|
3887 | |
|
|
3888 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3889 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3890 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3891 | any waiters. |
|
|
3892 | |
|
|
3893 | To embed libev, see L</EMBEDDING>, but in short, it's easiest to create two |
|
|
3894 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3895 | |
|
|
3896 | // my_ev.h |
|
|
3897 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3898 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3899 | #include "../libev/ev.h" |
|
|
3900 | |
|
|
3901 | // my_ev.c |
|
|
3902 | #define EV_H "my_ev.h" |
|
|
3903 | #include "../libev/ev.c" |
|
|
3904 | |
|
|
3905 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3906 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3907 | can even use F<ev.h> as header file name directly. |
2440 | |
3908 | |
2441 | |
3909 | |
2442 | =head1 LIBEVENT EMULATION |
3910 | =head1 LIBEVENT EMULATION |
2443 | |
3911 | |
2444 | Libev offers a compatibility emulation layer for libevent. It cannot |
3912 | Libev offers a compatibility emulation layer for libevent. It cannot |
2445 | emulate the internals of libevent, so here are some usage hints: |
3913 | emulate the internals of libevent, so here are some usage hints: |
2446 | |
3914 | |
2447 | =over 4 |
3915 | =over 4 |
|
|
3916 | |
|
|
3917 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3918 | |
|
|
3919 | This was the newest libevent version available when libev was implemented, |
|
|
3920 | and is still mostly unchanged in 2010. |
2448 | |
3921 | |
2449 | =item * Use it by including <event.h>, as usual. |
3922 | =item * Use it by including <event.h>, as usual. |
2450 | |
3923 | |
2451 | =item * The following members are fully supported: ev_base, ev_callback, |
3924 | =item * The following members are fully supported: ev_base, ev_callback, |
2452 | ev_arg, ev_fd, ev_res, ev_events. |
3925 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2458 | =item * Priorities are not currently supported. Initialising priorities |
3931 | =item * Priorities are not currently supported. Initialising priorities |
2459 | will fail and all watchers will have the same priority, even though there |
3932 | will fail and all watchers will have the same priority, even though there |
2460 | is an ev_pri field. |
3933 | is an ev_pri field. |
2461 | |
3934 | |
2462 | =item * In libevent, the last base created gets the signals, in libev, the |
3935 | =item * In libevent, the last base created gets the signals, in libev, the |
2463 | first base created (== the default loop) gets the signals. |
3936 | base that registered the signal gets the signals. |
2464 | |
3937 | |
2465 | =item * Other members are not supported. |
3938 | =item * Other members are not supported. |
2466 | |
3939 | |
2467 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3940 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2468 | to use the libev header file and library. |
3941 | to use the libev header file and library. |
2469 | |
3942 | |
2470 | =back |
3943 | =back |
2471 | |
3944 | |
2472 | =head1 C++ SUPPORT |
3945 | =head1 C++ SUPPORT |
|
|
3946 | |
|
|
3947 | =head2 C API |
|
|
3948 | |
|
|
3949 | The normal C API should work fine when used from C++: both ev.h and the |
|
|
3950 | libev sources can be compiled as C++. Therefore, code that uses the C API |
|
|
3951 | will work fine. |
|
|
3952 | |
|
|
3953 | Proper exception specifications might have to be added to callbacks passed |
|
|
3954 | to libev: exceptions may be thrown only from watcher callbacks, all |
|
|
3955 | other callbacks (allocator, syserr, loop acquire/release and periodioc |
|
|
3956 | reschedule callbacks) must not throw exceptions, and might need a C<throw |
|
|
3957 | ()> specification. If you have code that needs to be compiled as both C |
|
|
3958 | and C++ you can use the C<EV_THROW> macro for this: |
|
|
3959 | |
|
|
3960 | static void |
|
|
3961 | fatal_error (const char *msg) EV_THROW |
|
|
3962 | { |
|
|
3963 | perror (msg); |
|
|
3964 | abort (); |
|
|
3965 | } |
|
|
3966 | |
|
|
3967 | ... |
|
|
3968 | ev_set_syserr_cb (fatal_error); |
|
|
3969 | |
|
|
3970 | The only API functions that can currently throw exceptions are C<ev_run>, |
|
|
3971 | C<ev_invoke>, C<ev_invoke_pending> and C<ev_loop_destroy> (the latter |
|
|
3972 | because it runs cleanup watchers). |
|
|
3973 | |
|
|
3974 | Throwing exceptions in watcher callbacks is only supported if libev itself |
|
|
3975 | is compiled with a C++ compiler or your C and C++ environments allow |
|
|
3976 | throwing exceptions through C libraries (most do). |
|
|
3977 | |
|
|
3978 | =head2 C++ API |
2473 | |
3979 | |
2474 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
3980 | Libev comes with some simplistic wrapper classes for C++ that mainly allow |
2475 | you to use some convenience methods to start/stop watchers and also change |
3981 | you to use some convenience methods to start/stop watchers and also change |
2476 | the callback model to a model using method callbacks on objects. |
3982 | the callback model to a model using method callbacks on objects. |
2477 | |
3983 | |
… | |
… | |
2487 | Care has been taken to keep the overhead low. The only data member the C++ |
3993 | Care has been taken to keep the overhead low. The only data member the C++ |
2488 | classes add (compared to plain C-style watchers) is the event loop pointer |
3994 | classes add (compared to plain C-style watchers) is the event loop pointer |
2489 | that the watcher is associated with (or no additional members at all if |
3995 | that the watcher is associated with (or no additional members at all if |
2490 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3996 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2491 | |
3997 | |
2492 | Currently, functions, and static and non-static member functions can be |
3998 | Currently, functions, static and non-static member functions and classes |
2493 | used as callbacks. Other types should be easy to add as long as they only |
3999 | with C<operator ()> can be used as callbacks. Other types should be easy |
2494 | need one additional pointer for context. If you need support for other |
4000 | to add as long as they only need one additional pointer for context. If |
2495 | types of functors please contact the author (preferably after implementing |
4001 | you need support for other types of functors please contact the author |
2496 | it). |
4002 | (preferably after implementing it). |
|
|
4003 | |
|
|
4004 | For all this to work, your C++ compiler either has to use the same calling |
|
|
4005 | conventions as your C compiler (for static member functions), or you have |
|
|
4006 | to embed libev and compile libev itself as C++. |
2497 | |
4007 | |
2498 | Here is a list of things available in the C<ev> namespace: |
4008 | Here is a list of things available in the C<ev> namespace: |
2499 | |
4009 | |
2500 | =over 4 |
4010 | =over 4 |
2501 | |
4011 | |
… | |
… | |
2511 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
4021 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
2512 | |
4022 | |
2513 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
4023 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
2514 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
4024 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
2515 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
4025 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
2516 | defines by many implementations. |
4026 | defined by many implementations. |
2517 | |
4027 | |
2518 | All of those classes have these methods: |
4028 | All of those classes have these methods: |
2519 | |
4029 | |
2520 | =over 4 |
4030 | =over 4 |
2521 | |
4031 | |
2522 | =item ev::TYPE::TYPE () |
4032 | =item ev::TYPE::TYPE () |
2523 | |
4033 | |
2524 | =item ev::TYPE::TYPE (struct ev_loop *) |
4034 | =item ev::TYPE::TYPE (loop) |
2525 | |
4035 | |
2526 | =item ev::TYPE::~TYPE |
4036 | =item ev::TYPE::~TYPE |
2527 | |
4037 | |
2528 | The constructor (optionally) takes an event loop to associate the watcher |
4038 | The constructor (optionally) takes an event loop to associate the watcher |
2529 | with. If it is omitted, it will use C<EV_DEFAULT>. |
4039 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2561 | |
4071 | |
2562 | myclass obj; |
4072 | myclass obj; |
2563 | ev::io iow; |
4073 | ev::io iow; |
2564 | iow.set <myclass, &myclass::io_cb> (&obj); |
4074 | iow.set <myclass, &myclass::io_cb> (&obj); |
2565 | |
4075 | |
|
|
4076 | =item w->set (object *) |
|
|
4077 | |
|
|
4078 | This is a variation of a method callback - leaving out the method to call |
|
|
4079 | will default the method to C<operator ()>, which makes it possible to use |
|
|
4080 | functor objects without having to manually specify the C<operator ()> all |
|
|
4081 | the time. Incidentally, you can then also leave out the template argument |
|
|
4082 | list. |
|
|
4083 | |
|
|
4084 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
4085 | int revents)>. |
|
|
4086 | |
|
|
4087 | See the method-C<set> above for more details. |
|
|
4088 | |
|
|
4089 | Example: use a functor object as callback. |
|
|
4090 | |
|
|
4091 | struct myfunctor |
|
|
4092 | { |
|
|
4093 | void operator() (ev::io &w, int revents) |
|
|
4094 | { |
|
|
4095 | ... |
|
|
4096 | } |
|
|
4097 | } |
|
|
4098 | |
|
|
4099 | myfunctor f; |
|
|
4100 | |
|
|
4101 | ev::io w; |
|
|
4102 | w.set (&f); |
|
|
4103 | |
2566 | =item w->set<function> (void *data = 0) |
4104 | =item w->set<function> (void *data = 0) |
2567 | |
4105 | |
2568 | Also sets a callback, but uses a static method or plain function as |
4106 | Also sets a callback, but uses a static method or plain function as |
2569 | callback. The optional C<data> argument will be stored in the watcher's |
4107 | callback. The optional C<data> argument will be stored in the watcher's |
2570 | C<data> member and is free for you to use. |
4108 | C<data> member and is free for you to use. |
2571 | |
4109 | |
2572 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
4110 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2573 | |
4111 | |
2574 | See the method-C<set> above for more details. |
4112 | See the method-C<set> above for more details. |
2575 | |
4113 | |
2576 | Example: |
4114 | Example: Use a plain function as callback. |
2577 | |
4115 | |
2578 | static void io_cb (ev::io &w, int revents) { } |
4116 | static void io_cb (ev::io &w, int revents) { } |
2579 | iow.set <io_cb> (); |
4117 | iow.set <io_cb> (); |
2580 | |
4118 | |
2581 | =item w->set (struct ev_loop *) |
4119 | =item w->set (loop) |
2582 | |
4120 | |
2583 | Associates a different C<struct ev_loop> with this watcher. You can only |
4121 | Associates a different C<struct ev_loop> with this watcher. You can only |
2584 | do this when the watcher is inactive (and not pending either). |
4122 | do this when the watcher is inactive (and not pending either). |
2585 | |
4123 | |
2586 | =item w->set ([arguments]) |
4124 | =item w->set ([arguments]) |
2587 | |
4125 | |
2588 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
4126 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2589 | called at least once. Unlike the C counterpart, an active watcher gets |
4127 | method or a suitable start method must be called at least once. Unlike the |
2590 | automatically stopped and restarted when reconfiguring it with this |
4128 | C counterpart, an active watcher gets automatically stopped and restarted |
2591 | method. |
4129 | when reconfiguring it with this method. |
2592 | |
4130 | |
2593 | =item w->start () |
4131 | =item w->start () |
2594 | |
4132 | |
2595 | Starts the watcher. Note that there is no C<loop> argument, as the |
4133 | Starts the watcher. Note that there is no C<loop> argument, as the |
2596 | constructor already stores the event loop. |
4134 | constructor already stores the event loop. |
2597 | |
4135 | |
|
|
4136 | =item w->start ([arguments]) |
|
|
4137 | |
|
|
4138 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
4139 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
4140 | the configure C<set> method of the watcher. |
|
|
4141 | |
2598 | =item w->stop () |
4142 | =item w->stop () |
2599 | |
4143 | |
2600 | Stops the watcher if it is active. Again, no C<loop> argument. |
4144 | Stops the watcher if it is active. Again, no C<loop> argument. |
2601 | |
4145 | |
2602 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
4146 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2614 | |
4158 | |
2615 | =back |
4159 | =back |
2616 | |
4160 | |
2617 | =back |
4161 | =back |
2618 | |
4162 | |
2619 | Example: Define a class with an IO and idle watcher, start one of them in |
4163 | Example: Define a class with two I/O and idle watchers, start the I/O |
2620 | the constructor. |
4164 | watchers in the constructor. |
2621 | |
4165 | |
2622 | class myclass |
4166 | class myclass |
2623 | { |
4167 | { |
2624 | ev::io io; void io_cb (ev::io &w, int revents); |
4168 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
4169 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
2625 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
4170 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2626 | |
4171 | |
2627 | myclass (int fd) |
4172 | myclass (int fd) |
2628 | { |
4173 | { |
2629 | io .set <myclass, &myclass::io_cb > (this); |
4174 | io .set <myclass, &myclass::io_cb > (this); |
|
|
4175 | io2 .set <myclass, &myclass::io2_cb > (this); |
2630 | idle.set <myclass, &myclass::idle_cb> (this); |
4176 | idle.set <myclass, &myclass::idle_cb> (this); |
2631 | |
4177 | |
2632 | io.start (fd, ev::READ); |
4178 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
4179 | io.start (); // start it whenever convenient |
|
|
4180 | |
|
|
4181 | io2.start (fd, ev::READ); // set + start in one call |
2633 | } |
4182 | } |
2634 | }; |
4183 | }; |
2635 | |
4184 | |
2636 | |
4185 | |
2637 | =head1 OTHER LANGUAGE BINDINGS |
4186 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2646 | =item Perl |
4195 | =item Perl |
2647 | |
4196 | |
2648 | The EV module implements the full libev API and is actually used to test |
4197 | The EV module implements the full libev API and is actually used to test |
2649 | libev. EV is developed together with libev. Apart from the EV core module, |
4198 | libev. EV is developed together with libev. Apart from the EV core module, |
2650 | there are additional modules that implement libev-compatible interfaces |
4199 | there are additional modules that implement libev-compatible interfaces |
2651 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
4200 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2652 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
4201 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
4202 | and C<EV::Glib>). |
2653 | |
4203 | |
2654 | It can be found and installed via CPAN, its homepage is at |
4204 | It can be found and installed via CPAN, its homepage is at |
2655 | L<http://software.schmorp.de/pkg/EV>. |
4205 | L<http://software.schmorp.de/pkg/EV>. |
2656 | |
4206 | |
2657 | =item Python |
4207 | =item Python |
2658 | |
4208 | |
2659 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
4209 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2660 | seems to be quite complete and well-documented. Note, however, that the |
4210 | seems to be quite complete and well-documented. |
2661 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2662 | for everybody else, and therefore, should never be applied in an installed |
|
|
2663 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2664 | libev). |
|
|
2665 | |
4211 | |
2666 | =item Ruby |
4212 | =item Ruby |
2667 | |
4213 | |
2668 | Tony Arcieri has written a ruby extension that offers access to a subset |
4214 | Tony Arcieri has written a ruby extension that offers access to a subset |
2669 | of the libev API and adds file handle abstractions, asynchronous DNS and |
4215 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2670 | more on top of it. It can be found via gem servers. Its homepage is at |
4216 | more on top of it. It can be found via gem servers. Its homepage is at |
2671 | L<http://rev.rubyforge.org/>. |
4217 | L<http://rev.rubyforge.org/>. |
2672 | |
4218 | |
|
|
4219 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
4220 | makes rev work even on mingw. |
|
|
4221 | |
|
|
4222 | =item Haskell |
|
|
4223 | |
|
|
4224 | A haskell binding to libev is available at |
|
|
4225 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
4226 | |
2673 | =item D |
4227 | =item D |
2674 | |
4228 | |
2675 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4229 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2676 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4230 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
|
|
4231 | |
|
|
4232 | =item Ocaml |
|
|
4233 | |
|
|
4234 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
4235 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
4236 | |
|
|
4237 | =item Lua |
|
|
4238 | |
|
|
4239 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
4240 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
4241 | L<http://github.com/brimworks/lua-ev>. |
|
|
4242 | |
|
|
4243 | =item Javascript |
|
|
4244 | |
|
|
4245 | Node.js (L<http://nodejs.org>) uses libev as the underlying event library. |
|
|
4246 | |
|
|
4247 | =item Others |
|
|
4248 | |
|
|
4249 | There are others, and I stopped counting. |
2677 | |
4250 | |
2678 | =back |
4251 | =back |
2679 | |
4252 | |
2680 | |
4253 | |
2681 | =head1 MACRO MAGIC |
4254 | =head1 MACRO MAGIC |
… | |
… | |
2695 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
4268 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2696 | C<EV_A_> is used when other arguments are following. Example: |
4269 | C<EV_A_> is used when other arguments are following. Example: |
2697 | |
4270 | |
2698 | ev_unref (EV_A); |
4271 | ev_unref (EV_A); |
2699 | ev_timer_add (EV_A_ watcher); |
4272 | ev_timer_add (EV_A_ watcher); |
2700 | ev_loop (EV_A_ 0); |
4273 | ev_run (EV_A_ 0); |
2701 | |
4274 | |
2702 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
4275 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2703 | which is often provided by the following macro. |
4276 | which is often provided by the following macro. |
2704 | |
4277 | |
2705 | =item C<EV_P>, C<EV_P_> |
4278 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
2718 | suitable for use with C<EV_A>. |
4291 | suitable for use with C<EV_A>. |
2719 | |
4292 | |
2720 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4293 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2721 | |
4294 | |
2722 | Similar to the other two macros, this gives you the value of the default |
4295 | Similar to the other two macros, this gives you the value of the default |
2723 | loop, if multiple loops are supported ("ev loop default"). |
4296 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4297 | will be initialised if it isn't already initialised. |
|
|
4298 | |
|
|
4299 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4300 | to initialise the loop somewhere. |
2724 | |
4301 | |
2725 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4302 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
2726 | |
4303 | |
2727 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4304 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
2728 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4305 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
2745 | } |
4322 | } |
2746 | |
4323 | |
2747 | ev_check check; |
4324 | ev_check check; |
2748 | ev_check_init (&check, check_cb); |
4325 | ev_check_init (&check, check_cb); |
2749 | ev_check_start (EV_DEFAULT_ &check); |
4326 | ev_check_start (EV_DEFAULT_ &check); |
2750 | ev_loop (EV_DEFAULT_ 0); |
4327 | ev_run (EV_DEFAULT_ 0); |
2751 | |
4328 | |
2752 | =head1 EMBEDDING |
4329 | =head1 EMBEDDING |
2753 | |
4330 | |
2754 | Libev can (and often is) directly embedded into host |
4331 | Libev can (and often is) directly embedded into host |
2755 | applications. Examples of applications that embed it include the Deliantra |
4332 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2782 | |
4359 | |
2783 | #define EV_STANDALONE 1 |
4360 | #define EV_STANDALONE 1 |
2784 | #include "ev.h" |
4361 | #include "ev.h" |
2785 | |
4362 | |
2786 | Both header files and implementation files can be compiled with a C++ |
4363 | Both header files and implementation files can be compiled with a C++ |
2787 | compiler (at least, thats a stated goal, and breakage will be treated |
4364 | compiler (at least, that's a stated goal, and breakage will be treated |
2788 | as a bug). |
4365 | as a bug). |
2789 | |
4366 | |
2790 | You need the following files in your source tree, or in a directory |
4367 | You need the following files in your source tree, or in a directory |
2791 | in your include path (e.g. in libev/ when using -Ilibev): |
4368 | in your include path (e.g. in libev/ when using -Ilibev): |
2792 | |
4369 | |
… | |
… | |
2835 | libev.m4 |
4412 | libev.m4 |
2836 | |
4413 | |
2837 | =head2 PREPROCESSOR SYMBOLS/MACROS |
4414 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2838 | |
4415 | |
2839 | Libev can be configured via a variety of preprocessor symbols you have to |
4416 | Libev can be configured via a variety of preprocessor symbols you have to |
2840 | define before including any of its files. The default in the absence of |
4417 | define before including (or compiling) any of its files. The default in |
2841 | autoconf is noted for every option. |
4418 | the absence of autoconf is documented for every option. |
|
|
4419 | |
|
|
4420 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
4421 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
4422 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
4423 | to a compiled library. All other symbols change the ABI, which means all |
|
|
4424 | users of libev and the libev code itself must be compiled with compatible |
|
|
4425 | settings. |
2842 | |
4426 | |
2843 | =over 4 |
4427 | =over 4 |
2844 | |
4428 | |
|
|
4429 | =item EV_COMPAT3 (h) |
|
|
4430 | |
|
|
4431 | Backwards compatibility is a major concern for libev. This is why this |
|
|
4432 | release of libev comes with wrappers for the functions and symbols that |
|
|
4433 | have been renamed between libev version 3 and 4. |
|
|
4434 | |
|
|
4435 | You can disable these wrappers (to test compatibility with future |
|
|
4436 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
4437 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
4438 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
4439 | typedef in that case. |
|
|
4440 | |
|
|
4441 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
4442 | and in some even more future version the compatibility code will be |
|
|
4443 | removed completely. |
|
|
4444 | |
2845 | =item EV_STANDALONE |
4445 | =item EV_STANDALONE (h) |
2846 | |
4446 | |
2847 | Must always be C<1> if you do not use autoconf configuration, which |
4447 | Must always be C<1> if you do not use autoconf configuration, which |
2848 | keeps libev from including F<config.h>, and it also defines dummy |
4448 | keeps libev from including F<config.h>, and it also defines dummy |
2849 | implementations for some libevent functions (such as logging, which is not |
4449 | implementations for some libevent functions (such as logging, which is not |
2850 | supported). It will also not define any of the structs usually found in |
4450 | supported). It will also not define any of the structs usually found in |
2851 | F<event.h> that are not directly supported by the libev core alone. |
4451 | F<event.h> that are not directly supported by the libev core alone. |
2852 | |
4452 | |
|
|
4453 | In standalone mode, libev will still try to automatically deduce the |
|
|
4454 | configuration, but has to be more conservative. |
|
|
4455 | |
|
|
4456 | =item EV_USE_FLOOR |
|
|
4457 | |
|
|
4458 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4459 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4460 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4461 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4462 | function is not available will fail, so the safe default is to not enable |
|
|
4463 | this. |
|
|
4464 | |
2853 | =item EV_USE_MONOTONIC |
4465 | =item EV_USE_MONOTONIC |
2854 | |
4466 | |
2855 | If defined to be C<1>, libev will try to detect the availability of the |
4467 | If defined to be C<1>, libev will try to detect the availability of the |
2856 | monotonic clock option at both compile time and runtime. Otherwise no use |
4468 | monotonic clock option at both compile time and runtime. Otherwise no |
2857 | of the monotonic clock option will be attempted. If you enable this, you |
4469 | use of the monotonic clock option will be attempted. If you enable this, |
2858 | usually have to link against librt or something similar. Enabling it when |
4470 | you usually have to link against librt or something similar. Enabling it |
2859 | the functionality isn't available is safe, though, although you have |
4471 | when the functionality isn't available is safe, though, although you have |
2860 | to make sure you link against any libraries where the C<clock_gettime> |
4472 | to make sure you link against any libraries where the C<clock_gettime> |
2861 | function is hiding in (often F<-lrt>). |
4473 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2862 | |
4474 | |
2863 | =item EV_USE_REALTIME |
4475 | =item EV_USE_REALTIME |
2864 | |
4476 | |
2865 | If defined to be C<1>, libev will try to detect the availability of the |
4477 | If defined to be C<1>, libev will try to detect the availability of the |
2866 | real-time clock option at compile time (and assume its availability at |
4478 | real-time clock option at compile time (and assume its availability |
2867 | runtime if successful). Otherwise no use of the real-time clock option will |
4479 | at runtime if successful). Otherwise no use of the real-time clock |
2868 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
4480 | option will be attempted. This effectively replaces C<gettimeofday> |
2869 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
4481 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2870 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
4482 | correctness. See the note about libraries in the description of |
|
|
4483 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
4484 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
4485 | |
|
|
4486 | =item EV_USE_CLOCK_SYSCALL |
|
|
4487 | |
|
|
4488 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
4489 | of calling the system-provided C<clock_gettime> function. This option |
|
|
4490 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
4491 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
4492 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4493 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4494 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
4495 | higher, as it simplifies linking (no need for C<-lrt>). |
2871 | |
4496 | |
2872 | =item EV_USE_NANOSLEEP |
4497 | =item EV_USE_NANOSLEEP |
2873 | |
4498 | |
2874 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
4499 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2875 | and will use it for delays. Otherwise it will use C<select ()>. |
4500 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2891 | |
4516 | |
2892 | =item EV_SELECT_USE_FD_SET |
4517 | =item EV_SELECT_USE_FD_SET |
2893 | |
4518 | |
2894 | If defined to C<1>, then the select backend will use the system C<fd_set> |
4519 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2895 | structure. This is useful if libev doesn't compile due to a missing |
4520 | structure. This is useful if libev doesn't compile due to a missing |
2896 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
4521 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2897 | exotic systems. This usually limits the range of file descriptors to some |
4522 | on exotic systems. This usually limits the range of file descriptors to |
2898 | low limit such as 1024 or might have other limitations (winsocket only |
4523 | some low limit such as 1024 or might have other limitations (winsocket |
2899 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
4524 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2900 | influence the size of the C<fd_set> used. |
4525 | configures the maximum size of the C<fd_set>. |
2901 | |
4526 | |
2902 | =item EV_SELECT_IS_WINSOCKET |
4527 | =item EV_SELECT_IS_WINSOCKET |
2903 | |
4528 | |
2904 | When defined to C<1>, the select backend will assume that |
4529 | When defined to C<1>, the select backend will assume that |
2905 | select/socket/connect etc. don't understand file descriptors but |
4530 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2907 | be used is the winsock select). This means that it will call |
4532 | be used is the winsock select). This means that it will call |
2908 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4533 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2909 | it is assumed that all these functions actually work on fds, even |
4534 | it is assumed that all these functions actually work on fds, even |
2910 | on win32. Should not be defined on non-win32 platforms. |
4535 | on win32. Should not be defined on non-win32 platforms. |
2911 | |
4536 | |
2912 | =item EV_FD_TO_WIN32_HANDLE |
4537 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2913 | |
4538 | |
2914 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4539 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2915 | file descriptors to socket handles. When not defining this symbol (the |
4540 | file descriptors to socket handles. When not defining this symbol (the |
2916 | default), then libev will call C<_get_osfhandle>, which is usually |
4541 | default), then libev will call C<_get_osfhandle>, which is usually |
2917 | correct. In some cases, programs use their own file descriptor management, |
4542 | correct. In some cases, programs use their own file descriptor management, |
2918 | in which case they can provide this function to map fds to socket handles. |
4543 | in which case they can provide this function to map fds to socket handles. |
|
|
4544 | |
|
|
4545 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4546 | |
|
|
4547 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4548 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4549 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4550 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4551 | |
|
|
4552 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4553 | |
|
|
4554 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4555 | macro can be used to override the C<close> function, useful to unregister |
|
|
4556 | file descriptors again. Note that the replacement function has to close |
|
|
4557 | the underlying OS handle. |
|
|
4558 | |
|
|
4559 | =item EV_USE_WSASOCKET |
|
|
4560 | |
|
|
4561 | If defined to be C<1>, libev will use C<WSASocket> to create its internal |
|
|
4562 | communication socket, which works better in some environments. Otherwise, |
|
|
4563 | the normal C<socket> function will be used, which works better in other |
|
|
4564 | enviornments. |
2919 | |
4565 | |
2920 | =item EV_USE_POLL |
4566 | =item EV_USE_POLL |
2921 | |
4567 | |
2922 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4568 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2923 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4569 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
2959 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4605 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2960 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4606 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2961 | be detected at runtime. If undefined, it will be enabled if the headers |
4607 | be detected at runtime. If undefined, it will be enabled if the headers |
2962 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4608 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2963 | |
4609 | |
|
|
4610 | =item EV_NO_SMP |
|
|
4611 | |
|
|
4612 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4613 | between threads, that is, threads can be used, but threads never run on |
|
|
4614 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4615 | and makes libev faster. |
|
|
4616 | |
|
|
4617 | =item EV_NO_THREADS |
|
|
4618 | |
|
|
4619 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4620 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4621 | above. This reduces dependencies and makes libev faster. |
|
|
4622 | |
2964 | =item EV_ATOMIC_T |
4623 | =item EV_ATOMIC_T |
2965 | |
4624 | |
2966 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4625 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2967 | access is atomic with respect to other threads or signal contexts. No such |
4626 | access is atomic and serialised with respect to other threads or signal |
2968 | type is easily found in the C language, so you can provide your own type |
4627 | contexts. No such type is easily found in the C language, so you can |
2969 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4628 | provide your own type that you know is safe for your purposes. It is used |
2970 | as well as for signal and thread safety in C<ev_async> watchers. |
4629 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4630 | in C<ev_async> watchers. |
2971 | |
4631 | |
2972 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4632 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2973 | (from F<signal.h>), which is usually good enough on most platforms. |
4633 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4634 | although strictly speaking using a type that also implies a memory fence |
|
|
4635 | is required. |
2974 | |
4636 | |
2975 | =item EV_H |
4637 | =item EV_H (h) |
2976 | |
4638 | |
2977 | The name of the F<ev.h> header file used to include it. The default if |
4639 | The name of the F<ev.h> header file used to include it. The default if |
2978 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4640 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2979 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4641 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2980 | |
4642 | |
2981 | =item EV_CONFIG_H |
4643 | =item EV_CONFIG_H (h) |
2982 | |
4644 | |
2983 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4645 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2984 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4646 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2985 | C<EV_H>, above. |
4647 | C<EV_H>, above. |
2986 | |
4648 | |
2987 | =item EV_EVENT_H |
4649 | =item EV_EVENT_H (h) |
2988 | |
4650 | |
2989 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4651 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2990 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4652 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2991 | |
4653 | |
2992 | =item EV_PROTOTYPES |
4654 | =item EV_PROTOTYPES (h) |
2993 | |
4655 | |
2994 | If defined to be C<0>, then F<ev.h> will not define any function |
4656 | If defined to be C<0>, then F<ev.h> will not define any function |
2995 | prototypes, but still define all the structs and other symbols. This is |
4657 | prototypes, but still define all the structs and other symbols. This is |
2996 | occasionally useful if you want to provide your own wrapper functions |
4658 | occasionally useful if you want to provide your own wrapper functions |
2997 | around libev functions. |
4659 | around libev functions. |
… | |
… | |
3002 | will have the C<struct ev_loop *> as first argument, and you can create |
4664 | will have the C<struct ev_loop *> as first argument, and you can create |
3003 | additional independent event loops. Otherwise there will be no support |
4665 | additional independent event loops. Otherwise there will be no support |
3004 | for multiple event loops and there is no first event loop pointer |
4666 | for multiple event loops and there is no first event loop pointer |
3005 | argument. Instead, all functions act on the single default loop. |
4667 | argument. Instead, all functions act on the single default loop. |
3006 | |
4668 | |
|
|
4669 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4670 | default loop when multiplicity is switched off - you always have to |
|
|
4671 | initialise the loop manually in this case. |
|
|
4672 | |
3007 | =item EV_MINPRI |
4673 | =item EV_MINPRI |
3008 | |
4674 | |
3009 | =item EV_MAXPRI |
4675 | =item EV_MAXPRI |
3010 | |
4676 | |
3011 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4677 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
3016 | When doing priority-based operations, libev usually has to linearly search |
4682 | When doing priority-based operations, libev usually has to linearly search |
3017 | all the priorities, so having many of them (hundreds) uses a lot of space |
4683 | all the priorities, so having many of them (hundreds) uses a lot of space |
3018 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
4684 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3019 | fine. |
4685 | fine. |
3020 | |
4686 | |
3021 | If your embedding application does not need any priorities, defining these both to |
4687 | If your embedding application does not need any priorities, defining these |
3022 | C<0> will save some memory and CPU. |
4688 | both to C<0> will save some memory and CPU. |
3023 | |
4689 | |
3024 | =item EV_PERIODIC_ENABLE |
4690 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4691 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4692 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3025 | |
4693 | |
3026 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4694 | If undefined or defined to be C<1> (and the platform supports it), then |
3027 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4695 | the respective watcher type is supported. If defined to be C<0>, then it |
3028 | code. |
4696 | is not. Disabling watcher types mainly saves code size. |
3029 | |
4697 | |
3030 | =item EV_IDLE_ENABLE |
4698 | =item EV_FEATURES |
3031 | |
|
|
3032 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3033 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3034 | code. |
|
|
3035 | |
|
|
3036 | =item EV_EMBED_ENABLE |
|
|
3037 | |
|
|
3038 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3039 | defined to be C<0>, then they are not. |
|
|
3040 | |
|
|
3041 | =item EV_STAT_ENABLE |
|
|
3042 | |
|
|
3043 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3044 | defined to be C<0>, then they are not. |
|
|
3045 | |
|
|
3046 | =item EV_FORK_ENABLE |
|
|
3047 | |
|
|
3048 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3049 | defined to be C<0>, then they are not. |
|
|
3050 | |
|
|
3051 | =item EV_ASYNC_ENABLE |
|
|
3052 | |
|
|
3053 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3054 | defined to be C<0>, then they are not. |
|
|
3055 | |
|
|
3056 | =item EV_MINIMAL |
|
|
3057 | |
4699 | |
3058 | If you need to shave off some kilobytes of code at the expense of some |
4700 | If you need to shave off some kilobytes of code at the expense of some |
3059 | speed, define this symbol to C<1>. Currently this is used to override some |
4701 | speed (but with the full API), you can define this symbol to request |
3060 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4702 | certain subsets of functionality. The default is to enable all features |
3061 | much smaller 2-heap for timer management over the default 4-heap. |
4703 | that can be enabled on the platform. |
|
|
4704 | |
|
|
4705 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4706 | with some broad features you want) and then selectively re-enable |
|
|
4707 | additional parts you want, for example if you want everything minimal, |
|
|
4708 | but multiple event loop support, async and child watchers and the poll |
|
|
4709 | backend, use this: |
|
|
4710 | |
|
|
4711 | #define EV_FEATURES 0 |
|
|
4712 | #define EV_MULTIPLICITY 1 |
|
|
4713 | #define EV_USE_POLL 1 |
|
|
4714 | #define EV_CHILD_ENABLE 1 |
|
|
4715 | #define EV_ASYNC_ENABLE 1 |
|
|
4716 | |
|
|
4717 | The actual value is a bitset, it can be a combination of the following |
|
|
4718 | values (by default, all of these are enabled): |
|
|
4719 | |
|
|
4720 | =over 4 |
|
|
4721 | |
|
|
4722 | =item C<1> - faster/larger code |
|
|
4723 | |
|
|
4724 | Use larger code to speed up some operations. |
|
|
4725 | |
|
|
4726 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4727 | code size by roughly 30% on amd64). |
|
|
4728 | |
|
|
4729 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4730 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4731 | assertions. |
|
|
4732 | |
|
|
4733 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4734 | (e.g. gcc with C<-Os>). |
|
|
4735 | |
|
|
4736 | =item C<2> - faster/larger data structures |
|
|
4737 | |
|
|
4738 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4739 | hash table sizes and so on. This will usually further increase code size |
|
|
4740 | and can additionally have an effect on the size of data structures at |
|
|
4741 | runtime. |
|
|
4742 | |
|
|
4743 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4744 | (e.g. gcc with C<-Os>). |
|
|
4745 | |
|
|
4746 | =item C<4> - full API configuration |
|
|
4747 | |
|
|
4748 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4749 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4750 | |
|
|
4751 | =item C<8> - full API |
|
|
4752 | |
|
|
4753 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4754 | details on which parts of the API are still available without this |
|
|
4755 | feature, and do not complain if this subset changes over time. |
|
|
4756 | |
|
|
4757 | =item C<16> - enable all optional watcher types |
|
|
4758 | |
|
|
4759 | Enables all optional watcher types. If you want to selectively enable |
|
|
4760 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4761 | embed, async, child...) you can enable them manually by defining |
|
|
4762 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4763 | |
|
|
4764 | =item C<32> - enable all backends |
|
|
4765 | |
|
|
4766 | This enables all backends - without this feature, you need to enable at |
|
|
4767 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4768 | |
|
|
4769 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4770 | |
|
|
4771 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4772 | default. |
|
|
4773 | |
|
|
4774 | =back |
|
|
4775 | |
|
|
4776 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4777 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4778 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4779 | watchers, timers and monotonic clock support. |
|
|
4780 | |
|
|
4781 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4782 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4783 | your program might be left out as well - a binary starting a timer and an |
|
|
4784 | I/O watcher then might come out at only 5Kb. |
|
|
4785 | |
|
|
4786 | =item EV_API_STATIC |
|
|
4787 | |
|
|
4788 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4789 | will have static linkage. This means that libev will not export any |
|
|
4790 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4791 | when you embed libev, only want to use libev functions in a single file, |
|
|
4792 | and do not want its identifiers to be visible. |
|
|
4793 | |
|
|
4794 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4795 | wants to use libev. |
|
|
4796 | |
|
|
4797 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4798 | doesn't support the required declaration syntax. |
|
|
4799 | |
|
|
4800 | =item EV_AVOID_STDIO |
|
|
4801 | |
|
|
4802 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4803 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4804 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4805 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4806 | big. |
|
|
4807 | |
|
|
4808 | Note that error messages might become less precise when this option is |
|
|
4809 | enabled. |
|
|
4810 | |
|
|
4811 | =item EV_NSIG |
|
|
4812 | |
|
|
4813 | The highest supported signal number, +1 (or, the number of |
|
|
4814 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4815 | automatically, but sometimes this fails, in which case it can be |
|
|
4816 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4817 | good for about any system in existence) can save some memory, as libev |
|
|
4818 | statically allocates some 12-24 bytes per signal number. |
3062 | |
4819 | |
3063 | =item EV_PID_HASHSIZE |
4820 | =item EV_PID_HASHSIZE |
3064 | |
4821 | |
3065 | C<ev_child> watchers use a small hash table to distribute workload by |
4822 | C<ev_child> watchers use a small hash table to distribute workload by |
3066 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4823 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3067 | than enough. If you need to manage thousands of children you might want to |
4824 | usually more than enough. If you need to manage thousands of children you |
3068 | increase this value (I<must> be a power of two). |
4825 | might want to increase this value (I<must> be a power of two). |
3069 | |
4826 | |
3070 | =item EV_INOTIFY_HASHSIZE |
4827 | =item EV_INOTIFY_HASHSIZE |
3071 | |
4828 | |
3072 | C<ev_stat> watchers use a small hash table to distribute workload by |
4829 | C<ev_stat> watchers use a small hash table to distribute workload by |
3073 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4830 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3074 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4831 | disabled), usually more than enough. If you need to manage thousands of |
3075 | watchers you might want to increase this value (I<must> be a power of |
4832 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3076 | two). |
4833 | power of two). |
3077 | |
4834 | |
3078 | =item EV_USE_4HEAP |
4835 | =item EV_USE_4HEAP |
3079 | |
4836 | |
3080 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4837 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3081 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4838 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3082 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4839 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3083 | noticeably faster performance with many (thousands) of watchers. |
4840 | faster performance with many (thousands) of watchers. |
3084 | |
4841 | |
3085 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4842 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3086 | (disabled). |
4843 | will be C<0>. |
3087 | |
4844 | |
3088 | =item EV_HEAP_CACHE_AT |
4845 | =item EV_HEAP_CACHE_AT |
3089 | |
4846 | |
3090 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4847 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3091 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4848 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3092 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4849 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3093 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4850 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3094 | but avoids random read accesses on heap changes. This improves performance |
4851 | but avoids random read accesses on heap changes. This improves performance |
3095 | noticeably with with many (hundreds) of watchers. |
4852 | noticeably with many (hundreds) of watchers. |
3096 | |
4853 | |
3097 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4854 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3098 | (disabled). |
4855 | will be C<0>. |
3099 | |
4856 | |
3100 | =item EV_VERIFY |
4857 | =item EV_VERIFY |
3101 | |
4858 | |
3102 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4859 | Controls how much internal verification (see C<ev_verify ()>) will |
3103 | be done: If set to C<0>, no internal verification code will be compiled |
4860 | be done: If set to C<0>, no internal verification code will be compiled |
3104 | in. If set to C<1>, then verification code will be compiled in, but not |
4861 | in. If set to C<1>, then verification code will be compiled in, but not |
3105 | called. If set to C<2>, then the internal verification code will be |
4862 | called. If set to C<2>, then the internal verification code will be |
3106 | called once per loop, which can slow down libev. If set to C<3>, then the |
4863 | called once per loop, which can slow down libev. If set to C<3>, then the |
3107 | verification code will be called very frequently, which will slow down |
4864 | verification code will be called very frequently, which will slow down |
3108 | libev considerably. |
4865 | libev considerably. |
3109 | |
4866 | |
3110 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4867 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3111 | C<0.> |
4868 | will be C<0>. |
3112 | |
4869 | |
3113 | =item EV_COMMON |
4870 | =item EV_COMMON |
3114 | |
4871 | |
3115 | By default, all watchers have a C<void *data> member. By redefining |
4872 | By default, all watchers have a C<void *data> member. By redefining |
3116 | this macro to a something else you can include more and other types of |
4873 | this macro to something else you can include more and other types of |
3117 | members. You have to define it each time you include one of the files, |
4874 | members. You have to define it each time you include one of the files, |
3118 | though, and it must be identical each time. |
4875 | though, and it must be identical each time. |
3119 | |
4876 | |
3120 | For example, the perl EV module uses something like this: |
4877 | For example, the perl EV module uses something like this: |
3121 | |
4878 | |
… | |
… | |
3133 | and the way callbacks are invoked and set. Must expand to a struct member |
4890 | and the way callbacks are invoked and set. Must expand to a struct member |
3134 | definition and a statement, respectively. See the F<ev.h> header file for |
4891 | definition and a statement, respectively. See the F<ev.h> header file for |
3135 | their default definitions. One possible use for overriding these is to |
4892 | their default definitions. One possible use for overriding these is to |
3136 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4893 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3137 | method calls instead of plain function calls in C++. |
4894 | method calls instead of plain function calls in C++. |
|
|
4895 | |
|
|
4896 | =back |
3138 | |
4897 | |
3139 | =head2 EXPORTED API SYMBOLS |
4898 | =head2 EXPORTED API SYMBOLS |
3140 | |
4899 | |
3141 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
4900 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3142 | exported symbols, you can use the provided F<Symbol.*> files which list |
4901 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3172 | file. |
4931 | file. |
3173 | |
4932 | |
3174 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4933 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3175 | that everybody includes and which overrides some configure choices: |
4934 | that everybody includes and which overrides some configure choices: |
3176 | |
4935 | |
3177 | #define EV_MINIMAL 1 |
4936 | #define EV_FEATURES 8 |
3178 | #define EV_USE_POLL 0 |
4937 | #define EV_USE_SELECT 1 |
3179 | #define EV_MULTIPLICITY 0 |
|
|
3180 | #define EV_PERIODIC_ENABLE 0 |
4938 | #define EV_PREPARE_ENABLE 1 |
|
|
4939 | #define EV_IDLE_ENABLE 1 |
3181 | #define EV_STAT_ENABLE 0 |
4940 | #define EV_SIGNAL_ENABLE 1 |
3182 | #define EV_FORK_ENABLE 0 |
4941 | #define EV_CHILD_ENABLE 1 |
|
|
4942 | #define EV_USE_STDEXCEPT 0 |
3183 | #define EV_CONFIG_H <config.h> |
4943 | #define EV_CONFIG_H <config.h> |
3184 | #define EV_MINPRI 0 |
|
|
3185 | #define EV_MAXPRI 0 |
|
|
3186 | |
4944 | |
3187 | #include "ev++.h" |
4945 | #include "ev++.h" |
3188 | |
4946 | |
3189 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4947 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3190 | |
4948 | |
3191 | #include "ev_cpp.h" |
4949 | #include "ev_cpp.h" |
3192 | #include "ev.c" |
4950 | #include "ev.c" |
3193 | |
4951 | |
|
|
4952 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
3194 | |
4953 | |
3195 | =head1 THREADS AND COROUTINES |
4954 | =head2 THREADS AND COROUTINES |
3196 | |
4955 | |
3197 | =head2 THREADS |
4956 | =head3 THREADS |
3198 | |
4957 | |
3199 | Libev itself is completely thread-safe, but it uses no locking. This |
4958 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4959 | documented otherwise, but libev implements no locking itself. This means |
3200 | means that you can use as many loops as you want in parallel, as long as |
4960 | that you can use as many loops as you want in parallel, as long as there |
3201 | only one thread ever calls into one libev function with the same loop |
4961 | are no concurrent calls into any libev function with the same loop |
3202 | parameter. |
4962 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4963 | of course): libev guarantees that different event loops share no data |
|
|
4964 | structures that need any locking. |
3203 | |
4965 | |
3204 | Or put differently: calls with different loop parameters can be done in |
4966 | Or to put it differently: calls with different loop parameters can be done |
3205 | parallel from multiple threads, calls with the same loop parameter must be |
4967 | concurrently from multiple threads, calls with the same loop parameter |
3206 | done serially (but can be done from different threads, as long as only one |
4968 | must be done serially (but can be done from different threads, as long as |
3207 | thread ever is inside a call at any point in time, e.g. by using a mutex |
4969 | only one thread ever is inside a call at any point in time, e.g. by using |
3208 | per loop). |
4970 | a mutex per loop). |
|
|
4971 | |
|
|
4972 | Specifically to support threads (and signal handlers), libev implements |
|
|
4973 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4974 | concurrency on the same event loop, namely waking it up "from the |
|
|
4975 | outside". |
3209 | |
4976 | |
3210 | If you want to know which design (one loop, locking, or multiple loops |
4977 | If you want to know which design (one loop, locking, or multiple loops |
3211 | without or something else still) is best for your problem, then I cannot |
4978 | without or something else still) is best for your problem, then I cannot |
3212 | help you. I can give some generic advice however: |
4979 | help you, but here is some generic advice: |
3213 | |
4980 | |
3214 | =over 4 |
4981 | =over 4 |
3215 | |
4982 | |
3216 | =item * most applications have a main thread: use the default libev loop |
4983 | =item * most applications have a main thread: use the default libev loop |
3217 | in that thread, or create a separate thread running only the default loop. |
4984 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3229 | |
4996 | |
3230 | Choosing a model is hard - look around, learn, know that usually you can do |
4997 | Choosing a model is hard - look around, learn, know that usually you can do |
3231 | better than you currently do :-) |
4998 | better than you currently do :-) |
3232 | |
4999 | |
3233 | =item * often you need to talk to some other thread which blocks in the |
5000 | =item * often you need to talk to some other thread which blocks in the |
|
|
5001 | event loop. |
|
|
5002 | |
3234 | event loop - C<ev_async> watchers can be used to wake them up from other |
5003 | C<ev_async> watchers can be used to wake them up from other threads safely |
3235 | threads safely (or from signal contexts...). |
5004 | (or from signal contexts...). |
|
|
5005 | |
|
|
5006 | An example use would be to communicate signals or other events that only |
|
|
5007 | work in the default loop by registering the signal watcher with the |
|
|
5008 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
5009 | watcher callback into the event loop interested in the signal. |
3236 | |
5010 | |
3237 | =back |
5011 | =back |
3238 | |
5012 | |
|
|
5013 | See also L</THREAD LOCKING EXAMPLE>. |
|
|
5014 | |
3239 | =head2 COROUTINES |
5015 | =head3 COROUTINES |
3240 | |
5016 | |
3241 | Libev is much more accommodating to coroutines ("cooperative threads"): |
5017 | Libev is very accommodating to coroutines ("cooperative threads"): |
3242 | libev fully supports nesting calls to it's functions from different |
5018 | libev fully supports nesting calls to its functions from different |
3243 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
5019 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3244 | different coroutines and switch freely between both coroutines running the |
5020 | different coroutines, and switch freely between both coroutines running |
3245 | loop, as long as you don't confuse yourself). The only exception is that |
5021 | the loop, as long as you don't confuse yourself). The only exception is |
3246 | you must not do this from C<ev_periodic> reschedule callbacks. |
5022 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3247 | |
5023 | |
3248 | Care has been invested into making sure that libev does not keep local |
5024 | Care has been taken to ensure that libev does not keep local state inside |
3249 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
5025 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3250 | switches. |
5026 | they do not call any callbacks. |
3251 | |
5027 | |
|
|
5028 | =head2 COMPILER WARNINGS |
3252 | |
5029 | |
3253 | =head1 COMPLEXITIES |
5030 | Depending on your compiler and compiler settings, you might get no or a |
|
|
5031 | lot of warnings when compiling libev code. Some people are apparently |
|
|
5032 | scared by this. |
3254 | |
5033 | |
3255 | In this section the complexities of (many of) the algorithms used inside |
5034 | However, these are unavoidable for many reasons. For one, each compiler |
3256 | libev will be explained. For complexity discussions about backends see the |
5035 | has different warnings, and each user has different tastes regarding |
3257 | documentation for C<ev_default_init>. |
5036 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
5037 | targeting a specific compiler and compiler-version. |
3258 | |
5038 | |
3259 | All of the following are about amortised time: If an array needs to be |
5039 | Another reason is that some compiler warnings require elaborate |
3260 | extended, libev needs to realloc and move the whole array, but this |
5040 | workarounds, or other changes to the code that make it less clear and less |
3261 | happens asymptotically never with higher number of elements, so O(1) might |
5041 | maintainable. |
3262 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3263 | it is much faster and asymptotically approaches constant time. |
|
|
3264 | |
5042 | |
3265 | =over 4 |
5043 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
5044 | wrong (because they don't actually warn about the condition their message |
|
|
5045 | seems to warn about). For example, certain older gcc versions had some |
|
|
5046 | warnings that resulted in an extreme number of false positives. These have |
|
|
5047 | been fixed, but some people still insist on making code warn-free with |
|
|
5048 | such buggy versions. |
3266 | |
5049 | |
3267 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
5050 | While libev is written to generate as few warnings as possible, |
|
|
5051 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
5052 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
5053 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
5054 | warnings, not errors, or proof of bugs. |
3268 | |
5055 | |
3269 | This means that, when you have a watcher that triggers in one hour and |
|
|
3270 | there are 100 watchers that would trigger before that then inserting will |
|
|
3271 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3272 | |
5056 | |
3273 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
5057 | =head2 VALGRIND |
3274 | |
5058 | |
3275 | That means that changing a timer costs less than removing/adding them |
5059 | Valgrind has a special section here because it is a popular tool that is |
3276 | as only the relative motion in the event queue has to be paid for. |
5060 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3277 | |
5061 | |
3278 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
5062 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
5063 | in libev, then check twice: If valgrind reports something like: |
3279 | |
5064 | |
3280 | These just add the watcher into an array or at the head of a list. |
5065 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
5066 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
5067 | ==2274== still reachable: 256 bytes in 1 blocks. |
3281 | |
5068 | |
3282 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
5069 | Then there is no memory leak, just as memory accounted to global variables |
|
|
5070 | is not a memleak - the memory is still being referenced, and didn't leak. |
3283 | |
5071 | |
3284 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
5072 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
5073 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
5074 | although an acceptable workaround has been found here), or it might be |
|
|
5075 | confused. |
3285 | |
5076 | |
3286 | These watchers are stored in lists then need to be walked to find the |
5077 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3287 | correct watcher to remove. The lists are usually short (you don't usually |
5078 | make it into some kind of religion. |
3288 | have many watchers waiting for the same fd or signal). |
|
|
3289 | |
5079 | |
3290 | =item Finding the next timer in each loop iteration: O(1) |
5080 | If you are unsure about something, feel free to contact the mailing list |
|
|
5081 | with the full valgrind report and an explanation on why you think this |
|
|
5082 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
5083 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
5084 | of learning how to interpret valgrind properly. |
3291 | |
5085 | |
3292 | By virtue of using a binary or 4-heap, the next timer is always found at a |
5086 | If you need, for some reason, empty reports from valgrind for your project |
3293 | fixed position in the storage array. |
5087 | I suggest using suppression lists. |
3294 | |
5088 | |
3295 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3296 | |
5089 | |
3297 | A change means an I/O watcher gets started or stopped, which requires |
5090 | =head1 PORTABILITY NOTES |
3298 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3299 | on backend and whether C<ev_io_set> was used). |
|
|
3300 | |
5091 | |
3301 | =item Activating one watcher (putting it into the pending state): O(1) |
5092 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
3302 | |
5093 | |
3303 | =item Priority handling: O(number_of_priorities) |
5094 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
5095 | interfaces but I<disables> them by default. |
3304 | |
5096 | |
3305 | Priorities are implemented by allocating some space for each |
5097 | That means that libev compiled in the default environment doesn't support |
3306 | priority. When doing priority-based operations, libev usually has to |
5098 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
3307 | linearly search all the priorities, but starting/stopping and activating |
|
|
3308 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3309 | |
5099 | |
3310 | =item Sending an ev_async: O(1) |
5100 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
5101 | by enabling the large file API, which makes them incompatible with the |
|
|
5102 | standard libev compiled for their system. |
3311 | |
5103 | |
3312 | =item Processing ev_async_send: O(number_of_async_watchers) |
5104 | Likewise, libev cannot enable the large file API itself as this would |
|
|
5105 | suddenly make it incompatible to the default compile time environment, |
|
|
5106 | i.e. all programs not using special compile switches. |
3313 | |
5107 | |
3314 | =item Processing signals: O(max_signal_number) |
5108 | =head2 OS/X AND DARWIN BUGS |
3315 | |
5109 | |
3316 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5110 | The whole thing is a bug if you ask me - basically any system interface |
3317 | calls in the current loop iteration. Checking for async and signal events |
5111 | you touch is broken, whether it is locales, poll, kqueue or even the |
3318 | involves iterating over all running async watchers or all signal numbers. |
5112 | OpenGL drivers. |
3319 | |
5113 | |
3320 | =back |
5114 | =head3 C<kqueue> is buggy |
3321 | |
5115 | |
|
|
5116 | The kqueue syscall is broken in all known versions - most versions support |
|
|
5117 | only sockets, many support pipes. |
3322 | |
5118 | |
|
|
5119 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
5120 | rotten platform, but of course you can still ask for it when creating a |
|
|
5121 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
5122 | probably going to work well. |
|
|
5123 | |
|
|
5124 | =head3 C<poll> is buggy |
|
|
5125 | |
|
|
5126 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
5127 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
5128 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
5129 | |
|
|
5130 | Libev tries to work around this by not using C<poll> by default on |
|
|
5131 | this rotten platform, but of course you can still ask for it when creating |
|
|
5132 | a loop. |
|
|
5133 | |
|
|
5134 | =head3 C<select> is buggy |
|
|
5135 | |
|
|
5136 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
5137 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
5138 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
5139 | you use more. |
|
|
5140 | |
|
|
5141 | There is an undocumented "workaround" for this - defining |
|
|
5142 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
5143 | work on OS/X. |
|
|
5144 | |
|
|
5145 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
5146 | |
|
|
5147 | =head3 C<errno> reentrancy |
|
|
5148 | |
|
|
5149 | The default compile environment on Solaris is unfortunately so |
|
|
5150 | thread-unsafe that you can't even use components/libraries compiled |
|
|
5151 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
5152 | defined by default. A valid, if stupid, implementation choice. |
|
|
5153 | |
|
|
5154 | If you want to use libev in threaded environments you have to make sure |
|
|
5155 | it's compiled with C<_REENTRANT> defined. |
|
|
5156 | |
|
|
5157 | =head3 Event port backend |
|
|
5158 | |
|
|
5159 | The scalable event interface for Solaris is called "event |
|
|
5160 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
5161 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
5162 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
5163 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
5164 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
5165 | great. |
|
|
5166 | |
|
|
5167 | If you can't get it to work, you can try running the program by setting |
|
|
5168 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
5169 | C<select> backends. |
|
|
5170 | |
|
|
5171 | =head2 AIX POLL BUG |
|
|
5172 | |
|
|
5173 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
5174 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
5175 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
5176 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
5177 | |
3323 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
5178 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
5179 | |
|
|
5180 | =head3 General issues |
3324 | |
5181 | |
3325 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
5182 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3326 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5183 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3327 | model. Libev still offers limited functionality on this platform in |
5184 | model. Libev still offers limited functionality on this platform in |
3328 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5185 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3329 | descriptors. This only applies when using Win32 natively, not when using |
5186 | descriptors. This only applies when using Win32 natively, not when using |
3330 | e.g. cygwin. |
5187 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
5188 | as every compiler comes with a slightly differently broken/incompatible |
|
|
5189 | environment. |
3331 | |
5190 | |
3332 | Lifting these limitations would basically require the full |
5191 | Lifting these limitations would basically require the full |
3333 | re-implementation of the I/O system. If you are into these kinds of |
5192 | re-implementation of the I/O system. If you are into this kind of thing, |
3334 | things, then note that glib does exactly that for you in a very portable |
5193 | then note that glib does exactly that for you in a very portable way (note |
3335 | way (note also that glib is the slowest event library known to man). |
5194 | also that glib is the slowest event library known to man). |
3336 | |
5195 | |
3337 | There is no supported compilation method available on windows except |
5196 | There is no supported compilation method available on windows except |
3338 | embedding it into other applications. |
5197 | embedding it into other applications. |
|
|
5198 | |
|
|
5199 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
5200 | tries its best, but under most conditions, signals will simply not work. |
3339 | |
5201 | |
3340 | Not a libev limitation but worth mentioning: windows apparently doesn't |
5202 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3341 | accept large writes: instead of resulting in a partial write, windows will |
5203 | accept large writes: instead of resulting in a partial write, windows will |
3342 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
5204 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3343 | so make sure you only write small amounts into your sockets (less than a |
5205 | so make sure you only write small amounts into your sockets (less than a |
3344 | megabyte seems safe, but thsi apparently depends on the amount of memory |
5206 | megabyte seems safe, but this apparently depends on the amount of memory |
3345 | available). |
5207 | available). |
3346 | |
5208 | |
3347 | Due to the many, low, and arbitrary limits on the win32 platform and |
5209 | Due to the many, low, and arbitrary limits on the win32 platform and |
3348 | the abysmal performance of winsockets, using a large number of sockets |
5210 | the abysmal performance of winsockets, using a large number of sockets |
3349 | is not recommended (and not reasonable). If your program needs to use |
5211 | is not recommended (and not reasonable). If your program needs to use |
3350 | more than a hundred or so sockets, then likely it needs to use a totally |
5212 | more than a hundred or so sockets, then likely it needs to use a totally |
3351 | different implementation for windows, as libev offers the POSIX readiness |
5213 | different implementation for windows, as libev offers the POSIX readiness |
3352 | notification model, which cannot be implemented efficiently on windows |
5214 | notification model, which cannot be implemented efficiently on windows |
3353 | (Microsoft monopoly games). |
5215 | (due to Microsoft monopoly games). |
3354 | |
5216 | |
3355 | A typical way to use libev under windows is to embed it (see the embedding |
5217 | A typical way to use libev under windows is to embed it (see the embedding |
3356 | section for details) and use the following F<evwrap.h> header file instead |
5218 | section for details) and use the following F<evwrap.h> header file instead |
3357 | of F<ev.h>: |
5219 | of F<ev.h>: |
3358 | |
5220 | |
… | |
… | |
3360 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
5222 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3361 | |
5223 | |
3362 | #include "ev.h" |
5224 | #include "ev.h" |
3363 | |
5225 | |
3364 | And compile the following F<evwrap.c> file into your project (make sure |
5226 | And compile the following F<evwrap.c> file into your project (make sure |
3365 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
5227 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3366 | |
5228 | |
3367 | #include "evwrap.h" |
5229 | #include "evwrap.h" |
3368 | #include "ev.c" |
5230 | #include "ev.c" |
3369 | |
5231 | |
3370 | =over 4 |
|
|
3371 | |
|
|
3372 | =item The winsocket select function |
5232 | =head3 The winsocket C<select> function |
3373 | |
5233 | |
3374 | The winsocket C<select> function doesn't follow POSIX in that it |
5234 | The winsocket C<select> function doesn't follow POSIX in that it |
3375 | requires socket I<handles> and not socket I<file descriptors> (it is |
5235 | requires socket I<handles> and not socket I<file descriptors> (it is |
3376 | also extremely buggy). This makes select very inefficient, and also |
5236 | also extremely buggy). This makes select very inefficient, and also |
3377 | requires a mapping from file descriptors to socket handles (the Microsoft |
5237 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3386 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
5246 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3387 | |
5247 | |
3388 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
5248 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3389 | complexity in the O(n²) range when using win32. |
5249 | complexity in the O(n²) range when using win32. |
3390 | |
5250 | |
3391 | =item Limited number of file descriptors |
5251 | =head3 Limited number of file descriptors |
3392 | |
5252 | |
3393 | Windows has numerous arbitrary (and low) limits on things. |
5253 | Windows has numerous arbitrary (and low) limits on things. |
3394 | |
5254 | |
3395 | Early versions of winsocket's select only supported waiting for a maximum |
5255 | Early versions of winsocket's select only supported waiting for a maximum |
3396 | of C<64> handles (probably owning to the fact that all windows kernels |
5256 | of C<64> handles (probably owning to the fact that all windows kernels |
3397 | can only wait for C<64> things at the same time internally; Microsoft |
5257 | can only wait for C<64> things at the same time internally; Microsoft |
3398 | recommends spawning a chain of threads and wait for 63 handles and the |
5258 | recommends spawning a chain of threads and wait for 63 handles and the |
3399 | previous thread in each. Great). |
5259 | previous thread in each. Sounds great!). |
3400 | |
5260 | |
3401 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
5261 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3402 | to some high number (e.g. C<2048>) before compiling the winsocket select |
5262 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3403 | call (which might be in libev or elsewhere, for example, perl does its own |
5263 | call (which might be in libev or elsewhere, for example, perl and many |
3404 | select emulation on windows). |
5264 | other interpreters do their own select emulation on windows). |
3405 | |
5265 | |
3406 | Another limit is the number of file descriptors in the Microsoft runtime |
5266 | Another limit is the number of file descriptors in the Microsoft runtime |
3407 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
5267 | libraries, which by default is C<64> (there must be a hidden I<64> |
3408 | or something like this inside Microsoft). You can increase this by calling |
5268 | fetish or something like this inside Microsoft). You can increase this |
3409 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
5269 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3410 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
5270 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3411 | libraries. |
|
|
3412 | |
|
|
3413 | This might get you to about C<512> or C<2048> sockets (depending on |
5271 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3414 | windows version and/or the phase of the moon). To get more, you need to |
5272 | (depending on windows version and/or the phase of the moon). To get more, |
3415 | wrap all I/O functions and provide your own fd management, but the cost of |
5273 | you need to wrap all I/O functions and provide your own fd management, but |
3416 | calling select (O(n²)) will likely make this unworkable. |
5274 | the cost of calling select (O(n²)) will likely make this unworkable. |
3417 | |
5275 | |
3418 | =back |
|
|
3419 | |
|
|
3420 | |
|
|
3421 | =head1 PORTABILITY REQUIREMENTS |
5276 | =head2 PORTABILITY REQUIREMENTS |
3422 | |
5277 | |
3423 | In addition to a working ISO-C implementation, libev relies on a few |
5278 | In addition to a working ISO-C implementation and of course the |
3424 | additional extensions: |
5279 | backend-specific APIs, libev relies on a few additional extensions: |
3425 | |
5280 | |
3426 | =over 4 |
5281 | =over 4 |
3427 | |
5282 | |
3428 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
5283 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3429 | calling conventions regardless of C<ev_watcher_type *>. |
5284 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3432 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
5287 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
3433 | assumes that the same (machine) code can be used to call any watcher |
5288 | assumes that the same (machine) code can be used to call any watcher |
3434 | callback: The watcher callbacks have different type signatures, but libev |
5289 | callback: The watcher callbacks have different type signatures, but libev |
3435 | calls them using an C<ev_watcher *> internally. |
5290 | calls them using an C<ev_watcher *> internally. |
3436 | |
5291 | |
|
|
5292 | =item pointer accesses must be thread-atomic |
|
|
5293 | |
|
|
5294 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
5295 | writable in one piece - this is the case on all current architectures. |
|
|
5296 | |
3437 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
5297 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3438 | |
5298 | |
3439 | The type C<sig_atomic_t volatile> (or whatever is defined as |
5299 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3440 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
5300 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3441 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
5301 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3442 | believed to be sufficiently portable. |
5302 | believed to be sufficiently portable. |
3443 | |
5303 | |
3444 | =item C<sigprocmask> must work in a threaded environment |
5304 | =item C<sigprocmask> must work in a threaded environment |
3445 | |
5305 | |
… | |
… | |
3454 | except the initial one, and run the default loop in the initial thread as |
5314 | except the initial one, and run the default loop in the initial thread as |
3455 | well. |
5315 | well. |
3456 | |
5316 | |
3457 | =item C<long> must be large enough for common memory allocation sizes |
5317 | =item C<long> must be large enough for common memory allocation sizes |
3458 | |
5318 | |
3459 | To improve portability and simplify using libev, libev uses C<long> |
5319 | To improve portability and simplify its API, libev uses C<long> internally |
3460 | internally instead of C<size_t> when allocating its data structures. On |
5320 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3461 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
5321 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3462 | is still at least 31 bits everywhere, which is enough for hundreds of |
5322 | least 31 bits everywhere, which is enough for hundreds of millions of |
3463 | millions of watchers. |
5323 | watchers. |
3464 | |
5324 | |
3465 | =item C<double> must hold a time value in seconds with enough accuracy |
5325 | =item C<double> must hold a time value in seconds with enough accuracy |
3466 | |
5326 | |
3467 | The type C<double> is used to represent timestamps. It is required to |
5327 | The type C<double> is used to represent timestamps. It is required to |
3468 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
5328 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3469 | enough for at least into the year 4000. This requirement is fulfilled by |
5329 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
5330 | (the design goal for libev). This requirement is overfulfilled by |
3470 | implementations implementing IEEE 754 (basically all existing ones). |
5331 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5332 | |
|
|
5333 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5334 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5335 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5336 | something like that, just kidding). |
3471 | |
5337 | |
3472 | =back |
5338 | =back |
3473 | |
5339 | |
3474 | If you know of other additional requirements drop me a note. |
5340 | If you know of other additional requirements drop me a note. |
3475 | |
5341 | |
3476 | |
5342 | |
3477 | =head1 COMPILER WARNINGS |
5343 | =head1 ALGORITHMIC COMPLEXITIES |
3478 | |
5344 | |
3479 | Depending on your compiler and compiler settings, you might get no or a |
5345 | In this section the complexities of (many of) the algorithms used inside |
3480 | lot of warnings when compiling libev code. Some people are apparently |
5346 | libev will be documented. For complexity discussions about backends see |
3481 | scared by this. |
5347 | the documentation for C<ev_default_init>. |
3482 | |
5348 | |
3483 | However, these are unavoidable for many reasons. For one, each compiler |
5349 | All of the following are about amortised time: If an array needs to be |
3484 | has different warnings, and each user has different tastes regarding |
5350 | extended, libev needs to realloc and move the whole array, but this |
3485 | warning options. "Warn-free" code therefore cannot be a goal except when |
5351 | happens asymptotically rarer with higher number of elements, so O(1) might |
3486 | targeting a specific compiler and compiler-version. |
5352 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
5353 | average it is much faster and asymptotically approaches constant time. |
3487 | |
5354 | |
3488 | Another reason is that some compiler warnings require elaborate |
5355 | =over 4 |
3489 | workarounds, or other changes to the code that make it less clear and less |
|
|
3490 | maintainable. |
|
|
3491 | |
5356 | |
3492 | And of course, some compiler warnings are just plain stupid, or simply |
5357 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3493 | wrong (because they don't actually warn about the condition their message |
|
|
3494 | seems to warn about). |
|
|
3495 | |
5358 | |
3496 | While libev is written to generate as few warnings as possible, |
5359 | This means that, when you have a watcher that triggers in one hour and |
3497 | "warn-free" code is not a goal, and it is recommended not to build libev |
5360 | there are 100 watchers that would trigger before that, then inserting will |
3498 | with any compiler warnings enabled unless you are prepared to cope with |
5361 | have to skip roughly seven (C<ld 100>) of these watchers. |
3499 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3500 | warnings, not errors, or proof of bugs. |
|
|
3501 | |
5362 | |
|
|
5363 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3502 | |
5364 | |
3503 | =head1 VALGRIND |
5365 | That means that changing a timer costs less than removing/adding them, |
|
|
5366 | as only the relative motion in the event queue has to be paid for. |
3504 | |
5367 | |
3505 | Valgrind has a special section here because it is a popular tool that is |
5368 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3506 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3507 | |
5369 | |
3508 | If you think you found a bug (memory leak, uninitialised data access etc.) |
5370 | These just add the watcher into an array or at the head of a list. |
3509 | in libev, then check twice: If valgrind reports something like: |
|
|
3510 | |
5371 | |
3511 | ==2274== definitely lost: 0 bytes in 0 blocks. |
5372 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3512 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3513 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3514 | |
5373 | |
3515 | Then there is no memory leak. Similarly, under some circumstances, |
5374 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3516 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3517 | might be confused (it is a very good tool, but only a tool). |
|
|
3518 | |
5375 | |
3519 | If you are unsure about something, feel free to contact the mailing list |
5376 | These watchers are stored in lists, so they need to be walked to find the |
3520 | with the full valgrind report and an explanation on why you think this is |
5377 | correct watcher to remove. The lists are usually short (you don't usually |
3521 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
5378 | have many watchers waiting for the same fd or signal: one is typical, two |
3522 | no bug" answer and take the chance of learning how to interpret valgrind |
5379 | is rare). |
3523 | properly. |
|
|
3524 | |
5380 | |
3525 | If you need, for some reason, empty reports from valgrind for your project |
5381 | =item Finding the next timer in each loop iteration: O(1) |
3526 | I suggest using suppression lists. |
|
|
3527 | |
5382 | |
|
|
5383 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
5384 | fixed position in the storage array. |
|
|
5385 | |
|
|
5386 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
5387 | |
|
|
5388 | A change means an I/O watcher gets started or stopped, which requires |
|
|
5389 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
5390 | on backend and whether C<ev_io_set> was used). |
|
|
5391 | |
|
|
5392 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
5393 | |
|
|
5394 | =item Priority handling: O(number_of_priorities) |
|
|
5395 | |
|
|
5396 | Priorities are implemented by allocating some space for each |
|
|
5397 | priority. When doing priority-based operations, libev usually has to |
|
|
5398 | linearly search all the priorities, but starting/stopping and activating |
|
|
5399 | watchers becomes O(1) with respect to priority handling. |
|
|
5400 | |
|
|
5401 | =item Sending an ev_async: O(1) |
|
|
5402 | |
|
|
5403 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
5404 | |
|
|
5405 | =item Processing signals: O(max_signal_number) |
|
|
5406 | |
|
|
5407 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
5408 | calls in the current loop iteration and the loop is currently |
|
|
5409 | blocked. Checking for async and signal events involves iterating over all |
|
|
5410 | running async watchers or all signal numbers. |
|
|
5411 | |
|
|
5412 | =back |
|
|
5413 | |
|
|
5414 | |
|
|
5415 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5416 | |
|
|
5417 | The major version 4 introduced some incompatible changes to the API. |
|
|
5418 | |
|
|
5419 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5420 | for all changes, so most programs should still compile. The compatibility |
|
|
5421 | layer might be removed in later versions of libev, so better update to the |
|
|
5422 | new API early than late. |
|
|
5423 | |
|
|
5424 | =over 4 |
|
|
5425 | |
|
|
5426 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5427 | |
|
|
5428 | The backward compatibility mechanism can be controlled by |
|
|
5429 | C<EV_COMPAT3>. See L</PREPROCESSOR SYMBOLS/MACROS> in the L</EMBEDDING> |
|
|
5430 | section. |
|
|
5431 | |
|
|
5432 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5433 | |
|
|
5434 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5435 | |
|
|
5436 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5437 | ev_loop_fork (EV_DEFAULT); |
|
|
5438 | |
|
|
5439 | =item function/symbol renames |
|
|
5440 | |
|
|
5441 | A number of functions and symbols have been renamed: |
|
|
5442 | |
|
|
5443 | ev_loop => ev_run |
|
|
5444 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5445 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5446 | |
|
|
5447 | ev_unloop => ev_break |
|
|
5448 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5449 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5450 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5451 | |
|
|
5452 | EV_TIMEOUT => EV_TIMER |
|
|
5453 | |
|
|
5454 | ev_loop_count => ev_iteration |
|
|
5455 | ev_loop_depth => ev_depth |
|
|
5456 | ev_loop_verify => ev_verify |
|
|
5457 | |
|
|
5458 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5459 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5460 | associated constants have been renamed to not collide with the C<struct |
|
|
5461 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5462 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5463 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5464 | typedef. |
|
|
5465 | |
|
|
5466 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5467 | |
|
|
5468 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5469 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5470 | and work, but the library code will of course be larger. |
|
|
5471 | |
|
|
5472 | =back |
|
|
5473 | |
|
|
5474 | |
|
|
5475 | =head1 GLOSSARY |
|
|
5476 | |
|
|
5477 | =over 4 |
|
|
5478 | |
|
|
5479 | =item active |
|
|
5480 | |
|
|
5481 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5482 | See L</WATCHER STATES> for details. |
|
|
5483 | |
|
|
5484 | =item application |
|
|
5485 | |
|
|
5486 | In this document, an application is whatever is using libev. |
|
|
5487 | |
|
|
5488 | =item backend |
|
|
5489 | |
|
|
5490 | The part of the code dealing with the operating system interfaces. |
|
|
5491 | |
|
|
5492 | =item callback |
|
|
5493 | |
|
|
5494 | The address of a function that is called when some event has been |
|
|
5495 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5496 | received the event, and the actual event bitset. |
|
|
5497 | |
|
|
5498 | =item callback/watcher invocation |
|
|
5499 | |
|
|
5500 | The act of calling the callback associated with a watcher. |
|
|
5501 | |
|
|
5502 | =item event |
|
|
5503 | |
|
|
5504 | A change of state of some external event, such as data now being available |
|
|
5505 | for reading on a file descriptor, time having passed or simply not having |
|
|
5506 | any other events happening anymore. |
|
|
5507 | |
|
|
5508 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5509 | C<EV_TIMER>). |
|
|
5510 | |
|
|
5511 | =item event library |
|
|
5512 | |
|
|
5513 | A software package implementing an event model and loop. |
|
|
5514 | |
|
|
5515 | =item event loop |
|
|
5516 | |
|
|
5517 | An entity that handles and processes external events and converts them |
|
|
5518 | into callback invocations. |
|
|
5519 | |
|
|
5520 | =item event model |
|
|
5521 | |
|
|
5522 | The model used to describe how an event loop handles and processes |
|
|
5523 | watchers and events. |
|
|
5524 | |
|
|
5525 | =item pending |
|
|
5526 | |
|
|
5527 | A watcher is pending as soon as the corresponding event has been |
|
|
5528 | detected. See L</WATCHER STATES> for details. |
|
|
5529 | |
|
|
5530 | =item real time |
|
|
5531 | |
|
|
5532 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5533 | |
|
|
5534 | =item wall-clock time |
|
|
5535 | |
|
|
5536 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5537 | be wrong and jump forwards and backwards, e.g. when you adjust your |
|
|
5538 | clock. |
|
|
5539 | |
|
|
5540 | =item watcher |
|
|
5541 | |
|
|
5542 | A data structure that describes interest in certain events. Watchers need |
|
|
5543 | to be started (attached to an event loop) before they can receive events. |
|
|
5544 | |
|
|
5545 | =back |
3528 | |
5546 | |
3529 | =head1 AUTHOR |
5547 | =head1 AUTHOR |
3530 | |
5548 | |
3531 | Marc Lehmann <libev@schmorp.de>. |
5549 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5550 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
3532 | |
5551 | |