… | |
… | |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
|
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11 | // a single header file is required |
11 | #include <ev.h> |
12 | #include <ev.h> |
12 | |
13 | |
|
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14 | // every watcher type has its own typedef'd struct |
|
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15 | // with the name ev_<type> |
13 | ev_io stdin_watcher; |
16 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
15 | |
18 | |
|
|
19 | // all watcher callbacks have a similar signature |
16 | /* called when data readable on stdin */ |
20 | // this callback is called when data is readable on stdin |
17 | static void |
21 | static void |
18 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
19 | { |
23 | { |
20 | /* puts ("stdin ready"); */ |
24 | puts ("stdin ready"); |
21 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
25 | // for one-shot events, one must manually stop the watcher |
22 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
26 | // with its corresponding stop function. |
|
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27 | ev_io_stop (EV_A_ w); |
|
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28 | |
|
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29 | // this causes all nested ev_loop's to stop iterating |
|
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30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
31 | } |
24 | |
32 | |
|
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33 | // another callback, this time for a time-out |
25 | static void |
34 | static void |
26 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
27 | { |
36 | { |
28 | /* puts ("timeout"); */ |
37 | puts ("timeout"); |
29 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
38 | // this causes the innermost ev_loop to stop iterating |
|
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39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
30 | } |
40 | } |
31 | |
41 | |
32 | int |
42 | int |
33 | main (void) |
43 | main (void) |
34 | { |
44 | { |
|
|
45 | // use the default event loop unless you have special needs |
35 | struct ev_loop *loop = ev_default_loop (0); |
46 | struct ev_loop *loop = ev_default_loop (0); |
36 | |
47 | |
37 | /* initialise an io watcher, then start it */ |
48 | // initialise an io watcher, then start it |
|
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49 | // this one will watch for stdin to become readable |
38 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
39 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
40 | |
52 | |
|
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53 | // initialise a timer watcher, then start it |
41 | /* simple non-repeating 5.5 second timeout */ |
54 | // simple non-repeating 5.5 second timeout |
42 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
43 | ev_timer_start (loop, &timeout_watcher); |
56 | ev_timer_start (loop, &timeout_watcher); |
44 | |
57 | |
45 | /* loop till timeout or data ready */ |
58 | // now wait for events to arrive |
46 | ev_loop (loop, 0); |
59 | ev_loop (loop, 0); |
47 | |
60 | |
|
|
61 | // unloop was called, so exit |
48 | return 0; |
62 | return 0; |
49 | } |
63 | } |
50 | |
64 | |
51 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
52 | |
66 | |
53 | The newest version of this document is also available as a html-formatted |
67 | The newest version of this document is also available as an html-formatted |
54 | web page you might find easier to navigate when reading it for the first |
68 | web page you might find easier to navigate when reading it for the first |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
56 | |
70 | |
57 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
58 | file descriptor being readable or a timeout occurring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
59 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
60 | |
74 | |
… | |
… | |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
99 | for example). |
86 | |
100 | |
87 | =head2 CONVENTIONS |
101 | =head2 CONVENTIONS |
88 | |
102 | |
89 | Libev is very configurable. In this manual the default configuration will |
103 | Libev is very configurable. In this manual the default (and most common) |
90 | be described, which supports multiple event loops. For more info about |
104 | configuration will be described, which supports multiple event loops. For |
91 | various configuration options please have a look at B<EMBED> section in |
105 | more info about various configuration options please have a look at |
92 | this manual. If libev was configured without support for multiple event |
106 | B<EMBED> section in this manual. If libev was configured without support |
93 | loops, then all functions taking an initial argument of name C<loop> |
107 | for multiple event loops, then all functions taking an initial argument of |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
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109 | this argument. |
95 | |
110 | |
96 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
97 | |
112 | |
98 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
… | |
… | |
102 | to the C<double> type in C, and when you need to do any calculations on |
117 | to the C<double> type in C, and when you need to do any calculations on |
103 | it, you should treat it as some floatingpoint value. Unlike the name |
118 | it, you should treat it as some floatingpoint value. Unlike the name |
104 | component C<stamp> might indicate, it is also used for time differences |
119 | component C<stamp> might indicate, it is also used for time differences |
105 | throughout libev. |
120 | throughout libev. |
106 | |
121 | |
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122 | =head1 ERROR HANDLING |
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123 | |
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124 | Libev knows three classes of errors: operating system errors, usage errors |
|
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125 | and internal errors (bugs). |
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126 | |
|
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127 | When libev catches an operating system error it cannot handle (for example |
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128 | a syscall indicating a condition libev cannot fix), it calls the callback |
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129 | set via C<ev_set_syserr_cb>, which is supposed to fix the problem or |
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130 | abort. The default is to print a diagnostic message and to call C<abort |
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131 | ()>. |
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132 | |
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133 | When libev detects a usage error such as a negative timer interval, then |
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134 | it will print a diagnostic message and abort (via the C<assert> mechanism, |
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135 | so C<NDEBUG> will disable this checking): these are programming errors in |
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136 | the libev caller and need to be fixed there. |
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137 | |
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138 | Libev also has a few internal error-checking C<assert>ions, and also has |
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139 | extensive consistency checking code. These do not trigger under normal |
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140 | circumstances, as they indicate either a bug in libev or worse. |
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141 | |
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142 | |
107 | =head1 GLOBAL FUNCTIONS |
143 | =head1 GLOBAL FUNCTIONS |
108 | |
144 | |
109 | These functions can be called anytime, even before initialising the |
145 | These functions can be called anytime, even before initialising the |
110 | library in any way. |
146 | library in any way. |
111 | |
147 | |
… | |
… | |
181 | See the description of C<ev_embed> watchers for more info. |
217 | See the description of C<ev_embed> watchers for more info. |
182 | |
218 | |
183 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
184 | |
220 | |
185 | Sets the allocation function to use (the prototype is similar - the |
221 | Sets the allocation function to use (the prototype is similar - the |
186 | semantics is identical - to the realloc C function). It is used to |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
187 | allocate and free memory (no surprises here). If it returns zero when |
223 | used to allocate and free memory (no surprises here). If it returns zero |
188 | memory needs to be allocated, the library might abort or take some |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
189 | potentially destructive action. The default is your system realloc |
225 | or take some potentially destructive action. |
190 | function. |
226 | |
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227 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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228 | correct C<realloc> semantics, libev will use a wrapper around the system |
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229 | C<realloc> and C<free> functions by default. |
191 | |
230 | |
192 | You could override this function in high-availability programs to, say, |
231 | You could override this function in high-availability programs to, say, |
193 | free some memory if it cannot allocate memory, to use a special allocator, |
232 | free some memory if it cannot allocate memory, to use a special allocator, |
194 | or even to sleep a while and retry until some memory is available. |
233 | or even to sleep a while and retry until some memory is available. |
195 | |
234 | |
196 | Example: Replace the libev allocator with one that waits a bit and then |
235 | Example: Replace the libev allocator with one that waits a bit and then |
197 | retries). |
236 | retries (example requires a standards-compliant C<realloc>). |
198 | |
237 | |
199 | static void * |
238 | static void * |
200 | persistent_realloc (void *ptr, size_t size) |
239 | persistent_realloc (void *ptr, size_t size) |
201 | { |
240 | { |
202 | for (;;) |
241 | for (;;) |
… | |
… | |
241 | |
280 | |
242 | An event loop is described by a C<struct ev_loop *>. The library knows two |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
243 | types of such loops, the I<default> loop, which supports signals and child |
282 | types of such loops, the I<default> loop, which supports signals and child |
244 | events, and dynamically created loops which do not. |
283 | events, and dynamically created loops which do not. |
245 | |
284 | |
246 | If you use threads, a common model is to run the default event loop |
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247 | in your main thread (or in a separate thread) and for each thread you |
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248 | create, you also create another event loop. Libev itself does no locking |
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249 | whatsoever, so if you mix calls to the same event loop in different |
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250 | threads, make sure you lock (this is usually a bad idea, though, even if |
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251 | done correctly, because it's hideous and inefficient). |
|
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252 | |
|
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253 | =over 4 |
285 | =over 4 |
254 | |
286 | |
255 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
256 | |
288 | |
257 | This will initialise the default event loop if it hasn't been initialised |
289 | This will initialise the default event loop if it hasn't been initialised |
… | |
… | |
259 | false. If it already was initialised it simply returns it (and ignores the |
291 | false. If it already was initialised it simply returns it (and ignores the |
260 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
261 | |
293 | |
262 | If you don't know what event loop to use, use the one returned from this |
294 | If you don't know what event loop to use, use the one returned from this |
263 | function. |
295 | function. |
|
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296 | |
|
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297 | Note that this function is I<not> thread-safe, so if you want to use it |
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298 | from multiple threads, you have to lock (note also that this is unlikely, |
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299 | as loops cannot bes hared easily between threads anyway). |
264 | |
300 | |
265 | The default loop is the only loop that can handle C<ev_signal> and |
301 | The default loop is the only loop that can handle C<ev_signal> and |
266 | C<ev_child> watchers, and to do this, it always registers a handler |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
267 | for C<SIGCHLD>. If this is a problem for your app you can either |
303 | for C<SIGCHLD>. If this is a problem for your app you can either |
268 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
297 | enabling this flag. |
333 | enabling this flag. |
298 | |
334 | |
299 | This works by calling C<getpid ()> on every iteration of the loop, |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
300 | and thus this might slow down your event loop if you do a lot of loop |
336 | and thus this might slow down your event loop if you do a lot of loop |
301 | iterations and little real work, but is usually not noticeable (on my |
337 | iterations and little real work, but is usually not noticeable (on my |
302 | Linux system for example, C<getpid> is actually a simple 5-insn sequence |
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
303 | without a syscall and thus I<very> fast, but my Linux system also has |
339 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
304 | C<pthread_atfork> which is even faster). |
340 | C<pthread_atfork> which is even faster). |
305 | |
341 | |
306 | The big advantage of this flag is that you can forget about fork (and |
342 | The big advantage of this flag is that you can forget about fork (and |
307 | forget about forgetting to tell libev about forking) when you use this |
343 | forget about forgetting to tell libev about forking) when you use this |
308 | flag. |
344 | flag. |
… | |
… | |
321 | To get good performance out of this backend you need a high amount of |
357 | To get good performance out of this backend you need a high amount of |
322 | parallelity (most of the file descriptors should be busy). If you are |
358 | parallelity (most of the file descriptors should be busy). If you are |
323 | writing a server, you should C<accept ()> in a loop to accept as many |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
324 | connections as possible during one iteration. You might also want to have |
360 | connections as possible during one iteration. You might also want to have |
325 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
326 | readyness notifications you get per iteration. |
362 | readiness notifications you get per iteration. |
327 | |
363 | |
328 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
329 | |
365 | |
330 | And this is your standard poll(2) backend. It's more complicated |
366 | And this is your standard poll(2) backend. It's more complicated |
331 | than select, but handles sparse fds better and has no artificial |
367 | than select, but handles sparse fds better and has no artificial |
… | |
… | |
339 | For few fds, this backend is a bit little slower than poll and select, |
375 | For few fds, this backend is a bit little slower than poll and select, |
340 | but it scales phenomenally better. While poll and select usually scale |
376 | but it scales phenomenally better. While poll and select usually scale |
341 | like O(total_fds) where n is the total number of fds (or the highest fd), |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
342 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
343 | of shortcomings, such as silently dropping events in some hard-to-detect |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
344 | cases and rewiring a syscall per fd change, no fork support and bad |
380 | cases and requiring a syscall per fd change, no fork support and bad |
345 | support for dup. |
381 | support for dup. |
346 | |
382 | |
347 | While stopping, setting and starting an I/O watcher in the same iteration |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
348 | will result in some caching, there is still a syscall per such incident |
384 | will result in some caching, there is still a syscall per such incident |
349 | (because the fd could point to a different file description now), so its |
385 | (because the fd could point to a different file description now), so its |
… | |
… | |
410 | While this backend scales well, it requires one system call per active |
446 | While this backend scales well, it requires one system call per active |
411 | file descriptor per loop iteration. For small and medium numbers of file |
447 | file descriptor per loop iteration. For small and medium numbers of file |
412 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
413 | might perform better. |
449 | might perform better. |
414 | |
450 | |
415 | On the positive side, ignoring the spurious readyness notifications, this |
451 | On the positive side, ignoring the spurious readiness notifications, this |
416 | backend actually performed to specification in all tests and is fully |
452 | backend actually performed to specification in all tests and is fully |
417 | embeddable, which is a rare feat among the OS-specific backends. |
453 | embeddable, which is a rare feat among the OS-specific backends. |
418 | |
454 | |
419 | =item C<EVBACKEND_ALL> |
455 | =item C<EVBACKEND_ALL> |
420 | |
456 | |
… | |
… | |
450 | |
486 | |
451 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
452 | always distinct from the default loop. Unlike the default loop, it cannot |
488 | always distinct from the default loop. Unlike the default loop, it cannot |
453 | handle signal and child watchers, and attempts to do so will be greeted by |
489 | handle signal and child watchers, and attempts to do so will be greeted by |
454 | undefined behaviour (or a failed assertion if assertions are enabled). |
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
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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 |
|
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494 | default loop in the "main" or "initial" thread. |
455 | |
495 | |
456 | Example: Try to create a event loop that uses epoll and nothing else. |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
457 | |
497 | |
458 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
459 | if (!epoller) |
499 | if (!epoller) |
… | |
… | |
505 | =item ev_loop_fork (loop) |
545 | =item ev_loop_fork (loop) |
506 | |
546 | |
507 | Like C<ev_default_fork>, but acts on an event loop created by |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
508 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
509 | after fork, and how you do this is entirely your own problem. |
549 | after fork, and how you do this is entirely your own problem. |
|
|
550 | |
|
|
551 | =item int ev_is_default_loop (loop) |
|
|
552 | |
|
|
553 | Returns true when the given loop actually is the default loop, false otherwise. |
510 | |
554 | |
511 | =item unsigned int ev_loop_count (loop) |
555 | =item unsigned int ev_loop_count (loop) |
512 | |
556 | |
513 | Returns the count of loop iterations for the loop, which is identical to |
557 | Returns the count of loop iterations for the loop, which is identical to |
514 | the number of times libev did poll for new events. It starts at C<0> and |
558 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
666 | interval to a value near C<0.1> or so, which is often enough for |
710 | interval to a value near C<0.1> or so, which is often enough for |
667 | interactive servers (of course not for games), likewise for timeouts. It |
711 | interactive servers (of course not for games), likewise for timeouts. It |
668 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
712 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
669 | as this approsaches the timing granularity of most systems. |
713 | as this approsaches the timing granularity of most systems. |
670 | |
714 | |
|
|
715 | =item ev_loop_verify (loop) |
|
|
716 | |
|
|
717 | This function only does something when C<EV_VERIFY> support has been |
|
|
718 | compiled in. It tries to go through all internal structures and checks |
|
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719 | them for validity. If anything is found to be inconsistent, it will print |
|
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720 | an error message to standard error and call C<abort ()>. |
|
|
721 | |
|
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722 | This can be used to catch bugs inside libev itself: under normal |
|
|
723 | circumstances, this function will never abort as of course libev keeps its |
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724 | data structures consistent. |
|
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725 | |
671 | =back |
726 | =back |
672 | |
727 | |
673 | |
728 | |
674 | =head1 ANATOMY OF A WATCHER |
729 | =head1 ANATOMY OF A WATCHER |
675 | |
730 | |
… | |
… | |
1009 | If you must do this, then force the use of a known-to-be-good backend |
1064 | If you must do this, then force the use of a known-to-be-good backend |
1010 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1065 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1011 | C<EVBACKEND_POLL>). |
1066 | C<EVBACKEND_POLL>). |
1012 | |
1067 | |
1013 | Another thing you have to watch out for is that it is quite easy to |
1068 | Another thing you have to watch out for is that it is quite easy to |
1014 | receive "spurious" readyness notifications, that is your callback might |
1069 | receive "spurious" readiness notifications, that is your callback might |
1015 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1070 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1016 | because there is no data. Not only are some backends known to create a |
1071 | because there is no data. Not only are some backends known to create a |
1017 | lot of those (for example solaris ports), it is very easy to get into |
1072 | lot of those (for example solaris ports), it is very easy to get into |
1018 | this situation even with a relatively standard program structure. Thus |
1073 | this situation even with a relatively standard program structure. Thus |
1019 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1074 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
… | |
… | |
1066 | To support fork in your programs, you either have to call |
1121 | To support fork in your programs, you either have to call |
1067 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1122 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1068 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1123 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1069 | C<EVBACKEND_POLL>. |
1124 | C<EVBACKEND_POLL>. |
1070 | |
1125 | |
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1126 | =head3 The special problem of SIGPIPE |
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1127 | |
|
|
1128 | While not really specific to libev, it is easy to forget about SIGPIPE: |
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1129 | when reading from a pipe whose other end has been closed, your program |
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1130 | gets send a SIGPIPE, which, by default, aborts your program. For most |
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1131 | programs this is sensible behaviour, for daemons, this is usually |
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|
1132 | undesirable. |
|
|
1133 | |
|
|
1134 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1135 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1136 | somewhere, as that would have given you a big clue). |
|
|
1137 | |
1071 | |
1138 | |
1072 | =head3 Watcher-Specific Functions |
1139 | =head3 Watcher-Specific Functions |
1073 | |
1140 | |
1074 | =over 4 |
1141 | =over 4 |
1075 | |
1142 | |
… | |
… | |
1116 | |
1183 | |
1117 | Timer watchers are simple relative timers that generate an event after a |
1184 | Timer watchers are simple relative timers that generate an event after a |
1118 | given time, and optionally repeating in regular intervals after that. |
1185 | given time, and optionally repeating in regular intervals after that. |
1119 | |
1186 | |
1120 | The timers are based on real time, that is, if you register an event that |
1187 | The timers are based on real time, that is, if you register an event that |
1121 | times out after an hour and you reset your system clock to last years |
1188 | times out after an hour and you reset your system clock to january last |
1122 | time, it will still time out after (roughly) and hour. "Roughly" because |
1189 | year, it will still time out after (roughly) and hour. "Roughly" because |
1123 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1190 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1124 | monotonic clock option helps a lot here). |
1191 | monotonic clock option helps a lot here). |
1125 | |
1192 | |
1126 | The relative timeouts are calculated relative to the C<ev_now ()> |
1193 | The relative timeouts are calculated relative to the C<ev_now ()> |
1127 | time. This is usually the right thing as this timestamp refers to the time |
1194 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1129 | you suspect event processing to be delayed and you I<need> to base the timeout |
1196 | you suspect event processing to be delayed and you I<need> to base the timeout |
1130 | on the current time, use something like this to adjust for this: |
1197 | on the current time, use something like this to adjust for this: |
1131 | |
1198 | |
1132 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1199 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1133 | |
1200 | |
1134 | The callback is guarenteed to be invoked only when its timeout has passed, |
1201 | The callback is guarenteed to be invoked only after its timeout has passed, |
1135 | but if multiple timers become ready during the same loop iteration then |
1202 | but if multiple timers become ready during the same loop iteration then |
1136 | order of execution is undefined. |
1203 | order of execution is undefined. |
1137 | |
1204 | |
1138 | =head3 Watcher-Specific Functions and Data Members |
1205 | =head3 Watcher-Specific Functions and Data Members |
1139 | |
1206 | |
… | |
… | |
1141 | |
1208 | |
1142 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1209 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1143 | |
1210 | |
1144 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1211 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1145 | |
1212 | |
1146 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1213 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1147 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1214 | is C<0.>, then it will automatically be stopped once the timeout is |
1148 | timer will automatically be configured to trigger again C<repeat> seconds |
1215 | reached. If it is positive, then the timer will automatically be |
1149 | later, again, and again, until stopped manually. |
1216 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1217 | until stopped manually. |
1150 | |
1218 | |
1151 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1219 | The timer itself will do a best-effort at avoiding drift, that is, if |
1152 | configure a timer to trigger every 10 seconds, then it will trigger at |
1220 | you configure a timer to trigger every 10 seconds, then it will normally |
1153 | exactly 10 second intervals. If, however, your program cannot keep up with |
1221 | trigger at exactly 10 second intervals. If, however, your program cannot |
1154 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1222 | keep up with the timer (because it takes longer than those 10 seconds to |
1155 | timer will not fire more than once per event loop iteration. |
1223 | do stuff) the timer will not fire more than once per event loop iteration. |
1156 | |
1224 | |
1157 | =item ev_timer_again (loop) |
1225 | =item ev_timer_again (loop, ev_timer *) |
1158 | |
1226 | |
1159 | This will act as if the timer timed out and restart it again if it is |
1227 | This will act as if the timer timed out and restart it again if it is |
1160 | repeating. The exact semantics are: |
1228 | repeating. The exact semantics are: |
1161 | |
1229 | |
1162 | If the timer is pending, its pending status is cleared. |
1230 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1237 | Periodic watchers are also timers of a kind, but they are very versatile |
1305 | Periodic watchers are also timers of a kind, but they are very versatile |
1238 | (and unfortunately a bit complex). |
1306 | (and unfortunately a bit complex). |
1239 | |
1307 | |
1240 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1308 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1241 | but on wallclock time (absolute time). You can tell a periodic watcher |
1309 | but on wallclock time (absolute time). You can tell a periodic watcher |
1242 | to trigger "at" some specific point in time. For example, if you tell a |
1310 | to trigger after some specific point in time. For example, if you tell a |
1243 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1311 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1244 | + 10.>) and then reset your system clock to the last year, then it will |
1312 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1313 | clock to january of the previous year, then it will take more than year |
1245 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1314 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1246 | roughly 10 seconds later). |
1315 | roughly 10 seconds later as it uses a relative timeout). |
1247 | |
1316 | |
1248 | They can also be used to implement vastly more complex timers, such as |
1317 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1249 | triggering an event on each midnight, local time or other, complicated, |
1318 | such as triggering an event on each "midnight, local time", or other |
1250 | rules. |
1319 | complicated, rules. |
1251 | |
1320 | |
1252 | As with timers, the callback is guarenteed to be invoked only when the |
1321 | As with timers, the callback is guarenteed to be invoked only when the |
1253 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1322 | time (C<at>) has passed, but if multiple periodic timers become ready |
1254 | during the same loop iteration then order of execution is undefined. |
1323 | during the same loop iteration then order of execution is undefined. |
1255 | |
1324 | |
1256 | =head3 Watcher-Specific Functions and Data Members |
1325 | =head3 Watcher-Specific Functions and Data Members |
1257 | |
1326 | |
1258 | =over 4 |
1327 | =over 4 |
… | |
… | |
1266 | |
1335 | |
1267 | =over 4 |
1336 | =over 4 |
1268 | |
1337 | |
1269 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1338 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1270 | |
1339 | |
1271 | In this configuration the watcher triggers an event at the wallclock time |
1340 | In this configuration the watcher triggers an event after the wallclock |
1272 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1341 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1273 | that is, if it is to be run at January 1st 2011 then it will run when the |
1342 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1274 | system time reaches or surpasses this time. |
1343 | run when the system time reaches or surpasses this time. |
1275 | |
1344 | |
1276 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1345 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1277 | |
1346 | |
1278 | In this mode the watcher will always be scheduled to time out at the next |
1347 | In this mode the watcher will always be scheduled to time out at the next |
1279 | C<at + N * interval> time (for some integer N, which can also be negative) |
1348 | C<at + N * interval> time (for some integer N, which can also be negative) |
1280 | and then repeat, regardless of any time jumps. |
1349 | and then repeat, regardless of any time jumps. |
1281 | |
1350 | |
1282 | This can be used to create timers that do not drift with respect to system |
1351 | This can be used to create timers that do not drift with respect to system |
1283 | time: |
1352 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1353 | the hour: |
1284 | |
1354 | |
1285 | ev_periodic_set (&periodic, 0., 3600., 0); |
1355 | ev_periodic_set (&periodic, 0., 3600., 0); |
1286 | |
1356 | |
1287 | This doesn't mean there will always be 3600 seconds in between triggers, |
1357 | This doesn't mean there will always be 3600 seconds in between triggers, |
1288 | but only that the the callback will be called when the system time shows a |
1358 | but only that the the callback will be called when the system time shows a |
… | |
… | |
1293 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1363 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1294 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1364 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1295 | |
1365 | |
1296 | For numerical stability it is preferable that the C<at> value is near |
1366 | For numerical stability it is preferable that the C<at> value is near |
1297 | C<ev_now ()> (the current time), but there is no range requirement for |
1367 | C<ev_now ()> (the current time), but there is no range requirement for |
1298 | this value. |
1368 | this value, and in fact is often specified as zero. |
|
|
1369 | |
|
|
1370 | Note also that there is an upper limit to how often a timer can fire (cpu |
|
|
1371 | speed for example), so if C<interval> is very small then timing stability |
|
|
1372 | will of course detoriate. Libev itself tries to be exact to be about one |
|
|
1373 | millisecond (if the OS supports it and the machine is fast enough). |
1299 | |
1374 | |
1300 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1375 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1301 | |
1376 | |
1302 | In this mode the values for C<interval> and C<at> are both being |
1377 | In this mode the values for C<interval> and C<at> are both being |
1303 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1378 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1304 | reschedule callback will be called with the watcher as first, and the |
1379 | reschedule callback will be called with the watcher as first, and the |
1305 | current time as second argument. |
1380 | current time as second argument. |
1306 | |
1381 | |
1307 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1382 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1308 | ever, or make any event loop modifications>. If you need to stop it, |
1383 | ever, or make ANY event loop modifications whatsoever>. |
1309 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1310 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1311 | |
1384 | |
|
|
1385 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1386 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1387 | only event loop modification you are allowed to do). |
|
|
1388 | |
1312 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1389 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1313 | ev_tstamp now)>, e.g.: |
1390 | *w, ev_tstamp now)>, e.g.: |
1314 | |
1391 | |
1315 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1392 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1316 | { |
1393 | { |
1317 | return now + 60.; |
1394 | return now + 60.; |
1318 | } |
1395 | } |
… | |
… | |
1320 | It must return the next time to trigger, based on the passed time value |
1397 | It must return the next time to trigger, based on the passed time value |
1321 | (that is, the lowest time value larger than to the second argument). It |
1398 | (that is, the lowest time value larger than to the second argument). It |
1322 | will usually be called just before the callback will be triggered, but |
1399 | will usually be called just before the callback will be triggered, but |
1323 | might be called at other times, too. |
1400 | might be called at other times, too. |
1324 | |
1401 | |
1325 | NOTE: I<< This callback must always return a time that is later than the |
1402 | NOTE: I<< This callback must always return a time that is higher than or |
1326 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1403 | equal to the passed C<now> value >>. |
1327 | |
1404 | |
1328 | This can be used to create very complex timers, such as a timer that |
1405 | This can be used to create very complex timers, such as a timer that |
1329 | triggers on each midnight, local time. To do this, you would calculate the |
1406 | triggers on "next midnight, local time". To do this, you would calculate the |
1330 | next midnight after C<now> and return the timestamp value for this. How |
1407 | next midnight after C<now> and return the timestamp value for this. How |
1331 | you do this is, again, up to you (but it is not trivial, which is the main |
1408 | you do this is, again, up to you (but it is not trivial, which is the main |
1332 | reason I omitted it as an example). |
1409 | reason I omitted it as an example). |
1333 | |
1410 | |
1334 | =back |
1411 | =back |
… | |
… | |
1338 | Simply stops and restarts the periodic watcher again. This is only useful |
1415 | Simply stops and restarts the periodic watcher again. This is only useful |
1339 | when you changed some parameters or the reschedule callback would return |
1416 | when you changed some parameters or the reschedule callback would return |
1340 | a different time than the last time it was called (e.g. in a crond like |
1417 | a different time than the last time it was called (e.g. in a crond like |
1341 | program when the crontabs have changed). |
1418 | program when the crontabs have changed). |
1342 | |
1419 | |
|
|
1420 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1421 | |
|
|
1422 | When active, returns the absolute time that the watcher is supposed to |
|
|
1423 | trigger next. |
|
|
1424 | |
1343 | =item ev_tstamp offset [read-write] |
1425 | =item ev_tstamp offset [read-write] |
1344 | |
1426 | |
1345 | When repeating, this contains the offset value, otherwise this is the |
1427 | When repeating, this contains the offset value, otherwise this is the |
1346 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1428 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1347 | |
1429 | |
… | |
… | |
1357 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1439 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1358 | |
1440 | |
1359 | The current reschedule callback, or C<0>, if this functionality is |
1441 | The current reschedule callback, or C<0>, if this functionality is |
1360 | switched off. Can be changed any time, but changes only take effect when |
1442 | switched off. Can be changed any time, but changes only take effect when |
1361 | the periodic timer fires or C<ev_periodic_again> is being called. |
1443 | the periodic timer fires or C<ev_periodic_again> is being called. |
1362 | |
|
|
1363 | =item ev_tstamp at [read-only] |
|
|
1364 | |
|
|
1365 | When active, contains the absolute time that the watcher is supposed to |
|
|
1366 | trigger next. |
|
|
1367 | |
1444 | |
1368 | =back |
1445 | =back |
1369 | |
1446 | |
1370 | =head3 Examples |
1447 | =head3 Examples |
1371 | |
1448 | |
… | |
… | |
1415 | with the kernel (thus it coexists with your own signal handlers as long |
1492 | with the kernel (thus it coexists with your own signal handlers as long |
1416 | as you don't register any with libev). Similarly, when the last signal |
1493 | as you don't register any with libev). Similarly, when the last signal |
1417 | watcher for a signal is stopped libev will reset the signal handler to |
1494 | watcher for a signal is stopped libev will reset the signal handler to |
1418 | SIG_DFL (regardless of what it was set to before). |
1495 | SIG_DFL (regardless of what it was set to before). |
1419 | |
1496 | |
|
|
1497 | If possible and supported, libev will install its handlers with |
|
|
1498 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1499 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1500 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1501 | them in an C<ev_prepare> watcher. |
|
|
1502 | |
1420 | =head3 Watcher-Specific Functions and Data Members |
1503 | =head3 Watcher-Specific Functions and Data Members |
1421 | |
1504 | |
1422 | =over 4 |
1505 | =over 4 |
1423 | |
1506 | |
1424 | =item ev_signal_init (ev_signal *, callback, int signum) |
1507 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1432 | |
1515 | |
1433 | The signal the watcher watches out for. |
1516 | The signal the watcher watches out for. |
1434 | |
1517 | |
1435 | =back |
1518 | =back |
1436 | |
1519 | |
|
|
1520 | =head3 Examples |
|
|
1521 | |
|
|
1522 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1523 | |
|
|
1524 | static void |
|
|
1525 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1526 | { |
|
|
1527 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1528 | } |
|
|
1529 | |
|
|
1530 | struct ev_signal signal_watcher; |
|
|
1531 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1532 | ev_signal_start (loop, &sigint_cb); |
|
|
1533 | |
1437 | |
1534 | |
1438 | =head2 C<ev_child> - watch out for process status changes |
1535 | =head2 C<ev_child> - watch out for process status changes |
1439 | |
1536 | |
1440 | Child watchers trigger when your process receives a SIGCHLD in response to |
1537 | Child watchers trigger when your process receives a SIGCHLD in response to |
1441 | some child status changes (most typically when a child of yours dies). |
1538 | some child status changes (most typically when a child of yours dies). It |
|
|
1539 | is permissible to install a child watcher I<after> the child has been |
|
|
1540 | forked (which implies it might have already exited), as long as the event |
|
|
1541 | loop isn't entered (or is continued from a watcher). |
|
|
1542 | |
|
|
1543 | Only the default event loop is capable of handling signals, and therefore |
|
|
1544 | you can only rgeister child watchers in the default event loop. |
|
|
1545 | |
|
|
1546 | =head3 Process Interaction |
|
|
1547 | |
|
|
1548 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1549 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1550 | the first child watcher is started after the child exits. The occurance |
|
|
1551 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1552 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1553 | children, even ones not watched. |
|
|
1554 | |
|
|
1555 | =head3 Overriding the Built-In Processing |
|
|
1556 | |
|
|
1557 | Libev offers no special support for overriding the built-in child |
|
|
1558 | processing, but if your application collides with libev's default child |
|
|
1559 | handler, you can override it easily by installing your own handler for |
|
|
1560 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1561 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1562 | event-based approach to child reaping and thus use libev's support for |
|
|
1563 | that, so other libev users can use C<ev_child> watchers freely. |
1442 | |
1564 | |
1443 | =head3 Watcher-Specific Functions and Data Members |
1565 | =head3 Watcher-Specific Functions and Data Members |
1444 | |
1566 | |
1445 | =over 4 |
1567 | =over 4 |
1446 | |
1568 | |
… | |
… | |
1472 | |
1594 | |
1473 | =back |
1595 | =back |
1474 | |
1596 | |
1475 | =head3 Examples |
1597 | =head3 Examples |
1476 | |
1598 | |
1477 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1599 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1600 | its completion. |
|
|
1601 | |
|
|
1602 | ev_child cw; |
1478 | |
1603 | |
1479 | static void |
1604 | static void |
1480 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1605 | child_cb (EV_P_ struct ev_child *w, int revents) |
1481 | { |
1606 | { |
1482 | ev_unloop (loop, EVUNLOOP_ALL); |
1607 | ev_child_stop (EV_A_ w); |
|
|
1608 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1483 | } |
1609 | } |
1484 | |
1610 | |
1485 | struct ev_signal signal_watcher; |
1611 | pid_t pid = fork (); |
1486 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1612 | |
1487 | ev_signal_start (loop, &sigint_cb); |
1613 | if (pid < 0) |
|
|
1614 | // error |
|
|
1615 | else if (pid == 0) |
|
|
1616 | { |
|
|
1617 | // the forked child executes here |
|
|
1618 | exit (1); |
|
|
1619 | } |
|
|
1620 | else |
|
|
1621 | { |
|
|
1622 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1623 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1624 | } |
1488 | |
1625 | |
1489 | |
1626 | |
1490 | =head2 C<ev_stat> - did the file attributes just change? |
1627 | =head2 C<ev_stat> - did the file attributes just change? |
1491 | |
1628 | |
1492 | This watches a filesystem path for attribute changes. That is, it calls |
1629 | This watches a filesystem path for attribute changes. That is, it calls |
… | |
… | |
1515 | as even with OS-supported change notifications, this can be |
1652 | as even with OS-supported change notifications, this can be |
1516 | resource-intensive. |
1653 | resource-intensive. |
1517 | |
1654 | |
1518 | At the time of this writing, only the Linux inotify interface is |
1655 | At the time of this writing, only the Linux inotify interface is |
1519 | implemented (implementing kqueue support is left as an exercise for the |
1656 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1657 | reader, note, however, that the author sees no way of implementing ev_stat |
1520 | reader). Inotify will be used to give hints only and should not change the |
1658 | semantics with kqueue). Inotify will be used to give hints only and should |
1521 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1659 | not change the semantics of C<ev_stat> watchers, which means that libev |
1522 | to fall back to regular polling again even with inotify, but changes are |
1660 | sometimes needs to fall back to regular polling again even with inotify, |
1523 | usually detected immediately, and if the file exists there will be no |
1661 | but changes are usually detected immediately, and if the file exists there |
1524 | polling. |
1662 | will be no polling. |
|
|
1663 | |
|
|
1664 | =head3 ABI Issues (Largefile Support) |
|
|
1665 | |
|
|
1666 | Libev by default (unless the user overrides this) uses the default |
|
|
1667 | compilation environment, which means that on systems with optionally |
|
|
1668 | disabled large file support, you get the 32 bit version of the stat |
|
|
1669 | structure. When using the library from programs that change the ABI to |
|
|
1670 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1671 | compile libev with the same flags to get binary compatibility. This is |
|
|
1672 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1673 | most noticably with ev_stat and largefile support. |
1525 | |
1674 | |
1526 | =head3 Inotify |
1675 | =head3 Inotify |
1527 | |
1676 | |
1528 | When C<inotify (7)> support has been compiled into libev (generally only |
1677 | When C<inotify (7)> support has been compiled into libev (generally only |
1529 | available on Linux) and present at runtime, it will be used to speed up |
1678 | available on Linux) and present at runtime, it will be used to speed up |
1530 | change detection where possible. The inotify descriptor will be created lazily |
1679 | change detection where possible. The inotify descriptor will be created lazily |
1531 | when the first C<ev_stat> watcher is being started. |
1680 | when the first C<ev_stat> watcher is being started. |
1532 | |
1681 | |
1533 | Inotify presense does not change the semantics of C<ev_stat> watchers |
1682 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1534 | except that changes might be detected earlier, and in some cases, to avoid |
1683 | except that changes might be detected earlier, and in some cases, to avoid |
1535 | making regular C<stat> calls. Even in the presense of inotify support |
1684 | making regular C<stat> calls. Even in the presence of inotify support |
1536 | there are many cases where libev has to resort to regular C<stat> polling. |
1685 | there are many cases where libev has to resort to regular C<stat> polling. |
1537 | |
1686 | |
1538 | (There is no support for kqueue, as apparently it cannot be used to |
1687 | (There is no support for kqueue, as apparently it cannot be used to |
1539 | implement this functionality, due to the requirement of having a file |
1688 | implement this functionality, due to the requirement of having a file |
1540 | descriptor open on the object at all times). |
1689 | descriptor open on the object at all times). |
… | |
… | |
1543 | |
1692 | |
1544 | The C<stat ()> syscall only supports full-second resolution portably, and |
1693 | The C<stat ()> syscall only supports full-second resolution portably, and |
1545 | even on systems where the resolution is higher, many filesystems still |
1694 | even on systems where the resolution is higher, many filesystems still |
1546 | only support whole seconds. |
1695 | only support whole seconds. |
1547 | |
1696 | |
1548 | That means that, if the time is the only thing that changes, you might |
1697 | That means that, if the time is the only thing that changes, you can |
1549 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1698 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1550 | your callback, which does something. When there is another update within |
1699 | calls your callback, which does something. When there is another update |
1551 | the same second, C<ev_stat> will be unable to detect it. |
1700 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1701 | data does not change. |
1552 | |
1702 | |
1553 | The solution to this is to delay acting on a change for a second (or till |
1703 | The solution to this is to delay acting on a change for slightly more |
1554 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1704 | than a second (or till slightly after the next full second boundary), using |
1555 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1705 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1556 | is added to work around small timing inconsistencies of some operating |
1706 | ev_timer_again (loop, w)>). |
1557 | systems. |
1707 | |
|
|
1708 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1709 | of some operating systems (where the second counter of the current time |
|
|
1710 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1711 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1712 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1713 | update file times then there will be a small window where the kernel uses |
|
|
1714 | the previous second to update file times but libev might already execute |
|
|
1715 | the timer callback). |
1558 | |
1716 | |
1559 | =head3 Watcher-Specific Functions and Data Members |
1717 | =head3 Watcher-Specific Functions and Data Members |
1560 | |
1718 | |
1561 | =over 4 |
1719 | =over 4 |
1562 | |
1720 | |
… | |
… | |
1568 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1726 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1569 | be detected and should normally be specified as C<0> to let libev choose |
1727 | be detected and should normally be specified as C<0> to let libev choose |
1570 | a suitable value. The memory pointed to by C<path> must point to the same |
1728 | a suitable value. The memory pointed to by C<path> must point to the same |
1571 | path for as long as the watcher is active. |
1729 | path for as long as the watcher is active. |
1572 | |
1730 | |
1573 | The callback will be receive C<EV_STAT> when a change was detected, |
1731 | The callback will receive C<EV_STAT> when a change was detected, relative |
1574 | relative to the attributes at the time the watcher was started (or the |
1732 | to the attributes at the time the watcher was started (or the last change |
1575 | last change was detected). |
1733 | was detected). |
1576 | |
1734 | |
1577 | =item ev_stat_stat (ev_stat *) |
1735 | =item ev_stat_stat (loop, ev_stat *) |
1578 | |
1736 | |
1579 | Updates the stat buffer immediately with new values. If you change the |
1737 | Updates the stat buffer immediately with new values. If you change the |
1580 | watched path in your callback, you could call this fucntion to avoid |
1738 | watched path in your callback, you could call this function to avoid |
1581 | detecting this change (while introducing a race condition). Can also be |
1739 | detecting this change (while introducing a race condition if you are not |
1582 | useful simply to find out the new values. |
1740 | the only one changing the path). Can also be useful simply to find out the |
|
|
1741 | new values. |
1583 | |
1742 | |
1584 | =item ev_statdata attr [read-only] |
1743 | =item ev_statdata attr [read-only] |
1585 | |
1744 | |
1586 | The most-recently detected attributes of the file. Although the type is of |
1745 | The most-recently detected attributes of the file. Although the type is |
1587 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1746 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1588 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1747 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1748 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1589 | was some error while C<stat>ing the file. |
1749 | some error while C<stat>ing the file. |
1590 | |
1750 | |
1591 | =item ev_statdata prev [read-only] |
1751 | =item ev_statdata prev [read-only] |
1592 | |
1752 | |
1593 | The previous attributes of the file. The callback gets invoked whenever |
1753 | The previous attributes of the file. The callback gets invoked whenever |
1594 | C<prev> != C<attr>. |
1754 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1755 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1756 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1595 | |
1757 | |
1596 | =item ev_tstamp interval [read-only] |
1758 | =item ev_tstamp interval [read-only] |
1597 | |
1759 | |
1598 | The specified interval. |
1760 | The specified interval. |
1599 | |
1761 | |
… | |
… | |
1653 | } |
1815 | } |
1654 | |
1816 | |
1655 | ... |
1817 | ... |
1656 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1818 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1657 | ev_stat_start (loop, &passwd); |
1819 | ev_stat_start (loop, &passwd); |
1658 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1820 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1659 | |
1821 | |
1660 | |
1822 | |
1661 | =head2 C<ev_idle> - when you've got nothing better to do... |
1823 | =head2 C<ev_idle> - when you've got nothing better to do... |
1662 | |
1824 | |
1663 | Idle watchers trigger events when no other events of the same or higher |
1825 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1751 | |
1913 | |
1752 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1914 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1753 | priority, to ensure that they are being run before any other watchers |
1915 | priority, to ensure that they are being run before any other watchers |
1754 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1916 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1755 | too) should not activate ("feed") events into libev. While libev fully |
1917 | too) should not activate ("feed") events into libev. While libev fully |
1756 | supports this, they will be called before other C<ev_check> watchers |
1918 | supports this, they might get executed before other C<ev_check> watchers |
1757 | did their job. As C<ev_check> watchers are often used to embed other |
1919 | did their job. As C<ev_check> watchers are often used to embed other |
1758 | (non-libev) event loops those other event loops might be in an unusable |
1920 | (non-libev) event loops those other event loops might be in an unusable |
1759 | state until their C<ev_check> watcher ran (always remind yourself to |
1921 | state until their C<ev_check> watcher ran (always remind yourself to |
1760 | coexist peacefully with others). |
1922 | coexist peacefully with others). |
1761 | |
1923 | |
… | |
… | |
1776 | =head3 Examples |
1938 | =head3 Examples |
1777 | |
1939 | |
1778 | There are a number of principal ways to embed other event loops or modules |
1940 | There are a number of principal ways to embed other event loops or modules |
1779 | into libev. Here are some ideas on how to include libadns into libev |
1941 | into libev. Here are some ideas on how to include libadns into libev |
1780 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1942 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1781 | use for an actually working example. Another Perl module named C<EV::Glib> |
1943 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1782 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1944 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1783 | into the Glib event loop). |
1945 | Glib event loop). |
1784 | |
1946 | |
1785 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1947 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1786 | and in a check watcher, destroy them and call into libadns. What follows |
1948 | and in a check watcher, destroy them and call into libadns. What follows |
1787 | is pseudo-code only of course. This requires you to either use a low |
1949 | is pseudo-code only of course. This requires you to either use a low |
1788 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1950 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2078 | is that the author does not know of a simple (or any) algorithm for a |
2240 | is that the author does not know of a simple (or any) algorithm for a |
2079 | multiple-writer-single-reader queue that works in all cases and doesn't |
2241 | multiple-writer-single-reader queue that works in all cases and doesn't |
2080 | need elaborate support such as pthreads. |
2242 | need elaborate support such as pthreads. |
2081 | |
2243 | |
2082 | That means that if you want to queue data, you have to provide your own |
2244 | That means that if you want to queue data, you have to provide your own |
2083 | queue. And here is how you would implement locking: |
2245 | queue. But at least I can tell you would implement locking around your |
|
|
2246 | queue: |
2084 | |
2247 | |
2085 | =over 4 |
2248 | =over 4 |
2086 | |
2249 | |
2087 | =item queueing from a signal handler context |
2250 | =item queueing from a signal handler context |
2088 | |
2251 | |
… | |
… | |
2097 | { |
2260 | { |
2098 | sometype data; |
2261 | sometype data; |
2099 | |
2262 | |
2100 | // no locking etc. |
2263 | // no locking etc. |
2101 | queue_put (data); |
2264 | queue_put (data); |
2102 | ev_async_send (DEFAULT_ &mysig); |
2265 | ev_async_send (EV_DEFAULT_ &mysig); |
2103 | } |
2266 | } |
2104 | |
2267 | |
2105 | static void |
2268 | static void |
2106 | mysig_cb (EV_P_ ev_async *w, int revents) |
2269 | mysig_cb (EV_P_ ev_async *w, int revents) |
2107 | { |
2270 | { |
… | |
… | |
2125 | |
2288 | |
2126 | =item queueing from a thread context |
2289 | =item queueing from a thread context |
2127 | |
2290 | |
2128 | The strategy for threads is different, as you cannot (easily) block |
2291 | The strategy for threads is different, as you cannot (easily) block |
2129 | threads but you can easily preempt them, so to queue safely you need to |
2292 | threads but you can easily preempt them, so to queue safely you need to |
2130 | emply a traditional mutex lock, such as in this pthread example: |
2293 | employ a traditional mutex lock, such as in this pthread example: |
2131 | |
2294 | |
2132 | static ev_async mysig; |
2295 | static ev_async mysig; |
2133 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2296 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2134 | |
2297 | |
2135 | static void |
2298 | static void |
… | |
… | |
2138 | // only need to lock the actual queueing operation |
2301 | // only need to lock the actual queueing operation |
2139 | pthread_mutex_lock (&mymutex); |
2302 | pthread_mutex_lock (&mymutex); |
2140 | queue_put (data); |
2303 | queue_put (data); |
2141 | pthread_mutex_unlock (&mymutex); |
2304 | pthread_mutex_unlock (&mymutex); |
2142 | |
2305 | |
2143 | ev_async_send (DEFAULT_ &mysig); |
2306 | ev_async_send (EV_DEFAULT_ &mysig); |
2144 | } |
2307 | } |
2145 | |
2308 | |
2146 | static void |
2309 | static void |
2147 | mysig_cb (EV_P_ ev_async *w, int revents) |
2310 | mysig_cb (EV_P_ ev_async *w, int revents) |
2148 | { |
2311 | { |
… | |
… | |
2176 | section below on what exactly this means). |
2339 | section below on what exactly this means). |
2177 | |
2340 | |
2178 | This call incurs the overhead of a syscall only once per loop iteration, |
2341 | This call incurs the overhead of a syscall only once per loop iteration, |
2179 | so while the overhead might be noticable, it doesn't apply to repeated |
2342 | so while the overhead might be noticable, it doesn't apply to repeated |
2180 | calls to C<ev_async_send>. |
2343 | calls to C<ev_async_send>. |
|
|
2344 | |
|
|
2345 | =item bool = ev_async_pending (ev_async *) |
|
|
2346 | |
|
|
2347 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2348 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2349 | event loop. |
|
|
2350 | |
|
|
2351 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2352 | the loop iterates next and checks for the watcher to have become active, |
|
|
2353 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2354 | quickly check wether invoking the loop might be a good idea. |
|
|
2355 | |
|
|
2356 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2357 | wether it has been requested to make this watcher pending. |
2181 | |
2358 | |
2182 | =back |
2359 | =back |
2183 | |
2360 | |
2184 | |
2361 | |
2185 | =head1 OTHER FUNCTIONS |
2362 | =head1 OTHER FUNCTIONS |
… | |
… | |
2257 | |
2434 | |
2258 | =item * Priorities are not currently supported. Initialising priorities |
2435 | =item * Priorities are not currently supported. Initialising priorities |
2259 | will fail and all watchers will have the same priority, even though there |
2436 | will fail and all watchers will have the same priority, even though there |
2260 | is an ev_pri field. |
2437 | is an ev_pri field. |
2261 | |
2438 | |
|
|
2439 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2440 | first base created (== the default loop) gets the signals. |
|
|
2441 | |
2262 | =item * Other members are not supported. |
2442 | =item * Other members are not supported. |
2263 | |
2443 | |
2264 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2444 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2265 | to use the libev header file and library. |
2445 | to use the libev header file and library. |
2266 | |
2446 | |
… | |
… | |
2429 | io.start (fd, ev::READ); |
2609 | io.start (fd, ev::READ); |
2430 | } |
2610 | } |
2431 | }; |
2611 | }; |
2432 | |
2612 | |
2433 | |
2613 | |
|
|
2614 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2615 | |
|
|
2616 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2617 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2618 | any interesting language binding in addition to the ones listed here, drop |
|
|
2619 | me a note. |
|
|
2620 | |
|
|
2621 | =over 4 |
|
|
2622 | |
|
|
2623 | =item Perl |
|
|
2624 | |
|
|
2625 | The EV module implements the full libev API and is actually used to test |
|
|
2626 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2627 | there are additional modules that implement libev-compatible interfaces |
|
|
2628 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2629 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2630 | |
|
|
2631 | It can be found and installed via CPAN, its homepage is found at |
|
|
2632 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2633 | |
|
|
2634 | =item Ruby |
|
|
2635 | |
|
|
2636 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2637 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2638 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2639 | L<http://rev.rubyforge.org/>. |
|
|
2640 | |
|
|
2641 | =item D |
|
|
2642 | |
|
|
2643 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2644 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2645 | |
|
|
2646 | =back |
|
|
2647 | |
|
|
2648 | |
2434 | =head1 MACRO MAGIC |
2649 | =head1 MACRO MAGIC |
2435 | |
2650 | |
2436 | Libev can be compiled with a variety of options, the most fundamantal |
2651 | Libev can be compiled with a variety of options, the most fundamantal |
2437 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2652 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2438 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2653 | functions and callbacks have an initial C<struct ev_loop *> argument. |
… | |
… | |
2472 | |
2687 | |
2473 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2688 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2474 | |
2689 | |
2475 | Similar to the other two macros, this gives you the value of the default |
2690 | Similar to the other two macros, this gives you the value of the default |
2476 | loop, if multiple loops are supported ("ev loop default"). |
2691 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2692 | |
|
|
2693 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2694 | |
|
|
2695 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2696 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2697 | is undefined when the default loop has not been initialised by a previous |
|
|
2698 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2699 | |
|
|
2700 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2701 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2477 | |
2702 | |
2478 | =back |
2703 | =back |
2479 | |
2704 | |
2480 | Example: Declare and initialise a check watcher, utilising the above |
2705 | Example: Declare and initialise a check watcher, utilising the above |
2481 | macros so it will work regardless of whether multiple loops are supported |
2706 | macros so it will work regardless of whether multiple loops are supported |
… | |
… | |
2577 | |
2802 | |
2578 | libev.m4 |
2803 | libev.m4 |
2579 | |
2804 | |
2580 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2805 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2581 | |
2806 | |
2582 | Libev can be configured via a variety of preprocessor symbols you have to define |
2807 | Libev can be configured via a variety of preprocessor symbols you have to |
2583 | before including any of its files. The default is not to build for multiplicity |
2808 | define before including any of its files. The default in the absense of |
2584 | and only include the select backend. |
2809 | autoconf is noted for every option. |
2585 | |
2810 | |
2586 | =over 4 |
2811 | =over 4 |
2587 | |
2812 | |
2588 | =item EV_STANDALONE |
2813 | =item EV_STANDALONE |
2589 | |
2814 | |
… | |
… | |
2615 | =item EV_USE_NANOSLEEP |
2840 | =item EV_USE_NANOSLEEP |
2616 | |
2841 | |
2617 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2842 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2618 | and will use it for delays. Otherwise it will use C<select ()>. |
2843 | and will use it for delays. Otherwise it will use C<select ()>. |
2619 | |
2844 | |
|
|
2845 | =item EV_USE_EVENTFD |
|
|
2846 | |
|
|
2847 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2848 | available and will probe for kernel support at runtime. This will improve |
|
|
2849 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2850 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2851 | 2.7 or newer, otherwise disabled. |
|
|
2852 | |
2620 | =item EV_USE_SELECT |
2853 | =item EV_USE_SELECT |
2621 | |
2854 | |
2622 | If undefined or defined to be C<1>, libev will compile in support for the |
2855 | If undefined or defined to be C<1>, libev will compile in support for the |
2623 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2856 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2624 | other method takes over, select will be it. Otherwise the select backend |
2857 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2660 | |
2893 | |
2661 | =item EV_USE_EPOLL |
2894 | =item EV_USE_EPOLL |
2662 | |
2895 | |
2663 | If defined to be C<1>, libev will compile in support for the Linux |
2896 | If defined to be C<1>, libev will compile in support for the Linux |
2664 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2897 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2665 | otherwise another method will be used as fallback. This is the |
2898 | otherwise another method will be used as fallback. This is the preferred |
2666 | preferred backend for GNU/Linux systems. |
2899 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2900 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2667 | |
2901 | |
2668 | =item EV_USE_KQUEUE |
2902 | =item EV_USE_KQUEUE |
2669 | |
2903 | |
2670 | If defined to be C<1>, libev will compile in support for the BSD style |
2904 | If defined to be C<1>, libev will compile in support for the BSD style |
2671 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2905 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2690 | |
2924 | |
2691 | =item EV_USE_INOTIFY |
2925 | =item EV_USE_INOTIFY |
2692 | |
2926 | |
2693 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2927 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2694 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2928 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2695 | be detected at runtime. |
2929 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2930 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2696 | |
2931 | |
2697 | =item EV_ATOMIC_T |
2932 | =item EV_ATOMIC_T |
2698 | |
2933 | |
2699 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2934 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2700 | access is atomic with respect to other threads or signal contexts. No such |
2935 | access is atomic with respect to other threads or signal contexts. No such |
… | |
… | |
2787 | defined to be C<0>, then they are not. |
3022 | defined to be C<0>, then they are not. |
2788 | |
3023 | |
2789 | =item EV_MINIMAL |
3024 | =item EV_MINIMAL |
2790 | |
3025 | |
2791 | If you need to shave off some kilobytes of code at the expense of some |
3026 | If you need to shave off some kilobytes of code at the expense of some |
2792 | speed, define this symbol to C<1>. Currently only used for gcc to override |
3027 | speed, define this symbol to C<1>. Currently this is used to override some |
2793 | some inlining decisions, saves roughly 30% codesize of amd64. |
3028 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
3029 | much smaller 2-heap for timer management over the default 4-heap. |
2794 | |
3030 | |
2795 | =item EV_PID_HASHSIZE |
3031 | =item EV_PID_HASHSIZE |
2796 | |
3032 | |
2797 | C<ev_child> watchers use a small hash table to distribute workload by |
3033 | C<ev_child> watchers use a small hash table to distribute workload by |
2798 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3034 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2804 | C<ev_stat> watchers use a small hash table to distribute workload by |
3040 | C<ev_stat> watchers use a small hash table to distribute workload by |
2805 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3041 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2806 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3042 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2807 | watchers you might want to increase this value (I<must> be a power of |
3043 | watchers you might want to increase this value (I<must> be a power of |
2808 | two). |
3044 | two). |
|
|
3045 | |
|
|
3046 | =item EV_USE_4HEAP |
|
|
3047 | |
|
|
3048 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3049 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3050 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3051 | noticably faster performance with many (thousands) of watchers. |
|
|
3052 | |
|
|
3053 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3054 | (disabled). |
|
|
3055 | |
|
|
3056 | =item EV_HEAP_CACHE_AT |
|
|
3057 | |
|
|
3058 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3059 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3060 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3061 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3062 | but avoids random read accesses on heap changes. This improves performance |
|
|
3063 | noticably with with many (hundreds) of watchers. |
|
|
3064 | |
|
|
3065 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3066 | (disabled). |
|
|
3067 | |
|
|
3068 | =item EV_VERIFY |
|
|
3069 | |
|
|
3070 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
|
|
3071 | be done: If set to C<0>, no internal verification code will be compiled |
|
|
3072 | in. If set to C<1>, then verification code will be compiled in, but not |
|
|
3073 | called. If set to C<2>, then the internal verification code will be |
|
|
3074 | called once per loop, which can slow down libev. If set to C<3>, then the |
|
|
3075 | verification code will be called very frequently, which will slow down |
|
|
3076 | libev considerably. |
|
|
3077 | |
|
|
3078 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
|
|
3079 | C<0.> |
2809 | |
3080 | |
2810 | =item EV_COMMON |
3081 | =item EV_COMMON |
2811 | |
3082 | |
2812 | By default, all watchers have a C<void *data> member. By redefining |
3083 | By default, all watchers have a C<void *data> member. By redefining |
2813 | this macro to a something else you can include more and other types of |
3084 | this macro to a something else you can include more and other types of |
… | |
… | |
2887 | |
3158 | |
2888 | #include "ev_cpp.h" |
3159 | #include "ev_cpp.h" |
2889 | #include "ev.c" |
3160 | #include "ev.c" |
2890 | |
3161 | |
2891 | |
3162 | |
|
|
3163 | =head1 THREADS AND COROUTINES |
|
|
3164 | |
|
|
3165 | =head2 THREADS |
|
|
3166 | |
|
|
3167 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3168 | means that you can use as many loops as you want in parallel, as long as |
|
|
3169 | only one thread ever calls into one libev function with the same loop |
|
|
3170 | parameter. |
|
|
3171 | |
|
|
3172 | Or put differently: calls with different loop parameters can be done in |
|
|
3173 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3174 | done serially (but can be done from different threads, as long as only one |
|
|
3175 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3176 | per loop). |
|
|
3177 | |
|
|
3178 | If you want to know which design is best for your problem, then I cannot |
|
|
3179 | help you but by giving some generic advice: |
|
|
3180 | |
|
|
3181 | =over 4 |
|
|
3182 | |
|
|
3183 | =item * most applications have a main thread: use the default libev loop |
|
|
3184 | in that thread, or create a seperate thread running only the default loop. |
|
|
3185 | |
|
|
3186 | This helps integrating other libraries or software modules that use libev |
|
|
3187 | themselves and don't care/know about threading. |
|
|
3188 | |
|
|
3189 | =item * one loop per thread is usually a good model. |
|
|
3190 | |
|
|
3191 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3192 | exists, but it is always a good start. |
|
|
3193 | |
|
|
3194 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3195 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3196 | |
|
|
3197 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3198 | better than you currently do :-) |
|
|
3199 | |
|
|
3200 | =item * often you need to talk to some other thread which blocks in the |
|
|
3201 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3202 | threads safely (or from signal contexts...). |
|
|
3203 | |
|
|
3204 | =back |
|
|
3205 | |
|
|
3206 | =head2 COROUTINES |
|
|
3207 | |
|
|
3208 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3209 | libev fully supports nesting calls to it's functions from different |
|
|
3210 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3211 | different coroutines and switch freely between both coroutines running the |
|
|
3212 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3213 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3214 | |
|
|
3215 | Care has been invested into making sure that libev does not keep local |
|
|
3216 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3217 | switches. |
|
|
3218 | |
|
|
3219 | |
2892 | =head1 COMPLEXITIES |
3220 | =head1 COMPLEXITIES |
2893 | |
3221 | |
2894 | In this section the complexities of (many of) the algorithms used inside |
3222 | In this section the complexities of (many of) the algorithms used inside |
2895 | libev will be explained. For complexity discussions about backends see the |
3223 | libev will be explained. For complexity discussions about backends see the |
2896 | documentation for C<ev_default_init>. |
3224 | documentation for C<ev_default_init>. |
… | |
… | |
2926 | correct watcher to remove. The lists are usually short (you don't usually |
3254 | correct watcher to remove. The lists are usually short (you don't usually |
2927 | have many watchers waiting for the same fd or signal). |
3255 | have many watchers waiting for the same fd or signal). |
2928 | |
3256 | |
2929 | =item Finding the next timer in each loop iteration: O(1) |
3257 | =item Finding the next timer in each loop iteration: O(1) |
2930 | |
3258 | |
2931 | By virtue of using a binary heap, the next timer is always found at the |
3259 | By virtue of using a binary or 4-heap, the next timer is always found at a |
2932 | beginning of the storage array. |
3260 | fixed position in the storage array. |
2933 | |
3261 | |
2934 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3262 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2935 | |
3263 | |
2936 | A change means an I/O watcher gets started or stopped, which requires |
3264 | A change means an I/O watcher gets started or stopped, which requires |
2937 | libev to recalculate its status (and possibly tell the kernel, depending |
3265 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
2966 | model. Libev still offers limited functionality on this platform in |
3294 | model. Libev still offers limited functionality on this platform in |
2967 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3295 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
2968 | descriptors. This only applies when using Win32 natively, not when using |
3296 | descriptors. This only applies when using Win32 natively, not when using |
2969 | e.g. cygwin. |
3297 | e.g. cygwin. |
2970 | |
3298 | |
|
|
3299 | Lifting these limitations would basically require the full |
|
|
3300 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3301 | things, then note that glib does exactly that for you in a very portable |
|
|
3302 | way (note also that glib is the slowest event library known to man). |
|
|
3303 | |
2971 | There is no supported compilation method available on windows except |
3304 | There is no supported compilation method available on windows except |
2972 | embedding it into other applications. |
3305 | embedding it into other applications. |
2973 | |
3306 | |
2974 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3307 | Due to the many, low, and arbitrary limits on the win32 platform and |
2975 | abysmal performance of winsockets, using a large number of sockets is not |
3308 | the abysmal performance of winsockets, using a large number of sockets |
2976 | recommended (and not reasonable). If your program needs to use more than |
3309 | is not recommended (and not reasonable). If your program needs to use |
2977 | a hundred or so sockets, then likely it needs to use a totally different |
3310 | more than a hundred or so sockets, then likely it needs to use a totally |
2978 | implementation for windows, as libev offers the POSIX model, which cannot |
3311 | different implementation for windows, as libev offers the POSIX readiness |
2979 | be implemented efficiently on windows (microsoft monopoly games). |
3312 | notification model, which cannot be implemented efficiently on windows |
|
|
3313 | (microsoft monopoly games). |
2980 | |
3314 | |
2981 | =over 4 |
3315 | =over 4 |
2982 | |
3316 | |
2983 | =item The winsocket select function |
3317 | =item The winsocket select function |
2984 | |
3318 | |
2985 | The winsocket C<select> function doesn't follow POSIX in that it requires |
3319 | The winsocket C<select> function doesn't follow POSIX in that it |
2986 | socket I<handles> and not socket I<file descriptors>. This makes select |
3320 | requires socket I<handles> and not socket I<file descriptors> (it is |
2987 | very inefficient, and also requires a mapping from file descriptors |
3321 | also extremely buggy). This makes select very inefficient, and also |
2988 | to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>, |
3322 | requires a mapping from file descriptors to socket handles. See the |
2989 | C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor |
3323 | discussion of the C<EV_SELECT_USE_FD_SET>, C<EV_SELECT_IS_WINSOCKET> and |
2990 | symbols for more info. |
3324 | C<EV_FD_TO_WIN32_HANDLE> preprocessor symbols for more info. |
2991 | |
3325 | |
2992 | The configuration for a "naked" win32 using the microsoft runtime |
3326 | The configuration for a "naked" win32 using the microsoft runtime |
2993 | libraries and raw winsocket select is: |
3327 | libraries and raw winsocket select is: |
2994 | |
3328 | |
2995 | #define EV_USE_SELECT 1 |
3329 | #define EV_USE_SELECT 1 |
… | |
… | |
2998 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3332 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
2999 | complexity in the O(n²) range when using win32. |
3333 | complexity in the O(n²) range when using win32. |
3000 | |
3334 | |
3001 | =item Limited number of file descriptors |
3335 | =item Limited number of file descriptors |
3002 | |
3336 | |
3003 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3337 | Windows has numerous arbitrary (and low) limits on things. |
3004 | of winsocket's select only supported waiting for a max. of C<64> handles |
3338 | |
|
|
3339 | Early versions of winsocket's select only supported waiting for a maximum |
3005 | (probably owning to the fact that all windows kernels can only wait for |
3340 | of C<64> handles (probably owning to the fact that all windows kernels |
3006 | C<64> things at the same time internally; microsoft recommends spawning a |
3341 | can only wait for C<64> things at the same time internally; microsoft |
3007 | chain of threads and wait for 63 handles and the previous thread in each). |
3342 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3343 | previous thread in each. Great). |
3008 | |
3344 | |
3009 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3345 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3010 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3346 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3011 | call (which might be in libev or elsewhere, for example, perl does its own |
3347 | call (which might be in libev or elsewhere, for example, perl does its own |
3012 | select emulation on windows). |
3348 | select emulation on windows). |
… | |
… | |
3024 | calling select (O(n²)) will likely make this unworkable. |
3360 | calling select (O(n²)) will likely make this unworkable. |
3025 | |
3361 | |
3026 | =back |
3362 | =back |
3027 | |
3363 | |
3028 | |
3364 | |
|
|
3365 | =head1 PORTABILITY REQUIREMENTS |
|
|
3366 | |
|
|
3367 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3368 | additional extensions: |
|
|
3369 | |
|
|
3370 | =over 4 |
|
|
3371 | |
|
|
3372 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3373 | |
|
|
3374 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3375 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3376 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3377 | believed to be sufficiently portable. |
|
|
3378 | |
|
|
3379 | =item C<sigprocmask> must work in a threaded environment |
|
|
3380 | |
|
|
3381 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3382 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3383 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3384 | thread" or will block signals process-wide, both behaviours would |
|
|
3385 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3386 | C<pthread_sigmask> could complicate things, however. |
|
|
3387 | |
|
|
3388 | The most portable way to handle signals is to block signals in all threads |
|
|
3389 | except the initial one, and run the default loop in the initial thread as |
|
|
3390 | well. |
|
|
3391 | |
|
|
3392 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3393 | |
|
|
3394 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3395 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3396 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3397 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3398 | millions of watchers. |
|
|
3399 | |
|
|
3400 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3401 | |
|
|
3402 | The type C<double> is used to represent timestamps. It is required to |
|
|
3403 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3404 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3405 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3406 | |
|
|
3407 | =back |
|
|
3408 | |
|
|
3409 | If you know of other additional requirements drop me a note. |
|
|
3410 | |
|
|
3411 | |
|
|
3412 | =head1 COMPILER WARNINGS |
|
|
3413 | |
|
|
3414 | Depending on your compiler and compiler settings, you might get no or a |
|
|
3415 | lot of warnings when compiling libev code. Some people are apparently |
|
|
3416 | scared by this. |
|
|
3417 | |
|
|
3418 | However, these are unavoidable for many reasons. For one, each compiler |
|
|
3419 | has different warnings, and each user has different tastes regarding |
|
|
3420 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
3421 | targetting a specific compiler and compiler-version. |
|
|
3422 | |
|
|
3423 | Another reason is that some compiler warnings require elaborate |
|
|
3424 | workarounds, or other changes to the code that make it less clear and less |
|
|
3425 | maintainable. |
|
|
3426 | |
|
|
3427 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
3428 | wrong (because they don't actually warn about the cindition their message |
|
|
3429 | seems to warn about). |
|
|
3430 | |
|
|
3431 | While libev is written to generate as few warnings as possible, |
|
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3432 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
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3433 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
3434 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3435 | warnings, not errors, or proof of bugs. |
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3436 | |
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3437 | |
|
|
3438 | =head1 VALGRIND |
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3439 | |
|
|
3440 | Valgrind has a special section here because it is a popular tool that is |
|
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3441 | highly useful, but valgrind reports are very hard to interpret. |
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3442 | |
|
|
3443 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
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3444 | in libev, then check twice: If valgrind reports something like: |
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3445 | |
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3446 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
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3447 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3448 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
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3449 | |
|
|
3450 | then there is no memory leak. Similarly, under some circumstances, |
|
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3451 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
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3452 | might be confused (it is a very good tool, but only a tool). |
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3453 | |
|
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3454 | If you are unsure about something, feel free to contact the mailing list |
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3455 | with the full valgrind report and an explanation on why you think this is |
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3456 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
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|
3457 | no bug" answer and take the chance of learning how to interpret valgrind |
|
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3458 | properly. |
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3459 | |
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3460 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3461 | I suggest using suppression lists. |
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3462 | |
|
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3463 | |
3029 | =head1 AUTHOR |
3464 | =head1 AUTHOR |
3030 | |
3465 | |
3031 | Marc Lehmann <libev@schmorp.de>. |
3466 | Marc Lehmann <libev@schmorp.de>. |
3032 | |
3467 | |