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9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
13 | |
13 | |
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14 | #include <stdio.h> // for puts |
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15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_<type> |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
18 | |
20 | |
19 | // all watcher callbacks have a similar signature |
21 | // all watcher callbacks have a similar signature |
20 | // this callback is called when data is readable on stdin |
22 | // this callback is called when data is readable on stdin |
21 | static void |
23 | static void |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
24 | stdin_cb (EV_P_ ev_io *w, int revents) |
23 | { |
25 | { |
24 | puts ("stdin ready"); |
26 | puts ("stdin ready"); |
25 | // for one-shot events, one must manually stop the watcher |
27 | // for one-shot events, one must manually stop the watcher |
26 | // with its corresponding stop function. |
28 | // with its corresponding stop function. |
27 | ev_io_stop (EV_A_ w); |
29 | ev_io_stop (EV_A_ w); |
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30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_loop to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
40 | } |
42 | } |
… | |
… | |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // unloop was called, so exit |
62 | return 0; |
64 | return 0; |
63 | } |
65 | } |
64 | |
66 | |
65 | =head1 DESCRIPTION |
67 | =head1 ABOUT THIS DOCUMENT |
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68 | |
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69 | This document documents the libev software package. |
66 | |
70 | |
67 | The newest version of this document is also available as an html-formatted |
71 | The newest version of this document is also available as an html-formatted |
68 | web page you might find easier to navigate when reading it for the first |
72 | web page you might find easier to navigate when reading it for the first |
69 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
73 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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74 | |
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75 | While this document tries to be as complete as possible in documenting |
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76 | libev, its usage and the rationale behind its design, it is not a tutorial |
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77 | on event-based programming, nor will it introduce event-based programming |
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78 | with libev. |
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79 | |
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80 | Familarity with event based programming techniques in general is assumed |
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81 | throughout this document. |
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82 | |
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83 | =head1 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
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84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (somewhere |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | near the beginning of 1970, details are complicated, don't ask). This |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | type is called C<ev_tstamp>, which is what you should use too. It usually |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | aliases to the C<double> type in C. When you need to do any calculations |
118 | it, you should treat it as some floating point value. Unlike the name |
133 | on it, you should treat it as some floating point value. Unlike the name |
119 | component C<stamp> might indicate, it is also used for time differences |
134 | component C<stamp> might indicate, it is also used for time differences |
120 | throughout libev. |
135 | throughout libev. |
121 | |
136 | |
122 | =head1 ERROR HANDLING |
137 | =head1 ERROR HANDLING |
123 | |
138 | |
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214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
229 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
230 | recommended ones. |
216 | |
231 | |
217 | See the description of C<ev_embed> watchers for more info. |
232 | See the description of C<ev_embed> watchers for more info. |
218 | |
233 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
234 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
235 | |
221 | Sets the allocation function to use (the prototype is similar - the |
236 | Sets the allocation function to use (the prototype is similar - the |
222 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
237 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
223 | used to allocate and free memory (no surprises here). If it returns zero |
238 | used to allocate and free memory (no surprises here). If it returns zero |
224 | when memory needs to be allocated (C<size != 0>), the library might abort |
239 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
265 | } |
251 | |
266 | |
252 | ... |
267 | ... |
253 | ev_set_allocator (persistent_realloc); |
268 | ev_set_allocator (persistent_realloc); |
254 | |
269 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
270 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
271 | |
257 | Set the callback function to call on a retryable system call error (such |
272 | Set the callback function to call on a retryable system call error (such |
258 | as failed select, poll, epoll_wait). The message is a printable string |
273 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
274 | indicating the system call or subsystem causing the problem. If this |
260 | callback is set, then libev will expect it to remedy the situation, no |
275 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
276 | |
291 | |
277 | =back |
292 | =back |
278 | |
293 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
294 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
295 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
296 | An event loop is described by a C<struct ev_loop *> (the C<struct> |
282 | types of such loops, the I<default> loop, which supports signals and child |
297 | is I<not> optional in this case, as there is also an C<ev_loop> |
283 | events, and dynamically created loops which do not. |
298 | I<function>). |
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299 | |
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300 | The library knows two types of such loops, the I<default> loop, which |
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301 | supports signals and child events, and dynamically created loops which do |
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302 | not. |
284 | |
303 | |
285 | =over 4 |
304 | =over 4 |
286 | |
305 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
306 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
307 | |
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294 | If you don't know what event loop to use, use the one returned from this |
313 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
314 | function. |
296 | |
315 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
316 | Note that this function is I<not> thread-safe, so if you want to use it |
298 | from multiple threads, you have to lock (note also that this is unlikely, |
317 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
318 | as loops cannot be shared easily between threads anyway). |
300 | |
319 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
320 | The default loop is the only loop that can handle C<ev_signal> and |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
321 | C<ev_child> watchers, and to do this, it always registers a handler |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
322 | for C<SIGCHLD>. If this is a problem for your application you can either |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
323 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
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326 | useful to try out specific backends to test their performance, or to work |
345 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
346 | around bugs. |
328 | |
347 | |
329 | =item C<EVFLAG_FORKCHECK> |
348 | =item C<EVFLAG_FORKCHECK> |
330 | |
349 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
350 | Instead of calling C<ev_loop_fork> manually after a fork, you can also |
332 | a fork, you can also make libev check for a fork in each iteration by |
351 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
352 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
353 | This works by calling C<getpid ()> on every iteration of the loop, |
336 | and thus this might slow down your event loop if you do a lot of loop |
354 | and thus this might slow down your event loop if you do a lot of loop |
337 | iterations and little real work, but is usually not noticeable (on my |
355 | iterations and little real work, but is usually not noticeable (on my |
338 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
356 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
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344 | flag. |
362 | flag. |
345 | |
363 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
364 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
365 | environment variable. |
348 | |
366 | |
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367 | =item C<EVFLAG_NOINOTIFY> |
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368 | |
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369 | When this flag is specified, then libev will not attempt to use the |
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370 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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371 | testing, this flag can be useful to conserve inotify file descriptors, as |
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372 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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373 | |
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374 | =item C<EVFLAG_SIGNALFD> |
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375 | |
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376 | When this flag is specified, then libev will attempt to use the |
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377 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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378 | delivers signals synchronously, which makes it both faster and might make |
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379 | it possible to get the queued signal data. It can also simplify signal |
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380 | handling with threads, as long as you properly block signals in your |
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381 | threads that are not interested in handling them. |
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382 | |
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383 | Signalfd will not be used by default as this changes your signal mask, and |
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384 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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385 | example) that can't properly initialise their signal masks. |
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386 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
387 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
388 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
389 | This is your standard select(2) backend. Not I<completely> standard, as |
352 | libev tries to roll its own fd_set with no limits on the number of fds, |
390 | libev tries to roll its own fd_set with no limits on the number of fds, |
353 | but if that fails, expect a fairly low limit on the number of fds when |
391 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
415 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
416 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
379 | |
417 | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
418 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
419 | |
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420 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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421 | kernels). |
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422 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
423 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
424 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
425 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
426 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
427 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
428 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
429 | of the more advanced event mechanisms: mere annoyances include silently |
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430 | dropping file descriptors, requiring a system call per change per file |
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431 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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432 | so on. The biggest issue is fork races, however - if a program forks then |
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433 | I<both> parent and child process have to recreate the epoll set, which can |
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434 | take considerable time (one syscall per file descriptor) and is of course |
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435 | hard to detect. |
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436 | |
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437 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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438 | of course I<doesn't>, and epoll just loves to report events for totally |
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439 | I<different> file descriptors (even already closed ones, so one cannot |
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440 | even remove them from the set) than registered in the set (especially |
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441 | on SMP systems). Libev tries to counter these spurious notifications by |
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442 | employing an additional generation counter and comparing that against the |
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443 | events to filter out spurious ones, recreating the set when required. |
389 | |
444 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
445 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
446 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
447 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
448 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
449 | file descriptors might not work very well if you register events for both |
395 | |
450 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
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397 | need to use non-blocking I/O or other means to avoid blocking when no data |
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398 | (or space) is available. |
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399 | |
451 | |
400 | Best performance from this backend is achieved by not unregistering all |
452 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, i.e. |
453 | watchers for a file descriptor until it has been closed, if possible, |
402 | keep at least one watcher active per fd at all times. |
454 | i.e. keep at least one watcher active per fd at all times. Stopping and |
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455 | starting a watcher (without re-setting it) also usually doesn't cause |
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456 | extra overhead. A fork can both result in spurious notifications as well |
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457 | as in libev having to destroy and recreate the epoll object, which can |
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458 | take considerable time and thus should be avoided. |
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459 | |
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460 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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461 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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462 | the usage. So sad. |
403 | |
463 | |
404 | While nominally embeddable in other event loops, this feature is broken in |
464 | While nominally embeddable in other event loops, this feature is broken in |
405 | all kernel versions tested so far. |
465 | all kernel versions tested so far. |
406 | |
466 | |
407 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
467 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
… | |
… | |
410 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
470 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
411 | |
471 | |
412 | Kqueue deserves special mention, as at the time of this writing, it |
472 | Kqueue deserves special mention, as at the time of this writing, it |
413 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
473 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
414 | with anything but sockets and pipes, except on Darwin, where of course |
474 | with anything but sockets and pipes, except on Darwin, where of course |
415 | it's completely useless). For this reason it's not being "auto-detected" |
475 | it's completely useless). Unlike epoll, however, whose brokenness |
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476 | is by design, these kqueue bugs can (and eventually will) be fixed |
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477 | without API changes to existing programs. For this reason it's not being |
416 | unless you explicitly specify it explicitly in the flags (i.e. using |
478 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
417 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
479 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
418 | system like NetBSD. |
480 | system like NetBSD. |
419 | |
481 | |
420 | You still can embed kqueue into a normal poll or select backend and use it |
482 | You still can embed kqueue into a normal poll or select backend and use it |
421 | only for sockets (after having made sure that sockets work with kqueue on |
483 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
423 | |
485 | |
424 | It scales in the same way as the epoll backend, but the interface to the |
486 | It scales in the same way as the epoll backend, but the interface to the |
425 | kernel is more efficient (which says nothing about its actual speed, of |
487 | kernel is more efficient (which says nothing about its actual speed, of |
426 | course). While stopping, setting and starting an I/O watcher does never |
488 | course). While stopping, setting and starting an I/O watcher does never |
427 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
489 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
428 | two event changes per incident, support for C<fork ()> is very bad and it |
490 | two event changes per incident. Support for C<fork ()> is very bad (but |
429 | drops fds silently in similarly hard-to-detect cases. |
491 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
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492 | cases |
430 | |
493 | |
431 | This backend usually performs well under most conditions. |
494 | This backend usually performs well under most conditions. |
432 | |
495 | |
433 | While nominally embeddable in other event loops, this doesn't work |
496 | While nominally embeddable in other event loops, this doesn't work |
434 | everywhere, so you might need to test for this. And since it is broken |
497 | everywhere, so you might need to test for this. And since it is broken |
435 | almost everywhere, you should only use it when you have a lot of sockets |
498 | almost everywhere, you should only use it when you have a lot of sockets |
436 | (for which it usually works), by embedding it into another event loop |
499 | (for which it usually works), by embedding it into another event loop |
437 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
500 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
438 | sockets. |
501 | also broken on OS X)) and, did I mention it, using it only for sockets. |
439 | |
502 | |
440 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
503 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
441 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
504 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
442 | C<NOTE_EOF>. |
505 | C<NOTE_EOF>. |
443 | |
506 | |
… | |
… | |
460 | While this backend scales well, it requires one system call per active |
523 | While this backend scales well, it requires one system call per active |
461 | file descriptor per loop iteration. For small and medium numbers of file |
524 | file descriptor per loop iteration. For small and medium numbers of file |
462 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
525 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
463 | might perform better. |
526 | might perform better. |
464 | |
527 | |
465 | On the positive side, ignoring the spurious readiness notifications, this |
528 | On the positive side, with the exception of the spurious readiness |
466 | backend actually performed to specification in all tests and is fully |
529 | notifications, this backend actually performed fully to specification |
467 | embeddable, which is a rare feat among the OS-specific backends. |
530 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
531 | OS-specific backends (I vastly prefer correctness over speed hacks). |
468 | |
532 | |
469 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
533 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
470 | C<EVBACKEND_POLL>. |
534 | C<EVBACKEND_POLL>. |
471 | |
535 | |
472 | =item C<EVBACKEND_ALL> |
536 | =item C<EVBACKEND_ALL> |
… | |
… | |
477 | |
541 | |
478 | It is definitely not recommended to use this flag. |
542 | It is definitely not recommended to use this flag. |
479 | |
543 | |
480 | =back |
544 | =back |
481 | |
545 | |
482 | If one or more of these are or'ed into the flags value, then only these |
546 | If one or more of the backend flags are or'ed into the flags value, |
483 | backends will be tried (in the reverse order as listed here). If none are |
547 | then only these backends will be tried (in the reverse order as listed |
484 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
548 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
549 | ()> will be tried. |
485 | |
550 | |
486 | The most typical usage is like this: |
551 | Example: This is the most typical usage. |
487 | |
552 | |
488 | if (!ev_default_loop (0)) |
553 | if (!ev_default_loop (0)) |
489 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
554 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
490 | |
555 | |
491 | Restrict libev to the select and poll backends, and do not allow |
556 | Example: Restrict libev to the select and poll backends, and do not allow |
492 | environment settings to be taken into account: |
557 | environment settings to be taken into account: |
493 | |
558 | |
494 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
559 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
495 | |
560 | |
496 | Use whatever libev has to offer, but make sure that kqueue is used if |
561 | Example: Use whatever libev has to offer, but make sure that kqueue is |
497 | available (warning, breaks stuff, best use only with your own private |
562 | used if available (warning, breaks stuff, best use only with your own |
498 | event loop and only if you know the OS supports your types of fds): |
563 | private event loop and only if you know the OS supports your types of |
|
|
564 | fds): |
499 | |
565 | |
500 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
566 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
501 | |
567 | |
502 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
568 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
503 | |
569 | |
504 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
570 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
505 | always distinct from the default loop. Unlike the default loop, it cannot |
571 | always distinct from the default loop. |
506 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
507 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
508 | |
572 | |
509 | Note that this function I<is> thread-safe, and the recommended way to use |
573 | Note that this function I<is> thread-safe, and one common way to use |
510 | libev with threads is indeed to create one loop per thread, and using the |
574 | libev with threads is indeed to create one loop per thread, and using the |
511 | default loop in the "main" or "initial" thread. |
575 | default loop in the "main" or "initial" thread. |
512 | |
576 | |
513 | Example: Try to create a event loop that uses epoll and nothing else. |
577 | Example: Try to create a event loop that uses epoll and nothing else. |
514 | |
578 | |
… | |
… | |
516 | if (!epoller) |
580 | if (!epoller) |
517 | fatal ("no epoll found here, maybe it hides under your chair"); |
581 | fatal ("no epoll found here, maybe it hides under your chair"); |
518 | |
582 | |
519 | =item ev_default_destroy () |
583 | =item ev_default_destroy () |
520 | |
584 | |
521 | Destroys the default loop again (frees all memory and kernel state |
585 | Destroys the default loop (frees all memory and kernel state etc.). None |
522 | etc.). None of the active event watchers will be stopped in the normal |
586 | of the active event watchers will be stopped in the normal sense, so |
523 | sense, so e.g. C<ev_is_active> might still return true. It is your |
587 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
524 | responsibility to either stop all watchers cleanly yourself I<before> |
588 | either stop all watchers cleanly yourself I<before> calling this function, |
525 | calling this function, or cope with the fact afterwards (which is usually |
589 | or cope with the fact afterwards (which is usually the easiest thing, you |
526 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
590 | can just ignore the watchers and/or C<free ()> them for example). |
527 | for example). |
|
|
528 | |
591 | |
529 | Note that certain global state, such as signal state, will not be freed by |
592 | Note that certain global state, such as signal state (and installed signal |
530 | this function, and related watchers (such as signal and child watchers) |
593 | handlers), will not be freed by this function, and related watchers (such |
531 | would need to be stopped manually. |
594 | as signal and child watchers) would need to be stopped manually. |
532 | |
595 | |
533 | In general it is not advisable to call this function except in the |
596 | In general it is not advisable to call this function except in the |
534 | rare occasion where you really need to free e.g. the signal handling |
597 | rare occasion where you really need to free e.g. the signal handling |
535 | pipe fds. If you need dynamically allocated loops it is better to use |
598 | pipe fds. If you need dynamically allocated loops it is better to use |
536 | C<ev_loop_new> and C<ev_loop_destroy>). |
599 | C<ev_loop_new> and C<ev_loop_destroy>. |
537 | |
600 | |
538 | =item ev_loop_destroy (loop) |
601 | =item ev_loop_destroy (loop) |
539 | |
602 | |
540 | Like C<ev_default_destroy>, but destroys an event loop created by an |
603 | Like C<ev_default_destroy>, but destroys an event loop created by an |
541 | earlier call to C<ev_loop_new>. |
604 | earlier call to C<ev_loop_new>. |
… | |
… | |
547 | name, you can call it anytime, but it makes most sense after forking, in |
610 | name, you can call it anytime, but it makes most sense after forking, in |
548 | the child process (or both child and parent, but that again makes little |
611 | the child process (or both child and parent, but that again makes little |
549 | sense). You I<must> call it in the child before using any of the libev |
612 | sense). You I<must> call it in the child before using any of the libev |
550 | functions, and it will only take effect at the next C<ev_loop> iteration. |
613 | functions, and it will only take effect at the next C<ev_loop> iteration. |
551 | |
614 | |
|
|
615 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
616 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
617 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
618 | during fork. |
|
|
619 | |
552 | On the other hand, you only need to call this function in the child |
620 | On the other hand, you only need to call this function in the child |
553 | process if and only if you want to use the event library in the child. If |
621 | process if and only if you want to use the event loop in the child. If you |
554 | you just fork+exec, you don't have to call it at all. |
622 | just fork+exec or create a new loop in the child, you don't have to call |
|
|
623 | it at all. |
555 | |
624 | |
556 | The function itself is quite fast and it's usually not a problem to call |
625 | The function itself is quite fast and it's usually not a problem to call |
557 | it just in case after a fork. To make this easy, the function will fit in |
626 | it just in case after a fork. To make this easy, the function will fit in |
558 | quite nicely into a call to C<pthread_atfork>: |
627 | quite nicely into a call to C<pthread_atfork>: |
559 | |
628 | |
… | |
… | |
561 | |
630 | |
562 | =item ev_loop_fork (loop) |
631 | =item ev_loop_fork (loop) |
563 | |
632 | |
564 | Like C<ev_default_fork>, but acts on an event loop created by |
633 | Like C<ev_default_fork>, but acts on an event loop created by |
565 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
634 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
566 | after fork, and how you do this is entirely your own problem. |
635 | after fork that you want to re-use in the child, and how you keep track of |
|
|
636 | them is entirely your own problem. |
567 | |
637 | |
568 | =item int ev_is_default_loop (loop) |
638 | =item int ev_is_default_loop (loop) |
569 | |
639 | |
570 | Returns true when the given loop actually is the default loop, false otherwise. |
640 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
641 | otherwise. |
571 | |
642 | |
572 | =item unsigned int ev_loop_count (loop) |
643 | =item unsigned int ev_iteration (loop) |
573 | |
644 | |
574 | Returns the count of loop iterations for the loop, which is identical to |
645 | Returns the current iteration count for the loop, which is identical to |
575 | the number of times libev did poll for new events. It starts at C<0> and |
646 | the number of times libev did poll for new events. It starts at C<0> and |
576 | happily wraps around with enough iterations. |
647 | happily wraps around with enough iterations. |
577 | |
648 | |
578 | This value can sometimes be useful as a generation counter of sorts (it |
649 | This value can sometimes be useful as a generation counter of sorts (it |
579 | "ticks" the number of loop iterations), as it roughly corresponds with |
650 | "ticks" the number of loop iterations), as it roughly corresponds with |
580 | C<ev_prepare> and C<ev_check> calls. |
651 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
652 | prepare and check phases. |
|
|
653 | |
|
|
654 | =item unsigned int ev_depth (loop) |
|
|
655 | |
|
|
656 | Returns the number of times C<ev_loop> was entered minus the number of |
|
|
657 | times C<ev_loop> was exited, in other words, the recursion depth. |
|
|
658 | |
|
|
659 | Outside C<ev_loop>, this number is zero. In a callback, this number is |
|
|
660 | C<1>, unless C<ev_loop> was invoked recursively (or from another thread), |
|
|
661 | in which case it is higher. |
|
|
662 | |
|
|
663 | Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread |
|
|
664 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
665 | ungentleman behaviour unless it's really convenient. |
581 | |
666 | |
582 | =item unsigned int ev_backend (loop) |
667 | =item unsigned int ev_backend (loop) |
583 | |
668 | |
584 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
669 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
585 | use. |
670 | use. |
… | |
… | |
600 | |
685 | |
601 | This function is rarely useful, but when some event callback runs for a |
686 | This function is rarely useful, but when some event callback runs for a |
602 | very long time without entering the event loop, updating libev's idea of |
687 | very long time without entering the event loop, updating libev's idea of |
603 | the current time is a good idea. |
688 | the current time is a good idea. |
604 | |
689 | |
605 | See also "The special problem of time updates" in the C<ev_timer> section. |
690 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
691 | |
|
|
692 | =item ev_suspend (loop) |
|
|
693 | |
|
|
694 | =item ev_resume (loop) |
|
|
695 | |
|
|
696 | These two functions suspend and resume a loop, for use when the loop is |
|
|
697 | not used for a while and timeouts should not be processed. |
|
|
698 | |
|
|
699 | A typical use case would be an interactive program such as a game: When |
|
|
700 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
701 | would be best to handle timeouts as if no time had actually passed while |
|
|
702 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
703 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
704 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
705 | |
|
|
706 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
707 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
708 | will be rescheduled (that is, they will lose any events that would have |
|
|
709 | occured while suspended). |
|
|
710 | |
|
|
711 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
712 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
713 | without a previous call to C<ev_suspend>. |
|
|
714 | |
|
|
715 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
716 | event loop time (see C<ev_now_update>). |
606 | |
717 | |
607 | =item ev_loop (loop, int flags) |
718 | =item ev_loop (loop, int flags) |
608 | |
719 | |
609 | Finally, this is it, the event handler. This function usually is called |
720 | Finally, this is it, the event handler. This function usually is called |
610 | after you initialised all your watchers and you want to start handling |
721 | after you have initialised all your watchers and you want to start |
611 | events. |
722 | handling events. |
612 | |
723 | |
613 | If the flags argument is specified as C<0>, it will not return until |
724 | If the flags argument is specified as C<0>, it will not return until |
614 | either no event watchers are active anymore or C<ev_unloop> was called. |
725 | either no event watchers are active anymore or C<ev_unloop> was called. |
615 | |
726 | |
616 | Please note that an explicit C<ev_unloop> is usually better than |
727 | Please note that an explicit C<ev_unloop> is usually better than |
617 | relying on all watchers to be stopped when deciding when a program has |
728 | relying on all watchers to be stopped when deciding when a program has |
618 | finished (especially in interactive programs), but having a program that |
729 | finished (especially in interactive programs), but having a program |
619 | automatically loops as long as it has to and no longer by virtue of |
730 | that automatically loops as long as it has to and no longer by virtue |
620 | relying on its watchers stopping correctly is a thing of beauty. |
731 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
732 | beauty. |
621 | |
733 | |
622 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
734 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
623 | those events and any outstanding ones, but will not block your process in |
735 | those events and any already outstanding ones, but will not block your |
624 | case there are no events and will return after one iteration of the loop. |
736 | process in case there are no events and will return after one iteration of |
|
|
737 | the loop. |
625 | |
738 | |
626 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
739 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
627 | necessary) and will handle those and any outstanding ones. It will block |
740 | necessary) and will handle those and any already outstanding ones. It |
628 | your process until at least one new event arrives, and will return after |
741 | will block your process until at least one new event arrives (which could |
629 | one iteration of the loop. This is useful if you are waiting for some |
742 | be an event internal to libev itself, so there is no guarantee that a |
630 | external event in conjunction with something not expressible using other |
743 | user-registered callback will be called), and will return after one |
|
|
744 | iteration of the loop. |
|
|
745 | |
|
|
746 | This is useful if you are waiting for some external event in conjunction |
|
|
747 | with something not expressible using other libev watchers (i.e. "roll your |
631 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
748 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
632 | usually a better approach for this kind of thing. |
749 | usually a better approach for this kind of thing. |
633 | |
750 | |
634 | Here are the gory details of what C<ev_loop> does: |
751 | Here are the gory details of what C<ev_loop> does: |
635 | |
752 | |
636 | - Before the first iteration, call any pending watchers. |
753 | - Before the first iteration, call any pending watchers. |
… | |
… | |
646 | any active watchers at all will result in not sleeping). |
763 | any active watchers at all will result in not sleeping). |
647 | - Sleep if the I/O and timer collect interval say so. |
764 | - Sleep if the I/O and timer collect interval say so. |
648 | - Block the process, waiting for any events. |
765 | - Block the process, waiting for any events. |
649 | - Queue all outstanding I/O (fd) events. |
766 | - Queue all outstanding I/O (fd) events. |
650 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
767 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
651 | - Queue all outstanding timers. |
768 | - Queue all expired timers. |
652 | - Queue all outstanding periodics. |
769 | - Queue all expired periodics. |
653 | - Unless any events are pending now, queue all idle watchers. |
770 | - Unless any events are pending now, queue all idle watchers. |
654 | - Queue all check watchers. |
771 | - Queue all check watchers. |
655 | - Call all queued watchers in reverse order (i.e. check watchers first). |
772 | - Call all queued watchers in reverse order (i.e. check watchers first). |
656 | Signals and child watchers are implemented as I/O watchers, and will |
773 | Signals and child watchers are implemented as I/O watchers, and will |
657 | be handled here by queueing them when their watcher gets executed. |
774 | be handled here by queueing them when their watcher gets executed. |
… | |
… | |
674 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
791 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
675 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
792 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
676 | |
793 | |
677 | This "unloop state" will be cleared when entering C<ev_loop> again. |
794 | This "unloop state" will be cleared when entering C<ev_loop> again. |
678 | |
795 | |
|
|
796 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
|
|
797 | |
679 | =item ev_ref (loop) |
798 | =item ev_ref (loop) |
680 | |
799 | |
681 | =item ev_unref (loop) |
800 | =item ev_unref (loop) |
682 | |
801 | |
683 | Ref/unref can be used to add or remove a reference count on the event |
802 | Ref/unref can be used to add or remove a reference count on the event |
684 | loop: Every watcher keeps one reference, and as long as the reference |
803 | loop: Every watcher keeps one reference, and as long as the reference |
685 | count is nonzero, C<ev_loop> will not return on its own. If you have |
804 | count is nonzero, C<ev_loop> will not return on its own. |
686 | a watcher you never unregister that should not keep C<ev_loop> from |
805 | |
687 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
806 | This is useful when you have a watcher that you never intend to |
|
|
807 | unregister, but that nevertheless should not keep C<ev_loop> from |
|
|
808 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
809 | before stopping it. |
|
|
810 | |
688 | example, libev itself uses this for its internal signal pipe: It is not |
811 | As an example, libev itself uses this for its internal signal pipe: It |
689 | visible to the libev user and should not keep C<ev_loop> from exiting if |
812 | is not visible to the libev user and should not keep C<ev_loop> from |
690 | no event watchers registered by it are active. It is also an excellent |
813 | exiting if no event watchers registered by it are active. It is also an |
691 | way to do this for generic recurring timers or from within third-party |
814 | excellent way to do this for generic recurring timers or from within |
692 | libraries. Just remember to I<unref after start> and I<ref before stop> |
815 | third-party libraries. Just remember to I<unref after start> and I<ref |
693 | (but only if the watcher wasn't active before, or was active before, |
816 | before stop> (but only if the watcher wasn't active before, or was active |
694 | respectively). |
817 | before, respectively. Note also that libev might stop watchers itself |
|
|
818 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
819 | in the callback). |
695 | |
820 | |
696 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
821 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
697 | running when nothing else is active. |
822 | running when nothing else is active. |
698 | |
823 | |
699 | struct ev_signal exitsig; |
824 | ev_signal exitsig; |
700 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
825 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
701 | ev_signal_start (loop, &exitsig); |
826 | ev_signal_start (loop, &exitsig); |
702 | evf_unref (loop); |
827 | evf_unref (loop); |
703 | |
828 | |
704 | Example: For some weird reason, unregister the above signal handler again. |
829 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
718 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
843 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
719 | allows libev to delay invocation of I/O and timer/periodic callbacks |
844 | allows libev to delay invocation of I/O and timer/periodic callbacks |
720 | to increase efficiency of loop iterations (or to increase power-saving |
845 | to increase efficiency of loop iterations (or to increase power-saving |
721 | opportunities). |
846 | opportunities). |
722 | |
847 | |
723 | The background is that sometimes your program runs just fast enough to |
848 | The idea is that sometimes your program runs just fast enough to handle |
724 | handle one (or very few) event(s) per loop iteration. While this makes |
849 | one (or very few) event(s) per loop iteration. While this makes the |
725 | the program responsive, it also wastes a lot of CPU time to poll for new |
850 | program responsive, it also wastes a lot of CPU time to poll for new |
726 | events, especially with backends like C<select ()> which have a high |
851 | events, especially with backends like C<select ()> which have a high |
727 | overhead for the actual polling but can deliver many events at once. |
852 | overhead for the actual polling but can deliver many events at once. |
728 | |
853 | |
729 | By setting a higher I<io collect interval> you allow libev to spend more |
854 | By setting a higher I<io collect interval> you allow libev to spend more |
730 | time collecting I/O events, so you can handle more events per iteration, |
855 | time collecting I/O events, so you can handle more events per iteration, |
731 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
856 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
732 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
857 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
733 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
858 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
859 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
860 | once per this interval, on average. |
734 | |
861 | |
735 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
862 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
736 | to spend more time collecting timeouts, at the expense of increased |
863 | to spend more time collecting timeouts, at the expense of increased |
737 | latency (the watcher callback will be called later). C<ev_io> watchers |
864 | latency/jitter/inexactness (the watcher callback will be called |
738 | will not be affected. Setting this to a non-null value will not introduce |
865 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
739 | any overhead in libev. |
866 | value will not introduce any overhead in libev. |
740 | |
867 | |
741 | Many (busy) programs can usually benefit by setting the I/O collect |
868 | Many (busy) programs can usually benefit by setting the I/O collect |
742 | interval to a value near C<0.1> or so, which is often enough for |
869 | interval to a value near C<0.1> or so, which is often enough for |
743 | interactive servers (of course not for games), likewise for timeouts. It |
870 | interactive servers (of course not for games), likewise for timeouts. It |
744 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
871 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
745 | as this approaches the timing granularity of most systems. |
872 | as this approaches the timing granularity of most systems. Note that if |
|
|
873 | you do transactions with the outside world and you can't increase the |
|
|
874 | parallelity, then this setting will limit your transaction rate (if you |
|
|
875 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
876 | then you can't do more than 100 transations per second). |
746 | |
877 | |
747 | Setting the I<timeout collect interval> can improve the opportunity for |
878 | Setting the I<timeout collect interval> can improve the opportunity for |
748 | saving power, as the program will "bundle" timer callback invocations that |
879 | saving power, as the program will "bundle" timer callback invocations that |
749 | are "near" in time together, by delaying some, thus reducing the number of |
880 | are "near" in time together, by delaying some, thus reducing the number of |
750 | times the process sleeps and wakes up again. Another useful technique to |
881 | times the process sleeps and wakes up again. Another useful technique to |
751 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
882 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
752 | they fire on, say, one-second boundaries only. |
883 | they fire on, say, one-second boundaries only. |
753 | |
884 | |
|
|
885 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
886 | more often than 100 times per second: |
|
|
887 | |
|
|
888 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
889 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
890 | |
|
|
891 | =item ev_invoke_pending (loop) |
|
|
892 | |
|
|
893 | This call will simply invoke all pending watchers while resetting their |
|
|
894 | pending state. Normally, C<ev_loop> does this automatically when required, |
|
|
895 | but when overriding the invoke callback this call comes handy. |
|
|
896 | |
|
|
897 | =item int ev_pending_count (loop) |
|
|
898 | |
|
|
899 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
900 | are pending. |
|
|
901 | |
|
|
902 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
903 | |
|
|
904 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
905 | invoking all pending watchers when there are any, C<ev_loop> will call |
|
|
906 | this callback instead. This is useful, for example, when you want to |
|
|
907 | invoke the actual watchers inside another context (another thread etc.). |
|
|
908 | |
|
|
909 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
910 | callback. |
|
|
911 | |
|
|
912 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
913 | |
|
|
914 | Sometimes you want to share the same loop between multiple threads. This |
|
|
915 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
916 | each call to a libev function. |
|
|
917 | |
|
|
918 | However, C<ev_loop> can run an indefinite time, so it is not feasible to |
|
|
919 | wait for it to return. One way around this is to wake up the loop via |
|
|
920 | C<ev_unloop> and C<av_async_send>, another way is to set these I<release> |
|
|
921 | and I<acquire> callbacks on the loop. |
|
|
922 | |
|
|
923 | When set, then C<release> will be called just before the thread is |
|
|
924 | suspended waiting for new events, and C<acquire> is called just |
|
|
925 | afterwards. |
|
|
926 | |
|
|
927 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
928 | C<acquire> will just call the mutex_lock function again. |
|
|
929 | |
|
|
930 | While event loop modifications are allowed between invocations of |
|
|
931 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
932 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
933 | have no effect on the set of file descriptors being watched, or the time |
|
|
934 | waited. Use an C<ev_async> watcher to wake up C<ev_loop> when you want it |
|
|
935 | to take note of any changes you made. |
|
|
936 | |
|
|
937 | In theory, threads executing C<ev_loop> will be async-cancel safe between |
|
|
938 | invocations of C<release> and C<acquire>. |
|
|
939 | |
|
|
940 | See also the locking example in the C<THREADS> section later in this |
|
|
941 | document. |
|
|
942 | |
|
|
943 | =item ev_set_userdata (loop, void *data) |
|
|
944 | |
|
|
945 | =item ev_userdata (loop) |
|
|
946 | |
|
|
947 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
948 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
949 | C<0.> |
|
|
950 | |
|
|
951 | These two functions can be used to associate arbitrary data with a loop, |
|
|
952 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
953 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
954 | any other purpose as well. |
|
|
955 | |
754 | =item ev_loop_verify (loop) |
956 | =item ev_loop_verify (loop) |
755 | |
957 | |
756 | This function only does something when C<EV_VERIFY> support has been |
958 | This function only does something when C<EV_VERIFY> support has been |
757 | compiled in. It tries to go through all internal structures and checks |
959 | compiled in, which is the default for non-minimal builds. It tries to go |
758 | them for validity. If anything is found to be inconsistent, it will print |
960 | through all internal structures and checks them for validity. If anything |
759 | an error message to standard error and call C<abort ()>. |
961 | is found to be inconsistent, it will print an error message to standard |
|
|
962 | error and call C<abort ()>. |
760 | |
963 | |
761 | This can be used to catch bugs inside libev itself: under normal |
964 | This can be used to catch bugs inside libev itself: under normal |
762 | circumstances, this function will never abort as of course libev keeps its |
965 | circumstances, this function will never abort as of course libev keeps its |
763 | data structures consistent. |
966 | data structures consistent. |
764 | |
967 | |
765 | =back |
968 | =back |
766 | |
969 | |
767 | |
970 | |
768 | =head1 ANATOMY OF A WATCHER |
971 | =head1 ANATOMY OF A WATCHER |
769 | |
972 | |
|
|
973 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
974 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
975 | watchers and C<ev_io_start> for I/O watchers. |
|
|
976 | |
770 | A watcher is a structure that you create and register to record your |
977 | A watcher is a structure that you create and register to record your |
771 | interest in some event. For instance, if you want to wait for STDIN to |
978 | interest in some event. For instance, if you want to wait for STDIN to |
772 | become readable, you would create an C<ev_io> watcher for that: |
979 | become readable, you would create an C<ev_io> watcher for that: |
773 | |
980 | |
774 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
981 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
775 | { |
982 | { |
776 | ev_io_stop (w); |
983 | ev_io_stop (w); |
777 | ev_unloop (loop, EVUNLOOP_ALL); |
984 | ev_unloop (loop, EVUNLOOP_ALL); |
778 | } |
985 | } |
779 | |
986 | |
780 | struct ev_loop *loop = ev_default_loop (0); |
987 | struct ev_loop *loop = ev_default_loop (0); |
|
|
988 | |
781 | struct ev_io stdin_watcher; |
989 | ev_io stdin_watcher; |
|
|
990 | |
782 | ev_init (&stdin_watcher, my_cb); |
991 | ev_init (&stdin_watcher, my_cb); |
783 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
992 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
784 | ev_io_start (loop, &stdin_watcher); |
993 | ev_io_start (loop, &stdin_watcher); |
|
|
994 | |
785 | ev_loop (loop, 0); |
995 | ev_loop (loop, 0); |
786 | |
996 | |
787 | As you can see, you are responsible for allocating the memory for your |
997 | As you can see, you are responsible for allocating the memory for your |
788 | watcher structures (and it is usually a bad idea to do this on the stack, |
998 | watcher structures (and it is I<usually> a bad idea to do this on the |
789 | although this can sometimes be quite valid). |
999 | stack). |
|
|
1000 | |
|
|
1001 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1002 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
790 | |
1003 | |
791 | Each watcher structure must be initialised by a call to C<ev_init |
1004 | Each watcher structure must be initialised by a call to C<ev_init |
792 | (watcher *, callback)>, which expects a callback to be provided. This |
1005 | (watcher *, callback)>, which expects a callback to be provided. This |
793 | callback gets invoked each time the event occurs (or, in the case of I/O |
1006 | callback gets invoked each time the event occurs (or, in the case of I/O |
794 | watchers, each time the event loop detects that the file descriptor given |
1007 | watchers, each time the event loop detects that the file descriptor given |
795 | is readable and/or writable). |
1008 | is readable and/or writable). |
796 | |
1009 | |
797 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1010 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
798 | with arguments specific to this watcher type. There is also a macro |
1011 | macro to configure it, with arguments specific to the watcher type. There |
799 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1012 | is also a macro to combine initialisation and setting in one call: C<< |
800 | (watcher *, callback, ...) >>. |
1013 | ev_TYPE_init (watcher *, callback, ...) >>. |
801 | |
1014 | |
802 | To make the watcher actually watch out for events, you have to start it |
1015 | To make the watcher actually watch out for events, you have to start it |
803 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1016 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
804 | *) >>), and you can stop watching for events at any time by calling the |
1017 | *) >>), and you can stop watching for events at any time by calling the |
805 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1018 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
806 | |
1019 | |
807 | As long as your watcher is active (has been started but not stopped) you |
1020 | As long as your watcher is active (has been started but not stopped) you |
808 | must not touch the values stored in it. Most specifically you must never |
1021 | must not touch the values stored in it. Most specifically you must never |
809 | reinitialise it or call its C<set> macro. |
1022 | reinitialise it or call its C<ev_TYPE_set> macro. |
810 | |
1023 | |
811 | Each and every callback receives the event loop pointer as first, the |
1024 | Each and every callback receives the event loop pointer as first, the |
812 | registered watcher structure as second, and a bitset of received events as |
1025 | registered watcher structure as second, and a bitset of received events as |
813 | third argument. |
1026 | third argument. |
814 | |
1027 | |
… | |
… | |
823 | =item C<EV_WRITE> |
1036 | =item C<EV_WRITE> |
824 | |
1037 | |
825 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1038 | The file descriptor in the C<ev_io> watcher has become readable and/or |
826 | writable. |
1039 | writable. |
827 | |
1040 | |
828 | =item C<EV_TIMEOUT> |
1041 | =item C<EV_TIMER> |
829 | |
1042 | |
830 | The C<ev_timer> watcher has timed out. |
1043 | The C<ev_timer> watcher has timed out. |
831 | |
1044 | |
832 | =item C<EV_PERIODIC> |
1045 | =item C<EV_PERIODIC> |
833 | |
1046 | |
… | |
… | |
872 | |
1085 | |
873 | =item C<EV_ASYNC> |
1086 | =item C<EV_ASYNC> |
874 | |
1087 | |
875 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1088 | The given async watcher has been asynchronously notified (see C<ev_async>). |
876 | |
1089 | |
|
|
1090 | =item C<EV_CUSTOM> |
|
|
1091 | |
|
|
1092 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1093 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
|
|
1094 | |
877 | =item C<EV_ERROR> |
1095 | =item C<EV_ERROR> |
878 | |
1096 | |
879 | An unspecified error has occurred, the watcher has been stopped. This might |
1097 | An unspecified error has occurred, the watcher has been stopped. This might |
880 | happen because the watcher could not be properly started because libev |
1098 | happen because the watcher could not be properly started because libev |
881 | ran out of memory, a file descriptor was found to be closed or any other |
1099 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1100 | problem. Libev considers these application bugs. |
|
|
1101 | |
882 | problem. You best act on it by reporting the problem and somehow coping |
1102 | You best act on it by reporting the problem and somehow coping with the |
883 | with the watcher being stopped. |
1103 | watcher being stopped. Note that well-written programs should not receive |
|
|
1104 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1105 | bug in your program. |
884 | |
1106 | |
885 | Libev will usually signal a few "dummy" events together with an error, |
1107 | Libev will usually signal a few "dummy" events together with an error, for |
886 | for example it might indicate that a fd is readable or writable, and if |
1108 | example it might indicate that a fd is readable or writable, and if your |
887 | your callbacks is well-written it can just attempt the operation and cope |
1109 | callbacks is well-written it can just attempt the operation and cope with |
888 | with the error from read() or write(). This will not work in multi-threaded |
1110 | the error from read() or write(). This will not work in multi-threaded |
889 | programs, though, so beware. |
1111 | programs, though, as the fd could already be closed and reused for another |
|
|
1112 | thing, so beware. |
890 | |
1113 | |
891 | =back |
1114 | =back |
892 | |
1115 | |
893 | =head2 GENERIC WATCHER FUNCTIONS |
1116 | =head2 GENERIC WATCHER FUNCTIONS |
894 | |
|
|
895 | In the following description, C<TYPE> stands for the watcher type, |
|
|
896 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
897 | |
1117 | |
898 | =over 4 |
1118 | =over 4 |
899 | |
1119 | |
900 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1120 | =item C<ev_init> (ev_TYPE *watcher, callback) |
901 | |
1121 | |
… | |
… | |
907 | which rolls both calls into one. |
1127 | which rolls both calls into one. |
908 | |
1128 | |
909 | You can reinitialise a watcher at any time as long as it has been stopped |
1129 | You can reinitialise a watcher at any time as long as it has been stopped |
910 | (or never started) and there are no pending events outstanding. |
1130 | (or never started) and there are no pending events outstanding. |
911 | |
1131 | |
912 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1132 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
913 | int revents)>. |
1133 | int revents)>. |
914 | |
1134 | |
|
|
1135 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1136 | |
|
|
1137 | ev_io w; |
|
|
1138 | ev_init (&w, my_cb); |
|
|
1139 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1140 | |
915 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1141 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
916 | |
1142 | |
917 | This macro initialises the type-specific parts of a watcher. You need to |
1143 | This macro initialises the type-specific parts of a watcher. You need to |
918 | call C<ev_init> at least once before you call this macro, but you can |
1144 | call C<ev_init> at least once before you call this macro, but you can |
919 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1145 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
920 | macro on a watcher that is active (it can be pending, however, which is a |
1146 | macro on a watcher that is active (it can be pending, however, which is a |
921 | difference to the C<ev_init> macro). |
1147 | difference to the C<ev_init> macro). |
922 | |
1148 | |
923 | Although some watcher types do not have type-specific arguments |
1149 | Although some watcher types do not have type-specific arguments |
924 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1150 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
925 | |
1151 | |
|
|
1152 | See C<ev_init>, above, for an example. |
|
|
1153 | |
926 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1154 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
927 | |
1155 | |
928 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1156 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
929 | calls into a single call. This is the most convenient method to initialise |
1157 | calls into a single call. This is the most convenient method to initialise |
930 | a watcher. The same limitations apply, of course. |
1158 | a watcher. The same limitations apply, of course. |
931 | |
1159 | |
|
|
1160 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1161 | |
|
|
1162 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1163 | |
932 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1164 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
933 | |
1165 | |
934 | Starts (activates) the given watcher. Only active watchers will receive |
1166 | Starts (activates) the given watcher. Only active watchers will receive |
935 | events. If the watcher is already active nothing will happen. |
1167 | events. If the watcher is already active nothing will happen. |
936 | |
1168 | |
|
|
1169 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1170 | whole section. |
|
|
1171 | |
|
|
1172 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1173 | |
937 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1174 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
938 | |
1175 | |
939 | Stops the given watcher again (if active) and clears the pending |
1176 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1177 | the watcher was active or not). |
|
|
1178 | |
940 | status. It is possible that stopped watchers are pending (for example, |
1179 | It is possible that stopped watchers are pending - for example, |
941 | non-repeating timers are being stopped when they become pending), but |
1180 | non-repeating timers are being stopped when they become pending - but |
942 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1181 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
943 | you want to free or reuse the memory used by the watcher it is therefore a |
1182 | pending. If you want to free or reuse the memory used by the watcher it is |
944 | good idea to always call its C<ev_TYPE_stop> function. |
1183 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
945 | |
1184 | |
946 | =item bool ev_is_active (ev_TYPE *watcher) |
1185 | =item bool ev_is_active (ev_TYPE *watcher) |
947 | |
1186 | |
948 | Returns a true value iff the watcher is active (i.e. it has been started |
1187 | Returns a true value iff the watcher is active (i.e. it has been started |
949 | and not yet been stopped). As long as a watcher is active you must not modify |
1188 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
965 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1204 | =item ev_cb_set (ev_TYPE *watcher, callback) |
966 | |
1205 | |
967 | Change the callback. You can change the callback at virtually any time |
1206 | Change the callback. You can change the callback at virtually any time |
968 | (modulo threads). |
1207 | (modulo threads). |
969 | |
1208 | |
970 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1209 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
971 | |
1210 | |
972 | =item int ev_priority (ev_TYPE *watcher) |
1211 | =item int ev_priority (ev_TYPE *watcher) |
973 | |
1212 | |
974 | Set and query the priority of the watcher. The priority is a small |
1213 | Set and query the priority of the watcher. The priority is a small |
975 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1214 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
976 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1215 | (default: C<-2>). Pending watchers with higher priority will be invoked |
977 | before watchers with lower priority, but priority will not keep watchers |
1216 | before watchers with lower priority, but priority will not keep watchers |
978 | from being executed (except for C<ev_idle> watchers). |
1217 | from being executed (except for C<ev_idle> watchers). |
979 | |
1218 | |
980 | This means that priorities are I<only> used for ordering callback |
|
|
981 | invocation after new events have been received. This is useful, for |
|
|
982 | example, to reduce latency after idling, or more often, to bind two |
|
|
983 | watchers on the same event and make sure one is called first. |
|
|
984 | |
|
|
985 | If you need to suppress invocation when higher priority events are pending |
1219 | If you need to suppress invocation when higher priority events are pending |
986 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1220 | you need to look at C<ev_idle> watchers, which provide this functionality. |
987 | |
1221 | |
988 | You I<must not> change the priority of a watcher as long as it is active or |
1222 | You I<must not> change the priority of a watcher as long as it is active or |
989 | pending. |
1223 | pending. |
990 | |
1224 | |
|
|
1225 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1226 | fine, as long as you do not mind that the priority value you query might |
|
|
1227 | or might not have been clamped to the valid range. |
|
|
1228 | |
991 | The default priority used by watchers when no priority has been set is |
1229 | The default priority used by watchers when no priority has been set is |
992 | always C<0>, which is supposed to not be too high and not be too low :). |
1230 | always C<0>, which is supposed to not be too high and not be too low :). |
993 | |
1231 | |
994 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1232 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
995 | fine, as long as you do not mind that the priority value you query might |
1233 | priorities. |
996 | or might not have been adjusted to be within valid range. |
|
|
997 | |
1234 | |
998 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1235 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
999 | |
1236 | |
1000 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1237 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1001 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1238 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1002 | can deal with that fact. |
1239 | can deal with that fact, as both are simply passed through to the |
|
|
1240 | callback. |
1003 | |
1241 | |
1004 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1242 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1005 | |
1243 | |
1006 | If the watcher is pending, this function returns clears its pending status |
1244 | If the watcher is pending, this function clears its pending status and |
1007 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1245 | returns its C<revents> bitset (as if its callback was invoked). If the |
1008 | watcher isn't pending it does nothing and returns C<0>. |
1246 | watcher isn't pending it does nothing and returns C<0>. |
1009 | |
1247 | |
|
|
1248 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1249 | callback to be invoked, which can be accomplished with this function. |
|
|
1250 | |
|
|
1251 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1252 | |
|
|
1253 | Feeds the given event set into the event loop, as if the specified event |
|
|
1254 | had happened for the specified watcher (which must be a pointer to an |
|
|
1255 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1256 | not free the watcher as long as it has pending events. |
|
|
1257 | |
|
|
1258 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1259 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1260 | not started in the first place. |
|
|
1261 | |
|
|
1262 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1263 | functions that do not need a watcher. |
|
|
1264 | |
1010 | =back |
1265 | =back |
1011 | |
1266 | |
1012 | |
1267 | |
1013 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1268 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1014 | |
1269 | |
1015 | Each watcher has, by default, a member C<void *data> that you can change |
1270 | Each watcher has, by default, a member C<void *data> that you can change |
1016 | and read at any time, libev will completely ignore it. This can be used |
1271 | and read at any time: libev will completely ignore it. This can be used |
1017 | to associate arbitrary data with your watcher. If you need more data and |
1272 | to associate arbitrary data with your watcher. If you need more data and |
1018 | don't want to allocate memory and store a pointer to it in that data |
1273 | don't want to allocate memory and store a pointer to it in that data |
1019 | member, you can also "subclass" the watcher type and provide your own |
1274 | member, you can also "subclass" the watcher type and provide your own |
1020 | data: |
1275 | data: |
1021 | |
1276 | |
1022 | struct my_io |
1277 | struct my_io |
1023 | { |
1278 | { |
1024 | struct ev_io io; |
1279 | ev_io io; |
1025 | int otherfd; |
1280 | int otherfd; |
1026 | void *somedata; |
1281 | void *somedata; |
1027 | struct whatever *mostinteresting; |
1282 | struct whatever *mostinteresting; |
1028 | }; |
1283 | }; |
1029 | |
1284 | |
… | |
… | |
1032 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1287 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1033 | |
1288 | |
1034 | And since your callback will be called with a pointer to the watcher, you |
1289 | And since your callback will be called with a pointer to the watcher, you |
1035 | can cast it back to your own type: |
1290 | can cast it back to your own type: |
1036 | |
1291 | |
1037 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1292 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1038 | { |
1293 | { |
1039 | struct my_io *w = (struct my_io *)w_; |
1294 | struct my_io *w = (struct my_io *)w_; |
1040 | ... |
1295 | ... |
1041 | } |
1296 | } |
1042 | |
1297 | |
… | |
… | |
1053 | ev_timer t2; |
1308 | ev_timer t2; |
1054 | } |
1309 | } |
1055 | |
1310 | |
1056 | In this case getting the pointer to C<my_biggy> is a bit more |
1311 | In this case getting the pointer to C<my_biggy> is a bit more |
1057 | complicated: Either you store the address of your C<my_biggy> struct |
1312 | complicated: Either you store the address of your C<my_biggy> struct |
1058 | in the C<data> member of the watcher, or you need to use some pointer |
1313 | in the C<data> member of the watcher (for woozies), or you need to use |
1059 | arithmetic using C<offsetof> inside your watchers: |
1314 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1315 | programmers): |
1060 | |
1316 | |
1061 | #include <stddef.h> |
1317 | #include <stddef.h> |
1062 | |
1318 | |
1063 | static void |
1319 | static void |
1064 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1320 | t1_cb (EV_P_ ev_timer *w, int revents) |
1065 | { |
1321 | { |
1066 | struct my_biggy big = (struct my_biggy * |
1322 | struct my_biggy big = (struct my_biggy *) |
1067 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1323 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1068 | } |
1324 | } |
1069 | |
1325 | |
1070 | static void |
1326 | static void |
1071 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1327 | t2_cb (EV_P_ ev_timer *w, int revents) |
1072 | { |
1328 | { |
1073 | struct my_biggy big = (struct my_biggy * |
1329 | struct my_biggy big = (struct my_biggy *) |
1074 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1330 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1075 | } |
1331 | } |
|
|
1332 | |
|
|
1333 | =head2 WATCHER PRIORITY MODELS |
|
|
1334 | |
|
|
1335 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1336 | integers that influence the ordering of event callback invocation |
|
|
1337 | between watchers in some way, all else being equal. |
|
|
1338 | |
|
|
1339 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1340 | description for the more technical details such as the actual priority |
|
|
1341 | range. |
|
|
1342 | |
|
|
1343 | There are two common ways how these these priorities are being interpreted |
|
|
1344 | by event loops: |
|
|
1345 | |
|
|
1346 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1347 | of lower priority watchers, which means as long as higher priority |
|
|
1348 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1349 | |
|
|
1350 | The less common only-for-ordering model uses priorities solely to order |
|
|
1351 | callback invocation within a single event loop iteration: Higher priority |
|
|
1352 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1353 | before polling for new events. |
|
|
1354 | |
|
|
1355 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1356 | except for idle watchers (which use the lock-out model). |
|
|
1357 | |
|
|
1358 | The rationale behind this is that implementing the lock-out model for |
|
|
1359 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1360 | libraries will just poll for the same events again and again as long as |
|
|
1361 | their callbacks have not been executed, which is very inefficient in the |
|
|
1362 | common case of one high-priority watcher locking out a mass of lower |
|
|
1363 | priority ones. |
|
|
1364 | |
|
|
1365 | Static (ordering) priorities are most useful when you have two or more |
|
|
1366 | watchers handling the same resource: a typical usage example is having an |
|
|
1367 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1368 | timeouts. Under load, data might be received while the program handles |
|
|
1369 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1370 | handler will be executed before checking for data. In that case, giving |
|
|
1371 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1372 | handled first even under adverse conditions (which is usually, but not |
|
|
1373 | always, what you want). |
|
|
1374 | |
|
|
1375 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1376 | will only be executed when no same or higher priority watchers have |
|
|
1377 | received events, they can be used to implement the "lock-out" model when |
|
|
1378 | required. |
|
|
1379 | |
|
|
1380 | For example, to emulate how many other event libraries handle priorities, |
|
|
1381 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1382 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1383 | processing is done in the idle watcher callback. This causes libev to |
|
|
1384 | continously poll and process kernel event data for the watcher, but when |
|
|
1385 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1386 | workable. |
|
|
1387 | |
|
|
1388 | Usually, however, the lock-out model implemented that way will perform |
|
|
1389 | miserably under the type of load it was designed to handle. In that case, |
|
|
1390 | it might be preferable to stop the real watcher before starting the |
|
|
1391 | idle watcher, so the kernel will not have to process the event in case |
|
|
1392 | the actual processing will be delayed for considerable time. |
|
|
1393 | |
|
|
1394 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1395 | priority than the default, and which should only process data when no |
|
|
1396 | other events are pending: |
|
|
1397 | |
|
|
1398 | ev_idle idle; // actual processing watcher |
|
|
1399 | ev_io io; // actual event watcher |
|
|
1400 | |
|
|
1401 | static void |
|
|
1402 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1403 | { |
|
|
1404 | // stop the I/O watcher, we received the event, but |
|
|
1405 | // are not yet ready to handle it. |
|
|
1406 | ev_io_stop (EV_A_ w); |
|
|
1407 | |
|
|
1408 | // start the idle watcher to ahndle the actual event. |
|
|
1409 | // it will not be executed as long as other watchers |
|
|
1410 | // with the default priority are receiving events. |
|
|
1411 | ev_idle_start (EV_A_ &idle); |
|
|
1412 | } |
|
|
1413 | |
|
|
1414 | static void |
|
|
1415 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1416 | { |
|
|
1417 | // actual processing |
|
|
1418 | read (STDIN_FILENO, ...); |
|
|
1419 | |
|
|
1420 | // have to start the I/O watcher again, as |
|
|
1421 | // we have handled the event |
|
|
1422 | ev_io_start (EV_P_ &io); |
|
|
1423 | } |
|
|
1424 | |
|
|
1425 | // initialisation |
|
|
1426 | ev_idle_init (&idle, idle_cb); |
|
|
1427 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1428 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1429 | |
|
|
1430 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1431 | low-priority connections can not be locked out forever under load. This |
|
|
1432 | enables your program to keep a lower latency for important connections |
|
|
1433 | during short periods of high load, while not completely locking out less |
|
|
1434 | important ones. |
1076 | |
1435 | |
1077 | |
1436 | |
1078 | =head1 WATCHER TYPES |
1437 | =head1 WATCHER TYPES |
1079 | |
1438 | |
1080 | This section describes each watcher in detail, but will not repeat |
1439 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1104 | In general you can register as many read and/or write event watchers per |
1463 | In general you can register as many read and/or write event watchers per |
1105 | fd as you want (as long as you don't confuse yourself). Setting all file |
1464 | fd as you want (as long as you don't confuse yourself). Setting all file |
1106 | descriptors to non-blocking mode is also usually a good idea (but not |
1465 | descriptors to non-blocking mode is also usually a good idea (but not |
1107 | required if you know what you are doing). |
1466 | required if you know what you are doing). |
1108 | |
1467 | |
1109 | If you must do this, then force the use of a known-to-be-good backend |
1468 | If you cannot use non-blocking mode, then force the use of a |
1110 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1469 | known-to-be-good backend (at the time of this writing, this includes only |
1111 | C<EVBACKEND_POLL>). |
1470 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1471 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1472 | files) - libev doesn't guarentee any specific behaviour in that case. |
1112 | |
1473 | |
1113 | Another thing you have to watch out for is that it is quite easy to |
1474 | Another thing you have to watch out for is that it is quite easy to |
1114 | receive "spurious" readiness notifications, that is your callback might |
1475 | receive "spurious" readiness notifications, that is your callback might |
1115 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1476 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1116 | because there is no data. Not only are some backends known to create a |
1477 | because there is no data. Not only are some backends known to create a |
1117 | lot of those (for example Solaris ports), it is very easy to get into |
1478 | lot of those (for example Solaris ports), it is very easy to get into |
1118 | this situation even with a relatively standard program structure. Thus |
1479 | this situation even with a relatively standard program structure. Thus |
1119 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1480 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1120 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1481 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1121 | |
1482 | |
1122 | If you cannot run the fd in non-blocking mode (for example you should not |
1483 | If you cannot run the fd in non-blocking mode (for example you should |
1123 | play around with an Xlib connection), then you have to separately re-test |
1484 | not play around with an Xlib connection), then you have to separately |
1124 | whether a file descriptor is really ready with a known-to-be good interface |
1485 | re-test whether a file descriptor is really ready with a known-to-be good |
1125 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1486 | interface such as poll (fortunately in our Xlib example, Xlib already |
1126 | its own, so its quite safe to use). |
1487 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1488 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1489 | indefinitely. |
|
|
1490 | |
|
|
1491 | But really, best use non-blocking mode. |
1127 | |
1492 | |
1128 | =head3 The special problem of disappearing file descriptors |
1493 | =head3 The special problem of disappearing file descriptors |
1129 | |
1494 | |
1130 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1495 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1131 | descriptor (either by calling C<close> explicitly or by any other means, |
1496 | descriptor (either due to calling C<close> explicitly or any other means, |
1132 | such as C<dup>). The reason is that you register interest in some file |
1497 | such as C<dup2>). The reason is that you register interest in some file |
1133 | descriptor, but when it goes away, the operating system will silently drop |
1498 | descriptor, but when it goes away, the operating system will silently drop |
1134 | this interest. If another file descriptor with the same number then is |
1499 | this interest. If another file descriptor with the same number then is |
1135 | registered with libev, there is no efficient way to see that this is, in |
1500 | registered with libev, there is no efficient way to see that this is, in |
1136 | fact, a different file descriptor. |
1501 | fact, a different file descriptor. |
1137 | |
1502 | |
… | |
… | |
1168 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1533 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1169 | C<EVBACKEND_POLL>. |
1534 | C<EVBACKEND_POLL>. |
1170 | |
1535 | |
1171 | =head3 The special problem of SIGPIPE |
1536 | =head3 The special problem of SIGPIPE |
1172 | |
1537 | |
1173 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1538 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1174 | when writing to a pipe whose other end has been closed, your program gets |
1539 | when writing to a pipe whose other end has been closed, your program gets |
1175 | send a SIGPIPE, which, by default, aborts your program. For most programs |
1540 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1176 | this is sensible behaviour, for daemons, this is usually undesirable. |
1541 | this is sensible behaviour, for daemons, this is usually undesirable. |
1177 | |
1542 | |
1178 | So when you encounter spurious, unexplained daemon exits, make sure you |
1543 | So when you encounter spurious, unexplained daemon exits, make sure you |
1179 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1544 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1180 | somewhere, as that would have given you a big clue). |
1545 | somewhere, as that would have given you a big clue). |
1181 | |
1546 | |
|
|
1547 | =head3 The special problem of accept()ing when you can't |
|
|
1548 | |
|
|
1549 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1550 | found in port-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1551 | connection from the pending queue in all error cases. |
|
|
1552 | |
|
|
1553 | For example, larger servers often run out of file descriptors (because |
|
|
1554 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1555 | rejecting the connection, leading to libev signalling readiness on |
|
|
1556 | the next iteration again (the connection still exists after all), and |
|
|
1557 | typically causing the program to loop at 100% CPU usage. |
|
|
1558 | |
|
|
1559 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1560 | operating systems, there is usually little the app can do to remedy the |
|
|
1561 | situation, and no known thread-safe method of removing the connection to |
|
|
1562 | cope with overload is known (to me). |
|
|
1563 | |
|
|
1564 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1565 | - when the program encounters an overload, it will just loop until the |
|
|
1566 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1567 | event-based way to handle this situation, so it's the best one can do. |
|
|
1568 | |
|
|
1569 | A better way to handle the situation is to log any errors other than |
|
|
1570 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1571 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1572 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1573 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1574 | usage. |
|
|
1575 | |
|
|
1576 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1577 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1578 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1579 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1580 | clients under typical overload conditions. |
|
|
1581 | |
|
|
1582 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1583 | is often done with C<malloc> failures, but this results in an easy |
|
|
1584 | opportunity for a DoS attack. |
1182 | |
1585 | |
1183 | =head3 Watcher-Specific Functions |
1586 | =head3 Watcher-Specific Functions |
1184 | |
1587 | |
1185 | =over 4 |
1588 | =over 4 |
1186 | |
1589 | |
1187 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1590 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1188 | |
1591 | |
1189 | =item ev_io_set (ev_io *, int fd, int events) |
1592 | =item ev_io_set (ev_io *, int fd, int events) |
1190 | |
1593 | |
1191 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1594 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1192 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1595 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1193 | C<EV_READ | EV_WRITE> to receive the given events. |
1596 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1194 | |
1597 | |
1195 | =item int fd [read-only] |
1598 | =item int fd [read-only] |
1196 | |
1599 | |
1197 | The file descriptor being watched. |
1600 | The file descriptor being watched. |
1198 | |
1601 | |
… | |
… | |
1207 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1610 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1208 | readable, but only once. Since it is likely line-buffered, you could |
1611 | readable, but only once. Since it is likely line-buffered, you could |
1209 | attempt to read a whole line in the callback. |
1612 | attempt to read a whole line in the callback. |
1210 | |
1613 | |
1211 | static void |
1614 | static void |
1212 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1615 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1213 | { |
1616 | { |
1214 | ev_io_stop (loop, w); |
1617 | ev_io_stop (loop, w); |
1215 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1618 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1216 | } |
1619 | } |
1217 | |
1620 | |
1218 | ... |
1621 | ... |
1219 | struct ev_loop *loop = ev_default_init (0); |
1622 | struct ev_loop *loop = ev_default_init (0); |
1220 | struct ev_io stdin_readable; |
1623 | ev_io stdin_readable; |
1221 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1624 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1222 | ev_io_start (loop, &stdin_readable); |
1625 | ev_io_start (loop, &stdin_readable); |
1223 | ev_loop (loop, 0); |
1626 | ev_loop (loop, 0); |
1224 | |
1627 | |
1225 | |
1628 | |
… | |
… | |
1228 | Timer watchers are simple relative timers that generate an event after a |
1631 | Timer watchers are simple relative timers that generate an event after a |
1229 | given time, and optionally repeating in regular intervals after that. |
1632 | given time, and optionally repeating in regular intervals after that. |
1230 | |
1633 | |
1231 | The timers are based on real time, that is, if you register an event that |
1634 | The timers are based on real time, that is, if you register an event that |
1232 | times out after an hour and you reset your system clock to January last |
1635 | times out after an hour and you reset your system clock to January last |
1233 | year, it will still time out after (roughly) and hour. "Roughly" because |
1636 | year, it will still time out after (roughly) one hour. "Roughly" because |
1234 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1637 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1235 | monotonic clock option helps a lot here). |
1638 | monotonic clock option helps a lot here). |
1236 | |
1639 | |
1237 | The callback is guaranteed to be invoked only after its timeout has passed, |
1640 | The callback is guaranteed to be invoked only I<after> its timeout has |
1238 | but if multiple timers become ready during the same loop iteration then |
1641 | passed (not I<at>, so on systems with very low-resolution clocks this |
1239 | order of execution is undefined. |
1642 | might introduce a small delay). If multiple timers become ready during the |
|
|
1643 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1644 | before ones of the same priority with later time-out values (but this is |
|
|
1645 | no longer true when a callback calls C<ev_loop> recursively). |
|
|
1646 | |
|
|
1647 | =head3 Be smart about timeouts |
|
|
1648 | |
|
|
1649 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1650 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1651 | you want to raise some error after a while. |
|
|
1652 | |
|
|
1653 | What follows are some ways to handle this problem, from obvious and |
|
|
1654 | inefficient to smart and efficient. |
|
|
1655 | |
|
|
1656 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1657 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1658 | data or other life sign was received). |
|
|
1659 | |
|
|
1660 | =over 4 |
|
|
1661 | |
|
|
1662 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1663 | |
|
|
1664 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1665 | start the watcher: |
|
|
1666 | |
|
|
1667 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1668 | ev_timer_start (loop, timer); |
|
|
1669 | |
|
|
1670 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1671 | and start it again: |
|
|
1672 | |
|
|
1673 | ev_timer_stop (loop, timer); |
|
|
1674 | ev_timer_set (timer, 60., 0.); |
|
|
1675 | ev_timer_start (loop, timer); |
|
|
1676 | |
|
|
1677 | This is relatively simple to implement, but means that each time there is |
|
|
1678 | some activity, libev will first have to remove the timer from its internal |
|
|
1679 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1680 | still not a constant-time operation. |
|
|
1681 | |
|
|
1682 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1683 | |
|
|
1684 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1685 | C<ev_timer_start>. |
|
|
1686 | |
|
|
1687 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1688 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1689 | successfully read or write some data. If you go into an idle state where |
|
|
1690 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1691 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1692 | |
|
|
1693 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1694 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1695 | member and C<ev_timer_again>. |
|
|
1696 | |
|
|
1697 | At start: |
|
|
1698 | |
|
|
1699 | ev_init (timer, callback); |
|
|
1700 | timer->repeat = 60.; |
|
|
1701 | ev_timer_again (loop, timer); |
|
|
1702 | |
|
|
1703 | Each time there is some activity: |
|
|
1704 | |
|
|
1705 | ev_timer_again (loop, timer); |
|
|
1706 | |
|
|
1707 | It is even possible to change the time-out on the fly, regardless of |
|
|
1708 | whether the watcher is active or not: |
|
|
1709 | |
|
|
1710 | timer->repeat = 30.; |
|
|
1711 | ev_timer_again (loop, timer); |
|
|
1712 | |
|
|
1713 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1714 | you want to modify its timeout value, as libev does not have to completely |
|
|
1715 | remove and re-insert the timer from/into its internal data structure. |
|
|
1716 | |
|
|
1717 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1718 | |
|
|
1719 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1720 | |
|
|
1721 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1722 | relatively long compared to the intervals between other activity - in |
|
|
1723 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1724 | associated activity resets. |
|
|
1725 | |
|
|
1726 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1727 | but remember the time of last activity, and check for a real timeout only |
|
|
1728 | within the callback: |
|
|
1729 | |
|
|
1730 | ev_tstamp last_activity; // time of last activity |
|
|
1731 | |
|
|
1732 | static void |
|
|
1733 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1734 | { |
|
|
1735 | ev_tstamp now = ev_now (EV_A); |
|
|
1736 | ev_tstamp timeout = last_activity + 60.; |
|
|
1737 | |
|
|
1738 | // if last_activity + 60. is older than now, we did time out |
|
|
1739 | if (timeout < now) |
|
|
1740 | { |
|
|
1741 | // timeout occured, take action |
|
|
1742 | } |
|
|
1743 | else |
|
|
1744 | { |
|
|
1745 | // callback was invoked, but there was some activity, re-arm |
|
|
1746 | // the watcher to fire in last_activity + 60, which is |
|
|
1747 | // guaranteed to be in the future, so "again" is positive: |
|
|
1748 | w->repeat = timeout - now; |
|
|
1749 | ev_timer_again (EV_A_ w); |
|
|
1750 | } |
|
|
1751 | } |
|
|
1752 | |
|
|
1753 | To summarise the callback: first calculate the real timeout (defined |
|
|
1754 | as "60 seconds after the last activity"), then check if that time has |
|
|
1755 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1756 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1757 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1758 | a timeout then. |
|
|
1759 | |
|
|
1760 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1761 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1762 | |
|
|
1763 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1764 | minus half the average time between activity), but virtually no calls to |
|
|
1765 | libev to change the timeout. |
|
|
1766 | |
|
|
1767 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1768 | to the current time (meaning we just have some activity :), then call the |
|
|
1769 | callback, which will "do the right thing" and start the timer: |
|
|
1770 | |
|
|
1771 | ev_init (timer, callback); |
|
|
1772 | last_activity = ev_now (loop); |
|
|
1773 | callback (loop, timer, EV_TIMER); |
|
|
1774 | |
|
|
1775 | And when there is some activity, simply store the current time in |
|
|
1776 | C<last_activity>, no libev calls at all: |
|
|
1777 | |
|
|
1778 | last_actiivty = ev_now (loop); |
|
|
1779 | |
|
|
1780 | This technique is slightly more complex, but in most cases where the |
|
|
1781 | time-out is unlikely to be triggered, much more efficient. |
|
|
1782 | |
|
|
1783 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1784 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1785 | fix things for you. |
|
|
1786 | |
|
|
1787 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1788 | |
|
|
1789 | If there is not one request, but many thousands (millions...), all |
|
|
1790 | employing some kind of timeout with the same timeout value, then one can |
|
|
1791 | do even better: |
|
|
1792 | |
|
|
1793 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1794 | at the I<end> of the list. |
|
|
1795 | |
|
|
1796 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1797 | the list is expected to fire (for example, using the technique #3). |
|
|
1798 | |
|
|
1799 | When there is some activity, remove the timer from the list, recalculate |
|
|
1800 | the timeout, append it to the end of the list again, and make sure to |
|
|
1801 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1802 | |
|
|
1803 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1804 | starting, stopping and updating the timers, at the expense of a major |
|
|
1805 | complication, and having to use a constant timeout. The constant timeout |
|
|
1806 | ensures that the list stays sorted. |
|
|
1807 | |
|
|
1808 | =back |
|
|
1809 | |
|
|
1810 | So which method the best? |
|
|
1811 | |
|
|
1812 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1813 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1814 | better, and isn't very complicated either. In most case, choosing either |
|
|
1815 | one is fine, with #3 being better in typical situations. |
|
|
1816 | |
|
|
1817 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1818 | rather complicated, but extremely efficient, something that really pays |
|
|
1819 | off after the first million or so of active timers, i.e. it's usually |
|
|
1820 | overkill :) |
1240 | |
1821 | |
1241 | =head3 The special problem of time updates |
1822 | =head3 The special problem of time updates |
1242 | |
1823 | |
1243 | Establishing the current time is a costly operation (it usually takes at |
1824 | Establishing the current time is a costly operation (it usually takes at |
1244 | least two system calls): EV therefore updates its idea of the current |
1825 | least two system calls): EV therefore updates its idea of the current |
1245 | time only before and after C<ev_loop> polls for new events, which causes |
1826 | time only before and after C<ev_loop> collects new events, which causes a |
1246 | a growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1827 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1247 | lots of events. |
1828 | lots of events in one iteration. |
1248 | |
1829 | |
1249 | The relative timeouts are calculated relative to the C<ev_now ()> |
1830 | The relative timeouts are calculated relative to the C<ev_now ()> |
1250 | time. This is usually the right thing as this timestamp refers to the time |
1831 | time. This is usually the right thing as this timestamp refers to the time |
1251 | of the event triggering whatever timeout you are modifying/starting. If |
1832 | of the event triggering whatever timeout you are modifying/starting. If |
1252 | you suspect event processing to be delayed and you I<need> to base the |
1833 | you suspect event processing to be delayed and you I<need> to base the |
… | |
… | |
1256 | |
1837 | |
1257 | If the event loop is suspended for a long time, you can also force an |
1838 | If the event loop is suspended for a long time, you can also force an |
1258 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1839 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1259 | ()>. |
1840 | ()>. |
1260 | |
1841 | |
|
|
1842 | =head3 The special problems of suspended animation |
|
|
1843 | |
|
|
1844 | When you leave the server world it is quite customary to hit machines that |
|
|
1845 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1846 | |
|
|
1847 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1848 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1849 | to run until the system is suspended, but they will not advance while the |
|
|
1850 | system is suspended. That means, on resume, it will be as if the program |
|
|
1851 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1852 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1853 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1854 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1855 | be adjusted accordingly. |
|
|
1856 | |
|
|
1857 | I would not be surprised to see different behaviour in different between |
|
|
1858 | operating systems, OS versions or even different hardware. |
|
|
1859 | |
|
|
1860 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1861 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1862 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1863 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1864 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1865 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1866 | |
|
|
1867 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1868 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1869 | deterministic behaviour in this case (you can do nothing against |
|
|
1870 | C<SIGSTOP>). |
|
|
1871 | |
1261 | =head3 Watcher-Specific Functions and Data Members |
1872 | =head3 Watcher-Specific Functions and Data Members |
1262 | |
1873 | |
1263 | =over 4 |
1874 | =over 4 |
1264 | |
1875 | |
1265 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1876 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1288 | If the timer is started but non-repeating, stop it (as if it timed out). |
1899 | If the timer is started but non-repeating, stop it (as if it timed out). |
1289 | |
1900 | |
1290 | If the timer is repeating, either start it if necessary (with the |
1901 | If the timer is repeating, either start it if necessary (with the |
1291 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1902 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1292 | |
1903 | |
1293 | This sounds a bit complicated, but here is a useful and typical |
1904 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1294 | example: Imagine you have a TCP connection and you want a so-called idle |
1905 | usage example. |
1295 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1296 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1297 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1298 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1299 | you go into an idle state where you do not expect data to travel on the |
|
|
1300 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1301 | automatically restart it if need be. |
|
|
1302 | |
1906 | |
1303 | That means you can ignore the C<after> value and C<ev_timer_start> |
1907 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1304 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1305 | |
1908 | |
1306 | ev_timer_init (timer, callback, 0., 5.); |
1909 | Returns the remaining time until a timer fires. If the timer is active, |
1307 | ev_timer_again (loop, timer); |
1910 | then this time is relative to the current event loop time, otherwise it's |
1308 | ... |
1911 | the timeout value currently configured. |
1309 | timer->again = 17.; |
|
|
1310 | ev_timer_again (loop, timer); |
|
|
1311 | ... |
|
|
1312 | timer->again = 10.; |
|
|
1313 | ev_timer_again (loop, timer); |
|
|
1314 | |
1912 | |
1315 | This is more slightly efficient then stopping/starting the timer each time |
1913 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1316 | you want to modify its timeout value. |
1914 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1915 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1916 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1917 | too), and so on. |
1317 | |
1918 | |
1318 | =item ev_tstamp repeat [read-write] |
1919 | =item ev_tstamp repeat [read-write] |
1319 | |
1920 | |
1320 | The current C<repeat> value. Will be used each time the watcher times out |
1921 | The current C<repeat> value. Will be used each time the watcher times out |
1321 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1922 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1322 | which is also when any modifications are taken into account. |
1923 | which is also when any modifications are taken into account. |
1323 | |
1924 | |
1324 | =back |
1925 | =back |
1325 | |
1926 | |
1326 | =head3 Examples |
1927 | =head3 Examples |
1327 | |
1928 | |
1328 | Example: Create a timer that fires after 60 seconds. |
1929 | Example: Create a timer that fires after 60 seconds. |
1329 | |
1930 | |
1330 | static void |
1931 | static void |
1331 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1932 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1332 | { |
1933 | { |
1333 | .. one minute over, w is actually stopped right here |
1934 | .. one minute over, w is actually stopped right here |
1334 | } |
1935 | } |
1335 | |
1936 | |
1336 | struct ev_timer mytimer; |
1937 | ev_timer mytimer; |
1337 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1938 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1338 | ev_timer_start (loop, &mytimer); |
1939 | ev_timer_start (loop, &mytimer); |
1339 | |
1940 | |
1340 | Example: Create a timeout timer that times out after 10 seconds of |
1941 | Example: Create a timeout timer that times out after 10 seconds of |
1341 | inactivity. |
1942 | inactivity. |
1342 | |
1943 | |
1343 | static void |
1944 | static void |
1344 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1945 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1345 | { |
1946 | { |
1346 | .. ten seconds without any activity |
1947 | .. ten seconds without any activity |
1347 | } |
1948 | } |
1348 | |
1949 | |
1349 | struct ev_timer mytimer; |
1950 | ev_timer mytimer; |
1350 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1951 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1351 | ev_timer_again (&mytimer); /* start timer */ |
1952 | ev_timer_again (&mytimer); /* start timer */ |
1352 | ev_loop (loop, 0); |
1953 | ev_loop (loop, 0); |
1353 | |
1954 | |
1354 | // and in some piece of code that gets executed on any "activity": |
1955 | // and in some piece of code that gets executed on any "activity": |
… | |
… | |
1359 | =head2 C<ev_periodic> - to cron or not to cron? |
1960 | =head2 C<ev_periodic> - to cron or not to cron? |
1360 | |
1961 | |
1361 | Periodic watchers are also timers of a kind, but they are very versatile |
1962 | Periodic watchers are also timers of a kind, but they are very versatile |
1362 | (and unfortunately a bit complex). |
1963 | (and unfortunately a bit complex). |
1363 | |
1964 | |
1364 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1965 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1365 | but on wall clock time (absolute time). You can tell a periodic watcher |
1966 | relative time, the physical time that passes) but on wall clock time |
1366 | to trigger after some specific point in time. For example, if you tell a |
1967 | (absolute time, the thing you can read on your calender or clock). The |
1367 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1968 | difference is that wall clock time can run faster or slower than real |
1368 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1969 | time, and time jumps are not uncommon (e.g. when you adjust your |
1369 | clock to January of the previous year, then it will take more than year |
1970 | wrist-watch). |
1370 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1371 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1372 | |
1971 | |
|
|
1972 | You can tell a periodic watcher to trigger after some specific point |
|
|
1973 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1974 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1975 | not a delay) and then reset your system clock to January of the previous |
|
|
1976 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1977 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1978 | it, as it uses a relative timeout). |
|
|
1979 | |
1373 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1980 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1374 | such as triggering an event on each "midnight, local time", or other |
1981 | timers, such as triggering an event on each "midnight, local time", or |
1375 | complicated, rules. |
1982 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1983 | those cannot react to time jumps. |
1376 | |
1984 | |
1377 | As with timers, the callback is guaranteed to be invoked only when the |
1985 | As with timers, the callback is guaranteed to be invoked only when the |
1378 | time (C<at>) has passed, but if multiple periodic timers become ready |
1986 | point in time where it is supposed to trigger has passed. If multiple |
1379 | during the same loop iteration then order of execution is undefined. |
1987 | timers become ready during the same loop iteration then the ones with |
|
|
1988 | earlier time-out values are invoked before ones with later time-out values |
|
|
1989 | (but this is no longer true when a callback calls C<ev_loop> recursively). |
1380 | |
1990 | |
1381 | =head3 Watcher-Specific Functions and Data Members |
1991 | =head3 Watcher-Specific Functions and Data Members |
1382 | |
1992 | |
1383 | =over 4 |
1993 | =over 4 |
1384 | |
1994 | |
1385 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1995 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1386 | |
1996 | |
1387 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1997 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1388 | |
1998 | |
1389 | Lots of arguments, lets sort it out... There are basically three modes of |
1999 | Lots of arguments, let's sort it out... There are basically three modes of |
1390 | operation, and we will explain them from simplest to complex: |
2000 | operation, and we will explain them from simplest to most complex: |
1391 | |
2001 | |
1392 | =over 4 |
2002 | =over 4 |
1393 | |
2003 | |
1394 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2004 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1395 | |
2005 | |
1396 | In this configuration the watcher triggers an event after the wall clock |
2006 | In this configuration the watcher triggers an event after the wall clock |
1397 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2007 | time C<offset> has passed. It will not repeat and will not adjust when a |
1398 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2008 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1399 | run when the system time reaches or surpasses this time. |
2009 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2010 | this point in time. |
1400 | |
2011 | |
1401 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2012 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1402 | |
2013 | |
1403 | In this mode the watcher will always be scheduled to time out at the next |
2014 | In this mode the watcher will always be scheduled to time out at the next |
1404 | C<at + N * interval> time (for some integer N, which can also be negative) |
2015 | C<offset + N * interval> time (for some integer N, which can also be |
1405 | and then repeat, regardless of any time jumps. |
2016 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2017 | argument is merely an offset into the C<interval> periods. |
1406 | |
2018 | |
1407 | This can be used to create timers that do not drift with respect to system |
2019 | This can be used to create timers that do not drift with respect to the |
1408 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2020 | system clock, for example, here is an C<ev_periodic> that triggers each |
1409 | the hour: |
2021 | hour, on the hour (with respect to UTC): |
1410 | |
2022 | |
1411 | ev_periodic_set (&periodic, 0., 3600., 0); |
2023 | ev_periodic_set (&periodic, 0., 3600., 0); |
1412 | |
2024 | |
1413 | This doesn't mean there will always be 3600 seconds in between triggers, |
2025 | This doesn't mean there will always be 3600 seconds in between triggers, |
1414 | but only that the callback will be called when the system time shows a |
2026 | but only that the callback will be called when the system time shows a |
1415 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2027 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1416 | by 3600. |
2028 | by 3600. |
1417 | |
2029 | |
1418 | Another way to think about it (for the mathematically inclined) is that |
2030 | Another way to think about it (for the mathematically inclined) is that |
1419 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2031 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1420 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2032 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1421 | |
2033 | |
1422 | For numerical stability it is preferable that the C<at> value is near |
2034 | For numerical stability it is preferable that the C<offset> value is near |
1423 | C<ev_now ()> (the current time), but there is no range requirement for |
2035 | C<ev_now ()> (the current time), but there is no range requirement for |
1424 | this value, and in fact is often specified as zero. |
2036 | this value, and in fact is often specified as zero. |
1425 | |
2037 | |
1426 | Note also that there is an upper limit to how often a timer can fire (CPU |
2038 | Note also that there is an upper limit to how often a timer can fire (CPU |
1427 | speed for example), so if C<interval> is very small then timing stability |
2039 | speed for example), so if C<interval> is very small then timing stability |
1428 | will of course deteriorate. Libev itself tries to be exact to be about one |
2040 | will of course deteriorate. Libev itself tries to be exact to be about one |
1429 | millisecond (if the OS supports it and the machine is fast enough). |
2041 | millisecond (if the OS supports it and the machine is fast enough). |
1430 | |
2042 | |
1431 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2043 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1432 | |
2044 | |
1433 | In this mode the values for C<interval> and C<at> are both being |
2045 | In this mode the values for C<interval> and C<offset> are both being |
1434 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2046 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1435 | reschedule callback will be called with the watcher as first, and the |
2047 | reschedule callback will be called with the watcher as first, and the |
1436 | current time as second argument. |
2048 | current time as second argument. |
1437 | |
2049 | |
1438 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2050 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1439 | ever, or make ANY event loop modifications whatsoever>. |
2051 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2052 | allowed by documentation here>. |
1440 | |
2053 | |
1441 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2054 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1442 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2055 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1443 | only event loop modification you are allowed to do). |
2056 | only event loop modification you are allowed to do). |
1444 | |
2057 | |
1445 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2058 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1446 | *w, ev_tstamp now)>, e.g.: |
2059 | *w, ev_tstamp now)>, e.g.: |
1447 | |
2060 | |
|
|
2061 | static ev_tstamp |
1448 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2062 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1449 | { |
2063 | { |
1450 | return now + 60.; |
2064 | return now + 60.; |
1451 | } |
2065 | } |
1452 | |
2066 | |
1453 | It must return the next time to trigger, based on the passed time value |
2067 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1473 | a different time than the last time it was called (e.g. in a crond like |
2087 | a different time than the last time it was called (e.g. in a crond like |
1474 | program when the crontabs have changed). |
2088 | program when the crontabs have changed). |
1475 | |
2089 | |
1476 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2090 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1477 | |
2091 | |
1478 | When active, returns the absolute time that the watcher is supposed to |
2092 | When active, returns the absolute time that the watcher is supposed |
1479 | trigger next. |
2093 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2094 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2095 | rescheduling modes. |
1480 | |
2096 | |
1481 | =item ev_tstamp offset [read-write] |
2097 | =item ev_tstamp offset [read-write] |
1482 | |
2098 | |
1483 | When repeating, this contains the offset value, otherwise this is the |
2099 | When repeating, this contains the offset value, otherwise this is the |
1484 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2100 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2101 | although libev might modify this value for better numerical stability). |
1485 | |
2102 | |
1486 | Can be modified any time, but changes only take effect when the periodic |
2103 | Can be modified any time, but changes only take effect when the periodic |
1487 | timer fires or C<ev_periodic_again> is being called. |
2104 | timer fires or C<ev_periodic_again> is being called. |
1488 | |
2105 | |
1489 | =item ev_tstamp interval [read-write] |
2106 | =item ev_tstamp interval [read-write] |
1490 | |
2107 | |
1491 | The current interval value. Can be modified any time, but changes only |
2108 | The current interval value. Can be modified any time, but changes only |
1492 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2109 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1493 | called. |
2110 | called. |
1494 | |
2111 | |
1495 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2112 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1496 | |
2113 | |
1497 | The current reschedule callback, or C<0>, if this functionality is |
2114 | The current reschedule callback, or C<0>, if this functionality is |
1498 | switched off. Can be changed any time, but changes only take effect when |
2115 | switched off. Can be changed any time, but changes only take effect when |
1499 | the periodic timer fires or C<ev_periodic_again> is being called. |
2116 | the periodic timer fires or C<ev_periodic_again> is being called. |
1500 | |
2117 | |
1501 | =back |
2118 | =back |
1502 | |
2119 | |
1503 | =head3 Examples |
2120 | =head3 Examples |
1504 | |
2121 | |
1505 | Example: Call a callback every hour, or, more precisely, whenever the |
2122 | Example: Call a callback every hour, or, more precisely, whenever the |
1506 | system clock is divisible by 3600. The callback invocation times have |
2123 | system time is divisible by 3600. The callback invocation times have |
1507 | potentially a lot of jitter, but good long-term stability. |
2124 | potentially a lot of jitter, but good long-term stability. |
1508 | |
2125 | |
1509 | static void |
2126 | static void |
1510 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2127 | clock_cb (struct ev_loop *loop, ev_io *w, int revents) |
1511 | { |
2128 | { |
1512 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2129 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1513 | } |
2130 | } |
1514 | |
2131 | |
1515 | struct ev_periodic hourly_tick; |
2132 | ev_periodic hourly_tick; |
1516 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2133 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1517 | ev_periodic_start (loop, &hourly_tick); |
2134 | ev_periodic_start (loop, &hourly_tick); |
1518 | |
2135 | |
1519 | Example: The same as above, but use a reschedule callback to do it: |
2136 | Example: The same as above, but use a reschedule callback to do it: |
1520 | |
2137 | |
1521 | #include <math.h> |
2138 | #include <math.h> |
1522 | |
2139 | |
1523 | static ev_tstamp |
2140 | static ev_tstamp |
1524 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2141 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1525 | { |
2142 | { |
1526 | return fmod (now, 3600.) + 3600.; |
2143 | return now + (3600. - fmod (now, 3600.)); |
1527 | } |
2144 | } |
1528 | |
2145 | |
1529 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2146 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1530 | |
2147 | |
1531 | Example: Call a callback every hour, starting now: |
2148 | Example: Call a callback every hour, starting now: |
1532 | |
2149 | |
1533 | struct ev_periodic hourly_tick; |
2150 | ev_periodic hourly_tick; |
1534 | ev_periodic_init (&hourly_tick, clock_cb, |
2151 | ev_periodic_init (&hourly_tick, clock_cb, |
1535 | fmod (ev_now (loop), 3600.), 3600., 0); |
2152 | fmod (ev_now (loop), 3600.), 3600., 0); |
1536 | ev_periodic_start (loop, &hourly_tick); |
2153 | ev_periodic_start (loop, &hourly_tick); |
1537 | |
2154 | |
1538 | |
2155 | |
… | |
… | |
1541 | Signal watchers will trigger an event when the process receives a specific |
2158 | Signal watchers will trigger an event when the process receives a specific |
1542 | signal one or more times. Even though signals are very asynchronous, libev |
2159 | signal one or more times. Even though signals are very asynchronous, libev |
1543 | will try it's best to deliver signals synchronously, i.e. as part of the |
2160 | will try it's best to deliver signals synchronously, i.e. as part of the |
1544 | normal event processing, like any other event. |
2161 | normal event processing, like any other event. |
1545 | |
2162 | |
|
|
2163 | If you want signals to be delivered truly asynchronously, just use |
|
|
2164 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2165 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2166 | synchronously wake up an event loop. |
|
|
2167 | |
1546 | You can configure as many watchers as you like per signal. Only when the |
2168 | You can configure as many watchers as you like for the same signal, but |
|
|
2169 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2170 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2171 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2172 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2173 | |
1547 | first watcher gets started will libev actually register a signal watcher |
2174 | When the first watcher gets started will libev actually register something |
1548 | with the kernel (thus it coexists with your own signal handlers as long |
2175 | with the kernel (thus it coexists with your own signal handlers as long as |
1549 | as you don't register any with libev). Similarly, when the last signal |
2176 | you don't register any with libev for the same signal). |
1550 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1551 | SIG_DFL (regardless of what it was set to before). |
|
|
1552 | |
2177 | |
1553 | If possible and supported, libev will install its handlers with |
2178 | If possible and supported, libev will install its handlers with |
1554 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2179 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1555 | interrupted. If you have a problem with system calls getting interrupted by |
2180 | not be unduly interrupted. If you have a problem with system calls getting |
1556 | signals you can block all signals in an C<ev_check> watcher and unblock |
2181 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1557 | them in an C<ev_prepare> watcher. |
2182 | and unblock them in an C<ev_prepare> watcher. |
|
|
2183 | |
|
|
2184 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2185 | |
|
|
2186 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2187 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2188 | stopping it again), that is, libev might or might not block the signal, |
|
|
2189 | and might or might not set or restore the installed signal handler. |
|
|
2190 | |
|
|
2191 | While this does not matter for the signal disposition (libev never |
|
|
2192 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2193 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2194 | certain signals to be blocked. |
|
|
2195 | |
|
|
2196 | This means that before calling C<exec> (from the child) you should reset |
|
|
2197 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2198 | choice usually). |
|
|
2199 | |
|
|
2200 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2201 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2202 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2203 | |
|
|
2204 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2205 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2206 | the window of opportunity for problems, it will not go away, as libev |
|
|
2207 | I<has> to modify the signal mask, at least temporarily. |
|
|
2208 | |
|
|
2209 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2210 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2211 | is not a libev-specific thing, this is true for most event libraries. |
1558 | |
2212 | |
1559 | =head3 Watcher-Specific Functions and Data Members |
2213 | =head3 Watcher-Specific Functions and Data Members |
1560 | |
2214 | |
1561 | =over 4 |
2215 | =over 4 |
1562 | |
2216 | |
… | |
… | |
1573 | |
2227 | |
1574 | =back |
2228 | =back |
1575 | |
2229 | |
1576 | =head3 Examples |
2230 | =head3 Examples |
1577 | |
2231 | |
1578 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2232 | Example: Try to exit cleanly on SIGINT. |
1579 | |
2233 | |
1580 | static void |
2234 | static void |
1581 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2235 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1582 | { |
2236 | { |
1583 | ev_unloop (loop, EVUNLOOP_ALL); |
2237 | ev_unloop (loop, EVUNLOOP_ALL); |
1584 | } |
2238 | } |
1585 | |
2239 | |
1586 | struct ev_signal signal_watcher; |
2240 | ev_signal signal_watcher; |
1587 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2241 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1588 | ev_signal_start (loop, &sigint_cb); |
2242 | ev_signal_start (loop, &signal_watcher); |
1589 | |
2243 | |
1590 | |
2244 | |
1591 | =head2 C<ev_child> - watch out for process status changes |
2245 | =head2 C<ev_child> - watch out for process status changes |
1592 | |
2246 | |
1593 | Child watchers trigger when your process receives a SIGCHLD in response to |
2247 | Child watchers trigger when your process receives a SIGCHLD in response to |
1594 | some child status changes (most typically when a child of yours dies). It |
2248 | some child status changes (most typically when a child of yours dies or |
1595 | is permissible to install a child watcher I<after> the child has been |
2249 | exits). It is permissible to install a child watcher I<after> the child |
1596 | forked (which implies it might have already exited), as long as the event |
2250 | has been forked (which implies it might have already exited), as long |
1597 | loop isn't entered (or is continued from a watcher). |
2251 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2252 | forking and then immediately registering a watcher for the child is fine, |
|
|
2253 | but forking and registering a watcher a few event loop iterations later or |
|
|
2254 | in the next callback invocation is not. |
1598 | |
2255 | |
1599 | Only the default event loop is capable of handling signals, and therefore |
2256 | Only the default event loop is capable of handling signals, and therefore |
1600 | you can only register child watchers in the default event loop. |
2257 | you can only register child watchers in the default event loop. |
1601 | |
2258 | |
|
|
2259 | Due to some design glitches inside libev, child watchers will always be |
|
|
2260 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2261 | libev) |
|
|
2262 | |
1602 | =head3 Process Interaction |
2263 | =head3 Process Interaction |
1603 | |
2264 | |
1604 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2265 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1605 | initialised. This is necessary to guarantee proper behaviour even if |
2266 | initialised. This is necessary to guarantee proper behaviour even if the |
1606 | the first child watcher is started after the child exits. The occurrence |
2267 | first child watcher is started after the child exits. The occurrence |
1607 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2268 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1608 | synchronously as part of the event loop processing. Libev always reaps all |
2269 | synchronously as part of the event loop processing. Libev always reaps all |
1609 | children, even ones not watched. |
2270 | children, even ones not watched. |
1610 | |
2271 | |
1611 | =head3 Overriding the Built-In Processing |
2272 | =head3 Overriding the Built-In Processing |
… | |
… | |
1621 | =head3 Stopping the Child Watcher |
2282 | =head3 Stopping the Child Watcher |
1622 | |
2283 | |
1623 | Currently, the child watcher never gets stopped, even when the |
2284 | Currently, the child watcher never gets stopped, even when the |
1624 | child terminates, so normally one needs to stop the watcher in the |
2285 | child terminates, so normally one needs to stop the watcher in the |
1625 | callback. Future versions of libev might stop the watcher automatically |
2286 | callback. Future versions of libev might stop the watcher automatically |
1626 | when a child exit is detected. |
2287 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2288 | problem). |
1627 | |
2289 | |
1628 | =head3 Watcher-Specific Functions and Data Members |
2290 | =head3 Watcher-Specific Functions and Data Members |
1629 | |
2291 | |
1630 | =over 4 |
2292 | =over 4 |
1631 | |
2293 | |
… | |
… | |
1663 | its completion. |
2325 | its completion. |
1664 | |
2326 | |
1665 | ev_child cw; |
2327 | ev_child cw; |
1666 | |
2328 | |
1667 | static void |
2329 | static void |
1668 | child_cb (EV_P_ struct ev_child *w, int revents) |
2330 | child_cb (EV_P_ ev_child *w, int revents) |
1669 | { |
2331 | { |
1670 | ev_child_stop (EV_A_ w); |
2332 | ev_child_stop (EV_A_ w); |
1671 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2333 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1672 | } |
2334 | } |
1673 | |
2335 | |
… | |
… | |
1688 | |
2350 | |
1689 | |
2351 | |
1690 | =head2 C<ev_stat> - did the file attributes just change? |
2352 | =head2 C<ev_stat> - did the file attributes just change? |
1691 | |
2353 | |
1692 | This watches a file system path for attribute changes. That is, it calls |
2354 | This watches a file system path for attribute changes. That is, it calls |
1693 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2355 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1694 | compared to the last time, invoking the callback if it did. |
2356 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2357 | it did. |
1695 | |
2358 | |
1696 | The path does not need to exist: changing from "path exists" to "path does |
2359 | The path does not need to exist: changing from "path exists" to "path does |
1697 | not exist" is a status change like any other. The condition "path does |
2360 | not exist" is a status change like any other. The condition "path does not |
1698 | not exist" is signified by the C<st_nlink> field being zero (which is |
2361 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1699 | otherwise always forced to be at least one) and all the other fields of |
2362 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1700 | the stat buffer having unspecified contents. |
2363 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2364 | contents. |
1701 | |
2365 | |
1702 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2366 | The path I<must not> end in a slash or contain special components such as |
|
|
2367 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1703 | relative and your working directory changes, the behaviour is undefined. |
2368 | your working directory changes, then the behaviour is undefined. |
1704 | |
2369 | |
1705 | Since there is no standard to do this, the portable implementation simply |
2370 | Since there is no portable change notification interface available, the |
1706 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2371 | portable implementation simply calls C<stat(2)> regularly on the path |
1707 | can specify a recommended polling interval for this case. If you specify |
2372 | to see if it changed somehow. You can specify a recommended polling |
1708 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2373 | interval for this case. If you specify a polling interval of C<0> (highly |
1709 | unspecified default> value will be used (which you can expect to be around |
2374 | recommended!) then a I<suitable, unspecified default> value will be used |
1710 | five seconds, although this might change dynamically). Libev will also |
2375 | (which you can expect to be around five seconds, although this might |
1711 | impose a minimum interval which is currently around C<0.1>, but thats |
2376 | change dynamically). Libev will also impose a minimum interval which is |
1712 | usually overkill. |
2377 | currently around C<0.1>, but that's usually overkill. |
1713 | |
2378 | |
1714 | This watcher type is not meant for massive numbers of stat watchers, |
2379 | This watcher type is not meant for massive numbers of stat watchers, |
1715 | as even with OS-supported change notifications, this can be |
2380 | as even with OS-supported change notifications, this can be |
1716 | resource-intensive. |
2381 | resource-intensive. |
1717 | |
2382 | |
1718 | At the time of this writing, only the Linux inotify interface is |
2383 | At the time of this writing, the only OS-specific interface implemented |
1719 | implemented (implementing kqueue support is left as an exercise for the |
2384 | is the Linux inotify interface (implementing kqueue support is left as an |
1720 | reader, note, however, that the author sees no way of implementing ev_stat |
2385 | exercise for the reader. Note, however, that the author sees no way of |
1721 | semantics with kqueue). Inotify will be used to give hints only and should |
2386 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1722 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1723 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1724 | but changes are usually detected immediately, and if the file exists there |
|
|
1725 | will be no polling. |
|
|
1726 | |
2387 | |
1727 | =head3 ABI Issues (Largefile Support) |
2388 | =head3 ABI Issues (Largefile Support) |
1728 | |
2389 | |
1729 | Libev by default (unless the user overrides this) uses the default |
2390 | Libev by default (unless the user overrides this) uses the default |
1730 | compilation environment, which means that on systems with large file |
2391 | compilation environment, which means that on systems with large file |
1731 | support disabled by default, you get the 32 bit version of the stat |
2392 | support disabled by default, you get the 32 bit version of the stat |
1732 | structure. When using the library from programs that change the ABI to |
2393 | structure. When using the library from programs that change the ABI to |
1733 | use 64 bit file offsets the programs will fail. In that case you have to |
2394 | use 64 bit file offsets the programs will fail. In that case you have to |
1734 | compile libev with the same flags to get binary compatibility. This is |
2395 | compile libev with the same flags to get binary compatibility. This is |
1735 | obviously the case with any flags that change the ABI, but the problem is |
2396 | obviously the case with any flags that change the ABI, but the problem is |
1736 | most noticeably disabled with ev_stat and large file support. |
2397 | most noticeably displayed with ev_stat and large file support. |
1737 | |
2398 | |
1738 | The solution for this is to lobby your distribution maker to make large |
2399 | The solution for this is to lobby your distribution maker to make large |
1739 | file interfaces available by default (as e.g. FreeBSD does) and not |
2400 | file interfaces available by default (as e.g. FreeBSD does) and not |
1740 | optional. Libev cannot simply switch on large file support because it has |
2401 | optional. Libev cannot simply switch on large file support because it has |
1741 | to exchange stat structures with application programs compiled using the |
2402 | to exchange stat structures with application programs compiled using the |
1742 | default compilation environment. |
2403 | default compilation environment. |
1743 | |
2404 | |
1744 | =head3 Inotify |
2405 | =head3 Inotify and Kqueue |
1745 | |
2406 | |
1746 | When C<inotify (7)> support has been compiled into libev (generally only |
2407 | When C<inotify (7)> support has been compiled into libev and present at |
1747 | available on Linux) and present at runtime, it will be used to speed up |
2408 | runtime, it will be used to speed up change detection where possible. The |
1748 | change detection where possible. The inotify descriptor will be created lazily |
2409 | inotify descriptor will be created lazily when the first C<ev_stat> |
1749 | when the first C<ev_stat> watcher is being started. |
2410 | watcher is being started. |
1750 | |
2411 | |
1751 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2412 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1752 | except that changes might be detected earlier, and in some cases, to avoid |
2413 | except that changes might be detected earlier, and in some cases, to avoid |
1753 | making regular C<stat> calls. Even in the presence of inotify support |
2414 | making regular C<stat> calls. Even in the presence of inotify support |
1754 | there are many cases where libev has to resort to regular C<stat> polling. |
2415 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2416 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2417 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2418 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2419 | xfs are fully working) libev usually gets away without polling. |
1755 | |
2420 | |
1756 | (There is no support for kqueue, as apparently it cannot be used to |
2421 | There is no support for kqueue, as apparently it cannot be used to |
1757 | implement this functionality, due to the requirement of having a file |
2422 | implement this functionality, due to the requirement of having a file |
1758 | descriptor open on the object at all times). |
2423 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2424 | etc. is difficult. |
|
|
2425 | |
|
|
2426 | =head3 C<stat ()> is a synchronous operation |
|
|
2427 | |
|
|
2428 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2429 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2430 | ()>, which is a synchronous operation. |
|
|
2431 | |
|
|
2432 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2433 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2434 | as the path data is usually in memory already (except when starting the |
|
|
2435 | watcher). |
|
|
2436 | |
|
|
2437 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2438 | time due to network issues, and even under good conditions, a stat call |
|
|
2439 | often takes multiple milliseconds. |
|
|
2440 | |
|
|
2441 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2442 | paths, although this is fully supported by libev. |
1759 | |
2443 | |
1760 | =head3 The special problem of stat time resolution |
2444 | =head3 The special problem of stat time resolution |
1761 | |
2445 | |
1762 | The C<stat ()> system call only supports full-second resolution portably, and |
2446 | The C<stat ()> system call only supports full-second resolution portably, |
1763 | even on systems where the resolution is higher, many file systems still |
2447 | and even on systems where the resolution is higher, most file systems |
1764 | only support whole seconds. |
2448 | still only support whole seconds. |
1765 | |
2449 | |
1766 | That means that, if the time is the only thing that changes, you can |
2450 | That means that, if the time is the only thing that changes, you can |
1767 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2451 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1768 | calls your callback, which does something. When there is another update |
2452 | calls your callback, which does something. When there is another update |
1769 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2453 | within the same second, C<ev_stat> will be unable to detect unless the |
1770 | data does not change. |
2454 | stat data does change in other ways (e.g. file size). |
1771 | |
2455 | |
1772 | The solution to this is to delay acting on a change for slightly more |
2456 | The solution to this is to delay acting on a change for slightly more |
1773 | than a second (or till slightly after the next full second boundary), using |
2457 | than a second (or till slightly after the next full second boundary), using |
1774 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2458 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1775 | ev_timer_again (loop, w)>). |
2459 | ev_timer_again (loop, w)>). |
… | |
… | |
1795 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2479 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1796 | be detected and should normally be specified as C<0> to let libev choose |
2480 | be detected and should normally be specified as C<0> to let libev choose |
1797 | a suitable value. The memory pointed to by C<path> must point to the same |
2481 | a suitable value. The memory pointed to by C<path> must point to the same |
1798 | path for as long as the watcher is active. |
2482 | path for as long as the watcher is active. |
1799 | |
2483 | |
1800 | The callback will receive C<EV_STAT> when a change was detected, relative |
2484 | The callback will receive an C<EV_STAT> event when a change was detected, |
1801 | to the attributes at the time the watcher was started (or the last change |
2485 | relative to the attributes at the time the watcher was started (or the |
1802 | was detected). |
2486 | last change was detected). |
1803 | |
2487 | |
1804 | =item ev_stat_stat (loop, ev_stat *) |
2488 | =item ev_stat_stat (loop, ev_stat *) |
1805 | |
2489 | |
1806 | Updates the stat buffer immediately with new values. If you change the |
2490 | Updates the stat buffer immediately with new values. If you change the |
1807 | watched path in your callback, you could call this function to avoid |
2491 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1890 | |
2574 | |
1891 | |
2575 | |
1892 | =head2 C<ev_idle> - when you've got nothing better to do... |
2576 | =head2 C<ev_idle> - when you've got nothing better to do... |
1893 | |
2577 | |
1894 | Idle watchers trigger events when no other events of the same or higher |
2578 | Idle watchers trigger events when no other events of the same or higher |
1895 | priority are pending (prepare, check and other idle watchers do not |
2579 | priority are pending (prepare, check and other idle watchers do not count |
1896 | count). |
2580 | as receiving "events"). |
1897 | |
2581 | |
1898 | That is, as long as your process is busy handling sockets or timeouts |
2582 | That is, as long as your process is busy handling sockets or timeouts |
1899 | (or even signals, imagine) of the same or higher priority it will not be |
2583 | (or even signals, imagine) of the same or higher priority it will not be |
1900 | triggered. But when your process is idle (or only lower-priority watchers |
2584 | triggered. But when your process is idle (or only lower-priority watchers |
1901 | are pending), the idle watchers are being called once per event loop |
2585 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1912 | |
2596 | |
1913 | =head3 Watcher-Specific Functions and Data Members |
2597 | =head3 Watcher-Specific Functions and Data Members |
1914 | |
2598 | |
1915 | =over 4 |
2599 | =over 4 |
1916 | |
2600 | |
1917 | =item ev_idle_init (ev_signal *, callback) |
2601 | =item ev_idle_init (ev_idle *, callback) |
1918 | |
2602 | |
1919 | Initialises and configures the idle watcher - it has no parameters of any |
2603 | Initialises and configures the idle watcher - it has no parameters of any |
1920 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2604 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1921 | believe me. |
2605 | believe me. |
1922 | |
2606 | |
… | |
… | |
1926 | |
2610 | |
1927 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2611 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1928 | callback, free it. Also, use no error checking, as usual. |
2612 | callback, free it. Also, use no error checking, as usual. |
1929 | |
2613 | |
1930 | static void |
2614 | static void |
1931 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2615 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1932 | { |
2616 | { |
1933 | free (w); |
2617 | free (w); |
1934 | // now do something you wanted to do when the program has |
2618 | // now do something you wanted to do when the program has |
1935 | // no longer anything immediate to do. |
2619 | // no longer anything immediate to do. |
1936 | } |
2620 | } |
1937 | |
2621 | |
1938 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2622 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1939 | ev_idle_init (idle_watcher, idle_cb); |
2623 | ev_idle_init (idle_watcher, idle_cb); |
1940 | ev_idle_start (loop, idle_cb); |
2624 | ev_idle_start (loop, idle_watcher); |
1941 | |
2625 | |
1942 | |
2626 | |
1943 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2627 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1944 | |
2628 | |
1945 | Prepare and check watchers are usually (but not always) used in tandem: |
2629 | Prepare and check watchers are usually (but not always) used in pairs: |
1946 | prepare watchers get invoked before the process blocks and check watchers |
2630 | prepare watchers get invoked before the process blocks and check watchers |
1947 | afterwards. |
2631 | afterwards. |
1948 | |
2632 | |
1949 | You I<must not> call C<ev_loop> or similar functions that enter |
2633 | You I<must not> call C<ev_loop> or similar functions that enter |
1950 | the current event loop from either C<ev_prepare> or C<ev_check> |
2634 | the current event loop from either C<ev_prepare> or C<ev_check> |
… | |
… | |
1953 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2637 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1954 | C<ev_check> so if you have one watcher of each kind they will always be |
2638 | C<ev_check> so if you have one watcher of each kind they will always be |
1955 | called in pairs bracketing the blocking call. |
2639 | called in pairs bracketing the blocking call. |
1956 | |
2640 | |
1957 | Their main purpose is to integrate other event mechanisms into libev and |
2641 | Their main purpose is to integrate other event mechanisms into libev and |
1958 | their use is somewhat advanced. This could be used, for example, to track |
2642 | their use is somewhat advanced. They could be used, for example, to track |
1959 | variable changes, implement your own watchers, integrate net-snmp or a |
2643 | variable changes, implement your own watchers, integrate net-snmp or a |
1960 | coroutine library and lots more. They are also occasionally useful if |
2644 | coroutine library and lots more. They are also occasionally useful if |
1961 | you cache some data and want to flush it before blocking (for example, |
2645 | you cache some data and want to flush it before blocking (for example, |
1962 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2646 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1963 | watcher). |
2647 | watcher). |
1964 | |
2648 | |
1965 | This is done by examining in each prepare call which file descriptors need |
2649 | This is done by examining in each prepare call which file descriptors |
1966 | to be watched by the other library, registering C<ev_io> watchers for |
2650 | need to be watched by the other library, registering C<ev_io> watchers |
1967 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2651 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1968 | provide just this functionality). Then, in the check watcher you check for |
2652 | libraries provide exactly this functionality). Then, in the check watcher, |
1969 | any events that occurred (by checking the pending status of all watchers |
2653 | you check for any events that occurred (by checking the pending status |
1970 | and stopping them) and call back into the library. The I/O and timer |
2654 | of all watchers and stopping them) and call back into the library. The |
1971 | callbacks will never actually be called (but must be valid nevertheless, |
2655 | I/O and timer callbacks will never actually be called (but must be valid |
1972 | because you never know, you know?). |
2656 | nevertheless, because you never know, you know?). |
1973 | |
2657 | |
1974 | As another example, the Perl Coro module uses these hooks to integrate |
2658 | As another example, the Perl Coro module uses these hooks to integrate |
1975 | coroutines into libev programs, by yielding to other active coroutines |
2659 | coroutines into libev programs, by yielding to other active coroutines |
1976 | during each prepare and only letting the process block if no coroutines |
2660 | during each prepare and only letting the process block if no coroutines |
1977 | are ready to run (it's actually more complicated: it only runs coroutines |
2661 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1980 | loop from blocking if lower-priority coroutines are active, thus mapping |
2664 | loop from blocking if lower-priority coroutines are active, thus mapping |
1981 | low-priority coroutines to idle/background tasks). |
2665 | low-priority coroutines to idle/background tasks). |
1982 | |
2666 | |
1983 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2667 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1984 | priority, to ensure that they are being run before any other watchers |
2668 | priority, to ensure that they are being run before any other watchers |
|
|
2669 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2670 | |
1985 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2671 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1986 | too) should not activate ("feed") events into libev. While libev fully |
2672 | activate ("feed") events into libev. While libev fully supports this, they |
1987 | supports this, they might get executed before other C<ev_check> watchers |
2673 | might get executed before other C<ev_check> watchers did their job. As |
1988 | did their job. As C<ev_check> watchers are often used to embed other |
2674 | C<ev_check> watchers are often used to embed other (non-libev) event |
1989 | (non-libev) event loops those other event loops might be in an unusable |
2675 | loops those other event loops might be in an unusable state until their |
1990 | state until their C<ev_check> watcher ran (always remind yourself to |
2676 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1991 | coexist peacefully with others). |
2677 | others). |
1992 | |
2678 | |
1993 | =head3 Watcher-Specific Functions and Data Members |
2679 | =head3 Watcher-Specific Functions and Data Members |
1994 | |
2680 | |
1995 | =over 4 |
2681 | =over 4 |
1996 | |
2682 | |
… | |
… | |
1998 | |
2684 | |
1999 | =item ev_check_init (ev_check *, callback) |
2685 | =item ev_check_init (ev_check *, callback) |
2000 | |
2686 | |
2001 | Initialises and configures the prepare or check watcher - they have no |
2687 | Initialises and configures the prepare or check watcher - they have no |
2002 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2688 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2003 | macros, but using them is utterly, utterly and completely pointless. |
2689 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2690 | pointless. |
2004 | |
2691 | |
2005 | =back |
2692 | =back |
2006 | |
2693 | |
2007 | =head3 Examples |
2694 | =head3 Examples |
2008 | |
2695 | |
… | |
… | |
2021 | |
2708 | |
2022 | static ev_io iow [nfd]; |
2709 | static ev_io iow [nfd]; |
2023 | static ev_timer tw; |
2710 | static ev_timer tw; |
2024 | |
2711 | |
2025 | static void |
2712 | static void |
2026 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2713 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2027 | { |
2714 | { |
2028 | } |
2715 | } |
2029 | |
2716 | |
2030 | // create io watchers for each fd and a timer before blocking |
2717 | // create io watchers for each fd and a timer before blocking |
2031 | static void |
2718 | static void |
2032 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2719 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2033 | { |
2720 | { |
2034 | int timeout = 3600000; |
2721 | int timeout = 3600000; |
2035 | struct pollfd fds [nfd]; |
2722 | struct pollfd fds [nfd]; |
2036 | // actual code will need to loop here and realloc etc. |
2723 | // actual code will need to loop here and realloc etc. |
2037 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2724 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2038 | |
2725 | |
2039 | /* the callback is illegal, but won't be called as we stop during check */ |
2726 | /* the callback is illegal, but won't be called as we stop during check */ |
2040 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2727 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2041 | ev_timer_start (loop, &tw); |
2728 | ev_timer_start (loop, &tw); |
2042 | |
2729 | |
2043 | // create one ev_io per pollfd |
2730 | // create one ev_io per pollfd |
2044 | for (int i = 0; i < nfd; ++i) |
2731 | for (int i = 0; i < nfd; ++i) |
2045 | { |
2732 | { |
… | |
… | |
2052 | } |
2739 | } |
2053 | } |
2740 | } |
2054 | |
2741 | |
2055 | // stop all watchers after blocking |
2742 | // stop all watchers after blocking |
2056 | static void |
2743 | static void |
2057 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2744 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2058 | { |
2745 | { |
2059 | ev_timer_stop (loop, &tw); |
2746 | ev_timer_stop (loop, &tw); |
2060 | |
2747 | |
2061 | for (int i = 0; i < nfd; ++i) |
2748 | for (int i = 0; i < nfd; ++i) |
2062 | { |
2749 | { |
… | |
… | |
2101 | } |
2788 | } |
2102 | |
2789 | |
2103 | // do not ever call adns_afterpoll |
2790 | // do not ever call adns_afterpoll |
2104 | |
2791 | |
2105 | Method 4: Do not use a prepare or check watcher because the module you |
2792 | Method 4: Do not use a prepare or check watcher because the module you |
2106 | want to embed is too inflexible to support it. Instead, you can override |
2793 | want to embed is not flexible enough to support it. Instead, you can |
2107 | their poll function. The drawback with this solution is that the main |
2794 | override their poll function. The drawback with this solution is that the |
2108 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2795 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2109 | this. |
2796 | this approach, effectively embedding EV as a client into the horrible |
|
|
2797 | libglib event loop. |
2110 | |
2798 | |
2111 | static gint |
2799 | static gint |
2112 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2800 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2113 | { |
2801 | { |
2114 | int got_events = 0; |
2802 | int got_events = 0; |
… | |
… | |
2145 | prioritise I/O. |
2833 | prioritise I/O. |
2146 | |
2834 | |
2147 | As an example for a bug workaround, the kqueue backend might only support |
2835 | As an example for a bug workaround, the kqueue backend might only support |
2148 | sockets on some platform, so it is unusable as generic backend, but you |
2836 | sockets on some platform, so it is unusable as generic backend, but you |
2149 | still want to make use of it because you have many sockets and it scales |
2837 | still want to make use of it because you have many sockets and it scales |
2150 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2838 | so nicely. In this case, you would create a kqueue-based loop and embed |
2151 | into your default loop (which might use e.g. poll). Overall operation will |
2839 | it into your default loop (which might use e.g. poll). Overall operation |
2152 | be a bit slower because first libev has to poll and then call kevent, but |
2840 | will be a bit slower because first libev has to call C<poll> and then |
2153 | at least you can use both at what they are best. |
2841 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2842 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2154 | |
2843 | |
2155 | As for prioritising I/O: rarely you have the case where some fds have |
2844 | As for prioritising I/O: under rare circumstances you have the case where |
2156 | to be watched and handled very quickly (with low latency), and even |
2845 | some fds have to be watched and handled very quickly (with low latency), |
2157 | priorities and idle watchers might have too much overhead. In this case |
2846 | and even priorities and idle watchers might have too much overhead. In |
2158 | you would put all the high priority stuff in one loop and all the rest in |
2847 | this case you would put all the high priority stuff in one loop and all |
2159 | a second one, and embed the second one in the first. |
2848 | the rest in a second one, and embed the second one in the first. |
2160 | |
2849 | |
2161 | As long as the watcher is active, the callback will be invoked every time |
2850 | As long as the watcher is active, the callback will be invoked every |
2162 | there might be events pending in the embedded loop. The callback must then |
2851 | time there might be events pending in the embedded loop. The callback |
2163 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2852 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2164 | their callbacks (you could also start an idle watcher to give the embedded |
2853 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2165 | loop strictly lower priority for example). You can also set the callback |
2854 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2166 | to C<0>, in which case the embed watcher will automatically execute the |
2855 | to give the embedded loop strictly lower priority for example). |
2167 | embedded loop sweep. |
|
|
2168 | |
2856 | |
2169 | As long as the watcher is started it will automatically handle events. The |
2857 | You can also set the callback to C<0>, in which case the embed watcher |
2170 | callback will be invoked whenever some events have been handled. You can |
2858 | will automatically execute the embedded loop sweep whenever necessary. |
2171 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2172 | interested in that. |
|
|
2173 | |
2859 | |
2174 | Also, there have not currently been made special provisions for forking: |
2860 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2175 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2861 | is active, i.e., the embedded loop will automatically be forked when the |
2176 | but you will also have to stop and restart any C<ev_embed> watchers |
2862 | embedding loop forks. In other cases, the user is responsible for calling |
2177 | yourself. |
2863 | C<ev_loop_fork> on the embedded loop. |
2178 | |
2864 | |
2179 | Unfortunately, not all backends are embeddable, only the ones returned by |
2865 | Unfortunately, not all backends are embeddable: only the ones returned by |
2180 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2866 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2181 | portable one. |
2867 | portable one. |
2182 | |
2868 | |
2183 | So when you want to use this feature you will always have to be prepared |
2869 | So when you want to use this feature you will always have to be prepared |
2184 | that you cannot get an embeddable loop. The recommended way to get around |
2870 | that you cannot get an embeddable loop. The recommended way to get around |
2185 | this is to have a separate variables for your embeddable loop, try to |
2871 | this is to have a separate variables for your embeddable loop, try to |
2186 | create it, and if that fails, use the normal loop for everything. |
2872 | create it, and if that fails, use the normal loop for everything. |
|
|
2873 | |
|
|
2874 | =head3 C<ev_embed> and fork |
|
|
2875 | |
|
|
2876 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2877 | automatically be applied to the embedded loop as well, so no special |
|
|
2878 | fork handling is required in that case. When the watcher is not running, |
|
|
2879 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2880 | as applicable. |
2187 | |
2881 | |
2188 | =head3 Watcher-Specific Functions and Data Members |
2882 | =head3 Watcher-Specific Functions and Data Members |
2189 | |
2883 | |
2190 | =over 4 |
2884 | =over 4 |
2191 | |
2885 | |
… | |
… | |
2219 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2913 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2220 | used). |
2914 | used). |
2221 | |
2915 | |
2222 | struct ev_loop *loop_hi = ev_default_init (0); |
2916 | struct ev_loop *loop_hi = ev_default_init (0); |
2223 | struct ev_loop *loop_lo = 0; |
2917 | struct ev_loop *loop_lo = 0; |
2224 | struct ev_embed embed; |
2918 | ev_embed embed; |
2225 | |
2919 | |
2226 | // see if there is a chance of getting one that works |
2920 | // see if there is a chance of getting one that works |
2227 | // (remember that a flags value of 0 means autodetection) |
2921 | // (remember that a flags value of 0 means autodetection) |
2228 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2922 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2229 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2923 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2243 | kqueue implementation). Store the kqueue/socket-only event loop in |
2937 | kqueue implementation). Store the kqueue/socket-only event loop in |
2244 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2938 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2245 | |
2939 | |
2246 | struct ev_loop *loop = ev_default_init (0); |
2940 | struct ev_loop *loop = ev_default_init (0); |
2247 | struct ev_loop *loop_socket = 0; |
2941 | struct ev_loop *loop_socket = 0; |
2248 | struct ev_embed embed; |
2942 | ev_embed embed; |
2249 | |
2943 | |
2250 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2944 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2251 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2945 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2252 | { |
2946 | { |
2253 | ev_embed_init (&embed, 0, loop_socket); |
2947 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2268 | event loop blocks next and before C<ev_check> watchers are being called, |
2962 | event loop blocks next and before C<ev_check> watchers are being called, |
2269 | and only in the child after the fork. If whoever good citizen calling |
2963 | and only in the child after the fork. If whoever good citizen calling |
2270 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2964 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2271 | handlers will be invoked, too, of course. |
2965 | handlers will be invoked, too, of course. |
2272 | |
2966 | |
|
|
2967 | =head3 The special problem of life after fork - how is it possible? |
|
|
2968 | |
|
|
2969 | Most uses of C<fork()> consist of forking, then some simple calls to ste |
|
|
2970 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2971 | sequence should be handled by libev without any problems. |
|
|
2972 | |
|
|
2973 | This changes when the application actually wants to do event handling |
|
|
2974 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2975 | fork. |
|
|
2976 | |
|
|
2977 | The default mode of operation (for libev, with application help to detect |
|
|
2978 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2979 | when I<either> the parent I<or> the child process continues. |
|
|
2980 | |
|
|
2981 | When both processes want to continue using libev, then this is usually the |
|
|
2982 | wrong result. In that case, usually one process (typically the parent) is |
|
|
2983 | supposed to continue with all watchers in place as before, while the other |
|
|
2984 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
2985 | |
|
|
2986 | The cleanest and most efficient way to achieve that with libev is to |
|
|
2987 | simply create a new event loop, which of course will be "empty", and |
|
|
2988 | use that for new watchers. This has the advantage of not touching more |
|
|
2989 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
2990 | disadvantage of having to use multiple event loops (which do not support |
|
|
2991 | signal watchers). |
|
|
2992 | |
|
|
2993 | When this is not possible, or you want to use the default loop for |
|
|
2994 | other reasons, then in the process that wants to start "fresh", call |
|
|
2995 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
2996 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
2997 | have to be careful not to execute code that modifies those watchers. Note |
|
|
2998 | also that in that case, you have to re-register any signal watchers. |
|
|
2999 | |
2273 | =head3 Watcher-Specific Functions and Data Members |
3000 | =head3 Watcher-Specific Functions and Data Members |
2274 | |
3001 | |
2275 | =over 4 |
3002 | =over 4 |
2276 | |
3003 | |
2277 | =item ev_fork_init (ev_signal *, callback) |
3004 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2306 | =head3 Queueing |
3033 | =head3 Queueing |
2307 | |
3034 | |
2308 | C<ev_async> does not support queueing of data in any way. The reason |
3035 | C<ev_async> does not support queueing of data in any way. The reason |
2309 | is that the author does not know of a simple (or any) algorithm for a |
3036 | is that the author does not know of a simple (or any) algorithm for a |
2310 | multiple-writer-single-reader queue that works in all cases and doesn't |
3037 | multiple-writer-single-reader queue that works in all cases and doesn't |
2311 | need elaborate support such as pthreads. |
3038 | need elaborate support such as pthreads or unportable memory access |
|
|
3039 | semantics. |
2312 | |
3040 | |
2313 | That means that if you want to queue data, you have to provide your own |
3041 | That means that if you want to queue data, you have to provide your own |
2314 | queue. But at least I can tell you would implement locking around your |
3042 | queue. But at least I can tell you how to implement locking around your |
2315 | queue: |
3043 | queue: |
2316 | |
3044 | |
2317 | =over 4 |
3045 | =over 4 |
2318 | |
3046 | |
2319 | =item queueing from a signal handler context |
3047 | =item queueing from a signal handler context |
2320 | |
3048 | |
2321 | To implement race-free queueing, you simply add to the queue in the signal |
3049 | To implement race-free queueing, you simply add to the queue in the signal |
2322 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3050 | handler but you block the signal handler in the watcher callback. Here is |
2323 | some fictitious SIGUSR1 handler: |
3051 | an example that does that for some fictitious SIGUSR1 handler: |
2324 | |
3052 | |
2325 | static ev_async mysig; |
3053 | static ev_async mysig; |
2326 | |
3054 | |
2327 | static void |
3055 | static void |
2328 | sigusr1_handler (void) |
3056 | sigusr1_handler (void) |
… | |
… | |
2394 | =over 4 |
3122 | =over 4 |
2395 | |
3123 | |
2396 | =item ev_async_init (ev_async *, callback) |
3124 | =item ev_async_init (ev_async *, callback) |
2397 | |
3125 | |
2398 | Initialises and configures the async watcher - it has no parameters of any |
3126 | Initialises and configures the async watcher - it has no parameters of any |
2399 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3127 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2400 | believe me. |
3128 | trust me. |
2401 | |
3129 | |
2402 | =item ev_async_send (loop, ev_async *) |
3130 | =item ev_async_send (loop, ev_async *) |
2403 | |
3131 | |
2404 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3132 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2405 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3133 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2406 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3134 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2407 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3135 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2408 | section below on what exactly this means). |
3136 | section below on what exactly this means). |
2409 | |
3137 | |
|
|
3138 | Note that, as with other watchers in libev, multiple events might get |
|
|
3139 | compressed into a single callback invocation (another way to look at this |
|
|
3140 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3141 | reset when the event loop detects that). |
|
|
3142 | |
2410 | This call incurs the overhead of a system call only once per loop iteration, |
3143 | This call incurs the overhead of a system call only once per event loop |
2411 | so while the overhead might be noticeable, it doesn't apply to repeated |
3144 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2412 | calls to C<ev_async_send>. |
3145 | repeated calls to C<ev_async_send> for the same event loop. |
2413 | |
3146 | |
2414 | =item bool = ev_async_pending (ev_async *) |
3147 | =item bool = ev_async_pending (ev_async *) |
2415 | |
3148 | |
2416 | Returns a non-zero value when C<ev_async_send> has been called on the |
3149 | Returns a non-zero value when C<ev_async_send> has been called on the |
2417 | watcher but the event has not yet been processed (or even noted) by the |
3150 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2420 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3153 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2421 | the loop iterates next and checks for the watcher to have become active, |
3154 | the loop iterates next and checks for the watcher to have become active, |
2422 | it will reset the flag again. C<ev_async_pending> can be used to very |
3155 | it will reset the flag again. C<ev_async_pending> can be used to very |
2423 | quickly check whether invoking the loop might be a good idea. |
3156 | quickly check whether invoking the loop might be a good idea. |
2424 | |
3157 | |
2425 | Not that this does I<not> check whether the watcher itself is pending, only |
3158 | Not that this does I<not> check whether the watcher itself is pending, |
2426 | whether it has been requested to make this watcher pending. |
3159 | only whether it has been requested to make this watcher pending: there |
|
|
3160 | is a time window between the event loop checking and resetting the async |
|
|
3161 | notification, and the callback being invoked. |
2427 | |
3162 | |
2428 | =back |
3163 | =back |
2429 | |
3164 | |
2430 | |
3165 | |
2431 | =head1 OTHER FUNCTIONS |
3166 | =head1 OTHER FUNCTIONS |
… | |
… | |
2435 | =over 4 |
3170 | =over 4 |
2436 | |
3171 | |
2437 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3172 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2438 | |
3173 | |
2439 | This function combines a simple timer and an I/O watcher, calls your |
3174 | This function combines a simple timer and an I/O watcher, calls your |
2440 | callback on whichever event happens first and automatically stop both |
3175 | callback on whichever event happens first and automatically stops both |
2441 | watchers. This is useful if you want to wait for a single event on an fd |
3176 | watchers. This is useful if you want to wait for a single event on an fd |
2442 | or timeout without having to allocate/configure/start/stop/free one or |
3177 | or timeout without having to allocate/configure/start/stop/free one or |
2443 | more watchers yourself. |
3178 | more watchers yourself. |
2444 | |
3179 | |
2445 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3180 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2446 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3181 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2447 | C<events> set will be created and started. |
3182 | the given C<fd> and C<events> set will be created and started. |
2448 | |
3183 | |
2449 | If C<timeout> is less than 0, then no timeout watcher will be |
3184 | If C<timeout> is less than 0, then no timeout watcher will be |
2450 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3185 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2451 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3186 | repeat = 0) will be started. C<0> is a valid timeout. |
2452 | dubious value. |
|
|
2453 | |
3187 | |
2454 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3188 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2455 | passed an C<revents> set like normal event callbacks (a combination of |
3189 | passed an C<revents> set like normal event callbacks (a combination of |
2456 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3190 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2457 | value passed to C<ev_once>: |
3191 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3192 | a timeout and an io event at the same time - you probably should give io |
|
|
3193 | events precedence. |
|
|
3194 | |
|
|
3195 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2458 | |
3196 | |
2459 | static void stdin_ready (int revents, void *arg) |
3197 | static void stdin_ready (int revents, void *arg) |
2460 | { |
3198 | { |
|
|
3199 | if (revents & EV_READ) |
|
|
3200 | /* stdin might have data for us, joy! */; |
2461 | if (revents & EV_TIMEOUT) |
3201 | else if (revents & EV_TIMER) |
2462 | /* doh, nothing entered */; |
3202 | /* doh, nothing entered */; |
2463 | else if (revents & EV_READ) |
|
|
2464 | /* stdin might have data for us, joy! */; |
|
|
2465 | } |
3203 | } |
2466 | |
3204 | |
2467 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3205 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2468 | |
3206 | |
2469 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2470 | |
|
|
2471 | Feeds the given event set into the event loop, as if the specified event |
|
|
2472 | had happened for the specified watcher (which must be a pointer to an |
|
|
2473 | initialised but not necessarily started event watcher). |
|
|
2474 | |
|
|
2475 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3207 | =item ev_feed_fd_event (loop, int fd, int revents) |
2476 | |
3208 | |
2477 | Feed an event on the given fd, as if a file descriptor backend detected |
3209 | Feed an event on the given fd, as if a file descriptor backend detected |
2478 | the given events it. |
3210 | the given events it. |
2479 | |
3211 | |
2480 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3212 | =item ev_feed_signal_event (loop, int signum) |
2481 | |
3213 | |
2482 | Feed an event as if the given signal occurred (C<loop> must be the default |
3214 | Feed an event as if the given signal occurred (C<loop> must be the default |
2483 | loop!). |
3215 | loop!). |
2484 | |
3216 | |
2485 | =back |
3217 | =back |
… | |
… | |
2565 | |
3297 | |
2566 | =over 4 |
3298 | =over 4 |
2567 | |
3299 | |
2568 | =item ev::TYPE::TYPE () |
3300 | =item ev::TYPE::TYPE () |
2569 | |
3301 | |
2570 | =item ev::TYPE::TYPE (struct ev_loop *) |
3302 | =item ev::TYPE::TYPE (loop) |
2571 | |
3303 | |
2572 | =item ev::TYPE::~TYPE |
3304 | =item ev::TYPE::~TYPE |
2573 | |
3305 | |
2574 | The constructor (optionally) takes an event loop to associate the watcher |
3306 | The constructor (optionally) takes an event loop to associate the watcher |
2575 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3307 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2607 | |
3339 | |
2608 | myclass obj; |
3340 | myclass obj; |
2609 | ev::io iow; |
3341 | ev::io iow; |
2610 | iow.set <myclass, &myclass::io_cb> (&obj); |
3342 | iow.set <myclass, &myclass::io_cb> (&obj); |
2611 | |
3343 | |
|
|
3344 | =item w->set (object *) |
|
|
3345 | |
|
|
3346 | This is an B<experimental> feature that might go away in a future version. |
|
|
3347 | |
|
|
3348 | This is a variation of a method callback - leaving out the method to call |
|
|
3349 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3350 | functor objects without having to manually specify the C<operator ()> all |
|
|
3351 | the time. Incidentally, you can then also leave out the template argument |
|
|
3352 | list. |
|
|
3353 | |
|
|
3354 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3355 | int revents)>. |
|
|
3356 | |
|
|
3357 | See the method-C<set> above for more details. |
|
|
3358 | |
|
|
3359 | Example: use a functor object as callback. |
|
|
3360 | |
|
|
3361 | struct myfunctor |
|
|
3362 | { |
|
|
3363 | void operator() (ev::io &w, int revents) |
|
|
3364 | { |
|
|
3365 | ... |
|
|
3366 | } |
|
|
3367 | } |
|
|
3368 | |
|
|
3369 | myfunctor f; |
|
|
3370 | |
|
|
3371 | ev::io w; |
|
|
3372 | w.set (&f); |
|
|
3373 | |
2612 | =item w->set<function> (void *data = 0) |
3374 | =item w->set<function> (void *data = 0) |
2613 | |
3375 | |
2614 | Also sets a callback, but uses a static method or plain function as |
3376 | Also sets a callback, but uses a static method or plain function as |
2615 | callback. The optional C<data> argument will be stored in the watcher's |
3377 | callback. The optional C<data> argument will be stored in the watcher's |
2616 | C<data> member and is free for you to use. |
3378 | C<data> member and is free for you to use. |
2617 | |
3379 | |
2618 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3380 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2619 | |
3381 | |
2620 | See the method-C<set> above for more details. |
3382 | See the method-C<set> above for more details. |
2621 | |
3383 | |
2622 | Example: |
3384 | Example: Use a plain function as callback. |
2623 | |
3385 | |
2624 | static void io_cb (ev::io &w, int revents) { } |
3386 | static void io_cb (ev::io &w, int revents) { } |
2625 | iow.set <io_cb> (); |
3387 | iow.set <io_cb> (); |
2626 | |
3388 | |
2627 | =item w->set (struct ev_loop *) |
3389 | =item w->set (loop) |
2628 | |
3390 | |
2629 | Associates a different C<struct ev_loop> with this watcher. You can only |
3391 | Associates a different C<struct ev_loop> with this watcher. You can only |
2630 | do this when the watcher is inactive (and not pending either). |
3392 | do this when the watcher is inactive (and not pending either). |
2631 | |
3393 | |
2632 | =item w->set ([arguments]) |
3394 | =item w->set ([arguments]) |
… | |
… | |
2665 | Example: Define a class with an IO and idle watcher, start one of them in |
3427 | Example: Define a class with an IO and idle watcher, start one of them in |
2666 | the constructor. |
3428 | the constructor. |
2667 | |
3429 | |
2668 | class myclass |
3430 | class myclass |
2669 | { |
3431 | { |
2670 | ev::io io; void io_cb (ev::io &w, int revents); |
3432 | ev::io io ; void io_cb (ev::io &w, int revents); |
2671 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3433 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2672 | |
3434 | |
2673 | myclass (int fd) |
3435 | myclass (int fd) |
2674 | { |
3436 | { |
2675 | io .set <myclass, &myclass::io_cb > (this); |
3437 | io .set <myclass, &myclass::io_cb > (this); |
2676 | idle.set <myclass, &myclass::idle_cb> (this); |
3438 | idle.set <myclass, &myclass::idle_cb> (this); |
… | |
… | |
2692 | =item Perl |
3454 | =item Perl |
2693 | |
3455 | |
2694 | The EV module implements the full libev API and is actually used to test |
3456 | The EV module implements the full libev API and is actually used to test |
2695 | libev. EV is developed together with libev. Apart from the EV core module, |
3457 | libev. EV is developed together with libev. Apart from the EV core module, |
2696 | there are additional modules that implement libev-compatible interfaces |
3458 | there are additional modules that implement libev-compatible interfaces |
2697 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3459 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2698 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3460 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3461 | and C<EV::Glib>). |
2699 | |
3462 | |
2700 | It can be found and installed via CPAN, its homepage is at |
3463 | It can be found and installed via CPAN, its homepage is at |
2701 | L<http://software.schmorp.de/pkg/EV>. |
3464 | L<http://software.schmorp.de/pkg/EV>. |
2702 | |
3465 | |
2703 | =item Python |
3466 | =item Python |
2704 | |
3467 | |
2705 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3468 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2706 | seems to be quite complete and well-documented. Note, however, that the |
3469 | seems to be quite complete and well-documented. |
2707 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2708 | for everybody else, and therefore, should never be applied in an installed |
|
|
2709 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2710 | libev). |
|
|
2711 | |
3470 | |
2712 | =item Ruby |
3471 | =item Ruby |
2713 | |
3472 | |
2714 | Tony Arcieri has written a ruby extension that offers access to a subset |
3473 | Tony Arcieri has written a ruby extension that offers access to a subset |
2715 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3474 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2716 | more on top of it. It can be found via gem servers. Its homepage is at |
3475 | more on top of it. It can be found via gem servers. Its homepage is at |
2717 | L<http://rev.rubyforge.org/>. |
3476 | L<http://rev.rubyforge.org/>. |
2718 | |
3477 | |
|
|
3478 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3479 | makes rev work even on mingw. |
|
|
3480 | |
|
|
3481 | =item Haskell |
|
|
3482 | |
|
|
3483 | A haskell binding to libev is available at |
|
|
3484 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3485 | |
2719 | =item D |
3486 | =item D |
2720 | |
3487 | |
2721 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3488 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2722 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3489 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3490 | |
|
|
3491 | =item Ocaml |
|
|
3492 | |
|
|
3493 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3494 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3495 | |
|
|
3496 | =item Lua |
|
|
3497 | |
|
|
3498 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3499 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3500 | L<http://github.com/brimworks/lua-ev>. |
2723 | |
3501 | |
2724 | =back |
3502 | =back |
2725 | |
3503 | |
2726 | |
3504 | |
2727 | =head1 MACRO MAGIC |
3505 | =head1 MACRO MAGIC |
… | |
… | |
2828 | |
3606 | |
2829 | #define EV_STANDALONE 1 |
3607 | #define EV_STANDALONE 1 |
2830 | #include "ev.h" |
3608 | #include "ev.h" |
2831 | |
3609 | |
2832 | Both header files and implementation files can be compiled with a C++ |
3610 | Both header files and implementation files can be compiled with a C++ |
2833 | compiler (at least, thats a stated goal, and breakage will be treated |
3611 | compiler (at least, that's a stated goal, and breakage will be treated |
2834 | as a bug). |
3612 | as a bug). |
2835 | |
3613 | |
2836 | You need the following files in your source tree, or in a directory |
3614 | You need the following files in your source tree, or in a directory |
2837 | in your include path (e.g. in libev/ when using -Ilibev): |
3615 | in your include path (e.g. in libev/ when using -Ilibev): |
2838 | |
3616 | |
… | |
… | |
2881 | libev.m4 |
3659 | libev.m4 |
2882 | |
3660 | |
2883 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3661 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2884 | |
3662 | |
2885 | Libev can be configured via a variety of preprocessor symbols you have to |
3663 | Libev can be configured via a variety of preprocessor symbols you have to |
2886 | define before including any of its files. The default in the absence of |
3664 | define before including (or compiling) any of its files. The default in |
2887 | autoconf is noted for every option. |
3665 | the absence of autoconf is documented for every option. |
|
|
3666 | |
|
|
3667 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3668 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3669 | to redefine them before including F<ev.h> without breakign compatibility |
|
|
3670 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3671 | users of libev and the libev code itself must be compiled with compatible |
|
|
3672 | settings. |
2888 | |
3673 | |
2889 | =over 4 |
3674 | =over 4 |
2890 | |
3675 | |
2891 | =item EV_STANDALONE |
3676 | =item EV_STANDALONE (h) |
2892 | |
3677 | |
2893 | Must always be C<1> if you do not use autoconf configuration, which |
3678 | Must always be C<1> if you do not use autoconf configuration, which |
2894 | keeps libev from including F<config.h>, and it also defines dummy |
3679 | keeps libev from including F<config.h>, and it also defines dummy |
2895 | implementations for some libevent functions (such as logging, which is not |
3680 | implementations for some libevent functions (such as logging, which is not |
2896 | supported). It will also not define any of the structs usually found in |
3681 | supported). It will also not define any of the structs usually found in |
2897 | F<event.h> that are not directly supported by the libev core alone. |
3682 | F<event.h> that are not directly supported by the libev core alone. |
2898 | |
3683 | |
|
|
3684 | In standalone mode, libev will still try to automatically deduce the |
|
|
3685 | configuration, but has to be more conservative. |
|
|
3686 | |
2899 | =item EV_USE_MONOTONIC |
3687 | =item EV_USE_MONOTONIC |
2900 | |
3688 | |
2901 | If defined to be C<1>, libev will try to detect the availability of the |
3689 | If defined to be C<1>, libev will try to detect the availability of the |
2902 | monotonic clock option at both compile time and runtime. Otherwise no use |
3690 | monotonic clock option at both compile time and runtime. Otherwise no |
2903 | of the monotonic clock option will be attempted. If you enable this, you |
3691 | use of the monotonic clock option will be attempted. If you enable this, |
2904 | usually have to link against librt or something similar. Enabling it when |
3692 | you usually have to link against librt or something similar. Enabling it |
2905 | the functionality isn't available is safe, though, although you have |
3693 | when the functionality isn't available is safe, though, although you have |
2906 | to make sure you link against any libraries where the C<clock_gettime> |
3694 | to make sure you link against any libraries where the C<clock_gettime> |
2907 | function is hiding in (often F<-lrt>). |
3695 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2908 | |
3696 | |
2909 | =item EV_USE_REALTIME |
3697 | =item EV_USE_REALTIME |
2910 | |
3698 | |
2911 | If defined to be C<1>, libev will try to detect the availability of the |
3699 | If defined to be C<1>, libev will try to detect the availability of the |
2912 | real-time clock option at compile time (and assume its availability at |
3700 | real-time clock option at compile time (and assume its availability |
2913 | runtime if successful). Otherwise no use of the real-time clock option will |
3701 | at runtime if successful). Otherwise no use of the real-time clock |
2914 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3702 | option will be attempted. This effectively replaces C<gettimeofday> |
2915 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3703 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2916 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3704 | correctness. See the note about libraries in the description of |
|
|
3705 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3706 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3707 | |
|
|
3708 | =item EV_USE_CLOCK_SYSCALL |
|
|
3709 | |
|
|
3710 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3711 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3712 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3713 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3714 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3715 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3716 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3717 | higher, as it simplifies linking (no need for C<-lrt>). |
2917 | |
3718 | |
2918 | =item EV_USE_NANOSLEEP |
3719 | =item EV_USE_NANOSLEEP |
2919 | |
3720 | |
2920 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3721 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2921 | and will use it for delays. Otherwise it will use C<select ()>. |
3722 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2937 | |
3738 | |
2938 | =item EV_SELECT_USE_FD_SET |
3739 | =item EV_SELECT_USE_FD_SET |
2939 | |
3740 | |
2940 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3741 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2941 | structure. This is useful if libev doesn't compile due to a missing |
3742 | structure. This is useful if libev doesn't compile due to a missing |
2942 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3743 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2943 | exotic systems. This usually limits the range of file descriptors to some |
3744 | on exotic systems. This usually limits the range of file descriptors to |
2944 | low limit such as 1024 or might have other limitations (winsocket only |
3745 | some low limit such as 1024 or might have other limitations (winsocket |
2945 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3746 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2946 | influence the size of the C<fd_set> used. |
3747 | configures the maximum size of the C<fd_set>. |
2947 | |
3748 | |
2948 | =item EV_SELECT_IS_WINSOCKET |
3749 | =item EV_SELECT_IS_WINSOCKET |
2949 | |
3750 | |
2950 | When defined to C<1>, the select backend will assume that |
3751 | When defined to C<1>, the select backend will assume that |
2951 | select/socket/connect etc. don't understand file descriptors but |
3752 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2953 | be used is the winsock select). This means that it will call |
3754 | be used is the winsock select). This means that it will call |
2954 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3755 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2955 | it is assumed that all these functions actually work on fds, even |
3756 | it is assumed that all these functions actually work on fds, even |
2956 | on win32. Should not be defined on non-win32 platforms. |
3757 | on win32. Should not be defined on non-win32 platforms. |
2957 | |
3758 | |
2958 | =item EV_FD_TO_WIN32_HANDLE |
3759 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2959 | |
3760 | |
2960 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3761 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2961 | file descriptors to socket handles. When not defining this symbol (the |
3762 | file descriptors to socket handles. When not defining this symbol (the |
2962 | default), then libev will call C<_get_osfhandle>, which is usually |
3763 | default), then libev will call C<_get_osfhandle>, which is usually |
2963 | correct. In some cases, programs use their own file descriptor management, |
3764 | correct. In some cases, programs use their own file descriptor management, |
2964 | in which case they can provide this function to map fds to socket handles. |
3765 | in which case they can provide this function to map fds to socket handles. |
|
|
3766 | |
|
|
3767 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3768 | |
|
|
3769 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3770 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3771 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3772 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3773 | |
|
|
3774 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3775 | |
|
|
3776 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3777 | macro can be used to override the C<close> function, useful to unregister |
|
|
3778 | file descriptors again. Note that the replacement function has to close |
|
|
3779 | the underlying OS handle. |
2965 | |
3780 | |
2966 | =item EV_USE_POLL |
3781 | =item EV_USE_POLL |
2967 | |
3782 | |
2968 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3783 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2969 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3784 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3016 | as well as for signal and thread safety in C<ev_async> watchers. |
3831 | as well as for signal and thread safety in C<ev_async> watchers. |
3017 | |
3832 | |
3018 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3833 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3019 | (from F<signal.h>), which is usually good enough on most platforms. |
3834 | (from F<signal.h>), which is usually good enough on most platforms. |
3020 | |
3835 | |
3021 | =item EV_H |
3836 | =item EV_H (h) |
3022 | |
3837 | |
3023 | The name of the F<ev.h> header file used to include it. The default if |
3838 | The name of the F<ev.h> header file used to include it. The default if |
3024 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3839 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3025 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3840 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3026 | |
3841 | |
3027 | =item EV_CONFIG_H |
3842 | =item EV_CONFIG_H (h) |
3028 | |
3843 | |
3029 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3844 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3030 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3845 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3031 | C<EV_H>, above. |
3846 | C<EV_H>, above. |
3032 | |
3847 | |
3033 | =item EV_EVENT_H |
3848 | =item EV_EVENT_H (h) |
3034 | |
3849 | |
3035 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3850 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3036 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3851 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3037 | |
3852 | |
3038 | =item EV_PROTOTYPES |
3853 | =item EV_PROTOTYPES (h) |
3039 | |
3854 | |
3040 | If defined to be C<0>, then F<ev.h> will not define any function |
3855 | If defined to be C<0>, then F<ev.h> will not define any function |
3041 | prototypes, but still define all the structs and other symbols. This is |
3856 | prototypes, but still define all the structs and other symbols. This is |
3042 | occasionally useful if you want to provide your own wrapper functions |
3857 | occasionally useful if you want to provide your own wrapper functions |
3043 | around libev functions. |
3858 | around libev functions. |
… | |
… | |
3062 | When doing priority-based operations, libev usually has to linearly search |
3877 | When doing priority-based operations, libev usually has to linearly search |
3063 | all the priorities, so having many of them (hundreds) uses a lot of space |
3878 | all the priorities, so having many of them (hundreds) uses a lot of space |
3064 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3879 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3065 | fine. |
3880 | fine. |
3066 | |
3881 | |
3067 | If your embedding application does not need any priorities, defining these both to |
3882 | If your embedding application does not need any priorities, defining these |
3068 | C<0> will save some memory and CPU. |
3883 | both to C<0> will save some memory and CPU. |
3069 | |
3884 | |
3070 | =item EV_PERIODIC_ENABLE |
3885 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3886 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3887 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3071 | |
3888 | |
3072 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3889 | If undefined or defined to be C<1> (and the platform supports it), then |
3073 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3890 | the respective watcher type is supported. If defined to be C<0>, then it |
3074 | code. |
3891 | is not. Disabling watcher types mainly saves codesize. |
3075 | |
3892 | |
3076 | =item EV_IDLE_ENABLE |
3893 | =item EV_FEATURES |
3077 | |
|
|
3078 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3079 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3080 | code. |
|
|
3081 | |
|
|
3082 | =item EV_EMBED_ENABLE |
|
|
3083 | |
|
|
3084 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3085 | defined to be C<0>, then they are not. |
|
|
3086 | |
|
|
3087 | =item EV_STAT_ENABLE |
|
|
3088 | |
|
|
3089 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3090 | defined to be C<0>, then they are not. |
|
|
3091 | |
|
|
3092 | =item EV_FORK_ENABLE |
|
|
3093 | |
|
|
3094 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3095 | defined to be C<0>, then they are not. |
|
|
3096 | |
|
|
3097 | =item EV_ASYNC_ENABLE |
|
|
3098 | |
|
|
3099 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3100 | defined to be C<0>, then they are not. |
|
|
3101 | |
|
|
3102 | =item EV_MINIMAL |
|
|
3103 | |
3894 | |
3104 | If you need to shave off some kilobytes of code at the expense of some |
3895 | If you need to shave off some kilobytes of code at the expense of some |
3105 | speed, define this symbol to C<1>. Currently this is used to override some |
3896 | speed (but with the full API), you can define this symbol to request |
3106 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3897 | certain subsets of functionality. The default is to enable all features |
3107 | much smaller 2-heap for timer management over the default 4-heap. |
3898 | that can be enabled on the platform. |
|
|
3899 | |
|
|
3900 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
3901 | with some broad features you want) and then selectively re-enable |
|
|
3902 | additional parts you want, for example if you want everything minimal, |
|
|
3903 | but multiple event loop support, async and child watchers and the poll |
|
|
3904 | backend, use this: |
|
|
3905 | |
|
|
3906 | #define EV_FEATURES 0 |
|
|
3907 | #define EV_MULTIPLICITY 1 |
|
|
3908 | #define EV_USE_POLL 1 |
|
|
3909 | #define EV_CHILD_ENABLE 1 |
|
|
3910 | #define EV_ASYNC_ENABLE 1 |
|
|
3911 | |
|
|
3912 | The actual value is a bitset, it can be a combination of the following |
|
|
3913 | values: |
|
|
3914 | |
|
|
3915 | =over 4 |
|
|
3916 | |
|
|
3917 | =item C<1> - faster/larger code |
|
|
3918 | |
|
|
3919 | Use larger code to speed up some operations. |
|
|
3920 | |
|
|
3921 | Currently this is used to override some inlining decisions (enlarging the roughly |
|
|
3922 | 30% code size on amd64. |
|
|
3923 | |
|
|
3924 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3925 | gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3926 | assertions. |
|
|
3927 | |
|
|
3928 | =item C<2> - faster/larger data structures |
|
|
3929 | |
|
|
3930 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3931 | hash table sizes and so on. This will usually further increase codesize |
|
|
3932 | and can additionally have an effect on the size of data structures at |
|
|
3933 | runtime. |
|
|
3934 | |
|
|
3935 | =item C<4> - full API configuration |
|
|
3936 | |
|
|
3937 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3938 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3939 | |
|
|
3940 | =item C<8> - full API |
|
|
3941 | |
|
|
3942 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3943 | details on which parts of the API are still available without this |
|
|
3944 | feature, and do not complain if this subset changes over time. |
|
|
3945 | |
|
|
3946 | =item C<16> - enable all optional watcher types |
|
|
3947 | |
|
|
3948 | Enables all optional watcher types. If you want to selectively enable |
|
|
3949 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3950 | embed, async, child...) you can enable them manually by defining |
|
|
3951 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3952 | |
|
|
3953 | =item C<32> - enable all backends |
|
|
3954 | |
|
|
3955 | This enables all backends - without this feature, you need to enable at |
|
|
3956 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3957 | |
|
|
3958 | =item C<64> - enable OS-specific "helper" APIs |
|
|
3959 | |
|
|
3960 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
3961 | default. |
|
|
3962 | |
|
|
3963 | =back |
|
|
3964 | |
|
|
3965 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
3966 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
3967 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
3968 | watchers, timers and monotonic clock support. |
|
|
3969 | |
|
|
3970 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
3971 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
3972 | your program might be left out as well - a binary starting a timer and an |
|
|
3973 | I/O watcher then might come out at only 5Kb. |
|
|
3974 | |
|
|
3975 | =item EV_AVOID_STDIO |
|
|
3976 | |
|
|
3977 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
3978 | functions (printf, scanf, perror etc.). This will increase the codesize |
|
|
3979 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
3980 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
3981 | big. |
|
|
3982 | |
|
|
3983 | Note that error messages might become less precise when this option is |
|
|
3984 | enabled. |
|
|
3985 | |
|
|
3986 | =item EV_NSIG |
|
|
3987 | |
|
|
3988 | The highest supported signal number, +1 (or, the number of |
|
|
3989 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
3990 | automatically, but sometimes this fails, in which case it can be |
|
|
3991 | specified. Also, using a lower number than detected (C<32> should be |
|
|
3992 | good for about any system in existance) can save some memory, as libev |
|
|
3993 | statically allocates some 12-24 bytes per signal number. |
3108 | |
3994 | |
3109 | =item EV_PID_HASHSIZE |
3995 | =item EV_PID_HASHSIZE |
3110 | |
3996 | |
3111 | C<ev_child> watchers use a small hash table to distribute workload by |
3997 | C<ev_child> watchers use a small hash table to distribute workload by |
3112 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3998 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3113 | than enough. If you need to manage thousands of children you might want to |
3999 | usually more than enough. If you need to manage thousands of children you |
3114 | increase this value (I<must> be a power of two). |
4000 | might want to increase this value (I<must> be a power of two). |
3115 | |
4001 | |
3116 | =item EV_INOTIFY_HASHSIZE |
4002 | =item EV_INOTIFY_HASHSIZE |
3117 | |
4003 | |
3118 | C<ev_stat> watchers use a small hash table to distribute workload by |
4004 | C<ev_stat> watchers use a small hash table to distribute workload by |
3119 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4005 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3120 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4006 | disabled), usually more than enough. If you need to manage thousands of |
3121 | watchers you might want to increase this value (I<must> be a power of |
4007 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3122 | two). |
4008 | power of two). |
3123 | |
4009 | |
3124 | =item EV_USE_4HEAP |
4010 | =item EV_USE_4HEAP |
3125 | |
4011 | |
3126 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4012 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3127 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4013 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3128 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4014 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3129 | noticeably faster performance with many (thousands) of watchers. |
4015 | faster performance with many (thousands) of watchers. |
3130 | |
4016 | |
3131 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4017 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3132 | (disabled). |
4018 | will be C<0>. |
3133 | |
4019 | |
3134 | =item EV_HEAP_CACHE_AT |
4020 | =item EV_HEAP_CACHE_AT |
3135 | |
4021 | |
3136 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4022 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3137 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4023 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3138 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4024 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3139 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4025 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3140 | but avoids random read accesses on heap changes. This improves performance |
4026 | but avoids random read accesses on heap changes. This improves performance |
3141 | noticeably with with many (hundreds) of watchers. |
4027 | noticeably with many (hundreds) of watchers. |
3142 | |
4028 | |
3143 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4029 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3144 | (disabled). |
4030 | will be C<0>. |
3145 | |
4031 | |
3146 | =item EV_VERIFY |
4032 | =item EV_VERIFY |
3147 | |
4033 | |
3148 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4034 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
3149 | be done: If set to C<0>, no internal verification code will be compiled |
4035 | be done: If set to C<0>, no internal verification code will be compiled |
… | |
… | |
3151 | called. If set to C<2>, then the internal verification code will be |
4037 | called. If set to C<2>, then the internal verification code will be |
3152 | called once per loop, which can slow down libev. If set to C<3>, then the |
4038 | called once per loop, which can slow down libev. If set to C<3>, then the |
3153 | verification code will be called very frequently, which will slow down |
4039 | verification code will be called very frequently, which will slow down |
3154 | libev considerably. |
4040 | libev considerably. |
3155 | |
4041 | |
3156 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4042 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3157 | C<0.> |
4043 | will be C<0>. |
3158 | |
4044 | |
3159 | =item EV_COMMON |
4045 | =item EV_COMMON |
3160 | |
4046 | |
3161 | By default, all watchers have a C<void *data> member. By redefining |
4047 | By default, all watchers have a C<void *data> member. By redefining |
3162 | this macro to a something else you can include more and other types of |
4048 | this macro to a something else you can include more and other types of |
… | |
… | |
3179 | and the way callbacks are invoked and set. Must expand to a struct member |
4065 | and the way callbacks are invoked and set. Must expand to a struct member |
3180 | definition and a statement, respectively. See the F<ev.h> header file for |
4066 | definition and a statement, respectively. See the F<ev.h> header file for |
3181 | their default definitions. One possible use for overriding these is to |
4067 | their default definitions. One possible use for overriding these is to |
3182 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4068 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3183 | method calls instead of plain function calls in C++. |
4069 | method calls instead of plain function calls in C++. |
|
|
4070 | |
|
|
4071 | =back |
3184 | |
4072 | |
3185 | =head2 EXPORTED API SYMBOLS |
4073 | =head2 EXPORTED API SYMBOLS |
3186 | |
4074 | |
3187 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
4075 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3188 | exported symbols, you can use the provided F<Symbol.*> files which list |
4076 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3218 | file. |
4106 | file. |
3219 | |
4107 | |
3220 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4108 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3221 | that everybody includes and which overrides some configure choices: |
4109 | that everybody includes and which overrides some configure choices: |
3222 | |
4110 | |
3223 | #define EV_MINIMAL 1 |
4111 | #define EV_FEATURES 8 |
3224 | #define EV_USE_POLL 0 |
4112 | #define EV_USE_SELECT 1 |
3225 | #define EV_MULTIPLICITY 0 |
|
|
3226 | #define EV_PERIODIC_ENABLE 0 |
4113 | #define EV_PREPARE_ENABLE 1 |
|
|
4114 | #define EV_IDLE_ENABLE 1 |
3227 | #define EV_STAT_ENABLE 0 |
4115 | #define EV_SIGNAL_ENABLE 1 |
3228 | #define EV_FORK_ENABLE 0 |
4116 | #define EV_CHILD_ENABLE 1 |
|
|
4117 | #define EV_USE_STDEXCEPT 0 |
3229 | #define EV_CONFIG_H <config.h> |
4118 | #define EV_CONFIG_H <config.h> |
3230 | #define EV_MINPRI 0 |
|
|
3231 | #define EV_MAXPRI 0 |
|
|
3232 | |
4119 | |
3233 | #include "ev++.h" |
4120 | #include "ev++.h" |
3234 | |
4121 | |
3235 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4122 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3236 | |
4123 | |
3237 | #include "ev_cpp.h" |
4124 | #include "ev_cpp.h" |
3238 | #include "ev.c" |
4125 | #include "ev.c" |
3239 | |
4126 | |
|
|
4127 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3240 | |
4128 | |
3241 | =head1 THREADS AND COROUTINES |
4129 | =head2 THREADS AND COROUTINES |
3242 | |
4130 | |
3243 | =head2 THREADS |
4131 | =head3 THREADS |
3244 | |
4132 | |
3245 | Libev itself is thread-safe (unless the opposite is specifically |
4133 | All libev functions are reentrant and thread-safe unless explicitly |
3246 | documented for a function), but it uses no locking itself. This means that |
4134 | documented otherwise, but libev implements no locking itself. This means |
3247 | you can use as many loops as you want in parallel, as long as only one |
4135 | that you can use as many loops as you want in parallel, as long as there |
3248 | thread ever calls into one libev function with the same loop parameter: |
4136 | are no concurrent calls into any libev function with the same loop |
|
|
4137 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
3249 | libev guarentees that different event loops share no data structures that |
4138 | of course): libev guarantees that different event loops share no data |
3250 | need locking. |
4139 | structures that need any locking. |
3251 | |
4140 | |
3252 | Or to put it differently: calls with different loop parameters can be done |
4141 | Or to put it differently: calls with different loop parameters can be done |
3253 | concurrently from multiple threads, calls with the same loop parameter |
4142 | concurrently from multiple threads, calls with the same loop parameter |
3254 | must be done serially (but can be done from different threads, as long as |
4143 | must be done serially (but can be done from different threads, as long as |
3255 | only one thread ever is inside a call at any point in time, e.g. by using |
4144 | only one thread ever is inside a call at any point in time, e.g. by using |
3256 | a mutex per loop). |
4145 | a mutex per loop). |
3257 | |
4146 | |
3258 | Specifically to support threads (and signal handlers), libev implements |
4147 | Specifically to support threads (and signal handlers), libev implements |
3259 | so-called C<ev_async> watchers, which allow some limited form of |
4148 | so-called C<ev_async> watchers, which allow some limited form of |
3260 | concurrency on the same event loop. |
4149 | concurrency on the same event loop, namely waking it up "from the |
|
|
4150 | outside". |
3261 | |
4151 | |
3262 | If you want to know which design (one loop, locking, or multiple loops |
4152 | If you want to know which design (one loop, locking, or multiple loops |
3263 | without or something else still) is best for your problem, then I cannot |
4153 | without or something else still) is best for your problem, then I cannot |
3264 | help you. I can give some generic advice however: |
4154 | help you, but here is some generic advice: |
3265 | |
4155 | |
3266 | =over 4 |
4156 | =over 4 |
3267 | |
4157 | |
3268 | =item * most applications have a main thread: use the default libev loop |
4158 | =item * most applications have a main thread: use the default libev loop |
3269 | in that thread, or create a separate thread running only the default loop. |
4159 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3281 | |
4171 | |
3282 | Choosing a model is hard - look around, learn, know that usually you can do |
4172 | Choosing a model is hard - look around, learn, know that usually you can do |
3283 | better than you currently do :-) |
4173 | better than you currently do :-) |
3284 | |
4174 | |
3285 | =item * often you need to talk to some other thread which blocks in the |
4175 | =item * often you need to talk to some other thread which blocks in the |
|
|
4176 | event loop. |
|
|
4177 | |
3286 | event loop - C<ev_async> watchers can be used to wake them up from other |
4178 | C<ev_async> watchers can be used to wake them up from other threads safely |
3287 | threads safely (or from signal contexts...). |
4179 | (or from signal contexts...). |
3288 | |
4180 | |
3289 | =item * some watcher types are only supported in the default loop - use |
4181 | An example use would be to communicate signals or other events that only |
3290 | C<ev_async> watchers to tell your other loops about any such events. |
4182 | work in the default loop by registering the signal watcher with the |
|
|
4183 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
4184 | watcher callback into the event loop interested in the signal. |
3291 | |
4185 | |
3292 | =back |
4186 | =back |
3293 | |
4187 | |
|
|
4188 | =head4 THREAD LOCKING EXAMPLE |
|
|
4189 | |
|
|
4190 | Here is a fictitious example of how to run an event loop in a different |
|
|
4191 | thread than where callbacks are being invoked and watchers are |
|
|
4192 | created/added/removed. |
|
|
4193 | |
|
|
4194 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4195 | which uses exactly this technique (which is suited for many high-level |
|
|
4196 | languages). |
|
|
4197 | |
|
|
4198 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4199 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4200 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4201 | |
|
|
4202 | First, you need to associate some data with the event loop: |
|
|
4203 | |
|
|
4204 | typedef struct { |
|
|
4205 | mutex_t lock; /* global loop lock */ |
|
|
4206 | ev_async async_w; |
|
|
4207 | thread_t tid; |
|
|
4208 | cond_t invoke_cv; |
|
|
4209 | } userdata; |
|
|
4210 | |
|
|
4211 | void prepare_loop (EV_P) |
|
|
4212 | { |
|
|
4213 | // for simplicity, we use a static userdata struct. |
|
|
4214 | static userdata u; |
|
|
4215 | |
|
|
4216 | ev_async_init (&u->async_w, async_cb); |
|
|
4217 | ev_async_start (EV_A_ &u->async_w); |
|
|
4218 | |
|
|
4219 | pthread_mutex_init (&u->lock, 0); |
|
|
4220 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4221 | |
|
|
4222 | // now associate this with the loop |
|
|
4223 | ev_set_userdata (EV_A_ u); |
|
|
4224 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4225 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4226 | |
|
|
4227 | // then create the thread running ev_loop |
|
|
4228 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4229 | } |
|
|
4230 | |
|
|
4231 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4232 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4233 | that might have been added: |
|
|
4234 | |
|
|
4235 | static void |
|
|
4236 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4237 | { |
|
|
4238 | // just used for the side effects |
|
|
4239 | } |
|
|
4240 | |
|
|
4241 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4242 | protecting the loop data, respectively. |
|
|
4243 | |
|
|
4244 | static void |
|
|
4245 | l_release (EV_P) |
|
|
4246 | { |
|
|
4247 | userdata *u = ev_userdata (EV_A); |
|
|
4248 | pthread_mutex_unlock (&u->lock); |
|
|
4249 | } |
|
|
4250 | |
|
|
4251 | static void |
|
|
4252 | l_acquire (EV_P) |
|
|
4253 | { |
|
|
4254 | userdata *u = ev_userdata (EV_A); |
|
|
4255 | pthread_mutex_lock (&u->lock); |
|
|
4256 | } |
|
|
4257 | |
|
|
4258 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4259 | into C<ev_loop>: |
|
|
4260 | |
|
|
4261 | void * |
|
|
4262 | l_run (void *thr_arg) |
|
|
4263 | { |
|
|
4264 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4265 | |
|
|
4266 | l_acquire (EV_A); |
|
|
4267 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4268 | ev_loop (EV_A_ 0); |
|
|
4269 | l_release (EV_A); |
|
|
4270 | |
|
|
4271 | return 0; |
|
|
4272 | } |
|
|
4273 | |
|
|
4274 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4275 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4276 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4277 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4278 | and b) skipping inter-thread-communication when there are no pending |
|
|
4279 | watchers is very beneficial): |
|
|
4280 | |
|
|
4281 | static void |
|
|
4282 | l_invoke (EV_P) |
|
|
4283 | { |
|
|
4284 | userdata *u = ev_userdata (EV_A); |
|
|
4285 | |
|
|
4286 | while (ev_pending_count (EV_A)) |
|
|
4287 | { |
|
|
4288 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4289 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4290 | } |
|
|
4291 | } |
|
|
4292 | |
|
|
4293 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4294 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4295 | thread to continue: |
|
|
4296 | |
|
|
4297 | static void |
|
|
4298 | real_invoke_pending (EV_P) |
|
|
4299 | { |
|
|
4300 | userdata *u = ev_userdata (EV_A); |
|
|
4301 | |
|
|
4302 | pthread_mutex_lock (&u->lock); |
|
|
4303 | ev_invoke_pending (EV_A); |
|
|
4304 | pthread_cond_signal (&u->invoke_cv); |
|
|
4305 | pthread_mutex_unlock (&u->lock); |
|
|
4306 | } |
|
|
4307 | |
|
|
4308 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4309 | event loop, you will now have to lock: |
|
|
4310 | |
|
|
4311 | ev_timer timeout_watcher; |
|
|
4312 | userdata *u = ev_userdata (EV_A); |
|
|
4313 | |
|
|
4314 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4315 | |
|
|
4316 | pthread_mutex_lock (&u->lock); |
|
|
4317 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4318 | ev_async_send (EV_A_ &u->async_w); |
|
|
4319 | pthread_mutex_unlock (&u->lock); |
|
|
4320 | |
|
|
4321 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4322 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4323 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4324 | watchers in the next event loop iteration. |
|
|
4325 | |
3294 | =head2 COROUTINES |
4326 | =head3 COROUTINES |
3295 | |
4327 | |
3296 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4328 | Libev is very accommodating to coroutines ("cooperative threads"): |
3297 | libev fully supports nesting calls to it's functions from different |
4329 | libev fully supports nesting calls to its functions from different |
3298 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4330 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
3299 | different coroutines and switch freely between both coroutines running the |
4331 | different coroutines, and switch freely between both coroutines running |
3300 | loop, as long as you don't confuse yourself). The only exception is that |
4332 | the loop, as long as you don't confuse yourself). The only exception is |
3301 | you must not do this from C<ev_periodic> reschedule callbacks. |
4333 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3302 | |
4334 | |
3303 | Care has been invested into making sure that libev does not keep local |
4335 | Care has been taken to ensure that libev does not keep local state inside |
3304 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4336 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3305 | switches. |
4337 | they do not call any callbacks. |
3306 | |
4338 | |
|
|
4339 | =head2 COMPILER WARNINGS |
3307 | |
4340 | |
3308 | =head1 COMPLEXITIES |
4341 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4342 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4343 | scared by this. |
3309 | |
4344 | |
3310 | In this section the complexities of (many of) the algorithms used inside |
4345 | However, these are unavoidable for many reasons. For one, each compiler |
3311 | libev will be explained. For complexity discussions about backends see the |
4346 | has different warnings, and each user has different tastes regarding |
3312 | documentation for C<ev_default_init>. |
4347 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4348 | targeting a specific compiler and compiler-version. |
3313 | |
4349 | |
3314 | All of the following are about amortised time: If an array needs to be |
4350 | Another reason is that some compiler warnings require elaborate |
3315 | extended, libev needs to realloc and move the whole array, but this |
4351 | workarounds, or other changes to the code that make it less clear and less |
3316 | happens asymptotically never with higher number of elements, so O(1) might |
4352 | maintainable. |
3317 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3318 | it is much faster and asymptotically approaches constant time. |
|
|
3319 | |
4353 | |
3320 | =over 4 |
4354 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4355 | wrong (because they don't actually warn about the condition their message |
|
|
4356 | seems to warn about). For example, certain older gcc versions had some |
|
|
4357 | warnings that resulted an extreme number of false positives. These have |
|
|
4358 | been fixed, but some people still insist on making code warn-free with |
|
|
4359 | such buggy versions. |
3321 | |
4360 | |
3322 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4361 | While libev is written to generate as few warnings as possible, |
|
|
4362 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4363 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4364 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4365 | warnings, not errors, or proof of bugs. |
3323 | |
4366 | |
3324 | This means that, when you have a watcher that triggers in one hour and |
|
|
3325 | there are 100 watchers that would trigger before that then inserting will |
|
|
3326 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3327 | |
4367 | |
3328 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4368 | =head2 VALGRIND |
3329 | |
4369 | |
3330 | That means that changing a timer costs less than removing/adding them |
4370 | Valgrind has a special section here because it is a popular tool that is |
3331 | as only the relative motion in the event queue has to be paid for. |
4371 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3332 | |
4372 | |
3333 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4373 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4374 | in libev, then check twice: If valgrind reports something like: |
3334 | |
4375 | |
3335 | These just add the watcher into an array or at the head of a list. |
4376 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4377 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4378 | ==2274== still reachable: 256 bytes in 1 blocks. |
3336 | |
4379 | |
3337 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4380 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4381 | is not a memleak - the memory is still being referenced, and didn't leak. |
3338 | |
4382 | |
3339 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4383 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4384 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4385 | although an acceptable workaround has been found here), or it might be |
|
|
4386 | confused. |
3340 | |
4387 | |
3341 | These watchers are stored in lists then need to be walked to find the |
4388 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3342 | correct watcher to remove. The lists are usually short (you don't usually |
4389 | make it into some kind of religion. |
3343 | have many watchers waiting for the same fd or signal). |
|
|
3344 | |
4390 | |
3345 | =item Finding the next timer in each loop iteration: O(1) |
4391 | If you are unsure about something, feel free to contact the mailing list |
|
|
4392 | with the full valgrind report and an explanation on why you think this |
|
|
4393 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4394 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4395 | of learning how to interpret valgrind properly. |
3346 | |
4396 | |
3347 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4397 | If you need, for some reason, empty reports from valgrind for your project |
3348 | fixed position in the storage array. |
4398 | I suggest using suppression lists. |
3349 | |
4399 | |
3350 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3351 | |
4400 | |
3352 | A change means an I/O watcher gets started or stopped, which requires |
4401 | =head1 PORTABILITY NOTES |
3353 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3354 | on backend and whether C<ev_io_set> was used). |
|
|
3355 | |
4402 | |
3356 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
3357 | |
|
|
3358 | =item Priority handling: O(number_of_priorities) |
|
|
3359 | |
|
|
3360 | Priorities are implemented by allocating some space for each |
|
|
3361 | priority. When doing priority-based operations, libev usually has to |
|
|
3362 | linearly search all the priorities, but starting/stopping and activating |
|
|
3363 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3364 | |
|
|
3365 | =item Sending an ev_async: O(1) |
|
|
3366 | |
|
|
3367 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3368 | |
|
|
3369 | =item Processing signals: O(max_signal_number) |
|
|
3370 | |
|
|
3371 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
3372 | calls in the current loop iteration. Checking for async and signal events |
|
|
3373 | involves iterating over all running async watchers or all signal numbers. |
|
|
3374 | |
|
|
3375 | =back |
|
|
3376 | |
|
|
3377 | |
|
|
3378 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4403 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
3379 | |
4404 | |
3380 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4405 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3381 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4406 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3382 | model. Libev still offers limited functionality on this platform in |
4407 | model. Libev still offers limited functionality on this platform in |
3383 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4408 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
… | |
… | |
3390 | way (note also that glib is the slowest event library known to man). |
4415 | way (note also that glib is the slowest event library known to man). |
3391 | |
4416 | |
3392 | There is no supported compilation method available on windows except |
4417 | There is no supported compilation method available on windows except |
3393 | embedding it into other applications. |
4418 | embedding it into other applications. |
3394 | |
4419 | |
|
|
4420 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4421 | tries its best, but under most conditions, signals will simply not work. |
|
|
4422 | |
3395 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4423 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3396 | accept large writes: instead of resulting in a partial write, windows will |
4424 | accept large writes: instead of resulting in a partial write, windows will |
3397 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4425 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3398 | so make sure you only write small amounts into your sockets (less than a |
4426 | so make sure you only write small amounts into your sockets (less than a |
3399 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4427 | megabyte seems safe, but this apparently depends on the amount of memory |
3400 | available). |
4428 | available). |
3401 | |
4429 | |
3402 | Due to the many, low, and arbitrary limits on the win32 platform and |
4430 | Due to the many, low, and arbitrary limits on the win32 platform and |
3403 | the abysmal performance of winsockets, using a large number of sockets |
4431 | the abysmal performance of winsockets, using a large number of sockets |
3404 | is not recommended (and not reasonable). If your program needs to use |
4432 | is not recommended (and not reasonable). If your program needs to use |
3405 | more than a hundred or so sockets, then likely it needs to use a totally |
4433 | more than a hundred or so sockets, then likely it needs to use a totally |
3406 | different implementation for windows, as libev offers the POSIX readiness |
4434 | different implementation for windows, as libev offers the POSIX readiness |
3407 | notification model, which cannot be implemented efficiently on windows |
4435 | notification model, which cannot be implemented efficiently on windows |
3408 | (Microsoft monopoly games). |
4436 | (due to Microsoft monopoly games). |
3409 | |
4437 | |
3410 | A typical way to use libev under windows is to embed it (see the embedding |
4438 | A typical way to use libev under windows is to embed it (see the embedding |
3411 | section for details) and use the following F<evwrap.h> header file instead |
4439 | section for details) and use the following F<evwrap.h> header file instead |
3412 | of F<ev.h>: |
4440 | of F<ev.h>: |
3413 | |
4441 | |
… | |
… | |
3415 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4443 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3416 | |
4444 | |
3417 | #include "ev.h" |
4445 | #include "ev.h" |
3418 | |
4446 | |
3419 | And compile the following F<evwrap.c> file into your project (make sure |
4447 | And compile the following F<evwrap.c> file into your project (make sure |
3420 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
4448 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3421 | |
4449 | |
3422 | #include "evwrap.h" |
4450 | #include "evwrap.h" |
3423 | #include "ev.c" |
4451 | #include "ev.c" |
3424 | |
4452 | |
3425 | =over 4 |
4453 | =over 4 |
… | |
… | |
3449 | |
4477 | |
3450 | Early versions of winsocket's select only supported waiting for a maximum |
4478 | Early versions of winsocket's select only supported waiting for a maximum |
3451 | of C<64> handles (probably owning to the fact that all windows kernels |
4479 | of C<64> handles (probably owning to the fact that all windows kernels |
3452 | can only wait for C<64> things at the same time internally; Microsoft |
4480 | can only wait for C<64> things at the same time internally; Microsoft |
3453 | recommends spawning a chain of threads and wait for 63 handles and the |
4481 | recommends spawning a chain of threads and wait for 63 handles and the |
3454 | previous thread in each. Great). |
4482 | previous thread in each. Sounds great!). |
3455 | |
4483 | |
3456 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4484 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3457 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4485 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3458 | call (which might be in libev or elsewhere, for example, perl does its own |
4486 | call (which might be in libev or elsewhere, for example, perl and many |
3459 | select emulation on windows). |
4487 | other interpreters do their own select emulation on windows). |
3460 | |
4488 | |
3461 | Another limit is the number of file descriptors in the Microsoft runtime |
4489 | Another limit is the number of file descriptors in the Microsoft runtime |
3462 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4490 | libraries, which by default is C<64> (there must be a hidden I<64> |
3463 | or something like this inside Microsoft). You can increase this by calling |
4491 | fetish or something like this inside Microsoft). You can increase this |
3464 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4492 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3465 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4493 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3466 | libraries. |
|
|
3467 | |
|
|
3468 | This might get you to about C<512> or C<2048> sockets (depending on |
4494 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3469 | windows version and/or the phase of the moon). To get more, you need to |
4495 | (depending on windows version and/or the phase of the moon). To get more, |
3470 | wrap all I/O functions and provide your own fd management, but the cost of |
4496 | you need to wrap all I/O functions and provide your own fd management, but |
3471 | calling select (O(n²)) will likely make this unworkable. |
4497 | the cost of calling select (O(n²)) will likely make this unworkable. |
3472 | |
4498 | |
3473 | =back |
4499 | =back |
3474 | |
4500 | |
3475 | |
|
|
3476 | =head1 PORTABILITY REQUIREMENTS |
4501 | =head2 PORTABILITY REQUIREMENTS |
3477 | |
4502 | |
3478 | In addition to a working ISO-C implementation, libev relies on a few |
4503 | In addition to a working ISO-C implementation and of course the |
3479 | additional extensions: |
4504 | backend-specific APIs, libev relies on a few additional extensions: |
3480 | |
4505 | |
3481 | =over 4 |
4506 | =over 4 |
3482 | |
4507 | |
3483 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4508 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3484 | calling conventions regardless of C<ev_watcher_type *>. |
4509 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3490 | calls them using an C<ev_watcher *> internally. |
4515 | calls them using an C<ev_watcher *> internally. |
3491 | |
4516 | |
3492 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4517 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3493 | |
4518 | |
3494 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4519 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3495 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4520 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3496 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4521 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3497 | believed to be sufficiently portable. |
4522 | believed to be sufficiently portable. |
3498 | |
4523 | |
3499 | =item C<sigprocmask> must work in a threaded environment |
4524 | =item C<sigprocmask> must work in a threaded environment |
3500 | |
4525 | |
… | |
… | |
3509 | except the initial one, and run the default loop in the initial thread as |
4534 | except the initial one, and run the default loop in the initial thread as |
3510 | well. |
4535 | well. |
3511 | |
4536 | |
3512 | =item C<long> must be large enough for common memory allocation sizes |
4537 | =item C<long> must be large enough for common memory allocation sizes |
3513 | |
4538 | |
3514 | To improve portability and simplify using libev, libev uses C<long> |
4539 | To improve portability and simplify its API, libev uses C<long> internally |
3515 | internally instead of C<size_t> when allocating its data structures. On |
4540 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3516 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4541 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3517 | is still at least 31 bits everywhere, which is enough for hundreds of |
4542 | least 31 bits everywhere, which is enough for hundreds of millions of |
3518 | millions of watchers. |
4543 | watchers. |
3519 | |
4544 | |
3520 | =item C<double> must hold a time value in seconds with enough accuracy |
4545 | =item C<double> must hold a time value in seconds with enough accuracy |
3521 | |
4546 | |
3522 | The type C<double> is used to represent timestamps. It is required to |
4547 | The type C<double> is used to represent timestamps. It is required to |
3523 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4548 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
3524 | enough for at least into the year 4000. This requirement is fulfilled by |
4549 | enough for at least into the year 4000. This requirement is fulfilled by |
3525 | implementations implementing IEEE 754 (basically all existing ones). |
4550 | implementations implementing IEEE 754, which is basically all existing |
|
|
4551 | ones. With IEEE 754 doubles, you get microsecond accuracy until at least |
|
|
4552 | 2200. |
3526 | |
4553 | |
3527 | =back |
4554 | =back |
3528 | |
4555 | |
3529 | If you know of other additional requirements drop me a note. |
4556 | If you know of other additional requirements drop me a note. |
3530 | |
4557 | |
3531 | |
4558 | |
3532 | =head1 COMPILER WARNINGS |
4559 | =head1 ALGORITHMIC COMPLEXITIES |
3533 | |
4560 | |
3534 | Depending on your compiler and compiler settings, you might get no or a |
4561 | In this section the complexities of (many of) the algorithms used inside |
3535 | lot of warnings when compiling libev code. Some people are apparently |
4562 | libev will be documented. For complexity discussions about backends see |
3536 | scared by this. |
4563 | the documentation for C<ev_default_init>. |
3537 | |
4564 | |
3538 | However, these are unavoidable for many reasons. For one, each compiler |
4565 | All of the following are about amortised time: If an array needs to be |
3539 | has different warnings, and each user has different tastes regarding |
4566 | extended, libev needs to realloc and move the whole array, but this |
3540 | warning options. "Warn-free" code therefore cannot be a goal except when |
4567 | happens asymptotically rarer with higher number of elements, so O(1) might |
3541 | targeting a specific compiler and compiler-version. |
4568 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4569 | average it is much faster and asymptotically approaches constant time. |
3542 | |
4570 | |
3543 | Another reason is that some compiler warnings require elaborate |
4571 | =over 4 |
3544 | workarounds, or other changes to the code that make it less clear and less |
|
|
3545 | maintainable. |
|
|
3546 | |
4572 | |
3547 | And of course, some compiler warnings are just plain stupid, or simply |
4573 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3548 | wrong (because they don't actually warn about the condition their message |
|
|
3549 | seems to warn about). |
|
|
3550 | |
4574 | |
3551 | While libev is written to generate as few warnings as possible, |
4575 | This means that, when you have a watcher that triggers in one hour and |
3552 | "warn-free" code is not a goal, and it is recommended not to build libev |
4576 | there are 100 watchers that would trigger before that, then inserting will |
3553 | with any compiler warnings enabled unless you are prepared to cope with |
4577 | have to skip roughly seven (C<ld 100>) of these watchers. |
3554 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3555 | warnings, not errors, or proof of bugs. |
|
|
3556 | |
4578 | |
|
|
4579 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3557 | |
4580 | |
3558 | =head1 VALGRIND |
4581 | That means that changing a timer costs less than removing/adding them, |
|
|
4582 | as only the relative motion in the event queue has to be paid for. |
3559 | |
4583 | |
3560 | Valgrind has a special section here because it is a popular tool that is |
4584 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3561 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3562 | |
4585 | |
3563 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4586 | These just add the watcher into an array or at the head of a list. |
3564 | in libev, then check twice: If valgrind reports something like: |
|
|
3565 | |
4587 | |
3566 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4588 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3567 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3568 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3569 | |
4589 | |
3570 | Then there is no memory leak. Similarly, under some circumstances, |
4590 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3571 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3572 | might be confused (it is a very good tool, but only a tool). |
|
|
3573 | |
4591 | |
3574 | If you are unsure about something, feel free to contact the mailing list |
4592 | These watchers are stored in lists, so they need to be walked to find the |
3575 | with the full valgrind report and an explanation on why you think this is |
4593 | correct watcher to remove. The lists are usually short (you don't usually |
3576 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4594 | have many watchers waiting for the same fd or signal: one is typical, two |
3577 | no bug" answer and take the chance of learning how to interpret valgrind |
4595 | is rare). |
3578 | properly. |
|
|
3579 | |
4596 | |
3580 | If you need, for some reason, empty reports from valgrind for your project |
4597 | =item Finding the next timer in each loop iteration: O(1) |
3581 | I suggest using suppression lists. |
|
|
3582 | |
4598 | |
|
|
4599 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4600 | fixed position in the storage array. |
|
|
4601 | |
|
|
4602 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4603 | |
|
|
4604 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4605 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4606 | on backend and whether C<ev_io_set> was used). |
|
|
4607 | |
|
|
4608 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4609 | |
|
|
4610 | =item Priority handling: O(number_of_priorities) |
|
|
4611 | |
|
|
4612 | Priorities are implemented by allocating some space for each |
|
|
4613 | priority. When doing priority-based operations, libev usually has to |
|
|
4614 | linearly search all the priorities, but starting/stopping and activating |
|
|
4615 | watchers becomes O(1) with respect to priority handling. |
|
|
4616 | |
|
|
4617 | =item Sending an ev_async: O(1) |
|
|
4618 | |
|
|
4619 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4620 | |
|
|
4621 | =item Processing signals: O(max_signal_number) |
|
|
4622 | |
|
|
4623 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4624 | calls in the current loop iteration. Checking for async and signal events |
|
|
4625 | involves iterating over all running async watchers or all signal numbers. |
|
|
4626 | |
|
|
4627 | =back |
|
|
4628 | |
|
|
4629 | |
|
|
4630 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4631 | |
|
|
4632 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4633 | |
|
|
4634 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4635 | compatibility, so most programs should still compile. Those might be |
|
|
4636 | removed in later versions of libev, so better update early than late. |
|
|
4637 | |
|
|
4638 | =over 4 |
|
|
4639 | |
|
|
4640 | =item C<ev_loop_count> renamed to C<ev_iteration> |
|
|
4641 | |
|
|
4642 | =item C<ev_loop_depth> renamed to C<ev_depth> |
|
|
4643 | |
|
|
4644 | =item C<ev_loop_verify> renamed to C<ev_verify> |
|
|
4645 | |
|
|
4646 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4647 | C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is |
|
|
4648 | still called C<ev_loop_fork> because it would otherwise clash with the |
|
|
4649 | C<ev_frok> typedef. |
|
|
4650 | |
|
|
4651 | =item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents> |
|
|
4652 | |
|
|
4653 | This is a simple rename - all other watcher types use their name |
|
|
4654 | as revents flag, and now C<ev_timer> does, too. |
|
|
4655 | |
|
|
4656 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
|
|
4657 | and continue to be present for the forseeable future, so this is mostly a |
|
|
4658 | documentation change. |
|
|
4659 | |
|
|
4660 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4661 | |
|
|
4662 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4663 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4664 | and work, but the library code will of course be larger. |
|
|
4665 | |
|
|
4666 | =back |
|
|
4667 | |
|
|
4668 | |
|
|
4669 | =head1 GLOSSARY |
|
|
4670 | |
|
|
4671 | =over 4 |
|
|
4672 | |
|
|
4673 | =item active |
|
|
4674 | |
|
|
4675 | A watcher is active as long as it has been started (has been attached to |
|
|
4676 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4677 | |
|
|
4678 | =item application |
|
|
4679 | |
|
|
4680 | In this document, an application is whatever is using libev. |
|
|
4681 | |
|
|
4682 | =item callback |
|
|
4683 | |
|
|
4684 | The address of a function that is called when some event has been |
|
|
4685 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4686 | received the event, and the actual event bitset. |
|
|
4687 | |
|
|
4688 | =item callback invocation |
|
|
4689 | |
|
|
4690 | The act of calling the callback associated with a watcher. |
|
|
4691 | |
|
|
4692 | =item event |
|
|
4693 | |
|
|
4694 | A change of state of some external event, such as data now being available |
|
|
4695 | for reading on a file descriptor, time having passed or simply not having |
|
|
4696 | any other events happening anymore. |
|
|
4697 | |
|
|
4698 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4699 | C<EV_TIMER>). |
|
|
4700 | |
|
|
4701 | =item event library |
|
|
4702 | |
|
|
4703 | A software package implementing an event model and loop. |
|
|
4704 | |
|
|
4705 | =item event loop |
|
|
4706 | |
|
|
4707 | An entity that handles and processes external events and converts them |
|
|
4708 | into callback invocations. |
|
|
4709 | |
|
|
4710 | =item event model |
|
|
4711 | |
|
|
4712 | The model used to describe how an event loop handles and processes |
|
|
4713 | watchers and events. |
|
|
4714 | |
|
|
4715 | =item pending |
|
|
4716 | |
|
|
4717 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4718 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4719 | pending status is explicitly cleared by the application. |
|
|
4720 | |
|
|
4721 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4722 | its pending status. |
|
|
4723 | |
|
|
4724 | =item real time |
|
|
4725 | |
|
|
4726 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4727 | |
|
|
4728 | =item wall-clock time |
|
|
4729 | |
|
|
4730 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4731 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4732 | clock. |
|
|
4733 | |
|
|
4734 | =item watcher |
|
|
4735 | |
|
|
4736 | A data structure that describes interest in certain events. Watchers need |
|
|
4737 | to be started (attached to an event loop) before they can receive events. |
|
|
4738 | |
|
|
4739 | =item watcher invocation |
|
|
4740 | |
|
|
4741 | The act of calling the callback associated with a watcher. |
|
|
4742 | |
|
|
4743 | =back |
3583 | |
4744 | |
3584 | =head1 AUTHOR |
4745 | =head1 AUTHOR |
3585 | |
4746 | |
3586 | Marc Lehmann <libev@schmorp.de>. |
4747 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3587 | |
4748 | |