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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); |
28 | |
30 | |
29 | // this causes all nested ev_loop's to stop iterating |
31 | // this causes all nested ev_run's to stop iterating |
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
32 | ev_break (EV_A_ EVBREAK_ALL); |
31 | } |
33 | } |
32 | |
34 | |
33 | // another callback, this time for a time-out |
35 | // another callback, this time for a time-out |
34 | static void |
36 | static void |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
37 | timeout_cb (EV_P_ ev_timer *w, int revents) |
36 | { |
38 | { |
37 | puts ("timeout"); |
39 | puts ("timeout"); |
38 | // this causes the innermost ev_loop to stop iterating |
40 | // this causes the innermost ev_run to stop iterating |
39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
41 | ev_break (EV_A_ EVBREAK_ONE); |
40 | } |
42 | } |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
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54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // 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 | Familiarity 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 (in practise |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
119 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
121 | |
137 | |
122 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
123 | |
139 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
141 | and internal errors (bugs). |
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176 | as this indicates an incompatible change. Minor versions are usually |
192 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
193 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
194 | not a problem. |
179 | |
195 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
197 | version (note, however, that this will not detect ABI mismatches :). |
182 | |
198 | |
183 | assert (("libev version mismatch", |
199 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
200 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
202 | |
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214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
230 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
215 | recommended ones. |
231 | recommended ones. |
216 | |
232 | |
217 | See the description of C<ev_embed> watchers for more info. |
233 | See the description of C<ev_embed> watchers for more info. |
218 | |
234 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
235 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
236 | |
221 | Sets the allocation function to use (the prototype is similar - the |
237 | 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 |
238 | 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 |
239 | 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 |
240 | when memory needs to be allocated (C<size != 0>), the library might abort |
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250 | } |
266 | } |
251 | |
267 | |
252 | ... |
268 | ... |
253 | ev_set_allocator (persistent_realloc); |
269 | ev_set_allocator (persistent_realloc); |
254 | |
270 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
271 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
272 | |
257 | Set the callback function to call on a retryable system call error (such |
273 | 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 |
274 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
275 | 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 |
276 | callback is set, then libev will expect it to remedy the situation, no |
… | |
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276 | |
292 | |
277 | =back |
293 | =back |
278 | |
294 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
295 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
280 | |
296 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
297 | An event loop is described by a C<struct ev_loop *> (the C<struct> is |
282 | types of such loops, the I<default> loop, which supports signals and child |
298 | I<not> optional in case unless libev 3 compatibility is disabled, as libev |
283 | events, and dynamically created loops which do not. |
299 | 3 had an C<ev_loop> function colliding with the struct name). |
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300 | |
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301 | The library knows two types of such loops, the I<default> loop, which |
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302 | supports signals and child events, and dynamically created event loops |
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303 | which do not. |
284 | |
304 | |
285 | =over 4 |
305 | =over 4 |
286 | |
306 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
307 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
308 | |
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294 | If you don't know what event loop to use, use the one returned from this |
314 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
315 | function. |
296 | |
316 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
317 | 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, |
318 | from multiple threads, you have to lock (note also that this is unlikely, |
299 | as loops cannot bes hared easily between threads anyway). |
319 | as loops cannot be shared easily between threads anyway). |
300 | |
320 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
321 | 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 |
322 | 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 |
323 | 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 |
324 | 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 |
346 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
347 | around bugs. |
328 | |
348 | |
329 | =item C<EVFLAG_FORKCHECK> |
349 | =item C<EVFLAG_FORKCHECK> |
330 | |
350 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
351 | 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 |
352 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
353 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
354 | 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 |
355 | 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 |
356 | 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 |
357 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
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344 | flag. |
363 | flag. |
345 | |
364 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
365 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
366 | environment variable. |
348 | |
367 | |
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368 | =item C<EVFLAG_NOINOTIFY> |
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369 | |
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370 | When this flag is specified, then libev will not attempt to use the |
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371 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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372 | testing, this flag can be useful to conserve inotify file descriptors, as |
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373 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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374 | |
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375 | =item C<EVFLAG_SIGNALFD> |
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376 | |
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377 | When this flag is specified, then libev will attempt to use the |
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378 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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379 | delivers signals synchronously, which makes it both faster and might make |
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380 | it possible to get the queued signal data. It can also simplify signal |
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381 | handling with threads, as long as you properly block signals in your |
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382 | threads that are not interested in handling them. |
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383 | |
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384 | Signalfd will not be used by default as this changes your signal mask, and |
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385 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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386 | example) that can't properly initialise their signal masks. |
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387 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
388 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
389 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
390 | 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, |
391 | 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 |
392 | but if that fails, expect a fairly low limit on the number of fds when |
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359 | writing a server, you should C<accept ()> in a loop to accept as many |
398 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
399 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
400 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
401 | readiness notifications you get per iteration. |
363 | |
402 | |
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403 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
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404 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
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405 | C<exceptfds> set on that platform). |
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406 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
407 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
408 | |
366 | And this is your standard poll(2) backend. It's more complicated |
409 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
410 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
411 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
412 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
413 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
414 | performance tips. |
372 | |
415 | |
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416 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
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417 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
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418 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
419 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
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420 | |
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421 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
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422 | kernels). |
374 | |
423 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
424 | For few fds, this backend is a bit little slower than poll and select, |
376 | but it scales phenomenally better. While poll and select usually scale |
425 | but it scales phenomenally better. While poll and select usually scale |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
426 | like O(total_fds) where n is the total number of fds (or the highest fd), |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
427 | epoll scales either O(1) or O(active_fds). |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
428 | |
380 | cases and requiring a system call per fd change, no fork support and bad |
429 | The epoll mechanism deserves honorable mention as the most misdesigned |
381 | support for dup. |
430 | of the more advanced event mechanisms: mere annoyances include silently |
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431 | dropping file descriptors, requiring a system call per change per file |
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432 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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433 | so on. The biggest issue is fork races, however - if a program forks then |
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434 | I<both> parent and child process have to recreate the epoll set, which can |
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435 | take considerable time (one syscall per file descriptor) and is of course |
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436 | hard to detect. |
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437 | |
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438 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
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439 | of course I<doesn't>, and epoll just loves to report events for totally |
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440 | I<different> file descriptors (even already closed ones, so one cannot |
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441 | even remove them from the set) than registered in the set (especially |
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442 | on SMP systems). Libev tries to counter these spurious notifications by |
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443 | employing an additional generation counter and comparing that against the |
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444 | events to filter out spurious ones, recreating the set when required. Last |
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445 | not least, it also refuses to work with some file descriptors which work |
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446 | perfectly fine with C<select> (files, many character devices...). |
382 | |
447 | |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
448 | While stopping, setting and starting an I/O watcher in the same iteration |
384 | will result in some caching, there is still a system call per such incident |
449 | will result in some caching, there is still a system call per such |
385 | (because the fd could point to a different file description now), so its |
450 | incident (because the same I<file descriptor> could point to a different |
386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
451 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
387 | very well if you register events for both fds. |
452 | file descriptors might not work very well if you register events for both |
388 | |
453 | file descriptors. |
389 | Please note that epoll sometimes generates spurious notifications, so you |
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390 | need to use non-blocking I/O or other means to avoid blocking when no data |
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391 | (or space) is available. |
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392 | |
454 | |
393 | Best performance from this backend is achieved by not unregistering all |
455 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
456 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
457 | i.e. keep at least one watcher active per fd at all times. Stopping and |
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458 | starting a watcher (without re-setting it) also usually doesn't cause |
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459 | extra overhead. A fork can both result in spurious notifications as well |
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460 | as in libev having to destroy and recreate the epoll object, which can |
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461 | take considerable time and thus should be avoided. |
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462 | |
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463 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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464 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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465 | the usage. So sad. |
396 | |
466 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
467 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
468 | all kernel versions tested so far. |
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469 | |
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470 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
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471 | C<EVBACKEND_POLL>. |
399 | |
472 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
473 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
474 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
475 | Kqueue deserves special mention, as at the time of this writing, it |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
476 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
404 | with anything but sockets and pipes, except on Darwin, where of course |
477 | with anything but sockets and pipes, except on Darwin, where of course |
405 | it's completely useless). For this reason it's not being "auto-detected" |
478 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
479 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
480 | without API changes to existing programs. For this reason it's not being |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
481 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
482 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
408 | system like NetBSD. |
483 | system like NetBSD. |
409 | |
484 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
485 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
486 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
413 | |
488 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
489 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
490 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
491 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
492 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
493 | two event changes per incident. Support for C<fork ()> is very bad (but |
419 | drops fds silently in similarly hard-to-detect cases. |
494 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
495 | cases |
420 | |
496 | |
421 | This backend usually performs well under most conditions. |
497 | This backend usually performs well under most conditions. |
422 | |
498 | |
423 | While nominally embeddable in other event loops, this doesn't work |
499 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
500 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
501 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
502 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
503 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
428 | sockets. |
504 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
505 | |
|
|
506 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
507 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
508 | C<NOTE_EOF>. |
429 | |
509 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
510 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
511 | |
432 | This is not implemented yet (and might never be, unless you send me an |
512 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
513 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
526 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
527 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
528 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
529 | might perform better. |
450 | |
530 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
531 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
532 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
533 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
534 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
535 | |
|
|
536 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
537 | C<EVBACKEND_POLL>. |
454 | |
538 | |
455 | =item C<EVBACKEND_ALL> |
539 | =item C<EVBACKEND_ALL> |
456 | |
540 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
541 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
542 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
460 | |
544 | |
461 | It is definitely not recommended to use this flag. |
545 | It is definitely not recommended to use this flag. |
462 | |
546 | |
463 | =back |
547 | =back |
464 | |
548 | |
465 | If one or more of these are or'ed into the flags value, then only these |
549 | If one or more of the backend flags are or'ed into the flags value, |
466 | backends will be tried (in the reverse order as listed here). If none are |
550 | then only these backends will be tried (in the reverse order as listed |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
551 | here). If none are specified, all backends in C<ev_recommended_backends |
|
|
552 | ()> will be tried. |
468 | |
553 | |
469 | The most typical usage is like this: |
554 | Example: This is the most typical usage. |
470 | |
555 | |
471 | if (!ev_default_loop (0)) |
556 | if (!ev_default_loop (0)) |
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
557 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
473 | |
558 | |
474 | Restrict libev to the select and poll backends, and do not allow |
559 | Example: Restrict libev to the select and poll backends, and do not allow |
475 | environment settings to be taken into account: |
560 | environment settings to be taken into account: |
476 | |
561 | |
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
562 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
478 | |
563 | |
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
564 | Example: Use whatever libev has to offer, but make sure that kqueue is |
480 | available (warning, breaks stuff, best use only with your own private |
565 | used if available (warning, breaks stuff, best use only with your own |
481 | event loop and only if you know the OS supports your types of fds): |
566 | private event loop and only if you know the OS supports your types of |
|
|
567 | fds): |
482 | |
568 | |
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
569 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
484 | |
570 | |
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
571 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
486 | |
572 | |
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
573 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
488 | always distinct from the default loop. Unlike the default loop, it cannot |
574 | always distinct from the default loop. |
489 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
491 | |
575 | |
492 | Note that this function I<is> thread-safe, and the recommended way to use |
576 | Note that this function I<is> thread-safe, and one common way to use |
493 | libev with threads is indeed to create one loop per thread, and using the |
577 | libev with threads is indeed to create one loop per thread, and using the |
494 | default loop in the "main" or "initial" thread. |
578 | default loop in the "main" or "initial" thread. |
495 | |
579 | |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
580 | Example: Try to create a event loop that uses epoll and nothing else. |
497 | |
581 | |
… | |
… | |
499 | if (!epoller) |
583 | if (!epoller) |
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
584 | fatal ("no epoll found here, maybe it hides under your chair"); |
501 | |
585 | |
502 | =item ev_default_destroy () |
586 | =item ev_default_destroy () |
503 | |
587 | |
504 | Destroys the default loop again (frees all memory and kernel state |
588 | Destroys the default loop (frees all memory and kernel state etc.). None |
505 | etc.). None of the active event watchers will be stopped in the normal |
589 | of the active event watchers will be stopped in the normal sense, so |
506 | sense, so e.g. C<ev_is_active> might still return true. It is your |
590 | e.g. C<ev_is_active> might still return true. It is your responsibility to |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
591 | either stop all watchers cleanly yourself I<before> calling this function, |
508 | calling this function, or cope with the fact afterwards (which is usually |
592 | or cope with the fact afterwards (which is usually the easiest thing, you |
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
593 | can just ignore the watchers and/or C<free ()> them for example). |
510 | for example). |
|
|
511 | |
594 | |
512 | Note that certain global state, such as signal state, will not be freed by |
595 | Note that certain global state, such as signal state (and installed signal |
513 | this function, and related watchers (such as signal and child watchers) |
596 | handlers), will not be freed by this function, and related watchers (such |
514 | would need to be stopped manually. |
597 | as signal and child watchers) would need to be stopped manually. |
515 | |
598 | |
516 | In general it is not advisable to call this function except in the |
599 | In general it is not advisable to call this function except in the |
517 | rare occasion where you really need to free e.g. the signal handling |
600 | rare occasion where you really need to free e.g. the signal handling |
518 | pipe fds. If you need dynamically allocated loops it is better to use |
601 | pipe fds. If you need dynamically allocated loops it is better to use |
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
602 | C<ev_loop_new> and C<ev_loop_destroy>. |
520 | |
603 | |
521 | =item ev_loop_destroy (loop) |
604 | =item ev_loop_destroy (loop) |
522 | |
605 | |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
606 | Like C<ev_default_destroy>, but destroys an event loop created by an |
524 | earlier call to C<ev_loop_new>. |
607 | earlier call to C<ev_loop_new>. |
525 | |
608 | |
526 | =item ev_default_fork () |
609 | =item ev_default_fork () |
527 | |
610 | |
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
611 | This function sets a flag that causes subsequent C<ev_run> iterations |
529 | to reinitialise the kernel state for backends that have one. Despite the |
612 | to reinitialise the kernel state for backends that have one. Despite the |
530 | name, you can call it anytime, but it makes most sense after forking, in |
613 | name, you can call it anytime, but it makes most sense after forking, in |
531 | the child process (or both child and parent, but that again makes little |
614 | the child process (or both child and parent, but that again makes little |
532 | sense). You I<must> call it in the child before using any of the libev |
615 | sense). You I<must> call it in the child before using any of the libev |
533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
616 | functions, and it will only take effect at the next C<ev_run> iteration. |
|
|
617 | |
|
|
618 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
619 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
620 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
621 | during fork. |
534 | |
622 | |
535 | On the other hand, you only need to call this function in the child |
623 | On the other hand, you only need to call this function in the child |
536 | process if and only if you want to use the event library in the child. If |
624 | process if and only if you want to use the event loop in the child. If |
537 | you just fork+exec, you don't have to call it at all. |
625 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
626 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
627 | difference, but libev will usually detect this case on its own and do a |
|
|
628 | costly reset of the backend). |
538 | |
629 | |
539 | The function itself is quite fast and it's usually not a problem to call |
630 | The function itself is quite fast and it's usually not a problem to call |
540 | it just in case after a fork. To make this easy, the function will fit in |
631 | it just in case after a fork. To make this easy, the function will fit in |
541 | quite nicely into a call to C<pthread_atfork>: |
632 | quite nicely into a call to C<pthread_atfork>: |
542 | |
633 | |
… | |
… | |
544 | |
635 | |
545 | =item ev_loop_fork (loop) |
636 | =item ev_loop_fork (loop) |
546 | |
637 | |
547 | Like C<ev_default_fork>, but acts on an event loop created by |
638 | Like C<ev_default_fork>, but acts on an event loop created by |
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
639 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
549 | after fork, and how you do this is entirely your own problem. |
640 | after fork that you want to re-use in the child, and how you keep track of |
|
|
641 | them is entirely your own problem. |
550 | |
642 | |
551 | =item int ev_is_default_loop (loop) |
643 | =item int ev_is_default_loop (loop) |
552 | |
644 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
645 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
646 | otherwise. |
554 | |
647 | |
555 | =item unsigned int ev_loop_count (loop) |
648 | =item unsigned int ev_iteration (loop) |
556 | |
649 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
650 | Returns the current iteration count for the event loop, which is identical |
558 | the number of times libev did poll for new events. It starts at C<0> and |
651 | to the number of times libev did poll for new events. It starts at C<0> |
559 | happily wraps around with enough iterations. |
652 | and happily wraps around with enough iterations. |
560 | |
653 | |
561 | This value can sometimes be useful as a generation counter of sorts (it |
654 | This value can sometimes be useful as a generation counter of sorts (it |
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
655 | "ticks" the number of loop iterations), as it roughly corresponds with |
563 | C<ev_prepare> and C<ev_check> calls. |
656 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
657 | prepare and check phases. |
|
|
658 | |
|
|
659 | =item unsigned int ev_depth (loop) |
|
|
660 | |
|
|
661 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
662 | times C<ev_run> was exited, in other words, the recursion depth. |
|
|
663 | |
|
|
664 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
665 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
666 | in which case it is higher. |
|
|
667 | |
|
|
668 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
|
|
669 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
670 | ungentleman-like behaviour unless it's really convenient. |
564 | |
671 | |
565 | =item unsigned int ev_backend (loop) |
672 | =item unsigned int ev_backend (loop) |
566 | |
673 | |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
674 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
568 | use. |
675 | use. |
… | |
… | |
573 | received events and started processing them. This timestamp does not |
680 | received events and started processing them. This timestamp does not |
574 | change as long as callbacks are being processed, and this is also the base |
681 | change as long as callbacks are being processed, and this is also the base |
575 | time used for relative timers. You can treat it as the timestamp of the |
682 | time used for relative timers. You can treat it as the timestamp of the |
576 | event occurring (or more correctly, libev finding out about it). |
683 | event occurring (or more correctly, libev finding out about it). |
577 | |
684 | |
|
|
685 | =item ev_now_update (loop) |
|
|
686 | |
|
|
687 | Establishes the current time by querying the kernel, updating the time |
|
|
688 | returned by C<ev_now ()> in the progress. This is a costly operation and |
|
|
689 | is usually done automatically within C<ev_run ()>. |
|
|
690 | |
|
|
691 | This function is rarely useful, but when some event callback runs for a |
|
|
692 | very long time without entering the event loop, updating libev's idea of |
|
|
693 | the current time is a good idea. |
|
|
694 | |
|
|
695 | See also L<The special problem of time updates> in the C<ev_timer> section. |
|
|
696 | |
|
|
697 | =item ev_suspend (loop) |
|
|
698 | |
|
|
699 | =item ev_resume (loop) |
|
|
700 | |
|
|
701 | These two functions suspend and resume an event loop, for use when the |
|
|
702 | loop is not used for a while and timeouts should not be processed. |
|
|
703 | |
|
|
704 | A typical use case would be an interactive program such as a game: When |
|
|
705 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
706 | would be best to handle timeouts as if no time had actually passed while |
|
|
707 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
708 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
709 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
710 | |
|
|
711 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
712 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
713 | will be rescheduled (that is, they will lose any events that would have |
|
|
714 | occurred while suspended). |
|
|
715 | |
|
|
716 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
717 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
718 | without a previous call to C<ev_suspend>. |
|
|
719 | |
|
|
720 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
721 | event loop time (see C<ev_now_update>). |
|
|
722 | |
578 | =item ev_loop (loop, int flags) |
723 | =item ev_run (loop, int flags) |
579 | |
724 | |
580 | Finally, this is it, the event handler. This function usually is called |
725 | Finally, this is it, the event handler. This function usually is called |
581 | after you initialised all your watchers and you want to start handling |
726 | after you have initialised all your watchers and you want to start |
582 | events. |
727 | handling events. It will ask the operating system for any new events, call |
|
|
728 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
729 | is why event loops are called I<loops>. |
583 | |
730 | |
584 | If the flags argument is specified as C<0>, it will not return until |
731 | If the flags argument is specified as C<0>, it will keep handling events |
585 | either no event watchers are active anymore or C<ev_unloop> was called. |
732 | until either no event watchers are active anymore or C<ev_break> was |
|
|
733 | called. |
586 | |
734 | |
587 | Please note that an explicit C<ev_unloop> is usually better than |
735 | Please note that an explicit C<ev_break> is usually better than |
588 | relying on all watchers to be stopped when deciding when a program has |
736 | relying on all watchers to be stopped when deciding when a program has |
589 | finished (especially in interactive programs), but having a program that |
737 | finished (especially in interactive programs), but having a program |
590 | automatically loops as long as it has to and no longer by virtue of |
738 | that automatically loops as long as it has to and no longer by virtue |
591 | relying on its watchers stopping correctly is a thing of beauty. |
739 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
740 | beauty. |
592 | |
741 | |
593 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
742 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
594 | those events and any outstanding ones, but will not block your process in |
743 | those events and any already outstanding ones, but will not wait and |
595 | case there are no events and will return after one iteration of the loop. |
744 | block your process in case there are no events and will return after one |
|
|
745 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
746 | events while doing lengthy calculations, to keep the program responsive. |
596 | |
747 | |
597 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
748 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
598 | necessary) and will handle those and any outstanding ones. It will block |
749 | necessary) and will handle those and any already outstanding ones. It |
599 | your process until at least one new event arrives, and will return after |
750 | will block your process until at least one new event arrives (which could |
600 | one iteration of the loop. This is useful if you are waiting for some |
751 | be an event internal to libev itself, so there is no guarantee that a |
601 | external event in conjunction with something not expressible using other |
752 | user-registered callback will be called), and will return after one |
|
|
753 | iteration of the loop. |
|
|
754 | |
|
|
755 | This is useful if you are waiting for some external event in conjunction |
|
|
756 | with something not expressible using other libev watchers (i.e. "roll your |
602 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
757 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
603 | usually a better approach for this kind of thing. |
758 | usually a better approach for this kind of thing. |
604 | |
759 | |
605 | Here are the gory details of what C<ev_loop> does: |
760 | Here are the gory details of what C<ev_run> does: |
606 | |
761 | |
|
|
762 | - Increment loop depth. |
|
|
763 | - Reset the ev_break status. |
607 | - Before the first iteration, call any pending watchers. |
764 | - Before the first iteration, call any pending watchers. |
|
|
765 | LOOP: |
608 | * If EVFLAG_FORKCHECK was used, check for a fork. |
766 | - If EVFLAG_FORKCHECK was used, check for a fork. |
609 | - If a fork was detected (by any means), queue and call all fork watchers. |
767 | - If a fork was detected (by any means), queue and call all fork watchers. |
610 | - Queue and call all prepare watchers. |
768 | - Queue and call all prepare watchers. |
|
|
769 | - If ev_break was called, goto FINISH. |
611 | - If we have been forked, detach and recreate the kernel state |
770 | - If we have been forked, detach and recreate the kernel state |
612 | as to not disturb the other process. |
771 | as to not disturb the other process. |
613 | - Update the kernel state with all outstanding changes. |
772 | - Update the kernel state with all outstanding changes. |
614 | - Update the "event loop time" (ev_now ()). |
773 | - Update the "event loop time" (ev_now ()). |
615 | - Calculate for how long to sleep or block, if at all |
774 | - Calculate for how long to sleep or block, if at all |
616 | (active idle watchers, EVLOOP_NONBLOCK or not having |
775 | (active idle watchers, EVRUN_NOWAIT or not having |
617 | any active watchers at all will result in not sleeping). |
776 | any active watchers at all will result in not sleeping). |
618 | - Sleep if the I/O and timer collect interval say so. |
777 | - Sleep if the I/O and timer collect interval say so. |
|
|
778 | - Increment loop iteration counter. |
619 | - Block the process, waiting for any events. |
779 | - Block the process, waiting for any events. |
620 | - Queue all outstanding I/O (fd) events. |
780 | - Queue all outstanding I/O (fd) events. |
621 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
781 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
622 | - Queue all outstanding timers. |
782 | - Queue all expired timers. |
623 | - Queue all outstanding periodics. |
783 | - Queue all expired periodics. |
624 | - Unless any events are pending now, queue all idle watchers. |
784 | - Queue all idle watchers with priority higher than that of pending events. |
625 | - Queue all check watchers. |
785 | - Queue all check watchers. |
626 | - Call all queued watchers in reverse order (i.e. check watchers first). |
786 | - Call all queued watchers in reverse order (i.e. check watchers first). |
627 | Signals and child watchers are implemented as I/O watchers, and will |
787 | Signals and child watchers are implemented as I/O watchers, and will |
628 | be handled here by queueing them when their watcher gets executed. |
788 | be handled here by queueing them when their watcher gets executed. |
629 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
789 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
630 | were used, or there are no active watchers, return, otherwise |
790 | were used, or there are no active watchers, goto FINISH, otherwise |
631 | continue with step *. |
791 | continue with step LOOP. |
|
|
792 | FINISH: |
|
|
793 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
794 | - Decrement the loop depth. |
|
|
795 | - Return. |
632 | |
796 | |
633 | Example: Queue some jobs and then loop until no events are outstanding |
797 | Example: Queue some jobs and then loop until no events are outstanding |
634 | anymore. |
798 | anymore. |
635 | |
799 | |
636 | ... queue jobs here, make sure they register event watchers as long |
800 | ... queue jobs here, make sure they register event watchers as long |
637 | ... as they still have work to do (even an idle watcher will do..) |
801 | ... as they still have work to do (even an idle watcher will do..) |
638 | ev_loop (my_loop, 0); |
802 | ev_run (my_loop, 0); |
639 | ... jobs done or somebody called unloop. yeah! |
803 | ... jobs done or somebody called unloop. yeah! |
640 | |
804 | |
641 | =item ev_unloop (loop, how) |
805 | =item ev_break (loop, how) |
642 | |
806 | |
643 | Can be used to make a call to C<ev_loop> return early (but only after it |
807 | Can be used to make a call to C<ev_run> return early (but only after it |
644 | has processed all outstanding events). The C<how> argument must be either |
808 | has processed all outstanding events). The C<how> argument must be either |
645 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
809 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
646 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
810 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
647 | |
811 | |
648 | This "unloop state" will be cleared when entering C<ev_loop> again. |
812 | This "unloop state" will be cleared when entering C<ev_run> again. |
|
|
813 | |
|
|
814 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
649 | |
815 | |
650 | =item ev_ref (loop) |
816 | =item ev_ref (loop) |
651 | |
817 | |
652 | =item ev_unref (loop) |
818 | =item ev_unref (loop) |
653 | |
819 | |
654 | Ref/unref can be used to add or remove a reference count on the event |
820 | Ref/unref can be used to add or remove a reference count on the event |
655 | loop: Every watcher keeps one reference, and as long as the reference |
821 | loop: Every watcher keeps one reference, and as long as the reference |
656 | count is nonzero, C<ev_loop> will not return on its own. If you have |
822 | count is nonzero, C<ev_run> will not return on its own. |
657 | a watcher you never unregister that should not keep C<ev_loop> from |
823 | |
658 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
824 | This is useful when you have a watcher that you never intend to |
|
|
825 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
826 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
827 | before stopping it. |
|
|
828 | |
659 | example, libev itself uses this for its internal signal pipe: It is not |
829 | As an example, libev itself uses this for its internal signal pipe: It |
660 | visible to the libev user and should not keep C<ev_loop> from exiting if |
830 | is not visible to the libev user and should not keep C<ev_run> from |
661 | no event watchers registered by it are active. It is also an excellent |
831 | exiting if no event watchers registered by it are active. It is also an |
662 | way to do this for generic recurring timers or from within third-party |
832 | excellent way to do this for generic recurring timers or from within |
663 | libraries. Just remember to I<unref after start> and I<ref before stop> |
833 | third-party libraries. Just remember to I<unref after start> and I<ref |
664 | (but only if the watcher wasn't active before, or was active before, |
834 | before stop> (but only if the watcher wasn't active before, or was active |
665 | respectively). |
835 | before, respectively. Note also that libev might stop watchers itself |
|
|
836 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
837 | in the callback). |
666 | |
838 | |
667 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
839 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
668 | running when nothing else is active. |
840 | running when nothing else is active. |
669 | |
841 | |
670 | struct ev_signal exitsig; |
842 | ev_signal exitsig; |
671 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
843 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
672 | ev_signal_start (loop, &exitsig); |
844 | ev_signal_start (loop, &exitsig); |
673 | evf_unref (loop); |
845 | evf_unref (loop); |
674 | |
846 | |
675 | Example: For some weird reason, unregister the above signal handler again. |
847 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
689 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
861 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
690 | allows libev to delay invocation of I/O and timer/periodic callbacks |
862 | allows libev to delay invocation of I/O and timer/periodic callbacks |
691 | to increase efficiency of loop iterations (or to increase power-saving |
863 | to increase efficiency of loop iterations (or to increase power-saving |
692 | opportunities). |
864 | opportunities). |
693 | |
865 | |
694 | The background is that sometimes your program runs just fast enough to |
866 | The idea is that sometimes your program runs just fast enough to handle |
695 | handle one (or very few) event(s) per loop iteration. While this makes |
867 | one (or very few) event(s) per loop iteration. While this makes the |
696 | the program responsive, it also wastes a lot of CPU time to poll for new |
868 | program responsive, it also wastes a lot of CPU time to poll for new |
697 | events, especially with backends like C<select ()> which have a high |
869 | events, especially with backends like C<select ()> which have a high |
698 | overhead for the actual polling but can deliver many events at once. |
870 | overhead for the actual polling but can deliver many events at once. |
699 | |
871 | |
700 | By setting a higher I<io collect interval> you allow libev to spend more |
872 | By setting a higher I<io collect interval> you allow libev to spend more |
701 | time collecting I/O events, so you can handle more events per iteration, |
873 | time collecting I/O events, so you can handle more events per iteration, |
702 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
874 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
703 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
875 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
704 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
876 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
877 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
878 | once per this interval, on average. |
705 | |
879 | |
706 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
880 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
707 | to spend more time collecting timeouts, at the expense of increased |
881 | to spend more time collecting timeouts, at the expense of increased |
708 | latency (the watcher callback will be called later). C<ev_io> watchers |
882 | latency/jitter/inexactness (the watcher callback will be called |
709 | will not be affected. Setting this to a non-null value will not introduce |
883 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
710 | any overhead in libev. |
884 | value will not introduce any overhead in libev. |
711 | |
885 | |
712 | Many (busy) programs can usually benefit by setting the I/O collect |
886 | Many (busy) programs can usually benefit by setting the I/O collect |
713 | interval to a value near C<0.1> or so, which is often enough for |
887 | interval to a value near C<0.1> or so, which is often enough for |
714 | interactive servers (of course not for games), likewise for timeouts. It |
888 | interactive servers (of course not for games), likewise for timeouts. It |
715 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
889 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
716 | as this approaches the timing granularity of most systems. |
890 | as this approaches the timing granularity of most systems. Note that if |
|
|
891 | you do transactions with the outside world and you can't increase the |
|
|
892 | parallelity, then this setting will limit your transaction rate (if you |
|
|
893 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
894 | then you can't do more than 100 transactions per second). |
717 | |
895 | |
718 | Setting the I<timeout collect interval> can improve the opportunity for |
896 | Setting the I<timeout collect interval> can improve the opportunity for |
719 | saving power, as the program will "bundle" timer callback invocations that |
897 | saving power, as the program will "bundle" timer callback invocations that |
720 | are "near" in time together, by delaying some, thus reducing the number of |
898 | are "near" in time together, by delaying some, thus reducing the number of |
721 | times the process sleeps and wakes up again. Another useful technique to |
899 | times the process sleeps and wakes up again. Another useful technique to |
722 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
900 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
723 | they fire on, say, one-second boundaries only. |
901 | they fire on, say, one-second boundaries only. |
724 | |
902 | |
|
|
903 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
904 | more often than 100 times per second: |
|
|
905 | |
|
|
906 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
907 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
908 | |
|
|
909 | =item ev_invoke_pending (loop) |
|
|
910 | |
|
|
911 | This call will simply invoke all pending watchers while resetting their |
|
|
912 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
913 | but when overriding the invoke callback this call comes handy. |
|
|
914 | |
|
|
915 | =item int ev_pending_count (loop) |
|
|
916 | |
|
|
917 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
918 | are pending. |
|
|
919 | |
|
|
920 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
921 | |
|
|
922 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
923 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
924 | this callback instead. This is useful, for example, when you want to |
|
|
925 | invoke the actual watchers inside another context (another thread etc.). |
|
|
926 | |
|
|
927 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
928 | callback. |
|
|
929 | |
|
|
930 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
931 | |
|
|
932 | Sometimes you want to share the same loop between multiple threads. This |
|
|
933 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
934 | each call to a libev function. |
|
|
935 | |
|
|
936 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
937 | to wait for it to return. One way around this is to wake up the event |
|
|
938 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
939 | I<release> and I<acquire> callbacks on the loop. |
|
|
940 | |
|
|
941 | When set, then C<release> will be called just before the thread is |
|
|
942 | suspended waiting for new events, and C<acquire> is called just |
|
|
943 | afterwards. |
|
|
944 | |
|
|
945 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
946 | C<acquire> will just call the mutex_lock function again. |
|
|
947 | |
|
|
948 | While event loop modifications are allowed between invocations of |
|
|
949 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
950 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
951 | have no effect on the set of file descriptors being watched, or the time |
|
|
952 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
953 | to take note of any changes you made. |
|
|
954 | |
|
|
955 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
956 | invocations of C<release> and C<acquire>. |
|
|
957 | |
|
|
958 | See also the locking example in the C<THREADS> section later in this |
|
|
959 | document. |
|
|
960 | |
|
|
961 | =item ev_set_userdata (loop, void *data) |
|
|
962 | |
|
|
963 | =item ev_userdata (loop) |
|
|
964 | |
|
|
965 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
966 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
967 | C<0.> |
|
|
968 | |
|
|
969 | These two functions can be used to associate arbitrary data with a loop, |
|
|
970 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
971 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
972 | any other purpose as well. |
|
|
973 | |
725 | =item ev_loop_verify (loop) |
974 | =item ev_verify (loop) |
726 | |
975 | |
727 | This function only does something when C<EV_VERIFY> support has been |
976 | This function only does something when C<EV_VERIFY> support has been |
728 | compiled in. It tries to go through all internal structures and checks |
977 | compiled in, which is the default for non-minimal builds. It tries to go |
729 | them for validity. If anything is found to be inconsistent, it will print |
978 | through all internal structures and checks them for validity. If anything |
730 | an error message to standard error and call C<abort ()>. |
979 | is found to be inconsistent, it will print an error message to standard |
|
|
980 | error and call C<abort ()>. |
731 | |
981 | |
732 | This can be used to catch bugs inside libev itself: under normal |
982 | This can be used to catch bugs inside libev itself: under normal |
733 | circumstances, this function will never abort as of course libev keeps its |
983 | circumstances, this function will never abort as of course libev keeps its |
734 | data structures consistent. |
984 | data structures consistent. |
735 | |
985 | |
736 | =back |
986 | =back |
737 | |
987 | |
738 | |
988 | |
739 | =head1 ANATOMY OF A WATCHER |
989 | =head1 ANATOMY OF A WATCHER |
740 | |
990 | |
|
|
991 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
992 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
993 | watchers and C<ev_io_start> for I/O watchers. |
|
|
994 | |
741 | A watcher is a structure that you create and register to record your |
995 | A watcher is a structure that you create and register to record your |
742 | interest in some event. For instance, if you want to wait for STDIN to |
996 | interest in some event. For instance, if you want to wait for STDIN to |
743 | become readable, you would create an C<ev_io> watcher for that: |
997 | become readable, you would create an C<ev_io> watcher for that: |
744 | |
998 | |
745 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
999 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
746 | { |
1000 | { |
747 | ev_io_stop (w); |
1001 | ev_io_stop (w); |
748 | ev_unloop (loop, EVUNLOOP_ALL); |
1002 | ev_break (loop, EVBREAK_ALL); |
749 | } |
1003 | } |
750 | |
1004 | |
751 | struct ev_loop *loop = ev_default_loop (0); |
1005 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1006 | |
752 | struct ev_io stdin_watcher; |
1007 | ev_io stdin_watcher; |
|
|
1008 | |
753 | ev_init (&stdin_watcher, my_cb); |
1009 | ev_init (&stdin_watcher, my_cb); |
754 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1010 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
755 | ev_io_start (loop, &stdin_watcher); |
1011 | ev_io_start (loop, &stdin_watcher); |
|
|
1012 | |
756 | ev_loop (loop, 0); |
1013 | ev_run (loop, 0); |
757 | |
1014 | |
758 | As you can see, you are responsible for allocating the memory for your |
1015 | As you can see, you are responsible for allocating the memory for your |
759 | watcher structures (and it is usually a bad idea to do this on the stack, |
1016 | watcher structures (and it is I<usually> a bad idea to do this on the |
760 | although this can sometimes be quite valid). |
1017 | stack). |
|
|
1018 | |
|
|
1019 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1020 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
761 | |
1021 | |
762 | Each watcher structure must be initialised by a call to C<ev_init |
1022 | Each watcher structure must be initialised by a call to C<ev_init |
763 | (watcher *, callback)>, which expects a callback to be provided. This |
1023 | (watcher *, callback)>, which expects a callback to be provided. This |
764 | callback gets invoked each time the event occurs (or, in the case of I/O |
1024 | callback gets invoked each time the event occurs (or, in the case of I/O |
765 | watchers, each time the event loop detects that the file descriptor given |
1025 | watchers, each time the event loop detects that the file descriptor given |
766 | is readable and/or writable). |
1026 | is readable and/or writable). |
767 | |
1027 | |
768 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1028 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
769 | with arguments specific to this watcher type. There is also a macro |
1029 | macro to configure it, with arguments specific to the watcher type. There |
770 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1030 | is also a macro to combine initialisation and setting in one call: C<< |
771 | (watcher *, callback, ...) >>. |
1031 | ev_TYPE_init (watcher *, callback, ...) >>. |
772 | |
1032 | |
773 | To make the watcher actually watch out for events, you have to start it |
1033 | To make the watcher actually watch out for events, you have to start it |
774 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1034 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
775 | *) >>), and you can stop watching for events at any time by calling the |
1035 | *) >>), and you can stop watching for events at any time by calling the |
776 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1036 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
777 | |
1037 | |
778 | As long as your watcher is active (has been started but not stopped) you |
1038 | As long as your watcher is active (has been started but not stopped) you |
779 | must not touch the values stored in it. Most specifically you must never |
1039 | must not touch the values stored in it. Most specifically you must never |
780 | reinitialise it or call its C<set> macro. |
1040 | reinitialise it or call its C<ev_TYPE_set> macro. |
781 | |
1041 | |
782 | Each and every callback receives the event loop pointer as first, the |
1042 | Each and every callback receives the event loop pointer as first, the |
783 | registered watcher structure as second, and a bitset of received events as |
1043 | registered watcher structure as second, and a bitset of received events as |
784 | third argument. |
1044 | third argument. |
785 | |
1045 | |
… | |
… | |
794 | =item C<EV_WRITE> |
1054 | =item C<EV_WRITE> |
795 | |
1055 | |
796 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1056 | The file descriptor in the C<ev_io> watcher has become readable and/or |
797 | writable. |
1057 | writable. |
798 | |
1058 | |
799 | =item C<EV_TIMEOUT> |
1059 | =item C<EV_TIMER> |
800 | |
1060 | |
801 | The C<ev_timer> watcher has timed out. |
1061 | The C<ev_timer> watcher has timed out. |
802 | |
1062 | |
803 | =item C<EV_PERIODIC> |
1063 | =item C<EV_PERIODIC> |
804 | |
1064 | |
… | |
… | |
822 | |
1082 | |
823 | =item C<EV_PREPARE> |
1083 | =item C<EV_PREPARE> |
824 | |
1084 | |
825 | =item C<EV_CHECK> |
1085 | =item C<EV_CHECK> |
826 | |
1086 | |
827 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1087 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
828 | to gather new events, and all C<ev_check> watchers are invoked just after |
1088 | to gather new events, and all C<ev_check> watchers are invoked just after |
829 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1089 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
830 | received events. Callbacks of both watcher types can start and stop as |
1090 | received events. Callbacks of both watcher types can start and stop as |
831 | many watchers as they want, and all of them will be taken into account |
1091 | many watchers as they want, and all of them will be taken into account |
832 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1092 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
833 | C<ev_loop> from blocking). |
1093 | C<ev_run> from blocking). |
834 | |
1094 | |
835 | =item C<EV_EMBED> |
1095 | =item C<EV_EMBED> |
836 | |
1096 | |
837 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1097 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
838 | |
1098 | |
… | |
… | |
842 | C<ev_fork>). |
1102 | C<ev_fork>). |
843 | |
1103 | |
844 | =item C<EV_ASYNC> |
1104 | =item C<EV_ASYNC> |
845 | |
1105 | |
846 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1106 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1107 | |
|
|
1108 | =item C<EV_CUSTOM> |
|
|
1109 | |
|
|
1110 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1111 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
847 | |
1112 | |
848 | =item C<EV_ERROR> |
1113 | =item C<EV_ERROR> |
849 | |
1114 | |
850 | An unspecified error has occurred, the watcher has been stopped. This might |
1115 | An unspecified error has occurred, the watcher has been stopped. This might |
851 | happen because the watcher could not be properly started because libev |
1116 | happen because the watcher could not be properly started because libev |
852 | ran out of memory, a file descriptor was found to be closed or any other |
1117 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1118 | problem. Libev considers these application bugs. |
|
|
1119 | |
853 | problem. You best act on it by reporting the problem and somehow coping |
1120 | You best act on it by reporting the problem and somehow coping with the |
854 | with the watcher being stopped. |
1121 | watcher being stopped. Note that well-written programs should not receive |
|
|
1122 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1123 | bug in your program. |
855 | |
1124 | |
856 | Libev will usually signal a few "dummy" events together with an error, |
1125 | Libev will usually signal a few "dummy" events together with an error, for |
857 | for example it might indicate that a fd is readable or writable, and if |
1126 | example it might indicate that a fd is readable or writable, and if your |
858 | your callbacks is well-written it can just attempt the operation and cope |
1127 | callbacks is well-written it can just attempt the operation and cope with |
859 | with the error from read() or write(). This will not work in multi-threaded |
1128 | the error from read() or write(). This will not work in multi-threaded |
860 | programs, though, so beware. |
1129 | programs, though, as the fd could already be closed and reused for another |
|
|
1130 | thing, so beware. |
861 | |
1131 | |
862 | =back |
1132 | =back |
863 | |
1133 | |
864 | =head2 GENERIC WATCHER FUNCTIONS |
1134 | =head2 GENERIC WATCHER FUNCTIONS |
865 | |
|
|
866 | In the following description, C<TYPE> stands for the watcher type, |
|
|
867 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
868 | |
1135 | |
869 | =over 4 |
1136 | =over 4 |
870 | |
1137 | |
871 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1138 | =item C<ev_init> (ev_TYPE *watcher, callback) |
872 | |
1139 | |
… | |
… | |
878 | which rolls both calls into one. |
1145 | which rolls both calls into one. |
879 | |
1146 | |
880 | You can reinitialise a watcher at any time as long as it has been stopped |
1147 | You can reinitialise a watcher at any time as long as it has been stopped |
881 | (or never started) and there are no pending events outstanding. |
1148 | (or never started) and there are no pending events outstanding. |
882 | |
1149 | |
883 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1150 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
884 | int revents)>. |
1151 | int revents)>. |
885 | |
1152 | |
|
|
1153 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1154 | |
|
|
1155 | ev_io w; |
|
|
1156 | ev_init (&w, my_cb); |
|
|
1157 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1158 | |
886 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1159 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
887 | |
1160 | |
888 | This macro initialises the type-specific parts of a watcher. You need to |
1161 | This macro initialises the type-specific parts of a watcher. You need to |
889 | call C<ev_init> at least once before you call this macro, but you can |
1162 | call C<ev_init> at least once before you call this macro, but you can |
890 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1163 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
891 | macro on a watcher that is active (it can be pending, however, which is a |
1164 | macro on a watcher that is active (it can be pending, however, which is a |
892 | difference to the C<ev_init> macro). |
1165 | difference to the C<ev_init> macro). |
893 | |
1166 | |
894 | Although some watcher types do not have type-specific arguments |
1167 | Although some watcher types do not have type-specific arguments |
895 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1168 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
896 | |
1169 | |
|
|
1170 | See C<ev_init>, above, for an example. |
|
|
1171 | |
897 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1172 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
898 | |
1173 | |
899 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1174 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
900 | calls into a single call. This is the most convenient method to initialise |
1175 | calls into a single call. This is the most convenient method to initialise |
901 | a watcher. The same limitations apply, of course. |
1176 | a watcher. The same limitations apply, of course. |
902 | |
1177 | |
|
|
1178 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1179 | |
|
|
1180 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1181 | |
903 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1182 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
904 | |
1183 | |
905 | Starts (activates) the given watcher. Only active watchers will receive |
1184 | Starts (activates) the given watcher. Only active watchers will receive |
906 | events. If the watcher is already active nothing will happen. |
1185 | events. If the watcher is already active nothing will happen. |
907 | |
1186 | |
|
|
1187 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1188 | whole section. |
|
|
1189 | |
|
|
1190 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1191 | |
908 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1192 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
909 | |
1193 | |
910 | Stops the given watcher again (if active) and clears the pending |
1194 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1195 | the watcher was active or not). |
|
|
1196 | |
911 | status. It is possible that stopped watchers are pending (for example, |
1197 | It is possible that stopped watchers are pending - for example, |
912 | non-repeating timers are being stopped when they become pending), but |
1198 | non-repeating timers are being stopped when they become pending - but |
913 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1199 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
914 | you want to free or reuse the memory used by the watcher it is therefore a |
1200 | pending. If you want to free or reuse the memory used by the watcher it is |
915 | good idea to always call its C<ev_TYPE_stop> function. |
1201 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
916 | |
1202 | |
917 | =item bool ev_is_active (ev_TYPE *watcher) |
1203 | =item bool ev_is_active (ev_TYPE *watcher) |
918 | |
1204 | |
919 | Returns a true value iff the watcher is active (i.e. it has been started |
1205 | Returns a true value iff the watcher is active (i.e. it has been started |
920 | and not yet been stopped). As long as a watcher is active you must not modify |
1206 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
936 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1222 | =item ev_cb_set (ev_TYPE *watcher, callback) |
937 | |
1223 | |
938 | Change the callback. You can change the callback at virtually any time |
1224 | Change the callback. You can change the callback at virtually any time |
939 | (modulo threads). |
1225 | (modulo threads). |
940 | |
1226 | |
941 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1227 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
942 | |
1228 | |
943 | =item int ev_priority (ev_TYPE *watcher) |
1229 | =item int ev_priority (ev_TYPE *watcher) |
944 | |
1230 | |
945 | Set and query the priority of the watcher. The priority is a small |
1231 | Set and query the priority of the watcher. The priority is a small |
946 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1232 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
947 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1233 | (default: C<-2>). Pending watchers with higher priority will be invoked |
948 | before watchers with lower priority, but priority will not keep watchers |
1234 | before watchers with lower priority, but priority will not keep watchers |
949 | from being executed (except for C<ev_idle> watchers). |
1235 | from being executed (except for C<ev_idle> watchers). |
950 | |
1236 | |
951 | This means that priorities are I<only> used for ordering callback |
|
|
952 | invocation after new events have been received. This is useful, for |
|
|
953 | example, to reduce latency after idling, or more often, to bind two |
|
|
954 | watchers on the same event and make sure one is called first. |
|
|
955 | |
|
|
956 | If you need to suppress invocation when higher priority events are pending |
1237 | If you need to suppress invocation when higher priority events are pending |
957 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1238 | you need to look at C<ev_idle> watchers, which provide this functionality. |
958 | |
1239 | |
959 | You I<must not> change the priority of a watcher as long as it is active or |
1240 | You I<must not> change the priority of a watcher as long as it is active or |
960 | pending. |
1241 | pending. |
961 | |
1242 | |
|
|
1243 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1244 | fine, as long as you do not mind that the priority value you query might |
|
|
1245 | or might not have been clamped to the valid range. |
|
|
1246 | |
962 | The default priority used by watchers when no priority has been set is |
1247 | The default priority used by watchers when no priority has been set is |
963 | always C<0>, which is supposed to not be too high and not be too low :). |
1248 | always C<0>, which is supposed to not be too high and not be too low :). |
964 | |
1249 | |
965 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1250 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
966 | fine, as long as you do not mind that the priority value you query might |
1251 | priorities. |
967 | or might not have been adjusted to be within valid range. |
|
|
968 | |
1252 | |
969 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1253 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
970 | |
1254 | |
971 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1255 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
972 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1256 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
973 | can deal with that fact. |
1257 | can deal with that fact, as both are simply passed through to the |
|
|
1258 | callback. |
974 | |
1259 | |
975 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1260 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
976 | |
1261 | |
977 | If the watcher is pending, this function returns clears its pending status |
1262 | If the watcher is pending, this function clears its pending status and |
978 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1263 | returns its C<revents> bitset (as if its callback was invoked). If the |
979 | watcher isn't pending it does nothing and returns C<0>. |
1264 | watcher isn't pending it does nothing and returns C<0>. |
980 | |
1265 | |
|
|
1266 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1267 | callback to be invoked, which can be accomplished with this function. |
|
|
1268 | |
|
|
1269 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1270 | |
|
|
1271 | Feeds the given event set into the event loop, as if the specified event |
|
|
1272 | had happened for the specified watcher (which must be a pointer to an |
|
|
1273 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1274 | not free the watcher as long as it has pending events. |
|
|
1275 | |
|
|
1276 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1277 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1278 | not started in the first place. |
|
|
1279 | |
|
|
1280 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1281 | functions that do not need a watcher. |
|
|
1282 | |
981 | =back |
1283 | =back |
982 | |
1284 | |
983 | |
1285 | |
984 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1286 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
985 | |
1287 | |
986 | Each watcher has, by default, a member C<void *data> that you can change |
1288 | Each watcher has, by default, a member C<void *data> that you can change |
987 | and read at any time, libev will completely ignore it. This can be used |
1289 | and read at any time: libev will completely ignore it. This can be used |
988 | to associate arbitrary data with your watcher. If you need more data and |
1290 | to associate arbitrary data with your watcher. If you need more data and |
989 | don't want to allocate memory and store a pointer to it in that data |
1291 | don't want to allocate memory and store a pointer to it in that data |
990 | member, you can also "subclass" the watcher type and provide your own |
1292 | member, you can also "subclass" the watcher type and provide your own |
991 | data: |
1293 | data: |
992 | |
1294 | |
993 | struct my_io |
1295 | struct my_io |
994 | { |
1296 | { |
995 | struct ev_io io; |
1297 | ev_io io; |
996 | int otherfd; |
1298 | int otherfd; |
997 | void *somedata; |
1299 | void *somedata; |
998 | struct whatever *mostinteresting; |
1300 | struct whatever *mostinteresting; |
999 | } |
1301 | }; |
|
|
1302 | |
|
|
1303 | ... |
|
|
1304 | struct my_io w; |
|
|
1305 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1000 | |
1306 | |
1001 | And since your callback will be called with a pointer to the watcher, you |
1307 | And since your callback will be called with a pointer to the watcher, you |
1002 | can cast it back to your own type: |
1308 | can cast it back to your own type: |
1003 | |
1309 | |
1004 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1310 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1005 | { |
1311 | { |
1006 | struct my_io *w = (struct my_io *)w_; |
1312 | struct my_io *w = (struct my_io *)w_; |
1007 | ... |
1313 | ... |
1008 | } |
1314 | } |
1009 | |
1315 | |
1010 | More interesting and less C-conformant ways of casting your callback type |
1316 | More interesting and less C-conformant ways of casting your callback type |
1011 | instead have been omitted. |
1317 | instead have been omitted. |
1012 | |
1318 | |
1013 | Another common scenario is having some data structure with multiple |
1319 | Another common scenario is to use some data structure with multiple |
1014 | watchers: |
1320 | embedded watchers: |
1015 | |
1321 | |
1016 | struct my_biggy |
1322 | struct my_biggy |
1017 | { |
1323 | { |
1018 | int some_data; |
1324 | int some_data; |
1019 | ev_timer t1; |
1325 | ev_timer t1; |
1020 | ev_timer t2; |
1326 | ev_timer t2; |
1021 | } |
1327 | } |
1022 | |
1328 | |
1023 | In this case getting the pointer to C<my_biggy> is a bit more complicated, |
1329 | In this case getting the pointer to C<my_biggy> is a bit more |
1024 | you need to use C<offsetof>: |
1330 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1331 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1332 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1333 | programmers): |
1025 | |
1334 | |
1026 | #include <stddef.h> |
1335 | #include <stddef.h> |
1027 | |
1336 | |
1028 | static void |
1337 | static void |
1029 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1338 | t1_cb (EV_P_ ev_timer *w, int revents) |
1030 | { |
1339 | { |
1031 | struct my_biggy big = (struct my_biggy * |
1340 | struct my_biggy big = (struct my_biggy *) |
1032 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1341 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1033 | } |
1342 | } |
1034 | |
1343 | |
1035 | static void |
1344 | static void |
1036 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1345 | t2_cb (EV_P_ ev_timer *w, int revents) |
1037 | { |
1346 | { |
1038 | struct my_biggy big = (struct my_biggy * |
1347 | struct my_biggy big = (struct my_biggy *) |
1039 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1348 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1040 | } |
1349 | } |
|
|
1350 | |
|
|
1351 | =head2 WATCHER PRIORITY MODELS |
|
|
1352 | |
|
|
1353 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1354 | integers that influence the ordering of event callback invocation |
|
|
1355 | between watchers in some way, all else being equal. |
|
|
1356 | |
|
|
1357 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1358 | description for the more technical details such as the actual priority |
|
|
1359 | range. |
|
|
1360 | |
|
|
1361 | There are two common ways how these these priorities are being interpreted |
|
|
1362 | by event loops: |
|
|
1363 | |
|
|
1364 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1365 | of lower priority watchers, which means as long as higher priority |
|
|
1366 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1367 | |
|
|
1368 | The less common only-for-ordering model uses priorities solely to order |
|
|
1369 | callback invocation within a single event loop iteration: Higher priority |
|
|
1370 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1371 | before polling for new events. |
|
|
1372 | |
|
|
1373 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1374 | except for idle watchers (which use the lock-out model). |
|
|
1375 | |
|
|
1376 | The rationale behind this is that implementing the lock-out model for |
|
|
1377 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1378 | libraries will just poll for the same events again and again as long as |
|
|
1379 | their callbacks have not been executed, which is very inefficient in the |
|
|
1380 | common case of one high-priority watcher locking out a mass of lower |
|
|
1381 | priority ones. |
|
|
1382 | |
|
|
1383 | Static (ordering) priorities are most useful when you have two or more |
|
|
1384 | watchers handling the same resource: a typical usage example is having an |
|
|
1385 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1386 | timeouts. Under load, data might be received while the program handles |
|
|
1387 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1388 | handler will be executed before checking for data. In that case, giving |
|
|
1389 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1390 | handled first even under adverse conditions (which is usually, but not |
|
|
1391 | always, what you want). |
|
|
1392 | |
|
|
1393 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1394 | will only be executed when no same or higher priority watchers have |
|
|
1395 | received events, they can be used to implement the "lock-out" model when |
|
|
1396 | required. |
|
|
1397 | |
|
|
1398 | For example, to emulate how many other event libraries handle priorities, |
|
|
1399 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1400 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1401 | processing is done in the idle watcher callback. This causes libev to |
|
|
1402 | continuously poll and process kernel event data for the watcher, but when |
|
|
1403 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1404 | workable. |
|
|
1405 | |
|
|
1406 | Usually, however, the lock-out model implemented that way will perform |
|
|
1407 | miserably under the type of load it was designed to handle. In that case, |
|
|
1408 | it might be preferable to stop the real watcher before starting the |
|
|
1409 | idle watcher, so the kernel will not have to process the event in case |
|
|
1410 | the actual processing will be delayed for considerable time. |
|
|
1411 | |
|
|
1412 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1413 | priority than the default, and which should only process data when no |
|
|
1414 | other events are pending: |
|
|
1415 | |
|
|
1416 | ev_idle idle; // actual processing watcher |
|
|
1417 | ev_io io; // actual event watcher |
|
|
1418 | |
|
|
1419 | static void |
|
|
1420 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1421 | { |
|
|
1422 | // stop the I/O watcher, we received the event, but |
|
|
1423 | // are not yet ready to handle it. |
|
|
1424 | ev_io_stop (EV_A_ w); |
|
|
1425 | |
|
|
1426 | // start the idle watcher to handle the actual event. |
|
|
1427 | // it will not be executed as long as other watchers |
|
|
1428 | // with the default priority are receiving events. |
|
|
1429 | ev_idle_start (EV_A_ &idle); |
|
|
1430 | } |
|
|
1431 | |
|
|
1432 | static void |
|
|
1433 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1434 | { |
|
|
1435 | // actual processing |
|
|
1436 | read (STDIN_FILENO, ...); |
|
|
1437 | |
|
|
1438 | // have to start the I/O watcher again, as |
|
|
1439 | // we have handled the event |
|
|
1440 | ev_io_start (EV_P_ &io); |
|
|
1441 | } |
|
|
1442 | |
|
|
1443 | // initialisation |
|
|
1444 | ev_idle_init (&idle, idle_cb); |
|
|
1445 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1446 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1447 | |
|
|
1448 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1449 | low-priority connections can not be locked out forever under load. This |
|
|
1450 | enables your program to keep a lower latency for important connections |
|
|
1451 | during short periods of high load, while not completely locking out less |
|
|
1452 | important ones. |
1041 | |
1453 | |
1042 | |
1454 | |
1043 | =head1 WATCHER TYPES |
1455 | =head1 WATCHER TYPES |
1044 | |
1456 | |
1045 | This section describes each watcher in detail, but will not repeat |
1457 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1069 | In general you can register as many read and/or write event watchers per |
1481 | In general you can register as many read and/or write event watchers per |
1070 | fd as you want (as long as you don't confuse yourself). Setting all file |
1482 | fd as you want (as long as you don't confuse yourself). Setting all file |
1071 | descriptors to non-blocking mode is also usually a good idea (but not |
1483 | descriptors to non-blocking mode is also usually a good idea (but not |
1072 | required if you know what you are doing). |
1484 | required if you know what you are doing). |
1073 | |
1485 | |
1074 | If you must do this, then force the use of a known-to-be-good backend |
1486 | If you cannot use non-blocking mode, then force the use of a |
1075 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1487 | known-to-be-good backend (at the time of this writing, this includes only |
1076 | C<EVBACKEND_POLL>). |
1488 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1489 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1490 | files) - libev doesn't guarantee any specific behaviour in that case. |
1077 | |
1491 | |
1078 | Another thing you have to watch out for is that it is quite easy to |
1492 | Another thing you have to watch out for is that it is quite easy to |
1079 | receive "spurious" readiness notifications, that is your callback might |
1493 | receive "spurious" readiness notifications, that is your callback might |
1080 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1494 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1081 | because there is no data. Not only are some backends known to create a |
1495 | because there is no data. Not only are some backends known to create a |
1082 | lot of those (for example Solaris ports), it is very easy to get into |
1496 | lot of those (for example Solaris ports), it is very easy to get into |
1083 | this situation even with a relatively standard program structure. Thus |
1497 | this situation even with a relatively standard program structure. Thus |
1084 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1498 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1085 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1499 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1086 | |
1500 | |
1087 | If you cannot run the fd in non-blocking mode (for example you should not |
1501 | If you cannot run the fd in non-blocking mode (for example you should |
1088 | play around with an Xlib connection), then you have to separately re-test |
1502 | not play around with an Xlib connection), then you have to separately |
1089 | whether a file descriptor is really ready with a known-to-be good interface |
1503 | re-test whether a file descriptor is really ready with a known-to-be good |
1090 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1504 | interface such as poll (fortunately in our Xlib example, Xlib already |
1091 | its own, so its quite safe to use). |
1505 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1506 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1507 | indefinitely. |
|
|
1508 | |
|
|
1509 | But really, best use non-blocking mode. |
1092 | |
1510 | |
1093 | =head3 The special problem of disappearing file descriptors |
1511 | =head3 The special problem of disappearing file descriptors |
1094 | |
1512 | |
1095 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1513 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1096 | descriptor (either by calling C<close> explicitly or by any other means, |
1514 | descriptor (either due to calling C<close> explicitly or any other means, |
1097 | such as C<dup>). The reason is that you register interest in some file |
1515 | such as C<dup2>). The reason is that you register interest in some file |
1098 | descriptor, but when it goes away, the operating system will silently drop |
1516 | descriptor, but when it goes away, the operating system will silently drop |
1099 | this interest. If another file descriptor with the same number then is |
1517 | this interest. If another file descriptor with the same number then is |
1100 | registered with libev, there is no efficient way to see that this is, in |
1518 | registered with libev, there is no efficient way to see that this is, in |
1101 | fact, a different file descriptor. |
1519 | fact, a different file descriptor. |
1102 | |
1520 | |
… | |
… | |
1133 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1551 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1134 | C<EVBACKEND_POLL>. |
1552 | C<EVBACKEND_POLL>. |
1135 | |
1553 | |
1136 | =head3 The special problem of SIGPIPE |
1554 | =head3 The special problem of SIGPIPE |
1137 | |
1555 | |
1138 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1556 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1139 | when writing to a pipe whose other end has been closed, your program gets |
1557 | when writing to a pipe whose other end has been closed, your program gets |
1140 | send a SIGPIPE, which, by default, aborts your program. For most programs |
1558 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1141 | this is sensible behaviour, for daemons, this is usually undesirable. |
1559 | this is sensible behaviour, for daemons, this is usually undesirable. |
1142 | |
1560 | |
1143 | So when you encounter spurious, unexplained daemon exits, make sure you |
1561 | So when you encounter spurious, unexplained daemon exits, make sure you |
1144 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1562 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1145 | somewhere, as that would have given you a big clue). |
1563 | somewhere, as that would have given you a big clue). |
1146 | |
1564 | |
|
|
1565 | =head3 The special problem of accept()ing when you can't |
|
|
1566 | |
|
|
1567 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1568 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1569 | connection from the pending queue in all error cases. |
|
|
1570 | |
|
|
1571 | For example, larger servers often run out of file descriptors (because |
|
|
1572 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1573 | rejecting the connection, leading to libev signalling readiness on |
|
|
1574 | the next iteration again (the connection still exists after all), and |
|
|
1575 | typically causing the program to loop at 100% CPU usage. |
|
|
1576 | |
|
|
1577 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1578 | operating systems, there is usually little the app can do to remedy the |
|
|
1579 | situation, and no known thread-safe method of removing the connection to |
|
|
1580 | cope with overload is known (to me). |
|
|
1581 | |
|
|
1582 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1583 | - when the program encounters an overload, it will just loop until the |
|
|
1584 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1585 | event-based way to handle this situation, so it's the best one can do. |
|
|
1586 | |
|
|
1587 | A better way to handle the situation is to log any errors other than |
|
|
1588 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1589 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1590 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1591 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1592 | usage. |
|
|
1593 | |
|
|
1594 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1595 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1596 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1597 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1598 | clients under typical overload conditions. |
|
|
1599 | |
|
|
1600 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1601 | is often done with C<malloc> failures, but this results in an easy |
|
|
1602 | opportunity for a DoS attack. |
1147 | |
1603 | |
1148 | =head3 Watcher-Specific Functions |
1604 | =head3 Watcher-Specific Functions |
1149 | |
1605 | |
1150 | =over 4 |
1606 | =over 4 |
1151 | |
1607 | |
1152 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1608 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1153 | |
1609 | |
1154 | =item ev_io_set (ev_io *, int fd, int events) |
1610 | =item ev_io_set (ev_io *, int fd, int events) |
1155 | |
1611 | |
1156 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1612 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1157 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1613 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1158 | C<EV_READ | EV_WRITE> to receive the given events. |
1614 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1159 | |
1615 | |
1160 | =item int fd [read-only] |
1616 | =item int fd [read-only] |
1161 | |
1617 | |
1162 | The file descriptor being watched. |
1618 | The file descriptor being watched. |
1163 | |
1619 | |
… | |
… | |
1172 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1628 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1173 | readable, but only once. Since it is likely line-buffered, you could |
1629 | readable, but only once. Since it is likely line-buffered, you could |
1174 | attempt to read a whole line in the callback. |
1630 | attempt to read a whole line in the callback. |
1175 | |
1631 | |
1176 | static void |
1632 | static void |
1177 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1633 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1178 | { |
1634 | { |
1179 | ev_io_stop (loop, w); |
1635 | ev_io_stop (loop, w); |
1180 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1636 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1181 | } |
1637 | } |
1182 | |
1638 | |
1183 | ... |
1639 | ... |
1184 | struct ev_loop *loop = ev_default_init (0); |
1640 | struct ev_loop *loop = ev_default_init (0); |
1185 | struct ev_io stdin_readable; |
1641 | ev_io stdin_readable; |
1186 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1642 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1187 | ev_io_start (loop, &stdin_readable); |
1643 | ev_io_start (loop, &stdin_readable); |
1188 | ev_loop (loop, 0); |
1644 | ev_run (loop, 0); |
1189 | |
1645 | |
1190 | |
1646 | |
1191 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1647 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1192 | |
1648 | |
1193 | Timer watchers are simple relative timers that generate an event after a |
1649 | Timer watchers are simple relative timers that generate an event after a |
1194 | given time, and optionally repeating in regular intervals after that. |
1650 | given time, and optionally repeating in regular intervals after that. |
1195 | |
1651 | |
1196 | The timers are based on real time, that is, if you register an event that |
1652 | The timers are based on real time, that is, if you register an event that |
1197 | times out after an hour and you reset your system clock to January last |
1653 | times out after an hour and you reset your system clock to January last |
1198 | year, it will still time out after (roughly) and hour. "Roughly" because |
1654 | year, it will still time out after (roughly) one hour. "Roughly" because |
1199 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1655 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1200 | monotonic clock option helps a lot here). |
1656 | monotonic clock option helps a lot here). |
|
|
1657 | |
|
|
1658 | The callback is guaranteed to be invoked only I<after> its timeout has |
|
|
1659 | passed (not I<at>, so on systems with very low-resolution clocks this |
|
|
1660 | might introduce a small delay). If multiple timers become ready during the |
|
|
1661 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1662 | before ones of the same priority with later time-out values (but this is |
|
|
1663 | no longer true when a callback calls C<ev_run> recursively). |
|
|
1664 | |
|
|
1665 | =head3 Be smart about timeouts |
|
|
1666 | |
|
|
1667 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1668 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1669 | you want to raise some error after a while. |
|
|
1670 | |
|
|
1671 | What follows are some ways to handle this problem, from obvious and |
|
|
1672 | inefficient to smart and efficient. |
|
|
1673 | |
|
|
1674 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1675 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1676 | data or other life sign was received). |
|
|
1677 | |
|
|
1678 | =over 4 |
|
|
1679 | |
|
|
1680 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1681 | |
|
|
1682 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1683 | start the watcher: |
|
|
1684 | |
|
|
1685 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1686 | ev_timer_start (loop, timer); |
|
|
1687 | |
|
|
1688 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1689 | and start it again: |
|
|
1690 | |
|
|
1691 | ev_timer_stop (loop, timer); |
|
|
1692 | ev_timer_set (timer, 60., 0.); |
|
|
1693 | ev_timer_start (loop, timer); |
|
|
1694 | |
|
|
1695 | This is relatively simple to implement, but means that each time there is |
|
|
1696 | some activity, libev will first have to remove the timer from its internal |
|
|
1697 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1698 | still not a constant-time operation. |
|
|
1699 | |
|
|
1700 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1701 | |
|
|
1702 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1703 | C<ev_timer_start>. |
|
|
1704 | |
|
|
1705 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1706 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1707 | successfully read or write some data. If you go into an idle state where |
|
|
1708 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1709 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1710 | |
|
|
1711 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1712 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1713 | member and C<ev_timer_again>. |
|
|
1714 | |
|
|
1715 | At start: |
|
|
1716 | |
|
|
1717 | ev_init (timer, callback); |
|
|
1718 | timer->repeat = 60.; |
|
|
1719 | ev_timer_again (loop, timer); |
|
|
1720 | |
|
|
1721 | Each time there is some activity: |
|
|
1722 | |
|
|
1723 | ev_timer_again (loop, timer); |
|
|
1724 | |
|
|
1725 | It is even possible to change the time-out on the fly, regardless of |
|
|
1726 | whether the watcher is active or not: |
|
|
1727 | |
|
|
1728 | timer->repeat = 30.; |
|
|
1729 | ev_timer_again (loop, timer); |
|
|
1730 | |
|
|
1731 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1732 | you want to modify its timeout value, as libev does not have to completely |
|
|
1733 | remove and re-insert the timer from/into its internal data structure. |
|
|
1734 | |
|
|
1735 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1736 | |
|
|
1737 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1738 | |
|
|
1739 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1740 | relatively long compared to the intervals between other activity - in |
|
|
1741 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1742 | associated activity resets. |
|
|
1743 | |
|
|
1744 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1745 | but remember the time of last activity, and check for a real timeout only |
|
|
1746 | within the callback: |
|
|
1747 | |
|
|
1748 | ev_tstamp last_activity; // time of last activity |
|
|
1749 | |
|
|
1750 | static void |
|
|
1751 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1752 | { |
|
|
1753 | ev_tstamp now = ev_now (EV_A); |
|
|
1754 | ev_tstamp timeout = last_activity + 60.; |
|
|
1755 | |
|
|
1756 | // if last_activity + 60. is older than now, we did time out |
|
|
1757 | if (timeout < now) |
|
|
1758 | { |
|
|
1759 | // timeout occurred, take action |
|
|
1760 | } |
|
|
1761 | else |
|
|
1762 | { |
|
|
1763 | // callback was invoked, but there was some activity, re-arm |
|
|
1764 | // the watcher to fire in last_activity + 60, which is |
|
|
1765 | // guaranteed to be in the future, so "again" is positive: |
|
|
1766 | w->repeat = timeout - now; |
|
|
1767 | ev_timer_again (EV_A_ w); |
|
|
1768 | } |
|
|
1769 | } |
|
|
1770 | |
|
|
1771 | To summarise the callback: first calculate the real timeout (defined |
|
|
1772 | as "60 seconds after the last activity"), then check if that time has |
|
|
1773 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1774 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1775 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1776 | a timeout then. |
|
|
1777 | |
|
|
1778 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1779 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1780 | |
|
|
1781 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1782 | minus half the average time between activity), but virtually no calls to |
|
|
1783 | libev to change the timeout. |
|
|
1784 | |
|
|
1785 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1786 | to the current time (meaning we just have some activity :), then call the |
|
|
1787 | callback, which will "do the right thing" and start the timer: |
|
|
1788 | |
|
|
1789 | ev_init (timer, callback); |
|
|
1790 | last_activity = ev_now (loop); |
|
|
1791 | callback (loop, timer, EV_TIMER); |
|
|
1792 | |
|
|
1793 | And when there is some activity, simply store the current time in |
|
|
1794 | C<last_activity>, no libev calls at all: |
|
|
1795 | |
|
|
1796 | last_activity = ev_now (loop); |
|
|
1797 | |
|
|
1798 | This technique is slightly more complex, but in most cases where the |
|
|
1799 | time-out is unlikely to be triggered, much more efficient. |
|
|
1800 | |
|
|
1801 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1802 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1803 | fix things for you. |
|
|
1804 | |
|
|
1805 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1806 | |
|
|
1807 | If there is not one request, but many thousands (millions...), all |
|
|
1808 | employing some kind of timeout with the same timeout value, then one can |
|
|
1809 | do even better: |
|
|
1810 | |
|
|
1811 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1812 | at the I<end> of the list. |
|
|
1813 | |
|
|
1814 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1815 | the list is expected to fire (for example, using the technique #3). |
|
|
1816 | |
|
|
1817 | When there is some activity, remove the timer from the list, recalculate |
|
|
1818 | the timeout, append it to the end of the list again, and make sure to |
|
|
1819 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1820 | |
|
|
1821 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1822 | starting, stopping and updating the timers, at the expense of a major |
|
|
1823 | complication, and having to use a constant timeout. The constant timeout |
|
|
1824 | ensures that the list stays sorted. |
|
|
1825 | |
|
|
1826 | =back |
|
|
1827 | |
|
|
1828 | So which method the best? |
|
|
1829 | |
|
|
1830 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1831 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1832 | better, and isn't very complicated either. In most case, choosing either |
|
|
1833 | one is fine, with #3 being better in typical situations. |
|
|
1834 | |
|
|
1835 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1836 | rather complicated, but extremely efficient, something that really pays |
|
|
1837 | off after the first million or so of active timers, i.e. it's usually |
|
|
1838 | overkill :) |
|
|
1839 | |
|
|
1840 | =head3 The special problem of time updates |
|
|
1841 | |
|
|
1842 | Establishing the current time is a costly operation (it usually takes at |
|
|
1843 | least two system calls): EV therefore updates its idea of the current |
|
|
1844 | time only before and after C<ev_run> collects new events, which causes a |
|
|
1845 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
|
|
1846 | lots of events in one iteration. |
1201 | |
1847 | |
1202 | The relative timeouts are calculated relative to the C<ev_now ()> |
1848 | The relative timeouts are calculated relative to the C<ev_now ()> |
1203 | time. This is usually the right thing as this timestamp refers to the time |
1849 | time. This is usually the right thing as this timestamp refers to the time |
1204 | of the event triggering whatever timeout you are modifying/starting. If |
1850 | of the event triggering whatever timeout you are modifying/starting. If |
1205 | you suspect event processing to be delayed and you I<need> to base the timeout |
1851 | you suspect event processing to be delayed and you I<need> to base the |
1206 | on the current time, use something like this to adjust for this: |
1852 | timeout on the current time, use something like this to adjust for this: |
1207 | |
1853 | |
1208 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1854 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1209 | |
1855 | |
1210 | The callback is guaranteed to be invoked only after its timeout has passed, |
1856 | If the event loop is suspended for a long time, you can also force an |
1211 | but if multiple timers become ready during the same loop iteration then |
1857 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1212 | order of execution is undefined. |
1858 | ()>. |
|
|
1859 | |
|
|
1860 | =head3 The special problems of suspended animation |
|
|
1861 | |
|
|
1862 | When you leave the server world it is quite customary to hit machines that |
|
|
1863 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1864 | |
|
|
1865 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1866 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1867 | to run until the system is suspended, but they will not advance while the |
|
|
1868 | system is suspended. That means, on resume, it will be as if the program |
|
|
1869 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1870 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1871 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1872 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1873 | be adjusted accordingly. |
|
|
1874 | |
|
|
1875 | I would not be surprised to see different behaviour in different between |
|
|
1876 | operating systems, OS versions or even different hardware. |
|
|
1877 | |
|
|
1878 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1879 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1880 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1881 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1882 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1883 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1884 | |
|
|
1885 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1886 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1887 | deterministic behaviour in this case (you can do nothing against |
|
|
1888 | C<SIGSTOP>). |
1213 | |
1889 | |
1214 | =head3 Watcher-Specific Functions and Data Members |
1890 | =head3 Watcher-Specific Functions and Data Members |
1215 | |
1891 | |
1216 | =over 4 |
1892 | =over 4 |
1217 | |
1893 | |
… | |
… | |
1241 | If the timer is started but non-repeating, stop it (as if it timed out). |
1917 | If the timer is started but non-repeating, stop it (as if it timed out). |
1242 | |
1918 | |
1243 | If the timer is repeating, either start it if necessary (with the |
1919 | If the timer is repeating, either start it if necessary (with the |
1244 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1920 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1245 | |
1921 | |
1246 | This sounds a bit complicated, but here is a useful and typical |
1922 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1247 | example: Imagine you have a TCP connection and you want a so-called idle |
1923 | usage example. |
1248 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1249 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1250 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1251 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1252 | you go into an idle state where you do not expect data to travel on the |
|
|
1253 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1254 | automatically restart it if need be. |
|
|
1255 | |
1924 | |
1256 | That means you can ignore the C<after> value and C<ev_timer_start> |
1925 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1257 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1258 | |
1926 | |
1259 | ev_timer_init (timer, callback, 0., 5.); |
1927 | Returns the remaining time until a timer fires. If the timer is active, |
1260 | ev_timer_again (loop, timer); |
1928 | then this time is relative to the current event loop time, otherwise it's |
1261 | ... |
1929 | the timeout value currently configured. |
1262 | timer->again = 17.; |
|
|
1263 | ev_timer_again (loop, timer); |
|
|
1264 | ... |
|
|
1265 | timer->again = 10.; |
|
|
1266 | ev_timer_again (loop, timer); |
|
|
1267 | |
1930 | |
1268 | This is more slightly efficient then stopping/starting the timer each time |
1931 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1269 | you want to modify its timeout value. |
1932 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
1933 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
1934 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
1935 | too), and so on. |
1270 | |
1936 | |
1271 | =item ev_tstamp repeat [read-write] |
1937 | =item ev_tstamp repeat [read-write] |
1272 | |
1938 | |
1273 | The current C<repeat> value. Will be used each time the watcher times out |
1939 | The current C<repeat> value. Will be used each time the watcher times out |
1274 | or C<ev_timer_again> is called and determines the next timeout (if any), |
1940 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1275 | which is also when any modifications are taken into account. |
1941 | which is also when any modifications are taken into account. |
1276 | |
1942 | |
1277 | =back |
1943 | =back |
1278 | |
1944 | |
1279 | =head3 Examples |
1945 | =head3 Examples |
1280 | |
1946 | |
1281 | Example: Create a timer that fires after 60 seconds. |
1947 | Example: Create a timer that fires after 60 seconds. |
1282 | |
1948 | |
1283 | static void |
1949 | static void |
1284 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1950 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1285 | { |
1951 | { |
1286 | .. one minute over, w is actually stopped right here |
1952 | .. one minute over, w is actually stopped right here |
1287 | } |
1953 | } |
1288 | |
1954 | |
1289 | struct ev_timer mytimer; |
1955 | ev_timer mytimer; |
1290 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1956 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1291 | ev_timer_start (loop, &mytimer); |
1957 | ev_timer_start (loop, &mytimer); |
1292 | |
1958 | |
1293 | Example: Create a timeout timer that times out after 10 seconds of |
1959 | Example: Create a timeout timer that times out after 10 seconds of |
1294 | inactivity. |
1960 | inactivity. |
1295 | |
1961 | |
1296 | static void |
1962 | static void |
1297 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1963 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1298 | { |
1964 | { |
1299 | .. ten seconds without any activity |
1965 | .. ten seconds without any activity |
1300 | } |
1966 | } |
1301 | |
1967 | |
1302 | struct ev_timer mytimer; |
1968 | ev_timer mytimer; |
1303 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1969 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1304 | ev_timer_again (&mytimer); /* start timer */ |
1970 | ev_timer_again (&mytimer); /* start timer */ |
1305 | ev_loop (loop, 0); |
1971 | ev_run (loop, 0); |
1306 | |
1972 | |
1307 | // and in some piece of code that gets executed on any "activity": |
1973 | // and in some piece of code that gets executed on any "activity": |
1308 | // reset the timeout to start ticking again at 10 seconds |
1974 | // reset the timeout to start ticking again at 10 seconds |
1309 | ev_timer_again (&mytimer); |
1975 | ev_timer_again (&mytimer); |
1310 | |
1976 | |
… | |
… | |
1312 | =head2 C<ev_periodic> - to cron or not to cron? |
1978 | =head2 C<ev_periodic> - to cron or not to cron? |
1313 | |
1979 | |
1314 | Periodic watchers are also timers of a kind, but they are very versatile |
1980 | Periodic watchers are also timers of a kind, but they are very versatile |
1315 | (and unfortunately a bit complex). |
1981 | (and unfortunately a bit complex). |
1316 | |
1982 | |
1317 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1983 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1318 | but on wall clock time (absolute time). You can tell a periodic watcher |
1984 | relative time, the physical time that passes) but on wall clock time |
1319 | to trigger after some specific point in time. For example, if you tell a |
1985 | (absolute time, the thing you can read on your calender or clock). The |
1320 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1986 | difference is that wall clock time can run faster or slower than real |
1321 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1987 | time, and time jumps are not uncommon (e.g. when you adjust your |
1322 | clock to January of the previous year, then it will take more than year |
1988 | wrist-watch). |
1323 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1324 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1325 | |
1989 | |
|
|
1990 | You can tell a periodic watcher to trigger after some specific point |
|
|
1991 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1992 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1993 | not a delay) and then reset your system clock to January of the previous |
|
|
1994 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1995 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1996 | it, as it uses a relative timeout). |
|
|
1997 | |
1326 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1998 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1327 | such as triggering an event on each "midnight, local time", or other |
1999 | timers, such as triggering an event on each "midnight, local time", or |
1328 | complicated, rules. |
2000 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2001 | those cannot react to time jumps. |
1329 | |
2002 | |
1330 | As with timers, the callback is guaranteed to be invoked only when the |
2003 | As with timers, the callback is guaranteed to be invoked only when the |
1331 | time (C<at>) has passed, but if multiple periodic timers become ready |
2004 | point in time where it is supposed to trigger has passed. If multiple |
1332 | during the same loop iteration then order of execution is undefined. |
2005 | timers become ready during the same loop iteration then the ones with |
|
|
2006 | earlier time-out values are invoked before ones with later time-out values |
|
|
2007 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1333 | |
2008 | |
1334 | =head3 Watcher-Specific Functions and Data Members |
2009 | =head3 Watcher-Specific Functions and Data Members |
1335 | |
2010 | |
1336 | =over 4 |
2011 | =over 4 |
1337 | |
2012 | |
1338 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2013 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1339 | |
2014 | |
1340 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2015 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1341 | |
2016 | |
1342 | Lots of arguments, lets sort it out... There are basically three modes of |
2017 | Lots of arguments, let's sort it out... There are basically three modes of |
1343 | operation, and we will explain them from simplest to complex: |
2018 | operation, and we will explain them from simplest to most complex: |
1344 | |
2019 | |
1345 | =over 4 |
2020 | =over 4 |
1346 | |
2021 | |
1347 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2022 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1348 | |
2023 | |
1349 | In this configuration the watcher triggers an event after the wall clock |
2024 | In this configuration the watcher triggers an event after the wall clock |
1350 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2025 | time C<offset> has passed. It will not repeat and will not adjust when a |
1351 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2026 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1352 | run when the system time reaches or surpasses this time. |
2027 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2028 | this point in time. |
1353 | |
2029 | |
1354 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2030 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1355 | |
2031 | |
1356 | In this mode the watcher will always be scheduled to time out at the next |
2032 | In this mode the watcher will always be scheduled to time out at the next |
1357 | C<at + N * interval> time (for some integer N, which can also be negative) |
2033 | C<offset + N * interval> time (for some integer N, which can also be |
1358 | and then repeat, regardless of any time jumps. |
2034 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2035 | argument is merely an offset into the C<interval> periods. |
1359 | |
2036 | |
1360 | This can be used to create timers that do not drift with respect to system |
2037 | This can be used to create timers that do not drift with respect to the |
1361 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2038 | system clock, for example, here is an C<ev_periodic> that triggers each |
1362 | the hour: |
2039 | hour, on the hour (with respect to UTC): |
1363 | |
2040 | |
1364 | ev_periodic_set (&periodic, 0., 3600., 0); |
2041 | ev_periodic_set (&periodic, 0., 3600., 0); |
1365 | |
2042 | |
1366 | This doesn't mean there will always be 3600 seconds in between triggers, |
2043 | This doesn't mean there will always be 3600 seconds in between triggers, |
1367 | but only that the callback will be called when the system time shows a |
2044 | but only that the callback will be called when the system time shows a |
1368 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2045 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1369 | by 3600. |
2046 | by 3600. |
1370 | |
2047 | |
1371 | Another way to think about it (for the mathematically inclined) is that |
2048 | Another way to think about it (for the mathematically inclined) is that |
1372 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2049 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1373 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2050 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1374 | |
2051 | |
1375 | For numerical stability it is preferable that the C<at> value is near |
2052 | For numerical stability it is preferable that the C<offset> value is near |
1376 | C<ev_now ()> (the current time), but there is no range requirement for |
2053 | C<ev_now ()> (the current time), but there is no range requirement for |
1377 | this value, and in fact is often specified as zero. |
2054 | this value, and in fact is often specified as zero. |
1378 | |
2055 | |
1379 | Note also that there is an upper limit to how often a timer can fire (CPU |
2056 | Note also that there is an upper limit to how often a timer can fire (CPU |
1380 | speed for example), so if C<interval> is very small then timing stability |
2057 | speed for example), so if C<interval> is very small then timing stability |
1381 | will of course deteriorate. Libev itself tries to be exact to be about one |
2058 | will of course deteriorate. Libev itself tries to be exact to be about one |
1382 | millisecond (if the OS supports it and the machine is fast enough). |
2059 | millisecond (if the OS supports it and the machine is fast enough). |
1383 | |
2060 | |
1384 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2061 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1385 | |
2062 | |
1386 | In this mode the values for C<interval> and C<at> are both being |
2063 | In this mode the values for C<interval> and C<offset> are both being |
1387 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2064 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1388 | reschedule callback will be called with the watcher as first, and the |
2065 | reschedule callback will be called with the watcher as first, and the |
1389 | current time as second argument. |
2066 | current time as second argument. |
1390 | |
2067 | |
1391 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2068 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1392 | ever, or make ANY event loop modifications whatsoever>. |
2069 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2070 | allowed by documentation here>. |
1393 | |
2071 | |
1394 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2072 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1395 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2073 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1396 | only event loop modification you are allowed to do). |
2074 | only event loop modification you are allowed to do). |
1397 | |
2075 | |
1398 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2076 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1399 | *w, ev_tstamp now)>, e.g.: |
2077 | *w, ev_tstamp now)>, e.g.: |
1400 | |
2078 | |
|
|
2079 | static ev_tstamp |
1401 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2080 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1402 | { |
2081 | { |
1403 | return now + 60.; |
2082 | return now + 60.; |
1404 | } |
2083 | } |
1405 | |
2084 | |
1406 | It must return the next time to trigger, based on the passed time value |
2085 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1426 | a different time than the last time it was called (e.g. in a crond like |
2105 | a different time than the last time it was called (e.g. in a crond like |
1427 | program when the crontabs have changed). |
2106 | program when the crontabs have changed). |
1428 | |
2107 | |
1429 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2108 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1430 | |
2109 | |
1431 | When active, returns the absolute time that the watcher is supposed to |
2110 | When active, returns the absolute time that the watcher is supposed |
1432 | trigger next. |
2111 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2112 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2113 | rescheduling modes. |
1433 | |
2114 | |
1434 | =item ev_tstamp offset [read-write] |
2115 | =item ev_tstamp offset [read-write] |
1435 | |
2116 | |
1436 | When repeating, this contains the offset value, otherwise this is the |
2117 | When repeating, this contains the offset value, otherwise this is the |
1437 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2118 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2119 | although libev might modify this value for better numerical stability). |
1438 | |
2120 | |
1439 | Can be modified any time, but changes only take effect when the periodic |
2121 | Can be modified any time, but changes only take effect when the periodic |
1440 | timer fires or C<ev_periodic_again> is being called. |
2122 | timer fires or C<ev_periodic_again> is being called. |
1441 | |
2123 | |
1442 | =item ev_tstamp interval [read-write] |
2124 | =item ev_tstamp interval [read-write] |
1443 | |
2125 | |
1444 | The current interval value. Can be modified any time, but changes only |
2126 | The current interval value. Can be modified any time, but changes only |
1445 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2127 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1446 | called. |
2128 | called. |
1447 | |
2129 | |
1448 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2130 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1449 | |
2131 | |
1450 | The current reschedule callback, or C<0>, if this functionality is |
2132 | The current reschedule callback, or C<0>, if this functionality is |
1451 | switched off. Can be changed any time, but changes only take effect when |
2133 | switched off. Can be changed any time, but changes only take effect when |
1452 | the periodic timer fires or C<ev_periodic_again> is being called. |
2134 | the periodic timer fires or C<ev_periodic_again> is being called. |
1453 | |
2135 | |
1454 | =back |
2136 | =back |
1455 | |
2137 | |
1456 | =head3 Examples |
2138 | =head3 Examples |
1457 | |
2139 | |
1458 | Example: Call a callback every hour, or, more precisely, whenever the |
2140 | Example: Call a callback every hour, or, more precisely, whenever the |
1459 | system clock is divisible by 3600. The callback invocation times have |
2141 | system time is divisible by 3600. The callback invocation times have |
1460 | potentially a lot of jitter, but good long-term stability. |
2142 | potentially a lot of jitter, but good long-term stability. |
1461 | |
2143 | |
1462 | static void |
2144 | static void |
1463 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2145 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1464 | { |
2146 | { |
1465 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2147 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1466 | } |
2148 | } |
1467 | |
2149 | |
1468 | struct ev_periodic hourly_tick; |
2150 | ev_periodic hourly_tick; |
1469 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2151 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1470 | ev_periodic_start (loop, &hourly_tick); |
2152 | ev_periodic_start (loop, &hourly_tick); |
1471 | |
2153 | |
1472 | Example: The same as above, but use a reschedule callback to do it: |
2154 | Example: The same as above, but use a reschedule callback to do it: |
1473 | |
2155 | |
1474 | #include <math.h> |
2156 | #include <math.h> |
1475 | |
2157 | |
1476 | static ev_tstamp |
2158 | static ev_tstamp |
1477 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2159 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1478 | { |
2160 | { |
1479 | return fmod (now, 3600.) + 3600.; |
2161 | return now + (3600. - fmod (now, 3600.)); |
1480 | } |
2162 | } |
1481 | |
2163 | |
1482 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2164 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1483 | |
2165 | |
1484 | Example: Call a callback every hour, starting now: |
2166 | Example: Call a callback every hour, starting now: |
1485 | |
2167 | |
1486 | struct ev_periodic hourly_tick; |
2168 | ev_periodic hourly_tick; |
1487 | ev_periodic_init (&hourly_tick, clock_cb, |
2169 | ev_periodic_init (&hourly_tick, clock_cb, |
1488 | fmod (ev_now (loop), 3600.), 3600., 0); |
2170 | fmod (ev_now (loop), 3600.), 3600., 0); |
1489 | ev_periodic_start (loop, &hourly_tick); |
2171 | ev_periodic_start (loop, &hourly_tick); |
1490 | |
2172 | |
1491 | |
2173 | |
… | |
… | |
1494 | Signal watchers will trigger an event when the process receives a specific |
2176 | Signal watchers will trigger an event when the process receives a specific |
1495 | signal one or more times. Even though signals are very asynchronous, libev |
2177 | signal one or more times. Even though signals are very asynchronous, libev |
1496 | will try it's best to deliver signals synchronously, i.e. as part of the |
2178 | will try it's best to deliver signals synchronously, i.e. as part of the |
1497 | normal event processing, like any other event. |
2179 | normal event processing, like any other event. |
1498 | |
2180 | |
|
|
2181 | If you want signals to be delivered truly asynchronously, just use |
|
|
2182 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2183 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2184 | synchronously wake up an event loop. |
|
|
2185 | |
1499 | You can configure as many watchers as you like per signal. Only when the |
2186 | You can configure as many watchers as you like for the same signal, but |
|
|
2187 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2188 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2189 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2190 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2191 | |
1500 | first watcher gets started will libev actually register a signal watcher |
2192 | When the first watcher gets started will libev actually register something |
1501 | with the kernel (thus it coexists with your own signal handlers as long |
2193 | with the kernel (thus it coexists with your own signal handlers as long as |
1502 | as you don't register any with libev). Similarly, when the last signal |
2194 | you don't register any with libev for the same signal). |
1503 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1504 | SIG_DFL (regardless of what it was set to before). |
|
|
1505 | |
2195 | |
1506 | If possible and supported, libev will install its handlers with |
2196 | If possible and supported, libev will install its handlers with |
1507 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2197 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1508 | interrupted. If you have a problem with system calls getting interrupted by |
2198 | not be unduly interrupted. If you have a problem with system calls getting |
1509 | signals you can block all signals in an C<ev_check> watcher and unblock |
2199 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1510 | them in an C<ev_prepare> watcher. |
2200 | and unblock them in an C<ev_prepare> watcher. |
|
|
2201 | |
|
|
2202 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2203 | |
|
|
2204 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2205 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2206 | stopping it again), that is, libev might or might not block the signal, |
|
|
2207 | and might or might not set or restore the installed signal handler. |
|
|
2208 | |
|
|
2209 | While this does not matter for the signal disposition (libev never |
|
|
2210 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2211 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2212 | certain signals to be blocked. |
|
|
2213 | |
|
|
2214 | This means that before calling C<exec> (from the child) you should reset |
|
|
2215 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2216 | choice usually). |
|
|
2217 | |
|
|
2218 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2219 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2220 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2221 | |
|
|
2222 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2223 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2224 | the window of opportunity for problems, it will not go away, as libev |
|
|
2225 | I<has> to modify the signal mask, at least temporarily. |
|
|
2226 | |
|
|
2227 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2228 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2229 | is not a libev-specific thing, this is true for most event libraries. |
1511 | |
2230 | |
1512 | =head3 Watcher-Specific Functions and Data Members |
2231 | =head3 Watcher-Specific Functions and Data Members |
1513 | |
2232 | |
1514 | =over 4 |
2233 | =over 4 |
1515 | |
2234 | |
… | |
… | |
1526 | |
2245 | |
1527 | =back |
2246 | =back |
1528 | |
2247 | |
1529 | =head3 Examples |
2248 | =head3 Examples |
1530 | |
2249 | |
1531 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2250 | Example: Try to exit cleanly on SIGINT. |
1532 | |
2251 | |
1533 | static void |
2252 | static void |
1534 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2253 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1535 | { |
2254 | { |
1536 | ev_unloop (loop, EVUNLOOP_ALL); |
2255 | ev_break (loop, EVBREAK_ALL); |
1537 | } |
2256 | } |
1538 | |
2257 | |
1539 | struct ev_signal signal_watcher; |
2258 | ev_signal signal_watcher; |
1540 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2259 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1541 | ev_signal_start (loop, &sigint_cb); |
2260 | ev_signal_start (loop, &signal_watcher); |
1542 | |
2261 | |
1543 | |
2262 | |
1544 | =head2 C<ev_child> - watch out for process status changes |
2263 | =head2 C<ev_child> - watch out for process status changes |
1545 | |
2264 | |
1546 | Child watchers trigger when your process receives a SIGCHLD in response to |
2265 | Child watchers trigger when your process receives a SIGCHLD in response to |
1547 | some child status changes (most typically when a child of yours dies). It |
2266 | some child status changes (most typically when a child of yours dies or |
1548 | is permissible to install a child watcher I<after> the child has been |
2267 | exits). It is permissible to install a child watcher I<after> the child |
1549 | forked (which implies it might have already exited), as long as the event |
2268 | has been forked (which implies it might have already exited), as long |
1550 | loop isn't entered (or is continued from a watcher). |
2269 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2270 | forking and then immediately registering a watcher for the child is fine, |
|
|
2271 | but forking and registering a watcher a few event loop iterations later or |
|
|
2272 | in the next callback invocation is not. |
1551 | |
2273 | |
1552 | Only the default event loop is capable of handling signals, and therefore |
2274 | Only the default event loop is capable of handling signals, and therefore |
1553 | you can only register child watchers in the default event loop. |
2275 | you can only register child watchers in the default event loop. |
1554 | |
2276 | |
|
|
2277 | Due to some design glitches inside libev, child watchers will always be |
|
|
2278 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2279 | libev) |
|
|
2280 | |
1555 | =head3 Process Interaction |
2281 | =head3 Process Interaction |
1556 | |
2282 | |
1557 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2283 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1558 | initialised. This is necessary to guarantee proper behaviour even if |
2284 | initialised. This is necessary to guarantee proper behaviour even if the |
1559 | the first child watcher is started after the child exits. The occurrence |
2285 | first child watcher is started after the child exits. The occurrence |
1560 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2286 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1561 | synchronously as part of the event loop processing. Libev always reaps all |
2287 | synchronously as part of the event loop processing. Libev always reaps all |
1562 | children, even ones not watched. |
2288 | children, even ones not watched. |
1563 | |
2289 | |
1564 | =head3 Overriding the Built-In Processing |
2290 | =head3 Overriding the Built-In Processing |
… | |
… | |
1574 | =head3 Stopping the Child Watcher |
2300 | =head3 Stopping the Child Watcher |
1575 | |
2301 | |
1576 | Currently, the child watcher never gets stopped, even when the |
2302 | Currently, the child watcher never gets stopped, even when the |
1577 | child terminates, so normally one needs to stop the watcher in the |
2303 | child terminates, so normally one needs to stop the watcher in the |
1578 | callback. Future versions of libev might stop the watcher automatically |
2304 | callback. Future versions of libev might stop the watcher automatically |
1579 | when a child exit is detected. |
2305 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2306 | problem). |
1580 | |
2307 | |
1581 | =head3 Watcher-Specific Functions and Data Members |
2308 | =head3 Watcher-Specific Functions and Data Members |
1582 | |
2309 | |
1583 | =over 4 |
2310 | =over 4 |
1584 | |
2311 | |
… | |
… | |
1616 | its completion. |
2343 | its completion. |
1617 | |
2344 | |
1618 | ev_child cw; |
2345 | ev_child cw; |
1619 | |
2346 | |
1620 | static void |
2347 | static void |
1621 | child_cb (EV_P_ struct ev_child *w, int revents) |
2348 | child_cb (EV_P_ ev_child *w, int revents) |
1622 | { |
2349 | { |
1623 | ev_child_stop (EV_A_ w); |
2350 | ev_child_stop (EV_A_ w); |
1624 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2351 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1625 | } |
2352 | } |
1626 | |
2353 | |
… | |
… | |
1641 | |
2368 | |
1642 | |
2369 | |
1643 | =head2 C<ev_stat> - did the file attributes just change? |
2370 | =head2 C<ev_stat> - did the file attributes just change? |
1644 | |
2371 | |
1645 | This watches a file system path for attribute changes. That is, it calls |
2372 | This watches a file system path for attribute changes. That is, it calls |
1646 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2373 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1647 | compared to the last time, invoking the callback if it did. |
2374 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2375 | it did. |
1648 | |
2376 | |
1649 | The path does not need to exist: changing from "path exists" to "path does |
2377 | The path does not need to exist: changing from "path exists" to "path does |
1650 | not exist" is a status change like any other. The condition "path does |
2378 | not exist" is a status change like any other. The condition "path does not |
1651 | not exist" is signified by the C<st_nlink> field being zero (which is |
2379 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1652 | otherwise always forced to be at least one) and all the other fields of |
2380 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1653 | the stat buffer having unspecified contents. |
2381 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2382 | contents. |
1654 | |
2383 | |
1655 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2384 | The path I<must not> end in a slash or contain special components such as |
|
|
2385 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1656 | relative and your working directory changes, the behaviour is undefined. |
2386 | your working directory changes, then the behaviour is undefined. |
1657 | |
2387 | |
1658 | Since there is no standard to do this, the portable implementation simply |
2388 | Since there is no portable change notification interface available, the |
1659 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2389 | portable implementation simply calls C<stat(2)> regularly on the path |
1660 | can specify a recommended polling interval for this case. If you specify |
2390 | to see if it changed somehow. You can specify a recommended polling |
1661 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2391 | interval for this case. If you specify a polling interval of C<0> (highly |
1662 | unspecified default> value will be used (which you can expect to be around |
2392 | recommended!) then a I<suitable, unspecified default> value will be used |
1663 | five seconds, although this might change dynamically). Libev will also |
2393 | (which you can expect to be around five seconds, although this might |
1664 | impose a minimum interval which is currently around C<0.1>, but thats |
2394 | change dynamically). Libev will also impose a minimum interval which is |
1665 | usually overkill. |
2395 | currently around C<0.1>, but that's usually overkill. |
1666 | |
2396 | |
1667 | This watcher type is not meant for massive numbers of stat watchers, |
2397 | This watcher type is not meant for massive numbers of stat watchers, |
1668 | as even with OS-supported change notifications, this can be |
2398 | as even with OS-supported change notifications, this can be |
1669 | resource-intensive. |
2399 | resource-intensive. |
1670 | |
2400 | |
1671 | At the time of this writing, only the Linux inotify interface is |
2401 | At the time of this writing, the only OS-specific interface implemented |
1672 | implemented (implementing kqueue support is left as an exercise for the |
2402 | is the Linux inotify interface (implementing kqueue support is left as an |
1673 | reader, note, however, that the author sees no way of implementing ev_stat |
2403 | exercise for the reader. Note, however, that the author sees no way of |
1674 | semantics with kqueue). Inotify will be used to give hints only and should |
2404 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1675 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1676 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1677 | but changes are usually detected immediately, and if the file exists there |
|
|
1678 | will be no polling. |
|
|
1679 | |
2405 | |
1680 | =head3 ABI Issues (Largefile Support) |
2406 | =head3 ABI Issues (Largefile Support) |
1681 | |
2407 | |
1682 | Libev by default (unless the user overrides this) uses the default |
2408 | Libev by default (unless the user overrides this) uses the default |
1683 | compilation environment, which means that on systems with large file |
2409 | compilation environment, which means that on systems with large file |
1684 | support disabled by default, you get the 32 bit version of the stat |
2410 | support disabled by default, you get the 32 bit version of the stat |
1685 | structure. When using the library from programs that change the ABI to |
2411 | structure. When using the library from programs that change the ABI to |
1686 | use 64 bit file offsets the programs will fail. In that case you have to |
2412 | use 64 bit file offsets the programs will fail. In that case you have to |
1687 | compile libev with the same flags to get binary compatibility. This is |
2413 | compile libev with the same flags to get binary compatibility. This is |
1688 | obviously the case with any flags that change the ABI, but the problem is |
2414 | obviously the case with any flags that change the ABI, but the problem is |
1689 | most noticeably disabled with ev_stat and large file support. |
2415 | most noticeably displayed with ev_stat and large file support. |
1690 | |
2416 | |
1691 | The solution for this is to lobby your distribution maker to make large |
2417 | The solution for this is to lobby your distribution maker to make large |
1692 | file interfaces available by default (as e.g. FreeBSD does) and not |
2418 | file interfaces available by default (as e.g. FreeBSD does) and not |
1693 | optional. Libev cannot simply switch on large file support because it has |
2419 | optional. Libev cannot simply switch on large file support because it has |
1694 | to exchange stat structures with application programs compiled using the |
2420 | to exchange stat structures with application programs compiled using the |
1695 | default compilation environment. |
2421 | default compilation environment. |
1696 | |
2422 | |
1697 | =head3 Inotify |
2423 | =head3 Inotify and Kqueue |
1698 | |
2424 | |
1699 | When C<inotify (7)> support has been compiled into libev (generally only |
2425 | When C<inotify (7)> support has been compiled into libev and present at |
1700 | available on Linux) and present at runtime, it will be used to speed up |
2426 | runtime, it will be used to speed up change detection where possible. The |
1701 | change detection where possible. The inotify descriptor will be created lazily |
2427 | inotify descriptor will be created lazily when the first C<ev_stat> |
1702 | when the first C<ev_stat> watcher is being started. |
2428 | watcher is being started. |
1703 | |
2429 | |
1704 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2430 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1705 | except that changes might be detected earlier, and in some cases, to avoid |
2431 | except that changes might be detected earlier, and in some cases, to avoid |
1706 | making regular C<stat> calls. Even in the presence of inotify support |
2432 | making regular C<stat> calls. Even in the presence of inotify support |
1707 | there are many cases where libev has to resort to regular C<stat> polling. |
2433 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2434 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2435 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2436 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2437 | xfs are fully working) libev usually gets away without polling. |
1708 | |
2438 | |
1709 | (There is no support for kqueue, as apparently it cannot be used to |
2439 | There is no support for kqueue, as apparently it cannot be used to |
1710 | implement this functionality, due to the requirement of having a file |
2440 | implement this functionality, due to the requirement of having a file |
1711 | descriptor open on the object at all times). |
2441 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2442 | etc. is difficult. |
|
|
2443 | |
|
|
2444 | =head3 C<stat ()> is a synchronous operation |
|
|
2445 | |
|
|
2446 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2447 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2448 | ()>, which is a synchronous operation. |
|
|
2449 | |
|
|
2450 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2451 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2452 | as the path data is usually in memory already (except when starting the |
|
|
2453 | watcher). |
|
|
2454 | |
|
|
2455 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2456 | time due to network issues, and even under good conditions, a stat call |
|
|
2457 | often takes multiple milliseconds. |
|
|
2458 | |
|
|
2459 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2460 | paths, although this is fully supported by libev. |
1712 | |
2461 | |
1713 | =head3 The special problem of stat time resolution |
2462 | =head3 The special problem of stat time resolution |
1714 | |
2463 | |
1715 | The C<stat ()> system call only supports full-second resolution portably, and |
2464 | The C<stat ()> system call only supports full-second resolution portably, |
1716 | even on systems where the resolution is higher, many file systems still |
2465 | and even on systems where the resolution is higher, most file systems |
1717 | only support whole seconds. |
2466 | still only support whole seconds. |
1718 | |
2467 | |
1719 | That means that, if the time is the only thing that changes, you can |
2468 | That means that, if the time is the only thing that changes, you can |
1720 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2469 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1721 | calls your callback, which does something. When there is another update |
2470 | calls your callback, which does something. When there is another update |
1722 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2471 | within the same second, C<ev_stat> will be unable to detect unless the |
1723 | data does not change. |
2472 | stat data does change in other ways (e.g. file size). |
1724 | |
2473 | |
1725 | The solution to this is to delay acting on a change for slightly more |
2474 | The solution to this is to delay acting on a change for slightly more |
1726 | than a second (or till slightly after the next full second boundary), using |
2475 | than a second (or till slightly after the next full second boundary), using |
1727 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2476 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1728 | ev_timer_again (loop, w)>). |
2477 | ev_timer_again (loop, w)>). |
… | |
… | |
1748 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2497 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1749 | be detected and should normally be specified as C<0> to let libev choose |
2498 | be detected and should normally be specified as C<0> to let libev choose |
1750 | a suitable value. The memory pointed to by C<path> must point to the same |
2499 | a suitable value. The memory pointed to by C<path> must point to the same |
1751 | path for as long as the watcher is active. |
2500 | path for as long as the watcher is active. |
1752 | |
2501 | |
1753 | The callback will receive C<EV_STAT> when a change was detected, relative |
2502 | The callback will receive an C<EV_STAT> event when a change was detected, |
1754 | to the attributes at the time the watcher was started (or the last change |
2503 | relative to the attributes at the time the watcher was started (or the |
1755 | was detected). |
2504 | last change was detected). |
1756 | |
2505 | |
1757 | =item ev_stat_stat (loop, ev_stat *) |
2506 | =item ev_stat_stat (loop, ev_stat *) |
1758 | |
2507 | |
1759 | Updates the stat buffer immediately with new values. If you change the |
2508 | Updates the stat buffer immediately with new values. If you change the |
1760 | watched path in your callback, you could call this function to avoid |
2509 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1843 | |
2592 | |
1844 | |
2593 | |
1845 | =head2 C<ev_idle> - when you've got nothing better to do... |
2594 | =head2 C<ev_idle> - when you've got nothing better to do... |
1846 | |
2595 | |
1847 | Idle watchers trigger events when no other events of the same or higher |
2596 | Idle watchers trigger events when no other events of the same or higher |
1848 | priority are pending (prepare, check and other idle watchers do not |
2597 | priority are pending (prepare, check and other idle watchers do not count |
1849 | count). |
2598 | as receiving "events"). |
1850 | |
2599 | |
1851 | That is, as long as your process is busy handling sockets or timeouts |
2600 | That is, as long as your process is busy handling sockets or timeouts |
1852 | (or even signals, imagine) of the same or higher priority it will not be |
2601 | (or even signals, imagine) of the same or higher priority it will not be |
1853 | triggered. But when your process is idle (or only lower-priority watchers |
2602 | triggered. But when your process is idle (or only lower-priority watchers |
1854 | are pending), the idle watchers are being called once per event loop |
2603 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1865 | |
2614 | |
1866 | =head3 Watcher-Specific Functions and Data Members |
2615 | =head3 Watcher-Specific Functions and Data Members |
1867 | |
2616 | |
1868 | =over 4 |
2617 | =over 4 |
1869 | |
2618 | |
1870 | =item ev_idle_init (ev_signal *, callback) |
2619 | =item ev_idle_init (ev_idle *, callback) |
1871 | |
2620 | |
1872 | Initialises and configures the idle watcher - it has no parameters of any |
2621 | Initialises and configures the idle watcher - it has no parameters of any |
1873 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2622 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1874 | believe me. |
2623 | believe me. |
1875 | |
2624 | |
… | |
… | |
1879 | |
2628 | |
1880 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2629 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1881 | callback, free it. Also, use no error checking, as usual. |
2630 | callback, free it. Also, use no error checking, as usual. |
1882 | |
2631 | |
1883 | static void |
2632 | static void |
1884 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2633 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1885 | { |
2634 | { |
1886 | free (w); |
2635 | free (w); |
1887 | // now do something you wanted to do when the program has |
2636 | // now do something you wanted to do when the program has |
1888 | // no longer anything immediate to do. |
2637 | // no longer anything immediate to do. |
1889 | } |
2638 | } |
1890 | |
2639 | |
1891 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2640 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1892 | ev_idle_init (idle_watcher, idle_cb); |
2641 | ev_idle_init (idle_watcher, idle_cb); |
1893 | ev_idle_start (loop, idle_cb); |
2642 | ev_idle_start (loop, idle_watcher); |
1894 | |
2643 | |
1895 | |
2644 | |
1896 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2645 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1897 | |
2646 | |
1898 | Prepare and check watchers are usually (but not always) used in tandem: |
2647 | Prepare and check watchers are usually (but not always) used in pairs: |
1899 | prepare watchers get invoked before the process blocks and check watchers |
2648 | prepare watchers get invoked before the process blocks and check watchers |
1900 | afterwards. |
2649 | afterwards. |
1901 | |
2650 | |
1902 | You I<must not> call C<ev_loop> or similar functions that enter |
2651 | You I<must not> call C<ev_run> or similar functions that enter |
1903 | the current event loop from either C<ev_prepare> or C<ev_check> |
2652 | the current event loop from either C<ev_prepare> or C<ev_check> |
1904 | watchers. Other loops than the current one are fine, however. The |
2653 | watchers. Other loops than the current one are fine, however. The |
1905 | rationale behind this is that you do not need to check for recursion in |
2654 | rationale behind this is that you do not need to check for recursion in |
1906 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2655 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1907 | C<ev_check> so if you have one watcher of each kind they will always be |
2656 | C<ev_check> so if you have one watcher of each kind they will always be |
1908 | called in pairs bracketing the blocking call. |
2657 | called in pairs bracketing the blocking call. |
1909 | |
2658 | |
1910 | Their main purpose is to integrate other event mechanisms into libev and |
2659 | Their main purpose is to integrate other event mechanisms into libev and |
1911 | their use is somewhat advanced. This could be used, for example, to track |
2660 | their use is somewhat advanced. They could be used, for example, to track |
1912 | variable changes, implement your own watchers, integrate net-snmp or a |
2661 | variable changes, implement your own watchers, integrate net-snmp or a |
1913 | coroutine library and lots more. They are also occasionally useful if |
2662 | coroutine library and lots more. They are also occasionally useful if |
1914 | you cache some data and want to flush it before blocking (for example, |
2663 | you cache some data and want to flush it before blocking (for example, |
1915 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2664 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1916 | watcher). |
2665 | watcher). |
1917 | |
2666 | |
1918 | This is done by examining in each prepare call which file descriptors need |
2667 | This is done by examining in each prepare call which file descriptors |
1919 | to be watched by the other library, registering C<ev_io> watchers for |
2668 | need to be watched by the other library, registering C<ev_io> watchers |
1920 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2669 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1921 | provide just this functionality). Then, in the check watcher you check for |
2670 | libraries provide exactly this functionality). Then, in the check watcher, |
1922 | any events that occurred (by checking the pending status of all watchers |
2671 | you check for any events that occurred (by checking the pending status |
1923 | and stopping them) and call back into the library. The I/O and timer |
2672 | of all watchers and stopping them) and call back into the library. The |
1924 | callbacks will never actually be called (but must be valid nevertheless, |
2673 | I/O and timer callbacks will never actually be called (but must be valid |
1925 | because you never know, you know?). |
2674 | nevertheless, because you never know, you know?). |
1926 | |
2675 | |
1927 | As another example, the Perl Coro module uses these hooks to integrate |
2676 | As another example, the Perl Coro module uses these hooks to integrate |
1928 | coroutines into libev programs, by yielding to other active coroutines |
2677 | coroutines into libev programs, by yielding to other active coroutines |
1929 | during each prepare and only letting the process block if no coroutines |
2678 | during each prepare and only letting the process block if no coroutines |
1930 | are ready to run (it's actually more complicated: it only runs coroutines |
2679 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1933 | loop from blocking if lower-priority coroutines are active, thus mapping |
2682 | loop from blocking if lower-priority coroutines are active, thus mapping |
1934 | low-priority coroutines to idle/background tasks). |
2683 | low-priority coroutines to idle/background tasks). |
1935 | |
2684 | |
1936 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2685 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1937 | priority, to ensure that they are being run before any other watchers |
2686 | priority, to ensure that they are being run before any other watchers |
|
|
2687 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2688 | |
1938 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2689 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1939 | too) should not activate ("feed") events into libev. While libev fully |
2690 | activate ("feed") events into libev. While libev fully supports this, they |
1940 | supports this, they might get executed before other C<ev_check> watchers |
2691 | might get executed before other C<ev_check> watchers did their job. As |
1941 | did their job. As C<ev_check> watchers are often used to embed other |
2692 | C<ev_check> watchers are often used to embed other (non-libev) event |
1942 | (non-libev) event loops those other event loops might be in an unusable |
2693 | loops those other event loops might be in an unusable state until their |
1943 | state until their C<ev_check> watcher ran (always remind yourself to |
2694 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1944 | coexist peacefully with others). |
2695 | others). |
1945 | |
2696 | |
1946 | =head3 Watcher-Specific Functions and Data Members |
2697 | =head3 Watcher-Specific Functions and Data Members |
1947 | |
2698 | |
1948 | =over 4 |
2699 | =over 4 |
1949 | |
2700 | |
… | |
… | |
1951 | |
2702 | |
1952 | =item ev_check_init (ev_check *, callback) |
2703 | =item ev_check_init (ev_check *, callback) |
1953 | |
2704 | |
1954 | Initialises and configures the prepare or check watcher - they have no |
2705 | Initialises and configures the prepare or check watcher - they have no |
1955 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2706 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1956 | macros, but using them is utterly, utterly and completely pointless. |
2707 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2708 | pointless. |
1957 | |
2709 | |
1958 | =back |
2710 | =back |
1959 | |
2711 | |
1960 | =head3 Examples |
2712 | =head3 Examples |
1961 | |
2713 | |
… | |
… | |
1974 | |
2726 | |
1975 | static ev_io iow [nfd]; |
2727 | static ev_io iow [nfd]; |
1976 | static ev_timer tw; |
2728 | static ev_timer tw; |
1977 | |
2729 | |
1978 | static void |
2730 | static void |
1979 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2731 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
1980 | { |
2732 | { |
1981 | } |
2733 | } |
1982 | |
2734 | |
1983 | // create io watchers for each fd and a timer before blocking |
2735 | // create io watchers for each fd and a timer before blocking |
1984 | static void |
2736 | static void |
1985 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2737 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
1986 | { |
2738 | { |
1987 | int timeout = 3600000; |
2739 | int timeout = 3600000; |
1988 | struct pollfd fds [nfd]; |
2740 | struct pollfd fds [nfd]; |
1989 | // actual code will need to loop here and realloc etc. |
2741 | // actual code will need to loop here and realloc etc. |
1990 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2742 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1991 | |
2743 | |
1992 | /* the callback is illegal, but won't be called as we stop during check */ |
2744 | /* the callback is illegal, but won't be called as we stop during check */ |
1993 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2745 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
1994 | ev_timer_start (loop, &tw); |
2746 | ev_timer_start (loop, &tw); |
1995 | |
2747 | |
1996 | // create one ev_io per pollfd |
2748 | // create one ev_io per pollfd |
1997 | for (int i = 0; i < nfd; ++i) |
2749 | for (int i = 0; i < nfd; ++i) |
1998 | { |
2750 | { |
… | |
… | |
2005 | } |
2757 | } |
2006 | } |
2758 | } |
2007 | |
2759 | |
2008 | // stop all watchers after blocking |
2760 | // stop all watchers after blocking |
2009 | static void |
2761 | static void |
2010 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2762 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2011 | { |
2763 | { |
2012 | ev_timer_stop (loop, &tw); |
2764 | ev_timer_stop (loop, &tw); |
2013 | |
2765 | |
2014 | for (int i = 0; i < nfd; ++i) |
2766 | for (int i = 0; i < nfd; ++i) |
2015 | { |
2767 | { |
… | |
… | |
2054 | } |
2806 | } |
2055 | |
2807 | |
2056 | // do not ever call adns_afterpoll |
2808 | // do not ever call adns_afterpoll |
2057 | |
2809 | |
2058 | Method 4: Do not use a prepare or check watcher because the module you |
2810 | Method 4: Do not use a prepare or check watcher because the module you |
2059 | want to embed is too inflexible to support it. Instead, you can override |
2811 | want to embed is not flexible enough to support it. Instead, you can |
2060 | their poll function. The drawback with this solution is that the main |
2812 | override their poll function. The drawback with this solution is that the |
2061 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2813 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2062 | this. |
2814 | this approach, effectively embedding EV as a client into the horrible |
|
|
2815 | libglib event loop. |
2063 | |
2816 | |
2064 | static gint |
2817 | static gint |
2065 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2818 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2066 | { |
2819 | { |
2067 | int got_events = 0; |
2820 | int got_events = 0; |
… | |
… | |
2071 | |
2824 | |
2072 | if (timeout >= 0) |
2825 | if (timeout >= 0) |
2073 | // create/start timer |
2826 | // create/start timer |
2074 | |
2827 | |
2075 | // poll |
2828 | // poll |
2076 | ev_loop (EV_A_ 0); |
2829 | ev_run (EV_A_ 0); |
2077 | |
2830 | |
2078 | // stop timer again |
2831 | // stop timer again |
2079 | if (timeout >= 0) |
2832 | if (timeout >= 0) |
2080 | ev_timer_stop (EV_A_ &to); |
2833 | ev_timer_stop (EV_A_ &to); |
2081 | |
2834 | |
… | |
… | |
2098 | prioritise I/O. |
2851 | prioritise I/O. |
2099 | |
2852 | |
2100 | As an example for a bug workaround, the kqueue backend might only support |
2853 | As an example for a bug workaround, the kqueue backend might only support |
2101 | sockets on some platform, so it is unusable as generic backend, but you |
2854 | sockets on some platform, so it is unusable as generic backend, but you |
2102 | still want to make use of it because you have many sockets and it scales |
2855 | still want to make use of it because you have many sockets and it scales |
2103 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2856 | so nicely. In this case, you would create a kqueue-based loop and embed |
2104 | into your default loop (which might use e.g. poll). Overall operation will |
2857 | it into your default loop (which might use e.g. poll). Overall operation |
2105 | be a bit slower because first libev has to poll and then call kevent, but |
2858 | will be a bit slower because first libev has to call C<poll> and then |
2106 | at least you can use both at what they are best. |
2859 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2860 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2107 | |
2861 | |
2108 | As for prioritising I/O: rarely you have the case where some fds have |
2862 | As for prioritising I/O: under rare circumstances you have the case where |
2109 | to be watched and handled very quickly (with low latency), and even |
2863 | some fds have to be watched and handled very quickly (with low latency), |
2110 | priorities and idle watchers might have too much overhead. In this case |
2864 | and even priorities and idle watchers might have too much overhead. In |
2111 | you would put all the high priority stuff in one loop and all the rest in |
2865 | this case you would put all the high priority stuff in one loop and all |
2112 | a second one, and embed the second one in the first. |
2866 | the rest in a second one, and embed the second one in the first. |
2113 | |
2867 | |
2114 | As long as the watcher is active, the callback will be invoked every time |
2868 | As long as the watcher is active, the callback will be invoked every |
2115 | there might be events pending in the embedded loop. The callback must then |
2869 | time there might be events pending in the embedded loop. The callback |
2116 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2870 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2117 | their callbacks (you could also start an idle watcher to give the embedded |
2871 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2118 | loop strictly lower priority for example). You can also set the callback |
2872 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2119 | to C<0>, in which case the embed watcher will automatically execute the |
2873 | to give the embedded loop strictly lower priority for example). |
2120 | embedded loop sweep. |
|
|
2121 | |
2874 | |
2122 | As long as the watcher is started it will automatically handle events. The |
2875 | You can also set the callback to C<0>, in which case the embed watcher |
2123 | callback will be invoked whenever some events have been handled. You can |
2876 | will automatically execute the embedded loop sweep whenever necessary. |
2124 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2125 | interested in that. |
|
|
2126 | |
2877 | |
2127 | Also, there have not currently been made special provisions for forking: |
2878 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2128 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2879 | is active, i.e., the embedded loop will automatically be forked when the |
2129 | but you will also have to stop and restart any C<ev_embed> watchers |
2880 | embedding loop forks. In other cases, the user is responsible for calling |
2130 | yourself. |
2881 | C<ev_loop_fork> on the embedded loop. |
2131 | |
2882 | |
2132 | Unfortunately, not all backends are embeddable, only the ones returned by |
2883 | Unfortunately, not all backends are embeddable: only the ones returned by |
2133 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2884 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2134 | portable one. |
2885 | portable one. |
2135 | |
2886 | |
2136 | So when you want to use this feature you will always have to be prepared |
2887 | So when you want to use this feature you will always have to be prepared |
2137 | that you cannot get an embeddable loop. The recommended way to get around |
2888 | that you cannot get an embeddable loop. The recommended way to get around |
2138 | this is to have a separate variables for your embeddable loop, try to |
2889 | this is to have a separate variables for your embeddable loop, try to |
2139 | create it, and if that fails, use the normal loop for everything. |
2890 | create it, and if that fails, use the normal loop for everything. |
|
|
2891 | |
|
|
2892 | =head3 C<ev_embed> and fork |
|
|
2893 | |
|
|
2894 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2895 | automatically be applied to the embedded loop as well, so no special |
|
|
2896 | fork handling is required in that case. When the watcher is not running, |
|
|
2897 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2898 | as applicable. |
2140 | |
2899 | |
2141 | =head3 Watcher-Specific Functions and Data Members |
2900 | =head3 Watcher-Specific Functions and Data Members |
2142 | |
2901 | |
2143 | =over 4 |
2902 | =over 4 |
2144 | |
2903 | |
… | |
… | |
2153 | if you do not want that, you need to temporarily stop the embed watcher). |
2912 | if you do not want that, you need to temporarily stop the embed watcher). |
2154 | |
2913 | |
2155 | =item ev_embed_sweep (loop, ev_embed *) |
2914 | =item ev_embed_sweep (loop, ev_embed *) |
2156 | |
2915 | |
2157 | Make a single, non-blocking sweep over the embedded loop. This works |
2916 | Make a single, non-blocking sweep over the embedded loop. This works |
2158 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2917 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2159 | appropriate way for embedded loops. |
2918 | appropriate way for embedded loops. |
2160 | |
2919 | |
2161 | =item struct ev_loop *other [read-only] |
2920 | =item struct ev_loop *other [read-only] |
2162 | |
2921 | |
2163 | The embedded event loop. |
2922 | The embedded event loop. |
… | |
… | |
2172 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2931 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2173 | used). |
2932 | used). |
2174 | |
2933 | |
2175 | struct ev_loop *loop_hi = ev_default_init (0); |
2934 | struct ev_loop *loop_hi = ev_default_init (0); |
2176 | struct ev_loop *loop_lo = 0; |
2935 | struct ev_loop *loop_lo = 0; |
2177 | struct ev_embed embed; |
2936 | ev_embed embed; |
2178 | |
2937 | |
2179 | // see if there is a chance of getting one that works |
2938 | // see if there is a chance of getting one that works |
2180 | // (remember that a flags value of 0 means autodetection) |
2939 | // (remember that a flags value of 0 means autodetection) |
2181 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2940 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2182 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
2941 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2196 | kqueue implementation). Store the kqueue/socket-only event loop in |
2955 | kqueue implementation). Store the kqueue/socket-only event loop in |
2197 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2956 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2198 | |
2957 | |
2199 | struct ev_loop *loop = ev_default_init (0); |
2958 | struct ev_loop *loop = ev_default_init (0); |
2200 | struct ev_loop *loop_socket = 0; |
2959 | struct ev_loop *loop_socket = 0; |
2201 | struct ev_embed embed; |
2960 | ev_embed embed; |
2202 | |
2961 | |
2203 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2962 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2204 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2963 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2205 | { |
2964 | { |
2206 | ev_embed_init (&embed, 0, loop_socket); |
2965 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2221 | event loop blocks next and before C<ev_check> watchers are being called, |
2980 | event loop blocks next and before C<ev_check> watchers are being called, |
2222 | and only in the child after the fork. If whoever good citizen calling |
2981 | and only in the child after the fork. If whoever good citizen calling |
2223 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2982 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2224 | handlers will be invoked, too, of course. |
2983 | handlers will be invoked, too, of course. |
2225 | |
2984 | |
|
|
2985 | =head3 The special problem of life after fork - how is it possible? |
|
|
2986 | |
|
|
2987 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
2988 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
2989 | sequence should be handled by libev without any problems. |
|
|
2990 | |
|
|
2991 | This changes when the application actually wants to do event handling |
|
|
2992 | in the child, or both parent in child, in effect "continuing" after the |
|
|
2993 | fork. |
|
|
2994 | |
|
|
2995 | The default mode of operation (for libev, with application help to detect |
|
|
2996 | forks) is to duplicate all the state in the child, as would be expected |
|
|
2997 | when I<either> the parent I<or> the child process continues. |
|
|
2998 | |
|
|
2999 | When both processes want to continue using libev, then this is usually the |
|
|
3000 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3001 | supposed to continue with all watchers in place as before, while the other |
|
|
3002 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3003 | |
|
|
3004 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3005 | simply create a new event loop, which of course will be "empty", and |
|
|
3006 | use that for new watchers. This has the advantage of not touching more |
|
|
3007 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3008 | disadvantage of having to use multiple event loops (which do not support |
|
|
3009 | signal watchers). |
|
|
3010 | |
|
|
3011 | When this is not possible, or you want to use the default loop for |
|
|
3012 | other reasons, then in the process that wants to start "fresh", call |
|
|
3013 | C<ev_default_destroy ()> followed by C<ev_default_loop (...)>. Destroying |
|
|
3014 | the default loop will "orphan" (not stop) all registered watchers, so you |
|
|
3015 | have to be careful not to execute code that modifies those watchers. Note |
|
|
3016 | also that in that case, you have to re-register any signal watchers. |
|
|
3017 | |
2226 | =head3 Watcher-Specific Functions and Data Members |
3018 | =head3 Watcher-Specific Functions and Data Members |
2227 | |
3019 | |
2228 | =over 4 |
3020 | =over 4 |
2229 | |
3021 | |
2230 | =item ev_fork_init (ev_signal *, callback) |
3022 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2234 | believe me. |
3026 | believe me. |
2235 | |
3027 | |
2236 | =back |
3028 | =back |
2237 | |
3029 | |
2238 | |
3030 | |
2239 | =head2 C<ev_async> - how to wake up another event loop |
3031 | =head2 C<ev_async> - how to wake up an event loop |
2240 | |
3032 | |
2241 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3033 | In general, you cannot use an C<ev_run> from multiple threads or other |
2242 | asynchronous sources such as signal handlers (as opposed to multiple event |
3034 | asynchronous sources such as signal handlers (as opposed to multiple event |
2243 | loops - those are of course safe to use in different threads). |
3035 | loops - those are of course safe to use in different threads). |
2244 | |
3036 | |
2245 | Sometimes, however, you need to wake up another event loop you do not |
3037 | Sometimes, however, you need to wake up an event loop you do not control, |
2246 | control, for example because it belongs to another thread. This is what |
3038 | for example because it belongs to another thread. This is what C<ev_async> |
2247 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3039 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2248 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3040 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2249 | safe. |
|
|
2250 | |
3041 | |
2251 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3042 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2252 | too, are asynchronous in nature, and signals, too, will be compressed |
3043 | too, are asynchronous in nature, and signals, too, will be compressed |
2253 | (i.e. the number of callback invocations may be less than the number of |
3044 | (i.e. the number of callback invocations may be less than the number of |
2254 | C<ev_async_sent> calls). |
3045 | C<ev_async_sent> calls). |
… | |
… | |
2259 | =head3 Queueing |
3050 | =head3 Queueing |
2260 | |
3051 | |
2261 | C<ev_async> does not support queueing of data in any way. The reason |
3052 | C<ev_async> does not support queueing of data in any way. The reason |
2262 | is that the author does not know of a simple (or any) algorithm for a |
3053 | is that the author does not know of a simple (or any) algorithm for a |
2263 | multiple-writer-single-reader queue that works in all cases and doesn't |
3054 | multiple-writer-single-reader queue that works in all cases and doesn't |
2264 | need elaborate support such as pthreads. |
3055 | need elaborate support such as pthreads or unportable memory access |
|
|
3056 | semantics. |
2265 | |
3057 | |
2266 | That means that if you want to queue data, you have to provide your own |
3058 | That means that if you want to queue data, you have to provide your own |
2267 | queue. But at least I can tell you would implement locking around your |
3059 | queue. But at least I can tell you how to implement locking around your |
2268 | queue: |
3060 | queue: |
2269 | |
3061 | |
2270 | =over 4 |
3062 | =over 4 |
2271 | |
3063 | |
2272 | =item queueing from a signal handler context |
3064 | =item queueing from a signal handler context |
2273 | |
3065 | |
2274 | To implement race-free queueing, you simply add to the queue in the signal |
3066 | To implement race-free queueing, you simply add to the queue in the signal |
2275 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3067 | handler but you block the signal handler in the watcher callback. Here is |
2276 | some fictitious SIGUSR1 handler: |
3068 | an example that does that for some fictitious SIGUSR1 handler: |
2277 | |
3069 | |
2278 | static ev_async mysig; |
3070 | static ev_async mysig; |
2279 | |
3071 | |
2280 | static void |
3072 | static void |
2281 | sigusr1_handler (void) |
3073 | sigusr1_handler (void) |
… | |
… | |
2347 | =over 4 |
3139 | =over 4 |
2348 | |
3140 | |
2349 | =item ev_async_init (ev_async *, callback) |
3141 | =item ev_async_init (ev_async *, callback) |
2350 | |
3142 | |
2351 | Initialises and configures the async watcher - it has no parameters of any |
3143 | Initialises and configures the async watcher - it has no parameters of any |
2352 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3144 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2353 | believe me. |
3145 | trust me. |
2354 | |
3146 | |
2355 | =item ev_async_send (loop, ev_async *) |
3147 | =item ev_async_send (loop, ev_async *) |
2356 | |
3148 | |
2357 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3149 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2358 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3150 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2359 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3151 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2360 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3152 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2361 | section below on what exactly this means). |
3153 | section below on what exactly this means). |
2362 | |
3154 | |
|
|
3155 | Note that, as with other watchers in libev, multiple events might get |
|
|
3156 | compressed into a single callback invocation (another way to look at this |
|
|
3157 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3158 | reset when the event loop detects that). |
|
|
3159 | |
2363 | This call incurs the overhead of a system call only once per loop iteration, |
3160 | This call incurs the overhead of a system call only once per event loop |
2364 | so while the overhead might be noticeable, it doesn't apply to repeated |
3161 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2365 | calls to C<ev_async_send>. |
3162 | repeated calls to C<ev_async_send> for the same event loop. |
2366 | |
3163 | |
2367 | =item bool = ev_async_pending (ev_async *) |
3164 | =item bool = ev_async_pending (ev_async *) |
2368 | |
3165 | |
2369 | Returns a non-zero value when C<ev_async_send> has been called on the |
3166 | Returns a non-zero value when C<ev_async_send> has been called on the |
2370 | watcher but the event has not yet been processed (or even noted) by the |
3167 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2373 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3170 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2374 | the loop iterates next and checks for the watcher to have become active, |
3171 | the loop iterates next and checks for the watcher to have become active, |
2375 | it will reset the flag again. C<ev_async_pending> can be used to very |
3172 | it will reset the flag again. C<ev_async_pending> can be used to very |
2376 | quickly check whether invoking the loop might be a good idea. |
3173 | quickly check whether invoking the loop might be a good idea. |
2377 | |
3174 | |
2378 | Not that this does I<not> check whether the watcher itself is pending, only |
3175 | Not that this does I<not> check whether the watcher itself is pending, |
2379 | whether it has been requested to make this watcher pending. |
3176 | only whether it has been requested to make this watcher pending: there |
|
|
3177 | is a time window between the event loop checking and resetting the async |
|
|
3178 | notification, and the callback being invoked. |
2380 | |
3179 | |
2381 | =back |
3180 | =back |
2382 | |
3181 | |
2383 | |
3182 | |
2384 | =head1 OTHER FUNCTIONS |
3183 | =head1 OTHER FUNCTIONS |
… | |
… | |
2388 | =over 4 |
3187 | =over 4 |
2389 | |
3188 | |
2390 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3189 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2391 | |
3190 | |
2392 | This function combines a simple timer and an I/O watcher, calls your |
3191 | This function combines a simple timer and an I/O watcher, calls your |
2393 | callback on whichever event happens first and automatically stop both |
3192 | callback on whichever event happens first and automatically stops both |
2394 | watchers. This is useful if you want to wait for a single event on an fd |
3193 | watchers. This is useful if you want to wait for a single event on an fd |
2395 | or timeout without having to allocate/configure/start/stop/free one or |
3194 | or timeout without having to allocate/configure/start/stop/free one or |
2396 | more watchers yourself. |
3195 | more watchers yourself. |
2397 | |
3196 | |
2398 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3197 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2399 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3198 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2400 | C<events> set will be created and started. |
3199 | the given C<fd> and C<events> set will be created and started. |
2401 | |
3200 | |
2402 | If C<timeout> is less than 0, then no timeout watcher will be |
3201 | If C<timeout> is less than 0, then no timeout watcher will be |
2403 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3202 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2404 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3203 | repeat = 0) will be started. C<0> is a valid timeout. |
2405 | dubious value. |
|
|
2406 | |
3204 | |
2407 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3205 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2408 | passed an C<revents> set like normal event callbacks (a combination of |
3206 | passed an C<revents> set like normal event callbacks (a combination of |
2409 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3207 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2410 | value passed to C<ev_once>: |
3208 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3209 | a timeout and an io event at the same time - you probably should give io |
|
|
3210 | events precedence. |
|
|
3211 | |
|
|
3212 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2411 | |
3213 | |
2412 | static void stdin_ready (int revents, void *arg) |
3214 | static void stdin_ready (int revents, void *arg) |
2413 | { |
3215 | { |
|
|
3216 | if (revents & EV_READ) |
|
|
3217 | /* stdin might have data for us, joy! */; |
2414 | if (revents & EV_TIMEOUT) |
3218 | else if (revents & EV_TIMER) |
2415 | /* doh, nothing entered */; |
3219 | /* doh, nothing entered */; |
2416 | else if (revents & EV_READ) |
|
|
2417 | /* stdin might have data for us, joy! */; |
|
|
2418 | } |
3220 | } |
2419 | |
3221 | |
2420 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3222 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2421 | |
3223 | |
2422 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2423 | |
|
|
2424 | Feeds the given event set into the event loop, as if the specified event |
|
|
2425 | had happened for the specified watcher (which must be a pointer to an |
|
|
2426 | initialised but not necessarily started event watcher). |
|
|
2427 | |
|
|
2428 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3224 | =item ev_feed_fd_event (loop, int fd, int revents) |
2429 | |
3225 | |
2430 | Feed an event on the given fd, as if a file descriptor backend detected |
3226 | Feed an event on the given fd, as if a file descriptor backend detected |
2431 | the given events it. |
3227 | the given events it. |
2432 | |
3228 | |
2433 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3229 | =item ev_feed_signal_event (loop, int signum) |
2434 | |
3230 | |
2435 | Feed an event as if the given signal occurred (C<loop> must be the default |
3231 | Feed an event as if the given signal occurred (C<loop> must be the default |
2436 | loop!). |
3232 | loop!). |
2437 | |
3233 | |
2438 | =back |
3234 | =back |
… | |
… | |
2518 | |
3314 | |
2519 | =over 4 |
3315 | =over 4 |
2520 | |
3316 | |
2521 | =item ev::TYPE::TYPE () |
3317 | =item ev::TYPE::TYPE () |
2522 | |
3318 | |
2523 | =item ev::TYPE::TYPE (struct ev_loop *) |
3319 | =item ev::TYPE::TYPE (loop) |
2524 | |
3320 | |
2525 | =item ev::TYPE::~TYPE |
3321 | =item ev::TYPE::~TYPE |
2526 | |
3322 | |
2527 | The constructor (optionally) takes an event loop to associate the watcher |
3323 | The constructor (optionally) takes an event loop to associate the watcher |
2528 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3324 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2560 | |
3356 | |
2561 | myclass obj; |
3357 | myclass obj; |
2562 | ev::io iow; |
3358 | ev::io iow; |
2563 | iow.set <myclass, &myclass::io_cb> (&obj); |
3359 | iow.set <myclass, &myclass::io_cb> (&obj); |
2564 | |
3360 | |
|
|
3361 | =item w->set (object *) |
|
|
3362 | |
|
|
3363 | This is a variation of a method callback - leaving out the method to call |
|
|
3364 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3365 | functor objects without having to manually specify the C<operator ()> all |
|
|
3366 | the time. Incidentally, you can then also leave out the template argument |
|
|
3367 | list. |
|
|
3368 | |
|
|
3369 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3370 | int revents)>. |
|
|
3371 | |
|
|
3372 | See the method-C<set> above for more details. |
|
|
3373 | |
|
|
3374 | Example: use a functor object as callback. |
|
|
3375 | |
|
|
3376 | struct myfunctor |
|
|
3377 | { |
|
|
3378 | void operator() (ev::io &w, int revents) |
|
|
3379 | { |
|
|
3380 | ... |
|
|
3381 | } |
|
|
3382 | } |
|
|
3383 | |
|
|
3384 | myfunctor f; |
|
|
3385 | |
|
|
3386 | ev::io w; |
|
|
3387 | w.set (&f); |
|
|
3388 | |
2565 | =item w->set<function> (void *data = 0) |
3389 | =item w->set<function> (void *data = 0) |
2566 | |
3390 | |
2567 | Also sets a callback, but uses a static method or plain function as |
3391 | Also sets a callback, but uses a static method or plain function as |
2568 | callback. The optional C<data> argument will be stored in the watcher's |
3392 | callback. The optional C<data> argument will be stored in the watcher's |
2569 | C<data> member and is free for you to use. |
3393 | C<data> member and is free for you to use. |
2570 | |
3394 | |
2571 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3395 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2572 | |
3396 | |
2573 | See the method-C<set> above for more details. |
3397 | See the method-C<set> above for more details. |
2574 | |
3398 | |
2575 | Example: |
3399 | Example: Use a plain function as callback. |
2576 | |
3400 | |
2577 | static void io_cb (ev::io &w, int revents) { } |
3401 | static void io_cb (ev::io &w, int revents) { } |
2578 | iow.set <io_cb> (); |
3402 | iow.set <io_cb> (); |
2579 | |
3403 | |
2580 | =item w->set (struct ev_loop *) |
3404 | =item w->set (loop) |
2581 | |
3405 | |
2582 | Associates a different C<struct ev_loop> with this watcher. You can only |
3406 | Associates a different C<struct ev_loop> with this watcher. You can only |
2583 | do this when the watcher is inactive (and not pending either). |
3407 | do this when the watcher is inactive (and not pending either). |
2584 | |
3408 | |
2585 | =item w->set ([arguments]) |
3409 | =item w->set ([arguments]) |
2586 | |
3410 | |
2587 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3411 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2588 | called at least once. Unlike the C counterpart, an active watcher gets |
3412 | method or a suitable start method must be called at least once. Unlike the |
2589 | automatically stopped and restarted when reconfiguring it with this |
3413 | C counterpart, an active watcher gets automatically stopped and restarted |
2590 | method. |
3414 | when reconfiguring it with this method. |
2591 | |
3415 | |
2592 | =item w->start () |
3416 | =item w->start () |
2593 | |
3417 | |
2594 | Starts the watcher. Note that there is no C<loop> argument, as the |
3418 | Starts the watcher. Note that there is no C<loop> argument, as the |
2595 | constructor already stores the event loop. |
3419 | constructor already stores the event loop. |
2596 | |
3420 | |
|
|
3421 | =item w->start ([arguments]) |
|
|
3422 | |
|
|
3423 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3424 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3425 | the configure C<set> method of the watcher. |
|
|
3426 | |
2597 | =item w->stop () |
3427 | =item w->stop () |
2598 | |
3428 | |
2599 | Stops the watcher if it is active. Again, no C<loop> argument. |
3429 | Stops the watcher if it is active. Again, no C<loop> argument. |
2600 | |
3430 | |
2601 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3431 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2613 | |
3443 | |
2614 | =back |
3444 | =back |
2615 | |
3445 | |
2616 | =back |
3446 | =back |
2617 | |
3447 | |
2618 | Example: Define a class with an IO and idle watcher, start one of them in |
3448 | Example: Define a class with two I/O and idle watchers, start the I/O |
2619 | the constructor. |
3449 | watchers in the constructor. |
2620 | |
3450 | |
2621 | class myclass |
3451 | class myclass |
2622 | { |
3452 | { |
2623 | ev::io io; void io_cb (ev::io &w, int revents); |
3453 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3454 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2624 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3455 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2625 | |
3456 | |
2626 | myclass (int fd) |
3457 | myclass (int fd) |
2627 | { |
3458 | { |
2628 | io .set <myclass, &myclass::io_cb > (this); |
3459 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3460 | io2 .set <myclass, &myclass::io2_cb > (this); |
2629 | idle.set <myclass, &myclass::idle_cb> (this); |
3461 | idle.set <myclass, &myclass::idle_cb> (this); |
2630 | |
3462 | |
2631 | io.start (fd, ev::READ); |
3463 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3464 | io.start (); // start it whenever convenient |
|
|
3465 | |
|
|
3466 | io2.start (fd, ev::READ); // set + start in one call |
2632 | } |
3467 | } |
2633 | }; |
3468 | }; |
2634 | |
3469 | |
2635 | |
3470 | |
2636 | =head1 OTHER LANGUAGE BINDINGS |
3471 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2645 | =item Perl |
3480 | =item Perl |
2646 | |
3481 | |
2647 | The EV module implements the full libev API and is actually used to test |
3482 | The EV module implements the full libev API and is actually used to test |
2648 | libev. EV is developed together with libev. Apart from the EV core module, |
3483 | libev. EV is developed together with libev. Apart from the EV core module, |
2649 | there are additional modules that implement libev-compatible interfaces |
3484 | there are additional modules that implement libev-compatible interfaces |
2650 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3485 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2651 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3486 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3487 | and C<EV::Glib>). |
2652 | |
3488 | |
2653 | It can be found and installed via CPAN, its homepage is at |
3489 | It can be found and installed via CPAN, its homepage is at |
2654 | L<http://software.schmorp.de/pkg/EV>. |
3490 | L<http://software.schmorp.de/pkg/EV>. |
2655 | |
3491 | |
2656 | =item Python |
3492 | =item Python |
2657 | |
3493 | |
2658 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3494 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2659 | seems to be quite complete and well-documented. Note, however, that the |
3495 | seems to be quite complete and well-documented. |
2660 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2661 | for everybody else, and therefore, should never be applied in an installed |
|
|
2662 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2663 | libev). |
|
|
2664 | |
3496 | |
2665 | =item Ruby |
3497 | =item Ruby |
2666 | |
3498 | |
2667 | Tony Arcieri has written a ruby extension that offers access to a subset |
3499 | Tony Arcieri has written a ruby extension that offers access to a subset |
2668 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3500 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2669 | more on top of it. It can be found via gem servers. Its homepage is at |
3501 | more on top of it. It can be found via gem servers. Its homepage is at |
2670 | L<http://rev.rubyforge.org/>. |
3502 | L<http://rev.rubyforge.org/>. |
2671 | |
3503 | |
|
|
3504 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3505 | makes rev work even on mingw. |
|
|
3506 | |
|
|
3507 | =item Haskell |
|
|
3508 | |
|
|
3509 | A haskell binding to libev is available at |
|
|
3510 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3511 | |
2672 | =item D |
3512 | =item D |
2673 | |
3513 | |
2674 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3514 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2675 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3515 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3516 | |
|
|
3517 | =item Ocaml |
|
|
3518 | |
|
|
3519 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3520 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3521 | |
|
|
3522 | =item Lua |
|
|
3523 | |
|
|
3524 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3525 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3526 | L<http://github.com/brimworks/lua-ev>. |
2676 | |
3527 | |
2677 | =back |
3528 | =back |
2678 | |
3529 | |
2679 | |
3530 | |
2680 | =head1 MACRO MAGIC |
3531 | =head1 MACRO MAGIC |
… | |
… | |
2694 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3545 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2695 | C<EV_A_> is used when other arguments are following. Example: |
3546 | C<EV_A_> is used when other arguments are following. Example: |
2696 | |
3547 | |
2697 | ev_unref (EV_A); |
3548 | ev_unref (EV_A); |
2698 | ev_timer_add (EV_A_ watcher); |
3549 | ev_timer_add (EV_A_ watcher); |
2699 | ev_loop (EV_A_ 0); |
3550 | ev_run (EV_A_ 0); |
2700 | |
3551 | |
2701 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3552 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2702 | which is often provided by the following macro. |
3553 | which is often provided by the following macro. |
2703 | |
3554 | |
2704 | =item C<EV_P>, C<EV_P_> |
3555 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
2744 | } |
3595 | } |
2745 | |
3596 | |
2746 | ev_check check; |
3597 | ev_check check; |
2747 | ev_check_init (&check, check_cb); |
3598 | ev_check_init (&check, check_cb); |
2748 | ev_check_start (EV_DEFAULT_ &check); |
3599 | ev_check_start (EV_DEFAULT_ &check); |
2749 | ev_loop (EV_DEFAULT_ 0); |
3600 | ev_run (EV_DEFAULT_ 0); |
2750 | |
3601 | |
2751 | =head1 EMBEDDING |
3602 | =head1 EMBEDDING |
2752 | |
3603 | |
2753 | Libev can (and often is) directly embedded into host |
3604 | Libev can (and often is) directly embedded into host |
2754 | applications. Examples of applications that embed it include the Deliantra |
3605 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2781 | |
3632 | |
2782 | #define EV_STANDALONE 1 |
3633 | #define EV_STANDALONE 1 |
2783 | #include "ev.h" |
3634 | #include "ev.h" |
2784 | |
3635 | |
2785 | Both header files and implementation files can be compiled with a C++ |
3636 | Both header files and implementation files can be compiled with a C++ |
2786 | compiler (at least, thats a stated goal, and breakage will be treated |
3637 | compiler (at least, that's a stated goal, and breakage will be treated |
2787 | as a bug). |
3638 | as a bug). |
2788 | |
3639 | |
2789 | You need the following files in your source tree, or in a directory |
3640 | You need the following files in your source tree, or in a directory |
2790 | in your include path (e.g. in libev/ when using -Ilibev): |
3641 | in your include path (e.g. in libev/ when using -Ilibev): |
2791 | |
3642 | |
… | |
… | |
2834 | libev.m4 |
3685 | libev.m4 |
2835 | |
3686 | |
2836 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3687 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2837 | |
3688 | |
2838 | Libev can be configured via a variety of preprocessor symbols you have to |
3689 | Libev can be configured via a variety of preprocessor symbols you have to |
2839 | define before including any of its files. The default in the absence of |
3690 | define before including (or compiling) any of its files. The default in |
2840 | autoconf is noted for every option. |
3691 | the absence of autoconf is documented for every option. |
|
|
3692 | |
|
|
3693 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3694 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3695 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3696 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3697 | users of libev and the libev code itself must be compiled with compatible |
|
|
3698 | settings. |
2841 | |
3699 | |
2842 | =over 4 |
3700 | =over 4 |
2843 | |
3701 | |
|
|
3702 | =item EV_COMPAT3 (h) |
|
|
3703 | |
|
|
3704 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3705 | release of libev comes with wrappers for the functions and symbols that |
|
|
3706 | have been renamed between libev version 3 and 4. |
|
|
3707 | |
|
|
3708 | You can disable these wrappers (to test compatibility with future |
|
|
3709 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3710 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3711 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3712 | typedef in that case. |
|
|
3713 | |
|
|
3714 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3715 | and in some even more future version the compatibility code will be |
|
|
3716 | removed completely. |
|
|
3717 | |
2844 | =item EV_STANDALONE |
3718 | =item EV_STANDALONE (h) |
2845 | |
3719 | |
2846 | Must always be C<1> if you do not use autoconf configuration, which |
3720 | Must always be C<1> if you do not use autoconf configuration, which |
2847 | keeps libev from including F<config.h>, and it also defines dummy |
3721 | keeps libev from including F<config.h>, and it also defines dummy |
2848 | implementations for some libevent functions (such as logging, which is not |
3722 | implementations for some libevent functions (such as logging, which is not |
2849 | supported). It will also not define any of the structs usually found in |
3723 | supported). It will also not define any of the structs usually found in |
2850 | F<event.h> that are not directly supported by the libev core alone. |
3724 | F<event.h> that are not directly supported by the libev core alone. |
2851 | |
3725 | |
|
|
3726 | In standalone mode, libev will still try to automatically deduce the |
|
|
3727 | configuration, but has to be more conservative. |
|
|
3728 | |
2852 | =item EV_USE_MONOTONIC |
3729 | =item EV_USE_MONOTONIC |
2853 | |
3730 | |
2854 | If defined to be C<1>, libev will try to detect the availability of the |
3731 | If defined to be C<1>, libev will try to detect the availability of the |
2855 | monotonic clock option at both compile time and runtime. Otherwise no use |
3732 | monotonic clock option at both compile time and runtime. Otherwise no |
2856 | of the monotonic clock option will be attempted. If you enable this, you |
3733 | use of the monotonic clock option will be attempted. If you enable this, |
2857 | usually have to link against librt or something similar. Enabling it when |
3734 | you usually have to link against librt or something similar. Enabling it |
2858 | the functionality isn't available is safe, though, although you have |
3735 | when the functionality isn't available is safe, though, although you have |
2859 | to make sure you link against any libraries where the C<clock_gettime> |
3736 | to make sure you link against any libraries where the C<clock_gettime> |
2860 | function is hiding in (often F<-lrt>). |
3737 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2861 | |
3738 | |
2862 | =item EV_USE_REALTIME |
3739 | =item EV_USE_REALTIME |
2863 | |
3740 | |
2864 | If defined to be C<1>, libev will try to detect the availability of the |
3741 | If defined to be C<1>, libev will try to detect the availability of the |
2865 | real-time clock option at compile time (and assume its availability at |
3742 | real-time clock option at compile time (and assume its availability |
2866 | runtime if successful). Otherwise no use of the real-time clock option will |
3743 | at runtime if successful). Otherwise no use of the real-time clock |
2867 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3744 | option will be attempted. This effectively replaces C<gettimeofday> |
2868 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3745 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2869 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3746 | correctness. See the note about libraries in the description of |
|
|
3747 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3748 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3749 | |
|
|
3750 | =item EV_USE_CLOCK_SYSCALL |
|
|
3751 | |
|
|
3752 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3753 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3754 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3755 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3756 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3757 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3758 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3759 | higher, as it simplifies linking (no need for C<-lrt>). |
2870 | |
3760 | |
2871 | =item EV_USE_NANOSLEEP |
3761 | =item EV_USE_NANOSLEEP |
2872 | |
3762 | |
2873 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3763 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2874 | and will use it for delays. Otherwise it will use C<select ()>. |
3764 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2890 | |
3780 | |
2891 | =item EV_SELECT_USE_FD_SET |
3781 | =item EV_SELECT_USE_FD_SET |
2892 | |
3782 | |
2893 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3783 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2894 | structure. This is useful if libev doesn't compile due to a missing |
3784 | structure. This is useful if libev doesn't compile due to a missing |
2895 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3785 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2896 | exotic systems. This usually limits the range of file descriptors to some |
3786 | on exotic systems. This usually limits the range of file descriptors to |
2897 | low limit such as 1024 or might have other limitations (winsocket only |
3787 | some low limit such as 1024 or might have other limitations (winsocket |
2898 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3788 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2899 | influence the size of the C<fd_set> used. |
3789 | configures the maximum size of the C<fd_set>. |
2900 | |
3790 | |
2901 | =item EV_SELECT_IS_WINSOCKET |
3791 | =item EV_SELECT_IS_WINSOCKET |
2902 | |
3792 | |
2903 | When defined to C<1>, the select backend will assume that |
3793 | When defined to C<1>, the select backend will assume that |
2904 | select/socket/connect etc. don't understand file descriptors but |
3794 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2906 | be used is the winsock select). This means that it will call |
3796 | be used is the winsock select). This means that it will call |
2907 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3797 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2908 | it is assumed that all these functions actually work on fds, even |
3798 | it is assumed that all these functions actually work on fds, even |
2909 | on win32. Should not be defined on non-win32 platforms. |
3799 | on win32. Should not be defined on non-win32 platforms. |
2910 | |
3800 | |
2911 | =item EV_FD_TO_WIN32_HANDLE |
3801 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2912 | |
3802 | |
2913 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3803 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2914 | file descriptors to socket handles. When not defining this symbol (the |
3804 | file descriptors to socket handles. When not defining this symbol (the |
2915 | default), then libev will call C<_get_osfhandle>, which is usually |
3805 | default), then libev will call C<_get_osfhandle>, which is usually |
2916 | correct. In some cases, programs use their own file descriptor management, |
3806 | correct. In some cases, programs use their own file descriptor management, |
2917 | in which case they can provide this function to map fds to socket handles. |
3807 | in which case they can provide this function to map fds to socket handles. |
|
|
3808 | |
|
|
3809 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3810 | |
|
|
3811 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3812 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3813 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3814 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3815 | |
|
|
3816 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3817 | |
|
|
3818 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3819 | macro can be used to override the C<close> function, useful to unregister |
|
|
3820 | file descriptors again. Note that the replacement function has to close |
|
|
3821 | the underlying OS handle. |
2918 | |
3822 | |
2919 | =item EV_USE_POLL |
3823 | =item EV_USE_POLL |
2920 | |
3824 | |
2921 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3825 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2922 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3826 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
2969 | as well as for signal and thread safety in C<ev_async> watchers. |
3873 | as well as for signal and thread safety in C<ev_async> watchers. |
2970 | |
3874 | |
2971 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3875 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
2972 | (from F<signal.h>), which is usually good enough on most platforms. |
3876 | (from F<signal.h>), which is usually good enough on most platforms. |
2973 | |
3877 | |
2974 | =item EV_H |
3878 | =item EV_H (h) |
2975 | |
3879 | |
2976 | The name of the F<ev.h> header file used to include it. The default if |
3880 | The name of the F<ev.h> header file used to include it. The default if |
2977 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3881 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2978 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3882 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2979 | |
3883 | |
2980 | =item EV_CONFIG_H |
3884 | =item EV_CONFIG_H (h) |
2981 | |
3885 | |
2982 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3886 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2983 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3887 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2984 | C<EV_H>, above. |
3888 | C<EV_H>, above. |
2985 | |
3889 | |
2986 | =item EV_EVENT_H |
3890 | =item EV_EVENT_H (h) |
2987 | |
3891 | |
2988 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3892 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2989 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3893 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2990 | |
3894 | |
2991 | =item EV_PROTOTYPES |
3895 | =item EV_PROTOTYPES (h) |
2992 | |
3896 | |
2993 | If defined to be C<0>, then F<ev.h> will not define any function |
3897 | If defined to be C<0>, then F<ev.h> will not define any function |
2994 | prototypes, but still define all the structs and other symbols. This is |
3898 | prototypes, but still define all the structs and other symbols. This is |
2995 | occasionally useful if you want to provide your own wrapper functions |
3899 | occasionally useful if you want to provide your own wrapper functions |
2996 | around libev functions. |
3900 | around libev functions. |
… | |
… | |
3015 | When doing priority-based operations, libev usually has to linearly search |
3919 | When doing priority-based operations, libev usually has to linearly search |
3016 | all the priorities, so having many of them (hundreds) uses a lot of space |
3920 | all the priorities, so having many of them (hundreds) uses a lot of space |
3017 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3921 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3018 | fine. |
3922 | fine. |
3019 | |
3923 | |
3020 | If your embedding application does not need any priorities, defining these both to |
3924 | If your embedding application does not need any priorities, defining these |
3021 | C<0> will save some memory and CPU. |
3925 | both to C<0> will save some memory and CPU. |
3022 | |
3926 | |
3023 | =item EV_PERIODIC_ENABLE |
3927 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
3928 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
3929 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3024 | |
3930 | |
3025 | If undefined or defined to be C<1>, then periodic timers are supported. If |
3931 | If undefined or defined to be C<1> (and the platform supports it), then |
3026 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
3932 | the respective watcher type is supported. If defined to be C<0>, then it |
3027 | code. |
3933 | is not. Disabling watcher types mainly saves code size. |
3028 | |
3934 | |
3029 | =item EV_IDLE_ENABLE |
3935 | =item EV_FEATURES |
3030 | |
|
|
3031 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3032 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3033 | code. |
|
|
3034 | |
|
|
3035 | =item EV_EMBED_ENABLE |
|
|
3036 | |
|
|
3037 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3038 | defined to be C<0>, then they are not. |
|
|
3039 | |
|
|
3040 | =item EV_STAT_ENABLE |
|
|
3041 | |
|
|
3042 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3043 | defined to be C<0>, then they are not. |
|
|
3044 | |
|
|
3045 | =item EV_FORK_ENABLE |
|
|
3046 | |
|
|
3047 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3048 | defined to be C<0>, then they are not. |
|
|
3049 | |
|
|
3050 | =item EV_ASYNC_ENABLE |
|
|
3051 | |
|
|
3052 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3053 | defined to be C<0>, then they are not. |
|
|
3054 | |
|
|
3055 | =item EV_MINIMAL |
|
|
3056 | |
3936 | |
3057 | If you need to shave off some kilobytes of code at the expense of some |
3937 | If you need to shave off some kilobytes of code at the expense of some |
3058 | speed, define this symbol to C<1>. Currently this is used to override some |
3938 | speed (but with the full API), you can define this symbol to request |
3059 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
3939 | certain subsets of functionality. The default is to enable all features |
3060 | much smaller 2-heap for timer management over the default 4-heap. |
3940 | that can be enabled on the platform. |
|
|
3941 | |
|
|
3942 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
3943 | with some broad features you want) and then selectively re-enable |
|
|
3944 | additional parts you want, for example if you want everything minimal, |
|
|
3945 | but multiple event loop support, async and child watchers and the poll |
|
|
3946 | backend, use this: |
|
|
3947 | |
|
|
3948 | #define EV_FEATURES 0 |
|
|
3949 | #define EV_MULTIPLICITY 1 |
|
|
3950 | #define EV_USE_POLL 1 |
|
|
3951 | #define EV_CHILD_ENABLE 1 |
|
|
3952 | #define EV_ASYNC_ENABLE 1 |
|
|
3953 | |
|
|
3954 | The actual value is a bitset, it can be a combination of the following |
|
|
3955 | values: |
|
|
3956 | |
|
|
3957 | =over 4 |
|
|
3958 | |
|
|
3959 | =item C<1> - faster/larger code |
|
|
3960 | |
|
|
3961 | Use larger code to speed up some operations. |
|
|
3962 | |
|
|
3963 | Currently this is used to override some inlining decisions (enlarging the |
|
|
3964 | code size by roughly 30% on amd64). |
|
|
3965 | |
|
|
3966 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
3967 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
3968 | assertions. |
|
|
3969 | |
|
|
3970 | =item C<2> - faster/larger data structures |
|
|
3971 | |
|
|
3972 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
3973 | hash table sizes and so on. This will usually further increase code size |
|
|
3974 | and can additionally have an effect on the size of data structures at |
|
|
3975 | runtime. |
|
|
3976 | |
|
|
3977 | =item C<4> - full API configuration |
|
|
3978 | |
|
|
3979 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
3980 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
3981 | |
|
|
3982 | =item C<8> - full API |
|
|
3983 | |
|
|
3984 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
3985 | details on which parts of the API are still available without this |
|
|
3986 | feature, and do not complain if this subset changes over time. |
|
|
3987 | |
|
|
3988 | =item C<16> - enable all optional watcher types |
|
|
3989 | |
|
|
3990 | Enables all optional watcher types. If you want to selectively enable |
|
|
3991 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
3992 | embed, async, child...) you can enable them manually by defining |
|
|
3993 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
3994 | |
|
|
3995 | =item C<32> - enable all backends |
|
|
3996 | |
|
|
3997 | This enables all backends - without this feature, you need to enable at |
|
|
3998 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
3999 | |
|
|
4000 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4001 | |
|
|
4002 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4003 | default. |
|
|
4004 | |
|
|
4005 | =back |
|
|
4006 | |
|
|
4007 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4008 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4009 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4010 | watchers, timers and monotonic clock support. |
|
|
4011 | |
|
|
4012 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4013 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4014 | your program might be left out as well - a binary starting a timer and an |
|
|
4015 | I/O watcher then might come out at only 5Kb. |
|
|
4016 | |
|
|
4017 | =item EV_AVOID_STDIO |
|
|
4018 | |
|
|
4019 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4020 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4021 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4022 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4023 | big. |
|
|
4024 | |
|
|
4025 | Note that error messages might become less precise when this option is |
|
|
4026 | enabled. |
|
|
4027 | |
|
|
4028 | =item EV_NSIG |
|
|
4029 | |
|
|
4030 | The highest supported signal number, +1 (or, the number of |
|
|
4031 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4032 | automatically, but sometimes this fails, in which case it can be |
|
|
4033 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4034 | good for about any system in existence) can save some memory, as libev |
|
|
4035 | statically allocates some 12-24 bytes per signal number. |
3061 | |
4036 | |
3062 | =item EV_PID_HASHSIZE |
4037 | =item EV_PID_HASHSIZE |
3063 | |
4038 | |
3064 | C<ev_child> watchers use a small hash table to distribute workload by |
4039 | C<ev_child> watchers use a small hash table to distribute workload by |
3065 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4040 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3066 | than enough. If you need to manage thousands of children you might want to |
4041 | usually more than enough. If you need to manage thousands of children you |
3067 | increase this value (I<must> be a power of two). |
4042 | might want to increase this value (I<must> be a power of two). |
3068 | |
4043 | |
3069 | =item EV_INOTIFY_HASHSIZE |
4044 | =item EV_INOTIFY_HASHSIZE |
3070 | |
4045 | |
3071 | C<ev_stat> watchers use a small hash table to distribute workload by |
4046 | C<ev_stat> watchers use a small hash table to distribute workload by |
3072 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4047 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3073 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4048 | disabled), usually more than enough. If you need to manage thousands of |
3074 | watchers you might want to increase this value (I<must> be a power of |
4049 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3075 | two). |
4050 | power of two). |
3076 | |
4051 | |
3077 | =item EV_USE_4HEAP |
4052 | =item EV_USE_4HEAP |
3078 | |
4053 | |
3079 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4054 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3080 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4055 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3081 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4056 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3082 | noticeably faster performance with many (thousands) of watchers. |
4057 | faster performance with many (thousands) of watchers. |
3083 | |
4058 | |
3084 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4059 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3085 | (disabled). |
4060 | will be C<0>. |
3086 | |
4061 | |
3087 | =item EV_HEAP_CACHE_AT |
4062 | =item EV_HEAP_CACHE_AT |
3088 | |
4063 | |
3089 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4064 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3090 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4065 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3091 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4066 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3092 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4067 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3093 | but avoids random read accesses on heap changes. This improves performance |
4068 | but avoids random read accesses on heap changes. This improves performance |
3094 | noticeably with with many (hundreds) of watchers. |
4069 | noticeably with many (hundreds) of watchers. |
3095 | |
4070 | |
3096 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4071 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3097 | (disabled). |
4072 | will be C<0>. |
3098 | |
4073 | |
3099 | =item EV_VERIFY |
4074 | =item EV_VERIFY |
3100 | |
4075 | |
3101 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4076 | Controls how much internal verification (see C<ev_verify ()>) will |
3102 | be done: If set to C<0>, no internal verification code will be compiled |
4077 | be done: If set to C<0>, no internal verification code will be compiled |
3103 | in. If set to C<1>, then verification code will be compiled in, but not |
4078 | in. If set to C<1>, then verification code will be compiled in, but not |
3104 | called. If set to C<2>, then the internal verification code will be |
4079 | called. If set to C<2>, then the internal verification code will be |
3105 | called once per loop, which can slow down libev. If set to C<3>, then the |
4080 | called once per loop, which can slow down libev. If set to C<3>, then the |
3106 | verification code will be called very frequently, which will slow down |
4081 | verification code will be called very frequently, which will slow down |
3107 | libev considerably. |
4082 | libev considerably. |
3108 | |
4083 | |
3109 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4084 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3110 | C<0.> |
4085 | will be C<0>. |
3111 | |
4086 | |
3112 | =item EV_COMMON |
4087 | =item EV_COMMON |
3113 | |
4088 | |
3114 | By default, all watchers have a C<void *data> member. By redefining |
4089 | By default, all watchers have a C<void *data> member. By redefining |
3115 | this macro to a something else you can include more and other types of |
4090 | this macro to something else you can include more and other types of |
3116 | members. You have to define it each time you include one of the files, |
4091 | members. You have to define it each time you include one of the files, |
3117 | though, and it must be identical each time. |
4092 | though, and it must be identical each time. |
3118 | |
4093 | |
3119 | For example, the perl EV module uses something like this: |
4094 | For example, the perl EV module uses something like this: |
3120 | |
4095 | |
… | |
… | |
3132 | and the way callbacks are invoked and set. Must expand to a struct member |
4107 | and the way callbacks are invoked and set. Must expand to a struct member |
3133 | definition and a statement, respectively. See the F<ev.h> header file for |
4108 | definition and a statement, respectively. See the F<ev.h> header file for |
3134 | their default definitions. One possible use for overriding these is to |
4109 | their default definitions. One possible use for overriding these is to |
3135 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4110 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3136 | method calls instead of plain function calls in C++. |
4111 | method calls instead of plain function calls in C++. |
|
|
4112 | |
|
|
4113 | =back |
3137 | |
4114 | |
3138 | =head2 EXPORTED API SYMBOLS |
4115 | =head2 EXPORTED API SYMBOLS |
3139 | |
4116 | |
3140 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
4117 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3141 | exported symbols, you can use the provided F<Symbol.*> files which list |
4118 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3171 | file. |
4148 | file. |
3172 | |
4149 | |
3173 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4150 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3174 | that everybody includes and which overrides some configure choices: |
4151 | that everybody includes and which overrides some configure choices: |
3175 | |
4152 | |
3176 | #define EV_MINIMAL 1 |
4153 | #define EV_FEATURES 8 |
3177 | #define EV_USE_POLL 0 |
4154 | #define EV_USE_SELECT 1 |
3178 | #define EV_MULTIPLICITY 0 |
|
|
3179 | #define EV_PERIODIC_ENABLE 0 |
4155 | #define EV_PREPARE_ENABLE 1 |
|
|
4156 | #define EV_IDLE_ENABLE 1 |
3180 | #define EV_STAT_ENABLE 0 |
4157 | #define EV_SIGNAL_ENABLE 1 |
3181 | #define EV_FORK_ENABLE 0 |
4158 | #define EV_CHILD_ENABLE 1 |
|
|
4159 | #define EV_USE_STDEXCEPT 0 |
3182 | #define EV_CONFIG_H <config.h> |
4160 | #define EV_CONFIG_H <config.h> |
3183 | #define EV_MINPRI 0 |
|
|
3184 | #define EV_MAXPRI 0 |
|
|
3185 | |
4161 | |
3186 | #include "ev++.h" |
4162 | #include "ev++.h" |
3187 | |
4163 | |
3188 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4164 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3189 | |
4165 | |
3190 | #include "ev_cpp.h" |
4166 | #include "ev_cpp.h" |
3191 | #include "ev.c" |
4167 | #include "ev.c" |
3192 | |
4168 | |
|
|
4169 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3193 | |
4170 | |
3194 | =head1 THREADS AND COROUTINES |
4171 | =head2 THREADS AND COROUTINES |
3195 | |
4172 | |
3196 | =head2 THREADS |
4173 | =head3 THREADS |
3197 | |
4174 | |
3198 | Libev itself is completely thread-safe, but it uses no locking. This |
4175 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4176 | documented otherwise, but libev implements no locking itself. This means |
3199 | means that you can use as many loops as you want in parallel, as long as |
4177 | that you can use as many loops as you want in parallel, as long as there |
3200 | only one thread ever calls into one libev function with the same loop |
4178 | are no concurrent calls into any libev function with the same loop |
3201 | parameter. |
4179 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4180 | of course): libev guarantees that different event loops share no data |
|
|
4181 | structures that need any locking. |
3202 | |
4182 | |
3203 | Or put differently: calls with different loop parameters can be done in |
4183 | Or to put it differently: calls with different loop parameters can be done |
3204 | parallel from multiple threads, calls with the same loop parameter must be |
4184 | concurrently from multiple threads, calls with the same loop parameter |
3205 | done serially (but can be done from different threads, as long as only one |
4185 | must be done serially (but can be done from different threads, as long as |
3206 | thread ever is inside a call at any point in time, e.g. by using a mutex |
4186 | only one thread ever is inside a call at any point in time, e.g. by using |
3207 | per loop). |
4187 | a mutex per loop). |
|
|
4188 | |
|
|
4189 | Specifically to support threads (and signal handlers), libev implements |
|
|
4190 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4191 | concurrency on the same event loop, namely waking it up "from the |
|
|
4192 | outside". |
3208 | |
4193 | |
3209 | If you want to know which design (one loop, locking, or multiple loops |
4194 | If you want to know which design (one loop, locking, or multiple loops |
3210 | without or something else still) is best for your problem, then I cannot |
4195 | without or something else still) is best for your problem, then I cannot |
3211 | help you. I can give some generic advice however: |
4196 | help you, but here is some generic advice: |
3212 | |
4197 | |
3213 | =over 4 |
4198 | =over 4 |
3214 | |
4199 | |
3215 | =item * most applications have a main thread: use the default libev loop |
4200 | =item * most applications have a main thread: use the default libev loop |
3216 | in that thread, or create a separate thread running only the default loop. |
4201 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3228 | |
4213 | |
3229 | Choosing a model is hard - look around, learn, know that usually you can do |
4214 | Choosing a model is hard - look around, learn, know that usually you can do |
3230 | better than you currently do :-) |
4215 | better than you currently do :-) |
3231 | |
4216 | |
3232 | =item * often you need to talk to some other thread which blocks in the |
4217 | =item * often you need to talk to some other thread which blocks in the |
|
|
4218 | event loop. |
|
|
4219 | |
3233 | event loop - C<ev_async> watchers can be used to wake them up from other |
4220 | C<ev_async> watchers can be used to wake them up from other threads safely |
3234 | threads safely (or from signal contexts...). |
4221 | (or from signal contexts...). |
|
|
4222 | |
|
|
4223 | An example use would be to communicate signals or other events that only |
|
|
4224 | work in the default loop by registering the signal watcher with the |
|
|
4225 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
4226 | watcher callback into the event loop interested in the signal. |
3235 | |
4227 | |
3236 | =back |
4228 | =back |
3237 | |
4229 | |
|
|
4230 | =head4 THREAD LOCKING EXAMPLE |
|
|
4231 | |
|
|
4232 | Here is a fictitious example of how to run an event loop in a different |
|
|
4233 | thread than where callbacks are being invoked and watchers are |
|
|
4234 | created/added/removed. |
|
|
4235 | |
|
|
4236 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4237 | which uses exactly this technique (which is suited for many high-level |
|
|
4238 | languages). |
|
|
4239 | |
|
|
4240 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4241 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4242 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4243 | |
|
|
4244 | First, you need to associate some data with the event loop: |
|
|
4245 | |
|
|
4246 | typedef struct { |
|
|
4247 | mutex_t lock; /* global loop lock */ |
|
|
4248 | ev_async async_w; |
|
|
4249 | thread_t tid; |
|
|
4250 | cond_t invoke_cv; |
|
|
4251 | } userdata; |
|
|
4252 | |
|
|
4253 | void prepare_loop (EV_P) |
|
|
4254 | { |
|
|
4255 | // for simplicity, we use a static userdata struct. |
|
|
4256 | static userdata u; |
|
|
4257 | |
|
|
4258 | ev_async_init (&u->async_w, async_cb); |
|
|
4259 | ev_async_start (EV_A_ &u->async_w); |
|
|
4260 | |
|
|
4261 | pthread_mutex_init (&u->lock, 0); |
|
|
4262 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4263 | |
|
|
4264 | // now associate this with the loop |
|
|
4265 | ev_set_userdata (EV_A_ u); |
|
|
4266 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4267 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4268 | |
|
|
4269 | // then create the thread running ev_loop |
|
|
4270 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4271 | } |
|
|
4272 | |
|
|
4273 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4274 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4275 | that might have been added: |
|
|
4276 | |
|
|
4277 | static void |
|
|
4278 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4279 | { |
|
|
4280 | // just used for the side effects |
|
|
4281 | } |
|
|
4282 | |
|
|
4283 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4284 | protecting the loop data, respectively. |
|
|
4285 | |
|
|
4286 | static void |
|
|
4287 | l_release (EV_P) |
|
|
4288 | { |
|
|
4289 | userdata *u = ev_userdata (EV_A); |
|
|
4290 | pthread_mutex_unlock (&u->lock); |
|
|
4291 | } |
|
|
4292 | |
|
|
4293 | static void |
|
|
4294 | l_acquire (EV_P) |
|
|
4295 | { |
|
|
4296 | userdata *u = ev_userdata (EV_A); |
|
|
4297 | pthread_mutex_lock (&u->lock); |
|
|
4298 | } |
|
|
4299 | |
|
|
4300 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4301 | into C<ev_run>: |
|
|
4302 | |
|
|
4303 | void * |
|
|
4304 | l_run (void *thr_arg) |
|
|
4305 | { |
|
|
4306 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4307 | |
|
|
4308 | l_acquire (EV_A); |
|
|
4309 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4310 | ev_run (EV_A_ 0); |
|
|
4311 | l_release (EV_A); |
|
|
4312 | |
|
|
4313 | return 0; |
|
|
4314 | } |
|
|
4315 | |
|
|
4316 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4317 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4318 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4319 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4320 | and b) skipping inter-thread-communication when there are no pending |
|
|
4321 | watchers is very beneficial): |
|
|
4322 | |
|
|
4323 | static void |
|
|
4324 | l_invoke (EV_P) |
|
|
4325 | { |
|
|
4326 | userdata *u = ev_userdata (EV_A); |
|
|
4327 | |
|
|
4328 | while (ev_pending_count (EV_A)) |
|
|
4329 | { |
|
|
4330 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4331 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4332 | } |
|
|
4333 | } |
|
|
4334 | |
|
|
4335 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4336 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4337 | thread to continue: |
|
|
4338 | |
|
|
4339 | static void |
|
|
4340 | real_invoke_pending (EV_P) |
|
|
4341 | { |
|
|
4342 | userdata *u = ev_userdata (EV_A); |
|
|
4343 | |
|
|
4344 | pthread_mutex_lock (&u->lock); |
|
|
4345 | ev_invoke_pending (EV_A); |
|
|
4346 | pthread_cond_signal (&u->invoke_cv); |
|
|
4347 | pthread_mutex_unlock (&u->lock); |
|
|
4348 | } |
|
|
4349 | |
|
|
4350 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4351 | event loop, you will now have to lock: |
|
|
4352 | |
|
|
4353 | ev_timer timeout_watcher; |
|
|
4354 | userdata *u = ev_userdata (EV_A); |
|
|
4355 | |
|
|
4356 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4357 | |
|
|
4358 | pthread_mutex_lock (&u->lock); |
|
|
4359 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4360 | ev_async_send (EV_A_ &u->async_w); |
|
|
4361 | pthread_mutex_unlock (&u->lock); |
|
|
4362 | |
|
|
4363 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4364 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4365 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4366 | watchers in the next event loop iteration. |
|
|
4367 | |
3238 | =head2 COROUTINES |
4368 | =head3 COROUTINES |
3239 | |
4369 | |
3240 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4370 | Libev is very accommodating to coroutines ("cooperative threads"): |
3241 | libev fully supports nesting calls to it's functions from different |
4371 | libev fully supports nesting calls to its functions from different |
3242 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4372 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3243 | different coroutines and switch freely between both coroutines running the |
4373 | different coroutines, and switch freely between both coroutines running |
3244 | loop, as long as you don't confuse yourself). The only exception is that |
4374 | the loop, as long as you don't confuse yourself). The only exception is |
3245 | you must not do this from C<ev_periodic> reschedule callbacks. |
4375 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3246 | |
4376 | |
3247 | Care has been invested into making sure that libev does not keep local |
4377 | Care has been taken to ensure that libev does not keep local state inside |
3248 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4378 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3249 | switches. |
4379 | they do not call any callbacks. |
3250 | |
4380 | |
|
|
4381 | =head2 COMPILER WARNINGS |
3251 | |
4382 | |
3252 | =head1 COMPLEXITIES |
4383 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4384 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4385 | scared by this. |
3253 | |
4386 | |
3254 | In this section the complexities of (many of) the algorithms used inside |
4387 | However, these are unavoidable for many reasons. For one, each compiler |
3255 | libev will be explained. For complexity discussions about backends see the |
4388 | has different warnings, and each user has different tastes regarding |
3256 | documentation for C<ev_default_init>. |
4389 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4390 | targeting a specific compiler and compiler-version. |
3257 | |
4391 | |
3258 | All of the following are about amortised time: If an array needs to be |
4392 | Another reason is that some compiler warnings require elaborate |
3259 | extended, libev needs to realloc and move the whole array, but this |
4393 | workarounds, or other changes to the code that make it less clear and less |
3260 | happens asymptotically never with higher number of elements, so O(1) might |
4394 | maintainable. |
3261 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3262 | it is much faster and asymptotically approaches constant time. |
|
|
3263 | |
4395 | |
3264 | =over 4 |
4396 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4397 | wrong (because they don't actually warn about the condition their message |
|
|
4398 | seems to warn about). For example, certain older gcc versions had some |
|
|
4399 | warnings that resulted in an extreme number of false positives. These have |
|
|
4400 | been fixed, but some people still insist on making code warn-free with |
|
|
4401 | such buggy versions. |
3265 | |
4402 | |
3266 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4403 | While libev is written to generate as few warnings as possible, |
|
|
4404 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4405 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4406 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4407 | warnings, not errors, or proof of bugs. |
3267 | |
4408 | |
3268 | This means that, when you have a watcher that triggers in one hour and |
|
|
3269 | there are 100 watchers that would trigger before that then inserting will |
|
|
3270 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3271 | |
4409 | |
3272 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4410 | =head2 VALGRIND |
3273 | |
4411 | |
3274 | That means that changing a timer costs less than removing/adding them |
4412 | Valgrind has a special section here because it is a popular tool that is |
3275 | as only the relative motion in the event queue has to be paid for. |
4413 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3276 | |
4414 | |
3277 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4415 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4416 | in libev, then check twice: If valgrind reports something like: |
3278 | |
4417 | |
3279 | These just add the watcher into an array or at the head of a list. |
4418 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4419 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4420 | ==2274== still reachable: 256 bytes in 1 blocks. |
3280 | |
4421 | |
3281 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4422 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4423 | is not a memleak - the memory is still being referenced, and didn't leak. |
3282 | |
4424 | |
3283 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4425 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4426 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4427 | although an acceptable workaround has been found here), or it might be |
|
|
4428 | confused. |
3284 | |
4429 | |
3285 | These watchers are stored in lists then need to be walked to find the |
4430 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3286 | correct watcher to remove. The lists are usually short (you don't usually |
4431 | make it into some kind of religion. |
3287 | have many watchers waiting for the same fd or signal). |
|
|
3288 | |
4432 | |
3289 | =item Finding the next timer in each loop iteration: O(1) |
4433 | If you are unsure about something, feel free to contact the mailing list |
|
|
4434 | with the full valgrind report and an explanation on why you think this |
|
|
4435 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4436 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4437 | of learning how to interpret valgrind properly. |
3290 | |
4438 | |
3291 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4439 | If you need, for some reason, empty reports from valgrind for your project |
3292 | fixed position in the storage array. |
4440 | I suggest using suppression lists. |
3293 | |
4441 | |
3294 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3295 | |
4442 | |
3296 | A change means an I/O watcher gets started or stopped, which requires |
4443 | =head1 PORTABILITY NOTES |
3297 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3298 | on backend and whether C<ev_io_set> was used). |
|
|
3299 | |
4444 | |
3300 | =item Activating one watcher (putting it into the pending state): O(1) |
4445 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
3301 | |
4446 | |
3302 | =item Priority handling: O(number_of_priorities) |
4447 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4448 | interfaces but I<disables> them by default. |
3303 | |
4449 | |
3304 | Priorities are implemented by allocating some space for each |
4450 | That means that libev compiled in the default environment doesn't support |
3305 | priority. When doing priority-based operations, libev usually has to |
4451 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
3306 | linearly search all the priorities, but starting/stopping and activating |
|
|
3307 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3308 | |
4452 | |
3309 | =item Sending an ev_async: O(1) |
4453 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4454 | by enabling the large file API, which makes them incompatible with the |
|
|
4455 | standard libev compiled for their system. |
3310 | |
4456 | |
3311 | =item Processing ev_async_send: O(number_of_async_watchers) |
4457 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4458 | suddenly make it incompatible to the default compile time environment, |
|
|
4459 | i.e. all programs not using special compile switches. |
3312 | |
4460 | |
3313 | =item Processing signals: O(max_signal_number) |
4461 | =head2 OS/X AND DARWIN BUGS |
3314 | |
4462 | |
3315 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4463 | The whole thing is a bug if you ask me - basically any system interface |
3316 | calls in the current loop iteration. Checking for async and signal events |
4464 | you touch is broken, whether it is locales, poll, kqueue or even the |
3317 | involves iterating over all running async watchers or all signal numbers. |
4465 | OpenGL drivers. |
3318 | |
4466 | |
3319 | =back |
4467 | =head3 C<kqueue> is buggy |
3320 | |
4468 | |
|
|
4469 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4470 | only sockets, many support pipes. |
3321 | |
4471 | |
|
|
4472 | Libev tries to work around this by not using C<kqueue> by default on |
|
|
4473 | this rotten platform, but of course you can still ask for it when creating |
|
|
4474 | a loop. |
|
|
4475 | |
|
|
4476 | =head3 C<poll> is buggy |
|
|
4477 | |
|
|
4478 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4479 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4480 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4481 | |
|
|
4482 | Libev tries to work around this by not using C<poll> by default on |
|
|
4483 | this rotten platform, but of course you can still ask for it when creating |
|
|
4484 | a loop. |
|
|
4485 | |
|
|
4486 | =head3 C<select> is buggy |
|
|
4487 | |
|
|
4488 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4489 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4490 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4491 | you use more. |
|
|
4492 | |
|
|
4493 | There is an undocumented "workaround" for this - defining |
|
|
4494 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4495 | work on OS/X. |
|
|
4496 | |
|
|
4497 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4498 | |
|
|
4499 | =head3 C<errno> reentrancy |
|
|
4500 | |
|
|
4501 | The default compile environment on Solaris is unfortunately so |
|
|
4502 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4503 | without C<-D_REENTRANT> (as long as they use C<errno>), which, of course, |
|
|
4504 | isn't defined by default. |
|
|
4505 | |
|
|
4506 | If you want to use libev in threaded environments you have to make sure |
|
|
4507 | it's compiled with C<_REENTRANT> defined. |
|
|
4508 | |
|
|
4509 | =head3 Event port backend |
|
|
4510 | |
|
|
4511 | The scalable event interface for Solaris is called "event ports". Unfortunately, |
|
|
4512 | this mechanism is very buggy. If you run into high CPU usage, your program |
|
|
4513 | freezes or you get a large number of spurious wakeups, make sure you have |
|
|
4514 | all the relevant and latest kernel patches applied. No, I don't know which |
|
|
4515 | ones, but there are multiple ones. |
|
|
4516 | |
|
|
4517 | If you can't get it to work, you can try running the program by setting |
|
|
4518 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4519 | C<select> backends. |
|
|
4520 | |
|
|
4521 | =head2 AIX POLL BUG |
|
|
4522 | |
|
|
4523 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4524 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4525 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4526 | with large bitsets, and AIX is dead anyway. |
|
|
4527 | |
3322 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4528 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4529 | |
|
|
4530 | =head3 General issues |
3323 | |
4531 | |
3324 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4532 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3325 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4533 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3326 | model. Libev still offers limited functionality on this platform in |
4534 | model. Libev still offers limited functionality on this platform in |
3327 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4535 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3328 | descriptors. This only applies when using Win32 natively, not when using |
4536 | descriptors. This only applies when using Win32 natively, not when using |
3329 | e.g. cygwin. |
4537 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4538 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4539 | environment. |
3330 | |
4540 | |
3331 | Lifting these limitations would basically require the full |
4541 | Lifting these limitations would basically require the full |
3332 | re-implementation of the I/O system. If you are into these kinds of |
4542 | re-implementation of the I/O system. If you are into this kind of thing, |
3333 | things, then note that glib does exactly that for you in a very portable |
4543 | then note that glib does exactly that for you in a very portable way (note |
3334 | way (note also that glib is the slowest event library known to man). |
4544 | also that glib is the slowest event library known to man). |
3335 | |
4545 | |
3336 | There is no supported compilation method available on windows except |
4546 | There is no supported compilation method available on windows except |
3337 | embedding it into other applications. |
4547 | embedding it into other applications. |
|
|
4548 | |
|
|
4549 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4550 | tries its best, but under most conditions, signals will simply not work. |
3338 | |
4551 | |
3339 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4552 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3340 | accept large writes: instead of resulting in a partial write, windows will |
4553 | accept large writes: instead of resulting in a partial write, windows will |
3341 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4554 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3342 | so make sure you only write small amounts into your sockets (less than a |
4555 | so make sure you only write small amounts into your sockets (less than a |
3343 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4556 | megabyte seems safe, but this apparently depends on the amount of memory |
3344 | available). |
4557 | available). |
3345 | |
4558 | |
3346 | Due to the many, low, and arbitrary limits on the win32 platform and |
4559 | Due to the many, low, and arbitrary limits on the win32 platform and |
3347 | the abysmal performance of winsockets, using a large number of sockets |
4560 | the abysmal performance of winsockets, using a large number of sockets |
3348 | is not recommended (and not reasonable). If your program needs to use |
4561 | is not recommended (and not reasonable). If your program needs to use |
3349 | more than a hundred or so sockets, then likely it needs to use a totally |
4562 | more than a hundred or so sockets, then likely it needs to use a totally |
3350 | different implementation for windows, as libev offers the POSIX readiness |
4563 | different implementation for windows, as libev offers the POSIX readiness |
3351 | notification model, which cannot be implemented efficiently on windows |
4564 | notification model, which cannot be implemented efficiently on windows |
3352 | (Microsoft monopoly games). |
4565 | (due to Microsoft monopoly games). |
3353 | |
4566 | |
3354 | A typical way to use libev under windows is to embed it (see the embedding |
4567 | A typical way to use libev under windows is to embed it (see the embedding |
3355 | section for details) and use the following F<evwrap.h> header file instead |
4568 | section for details) and use the following F<evwrap.h> header file instead |
3356 | of F<ev.h>: |
4569 | of F<ev.h>: |
3357 | |
4570 | |
… | |
… | |
3359 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4572 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3360 | |
4573 | |
3361 | #include "ev.h" |
4574 | #include "ev.h" |
3362 | |
4575 | |
3363 | And compile the following F<evwrap.c> file into your project (make sure |
4576 | And compile the following F<evwrap.c> file into your project (make sure |
3364 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
4577 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3365 | |
4578 | |
3366 | #include "evwrap.h" |
4579 | #include "evwrap.h" |
3367 | #include "ev.c" |
4580 | #include "ev.c" |
3368 | |
4581 | |
3369 | =over 4 |
|
|
3370 | |
|
|
3371 | =item The winsocket select function |
4582 | =head3 The winsocket C<select> function |
3372 | |
4583 | |
3373 | The winsocket C<select> function doesn't follow POSIX in that it |
4584 | The winsocket C<select> function doesn't follow POSIX in that it |
3374 | requires socket I<handles> and not socket I<file descriptors> (it is |
4585 | requires socket I<handles> and not socket I<file descriptors> (it is |
3375 | also extremely buggy). This makes select very inefficient, and also |
4586 | also extremely buggy). This makes select very inefficient, and also |
3376 | requires a mapping from file descriptors to socket handles (the Microsoft |
4587 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3385 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4596 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3386 | |
4597 | |
3387 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4598 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3388 | complexity in the O(n²) range when using win32. |
4599 | complexity in the O(n²) range when using win32. |
3389 | |
4600 | |
3390 | =item Limited number of file descriptors |
4601 | =head3 Limited number of file descriptors |
3391 | |
4602 | |
3392 | Windows has numerous arbitrary (and low) limits on things. |
4603 | Windows has numerous arbitrary (and low) limits on things. |
3393 | |
4604 | |
3394 | Early versions of winsocket's select only supported waiting for a maximum |
4605 | Early versions of winsocket's select only supported waiting for a maximum |
3395 | of C<64> handles (probably owning to the fact that all windows kernels |
4606 | of C<64> handles (probably owning to the fact that all windows kernels |
3396 | can only wait for C<64> things at the same time internally; Microsoft |
4607 | can only wait for C<64> things at the same time internally; Microsoft |
3397 | recommends spawning a chain of threads and wait for 63 handles and the |
4608 | recommends spawning a chain of threads and wait for 63 handles and the |
3398 | previous thread in each. Great). |
4609 | previous thread in each. Sounds great!). |
3399 | |
4610 | |
3400 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4611 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3401 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4612 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3402 | call (which might be in libev or elsewhere, for example, perl does its own |
4613 | call (which might be in libev or elsewhere, for example, perl and many |
3403 | select emulation on windows). |
4614 | other interpreters do their own select emulation on windows). |
3404 | |
4615 | |
3405 | Another limit is the number of file descriptors in the Microsoft runtime |
4616 | Another limit is the number of file descriptors in the Microsoft runtime |
3406 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4617 | libraries, which by default is C<64> (there must be a hidden I<64> |
3407 | or something like this inside Microsoft). You can increase this by calling |
4618 | fetish or something like this inside Microsoft). You can increase this |
3408 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4619 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3409 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4620 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3410 | libraries. |
|
|
3411 | |
|
|
3412 | This might get you to about C<512> or C<2048> sockets (depending on |
4621 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3413 | windows version and/or the phase of the moon). To get more, you need to |
4622 | (depending on windows version and/or the phase of the moon). To get more, |
3414 | wrap all I/O functions and provide your own fd management, but the cost of |
4623 | you need to wrap all I/O functions and provide your own fd management, but |
3415 | calling select (O(n²)) will likely make this unworkable. |
4624 | the cost of calling select (O(n²)) will likely make this unworkable. |
3416 | |
4625 | |
3417 | =back |
|
|
3418 | |
|
|
3419 | |
|
|
3420 | =head1 PORTABILITY REQUIREMENTS |
4626 | =head2 PORTABILITY REQUIREMENTS |
3421 | |
4627 | |
3422 | In addition to a working ISO-C implementation, libev relies on a few |
4628 | In addition to a working ISO-C implementation and of course the |
3423 | additional extensions: |
4629 | backend-specific APIs, libev relies on a few additional extensions: |
3424 | |
4630 | |
3425 | =over 4 |
4631 | =over 4 |
3426 | |
4632 | |
3427 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4633 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3428 | calling conventions regardless of C<ev_watcher_type *>. |
4634 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3434 | calls them using an C<ev_watcher *> internally. |
4640 | calls them using an C<ev_watcher *> internally. |
3435 | |
4641 | |
3436 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4642 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3437 | |
4643 | |
3438 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4644 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3439 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4645 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3440 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4646 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3441 | believed to be sufficiently portable. |
4647 | believed to be sufficiently portable. |
3442 | |
4648 | |
3443 | =item C<sigprocmask> must work in a threaded environment |
4649 | =item C<sigprocmask> must work in a threaded environment |
3444 | |
4650 | |
… | |
… | |
3453 | except the initial one, and run the default loop in the initial thread as |
4659 | except the initial one, and run the default loop in the initial thread as |
3454 | well. |
4660 | well. |
3455 | |
4661 | |
3456 | =item C<long> must be large enough for common memory allocation sizes |
4662 | =item C<long> must be large enough for common memory allocation sizes |
3457 | |
4663 | |
3458 | To improve portability and simplify using libev, libev uses C<long> |
4664 | To improve portability and simplify its API, libev uses C<long> internally |
3459 | internally instead of C<size_t> when allocating its data structures. On |
4665 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3460 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4666 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3461 | is still at least 31 bits everywhere, which is enough for hundreds of |
4667 | least 31 bits everywhere, which is enough for hundreds of millions of |
3462 | millions of watchers. |
4668 | watchers. |
3463 | |
4669 | |
3464 | =item C<double> must hold a time value in seconds with enough accuracy |
4670 | =item C<double> must hold a time value in seconds with enough accuracy |
3465 | |
4671 | |
3466 | The type C<double> is used to represent timestamps. It is required to |
4672 | The type C<double> is used to represent timestamps. It is required to |
3467 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4673 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3468 | enough for at least into the year 4000. This requirement is fulfilled by |
4674 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4675 | (the design goal for libev). This requirement is overfulfilled by |
3469 | implementations implementing IEEE 754 (basically all existing ones). |
4676 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4677 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3470 | |
4678 | |
3471 | =back |
4679 | =back |
3472 | |
4680 | |
3473 | If you know of other additional requirements drop me a note. |
4681 | If you know of other additional requirements drop me a note. |
3474 | |
4682 | |
3475 | |
4683 | |
3476 | =head1 COMPILER WARNINGS |
4684 | =head1 ALGORITHMIC COMPLEXITIES |
3477 | |
4685 | |
3478 | Depending on your compiler and compiler settings, you might get no or a |
4686 | In this section the complexities of (many of) the algorithms used inside |
3479 | lot of warnings when compiling libev code. Some people are apparently |
4687 | libev will be documented. For complexity discussions about backends see |
3480 | scared by this. |
4688 | the documentation for C<ev_default_init>. |
3481 | |
4689 | |
3482 | However, these are unavoidable for many reasons. For one, each compiler |
4690 | All of the following are about amortised time: If an array needs to be |
3483 | has different warnings, and each user has different tastes regarding |
4691 | extended, libev needs to realloc and move the whole array, but this |
3484 | warning options. "Warn-free" code therefore cannot be a goal except when |
4692 | happens asymptotically rarer with higher number of elements, so O(1) might |
3485 | targeting a specific compiler and compiler-version. |
4693 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4694 | average it is much faster and asymptotically approaches constant time. |
3486 | |
4695 | |
3487 | Another reason is that some compiler warnings require elaborate |
4696 | =over 4 |
3488 | workarounds, or other changes to the code that make it less clear and less |
|
|
3489 | maintainable. |
|
|
3490 | |
4697 | |
3491 | And of course, some compiler warnings are just plain stupid, or simply |
4698 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3492 | wrong (because they don't actually warn about the condition their message |
|
|
3493 | seems to warn about). |
|
|
3494 | |
4699 | |
3495 | While libev is written to generate as few warnings as possible, |
4700 | This means that, when you have a watcher that triggers in one hour and |
3496 | "warn-free" code is not a goal, and it is recommended not to build libev |
4701 | there are 100 watchers that would trigger before that, then inserting will |
3497 | with any compiler warnings enabled unless you are prepared to cope with |
4702 | have to skip roughly seven (C<ld 100>) of these watchers. |
3498 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3499 | warnings, not errors, or proof of bugs. |
|
|
3500 | |
4703 | |
|
|
4704 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3501 | |
4705 | |
3502 | =head1 VALGRIND |
4706 | That means that changing a timer costs less than removing/adding them, |
|
|
4707 | as only the relative motion in the event queue has to be paid for. |
3503 | |
4708 | |
3504 | Valgrind has a special section here because it is a popular tool that is |
4709 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3505 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3506 | |
4710 | |
3507 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4711 | These just add the watcher into an array or at the head of a list. |
3508 | in libev, then check twice: If valgrind reports something like: |
|
|
3509 | |
4712 | |
3510 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4713 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3511 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3512 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3513 | |
4714 | |
3514 | Then there is no memory leak. Similarly, under some circumstances, |
4715 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3515 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3516 | might be confused (it is a very good tool, but only a tool). |
|
|
3517 | |
4716 | |
3518 | If you are unsure about something, feel free to contact the mailing list |
4717 | These watchers are stored in lists, so they need to be walked to find the |
3519 | with the full valgrind report and an explanation on why you think this is |
4718 | correct watcher to remove. The lists are usually short (you don't usually |
3520 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4719 | have many watchers waiting for the same fd or signal: one is typical, two |
3521 | no bug" answer and take the chance of learning how to interpret valgrind |
4720 | is rare). |
3522 | properly. |
|
|
3523 | |
4721 | |
3524 | If you need, for some reason, empty reports from valgrind for your project |
4722 | =item Finding the next timer in each loop iteration: O(1) |
3525 | I suggest using suppression lists. |
|
|
3526 | |
4723 | |
|
|
4724 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4725 | fixed position in the storage array. |
|
|
4726 | |
|
|
4727 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4728 | |
|
|
4729 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4730 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4731 | on backend and whether C<ev_io_set> was used). |
|
|
4732 | |
|
|
4733 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4734 | |
|
|
4735 | =item Priority handling: O(number_of_priorities) |
|
|
4736 | |
|
|
4737 | Priorities are implemented by allocating some space for each |
|
|
4738 | priority. When doing priority-based operations, libev usually has to |
|
|
4739 | linearly search all the priorities, but starting/stopping and activating |
|
|
4740 | watchers becomes O(1) with respect to priority handling. |
|
|
4741 | |
|
|
4742 | =item Sending an ev_async: O(1) |
|
|
4743 | |
|
|
4744 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4745 | |
|
|
4746 | =item Processing signals: O(max_signal_number) |
|
|
4747 | |
|
|
4748 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4749 | calls in the current loop iteration. Checking for async and signal events |
|
|
4750 | involves iterating over all running async watchers or all signal numbers. |
|
|
4751 | |
|
|
4752 | =back |
|
|
4753 | |
|
|
4754 | |
|
|
4755 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4756 | |
|
|
4757 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4758 | |
|
|
4759 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4760 | compatibility, so most programs should still compile. Those might be |
|
|
4761 | removed in later versions of libev, so better update early than late. |
|
|
4762 | |
|
|
4763 | =over 4 |
|
|
4764 | |
|
|
4765 | =item function/symbol renames |
|
|
4766 | |
|
|
4767 | A number of functions and symbols have been renamed: |
|
|
4768 | |
|
|
4769 | ev_loop => ev_run |
|
|
4770 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
4771 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
4772 | |
|
|
4773 | ev_unloop => ev_break |
|
|
4774 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
4775 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
4776 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
4777 | |
|
|
4778 | EV_TIMEOUT => EV_TIMER |
|
|
4779 | |
|
|
4780 | ev_loop_count => ev_iteration |
|
|
4781 | ev_loop_depth => ev_depth |
|
|
4782 | ev_loop_verify => ev_verify |
|
|
4783 | |
|
|
4784 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4785 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
4786 | associated constants have been renamed to not collide with the C<struct |
|
|
4787 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
4788 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
4789 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
4790 | typedef. |
|
|
4791 | |
|
|
4792 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4793 | |
|
|
4794 | The backward compatibility mechanism can be controlled by |
|
|
4795 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4796 | section. |
|
|
4797 | |
|
|
4798 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4799 | |
|
|
4800 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4801 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4802 | and work, but the library code will of course be larger. |
|
|
4803 | |
|
|
4804 | =back |
|
|
4805 | |
|
|
4806 | |
|
|
4807 | =head1 GLOSSARY |
|
|
4808 | |
|
|
4809 | =over 4 |
|
|
4810 | |
|
|
4811 | =item active |
|
|
4812 | |
|
|
4813 | A watcher is active as long as it has been started (has been attached to |
|
|
4814 | an event loop) but not yet stopped (disassociated from the event loop). |
|
|
4815 | |
|
|
4816 | =item application |
|
|
4817 | |
|
|
4818 | In this document, an application is whatever is using libev. |
|
|
4819 | |
|
|
4820 | =item callback |
|
|
4821 | |
|
|
4822 | The address of a function that is called when some event has been |
|
|
4823 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4824 | received the event, and the actual event bitset. |
|
|
4825 | |
|
|
4826 | =item callback invocation |
|
|
4827 | |
|
|
4828 | The act of calling the callback associated with a watcher. |
|
|
4829 | |
|
|
4830 | =item event |
|
|
4831 | |
|
|
4832 | A change of state of some external event, such as data now being available |
|
|
4833 | for reading on a file descriptor, time having passed or simply not having |
|
|
4834 | any other events happening anymore. |
|
|
4835 | |
|
|
4836 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4837 | C<EV_TIMER>). |
|
|
4838 | |
|
|
4839 | =item event library |
|
|
4840 | |
|
|
4841 | A software package implementing an event model and loop. |
|
|
4842 | |
|
|
4843 | =item event loop |
|
|
4844 | |
|
|
4845 | An entity that handles and processes external events and converts them |
|
|
4846 | into callback invocations. |
|
|
4847 | |
|
|
4848 | =item event model |
|
|
4849 | |
|
|
4850 | The model used to describe how an event loop handles and processes |
|
|
4851 | watchers and events. |
|
|
4852 | |
|
|
4853 | =item pending |
|
|
4854 | |
|
|
4855 | A watcher is pending as soon as the corresponding event has been detected, |
|
|
4856 | and stops being pending as soon as the watcher will be invoked or its |
|
|
4857 | pending status is explicitly cleared by the application. |
|
|
4858 | |
|
|
4859 | A watcher can be pending, but not active. Stopping a watcher also clears |
|
|
4860 | its pending status. |
|
|
4861 | |
|
|
4862 | =item real time |
|
|
4863 | |
|
|
4864 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4865 | |
|
|
4866 | =item wall-clock time |
|
|
4867 | |
|
|
4868 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4869 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4870 | clock. |
|
|
4871 | |
|
|
4872 | =item watcher |
|
|
4873 | |
|
|
4874 | A data structure that describes interest in certain events. Watchers need |
|
|
4875 | to be started (attached to an event loop) before they can receive events. |
|
|
4876 | |
|
|
4877 | =item watcher invocation |
|
|
4878 | |
|
|
4879 | The act of calling the callback associated with a watcher. |
|
|
4880 | |
|
|
4881 | =back |
3527 | |
4882 | |
3528 | =head1 AUTHOR |
4883 | =head1 AUTHOR |
3529 | |
4884 | |
3530 | Marc Lehmann <libev@schmorp.de>. |
4885 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3531 | |
4886 | |