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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 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | struct ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = EV_DEFAULT; |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
54 | // simple non-repeating 5.5 second timeout |
56 | // simple non-repeating 5.5 second timeout |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
57 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
56 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
57 | |
59 | |
58 | // now wait for events to arrive |
60 | // now wait for events to arrive |
59 | ev_loop (loop, 0); |
61 | ev_run (loop, 0); |
60 | |
62 | |
61 | // unloop was called, so exit |
63 | // 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 WHAT TO READ WHEN IN A HURRY |
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84 | |
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85 | This manual tries to be very detailed, but unfortunately, this also makes |
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86 | it very long. If you just want to know the basics of libev, I suggest |
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87 | reading L<ANATOMY OF A WATCHER>, then the L<EXAMPLE PROGRAM> above and |
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88 | look up the missing functions in L<GLOBAL FUNCTIONS> and the C<ev_io> and |
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89 | C<ev_timer> sections in L<WATCHER TYPES>. |
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90 | |
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91 | =head1 ABOUT LIBEV |
70 | |
92 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
93 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
94 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
95 | these event sources and provide your program with events. |
74 | |
96 | |
… | |
… | |
84 | =head2 FEATURES |
106 | =head2 FEATURES |
85 | |
107 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
108 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
109 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
110 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
111 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
112 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
113 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
114 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
115 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
116 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
117 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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118 | limited support for fork events (C<ev_fork>). |
96 | |
119 | |
97 | It also is quite fast (see this |
120 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
121 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
122 | for example). |
100 | |
123 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
131 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
132 | this argument. |
110 | |
133 | |
111 | =head2 TIME REPRESENTATION |
134 | =head2 TIME REPRESENTATION |
112 | |
135 | |
113 | Libev represents time as a single floating point number, representing the |
136 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
137 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
138 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
139 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
140 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
141 | any calculations on it, you should treat it as some floating point value. |
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142 | |
119 | component C<stamp> might indicate, it is also used for time differences |
143 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
144 | time differences (e.g. delays) throughout libev. |
121 | |
145 | |
122 | =head1 ERROR HANDLING |
146 | =head1 ERROR HANDLING |
123 | |
147 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
148 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
149 | and internal errors (bugs). |
… | |
… | |
149 | |
173 | |
150 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
151 | |
175 | |
152 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
153 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
178 | you actually want to know. Also interesting is the combination of |
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179 | C<ev_update_now> and C<ev_now>. |
155 | |
180 | |
156 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
157 | |
182 | |
158 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked until |
159 | either it is interrupted or the given time interval has passed. Basically |
184 | either it is interrupted or the given time interval has passed. Basically |
… | |
… | |
176 | as this indicates an incompatible change. Minor versions are usually |
201 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
202 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
203 | not a problem. |
179 | |
204 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
205 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
206 | version (note, however, that this will not detect other ABI mismatches, |
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207 | such as LFS or reentrancy). |
182 | |
208 | |
183 | assert (("libev version mismatch", |
209 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
210 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
211 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
212 | |
… | |
… | |
197 | assert (("sorry, no epoll, no sex", |
223 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
224 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
225 | |
200 | =item unsigned int ev_recommended_backends () |
226 | =item unsigned int ev_recommended_backends () |
201 | |
227 | |
202 | Return the set of all backends compiled into this binary of libev and also |
228 | Return the set of all backends compiled into this binary of libev and |
203 | recommended for this platform. This set is often smaller than the one |
229 | also recommended for this platform, meaning it will work for most file |
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230 | descriptor types. This set is often smaller than the one returned by |
204 | returned by C<ev_supported_backends>, as for example kqueue is broken on |
231 | C<ev_supported_backends>, as for example kqueue is broken on most BSDs |
205 | most BSDs and will not be auto-detected unless you explicitly request it |
232 | and will not be auto-detected unless you explicitly request it (assuming |
206 | (assuming you know what you are doing). This is the set of backends that |
233 | you know what you are doing). This is the set of backends that libev will |
207 | libev will probe for if you specify no backends explicitly. |
234 | probe for if you specify no backends explicitly. |
208 | |
235 | |
209 | =item unsigned int ev_embeddable_backends () |
236 | =item unsigned int ev_embeddable_backends () |
210 | |
237 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
238 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
239 | value is platform-specific but can include backends not available on the |
213 | might be supported on the current system, you would need to look at |
240 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
241 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
242 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
243 | |
217 | See the description of C<ev_embed> watchers for more info. |
244 | See the description of C<ev_embed> watchers for more info. |
218 | |
245 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
246 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
220 | |
247 | |
221 | Sets the allocation function to use (the prototype is similar - the |
248 | 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 |
249 | 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 |
250 | 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 |
251 | when memory needs to be allocated (C<size != 0>), the library might abort |
… | |
… | |
250 | } |
277 | } |
251 | |
278 | |
252 | ... |
279 | ... |
253 | ev_set_allocator (persistent_realloc); |
280 | ev_set_allocator (persistent_realloc); |
254 | |
281 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
282 | =item ev_set_syserr_cb (void (*cb)(const char *msg)) |
256 | |
283 | |
257 | Set the callback function to call on a retryable system call error (such |
284 | 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 |
285 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
286 | 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 |
287 | callback is set, then libev will expect it to remedy the situation, no |
… | |
… | |
272 | } |
299 | } |
273 | |
300 | |
274 | ... |
301 | ... |
275 | ev_set_syserr_cb (fatal_error); |
302 | ev_set_syserr_cb (fatal_error); |
276 | |
303 | |
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304 | =item ev_feed_signal (int signum) |
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305 | |
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306 | This function can be used to "simulate" a signal receive. It is completely |
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307 | safe to call this function at any time, from any context, including signal |
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308 | handlers or random threads. |
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309 | |
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310 | Its main use is to customise signal handling in your process, especially |
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311 | in the presence of threads. For example, you could block signals |
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312 | by default in all threads (and specifying C<EVFLAG_NOSIGMASK> when |
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313 | creating any loops), and in one thread, use C<sigwait> or any other |
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314 | mechanism to wait for signals, then "deliver" them to libev by calling |
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315 | C<ev_feed_signal>. |
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316 | |
277 | =back |
317 | =back |
278 | |
318 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
319 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
320 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
321 | 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 |
322 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
323 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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324 | |
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325 | The library knows two types of such loops, the I<default> loop, which |
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326 | supports child process events, and dynamically created event loops which |
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327 | do not. |
284 | |
328 | |
285 | =over 4 |
329 | =over 4 |
286 | |
330 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
331 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
332 | |
289 | This will initialise the default event loop if it hasn't been initialised |
333 | This returns the "default" event loop object, which is what you should |
290 | yet and return it. If the default loop could not be initialised, returns |
334 | normally use when you just need "the event loop". Event loop objects and |
291 | false. If it already was initialised it simply returns it (and ignores the |
335 | the C<flags> parameter are described in more detail in the entry for |
292 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
336 | C<ev_loop_new>. |
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337 | |
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338 | If the default loop is already initialised then this function simply |
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339 | returns it (and ignores the flags. If that is troubling you, check |
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340 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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341 | flags, which should almost always be C<0>, unless the caller is also the |
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342 | one calling C<ev_run> or otherwise qualifies as "the main program". |
293 | |
343 | |
294 | If you don't know what event loop to use, use the one returned from this |
344 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
345 | function (or via the C<EV_DEFAULT> macro). |
296 | |
346 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
347 | 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, |
348 | from multiple threads, you have to employ some kind of mutex (note also |
299 | as loops cannot bes hared easily between threads anyway). |
349 | that this case is unlikely, as loops cannot be shared easily between |
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350 | threads anyway). |
300 | |
351 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
352 | The default loop is the only loop that can handle C<ev_child> watchers, |
302 | C<ev_child> watchers, and to do this, it always registers a handler |
353 | and to do this, it always registers a handler for C<SIGCHLD>. If this is |
303 | for C<SIGCHLD>. If this is a problem for your application you can either |
354 | a problem for your application you can either create a dynamic loop with |
304 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
355 | C<ev_loop_new> which doesn't do that, or you can simply overwrite the |
305 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
356 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
306 | C<ev_default_init>. |
357 | |
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358 | Example: This is the most typical usage. |
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359 | |
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360 | if (!ev_default_loop (0)) |
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361 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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362 | |
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363 | Example: Restrict libev to the select and poll backends, and do not allow |
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364 | environment settings to be taken into account: |
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365 | |
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366 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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367 | |
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368 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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369 | |
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370 | This will create and initialise a new event loop object. If the loop |
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371 | could not be initialised, returns false. |
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372 | |
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373 | This function is thread-safe, and one common way to use libev with |
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374 | threads is indeed to create one loop per thread, and using the default |
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375 | loop in the "main" or "initial" thread. |
307 | |
376 | |
308 | The flags argument can be used to specify special behaviour or specific |
377 | The flags argument can be used to specify special behaviour or specific |
309 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
378 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
310 | |
379 | |
311 | The following flags are supported: |
380 | The following flags are supported: |
… | |
… | |
326 | useful to try out specific backends to test their performance, or to work |
395 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
396 | around bugs. |
328 | |
397 | |
329 | =item C<EVFLAG_FORKCHECK> |
398 | =item C<EVFLAG_FORKCHECK> |
330 | |
399 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
400 | 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 |
401 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
402 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
403 | 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 |
404 | 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 |
405 | 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 |
406 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
344 | flag. |
412 | flag. |
345 | |
413 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
414 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
415 | environment variable. |
348 | |
416 | |
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417 | =item C<EVFLAG_NOINOTIFY> |
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418 | |
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419 | When this flag is specified, then libev will not attempt to use the |
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420 | I<inotify> API for its C<ev_stat> watchers. Apart from debugging and |
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421 | testing, this flag can be useful to conserve inotify file descriptors, as |
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422 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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423 | |
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424 | =item C<EVFLAG_SIGNALFD> |
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425 | |
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426 | When this flag is specified, then libev will attempt to use the |
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427 | I<signalfd> API for its C<ev_signal> (and C<ev_child>) watchers. This API |
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428 | delivers signals synchronously, which makes it both faster and might make |
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429 | it possible to get the queued signal data. It can also simplify signal |
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430 | handling with threads, as long as you properly block signals in your |
|
|
431 | threads that are not interested in handling them. |
|
|
432 | |
|
|
433 | Signalfd will not be used by default as this changes your signal mask, and |
|
|
434 | there are a lot of shoddy libraries and programs (glib's threadpool for |
|
|
435 | example) that can't properly initialise their signal masks. |
|
|
436 | |
|
|
437 | =item C<EVFLAG_NOSIGMASK> |
|
|
438 | |
|
|
439 | When this flag is specified, then libev will avoid to modify the signal |
|
|
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
|
|
441 | when you want to receive them. |
|
|
442 | |
|
|
443 | This behaviour is useful when you want to do your own signal handling, or |
|
|
444 | want to handle signals only in specific threads and want to avoid libev |
|
|
445 | unblocking the signals. |
|
|
446 | |
|
|
447 | This flag's behaviour will become the default in future versions of libev. |
|
|
448 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
450 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
451 | 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, |
452 | 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 |
453 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
377 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
477 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
378 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
478 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
379 | |
479 | |
380 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
381 | |
481 | |
|
|
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
483 | kernels). |
|
|
484 | |
382 | For few fds, this backend is a bit little slower than poll and select, |
485 | For few fds, this backend is a bit little slower than poll and select, |
383 | but it scales phenomenally better. While poll and select usually scale |
486 | but it scales phenomenally better. While poll and select usually scale |
384 | like O(total_fds) where n is the total number of fds (or the highest fd), |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
385 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
488 | epoll scales either O(1) or O(active_fds). |
386 | of shortcomings, such as silently dropping events in some hard-to-detect |
489 | |
387 | cases and requiring a system call per fd change, no fork support and bad |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
388 | support for dup. |
491 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
492 | dropping file descriptors, requiring a system call per change per file |
|
|
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
|
|
494 | returning before the timeout value, resulting in additional iterations |
|
|
495 | (and only giving 5ms accuracy while select on the same platform gives |
|
|
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
|
|
497 | forks then I<both> parent and child process have to recreate the epoll |
|
|
498 | set, which can take considerable time (one syscall per file descriptor) |
|
|
499 | and is of course hard to detect. |
|
|
500 | |
|
|
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
502 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
503 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
504 | even remove them from the set) than registered in the set (especially |
|
|
505 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
506 | employing an additional generation counter and comparing that against the |
|
|
507 | events to filter out spurious ones, recreating the set when required. Last |
|
|
508 | not least, it also refuses to work with some file descriptors which work |
|
|
509 | perfectly fine with C<select> (files, many character devices...). |
|
|
510 | |
|
|
511 | Epoll is truly the train wreck analog among event poll mechanisms. |
389 | |
512 | |
390 | While stopping, setting and starting an I/O watcher in the same iteration |
513 | While stopping, setting and starting an I/O watcher in the same iteration |
391 | will result in some caching, there is still a system call per such incident |
514 | will result in some caching, there is still a system call per such |
392 | (because the fd could point to a different file description now), so its |
515 | incident (because the same I<file descriptor> could point to a different |
393 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
516 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
394 | very well if you register events for both fds. |
517 | file descriptors might not work very well if you register events for both |
395 | |
518 | file descriptors. |
396 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
397 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
398 | (or space) is available. |
|
|
399 | |
519 | |
400 | Best performance from this backend is achieved by not unregistering all |
520 | Best performance from this backend is achieved by not unregistering all |
401 | watchers for a file descriptor until it has been closed, if possible, |
521 | watchers for a file descriptor until it has been closed, if possible, |
402 | i.e. keep at least one watcher active per fd at all times. Stopping and |
522 | i.e. keep at least one watcher active per fd at all times. Stopping and |
403 | starting a watcher (without re-setting it) also usually doesn't cause |
523 | starting a watcher (without re-setting it) also usually doesn't cause |
404 | extra overhead. |
524 | extra overhead. A fork can both result in spurious notifications as well |
|
|
525 | as in libev having to destroy and recreate the epoll object, which can |
|
|
526 | take considerable time and thus should be avoided. |
|
|
527 | |
|
|
528 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
529 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
530 | the usage. So sad. |
405 | |
531 | |
406 | While nominally embeddable in other event loops, this feature is broken in |
532 | While nominally embeddable in other event loops, this feature is broken in |
407 | all kernel versions tested so far. |
533 | all kernel versions tested so far. |
408 | |
534 | |
409 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
535 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
410 | C<EVBACKEND_POLL>. |
536 | C<EVBACKEND_POLL>. |
411 | |
537 | |
412 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
538 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
413 | |
539 | |
414 | Kqueue deserves special mention, as at the time of this writing, it was |
540 | Kqueue deserves special mention, as at the time of this writing, it |
415 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
541 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
416 | anything but sockets and pipes, except on Darwin, where of course it's |
542 | with anything but sockets and pipes, except on Darwin, where of course |
417 | completely useless). For this reason it's not being "auto-detected" unless |
543 | it's completely useless). Unlike epoll, however, whose brokenness |
418 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
544 | is by design, these kqueue bugs can (and eventually will) be fixed |
419 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
545 | without API changes to existing programs. For this reason it's not being |
|
|
546 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
547 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
548 | system like NetBSD. |
420 | |
549 | |
421 | You still can embed kqueue into a normal poll or select backend and use it |
550 | You still can embed kqueue into a normal poll or select backend and use it |
422 | only for sockets (after having made sure that sockets work with kqueue on |
551 | only for sockets (after having made sure that sockets work with kqueue on |
423 | the target platform). See C<ev_embed> watchers for more info. |
552 | the target platform). See C<ev_embed> watchers for more info. |
424 | |
553 | |
425 | It scales in the same way as the epoll backend, but the interface to the |
554 | It scales in the same way as the epoll backend, but the interface to the |
426 | kernel is more efficient (which says nothing about its actual speed, of |
555 | kernel is more efficient (which says nothing about its actual speed, of |
427 | course). While stopping, setting and starting an I/O watcher does never |
556 | course). While stopping, setting and starting an I/O watcher does never |
428 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
557 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
429 | two event changes per incident. Support for C<fork ()> is very bad and it |
558 | two event changes per incident. Support for C<fork ()> is very bad (but |
430 | drops fds silently in similarly hard-to-detect cases. |
559 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
560 | cases |
431 | |
561 | |
432 | This backend usually performs well under most conditions. |
562 | This backend usually performs well under most conditions. |
433 | |
563 | |
434 | While nominally embeddable in other event loops, this doesn't work |
564 | While nominally embeddable in other event loops, this doesn't work |
435 | everywhere, so you might need to test for this. And since it is broken |
565 | everywhere, so you might need to test for this. And since it is broken |
436 | almost everywhere, you should only use it when you have a lot of sockets |
566 | almost everywhere, you should only use it when you have a lot of sockets |
437 | (for which it usually works), by embedding it into another event loop |
567 | (for which it usually works), by embedding it into another event loop |
438 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
568 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
439 | using it only for sockets. |
569 | also broken on OS X)) and, did I mention it, using it only for sockets. |
440 | |
570 | |
441 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
571 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
442 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
572 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
443 | C<NOTE_EOF>. |
573 | C<NOTE_EOF>. |
444 | |
574 | |
… | |
… | |
452 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
582 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
453 | |
583 | |
454 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
584 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
455 | it's really slow, but it still scales very well (O(active_fds)). |
585 | it's really slow, but it still scales very well (O(active_fds)). |
456 | |
586 | |
457 | Please note that Solaris event ports can deliver a lot of spurious |
|
|
458 | notifications, so you need to use non-blocking I/O or other means to avoid |
|
|
459 | blocking when no data (or space) is available. |
|
|
460 | |
|
|
461 | While this backend scales well, it requires one system call per active |
587 | While this backend scales well, it requires one system call per active |
462 | file descriptor per loop iteration. For small and medium numbers of file |
588 | file descriptor per loop iteration. For small and medium numbers of file |
463 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
589 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
464 | might perform better. |
590 | might perform better. |
465 | |
591 | |
466 | On the positive side, with the exception of the spurious readiness |
592 | On the positive side, this backend actually performed fully to |
467 | notifications, this backend actually performed fully to specification |
|
|
468 | in all tests and is fully embeddable, which is a rare feat among the |
593 | specification in all tests and is fully embeddable, which is a rare feat |
469 | OS-specific backends. |
594 | among the OS-specific backends (I vastly prefer correctness over speed |
|
|
595 | hacks). |
|
|
596 | |
|
|
597 | On the negative side, the interface is I<bizarre> - so bizarre that |
|
|
598 | even sun itself gets it wrong in their code examples: The event polling |
|
|
599 | function sometimes returning events to the caller even though an error |
|
|
600 | occurred, but with no indication whether it has done so or not (yes, it's |
|
|
601 | even documented that way) - deadly for edge-triggered interfaces where |
|
|
602 | you absolutely have to know whether an event occurred or not because you |
|
|
603 | have to re-arm the watcher. |
|
|
604 | |
|
|
605 | Fortunately libev seems to be able to work around these idiocies. |
470 | |
606 | |
471 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
607 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
472 | C<EVBACKEND_POLL>. |
608 | C<EVBACKEND_POLL>. |
473 | |
609 | |
474 | =item C<EVBACKEND_ALL> |
610 | =item C<EVBACKEND_ALL> |
475 | |
611 | |
476 | Try all backends (even potentially broken ones that wouldn't be tried |
612 | Try all backends (even potentially broken ones that wouldn't be tried |
477 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
613 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
478 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
614 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
479 | |
615 | |
480 | It is definitely not recommended to use this flag. |
616 | It is definitely not recommended to use this flag, use whatever |
|
|
617 | C<ev_recommended_backends ()> returns, or simply do not specify a backend |
|
|
618 | at all. |
|
|
619 | |
|
|
620 | =item C<EVBACKEND_MASK> |
|
|
621 | |
|
|
622 | Not a backend at all, but a mask to select all backend bits from a |
|
|
623 | C<flags> value, in case you want to mask out any backends from a flags |
|
|
624 | value (e.g. when modifying the C<LIBEV_FLAGS> environment variable). |
481 | |
625 | |
482 | =back |
626 | =back |
483 | |
627 | |
484 | If one or more of these are or'ed into the flags value, then only these |
628 | If one or more of the backend flags are or'ed into the flags value, |
485 | backends will be tried (in the reverse order as listed here). If none are |
629 | then only these backends will be tried (in the reverse order as listed |
486 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
630 | here). If none are specified, all backends in C<ev_recommended_backends |
487 | |
631 | ()> will be tried. |
488 | Example: This is the most typical usage. |
|
|
489 | |
|
|
490 | if (!ev_default_loop (0)) |
|
|
491 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
492 | |
|
|
493 | Example: Restrict libev to the select and poll backends, and do not allow |
|
|
494 | environment settings to be taken into account: |
|
|
495 | |
|
|
496 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
497 | |
|
|
498 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
499 | used if available (warning, breaks stuff, best use only with your own |
|
|
500 | private event loop and only if you know the OS supports your types of |
|
|
501 | fds): |
|
|
502 | |
|
|
503 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
504 | |
|
|
505 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
506 | |
|
|
507 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
508 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
509 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
510 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
511 | |
|
|
512 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
513 | libev with threads is indeed to create one loop per thread, and using the |
|
|
514 | default loop in the "main" or "initial" thread. |
|
|
515 | |
632 | |
516 | Example: Try to create a event loop that uses epoll and nothing else. |
633 | Example: Try to create a event loop that uses epoll and nothing else. |
517 | |
634 | |
518 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
635 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
519 | if (!epoller) |
636 | if (!epoller) |
520 | fatal ("no epoll found here, maybe it hides under your chair"); |
637 | fatal ("no epoll found here, maybe it hides under your chair"); |
521 | |
638 | |
|
|
639 | Example: Use whatever libev has to offer, but make sure that kqueue is |
|
|
640 | used if available. |
|
|
641 | |
|
|
642 | struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
643 | |
522 | =item ev_default_destroy () |
644 | =item ev_loop_destroy (loop) |
523 | |
645 | |
524 | Destroys the default loop again (frees all memory and kernel state |
646 | Destroys an event loop object (frees all memory and kernel state |
525 | etc.). None of the active event watchers will be stopped in the normal |
647 | etc.). None of the active event watchers will be stopped in the normal |
526 | sense, so e.g. C<ev_is_active> might still return true. It is your |
648 | sense, so e.g. C<ev_is_active> might still return true. It is your |
527 | responsibility to either stop all watchers cleanly yourself I<before> |
649 | responsibility to either stop all watchers cleanly yourself I<before> |
528 | calling this function, or cope with the fact afterwards (which is usually |
650 | calling this function, or cope with the fact afterwards (which is usually |
529 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
651 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
530 | for example). |
652 | for example). |
531 | |
653 | |
532 | Note that certain global state, such as signal state, will not be freed by |
654 | Note that certain global state, such as signal state (and installed signal |
533 | this function, and related watchers (such as signal and child watchers) |
655 | handlers), will not be freed by this function, and related watchers (such |
534 | would need to be stopped manually. |
656 | as signal and child watchers) would need to be stopped manually. |
535 | |
657 | |
536 | In general it is not advisable to call this function except in the |
658 | This function is normally used on loop objects allocated by |
537 | rare occasion where you really need to free e.g. the signal handling |
659 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
660 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
661 | |
|
|
662 | Note that it is not advisable to call this function on the default loop |
|
|
663 | except in the rare occasion where you really need to free its resources. |
538 | pipe fds. If you need dynamically allocated loops it is better to use |
664 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
539 | C<ev_loop_new> and C<ev_loop_destroy>). |
665 | and C<ev_loop_destroy>. |
540 | |
666 | |
541 | =item ev_loop_destroy (loop) |
667 | =item ev_loop_fork (loop) |
542 | |
668 | |
543 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
544 | earlier call to C<ev_loop_new>. |
|
|
545 | |
|
|
546 | =item ev_default_fork () |
|
|
547 | |
|
|
548 | This function sets a flag that causes subsequent C<ev_loop> iterations |
669 | This function sets a flag that causes subsequent C<ev_run> iterations to |
549 | to reinitialise the kernel state for backends that have one. Despite the |
670 | reinitialise the kernel state for backends that have one. Despite the |
550 | name, you can call it anytime, but it makes most sense after forking, in |
671 | name, you can call it anytime, but it makes most sense after forking, in |
551 | the child process (or both child and parent, but that again makes little |
672 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
552 | sense). You I<must> call it in the child before using any of the libev |
673 | child before resuming or calling C<ev_run>. |
553 | functions, and it will only take effect at the next C<ev_loop> iteration. |
674 | |
|
|
675 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
676 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
677 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
678 | during fork. |
554 | |
679 | |
555 | On the other hand, you only need to call this function in the child |
680 | On the other hand, you only need to call this function in the child |
556 | process if and only if you want to use the event library in the child. If |
681 | process if and only if you want to use the event loop in the child. If |
557 | you just fork+exec, you don't have to call it at all. |
682 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
683 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
684 | difference, but libev will usually detect this case on its own and do a |
|
|
685 | costly reset of the backend). |
558 | |
686 | |
559 | The function itself is quite fast and it's usually not a problem to call |
687 | The function itself is quite fast and it's usually not a problem to call |
560 | it just in case after a fork. To make this easy, the function will fit in |
688 | it just in case after a fork. |
561 | quite nicely into a call to C<pthread_atfork>: |
|
|
562 | |
689 | |
|
|
690 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
691 | using pthreads. |
|
|
692 | |
|
|
693 | static void |
|
|
694 | post_fork_child (void) |
|
|
695 | { |
|
|
696 | ev_loop_fork (EV_DEFAULT); |
|
|
697 | } |
|
|
698 | |
|
|
699 | ... |
563 | pthread_atfork (0, 0, ev_default_fork); |
700 | pthread_atfork (0, 0, post_fork_child); |
564 | |
|
|
565 | =item ev_loop_fork (loop) |
|
|
566 | |
|
|
567 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
568 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
569 | after fork that you want to re-use in the child, and how you do this is |
|
|
570 | entirely your own problem. |
|
|
571 | |
701 | |
572 | =item int ev_is_default_loop (loop) |
702 | =item int ev_is_default_loop (loop) |
573 | |
703 | |
574 | Returns true when the given loop is, in fact, the default loop, and false |
704 | Returns true when the given loop is, in fact, the default loop, and false |
575 | otherwise. |
705 | otherwise. |
576 | |
706 | |
577 | =item unsigned int ev_loop_count (loop) |
707 | =item unsigned int ev_iteration (loop) |
578 | |
708 | |
579 | Returns the count of loop iterations for the loop, which is identical to |
709 | Returns the current iteration count for the event loop, which is identical |
580 | the number of times libev did poll for new events. It starts at C<0> and |
710 | to the number of times libev did poll for new events. It starts at C<0> |
581 | happily wraps around with enough iterations. |
711 | and happily wraps around with enough iterations. |
582 | |
712 | |
583 | This value can sometimes be useful as a generation counter of sorts (it |
713 | This value can sometimes be useful as a generation counter of sorts (it |
584 | "ticks" the number of loop iterations), as it roughly corresponds with |
714 | "ticks" the number of loop iterations), as it roughly corresponds with |
585 | C<ev_prepare> and C<ev_check> calls. |
715 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
716 | prepare and check phases. |
|
|
717 | |
|
|
718 | =item unsigned int ev_depth (loop) |
|
|
719 | |
|
|
720 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
721 | times C<ev_run> was exited normally, in other words, the recursion depth. |
|
|
722 | |
|
|
723 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
724 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
725 | in which case it is higher. |
|
|
726 | |
|
|
727 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread, |
|
|
728 | throwing an exception etc.), doesn't count as "exit" - consider this |
|
|
729 | as a hint to avoid such ungentleman-like behaviour unless it's really |
|
|
730 | convenient, in which case it is fully supported. |
586 | |
731 | |
587 | =item unsigned int ev_backend (loop) |
732 | =item unsigned int ev_backend (loop) |
588 | |
733 | |
589 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
734 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
590 | use. |
735 | use. |
… | |
… | |
599 | |
744 | |
600 | =item ev_now_update (loop) |
745 | =item ev_now_update (loop) |
601 | |
746 | |
602 | Establishes the current time by querying the kernel, updating the time |
747 | Establishes the current time by querying the kernel, updating the time |
603 | returned by C<ev_now ()> in the progress. This is a costly operation and |
748 | returned by C<ev_now ()> in the progress. This is a costly operation and |
604 | is usually done automatically within C<ev_loop ()>. |
749 | is usually done automatically within C<ev_run ()>. |
605 | |
750 | |
606 | This function is rarely useful, but when some event callback runs for a |
751 | This function is rarely useful, but when some event callback runs for a |
607 | very long time without entering the event loop, updating libev's idea of |
752 | very long time without entering the event loop, updating libev's idea of |
608 | the current time is a good idea. |
753 | the current time is a good idea. |
609 | |
754 | |
610 | See also "The special problem of time updates" in the C<ev_timer> section. |
755 | See also L<The special problem of time updates> in the C<ev_timer> section. |
611 | |
756 | |
|
|
757 | =item ev_suspend (loop) |
|
|
758 | |
|
|
759 | =item ev_resume (loop) |
|
|
760 | |
|
|
761 | These two functions suspend and resume an event loop, for use when the |
|
|
762 | loop is not used for a while and timeouts should not be processed. |
|
|
763 | |
|
|
764 | A typical use case would be an interactive program such as a game: When |
|
|
765 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
766 | would be best to handle timeouts as if no time had actually passed while |
|
|
767 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
768 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
769 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
770 | |
|
|
771 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
772 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
773 | will be rescheduled (that is, they will lose any events that would have |
|
|
774 | occurred while suspended). |
|
|
775 | |
|
|
776 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
777 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
778 | without a previous call to C<ev_suspend>. |
|
|
779 | |
|
|
780 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
781 | event loop time (see C<ev_now_update>). |
|
|
782 | |
612 | =item ev_loop (loop, int flags) |
783 | =item ev_run (loop, int flags) |
613 | |
784 | |
614 | Finally, this is it, the event handler. This function usually is called |
785 | Finally, this is it, the event handler. This function usually is called |
615 | after you initialised all your watchers and you want to start handling |
786 | after you have initialised all your watchers and you want to start |
616 | events. |
787 | handling events. It will ask the operating system for any new events, call |
|
|
788 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
789 | is why event loops are called I<loops>. |
617 | |
790 | |
618 | If the flags argument is specified as C<0>, it will not return until |
791 | If the flags argument is specified as C<0>, it will keep handling events |
619 | either no event watchers are active anymore or C<ev_unloop> was called. |
792 | until either no event watchers are active anymore or C<ev_break> was |
|
|
793 | called. |
620 | |
794 | |
621 | Please note that an explicit C<ev_unloop> is usually better than |
795 | Please note that an explicit C<ev_break> is usually better than |
622 | relying on all watchers to be stopped when deciding when a program has |
796 | relying on all watchers to be stopped when deciding when a program has |
623 | finished (especially in interactive programs), but having a program |
797 | finished (especially in interactive programs), but having a program |
624 | that automatically loops as long as it has to and no longer by virtue |
798 | that automatically loops as long as it has to and no longer by virtue |
625 | of relying on its watchers stopping correctly, that is truly a thing of |
799 | of relying on its watchers stopping correctly, that is truly a thing of |
626 | beauty. |
800 | beauty. |
627 | |
801 | |
|
|
802 | This function is also I<mostly> exception-safe - you can break out of |
|
|
803 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
|
|
804 | exception and so on. This does not decrement the C<ev_depth> value, nor |
|
|
805 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
|
|
806 | |
628 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
807 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
629 | those events and any already outstanding ones, but will not block your |
808 | those events and any already outstanding ones, but will not wait and |
630 | process in case there are no events and will return after one iteration of |
809 | block your process in case there are no events and will return after one |
631 | the loop. |
810 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
811 | events while doing lengthy calculations, to keep the program responsive. |
632 | |
812 | |
633 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
813 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
634 | necessary) and will handle those and any already outstanding ones. It |
814 | necessary) and will handle those and any already outstanding ones. It |
635 | will block your process until at least one new event arrives (which could |
815 | will block your process until at least one new event arrives (which could |
636 | be an event internal to libev itself, so there is no guarentee that a |
816 | be an event internal to libev itself, so there is no guarantee that a |
637 | user-registered callback will be called), and will return after one |
817 | user-registered callback will be called), and will return after one |
638 | iteration of the loop. |
818 | iteration of the loop. |
639 | |
819 | |
640 | This is useful if you are waiting for some external event in conjunction |
820 | This is useful if you are waiting for some external event in conjunction |
641 | with something not expressible using other libev watchers (i.e. "roll your |
821 | with something not expressible using other libev watchers (i.e. "roll your |
642 | own C<ev_loop>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
822 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
643 | usually a better approach for this kind of thing. |
823 | usually a better approach for this kind of thing. |
644 | |
824 | |
645 | Here are the gory details of what C<ev_loop> does: |
825 | Here are the gory details of what C<ev_run> does: |
646 | |
826 | |
|
|
827 | - Increment loop depth. |
|
|
828 | - Reset the ev_break status. |
647 | - Before the first iteration, call any pending watchers. |
829 | - Before the first iteration, call any pending watchers. |
|
|
830 | LOOP: |
648 | * If EVFLAG_FORKCHECK was used, check for a fork. |
831 | - If EVFLAG_FORKCHECK was used, check for a fork. |
649 | - If a fork was detected (by any means), queue and call all fork watchers. |
832 | - If a fork was detected (by any means), queue and call all fork watchers. |
650 | - Queue and call all prepare watchers. |
833 | - Queue and call all prepare watchers. |
|
|
834 | - If ev_break was called, goto FINISH. |
651 | - If we have been forked, detach and recreate the kernel state |
835 | - If we have been forked, detach and recreate the kernel state |
652 | as to not disturb the other process. |
836 | as to not disturb the other process. |
653 | - Update the kernel state with all outstanding changes. |
837 | - Update the kernel state with all outstanding changes. |
654 | - Update the "event loop time" (ev_now ()). |
838 | - Update the "event loop time" (ev_now ()). |
655 | - Calculate for how long to sleep or block, if at all |
839 | - Calculate for how long to sleep or block, if at all |
656 | (active idle watchers, EVLOOP_NONBLOCK or not having |
840 | (active idle watchers, EVRUN_NOWAIT or not having |
657 | any active watchers at all will result in not sleeping). |
841 | any active watchers at all will result in not sleeping). |
658 | - Sleep if the I/O and timer collect interval say so. |
842 | - Sleep if the I/O and timer collect interval say so. |
|
|
843 | - Increment loop iteration counter. |
659 | - Block the process, waiting for any events. |
844 | - Block the process, waiting for any events. |
660 | - Queue all outstanding I/O (fd) events. |
845 | - Queue all outstanding I/O (fd) events. |
661 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
846 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
662 | - Queue all expired timers. |
847 | - Queue all expired timers. |
663 | - Queue all expired periodics. |
848 | - Queue all expired periodics. |
664 | - Unless any events are pending now, queue all idle watchers. |
849 | - Queue all idle watchers with priority higher than that of pending events. |
665 | - Queue all check watchers. |
850 | - Queue all check watchers. |
666 | - Call all queued watchers in reverse order (i.e. check watchers first). |
851 | - Call all queued watchers in reverse order (i.e. check watchers first). |
667 | Signals and child watchers are implemented as I/O watchers, and will |
852 | Signals and child watchers are implemented as I/O watchers, and will |
668 | be handled here by queueing them when their watcher gets executed. |
853 | be handled here by queueing them when their watcher gets executed. |
669 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
854 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
670 | were used, or there are no active watchers, return, otherwise |
855 | were used, or there are no active watchers, goto FINISH, otherwise |
671 | continue with step *. |
856 | continue with step LOOP. |
|
|
857 | FINISH: |
|
|
858 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
859 | - Decrement the loop depth. |
|
|
860 | - Return. |
672 | |
861 | |
673 | Example: Queue some jobs and then loop until no events are outstanding |
862 | Example: Queue some jobs and then loop until no events are outstanding |
674 | anymore. |
863 | anymore. |
675 | |
864 | |
676 | ... queue jobs here, make sure they register event watchers as long |
865 | ... queue jobs here, make sure they register event watchers as long |
677 | ... as they still have work to do (even an idle watcher will do..) |
866 | ... as they still have work to do (even an idle watcher will do..) |
678 | ev_loop (my_loop, 0); |
867 | ev_run (my_loop, 0); |
679 | ... jobs done or somebody called unloop. yeah! |
868 | ... jobs done or somebody called unloop. yeah! |
680 | |
869 | |
681 | =item ev_unloop (loop, how) |
870 | =item ev_break (loop, how) |
682 | |
871 | |
683 | Can be used to make a call to C<ev_loop> return early (but only after it |
872 | Can be used to make a call to C<ev_run> return early (but only after it |
684 | has processed all outstanding events). The C<how> argument must be either |
873 | has processed all outstanding events). The C<how> argument must be either |
685 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
874 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
686 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
875 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
687 | |
876 | |
688 | This "unloop state" will be cleared when entering C<ev_loop> again. |
877 | This "break state" will be cleared on the next call to C<ev_run>. |
|
|
878 | |
|
|
879 | It is safe to call C<ev_break> from outside any C<ev_run> calls, too, in |
|
|
880 | which case it will have no effect. |
689 | |
881 | |
690 | =item ev_ref (loop) |
882 | =item ev_ref (loop) |
691 | |
883 | |
692 | =item ev_unref (loop) |
884 | =item ev_unref (loop) |
693 | |
885 | |
694 | Ref/unref can be used to add or remove a reference count on the event |
886 | Ref/unref can be used to add or remove a reference count on the event |
695 | loop: Every watcher keeps one reference, and as long as the reference |
887 | loop: Every watcher keeps one reference, and as long as the reference |
696 | count is nonzero, C<ev_loop> will not return on its own. |
888 | count is nonzero, C<ev_run> will not return on its own. |
697 | |
889 | |
698 | If you have a watcher you never unregister that should not keep C<ev_loop> |
890 | This is useful when you have a watcher that you never intend to |
699 | from returning, call ev_unref() after starting, and ev_ref() before |
891 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
892 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
700 | stopping it. |
893 | before stopping it. |
701 | |
894 | |
702 | As an example, libev itself uses this for its internal signal pipe: It is |
895 | As an example, libev itself uses this for its internal signal pipe: It |
703 | not visible to the libev user and should not keep C<ev_loop> from exiting |
896 | is not visible to the libev user and should not keep C<ev_run> from |
704 | if no event watchers registered by it are active. It is also an excellent |
897 | exiting if no event watchers registered by it are active. It is also an |
705 | way to do this for generic recurring timers or from within third-party |
898 | excellent way to do this for generic recurring timers or from within |
706 | libraries. Just remember to I<unref after start> and I<ref before stop> |
899 | third-party libraries. Just remember to I<unref after start> and I<ref |
707 | (but only if the watcher wasn't active before, or was active before, |
900 | before stop> (but only if the watcher wasn't active before, or was active |
708 | respectively). |
901 | before, respectively. Note also that libev might stop watchers itself |
|
|
902 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
903 | in the callback). |
709 | |
904 | |
710 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
905 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
711 | running when nothing else is active. |
906 | running when nothing else is active. |
712 | |
907 | |
713 | struct ev_signal exitsig; |
908 | ev_signal exitsig; |
714 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
909 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
715 | ev_signal_start (loop, &exitsig); |
910 | ev_signal_start (loop, &exitsig); |
716 | evf_unref (loop); |
911 | ev_unref (loop); |
717 | |
912 | |
718 | Example: For some weird reason, unregister the above signal handler again. |
913 | Example: For some weird reason, unregister the above signal handler again. |
719 | |
914 | |
720 | ev_ref (loop); |
915 | ev_ref (loop); |
721 | ev_signal_stop (loop, &exitsig); |
916 | ev_signal_stop (loop, &exitsig); |
… | |
… | |
742 | |
937 | |
743 | By setting a higher I<io collect interval> you allow libev to spend more |
938 | By setting a higher I<io collect interval> you allow libev to spend more |
744 | time collecting I/O events, so you can handle more events per iteration, |
939 | time collecting I/O events, so you can handle more events per iteration, |
745 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
940 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
746 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
941 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
747 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
942 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
943 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
944 | once per this interval, on average. |
748 | |
945 | |
749 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
946 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
750 | to spend more time collecting timeouts, at the expense of increased |
947 | to spend more time collecting timeouts, at the expense of increased |
751 | latency/jitter/inexactness (the watcher callback will be called |
948 | latency/jitter/inexactness (the watcher callback will be called |
752 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
949 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
754 | |
951 | |
755 | Many (busy) programs can usually benefit by setting the I/O collect |
952 | Many (busy) programs can usually benefit by setting the I/O collect |
756 | interval to a value near C<0.1> or so, which is often enough for |
953 | interval to a value near C<0.1> or so, which is often enough for |
757 | interactive servers (of course not for games), likewise for timeouts. It |
954 | interactive servers (of course not for games), likewise for timeouts. It |
758 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
955 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
759 | as this approaches the timing granularity of most systems. |
956 | as this approaches the timing granularity of most systems. Note that if |
|
|
957 | you do transactions with the outside world and you can't increase the |
|
|
958 | parallelity, then this setting will limit your transaction rate (if you |
|
|
959 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
960 | then you can't do more than 100 transactions per second). |
760 | |
961 | |
761 | Setting the I<timeout collect interval> can improve the opportunity for |
962 | Setting the I<timeout collect interval> can improve the opportunity for |
762 | saving power, as the program will "bundle" timer callback invocations that |
963 | saving power, as the program will "bundle" timer callback invocations that |
763 | are "near" in time together, by delaying some, thus reducing the number of |
964 | are "near" in time together, by delaying some, thus reducing the number of |
764 | times the process sleeps and wakes up again. Another useful technique to |
965 | times the process sleeps and wakes up again. Another useful technique to |
765 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
966 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
766 | they fire on, say, one-second boundaries only. |
967 | they fire on, say, one-second boundaries only. |
767 | |
968 | |
|
|
969 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
970 | more often than 100 times per second: |
|
|
971 | |
|
|
972 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
973 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
974 | |
|
|
975 | =item ev_invoke_pending (loop) |
|
|
976 | |
|
|
977 | This call will simply invoke all pending watchers while resetting their |
|
|
978 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
979 | but when overriding the invoke callback this call comes handy. This |
|
|
980 | function can be invoked from a watcher - this can be useful for example |
|
|
981 | when you want to do some lengthy calculation and want to pass further |
|
|
982 | event handling to another thread (you still have to make sure only one |
|
|
983 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
984 | |
|
|
985 | =item int ev_pending_count (loop) |
|
|
986 | |
|
|
987 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
988 | are pending. |
|
|
989 | |
|
|
990 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
991 | |
|
|
992 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
993 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
994 | this callback instead. This is useful, for example, when you want to |
|
|
995 | invoke the actual watchers inside another context (another thread etc.). |
|
|
996 | |
|
|
997 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
998 | callback. |
|
|
999 | |
|
|
1000 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
1001 | |
|
|
1002 | Sometimes you want to share the same loop between multiple threads. This |
|
|
1003 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
1004 | each call to a libev function. |
|
|
1005 | |
|
|
1006 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
1007 | to wait for it to return. One way around this is to wake up the event |
|
|
1008 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
1009 | I<release> and I<acquire> callbacks on the loop. |
|
|
1010 | |
|
|
1011 | When set, then C<release> will be called just before the thread is |
|
|
1012 | suspended waiting for new events, and C<acquire> is called just |
|
|
1013 | afterwards. |
|
|
1014 | |
|
|
1015 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
1016 | C<acquire> will just call the mutex_lock function again. |
|
|
1017 | |
|
|
1018 | While event loop modifications are allowed between invocations of |
|
|
1019 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
1020 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
1021 | have no effect on the set of file descriptors being watched, or the time |
|
|
1022 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
1023 | to take note of any changes you made. |
|
|
1024 | |
|
|
1025 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
1026 | invocations of C<release> and C<acquire>. |
|
|
1027 | |
|
|
1028 | See also the locking example in the C<THREADS> section later in this |
|
|
1029 | document. |
|
|
1030 | |
|
|
1031 | =item ev_set_userdata (loop, void *data) |
|
|
1032 | |
|
|
1033 | =item void *ev_userdata (loop) |
|
|
1034 | |
|
|
1035 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
1036 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
1037 | C<0>. |
|
|
1038 | |
|
|
1039 | These two functions can be used to associate arbitrary data with a loop, |
|
|
1040 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
1041 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
1042 | any other purpose as well. |
|
|
1043 | |
768 | =item ev_loop_verify (loop) |
1044 | =item ev_verify (loop) |
769 | |
1045 | |
770 | This function only does something when C<EV_VERIFY> support has been |
1046 | This function only does something when C<EV_VERIFY> support has been |
771 | compiled in. which is the default for non-minimal builds. It tries to go |
1047 | compiled in, which is the default for non-minimal builds. It tries to go |
772 | through all internal structures and checks them for validity. If anything |
1048 | through all internal structures and checks them for validity. If anything |
773 | is found to be inconsistent, it will print an error message to standard |
1049 | is found to be inconsistent, it will print an error message to standard |
774 | error and call C<abort ()>. |
1050 | error and call C<abort ()>. |
775 | |
1051 | |
776 | This can be used to catch bugs inside libev itself: under normal |
1052 | This can be used to catch bugs inside libev itself: under normal |
… | |
… | |
780 | =back |
1056 | =back |
781 | |
1057 | |
782 | |
1058 | |
783 | =head1 ANATOMY OF A WATCHER |
1059 | =head1 ANATOMY OF A WATCHER |
784 | |
1060 | |
|
|
1061 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1062 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1063 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1064 | |
785 | A watcher is a structure that you create and register to record your |
1065 | A watcher is an opaque structure that you allocate and register to record |
786 | interest in some event. For instance, if you want to wait for STDIN to |
1066 | your interest in some event. To make a concrete example, imagine you want |
787 | become readable, you would create an C<ev_io> watcher for that: |
1067 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1068 | for that: |
788 | |
1069 | |
789 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1070 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
790 | { |
1071 | { |
791 | ev_io_stop (w); |
1072 | ev_io_stop (w); |
792 | ev_unloop (loop, EVUNLOOP_ALL); |
1073 | ev_break (loop, EVBREAK_ALL); |
793 | } |
1074 | } |
794 | |
1075 | |
795 | struct ev_loop *loop = ev_default_loop (0); |
1076 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1077 | |
796 | struct ev_io stdin_watcher; |
1078 | ev_io stdin_watcher; |
|
|
1079 | |
797 | ev_init (&stdin_watcher, my_cb); |
1080 | ev_init (&stdin_watcher, my_cb); |
798 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1081 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
799 | ev_io_start (loop, &stdin_watcher); |
1082 | ev_io_start (loop, &stdin_watcher); |
|
|
1083 | |
800 | ev_loop (loop, 0); |
1084 | ev_run (loop, 0); |
801 | |
1085 | |
802 | As you can see, you are responsible for allocating the memory for your |
1086 | As you can see, you are responsible for allocating the memory for your |
803 | watcher structures (and it is usually a bad idea to do this on the stack, |
1087 | watcher structures (and it is I<usually> a bad idea to do this on the |
804 | although this can sometimes be quite valid). |
1088 | stack). |
805 | |
1089 | |
|
|
1090 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1091 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1092 | |
806 | Each watcher structure must be initialised by a call to C<ev_init |
1093 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
807 | (watcher *, callback)>, which expects a callback to be provided. This |
1094 | *, callback)>, which expects a callback to be provided. This callback is |
808 | callback gets invoked each time the event occurs (or, in the case of I/O |
1095 | invoked each time the event occurs (or, in the case of I/O watchers, each |
809 | watchers, each time the event loop detects that the file descriptor given |
1096 | time the event loop detects that the file descriptor given is readable |
810 | is readable and/or writable). |
1097 | and/or writable). |
811 | |
1098 | |
812 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1099 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
813 | with arguments specific to this watcher type. There is also a macro |
1100 | macro to configure it, with arguments specific to the watcher type. There |
814 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1101 | is also a macro to combine initialisation and setting in one call: C<< |
815 | (watcher *, callback, ...) >>. |
1102 | ev_TYPE_init (watcher *, callback, ...) >>. |
816 | |
1103 | |
817 | To make the watcher actually watch out for events, you have to start it |
1104 | To make the watcher actually watch out for events, you have to start it |
818 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1105 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
819 | *) >>), and you can stop watching for events at any time by calling the |
1106 | *) >>), and you can stop watching for events at any time by calling the |
820 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1107 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
821 | |
1108 | |
822 | As long as your watcher is active (has been started but not stopped) you |
1109 | As long as your watcher is active (has been started but not stopped) you |
823 | must not touch the values stored in it. Most specifically you must never |
1110 | must not touch the values stored in it. Most specifically you must never |
824 | reinitialise it or call its C<set> macro. |
1111 | reinitialise it or call its C<ev_TYPE_set> macro. |
825 | |
1112 | |
826 | Each and every callback receives the event loop pointer as first, the |
1113 | Each and every callback receives the event loop pointer as first, the |
827 | registered watcher structure as second, and a bitset of received events as |
1114 | registered watcher structure as second, and a bitset of received events as |
828 | third argument. |
1115 | third argument. |
829 | |
1116 | |
… | |
… | |
838 | =item C<EV_WRITE> |
1125 | =item C<EV_WRITE> |
839 | |
1126 | |
840 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1127 | The file descriptor in the C<ev_io> watcher has become readable and/or |
841 | writable. |
1128 | writable. |
842 | |
1129 | |
843 | =item C<EV_TIMEOUT> |
1130 | =item C<EV_TIMER> |
844 | |
1131 | |
845 | The C<ev_timer> watcher has timed out. |
1132 | The C<ev_timer> watcher has timed out. |
846 | |
1133 | |
847 | =item C<EV_PERIODIC> |
1134 | =item C<EV_PERIODIC> |
848 | |
1135 | |
… | |
… | |
866 | |
1153 | |
867 | =item C<EV_PREPARE> |
1154 | =item C<EV_PREPARE> |
868 | |
1155 | |
869 | =item C<EV_CHECK> |
1156 | =item C<EV_CHECK> |
870 | |
1157 | |
871 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1158 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
872 | to gather new events, and all C<ev_check> watchers are invoked just after |
1159 | to gather new events, and all C<ev_check> watchers are invoked just after |
873 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1160 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
874 | received events. Callbacks of both watcher types can start and stop as |
1161 | received events. Callbacks of both watcher types can start and stop as |
875 | many watchers as they want, and all of them will be taken into account |
1162 | many watchers as they want, and all of them will be taken into account |
876 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1163 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
877 | C<ev_loop> from blocking). |
1164 | C<ev_run> from blocking). |
878 | |
1165 | |
879 | =item C<EV_EMBED> |
1166 | =item C<EV_EMBED> |
880 | |
1167 | |
881 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1168 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
882 | |
1169 | |
883 | =item C<EV_FORK> |
1170 | =item C<EV_FORK> |
884 | |
1171 | |
885 | The event loop has been resumed in the child process after fork (see |
1172 | The event loop has been resumed in the child process after fork (see |
886 | C<ev_fork>). |
1173 | C<ev_fork>). |
887 | |
1174 | |
|
|
1175 | =item C<EV_CLEANUP> |
|
|
1176 | |
|
|
1177 | The event loop is about to be destroyed (see C<ev_cleanup>). |
|
|
1178 | |
888 | =item C<EV_ASYNC> |
1179 | =item C<EV_ASYNC> |
889 | |
1180 | |
890 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1181 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1182 | |
|
|
1183 | =item C<EV_CUSTOM> |
|
|
1184 | |
|
|
1185 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1186 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
891 | |
1187 | |
892 | =item C<EV_ERROR> |
1188 | =item C<EV_ERROR> |
893 | |
1189 | |
894 | An unspecified error has occurred, the watcher has been stopped. This might |
1190 | An unspecified error has occurred, the watcher has been stopped. This might |
895 | happen because the watcher could not be properly started because libev |
1191 | happen because the watcher could not be properly started because libev |
896 | ran out of memory, a file descriptor was found to be closed or any other |
1192 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1193 | problem. Libev considers these application bugs. |
|
|
1194 | |
897 | problem. You best act on it by reporting the problem and somehow coping |
1195 | You best act on it by reporting the problem and somehow coping with the |
898 | with the watcher being stopped. |
1196 | watcher being stopped. Note that well-written programs should not receive |
|
|
1197 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1198 | bug in your program. |
899 | |
1199 | |
900 | Libev will usually signal a few "dummy" events together with an error, for |
1200 | Libev will usually signal a few "dummy" events together with an error, for |
901 | example it might indicate that a fd is readable or writable, and if your |
1201 | example it might indicate that a fd is readable or writable, and if your |
902 | callbacks is well-written it can just attempt the operation and cope with |
1202 | callbacks is well-written it can just attempt the operation and cope with |
903 | the error from read() or write(). This will not work in multi-threaded |
1203 | the error from read() or write(). This will not work in multi-threaded |
… | |
… | |
906 | |
1206 | |
907 | =back |
1207 | =back |
908 | |
1208 | |
909 | =head2 GENERIC WATCHER FUNCTIONS |
1209 | =head2 GENERIC WATCHER FUNCTIONS |
910 | |
1210 | |
911 | In the following description, C<TYPE> stands for the watcher type, |
|
|
912 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
913 | |
|
|
914 | =over 4 |
1211 | =over 4 |
915 | |
1212 | |
916 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1213 | =item C<ev_init> (ev_TYPE *watcher, callback) |
917 | |
1214 | |
918 | This macro initialises the generic portion of a watcher. The contents |
1215 | This macro initialises the generic portion of a watcher. The contents |
… | |
… | |
923 | which rolls both calls into one. |
1220 | which rolls both calls into one. |
924 | |
1221 | |
925 | You can reinitialise a watcher at any time as long as it has been stopped |
1222 | You can reinitialise a watcher at any time as long as it has been stopped |
926 | (or never started) and there are no pending events outstanding. |
1223 | (or never started) and there are no pending events outstanding. |
927 | |
1224 | |
928 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1225 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
929 | int revents)>. |
1226 | int revents)>. |
930 | |
1227 | |
931 | Example: Initialise an C<ev_io> watcher in two steps. |
1228 | Example: Initialise an C<ev_io> watcher in two steps. |
932 | |
1229 | |
933 | ev_io w; |
1230 | ev_io w; |
934 | ev_init (&w, my_cb); |
1231 | ev_init (&w, my_cb); |
935 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
1232 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
936 | |
1233 | |
937 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1234 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
938 | |
1235 | |
939 | This macro initialises the type-specific parts of a watcher. You need to |
1236 | This macro initialises the type-specific parts of a watcher. You need to |
940 | call C<ev_init> at least once before you call this macro, but you can |
1237 | call C<ev_init> at least once before you call this macro, but you can |
941 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1238 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
942 | macro on a watcher that is active (it can be pending, however, which is a |
1239 | macro on a watcher that is active (it can be pending, however, which is a |
… | |
… | |
955 | |
1252 | |
956 | Example: Initialise and set an C<ev_io> watcher in one step. |
1253 | Example: Initialise and set an C<ev_io> watcher in one step. |
957 | |
1254 | |
958 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
1255 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
959 | |
1256 | |
960 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1257 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
961 | |
1258 | |
962 | Starts (activates) the given watcher. Only active watchers will receive |
1259 | Starts (activates) the given watcher. Only active watchers will receive |
963 | events. If the watcher is already active nothing will happen. |
1260 | events. If the watcher is already active nothing will happen. |
964 | |
1261 | |
965 | Example: Start the C<ev_io> watcher that is being abused as example in this |
1262 | Example: Start the C<ev_io> watcher that is being abused as example in this |
966 | whole section. |
1263 | whole section. |
967 | |
1264 | |
968 | ev_io_start (EV_DEFAULT_UC, &w); |
1265 | ev_io_start (EV_DEFAULT_UC, &w); |
969 | |
1266 | |
970 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1267 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
971 | |
1268 | |
972 | Stops the given watcher again (if active) and clears the pending |
1269 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1270 | the watcher was active or not). |
|
|
1271 | |
973 | status. It is possible that stopped watchers are pending (for example, |
1272 | It is possible that stopped watchers are pending - for example, |
974 | non-repeating timers are being stopped when they become pending), but |
1273 | non-repeating timers are being stopped when they become pending - but |
975 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1274 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
976 | you want to free or reuse the memory used by the watcher it is therefore a |
1275 | pending. If you want to free or reuse the memory used by the watcher it is |
977 | good idea to always call its C<ev_TYPE_stop> function. |
1276 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
978 | |
1277 | |
979 | =item bool ev_is_active (ev_TYPE *watcher) |
1278 | =item bool ev_is_active (ev_TYPE *watcher) |
980 | |
1279 | |
981 | Returns a true value iff the watcher is active (i.e. it has been started |
1280 | Returns a true value iff the watcher is active (i.e. it has been started |
982 | and not yet been stopped). As long as a watcher is active you must not modify |
1281 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
998 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1297 | =item ev_cb_set (ev_TYPE *watcher, callback) |
999 | |
1298 | |
1000 | Change the callback. You can change the callback at virtually any time |
1299 | Change the callback. You can change the callback at virtually any time |
1001 | (modulo threads). |
1300 | (modulo threads). |
1002 | |
1301 | |
1003 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1302 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
1004 | |
1303 | |
1005 | =item int ev_priority (ev_TYPE *watcher) |
1304 | =item int ev_priority (ev_TYPE *watcher) |
1006 | |
1305 | |
1007 | Set and query the priority of the watcher. The priority is a small |
1306 | Set and query the priority of the watcher. The priority is a small |
1008 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1307 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1009 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1308 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1010 | before watchers with lower priority, but priority will not keep watchers |
1309 | before watchers with lower priority, but priority will not keep watchers |
1011 | from being executed (except for C<ev_idle> watchers). |
1310 | from being executed (except for C<ev_idle> watchers). |
1012 | |
1311 | |
1013 | This means that priorities are I<only> used for ordering callback |
|
|
1014 | invocation after new events have been received. This is useful, for |
|
|
1015 | example, to reduce latency after idling, or more often, to bind two |
|
|
1016 | watchers on the same event and make sure one is called first. |
|
|
1017 | |
|
|
1018 | If you need to suppress invocation when higher priority events are pending |
1312 | If you need to suppress invocation when higher priority events are pending |
1019 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1313 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1020 | |
1314 | |
1021 | You I<must not> change the priority of a watcher as long as it is active or |
1315 | You I<must not> change the priority of a watcher as long as it is active or |
1022 | pending. |
1316 | pending. |
1023 | |
1317 | |
|
|
1318 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1319 | fine, as long as you do not mind that the priority value you query might |
|
|
1320 | or might not have been clamped to the valid range. |
|
|
1321 | |
1024 | The default priority used by watchers when no priority has been set is |
1322 | The default priority used by watchers when no priority has been set is |
1025 | always C<0>, which is supposed to not be too high and not be too low :). |
1323 | always C<0>, which is supposed to not be too high and not be too low :). |
1026 | |
1324 | |
1027 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1325 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
1028 | fine, as long as you do not mind that the priority value you query might |
1326 | priorities. |
1029 | or might not have been adjusted to be within valid range. |
|
|
1030 | |
1327 | |
1031 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1328 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1032 | |
1329 | |
1033 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1330 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1034 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1331 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
… | |
… | |
1042 | watcher isn't pending it does nothing and returns C<0>. |
1339 | watcher isn't pending it does nothing and returns C<0>. |
1043 | |
1340 | |
1044 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1341 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
1045 | callback to be invoked, which can be accomplished with this function. |
1342 | callback to be invoked, which can be accomplished with this function. |
1046 | |
1343 | |
|
|
1344 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1345 | |
|
|
1346 | Feeds the given event set into the event loop, as if the specified event |
|
|
1347 | had happened for the specified watcher (which must be a pointer to an |
|
|
1348 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1349 | not free the watcher as long as it has pending events. |
|
|
1350 | |
|
|
1351 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1352 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1353 | not started in the first place. |
|
|
1354 | |
|
|
1355 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1356 | functions that do not need a watcher. |
|
|
1357 | |
1047 | =back |
1358 | =back |
1048 | |
|
|
1049 | |
1359 | |
1050 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1360 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1051 | |
1361 | |
1052 | Each watcher has, by default, a member C<void *data> that you can change |
1362 | Each watcher has, by default, a member C<void *data> that you can change |
1053 | and read at any time: libev will completely ignore it. This can be used |
1363 | and read at any time: libev will completely ignore it. This can be used |
… | |
… | |
1056 | member, you can also "subclass" the watcher type and provide your own |
1366 | member, you can also "subclass" the watcher type and provide your own |
1057 | data: |
1367 | data: |
1058 | |
1368 | |
1059 | struct my_io |
1369 | struct my_io |
1060 | { |
1370 | { |
1061 | struct ev_io io; |
1371 | ev_io io; |
1062 | int otherfd; |
1372 | int otherfd; |
1063 | void *somedata; |
1373 | void *somedata; |
1064 | struct whatever *mostinteresting; |
1374 | struct whatever *mostinteresting; |
1065 | }; |
1375 | }; |
1066 | |
1376 | |
… | |
… | |
1069 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1379 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1070 | |
1380 | |
1071 | And since your callback will be called with a pointer to the watcher, you |
1381 | And since your callback will be called with a pointer to the watcher, you |
1072 | can cast it back to your own type: |
1382 | can cast it back to your own type: |
1073 | |
1383 | |
1074 | static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
1384 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
1075 | { |
1385 | { |
1076 | struct my_io *w = (struct my_io *)w_; |
1386 | struct my_io *w = (struct my_io *)w_; |
1077 | ... |
1387 | ... |
1078 | } |
1388 | } |
1079 | |
1389 | |
… | |
… | |
1097 | programmers): |
1407 | programmers): |
1098 | |
1408 | |
1099 | #include <stddef.h> |
1409 | #include <stddef.h> |
1100 | |
1410 | |
1101 | static void |
1411 | static void |
1102 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1412 | t1_cb (EV_P_ ev_timer *w, int revents) |
1103 | { |
1413 | { |
1104 | struct my_biggy big = (struct my_biggy * |
1414 | struct my_biggy big = (struct my_biggy *) |
1105 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1415 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1106 | } |
1416 | } |
1107 | |
1417 | |
1108 | static void |
1418 | static void |
1109 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1419 | t2_cb (EV_P_ ev_timer *w, int revents) |
1110 | { |
1420 | { |
1111 | struct my_biggy big = (struct my_biggy * |
1421 | struct my_biggy big = (struct my_biggy *) |
1112 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1422 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1113 | } |
1423 | } |
|
|
1424 | |
|
|
1425 | =head2 WATCHER STATES |
|
|
1426 | |
|
|
1427 | There are various watcher states mentioned throughout this manual - |
|
|
1428 | active, pending and so on. In this section these states and the rules to |
|
|
1429 | transition between them will be described in more detail - and while these |
|
|
1430 | rules might look complicated, they usually do "the right thing". |
|
|
1431 | |
|
|
1432 | =over 4 |
|
|
1433 | |
|
|
1434 | =item initialiased |
|
|
1435 | |
|
|
1436 | Before a watcher can be registered with the event looop it has to be |
|
|
1437 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1438 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1439 | |
|
|
1440 | In this state it is simply some block of memory that is suitable for use |
|
|
1441 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1442 | |
|
|
1443 | =item started/running/active |
|
|
1444 | |
|
|
1445 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1446 | property of the event loop, and is actively waiting for events. While in |
|
|
1447 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1448 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1449 | and call libev functions on it that are documented to work on active watchers. |
|
|
1450 | |
|
|
1451 | =item pending |
|
|
1452 | |
|
|
1453 | If a watcher is active and libev determines that an event it is interested |
|
|
1454 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1455 | stay in this pending state until either it is stopped or its callback is |
|
|
1456 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1457 | callback. |
|
|
1458 | |
|
|
1459 | The watcher might or might not be active while it is pending (for example, |
|
|
1460 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1461 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1462 | but it is still property of the event loop at this time, so cannot be |
|
|
1463 | moved, freed or reused. And if it is active the rules described in the |
|
|
1464 | previous item still apply. |
|
|
1465 | |
|
|
1466 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1467 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1468 | active. |
|
|
1469 | |
|
|
1470 | =item stopped |
|
|
1471 | |
|
|
1472 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1473 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1474 | latter will clear any pending state the watcher might be in, regardless |
|
|
1475 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1476 | freeing it is often a good idea. |
|
|
1477 | |
|
|
1478 | While stopped (and not pending) the watcher is essentially in the |
|
|
1479 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1480 | you wish. |
|
|
1481 | |
|
|
1482 | =back |
|
|
1483 | |
|
|
1484 | =head2 WATCHER PRIORITY MODELS |
|
|
1485 | |
|
|
1486 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1487 | integers that influence the ordering of event callback invocation |
|
|
1488 | between watchers in some way, all else being equal. |
|
|
1489 | |
|
|
1490 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1491 | description for the more technical details such as the actual priority |
|
|
1492 | range. |
|
|
1493 | |
|
|
1494 | There are two common ways how these these priorities are being interpreted |
|
|
1495 | by event loops: |
|
|
1496 | |
|
|
1497 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1498 | of lower priority watchers, which means as long as higher priority |
|
|
1499 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1500 | |
|
|
1501 | The less common only-for-ordering model uses priorities solely to order |
|
|
1502 | callback invocation within a single event loop iteration: Higher priority |
|
|
1503 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1504 | before polling for new events. |
|
|
1505 | |
|
|
1506 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1507 | except for idle watchers (which use the lock-out model). |
|
|
1508 | |
|
|
1509 | The rationale behind this is that implementing the lock-out model for |
|
|
1510 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1511 | libraries will just poll for the same events again and again as long as |
|
|
1512 | their callbacks have not been executed, which is very inefficient in the |
|
|
1513 | common case of one high-priority watcher locking out a mass of lower |
|
|
1514 | priority ones. |
|
|
1515 | |
|
|
1516 | Static (ordering) priorities are most useful when you have two or more |
|
|
1517 | watchers handling the same resource: a typical usage example is having an |
|
|
1518 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1519 | timeouts. Under load, data might be received while the program handles |
|
|
1520 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1521 | handler will be executed before checking for data. In that case, giving |
|
|
1522 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1523 | handled first even under adverse conditions (which is usually, but not |
|
|
1524 | always, what you want). |
|
|
1525 | |
|
|
1526 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1527 | will only be executed when no same or higher priority watchers have |
|
|
1528 | received events, they can be used to implement the "lock-out" model when |
|
|
1529 | required. |
|
|
1530 | |
|
|
1531 | For example, to emulate how many other event libraries handle priorities, |
|
|
1532 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1533 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1534 | processing is done in the idle watcher callback. This causes libev to |
|
|
1535 | continuously poll and process kernel event data for the watcher, but when |
|
|
1536 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1537 | workable. |
|
|
1538 | |
|
|
1539 | Usually, however, the lock-out model implemented that way will perform |
|
|
1540 | miserably under the type of load it was designed to handle. In that case, |
|
|
1541 | it might be preferable to stop the real watcher before starting the |
|
|
1542 | idle watcher, so the kernel will not have to process the event in case |
|
|
1543 | the actual processing will be delayed for considerable time. |
|
|
1544 | |
|
|
1545 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1546 | priority than the default, and which should only process data when no |
|
|
1547 | other events are pending: |
|
|
1548 | |
|
|
1549 | ev_idle idle; // actual processing watcher |
|
|
1550 | ev_io io; // actual event watcher |
|
|
1551 | |
|
|
1552 | static void |
|
|
1553 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1554 | { |
|
|
1555 | // stop the I/O watcher, we received the event, but |
|
|
1556 | // are not yet ready to handle it. |
|
|
1557 | ev_io_stop (EV_A_ w); |
|
|
1558 | |
|
|
1559 | // start the idle watcher to handle the actual event. |
|
|
1560 | // it will not be executed as long as other watchers |
|
|
1561 | // with the default priority are receiving events. |
|
|
1562 | ev_idle_start (EV_A_ &idle); |
|
|
1563 | } |
|
|
1564 | |
|
|
1565 | static void |
|
|
1566 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1567 | { |
|
|
1568 | // actual processing |
|
|
1569 | read (STDIN_FILENO, ...); |
|
|
1570 | |
|
|
1571 | // have to start the I/O watcher again, as |
|
|
1572 | // we have handled the event |
|
|
1573 | ev_io_start (EV_P_ &io); |
|
|
1574 | } |
|
|
1575 | |
|
|
1576 | // initialisation |
|
|
1577 | ev_idle_init (&idle, idle_cb); |
|
|
1578 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1579 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1580 | |
|
|
1581 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1582 | low-priority connections can not be locked out forever under load. This |
|
|
1583 | enables your program to keep a lower latency for important connections |
|
|
1584 | during short periods of high load, while not completely locking out less |
|
|
1585 | important ones. |
1114 | |
1586 | |
1115 | |
1587 | |
1116 | =head1 WATCHER TYPES |
1588 | =head1 WATCHER TYPES |
1117 | |
1589 | |
1118 | This section describes each watcher in detail, but will not repeat |
1590 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1144 | descriptors to non-blocking mode is also usually a good idea (but not |
1616 | descriptors to non-blocking mode is also usually a good idea (but not |
1145 | required if you know what you are doing). |
1617 | required if you know what you are doing). |
1146 | |
1618 | |
1147 | If you cannot use non-blocking mode, then force the use of a |
1619 | If you cannot use non-blocking mode, then force the use of a |
1148 | known-to-be-good backend (at the time of this writing, this includes only |
1620 | known-to-be-good backend (at the time of this writing, this includes only |
1149 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). |
1621 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1622 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1623 | files) - libev doesn't guarantee any specific behaviour in that case. |
1150 | |
1624 | |
1151 | Another thing you have to watch out for is that it is quite easy to |
1625 | Another thing you have to watch out for is that it is quite easy to |
1152 | receive "spurious" readiness notifications, that is your callback might |
1626 | receive "spurious" readiness notifications, that is your callback might |
1153 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1627 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1154 | because there is no data. Not only are some backends known to create a |
1628 | because there is no data. Not only are some backends known to create a |
… | |
… | |
1219 | |
1693 | |
1220 | So when you encounter spurious, unexplained daemon exits, make sure you |
1694 | So when you encounter spurious, unexplained daemon exits, make sure you |
1221 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1695 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1222 | somewhere, as that would have given you a big clue). |
1696 | somewhere, as that would have given you a big clue). |
1223 | |
1697 | |
|
|
1698 | =head3 The special problem of accept()ing when you can't |
|
|
1699 | |
|
|
1700 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1701 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1702 | connection from the pending queue in all error cases. |
|
|
1703 | |
|
|
1704 | For example, larger servers often run out of file descriptors (because |
|
|
1705 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1706 | rejecting the connection, leading to libev signalling readiness on |
|
|
1707 | the next iteration again (the connection still exists after all), and |
|
|
1708 | typically causing the program to loop at 100% CPU usage. |
|
|
1709 | |
|
|
1710 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1711 | operating systems, there is usually little the app can do to remedy the |
|
|
1712 | situation, and no known thread-safe method of removing the connection to |
|
|
1713 | cope with overload is known (to me). |
|
|
1714 | |
|
|
1715 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1716 | - when the program encounters an overload, it will just loop until the |
|
|
1717 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1718 | event-based way to handle this situation, so it's the best one can do. |
|
|
1719 | |
|
|
1720 | A better way to handle the situation is to log any errors other than |
|
|
1721 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1722 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1723 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1724 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1725 | usage. |
|
|
1726 | |
|
|
1727 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1728 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1729 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1730 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1731 | clients under typical overload conditions. |
|
|
1732 | |
|
|
1733 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1734 | is often done with C<malloc> failures, but this results in an easy |
|
|
1735 | opportunity for a DoS attack. |
1224 | |
1736 | |
1225 | =head3 Watcher-Specific Functions |
1737 | =head3 Watcher-Specific Functions |
1226 | |
1738 | |
1227 | =over 4 |
1739 | =over 4 |
1228 | |
1740 | |
… | |
… | |
1249 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1761 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1250 | readable, but only once. Since it is likely line-buffered, you could |
1762 | readable, but only once. Since it is likely line-buffered, you could |
1251 | attempt to read a whole line in the callback. |
1763 | attempt to read a whole line in the callback. |
1252 | |
1764 | |
1253 | static void |
1765 | static void |
1254 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1766 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1255 | { |
1767 | { |
1256 | ev_io_stop (loop, w); |
1768 | ev_io_stop (loop, w); |
1257 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1769 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1258 | } |
1770 | } |
1259 | |
1771 | |
1260 | ... |
1772 | ... |
1261 | struct ev_loop *loop = ev_default_init (0); |
1773 | struct ev_loop *loop = ev_default_init (0); |
1262 | struct ev_io stdin_readable; |
1774 | ev_io stdin_readable; |
1263 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1775 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1264 | ev_io_start (loop, &stdin_readable); |
1776 | ev_io_start (loop, &stdin_readable); |
1265 | ev_loop (loop, 0); |
1777 | ev_run (loop, 0); |
1266 | |
1778 | |
1267 | |
1779 | |
1268 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1780 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1269 | |
1781 | |
1270 | Timer watchers are simple relative timers that generate an event after a |
1782 | Timer watchers are simple relative timers that generate an event after a |
… | |
… | |
1275 | year, it will still time out after (roughly) one hour. "Roughly" because |
1787 | year, it will still time out after (roughly) one hour. "Roughly" because |
1276 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1788 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1277 | monotonic clock option helps a lot here). |
1789 | monotonic clock option helps a lot here). |
1278 | |
1790 | |
1279 | The callback is guaranteed to be invoked only I<after> its timeout has |
1791 | The callback is guaranteed to be invoked only I<after> its timeout has |
1280 | passed, but if multiple timers become ready during the same loop iteration |
1792 | passed (not I<at>, so on systems with very low-resolution clocks this |
1281 | then order of execution is undefined. |
1793 | might introduce a small delay). If multiple timers become ready during the |
|
|
1794 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1795 | before ones of the same priority with later time-out values (but this is |
|
|
1796 | no longer true when a callback calls C<ev_run> recursively). |
|
|
1797 | |
|
|
1798 | =head3 Be smart about timeouts |
|
|
1799 | |
|
|
1800 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1801 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1802 | you want to raise some error after a while. |
|
|
1803 | |
|
|
1804 | What follows are some ways to handle this problem, from obvious and |
|
|
1805 | inefficient to smart and efficient. |
|
|
1806 | |
|
|
1807 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1808 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1809 | data or other life sign was received). |
|
|
1810 | |
|
|
1811 | =over 4 |
|
|
1812 | |
|
|
1813 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1814 | |
|
|
1815 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1816 | start the watcher: |
|
|
1817 | |
|
|
1818 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1819 | ev_timer_start (loop, timer); |
|
|
1820 | |
|
|
1821 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1822 | and start it again: |
|
|
1823 | |
|
|
1824 | ev_timer_stop (loop, timer); |
|
|
1825 | ev_timer_set (timer, 60., 0.); |
|
|
1826 | ev_timer_start (loop, timer); |
|
|
1827 | |
|
|
1828 | This is relatively simple to implement, but means that each time there is |
|
|
1829 | some activity, libev will first have to remove the timer from its internal |
|
|
1830 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1831 | still not a constant-time operation. |
|
|
1832 | |
|
|
1833 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1834 | |
|
|
1835 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1836 | C<ev_timer_start>. |
|
|
1837 | |
|
|
1838 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1839 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1840 | successfully read or write some data. If you go into an idle state where |
|
|
1841 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1842 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1843 | |
|
|
1844 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1845 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1846 | member and C<ev_timer_again>. |
|
|
1847 | |
|
|
1848 | At start: |
|
|
1849 | |
|
|
1850 | ev_init (timer, callback); |
|
|
1851 | timer->repeat = 60.; |
|
|
1852 | ev_timer_again (loop, timer); |
|
|
1853 | |
|
|
1854 | Each time there is some activity: |
|
|
1855 | |
|
|
1856 | ev_timer_again (loop, timer); |
|
|
1857 | |
|
|
1858 | It is even possible to change the time-out on the fly, regardless of |
|
|
1859 | whether the watcher is active or not: |
|
|
1860 | |
|
|
1861 | timer->repeat = 30.; |
|
|
1862 | ev_timer_again (loop, timer); |
|
|
1863 | |
|
|
1864 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1865 | you want to modify its timeout value, as libev does not have to completely |
|
|
1866 | remove and re-insert the timer from/into its internal data structure. |
|
|
1867 | |
|
|
1868 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1869 | |
|
|
1870 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1871 | |
|
|
1872 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1873 | relatively long compared to the intervals between other activity - in |
|
|
1874 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1875 | associated activity resets. |
|
|
1876 | |
|
|
1877 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1878 | but remember the time of last activity, and check for a real timeout only |
|
|
1879 | within the callback: |
|
|
1880 | |
|
|
1881 | ev_tstamp last_activity; // time of last activity |
|
|
1882 | |
|
|
1883 | static void |
|
|
1884 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1885 | { |
|
|
1886 | ev_tstamp now = ev_now (EV_A); |
|
|
1887 | ev_tstamp timeout = last_activity + 60.; |
|
|
1888 | |
|
|
1889 | // if last_activity + 60. is older than now, we did time out |
|
|
1890 | if (timeout < now) |
|
|
1891 | { |
|
|
1892 | // timeout occurred, take action |
|
|
1893 | } |
|
|
1894 | else |
|
|
1895 | { |
|
|
1896 | // callback was invoked, but there was some activity, re-arm |
|
|
1897 | // the watcher to fire in last_activity + 60, which is |
|
|
1898 | // guaranteed to be in the future, so "again" is positive: |
|
|
1899 | w->repeat = timeout - now; |
|
|
1900 | ev_timer_again (EV_A_ w); |
|
|
1901 | } |
|
|
1902 | } |
|
|
1903 | |
|
|
1904 | To summarise the callback: first calculate the real timeout (defined |
|
|
1905 | as "60 seconds after the last activity"), then check if that time has |
|
|
1906 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1907 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1908 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1909 | a timeout then. |
|
|
1910 | |
|
|
1911 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1912 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1913 | |
|
|
1914 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1915 | minus half the average time between activity), but virtually no calls to |
|
|
1916 | libev to change the timeout. |
|
|
1917 | |
|
|
1918 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1919 | to the current time (meaning we just have some activity :), then call the |
|
|
1920 | callback, which will "do the right thing" and start the timer: |
|
|
1921 | |
|
|
1922 | ev_init (timer, callback); |
|
|
1923 | last_activity = ev_now (loop); |
|
|
1924 | callback (loop, timer, EV_TIMER); |
|
|
1925 | |
|
|
1926 | And when there is some activity, simply store the current time in |
|
|
1927 | C<last_activity>, no libev calls at all: |
|
|
1928 | |
|
|
1929 | last_activity = ev_now (loop); |
|
|
1930 | |
|
|
1931 | This technique is slightly more complex, but in most cases where the |
|
|
1932 | time-out is unlikely to be triggered, much more efficient. |
|
|
1933 | |
|
|
1934 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1935 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1936 | fix things for you. |
|
|
1937 | |
|
|
1938 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1939 | |
|
|
1940 | If there is not one request, but many thousands (millions...), all |
|
|
1941 | employing some kind of timeout with the same timeout value, then one can |
|
|
1942 | do even better: |
|
|
1943 | |
|
|
1944 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1945 | at the I<end> of the list. |
|
|
1946 | |
|
|
1947 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1948 | the list is expected to fire (for example, using the technique #3). |
|
|
1949 | |
|
|
1950 | When there is some activity, remove the timer from the list, recalculate |
|
|
1951 | the timeout, append it to the end of the list again, and make sure to |
|
|
1952 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1953 | |
|
|
1954 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1955 | starting, stopping and updating the timers, at the expense of a major |
|
|
1956 | complication, and having to use a constant timeout. The constant timeout |
|
|
1957 | ensures that the list stays sorted. |
|
|
1958 | |
|
|
1959 | =back |
|
|
1960 | |
|
|
1961 | So which method the best? |
|
|
1962 | |
|
|
1963 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1964 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1965 | better, and isn't very complicated either. In most case, choosing either |
|
|
1966 | one is fine, with #3 being better in typical situations. |
|
|
1967 | |
|
|
1968 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1969 | rather complicated, but extremely efficient, something that really pays |
|
|
1970 | off after the first million or so of active timers, i.e. it's usually |
|
|
1971 | overkill :) |
1282 | |
1972 | |
1283 | =head3 The special problem of time updates |
1973 | =head3 The special problem of time updates |
1284 | |
1974 | |
1285 | Establishing the current time is a costly operation (it usually takes at |
1975 | Establishing the current time is a costly operation (it usually takes at |
1286 | least two system calls): EV therefore updates its idea of the current |
1976 | least two system calls): EV therefore updates its idea of the current |
1287 | time only before and after C<ev_loop> collects new events, which causes a |
1977 | time only before and after C<ev_run> collects new events, which causes a |
1288 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1978 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1289 | lots of events in one iteration. |
1979 | lots of events in one iteration. |
1290 | |
1980 | |
1291 | The relative timeouts are calculated relative to the C<ev_now ()> |
1981 | The relative timeouts are calculated relative to the C<ev_now ()> |
1292 | time. This is usually the right thing as this timestamp refers to the time |
1982 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1298 | |
1988 | |
1299 | If the event loop is suspended for a long time, you can also force an |
1989 | If the event loop is suspended for a long time, you can also force an |
1300 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1990 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1301 | ()>. |
1991 | ()>. |
1302 | |
1992 | |
|
|
1993 | =head3 The special problems of suspended animation |
|
|
1994 | |
|
|
1995 | When you leave the server world it is quite customary to hit machines that |
|
|
1996 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1997 | |
|
|
1998 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1999 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
2000 | to run until the system is suspended, but they will not advance while the |
|
|
2001 | system is suspended. That means, on resume, it will be as if the program |
|
|
2002 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
2003 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
2004 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
2005 | long suspend would be detected as a time jump by libev, and timers would |
|
|
2006 | be adjusted accordingly. |
|
|
2007 | |
|
|
2008 | I would not be surprised to see different behaviour in different between |
|
|
2009 | operating systems, OS versions or even different hardware. |
|
|
2010 | |
|
|
2011 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
2012 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
2013 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
2014 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
2015 | will be counted towards the timers. When no monotonic clock source is in |
|
|
2016 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
2017 | |
|
|
2018 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
2019 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
2020 | deterministic behaviour in this case (you can do nothing against |
|
|
2021 | C<SIGSTOP>). |
|
|
2022 | |
1303 | =head3 Watcher-Specific Functions and Data Members |
2023 | =head3 Watcher-Specific Functions and Data Members |
1304 | |
2024 | |
1305 | =over 4 |
2025 | =over 4 |
1306 | |
2026 | |
1307 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
2027 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1330 | If the timer is started but non-repeating, stop it (as if it timed out). |
2050 | If the timer is started but non-repeating, stop it (as if it timed out). |
1331 | |
2051 | |
1332 | If the timer is repeating, either start it if necessary (with the |
2052 | If the timer is repeating, either start it if necessary (with the |
1333 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2053 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1334 | |
2054 | |
1335 | This sounds a bit complicated, but here is a useful and typical |
2055 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1336 | example: Imagine you have a TCP connection and you want a so-called idle |
2056 | usage example. |
1337 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1338 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1339 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1340 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1341 | you go into an idle state where you do not expect data to travel on the |
|
|
1342 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1343 | automatically restart it if need be. |
|
|
1344 | |
2057 | |
1345 | That means you can ignore the C<after> value and C<ev_timer_start> |
2058 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1346 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1347 | |
2059 | |
1348 | ev_timer_init (timer, callback, 0., 5.); |
2060 | Returns the remaining time until a timer fires. If the timer is active, |
1349 | ev_timer_again (loop, timer); |
2061 | then this time is relative to the current event loop time, otherwise it's |
1350 | ... |
2062 | the timeout value currently configured. |
1351 | timer->again = 17.; |
|
|
1352 | ev_timer_again (loop, timer); |
|
|
1353 | ... |
|
|
1354 | timer->again = 10.; |
|
|
1355 | ev_timer_again (loop, timer); |
|
|
1356 | |
2063 | |
1357 | This is more slightly efficient then stopping/starting the timer each time |
2064 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1358 | you want to modify its timeout value. |
2065 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
1359 | |
2066 | will return C<4>. When the timer expires and is restarted, it will return |
1360 | Note, however, that it is often even more efficient to remember the |
2067 | roughly C<7> (likely slightly less as callback invocation takes some time, |
1361 | time of the last activity and let the timer time-out naturally. In the |
2068 | too), and so on. |
1362 | callback, you then check whether the time-out is real, or, if there was |
|
|
1363 | some activity, you reschedule the watcher to time-out in "last_activity + |
|
|
1364 | timeout - ev_now ()" seconds. |
|
|
1365 | |
2069 | |
1366 | =item ev_tstamp repeat [read-write] |
2070 | =item ev_tstamp repeat [read-write] |
1367 | |
2071 | |
1368 | The current C<repeat> value. Will be used each time the watcher times out |
2072 | The current C<repeat> value. Will be used each time the watcher times out |
1369 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
2073 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
… | |
… | |
1374 | =head3 Examples |
2078 | =head3 Examples |
1375 | |
2079 | |
1376 | Example: Create a timer that fires after 60 seconds. |
2080 | Example: Create a timer that fires after 60 seconds. |
1377 | |
2081 | |
1378 | static void |
2082 | static void |
1379 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2083 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1380 | { |
2084 | { |
1381 | .. one minute over, w is actually stopped right here |
2085 | .. one minute over, w is actually stopped right here |
1382 | } |
2086 | } |
1383 | |
2087 | |
1384 | struct ev_timer mytimer; |
2088 | ev_timer mytimer; |
1385 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2089 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1386 | ev_timer_start (loop, &mytimer); |
2090 | ev_timer_start (loop, &mytimer); |
1387 | |
2091 | |
1388 | Example: Create a timeout timer that times out after 10 seconds of |
2092 | Example: Create a timeout timer that times out after 10 seconds of |
1389 | inactivity. |
2093 | inactivity. |
1390 | |
2094 | |
1391 | static void |
2095 | static void |
1392 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2096 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1393 | { |
2097 | { |
1394 | .. ten seconds without any activity |
2098 | .. ten seconds without any activity |
1395 | } |
2099 | } |
1396 | |
2100 | |
1397 | struct ev_timer mytimer; |
2101 | ev_timer mytimer; |
1398 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2102 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1399 | ev_timer_again (&mytimer); /* start timer */ |
2103 | ev_timer_again (&mytimer); /* start timer */ |
1400 | ev_loop (loop, 0); |
2104 | ev_run (loop, 0); |
1401 | |
2105 | |
1402 | // and in some piece of code that gets executed on any "activity": |
2106 | // and in some piece of code that gets executed on any "activity": |
1403 | // reset the timeout to start ticking again at 10 seconds |
2107 | // reset the timeout to start ticking again at 10 seconds |
1404 | ev_timer_again (&mytimer); |
2108 | ev_timer_again (&mytimer); |
1405 | |
2109 | |
… | |
… | |
1407 | =head2 C<ev_periodic> - to cron or not to cron? |
2111 | =head2 C<ev_periodic> - to cron or not to cron? |
1408 | |
2112 | |
1409 | Periodic watchers are also timers of a kind, but they are very versatile |
2113 | Periodic watchers are also timers of a kind, but they are very versatile |
1410 | (and unfortunately a bit complex). |
2114 | (and unfortunately a bit complex). |
1411 | |
2115 | |
1412 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2116 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1413 | but on wall clock time (absolute time). You can tell a periodic watcher |
2117 | relative time, the physical time that passes) but on wall clock time |
1414 | to trigger after some specific point in time. For example, if you tell a |
2118 | (absolute time, the thing you can read on your calender or clock). The |
1415 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2119 | difference is that wall clock time can run faster or slower than real |
1416 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2120 | time, and time jumps are not uncommon (e.g. when you adjust your |
1417 | clock to January of the previous year, then it will take more than year |
2121 | wrist-watch). |
1418 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1419 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1420 | |
2122 | |
|
|
2123 | You can tell a periodic watcher to trigger after some specific point |
|
|
2124 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2125 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2126 | not a delay) and then reset your system clock to January of the previous |
|
|
2127 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2128 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2129 | it, as it uses a relative timeout). |
|
|
2130 | |
1421 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2131 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1422 | such as triggering an event on each "midnight, local time", or other |
2132 | timers, such as triggering an event on each "midnight, local time", or |
1423 | complicated rules. |
2133 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2134 | those cannot react to time jumps. |
1424 | |
2135 | |
1425 | As with timers, the callback is guaranteed to be invoked only when the |
2136 | As with timers, the callback is guaranteed to be invoked only when the |
1426 | time (C<at>) has passed, but if multiple periodic timers become ready |
2137 | point in time where it is supposed to trigger has passed. If multiple |
1427 | during the same loop iteration, then order of execution is undefined. |
2138 | timers become ready during the same loop iteration then the ones with |
|
|
2139 | earlier time-out values are invoked before ones with later time-out values |
|
|
2140 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1428 | |
2141 | |
1429 | =head3 Watcher-Specific Functions and Data Members |
2142 | =head3 Watcher-Specific Functions and Data Members |
1430 | |
2143 | |
1431 | =over 4 |
2144 | =over 4 |
1432 | |
2145 | |
1433 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2146 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1434 | |
2147 | |
1435 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2148 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1436 | |
2149 | |
1437 | Lots of arguments, lets sort it out... There are basically three modes of |
2150 | Lots of arguments, let's sort it out... There are basically three modes of |
1438 | operation, and we will explain them from simplest to most complex: |
2151 | operation, and we will explain them from simplest to most complex: |
1439 | |
2152 | |
1440 | =over 4 |
2153 | =over 4 |
1441 | |
2154 | |
1442 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2155 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1443 | |
2156 | |
1444 | In this configuration the watcher triggers an event after the wall clock |
2157 | In this configuration the watcher triggers an event after the wall clock |
1445 | time C<at> has passed. It will not repeat and will not adjust when a time |
2158 | time C<offset> has passed. It will not repeat and will not adjust when a |
1446 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2159 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1447 | only run when the system clock reaches or surpasses this time. |
2160 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2161 | this point in time. |
1448 | |
2162 | |
1449 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2163 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1450 | |
2164 | |
1451 | In this mode the watcher will always be scheduled to time out at the next |
2165 | In this mode the watcher will always be scheduled to time out at the next |
1452 | C<at + N * interval> time (for some integer N, which can also be negative) |
2166 | C<offset + N * interval> time (for some integer N, which can also be |
1453 | and then repeat, regardless of any time jumps. |
2167 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2168 | argument is merely an offset into the C<interval> periods. |
1454 | |
2169 | |
1455 | This can be used to create timers that do not drift with respect to the |
2170 | This can be used to create timers that do not drift with respect to the |
1456 | system clock, for example, here is a C<ev_periodic> that triggers each |
2171 | system clock, for example, here is an C<ev_periodic> that triggers each |
1457 | hour, on the hour: |
2172 | hour, on the hour (with respect to UTC): |
1458 | |
2173 | |
1459 | ev_periodic_set (&periodic, 0., 3600., 0); |
2174 | ev_periodic_set (&periodic, 0., 3600., 0); |
1460 | |
2175 | |
1461 | This doesn't mean there will always be 3600 seconds in between triggers, |
2176 | This doesn't mean there will always be 3600 seconds in between triggers, |
1462 | but only that the callback will be called when the system time shows a |
2177 | but only that the callback will be called when the system time shows a |
1463 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2178 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1464 | by 3600. |
2179 | by 3600. |
1465 | |
2180 | |
1466 | Another way to think about it (for the mathematically inclined) is that |
2181 | Another way to think about it (for the mathematically inclined) is that |
1467 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2182 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1468 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2183 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1469 | |
2184 | |
1470 | For numerical stability it is preferable that the C<at> value is near |
2185 | For numerical stability it is preferable that the C<offset> value is near |
1471 | C<ev_now ()> (the current time), but there is no range requirement for |
2186 | C<ev_now ()> (the current time), but there is no range requirement for |
1472 | this value, and in fact is often specified as zero. |
2187 | this value, and in fact is often specified as zero. |
1473 | |
2188 | |
1474 | Note also that there is an upper limit to how often a timer can fire (CPU |
2189 | Note also that there is an upper limit to how often a timer can fire (CPU |
1475 | speed for example), so if C<interval> is very small then timing stability |
2190 | speed for example), so if C<interval> is very small then timing stability |
1476 | will of course deteriorate. Libev itself tries to be exact to be about one |
2191 | will of course deteriorate. Libev itself tries to be exact to be about one |
1477 | millisecond (if the OS supports it and the machine is fast enough). |
2192 | millisecond (if the OS supports it and the machine is fast enough). |
1478 | |
2193 | |
1479 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2194 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1480 | |
2195 | |
1481 | In this mode the values for C<interval> and C<at> are both being |
2196 | In this mode the values for C<interval> and C<offset> are both being |
1482 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2197 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1483 | reschedule callback will be called with the watcher as first, and the |
2198 | reschedule callback will be called with the watcher as first, and the |
1484 | current time as second argument. |
2199 | current time as second argument. |
1485 | |
2200 | |
1486 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2201 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1487 | ever, or make ANY event loop modifications whatsoever>. |
2202 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2203 | allowed by documentation here>. |
1488 | |
2204 | |
1489 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2205 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1490 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2206 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1491 | only event loop modification you are allowed to do). |
2207 | only event loop modification you are allowed to do). |
1492 | |
2208 | |
1493 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2209 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1494 | *w, ev_tstamp now)>, e.g.: |
2210 | *w, ev_tstamp now)>, e.g.: |
1495 | |
2211 | |
|
|
2212 | static ev_tstamp |
1496 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2213 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1497 | { |
2214 | { |
1498 | return now + 60.; |
2215 | return now + 60.; |
1499 | } |
2216 | } |
1500 | |
2217 | |
1501 | It must return the next time to trigger, based on the passed time value |
2218 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1521 | a different time than the last time it was called (e.g. in a crond like |
2238 | a different time than the last time it was called (e.g. in a crond like |
1522 | program when the crontabs have changed). |
2239 | program when the crontabs have changed). |
1523 | |
2240 | |
1524 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2241 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1525 | |
2242 | |
1526 | When active, returns the absolute time that the watcher is supposed to |
2243 | When active, returns the absolute time that the watcher is supposed |
1527 | trigger next. |
2244 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2245 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2246 | rescheduling modes. |
1528 | |
2247 | |
1529 | =item ev_tstamp offset [read-write] |
2248 | =item ev_tstamp offset [read-write] |
1530 | |
2249 | |
1531 | When repeating, this contains the offset value, otherwise this is the |
2250 | When repeating, this contains the offset value, otherwise this is the |
1532 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2251 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2252 | although libev might modify this value for better numerical stability). |
1533 | |
2253 | |
1534 | Can be modified any time, but changes only take effect when the periodic |
2254 | Can be modified any time, but changes only take effect when the periodic |
1535 | timer fires or C<ev_periodic_again> is being called. |
2255 | timer fires or C<ev_periodic_again> is being called. |
1536 | |
2256 | |
1537 | =item ev_tstamp interval [read-write] |
2257 | =item ev_tstamp interval [read-write] |
1538 | |
2258 | |
1539 | The current interval value. Can be modified any time, but changes only |
2259 | The current interval value. Can be modified any time, but changes only |
1540 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2260 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1541 | called. |
2261 | called. |
1542 | |
2262 | |
1543 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2263 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1544 | |
2264 | |
1545 | The current reschedule callback, or C<0>, if this functionality is |
2265 | The current reschedule callback, or C<0>, if this functionality is |
1546 | switched off. Can be changed any time, but changes only take effect when |
2266 | switched off. Can be changed any time, but changes only take effect when |
1547 | the periodic timer fires or C<ev_periodic_again> is being called. |
2267 | the periodic timer fires or C<ev_periodic_again> is being called. |
1548 | |
2268 | |
… | |
… | |
1553 | Example: Call a callback every hour, or, more precisely, whenever the |
2273 | Example: Call a callback every hour, or, more precisely, whenever the |
1554 | system time is divisible by 3600. The callback invocation times have |
2274 | system time is divisible by 3600. The callback invocation times have |
1555 | potentially a lot of jitter, but good long-term stability. |
2275 | potentially a lot of jitter, but good long-term stability. |
1556 | |
2276 | |
1557 | static void |
2277 | static void |
1558 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2278 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1559 | { |
2279 | { |
1560 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2280 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1561 | } |
2281 | } |
1562 | |
2282 | |
1563 | struct ev_periodic hourly_tick; |
2283 | ev_periodic hourly_tick; |
1564 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2284 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1565 | ev_periodic_start (loop, &hourly_tick); |
2285 | ev_periodic_start (loop, &hourly_tick); |
1566 | |
2286 | |
1567 | Example: The same as above, but use a reschedule callback to do it: |
2287 | Example: The same as above, but use a reschedule callback to do it: |
1568 | |
2288 | |
1569 | #include <math.h> |
2289 | #include <math.h> |
1570 | |
2290 | |
1571 | static ev_tstamp |
2291 | static ev_tstamp |
1572 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2292 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1573 | { |
2293 | { |
1574 | return now + (3600. - fmod (now, 3600.)); |
2294 | return now + (3600. - fmod (now, 3600.)); |
1575 | } |
2295 | } |
1576 | |
2296 | |
1577 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2297 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1578 | |
2298 | |
1579 | Example: Call a callback every hour, starting now: |
2299 | Example: Call a callback every hour, starting now: |
1580 | |
2300 | |
1581 | struct ev_periodic hourly_tick; |
2301 | ev_periodic hourly_tick; |
1582 | ev_periodic_init (&hourly_tick, clock_cb, |
2302 | ev_periodic_init (&hourly_tick, clock_cb, |
1583 | fmod (ev_now (loop), 3600.), 3600., 0); |
2303 | fmod (ev_now (loop), 3600.), 3600., 0); |
1584 | ev_periodic_start (loop, &hourly_tick); |
2304 | ev_periodic_start (loop, &hourly_tick); |
1585 | |
2305 | |
1586 | |
2306 | |
1587 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
2307 | =head2 C<ev_signal> - signal me when a signal gets signalled! |
1588 | |
2308 | |
1589 | Signal watchers will trigger an event when the process receives a specific |
2309 | Signal watchers will trigger an event when the process receives a specific |
1590 | signal one or more times. Even though signals are very asynchronous, libev |
2310 | signal one or more times. Even though signals are very asynchronous, libev |
1591 | will try it's best to deliver signals synchronously, i.e. as part of the |
2311 | will try its best to deliver signals synchronously, i.e. as part of the |
1592 | normal event processing, like any other event. |
2312 | normal event processing, like any other event. |
1593 | |
2313 | |
1594 | If you want signals asynchronously, just use C<sigaction> as you would |
2314 | If you want signals to be delivered truly asynchronously, just use |
1595 | do without libev and forget about sharing the signal. You can even use |
2315 | C<sigaction> as you would do without libev and forget about sharing |
1596 | C<ev_async> from a signal handler to synchronously wake up an event loop. |
2316 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2317 | synchronously wake up an event loop. |
1597 | |
2318 | |
1598 | You can configure as many watchers as you like per signal. Only when the |
2319 | You can configure as many watchers as you like for the same signal, but |
|
|
2320 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2321 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2322 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2323 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2324 | |
1599 | first watcher gets started will libev actually register a signal handler |
2325 | When the first watcher gets started will libev actually register something |
1600 | with the kernel (thus it coexists with your own signal handlers as long as |
2326 | with the kernel (thus it coexists with your own signal handlers as long as |
1601 | you don't register any with libev for the same signal). Similarly, when |
2327 | you don't register any with libev for the same signal). |
1602 | the last signal watcher for a signal is stopped, libev will reset the |
|
|
1603 | signal handler to SIG_DFL (regardless of what it was set to before). |
|
|
1604 | |
2328 | |
1605 | If possible and supported, libev will install its handlers with |
2329 | If possible and supported, libev will install its handlers with |
1606 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2330 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1607 | interrupted. If you have a problem with system calls getting interrupted by |
2331 | not be unduly interrupted. If you have a problem with system calls getting |
1608 | signals you can block all signals in an C<ev_check> watcher and unblock |
2332 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1609 | them in an C<ev_prepare> watcher. |
2333 | and unblock them in an C<ev_prepare> watcher. |
|
|
2334 | |
|
|
2335 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2336 | |
|
|
2337 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2338 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2339 | stopping it again), that is, libev might or might not block the signal, |
|
|
2340 | and might or might not set or restore the installed signal handler. |
|
|
2341 | |
|
|
2342 | While this does not matter for the signal disposition (libev never |
|
|
2343 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2344 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2345 | certain signals to be blocked. |
|
|
2346 | |
|
|
2347 | This means that before calling C<exec> (from the child) you should reset |
|
|
2348 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2349 | choice usually). |
|
|
2350 | |
|
|
2351 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2352 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2353 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2354 | |
|
|
2355 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2356 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2357 | the window of opportunity for problems, it will not go away, as libev |
|
|
2358 | I<has> to modify the signal mask, at least temporarily. |
|
|
2359 | |
|
|
2360 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2361 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2362 | is not a libev-specific thing, this is true for most event libraries. |
|
|
2363 | |
|
|
2364 | =head3 The special problem of threads signal handling |
|
|
2365 | |
|
|
2366 | POSIX threads has problematic signal handling semantics, specifically, |
|
|
2367 | a lot of functionality (sigfd, sigwait etc.) only really works if all |
|
|
2368 | threads in a process block signals, which is hard to achieve. |
|
|
2369 | |
|
|
2370 | When you want to use sigwait (or mix libev signal handling with your own |
|
|
2371 | for the same signals), you can tackle this problem by globally blocking |
|
|
2372 | all signals before creating any threads (or creating them with a fully set |
|
|
2373 | sigprocmask) and also specifying the C<EVFLAG_NOSIGMASK> when creating |
|
|
2374 | loops. Then designate one thread as "signal receiver thread" which handles |
|
|
2375 | these signals. You can pass on any signals that libev might be interested |
|
|
2376 | in by calling C<ev_feed_signal>. |
1610 | |
2377 | |
1611 | =head3 Watcher-Specific Functions and Data Members |
2378 | =head3 Watcher-Specific Functions and Data Members |
1612 | |
2379 | |
1613 | =over 4 |
2380 | =over 4 |
1614 | |
2381 | |
… | |
… | |
1628 | =head3 Examples |
2395 | =head3 Examples |
1629 | |
2396 | |
1630 | Example: Try to exit cleanly on SIGINT. |
2397 | Example: Try to exit cleanly on SIGINT. |
1631 | |
2398 | |
1632 | static void |
2399 | static void |
1633 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2400 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1634 | { |
2401 | { |
1635 | ev_unloop (loop, EVUNLOOP_ALL); |
2402 | ev_break (loop, EVBREAK_ALL); |
1636 | } |
2403 | } |
1637 | |
2404 | |
1638 | struct ev_signal signal_watcher; |
2405 | ev_signal signal_watcher; |
1639 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2406 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1640 | ev_signal_start (loop, &signal_watcher); |
2407 | ev_signal_start (loop, &signal_watcher); |
1641 | |
2408 | |
1642 | |
2409 | |
1643 | =head2 C<ev_child> - watch out for process status changes |
2410 | =head2 C<ev_child> - watch out for process status changes |
… | |
… | |
1646 | some child status changes (most typically when a child of yours dies or |
2413 | some child status changes (most typically when a child of yours dies or |
1647 | exits). It is permissible to install a child watcher I<after> the child |
2414 | exits). It is permissible to install a child watcher I<after> the child |
1648 | has been forked (which implies it might have already exited), as long |
2415 | has been forked (which implies it might have already exited), as long |
1649 | as the event loop isn't entered (or is continued from a watcher), i.e., |
2416 | as the event loop isn't entered (or is continued from a watcher), i.e., |
1650 | forking and then immediately registering a watcher for the child is fine, |
2417 | forking and then immediately registering a watcher for the child is fine, |
1651 | but forking and registering a watcher a few event loop iterations later is |
2418 | but forking and registering a watcher a few event loop iterations later or |
1652 | not. |
2419 | in the next callback invocation is not. |
1653 | |
2420 | |
1654 | Only the default event loop is capable of handling signals, and therefore |
2421 | Only the default event loop is capable of handling signals, and therefore |
1655 | you can only register child watchers in the default event loop. |
2422 | you can only register child watchers in the default event loop. |
1656 | |
2423 | |
|
|
2424 | Due to some design glitches inside libev, child watchers will always be |
|
|
2425 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2426 | libev) |
|
|
2427 | |
1657 | =head3 Process Interaction |
2428 | =head3 Process Interaction |
1658 | |
2429 | |
1659 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2430 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1660 | initialised. This is necessary to guarantee proper behaviour even if |
2431 | initialised. This is necessary to guarantee proper behaviour even if the |
1661 | the first child watcher is started after the child exits. The occurrence |
2432 | first child watcher is started after the child exits. The occurrence |
1662 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2433 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1663 | synchronously as part of the event loop processing. Libev always reaps all |
2434 | synchronously as part of the event loop processing. Libev always reaps all |
1664 | children, even ones not watched. |
2435 | children, even ones not watched. |
1665 | |
2436 | |
1666 | =head3 Overriding the Built-In Processing |
2437 | =head3 Overriding the Built-In Processing |
… | |
… | |
1676 | =head3 Stopping the Child Watcher |
2447 | =head3 Stopping the Child Watcher |
1677 | |
2448 | |
1678 | Currently, the child watcher never gets stopped, even when the |
2449 | Currently, the child watcher never gets stopped, even when the |
1679 | child terminates, so normally one needs to stop the watcher in the |
2450 | child terminates, so normally one needs to stop the watcher in the |
1680 | callback. Future versions of libev might stop the watcher automatically |
2451 | callback. Future versions of libev might stop the watcher automatically |
1681 | when a child exit is detected. |
2452 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2453 | problem). |
1682 | |
2454 | |
1683 | =head3 Watcher-Specific Functions and Data Members |
2455 | =head3 Watcher-Specific Functions and Data Members |
1684 | |
2456 | |
1685 | =over 4 |
2457 | =over 4 |
1686 | |
2458 | |
… | |
… | |
1718 | its completion. |
2490 | its completion. |
1719 | |
2491 | |
1720 | ev_child cw; |
2492 | ev_child cw; |
1721 | |
2493 | |
1722 | static void |
2494 | static void |
1723 | child_cb (EV_P_ struct ev_child *w, int revents) |
2495 | child_cb (EV_P_ ev_child *w, int revents) |
1724 | { |
2496 | { |
1725 | ev_child_stop (EV_A_ w); |
2497 | ev_child_stop (EV_A_ w); |
1726 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2498 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1727 | } |
2499 | } |
1728 | |
2500 | |
… | |
… | |
1743 | |
2515 | |
1744 | |
2516 | |
1745 | =head2 C<ev_stat> - did the file attributes just change? |
2517 | =head2 C<ev_stat> - did the file attributes just change? |
1746 | |
2518 | |
1747 | This watches a file system path for attribute changes. That is, it calls |
2519 | This watches a file system path for attribute changes. That is, it calls |
1748 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2520 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1749 | compared to the last time, invoking the callback if it did. |
2521 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2522 | it did. |
1750 | |
2523 | |
1751 | The path does not need to exist: changing from "path exists" to "path does |
2524 | The path does not need to exist: changing from "path exists" to "path does |
1752 | not exist" is a status change like any other. The condition "path does |
2525 | not exist" is a status change like any other. The condition "path does not |
1753 | not exist" is signified by the C<st_nlink> field being zero (which is |
2526 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1754 | otherwise always forced to be at least one) and all the other fields of |
2527 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1755 | the stat buffer having unspecified contents. |
2528 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2529 | contents. |
1756 | |
2530 | |
1757 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2531 | The path I<must not> end in a slash or contain special components such as |
|
|
2532 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1758 | relative and your working directory changes, the behaviour is undefined. |
2533 | your working directory changes, then the behaviour is undefined. |
1759 | |
2534 | |
1760 | Since there is no standard kernel interface to do this, the portable |
2535 | Since there is no portable change notification interface available, the |
1761 | implementation simply calls C<stat (2)> regularly on the path to see if |
2536 | portable implementation simply calls C<stat(2)> regularly on the path |
1762 | it changed somehow. You can specify a recommended polling interval for |
2537 | to see if it changed somehow. You can specify a recommended polling |
1763 | this case. If you specify a polling interval of C<0> (highly recommended!) |
2538 | interval for this case. If you specify a polling interval of C<0> (highly |
1764 | then a I<suitable, unspecified default> value will be used (which |
2539 | recommended!) then a I<suitable, unspecified default> value will be used |
1765 | you can expect to be around five seconds, although this might change |
2540 | (which you can expect to be around five seconds, although this might |
1766 | dynamically). Libev will also impose a minimum interval which is currently |
2541 | change dynamically). Libev will also impose a minimum interval which is |
1767 | around C<0.1>, but thats usually overkill. |
2542 | currently around C<0.1>, but that's usually overkill. |
1768 | |
2543 | |
1769 | This watcher type is not meant for massive numbers of stat watchers, |
2544 | This watcher type is not meant for massive numbers of stat watchers, |
1770 | as even with OS-supported change notifications, this can be |
2545 | as even with OS-supported change notifications, this can be |
1771 | resource-intensive. |
2546 | resource-intensive. |
1772 | |
2547 | |
1773 | At the time of this writing, the only OS-specific interface implemented |
2548 | At the time of this writing, the only OS-specific interface implemented |
1774 | is the Linux inotify interface (implementing kqueue support is left as |
2549 | is the Linux inotify interface (implementing kqueue support is left as an |
1775 | an exercise for the reader. Note, however, that the author sees no way |
2550 | exercise for the reader. Note, however, that the author sees no way of |
1776 | of implementing C<ev_stat> semantics with kqueue). |
2551 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1777 | |
2552 | |
1778 | =head3 ABI Issues (Largefile Support) |
2553 | =head3 ABI Issues (Largefile Support) |
1779 | |
2554 | |
1780 | Libev by default (unless the user overrides this) uses the default |
2555 | Libev by default (unless the user overrides this) uses the default |
1781 | compilation environment, which means that on systems with large file |
2556 | compilation environment, which means that on systems with large file |
1782 | support disabled by default, you get the 32 bit version of the stat |
2557 | support disabled by default, you get the 32 bit version of the stat |
1783 | structure. When using the library from programs that change the ABI to |
2558 | structure. When using the library from programs that change the ABI to |
1784 | use 64 bit file offsets the programs will fail. In that case you have to |
2559 | use 64 bit file offsets the programs will fail. In that case you have to |
1785 | compile libev with the same flags to get binary compatibility. This is |
2560 | compile libev with the same flags to get binary compatibility. This is |
1786 | obviously the case with any flags that change the ABI, but the problem is |
2561 | obviously the case with any flags that change the ABI, but the problem is |
1787 | most noticeably disabled with ev_stat and large file support. |
2562 | most noticeably displayed with ev_stat and large file support. |
1788 | |
2563 | |
1789 | The solution for this is to lobby your distribution maker to make large |
2564 | The solution for this is to lobby your distribution maker to make large |
1790 | file interfaces available by default (as e.g. FreeBSD does) and not |
2565 | file interfaces available by default (as e.g. FreeBSD does) and not |
1791 | optional. Libev cannot simply switch on large file support because it has |
2566 | optional. Libev cannot simply switch on large file support because it has |
1792 | to exchange stat structures with application programs compiled using the |
2567 | to exchange stat structures with application programs compiled using the |
1793 | default compilation environment. |
2568 | default compilation environment. |
1794 | |
2569 | |
1795 | =head3 Inotify and Kqueue |
2570 | =head3 Inotify and Kqueue |
1796 | |
2571 | |
1797 | When C<inotify (7)> support has been compiled into libev (generally only |
2572 | When C<inotify (7)> support has been compiled into libev and present at |
1798 | available with Linux) and present at runtime, it will be used to speed up |
2573 | runtime, it will be used to speed up change detection where possible. The |
1799 | change detection where possible. The inotify descriptor will be created lazily |
2574 | inotify descriptor will be created lazily when the first C<ev_stat> |
1800 | when the first C<ev_stat> watcher is being started. |
2575 | watcher is being started. |
1801 | |
2576 | |
1802 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2577 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1803 | except that changes might be detected earlier, and in some cases, to avoid |
2578 | except that changes might be detected earlier, and in some cases, to avoid |
1804 | making regular C<stat> calls. Even in the presence of inotify support |
2579 | making regular C<stat> calls. Even in the presence of inotify support |
1805 | there are many cases where libev has to resort to regular C<stat> polling, |
2580 | there are many cases where libev has to resort to regular C<stat> polling, |
1806 | but as long as the path exists, libev usually gets away without polling. |
2581 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2582 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2583 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2584 | xfs are fully working) libev usually gets away without polling. |
1807 | |
2585 | |
1808 | There is no support for kqueue, as apparently it cannot be used to |
2586 | There is no support for kqueue, as apparently it cannot be used to |
1809 | implement this functionality, due to the requirement of having a file |
2587 | implement this functionality, due to the requirement of having a file |
1810 | descriptor open on the object at all times, and detecting renames, unlinks |
2588 | descriptor open on the object at all times, and detecting renames, unlinks |
1811 | etc. is difficult. |
2589 | etc. is difficult. |
1812 | |
2590 | |
|
|
2591 | =head3 C<stat ()> is a synchronous operation |
|
|
2592 | |
|
|
2593 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2594 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2595 | ()>, which is a synchronous operation. |
|
|
2596 | |
|
|
2597 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2598 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2599 | as the path data is usually in memory already (except when starting the |
|
|
2600 | watcher). |
|
|
2601 | |
|
|
2602 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2603 | time due to network issues, and even under good conditions, a stat call |
|
|
2604 | often takes multiple milliseconds. |
|
|
2605 | |
|
|
2606 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2607 | paths, although this is fully supported by libev. |
|
|
2608 | |
1813 | =head3 The special problem of stat time resolution |
2609 | =head3 The special problem of stat time resolution |
1814 | |
2610 | |
1815 | The C<stat ()> system call only supports full-second resolution portably, and |
2611 | The C<stat ()> system call only supports full-second resolution portably, |
1816 | even on systems where the resolution is higher, most file systems still |
2612 | and even on systems where the resolution is higher, most file systems |
1817 | only support whole seconds. |
2613 | still only support whole seconds. |
1818 | |
2614 | |
1819 | That means that, if the time is the only thing that changes, you can |
2615 | That means that, if the time is the only thing that changes, you can |
1820 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2616 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1821 | calls your callback, which does something. When there is another update |
2617 | calls your callback, which does something. When there is another update |
1822 | within the same second, C<ev_stat> will be unable to detect unless the |
2618 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
1965 | |
2761 | |
1966 | =head3 Watcher-Specific Functions and Data Members |
2762 | =head3 Watcher-Specific Functions and Data Members |
1967 | |
2763 | |
1968 | =over 4 |
2764 | =over 4 |
1969 | |
2765 | |
1970 | =item ev_idle_init (ev_signal *, callback) |
2766 | =item ev_idle_init (ev_idle *, callback) |
1971 | |
2767 | |
1972 | Initialises and configures the idle watcher - it has no parameters of any |
2768 | Initialises and configures the idle watcher - it has no parameters of any |
1973 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2769 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1974 | believe me. |
2770 | believe me. |
1975 | |
2771 | |
… | |
… | |
1979 | |
2775 | |
1980 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2776 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1981 | callback, free it. Also, use no error checking, as usual. |
2777 | callback, free it. Also, use no error checking, as usual. |
1982 | |
2778 | |
1983 | static void |
2779 | static void |
1984 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2780 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1985 | { |
2781 | { |
1986 | free (w); |
2782 | free (w); |
1987 | // now do something you wanted to do when the program has |
2783 | // now do something you wanted to do when the program has |
1988 | // no longer anything immediate to do. |
2784 | // no longer anything immediate to do. |
1989 | } |
2785 | } |
1990 | |
2786 | |
1991 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2787 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1992 | ev_idle_init (idle_watcher, idle_cb); |
2788 | ev_idle_init (idle_watcher, idle_cb); |
1993 | ev_idle_start (loop, idle_cb); |
2789 | ev_idle_start (loop, idle_watcher); |
1994 | |
2790 | |
1995 | |
2791 | |
1996 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2792 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1997 | |
2793 | |
1998 | Prepare and check watchers are usually (but not always) used in pairs: |
2794 | Prepare and check watchers are usually (but not always) used in pairs: |
1999 | prepare watchers get invoked before the process blocks and check watchers |
2795 | prepare watchers get invoked before the process blocks and check watchers |
2000 | afterwards. |
2796 | afterwards. |
2001 | |
2797 | |
2002 | You I<must not> call C<ev_loop> or similar functions that enter |
2798 | You I<must not> call C<ev_run> or similar functions that enter |
2003 | the current event loop from either C<ev_prepare> or C<ev_check> |
2799 | the current event loop from either C<ev_prepare> or C<ev_check> |
2004 | watchers. Other loops than the current one are fine, however. The |
2800 | watchers. Other loops than the current one are fine, however. The |
2005 | rationale behind this is that you do not need to check for recursion in |
2801 | rationale behind this is that you do not need to check for recursion in |
2006 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2802 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2007 | C<ev_check> so if you have one watcher of each kind they will always be |
2803 | C<ev_check> so if you have one watcher of each kind they will always be |
… | |
… | |
2077 | |
2873 | |
2078 | static ev_io iow [nfd]; |
2874 | static ev_io iow [nfd]; |
2079 | static ev_timer tw; |
2875 | static ev_timer tw; |
2080 | |
2876 | |
2081 | static void |
2877 | static void |
2082 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2878 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2083 | { |
2879 | { |
2084 | } |
2880 | } |
2085 | |
2881 | |
2086 | // create io watchers for each fd and a timer before blocking |
2882 | // create io watchers for each fd and a timer before blocking |
2087 | static void |
2883 | static void |
2088 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2884 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2089 | { |
2885 | { |
2090 | int timeout = 3600000; |
2886 | int timeout = 3600000; |
2091 | struct pollfd fds [nfd]; |
2887 | struct pollfd fds [nfd]; |
2092 | // actual code will need to loop here and realloc etc. |
2888 | // actual code will need to loop here and realloc etc. |
2093 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2889 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2094 | |
2890 | |
2095 | /* the callback is illegal, but won't be called as we stop during check */ |
2891 | /* the callback is illegal, but won't be called as we stop during check */ |
2096 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2892 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2097 | ev_timer_start (loop, &tw); |
2893 | ev_timer_start (loop, &tw); |
2098 | |
2894 | |
2099 | // create one ev_io per pollfd |
2895 | // create one ev_io per pollfd |
2100 | for (int i = 0; i < nfd; ++i) |
2896 | for (int i = 0; i < nfd; ++i) |
2101 | { |
2897 | { |
… | |
… | |
2108 | } |
2904 | } |
2109 | } |
2905 | } |
2110 | |
2906 | |
2111 | // stop all watchers after blocking |
2907 | // stop all watchers after blocking |
2112 | static void |
2908 | static void |
2113 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2909 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2114 | { |
2910 | { |
2115 | ev_timer_stop (loop, &tw); |
2911 | ev_timer_stop (loop, &tw); |
2116 | |
2912 | |
2117 | for (int i = 0; i < nfd; ++i) |
2913 | for (int i = 0; i < nfd; ++i) |
2118 | { |
2914 | { |
… | |
… | |
2175 | |
2971 | |
2176 | if (timeout >= 0) |
2972 | if (timeout >= 0) |
2177 | // create/start timer |
2973 | // create/start timer |
2178 | |
2974 | |
2179 | // poll |
2975 | // poll |
2180 | ev_loop (EV_A_ 0); |
2976 | ev_run (EV_A_ 0); |
2181 | |
2977 | |
2182 | // stop timer again |
2978 | // stop timer again |
2183 | if (timeout >= 0) |
2979 | if (timeout >= 0) |
2184 | ev_timer_stop (EV_A_ &to); |
2980 | ev_timer_stop (EV_A_ &to); |
2185 | |
2981 | |
… | |
… | |
2214 | some fds have to be watched and handled very quickly (with low latency), |
3010 | some fds have to be watched and handled very quickly (with low latency), |
2215 | and even priorities and idle watchers might have too much overhead. In |
3011 | and even priorities and idle watchers might have too much overhead. In |
2216 | this case you would put all the high priority stuff in one loop and all |
3012 | this case you would put all the high priority stuff in one loop and all |
2217 | the rest in a second one, and embed the second one in the first. |
3013 | the rest in a second one, and embed the second one in the first. |
2218 | |
3014 | |
2219 | As long as the watcher is active, the callback will be invoked every time |
3015 | As long as the watcher is active, the callback will be invoked every |
2220 | there might be events pending in the embedded loop. The callback must then |
3016 | time there might be events pending in the embedded loop. The callback |
2221 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
3017 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2222 | their callbacks (you could also start an idle watcher to give the embedded |
3018 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2223 | loop strictly lower priority for example). You can also set the callback |
3019 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2224 | to C<0>, in which case the embed watcher will automatically execute the |
3020 | to give the embedded loop strictly lower priority for example). |
2225 | embedded loop sweep. |
|
|
2226 | |
3021 | |
2227 | As long as the watcher is started it will automatically handle events. The |
3022 | You can also set the callback to C<0>, in which case the embed watcher |
2228 | callback will be invoked whenever some events have been handled. You can |
3023 | will automatically execute the embedded loop sweep whenever necessary. |
2229 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2230 | interested in that. |
|
|
2231 | |
3024 | |
2232 | Also, there have not currently been made special provisions for forking: |
3025 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2233 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
3026 | is active, i.e., the embedded loop will automatically be forked when the |
2234 | but you will also have to stop and restart any C<ev_embed> watchers |
3027 | embedding loop forks. In other cases, the user is responsible for calling |
2235 | yourself - but you can use a fork watcher to handle this automatically, |
3028 | C<ev_loop_fork> on the embedded loop. |
2236 | and future versions of libev might do just that. |
|
|
2237 | |
3029 | |
2238 | Unfortunately, not all backends are embeddable: only the ones returned by |
3030 | Unfortunately, not all backends are embeddable: only the ones returned by |
2239 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
3031 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2240 | portable one. |
3032 | portable one. |
2241 | |
3033 | |
… | |
… | |
2267 | if you do not want that, you need to temporarily stop the embed watcher). |
3059 | if you do not want that, you need to temporarily stop the embed watcher). |
2268 | |
3060 | |
2269 | =item ev_embed_sweep (loop, ev_embed *) |
3061 | =item ev_embed_sweep (loop, ev_embed *) |
2270 | |
3062 | |
2271 | Make a single, non-blocking sweep over the embedded loop. This works |
3063 | Make a single, non-blocking sweep over the embedded loop. This works |
2272 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
3064 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2273 | appropriate way for embedded loops. |
3065 | appropriate way for embedded loops. |
2274 | |
3066 | |
2275 | =item struct ev_loop *other [read-only] |
3067 | =item struct ev_loop *other [read-only] |
2276 | |
3068 | |
2277 | The embedded event loop. |
3069 | The embedded event loop. |
… | |
… | |
2286 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
3078 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2287 | used). |
3079 | used). |
2288 | |
3080 | |
2289 | struct ev_loop *loop_hi = ev_default_init (0); |
3081 | struct ev_loop *loop_hi = ev_default_init (0); |
2290 | struct ev_loop *loop_lo = 0; |
3082 | struct ev_loop *loop_lo = 0; |
2291 | struct ev_embed embed; |
3083 | ev_embed embed; |
2292 | |
3084 | |
2293 | // see if there is a chance of getting one that works |
3085 | // see if there is a chance of getting one that works |
2294 | // (remember that a flags value of 0 means autodetection) |
3086 | // (remember that a flags value of 0 means autodetection) |
2295 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3087 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2296 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3088 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2310 | kqueue implementation). Store the kqueue/socket-only event loop in |
3102 | kqueue implementation). Store the kqueue/socket-only event loop in |
2311 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3103 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2312 | |
3104 | |
2313 | struct ev_loop *loop = ev_default_init (0); |
3105 | struct ev_loop *loop = ev_default_init (0); |
2314 | struct ev_loop *loop_socket = 0; |
3106 | struct ev_loop *loop_socket = 0; |
2315 | struct ev_embed embed; |
3107 | ev_embed embed; |
2316 | |
3108 | |
2317 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3109 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2318 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3110 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2319 | { |
3111 | { |
2320 | ev_embed_init (&embed, 0, loop_socket); |
3112 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2335 | event loop blocks next and before C<ev_check> watchers are being called, |
3127 | event loop blocks next and before C<ev_check> watchers are being called, |
2336 | and only in the child after the fork. If whoever good citizen calling |
3128 | and only in the child after the fork. If whoever good citizen calling |
2337 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3129 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2338 | handlers will be invoked, too, of course. |
3130 | handlers will be invoked, too, of course. |
2339 | |
3131 | |
|
|
3132 | =head3 The special problem of life after fork - how is it possible? |
|
|
3133 | |
|
|
3134 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3135 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3136 | sequence should be handled by libev without any problems. |
|
|
3137 | |
|
|
3138 | This changes when the application actually wants to do event handling |
|
|
3139 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3140 | fork. |
|
|
3141 | |
|
|
3142 | The default mode of operation (for libev, with application help to detect |
|
|
3143 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3144 | when I<either> the parent I<or> the child process continues. |
|
|
3145 | |
|
|
3146 | When both processes want to continue using libev, then this is usually the |
|
|
3147 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3148 | supposed to continue with all watchers in place as before, while the other |
|
|
3149 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3150 | |
|
|
3151 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3152 | simply create a new event loop, which of course will be "empty", and |
|
|
3153 | use that for new watchers. This has the advantage of not touching more |
|
|
3154 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3155 | disadvantage of having to use multiple event loops (which do not support |
|
|
3156 | signal watchers). |
|
|
3157 | |
|
|
3158 | When this is not possible, or you want to use the default loop for |
|
|
3159 | other reasons, then in the process that wants to start "fresh", call |
|
|
3160 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3161 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3162 | watchers, so you have to be careful not to execute code that modifies |
|
|
3163 | those watchers. Note also that in that case, you have to re-register any |
|
|
3164 | signal watchers. |
|
|
3165 | |
2340 | =head3 Watcher-Specific Functions and Data Members |
3166 | =head3 Watcher-Specific Functions and Data Members |
2341 | |
3167 | |
2342 | =over 4 |
3168 | =over 4 |
2343 | |
3169 | |
2344 | =item ev_fork_init (ev_signal *, callback) |
3170 | =item ev_fork_init (ev_fork *, callback) |
2345 | |
3171 | |
2346 | Initialises and configures the fork watcher - it has no parameters of any |
3172 | Initialises and configures the fork watcher - it has no parameters of any |
2347 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
3173 | kind. There is a C<ev_fork_set> macro, but using it is utterly pointless, |
2348 | believe me. |
3174 | really. |
2349 | |
3175 | |
2350 | =back |
3176 | =back |
2351 | |
3177 | |
2352 | |
3178 | |
|
|
3179 | =head2 C<ev_cleanup> - even the best things end |
|
|
3180 | |
|
|
3181 | Cleanup watchers are called just before the event loop is being destroyed |
|
|
3182 | by a call to C<ev_loop_destroy>. |
|
|
3183 | |
|
|
3184 | While there is no guarantee that the event loop gets destroyed, cleanup |
|
|
3185 | watchers provide a convenient method to install cleanup hooks for your |
|
|
3186 | program, worker threads and so on - you just to make sure to destroy the |
|
|
3187 | loop when you want them to be invoked. |
|
|
3188 | |
|
|
3189 | Cleanup watchers are invoked in the same way as any other watcher. Unlike |
|
|
3190 | all other watchers, they do not keep a reference to the event loop (which |
|
|
3191 | makes a lot of sense if you think about it). Like all other watchers, you |
|
|
3192 | can call libev functions in the callback, except C<ev_cleanup_start>. |
|
|
3193 | |
|
|
3194 | =head3 Watcher-Specific Functions and Data Members |
|
|
3195 | |
|
|
3196 | =over 4 |
|
|
3197 | |
|
|
3198 | =item ev_cleanup_init (ev_cleanup *, callback) |
|
|
3199 | |
|
|
3200 | Initialises and configures the cleanup watcher - it has no parameters of |
|
|
3201 | any kind. There is a C<ev_cleanup_set> macro, but using it is utterly |
|
|
3202 | pointless, I assure you. |
|
|
3203 | |
|
|
3204 | =back |
|
|
3205 | |
|
|
3206 | Example: Register an atexit handler to destroy the default loop, so any |
|
|
3207 | cleanup functions are called. |
|
|
3208 | |
|
|
3209 | static void |
|
|
3210 | program_exits (void) |
|
|
3211 | { |
|
|
3212 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
3213 | } |
|
|
3214 | |
|
|
3215 | ... |
|
|
3216 | atexit (program_exits); |
|
|
3217 | |
|
|
3218 | |
2353 | =head2 C<ev_async> - how to wake up another event loop |
3219 | =head2 C<ev_async> - how to wake up an event loop |
2354 | |
3220 | |
2355 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3221 | In general, you cannot use an C<ev_run> from multiple threads or other |
2356 | asynchronous sources such as signal handlers (as opposed to multiple event |
3222 | asynchronous sources such as signal handlers (as opposed to multiple event |
2357 | loops - those are of course safe to use in different threads). |
3223 | loops - those are of course safe to use in different threads). |
2358 | |
3224 | |
2359 | Sometimes, however, you need to wake up another event loop you do not |
3225 | Sometimes, however, you need to wake up an event loop you do not control, |
2360 | control, for example because it belongs to another thread. This is what |
3226 | for example because it belongs to another thread. This is what C<ev_async> |
2361 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3227 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2362 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3228 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2363 | safe. |
|
|
2364 | |
3229 | |
2365 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3230 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2366 | too, are asynchronous in nature, and signals, too, will be compressed |
3231 | too, are asynchronous in nature, and signals, too, will be compressed |
2367 | (i.e. the number of callback invocations may be less than the number of |
3232 | (i.e. the number of callback invocations may be less than the number of |
2368 | C<ev_async_sent> calls). |
3233 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
|
|
3234 | of "global async watchers" by using a watcher on an otherwise unused |
|
|
3235 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
|
|
3236 | even without knowing which loop owns the signal. |
2369 | |
3237 | |
2370 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
3238 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
2371 | just the default loop. |
3239 | just the default loop. |
2372 | |
3240 | |
2373 | =head3 Queueing |
3241 | =head3 Queueing |
2374 | |
3242 | |
2375 | C<ev_async> does not support queueing of data in any way. The reason |
3243 | C<ev_async> does not support queueing of data in any way. The reason |
2376 | is that the author does not know of a simple (or any) algorithm for a |
3244 | is that the author does not know of a simple (or any) algorithm for a |
2377 | multiple-writer-single-reader queue that works in all cases and doesn't |
3245 | multiple-writer-single-reader queue that works in all cases and doesn't |
2378 | need elaborate support such as pthreads. |
3246 | need elaborate support such as pthreads or unportable memory access |
|
|
3247 | semantics. |
2379 | |
3248 | |
2380 | That means that if you want to queue data, you have to provide your own |
3249 | That means that if you want to queue data, you have to provide your own |
2381 | queue. But at least I can tell you how to implement locking around your |
3250 | queue. But at least I can tell you how to implement locking around your |
2382 | queue: |
3251 | queue: |
2383 | |
3252 | |
… | |
… | |
2461 | =over 4 |
3330 | =over 4 |
2462 | |
3331 | |
2463 | =item ev_async_init (ev_async *, callback) |
3332 | =item ev_async_init (ev_async *, callback) |
2464 | |
3333 | |
2465 | Initialises and configures the async watcher - it has no parameters of any |
3334 | Initialises and configures the async watcher - it has no parameters of any |
2466 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3335 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2467 | trust me. |
3336 | trust me. |
2468 | |
3337 | |
2469 | =item ev_async_send (loop, ev_async *) |
3338 | =item ev_async_send (loop, ev_async *) |
2470 | |
3339 | |
2471 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3340 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2472 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3341 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2473 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3342 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2474 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3343 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2475 | section below on what exactly this means). |
3344 | section below on what exactly this means). |
2476 | |
3345 | |
|
|
3346 | Note that, as with other watchers in libev, multiple events might get |
|
|
3347 | compressed into a single callback invocation (another way to look at this |
|
|
3348 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3349 | reset when the event loop detects that). |
|
|
3350 | |
2477 | This call incurs the overhead of a system call only once per loop iteration, |
3351 | This call incurs the overhead of a system call only once per event loop |
2478 | so while the overhead might be noticeable, it doesn't apply to repeated |
3352 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2479 | calls to C<ev_async_send>. |
3353 | repeated calls to C<ev_async_send> for the same event loop. |
2480 | |
3354 | |
2481 | =item bool = ev_async_pending (ev_async *) |
3355 | =item bool = ev_async_pending (ev_async *) |
2482 | |
3356 | |
2483 | Returns a non-zero value when C<ev_async_send> has been called on the |
3357 | Returns a non-zero value when C<ev_async_send> has been called on the |
2484 | watcher but the event has not yet been processed (or even noted) by the |
3358 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2487 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3361 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2488 | the loop iterates next and checks for the watcher to have become active, |
3362 | the loop iterates next and checks for the watcher to have become active, |
2489 | it will reset the flag again. C<ev_async_pending> can be used to very |
3363 | it will reset the flag again. C<ev_async_pending> can be used to very |
2490 | quickly check whether invoking the loop might be a good idea. |
3364 | quickly check whether invoking the loop might be a good idea. |
2491 | |
3365 | |
2492 | Not that this does I<not> check whether the watcher itself is pending, only |
3366 | Not that this does I<not> check whether the watcher itself is pending, |
2493 | whether it has been requested to make this watcher pending. |
3367 | only whether it has been requested to make this watcher pending: there |
|
|
3368 | is a time window between the event loop checking and resetting the async |
|
|
3369 | notification, and the callback being invoked. |
2494 | |
3370 | |
2495 | =back |
3371 | =back |
2496 | |
3372 | |
2497 | |
3373 | |
2498 | =head1 OTHER FUNCTIONS |
3374 | =head1 OTHER FUNCTIONS |
… | |
… | |
2515 | |
3391 | |
2516 | If C<timeout> is less than 0, then no timeout watcher will be |
3392 | If C<timeout> is less than 0, then no timeout watcher will be |
2517 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3393 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2518 | repeat = 0) will be started. C<0> is a valid timeout. |
3394 | repeat = 0) will be started. C<0> is a valid timeout. |
2519 | |
3395 | |
2520 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3396 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2521 | passed an C<revents> set like normal event callbacks (a combination of |
3397 | passed an C<revents> set like normal event callbacks (a combination of |
2522 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3398 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2523 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
3399 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
2524 | a timeout and an io event at the same time - you probably should give io |
3400 | a timeout and an io event at the same time - you probably should give io |
2525 | events precedence. |
3401 | events precedence. |
2526 | |
3402 | |
2527 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
3403 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2528 | |
3404 | |
2529 | static void stdin_ready (int revents, void *arg) |
3405 | static void stdin_ready (int revents, void *arg) |
2530 | { |
3406 | { |
2531 | if (revents & EV_READ) |
3407 | if (revents & EV_READ) |
2532 | /* stdin might have data for us, joy! */; |
3408 | /* stdin might have data for us, joy! */; |
2533 | else if (revents & EV_TIMEOUT) |
3409 | else if (revents & EV_TIMER) |
2534 | /* doh, nothing entered */; |
3410 | /* doh, nothing entered */; |
2535 | } |
3411 | } |
2536 | |
3412 | |
2537 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3413 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2538 | |
3414 | |
2539 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2540 | |
|
|
2541 | Feeds the given event set into the event loop, as if the specified event |
|
|
2542 | had happened for the specified watcher (which must be a pointer to an |
|
|
2543 | initialised but not necessarily started event watcher). |
|
|
2544 | |
|
|
2545 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3415 | =item ev_feed_fd_event (loop, int fd, int revents) |
2546 | |
3416 | |
2547 | Feed an event on the given fd, as if a file descriptor backend detected |
3417 | Feed an event on the given fd, as if a file descriptor backend detected |
2548 | the given events it. |
3418 | the given events it. |
2549 | |
3419 | |
2550 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3420 | =item ev_feed_signal_event (loop, int signum) |
2551 | |
3421 | |
2552 | Feed an event as if the given signal occurred (C<loop> must be the default |
3422 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
2553 | loop!). |
3423 | which is async-safe. |
|
|
3424 | |
|
|
3425 | =back |
|
|
3426 | |
|
|
3427 | |
|
|
3428 | =head1 COMMON OR USEFUL IDIOMS (OR BOTH) |
|
|
3429 | |
|
|
3430 | This section explains some common idioms that are not immediately |
|
|
3431 | obvious. Note that examples are sprinkled over the whole manual, and this |
|
|
3432 | section only contains stuff that wouldn't fit anywhere else. |
|
|
3433 | |
|
|
3434 | =over 4 |
|
|
3435 | |
|
|
3436 | =item Model/nested event loop invocations and exit conditions. |
|
|
3437 | |
|
|
3438 | Often (especially in GUI toolkits) there are places where you have |
|
|
3439 | I<modal> interaction, which is most easily implemented by recursively |
|
|
3440 | invoking C<ev_run>. |
|
|
3441 | |
|
|
3442 | This brings the problem of exiting - a callback might want to finish the |
|
|
3443 | main C<ev_run> call, but not the nested one (e.g. user clicked "Quit", but |
|
|
3444 | a modal "Are you sure?" dialog is still waiting), or just the nested one |
|
|
3445 | and not the main one (e.g. user clocked "Ok" in a modal dialog), or some |
|
|
3446 | other combination: In these cases, C<ev_break> will not work alone. |
|
|
3447 | |
|
|
3448 | The solution is to maintain "break this loop" variable for each C<ev_run> |
|
|
3449 | invocation, and use a loop around C<ev_run> until the condition is |
|
|
3450 | triggered, using C<EVRUN_ONCE>: |
|
|
3451 | |
|
|
3452 | // main loop |
|
|
3453 | int exit_main_loop = 0; |
|
|
3454 | |
|
|
3455 | while (!exit_main_loop) |
|
|
3456 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
|
|
3457 | |
|
|
3458 | // in a model watcher |
|
|
3459 | int exit_nested_loop = 0; |
|
|
3460 | |
|
|
3461 | while (!exit_nested_loop) |
|
|
3462 | ev_run (EV_A_ EVRUN_ONCE); |
|
|
3463 | |
|
|
3464 | To exit from any of these loops, just set the corresponding exit variable: |
|
|
3465 | |
|
|
3466 | // exit modal loop |
|
|
3467 | exit_nested_loop = 1; |
|
|
3468 | |
|
|
3469 | // exit main program, after modal loop is finished |
|
|
3470 | exit_main_loop = 1; |
|
|
3471 | |
|
|
3472 | // exit both |
|
|
3473 | exit_main_loop = exit_nested_loop = 1; |
2554 | |
3474 | |
2555 | =back |
3475 | =back |
2556 | |
3476 | |
2557 | |
3477 | |
2558 | =head1 LIBEVENT EMULATION |
3478 | =head1 LIBEVENT EMULATION |
2559 | |
3479 | |
2560 | Libev offers a compatibility emulation layer for libevent. It cannot |
3480 | Libev offers a compatibility emulation layer for libevent. It cannot |
2561 | emulate the internals of libevent, so here are some usage hints: |
3481 | emulate the internals of libevent, so here are some usage hints: |
2562 | |
3482 | |
2563 | =over 4 |
3483 | =over 4 |
|
|
3484 | |
|
|
3485 | =item * Only the libevent-1.4.1-beta API is being emulated. |
|
|
3486 | |
|
|
3487 | This was the newest libevent version available when libev was implemented, |
|
|
3488 | and is still mostly unchanged in 2010. |
2564 | |
3489 | |
2565 | =item * Use it by including <event.h>, as usual. |
3490 | =item * Use it by including <event.h>, as usual. |
2566 | |
3491 | |
2567 | =item * The following members are fully supported: ev_base, ev_callback, |
3492 | =item * The following members are fully supported: ev_base, ev_callback, |
2568 | ev_arg, ev_fd, ev_res, ev_events. |
3493 | ev_arg, ev_fd, ev_res, ev_events. |
… | |
… | |
2574 | =item * Priorities are not currently supported. Initialising priorities |
3499 | =item * Priorities are not currently supported. Initialising priorities |
2575 | will fail and all watchers will have the same priority, even though there |
3500 | will fail and all watchers will have the same priority, even though there |
2576 | is an ev_pri field. |
3501 | is an ev_pri field. |
2577 | |
3502 | |
2578 | =item * In libevent, the last base created gets the signals, in libev, the |
3503 | =item * In libevent, the last base created gets the signals, in libev, the |
2579 | first base created (== the default loop) gets the signals. |
3504 | base that registered the signal gets the signals. |
2580 | |
3505 | |
2581 | =item * Other members are not supported. |
3506 | =item * Other members are not supported. |
2582 | |
3507 | |
2583 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
3508 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2584 | to use the libev header file and library. |
3509 | to use the libev header file and library. |
… | |
… | |
2603 | Care has been taken to keep the overhead low. The only data member the C++ |
3528 | Care has been taken to keep the overhead low. The only data member the C++ |
2604 | classes add (compared to plain C-style watchers) is the event loop pointer |
3529 | classes add (compared to plain C-style watchers) is the event loop pointer |
2605 | that the watcher is associated with (or no additional members at all if |
3530 | that the watcher is associated with (or no additional members at all if |
2606 | you disable C<EV_MULTIPLICITY> when embedding libev). |
3531 | you disable C<EV_MULTIPLICITY> when embedding libev). |
2607 | |
3532 | |
2608 | Currently, functions, and static and non-static member functions can be |
3533 | Currently, functions, static and non-static member functions and classes |
2609 | used as callbacks. Other types should be easy to add as long as they only |
3534 | with C<operator ()> can be used as callbacks. Other types should be easy |
2610 | need one additional pointer for context. If you need support for other |
3535 | to add as long as they only need one additional pointer for context. If |
2611 | types of functors please contact the author (preferably after implementing |
3536 | you need support for other types of functors please contact the author |
2612 | it). |
3537 | (preferably after implementing it). |
2613 | |
3538 | |
2614 | Here is a list of things available in the C<ev> namespace: |
3539 | Here is a list of things available in the C<ev> namespace: |
2615 | |
3540 | |
2616 | =over 4 |
3541 | =over 4 |
2617 | |
3542 | |
… | |
… | |
2635 | |
3560 | |
2636 | =over 4 |
3561 | =over 4 |
2637 | |
3562 | |
2638 | =item ev::TYPE::TYPE () |
3563 | =item ev::TYPE::TYPE () |
2639 | |
3564 | |
2640 | =item ev::TYPE::TYPE (struct ev_loop *) |
3565 | =item ev::TYPE::TYPE (loop) |
2641 | |
3566 | |
2642 | =item ev::TYPE::~TYPE |
3567 | =item ev::TYPE::~TYPE |
2643 | |
3568 | |
2644 | The constructor (optionally) takes an event loop to associate the watcher |
3569 | The constructor (optionally) takes an event loop to associate the watcher |
2645 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3570 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2677 | |
3602 | |
2678 | myclass obj; |
3603 | myclass obj; |
2679 | ev::io iow; |
3604 | ev::io iow; |
2680 | iow.set <myclass, &myclass::io_cb> (&obj); |
3605 | iow.set <myclass, &myclass::io_cb> (&obj); |
2681 | |
3606 | |
|
|
3607 | =item w->set (object *) |
|
|
3608 | |
|
|
3609 | This is a variation of a method callback - leaving out the method to call |
|
|
3610 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3611 | functor objects without having to manually specify the C<operator ()> all |
|
|
3612 | the time. Incidentally, you can then also leave out the template argument |
|
|
3613 | list. |
|
|
3614 | |
|
|
3615 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3616 | int revents)>. |
|
|
3617 | |
|
|
3618 | See the method-C<set> above for more details. |
|
|
3619 | |
|
|
3620 | Example: use a functor object as callback. |
|
|
3621 | |
|
|
3622 | struct myfunctor |
|
|
3623 | { |
|
|
3624 | void operator() (ev::io &w, int revents) |
|
|
3625 | { |
|
|
3626 | ... |
|
|
3627 | } |
|
|
3628 | } |
|
|
3629 | |
|
|
3630 | myfunctor f; |
|
|
3631 | |
|
|
3632 | ev::io w; |
|
|
3633 | w.set (&f); |
|
|
3634 | |
2682 | =item w->set<function> (void *data = 0) |
3635 | =item w->set<function> (void *data = 0) |
2683 | |
3636 | |
2684 | Also sets a callback, but uses a static method or plain function as |
3637 | Also sets a callback, but uses a static method or plain function as |
2685 | callback. The optional C<data> argument will be stored in the watcher's |
3638 | callback. The optional C<data> argument will be stored in the watcher's |
2686 | C<data> member and is free for you to use. |
3639 | C<data> member and is free for you to use. |
… | |
… | |
2692 | Example: Use a plain function as callback. |
3645 | Example: Use a plain function as callback. |
2693 | |
3646 | |
2694 | static void io_cb (ev::io &w, int revents) { } |
3647 | static void io_cb (ev::io &w, int revents) { } |
2695 | iow.set <io_cb> (); |
3648 | iow.set <io_cb> (); |
2696 | |
3649 | |
2697 | =item w->set (struct ev_loop *) |
3650 | =item w->set (loop) |
2698 | |
3651 | |
2699 | Associates a different C<struct ev_loop> with this watcher. You can only |
3652 | Associates a different C<struct ev_loop> with this watcher. You can only |
2700 | do this when the watcher is inactive (and not pending either). |
3653 | do this when the watcher is inactive (and not pending either). |
2701 | |
3654 | |
2702 | =item w->set ([arguments]) |
3655 | =item w->set ([arguments]) |
2703 | |
3656 | |
2704 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3657 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2705 | called at least once. Unlike the C counterpart, an active watcher gets |
3658 | method or a suitable start method must be called at least once. Unlike the |
2706 | automatically stopped and restarted when reconfiguring it with this |
3659 | C counterpart, an active watcher gets automatically stopped and restarted |
2707 | method. |
3660 | when reconfiguring it with this method. |
2708 | |
3661 | |
2709 | =item w->start () |
3662 | =item w->start () |
2710 | |
3663 | |
2711 | Starts the watcher. Note that there is no C<loop> argument, as the |
3664 | Starts the watcher. Note that there is no C<loop> argument, as the |
2712 | constructor already stores the event loop. |
3665 | constructor already stores the event loop. |
2713 | |
3666 | |
|
|
3667 | =item w->start ([arguments]) |
|
|
3668 | |
|
|
3669 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3670 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3671 | the configure C<set> method of the watcher. |
|
|
3672 | |
2714 | =item w->stop () |
3673 | =item w->stop () |
2715 | |
3674 | |
2716 | Stops the watcher if it is active. Again, no C<loop> argument. |
3675 | Stops the watcher if it is active. Again, no C<loop> argument. |
2717 | |
3676 | |
2718 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3677 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2730 | |
3689 | |
2731 | =back |
3690 | =back |
2732 | |
3691 | |
2733 | =back |
3692 | =back |
2734 | |
3693 | |
2735 | Example: Define a class with an IO and idle watcher, start one of them in |
3694 | Example: Define a class with two I/O and idle watchers, start the I/O |
2736 | the constructor. |
3695 | watchers in the constructor. |
2737 | |
3696 | |
2738 | class myclass |
3697 | class myclass |
2739 | { |
3698 | { |
2740 | ev::io io ; void io_cb (ev::io &w, int revents); |
3699 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3700 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2741 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3701 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2742 | |
3702 | |
2743 | myclass (int fd) |
3703 | myclass (int fd) |
2744 | { |
3704 | { |
2745 | io .set <myclass, &myclass::io_cb > (this); |
3705 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3706 | io2 .set <myclass, &myclass::io2_cb > (this); |
2746 | idle.set <myclass, &myclass::idle_cb> (this); |
3707 | idle.set <myclass, &myclass::idle_cb> (this); |
2747 | |
3708 | |
2748 | io.start (fd, ev::READ); |
3709 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3710 | io.start (); // start it whenever convenient |
|
|
3711 | |
|
|
3712 | io2.start (fd, ev::READ); // set + start in one call |
2749 | } |
3713 | } |
2750 | }; |
3714 | }; |
2751 | |
3715 | |
2752 | |
3716 | |
2753 | =head1 OTHER LANGUAGE BINDINGS |
3717 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2772 | L<http://software.schmorp.de/pkg/EV>. |
3736 | L<http://software.schmorp.de/pkg/EV>. |
2773 | |
3737 | |
2774 | =item Python |
3738 | =item Python |
2775 | |
3739 | |
2776 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3740 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2777 | seems to be quite complete and well-documented. Note, however, that the |
3741 | seems to be quite complete and well-documented. |
2778 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2779 | for everybody else, and therefore, should never be applied in an installed |
|
|
2780 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2781 | libev). |
|
|
2782 | |
3742 | |
2783 | =item Ruby |
3743 | =item Ruby |
2784 | |
3744 | |
2785 | Tony Arcieri has written a ruby extension that offers access to a subset |
3745 | Tony Arcieri has written a ruby extension that offers access to a subset |
2786 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3746 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2787 | more on top of it. It can be found via gem servers. Its homepage is at |
3747 | more on top of it. It can be found via gem servers. Its homepage is at |
2788 | L<http://rev.rubyforge.org/>. |
3748 | L<http://rev.rubyforge.org/>. |
2789 | |
3749 | |
|
|
3750 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3751 | makes rev work even on mingw. |
|
|
3752 | |
|
|
3753 | =item Haskell |
|
|
3754 | |
|
|
3755 | A haskell binding to libev is available at |
|
|
3756 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3757 | |
2790 | =item D |
3758 | =item D |
2791 | |
3759 | |
2792 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3760 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2793 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3761 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3762 | |
|
|
3763 | =item Ocaml |
|
|
3764 | |
|
|
3765 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3766 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3767 | |
|
|
3768 | =item Lua |
|
|
3769 | |
|
|
3770 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3771 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3772 | L<http://github.com/brimworks/lua-ev>. |
2794 | |
3773 | |
2795 | =back |
3774 | =back |
2796 | |
3775 | |
2797 | |
3776 | |
2798 | =head1 MACRO MAGIC |
3777 | =head1 MACRO MAGIC |
… | |
… | |
2812 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3791 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2813 | C<EV_A_> is used when other arguments are following. Example: |
3792 | C<EV_A_> is used when other arguments are following. Example: |
2814 | |
3793 | |
2815 | ev_unref (EV_A); |
3794 | ev_unref (EV_A); |
2816 | ev_timer_add (EV_A_ watcher); |
3795 | ev_timer_add (EV_A_ watcher); |
2817 | ev_loop (EV_A_ 0); |
3796 | ev_run (EV_A_ 0); |
2818 | |
3797 | |
2819 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3798 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2820 | which is often provided by the following macro. |
3799 | which is often provided by the following macro. |
2821 | |
3800 | |
2822 | =item C<EV_P>, C<EV_P_> |
3801 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
2862 | } |
3841 | } |
2863 | |
3842 | |
2864 | ev_check check; |
3843 | ev_check check; |
2865 | ev_check_init (&check, check_cb); |
3844 | ev_check_init (&check, check_cb); |
2866 | ev_check_start (EV_DEFAULT_ &check); |
3845 | ev_check_start (EV_DEFAULT_ &check); |
2867 | ev_loop (EV_DEFAULT_ 0); |
3846 | ev_run (EV_DEFAULT_ 0); |
2868 | |
3847 | |
2869 | =head1 EMBEDDING |
3848 | =head1 EMBEDDING |
2870 | |
3849 | |
2871 | Libev can (and often is) directly embedded into host |
3850 | Libev can (and often is) directly embedded into host |
2872 | applications. Examples of applications that embed it include the Deliantra |
3851 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2899 | |
3878 | |
2900 | #define EV_STANDALONE 1 |
3879 | #define EV_STANDALONE 1 |
2901 | #include "ev.h" |
3880 | #include "ev.h" |
2902 | |
3881 | |
2903 | Both header files and implementation files can be compiled with a C++ |
3882 | Both header files and implementation files can be compiled with a C++ |
2904 | compiler (at least, thats a stated goal, and breakage will be treated |
3883 | compiler (at least, that's a stated goal, and breakage will be treated |
2905 | as a bug). |
3884 | as a bug). |
2906 | |
3885 | |
2907 | You need the following files in your source tree, or in a directory |
3886 | You need the following files in your source tree, or in a directory |
2908 | in your include path (e.g. in libev/ when using -Ilibev): |
3887 | in your include path (e.g. in libev/ when using -Ilibev): |
2909 | |
3888 | |
… | |
… | |
2952 | libev.m4 |
3931 | libev.m4 |
2953 | |
3932 | |
2954 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3933 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2955 | |
3934 | |
2956 | Libev can be configured via a variety of preprocessor symbols you have to |
3935 | Libev can be configured via a variety of preprocessor symbols you have to |
2957 | define before including any of its files. The default in the absence of |
3936 | define before including (or compiling) any of its files. The default in |
2958 | autoconf is documented for every option. |
3937 | the absence of autoconf is documented for every option. |
|
|
3938 | |
|
|
3939 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3940 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3941 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3942 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3943 | users of libev and the libev code itself must be compiled with compatible |
|
|
3944 | settings. |
2959 | |
3945 | |
2960 | =over 4 |
3946 | =over 4 |
2961 | |
3947 | |
|
|
3948 | =item EV_COMPAT3 (h) |
|
|
3949 | |
|
|
3950 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3951 | release of libev comes with wrappers for the functions and symbols that |
|
|
3952 | have been renamed between libev version 3 and 4. |
|
|
3953 | |
|
|
3954 | You can disable these wrappers (to test compatibility with future |
|
|
3955 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3956 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3957 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3958 | typedef in that case. |
|
|
3959 | |
|
|
3960 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3961 | and in some even more future version the compatibility code will be |
|
|
3962 | removed completely. |
|
|
3963 | |
2962 | =item EV_STANDALONE |
3964 | =item EV_STANDALONE (h) |
2963 | |
3965 | |
2964 | Must always be C<1> if you do not use autoconf configuration, which |
3966 | Must always be C<1> if you do not use autoconf configuration, which |
2965 | keeps libev from including F<config.h>, and it also defines dummy |
3967 | keeps libev from including F<config.h>, and it also defines dummy |
2966 | implementations for some libevent functions (such as logging, which is not |
3968 | implementations for some libevent functions (such as logging, which is not |
2967 | supported). It will also not define any of the structs usually found in |
3969 | supported). It will also not define any of the structs usually found in |
2968 | F<event.h> that are not directly supported by the libev core alone. |
3970 | F<event.h> that are not directly supported by the libev core alone. |
2969 | |
3971 | |
|
|
3972 | In standalone mode, libev will still try to automatically deduce the |
|
|
3973 | configuration, but has to be more conservative. |
|
|
3974 | |
2970 | =item EV_USE_MONOTONIC |
3975 | =item EV_USE_MONOTONIC |
2971 | |
3976 | |
2972 | If defined to be C<1>, libev will try to detect the availability of the |
3977 | If defined to be C<1>, libev will try to detect the availability of the |
2973 | monotonic clock option at both compile time and runtime. Otherwise no use |
3978 | monotonic clock option at both compile time and runtime. Otherwise no |
2974 | of the monotonic clock option will be attempted. If you enable this, you |
3979 | use of the monotonic clock option will be attempted. If you enable this, |
2975 | usually have to link against librt or something similar. Enabling it when |
3980 | you usually have to link against librt or something similar. Enabling it |
2976 | the functionality isn't available is safe, though, although you have |
3981 | when the functionality isn't available is safe, though, although you have |
2977 | to make sure you link against any libraries where the C<clock_gettime> |
3982 | to make sure you link against any libraries where the C<clock_gettime> |
2978 | function is hiding in (often F<-lrt>). |
3983 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2979 | |
3984 | |
2980 | =item EV_USE_REALTIME |
3985 | =item EV_USE_REALTIME |
2981 | |
3986 | |
2982 | If defined to be C<1>, libev will try to detect the availability of the |
3987 | If defined to be C<1>, libev will try to detect the availability of the |
2983 | real-time clock option at compile time (and assume its availability at |
3988 | real-time clock option at compile time (and assume its availability |
2984 | runtime if successful). Otherwise no use of the real-time clock option will |
3989 | at runtime if successful). Otherwise no use of the real-time clock |
2985 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3990 | option will be attempted. This effectively replaces C<gettimeofday> |
2986 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3991 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2987 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3992 | correctness. See the note about libraries in the description of |
|
|
3993 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3994 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3995 | |
|
|
3996 | =item EV_USE_CLOCK_SYSCALL |
|
|
3997 | |
|
|
3998 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3999 | of calling the system-provided C<clock_gettime> function. This option |
|
|
4000 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
4001 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
4002 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
4003 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
4004 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
4005 | higher, as it simplifies linking (no need for C<-lrt>). |
2988 | |
4006 | |
2989 | =item EV_USE_NANOSLEEP |
4007 | =item EV_USE_NANOSLEEP |
2990 | |
4008 | |
2991 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
4009 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2992 | and will use it for delays. Otherwise it will use C<select ()>. |
4010 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3008 | |
4026 | |
3009 | =item EV_SELECT_USE_FD_SET |
4027 | =item EV_SELECT_USE_FD_SET |
3010 | |
4028 | |
3011 | If defined to C<1>, then the select backend will use the system C<fd_set> |
4029 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3012 | structure. This is useful if libev doesn't compile due to a missing |
4030 | structure. This is useful if libev doesn't compile due to a missing |
3013 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
4031 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3014 | exotic systems. This usually limits the range of file descriptors to some |
4032 | on exotic systems. This usually limits the range of file descriptors to |
3015 | low limit such as 1024 or might have other limitations (winsocket only |
4033 | some low limit such as 1024 or might have other limitations (winsocket |
3016 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
4034 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3017 | influence the size of the C<fd_set> used. |
4035 | configures the maximum size of the C<fd_set>. |
3018 | |
4036 | |
3019 | =item EV_SELECT_IS_WINSOCKET |
4037 | =item EV_SELECT_IS_WINSOCKET |
3020 | |
4038 | |
3021 | When defined to C<1>, the select backend will assume that |
4039 | When defined to C<1>, the select backend will assume that |
3022 | select/socket/connect etc. don't understand file descriptors but |
4040 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3024 | be used is the winsock select). This means that it will call |
4042 | be used is the winsock select). This means that it will call |
3025 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
4043 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3026 | it is assumed that all these functions actually work on fds, even |
4044 | it is assumed that all these functions actually work on fds, even |
3027 | on win32. Should not be defined on non-win32 platforms. |
4045 | on win32. Should not be defined on non-win32 platforms. |
3028 | |
4046 | |
3029 | =item EV_FD_TO_WIN32_HANDLE |
4047 | =item EV_FD_TO_WIN32_HANDLE(fd) |
3030 | |
4048 | |
3031 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
4049 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3032 | file descriptors to socket handles. When not defining this symbol (the |
4050 | file descriptors to socket handles. When not defining this symbol (the |
3033 | default), then libev will call C<_get_osfhandle>, which is usually |
4051 | default), then libev will call C<_get_osfhandle>, which is usually |
3034 | correct. In some cases, programs use their own file descriptor management, |
4052 | correct. In some cases, programs use their own file descriptor management, |
3035 | in which case they can provide this function to map fds to socket handles. |
4053 | in which case they can provide this function to map fds to socket handles. |
|
|
4054 | |
|
|
4055 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
4056 | |
|
|
4057 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
4058 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
4059 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
4060 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
4061 | |
|
|
4062 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
4063 | |
|
|
4064 | If programs implement their own fd to handle mapping on win32, then this |
|
|
4065 | macro can be used to override the C<close> function, useful to unregister |
|
|
4066 | file descriptors again. Note that the replacement function has to close |
|
|
4067 | the underlying OS handle. |
3036 | |
4068 | |
3037 | =item EV_USE_POLL |
4069 | =item EV_USE_POLL |
3038 | |
4070 | |
3039 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
4071 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3040 | backend. Otherwise it will be enabled on non-win32 platforms. It |
4072 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
3087 | as well as for signal and thread safety in C<ev_async> watchers. |
4119 | as well as for signal and thread safety in C<ev_async> watchers. |
3088 | |
4120 | |
3089 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4121 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3090 | (from F<signal.h>), which is usually good enough on most platforms. |
4122 | (from F<signal.h>), which is usually good enough on most platforms. |
3091 | |
4123 | |
3092 | =item EV_H |
4124 | =item EV_H (h) |
3093 | |
4125 | |
3094 | The name of the F<ev.h> header file used to include it. The default if |
4126 | The name of the F<ev.h> header file used to include it. The default if |
3095 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4127 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3096 | used to virtually rename the F<ev.h> header file in case of conflicts. |
4128 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3097 | |
4129 | |
3098 | =item EV_CONFIG_H |
4130 | =item EV_CONFIG_H (h) |
3099 | |
4131 | |
3100 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
4132 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3101 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
4133 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3102 | C<EV_H>, above. |
4134 | C<EV_H>, above. |
3103 | |
4135 | |
3104 | =item EV_EVENT_H |
4136 | =item EV_EVENT_H (h) |
3105 | |
4137 | |
3106 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
4138 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3107 | of how the F<event.h> header can be found, the default is C<"event.h">. |
4139 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3108 | |
4140 | |
3109 | =item EV_PROTOTYPES |
4141 | =item EV_PROTOTYPES (h) |
3110 | |
4142 | |
3111 | If defined to be C<0>, then F<ev.h> will not define any function |
4143 | If defined to be C<0>, then F<ev.h> will not define any function |
3112 | prototypes, but still define all the structs and other symbols. This is |
4144 | prototypes, but still define all the structs and other symbols. This is |
3113 | occasionally useful if you want to provide your own wrapper functions |
4145 | occasionally useful if you want to provide your own wrapper functions |
3114 | around libev functions. |
4146 | around libev functions. |
… | |
… | |
3136 | fine. |
4168 | fine. |
3137 | |
4169 | |
3138 | If your embedding application does not need any priorities, defining these |
4170 | If your embedding application does not need any priorities, defining these |
3139 | both to C<0> will save some memory and CPU. |
4171 | both to C<0> will save some memory and CPU. |
3140 | |
4172 | |
3141 | =item EV_PERIODIC_ENABLE |
4173 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4174 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4175 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3142 | |
4176 | |
3143 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4177 | If undefined or defined to be C<1> (and the platform supports it), then |
3144 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4178 | the respective watcher type is supported. If defined to be C<0>, then it |
3145 | code. |
4179 | is not. Disabling watcher types mainly saves code size. |
3146 | |
4180 | |
3147 | =item EV_IDLE_ENABLE |
4181 | =item EV_FEATURES |
3148 | |
|
|
3149 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3150 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3151 | code. |
|
|
3152 | |
|
|
3153 | =item EV_EMBED_ENABLE |
|
|
3154 | |
|
|
3155 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3156 | defined to be C<0>, then they are not. Embed watchers rely on most other |
|
|
3157 | watcher types, which therefore must not be disabled. |
|
|
3158 | |
|
|
3159 | =item EV_STAT_ENABLE |
|
|
3160 | |
|
|
3161 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3162 | defined to be C<0>, then they are not. |
|
|
3163 | |
|
|
3164 | =item EV_FORK_ENABLE |
|
|
3165 | |
|
|
3166 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3167 | defined to be C<0>, then they are not. |
|
|
3168 | |
|
|
3169 | =item EV_ASYNC_ENABLE |
|
|
3170 | |
|
|
3171 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3172 | defined to be C<0>, then they are not. |
|
|
3173 | |
|
|
3174 | =item EV_MINIMAL |
|
|
3175 | |
4182 | |
3176 | If you need to shave off some kilobytes of code at the expense of some |
4183 | If you need to shave off some kilobytes of code at the expense of some |
3177 | speed, define this symbol to C<1>. Currently this is used to override some |
4184 | speed (but with the full API), you can define this symbol to request |
3178 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4185 | certain subsets of functionality. The default is to enable all features |
3179 | much smaller 2-heap for timer management over the default 4-heap. |
4186 | that can be enabled on the platform. |
|
|
4187 | |
|
|
4188 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4189 | with some broad features you want) and then selectively re-enable |
|
|
4190 | additional parts you want, for example if you want everything minimal, |
|
|
4191 | but multiple event loop support, async and child watchers and the poll |
|
|
4192 | backend, use this: |
|
|
4193 | |
|
|
4194 | #define EV_FEATURES 0 |
|
|
4195 | #define EV_MULTIPLICITY 1 |
|
|
4196 | #define EV_USE_POLL 1 |
|
|
4197 | #define EV_CHILD_ENABLE 1 |
|
|
4198 | #define EV_ASYNC_ENABLE 1 |
|
|
4199 | |
|
|
4200 | The actual value is a bitset, it can be a combination of the following |
|
|
4201 | values: |
|
|
4202 | |
|
|
4203 | =over 4 |
|
|
4204 | |
|
|
4205 | =item C<1> - faster/larger code |
|
|
4206 | |
|
|
4207 | Use larger code to speed up some operations. |
|
|
4208 | |
|
|
4209 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4210 | code size by roughly 30% on amd64). |
|
|
4211 | |
|
|
4212 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4213 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4214 | assertions. |
|
|
4215 | |
|
|
4216 | =item C<2> - faster/larger data structures |
|
|
4217 | |
|
|
4218 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4219 | hash table sizes and so on. This will usually further increase code size |
|
|
4220 | and can additionally have an effect on the size of data structures at |
|
|
4221 | runtime. |
|
|
4222 | |
|
|
4223 | =item C<4> - full API configuration |
|
|
4224 | |
|
|
4225 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4226 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4227 | |
|
|
4228 | =item C<8> - full API |
|
|
4229 | |
|
|
4230 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4231 | details on which parts of the API are still available without this |
|
|
4232 | feature, and do not complain if this subset changes over time. |
|
|
4233 | |
|
|
4234 | =item C<16> - enable all optional watcher types |
|
|
4235 | |
|
|
4236 | Enables all optional watcher types. If you want to selectively enable |
|
|
4237 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4238 | embed, async, child...) you can enable them manually by defining |
|
|
4239 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4240 | |
|
|
4241 | =item C<32> - enable all backends |
|
|
4242 | |
|
|
4243 | This enables all backends - without this feature, you need to enable at |
|
|
4244 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4245 | |
|
|
4246 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4247 | |
|
|
4248 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4249 | default. |
|
|
4250 | |
|
|
4251 | =back |
|
|
4252 | |
|
|
4253 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4254 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4255 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4256 | watchers, timers and monotonic clock support. |
|
|
4257 | |
|
|
4258 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4259 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4260 | your program might be left out as well - a binary starting a timer and an |
|
|
4261 | I/O watcher then might come out at only 5Kb. |
|
|
4262 | |
|
|
4263 | =item EV_AVOID_STDIO |
|
|
4264 | |
|
|
4265 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4266 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4267 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4268 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4269 | big. |
|
|
4270 | |
|
|
4271 | Note that error messages might become less precise when this option is |
|
|
4272 | enabled. |
|
|
4273 | |
|
|
4274 | =item EV_NSIG |
|
|
4275 | |
|
|
4276 | The highest supported signal number, +1 (or, the number of |
|
|
4277 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4278 | automatically, but sometimes this fails, in which case it can be |
|
|
4279 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4280 | good for about any system in existence) can save some memory, as libev |
|
|
4281 | statically allocates some 12-24 bytes per signal number. |
3180 | |
4282 | |
3181 | =item EV_PID_HASHSIZE |
4283 | =item EV_PID_HASHSIZE |
3182 | |
4284 | |
3183 | C<ev_child> watchers use a small hash table to distribute workload by |
4285 | C<ev_child> watchers use a small hash table to distribute workload by |
3184 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4286 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3185 | than enough. If you need to manage thousands of children you might want to |
4287 | usually more than enough. If you need to manage thousands of children you |
3186 | increase this value (I<must> be a power of two). |
4288 | might want to increase this value (I<must> be a power of two). |
3187 | |
4289 | |
3188 | =item EV_INOTIFY_HASHSIZE |
4290 | =item EV_INOTIFY_HASHSIZE |
3189 | |
4291 | |
3190 | C<ev_stat> watchers use a small hash table to distribute workload by |
4292 | C<ev_stat> watchers use a small hash table to distribute workload by |
3191 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4293 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3192 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4294 | disabled), usually more than enough. If you need to manage thousands of |
3193 | watchers you might want to increase this value (I<must> be a power of |
4295 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3194 | two). |
4296 | power of two). |
3195 | |
4297 | |
3196 | =item EV_USE_4HEAP |
4298 | =item EV_USE_4HEAP |
3197 | |
4299 | |
3198 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4300 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3199 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
4301 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3200 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
4302 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3201 | faster performance with many (thousands) of watchers. |
4303 | faster performance with many (thousands) of watchers. |
3202 | |
4304 | |
3203 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4305 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3204 | (disabled). |
4306 | will be C<0>. |
3205 | |
4307 | |
3206 | =item EV_HEAP_CACHE_AT |
4308 | =item EV_HEAP_CACHE_AT |
3207 | |
4309 | |
3208 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4310 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3209 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
4311 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3210 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4312 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3211 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4313 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3212 | but avoids random read accesses on heap changes. This improves performance |
4314 | but avoids random read accesses on heap changes. This improves performance |
3213 | noticeably with many (hundreds) of watchers. |
4315 | noticeably with many (hundreds) of watchers. |
3214 | |
4316 | |
3215 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4317 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3216 | (disabled). |
4318 | will be C<0>. |
3217 | |
4319 | |
3218 | =item EV_VERIFY |
4320 | =item EV_VERIFY |
3219 | |
4321 | |
3220 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4322 | Controls how much internal verification (see C<ev_verify ()>) will |
3221 | be done: If set to C<0>, no internal verification code will be compiled |
4323 | be done: If set to C<0>, no internal verification code will be compiled |
3222 | in. If set to C<1>, then verification code will be compiled in, but not |
4324 | in. If set to C<1>, then verification code will be compiled in, but not |
3223 | called. If set to C<2>, then the internal verification code will be |
4325 | called. If set to C<2>, then the internal verification code will be |
3224 | called once per loop, which can slow down libev. If set to C<3>, then the |
4326 | called once per loop, which can slow down libev. If set to C<3>, then the |
3225 | verification code will be called very frequently, which will slow down |
4327 | verification code will be called very frequently, which will slow down |
3226 | libev considerably. |
4328 | libev considerably. |
3227 | |
4329 | |
3228 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4330 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3229 | C<0>. |
4331 | will be C<0>. |
3230 | |
4332 | |
3231 | =item EV_COMMON |
4333 | =item EV_COMMON |
3232 | |
4334 | |
3233 | By default, all watchers have a C<void *data> member. By redefining |
4335 | By default, all watchers have a C<void *data> member. By redefining |
3234 | this macro to a something else you can include more and other types of |
4336 | this macro to something else you can include more and other types of |
3235 | members. You have to define it each time you include one of the files, |
4337 | members. You have to define it each time you include one of the files, |
3236 | though, and it must be identical each time. |
4338 | though, and it must be identical each time. |
3237 | |
4339 | |
3238 | For example, the perl EV module uses something like this: |
4340 | For example, the perl EV module uses something like this: |
3239 | |
4341 | |
… | |
… | |
3292 | file. |
4394 | file. |
3293 | |
4395 | |
3294 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4396 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3295 | that everybody includes and which overrides some configure choices: |
4397 | that everybody includes and which overrides some configure choices: |
3296 | |
4398 | |
3297 | #define EV_MINIMAL 1 |
4399 | #define EV_FEATURES 8 |
3298 | #define EV_USE_POLL 0 |
4400 | #define EV_USE_SELECT 1 |
3299 | #define EV_MULTIPLICITY 0 |
|
|
3300 | #define EV_PERIODIC_ENABLE 0 |
4401 | #define EV_PREPARE_ENABLE 1 |
|
|
4402 | #define EV_IDLE_ENABLE 1 |
3301 | #define EV_STAT_ENABLE 0 |
4403 | #define EV_SIGNAL_ENABLE 1 |
3302 | #define EV_FORK_ENABLE 0 |
4404 | #define EV_CHILD_ENABLE 1 |
|
|
4405 | #define EV_USE_STDEXCEPT 0 |
3303 | #define EV_CONFIG_H <config.h> |
4406 | #define EV_CONFIG_H <config.h> |
3304 | #define EV_MINPRI 0 |
|
|
3305 | #define EV_MAXPRI 0 |
|
|
3306 | |
4407 | |
3307 | #include "ev++.h" |
4408 | #include "ev++.h" |
3308 | |
4409 | |
3309 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4410 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3310 | |
4411 | |
… | |
… | |
3370 | default loop and triggering an C<ev_async> watcher from the default loop |
4471 | default loop and triggering an C<ev_async> watcher from the default loop |
3371 | watcher callback into the event loop interested in the signal. |
4472 | watcher callback into the event loop interested in the signal. |
3372 | |
4473 | |
3373 | =back |
4474 | =back |
3374 | |
4475 | |
|
|
4476 | =head4 THREAD LOCKING EXAMPLE |
|
|
4477 | |
|
|
4478 | Here is a fictitious example of how to run an event loop in a different |
|
|
4479 | thread than where callbacks are being invoked and watchers are |
|
|
4480 | created/added/removed. |
|
|
4481 | |
|
|
4482 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4483 | which uses exactly this technique (which is suited for many high-level |
|
|
4484 | languages). |
|
|
4485 | |
|
|
4486 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4487 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4488 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4489 | |
|
|
4490 | First, you need to associate some data with the event loop: |
|
|
4491 | |
|
|
4492 | typedef struct { |
|
|
4493 | mutex_t lock; /* global loop lock */ |
|
|
4494 | ev_async async_w; |
|
|
4495 | thread_t tid; |
|
|
4496 | cond_t invoke_cv; |
|
|
4497 | } userdata; |
|
|
4498 | |
|
|
4499 | void prepare_loop (EV_P) |
|
|
4500 | { |
|
|
4501 | // for simplicity, we use a static userdata struct. |
|
|
4502 | static userdata u; |
|
|
4503 | |
|
|
4504 | ev_async_init (&u->async_w, async_cb); |
|
|
4505 | ev_async_start (EV_A_ &u->async_w); |
|
|
4506 | |
|
|
4507 | pthread_mutex_init (&u->lock, 0); |
|
|
4508 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4509 | |
|
|
4510 | // now associate this with the loop |
|
|
4511 | ev_set_userdata (EV_A_ u); |
|
|
4512 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4513 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4514 | |
|
|
4515 | // then create the thread running ev_loop |
|
|
4516 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4517 | } |
|
|
4518 | |
|
|
4519 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4520 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4521 | that might have been added: |
|
|
4522 | |
|
|
4523 | static void |
|
|
4524 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4525 | { |
|
|
4526 | // just used for the side effects |
|
|
4527 | } |
|
|
4528 | |
|
|
4529 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4530 | protecting the loop data, respectively. |
|
|
4531 | |
|
|
4532 | static void |
|
|
4533 | l_release (EV_P) |
|
|
4534 | { |
|
|
4535 | userdata *u = ev_userdata (EV_A); |
|
|
4536 | pthread_mutex_unlock (&u->lock); |
|
|
4537 | } |
|
|
4538 | |
|
|
4539 | static void |
|
|
4540 | l_acquire (EV_P) |
|
|
4541 | { |
|
|
4542 | userdata *u = ev_userdata (EV_A); |
|
|
4543 | pthread_mutex_lock (&u->lock); |
|
|
4544 | } |
|
|
4545 | |
|
|
4546 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4547 | into C<ev_run>: |
|
|
4548 | |
|
|
4549 | void * |
|
|
4550 | l_run (void *thr_arg) |
|
|
4551 | { |
|
|
4552 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4553 | |
|
|
4554 | l_acquire (EV_A); |
|
|
4555 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4556 | ev_run (EV_A_ 0); |
|
|
4557 | l_release (EV_A); |
|
|
4558 | |
|
|
4559 | return 0; |
|
|
4560 | } |
|
|
4561 | |
|
|
4562 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4563 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4564 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4565 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4566 | and b) skipping inter-thread-communication when there are no pending |
|
|
4567 | watchers is very beneficial): |
|
|
4568 | |
|
|
4569 | static void |
|
|
4570 | l_invoke (EV_P) |
|
|
4571 | { |
|
|
4572 | userdata *u = ev_userdata (EV_A); |
|
|
4573 | |
|
|
4574 | while (ev_pending_count (EV_A)) |
|
|
4575 | { |
|
|
4576 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4577 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4578 | } |
|
|
4579 | } |
|
|
4580 | |
|
|
4581 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4582 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4583 | thread to continue: |
|
|
4584 | |
|
|
4585 | static void |
|
|
4586 | real_invoke_pending (EV_P) |
|
|
4587 | { |
|
|
4588 | userdata *u = ev_userdata (EV_A); |
|
|
4589 | |
|
|
4590 | pthread_mutex_lock (&u->lock); |
|
|
4591 | ev_invoke_pending (EV_A); |
|
|
4592 | pthread_cond_signal (&u->invoke_cv); |
|
|
4593 | pthread_mutex_unlock (&u->lock); |
|
|
4594 | } |
|
|
4595 | |
|
|
4596 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4597 | event loop, you will now have to lock: |
|
|
4598 | |
|
|
4599 | ev_timer timeout_watcher; |
|
|
4600 | userdata *u = ev_userdata (EV_A); |
|
|
4601 | |
|
|
4602 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4603 | |
|
|
4604 | pthread_mutex_lock (&u->lock); |
|
|
4605 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4606 | ev_async_send (EV_A_ &u->async_w); |
|
|
4607 | pthread_mutex_unlock (&u->lock); |
|
|
4608 | |
|
|
4609 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4610 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4611 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4612 | watchers in the next event loop iteration. |
|
|
4613 | |
3375 | =head3 COROUTINES |
4614 | =head3 COROUTINES |
3376 | |
4615 | |
3377 | Libev is very accommodating to coroutines ("cooperative threads"): |
4616 | Libev is very accommodating to coroutines ("cooperative threads"): |
3378 | libev fully supports nesting calls to its functions from different |
4617 | libev fully supports nesting calls to its functions from different |
3379 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4618 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3380 | different coroutines, and switch freely between both coroutines running the |
4619 | different coroutines, and switch freely between both coroutines running |
3381 | loop, as long as you don't confuse yourself). The only exception is that |
4620 | the loop, as long as you don't confuse yourself). The only exception is |
3382 | you must not do this from C<ev_periodic> reschedule callbacks. |
4621 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3383 | |
4622 | |
3384 | Care has been taken to ensure that libev does not keep local state inside |
4623 | Care has been taken to ensure that libev does not keep local state inside |
3385 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
4624 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3386 | they do not clal any callbacks. |
4625 | they do not call any callbacks. |
3387 | |
4626 | |
3388 | =head2 COMPILER WARNINGS |
4627 | =head2 COMPILER WARNINGS |
3389 | |
4628 | |
3390 | Depending on your compiler and compiler settings, you might get no or a |
4629 | Depending on your compiler and compiler settings, you might get no or a |
3391 | lot of warnings when compiling libev code. Some people are apparently |
4630 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3401 | maintainable. |
4640 | maintainable. |
3402 | |
4641 | |
3403 | And of course, some compiler warnings are just plain stupid, or simply |
4642 | And of course, some compiler warnings are just plain stupid, or simply |
3404 | wrong (because they don't actually warn about the condition their message |
4643 | wrong (because they don't actually warn about the condition their message |
3405 | seems to warn about). For example, certain older gcc versions had some |
4644 | seems to warn about). For example, certain older gcc versions had some |
3406 | warnings that resulted an extreme number of false positives. These have |
4645 | warnings that resulted in an extreme number of false positives. These have |
3407 | been fixed, but some people still insist on making code warn-free with |
4646 | been fixed, but some people still insist on making code warn-free with |
3408 | such buggy versions. |
4647 | such buggy versions. |
3409 | |
4648 | |
3410 | While libev is written to generate as few warnings as possible, |
4649 | While libev is written to generate as few warnings as possible, |
3411 | "warn-free" code is not a goal, and it is recommended not to build libev |
4650 | "warn-free" code is not a goal, and it is recommended not to build libev |
… | |
… | |
3425 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4664 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3426 | ==2274== possibly lost: 0 bytes in 0 blocks. |
4665 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3427 | ==2274== still reachable: 256 bytes in 1 blocks. |
4666 | ==2274== still reachable: 256 bytes in 1 blocks. |
3428 | |
4667 | |
3429 | Then there is no memory leak, just as memory accounted to global variables |
4668 | Then there is no memory leak, just as memory accounted to global variables |
3430 | is not a memleak - the memory is still being refernced, and didn't leak. |
4669 | is not a memleak - the memory is still being referenced, and didn't leak. |
3431 | |
4670 | |
3432 | Similarly, under some circumstances, valgrind might report kernel bugs |
4671 | Similarly, under some circumstances, valgrind might report kernel bugs |
3433 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
4672 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3434 | although an acceptable workaround has been found here), or it might be |
4673 | although an acceptable workaround has been found here), or it might be |
3435 | confused. |
4674 | confused. |
… | |
… | |
3447 | I suggest using suppression lists. |
4686 | I suggest using suppression lists. |
3448 | |
4687 | |
3449 | |
4688 | |
3450 | =head1 PORTABILITY NOTES |
4689 | =head1 PORTABILITY NOTES |
3451 | |
4690 | |
|
|
4691 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
|
|
4692 | |
|
|
4693 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4694 | interfaces but I<disables> them by default. |
|
|
4695 | |
|
|
4696 | That means that libev compiled in the default environment doesn't support |
|
|
4697 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
|
|
4698 | |
|
|
4699 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4700 | by enabling the large file API, which makes them incompatible with the |
|
|
4701 | standard libev compiled for their system. |
|
|
4702 | |
|
|
4703 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4704 | suddenly make it incompatible to the default compile time environment, |
|
|
4705 | i.e. all programs not using special compile switches. |
|
|
4706 | |
|
|
4707 | =head2 OS/X AND DARWIN BUGS |
|
|
4708 | |
|
|
4709 | The whole thing is a bug if you ask me - basically any system interface |
|
|
4710 | you touch is broken, whether it is locales, poll, kqueue or even the |
|
|
4711 | OpenGL drivers. |
|
|
4712 | |
|
|
4713 | =head3 C<kqueue> is buggy |
|
|
4714 | |
|
|
4715 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4716 | only sockets, many support pipes. |
|
|
4717 | |
|
|
4718 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4719 | rotten platform, but of course you can still ask for it when creating a |
|
|
4720 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4721 | probably going to work well. |
|
|
4722 | |
|
|
4723 | =head3 C<poll> is buggy |
|
|
4724 | |
|
|
4725 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4726 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4727 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4728 | |
|
|
4729 | Libev tries to work around this by not using C<poll> by default on |
|
|
4730 | this rotten platform, but of course you can still ask for it when creating |
|
|
4731 | a loop. |
|
|
4732 | |
|
|
4733 | =head3 C<select> is buggy |
|
|
4734 | |
|
|
4735 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4736 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4737 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4738 | you use more. |
|
|
4739 | |
|
|
4740 | There is an undocumented "workaround" for this - defining |
|
|
4741 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4742 | work on OS/X. |
|
|
4743 | |
|
|
4744 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4745 | |
|
|
4746 | =head3 C<errno> reentrancy |
|
|
4747 | |
|
|
4748 | The default compile environment on Solaris is unfortunately so |
|
|
4749 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4750 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4751 | defined by default. A valid, if stupid, implementation choice. |
|
|
4752 | |
|
|
4753 | If you want to use libev in threaded environments you have to make sure |
|
|
4754 | it's compiled with C<_REENTRANT> defined. |
|
|
4755 | |
|
|
4756 | =head3 Event port backend |
|
|
4757 | |
|
|
4758 | The scalable event interface for Solaris is called "event |
|
|
4759 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4760 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4761 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4762 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4763 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4764 | great. |
|
|
4765 | |
|
|
4766 | If you can't get it to work, you can try running the program by setting |
|
|
4767 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4768 | C<select> backends. |
|
|
4769 | |
|
|
4770 | =head2 AIX POLL BUG |
|
|
4771 | |
|
|
4772 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4773 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4774 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4775 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4776 | |
3452 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4777 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4778 | |
|
|
4779 | =head3 General issues |
3453 | |
4780 | |
3454 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4781 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3455 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4782 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3456 | model. Libev still offers limited functionality on this platform in |
4783 | model. Libev still offers limited functionality on this platform in |
3457 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4784 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3458 | descriptors. This only applies when using Win32 natively, not when using |
4785 | descriptors. This only applies when using Win32 natively, not when using |
3459 | e.g. cygwin. |
4786 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4787 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4788 | environment. |
3460 | |
4789 | |
3461 | Lifting these limitations would basically require the full |
4790 | Lifting these limitations would basically require the full |
3462 | re-implementation of the I/O system. If you are into these kinds of |
4791 | re-implementation of the I/O system. If you are into this kind of thing, |
3463 | things, then note that glib does exactly that for you in a very portable |
4792 | then note that glib does exactly that for you in a very portable way (note |
3464 | way (note also that glib is the slowest event library known to man). |
4793 | also that glib is the slowest event library known to man). |
3465 | |
4794 | |
3466 | There is no supported compilation method available on windows except |
4795 | There is no supported compilation method available on windows except |
3467 | embedding it into other applications. |
4796 | embedding it into other applications. |
|
|
4797 | |
|
|
4798 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4799 | tries its best, but under most conditions, signals will simply not work. |
3468 | |
4800 | |
3469 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4801 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3470 | accept large writes: instead of resulting in a partial write, windows will |
4802 | accept large writes: instead of resulting in a partial write, windows will |
3471 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4803 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3472 | so make sure you only write small amounts into your sockets (less than a |
4804 | so make sure you only write small amounts into your sockets (less than a |
… | |
… | |
3477 | the abysmal performance of winsockets, using a large number of sockets |
4809 | the abysmal performance of winsockets, using a large number of sockets |
3478 | is not recommended (and not reasonable). If your program needs to use |
4810 | is not recommended (and not reasonable). If your program needs to use |
3479 | more than a hundred or so sockets, then likely it needs to use a totally |
4811 | more than a hundred or so sockets, then likely it needs to use a totally |
3480 | different implementation for windows, as libev offers the POSIX readiness |
4812 | different implementation for windows, as libev offers the POSIX readiness |
3481 | notification model, which cannot be implemented efficiently on windows |
4813 | notification model, which cannot be implemented efficiently on windows |
3482 | (Microsoft monopoly games). |
4814 | (due to Microsoft monopoly games). |
3483 | |
4815 | |
3484 | A typical way to use libev under windows is to embed it (see the embedding |
4816 | A typical way to use libev under windows is to embed it (see the embedding |
3485 | section for details) and use the following F<evwrap.h> header file instead |
4817 | section for details) and use the following F<evwrap.h> header file instead |
3486 | of F<ev.h>: |
4818 | of F<ev.h>: |
3487 | |
4819 | |
… | |
… | |
3494 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
4826 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3495 | |
4827 | |
3496 | #include "evwrap.h" |
4828 | #include "evwrap.h" |
3497 | #include "ev.c" |
4829 | #include "ev.c" |
3498 | |
4830 | |
3499 | =over 4 |
|
|
3500 | |
|
|
3501 | =item The winsocket select function |
4831 | =head3 The winsocket C<select> function |
3502 | |
4832 | |
3503 | The winsocket C<select> function doesn't follow POSIX in that it |
4833 | The winsocket C<select> function doesn't follow POSIX in that it |
3504 | requires socket I<handles> and not socket I<file descriptors> (it is |
4834 | requires socket I<handles> and not socket I<file descriptors> (it is |
3505 | also extremely buggy). This makes select very inefficient, and also |
4835 | also extremely buggy). This makes select very inefficient, and also |
3506 | requires a mapping from file descriptors to socket handles (the Microsoft |
4836 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3515 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4845 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3516 | |
4846 | |
3517 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4847 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3518 | complexity in the O(n²) range when using win32. |
4848 | complexity in the O(n²) range when using win32. |
3519 | |
4849 | |
3520 | =item Limited number of file descriptors |
4850 | =head3 Limited number of file descriptors |
3521 | |
4851 | |
3522 | Windows has numerous arbitrary (and low) limits on things. |
4852 | Windows has numerous arbitrary (and low) limits on things. |
3523 | |
4853 | |
3524 | Early versions of winsocket's select only supported waiting for a maximum |
4854 | Early versions of winsocket's select only supported waiting for a maximum |
3525 | of C<64> handles (probably owning to the fact that all windows kernels |
4855 | of C<64> handles (probably owning to the fact that all windows kernels |
3526 | can only wait for C<64> things at the same time internally; Microsoft |
4856 | can only wait for C<64> things at the same time internally; Microsoft |
3527 | recommends spawning a chain of threads and wait for 63 handles and the |
4857 | recommends spawning a chain of threads and wait for 63 handles and the |
3528 | previous thread in each. Great). |
4858 | previous thread in each. Sounds great!). |
3529 | |
4859 | |
3530 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4860 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3531 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4861 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3532 | call (which might be in libev or elsewhere, for example, perl does its own |
4862 | call (which might be in libev or elsewhere, for example, perl and many |
3533 | select emulation on windows). |
4863 | other interpreters do their own select emulation on windows). |
3534 | |
4864 | |
3535 | Another limit is the number of file descriptors in the Microsoft runtime |
4865 | Another limit is the number of file descriptors in the Microsoft runtime |
3536 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4866 | libraries, which by default is C<64> (there must be a hidden I<64> |
3537 | or something like this inside Microsoft). You can increase this by calling |
4867 | fetish or something like this inside Microsoft). You can increase this |
3538 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4868 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3539 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4869 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3540 | libraries. |
|
|
3541 | |
|
|
3542 | This might get you to about C<512> or C<2048> sockets (depending on |
4870 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3543 | windows version and/or the phase of the moon). To get more, you need to |
4871 | (depending on windows version and/or the phase of the moon). To get more, |
3544 | wrap all I/O functions and provide your own fd management, but the cost of |
4872 | you need to wrap all I/O functions and provide your own fd management, but |
3545 | calling select (O(n²)) will likely make this unworkable. |
4873 | the cost of calling select (O(n²)) will likely make this unworkable. |
3546 | |
|
|
3547 | =back |
|
|
3548 | |
4874 | |
3549 | =head2 PORTABILITY REQUIREMENTS |
4875 | =head2 PORTABILITY REQUIREMENTS |
3550 | |
4876 | |
3551 | In addition to a working ISO-C implementation and of course the |
4877 | In addition to a working ISO-C implementation and of course the |
3552 | backend-specific APIs, libev relies on a few additional extensions: |
4878 | backend-specific APIs, libev relies on a few additional extensions: |
… | |
… | |
3559 | Libev assumes not only that all watcher pointers have the same internal |
4885 | Libev assumes not only that all watcher pointers have the same internal |
3560 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
4886 | structure (guaranteed by POSIX but not by ISO C for example), but it also |
3561 | assumes that the same (machine) code can be used to call any watcher |
4887 | assumes that the same (machine) code can be used to call any watcher |
3562 | callback: The watcher callbacks have different type signatures, but libev |
4888 | callback: The watcher callbacks have different type signatures, but libev |
3563 | calls them using an C<ev_watcher *> internally. |
4889 | calls them using an C<ev_watcher *> internally. |
|
|
4890 | |
|
|
4891 | =item pointer accesses must be thread-atomic |
|
|
4892 | |
|
|
4893 | Accessing a pointer value must be atomic, it must both be readable and |
|
|
4894 | writable in one piece - this is the case on all current architectures. |
3564 | |
4895 | |
3565 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4896 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3566 | |
4897 | |
3567 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4898 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3568 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
4899 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
… | |
… | |
3591 | watchers. |
4922 | watchers. |
3592 | |
4923 | |
3593 | =item C<double> must hold a time value in seconds with enough accuracy |
4924 | =item C<double> must hold a time value in seconds with enough accuracy |
3594 | |
4925 | |
3595 | The type C<double> is used to represent timestamps. It is required to |
4926 | The type C<double> is used to represent timestamps. It is required to |
3596 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4927 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3597 | enough for at least into the year 4000. This requirement is fulfilled by |
4928 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4929 | (the design goal for libev). This requirement is overfulfilled by |
3598 | implementations implementing IEEE 754 (basically all existing ones). |
4930 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4931 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3599 | |
4932 | |
3600 | =back |
4933 | =back |
3601 | |
4934 | |
3602 | If you know of other additional requirements drop me a note. |
4935 | If you know of other additional requirements drop me a note. |
3603 | |
4936 | |
… | |
… | |
3671 | involves iterating over all running async watchers or all signal numbers. |
5004 | involves iterating over all running async watchers or all signal numbers. |
3672 | |
5005 | |
3673 | =back |
5006 | =back |
3674 | |
5007 | |
3675 | |
5008 | |
|
|
5009 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
5010 | |
|
|
5011 | The major version 4 introduced some incompatible changes to the API. |
|
|
5012 | |
|
|
5013 | At the moment, the C<ev.h> header file provides compatibility definitions |
|
|
5014 | for all changes, so most programs should still compile. The compatibility |
|
|
5015 | layer might be removed in later versions of libev, so better update to the |
|
|
5016 | new API early than late. |
|
|
5017 | |
|
|
5018 | =over 4 |
|
|
5019 | |
|
|
5020 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
5021 | |
|
|
5022 | The backward compatibility mechanism can be controlled by |
|
|
5023 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
5024 | section. |
|
|
5025 | |
|
|
5026 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
5027 | |
|
|
5028 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
5029 | |
|
|
5030 | ev_loop_destroy (EV_DEFAULT_UC); |
|
|
5031 | ev_loop_fork (EV_DEFAULT); |
|
|
5032 | |
|
|
5033 | =item function/symbol renames |
|
|
5034 | |
|
|
5035 | A number of functions and symbols have been renamed: |
|
|
5036 | |
|
|
5037 | ev_loop => ev_run |
|
|
5038 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
5039 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
5040 | |
|
|
5041 | ev_unloop => ev_break |
|
|
5042 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
5043 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
5044 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
5045 | |
|
|
5046 | EV_TIMEOUT => EV_TIMER |
|
|
5047 | |
|
|
5048 | ev_loop_count => ev_iteration |
|
|
5049 | ev_loop_depth => ev_depth |
|
|
5050 | ev_loop_verify => ev_verify |
|
|
5051 | |
|
|
5052 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
5053 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
5054 | associated constants have been renamed to not collide with the C<struct |
|
|
5055 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
5056 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
5057 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
5058 | typedef. |
|
|
5059 | |
|
|
5060 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
5061 | |
|
|
5062 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
5063 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
5064 | and work, but the library code will of course be larger. |
|
|
5065 | |
|
|
5066 | =back |
|
|
5067 | |
|
|
5068 | |
|
|
5069 | =head1 GLOSSARY |
|
|
5070 | |
|
|
5071 | =over 4 |
|
|
5072 | |
|
|
5073 | =item active |
|
|
5074 | |
|
|
5075 | A watcher is active as long as it has been started and not yet stopped. |
|
|
5076 | See L<WATCHER STATES> for details. |
|
|
5077 | |
|
|
5078 | =item application |
|
|
5079 | |
|
|
5080 | In this document, an application is whatever is using libev. |
|
|
5081 | |
|
|
5082 | =item backend |
|
|
5083 | |
|
|
5084 | The part of the code dealing with the operating system interfaces. |
|
|
5085 | |
|
|
5086 | =item callback |
|
|
5087 | |
|
|
5088 | The address of a function that is called when some event has been |
|
|
5089 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
5090 | received the event, and the actual event bitset. |
|
|
5091 | |
|
|
5092 | =item callback/watcher invocation |
|
|
5093 | |
|
|
5094 | The act of calling the callback associated with a watcher. |
|
|
5095 | |
|
|
5096 | =item event |
|
|
5097 | |
|
|
5098 | A change of state of some external event, such as data now being available |
|
|
5099 | for reading on a file descriptor, time having passed or simply not having |
|
|
5100 | any other events happening anymore. |
|
|
5101 | |
|
|
5102 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
5103 | C<EV_TIMER>). |
|
|
5104 | |
|
|
5105 | =item event library |
|
|
5106 | |
|
|
5107 | A software package implementing an event model and loop. |
|
|
5108 | |
|
|
5109 | =item event loop |
|
|
5110 | |
|
|
5111 | An entity that handles and processes external events and converts them |
|
|
5112 | into callback invocations. |
|
|
5113 | |
|
|
5114 | =item event model |
|
|
5115 | |
|
|
5116 | The model used to describe how an event loop handles and processes |
|
|
5117 | watchers and events. |
|
|
5118 | |
|
|
5119 | =item pending |
|
|
5120 | |
|
|
5121 | A watcher is pending as soon as the corresponding event has been |
|
|
5122 | detected. See L<WATCHER STATES> for details. |
|
|
5123 | |
|
|
5124 | =item real time |
|
|
5125 | |
|
|
5126 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
5127 | |
|
|
5128 | =item wall-clock time |
|
|
5129 | |
|
|
5130 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
5131 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
5132 | clock. |
|
|
5133 | |
|
|
5134 | =item watcher |
|
|
5135 | |
|
|
5136 | A data structure that describes interest in certain events. Watchers need |
|
|
5137 | to be started (attached to an event loop) before they can receive events. |
|
|
5138 | |
|
|
5139 | =back |
|
|
5140 | |
3676 | =head1 AUTHOR |
5141 | =head1 AUTHOR |
3677 | |
5142 | |
3678 | Marc Lehmann <libev@schmorp.de>. |
5143 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
|
|
5144 | Magnusson and Emanuele Giaquinta. |
3679 | |
5145 | |