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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 ABOUT LIBEV |
70 | |
84 | |
71 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
72 | file descriptor being readable or a timeout occurring), and it will manage |
86 | file descriptor being readable or a timeout occurring), and it will manage |
73 | these event sources and provide your program with events. |
87 | these event sources and provide your program with events. |
74 | |
88 | |
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84 | =head2 FEATURES |
98 | =head2 FEATURES |
85 | |
99 | |
86 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
100 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
87 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
101 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
88 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
102 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
89 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
103 | (for C<ev_stat>), Linux eventfd/signalfd (for faster and cleaner |
90 | with customised rescheduling (C<ev_periodic>), synchronous signals |
104 | inter-thread wakeup (C<ev_async>)/signal handling (C<ev_signal>)) relative |
91 | (C<ev_signal>), process status change events (C<ev_child>), and event |
105 | timers (C<ev_timer>), absolute timers with customised rescheduling |
92 | watchers dealing with the event loop mechanism itself (C<ev_idle>, |
106 | (C<ev_periodic>), synchronous signals (C<ev_signal>), process status |
93 | C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as |
107 | change events (C<ev_child>), and event watchers dealing with the event |
94 | file watchers (C<ev_stat>) and even limited support for fork events |
108 | loop mechanism itself (C<ev_idle>, C<ev_embed>, C<ev_prepare> and |
95 | (C<ev_fork>). |
109 | C<ev_check> watchers) as well as file watchers (C<ev_stat>) and even |
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110 | limited support for fork events (C<ev_fork>). |
96 | |
111 | |
97 | It also is quite fast (see this |
112 | It also is quite fast (see this |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
113 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
99 | for example). |
114 | for example). |
100 | |
115 | |
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108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
123 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
109 | this argument. |
124 | this argument. |
110 | |
125 | |
111 | =head2 TIME REPRESENTATION |
126 | =head2 TIME REPRESENTATION |
112 | |
127 | |
113 | Libev represents time as a single floating point number, representing the |
128 | Libev represents time as a single floating point number, representing |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
129 | the (fractional) number of seconds since the (POSIX) epoch (in practice |
115 | the beginning of 1970, details are complicated, don't ask). This type is |
130 | somewhere near the beginning of 1970, details are complicated, don't |
116 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
131 | ask). This type is called C<ev_tstamp>, which is what you should use |
117 | to the C<double> type in C, and when you need to do any calculations on |
132 | too. It usually aliases to the C<double> type in C. When you need to do |
118 | it, you should treat it as some floating point value. Unlike the name |
133 | any calculations on it, you should treat it as some floating point value. |
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134 | |
119 | component C<stamp> might indicate, it is also used for time differences |
135 | Unlike the name component C<stamp> might indicate, it is also used for |
120 | throughout libev. |
136 | time differences (e.g. delays) throughout libev. |
121 | |
137 | |
122 | =head1 ERROR HANDLING |
138 | =head1 ERROR HANDLING |
123 | |
139 | |
124 | Libev knows three classes of errors: operating system errors, usage errors |
140 | Libev knows three classes of errors: operating system errors, usage errors |
125 | and internal errors (bugs). |
141 | and internal errors (bugs). |
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149 | |
165 | |
150 | =item ev_tstamp ev_time () |
166 | =item ev_tstamp ev_time () |
151 | |
167 | |
152 | Returns the current time as libev would use it. Please note that the |
168 | 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 |
169 | C<ev_now> function is usually faster and also often returns the timestamp |
154 | you actually want to know. |
170 | you actually want to know. Also interesting is the combination of |
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171 | C<ev_update_now> and C<ev_now>. |
155 | |
172 | |
156 | =item ev_sleep (ev_tstamp interval) |
173 | =item ev_sleep (ev_tstamp interval) |
157 | |
174 | |
158 | Sleep for the given interval: The current thread will be blocked until |
175 | 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 |
176 | either it is interrupted or the given time interval has passed. Basically |
… | |
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176 | as this indicates an incompatible change. Minor versions are usually |
193 | as this indicates an incompatible change. Minor versions are usually |
177 | compatible to older versions, so a larger minor version alone is usually |
194 | compatible to older versions, so a larger minor version alone is usually |
178 | not a problem. |
195 | not a problem. |
179 | |
196 | |
180 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | Example: Make sure we haven't accidentally been linked against the wrong |
181 | version. |
198 | version (note, however, that this will not detect other ABI mismatches, |
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199 | such as LFS or reentrancy). |
182 | |
200 | |
183 | assert (("libev version mismatch", |
201 | assert (("libev version mismatch", |
184 | ev_version_major () == EV_VERSION_MAJOR |
202 | ev_version_major () == EV_VERSION_MAJOR |
185 | && ev_version_minor () >= EV_VERSION_MINOR)); |
203 | && ev_version_minor () >= EV_VERSION_MINOR)); |
186 | |
204 | |
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197 | assert (("sorry, no epoll, no sex", |
215 | assert (("sorry, no epoll, no sex", |
198 | ev_supported_backends () & EVBACKEND_EPOLL)); |
216 | ev_supported_backends () & EVBACKEND_EPOLL)); |
199 | |
217 | |
200 | =item unsigned int ev_recommended_backends () |
218 | =item unsigned int ev_recommended_backends () |
201 | |
219 | |
202 | Return the set of all backends compiled into this binary of libev and also |
220 | 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 |
221 | also recommended for this platform, meaning it will work for most file |
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222 | 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 |
223 | 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 |
224 | 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 |
225 | 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. |
226 | probe for if you specify no backends explicitly. |
208 | |
227 | |
209 | =item unsigned int ev_embeddable_backends () |
228 | =item unsigned int ev_embeddable_backends () |
210 | |
229 | |
211 | Returns the set of backends that are embeddable in other event loops. This |
230 | Returns the set of backends that are embeddable in other event loops. This |
212 | is the theoretical, all-platform, value. To find which backends |
231 | 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 |
232 | current system. To find which embeddable backends might be supported on |
214 | C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for |
233 | the current system, you would need to look at C<ev_embeddable_backends () |
215 | recommended ones. |
234 | & ev_supported_backends ()>, likewise for recommended ones. |
216 | |
235 | |
217 | See the description of C<ev_embed> watchers for more info. |
236 | See the description of C<ev_embed> watchers for more info. |
218 | |
237 | |
219 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
238 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) [NOT REENTRANT] |
220 | |
239 | |
221 | Sets the allocation function to use (the prototype is similar - the |
240 | 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 |
241 | 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 |
242 | 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 |
243 | when memory needs to be allocated (C<size != 0>), the library might abort |
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250 | } |
269 | } |
251 | |
270 | |
252 | ... |
271 | ... |
253 | ev_set_allocator (persistent_realloc); |
272 | ev_set_allocator (persistent_realloc); |
254 | |
273 | |
255 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); |
274 | =item ev_set_syserr_cb (void (*cb)(const char *msg)); [NOT REENTRANT] |
256 | |
275 | |
257 | Set the callback function to call on a retryable system call error (such |
276 | 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 |
277 | as failed select, poll, epoll_wait). The message is a printable string |
259 | indicating the system call or subsystem causing the problem. If this |
278 | 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 |
279 | callback is set, then libev will expect it to remedy the situation, no |
… | |
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274 | ... |
293 | ... |
275 | ev_set_syserr_cb (fatal_error); |
294 | ev_set_syserr_cb (fatal_error); |
276 | |
295 | |
277 | =back |
296 | =back |
278 | |
297 | |
279 | =head1 FUNCTIONS CONTROLLING THE EVENT LOOP |
298 | =head1 FUNCTIONS CONTROLLING EVENT LOOPS |
280 | |
299 | |
281 | An event loop is described by a C<struct ev_loop *>. The library knows two |
300 | 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 |
301 | I<not> optional in this case unless libev 3 compatibility is disabled, as |
283 | events, and dynamically created loops which do not. |
302 | libev 3 had an C<ev_loop> function colliding with the struct name). |
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303 | |
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304 | The library knows two types of such loops, the I<default> loop, which |
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305 | supports signals and child events, and dynamically created event loops |
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306 | which do not. |
284 | |
307 | |
285 | =over 4 |
308 | =over 4 |
286 | |
309 | |
287 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
310 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
288 | |
311 | |
289 | This will initialise the default event loop if it hasn't been initialised |
312 | 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 |
313 | 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 |
314 | 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). |
315 | C<ev_loop_new>. |
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316 | |
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317 | If the default loop is already initialised then this function simply |
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318 | returns it (and ignores the flags. If that is troubling you, check |
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319 | C<ev_backend ()> afterwards). Otherwise it will create it with the given |
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320 | flags, which should almost always be C<0>, unless the caller is also the |
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321 | one calling C<ev_run> or otherwise qualifies as "the main program". |
293 | |
322 | |
294 | If you don't know what event loop to use, use the one returned from this |
323 | If you don't know what event loop to use, use the one returned from this |
295 | function. |
324 | function (or via the C<EV_DEFAULT> macro). |
296 | |
325 | |
297 | Note that this function is I<not> thread-safe, so if you want to use it |
326 | 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, |
327 | from multiple threads, you have to employ some kind of mutex (note also |
299 | as loops cannot bes hared easily between threads anyway). |
328 | that this case is unlikely, as loops cannot be shared easily between |
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329 | threads anyway). |
300 | |
330 | |
301 | The default loop is the only loop that can handle C<ev_signal> and |
331 | 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 |
332 | 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 |
333 | 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 |
334 | 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 |
335 | C<SIGCHLD> signal handler I<after> calling C<ev_default_init>. |
306 | C<ev_default_init>. |
336 | |
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337 | Example: This is the most typical usage. |
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338 | |
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339 | if (!ev_default_loop (0)) |
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340 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
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341 | |
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342 | Example: Restrict libev to the select and poll backends, and do not allow |
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343 | environment settings to be taken into account: |
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344 | |
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345 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
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346 | |
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347 | Example: Use whatever libev has to offer, but make sure that kqueue is |
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348 | used if available (warning, breaks stuff, best use only with your own |
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349 | private event loop and only if you know the OS supports your types of |
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350 | fds): |
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351 | |
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352 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
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353 | |
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354 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
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355 | |
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356 | This will create and initialise a new event loop object. If the loop |
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357 | could not be initialised, returns false. |
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358 | |
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359 | Note that this function I<is> thread-safe, and one common way to use |
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360 | libev with threads is indeed to create one loop per thread, and using the |
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361 | default loop in the "main" or "initial" thread. |
307 | |
362 | |
308 | The flags argument can be used to specify special behaviour or specific |
363 | 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>). |
364 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
310 | |
365 | |
311 | The following flags are supported: |
366 | The following flags are supported: |
… | |
… | |
326 | useful to try out specific backends to test their performance, or to work |
381 | useful to try out specific backends to test their performance, or to work |
327 | around bugs. |
382 | around bugs. |
328 | |
383 | |
329 | =item C<EVFLAG_FORKCHECK> |
384 | =item C<EVFLAG_FORKCHECK> |
330 | |
385 | |
331 | Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after |
386 | 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 |
387 | make libev check for a fork in each iteration by enabling this flag. |
333 | enabling this flag. |
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334 | |
388 | |
335 | This works by calling C<getpid ()> on every iteration of the loop, |
389 | 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 |
390 | 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 |
391 | 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 |
392 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
… | |
… | |
344 | flag. |
398 | flag. |
345 | |
399 | |
346 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
400 | This flag setting cannot be overridden or specified in the C<LIBEV_FLAGS> |
347 | environment variable. |
401 | environment variable. |
348 | |
402 | |
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403 | =item C<EVFLAG_NOINOTIFY> |
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404 | |
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405 | When this flag is specified, then libev will not attempt to use the |
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406 | I<inotify> API for it's C<ev_stat> watchers. Apart from debugging and |
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407 | testing, this flag can be useful to conserve inotify file descriptors, as |
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408 | otherwise each loop using C<ev_stat> watchers consumes one inotify handle. |
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409 | |
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410 | =item C<EVFLAG_SIGNALFD> |
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411 | |
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412 | When this flag is specified, then libev will attempt to use the |
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413 | I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API |
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414 | delivers signals synchronously, which makes it both faster and might make |
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415 | it possible to get the queued signal data. It can also simplify signal |
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416 | handling with threads, as long as you properly block signals in your |
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417 | threads that are not interested in handling them. |
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418 | |
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419 | Signalfd will not be used by default as this changes your signal mask, and |
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420 | there are a lot of shoddy libraries and programs (glib's threadpool for |
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421 | example) that can't properly initialise their signal masks. |
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422 | |
349 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
423 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
350 | |
424 | |
351 | This is your standard select(2) backend. Not I<completely> standard, as |
425 | 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, |
426 | 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 |
427 | but if that fails, expect a fairly low limit on the number of fds when |
… | |
… | |
359 | writing a server, you should C<accept ()> in a loop to accept as many |
433 | writing a server, you should C<accept ()> in a loop to accept as many |
360 | connections as possible during one iteration. You might also want to have |
434 | connections as possible during one iteration. You might also want to have |
361 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
435 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
362 | readiness notifications you get per iteration. |
436 | readiness notifications you get per iteration. |
363 | |
437 | |
|
|
438 | This backend maps C<EV_READ> to the C<readfds> set and C<EV_WRITE> to the |
|
|
439 | C<writefds> set (and to work around Microsoft Windows bugs, also onto the |
|
|
440 | C<exceptfds> set on that platform). |
|
|
441 | |
364 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
442 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
365 | |
443 | |
366 | And this is your standard poll(2) backend. It's more complicated |
444 | And this is your standard poll(2) backend. It's more complicated |
367 | than select, but handles sparse fds better and has no artificial |
445 | than select, but handles sparse fds better and has no artificial |
368 | limit on the number of fds you can use (except it will slow down |
446 | limit on the number of fds you can use (except it will slow down |
369 | considerably with a lot of inactive fds). It scales similarly to select, |
447 | considerably with a lot of inactive fds). It scales similarly to select, |
370 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
448 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
371 | performance tips. |
449 | performance tips. |
372 | |
450 | |
|
|
451 | This backend maps C<EV_READ> to C<POLLIN | POLLERR | POLLHUP>, and |
|
|
452 | C<EV_WRITE> to C<POLLOUT | POLLERR | POLLHUP>. |
|
|
453 | |
373 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
454 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
|
|
455 | |
|
|
456 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
|
|
457 | kernels). |
374 | |
458 | |
375 | For few fds, this backend is a bit little slower than poll and select, |
459 | For few fds, this backend is a bit little slower than poll and select, |
376 | but it scales phenomenally better. While poll and select usually scale |
460 | but it scales phenomenally better. While poll and select usually scale |
377 | like O(total_fds) where n is the total number of fds (or the highest fd), |
461 | like O(total_fds) where n is the total number of fds (or the highest fd), |
378 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
462 | epoll scales either O(1) or O(active_fds). |
379 | of shortcomings, such as silently dropping events in some hard-to-detect |
463 | |
380 | cases and requiring a system call per fd change, no fork support and bad |
464 | The epoll mechanism deserves honorable mention as the most misdesigned |
381 | support for dup. |
465 | of the more advanced event mechanisms: mere annoyances include silently |
|
|
466 | dropping file descriptors, requiring a system call per change per file |
|
|
467 | descriptor (and unnecessary guessing of parameters), problems with dup and |
|
|
468 | so on. The biggest issue is fork races, however - if a program forks then |
|
|
469 | I<both> parent and child process have to recreate the epoll set, which can |
|
|
470 | take considerable time (one syscall per file descriptor) and is of course |
|
|
471 | hard to detect. |
|
|
472 | |
|
|
473 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
|
|
474 | of course I<doesn't>, and epoll just loves to report events for totally |
|
|
475 | I<different> file descriptors (even already closed ones, so one cannot |
|
|
476 | even remove them from the set) than registered in the set (especially |
|
|
477 | on SMP systems). Libev tries to counter these spurious notifications by |
|
|
478 | employing an additional generation counter and comparing that against the |
|
|
479 | events to filter out spurious ones, recreating the set when required. Last |
|
|
480 | not least, it also refuses to work with some file descriptors which work |
|
|
481 | perfectly fine with C<select> (files, many character devices...). |
382 | |
482 | |
383 | While stopping, setting and starting an I/O watcher in the same iteration |
483 | While stopping, setting and starting an I/O watcher in the same iteration |
384 | will result in some caching, there is still a system call per such incident |
484 | will result in some caching, there is still a system call per such |
385 | (because the fd could point to a different file description now), so its |
485 | incident (because the same I<file descriptor> could point to a different |
386 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
486 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
387 | very well if you register events for both fds. |
487 | file descriptors might not work very well if you register events for both |
388 | |
488 | file descriptors. |
389 | Please note that epoll sometimes generates spurious notifications, so you |
|
|
390 | need to use non-blocking I/O or other means to avoid blocking when no data |
|
|
391 | (or space) is available. |
|
|
392 | |
489 | |
393 | Best performance from this backend is achieved by not unregistering all |
490 | Best performance from this backend is achieved by not unregistering all |
394 | watchers for a file descriptor until it has been closed, if possible, i.e. |
491 | watchers for a file descriptor until it has been closed, if possible, |
395 | keep at least one watcher active per fd at all times. |
492 | i.e. keep at least one watcher active per fd at all times. Stopping and |
|
|
493 | starting a watcher (without re-setting it) also usually doesn't cause |
|
|
494 | extra overhead. A fork can both result in spurious notifications as well |
|
|
495 | as in libev having to destroy and recreate the epoll object, which can |
|
|
496 | take considerable time and thus should be avoided. |
|
|
497 | |
|
|
498 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
499 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
500 | the usage. So sad. |
396 | |
501 | |
397 | While nominally embeddable in other event loops, this feature is broken in |
502 | While nominally embeddable in other event loops, this feature is broken in |
398 | all kernel versions tested so far. |
503 | all kernel versions tested so far. |
|
|
504 | |
|
|
505 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
506 | C<EVBACKEND_POLL>. |
399 | |
507 | |
400 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
508 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
401 | |
509 | |
402 | Kqueue deserves special mention, as at the time of this writing, it |
510 | Kqueue deserves special mention, as at the time of this writing, it |
403 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
511 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
404 | with anything but sockets and pipes, except on Darwin, where of course |
512 | with anything but sockets and pipes, except on Darwin, where of course |
405 | it's completely useless). For this reason it's not being "auto-detected" |
513 | it's completely useless). Unlike epoll, however, whose brokenness |
|
|
514 | is by design, these kqueue bugs can (and eventually will) be fixed |
|
|
515 | without API changes to existing programs. For this reason it's not being |
406 | unless you explicitly specify it explicitly in the flags (i.e. using |
516 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
407 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
517 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
408 | system like NetBSD. |
518 | system like NetBSD. |
409 | |
519 | |
410 | You still can embed kqueue into a normal poll or select backend and use it |
520 | You still can embed kqueue into a normal poll or select backend and use it |
411 | only for sockets (after having made sure that sockets work with kqueue on |
521 | only for sockets (after having made sure that sockets work with kqueue on |
… | |
… | |
413 | |
523 | |
414 | It scales in the same way as the epoll backend, but the interface to the |
524 | It scales in the same way as the epoll backend, but the interface to the |
415 | kernel is more efficient (which says nothing about its actual speed, of |
525 | kernel is more efficient (which says nothing about its actual speed, of |
416 | course). While stopping, setting and starting an I/O watcher does never |
526 | course). While stopping, setting and starting an I/O watcher does never |
417 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
527 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
418 | two event changes per incident, support for C<fork ()> is very bad and it |
528 | two event changes per incident. Support for C<fork ()> is very bad (but |
419 | drops fds silently in similarly hard-to-detect cases. |
529 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
530 | cases |
420 | |
531 | |
421 | This backend usually performs well under most conditions. |
532 | This backend usually performs well under most conditions. |
422 | |
533 | |
423 | While nominally embeddable in other event loops, this doesn't work |
534 | While nominally embeddable in other event loops, this doesn't work |
424 | everywhere, so you might need to test for this. And since it is broken |
535 | everywhere, so you might need to test for this. And since it is broken |
425 | almost everywhere, you should only use it when you have a lot of sockets |
536 | almost everywhere, you should only use it when you have a lot of sockets |
426 | (for which it usually works), by embedding it into another event loop |
537 | (for which it usually works), by embedding it into another event loop |
427 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
538 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
428 | sockets. |
539 | also broken on OS X)) and, did I mention it, using it only for sockets. |
|
|
540 | |
|
|
541 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
|
|
542 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
|
|
543 | C<NOTE_EOF>. |
429 | |
544 | |
430 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
545 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
431 | |
546 | |
432 | This is not implemented yet (and might never be, unless you send me an |
547 | This is not implemented yet (and might never be, unless you send me an |
433 | implementation). According to reports, C</dev/poll> only supports sockets |
548 | implementation). According to reports, C</dev/poll> only supports sockets |
… | |
… | |
446 | While this backend scales well, it requires one system call per active |
561 | While this backend scales well, it requires one system call per active |
447 | file descriptor per loop iteration. For small and medium numbers of file |
562 | file descriptor per loop iteration. For small and medium numbers of file |
448 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
563 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
449 | might perform better. |
564 | might perform better. |
450 | |
565 | |
451 | On the positive side, ignoring the spurious readiness notifications, this |
566 | On the positive side, with the exception of the spurious readiness |
452 | backend actually performed to specification in all tests and is fully |
567 | notifications, this backend actually performed fully to specification |
453 | embeddable, which is a rare feat among the OS-specific backends. |
568 | in all tests and is fully embeddable, which is a rare feat among the |
|
|
569 | OS-specific backends (I vastly prefer correctness over speed hacks). |
|
|
570 | |
|
|
571 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
|
|
572 | C<EVBACKEND_POLL>. |
454 | |
573 | |
455 | =item C<EVBACKEND_ALL> |
574 | =item C<EVBACKEND_ALL> |
456 | |
575 | |
457 | Try all backends (even potentially broken ones that wouldn't be tried |
576 | Try all backends (even potentially broken ones that wouldn't be tried |
458 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
577 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
… | |
… | |
460 | |
579 | |
461 | It is definitely not recommended to use this flag. |
580 | It is definitely not recommended to use this flag. |
462 | |
581 | |
463 | =back |
582 | =back |
464 | |
583 | |
465 | If one or more of these are or'ed into the flags value, then only these |
584 | If one or more of the backend flags are or'ed into the flags value, |
466 | backends will be tried (in the reverse order as listed here). If none are |
585 | then only these backends will be tried (in the reverse order as listed |
467 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
586 | here). If none are specified, all backends in C<ev_recommended_backends |
468 | |
587 | ()> will be tried. |
469 | The most typical usage is like this: |
|
|
470 | |
|
|
471 | if (!ev_default_loop (0)) |
|
|
472 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
|
|
473 | |
|
|
474 | Restrict libev to the select and poll backends, and do not allow |
|
|
475 | environment settings to be taken into account: |
|
|
476 | |
|
|
477 | ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
|
|
478 | |
|
|
479 | Use whatever libev has to offer, but make sure that kqueue is used if |
|
|
480 | available (warning, breaks stuff, best use only with your own private |
|
|
481 | event loop and only if you know the OS supports your types of fds): |
|
|
482 | |
|
|
483 | ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
|
|
484 | |
|
|
485 | =item struct ev_loop *ev_loop_new (unsigned int flags) |
|
|
486 | |
|
|
487 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
|
|
488 | always distinct from the default loop. Unlike the default loop, it cannot |
|
|
489 | handle signal and child watchers, and attempts to do so will be greeted by |
|
|
490 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
491 | |
|
|
492 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
493 | libev with threads is indeed to create one loop per thread, and using the |
|
|
494 | default loop in the "main" or "initial" thread. |
|
|
495 | |
588 | |
496 | Example: Try to create a event loop that uses epoll and nothing else. |
589 | Example: Try to create a event loop that uses epoll and nothing else. |
497 | |
590 | |
498 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
591 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
499 | if (!epoller) |
592 | if (!epoller) |
500 | fatal ("no epoll found here, maybe it hides under your chair"); |
593 | fatal ("no epoll found here, maybe it hides under your chair"); |
501 | |
594 | |
502 | =item ev_default_destroy () |
595 | =item ev_loop_destroy (loop) |
503 | |
596 | |
504 | Destroys the default loop again (frees all memory and kernel state |
597 | Destroys an event loop object (frees all memory and kernel state |
505 | etc.). None of the active event watchers will be stopped in the normal |
598 | etc.). None of the active event watchers will be stopped in the normal |
506 | sense, so e.g. C<ev_is_active> might still return true. It is your |
599 | sense, so e.g. C<ev_is_active> might still return true. It is your |
507 | responsibility to either stop all watchers cleanly yourself I<before> |
600 | responsibility to either stop all watchers cleanly yourself I<before> |
508 | calling this function, or cope with the fact afterwards (which is usually |
601 | calling this function, or cope with the fact afterwards (which is usually |
509 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
602 | the easiest thing, you can just ignore the watchers and/or C<free ()> them |
510 | for example). |
603 | for example). |
511 | |
604 | |
512 | Note that certain global state, such as signal state, will not be freed by |
605 | Note that certain global state, such as signal state (and installed signal |
513 | this function, and related watchers (such as signal and child watchers) |
606 | handlers), will not be freed by this function, and related watchers (such |
514 | would need to be stopped manually. |
607 | as signal and child watchers) would need to be stopped manually. |
515 | |
608 | |
516 | In general it is not advisable to call this function except in the |
609 | This function is normally used on loop objects allocated by |
517 | rare occasion where you really need to free e.g. the signal handling |
610 | C<ev_loop_new>, but it can also be used on the default loop returned by |
|
|
611 | C<ev_default_loop>, in which case it is not thread-safe. |
|
|
612 | |
|
|
613 | Note that it is not advisable to call this function on the default loop |
|
|
614 | except in the rare occasion where you really need to free it's resources. |
518 | pipe fds. If you need dynamically allocated loops it is better to use |
615 | If you need dynamically allocated loops it is better to use C<ev_loop_new> |
519 | C<ev_loop_new> and C<ev_loop_destroy>). |
616 | and C<ev_loop_destroy>. |
520 | |
617 | |
521 | =item ev_loop_destroy (loop) |
618 | =item ev_loop_fork (loop) |
522 | |
619 | |
523 | Like C<ev_default_destroy>, but destroys an event loop created by an |
|
|
524 | earlier call to C<ev_loop_new>. |
|
|
525 | |
|
|
526 | =item ev_default_fork () |
|
|
527 | |
|
|
528 | This function sets a flag that causes subsequent C<ev_loop> iterations |
620 | This function sets a flag that causes subsequent C<ev_run> iterations to |
529 | to reinitialise the kernel state for backends that have one. Despite the |
621 | reinitialise the kernel state for backends that have one. Despite the |
530 | name, you can call it anytime, but it makes most sense after forking, in |
622 | name, you can call it anytime, but it makes most sense after forking, in |
531 | the child process (or both child and parent, but that again makes little |
623 | the child process. You I<must> call it (or use C<EVFLAG_FORKCHECK>) in the |
532 | sense). You I<must> call it in the child before using any of the libev |
624 | child before resuming or calling C<ev_run>. |
533 | functions, and it will only take effect at the next C<ev_loop> iteration. |
625 | |
|
|
626 | Again, you I<have> to call it on I<any> loop that you want to re-use after |
|
|
627 | a fork, I<even if you do not plan to use the loop in the parent>. This is |
|
|
628 | because some kernel interfaces *cough* I<kqueue> *cough* do funny things |
|
|
629 | during fork. |
534 | |
630 | |
535 | On the other hand, you only need to call this function in the child |
631 | On the other hand, you only need to call this function in the child |
536 | process if and only if you want to use the event library in the child. If |
632 | process if and only if you want to use the event loop in the child. If |
537 | you just fork+exec, you don't have to call it at all. |
633 | you just fork+exec or create a new loop in the child, you don't have to |
|
|
634 | call it at all (in fact, C<epoll> is so badly broken that it makes a |
|
|
635 | difference, but libev will usually detect this case on its own and do a |
|
|
636 | costly reset of the backend). |
538 | |
637 | |
539 | The function itself is quite fast and it's usually not a problem to call |
638 | The function itself is quite fast and it's usually not a problem to call |
540 | it just in case after a fork. To make this easy, the function will fit in |
639 | it just in case after a fork. |
541 | quite nicely into a call to C<pthread_atfork>: |
|
|
542 | |
640 | |
|
|
641 | Example: Automate calling C<ev_loop_fork> on the default loop when |
|
|
642 | using pthreads. |
|
|
643 | |
|
|
644 | static void |
|
|
645 | post_fork_child (void) |
|
|
646 | { |
|
|
647 | ev_loop_fork (EV_DEFAULT); |
|
|
648 | } |
|
|
649 | |
|
|
650 | ... |
543 | pthread_atfork (0, 0, ev_default_fork); |
651 | pthread_atfork (0, 0, post_fork_child); |
544 | |
|
|
545 | =item ev_loop_fork (loop) |
|
|
546 | |
|
|
547 | Like C<ev_default_fork>, but acts on an event loop created by |
|
|
548 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
|
|
549 | after fork, and how you do this is entirely your own problem. |
|
|
550 | |
652 | |
551 | =item int ev_is_default_loop (loop) |
653 | =item int ev_is_default_loop (loop) |
552 | |
654 | |
553 | Returns true when the given loop actually is the default loop, false otherwise. |
655 | Returns true when the given loop is, in fact, the default loop, and false |
|
|
656 | otherwise. |
554 | |
657 | |
555 | =item unsigned int ev_loop_count (loop) |
658 | =item unsigned int ev_iteration (loop) |
556 | |
659 | |
557 | Returns the count of loop iterations for the loop, which is identical to |
660 | Returns the current iteration count for the event loop, which is identical |
558 | the number of times libev did poll for new events. It starts at C<0> and |
661 | to the number of times libev did poll for new events. It starts at C<0> |
559 | happily wraps around with enough iterations. |
662 | and happily wraps around with enough iterations. |
560 | |
663 | |
561 | This value can sometimes be useful as a generation counter of sorts (it |
664 | This value can sometimes be useful as a generation counter of sorts (it |
562 | "ticks" the number of loop iterations), as it roughly corresponds with |
665 | "ticks" the number of loop iterations), as it roughly corresponds with |
563 | C<ev_prepare> and C<ev_check> calls. |
666 | C<ev_prepare> and C<ev_check> calls - and is incremented between the |
|
|
667 | prepare and check phases. |
|
|
668 | |
|
|
669 | =item unsigned int ev_depth (loop) |
|
|
670 | |
|
|
671 | Returns the number of times C<ev_run> was entered minus the number of |
|
|
672 | times C<ev_run> was exited, in other words, the recursion depth. |
|
|
673 | |
|
|
674 | Outside C<ev_run>, this number is zero. In a callback, this number is |
|
|
675 | C<1>, unless C<ev_run> was invoked recursively (or from another thread), |
|
|
676 | in which case it is higher. |
|
|
677 | |
|
|
678 | Leaving C<ev_run> abnormally (setjmp/longjmp, cancelling the thread |
|
|
679 | etc.), doesn't count as "exit" - consider this as a hint to avoid such |
|
|
680 | ungentleman-like behaviour unless it's really convenient. |
564 | |
681 | |
565 | =item unsigned int ev_backend (loop) |
682 | =item unsigned int ev_backend (loop) |
566 | |
683 | |
567 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
684 | Returns one of the C<EVBACKEND_*> flags indicating the event backend in |
568 | use. |
685 | use. |
… | |
… | |
577 | |
694 | |
578 | =item ev_now_update (loop) |
695 | =item ev_now_update (loop) |
579 | |
696 | |
580 | Establishes the current time by querying the kernel, updating the time |
697 | Establishes the current time by querying the kernel, updating the time |
581 | returned by C<ev_now ()> in the progress. This is a costly operation and |
698 | returned by C<ev_now ()> in the progress. This is a costly operation and |
582 | is usually done automatically within C<ev_loop ()>. |
699 | is usually done automatically within C<ev_run ()>. |
583 | |
700 | |
584 | This function is rarely useful, but when some event callback runs for a |
701 | This function is rarely useful, but when some event callback runs for a |
585 | very long time without entering the event loop, updating libev's idea of |
702 | very long time without entering the event loop, updating libev's idea of |
586 | the current time is a good idea. |
703 | the current time is a good idea. |
587 | |
704 | |
588 | See also "The special problem of time updates" in the C<ev_timer> section. |
705 | See also L<The special problem of time updates> in the C<ev_timer> section. |
589 | |
706 | |
|
|
707 | =item ev_suspend (loop) |
|
|
708 | |
|
|
709 | =item ev_resume (loop) |
|
|
710 | |
|
|
711 | These two functions suspend and resume an event loop, for use when the |
|
|
712 | loop is not used for a while and timeouts should not be processed. |
|
|
713 | |
|
|
714 | A typical use case would be an interactive program such as a game: When |
|
|
715 | the user presses C<^Z> to suspend the game and resumes it an hour later it |
|
|
716 | would be best to handle timeouts as if no time had actually passed while |
|
|
717 | the program was suspended. This can be achieved by calling C<ev_suspend> |
|
|
718 | in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling |
|
|
719 | C<ev_resume> directly afterwards to resume timer processing. |
|
|
720 | |
|
|
721 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
|
|
722 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
|
|
723 | will be rescheduled (that is, they will lose any events that would have |
|
|
724 | occurred while suspended). |
|
|
725 | |
|
|
726 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
|
|
727 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
|
|
728 | without a previous call to C<ev_suspend>. |
|
|
729 | |
|
|
730 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
|
|
731 | event loop time (see C<ev_now_update>). |
|
|
732 | |
590 | =item ev_loop (loop, int flags) |
733 | =item ev_run (loop, int flags) |
591 | |
734 | |
592 | Finally, this is it, the event handler. This function usually is called |
735 | Finally, this is it, the event handler. This function usually is called |
593 | after you initialised all your watchers and you want to start handling |
736 | after you have initialised all your watchers and you want to start |
594 | events. |
737 | handling events. It will ask the operating system for any new events, call |
|
|
738 | the watcher callbacks, an then repeat the whole process indefinitely: This |
|
|
739 | is why event loops are called I<loops>. |
595 | |
740 | |
596 | If the flags argument is specified as C<0>, it will not return until |
741 | If the flags argument is specified as C<0>, it will keep handling events |
597 | either no event watchers are active anymore or C<ev_unloop> was called. |
742 | until either no event watchers are active anymore or C<ev_break> was |
|
|
743 | called. |
598 | |
744 | |
599 | Please note that an explicit C<ev_unloop> is usually better than |
745 | Please note that an explicit C<ev_break> is usually better than |
600 | relying on all watchers to be stopped when deciding when a program has |
746 | relying on all watchers to be stopped when deciding when a program has |
601 | finished (especially in interactive programs), but having a program that |
747 | finished (especially in interactive programs), but having a program |
602 | automatically loops as long as it has to and no longer by virtue of |
748 | that automatically loops as long as it has to and no longer by virtue |
603 | relying on its watchers stopping correctly is a thing of beauty. |
749 | of relying on its watchers stopping correctly, that is truly a thing of |
|
|
750 | beauty. |
604 | |
751 | |
605 | A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle |
752 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
606 | those events and any outstanding ones, but will not block your process in |
753 | those events and any already outstanding ones, but will not wait and |
607 | case there are no events and will return after one iteration of the loop. |
754 | block your process in case there are no events and will return after one |
|
|
755 | iteration of the loop. This is sometimes useful to poll and handle new |
|
|
756 | events while doing lengthy calculations, to keep the program responsive. |
608 | |
757 | |
609 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
758 | A flags value of C<EVRUN_ONCE> will look for new events (waiting if |
610 | necessary) and will handle those and any outstanding ones. It will block |
759 | necessary) and will handle those and any already outstanding ones. It |
611 | your process until at least one new event arrives, and will return after |
760 | will block your process until at least one new event arrives (which could |
612 | one iteration of the loop. This is useful if you are waiting for some |
761 | be an event internal to libev itself, so there is no guarantee that a |
613 | external event in conjunction with something not expressible using other |
762 | user-registered callback will be called), and will return after one |
|
|
763 | iteration of the loop. |
|
|
764 | |
|
|
765 | This is useful if you are waiting for some external event in conjunction |
|
|
766 | with something not expressible using other libev watchers (i.e. "roll your |
614 | libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is |
767 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
615 | usually a better approach for this kind of thing. |
768 | usually a better approach for this kind of thing. |
616 | |
769 | |
617 | Here are the gory details of what C<ev_loop> does: |
770 | Here are the gory details of what C<ev_run> does: |
618 | |
771 | |
|
|
772 | - Increment loop depth. |
|
|
773 | - Reset the ev_break status. |
619 | - Before the first iteration, call any pending watchers. |
774 | - Before the first iteration, call any pending watchers. |
|
|
775 | LOOP: |
620 | * If EVFLAG_FORKCHECK was used, check for a fork. |
776 | - If EVFLAG_FORKCHECK was used, check for a fork. |
621 | - If a fork was detected (by any means), queue and call all fork watchers. |
777 | - If a fork was detected (by any means), queue and call all fork watchers. |
622 | - Queue and call all prepare watchers. |
778 | - Queue and call all prepare watchers. |
|
|
779 | - If ev_break was called, goto FINISH. |
623 | - If we have been forked, detach and recreate the kernel state |
780 | - If we have been forked, detach and recreate the kernel state |
624 | as to not disturb the other process. |
781 | as to not disturb the other process. |
625 | - Update the kernel state with all outstanding changes. |
782 | - Update the kernel state with all outstanding changes. |
626 | - Update the "event loop time" (ev_now ()). |
783 | - Update the "event loop time" (ev_now ()). |
627 | - Calculate for how long to sleep or block, if at all |
784 | - Calculate for how long to sleep or block, if at all |
628 | (active idle watchers, EVLOOP_NONBLOCK or not having |
785 | (active idle watchers, EVRUN_NOWAIT or not having |
629 | any active watchers at all will result in not sleeping). |
786 | any active watchers at all will result in not sleeping). |
630 | - Sleep if the I/O and timer collect interval say so. |
787 | - Sleep if the I/O and timer collect interval say so. |
|
|
788 | - Increment loop iteration counter. |
631 | - Block the process, waiting for any events. |
789 | - Block the process, waiting for any events. |
632 | - Queue all outstanding I/O (fd) events. |
790 | - Queue all outstanding I/O (fd) events. |
633 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
791 | - Update the "event loop time" (ev_now ()), and do time jump adjustments. |
634 | - Queue all outstanding timers. |
792 | - Queue all expired timers. |
635 | - Queue all outstanding periodics. |
793 | - Queue all expired periodics. |
636 | - Unless any events are pending now, queue all idle watchers. |
794 | - Queue all idle watchers with priority higher than that of pending events. |
637 | - Queue all check watchers. |
795 | - Queue all check watchers. |
638 | - Call all queued watchers in reverse order (i.e. check watchers first). |
796 | - Call all queued watchers in reverse order (i.e. check watchers first). |
639 | Signals and child watchers are implemented as I/O watchers, and will |
797 | Signals and child watchers are implemented as I/O watchers, and will |
640 | be handled here by queueing them when their watcher gets executed. |
798 | be handled here by queueing them when their watcher gets executed. |
641 | - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
799 | - If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT |
642 | were used, or there are no active watchers, return, otherwise |
800 | were used, or there are no active watchers, goto FINISH, otherwise |
643 | continue with step *. |
801 | continue with step LOOP. |
|
|
802 | FINISH: |
|
|
803 | - Reset the ev_break status iff it was EVBREAK_ONE. |
|
|
804 | - Decrement the loop depth. |
|
|
805 | - Return. |
644 | |
806 | |
645 | Example: Queue some jobs and then loop until no events are outstanding |
807 | Example: Queue some jobs and then loop until no events are outstanding |
646 | anymore. |
808 | anymore. |
647 | |
809 | |
648 | ... queue jobs here, make sure they register event watchers as long |
810 | ... queue jobs here, make sure they register event watchers as long |
649 | ... as they still have work to do (even an idle watcher will do..) |
811 | ... as they still have work to do (even an idle watcher will do..) |
650 | ev_loop (my_loop, 0); |
812 | ev_run (my_loop, 0); |
651 | ... jobs done or somebody called unloop. yeah! |
813 | ... jobs done or somebody called unloop. yeah! |
652 | |
814 | |
653 | =item ev_unloop (loop, how) |
815 | =item ev_break (loop, how) |
654 | |
816 | |
655 | Can be used to make a call to C<ev_loop> return early (but only after it |
817 | Can be used to make a call to C<ev_run> return early (but only after it |
656 | has processed all outstanding events). The C<how> argument must be either |
818 | has processed all outstanding events). The C<how> argument must be either |
657 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
819 | C<EVBREAK_ONE>, which will make the innermost C<ev_run> call return, or |
658 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
820 | C<EVBREAK_ALL>, which will make all nested C<ev_run> calls return. |
659 | |
821 | |
660 | This "unloop state" will be cleared when entering C<ev_loop> again. |
822 | This "unloop state" will be cleared when entering C<ev_run> again. |
|
|
823 | |
|
|
824 | It is safe to call C<ev_break> from outside any C<ev_run> calls. ##TODO## |
661 | |
825 | |
662 | =item ev_ref (loop) |
826 | =item ev_ref (loop) |
663 | |
827 | |
664 | =item ev_unref (loop) |
828 | =item ev_unref (loop) |
665 | |
829 | |
666 | Ref/unref can be used to add or remove a reference count on the event |
830 | Ref/unref can be used to add or remove a reference count on the event |
667 | loop: Every watcher keeps one reference, and as long as the reference |
831 | loop: Every watcher keeps one reference, and as long as the reference |
668 | count is nonzero, C<ev_loop> will not return on its own. If you have |
832 | count is nonzero, C<ev_run> will not return on its own. |
669 | a watcher you never unregister that should not keep C<ev_loop> from |
833 | |
670 | returning, ev_unref() after starting, and ev_ref() before stopping it. For |
834 | This is useful when you have a watcher that you never intend to |
|
|
835 | unregister, but that nevertheless should not keep C<ev_run> from |
|
|
836 | returning. In such a case, call C<ev_unref> after starting, and C<ev_ref> |
|
|
837 | before stopping it. |
|
|
838 | |
671 | example, libev itself uses this for its internal signal pipe: It is not |
839 | As an example, libev itself uses this for its internal signal pipe: It |
672 | visible to the libev user and should not keep C<ev_loop> from exiting if |
840 | is not visible to the libev user and should not keep C<ev_run> from |
673 | no event watchers registered by it are active. It is also an excellent |
841 | exiting if no event watchers registered by it are active. It is also an |
674 | way to do this for generic recurring timers or from within third-party |
842 | excellent way to do this for generic recurring timers or from within |
675 | libraries. Just remember to I<unref after start> and I<ref before stop> |
843 | third-party libraries. Just remember to I<unref after start> and I<ref |
676 | (but only if the watcher wasn't active before, or was active before, |
844 | before stop> (but only if the watcher wasn't active before, or was active |
677 | respectively). |
845 | before, respectively. Note also that libev might stop watchers itself |
|
|
846 | (e.g. non-repeating timers) in which case you have to C<ev_ref> |
|
|
847 | in the callback). |
678 | |
848 | |
679 | Example: Create a signal watcher, but keep it from keeping C<ev_loop> |
849 | Example: Create a signal watcher, but keep it from keeping C<ev_run> |
680 | running when nothing else is active. |
850 | running when nothing else is active. |
681 | |
851 | |
682 | struct ev_signal exitsig; |
852 | ev_signal exitsig; |
683 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
853 | ev_signal_init (&exitsig, sig_cb, SIGINT); |
684 | ev_signal_start (loop, &exitsig); |
854 | ev_signal_start (loop, &exitsig); |
685 | evf_unref (loop); |
855 | evf_unref (loop); |
686 | |
856 | |
687 | Example: For some weird reason, unregister the above signal handler again. |
857 | Example: For some weird reason, unregister the above signal handler again. |
… | |
… | |
701 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
871 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
702 | allows libev to delay invocation of I/O and timer/periodic callbacks |
872 | allows libev to delay invocation of I/O and timer/periodic callbacks |
703 | to increase efficiency of loop iterations (or to increase power-saving |
873 | to increase efficiency of loop iterations (or to increase power-saving |
704 | opportunities). |
874 | opportunities). |
705 | |
875 | |
706 | The background is that sometimes your program runs just fast enough to |
876 | The idea is that sometimes your program runs just fast enough to handle |
707 | handle one (or very few) event(s) per loop iteration. While this makes |
877 | one (or very few) event(s) per loop iteration. While this makes the |
708 | the program responsive, it also wastes a lot of CPU time to poll for new |
878 | program responsive, it also wastes a lot of CPU time to poll for new |
709 | events, especially with backends like C<select ()> which have a high |
879 | events, especially with backends like C<select ()> which have a high |
710 | overhead for the actual polling but can deliver many events at once. |
880 | overhead for the actual polling but can deliver many events at once. |
711 | |
881 | |
712 | By setting a higher I<io collect interval> you allow libev to spend more |
882 | By setting a higher I<io collect interval> you allow libev to spend more |
713 | time collecting I/O events, so you can handle more events per iteration, |
883 | time collecting I/O events, so you can handle more events per iteration, |
714 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
884 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
715 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
885 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
716 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
886 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
|
|
887 | sleep time ensures that libev will not poll for I/O events more often then |
|
|
888 | once per this interval, on average. |
717 | |
889 | |
718 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
890 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
719 | to spend more time collecting timeouts, at the expense of increased |
891 | to spend more time collecting timeouts, at the expense of increased |
720 | latency (the watcher callback will be called later). C<ev_io> watchers |
892 | latency/jitter/inexactness (the watcher callback will be called |
721 | will not be affected. Setting this to a non-null value will not introduce |
893 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
722 | any overhead in libev. |
894 | value will not introduce any overhead in libev. |
723 | |
895 | |
724 | Many (busy) programs can usually benefit by setting the I/O collect |
896 | Many (busy) programs can usually benefit by setting the I/O collect |
725 | interval to a value near C<0.1> or so, which is often enough for |
897 | interval to a value near C<0.1> or so, which is often enough for |
726 | interactive servers (of course not for games), likewise for timeouts. It |
898 | interactive servers (of course not for games), likewise for timeouts. It |
727 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
899 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
728 | as this approaches the timing granularity of most systems. |
900 | as this approaches the timing granularity of most systems. Note that if |
|
|
901 | you do transactions with the outside world and you can't increase the |
|
|
902 | parallelity, then this setting will limit your transaction rate (if you |
|
|
903 | need to poll once per transaction and the I/O collect interval is 0.01, |
|
|
904 | then you can't do more than 100 transactions per second). |
729 | |
905 | |
730 | Setting the I<timeout collect interval> can improve the opportunity for |
906 | Setting the I<timeout collect interval> can improve the opportunity for |
731 | saving power, as the program will "bundle" timer callback invocations that |
907 | saving power, as the program will "bundle" timer callback invocations that |
732 | are "near" in time together, by delaying some, thus reducing the number of |
908 | are "near" in time together, by delaying some, thus reducing the number of |
733 | times the process sleeps and wakes up again. Another useful technique to |
909 | times the process sleeps and wakes up again. Another useful technique to |
734 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
910 | reduce iterations/wake-ups is to use C<ev_periodic> watchers and make sure |
735 | they fire on, say, one-second boundaries only. |
911 | they fire on, say, one-second boundaries only. |
736 | |
912 | |
|
|
913 | Example: we only need 0.1s timeout granularity, and we wish not to poll |
|
|
914 | more often than 100 times per second: |
|
|
915 | |
|
|
916 | ev_set_timeout_collect_interval (EV_DEFAULT_UC_ 0.1); |
|
|
917 | ev_set_io_collect_interval (EV_DEFAULT_UC_ 0.01); |
|
|
918 | |
|
|
919 | =item ev_invoke_pending (loop) |
|
|
920 | |
|
|
921 | This call will simply invoke all pending watchers while resetting their |
|
|
922 | pending state. Normally, C<ev_run> does this automatically when required, |
|
|
923 | but when overriding the invoke callback this call comes handy. This |
|
|
924 | function can be invoked from a watcher - this can be useful for example |
|
|
925 | when you want to do some lengthy calculation and want to pass further |
|
|
926 | event handling to another thread (you still have to make sure only one |
|
|
927 | thread executes within C<ev_invoke_pending> or C<ev_run> of course). |
|
|
928 | |
|
|
929 | =item int ev_pending_count (loop) |
|
|
930 | |
|
|
931 | Returns the number of pending watchers - zero indicates that no watchers |
|
|
932 | are pending. |
|
|
933 | |
|
|
934 | =item ev_set_invoke_pending_cb (loop, void (*invoke_pending_cb)(EV_P)) |
|
|
935 | |
|
|
936 | This overrides the invoke pending functionality of the loop: Instead of |
|
|
937 | invoking all pending watchers when there are any, C<ev_run> will call |
|
|
938 | this callback instead. This is useful, for example, when you want to |
|
|
939 | invoke the actual watchers inside another context (another thread etc.). |
|
|
940 | |
|
|
941 | If you want to reset the callback, use C<ev_invoke_pending> as new |
|
|
942 | callback. |
|
|
943 | |
|
|
944 | =item ev_set_loop_release_cb (loop, void (*release)(EV_P), void (*acquire)(EV_P)) |
|
|
945 | |
|
|
946 | Sometimes you want to share the same loop between multiple threads. This |
|
|
947 | can be done relatively simply by putting mutex_lock/unlock calls around |
|
|
948 | each call to a libev function. |
|
|
949 | |
|
|
950 | However, C<ev_run> can run an indefinite time, so it is not feasible |
|
|
951 | to wait for it to return. One way around this is to wake up the event |
|
|
952 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
|
|
953 | I<release> and I<acquire> callbacks on the loop. |
|
|
954 | |
|
|
955 | When set, then C<release> will be called just before the thread is |
|
|
956 | suspended waiting for new events, and C<acquire> is called just |
|
|
957 | afterwards. |
|
|
958 | |
|
|
959 | Ideally, C<release> will just call your mutex_unlock function, and |
|
|
960 | C<acquire> will just call the mutex_lock function again. |
|
|
961 | |
|
|
962 | While event loop modifications are allowed between invocations of |
|
|
963 | C<release> and C<acquire> (that's their only purpose after all), no |
|
|
964 | modifications done will affect the event loop, i.e. adding watchers will |
|
|
965 | have no effect on the set of file descriptors being watched, or the time |
|
|
966 | waited. Use an C<ev_async> watcher to wake up C<ev_run> when you want it |
|
|
967 | to take note of any changes you made. |
|
|
968 | |
|
|
969 | In theory, threads executing C<ev_run> will be async-cancel safe between |
|
|
970 | invocations of C<release> and C<acquire>. |
|
|
971 | |
|
|
972 | See also the locking example in the C<THREADS> section later in this |
|
|
973 | document. |
|
|
974 | |
|
|
975 | =item ev_set_userdata (loop, void *data) |
|
|
976 | |
|
|
977 | =item ev_userdata (loop) |
|
|
978 | |
|
|
979 | Set and retrieve a single C<void *> associated with a loop. When |
|
|
980 | C<ev_set_userdata> has never been called, then C<ev_userdata> returns |
|
|
981 | C<0.> |
|
|
982 | |
|
|
983 | These two functions can be used to associate arbitrary data with a loop, |
|
|
984 | and are intended solely for the C<invoke_pending_cb>, C<release> and |
|
|
985 | C<acquire> callbacks described above, but of course can be (ab-)used for |
|
|
986 | any other purpose as well. |
|
|
987 | |
737 | =item ev_loop_verify (loop) |
988 | =item ev_verify (loop) |
738 | |
989 | |
739 | This function only does something when C<EV_VERIFY> support has been |
990 | This function only does something when C<EV_VERIFY> support has been |
740 | compiled in. It tries to go through all internal structures and checks |
991 | compiled in, which is the default for non-minimal builds. It tries to go |
741 | them for validity. If anything is found to be inconsistent, it will print |
992 | through all internal structures and checks them for validity. If anything |
742 | an error message to standard error and call C<abort ()>. |
993 | is found to be inconsistent, it will print an error message to standard |
|
|
994 | error and call C<abort ()>. |
743 | |
995 | |
744 | This can be used to catch bugs inside libev itself: under normal |
996 | This can be used to catch bugs inside libev itself: under normal |
745 | circumstances, this function will never abort as of course libev keeps its |
997 | circumstances, this function will never abort as of course libev keeps its |
746 | data structures consistent. |
998 | data structures consistent. |
747 | |
999 | |
748 | =back |
1000 | =back |
749 | |
1001 | |
750 | |
1002 | |
751 | =head1 ANATOMY OF A WATCHER |
1003 | =head1 ANATOMY OF A WATCHER |
752 | |
1004 | |
|
|
1005 | In the following description, uppercase C<TYPE> in names stands for the |
|
|
1006 | watcher type, e.g. C<ev_TYPE_start> can mean C<ev_timer_start> for timer |
|
|
1007 | watchers and C<ev_io_start> for I/O watchers. |
|
|
1008 | |
753 | A watcher is a structure that you create and register to record your |
1009 | A watcher is an opaque structure that you allocate and register to record |
754 | interest in some event. For instance, if you want to wait for STDIN to |
1010 | your interest in some event. To make a concrete example, imagine you want |
755 | become readable, you would create an C<ev_io> watcher for that: |
1011 | to wait for STDIN to become readable, you would create an C<ev_io> watcher |
|
|
1012 | for that: |
756 | |
1013 | |
757 | static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1014 | static void my_cb (struct ev_loop *loop, ev_io *w, int revents) |
758 | { |
1015 | { |
759 | ev_io_stop (w); |
1016 | ev_io_stop (w); |
760 | ev_unloop (loop, EVUNLOOP_ALL); |
1017 | ev_break (loop, EVBREAK_ALL); |
761 | } |
1018 | } |
762 | |
1019 | |
763 | struct ev_loop *loop = ev_default_loop (0); |
1020 | struct ev_loop *loop = ev_default_loop (0); |
|
|
1021 | |
764 | struct ev_io stdin_watcher; |
1022 | ev_io stdin_watcher; |
|
|
1023 | |
765 | ev_init (&stdin_watcher, my_cb); |
1024 | ev_init (&stdin_watcher, my_cb); |
766 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
1025 | ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
767 | ev_io_start (loop, &stdin_watcher); |
1026 | ev_io_start (loop, &stdin_watcher); |
|
|
1027 | |
768 | ev_loop (loop, 0); |
1028 | ev_run (loop, 0); |
769 | |
1029 | |
770 | As you can see, you are responsible for allocating the memory for your |
1030 | As you can see, you are responsible for allocating the memory for your |
771 | watcher structures (and it is usually a bad idea to do this on the stack, |
1031 | watcher structures (and it is I<usually> a bad idea to do this on the |
772 | although this can sometimes be quite valid). |
1032 | stack). |
773 | |
1033 | |
|
|
1034 | Each watcher has an associated watcher structure (called C<struct ev_TYPE> |
|
|
1035 | or simply C<ev_TYPE>, as typedefs are provided for all watcher structs). |
|
|
1036 | |
774 | Each watcher structure must be initialised by a call to C<ev_init |
1037 | Each watcher structure must be initialised by a call to C<ev_init (watcher |
775 | (watcher *, callback)>, which expects a callback to be provided. This |
1038 | *, callback)>, which expects a callback to be provided. This callback is |
776 | callback gets invoked each time the event occurs (or, in the case of I/O |
1039 | invoked each time the event occurs (or, in the case of I/O watchers, each |
777 | watchers, each time the event loop detects that the file descriptor given |
1040 | time the event loop detects that the file descriptor given is readable |
778 | is readable and/or writable). |
1041 | and/or writable). |
779 | |
1042 | |
780 | Each watcher type has its own C<< ev_<type>_set (watcher *, ...) >> macro |
1043 | Each watcher type further has its own C<< ev_TYPE_set (watcher *, ...) >> |
781 | with arguments specific to this watcher type. There is also a macro |
1044 | macro to configure it, with arguments specific to the watcher type. There |
782 | to combine initialisation and setting in one call: C<< ev_<type>_init |
1045 | is also a macro to combine initialisation and setting in one call: C<< |
783 | (watcher *, callback, ...) >>. |
1046 | ev_TYPE_init (watcher *, callback, ...) >>. |
784 | |
1047 | |
785 | To make the watcher actually watch out for events, you have to start it |
1048 | To make the watcher actually watch out for events, you have to start it |
786 | with a watcher-specific start function (C<< ev_<type>_start (loop, watcher |
1049 | with a watcher-specific start function (C<< ev_TYPE_start (loop, watcher |
787 | *) >>), and you can stop watching for events at any time by calling the |
1050 | *) >>), and you can stop watching for events at any time by calling the |
788 | corresponding stop function (C<< ev_<type>_stop (loop, watcher *) >>. |
1051 | corresponding stop function (C<< ev_TYPE_stop (loop, watcher *) >>. |
789 | |
1052 | |
790 | As long as your watcher is active (has been started but not stopped) you |
1053 | As long as your watcher is active (has been started but not stopped) you |
791 | must not touch the values stored in it. Most specifically you must never |
1054 | must not touch the values stored in it. Most specifically you must never |
792 | reinitialise it or call its C<set> macro. |
1055 | reinitialise it or call its C<ev_TYPE_set> macro. |
793 | |
1056 | |
794 | Each and every callback receives the event loop pointer as first, the |
1057 | Each and every callback receives the event loop pointer as first, the |
795 | registered watcher structure as second, and a bitset of received events as |
1058 | registered watcher structure as second, and a bitset of received events as |
796 | third argument. |
1059 | third argument. |
797 | |
1060 | |
… | |
… | |
806 | =item C<EV_WRITE> |
1069 | =item C<EV_WRITE> |
807 | |
1070 | |
808 | The file descriptor in the C<ev_io> watcher has become readable and/or |
1071 | The file descriptor in the C<ev_io> watcher has become readable and/or |
809 | writable. |
1072 | writable. |
810 | |
1073 | |
811 | =item C<EV_TIMEOUT> |
1074 | =item C<EV_TIMER> |
812 | |
1075 | |
813 | The C<ev_timer> watcher has timed out. |
1076 | The C<ev_timer> watcher has timed out. |
814 | |
1077 | |
815 | =item C<EV_PERIODIC> |
1078 | =item C<EV_PERIODIC> |
816 | |
1079 | |
… | |
… | |
834 | |
1097 | |
835 | =item C<EV_PREPARE> |
1098 | =item C<EV_PREPARE> |
836 | |
1099 | |
837 | =item C<EV_CHECK> |
1100 | =item C<EV_CHECK> |
838 | |
1101 | |
839 | All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts |
1102 | All C<ev_prepare> watchers are invoked just I<before> C<ev_run> starts |
840 | to gather new events, and all C<ev_check> watchers are invoked just after |
1103 | to gather new events, and all C<ev_check> watchers are invoked just after |
841 | C<ev_loop> has gathered them, but before it invokes any callbacks for any |
1104 | C<ev_run> has gathered them, but before it invokes any callbacks for any |
842 | received events. Callbacks of both watcher types can start and stop as |
1105 | received events. Callbacks of both watcher types can start and stop as |
843 | many watchers as they want, and all of them will be taken into account |
1106 | many watchers as they want, and all of them will be taken into account |
844 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
1107 | (for example, a C<ev_prepare> watcher might start an idle watcher to keep |
845 | C<ev_loop> from blocking). |
1108 | C<ev_run> from blocking). |
846 | |
1109 | |
847 | =item C<EV_EMBED> |
1110 | =item C<EV_EMBED> |
848 | |
1111 | |
849 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
1112 | The embedded event loop specified in the C<ev_embed> watcher needs attention. |
850 | |
1113 | |
… | |
… | |
854 | C<ev_fork>). |
1117 | C<ev_fork>). |
855 | |
1118 | |
856 | =item C<EV_ASYNC> |
1119 | =item C<EV_ASYNC> |
857 | |
1120 | |
858 | The given async watcher has been asynchronously notified (see C<ev_async>). |
1121 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
1122 | |
|
|
1123 | =item C<EV_CUSTOM> |
|
|
1124 | |
|
|
1125 | Not ever sent (or otherwise used) by libev itself, but can be freely used |
|
|
1126 | by libev users to signal watchers (e.g. via C<ev_feed_event>). |
859 | |
1127 | |
860 | =item C<EV_ERROR> |
1128 | =item C<EV_ERROR> |
861 | |
1129 | |
862 | An unspecified error has occurred, the watcher has been stopped. This might |
1130 | An unspecified error has occurred, the watcher has been stopped. This might |
863 | happen because the watcher could not be properly started because libev |
1131 | happen because the watcher could not be properly started because libev |
864 | ran out of memory, a file descriptor was found to be closed or any other |
1132 | ran out of memory, a file descriptor was found to be closed or any other |
|
|
1133 | problem. Libev considers these application bugs. |
|
|
1134 | |
865 | problem. You best act on it by reporting the problem and somehow coping |
1135 | You best act on it by reporting the problem and somehow coping with the |
866 | with the watcher being stopped. |
1136 | watcher being stopped. Note that well-written programs should not receive |
|
|
1137 | an error ever, so when your watcher receives it, this usually indicates a |
|
|
1138 | bug in your program. |
867 | |
1139 | |
868 | Libev will usually signal a few "dummy" events together with an error, |
1140 | Libev will usually signal a few "dummy" events together with an error, for |
869 | for example it might indicate that a fd is readable or writable, and if |
1141 | example it might indicate that a fd is readable or writable, and if your |
870 | your callbacks is well-written it can just attempt the operation and cope |
1142 | callbacks is well-written it can just attempt the operation and cope with |
871 | with the error from read() or write(). This will not work in multi-threaded |
1143 | the error from read() or write(). This will not work in multi-threaded |
872 | programs, though, so beware. |
1144 | programs, though, as the fd could already be closed and reused for another |
|
|
1145 | thing, so beware. |
873 | |
1146 | |
874 | =back |
1147 | =back |
875 | |
1148 | |
|
|
1149 | =head2 WATCHER STATES |
|
|
1150 | |
|
|
1151 | There are various watcher states mentioned throughout this manual - |
|
|
1152 | active, pending and so on. In this section these states and the rules to |
|
|
1153 | transition between them will be described in more detail - and while these |
|
|
1154 | rules might look complicated, they usually do "the right thing". |
|
|
1155 | |
|
|
1156 | =over 4 |
|
|
1157 | |
|
|
1158 | =item initialiased |
|
|
1159 | |
|
|
1160 | Before a watcher can be registered with the event looop it has to be |
|
|
1161 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
|
|
1162 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
|
|
1163 | |
|
|
1164 | In this state it is simply some block of memory that is suitable for use |
|
|
1165 | in an event loop. It can be moved around, freed, reused etc. at will. |
|
|
1166 | |
|
|
1167 | =item started/running/active |
|
|
1168 | |
|
|
1169 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
|
|
1170 | property of the event loop, and is actively waiting for events. While in |
|
|
1171 | this state it cannot be accessed (except in a few documented ways), moved, |
|
|
1172 | freed or anything else - the only legal thing is to keep a pointer to it, |
|
|
1173 | and call libev functions on it that are documented to work on active watchers. |
|
|
1174 | |
|
|
1175 | =item pending |
|
|
1176 | |
|
|
1177 | If a watcher is active and libev determines that an event it is interested |
|
|
1178 | in has occurred (such as a timer expiring), it will become pending. It will |
|
|
1179 | stay in this pending state until either it is stopped or its callback is |
|
|
1180 | about to be invoked, so it is not normally pending inside the watcher |
|
|
1181 | callback. |
|
|
1182 | |
|
|
1183 | The watcher might or might not be active while it is pending (for example, |
|
|
1184 | an expired non-repeating timer can be pending but no longer active). If it |
|
|
1185 | is stopped, it can be freely accessed (e.g. by calling C<ev_TYPE_set>), |
|
|
1186 | but it is still property of the event loop at this time, so cannot be |
|
|
1187 | moved, freed or reused. And if it is active the rules described in the |
|
|
1188 | previous item still apply. |
|
|
1189 | |
|
|
1190 | It is also possible to feed an event on a watcher that is not active (e.g. |
|
|
1191 | via C<ev_feed_event>), in which case it becomes pending without being |
|
|
1192 | active. |
|
|
1193 | |
|
|
1194 | =item stopped |
|
|
1195 | |
|
|
1196 | A watcher can be stopped implicitly by libev (in which case it might still |
|
|
1197 | be pending), or explicitly by calling its C<ev_TYPE_stop> function. The |
|
|
1198 | latter will clear any pending state the watcher might be in, regardless |
|
|
1199 | of whether it was active or not, so stopping a watcher explicitly before |
|
|
1200 | freeing it is often a good idea. |
|
|
1201 | |
|
|
1202 | While stopped (and not pending) the watcher is essentially in the |
|
|
1203 | initialised state, that is it can be reused, moved, modified in any way |
|
|
1204 | you wish. |
|
|
1205 | |
|
|
1206 | =back |
|
|
1207 | |
876 | =head2 GENERIC WATCHER FUNCTIONS |
1208 | =head2 GENERIC WATCHER FUNCTIONS |
877 | |
|
|
878 | In the following description, C<TYPE> stands for the watcher type, |
|
|
879 | e.g. C<timer> for C<ev_timer> watchers and C<io> for C<ev_io> watchers. |
|
|
880 | |
1209 | |
881 | =over 4 |
1210 | =over 4 |
882 | |
1211 | |
883 | =item C<ev_init> (ev_TYPE *watcher, callback) |
1212 | =item C<ev_init> (ev_TYPE *watcher, callback) |
884 | |
1213 | |
… | |
… | |
890 | which rolls both calls into one. |
1219 | which rolls both calls into one. |
891 | |
1220 | |
892 | You can reinitialise a watcher at any time as long as it has been stopped |
1221 | You can reinitialise a watcher at any time as long as it has been stopped |
893 | (or never started) and there are no pending events outstanding. |
1222 | (or never started) and there are no pending events outstanding. |
894 | |
1223 | |
895 | The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, |
1224 | The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher, |
896 | int revents)>. |
1225 | int revents)>. |
897 | |
1226 | |
|
|
1227 | Example: Initialise an C<ev_io> watcher in two steps. |
|
|
1228 | |
|
|
1229 | ev_io w; |
|
|
1230 | ev_init (&w, my_cb); |
|
|
1231 | ev_io_set (&w, STDIN_FILENO, EV_READ); |
|
|
1232 | |
898 | =item C<ev_TYPE_set> (ev_TYPE *, [args]) |
1233 | =item C<ev_TYPE_set> (ev_TYPE *watcher, [args]) |
899 | |
1234 | |
900 | This macro initialises the type-specific parts of a watcher. You need to |
1235 | This macro initialises the type-specific parts of a watcher. You need to |
901 | call C<ev_init> at least once before you call this macro, but you can |
1236 | call C<ev_init> at least once before you call this macro, but you can |
902 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
1237 | call C<ev_TYPE_set> any number of times. You must not, however, call this |
903 | macro on a watcher that is active (it can be pending, however, which is a |
1238 | macro on a watcher that is active (it can be pending, however, which is a |
904 | difference to the C<ev_init> macro). |
1239 | difference to the C<ev_init> macro). |
905 | |
1240 | |
906 | Although some watcher types do not have type-specific arguments |
1241 | Although some watcher types do not have type-specific arguments |
907 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
1242 | (e.g. C<ev_prepare>) you still need to call its C<set> macro. |
908 | |
1243 | |
|
|
1244 | See C<ev_init>, above, for an example. |
|
|
1245 | |
909 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
1246 | =item C<ev_TYPE_init> (ev_TYPE *watcher, callback, [args]) |
910 | |
1247 | |
911 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
1248 | This convenience macro rolls both C<ev_init> and C<ev_TYPE_set> macro |
912 | calls into a single call. This is the most convenient method to initialise |
1249 | calls into a single call. This is the most convenient method to initialise |
913 | a watcher. The same limitations apply, of course. |
1250 | a watcher. The same limitations apply, of course. |
914 | |
1251 | |
|
|
1252 | Example: Initialise and set an C<ev_io> watcher in one step. |
|
|
1253 | |
|
|
1254 | ev_io_init (&w, my_cb, STDIN_FILENO, EV_READ); |
|
|
1255 | |
915 | =item C<ev_TYPE_start> (loop *, ev_TYPE *watcher) |
1256 | =item C<ev_TYPE_start> (loop, ev_TYPE *watcher) |
916 | |
1257 | |
917 | Starts (activates) the given watcher. Only active watchers will receive |
1258 | Starts (activates) the given watcher. Only active watchers will receive |
918 | events. If the watcher is already active nothing will happen. |
1259 | events. If the watcher is already active nothing will happen. |
919 | |
1260 | |
|
|
1261 | Example: Start the C<ev_io> watcher that is being abused as example in this |
|
|
1262 | whole section. |
|
|
1263 | |
|
|
1264 | ev_io_start (EV_DEFAULT_UC, &w); |
|
|
1265 | |
920 | =item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) |
1266 | =item C<ev_TYPE_stop> (loop, ev_TYPE *watcher) |
921 | |
1267 | |
922 | Stops the given watcher again (if active) and clears the pending |
1268 | Stops the given watcher if active, and clears the pending status (whether |
|
|
1269 | the watcher was active or not). |
|
|
1270 | |
923 | status. It is possible that stopped watchers are pending (for example, |
1271 | It is possible that stopped watchers are pending - for example, |
924 | non-repeating timers are being stopped when they become pending), but |
1272 | non-repeating timers are being stopped when they become pending - but |
925 | C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If |
1273 | calling C<ev_TYPE_stop> ensures that the watcher is neither active nor |
926 | you want to free or reuse the memory used by the watcher it is therefore a |
1274 | pending. If you want to free or reuse the memory used by the watcher it is |
927 | good idea to always call its C<ev_TYPE_stop> function. |
1275 | therefore a good idea to always call its C<ev_TYPE_stop> function. |
928 | |
1276 | |
929 | =item bool ev_is_active (ev_TYPE *watcher) |
1277 | =item bool ev_is_active (ev_TYPE *watcher) |
930 | |
1278 | |
931 | Returns a true value iff the watcher is active (i.e. it has been started |
1279 | Returns a true value iff the watcher is active (i.e. it has been started |
932 | and not yet been stopped). As long as a watcher is active you must not modify |
1280 | and not yet been stopped). As long as a watcher is active you must not modify |
… | |
… | |
948 | =item ev_cb_set (ev_TYPE *watcher, callback) |
1296 | =item ev_cb_set (ev_TYPE *watcher, callback) |
949 | |
1297 | |
950 | Change the callback. You can change the callback at virtually any time |
1298 | Change the callback. You can change the callback at virtually any time |
951 | (modulo threads). |
1299 | (modulo threads). |
952 | |
1300 | |
953 | =item ev_set_priority (ev_TYPE *watcher, priority) |
1301 | =item ev_set_priority (ev_TYPE *watcher, int priority) |
954 | |
1302 | |
955 | =item int ev_priority (ev_TYPE *watcher) |
1303 | =item int ev_priority (ev_TYPE *watcher) |
956 | |
1304 | |
957 | Set and query the priority of the watcher. The priority is a small |
1305 | Set and query the priority of the watcher. The priority is a small |
958 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
1306 | integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI> |
959 | (default: C<-2>). Pending watchers with higher priority will be invoked |
1307 | (default: C<-2>). Pending watchers with higher priority will be invoked |
960 | before watchers with lower priority, but priority will not keep watchers |
1308 | before watchers with lower priority, but priority will not keep watchers |
961 | from being executed (except for C<ev_idle> watchers). |
1309 | from being executed (except for C<ev_idle> watchers). |
962 | |
1310 | |
963 | This means that priorities are I<only> used for ordering callback |
|
|
964 | invocation after new events have been received. This is useful, for |
|
|
965 | example, to reduce latency after idling, or more often, to bind two |
|
|
966 | watchers on the same event and make sure one is called first. |
|
|
967 | |
|
|
968 | If you need to suppress invocation when higher priority events are pending |
1311 | If you need to suppress invocation when higher priority events are pending |
969 | you need to look at C<ev_idle> watchers, which provide this functionality. |
1312 | you need to look at C<ev_idle> watchers, which provide this functionality. |
970 | |
1313 | |
971 | You I<must not> change the priority of a watcher as long as it is active or |
1314 | You I<must not> change the priority of a watcher as long as it is active or |
972 | pending. |
1315 | pending. |
973 | |
1316 | |
|
|
1317 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
|
|
1318 | fine, as long as you do not mind that the priority value you query might |
|
|
1319 | or might not have been clamped to the valid range. |
|
|
1320 | |
974 | The default priority used by watchers when no priority has been set is |
1321 | The default priority used by watchers when no priority has been set is |
975 | always C<0>, which is supposed to not be too high and not be too low :). |
1322 | always C<0>, which is supposed to not be too high and not be too low :). |
976 | |
1323 | |
977 | Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is |
1324 | See L<WATCHER PRIORITY MODELS>, below, for a more thorough treatment of |
978 | fine, as long as you do not mind that the priority value you query might |
1325 | priorities. |
979 | or might not have been adjusted to be within valid range. |
|
|
980 | |
1326 | |
981 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
1327 | =item ev_invoke (loop, ev_TYPE *watcher, int revents) |
982 | |
1328 | |
983 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
1329 | Invoke the C<watcher> with the given C<loop> and C<revents>. Neither |
984 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
1330 | C<loop> nor C<revents> need to be valid as long as the watcher callback |
985 | can deal with that fact. |
1331 | can deal with that fact, as both are simply passed through to the |
|
|
1332 | callback. |
986 | |
1333 | |
987 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
1334 | =item int ev_clear_pending (loop, ev_TYPE *watcher) |
988 | |
1335 | |
989 | If the watcher is pending, this function returns clears its pending status |
1336 | If the watcher is pending, this function clears its pending status and |
990 | and returns its C<revents> bitset (as if its callback was invoked). If the |
1337 | returns its C<revents> bitset (as if its callback was invoked). If the |
991 | watcher isn't pending it does nothing and returns C<0>. |
1338 | watcher isn't pending it does nothing and returns C<0>. |
992 | |
1339 | |
|
|
1340 | Sometimes it can be useful to "poll" a watcher instead of waiting for its |
|
|
1341 | callback to be invoked, which can be accomplished with this function. |
|
|
1342 | |
|
|
1343 | =item ev_feed_event (loop, ev_TYPE *watcher, int revents) |
|
|
1344 | |
|
|
1345 | Feeds the given event set into the event loop, as if the specified event |
|
|
1346 | had happened for the specified watcher (which must be a pointer to an |
|
|
1347 | initialised but not necessarily started event watcher). Obviously you must |
|
|
1348 | not free the watcher as long as it has pending events. |
|
|
1349 | |
|
|
1350 | Stopping the watcher, letting libev invoke it, or calling |
|
|
1351 | C<ev_clear_pending> will clear the pending event, even if the watcher was |
|
|
1352 | not started in the first place. |
|
|
1353 | |
|
|
1354 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
|
|
1355 | functions that do not need a watcher. |
|
|
1356 | |
993 | =back |
1357 | =back |
994 | |
1358 | |
995 | |
1359 | |
996 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1360 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
997 | |
1361 | |
998 | 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 |
999 | 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 |
1000 | to associate arbitrary data with your watcher. If you need more data and |
1364 | to associate arbitrary data with your watcher. If you need more data and |
1001 | don't want to allocate memory and store a pointer to it in that data |
1365 | don't want to allocate memory and store a pointer to it in that data |
1002 | 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 |
1003 | data: |
1367 | data: |
1004 | |
1368 | |
1005 | struct my_io |
1369 | struct my_io |
1006 | { |
1370 | { |
1007 | struct ev_io io; |
1371 | ev_io io; |
1008 | int otherfd; |
1372 | int otherfd; |
1009 | void *somedata; |
1373 | void *somedata; |
1010 | struct whatever *mostinteresting; |
1374 | struct whatever *mostinteresting; |
1011 | }; |
1375 | }; |
1012 | |
1376 | |
… | |
… | |
1015 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1379 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
1016 | |
1380 | |
1017 | 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 |
1018 | can cast it back to your own type: |
1382 | can cast it back to your own type: |
1019 | |
1383 | |
1020 | 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) |
1021 | { |
1385 | { |
1022 | struct my_io *w = (struct my_io *)w_; |
1386 | struct my_io *w = (struct my_io *)w_; |
1023 | ... |
1387 | ... |
1024 | } |
1388 | } |
1025 | |
1389 | |
… | |
… | |
1036 | ev_timer t2; |
1400 | ev_timer t2; |
1037 | } |
1401 | } |
1038 | |
1402 | |
1039 | In this case getting the pointer to C<my_biggy> is a bit more |
1403 | In this case getting the pointer to C<my_biggy> is a bit more |
1040 | complicated: Either you store the address of your C<my_biggy> struct |
1404 | complicated: Either you store the address of your C<my_biggy> struct |
1041 | in the C<data> member of the watcher, or you need to use some pointer |
1405 | in the C<data> member of the watcher (for woozies), or you need to use |
1042 | arithmetic using C<offsetof> inside your watchers: |
1406 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1407 | programmers): |
1043 | |
1408 | |
1044 | #include <stddef.h> |
1409 | #include <stddef.h> |
1045 | |
1410 | |
1046 | static void |
1411 | static void |
1047 | t1_cb (EV_P_ struct ev_timer *w, int revents) |
1412 | t1_cb (EV_P_ ev_timer *w, int revents) |
1048 | { |
1413 | { |
1049 | struct my_biggy big = (struct my_biggy * |
1414 | struct my_biggy big = (struct my_biggy *) |
1050 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1415 | (((char *)w) - offsetof (struct my_biggy, t1)); |
1051 | } |
1416 | } |
1052 | |
1417 | |
1053 | static void |
1418 | static void |
1054 | t2_cb (EV_P_ struct ev_timer *w, int revents) |
1419 | t2_cb (EV_P_ ev_timer *w, int revents) |
1055 | { |
1420 | { |
1056 | struct my_biggy big = (struct my_biggy * |
1421 | struct my_biggy big = (struct my_biggy *) |
1057 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1422 | (((char *)w) - offsetof (struct my_biggy, t2)); |
1058 | } |
1423 | } |
|
|
1424 | |
|
|
1425 | =head2 WATCHER PRIORITY MODELS |
|
|
1426 | |
|
|
1427 | Many event loops support I<watcher priorities>, which are usually small |
|
|
1428 | integers that influence the ordering of event callback invocation |
|
|
1429 | between watchers in some way, all else being equal. |
|
|
1430 | |
|
|
1431 | In libev, Watcher priorities can be set using C<ev_set_priority>. See its |
|
|
1432 | description for the more technical details such as the actual priority |
|
|
1433 | range. |
|
|
1434 | |
|
|
1435 | There are two common ways how these these priorities are being interpreted |
|
|
1436 | by event loops: |
|
|
1437 | |
|
|
1438 | In the more common lock-out model, higher priorities "lock out" invocation |
|
|
1439 | of lower priority watchers, which means as long as higher priority |
|
|
1440 | watchers receive events, lower priority watchers are not being invoked. |
|
|
1441 | |
|
|
1442 | The less common only-for-ordering model uses priorities solely to order |
|
|
1443 | callback invocation within a single event loop iteration: Higher priority |
|
|
1444 | watchers are invoked before lower priority ones, but they all get invoked |
|
|
1445 | before polling for new events. |
|
|
1446 | |
|
|
1447 | Libev uses the second (only-for-ordering) model for all its watchers |
|
|
1448 | except for idle watchers (which use the lock-out model). |
|
|
1449 | |
|
|
1450 | The rationale behind this is that implementing the lock-out model for |
|
|
1451 | watchers is not well supported by most kernel interfaces, and most event |
|
|
1452 | libraries will just poll for the same events again and again as long as |
|
|
1453 | their callbacks have not been executed, which is very inefficient in the |
|
|
1454 | common case of one high-priority watcher locking out a mass of lower |
|
|
1455 | priority ones. |
|
|
1456 | |
|
|
1457 | Static (ordering) priorities are most useful when you have two or more |
|
|
1458 | watchers handling the same resource: a typical usage example is having an |
|
|
1459 | C<ev_io> watcher to receive data, and an associated C<ev_timer> to handle |
|
|
1460 | timeouts. Under load, data might be received while the program handles |
|
|
1461 | other jobs, but since timers normally get invoked first, the timeout |
|
|
1462 | handler will be executed before checking for data. In that case, giving |
|
|
1463 | the timer a lower priority than the I/O watcher ensures that I/O will be |
|
|
1464 | handled first even under adverse conditions (which is usually, but not |
|
|
1465 | always, what you want). |
|
|
1466 | |
|
|
1467 | Since idle watchers use the "lock-out" model, meaning that idle watchers |
|
|
1468 | will only be executed when no same or higher priority watchers have |
|
|
1469 | received events, they can be used to implement the "lock-out" model when |
|
|
1470 | required. |
|
|
1471 | |
|
|
1472 | For example, to emulate how many other event libraries handle priorities, |
|
|
1473 | you can associate an C<ev_idle> watcher to each such watcher, and in |
|
|
1474 | the normal watcher callback, you just start the idle watcher. The real |
|
|
1475 | processing is done in the idle watcher callback. This causes libev to |
|
|
1476 | continuously poll and process kernel event data for the watcher, but when |
|
|
1477 | the lock-out case is known to be rare (which in turn is rare :), this is |
|
|
1478 | workable. |
|
|
1479 | |
|
|
1480 | Usually, however, the lock-out model implemented that way will perform |
|
|
1481 | miserably under the type of load it was designed to handle. In that case, |
|
|
1482 | it might be preferable to stop the real watcher before starting the |
|
|
1483 | idle watcher, so the kernel will not have to process the event in case |
|
|
1484 | the actual processing will be delayed for considerable time. |
|
|
1485 | |
|
|
1486 | Here is an example of an I/O watcher that should run at a strictly lower |
|
|
1487 | priority than the default, and which should only process data when no |
|
|
1488 | other events are pending: |
|
|
1489 | |
|
|
1490 | ev_idle idle; // actual processing watcher |
|
|
1491 | ev_io io; // actual event watcher |
|
|
1492 | |
|
|
1493 | static void |
|
|
1494 | io_cb (EV_P_ ev_io *w, int revents) |
|
|
1495 | { |
|
|
1496 | // stop the I/O watcher, we received the event, but |
|
|
1497 | // are not yet ready to handle it. |
|
|
1498 | ev_io_stop (EV_A_ w); |
|
|
1499 | |
|
|
1500 | // start the idle watcher to handle the actual event. |
|
|
1501 | // it will not be executed as long as other watchers |
|
|
1502 | // with the default priority are receiving events. |
|
|
1503 | ev_idle_start (EV_A_ &idle); |
|
|
1504 | } |
|
|
1505 | |
|
|
1506 | static void |
|
|
1507 | idle_cb (EV_P_ ev_idle *w, int revents) |
|
|
1508 | { |
|
|
1509 | // actual processing |
|
|
1510 | read (STDIN_FILENO, ...); |
|
|
1511 | |
|
|
1512 | // have to start the I/O watcher again, as |
|
|
1513 | // we have handled the event |
|
|
1514 | ev_io_start (EV_P_ &io); |
|
|
1515 | } |
|
|
1516 | |
|
|
1517 | // initialisation |
|
|
1518 | ev_idle_init (&idle, idle_cb); |
|
|
1519 | ev_io_init (&io, io_cb, STDIN_FILENO, EV_READ); |
|
|
1520 | ev_io_start (EV_DEFAULT_ &io); |
|
|
1521 | |
|
|
1522 | In the "real" world, it might also be beneficial to start a timer, so that |
|
|
1523 | low-priority connections can not be locked out forever under load. This |
|
|
1524 | enables your program to keep a lower latency for important connections |
|
|
1525 | during short periods of high load, while not completely locking out less |
|
|
1526 | important ones. |
1059 | |
1527 | |
1060 | |
1528 | |
1061 | =head1 WATCHER TYPES |
1529 | =head1 WATCHER TYPES |
1062 | |
1530 | |
1063 | This section describes each watcher in detail, but will not repeat |
1531 | This section describes each watcher in detail, but will not repeat |
… | |
… | |
1087 | In general you can register as many read and/or write event watchers per |
1555 | In general you can register as many read and/or write event watchers per |
1088 | fd as you want (as long as you don't confuse yourself). Setting all file |
1556 | fd as you want (as long as you don't confuse yourself). Setting all file |
1089 | descriptors to non-blocking mode is also usually a good idea (but not |
1557 | descriptors to non-blocking mode is also usually a good idea (but not |
1090 | required if you know what you are doing). |
1558 | required if you know what you are doing). |
1091 | |
1559 | |
1092 | If you must do this, then force the use of a known-to-be-good backend |
1560 | If you cannot use non-blocking mode, then force the use of a |
1093 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1561 | known-to-be-good backend (at the time of this writing, this includes only |
1094 | C<EVBACKEND_POLL>). |
1562 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
|
|
1563 | descriptors for which non-blocking operation makes no sense (such as |
|
|
1564 | files) - libev doesn't guarantee any specific behaviour in that case. |
1095 | |
1565 | |
1096 | Another thing you have to watch out for is that it is quite easy to |
1566 | Another thing you have to watch out for is that it is quite easy to |
1097 | receive "spurious" readiness notifications, that is your callback might |
1567 | receive "spurious" readiness notifications, that is your callback might |
1098 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1568 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1099 | because there is no data. Not only are some backends known to create a |
1569 | because there is no data. Not only are some backends known to create a |
1100 | lot of those (for example Solaris ports), it is very easy to get into |
1570 | lot of those (for example Solaris ports), it is very easy to get into |
1101 | this situation even with a relatively standard program structure. Thus |
1571 | this situation even with a relatively standard program structure. Thus |
1102 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1572 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1103 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1573 | C<EAGAIN> is far preferable to a program hanging until some data arrives. |
1104 | |
1574 | |
1105 | If you cannot run the fd in non-blocking mode (for example you should not |
1575 | If you cannot run the fd in non-blocking mode (for example you should |
1106 | play around with an Xlib connection), then you have to separately re-test |
1576 | not play around with an Xlib connection), then you have to separately |
1107 | whether a file descriptor is really ready with a known-to-be good interface |
1577 | re-test whether a file descriptor is really ready with a known-to-be good |
1108 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1578 | interface such as poll (fortunately in our Xlib example, Xlib already |
1109 | its own, so its quite safe to use). |
1579 | does this on its own, so its quite safe to use). Some people additionally |
|
|
1580 | use C<SIGALRM> and an interval timer, just to be sure you won't block |
|
|
1581 | indefinitely. |
|
|
1582 | |
|
|
1583 | But really, best use non-blocking mode. |
1110 | |
1584 | |
1111 | =head3 The special problem of disappearing file descriptors |
1585 | =head3 The special problem of disappearing file descriptors |
1112 | |
1586 | |
1113 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1587 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
1114 | descriptor (either by calling C<close> explicitly or by any other means, |
1588 | descriptor (either due to calling C<close> explicitly or any other means, |
1115 | such as C<dup>). The reason is that you register interest in some file |
1589 | such as C<dup2>). The reason is that you register interest in some file |
1116 | descriptor, but when it goes away, the operating system will silently drop |
1590 | descriptor, but when it goes away, the operating system will silently drop |
1117 | this interest. If another file descriptor with the same number then is |
1591 | this interest. If another file descriptor with the same number then is |
1118 | registered with libev, there is no efficient way to see that this is, in |
1592 | registered with libev, there is no efficient way to see that this is, in |
1119 | fact, a different file descriptor. |
1593 | fact, a different file descriptor. |
1120 | |
1594 | |
… | |
… | |
1151 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1625 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1152 | C<EVBACKEND_POLL>. |
1626 | C<EVBACKEND_POLL>. |
1153 | |
1627 | |
1154 | =head3 The special problem of SIGPIPE |
1628 | =head3 The special problem of SIGPIPE |
1155 | |
1629 | |
1156 | While not really specific to libev, it is easy to forget about SIGPIPE: |
1630 | While not really specific to libev, it is easy to forget about C<SIGPIPE>: |
1157 | when writing to a pipe whose other end has been closed, your program gets |
1631 | when writing to a pipe whose other end has been closed, your program gets |
1158 | send a SIGPIPE, which, by default, aborts your program. For most programs |
1632 | sent a SIGPIPE, which, by default, aborts your program. For most programs |
1159 | this is sensible behaviour, for daemons, this is usually undesirable. |
1633 | this is sensible behaviour, for daemons, this is usually undesirable. |
1160 | |
1634 | |
1161 | So when you encounter spurious, unexplained daemon exits, make sure you |
1635 | So when you encounter spurious, unexplained daemon exits, make sure you |
1162 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1636 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
1163 | somewhere, as that would have given you a big clue). |
1637 | somewhere, as that would have given you a big clue). |
1164 | |
1638 | |
|
|
1639 | =head3 The special problem of accept()ing when you can't |
|
|
1640 | |
|
|
1641 | Many implementations of the POSIX C<accept> function (for example, |
|
|
1642 | found in post-2004 Linux) have the peculiar behaviour of not removing a |
|
|
1643 | connection from the pending queue in all error cases. |
|
|
1644 | |
|
|
1645 | For example, larger servers often run out of file descriptors (because |
|
|
1646 | of resource limits), causing C<accept> to fail with C<ENFILE> but not |
|
|
1647 | rejecting the connection, leading to libev signalling readiness on |
|
|
1648 | the next iteration again (the connection still exists after all), and |
|
|
1649 | typically causing the program to loop at 100% CPU usage. |
|
|
1650 | |
|
|
1651 | Unfortunately, the set of errors that cause this issue differs between |
|
|
1652 | operating systems, there is usually little the app can do to remedy the |
|
|
1653 | situation, and no known thread-safe method of removing the connection to |
|
|
1654 | cope with overload is known (to me). |
|
|
1655 | |
|
|
1656 | One of the easiest ways to handle this situation is to just ignore it |
|
|
1657 | - when the program encounters an overload, it will just loop until the |
|
|
1658 | situation is over. While this is a form of busy waiting, no OS offers an |
|
|
1659 | event-based way to handle this situation, so it's the best one can do. |
|
|
1660 | |
|
|
1661 | A better way to handle the situation is to log any errors other than |
|
|
1662 | C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such |
|
|
1663 | messages, and continue as usual, which at least gives the user an idea of |
|
|
1664 | what could be wrong ("raise the ulimit!"). For extra points one could stop |
|
|
1665 | the C<ev_io> watcher on the listening fd "for a while", which reduces CPU |
|
|
1666 | usage. |
|
|
1667 | |
|
|
1668 | If your program is single-threaded, then you could also keep a dummy file |
|
|
1669 | descriptor for overload situations (e.g. by opening F</dev/null>), and |
|
|
1670 | when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>, |
|
|
1671 | close that fd, and create a new dummy fd. This will gracefully refuse |
|
|
1672 | clients under typical overload conditions. |
|
|
1673 | |
|
|
1674 | The last way to handle it is to simply log the error and C<exit>, as |
|
|
1675 | is often done with C<malloc> failures, but this results in an easy |
|
|
1676 | opportunity for a DoS attack. |
1165 | |
1677 | |
1166 | =head3 Watcher-Specific Functions |
1678 | =head3 Watcher-Specific Functions |
1167 | |
1679 | |
1168 | =over 4 |
1680 | =over 4 |
1169 | |
1681 | |
1170 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1682 | =item ev_io_init (ev_io *, callback, int fd, int events) |
1171 | |
1683 | |
1172 | =item ev_io_set (ev_io *, int fd, int events) |
1684 | =item ev_io_set (ev_io *, int fd, int events) |
1173 | |
1685 | |
1174 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1686 | Configures an C<ev_io> watcher. The C<fd> is the file descriptor to |
1175 | receive events for and events is either C<EV_READ>, C<EV_WRITE> or |
1687 | receive events for and C<events> is either C<EV_READ>, C<EV_WRITE> or |
1176 | C<EV_READ | EV_WRITE> to receive the given events. |
1688 | C<EV_READ | EV_WRITE>, to express the desire to receive the given events. |
1177 | |
1689 | |
1178 | =item int fd [read-only] |
1690 | =item int fd [read-only] |
1179 | |
1691 | |
1180 | The file descriptor being watched. |
1692 | The file descriptor being watched. |
1181 | |
1693 | |
… | |
… | |
1190 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1702 | Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well |
1191 | readable, but only once. Since it is likely line-buffered, you could |
1703 | readable, but only once. Since it is likely line-buffered, you could |
1192 | attempt to read a whole line in the callback. |
1704 | attempt to read a whole line in the callback. |
1193 | |
1705 | |
1194 | static void |
1706 | static void |
1195 | stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1707 | stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents) |
1196 | { |
1708 | { |
1197 | ev_io_stop (loop, w); |
1709 | ev_io_stop (loop, w); |
1198 | .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1710 | .. read from stdin here (or from w->fd) and handle any I/O errors |
1199 | } |
1711 | } |
1200 | |
1712 | |
1201 | ... |
1713 | ... |
1202 | struct ev_loop *loop = ev_default_init (0); |
1714 | struct ev_loop *loop = ev_default_init (0); |
1203 | struct ev_io stdin_readable; |
1715 | ev_io stdin_readable; |
1204 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1716 | ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1205 | ev_io_start (loop, &stdin_readable); |
1717 | ev_io_start (loop, &stdin_readable); |
1206 | ev_loop (loop, 0); |
1718 | ev_run (loop, 0); |
1207 | |
1719 | |
1208 | |
1720 | |
1209 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1721 | =head2 C<ev_timer> - relative and optionally repeating timeouts |
1210 | |
1722 | |
1211 | Timer watchers are simple relative timers that generate an event after a |
1723 | Timer watchers are simple relative timers that generate an event after a |
1212 | given time, and optionally repeating in regular intervals after that. |
1724 | given time, and optionally repeating in regular intervals after that. |
1213 | |
1725 | |
1214 | The timers are based on real time, that is, if you register an event that |
1726 | The timers are based on real time, that is, if you register an event that |
1215 | times out after an hour and you reset your system clock to January last |
1727 | times out after an hour and you reset your system clock to January last |
1216 | year, it will still time out after (roughly) and hour. "Roughly" because |
1728 | year, it will still time out after (roughly) one hour. "Roughly" because |
1217 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1729 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1218 | monotonic clock option helps a lot here). |
1730 | monotonic clock option helps a lot here). |
1219 | |
1731 | |
1220 | The callback is guaranteed to be invoked only after its timeout has passed, |
1732 | The callback is guaranteed to be invoked only I<after> its timeout has |
1221 | but if multiple timers become ready during the same loop iteration then |
1733 | passed (not I<at>, so on systems with very low-resolution clocks this |
1222 | order of execution is undefined. |
1734 | might introduce a small delay). If multiple timers become ready during the |
|
|
1735 | same loop iteration then the ones with earlier time-out values are invoked |
|
|
1736 | before ones of the same priority with later time-out values (but this is |
|
|
1737 | no longer true when a callback calls C<ev_run> recursively). |
|
|
1738 | |
|
|
1739 | =head3 Be smart about timeouts |
|
|
1740 | |
|
|
1741 | Many real-world problems involve some kind of timeout, usually for error |
|
|
1742 | recovery. A typical example is an HTTP request - if the other side hangs, |
|
|
1743 | you want to raise some error after a while. |
|
|
1744 | |
|
|
1745 | What follows are some ways to handle this problem, from obvious and |
|
|
1746 | inefficient to smart and efficient. |
|
|
1747 | |
|
|
1748 | In the following, a 60 second activity timeout is assumed - a timeout that |
|
|
1749 | gets reset to 60 seconds each time there is activity (e.g. each time some |
|
|
1750 | data or other life sign was received). |
|
|
1751 | |
|
|
1752 | =over 4 |
|
|
1753 | |
|
|
1754 | =item 1. Use a timer and stop, reinitialise and start it on activity. |
|
|
1755 | |
|
|
1756 | This is the most obvious, but not the most simple way: In the beginning, |
|
|
1757 | start the watcher: |
|
|
1758 | |
|
|
1759 | ev_timer_init (timer, callback, 60., 0.); |
|
|
1760 | ev_timer_start (loop, timer); |
|
|
1761 | |
|
|
1762 | Then, each time there is some activity, C<ev_timer_stop> it, initialise it |
|
|
1763 | and start it again: |
|
|
1764 | |
|
|
1765 | ev_timer_stop (loop, timer); |
|
|
1766 | ev_timer_set (timer, 60., 0.); |
|
|
1767 | ev_timer_start (loop, timer); |
|
|
1768 | |
|
|
1769 | This is relatively simple to implement, but means that each time there is |
|
|
1770 | some activity, libev will first have to remove the timer from its internal |
|
|
1771 | data structure and then add it again. Libev tries to be fast, but it's |
|
|
1772 | still not a constant-time operation. |
|
|
1773 | |
|
|
1774 | =item 2. Use a timer and re-start it with C<ev_timer_again> inactivity. |
|
|
1775 | |
|
|
1776 | This is the easiest way, and involves using C<ev_timer_again> instead of |
|
|
1777 | C<ev_timer_start>. |
|
|
1778 | |
|
|
1779 | To implement this, configure an C<ev_timer> with a C<repeat> value |
|
|
1780 | of C<60> and then call C<ev_timer_again> at start and each time you |
|
|
1781 | successfully read or write some data. If you go into an idle state where |
|
|
1782 | you do not expect data to travel on the socket, you can C<ev_timer_stop> |
|
|
1783 | the timer, and C<ev_timer_again> will automatically restart it if need be. |
|
|
1784 | |
|
|
1785 | That means you can ignore both the C<ev_timer_start> function and the |
|
|
1786 | C<after> argument to C<ev_timer_set>, and only ever use the C<repeat> |
|
|
1787 | member and C<ev_timer_again>. |
|
|
1788 | |
|
|
1789 | At start: |
|
|
1790 | |
|
|
1791 | ev_init (timer, callback); |
|
|
1792 | timer->repeat = 60.; |
|
|
1793 | ev_timer_again (loop, timer); |
|
|
1794 | |
|
|
1795 | Each time there is some activity: |
|
|
1796 | |
|
|
1797 | ev_timer_again (loop, timer); |
|
|
1798 | |
|
|
1799 | It is even possible to change the time-out on the fly, regardless of |
|
|
1800 | whether the watcher is active or not: |
|
|
1801 | |
|
|
1802 | timer->repeat = 30.; |
|
|
1803 | ev_timer_again (loop, timer); |
|
|
1804 | |
|
|
1805 | This is slightly more efficient then stopping/starting the timer each time |
|
|
1806 | you want to modify its timeout value, as libev does not have to completely |
|
|
1807 | remove and re-insert the timer from/into its internal data structure. |
|
|
1808 | |
|
|
1809 | It is, however, even simpler than the "obvious" way to do it. |
|
|
1810 | |
|
|
1811 | =item 3. Let the timer time out, but then re-arm it as required. |
|
|
1812 | |
|
|
1813 | This method is more tricky, but usually most efficient: Most timeouts are |
|
|
1814 | relatively long compared to the intervals between other activity - in |
|
|
1815 | our example, within 60 seconds, there are usually many I/O events with |
|
|
1816 | associated activity resets. |
|
|
1817 | |
|
|
1818 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
|
|
1819 | but remember the time of last activity, and check for a real timeout only |
|
|
1820 | within the callback: |
|
|
1821 | |
|
|
1822 | ev_tstamp last_activity; // time of last activity |
|
|
1823 | |
|
|
1824 | static void |
|
|
1825 | callback (EV_P_ ev_timer *w, int revents) |
|
|
1826 | { |
|
|
1827 | ev_tstamp now = ev_now (EV_A); |
|
|
1828 | ev_tstamp timeout = last_activity + 60.; |
|
|
1829 | |
|
|
1830 | // if last_activity + 60. is older than now, we did time out |
|
|
1831 | if (timeout < now) |
|
|
1832 | { |
|
|
1833 | // timeout occurred, take action |
|
|
1834 | } |
|
|
1835 | else |
|
|
1836 | { |
|
|
1837 | // callback was invoked, but there was some activity, re-arm |
|
|
1838 | // the watcher to fire in last_activity + 60, which is |
|
|
1839 | // guaranteed to be in the future, so "again" is positive: |
|
|
1840 | w->repeat = timeout - now; |
|
|
1841 | ev_timer_again (EV_A_ w); |
|
|
1842 | } |
|
|
1843 | } |
|
|
1844 | |
|
|
1845 | To summarise the callback: first calculate the real timeout (defined |
|
|
1846 | as "60 seconds after the last activity"), then check if that time has |
|
|
1847 | been reached, which means something I<did>, in fact, time out. Otherwise |
|
|
1848 | the callback was invoked too early (C<timeout> is in the future), so |
|
|
1849 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1850 | a timeout then. |
|
|
1851 | |
|
|
1852 | Note how C<ev_timer_again> is used, taking advantage of the |
|
|
1853 | C<ev_timer_again> optimisation when the timer is already running. |
|
|
1854 | |
|
|
1855 | This scheme causes more callback invocations (about one every 60 seconds |
|
|
1856 | minus half the average time between activity), but virtually no calls to |
|
|
1857 | libev to change the timeout. |
|
|
1858 | |
|
|
1859 | To start the timer, simply initialise the watcher and set C<last_activity> |
|
|
1860 | to the current time (meaning we just have some activity :), then call the |
|
|
1861 | callback, which will "do the right thing" and start the timer: |
|
|
1862 | |
|
|
1863 | ev_init (timer, callback); |
|
|
1864 | last_activity = ev_now (loop); |
|
|
1865 | callback (loop, timer, EV_TIMER); |
|
|
1866 | |
|
|
1867 | And when there is some activity, simply store the current time in |
|
|
1868 | C<last_activity>, no libev calls at all: |
|
|
1869 | |
|
|
1870 | last_activity = ev_now (loop); |
|
|
1871 | |
|
|
1872 | This technique is slightly more complex, but in most cases where the |
|
|
1873 | time-out is unlikely to be triggered, much more efficient. |
|
|
1874 | |
|
|
1875 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1876 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1877 | fix things for you. |
|
|
1878 | |
|
|
1879 | =item 4. Wee, just use a double-linked list for your timeouts. |
|
|
1880 | |
|
|
1881 | If there is not one request, but many thousands (millions...), all |
|
|
1882 | employing some kind of timeout with the same timeout value, then one can |
|
|
1883 | do even better: |
|
|
1884 | |
|
|
1885 | When starting the timeout, calculate the timeout value and put the timeout |
|
|
1886 | at the I<end> of the list. |
|
|
1887 | |
|
|
1888 | Then use an C<ev_timer> to fire when the timeout at the I<beginning> of |
|
|
1889 | the list is expected to fire (for example, using the technique #3). |
|
|
1890 | |
|
|
1891 | When there is some activity, remove the timer from the list, recalculate |
|
|
1892 | the timeout, append it to the end of the list again, and make sure to |
|
|
1893 | update the C<ev_timer> if it was taken from the beginning of the list. |
|
|
1894 | |
|
|
1895 | This way, one can manage an unlimited number of timeouts in O(1) time for |
|
|
1896 | starting, stopping and updating the timers, at the expense of a major |
|
|
1897 | complication, and having to use a constant timeout. The constant timeout |
|
|
1898 | ensures that the list stays sorted. |
|
|
1899 | |
|
|
1900 | =back |
|
|
1901 | |
|
|
1902 | So which method the best? |
|
|
1903 | |
|
|
1904 | Method #2 is a simple no-brain-required solution that is adequate in most |
|
|
1905 | situations. Method #3 requires a bit more thinking, but handles many cases |
|
|
1906 | better, and isn't very complicated either. In most case, choosing either |
|
|
1907 | one is fine, with #3 being better in typical situations. |
|
|
1908 | |
|
|
1909 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
|
|
1910 | rather complicated, but extremely efficient, something that really pays |
|
|
1911 | off after the first million or so of active timers, i.e. it's usually |
|
|
1912 | overkill :) |
1223 | |
1913 | |
1224 | =head3 The special problem of time updates |
1914 | =head3 The special problem of time updates |
1225 | |
1915 | |
1226 | Establishing the current time is a costly operation (it usually takes at |
1916 | Establishing the current time is a costly operation (it usually takes at |
1227 | least two system calls): EV therefore updates its idea of the current |
1917 | least two system calls): EV therefore updates its idea of the current |
1228 | time only before and after C<ev_loop> polls for new events, which causes |
1918 | time only before and after C<ev_run> collects new events, which causes a |
1229 | a growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1919 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1230 | lots of events. |
1920 | lots of events in one iteration. |
1231 | |
1921 | |
1232 | The relative timeouts are calculated relative to the C<ev_now ()> |
1922 | The relative timeouts are calculated relative to the C<ev_now ()> |
1233 | time. This is usually the right thing as this timestamp refers to the time |
1923 | time. This is usually the right thing as this timestamp refers to the time |
1234 | of the event triggering whatever timeout you are modifying/starting. If |
1924 | of the event triggering whatever timeout you are modifying/starting. If |
1235 | you suspect event processing to be delayed and you I<need> to base the |
1925 | you suspect event processing to be delayed and you I<need> to base the |
… | |
… | |
1239 | |
1929 | |
1240 | If the event loop is suspended for a long time, you can also force an |
1930 | If the event loop is suspended for a long time, you can also force an |
1241 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1931 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1242 | ()>. |
1932 | ()>. |
1243 | |
1933 | |
|
|
1934 | =head3 The special problems of suspended animation |
|
|
1935 | |
|
|
1936 | When you leave the server world it is quite customary to hit machines that |
|
|
1937 | can suspend/hibernate - what happens to the clocks during such a suspend? |
|
|
1938 | |
|
|
1939 | Some quick tests made with a Linux 2.6.28 indicate that a suspend freezes |
|
|
1940 | all processes, while the clocks (C<times>, C<CLOCK_MONOTONIC>) continue |
|
|
1941 | to run until the system is suspended, but they will not advance while the |
|
|
1942 | system is suspended. That means, on resume, it will be as if the program |
|
|
1943 | was frozen for a few seconds, but the suspend time will not be counted |
|
|
1944 | towards C<ev_timer> when a monotonic clock source is used. The real time |
|
|
1945 | clock advanced as expected, but if it is used as sole clocksource, then a |
|
|
1946 | long suspend would be detected as a time jump by libev, and timers would |
|
|
1947 | be adjusted accordingly. |
|
|
1948 | |
|
|
1949 | I would not be surprised to see different behaviour in different between |
|
|
1950 | operating systems, OS versions or even different hardware. |
|
|
1951 | |
|
|
1952 | The other form of suspend (job control, or sending a SIGSTOP) will see a |
|
|
1953 | time jump in the monotonic clocks and the realtime clock. If the program |
|
|
1954 | is suspended for a very long time, and monotonic clock sources are in use, |
|
|
1955 | then you can expect C<ev_timer>s to expire as the full suspension time |
|
|
1956 | will be counted towards the timers. When no monotonic clock source is in |
|
|
1957 | use, then libev will again assume a timejump and adjust accordingly. |
|
|
1958 | |
|
|
1959 | It might be beneficial for this latter case to call C<ev_suspend> |
|
|
1960 | and C<ev_resume> in code that handles C<SIGTSTP>, to at least get |
|
|
1961 | deterministic behaviour in this case (you can do nothing against |
|
|
1962 | C<SIGSTOP>). |
|
|
1963 | |
1244 | =head3 Watcher-Specific Functions and Data Members |
1964 | =head3 Watcher-Specific Functions and Data Members |
1245 | |
1965 | |
1246 | =over 4 |
1966 | =over 4 |
1247 | |
1967 | |
1248 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1968 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
… | |
… | |
1271 | If the timer is started but non-repeating, stop it (as if it timed out). |
1991 | If the timer is started but non-repeating, stop it (as if it timed out). |
1272 | |
1992 | |
1273 | If the timer is repeating, either start it if necessary (with the |
1993 | If the timer is repeating, either start it if necessary (with the |
1274 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1994 | C<repeat> value), or reset the running timer to the C<repeat> value. |
1275 | |
1995 | |
1276 | This sounds a bit complicated, but here is a useful and typical |
1996 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
1277 | example: Imagine you have a TCP connection and you want a so-called idle |
1997 | usage example. |
1278 | timeout, that is, you want to be called when there have been, say, 60 |
|
|
1279 | seconds of inactivity on the socket. The easiest way to do this is to |
|
|
1280 | configure an C<ev_timer> with a C<repeat> value of C<60> and then call |
|
|
1281 | C<ev_timer_again> each time you successfully read or write some data. If |
|
|
1282 | you go into an idle state where you do not expect data to travel on the |
|
|
1283 | socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will |
|
|
1284 | automatically restart it if need be. |
|
|
1285 | |
1998 | |
1286 | That means you can ignore the C<after> value and C<ev_timer_start> |
1999 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
1287 | altogether and only ever use the C<repeat> value and C<ev_timer_again>: |
|
|
1288 | |
2000 | |
1289 | ev_timer_init (timer, callback, 0., 5.); |
2001 | Returns the remaining time until a timer fires. If the timer is active, |
1290 | ev_timer_again (loop, timer); |
2002 | then this time is relative to the current event loop time, otherwise it's |
1291 | ... |
2003 | the timeout value currently configured. |
1292 | timer->again = 17.; |
|
|
1293 | ev_timer_again (loop, timer); |
|
|
1294 | ... |
|
|
1295 | timer->again = 10.; |
|
|
1296 | ev_timer_again (loop, timer); |
|
|
1297 | |
2004 | |
1298 | This is more slightly efficient then stopping/starting the timer each time |
2005 | That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns |
1299 | you want to modify its timeout value. |
2006 | C<5>. When the timer is started and one second passes, C<ev_timer_remaining> |
|
|
2007 | will return C<4>. When the timer expires and is restarted, it will return |
|
|
2008 | roughly C<7> (likely slightly less as callback invocation takes some time, |
|
|
2009 | too), and so on. |
1300 | |
2010 | |
1301 | =item ev_tstamp repeat [read-write] |
2011 | =item ev_tstamp repeat [read-write] |
1302 | |
2012 | |
1303 | The current C<repeat> value. Will be used each time the watcher times out |
2013 | The current C<repeat> value. Will be used each time the watcher times out |
1304 | or C<ev_timer_again> is called and determines the next timeout (if any), |
2014 | or C<ev_timer_again> is called, and determines the next timeout (if any), |
1305 | which is also when any modifications are taken into account. |
2015 | which is also when any modifications are taken into account. |
1306 | |
2016 | |
1307 | =back |
2017 | =back |
1308 | |
2018 | |
1309 | =head3 Examples |
2019 | =head3 Examples |
1310 | |
2020 | |
1311 | Example: Create a timer that fires after 60 seconds. |
2021 | Example: Create a timer that fires after 60 seconds. |
1312 | |
2022 | |
1313 | static void |
2023 | static void |
1314 | one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2024 | one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1315 | { |
2025 | { |
1316 | .. one minute over, w is actually stopped right here |
2026 | .. one minute over, w is actually stopped right here |
1317 | } |
2027 | } |
1318 | |
2028 | |
1319 | struct ev_timer mytimer; |
2029 | ev_timer mytimer; |
1320 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
2030 | ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1321 | ev_timer_start (loop, &mytimer); |
2031 | ev_timer_start (loop, &mytimer); |
1322 | |
2032 | |
1323 | Example: Create a timeout timer that times out after 10 seconds of |
2033 | Example: Create a timeout timer that times out after 10 seconds of |
1324 | inactivity. |
2034 | inactivity. |
1325 | |
2035 | |
1326 | static void |
2036 | static void |
1327 | timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
2037 | timeout_cb (struct ev_loop *loop, ev_timer *w, int revents) |
1328 | { |
2038 | { |
1329 | .. ten seconds without any activity |
2039 | .. ten seconds without any activity |
1330 | } |
2040 | } |
1331 | |
2041 | |
1332 | struct ev_timer mytimer; |
2042 | ev_timer mytimer; |
1333 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
2043 | ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1334 | ev_timer_again (&mytimer); /* start timer */ |
2044 | ev_timer_again (&mytimer); /* start timer */ |
1335 | ev_loop (loop, 0); |
2045 | ev_run (loop, 0); |
1336 | |
2046 | |
1337 | // and in some piece of code that gets executed on any "activity": |
2047 | // and in some piece of code that gets executed on any "activity": |
1338 | // reset the timeout to start ticking again at 10 seconds |
2048 | // reset the timeout to start ticking again at 10 seconds |
1339 | ev_timer_again (&mytimer); |
2049 | ev_timer_again (&mytimer); |
1340 | |
2050 | |
… | |
… | |
1342 | =head2 C<ev_periodic> - to cron or not to cron? |
2052 | =head2 C<ev_periodic> - to cron or not to cron? |
1343 | |
2053 | |
1344 | Periodic watchers are also timers of a kind, but they are very versatile |
2054 | Periodic watchers are also timers of a kind, but they are very versatile |
1345 | (and unfortunately a bit complex). |
2055 | (and unfortunately a bit complex). |
1346 | |
2056 | |
1347 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
2057 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1348 | but on wall clock time (absolute time). You can tell a periodic watcher |
2058 | relative time, the physical time that passes) but on wall clock time |
1349 | to trigger after some specific point in time. For example, if you tell a |
2059 | (absolute time, the thing you can read on your calender or clock). The |
1350 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
2060 | difference is that wall clock time can run faster or slower than real |
1351 | + 10.>, that is, an absolute time not a delay) and then reset your system |
2061 | time, and time jumps are not uncommon (e.g. when you adjust your |
1352 | clock to January of the previous year, then it will take more than year |
2062 | wrist-watch). |
1353 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1354 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1355 | |
2063 | |
|
|
2064 | You can tell a periodic watcher to trigger after some specific point |
|
|
2065 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
2066 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
2067 | not a delay) and then reset your system clock to January of the previous |
|
|
2068 | year, then it will take a year or more to trigger the event (unlike an |
|
|
2069 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
2070 | it, as it uses a relative timeout). |
|
|
2071 | |
1356 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
2072 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1357 | such as triggering an event on each "midnight, local time", or other |
2073 | timers, such as triggering an event on each "midnight, local time", or |
1358 | complicated, rules. |
2074 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
2075 | those cannot react to time jumps. |
1359 | |
2076 | |
1360 | As with timers, the callback is guaranteed to be invoked only when the |
2077 | As with timers, the callback is guaranteed to be invoked only when the |
1361 | time (C<at>) has passed, but if multiple periodic timers become ready |
2078 | point in time where it is supposed to trigger has passed. If multiple |
1362 | during the same loop iteration then order of execution is undefined. |
2079 | timers become ready during the same loop iteration then the ones with |
|
|
2080 | earlier time-out values are invoked before ones with later time-out values |
|
|
2081 | (but this is no longer true when a callback calls C<ev_run> recursively). |
1363 | |
2082 | |
1364 | =head3 Watcher-Specific Functions and Data Members |
2083 | =head3 Watcher-Specific Functions and Data Members |
1365 | |
2084 | |
1366 | =over 4 |
2085 | =over 4 |
1367 | |
2086 | |
1368 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
2087 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1369 | |
2088 | |
1370 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
2089 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1371 | |
2090 | |
1372 | Lots of arguments, lets sort it out... There are basically three modes of |
2091 | Lots of arguments, let's sort it out... There are basically three modes of |
1373 | operation, and we will explain them from simplest to complex: |
2092 | operation, and we will explain them from simplest to most complex: |
1374 | |
2093 | |
1375 | =over 4 |
2094 | =over 4 |
1376 | |
2095 | |
1377 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
2096 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1378 | |
2097 | |
1379 | In this configuration the watcher triggers an event after the wall clock |
2098 | In this configuration the watcher triggers an event after the wall clock |
1380 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
2099 | time C<offset> has passed. It will not repeat and will not adjust when a |
1381 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
2100 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1382 | run when the system time reaches or surpasses this time. |
2101 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
2102 | this point in time. |
1383 | |
2103 | |
1384 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
2104 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1385 | |
2105 | |
1386 | In this mode the watcher will always be scheduled to time out at the next |
2106 | In this mode the watcher will always be scheduled to time out at the next |
1387 | C<at + N * interval> time (for some integer N, which can also be negative) |
2107 | C<offset + N * interval> time (for some integer N, which can also be |
1388 | and then repeat, regardless of any time jumps. |
2108 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
2109 | argument is merely an offset into the C<interval> periods. |
1389 | |
2110 | |
1390 | This can be used to create timers that do not drift with respect to system |
2111 | This can be used to create timers that do not drift with respect to the |
1391 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
2112 | system clock, for example, here is an C<ev_periodic> that triggers each |
1392 | the hour: |
2113 | hour, on the hour (with respect to UTC): |
1393 | |
2114 | |
1394 | ev_periodic_set (&periodic, 0., 3600., 0); |
2115 | ev_periodic_set (&periodic, 0., 3600., 0); |
1395 | |
2116 | |
1396 | This doesn't mean there will always be 3600 seconds in between triggers, |
2117 | This doesn't mean there will always be 3600 seconds in between triggers, |
1397 | but only that the callback will be called when the system time shows a |
2118 | but only that the callback will be called when the system time shows a |
1398 | full hour (UTC), or more correctly, when the system time is evenly divisible |
2119 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1399 | by 3600. |
2120 | by 3600. |
1400 | |
2121 | |
1401 | Another way to think about it (for the mathematically inclined) is that |
2122 | Another way to think about it (for the mathematically inclined) is that |
1402 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2123 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1403 | time where C<time = at (mod interval)>, regardless of any time jumps. |
2124 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1404 | |
2125 | |
1405 | For numerical stability it is preferable that the C<at> value is near |
2126 | For numerical stability it is preferable that the C<offset> value is near |
1406 | C<ev_now ()> (the current time), but there is no range requirement for |
2127 | C<ev_now ()> (the current time), but there is no range requirement for |
1407 | this value, and in fact is often specified as zero. |
2128 | this value, and in fact is often specified as zero. |
1408 | |
2129 | |
1409 | Note also that there is an upper limit to how often a timer can fire (CPU |
2130 | Note also that there is an upper limit to how often a timer can fire (CPU |
1410 | speed for example), so if C<interval> is very small then timing stability |
2131 | speed for example), so if C<interval> is very small then timing stability |
1411 | will of course deteriorate. Libev itself tries to be exact to be about one |
2132 | will of course deteriorate. Libev itself tries to be exact to be about one |
1412 | millisecond (if the OS supports it and the machine is fast enough). |
2133 | millisecond (if the OS supports it and the machine is fast enough). |
1413 | |
2134 | |
1414 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
2135 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1415 | |
2136 | |
1416 | In this mode the values for C<interval> and C<at> are both being |
2137 | In this mode the values for C<interval> and C<offset> are both being |
1417 | ignored. Instead, each time the periodic watcher gets scheduled, the |
2138 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1418 | reschedule callback will be called with the watcher as first, and the |
2139 | reschedule callback will be called with the watcher as first, and the |
1419 | current time as second argument. |
2140 | current time as second argument. |
1420 | |
2141 | |
1421 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
2142 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1422 | ever, or make ANY event loop modifications whatsoever>. |
2143 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
2144 | allowed by documentation here>. |
1423 | |
2145 | |
1424 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
2146 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1425 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
2147 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1426 | only event loop modification you are allowed to do). |
2148 | only event loop modification you are allowed to do). |
1427 | |
2149 | |
1428 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
2150 | The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic |
1429 | *w, ev_tstamp now)>, e.g.: |
2151 | *w, ev_tstamp now)>, e.g.: |
1430 | |
2152 | |
|
|
2153 | static ev_tstamp |
1431 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
2154 | my_rescheduler (ev_periodic *w, ev_tstamp now) |
1432 | { |
2155 | { |
1433 | return now + 60.; |
2156 | return now + 60.; |
1434 | } |
2157 | } |
1435 | |
2158 | |
1436 | It must return the next time to trigger, based on the passed time value |
2159 | It must return the next time to trigger, based on the passed time value |
… | |
… | |
1456 | a different time than the last time it was called (e.g. in a crond like |
2179 | a different time than the last time it was called (e.g. in a crond like |
1457 | program when the crontabs have changed). |
2180 | program when the crontabs have changed). |
1458 | |
2181 | |
1459 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
2182 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1460 | |
2183 | |
1461 | When active, returns the absolute time that the watcher is supposed to |
2184 | When active, returns the absolute time that the watcher is supposed |
1462 | trigger next. |
2185 | to trigger next. This is not the same as the C<offset> argument to |
|
|
2186 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
2187 | rescheduling modes. |
1463 | |
2188 | |
1464 | =item ev_tstamp offset [read-write] |
2189 | =item ev_tstamp offset [read-write] |
1465 | |
2190 | |
1466 | When repeating, this contains the offset value, otherwise this is the |
2191 | When repeating, this contains the offset value, otherwise this is the |
1467 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
2192 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
2193 | although libev might modify this value for better numerical stability). |
1468 | |
2194 | |
1469 | Can be modified any time, but changes only take effect when the periodic |
2195 | Can be modified any time, but changes only take effect when the periodic |
1470 | timer fires or C<ev_periodic_again> is being called. |
2196 | timer fires or C<ev_periodic_again> is being called. |
1471 | |
2197 | |
1472 | =item ev_tstamp interval [read-write] |
2198 | =item ev_tstamp interval [read-write] |
1473 | |
2199 | |
1474 | The current interval value. Can be modified any time, but changes only |
2200 | The current interval value. Can be modified any time, but changes only |
1475 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
2201 | take effect when the periodic timer fires or C<ev_periodic_again> is being |
1476 | called. |
2202 | called. |
1477 | |
2203 | |
1478 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
2204 | =item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write] |
1479 | |
2205 | |
1480 | The current reschedule callback, or C<0>, if this functionality is |
2206 | The current reschedule callback, or C<0>, if this functionality is |
1481 | switched off. Can be changed any time, but changes only take effect when |
2207 | switched off. Can be changed any time, but changes only take effect when |
1482 | the periodic timer fires or C<ev_periodic_again> is being called. |
2208 | the periodic timer fires or C<ev_periodic_again> is being called. |
1483 | |
2209 | |
1484 | =back |
2210 | =back |
1485 | |
2211 | |
1486 | =head3 Examples |
2212 | =head3 Examples |
1487 | |
2213 | |
1488 | Example: Call a callback every hour, or, more precisely, whenever the |
2214 | Example: Call a callback every hour, or, more precisely, whenever the |
1489 | system clock is divisible by 3600. The callback invocation times have |
2215 | system time is divisible by 3600. The callback invocation times have |
1490 | potentially a lot of jitter, but good long-term stability. |
2216 | potentially a lot of jitter, but good long-term stability. |
1491 | |
2217 | |
1492 | static void |
2218 | static void |
1493 | clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
2219 | clock_cb (struct ev_loop *loop, ev_periodic *w, int revents) |
1494 | { |
2220 | { |
1495 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
2221 | ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1496 | } |
2222 | } |
1497 | |
2223 | |
1498 | struct ev_periodic hourly_tick; |
2224 | ev_periodic hourly_tick; |
1499 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
2225 | ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1500 | ev_periodic_start (loop, &hourly_tick); |
2226 | ev_periodic_start (loop, &hourly_tick); |
1501 | |
2227 | |
1502 | Example: The same as above, but use a reschedule callback to do it: |
2228 | Example: The same as above, but use a reschedule callback to do it: |
1503 | |
2229 | |
1504 | #include <math.h> |
2230 | #include <math.h> |
1505 | |
2231 | |
1506 | static ev_tstamp |
2232 | static ev_tstamp |
1507 | my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
2233 | my_scheduler_cb (ev_periodic *w, ev_tstamp now) |
1508 | { |
2234 | { |
1509 | return fmod (now, 3600.) + 3600.; |
2235 | return now + (3600. - fmod (now, 3600.)); |
1510 | } |
2236 | } |
1511 | |
2237 | |
1512 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
2238 | ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1513 | |
2239 | |
1514 | Example: Call a callback every hour, starting now: |
2240 | Example: Call a callback every hour, starting now: |
1515 | |
2241 | |
1516 | struct ev_periodic hourly_tick; |
2242 | ev_periodic hourly_tick; |
1517 | ev_periodic_init (&hourly_tick, clock_cb, |
2243 | ev_periodic_init (&hourly_tick, clock_cb, |
1518 | fmod (ev_now (loop), 3600.), 3600., 0); |
2244 | fmod (ev_now (loop), 3600.), 3600., 0); |
1519 | ev_periodic_start (loop, &hourly_tick); |
2245 | ev_periodic_start (loop, &hourly_tick); |
1520 | |
2246 | |
1521 | |
2247 | |
… | |
… | |
1524 | Signal watchers will trigger an event when the process receives a specific |
2250 | Signal watchers will trigger an event when the process receives a specific |
1525 | signal one or more times. Even though signals are very asynchronous, libev |
2251 | signal one or more times. Even though signals are very asynchronous, libev |
1526 | will try it's best to deliver signals synchronously, i.e. as part of the |
2252 | will try it's best to deliver signals synchronously, i.e. as part of the |
1527 | normal event processing, like any other event. |
2253 | normal event processing, like any other event. |
1528 | |
2254 | |
|
|
2255 | If you want signals to be delivered truly asynchronously, just use |
|
|
2256 | C<sigaction> as you would do without libev and forget about sharing |
|
|
2257 | the signal. You can even use C<ev_async> from a signal handler to |
|
|
2258 | synchronously wake up an event loop. |
|
|
2259 | |
1529 | You can configure as many watchers as you like per signal. Only when the |
2260 | You can configure as many watchers as you like for the same signal, but |
|
|
2261 | only within the same loop, i.e. you can watch for C<SIGINT> in your |
|
|
2262 | default loop and for C<SIGIO> in another loop, but you cannot watch for |
|
|
2263 | C<SIGINT> in both the default loop and another loop at the same time. At |
|
|
2264 | the moment, C<SIGCHLD> is permanently tied to the default loop. |
|
|
2265 | |
1530 | first watcher gets started will libev actually register a signal watcher |
2266 | When the first watcher gets started will libev actually register something |
1531 | with the kernel (thus it coexists with your own signal handlers as long |
2267 | with the kernel (thus it coexists with your own signal handlers as long as |
1532 | as you don't register any with libev). Similarly, when the last signal |
2268 | you don't register any with libev for the same signal). |
1533 | watcher for a signal is stopped libev will reset the signal handler to |
|
|
1534 | SIG_DFL (regardless of what it was set to before). |
|
|
1535 | |
2269 | |
1536 | If possible and supported, libev will install its handlers with |
2270 | If possible and supported, libev will install its handlers with |
1537 | C<SA_RESTART> behaviour enabled, so system calls should not be unduly |
2271 | C<SA_RESTART> (or equivalent) behaviour enabled, so system calls should |
1538 | interrupted. If you have a problem with system calls getting interrupted by |
2272 | not be unduly interrupted. If you have a problem with system calls getting |
1539 | signals you can block all signals in an C<ev_check> watcher and unblock |
2273 | interrupted by signals you can block all signals in an C<ev_check> watcher |
1540 | them in an C<ev_prepare> watcher. |
2274 | and unblock them in an C<ev_prepare> watcher. |
|
|
2275 | |
|
|
2276 | =head3 The special problem of inheritance over fork/execve/pthread_create |
|
|
2277 | |
|
|
2278 | Both the signal mask (C<sigprocmask>) and the signal disposition |
|
|
2279 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
|
|
2280 | stopping it again), that is, libev might or might not block the signal, |
|
|
2281 | and might or might not set or restore the installed signal handler. |
|
|
2282 | |
|
|
2283 | While this does not matter for the signal disposition (libev never |
|
|
2284 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
|
|
2285 | C<execve>), this matters for the signal mask: many programs do not expect |
|
|
2286 | certain signals to be blocked. |
|
|
2287 | |
|
|
2288 | This means that before calling C<exec> (from the child) you should reset |
|
|
2289 | the signal mask to whatever "default" you expect (all clear is a good |
|
|
2290 | choice usually). |
|
|
2291 | |
|
|
2292 | The simplest way to ensure that the signal mask is reset in the child is |
|
|
2293 | to install a fork handler with C<pthread_atfork> that resets it. That will |
|
|
2294 | catch fork calls done by libraries (such as the libc) as well. |
|
|
2295 | |
|
|
2296 | In current versions of libev, the signal will not be blocked indefinitely |
|
|
2297 | unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces |
|
|
2298 | the window of opportunity for problems, it will not go away, as libev |
|
|
2299 | I<has> to modify the signal mask, at least temporarily. |
|
|
2300 | |
|
|
2301 | So I can't stress this enough: I<If you do not reset your signal mask when |
|
|
2302 | you expect it to be empty, you have a race condition in your code>. This |
|
|
2303 | is not a libev-specific thing, this is true for most event libraries. |
1541 | |
2304 | |
1542 | =head3 Watcher-Specific Functions and Data Members |
2305 | =head3 Watcher-Specific Functions and Data Members |
1543 | |
2306 | |
1544 | =over 4 |
2307 | =over 4 |
1545 | |
2308 | |
… | |
… | |
1556 | |
2319 | |
1557 | =back |
2320 | =back |
1558 | |
2321 | |
1559 | =head3 Examples |
2322 | =head3 Examples |
1560 | |
2323 | |
1561 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
2324 | Example: Try to exit cleanly on SIGINT. |
1562 | |
2325 | |
1563 | static void |
2326 | static void |
1564 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
2327 | sigint_cb (struct ev_loop *loop, ev_signal *w, int revents) |
1565 | { |
2328 | { |
1566 | ev_unloop (loop, EVUNLOOP_ALL); |
2329 | ev_break (loop, EVBREAK_ALL); |
1567 | } |
2330 | } |
1568 | |
2331 | |
1569 | struct ev_signal signal_watcher; |
2332 | ev_signal signal_watcher; |
1570 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
2333 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1571 | ev_signal_start (loop, &sigint_cb); |
2334 | ev_signal_start (loop, &signal_watcher); |
1572 | |
2335 | |
1573 | |
2336 | |
1574 | =head2 C<ev_child> - watch out for process status changes |
2337 | =head2 C<ev_child> - watch out for process status changes |
1575 | |
2338 | |
1576 | Child watchers trigger when your process receives a SIGCHLD in response to |
2339 | Child watchers trigger when your process receives a SIGCHLD in response to |
1577 | some child status changes (most typically when a child of yours dies). It |
2340 | some child status changes (most typically when a child of yours dies or |
1578 | is permissible to install a child watcher I<after> the child has been |
2341 | exits). It is permissible to install a child watcher I<after> the child |
1579 | forked (which implies it might have already exited), as long as the event |
2342 | has been forked (which implies it might have already exited), as long |
1580 | loop isn't entered (or is continued from a watcher). |
2343 | as the event loop isn't entered (or is continued from a watcher), i.e., |
|
|
2344 | forking and then immediately registering a watcher for the child is fine, |
|
|
2345 | but forking and registering a watcher a few event loop iterations later or |
|
|
2346 | in the next callback invocation is not. |
1581 | |
2347 | |
1582 | Only the default event loop is capable of handling signals, and therefore |
2348 | Only the default event loop is capable of handling signals, and therefore |
1583 | you can only register child watchers in the default event loop. |
2349 | you can only register child watchers in the default event loop. |
1584 | |
2350 | |
|
|
2351 | Due to some design glitches inside libev, child watchers will always be |
|
|
2352 | handled at maximum priority (their priority is set to C<EV_MAXPRI> by |
|
|
2353 | libev) |
|
|
2354 | |
1585 | =head3 Process Interaction |
2355 | =head3 Process Interaction |
1586 | |
2356 | |
1587 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
2357 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
1588 | initialised. This is necessary to guarantee proper behaviour even if |
2358 | initialised. This is necessary to guarantee proper behaviour even if the |
1589 | the first child watcher is started after the child exits. The occurrence |
2359 | first child watcher is started after the child exits. The occurrence |
1590 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
2360 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
1591 | synchronously as part of the event loop processing. Libev always reaps all |
2361 | synchronously as part of the event loop processing. Libev always reaps all |
1592 | children, even ones not watched. |
2362 | children, even ones not watched. |
1593 | |
2363 | |
1594 | =head3 Overriding the Built-In Processing |
2364 | =head3 Overriding the Built-In Processing |
… | |
… | |
1604 | =head3 Stopping the Child Watcher |
2374 | =head3 Stopping the Child Watcher |
1605 | |
2375 | |
1606 | Currently, the child watcher never gets stopped, even when the |
2376 | Currently, the child watcher never gets stopped, even when the |
1607 | child terminates, so normally one needs to stop the watcher in the |
2377 | child terminates, so normally one needs to stop the watcher in the |
1608 | callback. Future versions of libev might stop the watcher automatically |
2378 | callback. Future versions of libev might stop the watcher automatically |
1609 | when a child exit is detected. |
2379 | when a child exit is detected (calling C<ev_child_stop> twice is not a |
|
|
2380 | problem). |
1610 | |
2381 | |
1611 | =head3 Watcher-Specific Functions and Data Members |
2382 | =head3 Watcher-Specific Functions and Data Members |
1612 | |
2383 | |
1613 | =over 4 |
2384 | =over 4 |
1614 | |
2385 | |
… | |
… | |
1646 | its completion. |
2417 | its completion. |
1647 | |
2418 | |
1648 | ev_child cw; |
2419 | ev_child cw; |
1649 | |
2420 | |
1650 | static void |
2421 | static void |
1651 | child_cb (EV_P_ struct ev_child *w, int revents) |
2422 | child_cb (EV_P_ ev_child *w, int revents) |
1652 | { |
2423 | { |
1653 | ev_child_stop (EV_A_ w); |
2424 | ev_child_stop (EV_A_ w); |
1654 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
2425 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1655 | } |
2426 | } |
1656 | |
2427 | |
… | |
… | |
1671 | |
2442 | |
1672 | |
2443 | |
1673 | =head2 C<ev_stat> - did the file attributes just change? |
2444 | =head2 C<ev_stat> - did the file attributes just change? |
1674 | |
2445 | |
1675 | This watches a file system path for attribute changes. That is, it calls |
2446 | This watches a file system path for attribute changes. That is, it calls |
1676 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
2447 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1677 | compared to the last time, invoking the callback if it did. |
2448 | and sees if it changed compared to the last time, invoking the callback if |
|
|
2449 | it did. |
1678 | |
2450 | |
1679 | The path does not need to exist: changing from "path exists" to "path does |
2451 | The path does not need to exist: changing from "path exists" to "path does |
1680 | not exist" is a status change like any other. The condition "path does |
2452 | not exist" is a status change like any other. The condition "path does not |
1681 | not exist" is signified by the C<st_nlink> field being zero (which is |
2453 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1682 | otherwise always forced to be at least one) and all the other fields of |
2454 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1683 | the stat buffer having unspecified contents. |
2455 | least one) and all the other fields of the stat buffer having unspecified |
|
|
2456 | contents. |
1684 | |
2457 | |
1685 | The path I<should> be absolute and I<must not> end in a slash. If it is |
2458 | The path I<must not> end in a slash or contain special components such as |
|
|
2459 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1686 | relative and your working directory changes, the behaviour is undefined. |
2460 | your working directory changes, then the behaviour is undefined. |
1687 | |
2461 | |
1688 | Since there is no standard to do this, the portable implementation simply |
2462 | Since there is no portable change notification interface available, the |
1689 | calls C<stat (2)> regularly on the path to see if it changed somehow. You |
2463 | portable implementation simply calls C<stat(2)> regularly on the path |
1690 | can specify a recommended polling interval for this case. If you specify |
2464 | to see if it changed somehow. You can specify a recommended polling |
1691 | a polling interval of C<0> (highly recommended!) then a I<suitable, |
2465 | interval for this case. If you specify a polling interval of C<0> (highly |
1692 | unspecified default> value will be used (which you can expect to be around |
2466 | recommended!) then a I<suitable, unspecified default> value will be used |
1693 | five seconds, although this might change dynamically). Libev will also |
2467 | (which you can expect to be around five seconds, although this might |
1694 | impose a minimum interval which is currently around C<0.1>, but thats |
2468 | change dynamically). Libev will also impose a minimum interval which is |
1695 | usually overkill. |
2469 | currently around C<0.1>, but that's usually overkill. |
1696 | |
2470 | |
1697 | This watcher type is not meant for massive numbers of stat watchers, |
2471 | This watcher type is not meant for massive numbers of stat watchers, |
1698 | as even with OS-supported change notifications, this can be |
2472 | as even with OS-supported change notifications, this can be |
1699 | resource-intensive. |
2473 | resource-intensive. |
1700 | |
2474 | |
1701 | At the time of this writing, only the Linux inotify interface is |
2475 | At the time of this writing, the only OS-specific interface implemented |
1702 | implemented (implementing kqueue support is left as an exercise for the |
2476 | is the Linux inotify interface (implementing kqueue support is left as an |
1703 | reader, note, however, that the author sees no way of implementing ev_stat |
2477 | exercise for the reader. Note, however, that the author sees no way of |
1704 | semantics with kqueue). Inotify will be used to give hints only and should |
2478 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1705 | not change the semantics of C<ev_stat> watchers, which means that libev |
|
|
1706 | sometimes needs to fall back to regular polling again even with inotify, |
|
|
1707 | but changes are usually detected immediately, and if the file exists there |
|
|
1708 | will be no polling. |
|
|
1709 | |
2479 | |
1710 | =head3 ABI Issues (Largefile Support) |
2480 | =head3 ABI Issues (Largefile Support) |
1711 | |
2481 | |
1712 | Libev by default (unless the user overrides this) uses the default |
2482 | Libev by default (unless the user overrides this) uses the default |
1713 | compilation environment, which means that on systems with large file |
2483 | compilation environment, which means that on systems with large file |
1714 | support disabled by default, you get the 32 bit version of the stat |
2484 | support disabled by default, you get the 32 bit version of the stat |
1715 | structure. When using the library from programs that change the ABI to |
2485 | structure. When using the library from programs that change the ABI to |
1716 | use 64 bit file offsets the programs will fail. In that case you have to |
2486 | use 64 bit file offsets the programs will fail. In that case you have to |
1717 | compile libev with the same flags to get binary compatibility. This is |
2487 | compile libev with the same flags to get binary compatibility. This is |
1718 | obviously the case with any flags that change the ABI, but the problem is |
2488 | obviously the case with any flags that change the ABI, but the problem is |
1719 | most noticeably disabled with ev_stat and large file support. |
2489 | most noticeably displayed with ev_stat and large file support. |
1720 | |
2490 | |
1721 | The solution for this is to lobby your distribution maker to make large |
2491 | The solution for this is to lobby your distribution maker to make large |
1722 | file interfaces available by default (as e.g. FreeBSD does) and not |
2492 | file interfaces available by default (as e.g. FreeBSD does) and not |
1723 | optional. Libev cannot simply switch on large file support because it has |
2493 | optional. Libev cannot simply switch on large file support because it has |
1724 | to exchange stat structures with application programs compiled using the |
2494 | to exchange stat structures with application programs compiled using the |
1725 | default compilation environment. |
2495 | default compilation environment. |
1726 | |
2496 | |
1727 | =head3 Inotify |
2497 | =head3 Inotify and Kqueue |
1728 | |
2498 | |
1729 | When C<inotify (7)> support has been compiled into libev (generally only |
2499 | When C<inotify (7)> support has been compiled into libev and present at |
1730 | available on Linux) and present at runtime, it will be used to speed up |
2500 | runtime, it will be used to speed up change detection where possible. The |
1731 | change detection where possible. The inotify descriptor will be created lazily |
2501 | inotify descriptor will be created lazily when the first C<ev_stat> |
1732 | when the first C<ev_stat> watcher is being started. |
2502 | watcher is being started. |
1733 | |
2503 | |
1734 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2504 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1735 | except that changes might be detected earlier, and in some cases, to avoid |
2505 | except that changes might be detected earlier, and in some cases, to avoid |
1736 | making regular C<stat> calls. Even in the presence of inotify support |
2506 | making regular C<stat> calls. Even in the presence of inotify support |
1737 | there are many cases where libev has to resort to regular C<stat> polling. |
2507 | there are many cases where libev has to resort to regular C<stat> polling, |
|
|
2508 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2509 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2510 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2511 | xfs are fully working) libev usually gets away without polling. |
1738 | |
2512 | |
1739 | (There is no support for kqueue, as apparently it cannot be used to |
2513 | There is no support for kqueue, as apparently it cannot be used to |
1740 | implement this functionality, due to the requirement of having a file |
2514 | implement this functionality, due to the requirement of having a file |
1741 | descriptor open on the object at all times). |
2515 | descriptor open on the object at all times, and detecting renames, unlinks |
|
|
2516 | etc. is difficult. |
|
|
2517 | |
|
|
2518 | =head3 C<stat ()> is a synchronous operation |
|
|
2519 | |
|
|
2520 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2521 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2522 | ()>, which is a synchronous operation. |
|
|
2523 | |
|
|
2524 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2525 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2526 | as the path data is usually in memory already (except when starting the |
|
|
2527 | watcher). |
|
|
2528 | |
|
|
2529 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2530 | time due to network issues, and even under good conditions, a stat call |
|
|
2531 | often takes multiple milliseconds. |
|
|
2532 | |
|
|
2533 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2534 | paths, although this is fully supported by libev. |
1742 | |
2535 | |
1743 | =head3 The special problem of stat time resolution |
2536 | =head3 The special problem of stat time resolution |
1744 | |
2537 | |
1745 | The C<stat ()> system call only supports full-second resolution portably, and |
2538 | The C<stat ()> system call only supports full-second resolution portably, |
1746 | even on systems where the resolution is higher, many file systems still |
2539 | and even on systems where the resolution is higher, most file systems |
1747 | only support whole seconds. |
2540 | still only support whole seconds. |
1748 | |
2541 | |
1749 | That means that, if the time is the only thing that changes, you can |
2542 | That means that, if the time is the only thing that changes, you can |
1750 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2543 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1751 | calls your callback, which does something. When there is another update |
2544 | calls your callback, which does something. When there is another update |
1752 | within the same second, C<ev_stat> will be unable to detect it as the stat |
2545 | within the same second, C<ev_stat> will be unable to detect unless the |
1753 | data does not change. |
2546 | stat data does change in other ways (e.g. file size). |
1754 | |
2547 | |
1755 | The solution to this is to delay acting on a change for slightly more |
2548 | The solution to this is to delay acting on a change for slightly more |
1756 | than a second (or till slightly after the next full second boundary), using |
2549 | than a second (or till slightly after the next full second boundary), using |
1757 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
2550 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1758 | ev_timer_again (loop, w)>). |
2551 | ev_timer_again (loop, w)>). |
… | |
… | |
1778 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
2571 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1779 | be detected and should normally be specified as C<0> to let libev choose |
2572 | be detected and should normally be specified as C<0> to let libev choose |
1780 | a suitable value. The memory pointed to by C<path> must point to the same |
2573 | a suitable value. The memory pointed to by C<path> must point to the same |
1781 | path for as long as the watcher is active. |
2574 | path for as long as the watcher is active. |
1782 | |
2575 | |
1783 | The callback will receive C<EV_STAT> when a change was detected, relative |
2576 | The callback will receive an C<EV_STAT> event when a change was detected, |
1784 | to the attributes at the time the watcher was started (or the last change |
2577 | relative to the attributes at the time the watcher was started (or the |
1785 | was detected). |
2578 | last change was detected). |
1786 | |
2579 | |
1787 | =item ev_stat_stat (loop, ev_stat *) |
2580 | =item ev_stat_stat (loop, ev_stat *) |
1788 | |
2581 | |
1789 | Updates the stat buffer immediately with new values. If you change the |
2582 | Updates the stat buffer immediately with new values. If you change the |
1790 | watched path in your callback, you could call this function to avoid |
2583 | watched path in your callback, you could call this function to avoid |
… | |
… | |
1873 | |
2666 | |
1874 | |
2667 | |
1875 | =head2 C<ev_idle> - when you've got nothing better to do... |
2668 | =head2 C<ev_idle> - when you've got nothing better to do... |
1876 | |
2669 | |
1877 | Idle watchers trigger events when no other events of the same or higher |
2670 | Idle watchers trigger events when no other events of the same or higher |
1878 | priority are pending (prepare, check and other idle watchers do not |
2671 | priority are pending (prepare, check and other idle watchers do not count |
1879 | count). |
2672 | as receiving "events"). |
1880 | |
2673 | |
1881 | That is, as long as your process is busy handling sockets or timeouts |
2674 | That is, as long as your process is busy handling sockets or timeouts |
1882 | (or even signals, imagine) of the same or higher priority it will not be |
2675 | (or even signals, imagine) of the same or higher priority it will not be |
1883 | triggered. But when your process is idle (or only lower-priority watchers |
2676 | triggered. But when your process is idle (or only lower-priority watchers |
1884 | are pending), the idle watchers are being called once per event loop |
2677 | are pending), the idle watchers are being called once per event loop |
… | |
… | |
1895 | |
2688 | |
1896 | =head3 Watcher-Specific Functions and Data Members |
2689 | =head3 Watcher-Specific Functions and Data Members |
1897 | |
2690 | |
1898 | =over 4 |
2691 | =over 4 |
1899 | |
2692 | |
1900 | =item ev_idle_init (ev_signal *, callback) |
2693 | =item ev_idle_init (ev_idle *, callback) |
1901 | |
2694 | |
1902 | Initialises and configures the idle watcher - it has no parameters of any |
2695 | Initialises and configures the idle watcher - it has no parameters of any |
1903 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2696 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
1904 | believe me. |
2697 | believe me. |
1905 | |
2698 | |
… | |
… | |
1909 | |
2702 | |
1910 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
2703 | Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the |
1911 | callback, free it. Also, use no error checking, as usual. |
2704 | callback, free it. Also, use no error checking, as usual. |
1912 | |
2705 | |
1913 | static void |
2706 | static void |
1914 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
2707 | idle_cb (struct ev_loop *loop, ev_idle *w, int revents) |
1915 | { |
2708 | { |
1916 | free (w); |
2709 | free (w); |
1917 | // now do something you wanted to do when the program has |
2710 | // now do something you wanted to do when the program has |
1918 | // no longer anything immediate to do. |
2711 | // no longer anything immediate to do. |
1919 | } |
2712 | } |
1920 | |
2713 | |
1921 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
2714 | ev_idle *idle_watcher = malloc (sizeof (ev_idle)); |
1922 | ev_idle_init (idle_watcher, idle_cb); |
2715 | ev_idle_init (idle_watcher, idle_cb); |
1923 | ev_idle_start (loop, idle_cb); |
2716 | ev_idle_start (loop, idle_watcher); |
1924 | |
2717 | |
1925 | |
2718 | |
1926 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
2719 | =head2 C<ev_prepare> and C<ev_check> - customise your event loop! |
1927 | |
2720 | |
1928 | Prepare and check watchers are usually (but not always) used in tandem: |
2721 | Prepare and check watchers are usually (but not always) used in pairs: |
1929 | prepare watchers get invoked before the process blocks and check watchers |
2722 | prepare watchers get invoked before the process blocks and check watchers |
1930 | afterwards. |
2723 | afterwards. |
1931 | |
2724 | |
1932 | You I<must not> call C<ev_loop> or similar functions that enter |
2725 | You I<must not> call C<ev_run> or similar functions that enter |
1933 | the current event loop from either C<ev_prepare> or C<ev_check> |
2726 | the current event loop from either C<ev_prepare> or C<ev_check> |
1934 | watchers. Other loops than the current one are fine, however. The |
2727 | watchers. Other loops than the current one are fine, however. The |
1935 | rationale behind this is that you do not need to check for recursion in |
2728 | rationale behind this is that you do not need to check for recursion in |
1936 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
2729 | those watchers, i.e. the sequence will always be C<ev_prepare>, blocking, |
1937 | C<ev_check> so if you have one watcher of each kind they will always be |
2730 | C<ev_check> so if you have one watcher of each kind they will always be |
1938 | called in pairs bracketing the blocking call. |
2731 | called in pairs bracketing the blocking call. |
1939 | |
2732 | |
1940 | Their main purpose is to integrate other event mechanisms into libev and |
2733 | Their main purpose is to integrate other event mechanisms into libev and |
1941 | their use is somewhat advanced. This could be used, for example, to track |
2734 | their use is somewhat advanced. They could be used, for example, to track |
1942 | variable changes, implement your own watchers, integrate net-snmp or a |
2735 | variable changes, implement your own watchers, integrate net-snmp or a |
1943 | coroutine library and lots more. They are also occasionally useful if |
2736 | coroutine library and lots more. They are also occasionally useful if |
1944 | you cache some data and want to flush it before blocking (for example, |
2737 | you cache some data and want to flush it before blocking (for example, |
1945 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
2738 | in X programs you might want to do an C<XFlush ()> in an C<ev_prepare> |
1946 | watcher). |
2739 | watcher). |
1947 | |
2740 | |
1948 | This is done by examining in each prepare call which file descriptors need |
2741 | This is done by examining in each prepare call which file descriptors |
1949 | to be watched by the other library, registering C<ev_io> watchers for |
2742 | need to be watched by the other library, registering C<ev_io> watchers |
1950 | them and starting an C<ev_timer> watcher for any timeouts (many libraries |
2743 | for them and starting an C<ev_timer> watcher for any timeouts (many |
1951 | provide just this functionality). Then, in the check watcher you check for |
2744 | libraries provide exactly this functionality). Then, in the check watcher, |
1952 | any events that occurred (by checking the pending status of all watchers |
2745 | you check for any events that occurred (by checking the pending status |
1953 | and stopping them) and call back into the library. The I/O and timer |
2746 | of all watchers and stopping them) and call back into the library. The |
1954 | callbacks will never actually be called (but must be valid nevertheless, |
2747 | I/O and timer callbacks will never actually be called (but must be valid |
1955 | because you never know, you know?). |
2748 | nevertheless, because you never know, you know?). |
1956 | |
2749 | |
1957 | As another example, the Perl Coro module uses these hooks to integrate |
2750 | As another example, the Perl Coro module uses these hooks to integrate |
1958 | coroutines into libev programs, by yielding to other active coroutines |
2751 | coroutines into libev programs, by yielding to other active coroutines |
1959 | during each prepare and only letting the process block if no coroutines |
2752 | during each prepare and only letting the process block if no coroutines |
1960 | are ready to run (it's actually more complicated: it only runs coroutines |
2753 | are ready to run (it's actually more complicated: it only runs coroutines |
… | |
… | |
1963 | loop from blocking if lower-priority coroutines are active, thus mapping |
2756 | loop from blocking if lower-priority coroutines are active, thus mapping |
1964 | low-priority coroutines to idle/background tasks). |
2757 | low-priority coroutines to idle/background tasks). |
1965 | |
2758 | |
1966 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
2759 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1967 | priority, to ensure that they are being run before any other watchers |
2760 | priority, to ensure that they are being run before any other watchers |
|
|
2761 | after the poll (this doesn't matter for C<ev_prepare> watchers). |
|
|
2762 | |
1968 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
2763 | Also, C<ev_check> watchers (and C<ev_prepare> watchers, too) should not |
1969 | too) should not activate ("feed") events into libev. While libev fully |
2764 | activate ("feed") events into libev. While libev fully supports this, they |
1970 | supports this, they might get executed before other C<ev_check> watchers |
2765 | might get executed before other C<ev_check> watchers did their job. As |
1971 | did their job. As C<ev_check> watchers are often used to embed other |
2766 | C<ev_check> watchers are often used to embed other (non-libev) event |
1972 | (non-libev) event loops those other event loops might be in an unusable |
2767 | loops those other event loops might be in an unusable state until their |
1973 | state until their C<ev_check> watcher ran (always remind yourself to |
2768 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1974 | coexist peacefully with others). |
2769 | others). |
1975 | |
2770 | |
1976 | =head3 Watcher-Specific Functions and Data Members |
2771 | =head3 Watcher-Specific Functions and Data Members |
1977 | |
2772 | |
1978 | =over 4 |
2773 | =over 4 |
1979 | |
2774 | |
… | |
… | |
1981 | |
2776 | |
1982 | =item ev_check_init (ev_check *, callback) |
2777 | =item ev_check_init (ev_check *, callback) |
1983 | |
2778 | |
1984 | Initialises and configures the prepare or check watcher - they have no |
2779 | Initialises and configures the prepare or check watcher - they have no |
1985 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
2780 | parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> |
1986 | macros, but using them is utterly, utterly and completely pointless. |
2781 | macros, but using them is utterly, utterly, utterly and completely |
|
|
2782 | pointless. |
1987 | |
2783 | |
1988 | =back |
2784 | =back |
1989 | |
2785 | |
1990 | =head3 Examples |
2786 | =head3 Examples |
1991 | |
2787 | |
… | |
… | |
2004 | |
2800 | |
2005 | static ev_io iow [nfd]; |
2801 | static ev_io iow [nfd]; |
2006 | static ev_timer tw; |
2802 | static ev_timer tw; |
2007 | |
2803 | |
2008 | static void |
2804 | static void |
2009 | io_cb (ev_loop *loop, ev_io *w, int revents) |
2805 | io_cb (struct ev_loop *loop, ev_io *w, int revents) |
2010 | { |
2806 | { |
2011 | } |
2807 | } |
2012 | |
2808 | |
2013 | // create io watchers for each fd and a timer before blocking |
2809 | // create io watchers for each fd and a timer before blocking |
2014 | static void |
2810 | static void |
2015 | adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
2811 | adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents) |
2016 | { |
2812 | { |
2017 | int timeout = 3600000; |
2813 | int timeout = 3600000; |
2018 | struct pollfd fds [nfd]; |
2814 | struct pollfd fds [nfd]; |
2019 | // actual code will need to loop here and realloc etc. |
2815 | // actual code will need to loop here and realloc etc. |
2020 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2816 | adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
2021 | |
2817 | |
2022 | /* the callback is illegal, but won't be called as we stop during check */ |
2818 | /* the callback is illegal, but won't be called as we stop during check */ |
2023 | ev_timer_init (&tw, 0, timeout * 1e-3); |
2819 | ev_timer_init (&tw, 0, timeout * 1e-3, 0.); |
2024 | ev_timer_start (loop, &tw); |
2820 | ev_timer_start (loop, &tw); |
2025 | |
2821 | |
2026 | // create one ev_io per pollfd |
2822 | // create one ev_io per pollfd |
2027 | for (int i = 0; i < nfd; ++i) |
2823 | for (int i = 0; i < nfd; ++i) |
2028 | { |
2824 | { |
… | |
… | |
2035 | } |
2831 | } |
2036 | } |
2832 | } |
2037 | |
2833 | |
2038 | // stop all watchers after blocking |
2834 | // stop all watchers after blocking |
2039 | static void |
2835 | static void |
2040 | adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
2836 | adns_check_cb (struct ev_loop *loop, ev_check *w, int revents) |
2041 | { |
2837 | { |
2042 | ev_timer_stop (loop, &tw); |
2838 | ev_timer_stop (loop, &tw); |
2043 | |
2839 | |
2044 | for (int i = 0; i < nfd; ++i) |
2840 | for (int i = 0; i < nfd; ++i) |
2045 | { |
2841 | { |
… | |
… | |
2084 | } |
2880 | } |
2085 | |
2881 | |
2086 | // do not ever call adns_afterpoll |
2882 | // do not ever call adns_afterpoll |
2087 | |
2883 | |
2088 | Method 4: Do not use a prepare or check watcher because the module you |
2884 | Method 4: Do not use a prepare or check watcher because the module you |
2089 | want to embed is too inflexible to support it. Instead, you can override |
2885 | want to embed is not flexible enough to support it. Instead, you can |
2090 | their poll function. The drawback with this solution is that the main |
2886 | override their poll function. The drawback with this solution is that the |
2091 | loop is now no longer controllable by EV. The C<Glib::EV> module does |
2887 | main loop is now no longer controllable by EV. The C<Glib::EV> module uses |
2092 | this. |
2888 | this approach, effectively embedding EV as a client into the horrible |
|
|
2889 | libglib event loop. |
2093 | |
2890 | |
2094 | static gint |
2891 | static gint |
2095 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2892 | event_poll_func (GPollFD *fds, guint nfds, gint timeout) |
2096 | { |
2893 | { |
2097 | int got_events = 0; |
2894 | int got_events = 0; |
… | |
… | |
2101 | |
2898 | |
2102 | if (timeout >= 0) |
2899 | if (timeout >= 0) |
2103 | // create/start timer |
2900 | // create/start timer |
2104 | |
2901 | |
2105 | // poll |
2902 | // poll |
2106 | ev_loop (EV_A_ 0); |
2903 | ev_run (EV_A_ 0); |
2107 | |
2904 | |
2108 | // stop timer again |
2905 | // stop timer again |
2109 | if (timeout >= 0) |
2906 | if (timeout >= 0) |
2110 | ev_timer_stop (EV_A_ &to); |
2907 | ev_timer_stop (EV_A_ &to); |
2111 | |
2908 | |
… | |
… | |
2128 | prioritise I/O. |
2925 | prioritise I/O. |
2129 | |
2926 | |
2130 | As an example for a bug workaround, the kqueue backend might only support |
2927 | As an example for a bug workaround, the kqueue backend might only support |
2131 | sockets on some platform, so it is unusable as generic backend, but you |
2928 | sockets on some platform, so it is unusable as generic backend, but you |
2132 | still want to make use of it because you have many sockets and it scales |
2929 | still want to make use of it because you have many sockets and it scales |
2133 | so nicely. In this case, you would create a kqueue-based loop and embed it |
2930 | so nicely. In this case, you would create a kqueue-based loop and embed |
2134 | into your default loop (which might use e.g. poll). Overall operation will |
2931 | it into your default loop (which might use e.g. poll). Overall operation |
2135 | be a bit slower because first libev has to poll and then call kevent, but |
2932 | will be a bit slower because first libev has to call C<poll> and then |
2136 | at least you can use both at what they are best. |
2933 | C<kevent>, but at least you can use both mechanisms for what they are |
|
|
2934 | best: C<kqueue> for scalable sockets and C<poll> if you want it to work :) |
2137 | |
2935 | |
2138 | As for prioritising I/O: rarely you have the case where some fds have |
2936 | As for prioritising I/O: under rare circumstances you have the case where |
2139 | to be watched and handled very quickly (with low latency), and even |
2937 | some fds have to be watched and handled very quickly (with low latency), |
2140 | priorities and idle watchers might have too much overhead. In this case |
2938 | and even priorities and idle watchers might have too much overhead. In |
2141 | you would put all the high priority stuff in one loop and all the rest in |
2939 | this case you would put all the high priority stuff in one loop and all |
2142 | a second one, and embed the second one in the first. |
2940 | the rest in a second one, and embed the second one in the first. |
2143 | |
2941 | |
2144 | As long as the watcher is active, the callback will be invoked every time |
2942 | As long as the watcher is active, the callback will be invoked every |
2145 | there might be events pending in the embedded loop. The callback must then |
2943 | time there might be events pending in the embedded loop. The callback |
2146 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2944 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2147 | their callbacks (you could also start an idle watcher to give the embedded |
2945 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2148 | loop strictly lower priority for example). You can also set the callback |
2946 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2149 | to C<0>, in which case the embed watcher will automatically execute the |
2947 | to give the embedded loop strictly lower priority for example). |
2150 | embedded loop sweep. |
|
|
2151 | |
2948 | |
2152 | As long as the watcher is started it will automatically handle events. The |
2949 | You can also set the callback to C<0>, in which case the embed watcher |
2153 | callback will be invoked whenever some events have been handled. You can |
2950 | will automatically execute the embedded loop sweep whenever necessary. |
2154 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2155 | interested in that. |
|
|
2156 | |
2951 | |
2157 | Also, there have not currently been made special provisions for forking: |
2952 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2158 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2953 | is active, i.e., the embedded loop will automatically be forked when the |
2159 | but you will also have to stop and restart any C<ev_embed> watchers |
2954 | embedding loop forks. In other cases, the user is responsible for calling |
2160 | yourself. |
2955 | C<ev_loop_fork> on the embedded loop. |
2161 | |
2956 | |
2162 | Unfortunately, not all backends are embeddable, only the ones returned by |
2957 | Unfortunately, not all backends are embeddable: only the ones returned by |
2163 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2958 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2164 | portable one. |
2959 | portable one. |
2165 | |
2960 | |
2166 | So when you want to use this feature you will always have to be prepared |
2961 | So when you want to use this feature you will always have to be prepared |
2167 | that you cannot get an embeddable loop. The recommended way to get around |
2962 | that you cannot get an embeddable loop. The recommended way to get around |
2168 | this is to have a separate variables for your embeddable loop, try to |
2963 | this is to have a separate variables for your embeddable loop, try to |
2169 | create it, and if that fails, use the normal loop for everything. |
2964 | create it, and if that fails, use the normal loop for everything. |
|
|
2965 | |
|
|
2966 | =head3 C<ev_embed> and fork |
|
|
2967 | |
|
|
2968 | While the C<ev_embed> watcher is running, forks in the embedding loop will |
|
|
2969 | automatically be applied to the embedded loop as well, so no special |
|
|
2970 | fork handling is required in that case. When the watcher is not running, |
|
|
2971 | however, it is still the task of the libev user to call C<ev_loop_fork ()> |
|
|
2972 | as applicable. |
2170 | |
2973 | |
2171 | =head3 Watcher-Specific Functions and Data Members |
2974 | =head3 Watcher-Specific Functions and Data Members |
2172 | |
2975 | |
2173 | =over 4 |
2976 | =over 4 |
2174 | |
2977 | |
… | |
… | |
2183 | if you do not want that, you need to temporarily stop the embed watcher). |
2986 | if you do not want that, you need to temporarily stop the embed watcher). |
2184 | |
2987 | |
2185 | =item ev_embed_sweep (loop, ev_embed *) |
2988 | =item ev_embed_sweep (loop, ev_embed *) |
2186 | |
2989 | |
2187 | Make a single, non-blocking sweep over the embedded loop. This works |
2990 | Make a single, non-blocking sweep over the embedded loop. This works |
2188 | similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most |
2991 | similarly to C<ev_run (embedded_loop, EVRUN_NOWAIT)>, but in the most |
2189 | appropriate way for embedded loops. |
2992 | appropriate way for embedded loops. |
2190 | |
2993 | |
2191 | =item struct ev_loop *other [read-only] |
2994 | =item struct ev_loop *other [read-only] |
2192 | |
2995 | |
2193 | The embedded event loop. |
2996 | The embedded event loop. |
… | |
… | |
2202 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
3005 | C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be |
2203 | used). |
3006 | used). |
2204 | |
3007 | |
2205 | struct ev_loop *loop_hi = ev_default_init (0); |
3008 | struct ev_loop *loop_hi = ev_default_init (0); |
2206 | struct ev_loop *loop_lo = 0; |
3009 | struct ev_loop *loop_lo = 0; |
2207 | struct ev_embed embed; |
3010 | ev_embed embed; |
2208 | |
3011 | |
2209 | // see if there is a chance of getting one that works |
3012 | // see if there is a chance of getting one that works |
2210 | // (remember that a flags value of 0 means autodetection) |
3013 | // (remember that a flags value of 0 means autodetection) |
2211 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
3014 | loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
2212 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
3015 | ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
… | |
… | |
2226 | kqueue implementation). Store the kqueue/socket-only event loop in |
3029 | kqueue implementation). Store the kqueue/socket-only event loop in |
2227 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
3030 | C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). |
2228 | |
3031 | |
2229 | struct ev_loop *loop = ev_default_init (0); |
3032 | struct ev_loop *loop = ev_default_init (0); |
2230 | struct ev_loop *loop_socket = 0; |
3033 | struct ev_loop *loop_socket = 0; |
2231 | struct ev_embed embed; |
3034 | ev_embed embed; |
2232 | |
3035 | |
2233 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
3036 | if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) |
2234 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
3037 | if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) |
2235 | { |
3038 | { |
2236 | ev_embed_init (&embed, 0, loop_socket); |
3039 | ev_embed_init (&embed, 0, loop_socket); |
… | |
… | |
2251 | event loop blocks next and before C<ev_check> watchers are being called, |
3054 | event loop blocks next and before C<ev_check> watchers are being called, |
2252 | and only in the child after the fork. If whoever good citizen calling |
3055 | and only in the child after the fork. If whoever good citizen calling |
2253 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
3056 | C<ev_default_fork> cheats and calls it in the wrong process, the fork |
2254 | handlers will be invoked, too, of course. |
3057 | handlers will be invoked, too, of course. |
2255 | |
3058 | |
|
|
3059 | =head3 The special problem of life after fork - how is it possible? |
|
|
3060 | |
|
|
3061 | Most uses of C<fork()> consist of forking, then some simple calls to set |
|
|
3062 | up/change the process environment, followed by a call to C<exec()>. This |
|
|
3063 | sequence should be handled by libev without any problems. |
|
|
3064 | |
|
|
3065 | This changes when the application actually wants to do event handling |
|
|
3066 | in the child, or both parent in child, in effect "continuing" after the |
|
|
3067 | fork. |
|
|
3068 | |
|
|
3069 | The default mode of operation (for libev, with application help to detect |
|
|
3070 | forks) is to duplicate all the state in the child, as would be expected |
|
|
3071 | when I<either> the parent I<or> the child process continues. |
|
|
3072 | |
|
|
3073 | When both processes want to continue using libev, then this is usually the |
|
|
3074 | wrong result. In that case, usually one process (typically the parent) is |
|
|
3075 | supposed to continue with all watchers in place as before, while the other |
|
|
3076 | process typically wants to start fresh, i.e. without any active watchers. |
|
|
3077 | |
|
|
3078 | The cleanest and most efficient way to achieve that with libev is to |
|
|
3079 | simply create a new event loop, which of course will be "empty", and |
|
|
3080 | use that for new watchers. This has the advantage of not touching more |
|
|
3081 | memory than necessary, and thus avoiding the copy-on-write, and the |
|
|
3082 | disadvantage of having to use multiple event loops (which do not support |
|
|
3083 | signal watchers). |
|
|
3084 | |
|
|
3085 | When this is not possible, or you want to use the default loop for |
|
|
3086 | other reasons, then in the process that wants to start "fresh", call |
|
|
3087 | C<ev_loop_destroy (EV_DEFAULT)> followed by C<ev_default_loop (...)>. |
|
|
3088 | Destroying the default loop will "orphan" (not stop) all registered |
|
|
3089 | watchers, so you have to be careful not to execute code that modifies |
|
|
3090 | those watchers. Note also that in that case, you have to re-register any |
|
|
3091 | signal watchers. |
|
|
3092 | |
2256 | =head3 Watcher-Specific Functions and Data Members |
3093 | =head3 Watcher-Specific Functions and Data Members |
2257 | |
3094 | |
2258 | =over 4 |
3095 | =over 4 |
2259 | |
3096 | |
2260 | =item ev_fork_init (ev_signal *, callback) |
3097 | =item ev_fork_init (ev_signal *, callback) |
… | |
… | |
2264 | believe me. |
3101 | believe me. |
2265 | |
3102 | |
2266 | =back |
3103 | =back |
2267 | |
3104 | |
2268 | |
3105 | |
2269 | =head2 C<ev_async> - how to wake up another event loop |
3106 | =head2 C<ev_async> - how to wake up an event loop |
2270 | |
3107 | |
2271 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3108 | In general, you cannot use an C<ev_run> from multiple threads or other |
2272 | asynchronous sources such as signal handlers (as opposed to multiple event |
3109 | asynchronous sources such as signal handlers (as opposed to multiple event |
2273 | loops - those are of course safe to use in different threads). |
3110 | loops - those are of course safe to use in different threads). |
2274 | |
3111 | |
2275 | Sometimes, however, you need to wake up another event loop you do not |
3112 | Sometimes, however, you need to wake up an event loop you do not control, |
2276 | control, for example because it belongs to another thread. This is what |
3113 | for example because it belongs to another thread. This is what C<ev_async> |
2277 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
3114 | watchers do: as long as the C<ev_async> watcher is active, you can signal |
2278 | can signal it by calling C<ev_async_send>, which is thread- and signal |
3115 | it by calling C<ev_async_send>, which is thread- and signal safe. |
2279 | safe. |
|
|
2280 | |
3116 | |
2281 | This functionality is very similar to C<ev_signal> watchers, as signals, |
3117 | This functionality is very similar to C<ev_signal> watchers, as signals, |
2282 | too, are asynchronous in nature, and signals, too, will be compressed |
3118 | too, are asynchronous in nature, and signals, too, will be compressed |
2283 | (i.e. the number of callback invocations may be less than the number of |
3119 | (i.e. the number of callback invocations may be less than the number of |
2284 | C<ev_async_sent> calls). |
3120 | C<ev_async_sent> calls). |
… | |
… | |
2289 | =head3 Queueing |
3125 | =head3 Queueing |
2290 | |
3126 | |
2291 | C<ev_async> does not support queueing of data in any way. The reason |
3127 | C<ev_async> does not support queueing of data in any way. The reason |
2292 | is that the author does not know of a simple (or any) algorithm for a |
3128 | is that the author does not know of a simple (or any) algorithm for a |
2293 | multiple-writer-single-reader queue that works in all cases and doesn't |
3129 | multiple-writer-single-reader queue that works in all cases and doesn't |
2294 | need elaborate support such as pthreads. |
3130 | need elaborate support such as pthreads or unportable memory access |
|
|
3131 | semantics. |
2295 | |
3132 | |
2296 | That means that if you want to queue data, you have to provide your own |
3133 | That means that if you want to queue data, you have to provide your own |
2297 | queue. But at least I can tell you would implement locking around your |
3134 | queue. But at least I can tell you how to implement locking around your |
2298 | queue: |
3135 | queue: |
2299 | |
3136 | |
2300 | =over 4 |
3137 | =over 4 |
2301 | |
3138 | |
2302 | =item queueing from a signal handler context |
3139 | =item queueing from a signal handler context |
2303 | |
3140 | |
2304 | To implement race-free queueing, you simply add to the queue in the signal |
3141 | To implement race-free queueing, you simply add to the queue in the signal |
2305 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
3142 | handler but you block the signal handler in the watcher callback. Here is |
2306 | some fictitious SIGUSR1 handler: |
3143 | an example that does that for some fictitious SIGUSR1 handler: |
2307 | |
3144 | |
2308 | static ev_async mysig; |
3145 | static ev_async mysig; |
2309 | |
3146 | |
2310 | static void |
3147 | static void |
2311 | sigusr1_handler (void) |
3148 | sigusr1_handler (void) |
… | |
… | |
2377 | =over 4 |
3214 | =over 4 |
2378 | |
3215 | |
2379 | =item ev_async_init (ev_async *, callback) |
3216 | =item ev_async_init (ev_async *, callback) |
2380 | |
3217 | |
2381 | Initialises and configures the async watcher - it has no parameters of any |
3218 | Initialises and configures the async watcher - it has no parameters of any |
2382 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
3219 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2383 | believe me. |
3220 | trust me. |
2384 | |
3221 | |
2385 | =item ev_async_send (loop, ev_async *) |
3222 | =item ev_async_send (loop, ev_async *) |
2386 | |
3223 | |
2387 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3224 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2388 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3225 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2389 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
3226 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2390 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3227 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2391 | section below on what exactly this means). |
3228 | section below on what exactly this means). |
2392 | |
3229 | |
|
|
3230 | Note that, as with other watchers in libev, multiple events might get |
|
|
3231 | compressed into a single callback invocation (another way to look at this |
|
|
3232 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
3233 | reset when the event loop detects that). |
|
|
3234 | |
2393 | This call incurs the overhead of a system call only once per loop iteration, |
3235 | This call incurs the overhead of a system call only once per event loop |
2394 | so while the overhead might be noticeable, it doesn't apply to repeated |
3236 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2395 | calls to C<ev_async_send>. |
3237 | repeated calls to C<ev_async_send> for the same event loop. |
2396 | |
3238 | |
2397 | =item bool = ev_async_pending (ev_async *) |
3239 | =item bool = ev_async_pending (ev_async *) |
2398 | |
3240 | |
2399 | Returns a non-zero value when C<ev_async_send> has been called on the |
3241 | Returns a non-zero value when C<ev_async_send> has been called on the |
2400 | watcher but the event has not yet been processed (or even noted) by the |
3242 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2403 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
3245 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2404 | the loop iterates next and checks for the watcher to have become active, |
3246 | the loop iterates next and checks for the watcher to have become active, |
2405 | it will reset the flag again. C<ev_async_pending> can be used to very |
3247 | it will reset the flag again. C<ev_async_pending> can be used to very |
2406 | quickly check whether invoking the loop might be a good idea. |
3248 | quickly check whether invoking the loop might be a good idea. |
2407 | |
3249 | |
2408 | Not that this does I<not> check whether the watcher itself is pending, only |
3250 | Not that this does I<not> check whether the watcher itself is pending, |
2409 | whether it has been requested to make this watcher pending. |
3251 | only whether it has been requested to make this watcher pending: there |
|
|
3252 | is a time window between the event loop checking and resetting the async |
|
|
3253 | notification, and the callback being invoked. |
2410 | |
3254 | |
2411 | =back |
3255 | =back |
2412 | |
3256 | |
2413 | |
3257 | |
2414 | =head1 OTHER FUNCTIONS |
3258 | =head1 OTHER FUNCTIONS |
… | |
… | |
2418 | =over 4 |
3262 | =over 4 |
2419 | |
3263 | |
2420 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
3264 | =item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) |
2421 | |
3265 | |
2422 | This function combines a simple timer and an I/O watcher, calls your |
3266 | This function combines a simple timer and an I/O watcher, calls your |
2423 | callback on whichever event happens first and automatically stop both |
3267 | callback on whichever event happens first and automatically stops both |
2424 | watchers. This is useful if you want to wait for a single event on an fd |
3268 | watchers. This is useful if you want to wait for a single event on an fd |
2425 | or timeout without having to allocate/configure/start/stop/free one or |
3269 | or timeout without having to allocate/configure/start/stop/free one or |
2426 | more watchers yourself. |
3270 | more watchers yourself. |
2427 | |
3271 | |
2428 | If C<fd> is less than 0, then no I/O watcher will be started and events |
3272 | If C<fd> is less than 0, then no I/O watcher will be started and the |
2429 | is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and |
3273 | C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for |
2430 | C<events> set will be created and started. |
3274 | the given C<fd> and C<events> set will be created and started. |
2431 | |
3275 | |
2432 | If C<timeout> is less than 0, then no timeout watcher will be |
3276 | If C<timeout> is less than 0, then no timeout watcher will be |
2433 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
3277 | started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and |
2434 | repeat = 0) will be started. While C<0> is a valid timeout, it is of |
3278 | repeat = 0) will be started. C<0> is a valid timeout. |
2435 | dubious value. |
|
|
2436 | |
3279 | |
2437 | The callback has the type C<void (*cb)(int revents, void *arg)> and gets |
3280 | The callback has the type C<void (*cb)(int revents, void *arg)> and is |
2438 | passed an C<revents> set like normal event callbacks (a combination of |
3281 | passed an C<revents> set like normal event callbacks (a combination of |
2439 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> |
3282 | C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg> |
2440 | value passed to C<ev_once>: |
3283 | value passed to C<ev_once>. Note that it is possible to receive I<both> |
|
|
3284 | a timeout and an io event at the same time - you probably should give io |
|
|
3285 | events precedence. |
|
|
3286 | |
|
|
3287 | Example: wait up to ten seconds for data to appear on STDIN_FILENO. |
2441 | |
3288 | |
2442 | static void stdin_ready (int revents, void *arg) |
3289 | static void stdin_ready (int revents, void *arg) |
2443 | { |
3290 | { |
|
|
3291 | if (revents & EV_READ) |
|
|
3292 | /* stdin might have data for us, joy! */; |
2444 | if (revents & EV_TIMEOUT) |
3293 | else if (revents & EV_TIMER) |
2445 | /* doh, nothing entered */; |
3294 | /* doh, nothing entered */; |
2446 | else if (revents & EV_READ) |
|
|
2447 | /* stdin might have data for us, joy! */; |
|
|
2448 | } |
3295 | } |
2449 | |
3296 | |
2450 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3297 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
2451 | |
3298 | |
2452 | =item ev_feed_event (ev_loop *, watcher *, int revents) |
|
|
2453 | |
|
|
2454 | Feeds the given event set into the event loop, as if the specified event |
|
|
2455 | had happened for the specified watcher (which must be a pointer to an |
|
|
2456 | initialised but not necessarily started event watcher). |
|
|
2457 | |
|
|
2458 | =item ev_feed_fd_event (ev_loop *, int fd, int revents) |
3299 | =item ev_feed_fd_event (loop, int fd, int revents) |
2459 | |
3300 | |
2460 | Feed an event on the given fd, as if a file descriptor backend detected |
3301 | Feed an event on the given fd, as if a file descriptor backend detected |
2461 | the given events it. |
3302 | the given events it. |
2462 | |
3303 | |
2463 | =item ev_feed_signal_event (ev_loop *loop, int signum) |
3304 | =item ev_feed_signal_event (loop, int signum) |
2464 | |
3305 | |
2465 | Feed an event as if the given signal occurred (C<loop> must be the default |
3306 | Feed an event as if the given signal occurred (C<loop> must be the default |
2466 | loop!). |
3307 | loop!). |
2467 | |
3308 | |
2468 | =back |
3309 | =back |
… | |
… | |
2548 | |
3389 | |
2549 | =over 4 |
3390 | =over 4 |
2550 | |
3391 | |
2551 | =item ev::TYPE::TYPE () |
3392 | =item ev::TYPE::TYPE () |
2552 | |
3393 | |
2553 | =item ev::TYPE::TYPE (struct ev_loop *) |
3394 | =item ev::TYPE::TYPE (loop) |
2554 | |
3395 | |
2555 | =item ev::TYPE::~TYPE |
3396 | =item ev::TYPE::~TYPE |
2556 | |
3397 | |
2557 | The constructor (optionally) takes an event loop to associate the watcher |
3398 | The constructor (optionally) takes an event loop to associate the watcher |
2558 | with. If it is omitted, it will use C<EV_DEFAULT>. |
3399 | with. If it is omitted, it will use C<EV_DEFAULT>. |
… | |
… | |
2590 | |
3431 | |
2591 | myclass obj; |
3432 | myclass obj; |
2592 | ev::io iow; |
3433 | ev::io iow; |
2593 | iow.set <myclass, &myclass::io_cb> (&obj); |
3434 | iow.set <myclass, &myclass::io_cb> (&obj); |
2594 | |
3435 | |
|
|
3436 | =item w->set (object *) |
|
|
3437 | |
|
|
3438 | This is a variation of a method callback - leaving out the method to call |
|
|
3439 | will default the method to C<operator ()>, which makes it possible to use |
|
|
3440 | functor objects without having to manually specify the C<operator ()> all |
|
|
3441 | the time. Incidentally, you can then also leave out the template argument |
|
|
3442 | list. |
|
|
3443 | |
|
|
3444 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
3445 | int revents)>. |
|
|
3446 | |
|
|
3447 | See the method-C<set> above for more details. |
|
|
3448 | |
|
|
3449 | Example: use a functor object as callback. |
|
|
3450 | |
|
|
3451 | struct myfunctor |
|
|
3452 | { |
|
|
3453 | void operator() (ev::io &w, int revents) |
|
|
3454 | { |
|
|
3455 | ... |
|
|
3456 | } |
|
|
3457 | } |
|
|
3458 | |
|
|
3459 | myfunctor f; |
|
|
3460 | |
|
|
3461 | ev::io w; |
|
|
3462 | w.set (&f); |
|
|
3463 | |
2595 | =item w->set<function> (void *data = 0) |
3464 | =item w->set<function> (void *data = 0) |
2596 | |
3465 | |
2597 | Also sets a callback, but uses a static method or plain function as |
3466 | Also sets a callback, but uses a static method or plain function as |
2598 | callback. The optional C<data> argument will be stored in the watcher's |
3467 | callback. The optional C<data> argument will be stored in the watcher's |
2599 | C<data> member and is free for you to use. |
3468 | C<data> member and is free for you to use. |
2600 | |
3469 | |
2601 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
3470 | The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>. |
2602 | |
3471 | |
2603 | See the method-C<set> above for more details. |
3472 | See the method-C<set> above for more details. |
2604 | |
3473 | |
2605 | Example: |
3474 | Example: Use a plain function as callback. |
2606 | |
3475 | |
2607 | static void io_cb (ev::io &w, int revents) { } |
3476 | static void io_cb (ev::io &w, int revents) { } |
2608 | iow.set <io_cb> (); |
3477 | iow.set <io_cb> (); |
2609 | |
3478 | |
2610 | =item w->set (struct ev_loop *) |
3479 | =item w->set (loop) |
2611 | |
3480 | |
2612 | Associates a different C<struct ev_loop> with this watcher. You can only |
3481 | Associates a different C<struct ev_loop> with this watcher. You can only |
2613 | do this when the watcher is inactive (and not pending either). |
3482 | do this when the watcher is inactive (and not pending either). |
2614 | |
3483 | |
2615 | =item w->set ([arguments]) |
3484 | =item w->set ([arguments]) |
2616 | |
3485 | |
2617 | Basically the same as C<ev_TYPE_set>, with the same arguments. Must be |
3486 | Basically the same as C<ev_TYPE_set>, with the same arguments. Either this |
2618 | called at least once. Unlike the C counterpart, an active watcher gets |
3487 | method or a suitable start method must be called at least once. Unlike the |
2619 | automatically stopped and restarted when reconfiguring it with this |
3488 | C counterpart, an active watcher gets automatically stopped and restarted |
2620 | method. |
3489 | when reconfiguring it with this method. |
2621 | |
3490 | |
2622 | =item w->start () |
3491 | =item w->start () |
2623 | |
3492 | |
2624 | Starts the watcher. Note that there is no C<loop> argument, as the |
3493 | Starts the watcher. Note that there is no C<loop> argument, as the |
2625 | constructor already stores the event loop. |
3494 | constructor already stores the event loop. |
2626 | |
3495 | |
|
|
3496 | =item w->start ([arguments]) |
|
|
3497 | |
|
|
3498 | Instead of calling C<set> and C<start> methods separately, it is often |
|
|
3499 | convenient to wrap them in one call. Uses the same type of arguments as |
|
|
3500 | the configure C<set> method of the watcher. |
|
|
3501 | |
2627 | =item w->stop () |
3502 | =item w->stop () |
2628 | |
3503 | |
2629 | Stops the watcher if it is active. Again, no C<loop> argument. |
3504 | Stops the watcher if it is active. Again, no C<loop> argument. |
2630 | |
3505 | |
2631 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
3506 | =item w->again () (C<ev::timer>, C<ev::periodic> only) |
… | |
… | |
2643 | |
3518 | |
2644 | =back |
3519 | =back |
2645 | |
3520 | |
2646 | =back |
3521 | =back |
2647 | |
3522 | |
2648 | Example: Define a class with an IO and idle watcher, start one of them in |
3523 | Example: Define a class with two I/O and idle watchers, start the I/O |
2649 | the constructor. |
3524 | watchers in the constructor. |
2650 | |
3525 | |
2651 | class myclass |
3526 | class myclass |
2652 | { |
3527 | { |
2653 | ev::io io; void io_cb (ev::io &w, int revents); |
3528 | ev::io io ; void io_cb (ev::io &w, int revents); |
|
|
3529 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
2654 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
3530 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
2655 | |
3531 | |
2656 | myclass (int fd) |
3532 | myclass (int fd) |
2657 | { |
3533 | { |
2658 | io .set <myclass, &myclass::io_cb > (this); |
3534 | io .set <myclass, &myclass::io_cb > (this); |
|
|
3535 | io2 .set <myclass, &myclass::io2_cb > (this); |
2659 | idle.set <myclass, &myclass::idle_cb> (this); |
3536 | idle.set <myclass, &myclass::idle_cb> (this); |
2660 | |
3537 | |
2661 | io.start (fd, ev::READ); |
3538 | io.set (fd, ev::WRITE); // configure the watcher |
|
|
3539 | io.start (); // start it whenever convenient |
|
|
3540 | |
|
|
3541 | io2.start (fd, ev::READ); // set + start in one call |
2662 | } |
3542 | } |
2663 | }; |
3543 | }; |
2664 | |
3544 | |
2665 | |
3545 | |
2666 | =head1 OTHER LANGUAGE BINDINGS |
3546 | =head1 OTHER LANGUAGE BINDINGS |
… | |
… | |
2675 | =item Perl |
3555 | =item Perl |
2676 | |
3556 | |
2677 | The EV module implements the full libev API and is actually used to test |
3557 | The EV module implements the full libev API and is actually used to test |
2678 | libev. EV is developed together with libev. Apart from the EV core module, |
3558 | libev. EV is developed together with libev. Apart from the EV core module, |
2679 | there are additional modules that implement libev-compatible interfaces |
3559 | there are additional modules that implement libev-compatible interfaces |
2680 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
3560 | to C<libadns> (C<EV::ADNS>, but C<AnyEvent::DNS> is preferred nowadays), |
2681 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
3561 | C<Net::SNMP> (C<Net::SNMP::EV>) and the C<libglib> event core (C<Glib::EV> |
|
|
3562 | and C<EV::Glib>). |
2682 | |
3563 | |
2683 | It can be found and installed via CPAN, its homepage is at |
3564 | It can be found and installed via CPAN, its homepage is at |
2684 | L<http://software.schmorp.de/pkg/EV>. |
3565 | L<http://software.schmorp.de/pkg/EV>. |
2685 | |
3566 | |
2686 | =item Python |
3567 | =item Python |
2687 | |
3568 | |
2688 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
3569 | Python bindings can be found at L<http://code.google.com/p/pyev/>. It |
2689 | seems to be quite complete and well-documented. Note, however, that the |
3570 | seems to be quite complete and well-documented. |
2690 | patch they require for libev is outright dangerous as it breaks the ABI |
|
|
2691 | for everybody else, and therefore, should never be applied in an installed |
|
|
2692 | libev (if python requires an incompatible ABI then it needs to embed |
|
|
2693 | libev). |
|
|
2694 | |
3571 | |
2695 | =item Ruby |
3572 | =item Ruby |
2696 | |
3573 | |
2697 | Tony Arcieri has written a ruby extension that offers access to a subset |
3574 | Tony Arcieri has written a ruby extension that offers access to a subset |
2698 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3575 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2699 | more on top of it. It can be found via gem servers. Its homepage is at |
3576 | more on top of it. It can be found via gem servers. Its homepage is at |
2700 | L<http://rev.rubyforge.org/>. |
3577 | L<http://rev.rubyforge.org/>. |
2701 | |
3578 | |
|
|
3579 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3580 | makes rev work even on mingw. |
|
|
3581 | |
|
|
3582 | =item Haskell |
|
|
3583 | |
|
|
3584 | A haskell binding to libev is available at |
|
|
3585 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
|
|
3586 | |
2702 | =item D |
3587 | =item D |
2703 | |
3588 | |
2704 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3589 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2705 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3590 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
|
|
3591 | |
|
|
3592 | =item Ocaml |
|
|
3593 | |
|
|
3594 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
|
|
3595 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
|
|
3596 | |
|
|
3597 | =item Lua |
|
|
3598 | |
|
|
3599 | Brian Maher has written a partial interface to libev for lua (at the |
|
|
3600 | time of this writing, only C<ev_io> and C<ev_timer>), to be found at |
|
|
3601 | L<http://github.com/brimworks/lua-ev>. |
2706 | |
3602 | |
2707 | =back |
3603 | =back |
2708 | |
3604 | |
2709 | |
3605 | |
2710 | =head1 MACRO MAGIC |
3606 | =head1 MACRO MAGIC |
… | |
… | |
2724 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
3620 | loop argument"). The C<EV_A> form is used when this is the sole argument, |
2725 | C<EV_A_> is used when other arguments are following. Example: |
3621 | C<EV_A_> is used when other arguments are following. Example: |
2726 | |
3622 | |
2727 | ev_unref (EV_A); |
3623 | ev_unref (EV_A); |
2728 | ev_timer_add (EV_A_ watcher); |
3624 | ev_timer_add (EV_A_ watcher); |
2729 | ev_loop (EV_A_ 0); |
3625 | ev_run (EV_A_ 0); |
2730 | |
3626 | |
2731 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
3627 | It assumes the variable C<loop> of type C<struct ev_loop *> is in scope, |
2732 | which is often provided by the following macro. |
3628 | which is often provided by the following macro. |
2733 | |
3629 | |
2734 | =item C<EV_P>, C<EV_P_> |
3630 | =item C<EV_P>, C<EV_P_> |
… | |
… | |
2774 | } |
3670 | } |
2775 | |
3671 | |
2776 | ev_check check; |
3672 | ev_check check; |
2777 | ev_check_init (&check, check_cb); |
3673 | ev_check_init (&check, check_cb); |
2778 | ev_check_start (EV_DEFAULT_ &check); |
3674 | ev_check_start (EV_DEFAULT_ &check); |
2779 | ev_loop (EV_DEFAULT_ 0); |
3675 | ev_run (EV_DEFAULT_ 0); |
2780 | |
3676 | |
2781 | =head1 EMBEDDING |
3677 | =head1 EMBEDDING |
2782 | |
3678 | |
2783 | Libev can (and often is) directly embedded into host |
3679 | Libev can (and often is) directly embedded into host |
2784 | applications. Examples of applications that embed it include the Deliantra |
3680 | applications. Examples of applications that embed it include the Deliantra |
… | |
… | |
2811 | |
3707 | |
2812 | #define EV_STANDALONE 1 |
3708 | #define EV_STANDALONE 1 |
2813 | #include "ev.h" |
3709 | #include "ev.h" |
2814 | |
3710 | |
2815 | Both header files and implementation files can be compiled with a C++ |
3711 | Both header files and implementation files can be compiled with a C++ |
2816 | compiler (at least, thats a stated goal, and breakage will be treated |
3712 | compiler (at least, that's a stated goal, and breakage will be treated |
2817 | as a bug). |
3713 | as a bug). |
2818 | |
3714 | |
2819 | You need the following files in your source tree, or in a directory |
3715 | You need the following files in your source tree, or in a directory |
2820 | in your include path (e.g. in libev/ when using -Ilibev): |
3716 | in your include path (e.g. in libev/ when using -Ilibev): |
2821 | |
3717 | |
… | |
… | |
2864 | libev.m4 |
3760 | libev.m4 |
2865 | |
3761 | |
2866 | =head2 PREPROCESSOR SYMBOLS/MACROS |
3762 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2867 | |
3763 | |
2868 | Libev can be configured via a variety of preprocessor symbols you have to |
3764 | Libev can be configured via a variety of preprocessor symbols you have to |
2869 | define before including any of its files. The default in the absence of |
3765 | define before including (or compiling) any of its files. The default in |
2870 | autoconf is noted for every option. |
3766 | the absence of autoconf is documented for every option. |
|
|
3767 | |
|
|
3768 | Symbols marked with "(h)" do not change the ABI, and can have different |
|
|
3769 | values when compiling libev vs. including F<ev.h>, so it is permissible |
|
|
3770 | to redefine them before including F<ev.h> without breaking compatibility |
|
|
3771 | to a compiled library. All other symbols change the ABI, which means all |
|
|
3772 | users of libev and the libev code itself must be compiled with compatible |
|
|
3773 | settings. |
2871 | |
3774 | |
2872 | =over 4 |
3775 | =over 4 |
2873 | |
3776 | |
|
|
3777 | =item EV_COMPAT3 (h) |
|
|
3778 | |
|
|
3779 | Backwards compatibility is a major concern for libev. This is why this |
|
|
3780 | release of libev comes with wrappers for the functions and symbols that |
|
|
3781 | have been renamed between libev version 3 and 4. |
|
|
3782 | |
|
|
3783 | You can disable these wrappers (to test compatibility with future |
|
|
3784 | versions) by defining C<EV_COMPAT3> to C<0> when compiling your |
|
|
3785 | sources. This has the additional advantage that you can drop the C<struct> |
|
|
3786 | from C<struct ev_loop> declarations, as libev will provide an C<ev_loop> |
|
|
3787 | typedef in that case. |
|
|
3788 | |
|
|
3789 | In some future version, the default for C<EV_COMPAT3> will become C<0>, |
|
|
3790 | and in some even more future version the compatibility code will be |
|
|
3791 | removed completely. |
|
|
3792 | |
2874 | =item EV_STANDALONE |
3793 | =item EV_STANDALONE (h) |
2875 | |
3794 | |
2876 | Must always be C<1> if you do not use autoconf configuration, which |
3795 | Must always be C<1> if you do not use autoconf configuration, which |
2877 | keeps libev from including F<config.h>, and it also defines dummy |
3796 | keeps libev from including F<config.h>, and it also defines dummy |
2878 | implementations for some libevent functions (such as logging, which is not |
3797 | implementations for some libevent functions (such as logging, which is not |
2879 | supported). It will also not define any of the structs usually found in |
3798 | supported). It will also not define any of the structs usually found in |
2880 | F<event.h> that are not directly supported by the libev core alone. |
3799 | F<event.h> that are not directly supported by the libev core alone. |
2881 | |
3800 | |
|
|
3801 | In standalone mode, libev will still try to automatically deduce the |
|
|
3802 | configuration, but has to be more conservative. |
|
|
3803 | |
2882 | =item EV_USE_MONOTONIC |
3804 | =item EV_USE_MONOTONIC |
2883 | |
3805 | |
2884 | If defined to be C<1>, libev will try to detect the availability of the |
3806 | If defined to be C<1>, libev will try to detect the availability of the |
2885 | monotonic clock option at both compile time and runtime. Otherwise no use |
3807 | monotonic clock option at both compile time and runtime. Otherwise no |
2886 | of the monotonic clock option will be attempted. If you enable this, you |
3808 | use of the monotonic clock option will be attempted. If you enable this, |
2887 | usually have to link against librt or something similar. Enabling it when |
3809 | you usually have to link against librt or something similar. Enabling it |
2888 | the functionality isn't available is safe, though, although you have |
3810 | when the functionality isn't available is safe, though, although you have |
2889 | to make sure you link against any libraries where the C<clock_gettime> |
3811 | to make sure you link against any libraries where the C<clock_gettime> |
2890 | function is hiding in (often F<-lrt>). |
3812 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
2891 | |
3813 | |
2892 | =item EV_USE_REALTIME |
3814 | =item EV_USE_REALTIME |
2893 | |
3815 | |
2894 | If defined to be C<1>, libev will try to detect the availability of the |
3816 | If defined to be C<1>, libev will try to detect the availability of the |
2895 | real-time clock option at compile time (and assume its availability at |
3817 | real-time clock option at compile time (and assume its availability |
2896 | runtime if successful). Otherwise no use of the real-time clock option will |
3818 | at runtime if successful). Otherwise no use of the real-time clock |
2897 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3819 | option will be attempted. This effectively replaces C<gettimeofday> |
2898 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3820 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
2899 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3821 | correctness. See the note about libraries in the description of |
|
|
3822 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3823 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3824 | |
|
|
3825 | =item EV_USE_CLOCK_SYSCALL |
|
|
3826 | |
|
|
3827 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3828 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3829 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3830 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3831 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3832 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3833 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3834 | higher, as it simplifies linking (no need for C<-lrt>). |
2900 | |
3835 | |
2901 | =item EV_USE_NANOSLEEP |
3836 | =item EV_USE_NANOSLEEP |
2902 | |
3837 | |
2903 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3838 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2904 | and will use it for delays. Otherwise it will use C<select ()>. |
3839 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
2920 | |
3855 | |
2921 | =item EV_SELECT_USE_FD_SET |
3856 | =item EV_SELECT_USE_FD_SET |
2922 | |
3857 | |
2923 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3858 | If defined to C<1>, then the select backend will use the system C<fd_set> |
2924 | structure. This is useful if libev doesn't compile due to a missing |
3859 | structure. This is useful if libev doesn't compile due to a missing |
2925 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3860 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
2926 | exotic systems. This usually limits the range of file descriptors to some |
3861 | on exotic systems. This usually limits the range of file descriptors to |
2927 | low limit such as 1024 or might have other limitations (winsocket only |
3862 | some low limit such as 1024 or might have other limitations (winsocket |
2928 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3863 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
2929 | influence the size of the C<fd_set> used. |
3864 | configures the maximum size of the C<fd_set>. |
2930 | |
3865 | |
2931 | =item EV_SELECT_IS_WINSOCKET |
3866 | =item EV_SELECT_IS_WINSOCKET |
2932 | |
3867 | |
2933 | When defined to C<1>, the select backend will assume that |
3868 | When defined to C<1>, the select backend will assume that |
2934 | select/socket/connect etc. don't understand file descriptors but |
3869 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
2936 | be used is the winsock select). This means that it will call |
3871 | be used is the winsock select). This means that it will call |
2937 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
3872 | C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, |
2938 | it is assumed that all these functions actually work on fds, even |
3873 | it is assumed that all these functions actually work on fds, even |
2939 | on win32. Should not be defined on non-win32 platforms. |
3874 | on win32. Should not be defined on non-win32 platforms. |
2940 | |
3875 | |
2941 | =item EV_FD_TO_WIN32_HANDLE |
3876 | =item EV_FD_TO_WIN32_HANDLE(fd) |
2942 | |
3877 | |
2943 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
3878 | If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map |
2944 | file descriptors to socket handles. When not defining this symbol (the |
3879 | file descriptors to socket handles. When not defining this symbol (the |
2945 | default), then libev will call C<_get_osfhandle>, which is usually |
3880 | default), then libev will call C<_get_osfhandle>, which is usually |
2946 | correct. In some cases, programs use their own file descriptor management, |
3881 | correct. In some cases, programs use their own file descriptor management, |
2947 | in which case they can provide this function to map fds to socket handles. |
3882 | in which case they can provide this function to map fds to socket handles. |
|
|
3883 | |
|
|
3884 | =item EV_WIN32_HANDLE_TO_FD(handle) |
|
|
3885 | |
|
|
3886 | If C<EV_SELECT_IS_WINSOCKET> then libev maps handles to file descriptors |
|
|
3887 | using the standard C<_open_osfhandle> function. For programs implementing |
|
|
3888 | their own fd to handle mapping, overwriting this function makes it easier |
|
|
3889 | to do so. This can be done by defining this macro to an appropriate value. |
|
|
3890 | |
|
|
3891 | =item EV_WIN32_CLOSE_FD(fd) |
|
|
3892 | |
|
|
3893 | If programs implement their own fd to handle mapping on win32, then this |
|
|
3894 | macro can be used to override the C<close> function, useful to unregister |
|
|
3895 | file descriptors again. Note that the replacement function has to close |
|
|
3896 | the underlying OS handle. |
2948 | |
3897 | |
2949 | =item EV_USE_POLL |
3898 | =item EV_USE_POLL |
2950 | |
3899 | |
2951 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
3900 | If defined to be C<1>, libev will compile in support for the C<poll>(2) |
2952 | backend. Otherwise it will be enabled on non-win32 platforms. It |
3901 | backend. Otherwise it will be enabled on non-win32 platforms. It |
… | |
… | |
2999 | as well as for signal and thread safety in C<ev_async> watchers. |
3948 | as well as for signal and thread safety in C<ev_async> watchers. |
3000 | |
3949 | |
3001 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3950 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
3002 | (from F<signal.h>), which is usually good enough on most platforms. |
3951 | (from F<signal.h>), which is usually good enough on most platforms. |
3003 | |
3952 | |
3004 | =item EV_H |
3953 | =item EV_H (h) |
3005 | |
3954 | |
3006 | The name of the F<ev.h> header file used to include it. The default if |
3955 | The name of the F<ev.h> header file used to include it. The default if |
3007 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3956 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
3008 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3957 | used to virtually rename the F<ev.h> header file in case of conflicts. |
3009 | |
3958 | |
3010 | =item EV_CONFIG_H |
3959 | =item EV_CONFIG_H (h) |
3011 | |
3960 | |
3012 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3961 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
3013 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3962 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
3014 | C<EV_H>, above. |
3963 | C<EV_H>, above. |
3015 | |
3964 | |
3016 | =item EV_EVENT_H |
3965 | =item EV_EVENT_H (h) |
3017 | |
3966 | |
3018 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3967 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
3019 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3968 | of how the F<event.h> header can be found, the default is C<"event.h">. |
3020 | |
3969 | |
3021 | =item EV_PROTOTYPES |
3970 | =item EV_PROTOTYPES (h) |
3022 | |
3971 | |
3023 | If defined to be C<0>, then F<ev.h> will not define any function |
3972 | If defined to be C<0>, then F<ev.h> will not define any function |
3024 | prototypes, but still define all the structs and other symbols. This is |
3973 | prototypes, but still define all the structs and other symbols. This is |
3025 | occasionally useful if you want to provide your own wrapper functions |
3974 | occasionally useful if you want to provide your own wrapper functions |
3026 | around libev functions. |
3975 | around libev functions. |
… | |
… | |
3045 | When doing priority-based operations, libev usually has to linearly search |
3994 | When doing priority-based operations, libev usually has to linearly search |
3046 | all the priorities, so having many of them (hundreds) uses a lot of space |
3995 | all the priorities, so having many of them (hundreds) uses a lot of space |
3047 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3996 | and time, so using the defaults of five priorities (-2 .. +2) is usually |
3048 | fine. |
3997 | fine. |
3049 | |
3998 | |
3050 | If your embedding application does not need any priorities, defining these both to |
3999 | If your embedding application does not need any priorities, defining these |
3051 | C<0> will save some memory and CPU. |
4000 | both to C<0> will save some memory and CPU. |
3052 | |
4001 | |
3053 | =item EV_PERIODIC_ENABLE |
4002 | =item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE, |
|
|
4003 | EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, |
|
|
4004 | EV_ASYNC_ENABLE, EV_CHILD_ENABLE. |
3054 | |
4005 | |
3055 | If undefined or defined to be C<1>, then periodic timers are supported. If |
4006 | If undefined or defined to be C<1> (and the platform supports it), then |
3056 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
4007 | the respective watcher type is supported. If defined to be C<0>, then it |
3057 | code. |
4008 | is not. Disabling watcher types mainly saves code size. |
3058 | |
4009 | |
3059 | =item EV_IDLE_ENABLE |
4010 | =item EV_FEATURES |
3060 | |
|
|
3061 | If undefined or defined to be C<1>, then idle watchers are supported. If |
|
|
3062 | defined to be C<0>, then they are not. Disabling them saves a few kB of |
|
|
3063 | code. |
|
|
3064 | |
|
|
3065 | =item EV_EMBED_ENABLE |
|
|
3066 | |
|
|
3067 | If undefined or defined to be C<1>, then embed watchers are supported. If |
|
|
3068 | defined to be C<0>, then they are not. |
|
|
3069 | |
|
|
3070 | =item EV_STAT_ENABLE |
|
|
3071 | |
|
|
3072 | If undefined or defined to be C<1>, then stat watchers are supported. If |
|
|
3073 | defined to be C<0>, then they are not. |
|
|
3074 | |
|
|
3075 | =item EV_FORK_ENABLE |
|
|
3076 | |
|
|
3077 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
3078 | defined to be C<0>, then they are not. |
|
|
3079 | |
|
|
3080 | =item EV_ASYNC_ENABLE |
|
|
3081 | |
|
|
3082 | If undefined or defined to be C<1>, then async watchers are supported. If |
|
|
3083 | defined to be C<0>, then they are not. |
|
|
3084 | |
|
|
3085 | =item EV_MINIMAL |
|
|
3086 | |
4011 | |
3087 | If you need to shave off some kilobytes of code at the expense of some |
4012 | If you need to shave off some kilobytes of code at the expense of some |
3088 | speed, define this symbol to C<1>. Currently this is used to override some |
4013 | speed (but with the full API), you can define this symbol to request |
3089 | inlining decisions, saves roughly 30% code size on amd64. It also selects a |
4014 | certain subsets of functionality. The default is to enable all features |
3090 | much smaller 2-heap for timer management over the default 4-heap. |
4015 | that can be enabled on the platform. |
|
|
4016 | |
|
|
4017 | A typical way to use this symbol is to define it to C<0> (or to a bitset |
|
|
4018 | with some broad features you want) and then selectively re-enable |
|
|
4019 | additional parts you want, for example if you want everything minimal, |
|
|
4020 | but multiple event loop support, async and child watchers and the poll |
|
|
4021 | backend, use this: |
|
|
4022 | |
|
|
4023 | #define EV_FEATURES 0 |
|
|
4024 | #define EV_MULTIPLICITY 1 |
|
|
4025 | #define EV_USE_POLL 1 |
|
|
4026 | #define EV_CHILD_ENABLE 1 |
|
|
4027 | #define EV_ASYNC_ENABLE 1 |
|
|
4028 | |
|
|
4029 | The actual value is a bitset, it can be a combination of the following |
|
|
4030 | values: |
|
|
4031 | |
|
|
4032 | =over 4 |
|
|
4033 | |
|
|
4034 | =item C<1> - faster/larger code |
|
|
4035 | |
|
|
4036 | Use larger code to speed up some operations. |
|
|
4037 | |
|
|
4038 | Currently this is used to override some inlining decisions (enlarging the |
|
|
4039 | code size by roughly 30% on amd64). |
|
|
4040 | |
|
|
4041 | When optimising for size, use of compiler flags such as C<-Os> with |
|
|
4042 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
|
|
4043 | assertions. |
|
|
4044 | |
|
|
4045 | =item C<2> - faster/larger data structures |
|
|
4046 | |
|
|
4047 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
|
|
4048 | hash table sizes and so on. This will usually further increase code size |
|
|
4049 | and can additionally have an effect on the size of data structures at |
|
|
4050 | runtime. |
|
|
4051 | |
|
|
4052 | =item C<4> - full API configuration |
|
|
4053 | |
|
|
4054 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
|
|
4055 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
|
|
4056 | |
|
|
4057 | =item C<8> - full API |
|
|
4058 | |
|
|
4059 | This enables a lot of the "lesser used" API functions. See C<ev.h> for |
|
|
4060 | details on which parts of the API are still available without this |
|
|
4061 | feature, and do not complain if this subset changes over time. |
|
|
4062 | |
|
|
4063 | =item C<16> - enable all optional watcher types |
|
|
4064 | |
|
|
4065 | Enables all optional watcher types. If you want to selectively enable |
|
|
4066 | only some watcher types other than I/O and timers (e.g. prepare, |
|
|
4067 | embed, async, child...) you can enable them manually by defining |
|
|
4068 | C<EV_watchertype_ENABLE> to C<1> instead. |
|
|
4069 | |
|
|
4070 | =item C<32> - enable all backends |
|
|
4071 | |
|
|
4072 | This enables all backends - without this feature, you need to enable at |
|
|
4073 | least one backend manually (C<EV_USE_SELECT> is a good choice). |
|
|
4074 | |
|
|
4075 | =item C<64> - enable OS-specific "helper" APIs |
|
|
4076 | |
|
|
4077 | Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by |
|
|
4078 | default. |
|
|
4079 | |
|
|
4080 | =back |
|
|
4081 | |
|
|
4082 | Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0> |
|
|
4083 | reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb |
|
|
4084 | code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O |
|
|
4085 | watchers, timers and monotonic clock support. |
|
|
4086 | |
|
|
4087 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
|
|
4088 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
|
|
4089 | your program might be left out as well - a binary starting a timer and an |
|
|
4090 | I/O watcher then might come out at only 5Kb. |
|
|
4091 | |
|
|
4092 | =item EV_AVOID_STDIO |
|
|
4093 | |
|
|
4094 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
|
|
4095 | functions (printf, scanf, perror etc.). This will increase the code size |
|
|
4096 | somewhat, but if your program doesn't otherwise depend on stdio and your |
|
|
4097 | libc allows it, this avoids linking in the stdio library which is quite |
|
|
4098 | big. |
|
|
4099 | |
|
|
4100 | Note that error messages might become less precise when this option is |
|
|
4101 | enabled. |
|
|
4102 | |
|
|
4103 | =item EV_NSIG |
|
|
4104 | |
|
|
4105 | The highest supported signal number, +1 (or, the number of |
|
|
4106 | signals): Normally, libev tries to deduce the maximum number of signals |
|
|
4107 | automatically, but sometimes this fails, in which case it can be |
|
|
4108 | specified. Also, using a lower number than detected (C<32> should be |
|
|
4109 | good for about any system in existence) can save some memory, as libev |
|
|
4110 | statically allocates some 12-24 bytes per signal number. |
3091 | |
4111 | |
3092 | =item EV_PID_HASHSIZE |
4112 | =item EV_PID_HASHSIZE |
3093 | |
4113 | |
3094 | C<ev_child> watchers use a small hash table to distribute workload by |
4114 | C<ev_child> watchers use a small hash table to distribute workload by |
3095 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
4115 | pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled), |
3096 | than enough. If you need to manage thousands of children you might want to |
4116 | usually more than enough. If you need to manage thousands of children you |
3097 | increase this value (I<must> be a power of two). |
4117 | might want to increase this value (I<must> be a power of two). |
3098 | |
4118 | |
3099 | =item EV_INOTIFY_HASHSIZE |
4119 | =item EV_INOTIFY_HASHSIZE |
3100 | |
4120 | |
3101 | C<ev_stat> watchers use a small hash table to distribute workload by |
4121 | C<ev_stat> watchers use a small hash table to distribute workload by |
3102 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
4122 | inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES> |
3103 | usually more than enough. If you need to manage thousands of C<ev_stat> |
4123 | disabled), usually more than enough. If you need to manage thousands of |
3104 | watchers you might want to increase this value (I<must> be a power of |
4124 | C<ev_stat> watchers you might want to increase this value (I<must> be a |
3105 | two). |
4125 | power of two). |
3106 | |
4126 | |
3107 | =item EV_USE_4HEAP |
4127 | =item EV_USE_4HEAP |
3108 | |
4128 | |
3109 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4129 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3110 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
4130 | timer and periodics heaps, libev uses a 4-heap when this symbol is defined |
3111 | to C<1>. The 4-heap uses more complicated (longer) code but has |
4131 | to C<1>. The 4-heap uses more complicated (longer) code but has noticeably |
3112 | noticeably faster performance with many (thousands) of watchers. |
4132 | faster performance with many (thousands) of watchers. |
3113 | |
4133 | |
3114 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4134 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3115 | (disabled). |
4135 | will be C<0>. |
3116 | |
4136 | |
3117 | =item EV_HEAP_CACHE_AT |
4137 | =item EV_HEAP_CACHE_AT |
3118 | |
4138 | |
3119 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
4139 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
3120 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
4140 | timer and periodics heaps, libev can cache the timestamp (I<at>) within |
3121 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
4141 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
3122 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
4142 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
3123 | but avoids random read accesses on heap changes. This improves performance |
4143 | but avoids random read accesses on heap changes. This improves performance |
3124 | noticeably with with many (hundreds) of watchers. |
4144 | noticeably with many (hundreds) of watchers. |
3125 | |
4145 | |
3126 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
4146 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3127 | (disabled). |
4147 | will be C<0>. |
3128 | |
4148 | |
3129 | =item EV_VERIFY |
4149 | =item EV_VERIFY |
3130 | |
4150 | |
3131 | Controls how much internal verification (see C<ev_loop_verify ()>) will |
4151 | Controls how much internal verification (see C<ev_verify ()>) will |
3132 | be done: If set to C<0>, no internal verification code will be compiled |
4152 | be done: If set to C<0>, no internal verification code will be compiled |
3133 | in. If set to C<1>, then verification code will be compiled in, but not |
4153 | in. If set to C<1>, then verification code will be compiled in, but not |
3134 | called. If set to C<2>, then the internal verification code will be |
4154 | called. If set to C<2>, then the internal verification code will be |
3135 | called once per loop, which can slow down libev. If set to C<3>, then the |
4155 | called once per loop, which can slow down libev. If set to C<3>, then the |
3136 | verification code will be called very frequently, which will slow down |
4156 | verification code will be called very frequently, which will slow down |
3137 | libev considerably. |
4157 | libev considerably. |
3138 | |
4158 | |
3139 | The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be |
4159 | The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it |
3140 | C<0.> |
4160 | will be C<0>. |
3141 | |
4161 | |
3142 | =item EV_COMMON |
4162 | =item EV_COMMON |
3143 | |
4163 | |
3144 | By default, all watchers have a C<void *data> member. By redefining |
4164 | By default, all watchers have a C<void *data> member. By redefining |
3145 | this macro to a something else you can include more and other types of |
4165 | this macro to something else you can include more and other types of |
3146 | members. You have to define it each time you include one of the files, |
4166 | members. You have to define it each time you include one of the files, |
3147 | though, and it must be identical each time. |
4167 | though, and it must be identical each time. |
3148 | |
4168 | |
3149 | For example, the perl EV module uses something like this: |
4169 | For example, the perl EV module uses something like this: |
3150 | |
4170 | |
… | |
… | |
3162 | and the way callbacks are invoked and set. Must expand to a struct member |
4182 | and the way callbacks are invoked and set. Must expand to a struct member |
3163 | definition and a statement, respectively. See the F<ev.h> header file for |
4183 | definition and a statement, respectively. See the F<ev.h> header file for |
3164 | their default definitions. One possible use for overriding these is to |
4184 | their default definitions. One possible use for overriding these is to |
3165 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
4185 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
3166 | method calls instead of plain function calls in C++. |
4186 | method calls instead of plain function calls in C++. |
|
|
4187 | |
|
|
4188 | =back |
3167 | |
4189 | |
3168 | =head2 EXPORTED API SYMBOLS |
4190 | =head2 EXPORTED API SYMBOLS |
3169 | |
4191 | |
3170 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
4192 | If you need to re-export the API (e.g. via a DLL) and you need a list of |
3171 | exported symbols, you can use the provided F<Symbol.*> files which list |
4193 | exported symbols, you can use the provided F<Symbol.*> files which list |
… | |
… | |
3201 | file. |
4223 | file. |
3202 | |
4224 | |
3203 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
4225 | The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file |
3204 | that everybody includes and which overrides some configure choices: |
4226 | that everybody includes and which overrides some configure choices: |
3205 | |
4227 | |
3206 | #define EV_MINIMAL 1 |
4228 | #define EV_FEATURES 8 |
3207 | #define EV_USE_POLL 0 |
4229 | #define EV_USE_SELECT 1 |
3208 | #define EV_MULTIPLICITY 0 |
|
|
3209 | #define EV_PERIODIC_ENABLE 0 |
4230 | #define EV_PREPARE_ENABLE 1 |
|
|
4231 | #define EV_IDLE_ENABLE 1 |
3210 | #define EV_STAT_ENABLE 0 |
4232 | #define EV_SIGNAL_ENABLE 1 |
3211 | #define EV_FORK_ENABLE 0 |
4233 | #define EV_CHILD_ENABLE 1 |
|
|
4234 | #define EV_USE_STDEXCEPT 0 |
3212 | #define EV_CONFIG_H <config.h> |
4235 | #define EV_CONFIG_H <config.h> |
3213 | #define EV_MINPRI 0 |
|
|
3214 | #define EV_MAXPRI 0 |
|
|
3215 | |
4236 | |
3216 | #include "ev++.h" |
4237 | #include "ev++.h" |
3217 | |
4238 | |
3218 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4239 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
3219 | |
4240 | |
3220 | #include "ev_cpp.h" |
4241 | #include "ev_cpp.h" |
3221 | #include "ev.c" |
4242 | #include "ev.c" |
3222 | |
4243 | |
|
|
4244 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
3223 | |
4245 | |
3224 | =head1 THREADS AND COROUTINES |
4246 | =head2 THREADS AND COROUTINES |
3225 | |
4247 | |
3226 | =head2 THREADS |
4248 | =head3 THREADS |
3227 | |
4249 | |
3228 | Libev itself is completely thread-safe, but it uses no locking. This |
4250 | All libev functions are reentrant and thread-safe unless explicitly |
|
|
4251 | documented otherwise, but libev implements no locking itself. This means |
3229 | means that you can use as many loops as you want in parallel, as long as |
4252 | that you can use as many loops as you want in parallel, as long as there |
3230 | only one thread ever calls into one libev function with the same loop |
4253 | are no concurrent calls into any libev function with the same loop |
3231 | parameter. |
4254 | parameter (C<ev_default_*> calls have an implicit default loop parameter, |
|
|
4255 | of course): libev guarantees that different event loops share no data |
|
|
4256 | structures that need any locking. |
3232 | |
4257 | |
3233 | Or put differently: calls with different loop parameters can be done in |
4258 | Or to put it differently: calls with different loop parameters can be done |
3234 | parallel from multiple threads, calls with the same loop parameter must be |
4259 | concurrently from multiple threads, calls with the same loop parameter |
3235 | done serially (but can be done from different threads, as long as only one |
4260 | must be done serially (but can be done from different threads, as long as |
3236 | thread ever is inside a call at any point in time, e.g. by using a mutex |
4261 | only one thread ever is inside a call at any point in time, e.g. by using |
3237 | per loop). |
4262 | a mutex per loop). |
|
|
4263 | |
|
|
4264 | Specifically to support threads (and signal handlers), libev implements |
|
|
4265 | so-called C<ev_async> watchers, which allow some limited form of |
|
|
4266 | concurrency on the same event loop, namely waking it up "from the |
|
|
4267 | outside". |
3238 | |
4268 | |
3239 | If you want to know which design (one loop, locking, or multiple loops |
4269 | If you want to know which design (one loop, locking, or multiple loops |
3240 | without or something else still) is best for your problem, then I cannot |
4270 | without or something else still) is best for your problem, then I cannot |
3241 | help you. I can give some generic advice however: |
4271 | help you, but here is some generic advice: |
3242 | |
4272 | |
3243 | =over 4 |
4273 | =over 4 |
3244 | |
4274 | |
3245 | =item * most applications have a main thread: use the default libev loop |
4275 | =item * most applications have a main thread: use the default libev loop |
3246 | in that thread, or create a separate thread running only the default loop. |
4276 | in that thread, or create a separate thread running only the default loop. |
… | |
… | |
3258 | |
4288 | |
3259 | Choosing a model is hard - look around, learn, know that usually you can do |
4289 | Choosing a model is hard - look around, learn, know that usually you can do |
3260 | better than you currently do :-) |
4290 | better than you currently do :-) |
3261 | |
4291 | |
3262 | =item * often you need to talk to some other thread which blocks in the |
4292 | =item * often you need to talk to some other thread which blocks in the |
|
|
4293 | event loop. |
|
|
4294 | |
3263 | event loop - C<ev_async> watchers can be used to wake them up from other |
4295 | C<ev_async> watchers can be used to wake them up from other threads safely |
3264 | threads safely (or from signal contexts...). |
4296 | (or from signal contexts...). |
|
|
4297 | |
|
|
4298 | An example use would be to communicate signals or other events that only |
|
|
4299 | work in the default loop by registering the signal watcher with the |
|
|
4300 | default loop and triggering an C<ev_async> watcher from the default loop |
|
|
4301 | watcher callback into the event loop interested in the signal. |
3265 | |
4302 | |
3266 | =back |
4303 | =back |
3267 | |
4304 | |
|
|
4305 | =head4 THREAD LOCKING EXAMPLE |
|
|
4306 | |
|
|
4307 | Here is a fictitious example of how to run an event loop in a different |
|
|
4308 | thread than where callbacks are being invoked and watchers are |
|
|
4309 | created/added/removed. |
|
|
4310 | |
|
|
4311 | For a real-world example, see the C<EV::Loop::Async> perl module, |
|
|
4312 | which uses exactly this technique (which is suited for many high-level |
|
|
4313 | languages). |
|
|
4314 | |
|
|
4315 | The example uses a pthread mutex to protect the loop data, a condition |
|
|
4316 | variable to wait for callback invocations, an async watcher to notify the |
|
|
4317 | event loop thread and an unspecified mechanism to wake up the main thread. |
|
|
4318 | |
|
|
4319 | First, you need to associate some data with the event loop: |
|
|
4320 | |
|
|
4321 | typedef struct { |
|
|
4322 | mutex_t lock; /* global loop lock */ |
|
|
4323 | ev_async async_w; |
|
|
4324 | thread_t tid; |
|
|
4325 | cond_t invoke_cv; |
|
|
4326 | } userdata; |
|
|
4327 | |
|
|
4328 | void prepare_loop (EV_P) |
|
|
4329 | { |
|
|
4330 | // for simplicity, we use a static userdata struct. |
|
|
4331 | static userdata u; |
|
|
4332 | |
|
|
4333 | ev_async_init (&u->async_w, async_cb); |
|
|
4334 | ev_async_start (EV_A_ &u->async_w); |
|
|
4335 | |
|
|
4336 | pthread_mutex_init (&u->lock, 0); |
|
|
4337 | pthread_cond_init (&u->invoke_cv, 0); |
|
|
4338 | |
|
|
4339 | // now associate this with the loop |
|
|
4340 | ev_set_userdata (EV_A_ u); |
|
|
4341 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
|
|
4342 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
|
|
4343 | |
|
|
4344 | // then create the thread running ev_loop |
|
|
4345 | pthread_create (&u->tid, 0, l_run, EV_A); |
|
|
4346 | } |
|
|
4347 | |
|
|
4348 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
|
|
4349 | solely to wake up the event loop so it takes notice of any new watchers |
|
|
4350 | that might have been added: |
|
|
4351 | |
|
|
4352 | static void |
|
|
4353 | async_cb (EV_P_ ev_async *w, int revents) |
|
|
4354 | { |
|
|
4355 | // just used for the side effects |
|
|
4356 | } |
|
|
4357 | |
|
|
4358 | The C<l_release> and C<l_acquire> callbacks simply unlock/lock the mutex |
|
|
4359 | protecting the loop data, respectively. |
|
|
4360 | |
|
|
4361 | static void |
|
|
4362 | l_release (EV_P) |
|
|
4363 | { |
|
|
4364 | userdata *u = ev_userdata (EV_A); |
|
|
4365 | pthread_mutex_unlock (&u->lock); |
|
|
4366 | } |
|
|
4367 | |
|
|
4368 | static void |
|
|
4369 | l_acquire (EV_P) |
|
|
4370 | { |
|
|
4371 | userdata *u = ev_userdata (EV_A); |
|
|
4372 | pthread_mutex_lock (&u->lock); |
|
|
4373 | } |
|
|
4374 | |
|
|
4375 | The event loop thread first acquires the mutex, and then jumps straight |
|
|
4376 | into C<ev_run>: |
|
|
4377 | |
|
|
4378 | void * |
|
|
4379 | l_run (void *thr_arg) |
|
|
4380 | { |
|
|
4381 | struct ev_loop *loop = (struct ev_loop *)thr_arg; |
|
|
4382 | |
|
|
4383 | l_acquire (EV_A); |
|
|
4384 | pthread_setcanceltype (PTHREAD_CANCEL_ASYNCHRONOUS, 0); |
|
|
4385 | ev_run (EV_A_ 0); |
|
|
4386 | l_release (EV_A); |
|
|
4387 | |
|
|
4388 | return 0; |
|
|
4389 | } |
|
|
4390 | |
|
|
4391 | Instead of invoking all pending watchers, the C<l_invoke> callback will |
|
|
4392 | signal the main thread via some unspecified mechanism (signals? pipe |
|
|
4393 | writes? C<Async::Interrupt>?) and then waits until all pending watchers |
|
|
4394 | have been called (in a while loop because a) spurious wakeups are possible |
|
|
4395 | and b) skipping inter-thread-communication when there are no pending |
|
|
4396 | watchers is very beneficial): |
|
|
4397 | |
|
|
4398 | static void |
|
|
4399 | l_invoke (EV_P) |
|
|
4400 | { |
|
|
4401 | userdata *u = ev_userdata (EV_A); |
|
|
4402 | |
|
|
4403 | while (ev_pending_count (EV_A)) |
|
|
4404 | { |
|
|
4405 | wake_up_other_thread_in_some_magic_or_not_so_magic_way (); |
|
|
4406 | pthread_cond_wait (&u->invoke_cv, &u->lock); |
|
|
4407 | } |
|
|
4408 | } |
|
|
4409 | |
|
|
4410 | Now, whenever the main thread gets told to invoke pending watchers, it |
|
|
4411 | will grab the lock, call C<ev_invoke_pending> and then signal the loop |
|
|
4412 | thread to continue: |
|
|
4413 | |
|
|
4414 | static void |
|
|
4415 | real_invoke_pending (EV_P) |
|
|
4416 | { |
|
|
4417 | userdata *u = ev_userdata (EV_A); |
|
|
4418 | |
|
|
4419 | pthread_mutex_lock (&u->lock); |
|
|
4420 | ev_invoke_pending (EV_A); |
|
|
4421 | pthread_cond_signal (&u->invoke_cv); |
|
|
4422 | pthread_mutex_unlock (&u->lock); |
|
|
4423 | } |
|
|
4424 | |
|
|
4425 | Whenever you want to start/stop a watcher or do other modifications to an |
|
|
4426 | event loop, you will now have to lock: |
|
|
4427 | |
|
|
4428 | ev_timer timeout_watcher; |
|
|
4429 | userdata *u = ev_userdata (EV_A); |
|
|
4430 | |
|
|
4431 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
|
|
4432 | |
|
|
4433 | pthread_mutex_lock (&u->lock); |
|
|
4434 | ev_timer_start (EV_A_ &timeout_watcher); |
|
|
4435 | ev_async_send (EV_A_ &u->async_w); |
|
|
4436 | pthread_mutex_unlock (&u->lock); |
|
|
4437 | |
|
|
4438 | Note that sending the C<ev_async> watcher is required because otherwise |
|
|
4439 | an event loop currently blocking in the kernel will have no knowledge |
|
|
4440 | about the newly added timer. By waking up the loop it will pick up any new |
|
|
4441 | watchers in the next event loop iteration. |
|
|
4442 | |
3268 | =head2 COROUTINES |
4443 | =head3 COROUTINES |
3269 | |
4444 | |
3270 | Libev is much more accommodating to coroutines ("cooperative threads"): |
4445 | Libev is very accommodating to coroutines ("cooperative threads"): |
3271 | libev fully supports nesting calls to it's functions from different |
4446 | libev fully supports nesting calls to its functions from different |
3272 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
4447 | coroutines (e.g. you can call C<ev_run> on the same loop from two |
3273 | different coroutines and switch freely between both coroutines running the |
4448 | different coroutines, and switch freely between both coroutines running |
3274 | loop, as long as you don't confuse yourself). The only exception is that |
4449 | the loop, as long as you don't confuse yourself). The only exception is |
3275 | you must not do this from C<ev_periodic> reschedule callbacks. |
4450 | that you must not do this from C<ev_periodic> reschedule callbacks. |
3276 | |
4451 | |
3277 | Care has been invested into making sure that libev does not keep local |
4452 | Care has been taken to ensure that libev does not keep local state inside |
3278 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
4453 | C<ev_run>, and other calls do not usually allow for coroutine switches as |
3279 | switches. |
4454 | they do not call any callbacks. |
3280 | |
4455 | |
|
|
4456 | =head2 COMPILER WARNINGS |
3281 | |
4457 | |
3282 | =head1 COMPLEXITIES |
4458 | Depending on your compiler and compiler settings, you might get no or a |
|
|
4459 | lot of warnings when compiling libev code. Some people are apparently |
|
|
4460 | scared by this. |
3283 | |
4461 | |
3284 | In this section the complexities of (many of) the algorithms used inside |
4462 | However, these are unavoidable for many reasons. For one, each compiler |
3285 | libev will be explained. For complexity discussions about backends see the |
4463 | has different warnings, and each user has different tastes regarding |
3286 | documentation for C<ev_default_init>. |
4464 | warning options. "Warn-free" code therefore cannot be a goal except when |
|
|
4465 | targeting a specific compiler and compiler-version. |
3287 | |
4466 | |
3288 | All of the following are about amortised time: If an array needs to be |
4467 | Another reason is that some compiler warnings require elaborate |
3289 | extended, libev needs to realloc and move the whole array, but this |
4468 | workarounds, or other changes to the code that make it less clear and less |
3290 | happens asymptotically never with higher number of elements, so O(1) might |
4469 | maintainable. |
3291 | mean it might do a lengthy realloc operation in rare cases, but on average |
|
|
3292 | it is much faster and asymptotically approaches constant time. |
|
|
3293 | |
4470 | |
3294 | =over 4 |
4471 | And of course, some compiler warnings are just plain stupid, or simply |
|
|
4472 | wrong (because they don't actually warn about the condition their message |
|
|
4473 | seems to warn about). For example, certain older gcc versions had some |
|
|
4474 | warnings that resulted in an extreme number of false positives. These have |
|
|
4475 | been fixed, but some people still insist on making code warn-free with |
|
|
4476 | such buggy versions. |
3295 | |
4477 | |
3296 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
4478 | While libev is written to generate as few warnings as possible, |
|
|
4479 | "warn-free" code is not a goal, and it is recommended not to build libev |
|
|
4480 | with any compiler warnings enabled unless you are prepared to cope with |
|
|
4481 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
4482 | warnings, not errors, or proof of bugs. |
3297 | |
4483 | |
3298 | This means that, when you have a watcher that triggers in one hour and |
|
|
3299 | there are 100 watchers that would trigger before that then inserting will |
|
|
3300 | have to skip roughly seven (C<ld 100>) of these watchers. |
|
|
3301 | |
4484 | |
3302 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
4485 | =head2 VALGRIND |
3303 | |
4486 | |
3304 | That means that changing a timer costs less than removing/adding them |
4487 | Valgrind has a special section here because it is a popular tool that is |
3305 | as only the relative motion in the event queue has to be paid for. |
4488 | highly useful. Unfortunately, valgrind reports are very hard to interpret. |
3306 | |
4489 | |
3307 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
4490 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
4491 | in libev, then check twice: If valgrind reports something like: |
3308 | |
4492 | |
3309 | These just add the watcher into an array or at the head of a list. |
4493 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
4494 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
4495 | ==2274== still reachable: 256 bytes in 1 blocks. |
3310 | |
4496 | |
3311 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
4497 | Then there is no memory leak, just as memory accounted to global variables |
|
|
4498 | is not a memleak - the memory is still being referenced, and didn't leak. |
3312 | |
4499 | |
3313 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
4500 | Similarly, under some circumstances, valgrind might report kernel bugs |
|
|
4501 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
|
|
4502 | although an acceptable workaround has been found here), or it might be |
|
|
4503 | confused. |
3314 | |
4504 | |
3315 | These watchers are stored in lists then need to be walked to find the |
4505 | Keep in mind that valgrind is a very good tool, but only a tool. Don't |
3316 | correct watcher to remove. The lists are usually short (you don't usually |
4506 | make it into some kind of religion. |
3317 | have many watchers waiting for the same fd or signal). |
|
|
3318 | |
4507 | |
3319 | =item Finding the next timer in each loop iteration: O(1) |
4508 | If you are unsure about something, feel free to contact the mailing list |
|
|
4509 | with the full valgrind report and an explanation on why you think this |
|
|
4510 | is a bug in libev (best check the archives, too :). However, don't be |
|
|
4511 | annoyed when you get a brisk "this is no bug" answer and take the chance |
|
|
4512 | of learning how to interpret valgrind properly. |
3320 | |
4513 | |
3321 | By virtue of using a binary or 4-heap, the next timer is always found at a |
4514 | If you need, for some reason, empty reports from valgrind for your project |
3322 | fixed position in the storage array. |
4515 | I suggest using suppression lists. |
3323 | |
4516 | |
3324 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
3325 | |
4517 | |
3326 | A change means an I/O watcher gets started or stopped, which requires |
4518 | =head1 PORTABILITY NOTES |
3327 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
3328 | on backend and whether C<ev_io_set> was used). |
|
|
3329 | |
4519 | |
3330 | =item Activating one watcher (putting it into the pending state): O(1) |
4520 | =head2 GNU/LINUX 32 BIT LIMITATIONS |
3331 | |
4521 | |
3332 | =item Priority handling: O(number_of_priorities) |
4522 | GNU/Linux is the only common platform that supports 64 bit file/large file |
|
|
4523 | interfaces but I<disables> them by default. |
3333 | |
4524 | |
3334 | Priorities are implemented by allocating some space for each |
4525 | That means that libev compiled in the default environment doesn't support |
3335 | priority. When doing priority-based operations, libev usually has to |
4526 | files larger than 2GiB or so, which mainly affects C<ev_stat> watchers. |
3336 | linearly search all the priorities, but starting/stopping and activating |
|
|
3337 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3338 | |
4527 | |
3339 | =item Sending an ev_async: O(1) |
4528 | Unfortunately, many programs try to work around this GNU/Linux issue |
|
|
4529 | by enabling the large file API, which makes them incompatible with the |
|
|
4530 | standard libev compiled for their system. |
3340 | |
4531 | |
3341 | =item Processing ev_async_send: O(number_of_async_watchers) |
4532 | Likewise, libev cannot enable the large file API itself as this would |
|
|
4533 | suddenly make it incompatible to the default compile time environment, |
|
|
4534 | i.e. all programs not using special compile switches. |
3342 | |
4535 | |
3343 | =item Processing signals: O(max_signal_number) |
4536 | =head2 OS/X AND DARWIN BUGS |
3344 | |
4537 | |
3345 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
4538 | The whole thing is a bug if you ask me - basically any system interface |
3346 | calls in the current loop iteration. Checking for async and signal events |
4539 | you touch is broken, whether it is locales, poll, kqueue or even the |
3347 | involves iterating over all running async watchers or all signal numbers. |
4540 | OpenGL drivers. |
3348 | |
4541 | |
3349 | =back |
4542 | =head3 C<kqueue> is buggy |
3350 | |
4543 | |
|
|
4544 | The kqueue syscall is broken in all known versions - most versions support |
|
|
4545 | only sockets, many support pipes. |
3351 | |
4546 | |
|
|
4547 | Libev tries to work around this by not using C<kqueue> by default on this |
|
|
4548 | rotten platform, but of course you can still ask for it when creating a |
|
|
4549 | loop - embedding a socket-only kqueue loop into a select-based one is |
|
|
4550 | probably going to work well. |
|
|
4551 | |
|
|
4552 | =head3 C<poll> is buggy |
|
|
4553 | |
|
|
4554 | Instead of fixing C<kqueue>, Apple replaced their (working) C<poll> |
|
|
4555 | implementation by something calling C<kqueue> internally around the 10.5.6 |
|
|
4556 | release, so now C<kqueue> I<and> C<poll> are broken. |
|
|
4557 | |
|
|
4558 | Libev tries to work around this by not using C<poll> by default on |
|
|
4559 | this rotten platform, but of course you can still ask for it when creating |
|
|
4560 | a loop. |
|
|
4561 | |
|
|
4562 | =head3 C<select> is buggy |
|
|
4563 | |
|
|
4564 | All that's left is C<select>, and of course Apple found a way to fuck this |
|
|
4565 | one up as well: On OS/X, C<select> actively limits the number of file |
|
|
4566 | descriptors you can pass in to 1024 - your program suddenly crashes when |
|
|
4567 | you use more. |
|
|
4568 | |
|
|
4569 | There is an undocumented "workaround" for this - defining |
|
|
4570 | C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should> |
|
|
4571 | work on OS/X. |
|
|
4572 | |
|
|
4573 | =head2 SOLARIS PROBLEMS AND WORKAROUNDS |
|
|
4574 | |
|
|
4575 | =head3 C<errno> reentrancy |
|
|
4576 | |
|
|
4577 | The default compile environment on Solaris is unfortunately so |
|
|
4578 | thread-unsafe that you can't even use components/libraries compiled |
|
|
4579 | without C<-D_REENTRANT> in a threaded program, which, of course, isn't |
|
|
4580 | defined by default. A valid, if stupid, implementation choice. |
|
|
4581 | |
|
|
4582 | If you want to use libev in threaded environments you have to make sure |
|
|
4583 | it's compiled with C<_REENTRANT> defined. |
|
|
4584 | |
|
|
4585 | =head3 Event port backend |
|
|
4586 | |
|
|
4587 | The scalable event interface for Solaris is called "event |
|
|
4588 | ports". Unfortunately, this mechanism is very buggy in all major |
|
|
4589 | releases. If you run into high CPU usage, your program freezes or you get |
|
|
4590 | a large number of spurious wakeups, make sure you have all the relevant |
|
|
4591 | and latest kernel patches applied. No, I don't know which ones, but there |
|
|
4592 | are multiple ones to apply, and afterwards, event ports actually work |
|
|
4593 | great. |
|
|
4594 | |
|
|
4595 | If you can't get it to work, you can try running the program by setting |
|
|
4596 | the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and |
|
|
4597 | C<select> backends. |
|
|
4598 | |
|
|
4599 | =head2 AIX POLL BUG |
|
|
4600 | |
|
|
4601 | AIX unfortunately has a broken C<poll.h> header. Libev works around |
|
|
4602 | this by trying to avoid the poll backend altogether (i.e. it's not even |
|
|
4603 | compiled in), which normally isn't a big problem as C<select> works fine |
|
|
4604 | with large bitsets on AIX, and AIX is dead anyway. |
|
|
4605 | |
3352 | =head1 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
4606 | =head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS |
|
|
4607 | |
|
|
4608 | =head3 General issues |
3353 | |
4609 | |
3354 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
4610 | Win32 doesn't support any of the standards (e.g. POSIX) that libev |
3355 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4611 | requires, and its I/O model is fundamentally incompatible with the POSIX |
3356 | model. Libev still offers limited functionality on this platform in |
4612 | model. Libev still offers limited functionality on this platform in |
3357 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4613 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3358 | descriptors. This only applies when using Win32 natively, not when using |
4614 | descriptors. This only applies when using Win32 natively, not when using |
3359 | e.g. cygwin. |
4615 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
|
|
4616 | as every compielr comes with a slightly differently broken/incompatible |
|
|
4617 | environment. |
3360 | |
4618 | |
3361 | Lifting these limitations would basically require the full |
4619 | Lifting these limitations would basically require the full |
3362 | re-implementation of the I/O system. If you are into these kinds of |
4620 | re-implementation of the I/O system. If you are into this kind of thing, |
3363 | things, then note that glib does exactly that for you in a very portable |
4621 | then note that glib does exactly that for you in a very portable way (note |
3364 | way (note also that glib is the slowest event library known to man). |
4622 | also that glib is the slowest event library known to man). |
3365 | |
4623 | |
3366 | There is no supported compilation method available on windows except |
4624 | There is no supported compilation method available on windows except |
3367 | embedding it into other applications. |
4625 | embedding it into other applications. |
|
|
4626 | |
|
|
4627 | Sensible signal handling is officially unsupported by Microsoft - libev |
|
|
4628 | tries its best, but under most conditions, signals will simply not work. |
3368 | |
4629 | |
3369 | Not a libev limitation but worth mentioning: windows apparently doesn't |
4630 | Not a libev limitation but worth mentioning: windows apparently doesn't |
3370 | accept large writes: instead of resulting in a partial write, windows will |
4631 | accept large writes: instead of resulting in a partial write, windows will |
3371 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
4632 | either accept everything or return C<ENOBUFS> if the buffer is too large, |
3372 | so make sure you only write small amounts into your sockets (less than a |
4633 | so make sure you only write small amounts into your sockets (less than a |
3373 | megabyte seems safe, but thsi apparently depends on the amount of memory |
4634 | megabyte seems safe, but this apparently depends on the amount of memory |
3374 | available). |
4635 | available). |
3375 | |
4636 | |
3376 | Due to the many, low, and arbitrary limits on the win32 platform and |
4637 | Due to the many, low, and arbitrary limits on the win32 platform and |
3377 | the abysmal performance of winsockets, using a large number of sockets |
4638 | the abysmal performance of winsockets, using a large number of sockets |
3378 | is not recommended (and not reasonable). If your program needs to use |
4639 | is not recommended (and not reasonable). If your program needs to use |
3379 | more than a hundred or so sockets, then likely it needs to use a totally |
4640 | more than a hundred or so sockets, then likely it needs to use a totally |
3380 | different implementation for windows, as libev offers the POSIX readiness |
4641 | different implementation for windows, as libev offers the POSIX readiness |
3381 | notification model, which cannot be implemented efficiently on windows |
4642 | notification model, which cannot be implemented efficiently on windows |
3382 | (Microsoft monopoly games). |
4643 | (due to Microsoft monopoly games). |
3383 | |
4644 | |
3384 | A typical way to use libev under windows is to embed it (see the embedding |
4645 | A typical way to use libev under windows is to embed it (see the embedding |
3385 | section for details) and use the following F<evwrap.h> header file instead |
4646 | section for details) and use the following F<evwrap.h> header file instead |
3386 | of F<ev.h>: |
4647 | of F<ev.h>: |
3387 | |
4648 | |
… | |
… | |
3389 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
4650 | #define EV_SELECT_IS_WINSOCKET 1 /* configure libev for windows select */ |
3390 | |
4651 | |
3391 | #include "ev.h" |
4652 | #include "ev.h" |
3392 | |
4653 | |
3393 | And compile the following F<evwrap.c> file into your project (make sure |
4654 | And compile the following F<evwrap.c> file into your project (make sure |
3394 | you do I<not> compile the F<ev.c> or any other embedded soruce files!): |
4655 | you do I<not> compile the F<ev.c> or any other embedded source files!): |
3395 | |
4656 | |
3396 | #include "evwrap.h" |
4657 | #include "evwrap.h" |
3397 | #include "ev.c" |
4658 | #include "ev.c" |
3398 | |
4659 | |
3399 | =over 4 |
|
|
3400 | |
|
|
3401 | =item The winsocket select function |
4660 | =head3 The winsocket C<select> function |
3402 | |
4661 | |
3403 | The winsocket C<select> function doesn't follow POSIX in that it |
4662 | The winsocket C<select> function doesn't follow POSIX in that it |
3404 | requires socket I<handles> and not socket I<file descriptors> (it is |
4663 | requires socket I<handles> and not socket I<file descriptors> (it is |
3405 | also extremely buggy). This makes select very inefficient, and also |
4664 | also extremely buggy). This makes select very inefficient, and also |
3406 | requires a mapping from file descriptors to socket handles (the Microsoft |
4665 | requires a mapping from file descriptors to socket handles (the Microsoft |
… | |
… | |
3415 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
4674 | #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ |
3416 | |
4675 | |
3417 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
4676 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3418 | complexity in the O(n²) range when using win32. |
4677 | complexity in the O(n²) range when using win32. |
3419 | |
4678 | |
3420 | =item Limited number of file descriptors |
4679 | =head3 Limited number of file descriptors |
3421 | |
4680 | |
3422 | Windows has numerous arbitrary (and low) limits on things. |
4681 | Windows has numerous arbitrary (and low) limits on things. |
3423 | |
4682 | |
3424 | Early versions of winsocket's select only supported waiting for a maximum |
4683 | Early versions of winsocket's select only supported waiting for a maximum |
3425 | of C<64> handles (probably owning to the fact that all windows kernels |
4684 | of C<64> handles (probably owning to the fact that all windows kernels |
3426 | can only wait for C<64> things at the same time internally; Microsoft |
4685 | can only wait for C<64> things at the same time internally; Microsoft |
3427 | recommends spawning a chain of threads and wait for 63 handles and the |
4686 | recommends spawning a chain of threads and wait for 63 handles and the |
3428 | previous thread in each. Great). |
4687 | previous thread in each. Sounds great!). |
3429 | |
4688 | |
3430 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
4689 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3431 | to some high number (e.g. C<2048>) before compiling the winsocket select |
4690 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3432 | call (which might be in libev or elsewhere, for example, perl does its own |
4691 | call (which might be in libev or elsewhere, for example, perl and many |
3433 | select emulation on windows). |
4692 | other interpreters do their own select emulation on windows). |
3434 | |
4693 | |
3435 | Another limit is the number of file descriptors in the Microsoft runtime |
4694 | Another limit is the number of file descriptors in the Microsoft runtime |
3436 | libraries, which by default is C<64> (there must be a hidden I<64> fetish |
4695 | libraries, which by default is C<64> (there must be a hidden I<64> |
3437 | or something like this inside Microsoft). You can increase this by calling |
4696 | fetish or something like this inside Microsoft). You can increase this |
3438 | C<_setmaxstdio>, which can increase this limit to C<2048> (another |
4697 | by calling C<_setmaxstdio>, which can increase this limit to C<2048> |
3439 | arbitrary limit), but is broken in many versions of the Microsoft runtime |
4698 | (another arbitrary limit), but is broken in many versions of the Microsoft |
3440 | libraries. |
|
|
3441 | |
|
|
3442 | This might get you to about C<512> or C<2048> sockets (depending on |
4699 | runtime libraries. This might get you to about C<512> or C<2048> sockets |
3443 | windows version and/or the phase of the moon). To get more, you need to |
4700 | (depending on windows version and/or the phase of the moon). To get more, |
3444 | wrap all I/O functions and provide your own fd management, but the cost of |
4701 | you need to wrap all I/O functions and provide your own fd management, but |
3445 | calling select (O(n²)) will likely make this unworkable. |
4702 | the cost of calling select (O(n²)) will likely make this unworkable. |
3446 | |
4703 | |
3447 | =back |
|
|
3448 | |
|
|
3449 | |
|
|
3450 | =head1 PORTABILITY REQUIREMENTS |
4704 | =head2 PORTABILITY REQUIREMENTS |
3451 | |
4705 | |
3452 | In addition to a working ISO-C implementation, libev relies on a few |
4706 | In addition to a working ISO-C implementation and of course the |
3453 | additional extensions: |
4707 | backend-specific APIs, libev relies on a few additional extensions: |
3454 | |
4708 | |
3455 | =over 4 |
4709 | =over 4 |
3456 | |
4710 | |
3457 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
4711 | =item C<void (*)(ev_watcher_type *, int revents)> must have compatible |
3458 | calling conventions regardless of C<ev_watcher_type *>. |
4712 | calling conventions regardless of C<ev_watcher_type *>. |
… | |
… | |
3464 | calls them using an C<ev_watcher *> internally. |
4718 | calls them using an C<ev_watcher *> internally. |
3465 | |
4719 | |
3466 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
4720 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
3467 | |
4721 | |
3468 | The type C<sig_atomic_t volatile> (or whatever is defined as |
4722 | The type C<sig_atomic_t volatile> (or whatever is defined as |
3469 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
4723 | C<EV_ATOMIC_T>) must be atomic with respect to accesses from different |
3470 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
4724 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
3471 | believed to be sufficiently portable. |
4725 | believed to be sufficiently portable. |
3472 | |
4726 | |
3473 | =item C<sigprocmask> must work in a threaded environment |
4727 | =item C<sigprocmask> must work in a threaded environment |
3474 | |
4728 | |
… | |
… | |
3483 | except the initial one, and run the default loop in the initial thread as |
4737 | except the initial one, and run the default loop in the initial thread as |
3484 | well. |
4738 | well. |
3485 | |
4739 | |
3486 | =item C<long> must be large enough for common memory allocation sizes |
4740 | =item C<long> must be large enough for common memory allocation sizes |
3487 | |
4741 | |
3488 | To improve portability and simplify using libev, libev uses C<long> |
4742 | To improve portability and simplify its API, libev uses C<long> internally |
3489 | internally instead of C<size_t> when allocating its data structures. On |
4743 | instead of C<size_t> when allocating its data structures. On non-POSIX |
3490 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
4744 | systems (Microsoft...) this might be unexpectedly low, but is still at |
3491 | is still at least 31 bits everywhere, which is enough for hundreds of |
4745 | least 31 bits everywhere, which is enough for hundreds of millions of |
3492 | millions of watchers. |
4746 | watchers. |
3493 | |
4747 | |
3494 | =item C<double> must hold a time value in seconds with enough accuracy |
4748 | =item C<double> must hold a time value in seconds with enough accuracy |
3495 | |
4749 | |
3496 | The type C<double> is used to represent timestamps. It is required to |
4750 | The type C<double> is used to represent timestamps. It is required to |
3497 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
4751 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
3498 | enough for at least into the year 4000. This requirement is fulfilled by |
4752 | good enough for at least into the year 4000 with millisecond accuracy |
|
|
4753 | (the design goal for libev). This requirement is overfulfilled by |
3499 | implementations implementing IEEE 754 (basically all existing ones). |
4754 | implementations using IEEE 754, which is basically all existing ones. With |
|
|
4755 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
3500 | |
4756 | |
3501 | =back |
4757 | =back |
3502 | |
4758 | |
3503 | If you know of other additional requirements drop me a note. |
4759 | If you know of other additional requirements drop me a note. |
3504 | |
4760 | |
3505 | |
4761 | |
3506 | =head1 COMPILER WARNINGS |
4762 | =head1 ALGORITHMIC COMPLEXITIES |
3507 | |
4763 | |
3508 | Depending on your compiler and compiler settings, you might get no or a |
4764 | In this section the complexities of (many of) the algorithms used inside |
3509 | lot of warnings when compiling libev code. Some people are apparently |
4765 | libev will be documented. For complexity discussions about backends see |
3510 | scared by this. |
4766 | the documentation for C<ev_default_init>. |
3511 | |
4767 | |
3512 | However, these are unavoidable for many reasons. For one, each compiler |
4768 | All of the following are about amortised time: If an array needs to be |
3513 | has different warnings, and each user has different tastes regarding |
4769 | extended, libev needs to realloc and move the whole array, but this |
3514 | warning options. "Warn-free" code therefore cannot be a goal except when |
4770 | happens asymptotically rarer with higher number of elements, so O(1) might |
3515 | targeting a specific compiler and compiler-version. |
4771 | mean that libev does a lengthy realloc operation in rare cases, but on |
|
|
4772 | average it is much faster and asymptotically approaches constant time. |
3516 | |
4773 | |
3517 | Another reason is that some compiler warnings require elaborate |
4774 | =over 4 |
3518 | workarounds, or other changes to the code that make it less clear and less |
|
|
3519 | maintainable. |
|
|
3520 | |
4775 | |
3521 | And of course, some compiler warnings are just plain stupid, or simply |
4776 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
3522 | wrong (because they don't actually warn about the condition their message |
|
|
3523 | seems to warn about). |
|
|
3524 | |
4777 | |
3525 | While libev is written to generate as few warnings as possible, |
4778 | This means that, when you have a watcher that triggers in one hour and |
3526 | "warn-free" code is not a goal, and it is recommended not to build libev |
4779 | there are 100 watchers that would trigger before that, then inserting will |
3527 | with any compiler warnings enabled unless you are prepared to cope with |
4780 | have to skip roughly seven (C<ld 100>) of these watchers. |
3528 | them (e.g. by ignoring them). Remember that warnings are just that: |
|
|
3529 | warnings, not errors, or proof of bugs. |
|
|
3530 | |
4781 | |
|
|
4782 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3531 | |
4783 | |
3532 | =head1 VALGRIND |
4784 | That means that changing a timer costs less than removing/adding them, |
|
|
4785 | as only the relative motion in the event queue has to be paid for. |
3533 | |
4786 | |
3534 | Valgrind has a special section here because it is a popular tool that is |
4787 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
3535 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3536 | |
4788 | |
3537 | If you think you found a bug (memory leak, uninitialised data access etc.) |
4789 | These just add the watcher into an array or at the head of a list. |
3538 | in libev, then check twice: If valgrind reports something like: |
|
|
3539 | |
4790 | |
3540 | ==2274== definitely lost: 0 bytes in 0 blocks. |
4791 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
3541 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3542 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3543 | |
4792 | |
3544 | Then there is no memory leak. Similarly, under some circumstances, |
4793 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3545 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3546 | might be confused (it is a very good tool, but only a tool). |
|
|
3547 | |
4794 | |
3548 | If you are unsure about something, feel free to contact the mailing list |
4795 | These watchers are stored in lists, so they need to be walked to find the |
3549 | with the full valgrind report and an explanation on why you think this is |
4796 | correct watcher to remove. The lists are usually short (you don't usually |
3550 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
4797 | have many watchers waiting for the same fd or signal: one is typical, two |
3551 | no bug" answer and take the chance of learning how to interpret valgrind |
4798 | is rare). |
3552 | properly. |
|
|
3553 | |
4799 | |
3554 | If you need, for some reason, empty reports from valgrind for your project |
4800 | =item Finding the next timer in each loop iteration: O(1) |
3555 | I suggest using suppression lists. |
|
|
3556 | |
4801 | |
|
|
4802 | By virtue of using a binary or 4-heap, the next timer is always found at a |
|
|
4803 | fixed position in the storage array. |
|
|
4804 | |
|
|
4805 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
|
|
4806 | |
|
|
4807 | A change means an I/O watcher gets started or stopped, which requires |
|
|
4808 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
4809 | on backend and whether C<ev_io_set> was used). |
|
|
4810 | |
|
|
4811 | =item Activating one watcher (putting it into the pending state): O(1) |
|
|
4812 | |
|
|
4813 | =item Priority handling: O(number_of_priorities) |
|
|
4814 | |
|
|
4815 | Priorities are implemented by allocating some space for each |
|
|
4816 | priority. When doing priority-based operations, libev usually has to |
|
|
4817 | linearly search all the priorities, but starting/stopping and activating |
|
|
4818 | watchers becomes O(1) with respect to priority handling. |
|
|
4819 | |
|
|
4820 | =item Sending an ev_async: O(1) |
|
|
4821 | |
|
|
4822 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
4823 | |
|
|
4824 | =item Processing signals: O(max_signal_number) |
|
|
4825 | |
|
|
4826 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
|
|
4827 | calls in the current loop iteration. Checking for async and signal events |
|
|
4828 | involves iterating over all running async watchers or all signal numbers. |
|
|
4829 | |
|
|
4830 | =back |
|
|
4831 | |
|
|
4832 | |
|
|
4833 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
|
|
4834 | |
|
|
4835 | The major version 4 introduced some minor incompatible changes to the API. |
|
|
4836 | |
|
|
4837 | At the moment, the C<ev.h> header file tries to implement superficial |
|
|
4838 | compatibility, so most programs should still compile. Those might be |
|
|
4839 | removed in later versions of libev, so better update early than late. |
|
|
4840 | |
|
|
4841 | =over 4 |
|
|
4842 | |
|
|
4843 | =item C<ev_default_destroy> and C<ev_default_fork> have been removed |
|
|
4844 | |
|
|
4845 | These calls can be replaced easily by their C<ev_loop_xxx> counterparts: |
|
|
4846 | |
|
|
4847 | ev_loop_destroy (EV_DEFAULT); |
|
|
4848 | ev_loop_fork (EV_DEFAULT); |
|
|
4849 | |
|
|
4850 | =item function/symbol renames |
|
|
4851 | |
|
|
4852 | A number of functions and symbols have been renamed: |
|
|
4853 | |
|
|
4854 | ev_loop => ev_run |
|
|
4855 | EVLOOP_NONBLOCK => EVRUN_NOWAIT |
|
|
4856 | EVLOOP_ONESHOT => EVRUN_ONCE |
|
|
4857 | |
|
|
4858 | ev_unloop => ev_break |
|
|
4859 | EVUNLOOP_CANCEL => EVBREAK_CANCEL |
|
|
4860 | EVUNLOOP_ONE => EVBREAK_ONE |
|
|
4861 | EVUNLOOP_ALL => EVBREAK_ALL |
|
|
4862 | |
|
|
4863 | EV_TIMEOUT => EV_TIMER |
|
|
4864 | |
|
|
4865 | ev_loop_count => ev_iteration |
|
|
4866 | ev_loop_depth => ev_depth |
|
|
4867 | ev_loop_verify => ev_verify |
|
|
4868 | |
|
|
4869 | Most functions working on C<struct ev_loop> objects don't have an |
|
|
4870 | C<ev_loop_> prefix, so it was removed; C<ev_loop>, C<ev_unloop> and |
|
|
4871 | associated constants have been renamed to not collide with the C<struct |
|
|
4872 | ev_loop> anymore and C<EV_TIMER> now follows the same naming scheme |
|
|
4873 | as all other watcher types. Note that C<ev_loop_fork> is still called |
|
|
4874 | C<ev_loop_fork> because it would otherwise clash with the C<ev_fork> |
|
|
4875 | typedef. |
|
|
4876 | |
|
|
4877 | =item C<EV_COMPAT3> backwards compatibility mechanism |
|
|
4878 | |
|
|
4879 | The backward compatibility mechanism can be controlled by |
|
|
4880 | C<EV_COMPAT3>. See L<PREPROCESSOR SYMBOLS/MACROS> in the L<EMBEDDING> |
|
|
4881 | section. |
|
|
4882 | |
|
|
4883 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
|
|
4884 | |
|
|
4885 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
|
|
4886 | mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile |
|
|
4887 | and work, but the library code will of course be larger. |
|
|
4888 | |
|
|
4889 | =back |
|
|
4890 | |
|
|
4891 | |
|
|
4892 | =head1 GLOSSARY |
|
|
4893 | |
|
|
4894 | =over 4 |
|
|
4895 | |
|
|
4896 | =item active |
|
|
4897 | |
|
|
4898 | A watcher is active as long as it has been started and not yet stopped. |
|
|
4899 | See L<WATCHER STATES> for details. |
|
|
4900 | |
|
|
4901 | =item application |
|
|
4902 | |
|
|
4903 | In this document, an application is whatever is using libev. |
|
|
4904 | |
|
|
4905 | =item backend |
|
|
4906 | |
|
|
4907 | The part of the code dealing with the operating system interfaces. |
|
|
4908 | |
|
|
4909 | =item callback |
|
|
4910 | |
|
|
4911 | The address of a function that is called when some event has been |
|
|
4912 | detected. Callbacks are being passed the event loop, the watcher that |
|
|
4913 | received the event, and the actual event bitset. |
|
|
4914 | |
|
|
4915 | =item callback/watcher invocation |
|
|
4916 | |
|
|
4917 | The act of calling the callback associated with a watcher. |
|
|
4918 | |
|
|
4919 | =item event |
|
|
4920 | |
|
|
4921 | A change of state of some external event, such as data now being available |
|
|
4922 | for reading on a file descriptor, time having passed or simply not having |
|
|
4923 | any other events happening anymore. |
|
|
4924 | |
|
|
4925 | In libev, events are represented as single bits (such as C<EV_READ> or |
|
|
4926 | C<EV_TIMER>). |
|
|
4927 | |
|
|
4928 | =item event library |
|
|
4929 | |
|
|
4930 | A software package implementing an event model and loop. |
|
|
4931 | |
|
|
4932 | =item event loop |
|
|
4933 | |
|
|
4934 | An entity that handles and processes external events and converts them |
|
|
4935 | into callback invocations. |
|
|
4936 | |
|
|
4937 | =item event model |
|
|
4938 | |
|
|
4939 | The model used to describe how an event loop handles and processes |
|
|
4940 | watchers and events. |
|
|
4941 | |
|
|
4942 | =item pending |
|
|
4943 | |
|
|
4944 | A watcher is pending as soon as the corresponding event has been |
|
|
4945 | detected. See L<WATCHER STATES> for details. |
|
|
4946 | |
|
|
4947 | =item real time |
|
|
4948 | |
|
|
4949 | The physical time that is observed. It is apparently strictly monotonic :) |
|
|
4950 | |
|
|
4951 | =item wall-clock time |
|
|
4952 | |
|
|
4953 | The time and date as shown on clocks. Unlike real time, it can actually |
|
|
4954 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
|
|
4955 | clock. |
|
|
4956 | |
|
|
4957 | =item watcher |
|
|
4958 | |
|
|
4959 | A data structure that describes interest in certain events. Watchers need |
|
|
4960 | to be started (attached to an event loop) before they can receive events. |
|
|
4961 | |
|
|
4962 | =back |
3557 | |
4963 | |
3558 | =head1 AUTHOR |
4964 | =head1 AUTHOR |
3559 | |
4965 | |
3560 | Marc Lehmann <libev@schmorp.de>. |
4966 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3561 | |
4967 | |